47,064 research outputs found
Fermion Analogy for Layered Superconducting Films in Parallel Magnetic Field
The equivalence between the Lawrence-Doniach model for films of extreme
type-II layered superconductors and a generalization of the back-scattering
model for spin-1/2 electrons in one dimension is demonstrated. This fermion
analogy is then exploited to obtain an anomalous tail for
the parallel equilibrium magnetization of the minimal double layer case in the
limit of high parallel magnetic fields for temperatures in the
critical regime.Comment: 11 pages of plain TeX, 1 postscript figur
Time-Series Ensemble Photometry and the Search for Variable Stars in the Open Cluster M11
This work presents the first large-scale photometric variability survey of
the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over
two observing seasons were analyzed (using crowded field and ensemble
photometry techniques) to obtain high relative precision photometry. In this
study we focus on the detection of candidate member variable stars for
follow-up studies. A total of 39 variable stars were detected and can be
categorized as follows: 1 irregular (probably pulsating) variable, 6 delta
Scuti variables, 14 detached eclipsing binary systems, 17 W UMa variables, and
1 unidentified/candidate variable. While previous proper motion studies allow
for cluster membership determination for the brightest stars, we find that
membership determination is significantly hampered below V=15,R=15.5 by the
large population of field stars overlapping the cluster MS. Of the brightest
detected variables that have a high likelihood of cluster membership, we find
five systems where further work could help constrain theoretical stellar
models, including one potential W UMa member of this young cluster.Comment: 38 pages, 13 figures, accepted for December 2005 AJ, high-resolution
version available upon reques
Low polarized emission from the core of coronal mass ejections
In white-light coronagraph images, cool prominence material is sometimes
observed as bright patches in the core of coronal mass ejections (CMEs). If, as
generally assumed, this emission is caused by Thomson-scattered light from the
solar surface, it should be strongly polarised tangentially to the solar limb.
However, the observations of a CME made with the SECCHI/STEREO coronagraphs on
31 August 2007 show that the emission from these bright core patches is
exceptionally low polarised. We used the polarisation ratio method of Moran and
Davila (2004) to localise the barycentre of the CME cloud. By analysing the
data from both STEREO spacecraft we could resolve the plane-of-the-sky
ambiguity this method usually suffers from. Stereoscopic triangulation was used
to independently localise the low-polarisation patch relative to the cloud. We
demonstrated for the first time that the bright core material is located close
to the centre of the CME cloud. We show that the major part of the CME core
emission, more than 85% in our case, is H radiation and only a small
fraction is Thomson-scattered light. Recent calculations also imply that the
plasma density in the patch is 8 10 cm or more compared to 2.6
10 cm for the Thomson-scattering CME environment surrounding the
core material.Comment: 5 pages, 3 figure
Berezinskii-Kosterlitz-Thouless Transition in Spin-Charge Separated Superconductor
A model for spin-charge separated superconductivity in two dimensions is
introduced where the phases of the spinon and holon order parameters couple
gauge-invariantly to a statistical gauge-field representing chiral
spin-fluctuations. The model is analyzed in the continuum limit and in the
low-temperature limit. In both cases we find that physical electronic phase
correlations show a superconducting-normal phase transition of the
Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations
are found to be strictly gapless. The normal-to-superconductor phase boundary
for this model is also obtained as a function of carrier density, where we find
that its shape compares favorably with that of the experimentally observed
phase diagram for the oxide superconductors.Comment: 35 pages, TeX, CSLA-P-93-
Investigating risk and protective factors to mainstream safety and peace at the University of South Africa
Given the high fatality rates resulting from both unintentional and intentional injuries in South Africa, the identification and prevention of risk factors resulting in injurious incidents as well as the promotion of protective factors is central to the country’s research agenda. While social science and public health enquiries apply these objectives to various South African contexts, few studies investigate manifest risk and protective factors within South African universities. Accordingly, this study aims to develop the first record of both risk and protective factors at the University of South Africa (Unisa) Muckleneuk Campus as a means to inform future theoretical and practical initiatives in the area. Data was collected with photo-documentaries, unobtrusive field observations, and a peace and safety checklist. The collated data was subjected to a thematic content analysis, allowing for the emergence of four distinct peace and safety promotion themes. These themes include crime, fire injury and electrocution, road and traffic injury, in addition to unintentional injuries. These four themes are discussed, and recommendations are provided, with the intention of informing injury prevention and safety promotion initiatives at the level of both theory and practice in South African tertiary education contexts. This study provides a platform upon which further work in the field can be produced to ensure the safety of students attending tertiary education institutions in South Africa.Keywords: campus safety; crime; traffic; electrocution; injury; South Africa; Unis
Analytical results for a Bessel function times Legendre polynomials class integrals
When treating problems of vector diffraction in electromagnetic theory, the
evaluation of the integral involving Bessel and associated Legendre functions
is necessary. Here we present the analytical result for this integral that will
make unnecessary numerical quadrature techniques or localized approximations.
The solution is presented using the properties of the Bessel and associated
Legendre functions.Comment: 4 page
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Cardiovascular Risk Factors and Dehydroepiandrosterone Sulfate Among Latinos in the Boston Puerto Rican Health Study.
Low blood dehydroepiandrosterone sulfate (DHEAS) levels have strong positive associations with stroke and coronary heart disease. However, it is unclear whether DHEAS is independently associated with cardiovascular risk factors. Therefore, we examined the association between cardiovascular risk factors and DHEAS concentration among a high-risk population of Latinos (Puerto Ricans aged 45 to 75 years at baseline) in a cross-sectional analysis of the Boston Puerto Rican Health Study. Of eligible participants, 72% completed baseline interviews and provided blood samples. Complete data were available for 1355 participants. Associations between cardiovascular risk factors (age, sex, total cholesterol, high-density lipid cholesterol, triglycerides, and glucose) and log-transformed DHEAS (μg/dL) were assessed. In robust multivariable regression analyses, DHEAS was significantly inversely associated with age (β = -12.4; 95% CI: -15.2, -9.7; per 5 years), being female (vs. male) (β = -46; 95% CI: -55.3, -36.6), and plasma triglyceride concentration (β = -0.2; 95% CI: -0.3, -0.1; per 10 mg/dL) and was positively associated with total cholesterol and plasma glucose levels (β = 1.8; 95% CI: 0.6, 3 and β = 0.2; 95% CI: 0.04, 0.3, respectively, per 10 mg/dL) after adjustment for smoking, alcohol, and physical activity and for postmenopausal hormone use in women. Estimates were unchanged after adjustment for measures of chronic disease and inflammation. Women exhibited a stronger age-related decline in DHEAS and a positive association with glucose in contrast to findings among men (P interaction < 0.05). In conclusion, in this large study of Latinos with a heavy cardiovascular risk factor burden, we observed significant associations between cardiovascular disease (CVD) risk factors and DHEAS, with variations by sex. These findings improve our understanding of the role DHEAS may play in CVD etiology
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