10,432 research outputs found
Deposition of La2Zr2O7 Film by Chemical Solution Deposition
La2Zr2O7 (LZO) formation of bulk powders and of films by Chemical Solution
Deposition (CSD) process have been studied using propionates. The treatment
involved a one step cycle in the reducing forming gas (Ar-5%H2) to be
compatible with Ni-5at%W RABITS. Large amount of residual carbon was found in
LZO powders formed in these conditions (10 wt %). The volume fraction of the
cube texture in LZO films on Ni-5at%w RABITS was found to be a function of the
speed of the gas flown above sample. This phenomenon is discussed in
considering the C deposited from the carbon-containing gases emitted during the
pyrolysis of the precursor. Using proper conditions (950 ^\circC and the speed
of gas of 6.8\times10^{-2} m/s), LZO films with good surface crystallinity
could be obtained on Ni-5at%W RABITS as demonstrated by X-ray diffraction,
electron backscattered diffraction and RHEED. The existence of residual carbon
in oxide films is a common question to films deposited by CSD processes under
reducing condition
Discovery of a New Quadruple Lens HST 1411+5211
Gravitational lensing is an important tool for probing the mass distribution
of galaxies. In this letter we report the discovery of a new quadruple lens HST
1411+5211 found in archived WFPC2 images of the galaxy cluster CL140933+5226.
If the galaxy is a cluster member then its redshift is . The images of
the source appear unresolved in the WFC implying that the source is a quasar.
We have modeled the lens as both a single galaxy and a galaxy plus a cluster.
The latter model yields excellent fits to the image positions along with
reasonable parameters for the galaxy and cluster making HST 1411+5211 a likely
gravitational lens. Determination of the source redshift and confirmation of
the lens redshift would allow us to put strong constraints on the mass
distribution of the lensing galaxy.Comment: 11 pages including 1 postscript figure, aastex. Accepted to the ApJL.
Also available from:
http://www.astro.lsa.umich.edu:80/users/philf/www/papers/list.htm
Formation of Long Single Quantum Dots in High Quality InSb Nanowires Grown by Molecular Beam Epitaxy
We report on realization and transport spectroscopy study of single quantum
dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The
nanowires employed are 50-80 nm in diameter and the QDs are defined in the
nanowires between the source and drain contacts on a Si/SiO substrate. We
show that highly tunable QD devices can be realized with the MBE-grown InSb
nanowires and the gate-to-dot capacitance extracted in the many-electron
regimes is scaled linearly with the longitudinal dot size, demonstrating that
the devices are of single InSb nanowire QDs even with a longitudinal size of
~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved
and the Land\'e g-factors extracted for the quantum levels from the
magnetotransport measurements are found to be strongly level-dependent and
fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted
from the magnetic field evolutions of a ground state and its neighboring
excited state in an InSb nanowire QD and is on the order of ~300 eV. Our
results establish that the MBE-grown InSb nanowires are of high crystal quality
and are promising for the use in constructing novel quantum devices, such as
entangled spin qubits, one-dimensional Wigner crystals and topological quantum
computing devices.Comment: 19 pages, 5 figure
On Gravitational Waves in Spacetimes with a Nonvanishing Cosmological Constant
We study the effect of a cosmological constant on the propagation
and detection of gravitational waves. To this purpose we investigate the
linearised Einstein's equations with terms up to linear order in in a
de Sitter and an anti-de Sitter background spacetime. In this framework the
cosmological term does not induce changes in the polarization states of the
waves, whereas the amplitude gets modified with terms depending on .
Moreover, if a source emits a periodic waveform, its periodicity as measured by
a distant observer gets modified. These effects are, however, extremely tiny
and thus well below the detectability by some twenty orders of magnitude within
present gravitational wave detectors such as LIGO or future planned ones such
as LISA.Comment: 8 pages, 4 figures, accepted for publication in Physical Review
Statistical properties of stock order books: empirical results and models
We investigate several statistical properties of the order book of three
liquid stocks of the Paris Bourse. The results are to a large degree
independent of the stock studied. The most interesting features concern (i) the
statistics of incoming limit order prices, which follows a power-law around the
current price with a diverging mean; and (ii) the humped shape of the average
order book, which can be quantitatively reproduced using a `zero intelligence'
numerical model, and qualitatively predicted using a simple approximation.Comment: Revised version, 10 pages, 4 .eps figures. to appear in Quantitative
Financ
Access to Care and Cardiovascular Disease Prevention: A Cross-Sectional Study in 2 Latino Communities.
Cardiovascular disease (CVD) is the leading killer of Americans. CVD is understudied among Latinos, who have high levels of CVD risk factors. This study aimed to determine whether access to health care (ie, insurance status and having a usual source of care) is associated with 4 CVD prevention factors (ie, health care utilization, CVD screening, information received from health care providers, and lifestyle factors) among Latino adults and to evaluate whether the associations depended on CVD clinical risk/disease.Data were collected as part of a community-engaged food environment intervention study in East Los Angeles and Boyle Heights, CA. Logistic regressions were fitted with insurance status and usual source of care as predictors of the 4 CVD prevention factors while controlling for demographics. Analyses were repeated with interactions between self-reported CVD clinical risk/disease and access to care measures.Access to health care significantly increased the odds of CVD prevention. Having a usual source of care was associated with all factors of prevention, whereas being insured was only associated with some factors of prevention. CVD clinical risk/disease did not moderate any associations.Although efforts to reduce CVD risk among Latinos through the Affordable Care Act could be impactful, they might have limited impact in curbing CVD among Latinos, via the law's expansion of insurance coverage. CVD prevention efforts must expand beyond the provision of insurance to effectively lower CVD rates
Structural analysis of Salmonella enterica effector protein SopD
Salmonella outer protein D (SopD) is a type III secreted virulence effector protein from Salmonella enterica. Full-length SopD and SopD lacking 16 amino acids at the N-terminus (SopDDeltaN) have been expressed as fusions with GST in Escherichia coli, purified with a typical yield of 20-30 mg per litre of cell culture and crystallized. Biophysical characterization has been carried out mainly on SopDDeltaN. Analytical size exclusion chromatography shows that SopDDeltaN is monomeric and probably globular in aqueous solution. The secondary structure composition, calculated from the CD spectrum, is mixed (38% alpha-helix and 26% beta-strand). Sequence analysis indicates that SopD contains a coiled coil motif, as found in numerous other type III secretion system-associated proteins. This suggests that SopD has the potential for one or more heterotypic protein-protein interactions. Limited trypsin digestion of SopDDeltaN, monitored by both one-dimensional proton NMR spectroscopy and SDS-PAGE, shows that the protein has a large, protease-resistant core domain of 286 amino acid residues. This single-domain architecture suggests that SopD lacks a cognate chaperone. In crystallization trials, SopDDeltaN produced better crystals than either full-length SopD or trypsin-digested SopDDeltaN. Diffraction to 3.0 Angstrom resolution has so far been obtained from crystals of SopDDeltaN
Generation of ultra-short light pulses by a rapidly ionizing thin foil
A thin and dense plasma layer is created when a sufficiently strong laser
pulse impinges on a solid target. The nonlinearity introduced by the
time-dependent electron density leads to the generation of harmonics. The pulse
duration of the harmonic radiation is related to the risetime of the electron
density and thus can be affected by the shape of the incident pulse and its
peak field strength. Results are presented from numerical
particle-in-cell-simulations of an intense laser pulse interacting with a thin
foil target. An analytical model which shows how the harmonics are created is
introduced. The proposed scheme might be a promising way towards the generation
of attosecond pulses.
PACS number(s): 52.40.Nk, 52.50.Jm, 52.65.RrComment: Second Revised Version, 13 pages (REVTeX), 3 figures in ps-format,
submitted for publication to Physical Review E, WWW:
http://www.physik.tu-darmstadt.de/tqe
Quantum Einstein-Dirac Bianchi Universes
We study the mini--superspace quantization of spatially homogeneous (Bianchi)
cosmological universes sourced by a Dirac spinor field. The quantization of the
homogeneous spinor leads to a finite-dimensional fermionic Hilbert space and
thereby to a multi-component Wheeler-DeWitt equation whose main features are:
(i) the presence of spin-dependent Morse-type potentials, and (ii) the
appearance of a q-number squared-mass term, which is of order , and which is affected by ordering ambiguities. We give the exact
quantum solution of the Bianchi type-II system (which contains both scattering
states and bound states), and discuss the main qualitative features of the
quantum dynamics of the (classically chaotic) Bianchi type-IX system. We
compare the exact quantum dynamics of fermionic cosmological billiards to
previous works that described the spinor field as being either classical or
Grassmann-valued.Comment: 50 page
Brésil
Plus que la "frontière" pionnière de l'intérieur du pays, c'est la région du Centre-Sud, et notamment ses grandes villes, qui attire le plus grand nombre de migrants brésiliens, comme l'atteste l'analyse des recensements de 1985 et 1991. Le Centre-Sud, en effet, est la région la plus urbanisée, la plus industrialisée du pays; elle est en situation dominante dans les secteurs tertiaires, de l'agriculture et de l'élevage, et constitue ainsi le véritable moteur de l'organisation territoriale brésilienne. Ainsi, cette restructuration spatiale, placée sous le signe de l'urbanisation, s'opère aujourd'hui selon deux modèles. D'une part, des zones à la production agropastorale moderne, bien reliées aux circuits économiques et, notamment, au complexe agro-industriel. D'autre part, des régions, dotées d'une population nombreuse, tournées vers l'autoconsommation et, donc, peu intégrées dans les circuits commerciaux. (Résumé d'auteur
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