305 research outputs found
Selected Contemporary Challenges of Ageing Policy
Among the scholars trying to grasp the
nuances and trends of social policy, there are diverse perspectives,
resulting not only from the extensive knowledge of the authors on
the systematic approach to the issue of supporting older people but
also from the grounds of the represented social gerontology
schools. In the texts of Volume VII interesting are both distinct
and coherent elements presenting the role of local, regional and
global policies in the prism of the countries from which the
authors originate: the Czech Republic, Slovenia, Lithuania, Latvia,
Poland, Slovakia, Italy, Turkey, and the United States.
The chapters show a wealth of methodological approaches
to the perception of social policy and its tools. In the texts there
are issues related to the idea of active ageing, discrimination
against older people in the workplace, comparability of solutions
friendly to employment of older adults in the Czech Republic,
Poland, and Slovakia as well as focused on the importance of
educational forms (universities of the third age, senior clubs, folk
high schools, and other non-formal solutions) determining an
active life in old age.
This monograph also attempted to answer the question
regarding how to transfer the idea of intergenerational learning
into the realm of practice. This issue complements the chapter on
the implementation of intergenerational programs in institutions
providing long-term care support. The book also outlines a public
policy on ageing in the perspective of the changes over the last
few decades (Slovenia) and the case demonstrating solutions to
accelerate self-reliance as a key to active ageing (Turkey)
Correlations, compressibility, and capacitance in double-quantum-well systems in the quantum Hall regime
In the quantum Hall regime, electronic correlations in double-layer
two-dimensional electron systems are strong because the kinetic energy is
quenched by Landau quantization. In this article we point out that these
correlations are reflected in the way the partitioning of charge between the
two-layers responds to a bias potential. We report on illustrative calculations
based on an unrestricted Hartree-Fock approximation which allows for
spontaneous inter-layer phase coherence. The possibility of studying
inter-layer correlations by capacitive coupling to separately contacted
two-dimensional layers is discussed in detail.Comment: RevTex style, 21 pages, 6 postscript figures in a separate file;
Phys. Rev. B (in press
Thomas-Fermi-Dirac-von Weizsacker hydrodynamics in laterally modulated electronic systems
We have studied the collective plasma excitations of a two-dimensional
electron gas with an arbitrary lateral charge-density modulation. The dynamics
is formulated using a previously developed hydrodynamic theory based on the
Thomas-Fermi-Dirac-von Weizsacker approximation. In this approach, both the
equilibrium and dynamical properties of the periodically modulated electron gas
are treated in a consistent fashion. We pay particular attention to the
evolution of the collective excitations as the system undergoes the transition
from the ideal two-dimensional limit to the highly-localized one-dimensional
limit. We also calculate the power absorption in the long-wavelength limit to
illustrate the effect of the modulation on the modes probed by far-infrared
(FIR) transmission spectroscopy.Comment: 27 page Revtex file, 15 Postscript figure
Theory of spin-polarized bipolar transport in magnetic p-n junctions
The interplay between spin and charge transport in electrically and
magnetically inhomogeneous semiconductor systems is investigated theoretically.
In particular, the theory of spin-polarized bipolar transport in magnetic p-n
junctions is formulated, generalizing the classic Shockley model. The theory
assumes that in the depletion layer the nonequilibrium chemical potentials of
spin up and spin down carriers are constant and carrier recombination and spin
relaxation are inhibited. Under the general conditions of an applied bias and
externally injected (source) spin, the model formulates analytically carrier
and spin transport in magnetic p-n junctions at low bias. The evaluation of the
carrier and spin densities at the depletion layer establishes the necessary
boundary conditions for solving the diffusive transport equations in the bulk
regions separately, thus greatly simplifying the problem. The carrier and spin
density and current profiles in the bulk regions are calculated and the I-V
characteristics of the junction are obtained. It is demonstrated that spin
injection through the depletion layer of a magnetic p-n junction is not
possible unless nonequilibrium spin accumulates in the bulk regions--either by
external spin injection or by the application of a large bias. Implications of
the theory for majority spin injection across the depletion layer, minority
spin pumping and spin amplification, giant magnetoresistance, spin-voltaic
effect, biasing electrode spin injection, and magnetic drift in the bulk
regions are discussed in details, and illustrated using the example of a GaAs
based magnetic p-n junction.Comment: 36 pages, 11 figures, 2 table
Spin-polarized transport and Andreev reflection in semiconductor/superconductor hybrid structures
We show that spin-polarized electron transmission across
semiconductor/superconductor (Sm/S) hybrid structures depends sensitively on
the degree of spin polarization as well as the strengths of potential and
spin-flip scattering at the interface. We demonstrate that increasing the Fermi
velocity mismatch in the Sm and S regions can lead to enhanced junction
transparency in the presence of spin polarization. We find that the Andreev
reflection amplitude at the superconducting gap energy is a robust measure of
the spin polarization magnitude, being independent of the strengths of
potential and spin-flip scattering and the Fermi velocity of the
superconductor.Comment: 4 pages, 2 figure
Electron spin as a spectrometer of nuclear spin noise and other fluctuations
This chapter describes the relationship between low frequency noise and
coherence decay of localized spins in semiconductors. Section 2 establishes a
direct relationship between an arbitrary noise spectral function and spin
coherence as measured by a number of pulse spin resonance sequences. Section 3
describes the electron-nuclear spin Hamiltonian, including isotropic and
anisotropic hyperfine interactions, inter-nuclear dipolar interactions, and the
effective Hamiltonian for nuclear-nuclear coupling mediated by the electron
spin hyperfine interaction. Section 4 describes a microscopic calculation of
the nuclear spin noise spectrum arising due to nuclear spin dipolar flip-flops
with quasiparticle broadening included. Section 5 compares our explicit
numerical results to electron spin echo decay experiments for phosphorus doped
silicon in natural and nuclear spin enriched samples.Comment: Book chapter in "Electron spin resonance and related phenomena in low
dimensional structures", edited by Marco Fanciulli. To be published by
Springer-Verlag in the TAP series. 35 pages, 9 figure
Thermodynamics of Trapped Imbalanced Fermi Gases at Unitarity
We present a theory for the low-temperature properties of a resonantly
interacting Fermi mixture in a trap, that goes beyond the local-density
approximation. The theory corresponds essentially to a Landau-Ginzburg-like
approach that includes self-energy effects to account for the strong
interactions at unitarity. We show diagrammatically how these self-energy
effects arise from fluctuations in the superfluid order parameter. Gradient
terms of the order parameter are included to account for inhomogeneities. This
approach incorporates the state-of-the-art knowledge of the homogeneous mixture
with a population imbalance exactly and gives good agreement with the
experimental density profiles of Shin et al. [Nature 451, 689 (2008)]. This
allows us to calculate the universal surface tension of the interface between
the equal-density superfluid and the partially polarized normal state of the
mixture. We also discuss the possibility of a metastable state to explain the
deformation of the superfluid core that is seen in the experiment of Partridge
et al. [Science 311, 503 (2006)].Comment: 26 pages, 7 figures, contribution to Lecture Notes in Physics
"BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge
ϒ production in p–Pb collisions at √sNN=8.16 TeV
ϒ production in p–Pb interactions is studied at the centre-of-mass energy per nucleon–nucleon collision √sNN = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the ϒ(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the ϒ(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the ϒ(1S). A first measurement of the ϒ(3S) has also been performed. Finally, results are compared with previous ALICE measurements in p–Pb collisions at √sNN = 5.02 TeV and with theoretical calculations.publishedVersio
(Anti-)deuteron production in pp collisions at 1as=13TeV
The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at s=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity (d Nch/ d \u3b7 3c 26) as measured in p\u2013Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p\u2013Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM)
Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV
Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe
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