1,132 research outputs found
Probably Safe or Live
This paper presents a formal characterisation of safety and liveness
properties \`a la Alpern and Schneider for fully probabilistic systems. As for
the classical setting, it is established that any (probabilistic tree) property
is equivalent to a conjunction of a safety and liveness property. A simple
algorithm is provided to obtain such property decomposition for flat
probabilistic CTL (PCTL). A safe fragment of PCTL is identified that provides a
sound and complete characterisation of safety properties. For liveness
properties, we provide two PCTL fragments, a sound and a complete one. We show
that safety properties only have finite counterexamples, whereas liveness
properties have none. We compare our characterisation for qualitative
properties with the one for branching time properties by Manolios and Trefler,
and present sound and complete PCTL fragments for characterising the notions of
strong safety and absolute liveness coined by Sistla
Laser induced electron diffraction: a tool for molecular orbital imaging
We explore the laser-induced ionization dynamics of N2 and CO2 molecules
subjected to a few-cycle, linearly polarized, 800\,nm laser pulse using
effective two-dimensional single active electron time-dependent quantum
simulations. We show that the electron recollision process taking place after
an initial tunnel ionization stage results in quantum interference patterns in
the energy resolved photo-electron signals. If the molecule is initially
aligned perpendicular to the field polarization, the position and relative
heights of the associated fringes can be related to the molecular geometrical
and orbital structure, using a simple inversion algorithm which takes into
account the symmetry of the initial molecular orbital from which the ionized
electron is produced. We show that it is possible to extract inter-atomic
distances in the molecule from an averaged photon-electron signal with an
accuracy of a few percents
Two-Color Coherent Photodissociation of Nitrogen Oxide in Intense Laser Fields
A simple one-dimensional semi-classical model with a Morse potential is used
to investigate the possibility of two-color infrared multi-photon dissociation
of vibrationally excited nitrogen oxide. The amplitude ratio effects and
adiabatic effects are investigated. Some initial states are found to have
thresholds smaller than expected from single-mode considerations and multiple
thresholds exist for initial states up to 32.
PACS: 42.50.HzComment: 3 pages, old papers, add source files to replace original postscrip
Coherent Control of Isotope Separation in HD+ Photodissociation by Strong Fields
The photodissociation of the HD+ molecular ion in intense short- pulsed
linearly polarized laser fields is studied using a time- dependent wave-packet
approach where molecular rotation is fully included. We show that applying a
coherent superposition of the fundamental radiation with its second harmonic
can lead to asymmetries in the fragment angular distributions, with significant
differences between the hydrogen and deuterium distributions in the long
wavelength domain where the permanent dipole is most efficient. This effect is
used to induce an appreciable isotope separation.Comment: Physical Review Letters, 1995 (in press). 4 pages in revtex format, 3
uuencoded figures. Full postcript version available at:
http://chemphys.weizmann.ac.il/~charron/prl.ps or
ftp://scipion.ppm.u-psud.fr/coherent.control/prl.p
Monitoring Partially Synchronous Distributed Systems using SMT Solvers
In this paper, we discuss the feasibility of monitoring partially synchronous
distributed systems to detect latent bugs, i.e., errors caused by concurrency
and race conditions among concurrent processes. We present a monitoring
framework where we model both system constraints and latent bugs as
Satisfiability Modulo Theories (SMT) formulas, and we detect the presence of
latent bugs using an SMT solver. We demonstrate the feasibility of our
framework using both synthetic applications where latent bugs occur at any time
with random probability and an application involving exclusive access to a
shared resource with a subtle timing bug. We illustrate how the time required
for verification is affected by parameters such as communication frequency,
latency, and clock skew. Our results show that our framework can be used for
real-life applications, and because our framework uses SMT solvers, the range
of appropriate applications will increase as these solvers become more
efficient over time.Comment: Technical Report corresponding to the paper accepted at Runtime
Verification (RV) 201
In utero exposure to a maternal high-fat diet alters the epigenetic histone code in a murine model
OBJECTIVE: Data from animal models show that in utero exposure to a maternal high-fat diet (HFD) renders susceptibility of these offspring to the adult onset of metabolic syndrome. We and others have previously shown that epigenetic modifications to histones may serve as a molecular memory of the in utero exposure, rendering the risk of adult disease. Because mice heterozygous for the Glut4 gene (insulin sensitive glucose transporter) born to wild-type (WT) mothers demonstrate exacterbated metabolic syndrome when exposed to an HFD in utero, we sought to analyze the genome-wide epigenetic changes that occur in the fetal liver in susceptible offspring. STUDY DESIGN: WT and Glut4(+/-) (G4(+/-)) offspring of WT mothers that were exposed either to a control or an HFD in utero were studied. Immunoblotting was used to measure hepatic histone modifications of fetal and 5-week animals. Chromatin immunoprecipitation (ChIP) followed by hybridization to chip arrays (ChIP-on-chip) was used to detect genome-wide changes of histone modifications with HFD exposure. RESULTS: We found that levels of hepatic H3K14ac and H3K9me3 significantly increased with HFD exposure in WT and G4(+/-) fetal and 5-week offspring. Pathway analysis of our ChIP-on-chip data revealed differential H3K14ac and H3K9me3 enrichment along pathways that regulate lipid metabolism, specifically in the promoter regions of Pparg, Ppara, Rxra, and Rora. CONCLUSION: We conclude that HFD exposure in utero is associated with functional alterations to fetal hepatic histone modifications in both WT and G4(+/-) offspring, some of which persist up to 5 weeks of age
Quantum computing implementations with neutral particles
We review quantum information processing with cold neutral particles, that
is, atoms or polar molecules. First, we analyze the best suited degrees of
freedom of these particles for storing quantum information, and then we discuss
both single- and two-qubit gate implementations. We focus our discussion mainly
on collisional quantum gates, which are best suited for atom-chip-like devices,
as well as on gate proposals conceived for optical lattices. Additionally, we
analyze schemes both for cold atoms confined in optical cavities and hybrid
approaches to entanglement generation, and we show how optimal control theory
might be a powerful tool to enhance the speed up of the gate operations as well
as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on
Neutral Particles
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