6,589 research outputs found
Equation of state and opacities for hydrogen atmospheres of magnetars
The equation of state and radiative opacities of partially ionized, strongly
magnetized hydrogen plasmas, presented in a previous paper [ApJ 585, 955
(2003), astro-ph/0212062] for the magnetic field strengths 8.e11 G < B < 3.e13
G, are extended to the field strengths 3.e13 G < B < 1.e15 G, relevant for
magnetars. The first- and second-order thermodynamic functions and radiative
opacities are calculated and tabulated for 5.e5 < T < 4.e7 K in a wide range of
densities. We show that bound-free transitions give an important contribution
to the opacities in the considered range of B in the outer neutron-star
atmosphere layers. Unlike the case of weaker fields, bound-bound transitions
are unimportant.Comment: 7 pages, 6 figures, LaTeX using emulateapj.cls (included). Accepted
by Ap
Effects of environmental factors on development of Pyrenopeziza brassicae (light leaf spot) apothecia on oilseed rape debris
Publication no. P-2001-0221-01R. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2001The development of Pyrenopeziza brassicae (light leaf spot) apothecia was studied on petiole debris from artificially infected oilseed rape leaves incubated at temperatures from 6 to 22 degreesC under different wetness regimes and in 16 h light/8 h dark or continuous darkness. There was no significant difference between light treatments in numbers of apothecia that developed. Mature apothecia developed at temperatures from 5 to 18 degreesC but not at 22 degreesC. The rate of apothecial development decreased as temperature decreased from 18 to 5 degreesC; mature apothecia were first observed after 5 days at 18 degreesC and after 15 days at 6 degreesC. Models were fitted to estimates of the time (days) for 50% of the maximum number of apothecia to develop (t(1); model 1, t(1) = 7.6 + 55.8(0.839)(T)) and the time for 50% of the maximum number of apothecia to decay (t(2); model 2, t(2) = 24.2 + 387(0.730)(T)) at temperatures (T) from 6 to 18 degreesC. An interruption in wetness of the petiole debris for 4 days after 4, 7, or 10 days of wetness delayed the time to observation of the first mature apothecia for approximate to4 days and decreased the number of apothecia produced (by comparison with continuous wetness). A relationship was found between water content of pod debris and electrical resistance measured by a debris-wetness sensor. The differences between values of tl predicted by model 1 and observed values of t(1) were 1 to 9 days. Model 2 did not predict t(2); apothecia decayed more quickly under natural conditions than predicted by model 2.Peer reviewe
Automatic Detection of Expanding HI Shells Using Artificial Neural Networks
The identification of expanding HI shells is difficult because of their
variable morphological characteristics. The detection of HI bubbles on a global
scale therefore never has been attempted. In this paper, an automatic detector
for expanding HI shells is presented. The detection is based on the more stable
dynamical characteristics of expanding shells and is performed in two stages.
The first one is the recognition of the dynamical signature of an expanding
bubble in the velocity spectra, based on the classification of an artificial
neural network. The pixels associated with these recognized spectra are
identified on each velocity channel. The second stage consists in looking for
concentrations of those pixels that were firstly pointed out, and to decide if
they are potential detections by morphological and 21-cm emission variation
considerations. Two test bubbles are correctly detected and a potentially new
case of shell that is visually very convincing is discovered. About 0.6% of the
surveyed pixels are identified as part of a bubble. These may be false
detections, but still constitute regions of space with high probability of
finding an expanding shell. The subsequent search field is thus significantly
reduced. We intend to conduct in the near future a large scale HI shells
detection over the Perseus Arm using our detector.Comment: 39 pages, 11 figures, accepted by PAS
Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition
A low-light-power theory of nonlinear magneto-optical rotation of
frequency-modulated light resonant with a J=1->J'=0 transition is presented.
The theory is developed for a Doppler-free transition, and then modified to
account for Doppler broadening and velocity mixing due to collisions. The
results of the theory are shown to be in qualitative agreement with
experimental data obtained for the rubidium D1 line.Comment: 11 pages, 5 figures, v.2 edited for clarit
Formality theorems for Hochschild chains in the Lie algebroid setting
In this paper we prove Lie algebroid versions of Tsygan's formality
conjecture for Hochschild chains both in the smooth and holomorphic settings.
In the holomorphic setting our result implies a version of Tsygan's formality
conjecture for Hochschild chains of the structure sheaf of any complex manifold
and in the smooth setting this result allows us to describe quantum traces for
an arbitrary Poisson Lie algebroid. The proofs are based on the use of
Kontsevich's quasi-isomorphism for Hochschild cochains of R[[y_1,...,y_d]],
Shoikhet's quasi-isomorphism for Hochschild chains of R[[y_1,...,y_d]], and
Fedosov's resolutions of the natural analogues of Hochschild (co)chain
complexes associated with a Lie algebroid.Comment: 40 pages, no figure
Female Fertilization: Effects of Sex-Specific Density and Sex Ratio Determined Experimentally for Colorado Potato Beetles and Drosophila Fruit Flies
If males and females affect reproduction differentially, understanding and predicting sexual reproduction requires specification of response surfaces, that is, two-dimensional functions that relate reproduction to the (numeric) densities of both sexes. Aiming at rigorous measurement of female per capita fertilization response surfaces, we conducted a multifactorial experiment and reanalyzed an extensive data set. In our experiment, we varied the density of male and female Leptinotarsa decemlineata (Colorado potato beetles) by placing different numbers of the two sexes on enclosed Solanum tuberosum (potato plants) to determine the proportion of females fertilized after 3 or 22 hours. In the reanalysis, we investigated how the short-term fertilization probability of three Drosophila strains (melanogaster ebony, m. sepia, and simulans) depended on adult sex ratio (proportion of males) and total density. The fertilization probability of female Leptinotarsa decemlineata increased logistically with male density, but not with female density. These effects were robust to trial duration. The fertilization probability of female Drosophila increased logistically with both sex ratio and total density. Treatment effects interacted in m. sepia, and simulans. These findings highlight the importance of well-designed, multifactorial experiments and strengthen previous experimental evidence for the relevance of sex-specific densities to understanding and prediction of female fertilization probability.WKV, MEH, and HK acknowledge financial support from the Academy of Finland. GB and PM acknowledge financial support from Agriculture and Agri-Food Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
A rapid microwave-assisted procedure for easy access to Nx polydentate ligands for potential application in α-RIT
International audienceHeterocycles bearing a hydrazine moiety react with bisaldehydes or bisketones to afford new Nx polydentate ligands suitable for α-radioimmunotherapy. We developed a fast and efficient method using microwave-assisted technology to obtain chelators with variable size and number of coordination centres which were fully characterized. The complexation efficiency with astatine will be assessed
Oxidative stress and blood lipid profile in Cameroonian obese subjects
The relationship between obesity, blood lipids and oxidative stress was investigated in 200 participants. The Body Mass Index of the subjects were positively correlated with the percentage body fat, the systolic and diastolic blood pressure, the fasting blood glucose level, the oxidation of proteins and lipids as well as the concentrations of total and LDL cholesterol. On the other hand, the Body Mass Index was negatively correlated to sulhydryl and protein levels. Obese subjects also had significantly higher body fat (p<.001), waist circumference (p<.001), fasting blood glucose (p<.01) as well as systolic blood pressure (p<.05). Obesity, therefore, can be said to increase the oxidation of plasma proteins and lipids while reducing the antioxidant status as observed by the inverse relation between plasma sulfhydryl groups and the percentage body fat. This increase in oxidative stress can predispose obese people to illnesses such as cardiovascular diseases and diabetes mellitus
Equation of state of fully ionized electron-ion plasmas
Thermodynamic quantities of Coulomb plasmas consisting of point-like ions
immersed in a compressible, polarizable electron background are calculated for
ion charges Z=1 to 26 and for a wide domain of plasma parameters ranging from
the Debye-Hueckel limit to the crystallization point and from the region of
nondegenerate to fully degenerate nonrelativistic or relativistic electrons.
The calculations are based on the linear-response theory for the electron-ion
interaction, including the local-field corrections in the electronic dielectric
function. The thermodynamic quantities are calculated in the framework of the
N-body hypernetted-chain equations and fitted by analytic expressions. We
present also accurate analytic approximations for the free energy of the ideal
electron gas at arbitrary degeneracy and relativity and for the excess free
energy of the one-component plasma of ions (OCP) derived from Monte Carlo
simulations.
The extension to multi-ionic mixtures is discussed within the framework of
the linear mixing rule. These formulae provide a completely analytic, accurate
description of the thermodynamic quantities of fully ionized electron-ion
Coulomb plasmas, a useful tool for various applications from liquid state
theory to dense stellar matter.Comment: 13 pages, 2 tables, 7 figures, REVTeX using epsf.sty. To be published
in Phys. Rev. E, vol. 58 (1998
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