1,429 research outputs found
Effects of relative orientation of the molecules on electron transport in molecular devices
Effects of relative orientation of the molecules on electron transport in
molecular devices are studied by non-equilibrium Green's function method based
on density functional theory. In particular, two molecular devices, with the
planer Au and Ag clusters sandwiched between the Al(100) electrodes
are studied. In each device, two typical configurations with the clusters
parallel and vertical to the electrodes are considered. It is found that the
relative orientation affects the transport properties of these two devices
completely differently. In the Al(100)-Au-Al(100) device, the conductance
and the current of the parallel configuration are much larger than those in the
vertical configuration, while in the Al(100)-Ag-Al(100) device, an
opposite conclusion is obtained
Analysis of Y(4660) and related bound states with QCD sum rules
In this article, we take the vector charmonium-like state Y(4660) as a
bound state (irrespective of the hadro-charmonium and the
molecular state) tentatively, study its mass using the QCD sum rules, the
numerical value is consistent with the experimental
data. Considering the SU(3) symmetry of the light flavor quarks and the heavy
quark symmetry, we also study the bound states ,
and with the QCD sum rules,
and make reasonable predictions for their masses.Comment: 18 pages, 32 figures, revised versio
Cytotoxicity of Essential Oil of Chenopodium ambrosioides L against Human Breast Cancer MCF-7 Cells
Purpose: To investigate the cytotoxic activity of the essential oil of Chenopodium ambrosioides L. against human breast cancer MCF-7 cells.Methods: Cytotoxicity was characterized by 50 % inhibition (IC50) of human breast cancer cell lines (MCF-7) using 3-(4,5-dimethylthaizol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was analysed by Hoechst33258 staining and DNA ladder. MCF-7 cellular superoxide dismutase (SOD), catalase (CAT) vitality and malondialdehyde (MDA) content were evaluated.Results: The essential oil was cytotoxic to MCF-7 cell line. A dose- and time-dependent inhibition was observed with IC50 values of 18.75, 9.45 and 10.50 μg/ml at 6, 24 and 48 h, respectively. Analyses by Hoechst33258 staining and DNA ladder indicate that the essential oil induced apoptosis. SOD vitality significantly decreased (p< 0.05) by 51 % when the concentration of the essential oil increased from 1.25 to 12.5 μg/ml while CAT vitality significantly increased (p < 0.05) by 71 % when essential oil concentration was similarly increased. The MDA content of each treatment group, when compare to control, did not show any significant difference (p < 0.05).Conclusion: The essential oil of C. ambrosioides was cytotoxic to MCF-7 cell line and induced apoptosis.Keywords: Chenopodium ambrosioides L., Essential oil, Cytotoxicity, Apoptosis, Breast cancer, MCF-7 cells
Effects of supplementing lactic acid bacteria on fecal microbiota, total cholesterol, triglycerides and bile acids in rats.
Background: Probiotics (LAB) are normal components of the intestinal micro-flora in both humans and animals and its ingestion in decreasing the risk of atherosclerosis. In addition, the potential health effects of LAB were investigated by monitoring changes in intestinal micro-flora and lipid metabolism in a rat model.Materials and Methods: Rats were randomly assigned into four treatments and fecal samples were obtained on days 1, 3, 5, 9 and 14,to evaluate fecal micro biota, total cholesterol (TC), triglycerides (TG) and bile acids in rats (TBA).Results: The results indicated that Lactobacillus plantarum strain L.p X3-2B increased fecal lactic acid bacteria(LAB) and Bifidobacterium while resisting the growth of harmful bacteria. Viable counts of LAB and Bifidobacterium reached 8 log cfu/mL after feeding for 14 days. Fecal pH in the control group was high in comparison with the treatments at all times. Treatment increased the excretion of triglycerides (TG), total cholesterol (TC) and total bile acid (TBA). The results indicate that LAB and Bifidobacterium induce a positive correlation with fecal TC, TG and TBA and a negative correlation with fecal Enterobacteriaceae, Enterococcus and Escherichia coli.Conclusion: Lactic acid bacteria screened from Inner Mongolia native meat sausages in China had cholesterol-lowering effect.Keywords: Lactic acid bacteria, fecal micro biota, TC, TG, TB
Phenomenological Scaling of Rapidity Dependence for Anisotropic Flows in 25 MeV/nucleon Ca + Ca by Quantum Molecular Dynamics Model
Anisotropic flows (, , and ) of light fragments up till
the mass number 4 as a function of rapidity have been studied for 25
MeV/nucleon Ca + Ca at large impact parameters by Quantum
Molecular Dynamics model. A phenomenological scaling behavior of rapidity
dependent flow parameters (n = 1, 2, 3 and 4) has been found as a
function of mass number plus a constant term, which may arise from the
interplay of collective and random motions. In addition, keeps
almost independent of rapidity and remains a rough constant of 1/2 for all
light fragments.Comment: 4 pages, 5 figure
Method of determining cosmological parameter ranges with samples of candles with an intrinsic distribution
In this paper, the effect of the intrinsic distribution of cosmological
candles is investigated. We find that, in the case of a narrow distribution,
the deviation of the observed modulus of sources from the expected central
value could be estimated within a ceratin range. We thus introduce a lower and
upper limits of , and , to
estimate cosmological parameters by applying the conventional minimizing method. We apply this method to a gamma-ray burst (GRB) sample as well as
to a combined sample including this GRB sample and an SN Ia sample. Our
analysis shows that: a) in the case of assuming an intrinsic distribution of
candles of the GRB sample, the effect of the distribution is obvious and should
not be neglected; b) taking into account this effect would lead to a poorer
constraint of the cosmological parameter ranges. The analysis suggests that in
the attempt of constraining the cosmological model with current GRB samples,
the results tend to be worse than what previously thought if the mentioned
intrinsic distribution does exist.Comment: 6 pages,4 figures,1 tables.Data updated. Main conclusion unchange
A general model for collaboration networks
In this paper, we propose a general model for collaboration networks.
Depending on a single free parameter "{\bf preferential exponent}", this model
interpolates between networks with a scale-free and an exponential degree
distribution. The degree distribution in the present networks can be roughly
classified into four patterns, all of which are observed in empirical data. And
this model exhibits small-world effect, which means the corresponding networks
are of very short average distance and highly large clustering coefficient.
More interesting, we find a peak distribution of act-size from empirical data
which has not been emphasized before of some collaboration networks. Our model
can produce the peak act-size distribution naturally that agrees with the
empirical data well.Comment: 10 pages, 10 figure
Macrovoids Formation and Light Scattering of PMMA
[[abstract]]After desorption of PMMA with saturated methanol and ethanol and then desorption by distilled water, the macrovoids are formed because of the phase inversion. The macrovoids on the surface of the specimens are larger and more numerous than those in the bulk. The macrovoids are likely to be closed-type, if the hydrolysis temperature is lower. On the other hand, if the hydrolysis temperature is higher, the macrovoids are likely to be open-type. Due to the formation of macrovoids, smaller than visible wavelengths, the light will disperse, and therefore, reduces the transmittance of the specimens. The transmittance is decreased when the hydrolysis temperature and hydrolysis time are increased. Furthermore, it is much clearer when ethanol is used as solvent than methanol. The scattered intensity of the specimens after hydrolysis is inversely proportional to the visible wavelength with an exponent, n, in the range 0·04–2·83 for methanol and 0·02–0·21 for ethanol[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子
The effects of degree correlations on network topologies and robustness
Complex networks have been applied to model numerous interactive nonlinear
systems in the real world. Knowledge about network topology is crucial for
understanding the function, performance and evolution of complex systems. In
the last few years, many network metrics and models have been proposed to
illuminate the network topology, dynamics and evolution. Since these network
metrics and models derive from a wide range of studies, a systematic study is
required to investigate the correlations between them. The present paper
explores the effect of degree correlation on the other network metrics through
studying an ensemble of graphs where the degree sequence (set of degrees) is
fixed. We show that to some extent, the characteristic path length, clustering
coefficient, modular extent and robustness of networks are directly influenced
by the degree correlation.Comment: 13 pages, 6 figure
Alkaloids, Diarylheptanoid and Naphthalene Carboxylic Acid Ester from Rhoiptelea chiliantha
Two pyrrolidine alkaloids (1, 2) were isolated from the fruits of Rhoiptelea chiliantha DIEL et HAND.-MAZZ. (Rhoipteleaceae). A diphenyl ether-type diarylheptanoid (3), and a naphthalene carboxylic acid methyl ester (4) which is biogenetically-related to juglone were isolated from the branches of the same plant. Their chemical structures were elucidated on the basis of spectroscopic analysis and chemical evidence
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