1,051 research outputs found
Multicomponent fluids of hard hyperspheres in odd dimensions
Mixtures of hard hyperspheres in odd space dimensionalities are studied with
an analytical approximation method. This technique is based on the so-called
Rational Function Approximation and provides a procedure for evaluating
equations of state, structure factors, radial distribution functions, and
direct correlations functions of additive mixtures of hard hyperspheres with
any number of components and in arbitrary odd-dimension space. The method gives
the exact solution of the Ornstein--Zernike equation coupled with the
Percus--Yevick closure, thus extending to arbitrary odd dimension the solution
for hard-sphere mixtures [J. L. Lebowitz, Phys.\ Rev.\ \textbf{133}, 895
(1964)]. Explicit evaluations for binary mixtures in five dimensions are
performed. The results are compared with computer simulations and a good
agreement is found.Comment: 16 pages, 8 figures; v2: slight change of notatio
The Autographa californica Nucleopolyhedrovirus IE-1 Protein Complex Has Two Modes of Specific DNA Binding
AbstractMissing contact footprinting with formic acid as a modifying reagent was used to examine specific IE-1 binding contacts to double-stranded oligonucleotides that contained either a consensus hr repeat sequence or a sequence from the pe38 promoter, which is down regulated by IE-1. The hr repeat sequences contain two consensus IE-1 binding motifs (IBMs) flanking a central EcoRI site that are oriented in opposite directions with respect to each other. IE-1 was found to contact regions including both IBMs. The bases footprinted in the top strand included the left IBM (IBM-A), whereas bases in the bottom strand were footprinted in a region that included IBM-B and part of IBM-A. When substitution mutations were introduced into either IBM, bases on both strands of the remaining IBM were strongly footprinted. As with the hr IBM-mutant constructs, bases footprinted in the pe38 promoter construct included both strands of the single IBM
Structure of hard-hypersphere fluids in odd dimensions
The structural properties of single component fluids of hard hyperspheres in
odd space dimensionalities are studied with an analytical approximation
method that generalizes the Rational Function Approximation earlier introduced
in the study of hard-sphere fluids [S. B. Yuste and A. Santos, Phys. Rev. A
{\bf 43}, 5418 (1991)]. The theory makes use of the exact form of the radial
distribution function to first order in density and extends it to finite
density by assuming a rational form for a function defined in Laplace space,
the coefficients being determined by simple physical requirements. Fourier
transform in terms of reverse Bessel polynomials constitute the mathematical
framework of this approximation, from which an analytical expression for the
static structure factor is obtained. In its most elementary form, the method
recovers the solution of the Percus-Yevick closure to the Ornstein-Zernike
equation for hyperspheres at odd dimension. The present formalism allows one to
go beyond by yielding solutions with thermodynamic consistency between the
virial and compressibility routes to any desired equation of state. Excellent
agreement with available computer simulation data at and is
obtained. As a byproduct of this study, an exact and explicit polynomial
expression for the intersection volume of two identical hyperspheres in
arbitrary odd dimensions is given.Comment: 18 pages, 7 figures; v2: new references added plus minor changes; to
be published in PR
Thermo-statistical description of gas mixtures from space partitions
The new mathematical framework based on the free energy of pure classical
fluids presented in [R. D. Rohrmann, Physica A 347, 221 (2005)] is extended to
multi-component systems to determine thermodynamic and structural properties of
chemically complex fluids. Presently, the theory focuses on -dimensional
mixtures in the low-density limit (packing factor ). The formalism
combines the free-energy minimization technique with space partitions that
assign an available volume to each particle. is related to the
closeness of the nearest neighbor and provides an useful tool to evaluate the
perturbations experimented by particles in a fluid. The theory shows a close
relationship between statistical geometry and statistical mechanics. New,
unconventional thermodynamic variables and mathematical identities are derived
as a result of the space division. Thermodynamic potentials ,
conjugate variable of the populations of particles class with the
nearest neighbors of class are defined and their relationships with the
usual chemical potentials are established. Systems of hard spheres are
treated as illustrative examples and their thermodynamics functions are derived
analytically. The low-density expressions obtained agree nicely with those of
scaled-particle theory and Percus-Yevick approximation. Several pair
distribution functions are introduced and evaluated. Analytical expressions are
also presented for hard spheres with attractive forces due to K\^ac-tails and
square-well potentials. Finally, we derive general chemical equilibrium
conditions.Comment: 14 pages, 8 figures. Accepted for publication in Physical Review
Loneliness is adversely associated with physical and mental health and lifestyle factors: Results from a Swiss national survey.
Loneliness is a common, emotionally distressing experience and is associated with adverse physical and mental health and an unhealthy lifestyle. Nevertheless, little is known about the prevalence of loneliness in different age groups in Switzerland. Furthermore, the existing evidence about age and gender as potential effect modifiers of the associations between loneliness, physical and mental health and lifestyle characteristics warrants further investigation. Thus, the aim of the study was to examine the prevalence of loneliness among adults in Switzerland and to assess the associations of loneliness with several physical and mental health and behavioral factors, as well as to assess the modifying effect of sex and age.
Data from 20,007 participants of the cross-sectional population-based Swiss Health Survey 2012 (SHS) were analyzed. Logistic regression analyses were used to assess associations of loneliness with physical and mental health or lifestyle characteristics (e.g. diabetes, depression, physical activity). Wald tests were used to test for interactions.
Loneliness was distributed in a slight U-shaped form from 15 to 75+ year olds, with 64.1% of participants who had never felt lonely. Lonely individuals were more often affected by physical and mental health problems, such as self-reported chronic diseases (Odds ratio [OR] 1.41, 95% confidence interval [CI] 1.30-1.54), high cholesterol levels (OR 1.31, 95% CI 1.18-1.45), diabetes (OR 1.40, 95% CI 1.16-1.67), moderate and high psychological distress (OR 3.74, 95% CI 3.37-4.16), depression (OR 2.78, 95% CI 2.22-3.48) and impaired self-perceived health (OR 1.94, 95% CI 1.74-2.16). Loneliness was significantly associated with most lifestyle factors (e.g. smoking; OR 1.13, 95% 1.05-1.23). Age, but not sex, moderated loneliness' association with several variables.
Loneliness is associated with poorer physical and mental health and unhealthy lifestyle, modified by age, but not by sex. Our findings illustrate the importance of considering loneliness for physical and mental health and lifestyle factors, not only in older and younger, but also in middle-aged adults. Longitudinal studies are needed in Switzerland to elucidate the causal relationships of these associations
Evolution of white dwarf stars with high-metallicity progenitors: the role of 22Ne diffusion
Motivated by the strong discrepancy between the main sequence turn-off age
and the white dwarf cooling age in the metal-rich open cluster NGC 6791, we
compute a grid of white dwarf evolutionary sequences that incorporates for the
first time the energy released by the processes of 22Ne sedimentation and of
carbon/oxygen phase separation upon crystallization. The grid covers the mass
range from 0.52 to 1.0 Msun, and it is appropriate for the study of white
dwarfs in metal-rich clusters. The evolutionary calculations are based on a
detailed and self-consistent treatment of the energy released from these two
processes, as well as on the employment of realistic carbon/oxygen profiles, of
relevance for an accurate evaluation of the energy released by carbon/oxygen
phase separation. We find that 22Ne sedimentation strongly delays the cooling
rate of white dwarfs stemming from progenitors with high metallicities at
moderate luminosities, whilst carbon/oxygen phase separation adds considerable
delays at low luminosities. Cooling times are sensitive to possible
uncertainties in the actual value of the diffusion coefficient of 22Ne.
Changing the diffusion coefficient by a factor of 2, leads to maximum age
differences of approx. 8-20% depending on the stellar mass. We find that the
magnitude of the delays resulting from chemical changes in the core is
consistent with the slow down in the white dwarf cooling rate that is required
to solve the age discrepancy in NGC 6791.Comment: 10 pages, 6 figures, to be published in The Astrophysical Journa
Evolution of white dwarf stars with high-metallicity progenitors: The role of 22Ne diffusion
Motivated by the strong discrepancy between the main-sequence turnoff age and the white dwarf cooling age in the metal-rich open cluster NGC 6791, we compute a grid of white dwarf evolutionary sequences that incorporates for the first time the energy released by the processes of 22Ne sedimentation and of carbon/oxygen phase separation upon crystallization. The grid covers the mass range from 0.52 to 1.0M⊙, and is appropriate for the study of white dwarfs in metal-rich clusters. The evolutionary calculations are based on a detailed and self-consistent treatment of the energy released from these two processes, as well as on the employment of realistic carbon/oxygen profiles, of relevance for an accurate evaluation of the energy released by carbon/oxygen phase separation. We find that 22Ne sedimentation strongly delays the cooling rate of white dwarfs stemming from progenitors with high metallicities at moderate luminosities, while carbon/oxygen phase separation adds considerable delays at lowluminosities. Cooling times are sensitive to possible uncertainties in the actual value of the diffusion coefficient of 22Ne. Changing the diffusion coefficient by a factor of 2 leads to maximum age differences of ≈8%-20% depending on the stellar mass. We find that the magnitude of the delays resulting from chemical changes in the core is consistent with the slowdown in the white dwarf cooling rate that is required to solve the age discrepancy in NGC 6791.Facultad de Ciencias Astronómicas y Geofísica
Virial series for fluids of hard hyperspheres in odd dimensions
A recently derived method [R. D. Rohrmann and A. Santos, Phys. Rev. E. {\bf
76}, 051202 (2007)] to obtain the exact solution of the Percus-Yevick equation
for a fluid of hard spheres in (odd) dimensions is used to investigate the
convergence properties of the resulting virial series. This is done both for
the virial and compressibility routes, in which the virial coefficients
are expressed in terms of the solution of a set of coupled algebraic
equations which become nonlinear for . Results have been derived up
to . A confirmation of the alternating character of the series for , due to the existence of a branch point on the negative real axis, is found
and the radius of convergence is explicitly determined for each dimension. The
resulting scaled density per dimension , where is the
packing fraction, is wholly consistent with the limiting value of 1 for . Finally, the values for predicted by the virial and
compressibility routes in the Percus-Yevick approximation are compared with the
known exact values [N. Clisby and B. M. McCoy, J. Stat. Phys. {\bf 122}, 15
(2006)]Comment: 9 pages, 6 figure
Gender balance in ECEC : why is there s little progres?
Social attitudes about male participation in the upbringing of children have changed considerably over the past few decades. Men are now seen as important for children’s development and learning. Research from many countries worldwide shows that in early childhood care and education (ECEC), male workers are welcomed by female colleagues and parents. In the last two decades there have been initiatives for more men in ECEC in several European countries.
Nevertheless the proportion of male workers ECEC remains low worldwide. This article questions the persisting gender imbalance in ECEC and analyzes ambivalences regarding more men in the field. Based on recent gender theory, efforts and limits of strategies for more male students and workers in ECEC in Belgium, Norway and Germany are discussed. It is concluded that deeply held gendered attitudes and practices in the field of care and educational work with young children have to be put into question. More space in ECEC for embodied
subjectivities is needed to overcome essentialist conceptions of differences between body and mind, women and men
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