441 research outputs found
Twist Mode in Spherical Alkali Metal Clusters
A remarkable orbital quadrupole magnetic resonance, so-called twist mode, is
predicted in alkali metal clusters where it is represented by
low-energy excitations of valence electrons with strong M2 transitions to the
ground state. We treat the twist by both macroscopic and microscopic ways. In
the latter case, the shell structure of clusters is fully exploited, which is
crucial for the considered size region (). The
energy-weighted sum rule is derived for the pseudo-Hamiltonian. In medium and
heavy spherical clusters the twist dominates over its spin-dipole counterpart
and becomes the most strong multipole magnetic mode.Comment: 8 pages, 4 figures, to be published in Phys. Rev. Lett., v.85, n.15,
200
Infrared electron modes in light deformed clusters
Infrared quadrupole modes (IRQM) of the valence electrons in light deformed
sodium clusters are studied by means of the time-dependent local-density
approximation (TDLDA). IRQM are classified by angular momentum components
20, 21 and 22 whose branches are separated by cluster
deformation. In light clusters with a low spectral density, IRQM are
unambiguously related to specific electron-hole excitations, thus giving access
to the single-electron spectrum near the Fermi surface (HOMO-LUMO region). Most
of IRQM are determined by cluster deformation and so can serve as a sensitive
probe of the deformation effects in the mean field. The IRQM branch 21 is coupled with the magnetic scissors mode, which gives a chance to detect
the latter. We discuss two-photon processes, Raman scattering (RS), stimulated
emission pumping (SEP), and stimulated adiabatic Raman passage (STIRAP), as the
relevant tools to observe IRQM. A new method to detect the IRQM population in
clusters is proposed.Comment: 22 pages, 6 figure
Legal coercion, respect & reason-responsive agency
Legal coercion seems morally problematic because it is susceptible to the Hegelian objection that it fails to respect individuals in a way that is ‘due to them as men’. But in what sense does legal coercion fail to do so? And what are the grounds for this requirement to respect? This paper is an attempt to answer these questions. It argues that (a) legal coercion fails to respect individuals as reason-responsive agents; and (b) individuals ought to be respected as such in virtue of the fact that they are human beings. Thus it is in this sense that legal coercion fails to treat individuals with the kind of respect ‘due to them as men’.The Leverhulme Trust (ECF-2012-032); AHRC (AH/H015655/1
Integral representation of the RPA correlation energy
Using the spectral function F'(z)/F(z) the RPA correlation energy and other
properties of a finite system can be written as a contour integral in a compact
way. This yields a transparent expression and reduces drastically the numerical
efforts for obtaining reliable values. The method applied to pairing vibrations
in rotating nuclei as an illustrative example.Comment: 9 pages, 2 figures (eps files
Oscillatory Size-Dependence of the Surface Plasmon Linewidth in Metallic Nanoparticles
We study the linewidth of the surface plasmon resonance in the optical
absorption spectrum of metallic nanoparticles, when the decay into
electron-hole pairs is the dominant channel. Within a semiclassical approach,
we find that the electron-hole density-density correlation oscillates as a
function of the size of the particles, leading to oscillations of the
linewidth. This result is confirmed numerically for alkali and noble metal
particles. While the linewidth can increase strongly, the oscillations persist
when the particles are embedded in a matrix.Comment: RevTeX4, 5 pages, 2 figures, final versio
Wavelet signatures of -splitting of the Isoscalar Giant Quadrupole Resonance in deformed nuclei from high-resolution (p,p) scattering off Nd
The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance
(ISGQR) has been studied with high energy-resolution proton inelastic
scattering at iThemba LABS in the chain of stable even-mass Nd isotopes
covering the transition from spherical to deformed ground states. A wavelet
analysis of the background-subtracted spectra in the deformed 146,148,150Nd
isotopes reveals characteristic scales in correspondence with scales obtained
from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance
analysis shows that these scales arise from the energy shift between the main
fragments of the K = 0, 1 and K = 2 components.Comment: 7 pages, 6 figure
Police ethics and integrity: Can a new code overturn the blue code?
This paper analyses police officer perspectives on the seriousness of potential misconduct or unethical behaviour, and the factors that might shape whether they would report their colleagues' misdemeanours. It compares responses from police officers in UK three forces, looking at potentially corrupt behaviours described in a series of scenarios. The discussion includes why some types of misdemeanour seem more likely to be reported and the potential effects of a newly introduced formal Code of Ethics. In terms of differences between ranks and roles, and different responses from different services, the study suggests that the way police culture operates is significant and needs to be more widely addressed. The study used scenario based questionnaires to elicit views about the seriousness of certain police behaviours and to ask whether officers would report colleagues' misdemeanours. It develops a previous survey by one of the authors which conducted a similar survey published in 2005. Using the same questionnaire the new study examined a larger and more diverse sample of serving officers (n=520). This new study compares responses from police officers in UK three forces, geographically distributed across the country and have differing characteristics in terms of size, rurality, population density and policing priorities
How many species change names in a germplasm bank? Study of the Anhembi Experimental Station eucalypt germplasm bank and practical implications.
Eucalypts are a long-cycle crop that have been introduced in Brazil during several decades. The germplasm banks of the country make available several populations whose botanical classifications are somewhat outdated since these classifications have been subject to several modifications over the years. This study outlines a review of species with outdated classifications in the Anhembi Experimental Station of Forest Sciences (ESALQ/USP), one of Brazil?s main eucalypt germplasm banks and discusses the possible implications for the breeding programs that use said germplasm. In this survey, we found records that indicate introductions were made of populations of 20 eucalypts species. However, this number has increased according to the most recent update of botanical classifications, and the Anhembi Germplasm Bank has currently 22 species after a few species were reclassified. Furthermore, a major change has been the reclassification of some species from the genus Eucalyptus to the genus Corymbia. One original introduction, Eucalyptus maculata, is now considered to be (according to original provenances), Corymbia maculata and C. variegata. One species originally introduced as E. pellita has been renamed E. scias; E. pellita still exists in north Queensland, Australia and Papua New Guinea, while E. scias has a much smaller southerly distribution in New South Wales, Australia. Similarly, an introduction of E. phaeotricha is now generally considered to be E. tindaliae, and an introduction of E. resinifera is now considered to be E. macta (according to the provenance area of the introduction). The confusing classification of the species is aggravated, in some cases, by the lack of detailed studies that allow comparing the species introduced with the same name, regarding wood productivity, tolerance and/or traits that are fundamental for defining the species to be introduced or worked on by the breeding programs
Properties of odd nuclei and the impact of time-odd mean fields: A systematic Skyrme-Hartree-Fock analysis
We present a systematic analysis of the description of odd nuclei by the
Skyrme-Hartree-Fock approach augmented with pairing in BCS approximation and
blocking of the odd nucleon. Current and spin densities in the Skyrme
functional produce time-odd mean fields (TOMF) for odd nuclei. Their effect on
basic properties (binding energies, odd-even staggering, separation energies
and spectra) is investigated for the three Skyrme parameterizations SkI3, SLy6,
and SV-bas. About 1300 spherical and axially-deformed odd nuclei with 16 < Z <
92 are considered. The calculations demonstrate that the TOMF effect is
generally small, although not fully negligible. The influence of the Skyrme
parameterization and the consistency of the calculations are much more
important. With a proper choice of the parameterization, a good description of
binding energies and their differences is obtained, comparable to that for even
nuclei. The description of low-energy excitation spectra of odd nuclei is of
varying quality depending on the nucleus
Researching the use of force: The background to the international project
This article provides the background to an international project on use of force by the police that was carried out in eight countries. Force is often considered to be the defining characteristic of policing and much research has been conducted on the determinants, prevalence and control of the use of force, particularly in the United States. However, little work has looked at police officers’ own views on the use of force, in particular the way in which they justify it. Using a hypothetical encounter developed for this project, researchers in each country conducted focus groups with police officers in which they were encouraged to talk about the use of force. The results show interesting similarities and differences across countries and demonstrate the value of using this kind of research focus and methodology
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