24,752 research outputs found
The Solar Proton Burning Process Revisited In Chiral Perturbation Theory
The proton burning process p + p -> d + e(+) + \nu(e), important for the
stellar evolution of main-sequence stars of mass equal to or less than that of
the Sun, is computed in effective field theory using chiral perturbation
expansion to the next-to-next-to leading chiral order. This represents a
model-independent calculation consistent with low-energy effective theory of
QCD comparable in accuracy to the radiative np capture at thermal energy
previously calculated by first using very accurate two-nucleon wavefunctions
backed up by an effective field theory technique with a finite cut-off. The
result obtained thereby is found to support within theoretical uncertainties
the previous calculation of the same process by Bahcall and his co-workers.Comment: 30 pages, 2 eps files, aaspp4.sty needed, slightly modified, to be
published in Ap.
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Loss of muscleblind-like 1 results in cardiac pathology and persistence of embryonic splice isoforms.
Cardiac dysfunction is a prominent cause of mortality in myotonic dystrophy I (DM1), a disease where expanded CUG repeats bind and disable the muscleblind-like family of splice regulators. Deletion of muscleblind-like 1 (Mbnl1(ĪE2/ĪE2)) in 129ā
sv mice results in QRS, QTc widening, bundle block and STc narrowing at 2-4 months of age. With time, cardiac function deteriorates further and at 6 months, decreased R wave amplitudes, sinus node dysfunction, cardiac hypertrophy, interstitial fibrosis, multi-focal myocardial fiber death and calcification manifest. Sudden death, where no end point illness is overt, is observed at a median age of 6.5 and 4.8 months in ~67% and ~86% of male and female Mbnl1(ĪE2/ĪE2) mice, respectively. Mbnl1 depletion results in the persistence of embryonic splice isoforms in a network of cardiac RNAs, some of which have been previously implicated in DM1, regulating sodium and calcium currents, Scn5a, Junctin, Junctate, Atp2a1, Atp11a, Cacna1s, Ryr2, intra and inter cellular transport, Clta, Stx2, Tjp1, cell survival, Capn3, Sirt2, Csda, sarcomere and cytoskeleton organization and function, Trim55, Mapt, Pdlim3, Pdlim5, Sorbs1, Sorbs2, Fhod1, Spag9 and structural components of the sarcomere, Myom1, Tnnt2, Zasp. Thus this study supports a key role for Mbnl1 loss in the initiation of DM1 cardiac disease
Large single crystal growth of BaFe1.87Co0.13As2 using a nucleation pole
Co-doped iron arsenic single crystal of BaFe1.87Co0.13As2 with dimension up
to 20 x 10 x 2 mm3 were grown by a nucleation pole: an alumina stick served as
nucleation center during growth. The high quality of crystalline was
illustrated by the measurements of neutron rocking curve and X-ray diffraction
pattern. A very sharp superconducting transition temperature Tc~25 K was
revealed by both resistivity and susceptibility measurements. A nearly 100%
shielding fraction and bulk nature of the superconductivity for the single
crystal were confirmed using magnetic susceptibility data.Comment: 4 pages, 5 figure
Surface currents from hourly variations of suspended particulate matter from Geostationary Ocean Color Imager data
Surface currents in Korean coastal regions were obtained using the maximum cross-correlation method applied to hourly suspended particulate matter images from the Geostationary Ocean Color Imager. Preliminary current vectors were filtered out by applying a series of quality-control procedures. The current vectors resulting from the tests were compared with the currents from a numerical model with tide and wind field. It was found that the estimated currents were more similarly to the currents caused by both tide and wind. A high degree of discrepancy was detected in regions of strong tidal currents, where the fundamental assumption of horizontal movement was limited due to the dominant vertical tidal mixing in the shallow region. The hourly rotations of the current vectors within a day were clarified by a comparison of the time-varying orientation angles of tidal ellipses. This study emphasized how to understand the short-term surface flows from hourly high-resolution geostationary satellite images
Pressure induced enhancement of ferroelectricity in multiferroic MnO(=Tb,Dy, and Ho)
Measurements of ferroelectric polarization and dielectric constant were done
on MnO (=Tb, Dy, and Ho) with applied hydrostatic pressures of up
to 18 kbar. At ambient pressure, distinctive anomalies were observed in the
temperature profile of both physical properties at critical temperatures
marking the onset of long range AFM order (T), ferroelectricity
(T) as well as at temperatures when anomalous changes in the
polarization, dielectric constant and spin wave commensurability have been
previously reported. In particular, the step in the dielectric constant at low
temperatures (T), associated with both a drop in the ferroelectric
polarization and an incommensurate magnetic structure, was shown to be suddenly
quenched upon passing an -dependent critical pressure. This was shown to
correlate with the stabilization of the high ferroelectric polarization state
which is coincident with the commensurate magnetic structure. The observation
is suggested to be due to a pressure induced phase transition into a
commensurate magnetic structure as exemplified by the pressure-temperature
(-) phase diagrams constructed in this work. The - phase diagrams
are determined for all three compounds.Comment: 8 pages, 6 figures, submitted for review in Phys. Rev.
Designing rigid carbon foams
We use ab initio density functional calculations to study the stability,
elastic properties and electronic structure of sp2 carbon minimal surfaces with
negative Gaussian curvature, called schwarzites. We focus on two systems with
cubic unit cells containing 152 and 200 carbon atoms, which are metallic and
very rigid. The porous schwarzite structure allows for efficient and reversible
doping by electron donors and acceptors, making it a promising candidate for
the next generation of alkali ion batteries. We identify schwarzite structures
that act as arrays of interconnected quantum spin dots or become magnetic when
doped. We introduce two interpenetrating schwarzite structures that may find
their use as the ultimate super-capacitor.Comment: 6 pages, 5 figure
Equivalence of -bosons using the exponential phase operator
Various forms of the -boson are explained and their hidden symmetry
revealed by transformations using the exponential phase operator. Both the
one-component and the multicomponent -bosons are discussed. As a byproduct,
we obtain a new boson algebra having a shifted vacuum structure and define a
global operatal gauge transformation.Comment: 18 pages, LaTex(run twice), To appear in J. PHys.
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