1,016 research outputs found
(Z)-3-(4-Bromoanilino)-1-ferrocenylbut-2-en-1-one
In the title compound, [Fe(C5H5)(C15H13BrNO)], formed from the reaction of ferrocenoylacetone and 4-bromoaniline, the molecular structure is stabilized by an intramolecular N—H⋯O hydrogen bond between the amine and carbonyl groups
Plasma-enhanced chemical vapor deposition of thick silicon nitride films with low stress on InP
We have developed a low-temperature plasma-enhanced chemical vapor deposition process that facilitates the deposition of silicon nitride films with controlled stress by using periodically alternating high- and low-frequency power sources. Very thick films of 3 mu m with low stress were deposited on InP substrates. Suitable sidewall profiles for metallization are obtained at 250 degrees C deposition temperature. A 3- mu m-thick low-stress nitride film was successfully applied to reduce the capacitance of bond pad for an array of four InP based photodetectors, that were integrated with a four channel phased-array wavelength demultiplexer. The capacitance of the detectors was below 0.5 pF at -5 V bia
Plasma-enhanced chemical vapor deposition of thick silicon nitride films with low stress on InP
We have developed a low-temperature plasma-enhanced chemical vapor deposition process that facilitates the deposition of silicon nitride films with controlled stress by using periodically alternating high- and low-frequency power sources. Very thick films of 3 mu m with low stress were deposited on InP substrates. Suitable sidewall profiles for metallization are obtained at 250 degrees C deposition temperature. A 3- mu m-thick low-stress nitride film was successfully applied to reduce the capacitance of bond pad for an array of four InP based photodetectors, that were integrated with a four channel phased-array wavelength demultiplexer. The capacitance of the detectors was below 0.5 pF at -5 V bia
Kondo lattice model with a direct exchange interaction between localized moments
We study the Kondo lattice model with a direct antiferromagnetic exchange
interaction between localized moments. Ferromagnetically long-range ordered
state coexisting with the Kondo screening shows a continuous quantum phase
transition to the Kondo singlet state. We obtain the value of the critical
point where the magnetizations of the localized moments and the conduction
electrons vanish. The magnetization curves yield a universal critical exponent
independent of the filling factors and the strength of the interaction between
localized moments. It is shown that the direct exchange interaction between
localized moments introduces another phase transition from an antiferromagnetic
ordering to a ferromagnetic ordering for small Kondo exchange interaction. We
also explain the local minimum of the Kondo temperature in recent experiments.Comment: 6 pages, 5 figures, final versio
Giant magnetothermopower of magnon-assisted transport in ferromagnetic tunnel junctions
We present a theoretical description of the thermopower due to
magnon-assisted tunneling in a mesoscopic tunnel junction between two
ferromagnetic metals. The thermopower is generated in the course of thermal
equilibration between two baths of magnons, mediated by electrons. For a
junction between two ferromagnets with antiparallel polarizations, the ability
of magnon-assisted tunneling to create thermopower depends on the
difference between the size of the majority and
minority band Fermi surfaces and it is proportional to a temperature dependent
factor where is the magnon Debye
energy. The latter factor reflects the fractional change in the net
magnetization of the reservoirs due to thermal magnons at temperature
(Bloch's law). In contrast, the contribution of magnon-assisted
tunneling to the thermopower of a junction with parallel polarizations is
negligible. As the relative polarizations of ferromagnetic layers can be
manipulated by an external magnetic field, a large difference results in a magnetothermopower effect. This
magnetothermopower effect becomes giant in the extreme case of a junction
between two half-metallic ferromagnets, .Comment: 9 pages, 4 eps figure
Gravitational hedgehog, stringy hedgehog and stringy sphere
We investigate the solutions of Einstein equations such that a hedgehog
solution is matched to different exterior or interior solutions via a spherical
shell. In the case where both the exterior and the interior regions are
hedgehog solutions or one of them is flat, the resulting spherical shell
becomes a stringy shell. We also consider more general matchings and see that
in this case the shell deviates from its stringy character.Comment: 11 page
Expression of prtA from Photorhabdus luminescens in Bacillus thuringiensis enhances mortality in lepidopteran larvae by sub-cutaneous but not oral infection.
The prtA gene from Photorhabdus luminescens encodes the virulence factor Protease A. When P. luminescens is injected into the hemocoel of insects by entomopathogenic nematodes, PrtA is a key component of pathogenicity thought to help degrade the immune system. The prtA gene was cloned and introduced on a plasmid into Bacillus thuringiensis. PrtA was shown to be actively expressed in vitro by cleavage of a specific Dabcyl-Edans heptapeptide substrate. There was no difference in the speed or level of mortality when spores and δ-endotoxins crystals of the transformed strain were fed to larvae of Pieris brassicae, as compared to the wild-type strain. When vegetative cells were injected into the hemocoel of larvae of Galleriamellonella, however, there was a significant increase in the rate and level of mortality over the wild type. The yield of B. thuringiensis per cadaver was a hundred-fold greater in the PrtA-secreting strain. The increased pathogenicity from intrahemocoelic infection may have been due to a greater ability to overcome the immune response of G. mellonella while other factors such as resident gut bacteria may have negated this advantage after oral dosage
Association between central obesity indices and iron status indicators among Qatari adults
Co-existence of iron deficiency and obesity in adults has been reported in many countries. However, little is known on the association between obesity and iron deficiency in Qatar. This study aimed to investigate the link between abdominal obesity indices and iron status among adults in Qatar. A random sample of 1000 healthy Qatari adults, aged 20–50 years, was obtained from Qatar Biobank study. Body weight, waist circumference, dual x-ray absorptiometry (DXA) parameters and iron status indicators were measured using standard techniques. Multiple regression analysis was used to examine the associations. The prevalence of iron deficiency and anaemia were 35.4 and 25%, respectively. Of the participants with a large waist circumference, 31.7% had anaemia. Ferritin significantly increased with the increase in the android fat to gynoid fat ratio and visceral fat in both genders. Serum iron and transferring saturation decreased significantly with the increase in waist circumference in women. In both genders, C-reactive protein increased with the increase in all obesity indices. Standardized values of waist circumference, android fat, gynoid fat ratio and visceral fat were significantly associated with log transformed ferritin in men and women. Waist circumference was inversely related to serum iron (β:-0.95, 95% CI:-1.50,-0.39) and transferrin saturation (β:-1.45, 95%CI:-2.46, -0.43) in women. In men, waist circumference was positively associated with haemoglobin level (β: 0.16, 95% CI:0.04, 0.29). Central obesity coexists with anaemia among the study population. Elevated central obesity indices were associated with an increase in ferritin concentration. The increased ferritin concentration may be attributed to the increase in inflammatory status as a result of an increase in c-reactive protein concentration associated with central obesity.The project was funded by Qatar University, grant number QU-2-CHS-2018-2. The APC fees were handled by Qatar national Librar
Exact eigenstate analysis of finite-frequency conductivity in graphene
We employ the exact eigenstate basis formalism to study electrical
conductivity in graphene, in the presence of short-range diagonal disorder and
inter-valley scattering. We find that for disorder strength, 5, the
density of states is flat. We, then, make connection, using the MRG approach,
with the work of Abrahams \textit{et al.} and find a very good agreement for
disorder strength, = 5. For low disorder strength, = 2, we plot the
energy-resolved current matrix elements squared for different locations of the
Fermi energy from the band centre. We find that the states close to the band
centre are more extended and falls of nearly as as we move away
from the band centre. Further studies of current matrix elements versus
disorder strength suggests a cross-over from weakly localized to a very weakly
localized system. We calculate conductivity using Kubo Greenwood formula and
show that, for low disorder strength, conductivity is in a good qualitative
agreement with the experiments, even for the on-site disorder. The intensity
plots of the eigenstates also reveal clear signatures of puddle formation for
very small carrier concentration. We also make comparison with square lattice
and find that graphene is more easily localized when subject to disorder.Comment: 11 pages,15 figure
Large lepton asymmetry from Q-balls
We propose a scenario which can explain large lepton asymmetry and small
baryon asymmetry simultaneously. Large lepton asymmetry is generated through
Affleck-Dine (AD) mechanism and almost all the produced lepton numbers are
absorbed into Q-balls (L-balls). If the lifetime of the L-balls is longer than
the onset of electroweak phase transition but shorter than the epoch of big
bang nucleosynthesis (BBN), the large lepton asymmetry in the L-balls is
protected from sphaleron effects. On the other hand, small (negative) lepton
numbers are evaporated from the L-balls due to thermal effects, which are
converted into the observed small baryon asymmetry by virtue of sphaleron
effects. Large and positive lepton asymmetry of electron type is often
requested from BBN. In our scenario, choosing an appropriate flat direction in
the minimal supersymmetric standard model (MSSM), we can produce positive
lepton asymmetry of electron type but totally negative lepton asymmetry.Comment: 10 pages, 3 figures, ReVTeX
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