Yet another surprise in the problem of classical diamagnetism

The well known Bohr-van Leeuwen Theorem states that the orbital diamagnetism of classical charged particles is identically zero in equilibrium. However, results based on real space-time approach using the classical Langevin equation predicts non-zero diamagnetism for classical unbounded (finite or infinite) systems. Here we show that the recently discovered Fluctuation Theorems, namely, the Jarzynski Equality or the Crooks Fluctuation Theorem surprisingly predict a free energy that depends on magnetic field as well as on the friction coefficient, in outright contradiction to the canonical equilibrium results. However, in the cases where the Langevin approach is consistent with the equilibrium results, the Fluctuation Theorems lead to results in conformity with equilibrium statistical mechanics. The latter is demonstrated analytically through a simple example that has been discussed recently.Comment: 6 pages, 6 figure

Bohr-van Leeuwen theorem and the thermal Casimir effect for conductors

The problem of estimating the thermal corrections to Casimir and Casimir-Polder interactions in systems involving conducting plates has attracted considerable attention in the recent literature on dispersion forces. Alternative theoretical models, based on distinct low-frequency extrapolations of the plates reflection coefficient for transverse electric (TE) modes, provide widely different predictions for the magnitude of this correction. In this paper we examine the most widely used prescriptions for this reflection coefficient from the point of view of their consistency with the Bohr-van Leeuwen theorem of classical statistical physics, stating that at thermal equilibrium transverse electromagnetic fields decouple from matter in the classical limit. We find that the theorem is satisfied if and only if the TE reflection coefficient vanishes at zero frequency in the classical limit. This criterion appears to rule out some of the models that have been considered recently for describing the thermal correction to the Casimir pressure with non-magnetic metallic plates.Comment: 12 pages, no figures. Presentation has been significantly improved, more references included. The new version matches the one accepted for publication in Phys. Rev.

Impurity relaxation mechanism for dynamic magnetization reversal in a single domain grain

The interaction of coherent magnetization rotation with a system of two-level impurities is studied. Two different, but not contradictory mechanisms, the `slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system of integro-differential equations for the magnetization. In the case that the impurity relaxation rate is much greater than the magnetization precession frequency, these equations can be written in the form of the Landau-Lifshitz equation with damping. Thus the damping parameter can be directly calculated from these microscopic impurity relaxation processes

Sex and Exercise Intensity Do Not Influence Oxygen Uptake Kinetics in Submaximal Swimming.

The aim of this study was to compare the oxygen uptake ([Formula: see text]) kinetics in front crawl between male and female swimmers at moderate and heavy intensity. We hypothesized that the time constant for the primary phase [Formula: see text] kinetics was faster in men than in women, for both intensities. Nineteen well trained swimmers (8 females mean ± SD; age 17.9 ± 3.5 years; mass 55.2 ± 3.6 kg; height 1.66 ± 0.05 m and 11 male 21.9 ± 2.8 years; 78.2 ± 11.1 kg; 1.81 ± 0.08 m) performed a discontinuous maximal incremental test and two 600-m square wave transitions for both moderate and heavy intensities to determine the [Formula: see text] kinetics parameters using mono- and bi-exponential models, respectively. All the tests involved breath-by-breath analysis of front crawl swimming using a swimming snorkel. The maximal oxygen uptake [Formula: see text] was higher in men than in women [4,492 ± 585 ml·min(-1) and 57.7 ± 4.4 ml·kg(-1)·min(-1) vs. 2,752.4 ± 187.9 ml·min(-1) (p ≤ 0.001) and 50.0 ± 5.7 ml·kg(-1)·min(-1)(p = 0.007), respectively]. Similarly, the absolute amplitude of the primary component was higher in men for both intensities (moderate: 1,736 ± 164 vs. 1,121 ± 149 ml·min(-1); heavy: 2,948 ± 227 vs. 1,927 ± 243 ml·min(-1), p ≤ 0.001, for males and females, respectively). However, the time constant of the primary component (τp) was not influenced by sex (p = 0.527) or swimming intensity (p = 0.804) (moderate: 15.1 ± 5.6 vs. 14.4 ± 5.1 s; heavy: 13.5 ± 3.3 vs. 16.0 ± 4.5 s, for females and males, respectively). The slow component in the heavy domain was not significantly different between female and male swimmers (3.2 ± 2.4 vs. 3.8 ± 1.0 ml·kg(-1)·min(-1), p = 0.476). Overall, only the absolute amplitude of the primary component was higher in men, while the other [Formula: see text] kinetics parameters were similar between female and male swimmers at both moderate and heavy intensities. The mechanisms underlying these similarities remain unclear

Effect of competition on gain in feedlot bulls from Hereford selection lines

This study examined competition effects on ADG in the feedlot of 1,882 Hereford bulls representing 8 birth years from a selection experiment. Each year, 8 feedlot pens were used to feed bulls in groups, with 2 pens nested within each of the 4 selection lines. Gains were recorded for up to 8 periods of 28 d. Models for analyses included pen effects (fixed or random), fixed effects such as year and line, and random direct genetic, competition genetic (and in some analyses competition environmental), and environmental effects. Each pen mate as a competitor affected the records of all others in the pen. All lines traced to common foundation animals, so the numerator relationships among and within pens were the bases for separating direct and competition genetic effects and pen effects. For this population and pen conditions (average of 30 bulls per pen), the major results were 1) competition genetic effects seemed present for the first 28-d period but not for the following 7 periods; 2) models with pens considered as fixed effects could not separate variances and covariance due to direct and competition genetic effects; 3) models without competition effects had large estimates of the variance component due to pen effects for gain through 8 periods; and 4) models with genetic and environmental competition effects accounted for nearly all of the variance traditionally attributed to pen effects (even though estimates of the competition variance component were small, the estimates of pen variance were near zero)

Kinematic parameters and oxygen uptake kinetics during sub-maximal exercise in swimming

Trabalho apresentado no 19 th Annual Congress of the European College of Sport Science, 2-5 julho 2014, Amesterdão, Holand

The distance-time relationship and oxygen uptake kinetics in swimming

Trabalho apresentado no 19th Annual Congress of the European College of Sport Science, 2-5 julho, Amesterdão, Holand

Superconducting Fluctuations in a Multi-Band 1D Hubbard Model

A renormalization-group and bosonization approach for a multi-band Hubbard Hamiltonian in one dimension is described. Based on the limit of many bands, it is argued that this Hamiltonian with bare repulsive electron-electron interactions is scaled under specific conditions to a model in which superconducting fluctuations dominate.Comment: 12 pages + 1 fig, Revtex, Preprint - Los Alamo

Twinning in Cattle

Rate of reproduction has a major impact on life cycle costs of production of different animal species and upon their competitiveness for different types of production resources. For example, the average beef cow is capable of producing about .7 of her body weight per year in progeny market weight; comparable values are about 8 in pigs, more than 70 in meat chickens and more than 1,000 in catfish. More than 50% of the feed nutrients used by the beef cattle industry of the United States are needed to meet maintenance requirements of reproducing females. The comparable value in meat chickens is less than 3%. Further, high producing dairy cows produce five times as much milk protein per unit of feed as beef cattle produce as beef protein. Small differences in reproduction rate of beef cattle can have a major effect on costs of production and on the production resources for which beef cattle are competitive. Results from experimentation and computer simulation suggest that input costs per unit of beef output could be reduced by from 20 to 30% for the proportion of the herd that produces twins. A twinning technology would require a highly intensive production system. Initial calculations indicate that a twinning rate of about 40% may be needed to make a twinning technology economically viable. Because of the time and effort required to develop a population with a twinning frequency of 40% or greater, private sector interests are not likely to make the investment required. Thus, the development of a population of cattle that has a high breeding value for twinning (i.e., 40% or greater) and is competitive in production and carcass traits is an essential component of a twinning technology for use by the beef cattle industry

Slow spin relaxation in a highly polarized cooperative paramagnet

We report measurements of the ac susceptibility of the cooperative paramagnet Tb2Ti2O7 in a strong magnetic field. Our data show the expected saturation maximum in chi(T) and also an unexpected low frequency dependence (< 1 Hz) of this peak, suggesting very slow spin relaxations are occurring. Measurements on samples diluted with nonmagnetic Y3+ or Lu3+ and complementary measurements on pure and diluted Dy2Ti2O7 strongly suggest that the relaxation is associated with dipolar spin correlations, representing unusual cooperative behavior in a paramagnetic system.Comment: Accepted for publication in Physical Review Letter