742 research outputs found
Observational evidence of the influence of Antarctic stratospheric ozone variability on middle atmosphere dynamics
Modeling results have suggested that the circulation of the stratosphere and mesosphere in spring is strongly affected by the perturbations in heating induced by the Antarctic ozone hole. Here using both mesospheric MF radar wind observations from Rothera Antarctica (67°S, 68°W) as well as stratospheric analysis data, we present observational evidence that the stratospheric and mesospheric wind strengths are highly anti-correlated, and show their largest variability in November. We find that these changes are related to the total amount of ozone loss that occurs during the Antarctic spring ozone hole and particularly with the ozone gradients that develop between 57.5°S and 77.5°S. The results show that with increasing ozone loss during spring, winter conditions in the stratosphere and mesosphere persist longer into the summer. These results are discussed in the light of observations of the onset and duration of the Antarctic polar mesospheric cloud seaso
Genome-wide meta-analysis of 241,258 adults accounting for smoking behaviour identifies novel loci for obesity traits
Chromosome Xq23 is associated with lower atherogenic lipid concentrations and favorable cardiometabolic indices
Effective action and interaction energy of coupled quantum dots
We obtain the effective action of tunnel-coupled quantum dots, by modeling
the system as a Luttinger liquid with multiple barriers. For a double dot
system, we find that the resonance conditions for perfect conductance form a
hexagon in the plane of the two gate voltages controlling the density of
electrons in each dot. We also explicitly obtain the functional dependence of
the interaction energy and peak-splitting on the gate voltage controlling
tunneling between the dots and their charging energies. Our results are in good
agreement with recent experimental results, from which we obtain the Luttinger
interaction parameter .Comment: 5 pgs,latex,3 figs,revised version to be publshed in Phys.Rev.
Effect of exercise training on in vitro LDL oxidation and free radical-induced hemolysis: The HERITAGE family study
Spontaneous Chiral-Symmetry Breaking in Three-Dimensional QED with a Chern--Simons Term
In three-dimensional QED with a Chern--Simons term we study the phase
structure associated with chiral-symmetry breaking in the framework of the
Schwinger--Dyson equation. We give detailed analyses on the analytical and
numerical solutions for the Schwinger--Dyson equation of the fermion
propagator, where the nonlocal gauge-fixing procedure is adopted to avoid
wave-function renormalization for the fermion. In the absence of the
Chern--Simons term, there exists a finite critical number of four-component
fermion flavors, at which a continuous (infinite-order) chiral phase transition
takes place and below which the chiral symmetry is spontaneously broken. In the
presence of the Chern--Simons term, we find that the spontaneous
chiral-symmetry-breaking transition continues to exist, but the type of phase
transition turns into a discontinuous first-order transition. A simple
stability argument is given based on the effective potential, whose stationary
point gives the solution of the Schwinger-Dyson equation.Comment: 34 pages, revtex, with 9 postscriptfigures appended (uuencoded
The genetics of obesity and the metabolic syndrome
In this review, we discuss the genetic architecture of obesity and the metabolic syndrome, highlighting recent advances in identifying genetic variants and loci responsible for a portion of the variation in components of the metabolic syndrome, namely, adiposity traits, serum HDL and triglycerides, blood pressure, and glycemic traits. We focus particularly on recent progress from large-scale genome-wide association studies (GWAS), by detailing their successes and how lessons learned can pave the way for future discovery. Results from recent GWAS coalesce with earlier work suggesting numerous interconnections between obesity and the metabolic syndrome, developed through several potentially pleiotropic effects. We detail recent work by way of a case study on the cadherin 13 gene and its relation with adiponectin in the HyperGEN and the Framingham Heart Studies, and its association with obesity and the metabolic syndrome. We provide also a gene network analysis of recent variants related to obesity and metabolic syndrome discovered through genome-wide association studies, and 4 gene networks based on searching the NCBI database
Spin Susceptibility and Superexchange Interaction in the Antiferromagnet CuO
Evidence for the quasi one-dimensional (1D) antiferromagnetism of CuO is
presented in a framework of Heisenberg model. We have obtained an experimental
absolute value of the paramagnetic spin susceptibility of CuO by subtracting
the orbital susceptibility separately from the total susceptibility through the
Cu NMR shift measurement, and compared directly with the theoretical
predictions. The result is best described by a 1D antiferromagnetic
Heisenberg (AFH) model, supporting the speculation invoked by earlier authors.
We also present a semi-quantitative reason why CuO, seemingly of 3D structure,
is unexpectedly a quasi 1D antiferromagnet.Comment: 7 pages including 4 tables and 9 figure
Electronic structure, phase stability and chemical bonding in ThAl and ThAlH
We present the results of theoretical investigation on the electronic
structure, bonding nature and ground state properties of ThAl and
ThAlH using generalized-gradient-corrected first-principles
full-potential density-functional calculations. ThAlH has been reported
to violate the "2 \AA rule" of H-H separation in hydrides. From our total
energy as well as force-minimization calculations, we found a shortest H-H
separation of 1.95 {\AA} in accordance with recent high resolution powder
neutron diffraction experiments. When the ThAl matrix is hydrogenated, the
volume expansion is highly anisotropic, which is quite opposite to other
hydrides having the same crystal structure. The bonding nature of these
materials are analyzed from the density of states, crystal-orbital Hamiltonian
population and valence-charge-density analyses. Our calculation predicts
different nature of bonding for the H atoms along and . The strongest
bonding in ThAlH is between Th and H along which form dumb-bell
shaped H-Th-H subunits. Due to this strong covalent interaction there is very
small amount of electrons present between H atoms along which makes
repulsive interaction between the H atoms smaller and this is the precise
reason why the 2 {\AA} rule is violated. The large difference in the
interatomic distances between the interstitial region where one can accommodate
H in the and planes along with the strong covalent interaction
between Th and H are the main reasons for highly anisotropic volume expansion
on hydrogenation of ThAl.Comment: 14 pages, 9 figure
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