@article{2261, abstract = {To reveal the full potential of human pluripotent stem cells, new methods for rapid, site-specific genomic engineering are needed. Here, we describe a system for precise genetic modification of human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). We identified a novel human locus, H11, located in a safe, intergenic, transcriptionally active region of chromosome 22, as the recipient site, to provide robust, ubiquitous expression of inserted genes. Recipient cell lines were established by site-specific placement of a ‘landing pad’ cassette carrying attP sites for phiC31 and Bxb1 integrases at the H11 locus by spontaneous or TALEN-assisted homologous recombination. Dual integrase cassette exchange (DICE) mediated by phiC31 and Bxb1 integrases was used to insert genes of interest flanked by phiC31 and Bxb1 attB sites at the H11 locus, replacing the landing pad. This system provided complete control over content, direction and copy number of inserted genes, with a specificity of 100%. A series of genes, including mCherry and various combinations of the neural transcription factors LMX1a, FOXA2 and OTX2, were inserted in recipient cell lines derived from H9 ESC, as well as iPSC lines derived from a Parkinson’s disease patient and a normal sibling control. The DICE system offers rapid, efficient and precise gene insertion in ESC and iPSC and is particularly well suited for repeated modifications of the same locus.}, author = {Zhu, Fangfang and Gamboa, Matthew and Farruggio, Alfonso and Hippenmeyer, Simon and Tasic, Bosiljka and Schüle, Birgitt and Chen Tsai, Yanru and Calos, Michele}, journal = {Nucleic Acids Research}, number = {5}, publisher = {Oxford University Press}, title = {{DICE, an efficient system for iterative genomic editing in human pluripotent stem cells}}, doi = {10.1093/nar/gkt1290}, volume = {42}, year = {2014}, } @inbook{2265, abstract = {Coordinated migration of newly-born neurons to their target territories is essential for correct neuronal circuit assembly in the developing brain. Although a cohort of signaling pathways has been implicated in the regulation of cortical projection neuron migration, the precise molecular mechanisms and how a balanced interplay of cell-autonomous and non-autonomous functions of candidate signaling molecules controls the discrete steps in the migration process, are just being revealed. In this chapter, I will focally review recent advances that improved our understanding of the cell-autonomous and possible cell-nonautonomous functions of the evolutionarily conserved LIS1/NDEL1-complex in regulating the sequential steps of cortical projection neuron migration. I will then elaborate on the emerging concept that the Reelin signaling pathway, acts exactly at precise stages in the course of cortical projection neuron migration. Lastly, I will discuss how finely tuned transcriptional programs and downstream effectors govern particular aspects in driving radial migration at discrete stages and how they regulate the precise positioning of cortical projection neurons in the developing cerebral cortex.}, author = {Hippenmeyer, Simon}, booktitle = { Cellular and Molecular Control of Neuronal Migration}, editor = {Nguyen, Laurent}, pages = {1 -- 24}, publisher = {Springer}, title = {{Molecular pathways controlling the sequential steps of cortical projection neuron migration}}, doi = {10.1007/978-94-007-7687-6_1}, volume = {800}, year = {2014}, } @inproceedings{2275, abstract = {Energies with high-order non-submodular interactions have been shown to be very useful in vision due to their high modeling power. Optimization of such energies, however, is generally NP-hard. A naive approach that works for small problem instances is exhaustive search, that is, enumeration of all possible labelings of the underlying graph. We propose a general minimization approach for large graphs based on enumeration of labelings of certain small patches. This partial enumeration technique reduces complex high-order energy formulations to pairwise Constraint Satisfaction Problems with unary costs (uCSP), which can be efficiently solved using standard methods like TRW-S. Our approach outperforms a number of existing state-of-the-art algorithms on well known difficult problems (e.g. curvature regularization, stereo, deconvolution); it gives near global minimum and better speed. Our main application of interest is curvature regularization. In the context of segmentation, our partial enumeration technique allows to evaluate curvature directly on small patches using a novel integral geometry approach. }, author = {Olsson, Carl and Ulen, Johannes and Boykov, Yuri and Kolmogorov, Vladimir}, location = {Sydney, Australia}, pages = {2936 -- 2943}, publisher = {IEEE}, title = {{Partial enumeration and curvature regularization}}, doi = {10.1109/ICCV.2013.365}, year = {2014}, } @article{2285, abstract = {GABAergic inhibitory interneurons control fundamental aspects of neuronal network function. Their functional roles are assumed to be defined by the identity of their input synapses, the architecture of their dendritic tree, the passive and active membrane properties and finally the nature of their postsynaptic targets. Indeed, interneurons display a high degree of morphological and physiological heterogeneity. However, whether their morphological and physiological characteristics are correlated and whether interneuron diversity can be described by a continuum of GABAergic cell types or by distinct classes has remained unclear. Here we perform a detailed morphological and physiological characterization of GABAergic cells in the dentate gyrus, the input region of the hippocampus. To achieve an unbiased and efficient sampling and classification we used knock-in mice expressing the enhanced green fluorescent protein (eGFP) in glutamate decarboxylase 67 (GAD67)-positive neurons and performed cluster analysis. We identified five interneuron classes, each of them characterized by a distinct set of anatomical and physiological parameters. Cross-correlation analysis further revealed a direct relation between morphological and physiological properties indicating that dentate gyrus interneurons fall into functionally distinct classes which may differentially control neuronal network activity.}, author = {Hosp, Jonas and Strüber, Michael and Yanagawa, Yuchio and Obata, Kunihiko and Vida, Imre and Jonas, Peter M and Bartos, Marlene}, journal = {Hippocampus}, number = {2}, pages = {189 -- 203}, publisher = {Wiley-Blackwell}, title = {{Morpho-physiological criteria divide dentate gyrus interneurons into classes}}, doi = {10.1002/hipo.22214}, volume = {23}, year = {2014}, } @article{2407, abstract = {Two definitions of the effective mass of a particle interacting with a quantum field, such as a polaron, are considered and shown to be equal in models similar to the Fröhlich polaron model. These are: 1. the mass defined by the low momentum energy E(P)≈E(0)+P2/2 M of the translation invariant system constrained to have momentum P and 2. the mass M of a simple particle in an arbitrary slowly varying external potential, V, described by the nonrelativistic Schrödinger equation, whose ground state energy equals that of the combined particle/field system in a bound state in the same V.}, author = {Lieb, Élliott and Seiringer, Robert}, journal = {Journal of Statistical Physics}, number = {1-2}, pages = {51 -- 57}, publisher = {Springer}, title = {{Equivalence of two definitions of the effective mass of a polaron}}, doi = {10.1007/s10955-013-0791-z}, volume = {154}, year = {2014}, } @article{248, abstract = {For any pencil of conics or higher-dimensional quadrics over ℚ, with all degenerate fibres defined over ℚ, we show that the Brauer–Manin obstruction controls weak approximation. The proof is based on the Hasse principle and weak approximation for some special intersections of quadrics over ℚ, which is a consequence of recent advances in additive combinatorics.}, author = {Timothy Browning and Matthiesen, Lilian and Skorobogatov, Alexei N}, journal = {Annals of Mathematics}, number = {1}, pages = {381 -- 402}, publisher = {John Hopkins University Press}, title = {{Rational points on pencils of conics and quadrics with many degenerate fibres}}, doi = {https://doi.org/10.4007/annals.2014.180.1.8}, volume = {180}, year = {2014}, } @article{249, abstract = {A version of the Hardy-Littlewood circle method is developed for number fields K/ℚ and is used to show that nonsingular projective cubic hypersurfaces over K always have a K-rational point when they have dimension at least 8. }, author = {Timothy Browning and Vishe, Pankaj}, journal = {Duke Mathematical Journal}, number = {10}, pages = {1825 -- 1883}, publisher = {Duke University Press}, title = {{Cubic hypersurfaces and a version of the circle method for number fields}}, doi = {10.1215/00127094-2738530}, volume = {163}, year = {2014}, } @article{252, abstract = {For any number field k, upper bounds are established for the number of k-rational points of bounded height on non-singular del Pezzo surfaces defined over k, which are equipped with suitable conic bundle structures over k.}, author = {Timothy Browning and Jones, Michael S}, journal = {Acta Arithmetica}, number = {3}, pages = {271 -- 298}, publisher = {Instytut Matematyczny}, title = {{Counting rational points on del Pezzo surfaces with a conic bundle structure}}, doi = {10.4064/aa163-3-6}, volume = {163}, year = {2014}, } @article{254, abstract = {A new "polynomial sieve" is presented and used to show that almost all integers have at most one representation as a sum of two values of a given polynomial of degree at least 3.}, author = {Timothy Browning}, journal = {International Mathematics Research Notices}, number = {7}, pages = {1987 -- 2019}, publisher = {Oxford University Press}, title = {{The polynomial sieve and equal sums of like polynomials}}, doi = {10.1093/imrn/rnt350}, volume = {2015}, year = {2014}, } @article{255, abstract = {We investigate the Hasse principle for complete intersections cut out by a quadric hypersurface and a cubic hypersurface defined over the rational numbers.}, author = {Browning, Timothy D and Dietmann, Rainer and Heath Brown, Roger}, journal = {Journal of the Institute of Mathematics of Jussieu}, number = {4}, pages = {703 -- 749}, publisher = {Cambridge University Press}, title = {{Rational points on intersections of cubic and quadric hypersurfaces}}, doi = {10.1017/S1474748014000127}, volume = {14}, year = {2014}, } @article{2699, abstract = {We prove the universality of the β-ensembles with convex analytic potentials and for any β > 0, i.e. we show that the spacing distributions of log-gases at any inverse temperature β coincide with those of the Gaussian β-ensembles.}, author = {Erdös, László and Bourgade, Paul and Yau, Horng}, journal = {Duke Mathematical Journal}, number = {6}, pages = {1127 -- 1190}, publisher = {Duke University Press}, title = {{Universality of general β-ensembles}}, doi = {10.1215/00127094-2649752}, volume = {163}, year = {2014}, } @article{2716, abstract = {Multi-dimensional mean-payoff and energy games provide the mathematical foundation for the quantitative study of reactive systems, and play a central role in the emerging quantitative theory of verification and synthesis. In this work, we study the strategy synthesis problem for games with such multi-dimensional objectives along with a parity condition, a canonical way to express ω ω -regular conditions. While in general, the winning strategies in such games may require infinite memory, for synthesis the most relevant problem is the construction of a finite-memory winning strategy (if one exists). Our main contributions are as follows. First, we show a tight exponential bound (matching upper and lower bounds) on the memory required for finite-memory winning strategies in both multi-dimensional mean-payoff and energy games along with parity objectives. This significantly improves the triple exponential upper bound for multi energy games (without parity) that could be derived from results in literature for games on vector addition systems with states. Second, we present an optimal symbolic and incremental algorithm to compute a finite-memory winning strategy (if one exists) in such games. Finally, we give a complete characterization of when finite memory of strategies can be traded off for randomness. In particular, we show that for one-dimension mean-payoff parity games, randomized memoryless strategies are as powerful as their pure finite-memory counterparts.}, author = {Chatterjee, Krishnendu and Randour, Mickael and Raskin, Jean}, journal = {Acta Informatica}, number = {3-4}, pages = {129 -- 163}, publisher = {Springer}, title = {{Strategy synthesis for multi-dimensional quantitative objectives}}, doi = {10.1007/s00236-013-0182-6}, volume = {51}, year = {2014}, } @inproceedings{2905, abstract = {Persistent homology is a recent grandchild of homology that has found use in science and engineering as well as in mathematics. This paper surveys the method as well as the applications, neglecting completeness in favor of highlighting ideas and directions.}, author = {Edelsbrunner, Herbert and Morozovy, Dmitriy}, location = {Kraków, Poland}, pages = {31 -- 50}, publisher = {European Mathematical Society Publishing House}, title = {{Persistent homology: Theory and practice}}, doi = {10.4171/120-1/3}, year = {2014}, } @article{1733, abstract = {The classical (boolean) notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them) in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces, and how to synthesize an interface from incompatible requirements. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.}, author = {Cerny, Pavol and Chmelik, Martin and Henzinger, Thomas A and Radhakrishna, Arjun}, journal = {Theoretical Computer Science}, number = {3}, pages = {348 -- 363}, publisher = {Elsevier}, title = {{Interface simulation distances}}, doi = {10.1016/j.tcs.2014.08.019}, volume = {560}, year = {2014}, } @article{2141, abstract = {The computation of the winning set for Büchi objectives in alternating games on graphs is a central problem in computer-aided verification with a large number of applications. The long-standing best known upper bound for solving the problem is Õ(n ⋅ m), where n is the number of vertices and m is the number of edges in the graph. We are the first to break the Õ(n ⋅ m) boundary by presenting a new technique that reduces the running time to O(n2). This bound also leads to O(n2)-time algorithms for computing the set of almost-sure winning vertices for Büchi objectives (1) in alternating games with probabilistic transitions (improving an earlier bound of Õ(n ⋅ m)), (2) in concurrent graph games with constant actions (improving an earlier bound of O(n3)), and (3) in Markov decision processes (improving for m>n4/3 an earlier bound of O(m ⋅ √m)). We then show how to maintain the winning set for Büchi objectives in alternating games under a sequence of edge insertions or a sequence of edge deletions in O(n) amortized time per operation. Our algorithms are the first dynamic algorithms for this problem. We then consider another core graph theoretic problem in verification of probabilistic systems, namely computing the maximal end-component decomposition of a graph. We present two improved static algorithms for the maximal end-component decomposition problem. Our first algorithm is an O(m ⋅ √m)-time algorithm, and our second algorithm is an O(n2)-time algorithm which is obtained using the same technique as for alternating Büchi games. Thus, we obtain an O(min &lcu;m ⋅ √m,n2})-time algorithm improving the long-standing O(n ⋅ m) time bound. Finally, we show how to maintain the maximal end-component decomposition of a graph under a sequence of edge insertions or a sequence of edge deletions in O(n) amortized time per edge deletion, and O(m) worst-case time per edge insertion. Again, our algorithms are the first dynamic algorithms for this problem.}, author = {Chatterjee, Krishnendu and Henzinger, Monika H}, journal = {Journal of the ACM}, number = {3}, publisher = {ACM}, title = {{Efficient and dynamic algorithms for alternating Büchi games and maximal end-component decomposition}}, doi = {10.1145/2597631}, volume = {61}, year = {2014}, } @article{3263, abstract = {Adaptation in the retina is thought to optimize the encoding of natural light signals into sequences of spikes sent to the brain. While adaptive changes in retinal processing to the variations of the mean luminance level and second-order stimulus statistics have been documented before, no such measurements have been performed when higher-order moments of the light distribution change. We therefore measured the ganglion cell responses in the tiger salamander retina to controlled changes in the second (contrast), third (skew) and fourth (kurtosis) moments of the light intensity distribution of spatially uniform temporally independent stimuli. The skew and kurtosis of the stimuli were chosen to cover the range observed in natural scenes. We quantified adaptation in ganglion cells by studying linear-nonlinear models that capture well the retinal encoding properties across all stimuli. We found that the encoding properties of retinal ganglion cells change only marginally when higher-order statistics change, compared to the changes observed in response to the variation in contrast. By analyzing optimal coding in LN-type models, we showed that neurons can maintain a high information rate without large dynamic adaptation to changes in skew or kurtosis. This is because, for uncorrelated stimuli, spatio-temporal summation within the receptive field averages away non-gaussian aspects of the light intensity distribution.}, author = {Tkacik, Gasper and Ghosh, Anandamohan and Schneidman, Elad and Segev, Ronen}, journal = {PLoS One}, number = {1}, publisher = {Public Library of Science}, title = {{Adaptation to changes in higher-order stimulus statistics in the salamander retina}}, doi = {10.1371/journal.pone.0085841}, volume = {9}, year = {2014}, } @article{332, abstract = {Cu2ZnSnS4, based on abundant and environmental friendly elements and with a direct band gap of 1.5 eV, is a main candidate material for solar energy conversion through both photovoltaics and photocatalysis. We detail here the synthesis of quasi-spherical Cu 2ZnSnS4 nanoparticles with unprecedented narrow size distributions. We further detail their use as seeds to produce CZTS-Au and CZTS-Pt heterostructured nanoparticles. Such heterostructured nanoparticles are shown to have excellent photocatalytic properties toward degradation of Rhodamine B and hydrogen generation by water splitting. }, author = {Yu, Xuelian and Shavel, Alexey and An, Xiaoqiang and Luo, Zhishan and Ibáñez, Maria and Cabot, Andreu}, journal = {Journal of the American Chemical Society}, number = {26}, pages = {9236 -- 9239}, publisher = {ACS}, title = {{Cu2ZnSnS4-Pt and Cu2ZnSnS4-Au heterostructured nanoparticles for photocatalytic water splitting and pollutant degradation}}, doi = {10.1021/ja502076b}, volume = {136}, year = {2014}, } @inproceedings{2054, abstract = {We study two-player concurrent games on finite-state graphs played for an infinite number of rounds, where in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine the successor state. The objectives are ω-regular winning conditions specified as parity objectives. We consider the qualitative analysis problems: the computation of the almost-sure and limit-sure winning set of states, where player 1 can ensure to win with probability 1 and with probability arbitrarily close to 1, respectively. In general the almost-sure and limit-sure winning strategies require both infinite-memory as well as infinite-precision (to describe probabilities). While the qualitative analysis problem for concurrent parity games with infinite-memory, infinite-precision randomized strategies was studied before, we study the bounded-rationality problem for qualitative analysis of concurrent parity games, where the strategy set for player 1 is restricted to bounded-resource strategies. In terms of precision, strategies can be deterministic, uniform, finite-precision, or infinite-precision; and in terms of memory, strategies can be memoryless, finite-memory, or infinite-memory. We present a precise and complete characterization of the qualitative winning sets for all combinations of classes of strategies. In particular, we show that uniform memoryless strategies are as powerful as finite-precision infinite-memory strategies, and infinite-precision memoryless strategies are as powerful as infinite-precision finite-memory strategies. We show that the winning sets can be computed in (n2d+3) time, where n is the size of the game structure and 2d is the number of priorities (or colors), and our algorithms are symbolic. The membership problem of whether a state belongs to a winning set can be decided in NP ∩ coNP. Our symbolic algorithms are based on a characterization of the winning sets as μ-calculus formulas, however, our μ-calculus formulas are crucially different from the ones for concurrent parity games (without bounded rationality); and our memoryless witness strategy constructions are significantly different from the infinite-memory witness strategy constructions for concurrent parity games.}, author = {Chatterjee, Krishnendu}, booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)}, editor = {Baldan, Paolo and Gorla, Daniele}, location = {Rome, Italy}, pages = {544 -- 559}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Qualitative concurrent parity games: Bounded rationality}}, doi = {10.1007/978-3-662-44584-6_37}, volume = {8704}, year = {2014}, } @article{349, abstract = {Thermoelectricity is a key technology with the potential to improve the efficiency of energy conversion processes, which may strongly benefit from advances in the field of nanotechnology. Nanostructured materials are very appealing for thermoelectric applications, but the full development of their potential requires precise control of their properties at the nanoscale. Bottom-up assembly of nanoparticles provides access to a three-dimensional composition control at the nanoscale not attainable in any other technology. In particular, colloidal nanoheterostructures are especially interesting building blocks for the bottom-up production of functional nanomaterials. In the present work, we use PbTe@PbS core-shell nanoparticles as building blocks for the bottom-up production of PbTe-PbS nanocomposites. We used a ligand exchange strategy and a hot press process to promote the electrical conductivity of the nanocomposite and to increase its density. These two approaches allowed us to improve the performance of bottom-up assembled PbTe-PbS bulk nanostructured materials. }, author = {Ortega, Silvia and Ibáñez, Maria and Cadavid, Doris and Cabot, Andreu}, journal = {International Journal of Nanotechnology}, number = {9-11}, pages = {955 -- 970}, publisher = {Inderscience Enterprises Limited }, title = {{Bottom up processing of PbTe PbS thermoelectric nanocomposites}}, doi = {10.1504/IJNT.2014.063802}, volume = {11}, year = {2014}, } @article{355, abstract = {We report on the photocatalytic hydrogen evolution under full-arc light irradiation of CuIn1-xGaxS2 wurtzite nanocrystals in the presence of SO3 2- and S2- as sacrificial reagents. We analyzed the hydrogen generation rate as a function of the Ga content and associated it with the energy band positions. For photocatalytic water splitting, the CuInS2 bandgap is slightly too low to efficiently overcome the reaction over-potential. The presence of Ga shifts up the CuInS2 conduction band edge providing a larger driving force for photogenerated carriers to activate the water splitting reduction reaction. The larger the Ga content, the more energetically favorable the electron injection, and thus a more efficient use of the photogenerated carriers is reached. However, the band gap increase associated with the Ga incorporation reduces the concentration of photogenerated carriers available for water splitting, and consequently a lower hydrogen conversion rate is obtained for very high Ga contents. The optimum Ga concentration was experimentally found at CuIn0.3Ga0.7S2. }, author = {Yu, Xuelian and An, Xiaoqiang and Shavel, Alexey and Ibáñez, Maria and Cabot, Andreu}, journal = {Journal of Materials Chemistry A}, number = {31}, pages = {12317 -- 12322}, publisher = {Royal Society of Chemistry}, title = {{The effect of the Ga content on the photocatalytic hydrogen evolution of CuIn1-xGaxS2 nanocrystals}}, doi = {10.1039/c4ta01315h}, volume = {2}, year = {2014}, } @article{357, abstract = {Near-resonant Raman scattering measurements of zinc sulfide nanoparticles and thin films have been made and correlated to grain and particle size, respectively, using a 325 nm wavelength excitation source. The area ratios between the first, second, and third order peaks of ZnS identified as the T 2(LO) mode decrease with increasing ZnS grain size. This is an effect attributed to changes in the bandgap energy from quantum confinement due to the varying grain size between the films/particles, as noted by a shift in the room temperature photoluminescence emission corresponding to the free exciton emission energy. While Raman scattering spectroscopy is typically limited to identification of phases and their crystalline properties, it is possible to attain more than such straightforward information by calibrating the spectral features to variations between sets of samples. These results open the possibility of making a quantitative grain size estimation in ZnS thin films and nanostructures, as well as in other material systems where ZnS may be expected as a secondary phase, such as Cu2ZnSnS4. Additionally, more commonly used excitation wavelengths for Raman scattering, such as 514 and 532 nm, are shown to be of limited use in characterizing ZnS thin films due to the extremely low Raman scattering efficiency of ZnS in films with sub-micron thicknesses. }, author = {Fairbrother, Andrew and Izquierdo Roca, Victor and Fontané, Xavier and Ibáñez, Maria and Cabot, Andreu and Saucedo, Edgardo and Pérez Rodríguez, Alejandro}, journal = {CrystEngComm}, number = {20}, pages = {4120 -- 4125}, publisher = {Royal Society of Chemistry}, title = {{ZnS grain size effects on near-resonant Raman scattering: Optical non-destructive grain size estimation}}, doi = {10.1039/c3ce42578a}, volume = {16}, year = {2014}, } @article{359, abstract = {An appropriate way of realizing property nanoengineering in complex quaternary chalcogenide nanocrystals is presented for Cu2Cd xSnSey(CCTSe) polypods. The pivotal role of the polarity in determining morphology, growth, and the polytypic branching mechanism is demonstrated. Polarity is considered to be responsible for the formation of an initial seed that takes the form of a tetrahedron with four cation-polar facets. Size and shape confinement of the intermediate pentatetrahedral seed is also attributed to polarity, as their external facets are anion-polar. The final polypod extensions also branch out as a result of a cation-polarity-driven mechanism. Aberration-corrected scanning transmission electron microscopy is used to identify stannite cation ordering, while ab initio studies are used to show the influence of cation ordering/distortion, stoichiometry, and polytypic structural change on the electronic band structure.}, author = {Zamani, Reza and Ibáñez, Maria and Luysberg, Martina and García Castelló, Nuria and Houben, Lothar and Prades, Joan and Grillo, Vincenzo and Dunin Borkowski, Rafal and Morante, Joan and Cabot, Andreu and Arbiol, Jordi}, journal = {ACS Nano}, number = {3}, pages = {2290 -- 2301}, publisher = {American Chemical Society}, title = {{Polarity-driven polytypic branching in Cu-based quaternary chalcogenide nanostructures}}, doi = {10.1021/nn405747h}, volume = {8}, year = {2014}, } @article{2852, abstract = {A robust combiner for hash functions takes two candidate implementations and constructs a hash function which is secure as long as at least one of the candidates is secure. So far, hash function combiners only aim at preserving a single property such as collision-resistance or pseudorandomness. However, when hash functions are used in protocols like TLS they are often required to provide several properties simultaneously. We therefore put forward the notion of robust multi-property combiners and elaborate on different definitions for such combiners. We then propose a combiner that provably preserves (target) collision-resistance, pseudorandomness, and being a secure message authentication code. This combiner satisfies the strongest notion we propose, which requires that the combined function satisfies every security property which is satisfied by at least one of the underlying hash function. If the underlying hash functions have output length n, the combiner has output length 2 n. This basically matches a known lower bound for black-box combiners for collision-resistance only, thus the other properties can be achieved without penalizing the length of the hash values. We then propose a combiner which also preserves the property of being indifferentiable from a random oracle, slightly increasing the output length to 2 n+ω(log n). Moreover, we show how to augment our constructions in order to make them also robust for the one-wayness property, but in this case require an a priory upper bound on the input length.}, author = {Fischlin, Marc and Lehmann, Anja and Pietrzak, Krzysztof Z}, journal = {Journal of Cryptology}, number = {3}, pages = {397 -- 428}, publisher = {Springer}, title = {{Robust multi-property combiners for hash functions}}, doi = {10.1007/s00145-013-9148-7}, volume = {27}, year = {2014}, } @article{348, abstract = {Bi2S3-xTex bulk nanocomposites with crystal domain sizes in the range from 50 nm to 100 nm were obtained from the reaction of Bi2S3 nanorods with Te powder. The thermoelectric properties of the obtained nanocomposites were analysed in the temperature range from 0°C to 300°C. We observed how the thermoelectric properties of the material improved with the annealing temperature, being a spark plasma sintering process needed to maintain the material nanostructuration while maximising its electrical properties. Finally thermoelectric dimensionless figures of merit ZT up to 0.42 were obtained before any charge carrier concentration optimisation. Copyright © 2014 Inderscience Enterprises Ltd. }, author = {Cadavid, Doris and Ibáñez, Maria and Anselmi Tamburini, Umberto and Durá, Oscar and De La Torre, Marco and Cabot, Andreu}, journal = {International Journal of Nanotechnology}, number = {9-11}, pages = {773 -- 784}, publisher = {Inderscience Enterprises Limited }, title = {{Thermoelectric properties of bottom up assembled Bi2S 3-xTex nanocomposites}}, doi = {10.1504/IJNT.2014.063787}, volume = {11}, year = {2014}, } @article{350, abstract = {Herein, a colloidal synthetic route to produce highly monodisperse Cu2HgGeSe4 (CHGSe) nanoparticles (NPs) is presented in detail. The high yield of the developed procedure allowed the production of CHGSe NPs at the gram scale. A thorough analysis of their structural and optical properties is shown. CHGSe NPs displayed poly-tetrahedral morphology and narrow size distributions with average size in the range of 10–40 nm and size dispersions below 10 %. A 1.6 eV optical band gap was measured by mean of UV–Vis. By adjusting the cation ratio, an effective control of their electrical conductivity is achieved. The prepared NPs are used as building blocks for the production of CHGSe bulk nanostructured materials. The thermoelectric properties of CHGSe nanomaterials are studied in the temperature range from 300 to 730 K. CHGSe nanomaterials reached electrical conductivities up to 5 × 104 S m−1, Seebeck coefficients above 100 μV K−1, and thermal conductivities below 1.0 W m−1 K−1 which translated into thermoelectric figures of merit up to 0.34 at 730 K.}, author = {Li, Wenhua and Ibáñez, Maria and Cadavid, Doris and Zamani, Reza and Rubio Garcia, Javier and Gorsse, Stéphane and Morante, Joan and Arbiol, Jordi and Cabot, Andreu}, journal = {Journal of Nanoparticle Research}, number = {3}, publisher = {Kluwer}, title = {{Colloidal synthesis and functional properties of quaternary Cu based semiconductors: Cu2HgGeSe4}}, doi = {10.1007/s11051-014-2297-2}, volume = {16}, year = {2014}, } @article{356, abstract = {Cu2ZnSnS4, based on abundant and environmental friendly elements and with a direct band gap of 1.5 eV, is a main candidate material for solar energy conversion through both photovoltaics and photocatalysis. We detail here the synthesis of quasi-spherical Cu 2ZnSnS4 nanoparticles with unprecedented narrow size distributions. We further detail their use as seeds to produce CZTS-Au and CZTS-Pt heterostructured nanoparticles. Such heterostructured nanoparticles are shown to have excellent photocatalytic properties toward degradation of Rhodamine B and hydrogen generation by water splitting.}, author = {Yu, Xuelian and Shavel, Alexey and An, Xiaoqiang and Luo, Zhishan and Ibáñez, Maria and Cabot, Andreu}, journal = {Journal of the American Chemical Society}, number = {26}, pages = {9236 -- 9239}, publisher = {American Chemical Society}, title = {{Cu2ZnSnS4-Pt and Cu2ZnSnS4-Au heterostructured nanoparticles for photocatalytic water splitting and pollutant degradation}}, doi = {10.1021/ja502076b}, volume = {136}, year = {2014}, } @article{358, abstract = {Monodispersed Pt3Sn nanoparticles were prepared through a mild thermal synthesis in the presence of surfactants. The performance of Pt3Sn for the electrooxidation of ethanol and adsorbed carbon monoxide (COad) in acid medium was studied by a combination of electrochemical and insitu spectroscopic methods, namely, infrared reflection absorption spectroscopy and differential electrochemical mass spectrometry (DEMS), and the results were compared to those obtained with the use of Pt black. The formation of the Pt3Sn solid solution promoted the oxidation of COad at less-positive potentials than those required for Pt black. Also, the electrooxidation of ethanol, especially at lower potentials, was more favorable with Pt3Sn, as deduced from the higher faradaic currents recorded during the ethanol oxidation reaction (EOR). However, the distribution of products as deduced by DEMS analysis suggested that the formation of C1 products, CO2 inclusive, is less significant on Pt3Sn than on Pt. In fact, the higher faradaic current recorded with the former catalyst can be attributed to the greater amounts of acetaldehyde and acetic acid formed. After the EOR, the surface of both Pt and Pt3Sn remained covered by ethanol adsorbates. Whereas C2 fragments were the main adsorbates at the surface of Pt3Sn after the EOR, both C1 and C2 species remained adsorbed at Pt black.}, author = {Herranz, Tirma and Ibáñez, Maria and Gómez De La Fuente, José and Pérez Alonso, Francisco and Peña, Miguel and Cabot, Andreu and Rojas, Sergio}, journal = {ChemElectroChem}, number = {5}, pages = {885 -- 895}, publisher = {Wiley-Blackwell}, title = {{In situ study of ethanol electrooxidation on monodispersed Pt inf 3 inf Sn nanoparticles}}, doi = {10.1002/celc.201300254}, volume = {1}, year = {2014}, } @article{451, abstract = {We introduce algorithms for the computation of homology, cohomology, and related operations on cubical cell complexes, using the technique based on a chain contraction from the original chain complex to a reduced one that represents its homology. This work is based on previous results for simplicial complexes, and uses Serre’s diagonalization for cubical cells. An implementation in C++ of the introduced algorithms is available at http://www.pawelpilarczyk.com/chaincon/ together with some examples. The paper is self-contained as much as possible, and is written at a very elementary level, so that basic knowledge of algebraic topology should be sufficient to follow it.}, author = {Pawel Pilarczyk and Real, Pedro}, journal = {Advances in Computational Mathematics}, number = {1}, pages = {253 -- 275}, publisher = {Kluwer}, title = {{Computation of cubical homology, cohomology, and (co)homological operations via chain contraction}}, doi = {10.1007/s10444-014-9356-1}, volume = {41}, year = {2014}, } @article{468, abstract = {Invasive alien parasites and pathogens are a growing threat to biodiversity worldwide, which can contribute to the extinction of endemic species. On the Galápagos Islands, the invasive parasitic fly Philornis downsi poses a major threat to the endemic avifauna. Here, we investigated the influence of this parasite on the breeding success of two Darwin's finch species, the warbler finch (Certhidea olivacea) and the sympatric small tree finch (Camarhynchus parvulus), on Santa Cruz Island in 2010 and 2012. While the population of the small tree finch appeared to be stable, the warbler finch has experienced a dramatic decline in population size on Santa Cruz Island since 1997. We aimed to identify whether warbler finches are particularly vulnerable during different stages of the breeding cycle. Contrary to our prediction, breeding success was lower in the small tree finch than in the warbler finch. In both species P. downsi had a strong negative impact on breeding success and our data suggest that heavy rain events also lowered the fledging success. On the one hand parents might be less efficient in compensating their chicks' energy loss due to parasitism as they might be less efficient in foraging on days of heavy rain. On the other hand, intense rainfalls might lead to increased humidity and more rapid cooling of the nests. In the case of the warbler finch we found that the control of invasive plant species with herbicides had a significant additive negative impact on the breeding success. It is very likely that the availability of insects (i.e. food abundance) is lower in such controlled areas, as herbicide usage led to the removal of the entire understory. Predation seems to be a minor factor in brood loss.}, author = {Cimadom, Arno and Ulloa, Angel and Meidl, Patrick and Zöttl, Markus and Zöttl, Elisabet and Fessl, Birgit and Nemeth, Erwin and Dvorak, Michael and Cunninghame, Francesca and Tebbich, Sabine}, journal = {PLoS One}, number = {9}, publisher = {Public Library of Science}, title = {{Invasive parasites habitat change and heavy rainfall reduce breeding success in Darwin's finches}}, doi = {10.1371/journal.pone.0107518}, volume = {9}, year = {2014}, } @inproceedings{475, abstract = {First cycle games (FCG) are played on a finite graph by two players who push a token along the edges until a vertex is repeated, and a simple cycle is formed. The winner is determined by some fixed property Y of the sequence of labels of the edges (or nodes) forming this cycle. These games are traditionally of interest because of their connection with infinite-duration games such as parity and mean-payoff games. We study the memory requirements for winning strategies of FCGs and certain associated infinite duration games. We exhibit a simple FCG that is not memoryless determined (this corrects a mistake in Memoryless determinacy of parity and mean payoff games: a simple proof by Bj⋯orklund, Sandberg, Vorobyov (2004) that claims that FCGs for which Y is closed under cyclic permutations are memoryless determined). We show that θ (n)! memory (where n is the number of nodes in the graph), which is always sufficient, may be necessary to win some FCGs. On the other hand, we identify easy to check conditions on Y (i.e., Y is closed under cyclic permutations, and both Y and its complement are closed under concatenation) that are sufficient to ensure that the corresponding FCGs and their associated infinite duration games are memoryless determined. We demonstrate that many games considered in the literature, such as mean-payoff, parity, energy, etc., satisfy these conditions. On the complexity side, we show (for efficiently computable Y) that while solving FCGs is in PSPACE, solving some families of FCGs is PSPACE-hard. }, author = {Aminof, Benjamin and Rubin, Sasha}, booktitle = {Electronic Proceedings in Theoretical Computer Science, EPTCS}, location = {Grenoble, France}, pages = {83 -- 90}, publisher = {Open Publishing Association}, title = {{First cycle games}}, doi = {10.4204/EPTCS.146.11}, volume = {146}, year = {2014}, } @inproceedings{10892, abstract = {In this paper, we introduce planar matchings on directed pseudo-line arrangements, which yield a planar set of pseudo-line segments such that only matching-partners are adjacent. By translating the planar matching problem into a corresponding stable roommates problem we show that such matchings always exist. Using our new framework, we establish, for the first time, a complete, rigorous definition of weighted straight skeletons, which are based on a so-called wavefront propagation process. We present a generalized and unified approach to treat structural changes in the wavefront that focuses on the restoration of weak planarity by finding planar matchings.}, author = {Biedl, Therese and Huber, Stefan and Palfrader, Peter}, booktitle = {25th International Symposium, ISAAC 2014}, isbn = {9783319130743}, issn = {1611-3349}, location = {Jeonju, Korea}, pages = {117--127}, publisher = {Springer Nature}, title = {{Planar matchings for weighted straight skeletons}}, doi = {10.1007/978-3-319-13075-0_10}, volume = {8889}, year = {2014}, } @article{537, abstract = {Transgenerational effects are broader than only parental relationships. Despite mounting evidence that multigenerational effects alter phenotypic and life-history traits, our understanding of how they combine to determine fitness is not well developed because of the added complexity necessary to study them. Here, we derive a quantitative genetic model of adaptation to an extraordinary new environment by an additive genetic component, phenotypic plasticity, maternal and grandmaternal effects. We show how, at equilibrium, negative maternal and negative grandmaternal effects maximize expected population mean fitness. We define negative transgenerational effects as those that have a negative effect on trait expression in the subsequent generation, that is, they slow, or potentially reverse, the expected evolutionary dynamic. When maternal effects are positive, negative grandmaternal effects are preferred. As expected under Mendelian inheritance, the grandmaternal effects have a lower impact on fitness than the maternal effects, but this dual inheritance model predicts a more complex relationship between maternal and grandmaternal effects to constrain phenotypic variance and so maximize expected population mean fitness in the offspring.}, author = {Prizak, Roshan and Ezard, Thomas and Hoyle, Rebecca}, journal = {Ecology and Evolution}, number = {15}, pages = {3139 -- 3145}, publisher = {Wiley-Blackwell}, title = {{Fitness consequences of maternal and grandmaternal effects}}, doi = {10.1002/ece3.1150}, volume = {4}, year = {2014}, } @inproceedings{1903, abstract = {We consider two-player zero-sum partial-observation stochastic games on graphs. Based on the information available to the players these games can be classified as follows: (a) general partial-observation (both players have partial view of the game); (b) one-sided partial-observation (one player has partial-observation and the other player has complete-observation); and (c) perfect-observation (both players have complete view of the game). The one-sided partial-observation games subsumes the important special case of one-player partial-observation stochastic games (or partial-observation Markov decision processes (POMDPs)). Based on the randomization available for the strategies, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization. We consider all these classes of games with reachability, and parity objectives that can express all ω-regular objectives. The analysis problems are classified into the qualitative analysis that asks for the existence of a strategy that ensures the objective with probability 1; and the quantitative analysis that asks for the existence of a strategy that ensures the objective with probability at least λ (0,1). In this talk we will cover a wide range of results: for perfect-observation games; for POMDPs; for one-sided partial-observation games; and for general partial-observation games.}, author = {Chatterjee, Krishnendu}, location = {Budapest, Hungary}, number = {PART 1}, pages = {1 -- 4}, publisher = {Springer}, title = {{Partial-observation stochastic reachability and parity games}}, doi = {10.1007/978-3-662-44522-8_1}, volume = {8634}, year = {2014}, } @article{2211, abstract = {In two-player finite-state stochastic games of partial observation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distribution over the successor states. The game is played for infinitely many rounds and thus the players construct an infinite path in the graph. We consider reachability objectives where the first player tries to ensure a target state to be visited almost-surely (i.e., with probability 1) or positively (i.e., with positive probability), no matter the strategy of the second player. We classify such games according to the information and to the power of randomization available to the players. On the basis of information, the game can be one-sided with either (a) player 1, or (b) player 2 having partial observation (and the other player has perfect observation), or two-sided with (c) both players having partial observation. On the basis of randomization, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization. Our main results for pure strategies are as follows: (1) For one-sided games with player 2 having perfect observation we show that (in contrast to full randomized strategies) belief-based (subset-construction based) strategies are not sufficient, and we present an exponential upper bound on memory both for almost-sure and positive winning strategies; we show that the problem of deciding the existence of almost-sure and positive winning strategies for player 1 is EXPTIME-complete and present symbolic algorithms that avoid the explicit exponential construction. (2) For one-sided games with player 1 having perfect observation we show that nonelementarymemory is both necessary and sufficient for both almost-sure and positive winning strategies. (3) We show that for the general (two-sided) case finite-memory strategies are sufficient for both positive and almost-sure winning, and at least nonelementary memory is required. We establish the equivalence of the almost-sure winning problems for pure strategies and for randomized strategies with actions invisible. Our equivalence result exhibit serious flaws in previous results of the literature: we show a nonelementary memory lower bound for almost-sure winning whereas an exponential upper bound was previously claimed.}, author = {Chatterjee, Krishnendu and Doyen, Laurent}, journal = {ACM Transactions on Computational Logic (TOCL)}, number = {2}, publisher = {ACM}, title = {{Partial-observation stochastic games: How to win when belief fails}}, doi = {10.1145/2579821}, volume = {15}, year = {2014}, } @article{2038, abstract = {Recently, there has been an effort to add quantitative objectives to formal verification and synthesis. We introduce and investigate the extension of temporal logics with quantitative atomic assertions. At the heart of quantitative objectives lies the accumulation of values along a computation. It is often the accumulated sum, as with energy objectives, or the accumulated average, as with mean-payoff objectives. We investigate the extension of temporal logics with the prefix-accumulation assertions Sum(v) ≥ c and Avg(v) ≥ c, where v is a numeric (or Boolean) variable of the system, c is a constant rational number, and Sum(v) and Avg(v) denote the accumulated sum and average of the values of v from the beginning of the computation up to the current point in time. We also allow the path-accumulation assertions LimInfAvg(v) ≥ c and LimSupAvg(v) ≥ c, referring to the average value along an entire infinite computation. We study the border of decidability for such quantitative extensions of various temporal logics. In particular, we show that extending the fragment of CTL that has only the EX, EF, AX, and AG temporal modalities with both prefix-accumulation assertions, or extending LTL with both path-accumulation assertions, results in temporal logics whose model-checking problem is decidable. Moreover, the prefix-accumulation assertions may be generalized with "controlled accumulation," allowing, for example, to specify constraints on the average waiting time between a request and a grant. On the negative side, we show that this branching-time logic is, in a sense, the maximal logic with one or both of the prefix-accumulation assertions that permits a decidable model-checking procedure. Extending a temporal logic that has the EG or EU modalities, such as CTL or LTL, makes the problem undecidable.}, author = {Boker, Udi and Chatterjee, Krishnendu and Henzinger, Thomas A and Kupferman, Orna}, journal = {ACM Transactions on Computational Logic (TOCL)}, number = {4}, publisher = {ACM}, title = {{Temporal specifications with accumulative values}}, doi = {10.1145/2629686}, volume = {15}, year = {2014}, } @inproceedings{2162, abstract = {We study two-player (zero-sum) concurrent mean-payoff games played on a finite-state graph. We focus on the important sub-class of ergodic games where all states are visited infinitely often with probability 1. The algorithmic study of ergodic games was initiated in a seminal work of Hoffman and Karp in 1966, but all basic complexity questions have remained unresolved. Our main results for ergodic games are as follows: We establish (1) an optimal exponential bound on the patience of stationary strategies (where patience of a distribution is the inverse of the smallest positive probability and represents a complexity measure of a stationary strategy); (2) the approximation problem lies in FNP; (3) the approximation problem is at least as hard as the decision problem for simple stochastic games (for which NP ∩ coNP is the long-standing best known bound). We present a variant of the strategy-iteration algorithm by Hoffman and Karp; show that both our algorithm and the classical value-iteration algorithm can approximate the value in exponential time; and identify a subclass where the value-iteration algorithm is a FPTAS. We also show that the exact value can be expressed in the existential theory of the reals, and establish square-root sum hardness for a related class of games.}, author = {Chatterjee, Krishnendu and Ibsen-Jensen, Rasmus}, location = {Copenhagen, Denmark}, number = {Part 2}, pages = {122 -- 133}, publisher = {Springer}, title = {{The complexity of ergodic mean payoff games}}, doi = {10.1007/978-3-662-43951-7_11}, volume = {8573}, year = {2014}, } @inproceedings{2213, abstract = {We consider two-player partial-observation stochastic games on finitestate graphs where player 1 has partial observation and player 2 has perfect observation. The winning condition we study are ε-regular conditions specified as parity objectives. The qualitative-analysis problem given a partial-observation stochastic game and a parity objective asks whether there is a strategy to ensure that the objective is satisfied with probability 1 (resp. positive probability). These qualitative-analysis problems are known to be undecidable. However in many applications the relevant question is the existence of finite-memory strategies, and the qualitative-analysis problems under finite-memory strategies was recently shown to be decidable in 2EXPTIME.We improve the complexity and show that the qualitative-analysis problems for partial-observation stochastic parity games under finite-memory strategies are EXPTIME-complete; and also establish optimal (exponential) memory bounds for finite-memory strategies required for qualitative analysis.}, author = {Chatterjee, Krishnendu and Doyen, Laurent and Nain, Sumit and Vardi, Moshe}, location = {Grenoble, France}, pages = {242 -- 257}, publisher = {Springer}, title = {{The complexity of partial-observation stochastic parity games with finite-memory strategies}}, doi = {10.1007/978-3-642-54830-7_16}, volume = {8412}, year = {2014}, } @inproceedings{2212, abstract = {The theory of graph games is the foundation for modeling and synthesizing reactive processes. In the synthesis of stochastic processes, we use 2 1/2-player games where some transitions of the game graph are controlled by two adversarial players, the System and the Environment, and the other transitions are determined probabilistically. We consider 2 1/2-player games where the objective of the System is the conjunction of a qualitative objective (specified as a parity condition) and a quantitative objective (specified as a mean-payoff condition). We establish that the problem of deciding whether the System can ensure that the probability to satisfy the mean-payoff parity objective is at least a given threshold is in NP ∩ coNP, matching the best known bound in the special case of 2-player games (where all transitions are deterministic). We present an algorithm running in time O(d·n2d·MeanGame) to compute the set of almost-sure winning states from which the objective can be ensured with probability 1, where n is the number of states of the game, d the number of priorities of the parity objective, and MeanGame is the complexity to compute the set of almost-sure winning states in 2 1/2-player mean-payoff games. Our results are useful in the synthesis of stochastic reactive systems with both functional requirement (given as a qualitative objective) and performance requirement (given as a quantitative objective). }, author = {Chatterjee, Krishnendu and Doyen, Laurent and Gimbert, Hugo and Oualhadj, Youssouf}, location = {Grenoble, France}, pages = {210 -- 225}, publisher = {Springer}, title = {{Perfect-information stochastic mean-payoff parity games}}, doi = {10.1007/978-3-642-54830-7_14}, volume = {8412}, year = {2014}, } @inproceedings{2216, abstract = {The edit distance between two (untimed) traces is the minimum cost of a sequence of edit operations (insertion, deletion, or substitution) needed to transform one trace to the other. Edit distances have been extensively studied in the untimed setting, and form the basis for approximate matching of sequences in different domains such as coding theory, parsing, and speech recognition. In this paper, we lift the study of edit distances from untimed languages to the timed setting. We define an edit distance between timed words which incorporates both the edit distance between the untimed words and the absolute difference in time stamps. Our edit distance between two timed words is computable in polynomial time. Further, we show that the edit distance between a timed word and a timed language generated by a timed automaton, defined as the edit distance between the word and the closest word in the language, is PSPACE-complete. While computing the edit distance between two timed automata is undecidable, we show that the approximate version, where we decide if the edit distance between two timed automata is either less than a given parameter or more than δ away from the parameter, for δ > 0, can be solved in exponential space and is EXPSPACE-hard. Our definitions and techniques can be generalized to the setting of hybrid systems, and analogous decidability results hold for rectangular automata.}, author = {Chatterjee, Krishnendu and Ibsen-Jensen, Rasmus and Majumdar, Ritankar}, location = {Berlin, Germany}, pages = {303 -- 312}, publisher = {Springer}, title = {{Edit distance for timed automata}}, doi = {10.1145/2562059.2562141}, year = {2014}, } @misc{5411, abstract = {Model-based testing is a promising technology for black-box software and hardware testing, in which test cases are generated automatically from high-level specifications. Nowadays, systems typically consist of multiple interacting components and, due to their complexity, testing presents a considerable portion of the effort and cost in the design process. Exploiting the compositional structure of system specifications can considerably reduce the effort in model-based testing. Moreover, inferring properties about the system from testing its individual components allows the designer to reduce the amount of integration testing. In this paper, we study compositional properties of the IOCO-testing theory. We propose a new approach to composition and hiding operations, inspired by contract-based design and interface theories. These operations preserve behaviors that are compatible under composition and hiding, and prune away incompatible ones. The resulting specification characterizes the input sequences for which the unit testing of components is sufficient to infer the correctness of component integration without the need for further tests. We provide a methodology that uses these results to minimize integration testing effort, but also to detect potential weaknesses in specifications. While we focus on asynchronous models and the IOCO conformance relation, the resulting methodology can be applied to a broader class of systems.}, author = {Daca, Przemyslaw and Henzinger, Thomas A and Krenn, Willibald and Nickovic, Dejan}, issn = {2664-1690}, pages = {20}, publisher = {IST Austria}, title = {{Compositional specifications for IOCO testing}}, doi = {10.15479/AT:IST-2014-148-v2-1}, year = {2014}, } @misc{5413, abstract = {We consider Markov decision processes (MDPs) which are a standard model for probabilistic systems. We focus on qualitative properties for MDPs that can express that desired behaviors of the system arise almost-surely (with probability 1) or with positive probability. We introduce a new simulation relation to capture the refinement relation of MDPs with respect to qualitative properties, and present discrete graph theoretic algorithms with quadratic complexity to compute the simulation relation. We present an automated technique for assume-guarantee style reasoning for compositional analysis of MDPs with qualitative properties by giving a counter-example guided abstraction-refinement approach to compute our new simulation relation. We have implemented our algorithms and show that the compositional analysis leads to significant improvements. }, author = {Chatterjee, Krishnendu and Daca, Przemyslaw and Chmelik, Martin}, issn = {2664-1690}, pages = {33}, publisher = {IST Austria}, title = {{CEGAR for qualitative analysis of probabilistic systems}}, doi = {10.15479/AT:IST-2014-153-v2-2}, year = {2014}, } @misc{5414, abstract = {We consider Markov decision processes (MDPs) which are a standard model for probabilistic systems. We focus on qualitative properties for MDPs that can express that desired behaviors of the system arise almost-surely (with probability 1) or with positive probability. We introduce a new simulation relation to capture the refinement relation of MDPs with respect to qualitative properties, and present discrete graph theoretic algorithms with quadratic complexity to compute the simulation relation. We present an automated technique for assume-guarantee style reasoning for compositional analysis of MDPs with qualitative properties by giving a counter-example guided abstraction-refinement approach to compute our new simulation relation. We have implemented our algorithms and show that the compositional analysis leads to significant improvements. }, author = {Chatterjee, Krishnendu and Daca, Przemyslaw and Chmelik, Martin}, issn = {2664-1690}, pages = {33}, publisher = {IST Austria}, title = {{CEGAR for qualitative analysis of probabilistic systems}}, doi = {10.15479/AT:IST-2014-153-v3-1}, year = {2014}, } @misc{5412, abstract = {We consider Markov decision processes (MDPs) which are a standard model for probabilistic systems. We focus on qualitative properties for MDPs that can express that desired behaviors of the system arise almost-surely (with probability 1) or with positive probability. We introduce a new simulation relation to capture the refinement relation of MDPs with respect to qualitative properties, and present discrete graph theoretic algorithms with quadratic complexity to compute the simulation relation. We present an automated technique for assume-guarantee style reasoning for compositional analysis of MDPs with qualitative properties by giving a counter-example guided abstraction-refinement approach to compute our new simulation relation. We have implemented our algorithms and show that the compositional analysis leads to significant improvements. }, author = {Chatterjee, Krishnendu and Daca, Przemyslaw and Chmelik, Martin}, issn = {2664-1690}, pages = {31}, publisher = {IST Austria}, title = {{CEGAR for qualitative analysis of probabilistic systems}}, doi = {10.15479/AT:IST-2014-153-v1-1}, year = {2014}, } @inproceedings{2163, abstract = {We consider multi-player graph games with partial-observation and parity objective. While the decision problem for three-player games with a coalition of the first and second players against the third player is undecidable in general, we present a decidability result for partial-observation games where the first and third player are in a coalition against the second player, thus where the second player is adversarial but weaker due to partial-observation. We establish tight complexity bounds in the case where player 1 is less informed than player 2, namely 2-EXPTIME-completeness for parity objectives. The symmetric case of player 1 more informed than player 2 is much more complicated, and we show that already in the case where player 1 has perfect observation, memory of size non-elementary is necessary in general for reachability objectives, and the problem is decidable for safety and reachability objectives. From our results we derive new complexity results for partial-observation stochastic games.}, author = {Chatterjee, Krishnendu and Doyen, Laurent}, booktitle = {Lecture Notes in Computer Science}, location = {Copenhagen, Denmark}, number = {Part 2}, pages = {110 -- 121}, publisher = {Springer}, title = {{Games with a weak adversary}}, doi = {10.1007/978-3-662-43951-7_10}, volume = {8573}, year = {2014}, } @misc{5419, abstract = {We consider the reachability and shortest path problems on low tree-width graphs, with n nodes, m edges, and tree-width t, on a standard RAM with wordsize W. We use O to hide polynomial factors of the inverse of the Ackermann function. Our main contributions are three fold: 1. For reachability, we present an algorithm that requires O(n·t2·log(n/t)) preprocessing time, O(n·(t·log(n/t))/W) space, and O(t/W) time for pair queries and O((n·t)/W) time for single-source queries. Note that for constant t our algorithm uses O(n·logn) time for preprocessing; and O(n/W) time for single-source queries, which is faster than depth first search/breath first search (after the preprocessing). 2. We present an algorithm for shortest path that requires O(n·t2) preprocessing time, O(n·t) space, and O(t2) time for pair queries and O(n·t) time single-source queries. 3. We give a space versus query time trade-off algorithm for shortest path that, given any constant >0, requires O(n·t2) preprocessing time, O(n·t2) space, and O(n1−·t2) time for pair queries. Our algorithms improve all existing results, and use very simple data structures.}, author = {Chatterjee, Krishnendu and Ibsen-Jensen, Rasmus and Pavlogiannis, Andreas}, issn = {2664-1690}, pages = {34}, publisher = {IST Austria}, title = {{Improved algorithms for reachability and shortest path on low tree-width graphs}}, doi = {10.15479/AT:IST-2014-187-v1-1}, year = {2014}, } @inproceedings{2217, abstract = {As hybrid systems involve continuous behaviors, they should be evaluated by quantitative methods, rather than qualitative methods. In this paper we adapt a quantitative framework, called model measuring, to the hybrid systems domain. The model-measuring problem asks, given a model M and a specification, what is the maximal distance such that all models within that distance from M satisfy (or violate) the specification. A distance function on models is given as part of the input of the problem. Distances, especially related to continuous behaviors are more natural in the hybrid case than the discrete case. We are interested in distances represented by monotonic hybrid automata, a hybrid counterpart of (discrete) weighted automata, whose recognized timed languages are monotone (w.r.t. inclusion) in the values of parameters. The contributions of this paper are twofold. First, we give sufficient conditions under which the model-measuring problem can be solved. Second, we discuss the modeling of distances and applications of the model-measuring problem.}, author = {Henzinger, Thomas A and Otop, Jan}, booktitle = {Proceedings of the 17th international conference on Hybrid systems: computation and control}, location = {Berlin, Germany}, pages = {213 -- 222}, publisher = {Springer}, title = {{Model measuring for hybrid systems}}, doi = {10.1145/2562059.2562130}, year = {2014}, } @misc{5417, abstract = {We define the model-measuring problem: given a model M and specification φ, what is the maximal distance ρ such that all models M'within distance ρ from M satisfy (or violate)φ. The model measuring problem presupposes a distance function on models. We concentrate on automatic distance functions, which are defined by weighted automata. The model-measuring problem subsumes several generalizations of the classical model-checking problem, in particular, quantitative model-checking problems that measure the degree of satisfaction of a specification, and robustness problems that measure how much a model can be perturbed without violating the specification. We show that for automatic distance functions, and ω-regular linear-time and branching-time specifications, the model-measuring problem can be solved. We use automata-theoretic model-checking methods for model measuring, replacing the emptiness question for standard word and tree automata by the optimal-weight question for the weighted versions of these automata. We consider weighted automata that accumulate weights by maximizing, summing, discounting, and limit averaging. We give several examples of using the model-measuring problem to compute various notions of robustness and quantitative satisfaction for temporal specifications.}, author = {Henzinger, Thomas A and Otop, Jan}, issn = {2664-1690}, pages = {14}, publisher = {IST Austria}, title = {{From model checking to model measuring}}, doi = {10.15479/AT:IST-2014-172-v1-1}, year = {2014}, } @misc{5416, abstract = {As hybrid systems involve continuous behaviors, they should be evaluated by quantitative methods, rather than qualitative methods. In this paper we adapt a quantitative framework, called model measuring, to the hybrid systems domain. The model-measuring problem asks, given a model M and a specification, what is the maximal distance such that all models within that distance from M satisfy (or violate) the specification. A distance function on models is given as part of the input of the problem. Distances, especially related to continuous behaviors are more natural in the hybrid case than the discrete case. We are interested in distances represented by monotonic hybrid automata, a hybrid counterpart of (discrete) weighted automata, whose recognized timed languages are monotone (w.r.t. inclusion) in the values of parameters.The contributions of this paper are twofold. First, we give sufficient conditions under which the model-measuring problem can be solved. Second, we discuss the modeling of distances and applications of the model-measuring problem.}, author = {Henzinger, Thomas A and Otop, Jan}, issn = {2664-1690}, pages = {22}, publisher = {IST Austria}, title = {{Model measuring for hybrid systems}}, doi = {10.15479/AT:IST-2014-171-v1-1}, year = {2014}, } @misc{5418, abstract = {We consider multi-player graph games with partial-observation and parity objective. While the decision problem for three-player games with a coalition of the first and second players against the third player is undecidable, we present a decidability result for partial-observation games where the first and third player are in a coalition against the second player, thus where the second player is adversarial but weaker due to partial-observation. We establish tight complexity bounds in the case where player 1 is less informed than player 2, namely 2-EXPTIME-completeness for parity objectives. The symmetric case of player 1 more informed than player 2 is much more complicated, and we show that already in the case where player 1 has perfect observation, memory of size non-elementary is necessary in general for reachability objectives, and the problem is decidable for safety and reachability objectives. Our results have tight connections with partial-observation stochastic games for which we derive new complexity results.}, author = {Chatterjee, Krishnendu and Doyen, Laurent}, issn = {2664-1690}, pages = {18}, publisher = {IST Austria}, title = {{Games with a weak adversary}}, doi = {10.15479/AT:IST-2014-176-v1-1}, year = {2014}, } @misc{5420, abstract = {We consider concurrent mean-payoff games, a very well-studied class of two-player (player 1 vs player 2) zero-sum games on finite-state graphs where every transition is assigned a reward between 0 and 1, and the payoff function is the long-run average of the rewards. The value is the maximal expected payoff that player 1 can guarantee against all strategies of player 2. We consider the computation of the set of states with value 1 under finite-memory strategies for player 1, and our main results for the problem are as follows: (1) we present a polynomial-time algorithm; (2) we show that whenever there is a finite-memory strategy, there is a stationary strategy that does not need memory at all; and (3) we present an optimal bound (which is double exponential) on the patience of stationary strategies (where patience of a distribution is the inverse of the smallest positive probability and represents a complexity measure of a stationary strategy).}, author = {Chatterjee, Krishnendu and Ibsen-Jensen, Rasmus}, issn = {2664-1690}, pages = {49}, publisher = {IST Austria}, title = {{The value 1 problem for concurrent mean-payoff games}}, doi = {10.15479/AT:IST-2014-191-v1-1}, year = {2014}, }