@article{3382,
abstract = {Dynamic tactile sensing is a fundamental ability to recognize materials and objects. However, while humans are born with partially developed dynamic tactile sensing and quickly master this skill, today's robots remain in their infancy. The development of such a sense requires not only better sensors but the right algorithms to deal with these sensors' data as well. For example, when classifying a material based on touch, the data are noisy, high-dimensional, and contain irrelevant signals as well as essential ones. Few classification methods from machine learning can deal with such problems. In this paper, we propose an efficient approach to infer suitable lower dimensional representations of the tactile data. In order to classify materials based on only the sense of touch, these representations are autonomously discovered using visual information of the surfaces during training. However, accurately pairing vision and tactile samples in real-robot applications is a difficult problem. The proposed approach, therefore, works with weak pairings between the modalities. Experiments show that the resulting approach is very robust and yields significantly higher classification performance based on only dynamic tactile sensing.},
author = {Kroemer, Oliver and Lampert, Christoph and Peters, Jan},
journal = {IEEE Transactions on Robotics},
number = {3},
pages = {545 -- 557},
publisher = {IEEE},
title = {{Learning dynamic tactile sensing with robust vision based training}},
doi = {10.1109/TRO.2011.2121130},
volume = {27},
year = {2011},
}
@article{3383,
author = {Heisenberg, Carl-Philipp J},
journal = {FEBS Journal},
number = {S1},
pages = {24 -- 24},
publisher = {Wiley-Blackwell},
title = {{Invited Lectures ‐ Symposia Area}},
doi = {10.1111/j.1742-4658.2011.08136.x},
volume = {278},
year = {2011},
}
@article{3384,
abstract = {Here we introduce a database of calibrated natural images publicly available through an easy-to-use web interface. Using a Nikon D70 digital SLR camera, we acquired about six-megapixel images of Okavango Delta of Botswana, a tropical savanna habitat similar to where the human eye is thought to have evolved. Some sequences of images were captured unsystematically while following a baboon troop, while others were designed to vary a single parameter such as aperture, object distance, time of day or position on the horizon. Images are available in the raw RGB format and in grayscale. Images are also available in units relevant to the physiology of human cone photoreceptors, where pixel values represent the expected number of photoisomerizations per second for cones sensitive to long (L), medium (M) and short (S) wavelengths. This database is distributed under a Creative Commons Attribution-Noncommercial Unported license to facilitate research in computer vision, psychophysics of perception, and visual neuroscience.},
author = {Tkacik, Gasper and Garrigan, Patrick and Ratliff, Charles and Milcinski, Grega and Klein, Jennifer and Seyfarth, Lucia and Sterling, Peter and Brainard, David and Balasubramanian, Vijay},
journal = {PLoS One},
number = {6},
publisher = {Public Library of Science},
title = {{Natural images from the birthplace of the human eye}},
doi = {10.1371/journal.pone.0020409},
volume = {6},
year = {2011},
}
@article{3385,
author = {Sixt, Michael K},
journal = {Immunology Letters},
number = {1},
pages = {32 -- 34},
publisher = {Elsevier},
title = {{Interstitial locomotion of leukocytes}},
doi = {10.1016/j.imlet.2011.02.013},
volume = {138},
year = {2011},
}
@article{3386,
abstract = {Evolutionary theories of ageing predict that life span increases with decreasing extrinsic mortality, and life span variation among queens in ant species seems to corroborate this prediction: queens, which are the only reproductive in a colony, live much longer than queens in multi-queen colonies. The latter often inhabit ephemeral nest sites and accordingly are assumed to experience a higher mortality risk. Yet, all prior studies compared queens from different single- and multi-queen species. Here, we demonstrate an effect of queen number on longevity and fecundity within a single, socially plastic species, where queens experience the similar level of extrinsic mortality. Queens from single- and two-queen colonies had significantly longer lifespan and higher fecundity than queens living in associations of eight queens. As queens also differ neither in morphology nor the mode of colony foundation, our study shows that the social environment itself strongly affects ageing rate.},
author = {Schrempf, Alexandra and Cremer, Sylvia and Heinze, Jürgen},
journal = {Journal of Evolutionary Biology},
number = {7},
pages = {1455 -- 1461},
publisher = {Wiley-Blackwell},
title = {{Social influence on age and reproduction reduced lifespan and fecundity in multi queen ant colonies}},
doi = {10.1111/j.1420-9101.2011.02278.x},
volume = {24},
year = {2011},
}
@article{3387,
abstract = {Background: Supertree methods combine overlapping input trees into a larger supertree. Here, I consider split-based supertree methods that first extract the split information of the input trees and subsequently combine this split information into a phylogeny. Well known split-based supertree methods are matrix representation with parsimony and matrix representation with compatibility. Combining input trees on the same taxon set, as in the consensus setting, is a well-studied task and it is thus desirable to generalize consensus methods to supertree methods. Results: Here, three variants of majority-rule (MR) supertrees that generalize majority-rule consensus trees are investigated. I provide simple formulas for computing the respective score for bifurcating input- and supertrees. These score computations, together with a heuristic tree search minmizing the scores, were implemented in the python program PluMiST (Plus- and Minus SuperTrees) available from http://www.cibiv.at/software/ plumist. The different MR methods were tested by simulation and on real data sets. The search heuristic was successful in combining compatible input trees. When combining incompatible input trees, especially one variant, MR(-) supertrees, performed well. Conclusions: The presented framework allows for an efficient score computation of three majority-rule supertree variants and input trees. I combined the score computation with a heuristic search over the supertree space. The implementation was tested by simulation and on real data sets and showed promising results. Especially the MR(-) variant seems to be a reasonable score for supertree reconstruction. Generalizing these computations to multifurcating trees is an open problem, which may be tackled using this framework.},
author = {Kupczok, Anne},
journal = {BMC Evolutionary Biology},
number = {205},
publisher = {BioMed Central},
title = {{Split based computation of majority rule supertrees}},
doi = {10.1186/1471-2148-11-205},
volume = {11},
year = {2011},
}
@article{3388,
abstract = {Background: Fragmentation of terrestrial ecosystems has had detrimental effects on metapopulations of habitat specialists. Maculinea butterflies have been particularly affected because of their specialized lifecycles, requiring both specific food-plants and host-ants. However, the interaction between dispersal, effective population size, and long-term genetic erosion of these endangered butterflies remains unknown. Using non-destructive sampling, we investigated the genetic diversity of the last extant population of M. arion in Denmark, which experienced critically low numbers in the 1980s. Results: Using nine microsatellite markers, we show that the population is genetically impoverished compared to nearby populations in Sweden, but less so than monitoring programs suggested. Ten additional short repeat microsatellites were used to reconstruct changes in genetic diversity and population structure over the last 77 years from museum specimens. We also tested amplification efficiency in such historical samples as a function of repeat length and sample age. Low population numbers in the 1980s did not affect genetic diversity, but considerable turnover of alleles has characterized this population throughout the time-span of our analysis. Conclusions: Our results suggest that M. arion is less sensitive to genetic erosion via population bottlenecks than previously thought, and that managing clusters of high quality habitat may be key for long-term conservation.},
author = {Ugelvig, Line V and Nielsen, Per and Boomsma, Jacobus and Nash, David},
journal = {BMC Evolutionary Biology},
number = {201},
publisher = {BioMed Central},
title = {{Reconstructing eight decades of genetic variation in an isolated Danish population of the large blue butterfly Maculinea arion}},
doi = {10.1186/1471-2148-11-201},
volume = {11},
year = {2011},
}
@article{3389,
abstract = {Kernel canonical correlation analysis (KCCA) is a general technique for subspace learning that incorporates principal components analysis (PCA) and Fisher linear discriminant analysis (LDA) as special cases. By finding directions that maximize correlation, KCCA learns representations that are more closely tied to the underlying process that generates the data and can ignore high-variance noise directions. However, for data where acquisition in one or more modalities is expensive or otherwise limited, KCCA may suffer from small sample effects. We propose to use semi-supervised Laplacian regularization to utilize data that are present in only one modality. This approach is able to find highly correlated directions that also lie along the data manifold, resulting in a more robust estimate of correlated subspaces. Functional magnetic resonance imaging (fMRI) acquired data are naturally amenable to subspace techniques as data are well aligned. fMRI data of the human brain are a particularly interesting candidate. In this study we implemented various supervised and semi-supervised versions of KCCA on human fMRI data, with regression to single and multi-variate labels (corresponding to video content subjects viewed during the image acquisition). In each variate condition, the semi-supervised variants of KCCA performed better than the supervised variants, including a supervised variant with Laplacian regularization. We additionally analyze the weights learned by the regression in order to infer brain regions that are important to different types of visual processing.},
author = {Blaschko, Matthew and Shelton, Jacquelyn and Bartels, Andreas and Lampert, Christoph and Gretton, Arthur},
journal = {Pattern Recognition Letters},
number = {11},
pages = {1572 -- 1583},
publisher = {Elsevier},
title = {{Semi supervised kernel canonical correlation analysis with application to human fMRI}},
doi = {10.1016/j.patrec.2011.02.011},
volume = {32},
year = {2011},
}
@article{3390,
abstract = {What determines the genetic contribution that an individual makes to future generations? With biparental reproduction, each individual leaves a 'pedigree' of descendants, determined by the biparental relationships in the population. The pedigree of an individual constrains the lines of descent of each of its genes. An individual's reproductive value is the expected number of copies of each of its genes that is passed on to distant generations conditional on its pedigree. For the simplest model of biparental reproduction analogous to the Wright-Fisher model, an individual's reproductive value is determined within ~10 generations, independent of population size. Partial selfing and subdivision do not greatly slow this convergence. Our central result is that the probability that a gene will survive is proportional to the reproductive value of the individual that carries it, and that conditional on survival, after a few tens of generations, the distribution of the number of surviving copies is the same for all individuals, whatever their reproductive value. These results can be generalized to the joint distribution of surviving blocks of ancestral genome. Selection on unlinked loci in the genetic background may greatly increase the variance in reproductive value, but the above results nevertheless still hold. The almost linear relationship between survival probability and reproductive value also holds for weakly favored alleles. Thus, the influence of the complex pedigree of descendants on an individual's genetic contribution to the population can be summarized through a single number: its reproductive value.},
author = {Barton, Nicholas H and Etheridge, Alison},
journal = {Genetics},
number = {4},
pages = {953 -- 973},
publisher = {Genetics Society of America},
title = {{The relation between reproductive value and genetic contribution}},
doi = {10.1534/genetics.111.127555},
volume = {188},
year = {2011},
}
@article{3391,
abstract = {Evolutionary biology shares many concepts with statistical physics: both deal with populations, whether of molecules or organisms, and both seek to simplify evolution in very many dimensions. Often, methodologies have undergone parallel and independent development, as with stochastic methods in population genetics. Here, we discuss aspects of population genetics that have embraced methods from physics: non-equilibrium statistical mechanics, travelling waves and Monte-Carlo methods, among others, have been used to study polygenic evolution, rates of adaptation and range expansions. These applications indicate that evolutionary biology can further benefit from interactions with other areas of statistical physics; for example, by following the distribution of paths taken by a population through time},
author = {de Vladar, Harold and Barton, Nicholas H},
journal = {Trends in Ecology and Evolution},
number = {8},
pages = {424 -- 432},
publisher = {Cell Press},
title = {{The contribution of statistical physics to evolutionary biology}},
doi = {10.1016/j.tree.2011.04.002},
volume = {26},
year = {2011},
}
@article{3392,
abstract = {Migrating lymphocytes acquire a polarized phenotype with a leading and a trailing edge, or uropod. Although in vitro experiments in cell lines or activated primary cell cultures have established that Rho-p160 coiled-coil kinase (ROCK)-myosin II-mediated uropod contractility is required for integrin de-adhesion on two-dimensional surfaces and nuclear propulsion through narrow pores in three-dimensional matrices, less is known about the role of these two events during the recirculation of primary, nonactivated lymphocytes. Using pharmacological antagonists of ROCK and myosin II, we report that inhibition of uropod contractility blocked integrin-independent mouse T cell migration through narrow, but not large, pores in vitro. T cell crawling on chemokine-coated endothelial cells under shear was severely impaired by ROCK inhibition, whereas transendothelial migration was only reduced through endothelial cells with high, but not low, barrier properties. Using three-dimensional thick-tissue imaging and dynamic two-photon microscopy of T cell motility in lymphoid tissue, we demonstrated a significant role for uropod contractility in intraluminal crawling and transendothelial migration through lymph node, but not bone marrow, endothelial cells. Finally, we demonstrated that ICAM-1, but not anatomical constraints or integrin-independent interactions, reduced parenchymal motility of inhibitor-treated T cells within the dense lymphoid microenvironment, thus assigning context-dependent roles for uropod contraction during lymphocyte recirculation.},
author = {Soriano, Silvia and Hons, Miroslav and Schumann, Kathrin and Kumar, Varsha and Dennier, Timo and Lyck, Ruth and Sixt, Michael K and Stein, Jens},
journal = {Journal of Immunology},
number = {5},
pages = {2356 -- 2364},
publisher = {American Association of Immunologists},
title = {{In vivo analysis of uropod function during physiological T cell trafficking}},
doi = {10.4049/jimmunol.1100935},
volume = {187},
year = {2011},
}
@article{3393,
abstract = {Unlike unconditionally advantageous “Fisherian” variants that tend to spread throughout a species range once introduced anywhere, “bistable” variants, such as chromosome translocations, have two alternative stable frequencies, absence and (near) fixation. Analogous to populations with Allee effects, bistable variants tend to increase locally only once they become sufficiently common, and their spread depends on their rate of increase averaged over all frequencies. Several proposed manipulations of insect populations, such as using Wolbachia or “engineered underdominance” to suppress vector-borne diseases, produce bistable rather than Fisherian dynamics. We synthesize and extend theoretical analyses concerning three features of their spatial behavior: rate of spread, conditions to initiate spread from a localized introduction, and wave stopping caused by variation in population densities or dispersal rates. Unlike Fisherian variants, bistable variants tend to spread spatially only for particular parameter combinations and initial conditions. Wave initiation requires introduction over an extended region, while subsequent spatial spread is slower than for Fisherian waves and can easily be halted by local spatial inhomogeneities. We present several new results, including robust sufficient conditions to initiate (and stop) spread, using a one-parameter cubic approximation applicable to several models. The results have both basic and applied implications.},
author = {Barton, Nicholas H and Turelli, Michael},
journal = {American Naturalist},
number = {3},
pages = {E48 -- E75},
publisher = {University of Chicago Press},
title = {{Spatial waves of advance with bistable dynamics: Cytoplasmic and genetic analogues of Allee effects}},
doi = {10.1086/661246},
volume = {178},
year = {2011},
}
@article{3394,
abstract = {Random genetic drift shifts clines in space, alters their width, and distorts their shape. Such random fluctuations complicate inferences from cline width and position. Notably, the effect of genetic drift on the expected shape of the cline is opposite to the naive (but quite common) misinterpretation of classic results on the expected cline. While random drift on average broadens the overall cline in expected allele frequency, it narrows the width of any particular cline. The opposing effects arise because locally, drift drives alleles to fixation—but fluctuations in position widen the expected cline. The effect of genetic drift can be predicted from standardized variance in allele frequencies, averaged across the habitat: 〈F〉. A cline maintained by spatially varying selection (step change) is expected to be narrower by a factor of relative to the cline in the absence of drift. The expected cline is broader by the inverse of this factor. In a tension zone maintained by underdominance, the expected cline width is narrower by about 1 – 〈F〉relative to the width in the absence of drift. Individual clines can differ substantially from the expectation, and we give quantitative predictions for the variance in cline position and width. The predictions apply to clines in almost one-dimensional circumstances such as hybrid zones in rivers, deep valleys, or along a coast line and give a guide to what patterns to expect in two dimensions.},
author = {Polechova, Jitka and Barton, Nicholas H},
journal = {Genetics},
number = {1},
pages = {227 -- 235},
publisher = {Genetics Society of America},
title = {{Genetic drift widens the expected cline but narrows the expected cline width}},
doi = {10.1534/genetics.111.129817},
volume = {189},
year = {2011},
}
@article{3395,
abstract = {Defining population structure and genetic diversity levels is of the utmost importance for developing efficient conservation strategies. Overfishing has caused mean annual catches of the European spiny lobster (Palinurus elephas) to decrease alarmingly along its distribution area. In this context, there is a need for comprehensive studies aiming to evaluate the genetic health of the exploited populations. The present study is based on a set of ten nuclear markers amplified in 331 individuals from ten different localities covering most of P. elephas distribution area. Samples from Atlantic and Mediterranean basins showed small but significant differences, indicating that P. elephas populations do not behave as a single panmictic unit but form two partially-overlapping groups. Despite intense overfishing, our dataset did not recover a recent bottleneck signal, and instead showed a large and stable historical effective size. This result could be accounted for by specific life-history traits (reproduction and longevity) and the limitations of molecular markers in covering recent timescales for nontemporal samples. The findings of the present study emphasize the need to integrate information on effective population sizes and life-history parameters when evaluating population connectivity levels from genetic data.},
author = {Palero, Ferran and Abello, Pere and Macpherson, Enrique and Beaumont, Mark and Pascual, Marta},
journal = {Biological Journal of the Linnean Society},
number = {2},
pages = {407 -- 418},
publisher = {Wiley-Blackwell},
title = {{Effect of oceanographic barriers and overfishing on the population genetic structure of the European spiny lobster Palinurus elephas }},
doi = {10.1111/j.1095-8312.2011.01728.x},
volume = {104},
year = {2011},
}
@article{3396,
abstract = {Facial branchiomotor neurons (FBMNs) in zebrafish and mouse embryonic hindbrain undergo a characteristic tangential migration from rhombomere (r) 4, where they are born, to r6/7. Cohesion among neuroepithelial cells (NCs) has been suggested to function in FBMN migration by inhibiting FBMNs positioned in the basal neuroepithelium such that they move apically between NCs towards the midline of the neuroepithelium instead of tangentially along the basal side of the neuroepithelium towards r6/7. However, direct experimental evaluation of this hypothesis is still lacking. Here, we have used a combination of biophysical cell adhesion measurements and high-resolution time-lapse microscopy to determine the role of NC cohesion in FBMN migration. We show that reducing NC cohesion by interfering with Cadherin 2 (Cdh2) activity results in FBMNs positioned at the basal side of the neuroepithelium moving apically towards the neural tube midline instead of tangentially towards r6/7. In embryos with strongly reduced NC cohesion, ectopic apical FBMN movement frequently results in fusion of the bilateral FBMN clusters over the apical midline of the neural tube. By contrast, reducing cohesion among FBMNs by interfering with Contactin 2 (Cntn2) expression in these cells has little effect on apical FBMN movement, but reduces the fusion of the bilateral FBMN clusters in embryos with strongly diminished NC cohesion. These data provide direct experimental evidence that NC cohesion functions in tangential FBMN migration by restricting their apical movement.},
author = {Stockinger, Petra and Heisenberg, Carl-Philipp J and Maître, Jean-Léon},
journal = {Development},
number = {21},
pages = {4673 -- 4683},
publisher = {Company of Biologists},
title = {{Defective neuroepithelial cell cohesion affects tangential branchiomotor neuron migration in the zebrafish neural tube}},
doi = {10.1242/dev.071233},
volume = {138},
year = {2011},
}
@article{3397,
abstract = {Recent advances in microscopy techniques and biophysical measurements have provided novel insight into the molecular, cellular and biophysical basis of cell adhesion. However, comparably little is known about a core element of cell–cell adhesion—the energy of adhesion at the cell–cell contact. In this review, we discuss approaches to understand the nature and regulation of adhesion energy, and propose strategies to determine adhesion energy between cells in vitro and in vivo.},
author = {Maître, Jean-Léon and Heisenberg, Carl-Philipp J},
journal = {Current Opinion in Cell Biology},
number = {5},
pages = {508 -- 514},
publisher = {Elsevier},
title = {{The role of adhesion energy in controlling cell-cell contacts}},
doi = {10.1016/j.ceb.2011.07.004},
volume = {23},
year = {2011},
}
@article{3399,
abstract = {Context-dependent adjustment of mating tactics can drastically increase the mating success of behaviourally flexible animals. We used the ant Cardiocondyla obscurior as a model system to study adaptive adjustment of male mating tactics. This species shows a male diphenism of wingless fighter males and peaceful winged males. Whereas the wingless males stay and exclusively mate in the maternal colony, the mating behaviour of winged males is plastic. They copulate with female sexuals in their natal nests early in life but later disperse in search for sexuals outside. In this study, we observed the nest-leaving behaviour of winged males under different conditions and found that they adaptively adjust the timing of their dispersal to the availability of mating partners, as well as the presence, and even the type of competitors in their natal nests. In colonies with virgin female queens winged males stayed longest when they were the only male in the nest. They left earlier when mating partners were not available or when other males were present. In the presence of wingless, locally mating fighter males, winged males dispersed earlier than in the presence of docile, winged competitors. This suggests that C. obscurior males are capable of estimating their local breeding chances and adaptively adjust their dispersal behaviour in both an opportunistic and a risk-sensitive way, thus showing hitherto unknown behavioural plasticity in social insect males.},
author = {Cremer, Sylvia and Schrempf, Alexandra and Heinze, Jürgen},
journal = {PLoS One},
number = {3},
publisher = {Public Library of Science},
title = {{Competition and opportunity shape the reproductive tactics of males in the ant Cardiocondyla obscurior}},
doi = {10.1371/journal.pone.0017323},
volume = {6},
year = {2011},
}
@article{3405,
abstract = {Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and gates non-selective cation channels. The origins of glutamate receptors are not well understood as they differ structurally and functionally from simple bacterial ligand-gated ion channels. Here we report the discovery of an ionotropic glutamate receptor that combines the typical eukaryotic domain architecture with the 'TXVGYG' signature sequence of the selectivity filter found in K+ channels. This receptor exhibits functional properties intermediate between bacterial and eukaryotic glutamate-gated ion channels, suggesting a link in the evolution of ionotropic glutamate receptors.},
author = {Janovjak, Harald L and Sandoz, Guillaume and Isacoff, Ehud},
journal = {Nature Communications},
number = {232},
pages = {1 -- 6},
publisher = {Nature Publishing Group},
title = {{Modern ionotropic glutamate receptor with a K+ selectivity signature sequence}},
doi = {10.1038/ncomms1231},
volume = {2},
year = {2011},
}
@article{3429,
abstract = {Transcription factors are central to sustaining pluripotency, yet little is known about transcription factor dynamics in defining pluripotency in the early mammalian embryo. Here, we establish a fluorescence decay after photoactivation (FDAP) assay to quantitatively study the kinetic behaviour of Oct4, a key transcription factor controlling pre-implantation development in the mouse embryo. FDAP measurements reveal that each cell in a developing embryo shows one of two distinct Oct4 kinetics, before there are any morphologically distinguishable differences or outward signs of lineage patterning. The differences revealed by FDAP are due to differences in the accessibility of Oct4 to its DNA binding sites in the nucleus. Lineage tracing of the cells in the two distinct sub-populations demonstrates that the Oct4 kinetics predict lineages of the early embryo. Cells with slower Oct4 kinetics are more likely to give rise to the pluripotent cell lineage that contributes to the inner cell mass. Those with faster Oct4 kinetics contribute mostly to the extra-embryonic lineage. Our findings identify Oct4 kinetics, rather than differences in total transcription factor expression levels, as a predictive measure of developmental cell lineage patterning in the early mouse embryo.},
author = {Plachta, Nicolas and Bollenbach, Mark Tobias and Pease, Shirley and Fraser, Scott and Pantazis, Periklis},
journal = {Nature Cell Biology},
number = {2},
pages = {117 -- 123},
publisher = {Nature Publishing Group},
title = {{Oct4 kinetics predict cell lineage patterning in the early mammalian embryo}},
doi = {10.1038/ncb2154},
volume = {13},
year = {2011},
}
@article{3505,
abstract = {Cell migration on two-dimensional (2D) substrates follows entirely different rules than cell migration in three-dimensional (3D) environments. This is especially relevant for leukocytes that are able to migrate in the absence of adhesion receptors within the confined geometry of artificial 3D extracellular matrix scaffolds and within the interstitial space in vivo. Here, we describe in detail a simple and economical protocol to visualize dendritic cell migration in 3D collagen scaffolds along chemotactic gradients. This method can be adapted to other cell types and may serve as a physiologically relevant paradigm for the directed locomotion of most amoeboid cells.},
author = {Sixt, Michael K and Lämmermann, Tim},
journal = {Cell Migration},
pages = {149 -- 165},
publisher = {Springer},
title = {{In vitro analysis of chemotactic leukocyte migration in 3D environments}},
doi = {10.1007/978-1-61779-207-6_11},
volume = {769},
year = {2011},
}
@inproceedings{3367,
abstract = {In this paper, we present the first output-sensitive algorithm to compute the persistence diagram of a filtered simplicial complex. For any Γ>0, it returns only those homology classes with persistence at least Γ. Instead of the classical reduction via column operations, our algorithm performs rank computations on submatrices of the boundary matrix. For an arbitrary constant δ ∈ (0,1), the running time is O(C(1-δ)ΓR(n)log n), where C(1-δ)Γ is the number of homology classes with persistence at least (1-δ)Γ, n is the total number of simplices, and R(n) is the complexity of computing the rank of an n x n matrix with O(n) nonzero entries. Depending on the choice of the rank algorithm, this yields a deterministic O(C(1-δ)Γn2.376) algorithm, a O(C(1-δ)Γn2.28) Las-Vegas algorithm, or a O(C(1-δ)Γn2+ε) Monte-Carlo algorithm for an arbitrary ε>0.},
author = {Chen, Chao and Kerber, Michael},
location = {Paris, France},
pages = {207 -- 216},
publisher = {ACM},
title = {{An output sensitive algorithm for persistent homology}},
doi = {10.1145/1998196.1998228},
year = {2011},
}
@article{3368,
abstract = {Tissue surface tension (TST) is an important mechanical property influencing cell sorting and tissue envelopment. The study by Manning et al. (1) reported on a mathematical model describing TST on the basis of the balance between adhesive and tensile properties of the constituent cells. The model predicts that, in high-adhesion cell aggregates, surface cells will be stretched to maintain the same area of cell–cell contact as interior bulk cells, resulting in an elongated and flattened cell shape. The authors (1) observed flat and elongated cells at the surface of high-adhesion zebrafish germ-layer explants, which they argue are undifferentiated stretched germ-layer progenitor cells, and they use this observation as a validation of their model.},
author = {Krens, Gabriel and Möllmert, Stephanie and Heisenberg, Carl-Philipp J},
journal = {PNAS},
number = {3},
pages = {E9 -- E10},
publisher = {National Academy of Sciences},
title = {{Enveloping cell layer differentiation at the surface of zebrafish germ layer tissue explants}},
doi = {10.1073/pnas.1010767108},
volume = {108},
year = {2011},
}
@article{3369,
abstract = {Rab3 interacting molecules (RIMs) are highly enriched in the active zones of presynaptic terminals. It is generally thought that they operate as effectors of the small G protein Rab3. Three recent papers, by Han et al. (this issue of Neuron), Deng et al. (this issue of Neuron), and Kaeser et al. (a recent issue of Cell), shed new light on the functional role of RIM in presynaptic terminals. First, RIM tethers Ca2+ channels to active zones. Second, RIM contributes to priming of synaptic vesicles by interacting with another presynaptic protein, Munc13.},
author = {Pernia-Andrade, Alejandro and Jonas, Peter M},
journal = {Neuron},
number = {2},
pages = {185 -- 187},
publisher = {Elsevier},
title = {{The multiple faces of RIM}},
doi = {10.1016/j.neuron.2011.01.010},
volume = {69},
year = {2011},
}
@article{3370,
abstract = {Supertree methods are widely applied and give rise to new conclusions about phylogenies (e.g., Bininda-Emonds et al. 2007). Although several desiderata for supertree methods exist (Wilkinson, Thorley, et al. 2004), only few of them have been studied in greater detail, examples include shape bias (Wilkinson et al. 2005) or pareto properties (Wilkinson et al. 2007). Here I look more closely at two matrix representation methods, matrix representation with compatibility (MRC) and matrix representation with parsimony (MRP). Different null models of random data are studied and the resulting tree shapes are investigated. Thereby I consider unrooted trees and a bias in tree shape is determined by a tree balance measure. The measure for unrooted trees is a modification of a tree balance measure for rooted trees. I observe that depending on the underlying null model of random data, the methods may resolve conflict in favor of more balanced tree shapes. The analyses refer only to trees with the same taxon set, also known as the consensus setting (e.g., Wilkinson et al. 2007), but I will be able to draw conclusions on how to deal with missing data.},
author = {Kupczok, Anne},
journal = {Systematic Biology},
number = {2},
pages = {218 -- 225},
publisher = {Oxford University Press},
title = {{Consequences of different null models on the tree shape bias of supertree methods}},
doi = {10.1093/sysbio/syq086},
volume = {60},
year = {2011},
}
@article{3371,
abstract = {The Minisymposium “Cell Migration and Motility” was attended by approximately 500 visitors and covered a broad range of questions in the field using diverse model systems. Topics comprised actin dynamics, cell polarity, force transduction, signal transduction, bar- rier transmigration, and chemotactic guidance.},
author = {Sixt, Michael K and Parent, Carole},
journal = {Molecular Biology and Evolution},
number = {6},
pages = {724},
publisher = {Oxford University Press},
title = {{Cells on the move in Philadelphia}},
doi = {10.1091/mbc.E10-12-0958},
volume = {22},
year = {2011},
}
@article{3372,
abstract = {Nowak et al.1 argue that inclusive fitness theory has been of little value in explaining the natural world, and that it has led to negligible progress in explaining the evolution of eusociality. However, we believe that their arguments are based upon a misunderstanding of evolutionary theory and a misrepresentation of the empirical literature. We will focus our comments on three general issues.},
author = {Abbot, Patrick and Abe, Jun and Alcock, John and Alizon, Samuel and Alpedrinha, Joao and Andersson, Malte and Andre, Jean and Van Baalen, Minus and Balloux, Francois and Balshine, Sigal and Barton, Nicholas H and Beukeboom, Leo and Biernaskie, Jay and Bilde, Trine and Borgia, Gerald and Breed, Michael and Brown, Sam and Bshary, Redouan and Buckling, Angus and Burley, Nancy and Burton Chellew, Max and Cant, Michael and Chapuisat, Michel and Charnov, Eric and Clutton Brock, Tim and Cockburn, Andrew and Cole, Blaine and Colegrave, Nick and Cosmides, Leda and Couzin, Iain and Coyne, Jerry and Creel, Scott and Crespi, Bernard and Curry, Robert and Dall, Sasha and Day, Troy and Dickinson, Janis and Dugatkin, Lee and El Mouden, Claire and Emlen, Stephen and Evans, Jay and Ferriere, Regis and Field, Jeremy and Foitzik, Susanne and Foster, Kevin and Foster, William and Fox, Charles and Gadau, Juergen and Gandon, Sylvain and Gardner, Andy and Gardner, Michael and Getty, Thomas and Goodisman, Michael and Grafen, Alan and Grosberg, Rick and Grozinger, Christina and Gouyon, Pierre and Gwynne, Darryl and Harvey, Paul and Hatchwell, Ben and Heinze, Jürgen and Helantera, Heikki and Helms, Ken and Hill, Kim and Jiricny, Natalie and Johnstone, Rufus and Kacelnik, Alex and Kiers, E Toby and Kokko, Hanna and Komdeur, Jan and Korb, Judith and Kronauer, Daniel and Kümmerli, Rolf and Lehmann, Laurent and Linksvayer, Timothy and Lion, Sébastien and Lyon, Bruce and Marshall, James and Mcelreath, Richard and Michalakis, Yannis and Michod, Richard and Mock, Douglas and Monnin, Thibaud and Montgomerie, Robert and Moore, Allen and Mueller, Ulrich and Noë, Ronald and Okasha, Samir and Pamilo, Pekka and Parker, Geoff and Pedersen, Jes and Pen, Ido and Pfennig, David and Queller, David and Rankin, Daniel and Reece, Sarah and Reeve, Hudson and Reuter, Max and Roberts, Gilbert and Robson, Simon and Roze, Denis and Rousset, Francois and Rueppell, Olav and Sachs, Joel and Santorelli, Lorenzo and Schmid Hempel, Paul and Schwarz, Michael and Scott Phillips, Tom and Shellmann Sherman, Janet and Sherman, Paul and Shuker, David and Smith, Jeff and Spagna, Joseph and Strassmann, Beverly and Suarez, Andrew and Sundström, Liselotte and Taborsky, Michael and Taylor, Peter and Thompson, Graham and Tooby, John and Tsutsui, Neil and Tsuji, Kazuki and Turillazzi, Stefano and Úbeda, Francisco and Vargo, Edward and Voelkl, Bernard and Wenseleers, Tom and West, Stuart and West Eberhard, Mary and Westneat, David and Wiernasz, Diane and Wild, Geoff and Wrangham, Richard and Young, Andrew and Zeh, David and Zeh, Jeanne and Zink, Andrew},
journal = {Nature},
number = {7339},
pages = {E1 -- E4},
publisher = {Nature Publishing Group},
title = {{Inclusive fitness theory and eusociality}},
doi = {10.1038/nature09831},
volume = {471},
year = {2011},
}
@article{3373,
abstract = {The use of optical traps to measure or apply forces on the molecular level requires a precise knowledge of the trapping force field. Close to the trap center, this field is typically approximated as linear in the displacement of the trapped microsphere. However, applications demanding high forces at low laser intensities can probe the light-microsphere interaction beyond the linear regime. Here, we measured the full nonlinear force and displacement response of an optical trap in two dimensions using a dual-beam optical trap setup with back-focal-plane photodetection. We observed a substantial stiffening of the trap beyond the linear regime that depends on microsphere size, in agreement with Mie theory calculations. Surprisingly, we found that the linear detection range for forces exceeds the one for displacement by far. Our approach allows for a complete calibration of an optical trap.},
author = {Jahnel, Marcus and Behrndt, Martin and Jannasch, Anita and Schaeffer, Erik and Grill, Stephan},
journal = {Optics Letters},
number = {7},
pages = {1260 -- 1262},
publisher = {OSA},
title = {{Measuring the complete force field of an optical trap}},
doi = {10.1364/OL.36.001260},
volume = {36},
year = {2011},
}
@article{3374,
abstract = {Genetic regulatory networks enable cells to respond to changes in internal and external conditions by dynamically coordinating their gene expression profiles. Our ability to make quantitative measurements in these biochemical circuits has deepened our understanding of what kinds of computations genetic regulatory networks can perform, and with what reliability. These advances have motivated researchers to look for connections between the architecture and function of genetic regulatory networks. Transmitting information between a network's inputs and outputs has been proposed as one such possible measure of function, relevant in certain biological contexts. Here we summarize recent developments in the application of information theory to gene regulatory networks. We first review basic concepts in information theory necessary for understanding recent work. We then discuss the functional complexity of gene regulation, which arises from the molecular nature of the regulatory interactions. We end by reviewing some experiments that support the view that genetic networks responsible for early development of multicellular organisms might be maximizing transmitted 'positional information'.},
author = {Tkacik, Gasper and Walczak, Aleksandra},
journal = {Journal of Physics: Condensed Matter},
number = {15},
publisher = {IOP Publishing Ltd.},
title = {{Information transmission in genetic regulatory networks a review}},
doi = {10.1088/0953-8984/23/15/153102},
volume = {23},
year = {2011},
}
@article{3375,
abstract = {By exploiting an analogy between population genetics and statistical mechanics, we study the evolution of a polygenic trait under stabilizing selection, mutation and genetic drift. This requires us to track only four macroscopic variables, instead of the distribution of all the allele frequencies that influence the trait. These macroscopic variables are the expectations of: the trait mean and its square, the genetic variance, and of a measure of heterozygosity, and are derived from a generating function that is in turn derived by maximizing an entropy measure. These four macroscopics are enough to accurately describe the dynamics of the trait mean and of its genetic variance (and in principle of any other quantity). Unlike previous approaches that were based on an infinite series of moments or cumulants, which had to be truncated arbitrarily, our calculations provide a well-defined approximation procedure. We apply the framework to abrupt and gradual changes in the optimum, as well as to changes in the strength of stabilizing selection. Our approximations are surprisingly accurate, even for systems with as few as five loci. We find that when the effects of drift are included, the expected genetic variance is hardly altered by directional selection, even though it fluctuates in any particular instance. We also find hysteresis, showing that even after averaging over the microscopic variables, the macroscopic trajectories retain a memory of the underlying genetic states.},
author = {de Vladar, Harold and Barton, Nicholas H},
journal = {Journal of the Royal Society Interface},
number = {58},
pages = {720 -- 739},
publisher = {Royal Society of London},
title = {{The statistical mechanics of a polygenic character under stabilizing selection mutation and drift}},
doi = {10.1098/rsif.2010.0438},
volume = {8},
year = {2011},
}
@article{3376,
abstract = {Regulatory conflicts occur when two signals that individually trigger opposite cellular responses are present simultaneously. Here, we investigate regulatory conflicts in the bacterial response to antibiotic combinations. We use an Escherichia coli promoter-GFP library to study the transcriptional response of many promoters to either additive or antagonistic drug pairs at fine two-dimensional (2D) resolution of drug concentration. Surprisingly, we find that this data set can be characterized as a linear sum of only two principal components. Component one, accounting for over 70% of the response, represents the response to growth inhibition by the drugs. Component two describes how regulatory conflicts are resolved. For the additive drug pair, conflicts are resolved by linearly interpolating the single drug responses, while for the antagonistic drug pair, the growth-limiting drug dominates the response. Importantly, for a given drug pair, the same conflict resolution strategy applies to almost all genes. These results provide a recipe for predicting gene expression responses to antibiotic combinations.},
author = {Bollenbach, Mark Tobias and Kishony, Roy},
journal = {Molecular Cell},
number = {4},
pages = {413 -- 425},
publisher = {Cell Press},
title = {{Resolution of gene regulatory conflicts caused by combinations of antibiotics}},
doi = {10.1016/j.molcel.2011.04.016},
volume = {42},
year = {2011},
}
@article{3377,
abstract = {By definition, transverse intersections are stable under in- finitesimal perturbations. Using persistent homology, we ex- tend this notion to sizeable perturbations. Specifically, we assign to each homology class of the intersection its robust- ness, the magnitude of a perturbation necessary to kill it, and prove that robustness is stable. Among the applications of this result is a stable notion of robustness for fixed points of continuous mappings and a statement of stability for con- tours of smooth mappings.},
author = {Edelsbrunner, Herbert and Morozov, Dmitriy and Patel, Amit},
journal = {Foundations of Computational Mathematics},
number = {3},
pages = {345 -- 361},
publisher = {Springer},
title = {{Quantifying transversality by measuring the robustness of intersections}},
doi = {10.1007/s10208-011-9090-8},
volume = {11},
year = {2011},
}
@article{3378,
abstract = {The theory of intersection homology was developed to study the singularities of a topologically stratified space. This paper in- corporates this theory into the already developed framework of persistent homology. We demonstrate that persistent intersec- tion homology gives useful information about the relationship between an embedded stratified space and its singularities. We give, and prove the correctness of, an algorithm for the computa- tion of the persistent intersection homology groups of a filtered simplicial complex equipped with a stratification by subcom- plexes. We also derive, from Poincare ́ Duality, some structural results about persistent intersection homology.},
author = {Bendich, Paul and Harer, John},
journal = {Foundations of Computational Mathematics},
number = {3},
pages = {305 -- 336},
publisher = {Springer},
title = {{Persistent intersection homology}},
doi = {10.1007/s10208-010-9081-1},
volume = {11},
year = {2011},
}
@article{3379,
abstract = {The process of gastrulation is highly conserved across vertebrates on both the genetic and morphological levels, despite great variety in embryonic shape and speed of development. This mechanism spatially separates the germ layers and establishes the organizational foundation for future development. Mesodermal identity is specified in a superficial layer of cells, the epiblast, where cells maintain an epithelioid morphology. These cells involute to join the deeper hypoblast layer where they adopt a migratory, mesenchymal morphology. Expression of a cascade of related transcription factors orchestrates the parallel genetic transition from primitive to mature mesoderm. Although the early and late stages of this process are increasingly well understood, the transition between them has remained largely mysterious. We present here the first high resolution in vivo observations of the blebby transitional morphology of involuting mesodermal cells in a vertebrate embryo. We further demonstrate that the zebrafish spadetail mutation creates a reversible block in the maturation program, stalling cells in the transition state. This mutation creates an ideal system for dissecting the specific properties of cells undergoing the morphological transition of maturing mesoderm, as we demonstrate with a direct measurement of cell–cell adhesion.},
author = {Row, Richard and Maître, Jean-Léon and Martin, Benjamin and Stockinger, Petra and Heisenberg, Carl-Philipp J and Kimelman, David},
journal = {Developmental Biology},
number = {1},
pages = {102 -- 110},
publisher = {Elsevier},
title = {{Completion of the epithelial to mesenchymal transition in zebrafish mesoderm requires Spadetail}},
doi = {10.1016/j.ydbio.2011.03.025},
volume = {354},
year = {2011},
}
@article{3380,
abstract = {Linkage between markers and genes that affect a phenotype of interest may be determined by examining differences in marker allele frequency in the extreme progeny of a cross between two inbred lines. This strategy is usually employed when pooling is used to reduce genotyping costs. When the cross progeny are asexual, the extreme progeny may be selected by multiple generations of asexual reproduction and selection. We analyse this method of measuring phenotype in asexual progeny and examine the changes in marker allele frequency due to selection over many generations. Stochasticity in marker frequency in the selected population arises due to the finite initial population size. We derive the distribution of marker frequency as a result of selection at a single major locus, and show that in order to avoid spurious changes in marker allele frequency in the selected population, the initial population size should be in the low to mid hundreds.},
author = {Logeswaran, Sayanthan and Barton, Nicholas H},
journal = {Genetical Research},
number = {3},
pages = {221 -- 232},
publisher = {Cambridge University Press},
title = {{Mapping Mendelian traits in asexual progeny using changes in marker allele frequency}},
doi = {10.1017/S0016672311000115},
volume = {93},
year = {2011},
}
@article{3771,
abstract = {The small-sized frugivorous bat Carollia perspicillata is an understory specialist and occurs in a wide range of lowland habitats, tending to be more common in tropical dry or moist forests of South and Central America. Its sister species, Carollia brevicauda, occurs almost exclusively in the Amazon rainforest. A recent phylogeographic study proposed a hypothesis of origin and subsequent diversification for C. perspicillata along the Atlantic coastal forest of Brazil. Additionally, it also found two allopatric clades for C. brevicauda separated by the Amazon Basin. We used cytochrome b gene sequences and a more extensive sampling to test hypotheses related to the origin and diversification of C. perspicillata plus C. brevicauda clade in South America. The results obtained indicate that there are two sympatric evolutionary lineages within each species. In C. perspicillata, one lineage is limited to the Southern Atlantic Forest, whereas the other is widely distributed. Coalescent analysis points to a simultaneous origin for C. perspicillata and C. brevicauda, although no place for the diversification of each species can be firmly suggested. The phylogeographic pattern shown by C. perspicillata is also congruent with the Pleistocene refugia hypothesis as a likely vicariant phenomenon shaping the present distribution of its intraspecific lineages.},
author = {Pavan, Ana and Martins, Felipe and Santos, Fabrício and Ditchfield, Albert and Fernandes Redondo, Rodrigo A},
journal = {Biological Journal of the Linnean Society},
number = {3},
pages = {527 -- 539},
publisher = {Wiley-Blackwell},
title = {{Patterns of diversification in two species of short-tailed bats (Carollia Gray, 1838): the effects of historical fragmentation of Brazilian rainforests.}},
doi = {10.1111/j.1095-8312.2010.01601.x},
volume = {102},
year = {2011},
}
@article{3778,
author = {Barton, Nicholas H},
journal = {Heredity},
number = {2},
pages = {205 -- 206},
publisher = {Nature Publishing Group},
title = {{Estimating linkage disequilibria}},
doi = {10.1038/hdy.2010.67},
volume = {106},
year = {2011},
}
@article{3781,
abstract = {We bound the difference in length of two curves in terms of their total curvatures and the Fréchet distance. The bound is independent of the dimension of the ambient Euclidean space, it improves upon a bound by Cohen-Steiner and Edelsbrunner, and it generalizes a result by Fáry and Chakerian.},
author = {Fasy, Brittany Terese},
journal = {Acta Sci. Math. (Szeged)},
number = {1-2},
pages = {359 -- 367},
publisher = {Szegedi Tudományegyetem},
title = {{The difference in length of curves in R^n}},
volume = {77},
year = {2011},
}
@article{3784,
abstract = {Advanced stages of Scyllarus phyllosoma larvae were collected by demersal trawling during fishery research surveys in the western Mediterranean Sea in 2003–2005. Nucleotide sequence analysis of the mitochondrial 16S rDNA gene allowed the final-stage phyllosoma of Scyllarus arctus to be identified among these larvae. Its morphology is described and illustrated. This constitutes the second complete description of a Scyllaridae phyllosoma with its specific identity being validated by molecular techniques (the first was S. pygmaeus). These results also solved a long lasting taxonomic anomaly of several species assigned to the ancient genus Phyllosoma Leach, 1814. Detailed examination indicated that the final-stage phyllosoma of S. arctus shows closer affinities with the American scyllarid Scyllarus depressus or with the Australian Scyllarus sp. b (sensu Phillips et al., 1981) than to its sympatric species S. pygmaeus.},
author = {Palero, Ferran and Guerao, Guillermo and Clark, Paul and Abello, Pere},
journal = {Journal of the Marine Biological Association of the United Kingdom},
number = {2},
pages = {485 -- 492},
publisher = {Cambridge University Press},
title = {{Scyllarus arctus (Crustacea: Decapoda: Scyllaridae) final stage phyllosoma identified by DNA analysis, with morphological description}},
doi = {10.1017/S0025315410000287},
volume = {91},
year = {2011},
}
@inbook{3791,
abstract = {During the development of multicellular organisms, cell fate specification is followed by the sorting of different cell types into distinct domains from where the different tissues and organs are formed. Cell sorting involves both the segregation of a mixed population of cells with different fates and properties into distinct domains, and the active maintenance of their segregated state. Because of its biological importance and apparent resemblance to fluid segregation in physics, cell sorting was extensively studied by both biologists and physicists over the last decades. Different theories were developed that try to explain cell sorting on the basis of the physical properties of the constituent cells. However, only recently the molecular and cellular mechanisms that control the physical properties driving cell sorting, have begun to be unraveled. In this review, we will provide an overview of different cell-sorting processes in development and discuss how these processes can be explained by the different sorting theories, and how these theories in turn can be connected to the molecular and cellular mechanisms driving these processes.},
author = {Krens, Gabriel and Heisenberg, Carl-Philipp J},
booktitle = {Forces and Tension in Development},
editor = {Labouesse, Michel},
pages = {189 -- 213},
publisher = {Elsevier},
title = {{Cell sorting in development}},
doi = {10.1016/B978-0-12-385065-2.00006-2},
volume = {95},
year = {2011},
}
@inbook{3796,
abstract = {We address the problem of covering ℝ n with congruent balls, while minimizing the number of balls that contain an average point. Considering the 1-parameter family of lattices defined by stretching or compressing the integer grid in diagonal direction, we give a closed formula for the covering density that depends on the distortion parameter. We observe that our family contains the thinnest lattice coverings in dimensions 2 to 5. We also consider the problem of packing congruent balls in ℝ n , for which we give a closed formula for the packing density as well. Again we observe that our family contains optimal configurations, this time densest packings in dimensions 2 and 3.},
author = {Edelsbrunner, Herbert and Kerber, Michael},
booktitle = {Rainbow of Computer Science},
editor = {Calude, Cristian and Rozenberg, Grzegorz and Salomaa, Arto},
pages = {20 -- 35},
publisher = {Springer},
title = {{Covering and packing with spheres by diagonal distortion in R^n}},
doi = {10.1007/978-3-642-19391-0_2},
volume = {6570},
year = {2011},
}
@article{3381,
abstract = {In this survey, we compare several languages for specifying Markovian population models such as queuing networks and chemical reaction networks. All these languages — matrix descriptions, stochastic Petri nets, stoichiometric equations, stochastic process algebras, and guarded command models — describe continuous-time Markov chains, but they differ according to important properties, such as compositionality, expressiveness and succinctness, executability, and ease of use. Moreover, they provide different support for checking the well-formedness of a model and for analyzing a model.},
author = {Henzinger, Thomas A and Jobstmann, Barbara and Wolf, Verena},
journal = {IJFCS: International Journal of Foundations of Computer Science},
number = {4},
pages = {823 -- 841},
publisher = {World Scientific Publishing},
title = {{Formalisms for specifying Markovian population models}},
doi = {10.1142/S0129054111008441},
volume = {22},
year = {2011},
}
@article{3315,
abstract = {We consider two-player games played in real time on game structures with clocks where the objectives of players are described using parity conditions. The games are concurrent in that at each turn, both players independently propose a time delay and an action, and the action with the shorter delay is chosen. To prevent a player from winning by blocking time, we restrict each player to play strategies that ensure that the player cannot be responsible for causing a zeno run. First, we present an efficient reduction of these games to turn-based (i.e., not concurrent) finite-state (i.e., untimed) parity games. Our reduction improves the best known complexity for solving timed parity games. Moreover, the rich class of algorithms for classical parity games can now be applied to timed parity games. The states of the resulting game are based on clock regions of the original game, and the state space of the finite game is linear in the size of the region graph. Second, we consider two restricted classes of strategies for the player that represents the controller in a real-time synthesis problem, namely, limit-robust and bounded-robust winning strategies. Using a limit-robust winning strategy, the controller cannot choose an exact real-valued time delay but must allow for some nonzero jitter in each of its actions. If there is a given lower bound on the jitter, then the strategy is bounded-robust winning. We show that exact strategies are more powerful than limit-robust strategies, which are more powerful than bounded-robust winning strategies for any bound. For both kinds of robust strategies, we present efficient reductions to standard timed automaton games. These reductions provide algorithms for the synthesis of robust real-time controllers.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Prabhu, Vinayak},
journal = {Logical Methods in Computer Science},
number = {4},
publisher = {International Federation of Computational Logic},
title = {{Timed parity games: Complexity and robustness}},
doi = {10.2168/LMCS-7(4:8)2011},
volume = {7},
year = {2011},
}
@article{3965,
abstract = {The elevation function on a smoothly embedded 2-manifold in R-3 reflects the multiscale topography of cavities and protrusions as local maxima. The function has been useful in identifying coarse docking configurations for protein pairs. Transporting the concept from the smooth to the piecewise linear category, this paper describes an algorithm for finding all local maxima. While its worst-case running time is the same as of the algorithm used in prior work, its performance in practice is orders of magnitudes superior. We cast light on this improvement by relating the running time to the total absolute Gaussian curvature of the 2-manifold.},
author = {Wang, Bei and Edelsbrunner, Herbert and Morozov, Dmitriy},
journal = {Journal of Experimental Algorithmics},
number = {2.2},
pages = {1 -- 13},
publisher = {ACM},
title = {{Computing elevation maxima by searching the Gauss sphere}},
doi = {10.1145/1963190.1970375},
volume = {16},
year = {2011},
}
@article{3364,
abstract = {Molecular noise, which arises from the randomness of the discrete events in the cell, significantly influences fundamental biological processes. Discrete-state continuous-time stochastic models (CTMC) can be used to describe such effects, but the calculation of the probabilities of certain events is computationally expensive. We present a comparison of two analysis approaches for CTMC. On one hand, we estimate the probabilities of interest using repeated Gillespie simulation and determine the statistical accuracy that we obtain. On the other hand, we apply a numerical reachability analysis that approximates the probability distributions of the system at several time instances. We use examples of cellular processes to demonstrate the superiority of the reachability analysis if accurate results are required.},
author = {Didier, Frédéric and Henzinger, Thomas A and Mateescu, Maria and Wolf, Verena},
journal = {Theoretical Computer Science},
number = {21},
pages = {2128 -- 2141},
publisher = {Elsevier},
title = {{Approximation of event probabilities in noisy cellular processes}},
doi = {10.1016/j.tcs.2010.10.022},
volume = {412},
year = {2011},
}
@article{490,
abstract = {BioSig is an open source software library for biomedical signal processing. The aim of the BioSig project is to foster research in biomedical signal processing by providing free and open source software tools for many different application areas. Some of the areas where BioSig can be employed are neuroinformatics, brain-computer interfaces, neurophysiology, psychology, cardiovascular systems, and sleep research. Moreover, the analysis of biosignals such as the electroencephalogram (EEG), electrocorticogram (ECoG), electrocardiogram (ECG), electrooculogram (EOG), electromyogram (EMG), or respiration signals is a very relevant element of the BioSig project. Specifically, BioSig provides solutions for data acquisition, artifact processing, quality control, feature extraction, classification, modeling, and data visualization, to name a few. In this paper, we highlight several methods to help students and researchers to work more efficiently with biomedical signals. },
author = {Schlögl, Alois and Vidaurre, Carmen and Sander, Tilmann},
journal = {Computational Intelligence and Neuroscience},
publisher = {Hindawi Publishing Corporation},
title = {{BioSig: The free and open source software library for biomedical signal processing}},
doi = {10.1155/2011/935364},
volume = {2011},
year = {2011},
}
@article{491,
abstract = {In their search for antigens, lymphocytes continuously shuttle among blood vessels, lymph vessels, and lymphatic tissues. Chemokines mediate entry of lymphocytes into lymphatic tissues, and sphingosine 1-phosphate (S1P) promotes localization of lymphocytes to the vasculature. Both signals are sensed through G protein-coupled receptors (GPCRs). Most GPCRs undergo ligand-dependent homologous receptor desensitization, a process that decreases their signaling output after previous exposure to high ligand concentration. Such desensitization can explain why lymphocytes do not take an intermediate position between two signals but rather oscillate between them. The desensitization of S1P receptor 1 (S1PR1) is mediated by GPCR kinase 2 (GRK2). Deletion of GRK2 in lymphocytes compromises desensitization by high vascular S1P concentrations, thereby reducing responsiveness to the chemokine signal and trapping the cells in the vascular compartment. The desensitization kinetics of S1PR1 allows lymphocytes to dynamically shuttle between vasculature and lymphatic tissue, although the positional information in both compartments is static.},
author = {Eichner, Alexander and Sixt, Michael K},
journal = {Science Signaling},
number = {198},
publisher = {American Association for the Advancement of Science},
title = {{Setting the clock for recirculating lymphocytes}},
doi = {10.1126/scisignal.2002617},
volume = {4},
year = {2011},
}
@article{469,
abstract = {Spontaneous release of glutamate is important for maintaining synaptic strength and controlling spike timing in the brain. Mechanisms regulating spontaneous exocytosis remain poorly understood. Extracellular calcium concentration ([Ca2+]o) regulates Ca2+ entry through voltage-activated calcium channels (VACCs) and consequently is a pivotal determinant of action potential-evoked vesicle fusion. Extracellular Ca 2+ also enhances spontaneous release, but via unknown mechanisms. Here we report that external Ca2+ triggers spontaneous glutamate release more weakly than evoked release in mouse neocortical neurons. Blockade of VACCs has no effect on the spontaneous release rate or its dependence on [Ca2+]o. Intracellular [Ca2+] slowly increases in a minority of neurons following increases in [Ca2+]o. Furthermore, the enhancement of spontaneous release by extracellular calcium is insensitive to chelation of intracellular calcium by BAPTA. Activation of the calcium-sensing receptor (CaSR), a G-protein-coupled receptor present in nerve terminals, by several specific agonists increased spontaneous glutamate release. The frequency of spontaneous synaptic transmission was decreased in CaSR mutant neurons. The concentration-effect relationship for extracellular calcium regulation of spontaneous release was well described by a combination of CaSR-dependent and CaSR-independent mechanisms. Overall these results indicate that extracellular Ca2+ does not trigger spontaneous glutamate release by simply increasing calcium influx but stimulates CaSR and thereby promotes resting spontaneous glutamate release. },
author = {Vyleta, Nicholas and Smith, Stephen},
journal = {European Journal of Neuroscience},
number = {12},
pages = {4593 -- 4606},
publisher = {Wiley-Blackwell},
title = {{Spontaneous glutamate release is independent of calcium influx and tonically activated by the calcium-sensing receptor}},
doi = {10.1523/JNEUROSCI.6398-10.2011},
volume = {31},
year = {2011},
}
@article{518,
abstract = {Cancer stem cells or cancer initiating cells are believed to contribute to cancer recurrence after therapy. MicroRNAs (miRNAs) are short RNA molecules with fundamental roles in gene regulation. The role of miRNAs in cancer stem cells is only poorly understood. Here, we report miRNA expression profiles of glioblastoma stem cell-containing CD133 + cell populations. We find that miR-9, miR-9 * (referred to as miR-9/9 *), miR-17 and miR-106b are highly abundant in CD133 + cells. Furthermore, inhibition of miR-9/9 * or miR-17 leads to reduced neurosphere formation and stimulates cell differentiation. Calmodulin-binding transcription activator 1 (CAMTA1) is a putative transcription factor, which induces the expression of the anti-proliferative cardiac hormone natriuretic peptide A (NPPA). We identify CAMTA1 as an miR-9/9 * and miR-17 target. CAMTA1 expression leads to reduced neurosphere formation and tumour growth in nude mice, suggesting that CAMTA1 can function as tumour suppressor. Consistently, CAMTA1 and NPPA expression correlate with patient survival. Our findings could provide a basis for novel strategies of glioblastoma therapy.},
author = {Schraivogel, Daniel and Weinmann, Lasse and Beier, Dagmar and Tabatabai, Ghazaleh and Eichner, Alexander and Zhu, Jia and Anton, Martina and Sixt, Michael K and Weller, Michael and Beier, Christoph and Meister, Gunter},
journal = {EMBO Journal},
number = {20},
pages = {4309 -- 4322},
publisher = {Wiley-Blackwell},
title = {{CAMTA1 is a novel tumour suppressor regulated by miR-9/9 * in glioblastoma stem cells}},
doi = {10.1038/emboj.2011.301},
volume = {30},
year = {2011},
}
@article{531,
abstract = {Software transactional memories (STM) are described in the literature with assumptions of sequentially consistent program execution and atomicity of high level operations like read, write, and abort. However, in a realistic setting, processors use relaxed memory models to optimize hardware performance. Moreover, the atomicity of operations depends on the underlying hardware. This paper presents the first approach to verify STMs under relaxed memory models with atomicity of 32 bit loads and stores, and read-modify-write operations. We describe RML, a simple language for expressing concurrent programs. We develop a semantics of RML parametrized by a relaxed memory model. We then present our tool, FOIL, which takes as input the RML description of an STM algorithm restricted to two threads and two variables, and the description of a memory model, and automatically determines the locations of fences, which if inserted, ensure the correctness of the restricted STM algorithm under the given memory model. We use FOIL to verify DSTM, TL2, and McRT STM under the memory models of sequential consistency, total store order, partial store order, and relaxed memory order for two threads and two variables. Finally, we extend the verification results for DSTM and TL2 to an arbitrary number of threads and variables by manually proving that the structural properties of STMs are satisfied at the hardware level of atomicity under the considered relaxed memory models.},
author = {Guerraoui, Rachid and Henzinger, Thomas A and Singh, Vasu},
journal = {Formal Methods in System Design},
number = {3},
pages = {297 -- 331},
publisher = {Springer},
title = {{Verification of STM on relaxed memory models}},
doi = {10.1007/s10703-011-0131-3},
volume = {39},
year = {2011},
}
@misc{5379,
abstract = {Computing the winning set for Büchi objectives in alternating games on graphs is a central problem in computer aided verification with a large number of applications. The long standing best known upper bound for solving the problem is ̃O(n·m), where n is the number of vertices and m is the number of edges in the graph. We are the first to break the ̃O(n·m) boundary by presenting a new technique that reduces the running time to O(n2). This bound also leads to O(n2) time algorithms for computing the set of almost-sure winning vertices for Büchi objectives (1) in alternating games with probabilistic transitions (improving an earlier bound of O(n·m)), (2) in concurrent graph games with constant actions (improving an earlier bound of O(n3)), and (3) in Markov decision processes (improving for m > n4/3 an earlier bound of O(min(m1.5, m·n2/3)). We also show that the same technique can be used to compute the maximal end-component decomposition of a graph in time O(n2), which is an improvement over earlier bounds for m > n4/3. Finally, we show how to maintain the winning set for Büchi objectives in alternating games under a sequence of edge insertions or a sequence of edge deletions in O(n) amortized time per operation. This is the first dynamic algorithm for this problem.},
author = {Chatterjee, Krishnendu and Henzinger, Monika},
issn = {2664-1690},
pages = {20},
publisher = {IST Austria},
title = {{An O(n2) time algorithm for alternating Büchi games}},
doi = {10.15479/AT:IST-2011-0009},
year = {2011},
}
@unpublished{3338,
abstract = {We consider 2-player games played on a finite state space for an infinite number of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves inde- pendently and simultaneously; the current state and the two moves determine the successor state. We study concurrent games with ω-regular winning conditions specified as parity objectives. We consider the qualitative analysis problems: the computation of the almost-sure and limit-sure winning set of states, where player 1 can ensure to win with probability 1 and with probability arbitrarily close to 1, respec- tively. In general the almost-sure and limit-sure winning strategies require both infinite-memory as well as infinite-precision (to describe probabilities). We study the bounded-rationality problem for qualitative analysis of concurrent parity games, where the strategy set for player 1 is restricted to bounded-resource strategies. In terms of precision, strategies can be deterministic, uniform, finite-precision or infinite- precision; and in terms of memory, strategies can be memoryless, finite-memory or infinite-memory. We present a precise and complete characterization of the qualitative winning sets for all combinations of classes of strategies. In particular, we show that uniform memoryless strategies are as powerful as finite-precision infinite-memory strategies, and infinite-precision memoryless strategies are as power- ful as infinite-precision finite-memory strategies. We show that the winning sets can be computed in O(n2d+3) time, where n is the size of the game structure and 2d is the number of priorities (or colors), and our algorithms are symbolic. The membership problem of whether a state belongs to a winning set can be decided in NP ∩ coNP. While this complexity is the same as for the simpler class of turn-based parity games, where in each state only one of the two players has a choice of moves, our algorithms, that are obtained by characterization of the winning sets as μ-calculus formulas, are considerably more involved than those for turn-based games.},
author = {Chatterjee, Krishnendu},
booktitle = {arXiv},
pages = {1 -- 51},
publisher = {ArXiv},
title = {{Bounded rationality in concurrent parity games}},
year = {2011},
}
@misc{5383,
abstract = {We present a new decidable logic called TREX for expressing constraints about imperative tree data structures. In particular, TREX supports a transitive closure operator that can express reachability constraints, which often appear in data structure invariants. We show that our logic is closed under weakest precondition computation, which enables its use for automated software verification. We further show that satisfiability of formulas in TREX is decidable in NP. The low complexity makes it an attractive alternative to more expensive logics such as monadic second-order logic (MSOL) over trees, which have been traditionally used for reasoning about tree data structures.},
author = {Wies, Thomas and Muñiz, Marco and Kuncak, Viktor},
issn = {2664-1690},
pages = {25},
publisher = {IST Austria},
title = {{On an efficient decision procedure for imperative tree data structures}},
doi = {10.15479/AT:IST-2011-0005},
year = {2011},
}
@inproceedings{3323,
abstract = {We present a new decidable logic called TREX for expressing constraints about imperative tree data structures. In particular, TREX supports a transitive closure operator that can express reachability constraints, which often appear in data structure invariants. We show that our logic is closed under weakest precondition computation, which enables its use for automated software verification. We further show that satisfiability of formulas in TREX is decidable in NP. The low complexity makes it an attractive alternative to more expensive logics such as monadic second-order logic (MSOL) over trees, which have been traditionally used for reasoning about tree data structures.},
author = {Wies, Thomas and Muñiz, Marco and Kuncak, Viktor},
location = {Wrocław, Poland},
pages = {476 -- 491},
publisher = {Springer},
title = {{An efficient decision procedure for imperative tree data structures}},
doi = {10.1007/978-3-642-22438-6_36},
volume = {6803},
year = {2011},
}
@misc{5381,
abstract = {In two-player finite-state stochastic games of partial obser- vation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distri- bution over the successor states. The game is played for infinitely many rounds and thus the players construct an infinite path in the graph. We consider reachability objectives where the first player tries to ensure a target state to be visited almost-surely (i.e., with probability 1) or pos- itively (i.e., with positive probability), no matter the strategy of the second player.
We classify such games according to the information and to the power of randomization available to the players. On the basis of information, the game can be one-sided with either (a) player 1, or (b) player 2 having partial observation (and the other player has perfect observation), or two- sided with (c) both players having partial observation. On the basis of randomization, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization.
Our main results for pure strategies are as follows: (1) For one-sided games with player 2 perfect observation we show that (in contrast to full randomized strategies) belief-based (subset-construction based) strate- gies are not sufficient, and present an exponential upper bound on mem- ory both for almost-sure and positive winning strategies; we show that the problem of deciding the existence of almost-sure and positive winning strategies for player 1 is EXPTIME-complete and present symbolic algo- rithms that avoid the explicit exponential construction. (2) For one-sided games with player 1 perfect observation we show that non-elementary memory is both necessary and sufficient for both almost-sure and posi- tive winning strategies. (3) We show that for the general (two-sided) case finite-memory strategies are sufficient for both positive and almost-sure winning, and at least non-elementary memory is required. We establish the equivalence of the almost-sure winning problems for pure strategies and for randomized strategies with actions invisible. Our equivalence re- sult exhibit serious flaws in previous results in the literature: we show a non-elementary memory lower bound for almost-sure winning whereas an exponential upper bound was previously claimed.},
author = {Chatterjee, Krishnendu and Doyen, Laurent},
issn = {2664-1690},
pages = {43},
publisher = {IST Austria},
title = {{Partial-observation stochastic games: How to win when belief fails}},
doi = {10.15479/AT:IST-2011-0007},
year = {2011},
}
@misc{5380,
abstract = {We consider 2-player games played on a finite state space for an infinite number of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine the successor state. We study concurrent games with ω-regular winning conditions specified as parity objectives. We consider the qualitative analysis problems: the computation of the almost-sure and limit-sure winning set of states, where player 1 can ensure to win with probability 1 and with probability arbitrarily close to 1, respectively. In general the almost-sure and limit-sure winning strategies require both infinite-memory as well as infinite-precision (to describe probabilities). We study the bounded-rationality problem for qualitative analysis of concurrent parity games, where the strategy set for player 1 is restricted to bounded-resource strategies. In terms of precision, strategies can be deterministic, uniform, finite-precision or infinite-precision; and in terms of memory, strategies can be memoryless, finite-memory or infinite-memory. We present a precise and complete characterization of the qualitative winning sets for all combinations of classes of strategies. In particular, we show that uniform memoryless strategies are as powerful as finite-precision infinite-memory strategies, and infinite-precision memoryless strategies are as powerful as infinite-precision finite-memory strategies. We show that the winning sets can be computed in O(n2d+3) time, where n is the size of the game structure and 2d is the number of priorities (or colors), and our algorithms are symbolic. The membership problem of whether a state belongs to a winning set can be decided in NP ∩ coNP. While this complexity is the same as for the simpler class of turn-based parity games, where in each state only one of the two players has a choice of moves, our algorithms,that are obtained by characterization of the winning sets as μ-calculus formulas, are considerably more involved than those for turn-based games.},
author = {Chatterjee, Krishnendu},
issn = {2664-1690},
pages = {53},
publisher = {IST Austria},
title = {{Bounded rationality in concurrent parity games}},
doi = {10.15479/AT:IST-2011-0008},
year = {2011},
}
@misc{5382,
abstract = {We consider two-player stochastic games played on a finite state space for an infinite num- ber of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine a probability distribution over the successor states. We also consider the important special case of turn-based stochastic games where players make moves in turns, rather than concurrently. We study concurrent games with ω-regular winning conditions specified as parity objectives. The value for player 1 for a parity objective is the maximal probability with which the player can guarantee the satisfaction of the objective against all strategies of the opponent. We study the problem of continuity and robustness of the value function in concurrent and turn-based stochastic parity games with respect to imprecision in the transition probabilities. We present quantitative bounds on the difference of the value function (in terms of the imprecision of the transition probabilities) and show the value continuity for structurally equivalent concurrent games (two games are structurally equivalent if the support of the transition func- tion is same and the probabilities differ). We also show robustness of optimal strategies for structurally equivalent turn-based stochastic parity games. Finally we show that the value continuity property breaks without the structurally equivalent assumption (even for Markov chains) and show that our quantitative bound is asymptotically optimal. Hence our results are tight (the assumption is both necessary and sufficient) and optimal (our quantitative bound is asymptotically optimal).},
author = {Chatterjee, Krishnendu},
issn = {2664-1690},
pages = {18},
publisher = {IST Austria},
title = {{Robustness of structurally equivalent concurrent parity games}},
doi = {10.15479/AT:IST-2011-0006},
year = {2011},
}
@misc{5387,
abstract = {We consider Markov Decision Processes (MDPs) with mean-payoff parity and energy parity objectives. In system design, the parity objective is used to encode ω-regular specifications, and the mean-payoff and energy objectives can be used to model quantitative resource constraints. The energy condition re- quires that the resource level never drops below 0, and the mean-payoff condi- tion requires that the limit-average value of the resource consumption is within a threshold. While these two (energy and mean-payoff) classical conditions are equivalent for two-player games, we show that they differ for MDPs. We show that the problem of deciding whether a state is almost-sure winning (i.e., winning with probability 1) in energy parity MDPs is in NP ∩ coNP, while for mean- payoff parity MDPs, the problem is solvable in polynomial time, improving a recent PSPACE bound.},
author = {Chatterjee, Krishnendu and Doyen, Laurent},
issn = {2664-1690},
pages = {20},
publisher = {IST Austria},
title = {{Energy and mean-payoff parity Markov decision processes}},
doi = {10.15479/AT:IST-2011-0001},
year = {2011},
}
@inproceedings{3356,
abstract = {There is recently a significant effort to add quantitative objectives to formal verification and synthesis. We introduce and investigate the extension of temporal logics with quantitative atomic assertions, aiming for a general and flexible framework for quantitative-oriented specifications. In the heart of quantitative objectives lies the accumulation of values along a computation. It is either the accumulated summation, as with the energy objectives, or the accumulated average, as with the mean-payoff objectives. We investigate the extension of temporal logics with the prefix-accumulation assertions Sum(v) ≥ c and Avg(v) ≥ c, where v is a numeric variable of the system, c is a constant rational number, and Sum(v) and Avg(v) denote the accumulated sum and average of the values of v from the beginning of the computation up to the current point of time. We also allow the path-accumulation assertions LimInfAvg(v) ≥ c and LimSupAvg(v) ≥ c, referring to the average value along an entire computation. We study the border of decidability for extensions of various temporal logics. In particular, we show that extending the fragment of CTL that has only the EX, EF, AX, and AG temporal modalities by prefix-accumulation assertions and extending LTL with path-accumulation assertions, result in temporal logics whose model-checking problem is decidable. The extended logics allow to significantly extend the currently known energy and mean-payoff objectives. Moreover, the prefix-accumulation assertions may be refined with "controlled-accumulation", allowing, for example, to specify constraints on the average waiting time between a request and a grant. On the negative side, we show that the fragment we point to is, in a sense, the maximal logic whose extension with prefix-accumulation assertions permits a decidable model-checking procedure. Extending a temporal logic that has the EG or EU modalities, and in particular CTL and LTL, makes the problem undecidable.},
author = {Boker, Udi and Chatterjee, Krishnendu and Henzinger, Thomas A and Kupferman, Orna},
location = {Toronto, Canada},
publisher = {IEEE},
title = {{Temporal specifications with accumulative values}},
doi = {10.1109/LICS.2011.33},
year = {2011},
}
@inproceedings{3345,
abstract = {We consider Markov Decision Processes (MDPs) with mean-payoff parity and energy parity objectives. In system design, the parity objective is used to encode ω-regular specifications, and the mean-payoff and energy objectives can be used to model quantitative resource constraints. The energy condition re- quires that the resource level never drops below 0, and the mean-payoff condi- tion requires that the limit-average value of the resource consumption is within a threshold. While these two (energy and mean-payoff) classical conditions are equivalent for two-player games, we show that they differ for MDPs. We show that the problem of deciding whether a state is almost-sure winning (i.e., winning with probability 1) in energy parity MDPs is in NP ∩ coNP, while for mean- payoff parity MDPs, the problem is solvable in polynomial time, improving a recent PSPACE bound.},
author = {Chatterjee, Krishnendu and Doyen, Laurent},
location = {Warsaw, Poland},
pages = {206 -- 218},
publisher = {Springer},
title = {{Energy and mean-payoff parity Markov Decision Processes}},
doi = {10.1007/978-3-642-22993-0_21},
volume = {6907},
year = {2011},
}
@inproceedings{3336,
abstract = {We introduce TopoCut: a new way to integrate knowledge about topological properties (TPs) into random field image segmentation model. Instead of including TPs as additional constraints during minimization of the energy function, we devise an efficient algorithm for modifying the unary potentials such that the resulting segmentation is guaranteed with the desired properties. Our method is more flexible in the sense that it handles more topology constraints than previous methods, which were only able to enforce pairwise or global connectivity. In particular, our method is very fast, making it for the first time possible to enforce global topological properties in practical image segmentation tasks.},
author = {Chen, Chao and Freedman, Daniel and Lampert, Christoph},
booktitle = {CVPR: Computer Vision and Pattern Recognition},
location = {Colorado Springs, CO, USA},
pages = {2089 -- 2096},
publisher = {IEEE},
title = {{Enforcing topological constraints in random field image segmentation}},
doi = {10.1109/CVPR.2011.5995503},
year = {2011},
}
@misc{5385,
abstract = {There is recently a significant effort to add quantitative objectives to formal verification and synthesis. We introduce and investigate the extension of temporal logics with quantitative atomic assertions, aiming for a general and flexible framework for quantitative-oriented specifications. In the heart of quantitative objectives lies the accumulation of values along a computation. It is either the accumulated summation, as with the energy objectives, or the accumulated average, as with the mean-payoff objectives. We investigate the extension of temporal logics with the prefix-accumulation assertions Sum(v) ≥ c and Avg(v) ≥ c, where v is a numeric variable of the system, c is a constant rational number, and Sum(v) and Avg(v) denote the accumulated sum and average of the values of v from the beginning of the computation up to the current point of time. We also allow the path-accumulation assertions LimInfAvg(v) ≥ c and LimSupAvg(v) ≥ c, referring to the average value along an entire computation. We study the border of decidability for extensions of various temporal logics. In particular, we show that extending the fragment of CTL that has only the EX, EF, AX, and AG temporal modalities by prefix-accumulation assertions and extending LTL with path-accumulation assertions, result in temporal logics whose model-checking problem is decidable. The extended logics allow to significantly extend the currently known energy and mean-payoff objectives. Moreover, the prefix-accumulation assertions may be refined with “controlled-accumulation”, allowing, for example, to specify constraints on the average waiting time between a request and a grant. On the negative side, we show that the fragment we point to is, in a sense, the maximal logic whose extension with prefix-accumulation assertions permits a decidable model-checking procedure. Extending a temporal logic that has the EG or EU modalities, and in particular CTL and LTL, makes the problem undecidable.},
author = {Boker, Udi and Chatterjee, Krishnendu and Henzinger, Thomas A and Kupferman, Orna},
issn = {2664-1690},
pages = {14},
publisher = {IST Austria},
title = {{Temporal specifications with accumulative values}},
doi = {10.15479/AT:IST-2011-0003},
year = {2011},
}
@misc{5384,
abstract = {We consider probabilistic automata on infinite words with acceptance defined by parity conditions. We consider three qualitative decision problems: (i) the positive decision problem asks whether there is a word that is accepted with positive probability; (ii) the almost decision problem asks whether there is a word that is accepted with probability 1; and (iii) the limit decision problem asks whether for every ε > 0 there is a word that is accepted with probability at least 1 − ε. We unify and generalize several decidability results for probabilistic automata over infinite words, and identify a robust (closed under union and intersection) subclass of probabilistic automata for which all the qualitative decision problems are decidable for parity conditions. We also show that if the input words are restricted to lasso shape words, then the positive and almost problems are decidable for all probabilistic automata with parity conditions.},
author = {Chatterjee, Krishnendu and Tracol, Mathieu},
issn = {2664-1690},
pages = {30},
publisher = {IST Austria},
title = {{Decidable problems for probabilistic automata on infinite words}},
doi = {10.15479/AT:IST-2011-0004},
year = {2011},
}
@misc{5386,
abstract = {We introduce TopoCut: a new way to integrate knowledge about topological properties (TPs) into random field image segmentation model. Instead of including TPs as additional constraints during minimization of the energy function, we devise an efficient algorithm for modifying the unary potentials such that the resulting segmentation is guaranteed with the desired properties. Our method is more flexible in the sense that it handles more topology constraints than previous methods, which were only able to enforce pairwise or global connectivity. In particular, our method is very fast, making it for the first time possible to enforce global topological properties in practical image segmentation tasks.},
author = {Chen, Chao and Freedman, Daniel and Lampert, Christoph},
issn = {2664-1690},
pages = {69},
publisher = {IST Austria},
title = {{Enforcing topological constraints in random field image segmentation}},
doi = {10.15479/AT:IST-2011-0002},
year = {2011},
}
@inproceedings{3366,
abstract = {We present an algorithmic method for the quantitative, performance-aware synthesis of concurrent programs. The input consists of a nondeterministic partial program and of a parametric performance model. The nondeterminism allows the programmer to omit which (if any) synchronization construct is used at a particular program location. The performance model, specified as a weighted automaton, can capture system architectures by assigning different costs to actions such as locking, context switching, and memory and cache accesses. The quantitative synthesis problem is to automatically resolve the nondeterminism of the partial program so that both correctness is guaranteed and performance is optimal. As is standard for shared memory concurrency, correctness is formalized "specification free", in particular as race freedom or deadlock freedom. For worst-case (average-case) performance, we show that the problem can be reduced to 2-player graph games (with probabilistic transitions) with quantitative objectives. While we show, using game-theoretic methods, that the synthesis problem is Nexp-complete, we present an algorithmic method and an implementation that works efficiently for concurrent programs and performance models of practical interest. We have implemented a prototype tool and used it to synthesize finite-state concurrent programs that exhibit different programming patterns, for several performance models representing different architectures. },
author = {Cerny, Pavol and Chatterjee, Krishnendu and Henzinger, Thomas A and Radhakrishna, Arjun and Singh, Rohit},
editor = {Gopalakrishnan, Ganesh and Qadeer, Shaz},
location = {Snowbird, USA},
pages = {243 -- 259},
publisher = {Springer},
title = {{Quantitative synthesis for concurrent programs}},
doi = {10.1007/978-3-642-22110-1_20},
volume = {6806},
year = {2011},
}
@article{6496,
abstract = {We report the switching behavior of the full bacterial flagellum system that includes the filament and the motor in wild-type Escherichia coli cells. In sorting the motor behavior by the clockwise bias, we find that the distributions of the clockwise (CW) and counterclockwise (CCW) intervals are either exponential or nonexponential with long tails. At low bias, CW intervals are exponentially distributed and CCW intervals exhibit long tails. At intermediate CW bias (0.5) both CW and CCW intervals are mainly exponentially distributed. A simple model suggests that these two distinct switching behaviors are governed by the presence of signaling noise within the chemotaxis network. Low noise yields exponentially distributed intervals, whereas large noise yields nonexponential behavior with long tails. These drastically different motor statistics may play a role in optimizing bacterial behavior for a wide range of environmental conditions.},
author = {Park, Heungwon and Oikonomou, Panos and Guet, Calin C and Cluzel, Philippe},
issn = {0006-3495},
journal = {Biophysical Journal},
number = {10},
pages = {2336--2340},
publisher = {Elsevier BV},
title = {{Noise underlies switching behavior of the bacterial flagellum}},
doi = {10.1016/j.bpj.2011.09.040},
volume = {101},
year = {2011},
}
@article{2409,
abstract = {Background: The availability of many gene alignments with overlapping taxon sets raises the question of which strategy is the best to infer species phylogenies from multiple gene information. Methods and programs abound that use the gene alignment in different ways to reconstruct the species tree. In particular, different methods combine the original data at different points along the way from the underlying sequences to the final tree. Accordingly, they are classified into superalignment, supertree and medium-level approaches. Here, we present a simulation study to compare different methods from each of these three approaches.
Results: We observe that superalignment methods usually outperform the other approaches over a wide range of parameters including sparse data and gene-specific evolutionary parameters. In the presence of high incongruency among gene trees, however, other combination methods show better performance than the superalignment approach. Surprisingly, some supertree and medium-level methods exhibit, on average, worse results than a single gene phylogeny with complete taxon information.
Conclusions: For some methods, using the reconstructed gene tree as an estimation of the species tree is superior to the combination of incomplete information. Superalignment usually performs best since it is less susceptible to stochastic error. Supertree methods can outperform superalignment in the presence of gene-tree conflict.},
author = {Kupczok, Anne and Schmidt, Heiko and Von Haeseler, Arndt},
journal = {Algorithms for Molecular Biology},
number = {1},
publisher = {BioMed Central},
title = {{Accuracy of phylogeny reconstruction methods combining overlapping gene data sets }},
doi = {10.1186/1748-7188-5-37},
volume = {5},
year = {2010},
}
@article{3303,
abstract = {Biological traits result in part from interactions between different genetic loci. This can lead to sign epistasis, in which a beneficial adaptation involves a combination of individually deleterious or neutral mutations; in this case, a population must cross a “fitness valley” to adapt. Recombination can assist this process by combining mutations from different individuals or retard it by breaking up the adaptive combination. Here, we analyze the simplest fitness valley, in which an adaptation requires one mutation at each of two loci to provide a fitness benefit. We present a theoretical analysis of the effect of recombination on the valley-crossing process across the full spectrum of possible parameter regimes. We find that low recombination rates can speed up valley crossing relative to the asexual case, while higher recombination rates slow down valley crossing, with the transition between the two regimes occurring when the recombination rate between the loci is approximately equal to the selective advantage provided by the adaptation. In large populations, if the recombination rate is high and selection against single mutants is substantial, the time to cross the valley grows exponentially with population size, effectively meaning that the population cannot acquire the adaptation. Recombination at the optimal (low) rate can reduce the valley-crossing time by up to several orders of magnitude relative to that in an asexual population. },
author = {Weissman, Daniel and Feldman, Marcus and Fisher, Daniel},
journal = {Genetics},
number = {4},
pages = {1389 -- 1410},
publisher = {Genetics Society of America},
title = {{The rate of fitness-valley crossing in sexual populations}},
doi = {10.1534/genetics.110.123240},
volume = {186},
year = {2010},
}
@article{3867,
abstract = {Weighted automata are nondeterministic automata with numerical weights on transitions. They can define quantitative languages L that assign to each word w a real number L(w). In the case of infinite words, the value of a run is naturally computed as the maximum, limsup, liminf, limit-average, or discounted-sum of the transition weights. The value of a word w is the supremum of the values of the runs over w. We study expressiveness and closure questions about these quantitative languages. We first show that the set of words with value greater than a threshold can be omega-regular for deterministic limit-average and discounted-sum automata, while this set is always omega-regular when the threshold is isolated (i.e., some neighborhood around the threshold contains no word). In the latter case, we prove that the omega-regular language is robust against small perturbations of the transition weights. We next consider automata with transition weights 0 or 1 and show that they are as expressive as general weighted automata in the limit-average case, but not in the discounted-sum case. Third, for quantitative languages L-1 and L-2, we consider the operations max(L-1, L-2), min(L-1, L-2), and 1 - L-1, which generalize the boolean operations on languages, as well as the sum L-1 + L-2. We establish the closure properties of all classes of quantitative languages with respect to these four operations.},
author = {Chatterjee, Krishnendu and Doyen, Laurent and Henzinger, Thomas A},
journal = {Logical Methods in Computer Science},
number = {3},
pages = {1 -- 23},
publisher = {International Federation of Computational Logic},
title = {{Expressiveness and closure properties for quantitative languages}},
doi = {10.2168/LMCS-6(3:10)2010},
volume = {6},
year = {2010},
}
@inproceedings{3719,
abstract = {The induction of a signaling pathway is characterized by transient complex formation and mutual posttranslational modification of proteins. To faithfully capture this combinatorial process in a math- ematical model is an important challenge in systems biology. Exploiting the limited context on which most binding and modification events are conditioned, attempts have been made to reduce the com- binatorial complexity by quotienting the reachable set of molecular species, into species aggregates while preserving the deterministic semantics of the thermodynamic limit. Recently we proposed a quotienting that also preserves the stochastic semantics and that is complete in the sense that the semantics of individual species can be recovered from the aggregate semantics. In this paper we prove that this quotienting yields a sufficient condition for weak lumpability and that it gives rise to a backward Markov bisimulation between the original and aggregated transition system. We illustrate the framework on a case study of the EGF/insulin receptor crosstalk.},
author = {Feret, Jérôme and Henzinger, Thomas A and Koeppl, Heinz and Petrov, Tatjana},
location = {Jena, Germany},
pages = {142--161},
publisher = {Open Publishing Association},
title = {{Lumpability abstractions of rule-based systems}},
volume = {40},
year = {2010},
}
@article{3772,
author = {Barton, Nicholas H},
journal = {PLoS Genetics},
number = {6},
publisher = {Public Library of Science},
title = {{Understanding adaptation in large populations}},
doi = {10.1371/journal.pgen.1000987},
volume = {6},
year = {2010},
}
@article{3773,
abstract = {If distinct biological species are to coexist in sympatry, they must be reproductively isolated and must exploit different limiting resources. A two-niche Levene model is analysed, in which habitat preference and survival depend on underlying additive traits. The population genetics of preference and viability are equivalent. However, there is a linear trade-off between the chances of settling in either niche, whereas viabilities may be constrained arbitrarily. With a convex trade-off, a sexual population evolves a single generalist genotype, whereas with a concave trade-off, disruptive selection favours maximal variance. A pure habitat preference evolves to global linkage equilibrium if mating occurs in a single pool, but remarkably, evolves to pairwise linkage equilibrium within niches if mating is within those niches--independent of the genetics. With a concave trade-off, the population shifts sharply between a unimodal distribution with high gene flow and a bimodal distribution with strong isolation, as the underlying genetic variance increases. However, these alternative states are only simultaneously stable for a narrow parameter range. A sharp threshold is only seen if survival in the 'wrong' niche is low; otherwise, strong isolation is impossible. Gene flow from divergent demes makes speciation much easier in parapatry than in sympatry.},
author = {Barton, Nicholas H},
journal = {Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences},
number = {1547},
pages = {1825 -- 1840},
publisher = {Royal Society},
title = {{What role does natural selection play in speciation?}},
doi = {10.1098/rstb.2010.0001},
volume = {365},
year = {2010},
}
@article{3774,
abstract = {1. Hybridisation with an invasive species has the potential to alter the phenotype and hence the ecology of a native counterpart. 2. Here data from populations of native red deer Cervus elaphus and invasive sika deer Cervus nippon in Scotland is used to assess the extent to which hybridisation between them is causing phenotypic change. This is done by regression of phenotypic traits against genetic hybrid scores. 3. Hybridisation is causing increases in the body weight of sika-like deer and decreases in the body weight of red-like females. Hybridisation is causing increases in jaw length and increases in incisor arcade breadth in sika-like females. Hybridisation is also causing decreases in incisor arcade breadth in red-like females. 4. There is currently no evidence that hybridisation is causing changes in the kidney fat weight or pregnancy rates of either population. 5. Increased phenotypic similarity between the two species is likely to lead to further hybridisation. The ecological consequences of this are difficult to predict.},
author = {Senn, Helen and Swanson, Graeme and Goodman, Simon and Barton, Nicholas H and Pemberton, Josephine},
journal = {Journal of Animal Ecology},
number = {2},
pages = {414 -- 425},
publisher = {Wiley-Blackwell},
title = {{Phenotypic correlates of hybridisation between red and sika deer (genus Cervus)}},
doi = {10.1111/j.1365-2656.2009.01633.x},
volume = {79},
year = {2010},
}
@article{3776,
abstract = {The prevalence of recombination in eukaryotes poses one of the most puzzling questions in biology. The most compelling general explanation is that recombination facilitates selection by breaking down the negative associations generated by random drift (i.e. Hill-Robertson interference, HRI). I classify the effects of HRI owing to: deleterious mutation, balancing selection and selective sweeps on: neutral diversity, rates of adaptation and the mutation load. These effects are mediated primarily by the density of deleterious mutations and of selective sweeps. Sequence polymorphism and divergence suggest that these rates may be high enough to cause significant interference even in genomic regions of high recombination. However, neither seems able to generate enough variance in fitness to select strongly for high rates of recombination. It is plausible that spatial and temporal fluctuations in selection generate much more fitness variance, and hence selection for recombination, than can be explained by uniformly deleterious mutations or species-wide selective sweeps.},
author = {Barton, Nicholas H},
journal = {Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences},
number = {1552},
pages = {2559 -- 2569},
publisher = {Royal Society},
title = {{Genetic linkage and natural selection}},
doi = {10.1098/rstb.2010.0106},
volume = {365},
year = {2010},
}
@article{3777,
abstract = {Under the classical view, selection depends more or less directly on mutation: standing genetic variance is maintained by a balance between selection and mutation, and adaptation is fuelled by new favourable mutations. Recombination is favoured if it breaks negative associations among selected alleles, which interfere with adaptation. Such associations may be generated by negative epistasis, or by random drift (leading to the Hill-Robertson effect). Both deterministic and stochastic explanations depend primarily on the genomic mutation rate, U. This may be large enough to explain high recombination rates in some organisms, but seems unlikely to be so in general. Random drift is a more general source of negative linkage disequilibria, and can cause selection for recombination even in large populations, through the chance loss of new favourable mutations. The rate of species-wide substitutions is much too low to drive this mechanism, but local fluctuations in selection, combined with gene flow, may suffice. These arguments are illustrated by comparing the interaction between good and bad mutations at unlinked loci under the infinitesimal model.},
author = {Barton, Nicholas H},
journal = {Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences},
number = {1544},
pages = {1281 -- 1294},
publisher = {Royal Society},
title = {{Mutation and the evolution of recombination}},
doi = {10.1098/rstb.2009.0320},
volume = {365},
year = {2010},
}
@article{3779,
abstract = {Crosses between closely related species give two contrasting results. One result is that species hybrids may be inferior to their parents, for example, being less fertile [1]. The other is that F1 hybrids may display superior performance (heterosis), for example with increased vigour [2]. Although various hypotheses have been proposed to account for these two aspects of hybridisation, their biological basis is still poorly understood [3]. To gain further insights into this issue, we analysed the role that variation in gene expression may play. We took a conserved trait, flower asymmetry in Antirrhinum, and determined the extent to which the underlying regulatory genes varied in expression among closely related species. We show that expression of both genes analysed, CYC and RAD, varies significantly between species because of cis-acting differences. By making a quantitative genotype-phenotype map, using a range of mutant alleles, we demonstrate that the species lie on a plateau in gene expression-morphology space, so that the variation has no detectable phenotypic effect. However, phenotypic differences can be revealed by shifting genotypes off the plateau through genetic crosses. Our results can be readily explained if genomes are free to evolve within an effectively neutral zone in gene expression space. The consequences of this drift will be negligible for individual loci, but when multiple loci across the genome are considered, we show that the variation may have significant effects on phenotype and fitness, causing a significant drift load. By considering these consequences for various gene-expression-fitness landscapes, we conclude that F1 hybrids might be expected to show increased performance with regard to conserved traits, such as basic physiology, but reduced performance with regard to others. Thus, our study provides a new way of explaining how various aspects of hybrid performance may arise through natural variation in gene activity.},
author = {Rosas, Ulises and Barton, Nicholas H and Copsey, Lucy and Barbier De Reuille, Pierre and Coen, Enrico},
journal = {PLoS Biology},
number = {7},
publisher = {Public Library of Science},
title = {{Cryptic variation between species and the basis of hybrid performance}},
doi = {10.1371/journal.pbio.1000429},
volume = {8},
year = {2010},
}
@inproceedings{3782,
abstract = {In cortex surface segmentation, the extracted surface is required to have a particular topology, namely, a two-sphere. We present a new method for removing topology noise of a curve or surface within the level set framework, and thus produce a cortical surface with correct topology. We define a new energy term which quantifies topology noise. We then show how to minimize this term by computing its functional derivative with respect to the level set function. This method differs from existing methods in that it is inherently continuous and not digital; and in the way that our energy directly relates to the topology of the underlying curve or surface, versus existing knot-based measures which are related in a more indirect fashion. The proposed flow is validated empirically.},
author = {Chen, Chao and Freedman, Daniel},
booktitle = { Conference proceedings MCV 2010},
location = {Beijing, China},
pages = {31 -- 42},
publisher = {Springer},
title = {{Topology noise removal for curve and surface evolution}},
doi = {10.1007/978-3-642-18421-5_4},
volume = {6533},
year = {2010},
}
@article{3783,
abstract = {MICROSATELIGHT is a Perl/Tk pipeline with a graphical user interface that facilitates several tasks when scoring microsatellites. It implements new subroutines in R and PERL and takes advantage of features provided by previously developed freeware. MICROSATELIGHT takes raw genotype data and automates the peak identification through PeakScanner. The PeakSelect subroutine assigns peaks to different microsatellite markers according to their multiplex group, fluorochrome type, and size range. After peak selection, binning of alleles can be carried out 1) automatically through AlleloBin or 2) by manual bin definition through Binator. In both cases, several features for quality checking and further binning improvement are provided. The genotype table can then be converted into input files for several population genetics programs through CREATE. Finally, Hardy–Weinberg equilibrium tests and confidence intervals for null allele frequency can be obtained through GENEPOP. MICROSATELIGHT is the only freely available public-domain software that facilitates full multiplex microsatellite scoring, from electropherogram files to user-defined text files to be used with population genetics software. MICROSATELIGHT has been created for the Windows XP operating system and has been successfully tested under Windows 7. It is available at http://sourceforge.net/projects/microsatelight/.},
author = {Palero, Ferran and González Candelas, Fernando and Pascual, Marta},
journal = {Journal of Heredity},
number = {2},
pages = {247 -- 249},
publisher = {Oxford University Press},
title = {{Microsatelight – Pipeline to expedite microsatellite analysis}},
doi = {10.1093/jhered/esq111},
volume = {102},
year = {2010},
}
@article{3785,
abstract = {Most fisheries involving spiny lobsters of the genus Palinurus have been over exploited during the last decades, so there is a raising concern about management decisions for these valuable resources. A total of 13 microsatellite DNA loci recently developed in Palinurus elephas were assayed in order to assess genetic diversity levels in every known species of the genus. Microsatellite markers gave amplifications and showed polymorphism in all species, with gene diversity values varying from 0.65060.077 SD (Palinurus barbarae) to 0.79260.051 SD (Palinurus elephas). Most importantly, when depth distribution was taken into account, shallower waters pecies consistently showed larger historical effective population sizes than their deeper-water counterparts. This could explain why deeper-water species are more sensitive to overfishing, and would indicate that overexploitation may have a larger impact on their long-term genetic diversity.},
author = {Palero, Ferran and Abello, Pere and Macpherson, E. and Matthee, C. and Pascual, Marta},
journal = {Journal of Crustacean Biology},
number = {4},
pages = {658 -- 663},
publisher = {BioOne},
title = {{Genetic diversity levels in fishery-exploited spiny lobsters of the Genus Palinurus (Decapoda: Achelata)}},
doi = {10.1651/09-3192.1},
volume = {30},
year = {2010},
}
@article{3787,
abstract = {DNA samples were extracted from ethanol and formalin-fixed decapod crustacean tissue using a new method based on Tetramethylsilane (TMS)-Chelex. It is shown that neither an indigestible matrix of cross-linked protein nor soluble PCR inhibitors impede PCR success when dealing with formalin-fixed material. Instead, amplification success from formalin-fixed tissue appears to depend on the presence of unmodified DNA in the extracted sample. A staining method that facilitates the targeting of samples with a high content of unmodified DNA is provided.},
author = {Palero, Ferran and Hall, Sally and Clark, Paul and Johnston, David and Mackenzie Dodds, Jackie and Thatje, Sven},
journal = {Scientia Marina},
number = {3},
pages = {465 -- 470},
publisher = {Consejo Superior de Investigaciones Científicas},
title = {{DNA extraction from formalin-fixed tissue: new light from the deep sea}},
doi = {10.3989/scimar.2010.74n3465},
volume = {74},
year = {2010},
}
@article{3788,
abstract = {Cell sorting is a widespread phenomenon pivotal to the early development of multicellular organisms. In vitro cell sorting studies have been instrumental in revealing the cellular properties driving this process. However, these studies have as yet been limited to two-dimensional analysis of three-dimensional cell sorting events. Here we describe a method to record the sorting of primary zebrafish ectoderm and mesoderm germ layer progenitor cells in three dimensions over time, and quantitatively analyze their sorting behavior using an order parameter related to heterotypic interface length. We investigate the cell population size dependence of sorted aggregates and find that the germ layer progenitor cells engulfed in the final configuration display a relationship between total interfacial length and system size according to a simple geometrical argument, subject to a finite-size effect.},
author = {Klopper, Abigail and Krens, Gabriel and Grill, Stephan and Heisenberg, Carl-Philipp J},
journal = {The European Physical Journal E: Soft Matter and Biological Physics},
number = {2},
pages = {99 -- 103},
publisher = {Springer},
title = {{Finite-size corrections to scaling behavior in sorted cell aggregates}},
doi = {10.1140/epje/i2010-10642-y},
volume = {33},
year = {2010},
}
@article{3789,
abstract = {The development of multicellular organisms is dependent on the tight coordination between tissue growth and morphogenesis. The stereotypical orientation of cell divisions has been proposed to be a fundamental mechanism by which proliferating and growing tissues take shape. However, the actual contribution of stereotypical division orientation (SDO) to tissue morphogenesis is unclear. In zebrafish, cell divisions with stereotypical orientation have been implicated in both body-axis elongation and neural rod formation [1, 2], although there is little direct evidence for a critical function of SDO in either of these processes. Here we show that SDO is required for formation of the neural rod midline during neurulation but dispensable for elongation of the body axis during gastrulation. Our data indicate that SDO during both gastrulation and neurulation is dependent on the noncanonical Wnt receptor Frizzled 7 (Fz7) and that interfering with cell division orientation leads to severe defects in neural rod midline formation but not body-axis elongation. These findings suggest a novel function for Fz7-controlled cell division orientation in neural rod midline formation during neurulation. },
author = {Quesada-Hernández, Elena and Caneparo, Luca and Schneider, Sylvia and Winkler, Sylke and Liebling, Michael and Fraser, Scott and Heisenberg, Carl-Philipp J},
journal = {Current Biology},
number = {21},
pages = {1966 -- 1972},
publisher = {Cell Press},
title = {{Stereotypical cell division orientation controls neural rod midline formation in zebrafish}},
doi = {10.1016/j.cub.2010.10.009},
volume = {20},
year = {2010},
}
@article{3790,
abstract = {Cell shape and motility are primarily controlled by cellular mechanics. The attachment of the plasma membrane to the underlying actomyosin cortex has been proposed to be important for cellular processes involving membrane deformation. However, little is known about the actual function of membrane-to-cortex attachment (MCA) in cell protrusion formation and migration, in particular in the context of the developing embryo. Here, we use a multidisciplinary approach to study MCA in zebrafish mesoderm and endoderm (mesendoderm) germ layer progenitor cells, which migrate using a combination of different protrusion types, namely, lamellipodia, filopodia, and blebs, during zebrafish gastrulation. By interfering with the activity of molecules linking the cortex to the membrane and measuring resulting changes in MCA by atomic force microscopy, we show that reducing MCA in mesendoderm progenitors increases the proportion of cellular blebs and reduces the directionality of cell migration. We propose that MCA is a key parameter controlling the relative proportions of different cell protrusion types in mesendoderm progenitors, and thus is key in controlling directed migration during gastrulation.},
author = {Diz Muñoz, Alba and Krieg, Michael and Bergert, Martin and Ibarlucea Benitez, Itziar and Müller, Daniel and Paluch, Ewa and Heisenberg, Carl-Philipp J},
journal = {PLoS Biology},
number = {11},
publisher = {Public Library of Science},
title = {{Control of directed cell migration in vivo by membrane-to-cortex attachment}},
doi = {10.1371/journal.pbio.1000544},
volume = {8},
year = {2010},
}
@inproceedings{3793,
abstract = {Recent progress in per-pixel object class labeling of natural images can be attributed to the use of multiple types of image features and sound statistical learning approaches. Within the latter, Conditional Random Fields (CRF) are prominently used for their ability to represent interactions between random variables. Despite their popularity in computer vision, parameter learning for CRFs has remained difficult, popular approaches being cross-validation and piecewise training.
In this work, we propose a simple yet expressive tree-structured CRF based on a recent hierarchical image segmentation method. Our model combines and weights multiple image features within a hierarchical representation and allows simple and efficient globally-optimal learning of ≈ 105 parameters. The tractability of our model allows us to pose and answer some of the open questions regarding parameter learning applying to CRF-based approaches. The key findings for learning CRF models are, from the obvious to the surprising, i) multiple image features always help, ii) the limiting dimension with respect to current models is the amount of training data, iii) piecewise training is competitive, iv) current methods for max-margin training fail for models with many parameters.
},
author = {Nowozin, Sebastian and Gehler, Peter and Lampert, Christoph},
location = {Heraklion, Crete, Greece},
pages = {98 -- 111},
publisher = {Springer},
title = {{On parameter learning in CRF-based approaches to object class image segmentation}},
doi = {10.1007/978-3-642-15567-3_8},
volume = {6316},
year = {2010},
}
@inproceedings{3794,
abstract = {We study the problem of multimodal dimensionality reduction assuming that data samples can be missing at training time, and not all data modalities may be present at application time. Maximum covariance analysis, as a generalization of PCA, has many desirable properties, but its application to practical problems is limited by its need for perfectly paired data. We overcome this limitation by a latent variable approach that allows working with weakly paired data and is still able to efficiently process large datasets using standard numerical routines. The resulting weakly paired maximum covariance analysis often finds better representations than alternative methods, as we show in two exemplary tasks: texture discrimination and transfer learning.},
author = {Lampert, Christoph and Krömer, Oliver},
location = {Heraklion, Crete, Greece},
pages = {566 -- 579},
publisher = {Springer},
title = {{Weakly-paired maximum covariance analysis for multimodal dimensionality reduction and transfer learning}},
doi = {10.1007/978-3-642-15552-9_41},
volume = {6312},
year = {2010},
}
@inbook{3795,
abstract = {The (apparent) contour of a smooth mapping from a 2-manifold to the plane, f: M → R2 , is the set of critical values, that is, the image of the points at which the gradients of the two component functions are linearly dependent. Assuming M is compact and orientable and measuring difference with the erosion distance, we prove that the contour is stable.},
author = {Edelsbrunner, Herbert and Morozov, Dmitriy and Patel, Amit},
booktitle = {Topological Data Analysis and Visualization: Theory, Algorithms and Applications},
pages = {27 -- 42},
publisher = {Springer},
title = {{The stability of the apparent contour of an orientable 2-manifold}},
doi = {10.1007/978-3-642-15014-2_3},
year = {2010},
}
@article{3604,
abstract = {We investigated temporal changes in hybridization and introgression between native red deer (Cervus elaphus) and invasive Japanese sika (Cervus nippon) on the Kintyre Peninsula, Scotland, over 15 years, through analysis of 1513 samples of deer at 20 microsatellite loci and a mtDNA marker. We found no evidence that either the proportion of recent hybrids, or the levels of introgression had changed over the study period. Nevertheless, in one population where the two species have been in contact since ∼1970, 44% of individuals sampled during the study were hybrids. This suggests that hybridization between these species can proceed fairly rapidly. By analysing the number of alleles that have introgressed from polymorphic red deer into the genetically homogenous sika population, we reconstructed the haplotypes of red deer alleles introduced by backcrossing. Five separate hybridization events could account for all the recently hybridized sika-like individuals found across a large section of the Peninsula. Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales.},
author = {Senn, Helen and Goodman, Simon and Swanson, Graeme and Barton, Nicholas H and Pemberton, Josephine},
journal = {Molecular Ecology},
number = {5},
pages = {910 -- 924},
publisher = {Wiley-Blackwell},
title = {{Investigating temporal changes in hybridisation and introgression between invasive sika (Cervus nippon) and native red deer (Cervus elaphus) on the Kintyre Peninsula, Scotland}},
doi = {10.1111/j.1365-294X.2009.04497.x},
volume = {19},
year = {2010},
}
@article{3832,
abstract = {A recent paper by von Engelhardt et al. identifies a novel auxiliary subunit of native AMPARs, termedCKAMP44. Unlike other auxiliary subunits, CKAMP44 accelerates desensitization and prolongs recovery from desensitization. CKAMP44 is highly expressed in hippocampal dentate gyrus granule cells and decreases the paired-pulse ratio at perforant path input synapses. Thus, both principal and auxiliary AMPAR subunits control the time course of signaling at glutamatergic synapses.},
author = {Guzmán, José and Jonas, Peter M},
journal = {Neuron},
number = {1},
pages = {8 -- 10},
publisher = {Elsevier},
title = {{Beyond TARPs: The growing list of auxiliary AMPAR subunits}},
doi = {10.1016/j.neuron.2010.04.003},
volume = {66},
year = {2010},
}
@article{3833,
author = {Jonas, Peter M and Hefft, Stefan},
journal = {The European Journal of Neuroscience},
number = {7},
pages = {1194 -- 1195},
publisher = {Wiley-Blackwell},
title = {{GABA release at terminals of CCK-interneurons: synchrony, asynchrony and modulation by cannabinoid receptors (commentary on Ali & Todorova)}},
doi = {10.1111/j.1460-9568.2010.07189.x},
volume = {31},
year = {2010},
}
@article{3834,
abstract = {Background
The chemical master equation (CME) is a system of ordinary differential equations that describes the evolution of a network of chemical reactions as a stochastic process. Its solution yields the probability density vector of the system at each point in time. Solving the CME numerically is in many cases computationally expensive or even infeasible as the number of reachable states can be very large or infinite. We introduce the sliding window method, which computes an approximate solution of the CME by performing a sequence of local analysis steps. In each step, only a manageable subset of states is considered, representing a "window" into the state space. In subsequent steps, the window follows the direction in which the probability mass moves, until the time period of interest has elapsed. We construct the window based on a deterministic approximation of the future behavior of the system by estimating upper and lower bounds on the populations of the chemical species.
Results
In order to show the effectiveness of our approach, we apply it to several examples previously described in the literature. The experimental results show that the proposed method speeds up the analysis considerably, compared to a global analysis, while still providing high accuracy.
Conclusions
The sliding window method is a novel approach to address the performance problems of numerical algorithms for the solution of the chemical master equation. The method efficiently approximates the probability distributions at the time points of interest for a variety of chemically reacting systems, including systems for which no upper bound on the population sizes of the chemical species is known a priori.},
author = {Wolf, Verena and Goel, Rushil and Mateescu, Maria and Henzinger, Thomas A},
journal = {BMC Systems Biology},
number = {42},
pages = {1 -- 19},
publisher = {BioMed Central},
title = {{Solving the chemical master equation using sliding windows}},
doi = {10.1186/1752-0509-4-42},
volume = {4},
year = {2010},
}
@inproceedings{3838,
abstract = {We present a numerical approximation technique for the analysis of continuous-time Markov chains that describe net- works of biochemical reactions and play an important role in the stochastic modeling of biological systems. Our approach is based on the construction of a stochastic hybrid model in which certain discrete random variables of the original Markov chain are approximated by continuous deterministic variables. We compute the solution of the stochastic hybrid model using a numerical algorithm that discretizes time and in each step performs a mutual update of the transient prob- ability distribution of the discrete stochastic variables and the values of the continuous deterministic variables. We im- plemented the algorithm and we demonstrate its usefulness and efficiency on several case studies from systems biology.},
author = {Henzinger, Thomas A and Mateescu, Maria and Mikeev, Linar and Wolf, Verena},
location = {Trento, Italy},
pages = {55 -- 65},
publisher = {Springer},
title = {{Hybrid numerical solution of the chemical master equation}},
doi = {10.1145/1839764.1839772},
year = {2010},
}
@inproceedings{3839,
abstract = {We present a loop property generation method for loops iterating over multi-dimensional arrays. When used on matrices, our method is able to infer their shapes (also called types), such as upper-triangular, diagonal, etc. To gen- erate loop properties, we first transform a nested loop iterating over a multi- dimensional array into an equivalent collection of unnested loops. Then, we in- fer quantified loop invariants for each unnested loop using a generalization of a recurrence-based invariant generation technique. These loop invariants give us conditions on matrices from which we can derive matrix types automatically us- ing theorem provers. Invariant generation is implemented in the software package Aligator and types are derived by theorem provers and SMT solvers, including Vampire and Z3. When run on the Java matrix package JAMA, our tool was able to infer automatically all matrix types describing the matrix shapes guaranteed by JAMA’s API.},
author = {Henzinger, Thomas A and Hottelier, Thibaud and Kovács, Laura and Voronkov, Andrei},
location = {Madrid, Spain},
pages = {163 -- 179},
publisher = {Springer},
title = {{Invariant and type inference for matrices}},
doi = {10.1007/978-3-642-11319-2_14},
volume = {5944},
year = {2010},
}
@inproceedings{3840,
abstract = {Classical formalizations of systems and properties are boolean: given a system and a property, the property is either true or false of the system. Correspondingly, classical methods for system analysis determine the truth value of a property, preferably giving a proof if the property is true, and a counterexample if the property is false; classical methods for system synthesis construct a system for which a property is true; classical methods for system transformation, composition, and abstraction aim to preserve the truth of properties. The boolean view is prevalent even if the system, the property, or both refer to numerical quantities, such as the times or probabilities of events. For example, a timed automaton either satisfies or violates a formula of a real-time logic; a stochastic process either satisfies or violates a formula of a probabilistic logic. The classical black-and-white view partitions the world into "correct" and "incorrect" systems, offering few nuances. In reality, of several systems that satisfy a property in the boolean sense, often some are more desirable than others, and of the many systems that violate a property, usually some are less objectionable than others. For instance, among the systems that satisfy the response property that every request be granted, we may prefer systems that grant requests quickly (the quicker, the better), or we may prefer systems that issue few unnecessary grants (the fewer, the better); and among the systems that violate the response property, we may prefer systems that serve many initial requests (the more, the better), or we may prefer systems that serve many requests in the long run (the greater the fraction of served to unserved requests, the better). Formally, while a boolean notion of correctness is given by a preorder on systems and properties, a quantitative notion of correctness is defined by a directed metric on systems and properties, where the distance between a system and a property provides a measure of "fit" or "desirability." There are many ways how such distances can be defined. In a linear-time framework, one assigns numerical values to individual behaviors before assigning values to systems and properties, which are sets of behaviors. For example, the value of a single behavior may be a discounted value, which is largely determined by a prefix of the behavior, e.g., by the number of requests that are granted before the first request that is not granted; or a limit value, which is independent of any finite prefix. A limit value may be an average, such as the average response time over an infinite sequence of requests and grants, or a supremum, such as the worst-case response time. Similarly, the value of a set of behaviors may be an extremum or an average across the values of all behaviors in the set: in this way one can measure the worst of all possible average-case response times, or the average of all possible worst-case response times, etc. Accordingly, the distance between two sets of behaviors may be defined as the worst or average difference between the values of corresponding behaviors. In summary, we propagate replacing boolean specifications for the correctness of systems with quantitative measures for the desirability of systems. In quantitative analysis, the aim is to compute the distance between a system and a property (or between two systems, or two properties); in quantitative synthesis, the objective is to construct a system that has minimal distance from a given property. Multiple quantitative measures can be prioritized (e.g., combined lexicographically into a single measure) or studied along the Pareto curve. Quantitative transformations, compositions, and abstractions of systems are useful if they allow us to bound the induced change in distance from a property. We present some initial results in some of these directions. We also give some potential applications, which not only generalize tradiditional correctness concerns in the functional, timed, and probabilistic domains, but also capture such system measures as resource use, performance, cost, reliability, and robustness.},
author = {Henzinger, Thomas A},
location = {Madrid, Spain},
number = {1},
pages = {157 -- 158},
publisher = {ACM},
title = {{From boolean to quantitative notions of correctness}},
doi = {10.1145/1706299.1706319},
volume = {45},
year = {2010},
}
@article{3718,
abstract = {Long-term depression (LTD) is a form of synaptic plasticity that may contribute to information storage in the central nervous system. Here we report that LTD can be elicited in layer 5 pyramidal neurons of the rat prefrontal cortex by pairing low frequency stimulation with a modest postsynaptic depolarization. The induction of LTD required the activation of both metabotropic glutamate receptors of the mGlu1 subtype and voltage-sensitive Ca(2+) channels (VSCCs) of the T/R, P/Q and N types, leading to the stimulation of intracellular inositol trisphosphate (IP3) receptors by IP3 and Ca(2+). The subsequent release of Ca(2+) from intracellular stores activated the protein phosphatase cascade involving calcineurin and protein phosphatase 1. The activation of purinergic P2Y(1) receptors blocked LTD. This effect was prevented by P2Y(1) receptor antagonists and was absent in mice lacking P2Y(1) but not P2Y(2) receptors. We also found that activation of P2Y(1) receptors inhibits Ca(2+) transients via VSCCs in the apical dendrites and spines of pyramidal neurons. In addition, we show that the release of ATP under hypoxia is able to inhibit LTD by acting on postsynaptic P2Y(1) receptors. In conclusion, these data suggest that the reduction of Ca(2+) influx via VSCCs caused by the activation of P2Y(1) receptors by ATP is the possible mechanism for the inhibition of LTD in prefrontal cortex.},
author = {Guzmán, José and Schmidt, Hartmut and Franke, Heike and Krügel, Ute and Eilers, Jens and Illes, Peter and Gerevich, Zoltan},
journal = {Neuropharmacology},
number = {6},
pages = {406 -- 415},
publisher = {Elsevier},
title = {{P2Y1 receptors inhibit long-term depression in the prefrontal cortex.}},
doi = {10.1016/j.neuropharm.2010.05.013},
volume = {59},
year = {2010},
}
@inproceedings{3845,
abstract = {This paper presents Aligators, a tool for the generation of universally quantified array invariants. Aligators leverages recurrence solving and algebraic techniques to carry out inductive reasoning over array content. The Aligators’ loop extraction module allows treatment of multi-path loops by exploiting their commutativity and serializability properties. Our experience in applying Aligators on a collection of loops from open source software projects indicates the applicability of recurrence and algebraic solving techniques for reasoning about arrays.},
author = {Henzinger, Thomas A and Hottelier, Thibaud and Kovács, Laura and Rybalchenko, Andrey},
location = {Yogyakarta, Indonesia},
pages = {348 -- 356},
publisher = {Springer},
title = {{Aligators for arrays}},
doi = {10.1007/978-3-642-16242-8_25},
volume = {6397},
year = {2010},
}
@inproceedings{3847,
abstract = {The importance of stochasticity within biological systems has been shown repeatedly during the last years and has raised the need for efficient stochastic tools. We present SABRE, a tool for stochastic analysis of biochemical reaction networks. SABRE implements fast adaptive uniformization (FAU), a direct numerical approximation algorithm for computing transient solutions of biochemical reaction networks. Biochemical reactions networks represent biological systems studied at a molecular level and these reactions can be modeled as transitions of a Markov chain. SABRE accepts as input the formalism of guarded commands, which it interprets either as continuous-time or as discrete-time Markov chains. Besides operating in a stochastic mode, SABRE may also perform a deterministic analysis by directly computing a mean-field approximation of the system under study. We illustrate the different functionalities of SABRE by means of biological case studies.},
author = {Didier, Frédéric and Henzinger, Thomas A and Mateescu, Maria and Wolf, Verena},
location = {Williamsburg, USA},
pages = {193 -- 194},
publisher = {IEEE},
title = {{SABRE: A tool for the stochastic analysis of biochemical reaction networks}},
doi = {10.1109/QEST.2010.33},
year = {2010},
}
@inproceedings{3848,
abstract = {We define the robustness of a level set homology class of a function f:XR as the magnitude of a perturbation necessary to kill the class. Casting this notion into a group theoretic framework, we compute the robustness for each class, using a connection to extended persistent homology. The special case X=R3 has ramifications in medical imaging and scientific visualization.},
author = {Bendich, Paul and Edelsbrunner, Herbert and Morozov, Dmitriy and Patel, Amit},
location = {Liverpool, UK},
pages = {1 -- 10},
publisher = {Springer},
title = {{The robustness of level sets}},
doi = {10.1007/978-3-642-15775-2_1},
volume = {6346},
year = {2010},
}
@inproceedings{3849,
abstract = {Using ideas from persistent homology, the robustness of a level set of a real-valued function is defined in terms of the magnitude of the perturbation necessary to kill the classes. Prior work has shown that the homology and robustness information can be read off the extended persistence diagram of the function. This paper extends these results to a non-uniform error model in which perturbations vary in their magnitude across the domain.},
author = {Bendich, Paul and Edelsbrunner, Herbert and Kerber, Michael and Patel, Amit},
location = {Brno, Czech Republic},
pages = {12 -- 23},
publisher = {Springer},
title = {{Persistent homology under non-uniform error}},
doi = {10.1007/978-3-642-15155-2_2},
volume = {6281},
year = {2010},
}
@inproceedings{3850,
abstract = {Given a polygonal shape Q with n vertices, can it be expressed, up to a tolerance ε in Hausdorff distance, as the Minkowski sum of another polygonal shape with a disk of fixed radius? If it does, we also seek a preferably simple solution shape P;P’s offset constitutes an accurate, vertex-reduced, and smoothened approximation of Q. We give a decision algorithm for fixed radius in O(nlogn) time that handles any polygonal shape. For convex shapes, the complexity drops to O(n), which is also the time required to compute a solution shape P with at most one more vertex than a vertex-minimal one.},
author = {Berberich, Eric and Halperin, Dan and Kerber, Michael and Pogalnikova, Roza},
location = {Dortmund, Germany},
pages = {12 -- 23},
publisher = {TU Dortmund},
title = {{Polygonal reconstruction from approximate offsets}},
year = {2010},
}
@inproceedings{3851,
abstract = {Energy parity games are infinite two-player turn-based games played on weighted graphs. The objective of the game combines a (qualitative) parity condition with the (quantitative) requirement that the sum of the weights (i.e., the level of energy in the game) must remain positive. Beside their own interest in the design and synthesis of resource-constrained omega-regular specifications, energy parity games provide one of the simplest model of games with combined qualitative and quantitative objective. Our main results are as follows: (a) exponential memory is sufficient and may be necessary for winning strategies in energy parity games; (b) the problem of deciding the winner in energy parity games can be solved in NP ∩ coNP; and (c) we give an algorithm to solve energy parity by reduction to energy games. We also show that the problem of deciding the winner in energy parity games is polynomially equivalent to the problem of deciding the winner in mean-payoff parity games, which can thus be solved in NP ∩ coNP. As a consequence we also obtain a conceptually simple algorithm to solve mean-payoff parity games.},
author = {Chatterjee, Krishnendu and Doyen, Laurent},
location = {Bordeaux, France},
pages = {599 -- 610},
publisher = {Springer},
title = {{Energy parity games}},
doi = {10.1007/978-3-642-14162-1_50},
volume = {6199},
year = {2010},
}
@inproceedings{3852,
abstract = {We introduce two-level discounted games played by two players on a perfect-information stochastic game graph. The upper level game is a discounted game and the lower level game is an undiscounted reachability game. Two-level games model hierarchical and sequential decision making under uncertainty across different time scales. We show the existence of pure memoryless optimal strategies for both players and an ordered field property for such games. We show that if there is only one player (Markov decision processes), then the values can be computed in polynomial time. It follows that whether the value of a player is equal to a given rational constant in two-level discounted games can be decided in NP intersected coNP. We also give an alternate strategy improvement algorithm to compute the value. },
author = {Chatterjee, Krishnendu and Majumdar, Ritankar},
location = {Minori, Italy},
pages = {22 -- 29},
publisher = {EPTCS},
title = {{Discounting in games across time scales}},
doi = {10.4204/EPTCS.25.6},
volume = {25},
year = {2010},
}