994 research outputs found
Quantum Criticality from in-situ Density Imaging
We perform large-scale Quantum Monte Carlo (QMC) simulations for strongly
interacting bosons in a 2D optical lattice trap, and confirm an excellent
agreement with the benchmarking in-situ density measurements by the Chicago
group [1]. We further present a general finite temperature phase diagram both
for the uniform and the trapped systems, and demonstrate how the universal
scaling properties near the superfluid(SF)-to-Mott insulator(MI) transition can
be observed by analysing the in-situ density profile. The characteristic
temperature to find such quantum criticality is estimated to be of the order of
the single-particle bandwidth, which should be achievable in the present or
near future experiments. Finally, we examine the validity regime of the local
fluctuation-dissipation theorem (FDT), which can be a used as a thermometry in
the strongly interacting regime.Comment: 4 page
Expression of concern: Prevalence of hepatitis B and hepatitis C infection in Libya: results from a national population based survey
A framework for analyzing both linkage and association: An analysis of Genetic Analysis Workshop 16 simulated data
We examine a Bayesian Markov-chain Monte Carlo framework for simultaneous segregation and linkage analysis in the simulated single-nucleotide polymorphism data provided for Genetic Analysis Workshop 16. We conducted linkage only, linkage and association, and association only tests under this framework. We also compared these results with variance-component linkage analysis and regression analyses. The results indicate that the method shows some promise, but finding genes that have very small (<0.1%) contributions to trait variance may require additional sources of information. All methods examined fared poorly for the smallest in the simulated "polygene" range (h(2 )of 0.0015 to 0.0002)
Assessment of long-range correlation in animal behaviour time series: the temporal pattern of locomotor activity of Japanese quail (Coturnix coturnix) and mosquito larva (Culex quinquefasciatus)
The aim of this study was to evaluate the performance of a classical method
of fractal analysis, Detrended Fluctuation Analysis (DFA), in the analysis of
the dynamics of animal behavior time series. In order to correctly use DFA to
assess the presence of long-range correlation, previous authors using
statistical model systems have stated that different aspects should be taken
into account such as: 1) the establishment by hypothesis testing of the absence
of short term correlation, 2) an accurate estimation of a straight line in the
log-log plot of the fluctuation function, 3) the elimination of artificial
crossovers in the fluctuation function, and 4) the length of the time series.
Taking into consideration these factors, herein we evaluated the presence of
long-range correlation in the temporal pattern of locomotor activity of
Japanese quail ({\sl Coturnix coturnix}) and mosquito larva ({\sl Culex
quinquefasciatus}). In our study, modeling the data with the general ARFIMA
model, we rejected the hypothesis of short range correlations (d=0) in all
cases. We also observed that DFA was able to distinguish between the artificial
crossover observed in the temporal pattern of locomotion of Japanese quail, and
the crossovers in the correlation behavior observed in mosquito larvae
locomotion. Although the test duration can slightly influence the parameter
estimation, no qualitative differences were observed between different test
durations
Candidate gene resequencing to identify rare, pedigree-specific variants influencing healthy aging phenotypes in the long life family study
Background: The Long Life Family Study (LLFS) is an international study to identify the genetic components of various healthy aging phenotypes. We hypothesized that pedigree-specific rare variants at longevity-associated genes could have a similar functional impact on healthy phenotypes. Methods: We performed custom hybridization capture sequencing to identify the functional variants in 464 candidate genes for longevity or the major diseases of aging in 615 pedigrees (4,953 individuals) from the LLFS, using a multiplexed, custom hybridization capture. Variants were analyzed individually or as a group across an entire gene for association to aging phenotypes using family based tests. Results: We found significant associations to three genes and nine single variants. Most notably, we found a novel variant significantly associated with exceptional survival in the 3' UTR OBFC1 in 13 individuals from six pedigrees. OBFC1 (chromosome 10) is involved in telomere maintenance, and falls within a linkage peak recently reported from an analysis of telomere length in LLFS families. Two different algorithms for single gene associations identified three genes with an enrichment of variation that was significantly associated with three phenotypes (GSK3B with the Healthy Aging Index, NOTCH1 with diastolic blood pressure and TP53 with serum HDL). Conclusions: Sequencing analysis of family-based associations for age-related phenotypes can identify rare or novel variants
Ab initio study of the modification of elastic properties of alpha-iron by hydrostatic strain and by hydrogen interstitials
The effect of hydrostatic strain and of interstitial hydrogen on the elastic
properties of -iron is investigated using \textit{ab initio}
density-functional theory calculations. We find that the cubic elastic
constants and the polycrystalline elastic moduli to a good approximation
decrease linearly with increasing hydrogen concentration. This net strength
reduction can be partitioned into a strengthening electronic effect which is
overcome by a softening volumetric effect. The calculated hydrogen-dependent
elastic constants are used to determine the polycrystalline elastic moduli and
anisotropic elastic shear moduli. For the key slip planes in -iron,
and , we find a shear modulus reduction of
approximately 1.6% per at.% H.Comment: Updated first part of 1009.378
Geographic distribution of HCV genotypes in Libya and analysis of risk factors involved in their transmission
Pair vs many-body potentials: influence on elastic and plastic behavior in nanoindentation
Molecular-dynamics simulation can give atomistic information on the processes
occurring in nanoindentation experiments. In particular, the nucleation of
dislocation loops, their growth, interaction and motion can be studied. We
investigate how realistic the interatomic potentials underlying the simulations
have to be in order to describe these complex processes. Specifically we
investigate nanoindentation into a Cu single crystal. We compare simulations
based on a realistic many-body interaction potential of the
embedded-atom-method type with two simple pair potentials, a Lennard-Jones and
a Morse potential. We find that qualitatively many aspects of nanoindentation
are fairly well reproduced by the simple pair potentials: elastic regime,
critical stress and indentation depth for yielding, dependence on the crystal
orientation, and even the level of the hardness. The quantitative deficits of
the pair potential predictions can be traced back (i) to the fact that the pair
potentials are unable in principle to model the elastic anisotropy of cubic
crystals; (ii) as the major drawback of pair potentials we identify the gross
underestimation of the stable stacking fault energy. As a consequence these
potentials predict the formation of too large dislocation loops, the too rapid
expansion of partials, too little cross slip and in consequence a severe
overestimation of work hardening.Comment: 28 page
Transcranial direct current stimulation of right dorsolateral prefrontal cortex does not affect model-based or model-free reinforcement learning in humans
There is broad consensus that the prefrontal cortex supports goal-directed, model-based decision-making. Consistent with this, we have recently shown that model-based control can be impaired through transcranial magnetic stimulation of right dorsolateral prefrontal cortex in humans. We hypothesized that an enhancement of model-based control might be achieved by anodal transcranial direct current stimulation of the same region. We tested 22 healthy adult human participants in a within-subject, double-blind design in which participants were given Active or Sham stimulation over two sessions. We show Active stimulation had no effect on model-based control or on model-free ('habitual') control compared to Sham stimulation. These null effects are substantiated by a power analysis, which suggests that our study had at least 60% power to detect a true effect, and by a Bayesian model comparison, which favors a model of the data that assumes stimulation had no effect over models that assume stimulation had an effect on behavioral control. Although we cannot entirely exclude more trivial explanations for our null effect, for example related to (faults in) our experimental setup, these data suggest that anodal transcranial direct current stimulation over right dorsolateral prefrontal cortex does not improve model-based control, despite existing evidence that transcranial magnetic stimulation can disrupt such control in the same brain region
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