5,937 research outputs found
Evolution of surface grain structure and mechanical properties in orthogonal cutting of titanium alloy
In this study, a mesoscale dislocation simulation method was developed to study the orthogonal cutting of Titanium alloy. The evolution of surface grain structure and its effects on the surface mechanical properties were studied by using two-dimensional climb assisted dislocation dynamics technology. The motions of edge dislocations such as dislocation nucleation, junction, interaction with obstacles and grain boundaries, and annihilation were tracked. The results indicated that the machined surface has a microstructure composed of refined grains. The fine-grains bring appreciable scale effect and a mass of dislocations are piled up in the grain boundaries and persistent slip bands. In particular, dislocation climb can induce a perfect softening effect, but this effect is significantly weakened when grain size is less than 1.65 μm. In addition, a Hall-Petch type relation was predicted according to the arrangement of grain, the range of grain sizes and the distribution of dislocations
CELLULASE6 and MANNANASE7 affect cell differentiation and silique dehiscence in Arabidopsis
Cellulases, hemicellulases and pectinases play important roles in fruit development and maturation, but mutants with defects in the fruit have not been reported for cellulase or hemicellulase genes. Here we report the functional characterization of cellulase gene CEL6 and hemicellulase gene MAN7 in silique development and dehiscence in Arabidopsis. These genes were found to be expressed in vegetative and reproductive organs, and their expression in the silique partially depended on the IND and ALC transcriptional factors. Mutant alleles of cel6 and man7 exhibited delayed secondary cell wall thickening and altered cell morphology in the valve margin and impaired silique dehiscence. Cells in the separation layer in nearly mature siliques of the single mutants and the cel6-1 man7-3 double mutant remained intact whereas they degenerated in the wild-type control. Phenotypic studies of single, double, triple and quadruple mutants revealed that the higher-order mutant combinations of the cel6-1, man7-3, and pectinase adpg1-1 and adpg2- 1 mutations produced more severe silique indehiscent phenotypes than the corresponding lower-order mutant combinations, except for some combinations involving cel6-1, man7-3, and adpg2-1. Our results demonstrate that the ability of the silique to dehisce can be manipulated to different degrees by altering the activities of proteins of different types.Plant Biology, Ecology and Evolutio
Determining the upper limit of Gamma_{ee} for the Y(4260)
By fitting the R values between 3.7 and 5.0 GeV measured by the BES
collaboration, the upper limit of the electron width of the newly discovered
resonance Y(4260) is determined to be 580 eV at 90% C.L. Together with the
BABAR measurement on the product of Gamma_{ee} and BR(Y(4260) --> pi+pi-
J/psi), this implies a large decay width of Y(4260) --> pi+pi- J/psi final
states.Comment: 8 pages, 4 figure
Observation of Two New N* Peaks in J/psi -> and Decays
The system in decays of is limited to be
isospin 1/2 by isospin conservation. This provides a big advantage in studying
compared with and experiments which mix
isospin 1/2 and 3/2 for the system. Using 58 million decays
collected with the Beijing Electron Positron Collider, more than 100 thousand
events are obtained. Besides two well known
peaks at 1500 MeV and 1670 MeV, there are two new, clear peaks in
the invariant mass spectrum around 1360 MeV and 2030 MeV. They are the
first direct observation of the peak and a long-sought "missing"
peak above 2 GeV in the invariant mass spectrum. A simple
Breit-Wigner fit gives the mass and width for the peak as MeV and MeV, and for the new peak above 2 GeV
as MeV and MeV, respectively
Food safety analysis and management of Shiga toxin-producing Escherichia coli in edible agricultural products and kitchen
The sources and transmission routes of Shiga toxin-producing Escherichia coli (STEC) in edible agricultural products are analyzed. And the relationship between STEC contamination and food safety in home kitchen is discussed. The current supervision of STEC in edible agricultural products around the world is introduced. The solution and suggestion for the control of STEC in the home kitchen of China are proposed
Search for Invisible Decays of and in and
Using a data sample of decays collected with the BES
II detector at the BEPC, searches for invisible decays of and
in to and are performed.
The signals, which are reconstructed in final states, are used
to tag the and decays. No signals are found for the
invisible decays of either or , and upper limits at the 90%
confidence level are determined to be for the ratio
and for . These are the first
searches for and decays into invisible final states.Comment: 5 pages, 4 figures; Added references, Corrected typo
Sufentanil for carboprost-induced adverse reactions during cesarean delivery under combined spinal-epidural anesthesia
Objective: Carboprost plays an important role in managing refractory uterine atony and severe postpartum hemorrhage. However, it is associated with challenging adverse reactions. We aimed to evaluate the clinical effects of low-dose sufentanil on the prevention of adverse events associated with carboprost during cesarean delivery. Study Design: Patients were randomly divided into two groups: a placebo control group (group C, n = 15) that received an intravenous infusion of 1 mL of normal saline 2 min before carboprost and a sufentanil group (group S, n = 15) that received 5 µg of sufentanil. The primary outcome was the incidence of nausea and vomiting following carboprost administration. Results: The incidence of nausea, vomiting, and gastrointestinal discomfort was significantly lower in group S than in group C (P < 0.05). Conclusions: The prophylactic use of low-dose sufentanil reduces the incidence of gastrointestinal side effects caused by carboprost administration during cesarean section
Parameters in a Class of Leptophilic Dark Matter Models from PAMELA, ATIC and FERMI
In this work we study a class of leptophilic dark matter models, where the
dark matter interacts with the standard model particles via the
gauge boson, to explain the excess in cosmic rays
observed by ATIC and PAMELA experiments, and more recently by Fermi experiment.
There are three types of models: a) , b)
, and c) . Although ATIC or Fermi
data is consistent with PAMELA data separately, ATIC and Fermi data do not
agree with each other. We therefore aim to identify which of the three models
can explain which data set better. We find that models a) and b) can give
correct dark matter relic density and explain the ATIC and PAMELA data
simultaneously recur to the Breit-Wigner enhancement. Whereas model c) with a
larger mass can explain Fermi and PAMELA data simultaneously. In all
cases the model parameters are restricted to narrow regions. Future improved
data will decide which set of data are correct and also help to decide the
correct dark matter model.Comment: Latex 15 pages with 5 figures. Modified to include discussions of
recent Fermi data on the leptophilic models studied in this paper. Title also
modifie
Determination of astrophysical 12N(p,g)13O reaction rate from the 2H(12N, 13O)n reaction and its astrophysical implications
The evolution of massive stars with very low-metallicities depends critically
on the amount of CNO nuclides which they produce. The
N(,\,)O reaction is an important branching point in
the rap-processes, which are believed to be alternative paths to the slow
3 process for producing CNO seed nuclei and thus could change the fate
of massive stars. In the present work, the angular distribution of the
H(N,\,O) proton transfer reaction at =
8.4 MeV has been measured for the first time. Based on the Johnson-Soper
approach, the square of the asymptotic normalization coefficient (ANC) for the
virtual decay of O N + was
extracted to be 3.92 1.47 fm from the measured angular
distribution and utilized to compute the direct component in the
N(,\,)O reaction. The direct astrophysical S-factor at
zero energy was then found to be 0.39 0.15 keV b. By considering the
direct capture into the ground state of O, the resonant capture via the
first excited state of O and their interference, we determined the total
astrophysical S-factors and rates of the N(,\,)O
reaction. The new rate is two orders of magnitude slower than that from the
REACLIB compilation. Our reaction network calculations with the present rate
imply that N()O will only compete successfully with
the decay of N at higher (two orders of magnitude)
densities than initially predicted.Comment: 8 figures, 2 tables, Submitted to Physical Review
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