@article{18742, abstract = {Recent improved determinations of the mass density ρBH of supermassive black holes (SMBHs) in the local universe have allowed accurate comparisons of ρBH with the amount of light received from past quasar activity. These comparisons support the notion that local SMBHs are "dead quasars" and yield a value epsilon ≳ 0.1 for the average radiative efficiency of cosmic SMBH accretion. BH coalescences may represent an important component of the quasar mass assembly and yet not produce any observable electromagnetic signature. Therefore, ignoring gravitational wave (GW) emission during such coalescences, which reduces the amount of mass locked into remnant BHs, results in an overestimate of epsilon. Here we put constraints on the magnitude of this bias. We calculate the cumulative mass loss to GWs experienced by a representative population of BHs during repeated cosmological mergers, using loss prescriptions based on detailed general relativistic calculations. Despite the possibly large number of mergers in the assembly history of each individual SMBH, we find that near-equal mass mergers are rare; therefore, the cumulative loss is likely to be modest, amounting at most to a 20% increase in the inferred epsilon value. Thus, recent estimates of epsilon ≳ 0.1 appear robust. The space interferometer LISA should provide empirical constraints on the dark side of quasar evolution by measuring the masses and rates of coalescence of massive BHs to cosmological distances.}, author = {Menou, Kristen and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, pages = {130--134}, publisher = {American Astronomical Society}, title = {{On the dark side of quasar evolution}}, doi = {10.1086/423951}, volume = {615}, year = {2004}, } @article{1963, abstract = {The mechanism coupling electron transfer and proton pumping in respiratory complex I (NADH-ubiquinone oxidoreductase) has not been established, but it has been suggested that it involves conformational changes. Here, the influence of substrates on the conformation of purified complex I from Escherichia coli was studied by cross-linking and electron microscopy. When a zero-length cross-linking reagent was used, the presence of NAD(P)H, in contrast to that of NAD+, prevented the formation of cross-links between the hydrophilic subunits of the complex, including NuoB, NuoI, and NuoCD. Comparisons using different cross-linkers suggested that NuoB, which is likely to coordinate the key iron-sulfur cluster N2, is the most mobile subunit. The presence of NAD(P)H led also to enhanced proteolysis of subunit NuoG. These data indicate that upon NAD(P)H binding, the peripheral arm of the complex adopts a more open conformation, with increased distances between subunits. Single particle analysis showed the nature of this conformational change. The enzyme retains its L-shape in the presence of NADH, but exhibits a significantly more open or expanded structure both in the peripheral arm and, unexpectedly, in the membrane domain also.}, author = {Mamedova, Aygun A and Holt, Peter J and Carroll, Joe D and Leonid Sazanov}, journal = {Journal of Biological Chemistry}, number = {22}, pages = {23830 -- 23836}, publisher = {American Society for Biochemistry and Molecular Biology}, title = {{Substrate-induced conformational change in bacterial complex I}}, doi = {10.1074/jbc.M401539200}, volume = {279}, year = {2004}, } @inproceedings{4372, author = {Maler, Oded and Nickovic, Dejan}, pages = {152 -- 166}, publisher = {Springer}, title = {{Monitoring Temporal Properties of Continuous Signals}}, doi = {10.1007/978-3-540-30206-3_12}, year = {2004}, } @phdthesis{4424, abstract = {The enormous cost and ubiquity of software errors necessitates the need for techniques and tools that can precisely analyze large systems and prove that they meet given specifications, or if they don't, return counterexample behaviors showing how the system fails. Recent advances in model checking, decision procedures, program analysis and type systems, and a shift of focus to partial specifications common to several systems (e.g., memory safety and race freedom) have resulted in several practical verification methods. However, these methods are either precise or they are scalable, depending on whether they track the values of variables or only a fixed small set of dataflow facts (e.g., types), and are usually insufficient for precisely verifying large programs. We describe a new technique called Lazy Abstraction (LA) which achieves both precision and scalability by localizing the use of precise information. LA automatically builds, explores and refines a single abstract model of the program in a way that different parts of the model exhibit different degrees of precision, namely just enough to verify the desired property. The algorithm automatically mines the information required by partitioning mechanical proofs of unsatisfiability of spurious counterexamples into Craig Interpolants. For multithreaded systems, we give a new technique based on analyzing the behavior of a single thread executing in a context which is an abstraction of the other (arbitrarily many) threads. We define novel context models and show how to automatically infer them and analyze the full system (thread + context) using LA. LA is implemented in BLAST. We have run BLAST on Windows and Linux Device Drivers to verify API conformance properties, and have used it to find (or guarantee the absence of) data races in multithreaded Networked Embedded Systems (NESC) applications. BLAST is able to prove the absence of races in several cases where earlier methods, which depend on lock-based synchronization, fail.}, author = {Jhala, Ranjit}, pages = {1 -- 165}, publisher = {University of California, Berkeley}, title = {{Program verification by lazy abstraction}}, year = {2004}, } @inproceedings{4445, abstract = {We present a type system for E code, which is an assembly language that manages the release, interaction, and termination of real-time tasks. E code specifies a deadline for each task, and the type system ensures that the deadlines are path-insensitive. We show that typed E programs allow, for given worst-case execution times of tasks, a simple schedulability analysis. Moreover, the real-time programming language Giotto can be compiled into typed E~code. This shows that typed E~code identifies an easily schedulable yet expressive class of real-time programs. We have extended the Giotto compiler to generate typed E code, and enabled the run-time system for E code to perform a type and schedulability check before executing the code.}, author = {Henzinger, Thomas A and Kirsch, Christoph}, booktitle = {Proceedings of the 4th ACM international conference on Embedded software}, isbn = {9781581138603}, location = {Pisa, Italy}, pages = {104 -- 113}, publisher = {Association for Computing Machinery}, title = {{A typed assembly language for real-time programs}}, doi = {10.1145/1017753.1017774}, year = {2004}, } @inproceedings{4458, abstract = {The success of model checking for large programs depends crucially on the ability to efficiently construct parsimonious abstractions. A predicate abstraction is parsimonious if at each control location, it specifies only relationships between current values of variables, and only those which are required for proving correctness. Previous methods for automatically refining predicate abstractions until sufficient precision is obtained do not systematically construct parsimonious abstractions: predicates usually contain symbolic variables, and are added heuristically and often uniformly to many or all control locations at once. We use Craig interpolation to efficiently construct, from a given abstract error trace which cannot be concretized, a parsominous abstraction that removes the trace. At each location of the trace, we infer the relevant predicates as an interpolant between the two formulas that define the past and the future segment of the trace. Each interpolant is a relationship between current values of program variables, and is relevant only at that particular program location. It can be found by a linear scan of the proof of infeasibility of the trace.We develop our method for programs with arithmetic and pointer expressions, and call-by-value function calls. For function calls, Craig interpolation offers a systematic way of generating relevant predicates that contain only the local variables of the function and the values of the formal parameters when the function was called. We have extended our model checker Blast with predicate discovery by Craig interpolation, and applied it successfully to C programs with more than 130,000 lines of code, which was not possible with approaches that build less parsimonious abstractions.}, author = {Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar and Mcmillan, Kenneth}, booktitle = {Proceedings of the 31st ACM SIGPLAN-SIGACT symposium on Principles of programming languages}, isbn = {9781581137293}, location = {Venice, Italy}, pages = {232 -- 244}, publisher = {Association for Computing Machinery}, title = {{Abstractions from proofs}}, doi = {10.1145/964001.964021}, year = {2004}, } @inproceedings{4459, abstract = {Software model checking has been successful for sequential programs, where predicate abstraction offers suitable models, and counterexample-guided abstraction refinement permits the automatic inference of models. When checking concurrent programs, we need to abstract threads as well as the contexts in which they execute. Stateless context models, such as predicates on global variables, prove insufficient for showing the absence of race conditions in many examples. We therefore use richer context models, which combine (1) predicates for abstracting data state, (2) control flow quotients for abstracting control state, and (3) counters for abstracting an unbounded number of threads. We infer suitable context models automatically by a combination of counterexample-guided abstraction refinement, bisimulation minimization, circular assume-guarantee reasoning, and parametric reasoning about an unbounded number of threads. This algorithm, called CIRC, has been implemented in BLAST and succeeds in checking many examples of NESC code for data races. In particular, BLAST proves the absence of races in several cases where previous race checkers give false positives.}, author = {Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar}, booktitle = {Proceedings of the ACM SIGPLAN 2004 conference on Programming language design and implementation}, isbn = {1581138075}, location = {Washington, DC, United States}, pages = {1 -- 13}, publisher = {Association for Computing Machinery}, title = {{Race checking by context inference}}, doi = {10.1145/996841.996844}, year = {2004}, } @inbook{4461, abstract = {One of the central axioms of extreme programming is the disciplined use of regression testing during stepwise software development. Due to recent progress in software model checking, it has become possible to supplement this process with automatic checks for behavioral safety properties of programs, such as conformance with locking idioms and other programming protocols and patterns. For efficiency reasons, all checks must be incremental, i.e., they must reuse partial results from previous checks in order to avoid all unnecessary repetition of expensive verification tasks. We show that the lazy-abstraction algorithm, and its implementation in Blast, can be extended to support the fully automatic and incremental checking of temporal safety properties during software development.}, author = {Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar and Sanvido, Marco}, booktitle = {Verification: Theory and Practice}, isbn = {9783540210023}, pages = {332 -- 358}, publisher = {Springer Nature}, title = {{Extreme Model Checking}}, doi = {10.1007/978-3-540-39910-0_16}, volume = {2772}, year = {2004}, } @inproceedings{4525, abstract = {We present a new high-level programming language, called xGiotto, for programming applications with hard real-time constraints. Like its predecessor, xGiotto is based on the LET (logical execution time) assumption: the programmer specifies when the outputs of a task become available, and the compiler checks if the specification can be implemented on a given platform. However, while the predecessor language xGiotto was purely time-triggered, xGiotto accommodates also asynchronous events. Indeed, through a mechanism called event scoping, events are the main structuring principle of the new language. The xGiotto compiler and run-time system implement event scoping through a tree-based event filter. The compiler also checks programs for determinism (absence of race conditions).}, author = {Ghosal, Arkadeb and Henzinger, Thomas A and Kirsch, Christoph and Sanvido, Marco}, isbn = {9783540212591}, location = {Philadelphia, PA, United States}, pages = {357--371}, publisher = {Springer Nature}, title = {{Event-driven programming with logical execution times}}, doi = {10.1007/978-3-540-24743-2_24}, year = {2004}, } @inproceedings{4555, abstract = {Strategies in repeated games can be classified as to whether or not they use memory and/or randomization. We consider Markov decision processes and 2-player graph games, both of the deterministic and probabilistic varieties. We characterize when memory and/or randomization are required for winning with respect to various classes of w-regular objectives, noting particularly when the use of memory can be traded for the use of randomization. In particular, we show that Markov decision processes allow randomized memoryless optimal strategies for all M?ller objectives. Furthermore, we show that 2-player probabilistic graph games allow randomized memoryless strategies for winning with probability 1 those M?ller objectives which are upward-closed. Upward-closure means that if a set α of infinitely repeating vertices is winning, then all supersets of α are also winning.}, author = {Chatterjee, Krishnendu and De Alfaro, Luca and Henzinger, Thomas A}, isbn = {0769521851}, location = {Enschede, Netherlands}, pages = {206 -- 217}, publisher = {IEEE}, title = {{Trading memory for randomness}}, doi = {10.1109/QEST.2004.10051}, year = {2004}, } @article{4556, abstract = {We study the problem of determining stack boundedness and the exact maximum stack size for three classes of interrupt-driven programs. Interrupt-driven programs are used in many real-time applications that require responsive interrupt handling. In order to ensure responsiveness, programmers often enable interrupt processing in the body of lower-priority interrupt handlers. In such programs a programming error can allow interrupt handlers to be interrupted in a cyclic fashion to lead to an unbounded stack, causing the system to crash. For a restricted class of interrupt-driven programs, we show that there is a polynomial-time procedure to check stack boundedness, while determining the exact maximum stack size is PSPACE-complete. For a larger class of programs, the two problems are both PSPACE-complete, and for the largest class of programs we consider, the two problems are PSPACE-hard and can be solved in exponential time. While the complexities are high, our algorithms are exponential only in the number of handlers, and polynomial in the size of the program.}, author = {Chatterjee, Krishnendu and Ma, Di and Majumdar, Ritankar and Zhao, Tian and Henzinger, Thomas A and Palsberg, Jens}, issn = {1090-2651}, journal = {Information and Computation}, number = {2}, pages = {144 -- 174}, publisher = {Elsevier}, title = {{Stack size analysis for interrupt-driven programs}}, doi = {10.1016/j.ic.2004.06.001}, volume = {194}, year = {2004}, } @inproceedings{4558, abstract = {We study perfect-information stochastic parity games. These are two-player nonterminating games which are played on a graph with turn-based probabilistic transitions. A play results in an infinite path and the conflicting goals of the two players are ω-regular path properties, formalized as parity winning conditions. The qualitative solution of such a game amounts to computing the set of vertices from which a player has a strategy to win with probability 1 (or with positive probability). The quantitative solution amounts to computing the value of the game in every vertex, i.e., the highest probability with which a player can guarantee satisfaction of his own objective in a play that starts from the vertex.For the important special case of one-player stochastic parity games (parity Markov decision processes) we give polynomial-time algorithms both for the qualitative and the quantitative solution. The running time of the qualitative solution is O(d · m3/2) for graphs with m edges and d priorities. The quantitative solution is based on a linear-programming formulation.For the two-player case, we establish the existence of optimal pure memoryless strategies. This has several important ramifications. First, it implies that the values of the games are rational. This is in contrast to the concurrent stochastic parity games of de Alfaro et al.; there, values are in general algebraic numbers, optimal strategies do not exist, and ε-optimal strategies have to be mixed and with infinite memory. Second, the existence of optimal pure memoryless strategies together with the polynomial-time solution forone-player case implies that the quantitative two-player stochastic parity game problem is in NP ∩ co-NP. This generalizes a result of Condon for stochastic games with reachability objectives. It also constitutes an exponential improvement over the best previous algorithm, which is based on a doubly exponential procedure of de Alfaro and Majumdar for concurrent stochastic parity games and provides only ε-approximations of the values.}, author = {Chatterjee, Krishnendu and Jurdziński, Marcin and Henzinger, Thomas A}, booktitle = {Proceedings of the 15th annual ACM-SIAM symposium on Discrete algorithms}, isbn = {089871558X}, location = {New Orleans, LA, United States}, pages = {121 -- 130}, publisher = {Association for Computing Machinery}, title = {{Quantitative stochastic parity games}}, doi = {10.5555/982792.982808}, year = {2004}, } @inproceedings{4577, abstract = {While model checking has been successful in uncovering subtle bugs in code, its adoption in software engineering practice has been hampered by the absence of a simple interface to the programmer in an integrated development environment. We describe an integration of the software model checker BLAST into the Eclipse development environment. We provide a verification interface for practical solutions for some typical program analysis problems - assertion checking, reachability analysis, dead code analysis, and test generation - directly on the source code. The analysis is completely automatic, and assumes no knowledge of model checking or formal notation. Moreover, the interface supports incremental program verification to support incremental design and evolution of code.}, author = {Beyer, Dirk and Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar}, booktitle = {Proceedings of the 12th IEEE International Workshop on Program Comprehension}, isbn = {0769521495}, issn = {1092-8138}, location = {Bari, Italy}, pages = {251 -- 255}, publisher = {IEEE}, title = {{An eclipse plug-in for model checking}}, doi = {10.1109/WPC.2004.1311069 }, year = {2004}, } @inproceedings{4578, abstract = {BLAST is an automatic verification tool for checking temporal safety properties of C programs. Blast is based on lazy predicate abstraction driven by interpolation-based predicate discovery. In this paper, we present the Blast specification language. The language specifies program properties at two levels of precision. At the lower level, monitor automata are used to specify temporal safety properties of program executions (traces). At the higher level, relational reachability queries over program locations are used to combine lower-level trace properties. The two-level specification language can be used to break down a verification task into several independent calls of the model-checking engine. In this way, each call to the model checker may have to analyze only part of the program, or part of the specification, and may thus succeed in a reduction of the number of predicates needed for the analysis. In addition, the two-level specification language provides a means for structuring and maintaining specifications. }, author = {Beyer, Dirk and Chlipala, Adam and Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar}, isbn = {9783540227915}, issn = {0302-9743}, location = {Verona, Italy}, pages = {2 -- 18}, publisher = {Springer}, title = {{The BLAST query language for software verification}}, doi = {10.1007/978-3-540-27864-1_2}, volume = {3148}, year = {2004}, } @inproceedings{4581, abstract = {We have extended the software model checker BLAST to automatically generate test suites that guarantee full coverage with respect to a given predicate. More precisely, given a C program and a target predicate p, BLAST determines the set L of program locations which program execution can reach with p true, and automatically generates a set of test vectors that exhibit the truth of p at all locations in L. We have used BLAST to generate test suites and to detect dead code in C programs with up to 30 K lines of code. The analysis and test vector generation is fully automatic (no user intervention) and exact (no false positives).}, author = {Beyer, Dirk and Chlipala, Adam and Henzinger, Thomas A and Jhala, Ranjit and Majumdar, Ritankar}, booktitle = {Proceedings of the 26th International Conference on Software Engineering}, isbn = {0769521630}, issn = {0270-5257}, location = {Edinburgh, United Kingdom}, pages = {326 -- 335}, publisher = {IEEE}, title = {{Generating tests from counterexamples}}, doi = {10.1109/ICSE.2004.1317455}, year = {2004}, } @inproceedings{4629, abstract = {Temporal logic is two-valued: a property is either true or false. When applied to the analysis of stochastic systems, or systems with imprecise formal models, temporal logic is therefore fragile: even small changes in the model can lead to opposite truth values for a specification. We present a generalization of the branching-time logic Ctl which achieves robustness with respect to model perturbations by giving a quantitative interpretation to predicates and logical operators, and by discounting the importance of events according to how late they occur. In every state, the value of a formula is a real number in the interval [0,1], where 1 corresponds to truth and 0 to falsehood. The boolean operators and and or are replaced by min and max, the path quantifiers ∃ and ∀ determine sup and inf over all paths from a given state, and the temporal operators and □ specify sup and inf over a given path; a new operator averages all values along a path. Furthermore, all path operators are discounted by a parameter that can be chosen to give more weight to states that are closer to the beginning of the path. We interpret the resulting logic Dctl over transition systems, Markov chains, and Markov decision processes. We present two semantics for Dctl: a path semantics, inspired by the standard interpretation of state and path formulas in CTL, and a fixpoint semantics, inspired by the μ-calculus evaluation of CTL formulas. We show that, while these semantics coincide for CTL, they differ for Dctl, and we provide model-checking algorithms for both semantics.}, author = {De Alfaro, Luca and Faella, Marco and Henzinger, Thomas A and Majumdar, Ritankar and Stoelinga, Mariëlle}, isbn = {9783540212997}, location = {Barcelona, Spain}, pages = {77 -- 92}, publisher = {Springer Nature}, title = {{Model checking discounted temporal properties}}, doi = {10.1007/978-3-540-24730-2_6}, volume = {2988}, year = {2004}, } @article{6155, abstract = {The genome of the nematode Caenorhabditis elegans encodes seven soluble guanylate cyclases (sGCs) [1]. In mammals, sGCs function as α/β heterodimers activated by gaseous ligands binding to a haem prosthetic group 2, 3. The principal activator is nitric oxide, which acts through sGCs to regulate diverse cellular events. In C. elegans the function of sGCs is mysterious: the worm genome does not appear to encode nitric oxide synthase, and all C. elegans sGC subunits are more closely related to mammalian β than α subunits [1]. Here, we show that two of the seven C. elegans sGCs, GCY-35 and GCY-36, promote aggregation behavior. gcy-35 and gcy-36 are expressed in a small number of neurons. These include the body cavity neurons AQR, PQR, and URX, which are directly exposed to the blood equivalent of C. elegans and regulate aggregation behavior [4]. We show that GCY-35 and GCY-36 act as α-like and β-like sGC subunits and that their function in the URX sensory neurons is sufficient for strong nematode aggregation. Neither GCY-35 nor GCY-36 is absolutely required for C. elegans to aggregate. Instead, these molecules may transduce one of several pathways that induce C. elegans to aggregate or may modulate aggregation by responding to cues in C. elegans body fluid.}, author = {Cheung, Benny H.H and Arellano-Carbajal, Fausto and Rybicki, Irene and de Bono, Mario}, issn = {0960-9822}, journal = {Current Biology}, number = {12}, pages = {1105--1111}, publisher = {Elsevier}, title = {{Soluble guanylate cyclases act in neurons exposed to the body fluid to promote C. elegans aggregation behavior}}, doi = {10.1016/j.cub.2004.06.027}, volume = {14}, year = {2004}, } @article{7706, abstract = {The Sir2 deacetylase modulates organismal life-span in various species. However, the molecular mechanisms by which Sir2 increases longevity are largely unknown. We show that in mammalian cells, the Sir2 homolog SIRT1 appears to control the cellular response to stress by regulating the FOXO family of Forkhead transcription factors, a family of proteins that function as sensors of the insulin signaling pathway and as regulators of organismal longevity. SIRT1 and the FOXO transcription factor FOXO3 formed a complex in cells in response to oxidative stress, and SIRT1 deacetylated FOXO3 in vitro and within cells. SIRT1 had a dual effect on FOXO3 function: SIRT1 increased FOXO3's ability to induce cell cycle arrest and resistance to oxidative stress but inhibited FOXO3's ability to induce cell death. Thus, one way in which members of the Sir2 family of proteins may increase organismal longevity is by tipping FOXO-dependent responses away from apoptosis and toward stress resistance.}, author = {Brunet, Anne and Sweeney, Lora Beatrice Jaeger and Sturgill, J Fitzhugh and Chua, Katrin and Greer, Paul and Lin, Yingxi and Tran, Hien and Ross, Sarah and Mostoslavsky, Raul and Cohen, Haim and Hu, Linda and Chen, Hwei-Ling and Jedrychowski, Mark and Gygi, Steven and Sinclair, David and Alt, Frederick and Greenberg, Michael}, issn = {0036-8075}, journal = {Science}, number = {5666}, pages = {2011--2015}, publisher = {American Association for the Advancement of Science}, title = {{Stress-dependent regulation of FOXO transcription factors by the SIRT1 deacetylase}}, doi = {10.1126/science.1094637}, volume = {303}, year = {2004}, } @article{8517, abstract = {We consider the evolution of a connected set on the plane carried by a space periodic incompressible stochastic flow. While for almost every realization of the stochastic flow at time t most of the particles are at a distance of order equation image away from the origin, there is a measure zero set of points that escape to infinity at the linear rate. We study the set of points visited by the original set by time t and show that such a set, when scaled down by the factor of t, has a limiting nonrandom shape.}, author = {Dolgopyat, Dmitry and Kaloshin, Vadim and Koralov, Leonid}, issn = {0010-3640}, journal = {Communications on Pure and Applied Mathematics}, keywords = {Applied Mathematics, General Mathematics}, number = {9}, pages = {1127--1158}, publisher = {Wiley}, title = {{A limit shape theorem for periodic stochastic dispersion}}, doi = {10.1002/cpa.20032}, volume = {57}, year = {2004}, } @article{8518, author = {Koralov, Leonid and Kaloshin, Vadim and Dolgopyat, Dmitry}, issn = {0091-1798}, journal = {The Annals of Probability}, number = {1A}, pages = {1--27}, publisher = {Institute of Mathematical Statistics}, title = {{Sample path properties of the stochastic flows}}, doi = {10.1214/aop/1078415827}, volume = {32}, year = {2004}, }