168,712 research outputs found
Nearly Mass-Degenerate Majorana Neutrinos: Double Beta Decay and Neutrino Oscillations
Assuming equal tree-level Majorana masses for the standard-model neutrinos,
either from the canonical seesaw mechanism or from a heavy scalar triplet, I
discuss how their radiative splitting may be relevant to neutrinoless double
beta decay and neutrino oscillations.Comment: 12 pages, including 4 figures, talk at NANP9
Complete relativistic equation of state for neutron stars
We construct the equation of state (EOS) in a wide density range for neutron
stars using the relativistic mean field theory. The properties of neutron star
matter with both uniform and non-uniform distributions are studied
consistently. The inclusion of hyperons considerably softens the EOS at high
densities. The Thomas-Fermi approximation is used to describe the non-uniform
matter, which is composed of a lattice of heavy nuclei. The phase transition
from uniform matter to non-uniform matter occurs around ,
and the free neutrons drip out of nuclei at about $2.4 \times 10^{-4}\
\rm{fm^{-3}}$. We apply the resulting EOS to investigate the neutron star
properties such as maximum mass and composition of neutron stars.Comment: 23 pages, REVTeX, 9 ps figures, to appear in Phys. Rev.
Spiral Chain O4 Form of Dense Oxygen
Oxygen is in many ways a unique element: the only known diatomic molecular
magnet and the capability of stabilization of the hitherto unexpected O8
cluster structure in its solid form at high pressure. Molecular dissociations
upon compression as one of the fundamental problems were reported for other
diatomic solids (e.g., H2, I2, Br2, and N2), but it remains elusive for solid
oxygen, making oxygen an intractable system. We here report the theoretical
prediction on the dissociation of molecular oxygen into a polymeric spiral
chain O4 structure (\theta-O4) by using first-principles calypso method on
crystal structure prediction. The \theta-O4 stabilizes above 2 TPa and has been
observed as the third high pressure phase of sulfur (S-III). We find that the
molecular O8 phase remains extremely stable in a large pressure range of 0.008
- 2 TPa, whose breakdown is driven by the pressure-induced instability of a
transverse acoustic phonon mode at zone boundary, leading to the ultimate
formation of \theta-O4. Remarkably, stabilization of \theta-O4 turns oxygen
from a superconductor into an insulator with a wide band gap (approximately 5.9
eV) originating from the sp3-like hybridized orbitals of oxygen and the
localization of valence electrons. (This is a pre-print version of the
following article: Li Zhu et al, Spiral chain O4 form of dense oxygen, Proc.
Natl. Acad. Sci. U.S.A. (2011), doi: 10.1073/pnas.1119375109, which has been
published online at http://www.pnas.org/content/early/2011/12/27/1119375109 .)Comment: 13 apages, 3 figure
Low-Temperature Solution-Processed Electron Transport Layers for Inverted Polymer Solar Cells
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimProcessing temperature is highlighted as a convenient means of controlling the optical and charge transport properties of solution processed electron transport layers (ETLs) in inverted polymer solar cells. Using the well-studied active layer â poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct â the influence of ETL processing temperatures from 25 to 450 °C is shown, reporting the role of crystallinity, structure, charge transport, and Fermi level (EF) on numerous device performance characteristics. It has been determined that an exceptionally low temperature processed ETL (110 °C) increases device power conversion efficiency by a factor greater than 50% compared with a high temperature (450 °C) processed ETL. Modulations in device series and shunt resistance, induced by changes in the ETL transport properties, are observed in parallel to significant changes in device open circuit voltage attributed to changes on the EF of the ETLs. This work highlights the importance of interlayer control in multilayer photovoltaic devices and presents a convenient material compatible with future flexible and roll-to-roll processes
Radio Polarization Observations of the Snail: A Crushed Pulsar Wind Nebula in G327.1-1.1 with a Highly Ordered Magnetic Field
Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic
rays in the Galaxy. While the magnetic field plays an important role in the
acceleration process, previous observations of magnetic field configurations of
PWNe are rare, particularly for evolved systems. We present a radio
polarization study of the "Snail" PWN inside the supernova remnant G327.1-1.1
using the Australia Telescope Compact Array. This PWN is believed to have been
recently crushed by the supernova (SN) reverse shock. The radio morphology is
composed of a main circular body with a finger-like protrusion. We detected a
strong linear polarization signal from the emission, which reflects a highly
ordered magnetic field in the PWN and is in contrast to the turbulent
environment with a tangled magnetic field generally expected from
hydrodynamical simulations. This could suggest that the characteristic
turbulence scale is larger than the radio beam size. We built a toy model to
explore this possibility, and found that a simulated PWN with a turbulence
scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind
filling factor of 50--75% provides the best match to observations. This implies
substantial mixing between the SN ejecta and pulsar wind material in this
system.Comment: 13 pages, 10 figures, Accepted for publication in Ap
Fluorescence studies of the binding of amphiphilic amines with phospholipids.
The binding characteristics of several amine drugs with dispersed phospholipids (phosphatidylcholine, phosphatidylserine, and phosphatidylglycerol) have been studied using the fluorometric method and 1-anilino-8-naphthalene sulfonate and 1,6 diphenyl-1,3,5-hexatriene as fluorescence probes. The results show that amphiphilic amines, such as chlorphentermine, interact with phospholipids via both ionic and hydrophobic forces. The ionic interaction, which occurs between the protonated amine group of the drug and the phosphate oxygen of the lipid, changes the amphiphilic characteristics of the lipid by reducing the number of negative charges on the lipid vesicles, and inhibits the Ca2+-dependent lipid hydrolysis by blocking the Ca2+ binding sites on the lipid vesicles. The hydrophobic interaction, which involves the nonpolar moieties of the drug and the lipid, is of primary importance to the overall drug-lipid binding stability. Drugs without a strong hydrophobic moiety, such as dopamine, do not interact with phospholipids
-scaling and Information Entropy in Ultra-Relativistic Nucleus-Nucleus Collisions
The -scaling method has been applied to ultra-relativistic p+p, C+C
and Pb+Pb collision data simulated using a high energy Monte Carlo package,
LUCIAE 3.0. The -scaling is found to be valid for some physical
variables, such as charged particle multiplicity, strange particle multiplicity
and number of binary nucleon-nucleon collisions from these simulated
nucleus-nucleus collisions over an extended energy ranging from = 20
to 200 A GeV. In addition we derived information entropy from the multiplicity
distribution as a function of beam energy for these collisions.Comment: 4 pages, 4 figures, 1 table; to appear in the July Issue of Chin.
Phys. Lett.. Web Page: http://www.iop.org/EJ/journal/CP
Statistical nature of cluster emission in nuclear liquid-vapour phase coexistence
The emission of nuclear clusters is investigated within the framework of
isospin dependent lattice gas model and classical molecular dynamics model. It
is found that the emission of individual cluster which is heavier than proton
is almost Poissonian except near the transition temperature at which the system
is leaving the liquid-vapor phase coexistence and the thermal scaling is
observed by the linear Arrhenius plots which is made from the average
multiplicity of each cluster versus the inverse of temperature in the liquid
vapor phase coexistence. The slopes of the Arrhenius plots, {\it i.e.} the
"emission barriers", are extracted as a function of the mass or charge number
and fitted by the formula embodied with the contributions of the surface energy
and Coulomb interaction. The good agreements are obtained in comparison with
the data for low energy conditional barriers. In addition, the possible
influences of the source size, Coulomb interaction and "freeze-out" density and
related physical implications are discussed
LSD1 is essential for oocyte meiotic progression by regulating CDC25B expression in mice
Mammalian oocytes are arrested at prophase I until puberty when hormonal signals induce the resumption of meiosis I and progression to meiosis II. Meiotic progression is controlled by CDK1 activity and is accompanied by dynamic epigenetic changes. Although the signalling pathways regulating CDK1 activity are well defined, the functional significance of epigenetic changes remains largely unknown. Here we show that LSD1, a lysine demethylase, regulates histone H3 lysine 4 di-methylation (H3K4me2) in mouse oocytes and is essential for meiotic progression. Conditional deletion of Lsd1 in growing oocytes results in precocious resumption of meiosis and spindle and chromosomal abnormalities. Consequently, most Lsd1-null oocytes fail to complete meiosis I and undergo apoptosis. Mechanistically, upregulation of CDC25B, a phosphatase that activates CDK1, is responsible for precocious meiotic resumption and also contributes to subsequent spindle and chromosomal defects. Our findings uncover a functional link between LSD1 and the major signalling pathway governing meiotic progression
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