5,279 research outputs found
Primordial magnetic fields and gravitational baryogenesis in nonlinear electrodynamics
The amplification of the primordial magnetic fields and the gravitational
baryogenesis, a mechanism that allows to generate the baryon asymmetry in the
Universe by means of the coupling between the Ricci scalar curvature and the
baryon current, are reviewed in the framework of the nonlinear electrodynamics.
To study the amplification of the primordial magnetic field strength, we write
down the gauge invariant wave equations and then solve them (in the long
wavelength approximation) for three different eras of the Universe: de Sitter,
the reheating and the radiation dominated era. Constraints on parameters
entering the nonlinear electrodynamics are obtained by using the amplitude of
the observed galactic magnetic fields and the baryon asymmetry, which are
characterized by the dimensionless parameters and
, respectively.Comment: 10 pages, 3 tables, 6 figures. Accepted for publication in Physical
Review
Monetary Equilibria over an Infinite Horizon.
Money provides liquidity services through a cash-in-advance constraint. The exchange of commodities and assets extends over an infinite horizon under uncertainty and a sequentially complete asset market. Monetary policy sets the path of rates of interest and accommodates the demand for balances. A public authority, inheriting a strictly positive public debt, raises revenue from taxes and seignorage. Competitive equilibria exist, under mild solvency conditions. But, for a fixed path of rates of interest, there is a nontrivial multiplicity of equilibrium paths of prices of commodities. Determinacy requires that, subject to no-arbitrage and in addition to rates of interest, the prices of state-contingent revenues be somehow determined.money; equilibrium; indeterminacy; monetary policy; fiscal policy
Dielectric matrix and plasmon dispersion in strongly coupled electronic bilayer liquids
We develop a dielectric matrix and analyze plasmon dispersion in strongly
coupled charged-particle bilayers in the quantum domain. The formulation is
based on the classical quasi-localized charge approximation (QLCA) and extends
the QLCA formalism into the quantum domain. Its development, which parallels
that of 2D companion paper [Phys. Rev. E 70, 026406 (2004)] by three of the
authors, generalizes the single-layer scalar formalism therein to a bilayer
matrix formalism. Using pair correlation function data generated from diffusion
Monte Carlo simulations, we calculate the dispersion of the in-phase and
out-of-phase plasmon modes over a wide range of in-layer coupling values and
layer spacings. The out-of-phase spectrum exhibits an exchange-correlation
induced long-wavelength energy gap in contrast to earlier predictions of
acoustic dispersion softened by exchange-correlations. The energy gap is
similar to what has been previously predicted for classical charged-particle
bilayers and subsequently confirmed by recent molecular dynamics computer
simulations.Comment: 53 pages including 15 Figures with their captions. Submitted to
Physical Review
Hormonal and Morphological Aspects of Growth and Sexual Maturation in Wild-Caught Male Vervet Monkeys (Chlorocebus aethiops pygerythrus)
Knowledge of baseline changes in testosterone (T) and other androgens is central to both investigations of morphological, physiological, and behavioral correlates of inter-individual variation in the timing and shape of key events and transitions over the life course and questions of the evolution of species-specific schedules of maturation in primates. T represents an important determinant of spermatogenesis in male mammals and plays a central role in the expression of male sexual behavior and the development of secondary sex characteristics. This research integrates hormonal and morphometric methods to determine age-related changes in fecal testosterone (fT) metabolites and morphological markers of sexual maturation, including testicular volume, body mass (measured as BMI), and canine length, over the life course in a cross-sectional sample (n = 56) of wild-caught South African male vervet monkeys (Chlorocebus aethiops pygerythrus). Contrary to expectations of this study, T was not significantly associated with age (p = 0.1316 by ANOVA). However, BMI (p = 0.00022) and testis volume (p = 4.335e-06) were strongly related to age, corresponding to the eruption of the canine teeth at adolescence (3-4 years of age). These results strongly suggest the existence of an adolescent growth spurt in male vervets. An interpretation of activation of the development of these maturational markers in preparation for challenges encountered at reproductive maturity, including dispersal and reproduction, is tentatively adopted here following Jolly and Phillips-Conroy (2003, 2006). However, future longitudinal observations to determine changes within individuals are necessary to provide greater confidence in this interpretation
Mapping Moral Landscapes: Cartographies of Ascent and Descent in the Narratives of Pro-Life Activists
The Supreme Court ruling of Roe v. Wade in 1973 brought to the fore of public consciousness in the United States two dominant stances on the issue of abortion (i.e. pro-life and pro-choice), each organized around a rhetoric of moral vilification. As the sites of abortion practice, abortion clinics have since become theatres of contention, where conflicting imaginings of agency, reproduction, and personhood take shape and are experienced. This paper seeks to explore the relationship between morality, place, and imaginative practice in the narratives of pro-life activists working at the doors of Affiliated Medical Services, a women’s health clinic providing abortions in Milwaukee, Wisconsin. Discourse about abortion experiences and activisms is treated reflexively as landscape talk – talk of how places are culturally recruited to stake out the values, histories, and identities of the individuals who occupy them. This paper argues that to better understand this process, there is a need to investigate how talk temporally and spatially located in the lived landscape is rooted in the imaginative landscape. How is abortion imaginatively rendered in talk? An answer to this question is approached by adopting Randall Lake’s (1984) heuristic model of an ascent-descent structure of moral discourse
Solid particle erosion and viscoelastic properties of thermoplastic polyurethanes
The wear resistance of several thermoplastic polyurethanes (TPUs) having different chemical nature and micronscale
arrangement of the hard and soft segments has been investigated by means of erosion and abrasion tests. The goal was
correlating the erosion performances of the materials to their macroscopic mechanical properties. Unlike conventional tests,
such as hardness and tensile measurements, viscoelastic analysis proved to be a valuable tool to study the erosion resistance
of TPUs. In particular, a strict correlation was found between the erosion rate and the high-frequency (~10^7 Hz) loss modulus.
The latter reflects the actual ability of TPU to dissipate the impact energy of the erodent particles
Electromagnetic shape resonances of a dielectric sphere and radiation of portable telephones
The frequency band used by cellular telephones includes the eigenfrequencies
of a dielectric sphere with physical characteristics close to those of a human
head. Proceeding from the spatial features of the natural modes of such a
sphere we propose an independent and clear evident accuracy test for the
complicated numerical calculations which are conducted when estimating the
potential hazard due to the use of cellular telephones, in particular, for the
check of a proper handling of the electromagnetic shape resonances of a human
head.Comment: 10 pages, 1 figure with 2 eps file
The static allometry of sexual and non-sexual traits in vervet monkeys
Sexual traits vary tremendously in static allometry. This variation may be explained in part by body size-related differences in the strength of selection. We tested this hypothesis in two populations of vervet monkeys, using estimates of the level of condition dependence for different morphological traits as a proxy for body size-related variation in the strength of selection. In support of the hypothesis, we found that the steepness of allometric slopes increased with the level of condition dependence. One trait of particular interest, the penis, had shallow allometric slopes and low levels of condition dependence, in agreement with one of the most consistent patterns yet detected in the study of allometry, namely that of genitalia exhibiting shallow allometries.This research was supported by NIH grant R01RR0163009
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