788 research outputs found
Validity-Guided Synthesis of Reactive Systems from Assume-Guarantee Contracts
Automated synthesis of reactive systems from specifications has been a topic
of research for decades. Recently, a variety of approaches have been proposed
to extend synthesis of reactive systems from proposi- tional specifications
towards specifications over rich theories. We propose a novel, completely
automated approach to program synthesis which reduces the problem to deciding
the validity of a set of forall-exists formulas. In spirit of IC3 / PDR, our
problem space is recursively refined by blocking out regions of unsafe states,
aiming to discover a fixpoint that describes safe reactions. If such a fixpoint
is found, we construct a witness that is directly translated into an
implementation. We implemented the algorithm on top of the JKind model checker,
and exercised it against contracts written using the Lustre specification
language. Experimental results show how the new algorithm outperforms JKinds
already existing synthesis procedure based on k-induction and addresses
soundness issues in the k-inductive approach with respect to unrealizable
results.Comment: 18 pages, 5 figures, 2 table
The Extragalactic Distance Database: Color-Magnitude Diagrams
The CMDs/TRGB (Color-Magnitude Diagrams/Tip of the Red Giant Branch) section
of the Extragalactic Distance Database contains a compilation of observations
of nearby galaxies from the Hubble Space Telescope. Approximately 250 (and
increasing) galaxies in the Local Volume have CMDs and the stellar photometry
tables used to produce them available through the web. Various stellar
populations that make up a galaxy are visible in the CMDs, but our primary
purpose for collecting and analyzing these galaxy images is to measure the TRGB
in each. We can estimate the distance to a galaxy by using stars at the TRGB as
standard candles. In this paper we describe the process of constructing the
CMDs and make the results available to the public.Comment: 8 pages, 5 figures, 1 long table, submitted to Astronomical Journa
Single shot parameter estimation via continuous quantum measurement
We present filtering equations for single shot parameter estimation using
continuous quantum measurement. By embedding parameter estimation in the
standard quantum filtering formalism, we derive the optimal Bayesian filter for
cases when the parameter takes on a finite range of values. Leveraging recent
convergence results [van Handel, arXiv:0709.2216 (2008)], we give a condition
which determines the asymptotic convergence of the estimator. For cases when
the parameter is continuous valued, we develop quantum particle filters as a
practical computational method for quantum parameter estimation.Comment: 9 pages, 5 image
Thin endometrial lining during frozen embryo cycles: a case-control study of risk factors and natural history
Objective: To identify predictors of thin endometrial lining in the first frozen embryo transfer cycles and to characterize the natural history of this condition over subsequent cycles.
Design: Retrospective case-control study
Conclusions: This study shows that prognosis after a diagnosis of thin endometrial lining is favorable. Lower weight and thinner fresh cycle lining are predictors of thin endometrial lining in FET cycles. Most importantly, women with a diagnosis of thin endometrial lining have similar live birth rates as those with adequate endometrial lining, although their time to achieve live birth is slightly longer
Cosmicflows-2: The Data
Cosmicflows-2 is a compilation of distances and peculiar velocities for over
8000 galaxies. Numerically the largest contributions come from the
luminosity-linewidth correlation for spirals, the TFR, and the related
Fundamental Plane relation for E/S0 systems, but over 1000 distances are
contributed by methods that provide more accurate individual distances:
Cepheid, Tip of the Red Giant Branch, Surface Brightness Fluctuation, SNIa, and
several miscellaneous but accurate procedures. Our collaboration is making
important contributions to two of these inputs: Tip of the Red Giant Branch and
TFR. A large body of new distance material is presented. In addition, an effort
is made to assure that all the contributions, our own and those from the
literature, are on the same scale. Overall, the distances are found to be
compatible with a Hubble Constant H_0 = 74.4 +-3.0 km/s/Mpc. The great interest
going forward with this data set will be with velocity field studies.
Cosmicflows-2 is characterized by a great density and high accuracy of distance
measures locally, falling to sparse and coarse sampling extending to z=0.1.Comment: To be published in Astronomical Journal. Two extensive tables to be
available on-line. Table 1 available at http://edd.ifa.hawaii.edu select
catalog `Cosmicflows-2 Distances
Electrophysiological Signatures of Spatial Boundaries in the Human Subiculum.
Environmental boundaries play a crucial role in spatial navigation and memory across a wide range of distantly related species. In rodents, boundary representations have been identified at the single-cell level in the subiculum and entorhinal cortex of the hippocampal formation. Although studies of hippocampal function and spatial behavior suggest that similar representations might exist in humans, boundary-related neural activity has not been identified electrophysiologically in humans until now. To address this gap in the literature, we analyzed intracranial recordings from the hippocampal formation of surgical epilepsy patients (of both sexes) while they performed a virtual spatial navigation task and compared the power in three frequency bands (1-4, 4-10, and 30-90 Hz) for target locations near and far from the environmental boundaries. Our results suggest that encoding locations near boundaries elicited stronger theta oscillations than for target locations near the center of the environment and that this difference cannot be explained by variables such as trial length, speed, movement, or performance. These findings provide direct evidence of boundary-dependent neural activity localized in humans to the subiculum, the homolog of the hippocampal subregion in which most boundary cells are found in rodents, and indicate that this system can represent attended locations that rather than the position of one\u27s own body
On Deciding Local Theory Extensions via E-matching
Satisfiability Modulo Theories (SMT) solvers incorporate decision procedures
for theories of data types that commonly occur in software. This makes them
important tools for automating verification problems. A limitation frequently
encountered is that verification problems are often not fully expressible in
the theories supported natively by the solvers. Many solvers allow the
specification of application-specific theories as quantified axioms, but their
handling is incomplete outside of narrow special cases.
In this work, we show how SMT solvers can be used to obtain complete decision
procedures for local theory extensions, an important class of theories that are
decidable using finite instantiation of axioms. We present an algorithm that
uses E-matching to generate instances incrementally during the search,
significantly reducing the number of generated instances compared to eager
instantiation strategies. We have used two SMT solvers to implement this
algorithm and conducted an extensive experimental evaluation on benchmarks
derived from verification conditions for heap-manipulating programs. We believe
that our results are of interest to both the users of SMT solvers as well as
their developers
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