6,165 research outputs found
Gauge covariant formulation of Wigner representation through deformational quantization --Application to Keldysh formalism with electromagnetic field--
We developed a gauge-covariant formulation of the non-equilibrium Green
function method for the dynamical and/or non-uniform electromagnetic field by
means of the deformational quantization method. Such a formulation is realized
by replacing the Moyal product in the so-called Wigner space by the star
product, and facilitates the order-by-order calculation of a gauge-invariant
observable in terms of the electromagnetic field. An application of this
formalism to the linear response theory is discussed
Pre-suprenova evolution of rotating massive stars
The Geneva evolutionary code has been modified to study the advanced stages
(Ne, O, Si burnings) of rotating massive stars. Here we present the results of
four 20 solar mass stars at solar metallicity with initial rotational
velocities of 0, 100, 200 and 300 km/s in order to show the crucial role of
rotation in stellar evolution. As already known, rotation increases mass loss
and core masses (Meynet and Maeder 2000). A fast rotating 20 solar mass star
has the same central evolution as a non-rotating 26 solar mass star. Rotation
also increases strongly net total metal yields. Furthermore, rotation changes
the SN type so that more SNIb are predicted (see Meynet and Maeder 2003 and N.
Prantzos and S. Boissier 2003). Finally, SN1987A-like supernovae progenitor
colour can be explained in a single rotating star scenario.Comment: To appear in proceedings of IAU Colloquium 192, "Supernovae (10 years
of 1993J)", Valencia, Spain 22-26 April 2003, eds. J.M. Marcaide, K.W.
Weiler, 5 pages, 8 figure
Oxygen reduction behavior of rutile-type iridium oxide in sulfuric acid solution
ArticleELECTROCHIMICA ACTA. 54(2):566-573 (2008)journal articl
Changes of variables in modulation and Wiener amalgam spaces
In this paper various properties of global and local changes of variables as well as properties of canonical transforms are investigated on modulation and Wiener amalgam spaces. We establish several relations among localisations of such spaces and, as a consequence, we obtain several versions of local and global Beurling–Helson type theorems. We also establish a number of positive results such as local boundedness of canonical transforms on modulation spaces, properties of homogeneous changes of variables, and local continuity of Fourier integral operators on equation image. Finally, counterparts of these results are discussed for spaces on the torus
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Chemical characterization of water-soluble organic carbon aerosols at a rural site in the Pearl River Delta, China, in the summer of 2006
Online measurements of water-soluble organic carbon (WSOC) aerosols were made using a particle-into-liquid sampler (PILS) combined with a total organic carbon (TOC) analyzer at a rural site in the Pearl River Delta region, China, in July 2006. A macroporous nonionic (DAX-8) resin was used to quantify hydrophilic and hydrophobic WSOC, which are defined as the fractions of WSOC that penetrated through and retained on the DAX-8 column, respectively. Laboratory calibrations showed that hydrophilic WSOC (WSOCHPI) included low-molecular aliphatic dicarboxylic acids and carbonyls, saccharides, and amines, while hydrophobic WSOC (WSOCHPO) included longer-chain aliphatic dicarboxylic acids and carbonyls, aromatic acids, phenols, organic nitrates, cyclic acids, and fulvic acids. On average, total WSOC (TWSOC) accounted for 60% of OC, and WSOCHPO accounted for 60% of TWSOC. Both WSOC HIP and WSOCHPO increased with photochemical aging determined from the NOx/NOy ratio. In particular, the average WSOCHPO mass was found to increase by a factor of five within a timescale of ∼10 hours, which was substantially larger than that of WSOCHPI (by a factor of 2-3). The total increase in OC mass with photochemical aging was associated with the large increase in WSOCHPO mass. These results, combined with the laboratory calibrations, suggest that significant amounts of hydrophobic organic compounds (likely containing large carbon numbers) were produced by photochemical processing. By contrast, water-insoluble OC (WIOC) mass did not exhibit significant changes with photochemical aging, suggesting that chemical transformation of WIOC to WSOC was not a dominant process for the production of WSOC during the study period. Copyright 2009 by the American Geophysical Union
An Examination of the Oxygen Reduction Reaction on RuO2-based Oxide Coatings Formed on Titanium Substrates
The RuO2-based electrocatalysts were prepared by using a dip-coating method on Ti plate substrates at 400 degrees C. The catalytic activity of the oxide-coated electrodes for the oxygen reduction reaction (ORR) was evaluated by cyclic voltammetry in 0.5 M H2SO4 at 60 degrees C in a stationary state. The examination was focused on the enhancement of the catalytic activity in the reaction by the enlargement of the surface area of the RuO2 coating with the help of lanthunum. The onset potential for the ORR, EORR-0, of the RuO2/Ti electrode showed that the highest value was 0.84 V vs. RHE.ArticleCatalysis Today. 146(1-2):248-252. (2009)journal articl
Interstitial Fe-Cr alloys: Tuning of magnetism by nanoscale structural control and by implantation of nonmagnetic atoms
Using the density functional theory, we perform a full atomic relaxation of
the bulk ferrite with 12.5%-concentration of monoatomic interstitial Cr
periodically located at the edges of the bcc Fe cell. We show that
structural relaxation in such artificially engineered alloys leads to
significant atomic displacements and results in the formation of novel highly
stable configurations with parallel chains of octahedrically arranged Fe. The
enhanced magnetic polarization in the low-symmetry metallic state of this type
of alloys can be externally controlled by additional inclusion of nonmagnetic
impurities like nitrogen. We discuss possible applications of generated
interstitial alloys in spintronic devices and propose to consider them as a
basis of novel durable types of stainless steels.Comment: 8 pages, 10 figure
A male-killing Wolbachia carries a feminizing factor and is associated with degradation of the sex-determining system of its host
Endosymbiotic bacteria of the genus Wolbachia induce diverse reproductive alterations in their insect hosts. Wolbachia (wSca) infecting the moth Ostrinia scapulalis causes unusual male killing, in which males (genotype: ZZ) selectively die during embryonic and larval development, whereas females (genotype: ZW), in turn, selectively die when cured of infection. To gain insight into the interaction between wSca and the host, we analysed phenotypic and genetic sexes of the embryos and larvae of normal, wSca-infected, and infected-and-cured O. scapulalis by diagnosing the sex-specifically spliced transcripts of Osdsx—a homologue of the sex-determining gene doublesex—and sex chromatin in interphase nuclei, respectively. It was observed that the female-type Osdsx was expressed in the infected male (ZZ) progenies destined to die, whereas the male-type Osdsx was expressed in the cured female (ZW) progenies destined to die. These findings suggest that (i) wSca, a male killer, carries a genetic factor that feminizes the male host, (ii) the sex-determining system of the host is degraded, and (iii) a mismatch between the genetic and phenotypic sexes underlies the sex-specific death
Bunching visibility for correlated photons from single GaAs quantum dots
We study photon bunching phenomena associated with biexciton-exciton cascade
in single GaAs self-assembled quantum dots. Experiments carried out with a
pulsed excitation source show that significant bunching is only detectable at
very low excitation, where the typical intensity of photon streams is less than
the half of their saturation value. Our findings are qualitatively understood
with a model which accounts for Poissonian statistics in the number of
excitons, predicting the height of a bunching peak being determined by the
inverse of probability of finding more than one exciton.Comment: 6 pages, 6 figs to appear in Phys. Rev.
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