@article{333,
abstract = {We present a hybrid intercalation battery based on a sodium/magnesium (Na/Mg) dual salt electrolyte, metallic magnesium anode, and a cathode based on FeS2 nanocrystals (NCs). Compared to lithium or sodium, metallic magnesium anode is safer due to dendrite-free electroplating and offers extremely high volumetric (3833 mAh cm-3) and gravimetric capacities (2205 mAh g-1). Na-ion cathodes, FeS2 NCs in the present study, may serve as attractive alternatives to Mg-ion cathodes due to the higher voltage of operation and fast, highly reversible insertion of Na-ions. In this proof-of-concept study, electrochemical cycling of the Na/Mg hybrid battery was characterized by high rate capability, high Coulombic efficiency of 99.8%, and high energy density. In particular, with an average discharge voltage of ∼1.1 V and a cathodic capacity of 189 mAh g-1 at a current of 200 mA g-1, the presented Mg/FeS2 hybrid battery delivers energy densities of up to 210 Wh kg-1, comparable to commercial Li-ion batteries and approximately twice as high as state-of-the-art Mg-ion batteries based on Mo6S8 cathodes. Further significant gains in the energy density are expected from the development of Na/Mg electrolytes with a broader electrochemical stability window. Fully based on Earth-abundant elements, hybrid Na-Mg batteries are highly promising for large-scale stationary energy storage. },
author = {Walter, Marc and Kravchyk, Kostiantyn V and Ibanez, Maria and Kovalenko, Maksym V},
journal = {Chemistry of Materials},
number = {21},
pages = {7452 -- 7458},
publisher = {American Chemical Society},
title = {{Efficient and Inexpensive Sodium Magnesium Hybrid Battery}},
doi = {10.1021/acs.chemmater.5b03531},
volume = {27},
year = {2015},
}
@article{3585,
abstract = {We prove that the dual of the digital Voronoi diagram constructed by flooding the plane from the data points gives a geometrically and topologically correct dual triangulation. This provides the proof of correctness for
recently developed GPU algorithms that outperform traditional CPU algorithms for constructing two-dimensional
Delaunay triangulations.},
author = {Cao, Thanh and Edelsbrunner, Herbert and Tan, Tiow},
journal = {Computational Geometry: Theory and Applications},
number = {7},
pages = {507 -- 519},
publisher = {Elsevier},
title = {{Proof of correctness of the digital Delaunay triangulation algorithm}},
doi = {10.1016/j.comgeo.2015.04.001},
volume = {48},
year = {2015},
}
@article{388,
abstract = {We use ultrafast optical spectroscopy to observe binding of charged single-particle excitations (SE) in the magnetically frustrated Mott insulator Na2IrO3. Above the antiferromagnetic ordering temperature (TN) the system response is due to both Hubbard excitons (HE) and their constituent unpaired SE. The SE response becomes strongly suppressed immediately below TN. We argue that this increase in binding energy is due to a unique interplay between the frustrated Kitaev and the weak Heisenberg-type ordering term in the Hamiltonian, mediating an effective interaction between the spin-singlet SE. This interaction grows with distance causing the SE to become trapped in the HE, similar to quark confinement inside hadrons. This binding of charged particles, induced by magnetic ordering, is a result of a confinement-deconfinement transition of spin excitations. This observation provides evidence for spin liquid type behavior which is expected in Na2IrO3.},
author = {Alpichshe, Zhanybek and Mahmood, Fahad and Cao, Gang and Gedik, Nuh},
journal = {Physical Review Letters},
number = {1},
publisher = {American Physical Society},
title = {{Confinement deconfinement transition as an indication of spin liquid type behavior in Na2IrO3}},
doi = {10.1103/PhysRevLett.114.017203},
volume = {114},
year = {2015},
}
@article{477,
abstract = {Dendritic cells are potent antigen-presenting cells endowed with the unique ability to initiate adaptive immune responses upon inflammation. Inflammatory processes are often associated with an increased production of serotonin, which operates by activating specific receptors. However, the functional role of serotonin receptors in regulation of dendritic cell functions is poorly understood. Here, we demonstrate that expression of serotonin receptor 5-HT7 (5-HT7TR) as well as its downstream effector Cdc42 is upregulated in dendritic cells upon maturation. Although dendritic cell maturation was independent of 5-HT7TR, receptor stimulation affected dendritic cell morphology through Cdc42-mediated signaling. In addition, basal activity of 5-HT7TR was required for the proper expression of the chemokine receptor CCR7, which is a key factor that controls dendritic cell migration. Consistent with this, we observed that 5-HT7TR enhances chemotactic motility of dendritic cells in vitro by modulating their directionality and migration velocity. Accordingly, migration of dendritic cells in murine colon explants was abolished after pharmacological receptor inhibition. Our results indicate that there is a crucial role for 5-HT7TR-Cdc42-mediated signaling in the regulation of dendritic cell morphology and motility, suggesting that 5-HT7TR could be a new target for treatment of a variety of inflammatory and immune disorders.},
author = {Holst, Katrin and Guseva, Daria and Schindler, Susann and Sixt, Michael K and Braun, Armin and Chopra, Himpriya and Pabst, Oliver and Ponimaskin, Evgeni},
journal = {Journal of Cell Science},
number = {15},
pages = {2866 -- 2880},
publisher = {Company of Biologists},
title = {{The serotonin receptor 5-HT7R regulates the morphology and migratory properties of dendritic cells}},
doi = {10.1242/jcs.167999},
volume = {128},
year = {2015},
}
@article{5808,
author = {Biswas, Ranita and Bhowmick, Partha},
issn = {0178-2789},
journal = {The Visual Computer},
number = {6-8},
pages = {787--797},
publisher = {Springer Nature},
title = {{Layer the sphere}},
doi = {10.1007/s00371-015-1101-3},
volume = {31},
year = {2015},
}
@article{6736,
abstract = {Motivated by the significant performance gains which polar codes experience under successive cancellation list decoding, their scaling exponent is studied as a function of the list size. In particular, the error probability is fixed, and the tradeoff between the block length and back-off from capacity is analyzed. A lower bound is provided on the error probability under MAP decoding with list size L for any binary-input memoryless output-symmetric channel and for any class of linear codes such that their minimum distance is unbounded as the block length grows large. Then, it is shown that under MAP decoding, although the introduction of a list can significantly improve the involved constants, the scaling exponent itself, i.e., the speed at which capacity is approached, stays unaffected for any finite list size. In particular, this result applies to polar codes, since their minimum distance tends to infinity as the block length increases. A similar result is proved for genie-aided successive cancellation decoding when transmission takes place over the binary erasure channel, namely, the scaling exponent remains constant for any fixed number of helps from the genie. Note that since genie-aided successive cancellation decoding might be strictly worse than successive cancellation list decoding, the problem of establishing the scaling exponent of the latter remains open.},
author = {Mondelli, Marco and Hassani, Hamed and Urbanke, Rudiger},
journal = {IEEE Transactions on Information Theory},
number = {9},
pages = {4838--4851},
publisher = {IEEE},
title = {{Scaling exponent of list decoders with applications to polar codes}},
doi = {10.1109/tit.2015.2453315},
volume = {61},
year = {2015},
}
@article{7070,
abstract = {Torque magnetization measurements on YBa2Cu3Oy (YBCO) at doping y=6.67 (p=0.12), in dc fields (B) up to 33 T and temperatures down to 4.5 K, show that weak diamagnetism persists above the extrapolated irreversibility field Hirr(T=0)≈24 T. The differential susceptibility dM/dB, however, is more rapidly suppressed for B≳16 T than expected from the properties of the low field superconducting state, and saturates at a low value for fields B≳24 T. In addition, torque measurements on a p=0.11 YBCO crystal in pulsed field up to 65 T and temperatures down to 8 K show similar behavior, with no additional features at higher fields. We offer two candidate scenarios to explain these observations: (a) superconductivity survives but is heavily suppressed at high field by competition with charge-density-wave (CDW) order; (b) static superconductivity disappears near 24 T and is followed by a region of fluctuating superconductivity, which causes dM/dB to saturate at high field. The diamagnetic signal observed above 50 T for the p=0.11 crystal at 40 K and below may be caused by changes in the normal state susceptibility rather than bulk or fluctuating superconductivity. There will be orbital (Landau) diamagnetism from electron pockets and possibly a reduction in spin susceptibility caused by the stronger three-dimensional ordered CDW.},
author = {Yu, Jing Fei and Ramshaw, B. J. and Kokanović, I. and Modic, Kimberly A and Harrison, N. and Day, James and Liang, Ruixing and Hardy, W. N. and Bonn, D. A. and McCollam, A. and Julian, S. R. and Cooper, J. R.},
issn = {1098-0121},
journal = {Physical Review B},
number = {18},
publisher = {APS},
title = {{Magnetization of underdoped YBa2Cu3Oy above the irreversibility field}},
doi = {10.1103/physrevb.92.180509},
volume = {92},
year = {2015},
}
@article{802,
abstract = {Glycoinositolphosphoceramides (GIPCs) are complex sphingolipids present at the plasma membrane of various eukaryotes with the important exception of mammals. In fungi, these glycosphingolipids commonly contain an alpha-mannose residue (Man) linked at position 2 of the inositol. However, several pathogenic fungi additionally synthesize zwitterionic GIPCs carrying an alpha-glucosamine residue (GlcN) at this position. In the human pathogen Aspergillus fumigatus, the GlcNalpha1,2IPC core (where IPC is inositolphosphoceramide) is elongated to Manalpha1,3Manalpha1,6GlcNalpha1,2IPC, which is the most abundant GIPC synthesized by this fungus. In this study, we identified an A. fumigatus N-acetylglucosaminyltransferase, named GntA, and demonstrate its involvement in the initiation of zwitterionic GIPC biosynthesis. Targeted deletion of the gene encoding GntA in A. fumigatus resulted in complete absence of zwitterionic GIPC; a phenotype that could be reverted by episomal expression of GntA in the mutant. The N-acetylhexosaminyltransferase activity of GntA was substantiated by production of N-acetylhexosamine-IPC in the yeast Saccharomyces cerevisiae upon GntA expression. Using an in vitro assay, GntA was furthermore shown to use UDP-N-acetylglucosamine as donor substrate to generate a glycolipid product resistant to saponification and to digestion by phosphatidylinositol-phospholipase C as expected for GlcNAcalpha1,2IPC. Finally, as the enzymes involved in mannosylation of IPC, GntA was localized to the Golgi apparatus, the site of IPC synthesis.},
author = {Engel, Jakob and Schmalhorst, Philipp S and Kruger, Anke and Muller, Christina and Buettner, Falk and Routier, Françoise},
journal = {Glycobiology},
number = {12},
pages = {1423 -- 1430},
publisher = {Oxford University Press},
title = {{Characterization of an N-acetylglucosaminyltransferase involved in Aspergillus fumigatus zwitterionic glycoinositolphosphoceramide biosynthesis}},
doi = {10.1093/glycob/cwv059},
volume = {25},
year = {2015},
}
@inproceedings{782,
abstract = {In this work, we consider the following random process, mo- Tivated by the analysis of lock-free concurrent algorithms under high memory contention. In each round, a new scheduling step is allocated to one of n threads, according to a distribution p = (p1; p2; : : : ; pn), where thread i is scheduled with probability pi. When some thread first reaches a set threshold of executed steps, it registers a win, completing its current operation, and resets its step count to 1. At the same time, threads whose step count was close to the threshold also get reset because of the win, but to 0 steps, being penalized for almost winning. We are interested in two questions: how often does some thread complete an operation (system latency), and how often does a specific thread complete an operation (individual latency)? We provide asymptotically tight bounds for the system and individual latency of this general concurrency pattern, for arbitrary scheduling distributions p. Surprisingly, a sim- ple characterization exists: in expectation, the system will complete a new operation every Θ(1/p 2) steps, while thread i will complete a new operation every Θ(1/2=p i ) steps. The proof is interesting in its own right, as it requires a careful analysis of how the higher norms of the vector p inuence the thread step counts and latencies in this random process. Our result offers a simple connection between the scheduling distribution and the average performance of concurrent algorithms, which has several applications.},
author = {Alistarh, Dan and Sauerwald, Thomas and Vojnović, Milan},
pages = {251 -- 260},
publisher = {ACM},
title = {{Lock-Free algorithms under stochastic schedulers}},
doi = {10.1145/2767386.2767430},
volume = {2015-July},
year = {2015},
}
@article{814,
abstract = {Human immunodeficiency virus type 1 (HIV-1) assembly proceeds in two stages. First, the 55 kilodalton viral Gag polyprotein assembles into a hexameric protein lattice at the plasma membrane of the infected cell, inducing budding and release of an immature particle. Second, Gag is cleaved by the viral protease, leading to internal rearrangement of the virus into the mature, infectious form. Immature and mature HIV-1 particles are heterogeneous in size and morphology, preventing high-resolution analysis of their protein arrangement in situ by conventional structural biology methods. Here we apply cryo-electron tomography and sub-tomogram averaging methods to resolve the structure of the capsid lattice within intact immature HIV-1 particles at subnanometre resolution, allowing unambiguous positioning of all Î±-helices. The resulting model reveals tertiary and quaternary structural interactions that mediate HIV-1 assembly. Strikingly, these interactions differ from those predicted by the current model based on in vitro-assembled arrays of Gag-derived proteins from Mason-Pfizer monkey virus. To validate this difference, we solve the structure of the capsid lattice within intact immature Mason-Pfizer monkey virus particles. Comparison with the immature HIV-1 structure reveals that retroviral capsid proteins, while having conserved tertiary structures, adopt different quaternary arrangements during virus assembly. The approach demonstrated here should be applicable to determine structures of other proteins at subnanometre resolution within heterogeneous environments.},
author = {Florian Schur and Hagen, Wim J and Rumlová, Michaela and Ruml, Tomáš and Müller B and Kraüsslich, Hans Georg and Briggs, John A},
journal = {Nature},
number = {7535},
pages = {505 -- 508},
publisher = {Nature Publishing Group},
title = {{Structure of the immature HIV-1 capsid in intact virus particles at 8.8 Å resolution}},
doi = {10.1038/nature13838},
volume = {517},
year = {2015},
}
@article{1591,
abstract = {Auxin participates in a multitude of developmental processes, as well as responses to environmental cues. Compared with other plant hormones, auxin exhibits a unique property, as it undergoes directional, cell-to-cell transport facilitated by plasma membrane-localized transport proteins. Among them, a prominent role has been ascribed to the PIN family of auxin efflux facilitators. PIN proteins direct polar auxin transport on account of their asymmetric subcellular localizations. In this review, we provide an overview of the multiple developmental roles of PIN proteins, including the atypical endoplasmic reticulum-localized members of the family, and look at the family from an evolutionary perspective. Next, we cover the cell biological and molecular aspects of PIN function, in particular the establishment of their polar subcellular localization. Hormonal and environmental inputs into the regulation of PIN action are summarized as well.},
author = {Adamowski, Maciek and Friml, Jirí},
journal = {Plant Cell},
number = {1},
pages = {20 -- 32},
publisher = {American Society of Plant Biologists},
title = {{PIN-dependent auxin transport: Action, regulation, and evolution}},
doi = {10.1105/tpc.114.134874},
volume = {27},
year = {2015},
}
@inproceedings{1510,
abstract = {The concept of well group in a special but important case captures homological properties of the zero set of a continuous map f from K to R^n on a compact space K that are invariant with respect to perturbations of f. The perturbations are arbitrary continuous maps within L_infty distance r from f for a given r > 0. The main drawback of the approach is that the computability of well groups was shown only when dim K = n or n = 1. Our contribution to the theory of well groups is twofold: on the one hand we improve on the computability issue, but on the other hand we present a range of examples where the well groups are incomplete invariants, that is, fail to capture certain important robust properties of the zero set. For the first part, we identify a computable subgroup of the well group that is obtained by cap product with the pullback of the orientation of R^n by f. In other words, well groups can be algorithmically approximated from below. When f is smooth and dim K < 2n-2, our approximation of the (dim K-n)th well group is exact. For the second part, we find examples of maps f, f' from K to R^n with all well groups isomorphic but whose perturbations have different zero sets. We discuss on a possible replacement of the well groups of vector valued maps by an invariant of a better descriptive power and computability status. },
author = {Franek, Peter and Krcál, Marek},
location = {Eindhoven, Netherlands},
pages = {842 -- 856},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{On computability and triviality of well groups}},
doi = {10.4230/LIPIcs.SOCG.2015.842},
volume = {34},
year = {2015},
}
@misc{5442,
abstract = {We study algorithmic questions for concurrent systems where the transitions are labeled from a complete, closed semiring, and path properties are algebraic with semiring operations. The algebraic path properties can model dataflow analysis problems, the shortest path problem, and many other natural properties that arise in program analysis.
We consider that each component of the concurrent system is a graph with constant treewidth, and it is known that the controlflow graphs of most programs have constant treewidth. We allow for multiple possible queries, which arise naturally in demand driven dataflow analysis problems (e.g., alias analysis). The study of multiple queries allows us to consider the tradeoff between the resource usage of the \emph{one-time} preprocessing and for \emph{each individual} query. The traditional approaches construct the product graph of all components and apply the best-known graph algorithm on the product. In the traditional approach, even the answer to a single query requires the transitive closure computation (i.e., the results of all possible queries), which provides no room for tradeoff between preprocessing and query time.
Our main contributions are algorithms that significantly improve the worst-case running time of the traditional approach, and provide various tradeoffs depending on the number of queries. For example, in a concurrent system of two components, the traditional approach requires hexic time in the worst case for answering one query as well as computing the transitive closure, whereas we show that with one-time preprocessing in almost cubic time,
each subsequent query can be answered in at most linear time, and even the transitive closure can be computed in almost quartic time. Furthermore, we establish conditional optimality results that show that the worst-case running times of our algorithms cannot be improved without achieving major breakthroughs in graph algorithms (such as improving
the worst-case bounds for the shortest path problem in general graphs whose current best-known bound has not been improved in five decades). Finally, we provide a prototype implementation of our algorithms which significantly outperforms the existing algorithmic methods on several benchmarks.},
author = {Anonymous, 1 and Anonymous, 2 and Anonymous, 3 and Anonymous, 4},
issn = {2664-1690},
pages = {22},
publisher = {IST Austria},
title = {{Algorithms for algebraic path properties in concurrent systems of constant treewidth components}},
year = {2015},
}
@misc{5430,
abstract = {We consider the core algorithmic problems related to verification of systems with respect to three classical quantitative properties, namely, the mean- payoff property, the ratio property, and the minimum initial credit for energy property. The algorithmic problem given a graph and a quantitative property asks to compute the optimal value (the infimum value over all traces) from every node of the graph. We consider graphs with constant treewidth, and it is well-known that the control-flow graphs of most programs have constant treewidth. Let n denote the number of nodes of a graph, m the number of edges (for constant treewidth graphs m = O ( n ) ) and W the largest absolute value of the weights. Our main theoretical results are as follows. First, for constant treewidth graphs we present an algorithm that approximates the mean-payoff value within a mul- tiplicative factor of ∊ in time O ( n · log( n/∊ )) and linear space, as compared to the classical algorithms that require quadratic time. Second, for the ratio property we present an algorithm that for constant treewidth graphs works in time O ( n · log( | a · b · n | )) = O ( n · log( n · W )) , when the output is a b , as compared to the previously best known algorithm with running time O ( n 2 · log( n · W )) . Third, for the minimum initial credit problem we show that (i) for general graphs the problem can be solved in O ( n 2 · m ) time and the associated decision problem can be solved in O ( n · m ) time, improving the previous known O ( n 3 · m · log( n · W )) and O ( n 2 · m ) bounds, respectively; and (ii) for constant treewidth graphs we present an algorithm that requires O ( n · log n ) time, improving the previous known O ( n 4 · log( n · W )) bound. We have implemented some of our algorithms and show that they present a significant speedup on standard benchmarks.},
author = {Chatterjee, Krishnendu and Ibsen-Jensen, Rasmus and Pavlogiannis, Andreas},
issn = {2664-1690},
pages = {31},
publisher = {IST Austria},
title = {{Faster algorithms for quantitative verification in constant treewidth graphs}},
doi = {10.15479/AT:IST-2015-319-v1-1},
year = {2015},
}
@inproceedings{1541,
abstract = {We present XSpeed a parallel state-space exploration algorithm for continuous systems with linear dynamics and nondeterministic inputs. The motivation of having parallel algorithms is to exploit the computational power of multi-core processors to speed-up performance. The parallelization is achieved on two fronts. First, we propose a parallel implementation of the support function algorithm by sampling functions in parallel. Second, we propose a parallel state-space exploration by slicing the time horizon and computing the reachable states in the time slices in parallel. The second method can be however applied only to a class of linear systems with invertible dynamics and fixed input. A GP-GPU implementation is also presented following a lazy evaluation strategy on support functions. The parallel algorithms are implemented in the tool XSpeed. We evaluated the performance on two benchmarks including an 28 dimension Helicopter model. Comparison with the sequential counterpart shows a maximum speed-up of almost 7× on a 6 core, 12 thread Intel Xeon CPU E5-2420 processor. Our GP-GPU implementation shows a maximum speed-up of 12× over the sequential implementation and 53× over SpaceEx (LGG scenario), the state of the art tool for reachability analysis of linear hybrid systems. Experiments illustrate that our parallel algorithm with time slicing not only speeds-up performance but also improves precision.},
author = {Ray, Rajarshi and Gurung, Amit and Das, Binayak and Bartocci, Ezio and Bogomolov, Sergiy and Grosu, Radu},
location = {Haifa, Israel},
pages = {3 -- 18},
publisher = {Springer},
title = {{XSpeed: Accelerating reachability analysis on multi-core processors}},
doi = {10.1007/978-3-319-26287-1_1},
volume = {9434},
year = {2015},
}
@article{1553,
abstract = {Cell movement has essential functions in development, immunity, and cancer. Various cell migration patterns have been reported, but no general rule has emerged so far. Here, we show on the basis of experimental data in vitro and in vivo that cell persistence, which quantifies the straightness of trajectories, is robustly coupled to cell migration speed. We suggest that this universal coupling constitutes a generic law of cell migration, which originates in the advection of polarity cues by an actin cytoskeleton undergoing flows at the cellular scale. Our analysis relies on a theoretical model that we validate by measuring the persistence of cells upon modulation of actin flow speeds and upon optogenetic manipulation of the binding of an actin regulator to actin filaments. Beyond the quantitative prediction of the coupling, the model yields a generic phase diagram of cellular trajectories, which recapitulates the full range of observed migration patterns.},
author = {Maiuri, Paolo and Rupprecht, Jean and Wieser, Stefan and Ruprecht, Verena and Bénichou, Olivier and Carpi, Nicolas and Coppey, Mathieu and De Beco, Simon and Gov, Nir and Heisenberg, Carl-Philipp J and Lage Crespo, Carolina and Lautenschlaeger, Franziska and Le Berre, Maël and Lennon Duménil, Ana and Raab, Matthew and Thiam, Hawa and Piel, Matthieu and Sixt, Michael K and Voituriez, Raphaël},
journal = {Cell},
number = {2},
pages = {374 -- 386},
publisher = {Cell Press},
title = {{Actin flows mediate a universal coupling between cell speed and cell persistence}},
doi = {10.1016/j.cell.2015.01.056},
volume = {161},
year = {2015},
}
@article{1539,
abstract = {Many stochastic models of biochemical reaction networks contain some chemical species for which the number of molecules that are present in the system can only be finite (for instance due to conservation laws), but also other species that can be present in arbitrarily large amounts. The prime example of such networks are models of gene expression, which typically contain a small and finite number of possible states for the promoter but an infinite number of possible states for the amount of mRNA and protein. One of the main approaches to analyze such models is through the use of equations for the time evolution of moments of the chemical species. Recently, a new approach based on conditional moments of the species with infinite state space given all the different possible states of the finite species has been proposed. It was argued that this approach allows one to capture more details about the full underlying probability distribution with a smaller number of equations. Here, I show that the result that less moments provide more information can only stem from an unnecessarily complicated description of the system in the classical formulation. The foundation of this argument will be the derivation of moment equations that describe the complete probability distribution over the finite state space but only low-order moments over the infinite state space. I will show that the number of equations that is needed is always less than what was previously claimed and always less than the number of conditional moment equations up to the same order. To support these arguments, a symbolic algorithm is provided that can be used to derive minimal systems of unconditional moment equations for models with partially finite state space. },
author = {Ruess, Jakob},
journal = {Journal of Chemical Physics},
number = {24},
publisher = {American Institute of Physics},
title = {{Minimal moment equations for stochastic models of biochemical reaction networks with partially finite state space}},
doi = {10.1063/1.4937937},
volume = {143},
year = {2015},
}
@inproceedings{1609,
abstract = {The synthesis problem asks for the automatic construction of a system from its specification. In the traditional setting, the system is “constructed from scratch” rather than composed from reusable components. However, this is rare in practice, and almost every non-trivial software system relies heavily on the use of libraries of reusable components. Recently, Lustig and Vardi introduced dataflow and controlflow synthesis from libraries of reusable components. They proved that dataflow synthesis is undecidable, while controlflow synthesis is decidable. The problem of controlflow synthesis from libraries of probabilistic components was considered by Nain, Lustig and Vardi, and was shown to be decidable for qualitative analysis (that asks that the specification be satisfied with probability 1). Our main contribution for controlflow synthesis from probabilistic components is to establish better complexity bounds for the qualitative analysis problem, and to show that the more general quantitative problem is undecidable. For the qualitative analysis, we show that the problem (i) is EXPTIME-complete when the specification is given as a deterministic parity word automaton, improving the previously known 2EXPTIME upper bound; and (ii) belongs to UP ∩ coUP and is parity-games hard, when the specification is given directly as a parity condition on the components, improving the previously known EXPTIME upper bound.},
author = {Chatterjee, Krishnendu and Doyen, Laurent and Vardi, Moshe},
location = {Kyoto, Japan},
pages = {108 -- 120},
publisher = {Springer},
title = {{The complexity of synthesis from probabilistic components}},
doi = {10.1007/978-3-662-47666-6_9},
volume = {9135},
year = {2015},
}
@inproceedings{1692,
abstract = {Computing an approximation of the reachable states of a hybrid system is a challenge, mainly because overapproximating the solutions of ODEs with a finite number of sets does not scale well. Using template polyhedra can greatly reduce the computational complexity, since it replaces complex operations on sets with a small number of optimization problems. However, the use of templates may make the over-approximation too conservative. Spurious transitions, which are falsely considered reachable, are particularly detrimental to performance and accuracy, and may exacerbate the state explosion problem. In this paper, we examine how spurious transitions can be avoided with minimal computational effort. To this end, detecting spurious transitions is reduced to the well-known problem of showing that two convex sets are disjoint by finding a hyperplane that separates them. We generalize this to owpipes by considering hyperplanes that evolve with time in correspondence to the dynamics of the system. The approach is implemented in the model checker SpaceEx and demonstrated on examples.},
author = {Frehse, Goran and Bogomolov, Sergiy and Greitschus, Marius and Strump, Thomas and Podelski, Andreas},
booktitle = {Proceedings of the 18th International Conference on Hybrid Systems: Computation and Control},
isbn = {978-1-4503-3433-4},
location = {Seattle, WA, United States},
pages = {149 -- 158},
publisher = {ACM},
title = {{Eliminating spurious transitions in reachability with support functions}},
doi = {10.1145/2728606.2728622},
year = {2015},
}
@article{1697,
abstract = {Motion tracking is a challenge the visual system has to solve by reading out the retinal population. It is still unclear how the information from different neurons can be combined together to estimate the position of an object. Here we recorded a large population of ganglion cells in a dense patch of salamander and guinea pig retinas while displaying a bar moving diffusively. We show that the bar’s position can be reconstructed from retinal activity with a precision in the hyperacuity regime using a linear decoder acting on 100+ cells. We then took advantage of this unprecedented precision to explore the spatial structure of the retina’s population code. The classical view would have suggested that the firing rates of the cells form a moving hill of activity tracking the bar’s position. Instead, we found that most ganglion cells in the salamander fired sparsely and idiosyncratically, so that their neural image did not track the bar. Furthermore, ganglion cell activity spanned an area much larger than predicted by their receptive fields, with cells coding for motion far in their surround. As a result, population redundancy was high, and we could find multiple, disjoint subsets of neurons that encoded the trajectory with high precision. This organization allows for diverse collections of ganglion cells to represent high-accuracy motion information in a form easily read out by downstream neural circuits.},
author = {Marre, Olivier and Botella Soler, Vicente and Simmons, Kristina and Mora, Thierry and Tkacik, Gasper and Berry, Michael},
journal = {PLoS Computational Biology},
number = {7},
publisher = {Public Library of Science},
title = {{High accuracy decoding of dynamical motion from a large retinal population}},
doi = {10.1371/journal.pcbi.1004304},
volume = {11},
year = {2015},
}