473 research outputs found
Heme Oxygenase-1 Attenuates Hypoxia-Induced sFlt-1 and Oxidative Stress in Placental Villi through Its Metabolic Products CO and Bilirubin
One of the most prevalent complications of pregnancy is preeclampsia, a hypertensive disorder which is a leading cause of maternal and perinatal morbidity and premature birth with no effective pharmacological intervention. While the underlying cause is unclear, it is believed that placental ischemia/hypoxia induces the release of factors into the maternal vasculature and lead to widespread maternal endothelial dysfunction. Recently, HO-1 has been shown to downregulate two of these factors, reactive oxygen species and sFlt-1, and we have reported that HO-1 induction attenuates many of the pathological factors of placental ischemia experimentally. Here, we have examined the direct effect of HO-1 and its bioactive metabolites on hypoxia-induced changes in superoxide and sFlt-1 in placental vascular explants and showed that HO-1 and its metabolites attenuate the production of both factors in this system. These findings suggest that the HO-1 pathway may be a promising therapeutic approach for the treatment of preeclampsia
NdBaScO4: aristotype of a new family of geometric ferroelectrics?
The authors acknowledge the University of St Andrews and the EPSRC (DTG: EP/K503162/1) for a studentship (to CALD). WZ and PSH thank the Welch Foundation (Grant E-1457), NSF DMR-1503573, and the Texas Center for Superconductivity for support. EB thanks the FRS-FNRS for supports and the Consortium des Equipements de Calcul Intensif (CECI), funded by the FRS-FNRS (Grants No. 2.5020.11 and No. 1175545). The research data supporting this publication can be accessed atat http://dx.doi.org/10.17630/197519dd-5b67-49f8-bd50-7f1fb98bec73NdBaScO4 represents the aristotype structure of a new series of -cut layered perovskites; it is suggested that compositional fine-tuning is likely to produce a family of new geometric ferroelectrics, driven primarily by octahedral tilting.PostprintPostprintPeer reviewe
Anomalous Exponent of the Spin Correlation Function of a Quantum Hall Edge
The charge and spin correlation functions of partially spin-polarized edge
electrons of a quantum Hall bar are studied using effective Hamiltonian and
bosonization techniques. In the presence of the Coulomb interaction between the
edges with opposite chirality we find a different crossover behavior in spin
and charge correlation functions. The crossover of the spin correlation
function in the Coulomb dominated regime is characterized by an anomalous
exponent, which originates from the finite value of the effective interaction
for the spin degree of freedom in the long wavelength limit. The anomalous
exponent may be determined by measuring nuclear spin relaxation rates in a
narrow quantum Hall bar or in a quantum wire in strong magnetic fields.Comment: 4 pages, Revtex file, no figures. To appear in Physical Revews B,
Rapid communication
On Maximal Massive 3D Supergravity
We construct, at the linearized level, the three-dimensional (3D) N = 4
supersymmetric "general massive supergravity" and the maximally supersymmetric
N = 8 "new massive supergravity". We also construct the maximally
supersymmetric linearized N = 7 topologically massive supergravity, although we
expect N = 6 to be maximal at the non-linear level.Comment: 33 page
Topological Orbifold Models and Quantum Cohomology Rings
We discuss the toplogical sigma model on an orbifold target space. We
describe the moduli space of classical minima for computing correlation
functions involving twisted operators, and show, through a detailed computation
of an orbifold of by the dihedral group how to compute
the complete ring of observables. Through this procedure, we compute all the
rings from dihedral orbifolds; we note a similarity with rings
derived from perturbed series superpotentials of the classification
of minimal models. We then consider and show how the
techniques of topological-anti-topological fusion might be used to compute
twist field correlation functions for nonabelian orbifolds.Comment: 48 pages, harvmac, HUTP-92/A06
Antarctic Temperatures Over the Past Two Centuries from Ice Cores
We present a reconstruction of Antarctic mean surface temperatures over the past two centuries based on water stable isotope records from high-resolution, precisely dated ice cores. Both instrumental and reconstructed temperatures indicate large interannual to decadal scale variability, with the dominant pattern being anti-phase anomalies between the main Antarctic continent and the Antarctic Peninsula region. Comparative analysis of the instrumental Southern Hemisphere (SH) mean temperature record and the reconstruction suggests that at longer timescales, temperatures over the Antarctic continent vary in phase with the SH mean. Our reconstruction suggests that Antarctic temperatures have increased by about 0.2 degrees C since the late nineteenth century. The variability and the long-term trends are strongly modulated by the SH Annular Mode in the atmospheric circulation
Anomalous tunneling conductances of a spin singlet \nu=2/3 edge states: Interplay of Zeeman splitting and Long Range Coulomb Interaction
The point contact tunneling conductance between edges of the spin singlet
quantum Hall states is studied both in the
quasiparticle tunneling picture and in the electron tunneling picture. Due to
the interplay of Zeeman splitting and the long range Coulomb interaction
between edges of opposite chirality novel spin excitations emerge, and their
effect is characterized by anomalous exponents of the charge and spin tunneling
conductances in various temperature ranges. Depending on the kinds of
scatterings at the point contact and the tunneling mechanism the anomalous
interaction in spin sector may enhance or suppress the tunneling conductances.
The effects of novel spin excitation are also relevant to the recent NMR
experiments on quantum Hall edges.Comment: Revtex File, 7 pages: To be published in Physical Reviews
Heralding efficiency and correlated-mode coupling of near-IR fiber-coupled photon pairs
We report on a systematic experimental study of the heralding efficiency and generation rate of telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single-mode optical fibers. We define the correlated-mode coupling efficiency, an inherent source efficiency, and explain its relation to heralding efficiency. For our experiment, we developed a reconfigurable computer-controlled pump-beam and collection-mode optical apparatus which we used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise, high-efficiency superconducting nanowire single-photon detectors in this setup allowed us to explore focus configurations with low overall photon flux. The measured data agree well with theory, and we demonstrated a correlated-mode coupling efficiency of 97% ± 2%, which is the highest efficiency yet achieved for this type of system. These results confirm theoretical treatments and demonstrate that very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. It is expected that these results and techniques will be widely incorporated into future systems that require, or benefit from, a high heralding efficiency.United States. Dept. of Defense. Assistant Secretary of Defense for Research & Engineering (Air Force Contract FA8721-05-C-0002
An algebraic/numerical formalism for one-loop multi-leg amplitudes
We present a formalism for the calculation of multi-particle one-loop
amplitudes, valid for an arbitrary number N of external legs, and for massive
as well as massless particles. A new method for the tensor reduction is
suggested which naturally isolates infrared divergences by construction. We
prove that for N>4, higher dimensional integrals can be avoided. We derive many
useful relations which allow for algebraic simplifications of one-loop
amplitudes. We introduce a form factor representation of tensor integrals which
contains no inverse Gram determinants by choosing a convenient set of basis
integrals. For the evaluation of these basis integrals we propose two methods:
An evaluation based on the analytical representation, which is fast and
accurate away from exceptional kinematical configurations, and a robust
numerical one, based on multi-dimensional contour deformation. The formalism
can be implemented straightforwardly into a computer program to calculate
next-to-leading order corrections to multi-particle processes in a largely
automated way.Comment: 71 pages, 7 figures, formulas for rank 6 pentagons added in Appendix
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