@article{2786,
abstract = {Transition to turbulence in pipe flow is one of the most fundamental and longest- standing problems in fluid dynamics. Stability theory suggests that the flow remains laminar for all flow rates, but in practice pipe flow becomes turbulent even at moderate speeds. This transition drastically affects the transport efficiency of mass, momentum, and heat. On the basis of the recent discovery of unstable traveling waves in computational studies of the Navier-Stokes equations and ideas from dynamical systems theory, a model for the transition process has been suggested. We report experimental observation of these traveling waves in pipe flow, confirming the proposed transition scenario and suggesting that the dynamics associated with these unstable states may indeed capture the nature of fluid turbulence.},
author = {Björn Hof and van Doorne, Casimir W and Westerweel, Jerry and Nieuwstadt, Frans T and Faisst, Holger and Eckhardt, Bruno and Wedin, Håkan and Kersweli, Richard R and Waleffe, Fabian},
journal = {Science},
number = {5690},
pages = {1594 -- 1598},
publisher = {American Association for the Advancement of Science},
title = {{Experimental observation of nonlinear traveling waves in turbulent pipe flow}},
doi = {10.1126/science.1100393},
volume = {305},
year = {2004},
}
@article{2787,
abstract = {The results of experimental and numerical investigations of the onset of oscillatory convection in a sidewall heated rectangular cavity of molten gallium are reported. Detailed comparisons are made between experimental observations and calculations from numerical simulations of a three-dimensional Boussinesq model. The onset of time-dependence takes place through supercritical Hopf bifurcations and the loci of critical points in the (Gr, Pr)-plane are qualitatively similar with excellent agreement between the frequencies of the oscillatory motion. This provides a severe test of the control of the experiment since the mode of oscillation is extremely sensitive to imperfections. Detailed numerical investigations reveal that there are a pair of Hopf bifurcations which exist on two asymmetric states which themselves arise at a subcritical pitchfork from the symmetric state. There is no evidence for this in the experiment and this qualitative difference is attributed to non-Boussinesq perturbations which increase with Gr. However, the antisymmetric spatial structure of the oscillatory state is robust and is present in both the experiment and the numerical model. Moreover, the detailed analysis of the numerical results reveals the origins of the oscillatory instability.},
author = {Björn Hof and Juel, Anne and Zhao, Li and Henry, Daniel and Ben Hadid, Hamda and Mullin, Tom P},
journal = {Journal of Fluid Mechanics},
pages = {391 -- 413},
publisher = {Cambridge University Press},
title = {{On the onset of oscillatory convection in molten gallium}},
doi = {10.1017/S0022112004000527},
volume = {515},
year = {2004},
}
@article{2997,
abstract = {Polar transport-dependent local accumulation of auxin provides positional cues for multiple plant patterning processes. This directional auxin flow depends on the polar subcellular localization of the PIN auxin efflux regulators. Overexpression of the PINOID protein kinase induces a basal-to-apical shift in PIN localization, resulting in the loss of auxin gradients and strong defects in embryo and seedling roots. Conversely, pid loss of function induces an apical-to-basal shift in PIN1 polar targeting at the inflorescence apex, accompanied by defective organogenesis. Our results show that a PINOID-dependent binary switch controls PIN polarity and mediates changes in auxin flow to create local gradients for patterning processes.},
author = {Jirí Friml and Yang, Xiong and Michniewicz, Marta and Weijers, Dolf and Quint, Ab and Tietz, Olaf and Benjamins, René and Ouwerkerk, Pieter B and Ljung, Karin and Sandberg, Göran and Hooykaas, Paul J and Palme, Klaus and Offringa, Remko},
journal = {Science},
number = {5697},
pages = {862 -- 865},
publisher = {American Association for the Advancement of Science},
title = {{A PINOID-dependent binary switch in apical-basal PIN polar targeting directs auxin efflux}},
doi = {10.1126/science.1100618},
volume = {306},
year = {2004},
}
@article{2998,
abstract = {The packaging of the genomic DNA into chromatin in the cell nucleus requires machineries that facilitate DNA-dependent processes such as transcription in the presence of repressive chromatin structures. Using co-immunoprecipitation we have identified in Arabidopsis thaliana cells the FAcilitates Chromatin Transcription (FACT) complex, consisting of the 120-kDa Spt16 and the 71-kDa SSRP1 proteins. Indirect immunofluorecence analyses revealed that both FACT subunits co-localize to nuclei of the majority of cell types in embryos, shoots and roots, whereas FACT is not present in terminally differentiated cells such as mature trichoblasts or cells of the root cap. In the nucleus, Spt16 and SSRP1 are found in the cytologically defined euchromatin of interphase cells independent of the status of DNA replication, but the proteins are not associated with heterochromatic chromocentres and condensed mitotic chromosomes. FACT can be detected by chromatin immunoprecipitation over the entire transcribed region (5′-UTR, coding sequence, 3′-UTR) of actively transcribed genes, whereas it does not occur at transcriptionally inactive heterochromatic regions and intergenic regions. FACT localizes to inducible genes only after induction of transcription, and the association of the complex with the genes correlates with the level of transcription. Collectively, these results indicate that FACT assists transcription elongation through plant chromatin.},
author = {Duroux, Meg and Houben, Andreas and Růžička, Kamil and Jirí Friml and Grasser, Klaus D},
journal = {Plant Journal},
number = {5},
pages = {660 -- 671},
publisher = {Wiley-Blackwell},
title = {{The chromatin remodelling complex FACT associates with actively transcribed regions of the Arabidopsis genome}},
doi = {10.1111/j.1365-313X.2004.02242.x},
volume = {40},
year = {2004},
}
@article{2999,
abstract = {Embryogenesis of flowering plants establishes a basic body plan with apical-basal, radial and bilateral patterns from the single-celled zygote. Arabidopsis embryogenesis exhibits a nearly invariant cell division pattern and therefore is an ideal system for studies of early plant development. However, plant embryos are difficult to access for experimental manipulation, as they develop deeply inside maternal tissues. Here we present a method for the culture of zygotic Arabidopsis embryos in vitro. The technique omits excision of the embryo by culturing the entire ovule, thus greatly facilitating the time and effort involved. It enables external manipulation of embryo development and culture from the earliest developmental stages up to maturity. Administration of various chemical treatments as well as the use of different molecular markers is demonstrated together with standard techniques for visualizing gene expression and protein localization in in vitro cultivated embryos. The presented set of techniques allows for so far unavailable molecular physiology approaches in the study of early plant development.},
author = {Sauer, Michael and Jirí Friml},
journal = {Plant Journal},
number = {5},
pages = {835 -- 843},
publisher = {Wiley-Blackwell},
title = {{In vitro culture of Arabidopsis embryos within their ovules}},
doi = {10.1111/j.1365-313X.2004.02248.x},
volume = {40},
year = {2004},
}
@misc{3142,
abstract = {Assembly of neuronal circuits is controlled by the sequential acquisition of neuronal subpopulation-specific identities at progressive developmental steps. Whereas neuronal features involved in initial phases of differentiation are already established at cell-cycle exit, recent findings, based mainly on work in the peripheral nervous system, suggest that the timely integration of signals encountered en route to targets and from the target region itself is essential to control late steps in connectivity. As neurons project towards their targets they require target-derived signals to establish mature axonal projections and acquire neuronal traits such as the expression of distinct combinations of neurotransmitters. Recent evidence presented in this review shows that this principle, of a signaling interplay between target-derived signals and neuronal cell bodies, is often mediated through transcriptional events and is evolutionarily conserved.},
author = {Simon Hippenmeyer and Kramer, Ina and Arber, Silvia},
booktitle = {Trends in Neurosciences},
number = {8},
pages = {482 -- 488},
publisher = {Elsevier},
title = {{Control of neuronal phenotype: What targets tell the cell bodies}},
doi = {10.1016/j.tins.2004.05.012},
volume = {27},
year = {2004},
}
@article{1963,
abstract = {The mechanism coupling electron transfer and proton pumping in respiratory complex I (NADH-ubiquinone oxidoreductase) has not been established, but it has been suggested that it involves conformational changes. Here, the influence of substrates on the conformation of purified complex I from Escherichia coli was studied by cross-linking and electron microscopy. When a zero-length cross-linking reagent was used, the presence of NAD(P)H, in contrast to that of NAD+, prevented the formation of cross-links between the hydrophilic subunits of the complex, including NuoB, NuoI, and NuoCD. Comparisons using different cross-linkers suggested that NuoB, which is likely to coordinate the key iron-sulfur cluster N2, is the most mobile subunit. The presence of NAD(P)H led also to enhanced proteolysis of subunit NuoG. These data indicate that upon NAD(P)H binding, the peripheral arm of the complex adopts a more open conformation, with increased distances between subunits. Single particle analysis showed the nature of this conformational change. The enzyme retains its L-shape in the presence of NADH, but exhibits a significantly more open or expanded structure both in the peripheral arm and, unexpectedly, in the membrane domain also.},
author = {Mamedova, Aygun A and Holt, Peter J and Carroll, Joe D and Leonid Sazanov},
journal = {Journal of Biological Chemistry},
number = {22},
pages = {23830 -- 23836},
publisher = {American Society for Biochemistry and Molecular Biology},
title = {{Substrate-induced conformational change in bacterial complex I}},
doi = {10.1074/jbc.M401539200},
volume = {279},
year = {2004},
}
@article{864,
abstract = {We present a method for prediction of functional sites in a set of aligned protein sequences. The method selects sites which are both well conserved and clustered together in space, as inferred from the 3D structures of proteins included in the alignment. We tested the method using 86 alignments from the NCBI CDD database, where the sites of experimentally determined ligand and/or macromolecular interactions are annotated. In agreement with earlier investigations, we found that functional site predictions are most successful when overall background sequence conservation is low, such that sites under evolutionary constraint become apparent. In addition, we found that averaging of conservation values across spatially clustered sites improves predictions under certain conditions: that is, when overall conservation is relatively high and when the site in question involves a large macromolecular binding interface. Under these conditions it is better to look for clusters of conserved sites than to look for particular conserved sites.},
author = {Panchenko, Anna R and Fyodor Kondrashov and Bryant, Stephen H},
journal = {Protein Science},
number = {4},
pages = {884 -- 892},
publisher = {Wiley-Blackwell},
title = {{Prediction of functional sites by analysis of sequence and structure conservation}},
doi = {10.1110/ps.03465504},
volume = {13},
year = {2004},
}
@article{870,
abstract = {Only a fraction of eukaryotic genes affect the phenotype drastically. We compared 18 parameters in 1273 human morbid genes, known to cause diseases, and in the remaining 16 580 unambiguous human genes. Morbid genes evolve more slowly, have wider phylogenetic distributions, are more similar to essential genes of Drosophila melanogaster, code for longer proteins containing more alanine and glycine and less histidine, lysine and methionine, possess larger numbers of longer introns with more accurate splicing signals and have higher and broader expressions. These differences make it possible to classify as non-morbid 34% of human genes with unknown morbidity, when only 5% of known morbid genes are incorrectly classified as non-morbid. This classification can help to identify disease-causing genes among multiple candidates.},
author = {Fyodor Kondrashov and Ogurtsov, Aleksey Yu and Kondrashov, Alexey S},
journal = {Nucleic Acids Research},
number = {5},
pages = {1731 -- 1737},
publisher = {Oxford University Press},
title = {{Bioinformatical assay of human gene morbidity}},
doi = {10.1093/nar/gkh330},
volume = {32},
year = {2004},
}
@article{875,
abstract = {The dominance of wild-type alleles and the concomitant recessivity of deleterious mutant alleles might have evolved by natural selection or could be a by-product of the molecular and physiological mechanisms of gene action. We compared the properties of human haplosufficient genes, whose wild-type alleles are dominant over loss-of-function alleles, with haploinsufficient (recessive wild-type) genes, which produce an abnormal phenotype when heterozygous for a loss-of-function allele. The fraction of haplosufficient genes is the highest among the genes that encode enzymes, which is best compatible with the physiological theory. Haploinsufficient genes, on average, have more paralogs than haplosufficient genes, supporting the idea that gene dosage could be important for the initial fixation of duplications. Thus, haplo(in)sufficiency of a gene and its propensity for duplication might have a common evolutionary basis.},
author = {Fyodor Kondrashov and Koonin, Eugene V},
journal = {Trends in Genetics},
number = {7},
pages = {287 -- 291},
publisher = {Elsevier},
title = {{A common framework for understanding the origin of genetic dominance and evolutionary fates of gene duplications}},
doi = {10.1016/j.tig.2004.05.001},
volume = {20},
year = {2004},
}
@article{889,
abstract = {The function of protein and RNA molecules depends on complex epistatic interactions between sites. Therefore, the deleterious effect of a mutation can be suppressed by a compensatory second-site substitution. In relating a list of 86 pathogenic mutations in human IRNAs encoded by mitochondrial genes to the sequences of their mammalian orthologs, we noted that 52 pathogenic mutations were present in normal tRNAs of one or several nonhuman mammals. We found at least five mechanisms of compensation for 32 pathogenic mutations that destroyed a Watson-Crick pair in one of the four tRNA stems: restoration of the affected Watson-Crick interaction (25 cases), strengthening of another pair (4 cases), creation of a new pair (8 cases), changes of multiple interactions in the affected stem (11 cases) and changes involving the interaction between the loop and stem structures (3 cases). A pathogenic mutation and its compensating substitution are fixed in a lineage in rapid succession, and often a compensatory interaction evolves convergently in different clades. At least 10%, and perhaps as many as 50%, of all nucleotide substitutions in evolving mammalian (RNAs participate in such interactions, indicating that the evolution of tRNAs proceeds along highly epistatic fitness ridges.},
author = {Kern, Andrew D and Fyodor Kondrashov},
journal = {Nature Genetics},
number = {11},
pages = {1207 -- 1212},
publisher = {Nature Publishing Group},
title = {{Mechanisms and convergence of compensatory evolution in mammalian mitochondrial tRNAs}},
doi = {10.1038/ng1451},
volume = {36},
year = {2004},
}
@article{898,
abstract = {New alleles become fixed owing to random drift of nearly neutral mutations or to positive selection of substantially advantageous mutations. After decades of debate, the fraction of fixations driven by selection remains uncertain. Within 9,390 genes, we analysed 28,196 codons at which rat and mouse differ from each other at two nucleotide sites and 1,982 codons with three differences. At codons where rat-mouse divergence involved two non-synonymous substitutions, both of them occurred in the same lineage, either rat or mouse, in 64% of cases; however, independent substitutions would occur in the same lineage with a probability of only 50%. All three non-synonymous substitutions occurred in the same lineage for 46% of codons, instead of the 25% expected. Furthermore, comparison of 12 pairs of prokaryotic genomes also shows clumping of multiple non-synonymous substitutions in the same lineage. This pattern cannot be explained by correlated mutation or episodes of relaxed negative selection, but instead indicates that positive selection acts at many sites of rapid, successive amino acid replacement.},
author = {Bazykin, Georgii A and Fyodor Kondrashov and Ogurtsov, Aleksey Yu and Sunyaev, Shamil R and Kondrashov, Alexey S},
journal = {Nature},
number = {6991},
pages = {558 -- 562},
publisher = {Nature Publishing Group},
title = {{Positive selection at sites of multiple amino acid replacements since rat-mouse divergence}},
doi = {10.1038/nature02601},
volume = {429},
year = {2004},
}
@article{902,
abstract = {We compare the functional spectrum of protein evolution in two separate animal lineages with respect to two hypotheses: (1) rates of divergence are distributed similarly among functional classes within both lineages, indicating that selective pressure on the proteome is largely independent of organismic-level biological requirements; and (2) rates of divergence are distributed differently among functional classes within each lineage, indicating species-specific selective regimes impact genome-wide substitutional patterns. Integrating comparative genome sequence with data from tissue-specific expressed-sequence-tag (EST) libraries and detailed database annotations, we find a functional genomic signature of rapid evolution and selective constraint shared between mammalian and nematode lineages despite their extensive morphological and ecological differences and distant common ancestry. In both phyla, we find evidence of accelerated evolution among components of molecular systems involved in coevolutionary change. In mammals, lineage-specific fast evolving genes include those involved in reproduction, immunity, and possibly, maternal-fetal conflict. Likelihood ratio tests provide evidence for positive selection in these rapidly evolving functional categories in mammals. In contrast, slowly evolving genes, in terms of amino acid or insertion/deletion (indel) change, in both phyla are involved in core molecular processes such as transcription, translation, and protein transport. Thus, strong purifying selection appears to act on the same core cellular processes in both mammalian and nematode lineages, whereas positive and/or relaxed selection acts on different biological processes in each lineage.},
author = {Castillo-Davis, Cristian I and Fyodor Kondrashov and Hartl, Daniel L and Kulathinal, Rob J},
journal = {Genome Research},
number = {5},
pages = {802 -- 811},
publisher = {Cold Spring Harbor Laboratory Press},
title = {{The functional genomic distribution of protein divergence in two animal phyla: Coevolution, genomic conflict, and constraint}},
doi = {10.1101/gr.2195604},
volume = {14},
year = {2004},
}
@article{1456,
abstract = {We study the space of L2 harmonic forms on complete manifolds with metrics of fibred boundary or fibred cusp type. These metrics generalize the geometric structures at infinity of several different well-known classes of metrics, including asymptotically locally Euclidean manifolds, the (known types of) gravitational instantons, and also Poincaré metrics on ℚ-rank 1 ends of locally symmetric spaces and on the complements of smooth divisors in Kähler manifolds. The answer in all cases is given in terms of intersection cohomology of a stratified compactification of the manifold. The L2 signature formula implied by our result is closely related to the one proved by Dai and more generally by Vaillant and identifies Dai's τ-invariant directly in terms of intersection cohomology of differing perversities. This work is also closely related to a recent paper of Carron and the forthcoming paper of Cheeger and Dai. We apply our results to a number of examples, gravitational instantons among them, arising in predictions about L2 harmonic forms in duality theories in string theory.},
author = {Tamas Hausel and Hunsicker, Eugénie and Mazzeo, Rafe R},
journal = {Duke Mathematical Journal},
number = {3},
pages = {485 -- 548},
publisher = {Duke University Press},
title = {{Hodge cohomology of gravitational instantons}},
doi = {10.1215/S0012-7094-04-12233-X},
volume = {122},
year = {2004},
}
@article{1464,
abstract = {The moduli space of stable vector bundles on a Riemann surface is smooth when the rank and degree are coprime, and is diffeomorphic to the space of unitary connections of central constant curvature. A classic result of Newstead and Atiyah and Bott asserts that its rational cohomology ring is generated by the universal classes, that is, by the Kunneth components of the Chern classes of the universal bundle.
This paper studies the larger, non-compact moduli space of Higgs bundles, as introduced by Hitchin and Simpson, with values in the canonical bundle K. This is diffeomorphic to the space of all connections of central constant curvature, whether unitary or not. The main result of the paper is that, in the rank 2 case, the rational cohomology ring of this space is again generated by universal classes.
The spaces of Higgs bundles with values in K(n) for n > 0 turn out to be essential to the story. Indeed, we show that their direct limit has the homotopy type of the classifying space of the gauge group, and hence has cohomology generated by universal classes. 2000 Mathematics Subject Classification 14H60 (primary), 14D20, 14H81, 32Q55, 58D27 (secondary). },
author = {Tamas Hausel and Thaddeus, Michael},
journal = {Proceedings of the London Mathematical Society},
number = {3},
pages = {632 -- 658},
publisher = {Oxford University Press},
title = {{Generators for the cohomology ring of the moduli space of rank 2 higgs bundles}},
doi = {10.1112/S0024611503014618},
volume = {88},
year = {2004},
}
@article{3172,
abstract = {The simultaneous multiple volume (SMV) approach in navigator-gated MRI allows the use of the whole motion range or the entire scan time for the reconstruction of final images by simultaneously acquiring different image volumes at different motion states. The motion tolerance range for each volume is kept small, thus SMV substantially increases the scan efficiency of navigator methods while maintaining the effectiveness of motion suppression. This article reports a general implementation of the SMV approach using a multiprocessor scheduling algorithm. Each motion state is regarded as a processor and each volume is regarded as a job. An efficient scheduling that completes all jobs in minimal time is maintained even when the motion pattern changes. Initial experiments demonstrated that SMV significantly increased the scan efficiency of navigatorgated MRI.},
author = {Vladimir Kolmogorov and Nguyen, Thành D and Nuval, Anthony and Spincemaille, Pascal and Prince, Martin R and Zabih, Ramin and Wang, Yusu},
journal = {Magnetic Resonance in Medicine},
number = {2},
pages = {362 -- 367},
publisher = {Wiley-Blackwell},
title = {{Multiprocessor scheduling implementation of the simultaneous multiple volume SMV navigator method}},
doi = {10.1002/mrm.20162},
volume = {52},
year = {2004},
}
@article{3173,
abstract = {In the last few years, several new algorithms based on graph cuts have been developed to solve energy minimization problems in computer vision. Each of these techniques constructs a graph such that the minimum cut on the graph also minimizes the energy. Yet, because these graph constructions are complex and highly specific to a particular energy function, graph cuts have seen limited application to date. In this paper, we give a characterization of the energy functions that can be minimized by graph cuts. Our results are restricted to functions of binary variables. However, our work generalizes many previous constructions and is easily applicable to vision problems that involve large numbers of labels, such as stereo, motion, image restoration, and scene reconstruction. We give a precise characterization of what energy functions can be minimized using graph cuts, among the energy functions that can be written as a sum of terms containing three or fewer binary variables. We also provide a general-purpose construction to minimize such an energy function. Finally, we give a necessary condition for any energy function of binary variables to be minimized by graph cuts. Researchers who are considering the use of graph cuts to optimize a particular energy function can use our results to determine if this is possible and then follow our construction to create the appropriate graph. A software implementation is freely available.},
author = {Vladimir Kolmogorov and Zabih, Ramin},
journal = {IEEE Transactions on Pattern Analysis and Machine Intelligence},
number = {2},
pages = {147 -- 159},
publisher = {IEEE},
title = {{What energy functions can be minimized via graph cuts? }},
doi = {10.1109/TPAMI.2004.1262177},
volume = {26},
year = {2004},
}
@inproceedings{3177,
abstract = {Feature space clustering is a popular approach to image segmentation, in which a feature vector of local properties (such as intensity, texture or motion) is computed at each pixel. The feature space is then clustered, and each pixel is labeled with the cluster that contains its feature vector. A major limitation of this approach is that feature space clusters generally lack spatial coherence (i.e., they do not correspond to a compact grouping of pixels). In this paper, we propose a segmentation algorithm that operates simultaneously in feature space and in image space. We define an energy function over both a set of clusters and a labeling of pixels with clusters. In our framework, a pixel is labeled with a single cluster (rather than, for example, a distribution over clusters). Our energy function penalizes clusters that are a poor fit to the data in feature space, and also penalizes clusters whose pixels lack spatial coherence. The energy function can be efficiently minimized using graph cuts. Our algorithm can incorporate both parametric and non-parametric clustering methods. It can be applied to many optimization-based clustering methods, including k-means and k-medians, and can handle models which are very close in feature space. Preliminary results are presented on segmenting real and synthetic images, using both parametric and non-parametric clustering.},
author = {Zabih, Ramin and Vladimir Kolmogorov},
pages = {437 -- 444},
publisher = {IEEE},
title = {{Spatially coherent clustering using graph cuts}},
doi = {10.1109/CVPR.2004.1315196},
volume = {2},
year = {2004},
}
@article{3178,
abstract = {Minimum cut/maximum flow algorithms on graphs have emerged as an increasingly useful tool for exactor approximate energy minimization in low-level vision. The combinatorial optimization literature provides many min-cut/max-flow algorithms with different polynomial time complexity. Their practical efficiency, however, has to date been studied mainly outside the scope of computer vision. The goal of this paper is to provide an experimental comparison of the efficiency of min-cut/max flow algorithms for applications in vision. We compare the running times of several standard algorithms, as well as a new algorithm that we have recently developed. The algorithms we study include both Goldberg-Tarjan style "push -relabel" methods and algorithms based on Ford-Fulkerson style "augmenting paths." We benchmark these algorithms on a number of typical graphs in the contexts of image restoration, stereo, and segmentation. In many cases, our new algorithm works several times faster than any of the other methods, making near real-time performance possible. An implementation of our max-flow/min-cut algorithm is available upon request for research purposes.},
author = {Boykov, Yuri and Vladimir Kolmogorov},
journal = {IEEE Transactions on Pattern Analysis and Machine Intelligence},
number = {9},
pages = {1124 -- 1137},
publisher = {IEEE},
title = {{An experimental comparison of min-cut/max-flow algorithms for energy minimization in vision}},
doi = {10.1109/TPAMI.2004.60},
volume = {26},
year = {2004},
}
@inproceedings{3179,
abstract = {The problem of efficient, interactive foreground/background segmentation in still images is of great practical importance in image editing. Classical image segmentation tools use either texture (colour) information, e.g. Magic Wand, or edge (contrast) information, e.g. Intelligent Scissors. Recently, an approach based on optimization by graph-cut has been developed which successfully combines both types of information. In this paper we extend the graph-cut approach in three respects. First, we have developed a more powerful, iterative version of the optimisation. Secondly, the power of the iterative algorithm is used to simplify substantially the user interaction needed for a given quality of result. Thirdly, a robust algorithm for "border matting" has been developed to estimate simultaneously the alpha-matte around an object boundary and the colours of foreground pixels. We show that for moderately difficult examples the proposed method outperforms competitive tools.},
author = {Rother, Carsten and Vladimir Kolmogorov and Blake, Andrew},
number = {3},
pages = {309 -- 314},
publisher = {ACM},
title = {{"GrabCut" - Interactive foreground extraction using iterated graph cuts }},
doi = {10.1145/1015706.1015720},
volume = {23},
year = {2004},
}
@inproceedings{3208,
abstract = {A new technique for proving the adaptive indistinguishability of two systems, each composed of some component systems, is presented, using only the fact that corresponding component systems are non-adaptively indistinguishable. The main tool is the definition of a special monotone condition for a random system F, relative to another random system G, whose probability of occurring for a given distinguisher D is closely related to the distinguishing advantage ε of D for F and G, namely it is lower and upper bounded by ε and (1+ln1), respectively.
A concrete instantiation of this result shows that the cascade of two random permutations (with the second one inverted) is indistinguishable from a uniform random permutation by adaptive distinguishers which may query the system from both sides, assuming the components’ security only against non-adaptive one-sided distinguishers.
As applications we provide some results in various fields as almost k-wise independent probability spaces, decorrelation theory and computational indistinguishability (i.e., pseudo-randomness).},
author = {Maurer, Ueli M and Krzysztof Pietrzak},
pages = {410 -- 427},
publisher = {Springer},
title = {{Composition of random systems: When two weak make one strong}},
doi = {10.1007/978-3-540-24638-1_23},
volume = {2951},
year = {2004},
}
@article{3419,
abstract = {The folding and stability of transmembrane proteins is a fundamental and unsolved biological problem. Here, single bacteriorhodopsin molecules were mechanically unfolded from native purple membranes using atomic force microscopy and force spectroscopy. The energy landscape of individual transmembrane α helices and polypeptide loops was mapped by monitoring the pulling speed dependence of the unfolding forces and applying Monte Carlo simulations. Single helices formed independently stable units stabilized by a single potential barrier. Mechanical unfolding of the helices was triggered by 3.9–7.7 Å extension, while natural unfolding rates were of the order of 10−3 s−1. Besides acting as individually stable units, helices associated pairwise, establishing a collective potential barrier. The unfolding pathways of individual proteins reflect distinct pulling speed-dependent unfolding routes in their energy landscapes. These observations support the two-stage model of membrane protein folding in which α helices insert into the membrane as stable units and then assemble into the functional protein.},
author = {Harald Janovjak and Struckmeier, Jens and Hubain, Maurice and Kessler, Max and Kedrov, Alexej and Mueller, Daniel J},
journal = {Structure},
number = {5},
pages = {871 -- 879},
publisher = {Cell Press},
title = {{Probing the energy landscape of the membrane protein bacteriorhodopsin}},
doi = {10.1016/j.str.2004.03.016},
volume = {12},
year = {2004},
}
@article{3420,
abstract = {Single-molecule force-spectroscopy was employed to unfold and refold single sodium-proton antiporters (NhaA) of Escherichia coli from membrane patches. Although transmembrane α-helices and extracellular polypeptide loops exhibited sufficient stability to individually establish potential barriers against unfolding, two helices predominantly unfolded pairwise, thereby acting as one structural unit. Many of the potential barriers were detected unfolding NhaA either from the C-terminal or the N-terminal end. It was found that some molecular interactions stabilizing secondary structural elements were directional, while others were not. Additionally, some interactions appeared to occur between the secondary structural elements. After unfolding ten of the 12 helices, the extracted polypeptide was allowed to refold back into the membrane. After five seconds, the refolded polypeptide established all secondary structure elements of the native protein. One helical pair showed a characteristic spring like “snap in” into its folded conformation, while the refolding process of other helices was not detected in particular. Additionally, individual helices required characteristic periods of time to fold. Correlating these results with the primary structure of NhaA allowed us to obtain the first insights into how potential barriers establish and determine the folding kinetics of the secondary structure elements.},
author = {Kedrov, Alexej and Ziegler, Christine and Harald Janovjak and Kühlbrandt, Werner and Mueller, Daniel J},
journal = {Journal of Molecular Biology},
number = {5},
pages = {1143 -- 1152},
publisher = {Elsevier},
title = {{Controlled unfolding and refolding of a single sodium/proton antiporter using atomic force microscopy}},
doi = {10.1016/j.jmb.2004.05.026},
volume = {340},
year = {2004},
}
@inbook{3574,
author = {Herbert Edelsbrunner},
booktitle = {Handbook of Discrete and Computational Geometry},
pages = {1395 -- 1412},
publisher = {CRC Press},
title = {{Biological applications of computational topology}},
year = {2004},
}
@inbook{3575,
abstract = {The Jacobi set of two Morse functions defined on a common - manifold is the set of critical points of the restrictions of one func- tion to the level sets of the other function. Equivalently, it is the set of points where the gradients of the functions are parallel. For a generic pair of Morse functions, the Jacobi set is a smoothly embed- ded 1-manifold. We give a polynomial-time algorithm that com- putes the piecewise linear analog of the Jacobi set for functions specified at the vertices of a triangulation, and we generalize all results to more than two but at most Morse functions.},
author = {Herbert Edelsbrunner and Harer, John},
booktitle = {Foundations of Computational Mathematics},
pages = {37 -- 57},
publisher = {Springer},
title = {{Jacobi sets of multiple Morse functions}},
doi = {10.1017/CBO9781139106962.003},
volume = {312},
year = {2004},
}
@misc{3595,
abstract = {Genome sizes vary enormously. This variation in DNA content correlates with effective population size, suggesting that deleterious additions to the genome can accumulate in small populations. On this view, the increased complexity of biological functions associated with large genomes partly reflects evolutionary degeneration.},
author = {Charlesworth, Brian and Nicholas Barton},
booktitle = {Current Biology},
number = {6},
pages = {R233 -- R235},
publisher = {Cell Press},
title = {{Genome size: Does bigger mean worse?}},
doi = {10.1016/j.cub.2004.02.054},
volume = {14},
year = {2004},
}
@article{3614,
abstract = {We analyze the changes in the mean and variance components of a quantitative trait caused by changes in allele frequencies, concentrating on the effects of genetic drift. We use a general representation of epistasis and dominance that allows an arbitrary relation between genotype and phenotype for any number of diallelic loci. We assume initial and final Hardy-Weinberg and linkage equilibrium in our analyses of drift-induced changes. Random drift generates transient linkage disequilibria that cause correlations between allele frequency fluctuations at different loci. However, we show that these have negligible effects, at least for interactions among small numbers of loci. Our analyses are based on diffusion approximations that summarize the effects of drift in terms of F, the inbreeding coefficient, interpreted as the expected proportional decrease in heterozygosity at each locus. For haploids, the variance of the trait mean after a population bottleneck is var(Δz̄) =inline imagewhere n is the number of loci contributing to the trait variance, VA(1)=VA is the additive genetic variance, and VA(k) is the kth-order additive epistatic variance. The expected additive genetic variance after the bottleneck, denoted (V*A), is closely related to var(Δz̄); (V*A) (1 –F)inline imageThus, epistasis inflates the expected additive variance above VA(1 –F), the expectation under additivity. For haploids (and diploids without dominance), the expected value of every variance component is inflated by the existence of higher order interactions (e.g., third-order epistasis inflates (V*AA)). This is not true in general with diploidy, because dominance alone can reduce (V*A) below VA(1 –F) (e.g., when dominant alleles are rare). Without dominance, diploidy produces simple expressions: var(Δz̄)=inline image=1 (2F) kVA(k) and (V*A) = (1 –F)inline imagek(2F)k-1VA(k) With dominance (and even without epistasis), var(Δz̄)and (V*A) no longer depend solely on the variance components in the base population. For small F, the expected additive variance simplifies to (V*A)(1 –F) VA+ 4FVAA+2FVD+2FCAD, where CAD is a sum of two terms describing covariances between additive effects and dominance and additive × dominance interactions. Whether population bottlenecks lead to expected increases in additive variance depends primarily on the ratio of nonadditive to additive genetic variance in the base population, but dominance precludes simple predictions based solely on variance components. We illustrate these results using a model in which genotypic values are drawn at random, allowing extreme and erratic epistatic interactions. Although our analyses clarify the conditions under which drift is expected to increase VA, we question the evolutionary importance of such increases.},
author = {Nicholas Barton and Turelli, Michael},
journal = {Evolution; International Journal of Organic Evolution},
number = {10},
pages = {2111 -- 2132},
publisher = {Wiley-Blackwell},
title = {{Effects of allele frequency changes on variance components under a general model of epistasis}},
doi = {10.1111/j.0014-3820.2004.tb01591.x},
volume = {58},
year = {2004},
}
@article{3615,
abstract = {We investigate three alternative selection-based scenarios proposed to maintain polygenic variation: pleiotropic balancing selection, G x E interactions (with spatial or temporal variation in allelic effects), and sex-dependent allelic effects. Each analysis assumes an additive polygenic trait with n diallelic loci under stabilizing selection. We allow loci to have different effects and consider equilibria at which the population mean departs from the stabilizing-selection optimum. Under weak selection, each model produces essentially identical, approximate allele-frequency dynamics. Variation is maintained under pleiotropic balancing selection only at loci for which the strength of balancing selection exceeds the effective strength of stabilizing selection. In addition, for all models, polymorphism requires that the population mean be close enough to the optimum that directional selection does not overwhelm balancing selection. This balance allows many simultaneously stable equilibria, and we explore their properties numerically. Both spatial and temporal G x E can maintain variation at loci for which the coefficient of variation (across environments) of the effect of a substitution exceeds a critical value greater than one. The critical value depends on the correlation between substitution effects at different loci. For large positive correlations (e.g., ρ2ij > 3/4), even extreme fluctuations in allelic effects cannot maintain variation. Surprisingly, this constraint on correlations implies that sex-dependent allelic effects cannot maintain polygenic variation. We present numerical results that support our analytical approximations and discuss our results in connection to relevant data and alternative variance-maintaining mechanisms.},
author = {Turelli, Michael and Nicholas Barton},
journal = {Genetics},
number = {2},
pages = {1053 -- 1079},
publisher = {Genetics Society of America},
title = {{Polygenic variation maintained by balancing selection: pleiotropy, sex-dependent allelic effects and GxE interactions}},
doi = {10.1534/genetics.166.2.1053},
volume = {166},
year = {2004},
}
@misc{3616,
author = {Nicholas Barton},
booktitle = {Current Biology},
number = {15},
pages = {R603 -- R604},
publisher = {Cell Press},
title = {{Speciation: Why, how, where and when?}},
doi = {10.1016/j.cub.2004.07.037},
volume = {14},
year = {2004},
}
@article{3617,
abstract = {The coalescent process can describe the effects of selection at linked loci only if selection is so strong that genotype frequencies evolve deterministically. Here, we develop methods proposed by Kaplan, Darden, and Hudson to find the effects of weak selection. We show that the overall effect is given by an extension to Price's equation: the change in properties such as moments of coalescence times is equal to the covariance between those properties and the fitness of the sample of genes. The distribution of coalescence times differs substantially between allelic classes, even in the absence of selection. However, the average coalescence time between randomly chosen genes is insensitive to the current allele frequency and is affected significantly by purifying selection only if deleterious mutations are common and selection is strong (i.e., the product of population size and selection coefficient, Ns > 3). Balancing selection increases mean coalescence times, but the effect becomes large only when mutation rates between allelic classes are low and when selection is extremely strong. Our analysis supports previous simulations that show that selection has surprisingly little effect on genealogies. Moreover, small fluctuations in allele frequency due to random drift can greatly reduce any such effects. This will make it difficult to detect the action of selection from neutral variation alone.},
author = {Nicholas Barton and Etheridge, Alison M},
journal = {Genetics},
number = {2},
pages = {1115 -- 1131},
publisher = {Genetics Society of America},
title = {{The effect of selection on genealogies}},
doi = {10.1534/genetics.166.2.1115},
volume = {166},
year = {2004},
}
@inproceedings{3688,
abstract = {Capturing images of documents using handheld digital cameras has a variety of applications in academia, research, knowledge management, retail, and office settings. The ultimate goal of such systems is to achieve image quality comparable to that currently achieved with flatbed scanners even for curved, warped, or curled pages. This can be achieved by high-accuracy 3D modeling of the page surface, followed by a "flattening" of the surface. A number of previous systems have either assumed only perspective distortions, or used techniques like structured lighting, shading, or side-imaging for obtaining 3D shape. This paper describes a system for handheld camera-based document capture using general purpose stereo vision methods followed by a new document dewarping technique. Examples of shape modeling and dewarping of book images is shown.},
author = {Ulges, Adrian and Christoph Lampert and Breuel,Thomas M},
pages = {198 -- 200},
publisher = {ACM},
title = {{Document capture using stereo vision}},
doi = {10.1145/1030397.1030434},
year = {2004},
}
@article{3805,
abstract = {The operation of neuronal networks crucially depends on a fast time course of signaling in inhibitory interneurons. Synapses that excite interneurons generate fast currents, owing to the expression of glutamate receptors of specific subunit composition. Interneurons generate brief action potentials in response to transient synaptic activation and discharge repetitively at very high frequencies during sustained stimulation. The ability to generate short-duration action potentials at high frequencies depends on the expression of specific voltage-gated K+ channels. Factors facilitating fast action potential initiation following synaptic excitation include depolarized interneuron resting potential, subthreshold conductances and active dendrites. Finally, GABA release at interneuron output synapses is rapid and highly synchronized, leading to a faster inhibition in postsynaptic interneurons than in principal cells. Thus, the expression of distinct transmitter receptors and voltage-gated ion channels ensures that interneurons operate with high speed and temporal precision.},
author = {Peter Jonas and Bischofberger, Josef and Fricker, Desdemona and Miles, Richard},
journal = {Trends in Neurosciences},
number = {1},
pages = {30 -- 40},
publisher = {Elsevier},
title = {{Interneuron Diversity series: Fast in, fast out--temporal and spatial signal processing in hippocampal interneurons}},
doi = {doi:10.1016/j.tins.2003.10.010},
volume = {27},
year = {2004},
}
@article{3807,
abstract = {The time course of Mg(2+) block and unblock of NMDA receptors (NMDARs) determines the extent they are activated by depolarization. Here, we directly measure the rate of NMDAR channel opening in response to depolarizations at different times after brief (1 ms) and sustained (4.6 s) applications of glutamate to nucleated patches from neocortical pyramidal neurons. The kinetics of Mg(2+) unblock were found to be non-instantaneous and complex, consisting of a prominent fast component (time constant approximately 100 micros) and slower components (time constants 4 and approximately 300 ms), the relative amplitudes of which depended on the timing of the depolarizing pulse. Fitting a kinetic model to these data indicated that Mg(2+) not only blocks the NMDAR channel, but reduces both the open probability and affinity for glutamate, while enhancing desensitization. These effects slow the rate of NMDAR channel opening in response to depolarization in a time-dependent manner such that the slower components of Mg(2+) unblock are enhanced during depolarizations at later times after glutamate application. One physiological consequence of this is that brief depolarizations occurring earlier in time after glutamate application are better able to open NMDAR channels. This finding has important implications for spike-timing-dependent synaptic plasticity (STDP), where the precise (millisecond) timing of action potentials relative to synaptic inputs determines the magnitude and sign of changes in synaptic strength. Indeed, we find that STDP timing curves of NMDAR channel activation elicited by realistic dendritic action potential waveforms are narrower than expected assuming instantaneous Mg(2+) unblock, indicating that slow Mg(2+) unblock of NMDAR channels makes the STDP timing window more precise.},
author = {Kampa, Bjorn M and Clements, John and Peter Jonas and Stuart, Greg J},
journal = {Journal of Physiology},
number = {Pt 2},
pages = {337 -- 45},
publisher = {Wiley-Blackwell},
title = {{Kinetics of Mg(2+) unblock of NMDA receptors: implications for spike-timing dependent synaptic plasticity}},
doi = {10.1113/jphysiol.2003.058842 },
volume = {556},
year = {2004},
}
@article{3809,
abstract = {Neural stem cells in various regions of the vertebrate brain continuously generate neurons throughout life. In the mammalian hippocampus, a region important for spatial and episodic memory, thousands of new granule cells are produced per day, with the exact number depending on environmental conditions and physical exercise. The survival of these neurons is improved by learning and conversely learning may be promoted by neurogenesis. Although it has been suggested that newly generated neurons may have specific properties to facilitate learning, the cellular and synaptic mechanisms of plasticity in these neurons are largely unknown. Here we show that young granule cells in the adult hippocampus differ substantially from mature granule cells in both active and passive membrane properties. In young neurons, T-type Ca2+ channels can generate isolated Ca2+ spikes and boost fast Na+ action potentials, contributing to the induction of synaptic plasticity. Associative long-term potentiation can be induced more easily in young neurons than in mature neurons under identical conditions. Thus, newly generated neurons express unique mechanisms to facilitate synaptic plasticity, which may be important for the formation of new memories.},
author = {Schmidt-Hieber, Christoph and Peter Jonas and Bischofberger, Josef},
journal = {Nature},
number = {6988},
pages = {184 -- 7},
publisher = {Nature Publishing Group},
title = {{Enhanced synaptic plasticity in newly generated granule cells of the adult hippocampus}},
doi = {10.1038/nature02553},
volume = {429},
year = {2004},
}
@article{3810,
abstract = {Voltage-gated potassium (Kv) channels control action potential repolarization, interspike membrane potential, and action potential frequency in excitable cells. It is thought that the combinatorial association between distinct alpha and beta subunits determines whether Kv channels function as non-inactivating delayed rectifiers or as rapidly inactivating A-type channels. We show that membrane lipids can convert A-type channels into delayed rectifiers and vice versa. Phosphoinositides remove N-type inactivation from A-type channels by immobilizing the inactivation domains. Conversely, arachidonic acid and its amide anandamide endow delayed rectifiers with rapid voltage-dependent inactivation. The bidirectional control of Kv channel gating by lipids may provide a mechanism for the dynamic regulation of electrical signaling in the nervous system.},
author = {Oliver, Dominik and Lien, Cheng-Chang and Soom, Malle and Baukrowitz, Thomas and Peter Jonas and Fakler, Bernd},
journal = {Science},
number = {5668},
pages = {265 -- 70},
publisher = {American Association for the Advancement of Science},
title = {{Functional conversion between A-type and delayed rectifier K+ channels by membrane lipids}},
doi = {10.1126/science.1094113},
volume = {304},
year = {2004},
}
@inproceedings{3894,
abstract = {We study infinite stochastic games played by n-players on a finite graph with goals given by sets of infinite traces. The games are stochastic (each player simultaneously and independently chooses an action at each round, and the next state is determined by a probability distribution depending on the current state and the chosen actions), infinite (the game continues for an infinite number of rounds), nonzero sum (the players' goals are not necessarily conflicting), and undiscounted. We show that if each player has a reachability objective, that is, if the goal for each player i is to visit some subset R-i of the states, then there exists an epsilon-Nash equilibrium in memoryless strategies, for every epsilon > 0. However, exact Nash equilibria need not exist. We study the complexity of finding such Nash equilibria, and show that the payoff of some epsilon-Nash equilibrium in memoryless strategies can be epsilon-approximated in NP. We study the important subclass of n-player turn-based probabilistic games, where at each state at most one player has a nontrivial choice of moves. For turn-based probabilistic games, we show the existence of epsilon-Nash equilibria in pure strategies for games where the objective of player i is a Borel set B-i of infinite traces. However, exact Nash equilibria may not exist. For the special case of omega-regular objectives, we show exact Nash equilibria exist, and can be computed in NP when the omega-regular objectives are expressed as parity objectives.},
author = {Krishnendu Chatterjee and Majumdar, Ritankar S and Jurdziński, Marcin},
pages = {26 -- 40},
publisher = {Springer},
title = {{On Nash equilibria in stochastic games}},
doi = {10.1007/978-3-540-30124-0_6},
volume = {3210},
year = {2004},
}
@inproceedings{3895,
abstract = {In 2-player non-zero-sum games, Nash equilibria capture the options for rational behavior if each player attempts to maximize her payoff. In contrast to classical game theory, we consider lexicographic objectives: first, each player tries to maximize her own payoff, and then, the player tries to minimize the opponent's payoff. Such objectives arise naturally in the verification of systems with multiple components. There, instead of proving that each component satisfies its specification no matter how the other components behave, it often suffices to prove that each component satisfies its specification provided that the other components satisfy their specifications. We say that a Nash equilibrium is secure if it is an equilibrium with respect to the lexicographic objectives of both players. We prove that in graph games with Borel objectives, which include the games that arise in verification, there may be several Nash equilibria, but there is always a unique maximal payoff profile of secure equilibria. We show how this equilibrium can be computed in the case of omega-regular objectives, and we characterize the memory requirements of strategies that achieve the equilibrium.},
author = {Krishnendu Chatterjee and Thomas Henzinger and Jurdziński, Marcin},
pages = {160 -- 169},
publisher = {IEEE},
title = {{Games with secure equilibria}},
doi = {10.1109/LICS.2004.1319610},
year = {2004},
}
@inbook{3587,
author = {Ulrich, Florian and Heisenberg, Carl-Philipp J},
booktitle = {Fish development and genetics : the zebrafish and medaka models},
editor = {Korzh, Vladimir and Gong, Zhiyuan},
pages = {39 -- 86},
publisher = {World Scientific Publishing},
title = {{Gastrulation in zebrafish}},
volume = {2},
year = {2004},
}
@article{4172,
abstract = {During vertebrate gastrulation, a relatively limited number of blastodermal cells undergoes a stereotypical set of cellular movements that leads to formation of the three germ layers: ectoderm, mesoderm and endoderm. Gastrulation, therefore, provides a unique developmental system in which to study cell movements in vivo in a fairly simple cellular context. Recent advances have been made in elucidating the cellular and molecular mechanisms that underlie cell movements during zebrafish gastrulation. These findings can be compared with observations made in other model systems to identify potential general mechanisms of cell migration during development.},
author = {Montero, Juan and Heisenberg, Carl-Philipp J},
journal = {Trends in Cell Biology},
number = {11},
pages = {620 -- 627},
publisher = {Cell Press},
title = {{Gastrulation dynamics: cells move into focus}},
doi = {10.1016/j.tcb.2004.09.008},
volume = {14},
year = {2004},
}
@article{4238,
abstract = {The dynamical basis of tumoral growth has been controversial. Many models have been proposed to explain cancer development. The descriptions employ exponential, potential, logistic or Gompertzian growth laws. Some of these models are concerned with the interaction between cancer and the immunological, system. Among other properties, these models are concerned with the microscopic behavior of tumors and the emergence of cancer. We propose a modification of a previous model by Stepanova, which describes the specific immunological response against cancer. The modification consists of the substitution of a Gompertian law for the exponential rate used for tumoral growth. This modification is motivated by the numerous works confirming that Gompertz's equation correctly describes solid tumor growth. The modified model predicts that near zero, tumors always tend to grow. Immunological contraposition never suffices to induce a complete regression of the tumor. Instead, a stable microscopic equilibrium between cancer and immunological activity can be attained. In other words, our model predicts that the theory of immune surveillance is plausible. A macroscopic equilibrium in which the system develops cancer is also possible. In this case, immunological activity is depleted. This is consistent with the phenomena of cancer tolerance. Both equilibrium points can coexist or can exist without the other. In all cases the fixed point at zero tumor size is unstable. Since immunity cannot induce a complete tumor regression, a therapy is required. We include constant-dose therapies and show that they are insufficient. Final levels of immunocompetent cells and tumoral cells are finite, thus post-treatment regrowth of the tumor is certain. We also evaluate late-intensification therapies which are successful. They induce an asymptotic regression to zero tumor size. Immune response is also suppressed by the therapy, and thus plays a negligible role in the remission. We conclude that treatment evaluation should be successful without taking into account immunological effects. (C) 2003 Elsevier Ltd. All rights reserved.},
author = {de Vladar, Harold and González, J.},
journal = {Journal of Theoretical Biology},
number = {3},
pages = {335 -- 348},
publisher = {Elsevier},
title = {{Dynamic response of cancer under the influence of immunological activity and therapy}},
doi = {3801},
volume = {227},
year = {2004},
}
@article{4224,
abstract = {Developing cells acquire positional information by reading the graded distribution of morphogens. In Drosophila, the Dpp morphogen forms a long-range concentration gradient by spreading from a restricted source in the developing wing. It has been assumed that Dpp spreads by extracellular diffusion. Under this assumption, the main role of endocytosis in gradient formation is to downregulate receptors at the cell surface. These surface receptors bind to the ligand and thereby interfere with its long-range movement. Recent experiments indicate that Dpp spreading is mediated by Dynamin-dependent endocytosis in the target tissue, suggesting that extracellular diffusion alone cannot account for Dpp dispersal. Here, we perform a theoretical study of a model for morphogen spreading based on extracellular diffusion, which takes into account receptor binding and trafficking. We compare profiles of ligand and surface receptors obtained in this model with experimental data. To this end, we monitored directly the pool of surface receptors and extracellular Dpp with specific antibodies. We conclude that current models considering pure extracellular diffusion cannot explain the observed role of endocytosis during Dpp long-range movement.},
author = {Kruse, Karsten and Pantazis, Periklis and Bollenbach, Mark Tobias and Julicher, Frank and Gonzalez Gaitan, Marcos},
journal = {Development},
number = {19},
pages = {4843 -- 4856},
publisher = {Company of Biologists},
title = {{Dpp gradient formation by dynamin-dependent endocytosis: receptor trafficking and the diffusion model}},
doi = {10.1242/dev.01335},
volume = {131},
year = {2004},
}
@phdthesis{4236,
author = {de Vladar, Harold},
publisher = {Centro de estudios avazados, IVIC},
title = {{Métodos no lineales y sus aplicaciones en dinámicas aleatorias de poblaciones celulares}},
doi = {3810},
year = {2004},
}
@phdthesis{4424,
abstract = {The enormous cost and ubiquity of software errors necessitates the need for techniques and tools that can precisely analyze large systems and prove that they meet given specifications, or if they don't, return counterexample behaviors showing how the system fails. Recent advances in model checking, decision procedures, program analysis and type systems, and a shift of focus to partial specifications common to several systems (e.g., memory safety and race freedom) have resulted in several practical verification methods. However, these methods are either precise or they are scalable, depending on whether they track the values of variables or only a fixed small set of dataflow facts (e.g., types), and are usually insufficient for precisely verifying large programs.
We describe a new technique called Lazy Abstraction (LA) which achieves both precision and scalability by localizing the use of precise information. LA automatically builds, explores and refines a single abstract model of the program in a way that different parts of the model exhibit different degrees of precision, namely just enough to verify the desired property. The algorithm automatically mines the information required by partitioning mechanical proofs of unsatisfiability of spurious counterexamples into Craig Interpolants. For multithreaded systems, we give a new technique based on analyzing the behavior of a single thread executing in a context which is an abstraction of the other (arbitrarily many) threads. We define novel context models and show how to automatically infer them and analyze the full system (thread + context) using LA.
LA is implemented in BLAST. We have run BLAST on Windows and Linux Device Drivers to verify API conformance properties, and have used it to find (or guarantee the absence of) data races in multithreaded Networked Embedded Systems (NESC) applications. BLAST is able to prove the absence of races in several cases where earlier methods, which depend on lock-based synchronization, fail.},
author = {Jhala, Ranjit},
pages = {1 -- 165},
publisher = {University of California, Berkeley},
title = {{Program verification by lazy abstraction}},
year = {2004},
}
@article{8517,
abstract = {We consider the evolution of a connected set on the plane carried by a space periodic incompressible stochastic flow. While for almost every realization of the stochastic flow at time t most of the particles are at a distance of order equation image away from the origin, there is a measure zero set of points that escape to infinity at the linear rate. We study the set of points visited by the original set by time t and show that such a set, when scaled down by the factor of t, has a limiting nonrandom shape.},
author = {Dolgopyat, Dmitry and Kaloshin, Vadim and Koralov, Leonid},
issn = {0010-3640},
journal = {Communications on Pure and Applied Mathematics},
keywords = {Applied Mathematics, General Mathematics},
number = {9},
pages = {1127--1158},
publisher = {Wiley},
title = {{A limit shape theorem for periodic stochastic dispersion}},
doi = {10.1002/cpa.20032},
volume = {57},
year = {2004},
}
@article{8518,
author = {Koralov, Leonid and Kaloshin, Vadim and Dolgopyat, Dmitry},
issn = {0091-1798},
journal = {The Annals of Probability},
number = {1A},
pages = {1--27},
publisher = {Institute of Mathematical Statistics},
title = {{Sample path properties of the stochastic flows}},
doi = {10.1214/aop/1078415827},
volume = {32},
year = {2004},
}
@article{205,
author = {Timothy Browning},
journal = {Acta Arithmetica},
number = {3},
pages = {275 -- 295},
publisher = {Instytut Matematyczny},
title = {{Counting rational points on cubic and quartic surfaces}},
doi = {10.4064/aa108-3-7},
volume = {108},
year = {2003},
}
@article{206,
abstract = {Let T ⊂ ℙ 4 be a non-singular threefold of degree at least four. Then we show that the number of points in T(ℚ), with height at most B, is o(B 3) or B → ∞.},
author = {Timothy Browning},
journal = {Quarterly Journal of Mathematics},
number = {1},
pages = {33 -- 39},
publisher = {Unknown},
title = {{A note on the distribution of rational points on threefolds}},
doi = {10.1093/qjmath/54.1.33},
volume = {54},
year = {2003},
}
@article{207,
author = {Browning, Timothy D},
journal = {Mathematical Proceedings of the Cambridge Philosophical Society},
number = {3},
pages = {385 -- 395},
publisher = {Cambridge University Press},
title = {{Sums of four biquadrates}},
doi = {10.1017/S0305004102006382},
volume = {134},
year = {2003},
}
@article{208,
abstract = {For any ε > 0 and any diagonal quadratic form Q ∈ ℤ[x 1, x 2, x 3, x 4] with a square-free discriminant of modulus Δ Q ≠ 0, we establish the uniform estimate ≪ε B 3/2+ε + B 2+ε/Δ Q 1/6 for the number of rational points of height at most B lying in the projective surface Q = 0.},
author = {Timothy Browning},
journal = {Quarterly Journal of Mathematics},
number = {1},
pages = {11 -- 31},
publisher = {Oxford University Press},
title = {{Counting rational points on diagonal quadratic surfaces}},
doi = {10.1093/qjmath/54.1.11},
volume = {54},
year = {2003},
}
@inproceedings{2337,
author = {Lieb, Élliott H and Robert Seiringer},
editor = {Karpeshina, Yulia and Weikard, Rudi and Zeng, Yanni},
pages = {239 -- 250},
publisher = {American Mathematical Society},
title = {{Bose-Einstein condensation of dilute gases in traps }},
doi = {10.1090/conm/327/05818},
volume = {327},
year = {2003},
}