8,200 research outputs found
Algorithms For Extracting Timeliness Graphs
We consider asynchronous message-passing systems in which some links are
timely and processes may crash. Each run defines a timeliness graph among
correct processes: (p; q) is an edge of the timeliness graph if the link from p
to q is timely (that is, there is bound on communication delays from p to q).
The main goal of this paper is to approximate this timeliness graph by graphs
having some properties (such as being trees, rings, ...). Given a family S of
graphs, for runs such that the timeliness graph contains at least one graph in
S then using an extraction algorithm, each correct process has to converge to
the same graph in S that is, in a precise sense, an approximation of the
timeliness graph of the run. For example, if the timeliness graph contains a
ring, then using an extraction algorithm, all correct processes eventually
converge to the same ring and in this ring all nodes will be correct processes
and all links will be timely. We first present a general extraction algorithm
and then a more specific extraction algorithm that is communication efficient
(i.e., eventually all the messages of the extraction algorithm use only links
of the extracted graph)
Clock spectroscopy of interacting bosons in deep optical lattices
We report on high-resolution optical spectroscopy of interacting bosonic
Yb atoms in deep optical lattices with negligible tunneling. We prepare
Mott insulator phases with singly- and doubly-occupied isolated sites and probe
the atoms using an ultra-narrow "clock" transition. Atoms in singly-occupied
sites undergo long-lived Rabi oscillations. Atoms in doubly-occupied sites are
strongly affected by interatomic interactions, and we measure their inelastic
decay rates and energy shifts. We deduce from these measurements all relevant
collisional parameters involving both clock states, in particular the intra-
and inter-state scattering lengths
Collinear versus non-collinear magnetic order in Pd atomic clusters: ab-initio calculations
We present a thorough theoretical assessment of the stability of
non-collinear spin arrangements in small palladium clusters. We generally find
that ferromagnetic order is always preferred, but that antiferromagnetic and
non-collinear configurations of different sorts exist and compete for the first
excited isomers. We also show that the ground state is insensitive to the
choice of atomic configuration for the pseudopotential used and to the
approximation taken for the exchange and correlation potential. Moreover, the
existence and relative stability of the different excited configurations also
depends weakly on the approximations employed. These results provide strong
evidence on the transferability of pseudopotential and exchange and correlation
functionals for palladium clusters as opposed to the situation found for the
bulk phases of palladium.Comment: 5 pages, 4 figure
Quiescent thermal emission from neutron stars in LMXBs
We monitored the quiescent thermal emission from neutron stars in low-mass
X-ray binaries after active periods of intense activity in x-rays (outbursts).
The theoretical modeling of the thermal relaxation of the neutron star crust
may be used to establish constraints on the crust composition and transport
properties, depending on the astrophysical scenarios assumed. We numerically
simulated the thermal evolution of the neutron star crust and compared them
with inferred surface temperatures for five sources: MXB 1659-29, KS 1731-260,
EXO 0748-676, XTE J1701-462 and IGR J17480-2446. We find that the evolution of
MXB 1659-29, KS 1731-260 and EXO 0748-676 can be well described within a deep
crustal cooling scenario. Conversely, we find that the other two sources can
only be explained with models beyond crustal cooling. For the peculiar emission
of XTE J1701-462 we propose alternative scenarios such as residual accretion
during quiescence, additional heat sources in the outer crust, and/or thermal
isolation of the inner crust due to a buried magnetic field. We also explain
the very recent reported temperature of IGR J17480-2446 with an additional heat
deposition in the outer crust from shallow sources.Comment: 19 pages, 32 figures, 2 Append., revised version accepted for
publication in Astronomy & Astrophysic
Usability and Feasibility Study of a Remote Cognitive Behavioral Therapy System with Long-Term Unemployed Women
We present the results of the use of a cognitive behavioral therapeutic intervention tool to improve the mental, physical, and social health of a group of long-term unemployed women in Spain. Method: We sent automated text messages (SMS) to the mobile phones of long-term unemployed women selected at random from public social services. During a 28-day intervention period, women received four daily automated text messages on her mobile phone on a predetermined hourly schedule. We measured depression symptoms at the start and end of the intervention and we analyzed qualitative data to determine the acceptability of a remote SMS program. Results: Depression symptoms using the Personal Health Questionnaire-9 (PHQ-9), went from an average of 13.8 at baseline to 4.9 at the end of 28 days (p = 0.89). One hundred percent of the women reported that they liked receiving the text messages and most found them helpful
Non-linear Relaxation of Interacting Bosons Coherently Driven on a Narrow Optical Transition
We study the dynamics of a two-component Bose-Einstein condensate (BEC) of
Yb atoms coherently driven on a narrow optical transition. The
excitation transfers the BEC to a superposition of states with different
internal and momentum quantum numbers. We observe a crossover with decreasing
driving strength between a regime of damped oscillations, where coherent
driving prevails, and an incoherent regime, where relaxation takes over.
Several relaxation mechanisms are involved: inelastic losses involving two
excited atoms, leading to a non-exponential decay of populations; Doppler
broadening due to the finite momentum width of the BEC and inhomogeneous
elastic interactions, both leading to dephasing and to damping of the
oscillations. We compare our observations to a two-component Gross-Pitaevskii
(GP) model that fully includes these effects. For small or moderate densities,
the damping of the oscillations is mostly due to Doppler broadening. In this
regime, we find excellent agreement between the model and the experimental
results. For higher densities, the role of interactions increases and so does
the damping rate of the oscillations. The damping in the GP model is less
pronounced than in the experiment, possibly a hint for many-body effects not
captured by the mean-field description.Comment: 7 pages, 4 figures; supplementary material available as ancillary
fil
Fast connected component labeling algorithm: a non voxel-based approach
This paper presents a new approach to achieve connected component labeling on both binary images and volumes by using the Extreme Vertices Model (EVM), a representation model for orthogonal
polyhedra, applied to digital images and volume datasets recently. In contrast with previous techniques, this method does not use a voxel-based approach but deals with the inner sections of the object.Postprint (published version
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