5,642 research outputs found
Isospin Effect on the Process of Multifragmentation and Dissipation at Intermediate Energy Heavy Ion Collisions
In the simulation of intermediate energy heavy ion collisions by using the
isospin dependent quantum molecular dynamics, the isospin effect on the process
of multifragmentation and dissipation has been studied. It is found that the
multiplicity of intermediate mass fragments for the neutron-poor
colliding system is always larger than that for the neutron-rich system, while
the quadrupole of single particle momentum distribution for the
neutron-poor colliding system is smaller than that of the neutron-rich system
for all projectile-target combinations studied at the beam energies from about
50MeV/nucleon to 150MeV/nucleon. Since depends strongly on isospin
dependence of in-medium nucleon-nucleon cross section and weakly on symmetry
potential at the above beam energies, it may serve as a good probe to extract
the information on the in-medium nucleon-nucleon cross section. The correlation
between the multiplicity of intermediate mass fragments and the total
numer of charged particles has the behavior similar to , which
can be used as a complementary probe to the in-medium nucleon-nucleon cross
section.Comment: 18 pages, 9 figure
Surface Fractal Dimension of Single-walled Carbon Nanotubes
Isolated single-walled carbon nanotubes (SWNTs), SWNT bundles, and ropes (or strands) show a structural self-similar characteristic. By calculating the Hausdorff dimension, it was found that their self-similar organization leads to surface fractality and the value of the surface dimension (Ds) depends on self-similar patterns. Experimentally, Ds obtained by nitrogen adsorption measurements at 77.3 K and by the small-angle x-ray scattering technique in our study proved our calculation that the surface dimension of SWNTs is nonintegral,
Relative energetics and structural properties of zirconia using a self-consistent tight-binding model
We describe an empirical, self-consistent, orthogonal tight-binding model for
zirconia, which allows for the polarizability of the anions at dipole and
quadrupole levels and for crystal field splitting of the cation d orbitals.
This is achieved by mixing the orbitals of different symmetry on a site with
coupling coefficients driven by the Coulomb potentials up to octapole level.
The additional forces on atoms due to the self-consistency and polarizabilities
are exactly obtained by straightforward electrostatics, by analogy with the
Hellmann-Feynman theorem as applied in first-principles calculations. The model
correctly orders the zero temperature energies of all zirconia polymorphs. The
Zr-O matrix elements of the Hamiltonian, which measure covalency, make a
greater contribution than the polarizability to the energy differences between
phases. Results for elastic constants of the cubic and tetragonal phases and
phonon frequencies of the cubic phase are also presented and compared with some
experimental data and first-principles calculations. We suggest that the model
will be useful for studying finite temperature effects by means of molecular
dynamics.Comment: to be published in Physical Review B (1 march 2000
Coexistence of superconductivity and antiferromagnetism in single crystals (A= K, Rb, Cs, Tl/K and Tl/Rb): evidence from magnetization and resistivity
We measure the resistivity and magnetic susceptibility in the temperature
range from 5 K to 600 K for the single crystals FeSe ( =
K, Rb, Cs, TlK and
TlRb). A sharp superconducting transition is observed in low
temperature resistivity and susceptibility, and susceptibility shows 100%
Meissner volume fraction for all crystals, while an antiferromagnetic
transition is observed in susceptibility at Neel temperature () as high as
500 K to 540 K depending on A. It indicates the coexistence of
superconductivity and antiferromagnetism. A sharp increase in resistivity
arises from the structural transition due to Fe vacancy ordering at the
temperature slightly higher than . Occurrence of superconductivity
in an antiferromagnetic ordered state with so high may suggest new
physics in this type of unconventional superconductors.Comment: 5 pages, 4 figure
Fine Mapping of the Bsr1 Barley Stripe Mosaic Virus Resistance Gene in the Model Grass Brachypodium distachyon
The ND18 strain of Barley stripe mosaic virus (BSMV) infects several lines of Brachypodium distachyon, a recently developed model system for genomics research in cereals. Among the inbred lines tested, Bd3-1 is highly resistant at 20 to 25°C, whereas Bd21 is susceptible and infection results in an intense mosaic phenotype accompanied by high levels of replicating virus. We generated an F6∶7 recombinant inbred line (RIL) population from a cross between Bd3-1 and Bd21 and used the RILs, and an F2 population of a second Bd21 × Bd3-1 cross to evaluate the inheritance of resistance. The results indicate that resistance segregates as expected for a single dominant gene, which we have designated Barley stripe mosaic virus resistance 1 (Bsr1). We constructed a genetic linkage map of the RIL population using SNP markers to map this gene to within 705 Kb of the distal end of the top of chromosome 3. Additional CAPS and Indel markers were used to fine map Bsr1 to a 23 Kb interval containing five putative genes. Our study demonstrates the power of using RILs to rapidly map the genetic determinants of BSMV resistance in Brachypodium. Moreover, the RILs and their associated genetic map, when combined with the complete genomic sequence of Brachypodium, provide new resources for genetic analyses of many other traits
Nernst effect of the new iron-based superconductor LaOFFeAs
We report the first Nernst effect measurement on the new iron-based
superconductor LaOFFeAs . In the normal state, the
Nernst signal is negative and very small. Below a large positive peak
caused by vortex motion is observed. The flux flowing regime is quite large
compared to conventional type-II superconductors. However, a clear deviation of
the Nernst signal from normal state background and an anomalous depression of
off-diagonal thermoelectric current in the normal state between and 50
K are observed. We propose that this anomaly in the normal state Nernst effect
could correlate with the SDW fluctuations.Comment: 8 pages, 4 figures; Latex file changed, references adde
Pressure Effect on the superconducting properties of LaO_{1-x}F_{x}FeAs(x=0.11) superconductor
Diamagnetic susceptibility measurements under high hydrostatic pressure (up
to 1.03 GPa) were carried out on the newly discovered Fe-based superconductor
LaO_{1-x}F_{x}FeAs(x=0.11). The transition temperature T_c, defined as the
point at the maximum slope of superconducting transition, was enhanced almost
linearly by hydrostatic pressure, yielding a dT_c/dP of about 1.2 K/GPa.
Differential diamagnetic susceptibility curves indicate that the underlying
superconducting state is complicated. It is suggested that pressure plays an
important role on pushing low T_c superconducting phase toward the main
(optimal) superconducting phase.Comment: 7 pages, 4 figure
Transcriptome Analysis of the Chinese White Wax Scale Ericerus pela with Focus on Genes Involved in Wax Biosynthesis
BACKGROUND: The Chinese white wax scale, Ericerus pela Chavannes is economically significant for its role in wax production. This insect has been bred in China for over a thousand years. The wax secreted by the male scale insect during the second-instar larval stage has been widespread used in wax candle production, wax printing, engraving, Chinese medicine, and more recently in the chemical, pharmaceutical, food, and cosmetics industries. However, little is known about the mechanisms responsible for white wax biosynthesis. The characterization of its larval transcriptome may promote better understanding of wax biosynthesis. METHODOLOGY/PRINCIPAL FINDINGS: In this study, characterization of the transcriptome of E. pela during peak wax secretion was performed using Illumina sequencing technology. Illumina sequencing produced 41,839 unigenes. These unigenes were annotated by blastx alignment against the NCBI Non-Redundant (NR), Swiss-Prot, KEGG, and COG databases. A total of 104 unigenes related to white wax biosynthesis were identified, and 15 of them were selected for quantitative real-time PCR analysis. We evaluated the variations in gene expression across different development stages, including egg, first/second instar larvae, male pupae, and male and female adults. Then we identified five genes involved in white wax biosynthesis. These genes were expressed most strongly during the second-instar larval stage of male E. pela. CONCLUSION/SIGNIFICANCE: The transcriptome analysis of E. pela during peak wax secretion provided an overview of gene expression information at the transcriptional level and a resource for gene mining. Five genes related to white wax biosynthesis were identified
Measurements of h_c(^1P_1) in psi' Decays
We present measurements of the charmonium state made with 106M
events collected by BESIII at BEPCII. Clear signals are observed for
with and without the subsequent radiative decay
. First measurements of the absolute branching ratios
and
are presented. A
statistics-limited determination of the previously unmeasured width leads
to an upper limit MeV (90% confidence). Measurements of
MeV/ and are consistent with previous results.Comment: 5 pages, 1 figure, accepted for publication in Physical Review
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