18,919 research outputs found
Correlations and fluctuations of a confined electron gas
The grand potential and the response of a phase-coherent confined noninteracting electron gas depend
sensitively on chemical potential or external parameter . We compute
their autocorrelation as a function of , and temperature. The result
is related to the short-time dynamics of the corresponding classical system,
implying in general the absence of a universal regime. Chaotic, diffusive and
integrable motions are investigated, and illustrated numerically. The
autocorrelation of the persistent current of a disordered mesoscopic ring is
also computed.Comment: 12 pages, 1 figure, to appear in Phys. Rev.
A Bayesian Approach to Comparing Cosmic Ray Energy Spectra
A common problem in ultra-high energy cosmic ray physics is the comparison of
energy spectra. The question is whether the spectra from two experiments or two
regions of the sky agree within their statistical and systematic uncertainties.
We develop a method to directly compare energy spectra for ultra-high energy
cosmic rays from two different regions of the sky in the same experiment
without reliance on agreement with a theoretical model of the energy spectra.
The consistency between the two spectra is expressed in terms of a Bayes
factor, defined here as the ratio of the likelihood of the two-parent source
hypothesis to the likelihood of the one-parent source hypothesis. Unlike other
methods, for example chi^2 tests, the Bayes factor allows for the calculation
of the posterior odds ratio and correctly accounts for non-Gaussian
uncertainties. The latter is particularly important at the highest energies,
where the number of events is very small.Comment: 22 pages, 10 figures, accepted for publication in Ap
Ice in the Antarctic polar stratosphere
On six occasions during the 1987 Airborne Antarctic Ozone Experiment, the Polar Stratospheric Cloud (PSC) ice crystals were replicated over the Palmer Peninsula at approximately 70 deg South. The sampling altitude was approximately 60 to 65 thousand feet, the temperature range was -83.5 to -72C and the atmosphere was subsaturated in all cases. The collected crystals were predominantly complete and hollow prismatic columns with maximum dimensions up to 217 microns. Evidence of scavenging of submicron particles was detected on several crystals. While the replicated crystal sizes were larger than anticipated, their relatively low concentration results in a total surface area less than one tenth that of the sampled aerosol particles. The presence of large crystals suggest that PSC ice crystals can play a very important role in stratospheric dehydration processes
Study of muons near shower cores at sea level using the E594 neutrino detector
The E594 neutrino detector has been used to study the lateral distribution of muons of energy 3 GeV near shower cores. The detector consists of a 340 ton fine grain calorimeter with 400,000 cells of flash chamber and dimensions of 3.7 m x 20 m x 3.7 m (height). The average density in the calorimeter is 1.4 gm/sq cm, and the average Z is 21. The detector was triggered by four 0.6 sq m scintillators placed immediately on the top of the calorimeter. The trigger required at least two of these four counters. The accompanying extensive air showers (EAS) was sampled by 14 scintillation counters located up to 15 m from the calorimeter. Several off line cuts have been applied to the data. Demanding five particles in at least two of the trigger detectors, a total of 20 particles in all of them together, and an arrival angle for the shower 450 deg reduced the data sample to 11053 events. Of these in 4869 cases, a computer algorithm found at least three muons in the calorimeter
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The APHEKOM Project: A literature review of air pollution interventions and their impact of public health
Intervention studies play an important role in supporting and complementing scientific validation of results of epidemiological non-intervention studies linking air pollution and health. In this paper a collection of existing published intervention studies is reviewed with the aim to give a summarized overview spanning a variety of approaches regarding the type of the intervention and findings with the main focus on studies that assessed interventions that improved air quality and the associated positive impact on public health. Air pollution interventions were defined as events aimed at reducing air pollution and also events where air pollution reductions occurred as a side effect
Surface-Enhanced Plasmon Splitting in a Liquid-Crystal-Coated Gold Nanoparticle
We show that, when a gold nanoparticle is coated by a thin layer of nematic
liquid crystal, the deformation produced by the nanoparticle surface can
enhance the splitting of the nanoparticle surface plasmon. We consider three
plausible liquid crystal director configurations in zero electric field: boojum
pair (north-south pole configuration), baseball (tetrahedral), and homogeneous.
From a calculation using the Discrete Dipole Approximation, we find that the
surface plasmon splitting is largest for the boojum pair, intermediate for the
homogeneous, and smallest for the baseball configuration. The boojum pair
results are in good agreement with experiment. We conclude that the
nanoparticle surface has a strong effect on the director orientation, but,
surprisingly, that this deformation can actually enhance the surface plasmon
splitting.Comment: 5 pages, 3 figures To be published in PR
The composition of cosmic rays near the Bend (10 to the 15th power eV) from a study of muons in air showers at sea level
The distribution of muons near shower cores was studied at sea level at Fermilab using the E594 neutrino detector to sample the muon with E testing 3 GeV. These data are compared with detailed Monte Carlo simulations to derive conclusions about the composition of cosmic rays near the bend in the all particle spectrum. Monte Carlo simulations generating extensive air showers (EAS) with primary energy in excess of 50 TeV are described. Each shower record contains details of the electron lateral distribution and the muon and hadron lateral distributions as a function of energy, at the observation level of 100g/cm. The number of detected electrons and muons in each case was determined by a Poisson fluctuation of the number incident. The resultant predicted distribution of muons, electrons, the rate events are compared to those observed. Preliminary results on the rate favor a heavy primary dominated cosmic ray spectrum in energy range 50 to 1000 TeV
Systematic study of proton-neutron pairing correlations in the nuclear shell model
A shell-model study of proton-neutron pairing in shell nuclei using a
parametrized hamiltonian that includes deformation and spin-orbit effects as
well as isoscalar and isovector pairing is reported. By working in a
shell-model framework we are able to assess the role of the various modes of
proton-neutron pairing in the presence of nuclear deformation without violating
symmetries. Results are presented for Ti, Ti, Ti, V
and Cr to assess how proton-neutron pair correlations emerge under
different scenarios. We also study how the presence of a one-body spin-obit
interaction affects the contribution of the various pairing modes.Comment: 12 pages, 16 figure
Living longer but not necessarily healthier: The joint progress of health and mortality in the working-age population of England
Despite improvements in life expectancy, there is uncertainty on whether the increase in years of healthy life expectancy has kept pace. In this paper we explore whether there is empirical support for the expansion of morbidity hypothesis in the population aged 25–64 living in England. Nationally representative cohorts born between 1945 and 1980 are constructed from repeated annual cross-sections of the Health Survey for England, 1991–2014. Later-born cohorts at a given age have the same or higher prevalence of self-reported bad general health and long-term illness, self-reported high blood pressure (in men), self-reported and objectively-measured diabetes, circulatory illnesses, clinical hypertension, and overweight BMI. We also find that healthy life expectancies (in the sense of absence of each of these problems) at age 25 have increased at a slower pace than life expectancy between 1993 and 2013. Our findings lend support to the expansion of morbidity hypothesis and point to increased future demand for specific healthcare services at younger ages
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