5,115 research outputs found
Capacitors can radiate - some consequences of the two-capacitor problem with radiation
We fill a gap in the arguments of Boykin et al [American Journal of Physics,
Vol 70 No. 4, pp 415-420 (2002)] by not invoking an electric current loop (i.e.
magnetic dipole model) to account for the radiation energy loss, since an
obvious corollary of their results is that the capacitors should radiate
directly even if the connecting wires are shrunk to zero length. That this is
so is shown here by a direct derivation of capacitor radiation using an
oscillating electric dipole radiator model for the capacitors as well as the
alternative less widely known magnetic 'charge' current loop representation for
an electric dipole [see for example "Electromagnetic Waves" by S.A.Schlekunoff,
van Nostrand (1948)]. Implications for Electromagnetic Compliance (EMC) issues
as well as novel antenna designs further motivate the purpose of this paper.Comment: 5 Pages with No figure
Feasibility study of an Integrated Program for Aerospace vehicle Design (IPAD). Volume 3: Support of the design process
The user requirements for computer support of the IPAD design process are identified. The user-system interface, language, equipment, and computational requirements are considered
Perturbation theory in radial quantization approach and the expectation values of exponential fields in sine-Gordon model
A perturbation theory for Massive Thirring Model (MTM) in radial quantization
approach is developed. Investigation of the twisted sector in this theory
allows us to calculate the vacuum expectation values of exponential fields of the sine-Gordon theory in first order over Massive Thirring
Models coupling constant. It appears that the apparent difficulty in radial
quantization of massive theories, namely the explicite ''time'' dependence of
the Hamiltonian, may be successfully overcome. The result we have obtained
agrees with the exact formula conjectured by Lukyanov and Zamolodchikov and
coincides with the analogous calculations recently carried out in dual angular
quantization approach by one of the authors.Comment: 16 pages, no figures, LaTe
BZ-MC-BP Model for Jet Production from Black Hole Accretion Disc
Three energy mechanisms invoking large-scale magnetic fields are incorporated
in a model to interpret jet production in black hole (BH) systems, i.e., the
Blandford-Znajek (BZ), the magnetic coupling (MC) and Blandford-Payne (BP)
processes. These energy mechanisms can coexist in BH accretion disc based on
the magnetic field configurations constrained by the screw instability,
provided that the BH spin and the power-law index indicating the variation of
the magnetic field at an accretion disc are greater than some critical values.
In this model the jets are driven by the BZ process in the Poynting flux regime
and by the BP process in the hydromagnetic regime, being consistent with the
spine/sheath jet structure observed in BH sources of stellar and supermassive
size.Comment: 9 pages, 6 figures, accepted by MNRA
Hot Electron Capture Dissociation Distinguishes Leucine from Isoleucine in a Novel Hemoglobin Variant, Hb Askew, β54(D5)Val→Ile
Population migration has led to the global dispersion of human hemoglobinopathies and has precipitated a need for their identification. An effective mass spectrometry-based procedure involves analysis of the intact α- and β-globin chains to determine their mass, followed by location of the variant amino acid residue by direct analysis of the enzymatically digested chains and low-energy collision induced dissociation of the variant peptide. Using this procedure, a variant was identified as either β54Val→Leu or β54Val→Ile, since the amino acids leucine and isoleucine cannot be distinguished using low-energy collisions. Here, we describe how hot electron capture dissociation on a Fourier transform-ion cyclotron resonance mass spectrometer was used to distinguish isoleucine from leucine and identify the mutation as β54(D5)Val→Ile. This is a novel variant, and we have named it Hb Askew
Relativistic phase space: dimensional recurrences
We derive recurrence relations between phase space expressions in different
dimensions by confining some of the coordinates to tori or spheres of radius
and taking the limit as . These relations take the form of
mass integrals, associated with extraneous momenta (relative to the lower
dimension), and produce the result in the higher dimension.Comment: 13 pages, Latex, to appear in J Phys
Fuels treatment and wildfire effects on runoff from Sierra Nevada mixed-conifer forests
We applied an eco-hydrologic model (Regional Hydro-Ecologic Simulation System [RHESSys]), constrained with spatially distributed field measurements, to assess the impacts of forest-fuel treatments and wildfire on hydrologic fluxes in two Sierra Nevada firesheds. Strategically placed fuels treatments were implemented during 2011–2012 in the upper American River in the central Sierra Nevada (43 km2) and in the upper Fresno River in the southern Sierra Nevada (24 km2). This study used the measured vegetation changes from mechanical treatments and modelled vegetation change from wildfire to determine impacts on the water balance. The well-constrained headwater model was transferred to larger catchments based on geologic and hydrologic similarities. Fuels treatments covered 18% of the American and 29% of the Lewis catchment. Averaged over the entire catchment, treatments in the wetter central Sierra Nevada resulted in a relatively light vegetation decrease (8%), leading to a 12% runoff increase, averaged over wet and dry years. Wildfire with and without forest treatments reduced vegetation by 38% and 50% and increased runoff by 55% and 67%, respectively. Treatments in the drier southern Sierra Nevada also reduced the spatially averaged vegetation by 8%, but the runoff response was limited to an increase of less than 3% compared with no treatment. Wildfire following treatments reduced vegetation by 40%, increasing runoff by 13%. Changes to catchment-scale water-balance simulations were more sensitive to canopy cover than to leaf area index, indicating that the pattern as well as amount of vegetation treatment is important to hydrologic response
Five-year follow-up of participants diagnosed with chronic airflow obstruction in a South African Burden of Obstructive Lung Disease (BOLD) survey
Background. A community-based prevalence survey performed in two suburbs in Cape Town, South Africa (SA), in 2005, using the
international Burden of Obstructive Lung Disease (BOLD) method, confirmed a prevalence of chronic airflow obstruction (CAO) in 23.1%
of adults aged >40 years.
Objectives. To study the clinical course and prognosis over 5 years of patients with CAO identified in the 2005 survey.
Methods. Patients with CAO in 2005 were invited to participate. Standard BOLD and modified questionnaires were completed. Spirometry
was performed using spirometers of the same make as in 2005.
Results. Of 196 eligible participants from BOLD 2005, 45 (23.0%) had died, 8 from respiratory causes, 10 from cardiovascular causes and 6
from other known causes, while in 21 cases the cause of death was not known. On multivariate analysis, only age and Global initiative for
Obstructive Lung Disease (GOLD) stage 4 disease at baseline were significantly associated with death. Of the 151 survivors, 11 (5.6% of the
original cohort) were unavailable and 33 (16.8%) declined or had medical exclusions. One hundred and seven survivors were enrolled in
the follow-up study (54.6%, median age 63.1 years, 45.8% males). Post-bronchodilator spirometry performed in 106 participants failed to
confirm CAO, defined as a forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio of <0.7, in 16 participants (15.1%),
but CAO was present in 90. The median decline in FEV1 was 28.9 mL/year (interquartile range –54.8 - 0.0) and was similar between GOLD
stages. The median total decline in FVC was 75 mL, and was significantly greater in GOLD stage 1 (–350 mL) than in stages 2 or 3 (–80 mL
and +140 mL, respectively; p<0.01). Fifty-eight participants with CAO in 2005 (64.4%) remained in the same GOLD stage, while 21 (23.3%)
deteriorated and 11 (12.2%) improved by ≥1 stage. Only one-third were receiving any treatment for chronic obstructive pulmonary disease
(COPD).
Conclusions. The prevalence, morbidity and mortality of CAO and COPD in SA are high and the level of appropriate treatment is very low,
pointing to underdiagnosis and inadequate provision of and access to effective treatments and preventive strategies for this priority chronic
non-communicable disease.info:eu-repo/semantics/publishedVersio
Spectral Asymptotics of Eigen-value Problems with Non-linear Dependence on the Spectral Parameter
We study asymptotic distribution of eigen-values of a quadratic
operator polynomial of the following form ,
where is a second order differential positive elliptic operator
with quadratic dependence on the spectral parameter . We derive
asymptotics of the spectral density in this problem and show how to compute
coefficients of its asymptotic expansion from coefficients of the asymptotic
expansion of the trace of the heat kernel of . The leading term in
the spectral asymptotics is the same as for a Laplacian in a cavity. The
results have a number of physical applications. We illustrate them by examples
of field equations in external stationary gravitational and gauge backgrounds.Comment: latex, 20 page
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