451 research outputs found
The Coulomb-Higgs transition of the three-parameter U(1)-Higgs model
We find a first order Coulomb--Higgs phase transition at moderately large
values of the coupling , and no evidence for a change of order at any
finite value of it.Comment: 3 pages, uuencoded compressed ps file. Contribution to Lattice '9
Universal Finite Size Scaling Functions in the 3D Ising Spin Glass
We study the three-dimensional Edwards-Anderson model with binary
interactions by Monte Carlo simulations. Direct evidence of finite-size scaling
is provided, and the universal finite-size scaling functions are determined.
Monte Carlo data are extrapolated to infinite volume with an iterative
procedure up to correlation lengths xi \approx 140. The infinite volume data
are consistent with a conventional power law singularity at finite temperature
Tc. Taking into account corrections to scaling, we find Tc = 1.156 +/- 0.015,
nu = 1.8 +/- 0.2 and eta = -0.26 +/- 0.04. The data are also consistent with an
exponential singularity at finite Tc, but not with an exponential singularity
at zero temperature.Comment: 4 pages, Revtex, 4 postscript figures include
The three dimensional Ising spin glass in an external magnetic field: the role of the silent majority
We perform equilibrium parallel-tempering simulations of the 3D Ising
Edwards-Anderson spin glass in a field. A traditional analysis shows no signs
of a phase transition. Yet, we encounter dramatic fluctuations in the behaviour
of the model: Averages over all the data only describe the behaviour of a small
fraction of it. Therefore we develop a new approach to study the equilibrium
behaviour of the system, by classifying the measurements as a function of a
conditioning variate. We propose a finite-size scaling analysis based on the
probability distribution function of the conditioning variate, which may
accelerate the convergence to the thermodynamic limit. In this way, we find a
non-trivial spectrum of behaviours, where a part of the measurements behaves as
the average, while the majority of them shows signs of scale invariance. As a
result, we can estimate the temperature interval where the phase transition in
a field ought to lie, if it exists. Although this would-be critical regime is
unreachable with present resources, the numerical challenge is finally well
posed.Comment: 42 pages, 19 figures. Minor changes and added figure (results
unchanged
Thermodynamic glass transition in a spin glass without time-reversal symmetry
Spin glasses are a longstanding model for the sluggish dynamics that appears
at the glass transition. However, spin glasses differ from structural glasses
for a crucial feature: they enjoy a time reversal symmetry. This symmetry can
be broken by applying an external magnetic field, but embarrassingly little is
known about the critical behaviour of a spin glass in a field. In this context,
the space dimension is crucial. Simulations are easier to interpret in a large
number of dimensions, but one must work below the upper critical dimension
(i.e., in d<6) in order for results to have relevance for experiments. Here we
show conclusive evidence for the presence of a phase transition in a
four-dimensional spin glass in a field. Two ingredients were crucial for this
achievement: massive numerical simulations were carried out on the Janus
special-purpose computer, and a new and powerful finite-size scaling method.Comment: 10 pages, 6 figure
4D Spin Glasses in Magnetic Field Have a Mean Field like Phase
By using numerical simulations we show that the 4D Edwards Anderson
spin glass in magnetic field undergoes a mean field like phase transition. We
use a dynamical approach: we simulate large lattices (of volume ) and work
out the behavior of the system in limit where both and go to infinity,
but where the limit is taken first. By showing that the dynamic
overlap converges to a value smaller than the static one we exhibit replica
symmetry breaking. The critical exponents are compatible with the ones obtained
by mean field computations.Comment: Physrev format, 5 ps figures include
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Failure of Working Memory Training to Enhance Cognition or Intelligence
Fluid intelligence is important for successful functioning in the modern world, but much evidence suggests that fluid intelligence is largely immutable after childhood. Recently, however, researchers have reported gains in fluid intelligence after multiple sessions of adaptive working memory training in adults. The current study attempted to replicate and expand those results by administering a broad assessment of cognitive abilities and personality traits to young adults who underwent 20 sessions of an adaptive dual n-back working memory training program and comparing their post-training performance on those tests to a matched set of young adults who underwent 20 sessions of an adaptive attentional tracking program. Pre- and post-training measurements of fluid intelligence, standardized intelligence tests, speed of processing, reading skills, and other tests of working memory were assessed. Both training groups exhibited substantial and specific improvements on the trained tasks that persisted for at least 6 months post-training, but no transfer of improvement was observed to any of the non-trained measurements when compared to a third untrained group serving as a passive control. These findings fail to support the idea that adaptive working memory training in healthy young adults enhances working memory capacity in non-trained tasks, fluid intelligence, or other measures of cognitive abilities.</p
Multiferroic phase transition near room temperature in BiFeO3 films
In multiferroic BiFeO3 thin films grown on highly mismatched LaAlO3
substrates, we reveal the coexistence of two differently distorted polymorphs
that leads to striking features in the temperature dependence of the structural
and multiferroic properties. Notably, the highly distorted phase
quasi-concomitantly presents an abrupt structural change, transforms from a
hard to a soft ferroelectric and transitions from antiferromagnetic to
paramagnetic at 360+/-20 K. These coupled ferroic transitions just above room
temperature hold promises of giant piezoelectric, magnetoelectric and
piezomagnetic responses, with potential in many applications fields
Porcine colonization of the Americas: a 60k SNP story.
Made available in DSpace on 2018-07-01T01:24:17Z (GMT). No. of bitstreams: 1
hdy2012109a.pdf: 1129860 bytes, checksum: 44683cde430ba3f771242018513366b0 (MD5)
Previous issue date: 2013-02-26bitstream/item/179305/1/hdy2012109a.pd
Blood pressure and metabolic effects of acetyl-L-carnitine in type 2 diabetes: DIABASI randomized controlled trial
Context: Acetyl-L-carnitine (ALC), a mitochondrial carrier involved in lipid oxidation and glucose metabolism, decreased systolic blood pressure (SBP), and ameliorated insulin sensitivity in hypertensive nondiabetic subjects at high cardiovascular risk. Objective: To assess the effects of ALC on SBP and glycemic and lipid control in patients with hypertension, type 2 diabetes mellitus (T2D), and dyslipidemia on background statin therapy. Design: After 4-week run-in period and stratification according to previous statin therapy, patients were randomized to 6-month, double-blind treatment with ALC or placebo added-on simvastatin. Setting: Five diabetology units and one clinical research center in Italy. Patients: Two hundred twenty-nine patients with hypertension and dyslipidemic T2D > 40 years with stable background antihypertensive, hypoglycemic, and statin therapy and serum creatinine < 1.5 mg/ dL. Interventions: Oral ALC 1000 mg or placebo twice daily on top of stable simvastatin therapy. Outcome and Measures: Primary outcome was SBP. Secondary outcomes included lipid and glycemic profiles. Total-body glucose disposal rate and glomerular filtration rate were measured in subgroups by hyperinsulinemic-euglycemic clamp and iohexol plasma clearance, respectively. Results: SBP did not significantly change after 6-month treatment with ALC compared with placebo (-2.09mmHg vs-3.57mmHg, P = 0.9539). Serum cholesterol, triglycerides, and lipoprotein(a), as well as blood glucose, glycated hemoglobin, fasting insulin levels, homeostatic model assessment of insulin resistance index, glucose disposal rate, and glomerular filtration rate did not significantly differ between treatments. Adverse events were comparable between groups. Conclusions: Six-month oral ALC supplementation did not affect blood pressure, lipid and glycemic control, insulin sensitivity and kidney function in hypertensive normoalbuminuric and microalbuminuric T2D patients on background statin therapy
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