3,756 research outputs found
The hyperon mean free paths in the relativistic mean field
The - and -hyperon mean free paths in nuclei are firstly
calculated in the relativistic mean field (RMF) theory. The real parts of the
optical potential are derived from the RMF approach, while the imaginary parts
are obtained from those of nucleons with the relations:
and . With the
assumption, the depth of the imaginary potential for is
3.5 MeV, and for is 7 MeV at
low incident energy. We find that, the hyperon mean free path decreases with
the increase of the hyperon incident energies, from 200 MeV to 800 MeV; and in
the interior of the nuclei, the mean free path is about fm for
, and about fm for , depending on the hyperon
incident energy.Comment: 5 figures, 6 page
Electronic structures of [001]- and [111]-oriented InSb and GaSb free-standing nanowires
We report on a theoretical study of the electronic structures of InSb and
GaSb nanowires oriented along the [001] and [111] crystallographic directions.
The nanowires are described by atomistic, spin-orbit inteaction included,
tight-binding models, and the band structures and the wave functions of the
nanowires are calculated by means of a Lanczos iteration algorithm. For the
[001]-oriented InSb and GaSb nanowires, the systems with both square and
rectangular cross sections are considered. Here, it is found that all the
energy bands are double degenerate. Furthermore, although the lowest conduction
bands in these nanowires show good parabolic dispersions, the top valence bands
show rich and complex structures. In particular, the topmost valence bands of
these nanowires with a square cross section show a double maximum structure. In
the nanowires with a rectangular cross section, this double maximum structure
is suppressed and top valence bands gradually develop into parabolic bands as
the aspect ratio of the cross section is increased. For the [111]-oriented InSb
and GaSb nanowires, the systems with hexagonal cross sections are considered.
It is found that all the bands at the \Gamma-point are again double degenerate.
However, some of them will split into non-degenerate bands when the wave vector
moves away from the \Gamma-point. Furthermore, although the lowest conduction
bands again show good parabolic dispersions, the topmost valence bands do not
show the double maximum structure but, instead, a single maximum structure with
its maximum at a wave vector slightly away from the \Gamma-point. We also
investigate the effects of quantum confinement on the band structures of the
[001]- and [111]-oriented InSb and GaSb nanowires and present an empirical
formula for the description of quantization energies of the band edge states in
the nanowires.Comment: 17 pages, 19 figure
Molecular Cloning and Identification of Novel ω-gliadin Genes from Species
Gliadin is a main component of gluten proteins that affect functional properties of bread making and contributes to the viscous nature of doughs. In this study, thirteen novel ω-gliadin genes were identified in several Triticum species, which encode the ARH-, ATDand ATN-type proteins. Two novel types of ω-gliadins: ATD- and ATN- have not yet been reported. The lengths of 13 sequences were ranged from 927 to 1269 bp and the deduced mature proteins were varied from 309 to 414 residues. All 13 genes were pseudogenes because of the presence of internal stop codons. The primary structure of these ω-gliadin genes included a signal peptide, a conserved N-terminal domain, a repetitive domain and a conserved C-terminus. In this paper, we first characterize ω-gliadin genes from T. timopheevi ssp. timopheevi and T. timopheevi ssp. araraticum. The ω-gliadin gene variation and the evolutionary relationship of ω-gliadin family genes were also discussed
CoO2-Layer-Thickness Dependence of Magnetic Properties and Possible Two Different Superconducting States in NaxCoO2.yH2O
In order to understand the experimentally proposed phase diagrams of
NaxCoO2.yH2O, we theoretically study the CoO2-layer-thickness dependence of
magnetic and superconducting (SC) properties by analyzing a multiorbital
Hubbard model using the random phase approximation. When the Co valence (s) is
+3.4, we show that the magnetic fluctuation exhibits strong layer-thickness
dependence where it is enhanced at finite (zero) momentum in the thicker
(thinner) layer system. A magnetic order phase appears sandwiched by two SC
phases, consistent with the experiments. These two SC phases have different
pairing states where one is the singlet extended s-wave state and the other is
the triplet p-wave state. On the other hand, only a triplet p-wave SC phase
with dome-shaped behavior of Tc is predicted when s=+3.5, which is also
consistent with the experiments. Controversial experimental results on the
magnetic properties are also discussed.Comment: 5 pages, 4 figures. Submitted to Journal of the Physical Society of
Japa
Improving the electrochemical performances of Li rich Li1.20Ni0.13Co0.13Mn0.54O2 through a cooperative doping of Na and PO4 3 with Na3PO4
Li rich layered oxide cathodes suffer from poor rate capability, voltage decay and inferior cycling stability. Herein, we propose a novel synergistic strategy to improve the electrochemical performances of Li rich Li1.20Ni0.13Co0.13Mn0.54O2 by the co doping of Na and PO4 3 amp; 8722; . The co doping of Na for Li and PO4 3 amp; 8722; for Mn is simultaneously achieved using Na3PO4 as a dopant. The co doping of Na and PO4 3 amp; 8722; not only enhances the high rate performance 106.4 mAhg amp; 8722;1 10C and capacity retention 93.8 1C 100 cycles but also mitigates the voltage decay owing to the synergistic effect of Na and PO4 3 amp; 8722; co doping. The synergistic mechanism is unraveled based on neutron diffraction, aberration corrected scanning transmission electron microscope, Xray photoelectron spectroscopy, ex situ X ray absorption spectra, ex situ X ray diffraction, electrochemical impedance spectroscopy and electrochemical measurements. The co doping of Na and PO4 3 amp; 8722; enlarges the interlayer spacing and suppresses Li Ni mixing which increases Li diffusivity and enhances the rate capability. Meanwhile, the co doping of Na and PO4 3 amp; 8722; shrinks the thickness of the slabs, weakens the TM O covalency and alleviates the volume change in the charge discharge process which improves the layered structure stability and the cycling performances. This study presents some new insights into designing high performance cathode materials through a cooperative modulation of different crystal sites dopin
Optical properties of light-hole excitons in GaN epilayers
Optical properties of light-hole free exciton (FX B) in GaN epilayers were investigated by using near-resonance photoluminescence (PL) and time-resolved PL techniques. In contrast to the case of off-resonance PL where only heavy-hole free excitons (FX A) have strong response, FX B band can be well resolved in the near-resonance PL spectra. The variable-temperature near-resonance PL spectra show that the linewidth of FX B broadens faster than the FX A with increasing temperature. Moreover, the luminescence lifetime of FX B is found to be shorter than that of FX A. © 2010 American Institute of Physics.published_or_final_versio
Carbon emissions from fossil fuel consumption of Beijing in 2012
The present study analyzed the consumption-based carbon emissions from fossil fuel consumption of Beijing in 2012. The multi-scale input–output analysis method was applied. It is capable of tracing the carbon emissions embodied in imports based on a global multi-regional input–output analysis using Eora data. The results show that the consumption-based carbon emission of Beijing has increased by 18% since 2007, which is 2.57 times higher than the production-based carbon emission in 2012. Only approximately 1/10 of the total carbon emissions embodied in Beijing's local final demand originated from local direct carbon emissions. Meanwhile, more than 4/5 were from domestically imported products. The carbon emission nexus between Beijing and other Chinese regions has become closer since 2007, while the imbalance as the carbon emission transfer from Beijing to other regions has been mitigated. Instead, Beijing has imported more carbon emissions from foreign countries. Some carbon emission reduction strategies for Beijing concerning different goals are presented on the basis of detailed discussion
Pressure effects on the electron-doped high Tc superconductor BaFe(2-x)Co(x)As(2)
Application of pressures or electron-doping through Co substitution into Fe
sites transforms the itinerant antiferromagnet BaFe(2)As(2) into a
superconductor with the Tc exceeding 20K. We carried out systematic transport
measurements of BaFe(2-x)Co(x)As(2) superconductors in pressures up to 2.5GPa,
and elucidate the interplay between the effects of electron-doping and
pressures. For the underdoped sample with nominal composition x = 0.08,
application of pressure strongly suppresses a magnetic instability while
enhancing Tc by nearly a factor of two from 11K to 21K. In contrast, the
optimally doped x=0.20 sample shows very little enhancement of Tc=22K under
applied pressure. Our results strongly suggest that the proximity to a magnetic
instability is the key to the mechanism of superconductivity in iron-pnictides.Comment: 5 figure
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