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101.
The conductance through a mesoscopic system of interacting electrons coupled to two adjacent leads is conventionally derived via the Keldysh nonequilibrium Green’s function technique, in the limit of noninteracting leads [Y. Meir, N.S. Wingreen, Phys. Rev. Lett. 68 (1992) 2512]. We extend the standard formalism to cater for a quantum dot system with Coulombic interactions between the quantum dot and the leads. The general current expression is obtained by considering the equation of motion of the time-ordered Green’s function of the system. The nonequilibrium effects of the interacting leads are then incorporated by determining the contour-ordered Green’s function over the Keldysh loop and applying Langreth’s theorem. The dot–lead interactions significantly increase the height of the Kondo peaks in density of states of the quantum dot. This translates into two Kondo peaks in the spin differential conductance when the magnitude of the spin bias equals that of the Zeeman splitting. There also exists a plateau in the charge differential conductance due to the combined effect of spin bias and the Zeeman splitting. The low-bias conductance plateau with sharp edges is also a characteristic of the Kondo effect. The conductance plateau disappears for the case of asymmetric dot–lead interaction. 相似文献
102.
The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using 3H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC50 values of 28.0 and 20.4 μM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant. 相似文献
103.
An efficient method based on operational Tau matrix is developed, to solve a type of system of nonlinear Volterra integro-differential
equations (IDEs). The presented method is also modified for the problems with separable kernel. Error estimation of the new
schemes are analyzed and discussed. The advantages of this approach and its modification is that, the solution can be expressed
as a truncated Taylor series, and the error function at any stage can be estimated. Methods are applied on the four problems
with separable kernel to show the applicability and efficiency of our schemes, specially for those problems at broad intervals. 相似文献
104.
Jalil Manafian Onur Alp Ilhan Ladan Avazpour As'ad Alizadeh 《Mathematical Methods in the Applied Sciences》2020,43(17):9904-9927
The present article deals with M-soliton solution and N-soliton solution of the (2 + 1)-dimensional asymmetrical Nizhnik–Novikov–Veselov equation by virtue of Hirota bilinear operator method. The obtained solutions for solving the current equation represent some localized waves including soliton, breather, lump, and their interactions, which have been investigated by the approach of the long-wave limit. Mainly, by choosing the specific parameter constraints in the M-soliton and N-soliton solutions, all cases of the one breather or one lump can be captured from the two, three, four, and five solitons. In addition, the performances of the mentioned technique, namely, the Hirota bilinear technique, are substantially powerful and absolutely reliable to search for new explicit solutions of nonlinear models. Meanwhile, the obtained solutions are extended with numerical simulation to analyze graphically, which results in localized waves and their interaction from the two-, three-, four-, and five-soliton solutions profiles. They will be extensively used to report many attractive physical phenomena in the fields of acoustics, heat transfer, fluid dynamics, classical mechanics, and so on. 相似文献
105.
106.
Samarghandian S Tavakkol Afshari J Davoodi S 《Applied biochemistry and biotechnology》2011,164(2):238-247
Crocus sativus L., commonly known as saffron, is the raw material for one of the most expensive spice in the world, and it has been used
in folk medicine for centuries. We investigated the potential of the ethanolic extract of saffron to induce cytotoxic and
apoptosis effects in carcinomic human alveolar basal epithelial cells (A549), a commonly used cell culture system for in vitro
studies on lung cancer. The cells were cultured in Dulbecco’s modified Eagle’s medium with 10% fetal bovine serum treated
with different concentrations of the ethanolic extract of saffron for two consecutive days. Cell viability was quantitated
by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Apoptotic cells were determined using annexin
V–fluorescein isothiocyanate by flow cytometry. Saffron could decrease the cell viability in the malignant cells as a concentration-
and time-dependent manner. The IC50 values against the A549 cell lines were determined as 1,200 and 650 μg/ml after 24 and 48 h, respectively. Saffron-induced
apoptosis of the A549 cells in a concentration-dependent manner, as determined by flow cytometry histogram of treated cells
that induced apoptotic cell death, is involved in the toxicity of saffron. It might be concluded that saffron could cause
cell death in the A549 cells, in which apoptosis plays an important role. Saffron could also be considered as a promising
chemotherapeutic agent in lung cancer treatment in future. 相似文献
107.
Lycopene is a well-known compound found commonly in tomatoes which brings wide range of health benefits against cardiovascular diseases and cancers. From an anti-cancer perspective, lycopene is often associated with reduced risk of prostate cancer and people often look for it as a dietary supplement which may help to prevent cancer. Previous scientific evidence exhibited that the anti-cancer activity of lycopene relies on its ability to suppress oncogene expressions and induce proapoptotic pathways. To further explore the real potential of lycopene in cancer prevention, this review discusses the new insights and perspectives on the anti-cancer activities of lycopene which could help to drive new direction for research. The relationship between inflammation and cancer is being highlighted, whereby lycopene suppresses cancer via resolution of inflammation are also discussed herein. The immune system was found to be a part of the anti-cancer system of lycopene as it modulates immune cells to suppress tumor growth and progression. Lycopene, which is under the family of carotenoids, was found to play special role in suppressing lung cancer. 相似文献
108.
The sine-Gordon equation plays an important role in modern physics. By using spline function approximation, two implicit finite
difference schemes are developed for the numerical solution of one-dimensional sine-Gordon equation. Stability analysis of
the method has been given. It has been shown that by choosing the parameters suitably, we can obtain two schemes of orders
O(k2+k2h2+h2)\mathcal{O}(k^{2}+k^{2}h^{2}+h^{2}) and O(k2+k2h2+h4)\mathcal{O}(k^{2}+k^{2}h^{2}+h^{4}). At the end, some numerical examples are provided to demonstrate the effectiveness of the proposed schemes. 相似文献
109.
M. J. Ma M. B. A. Jalil S. G. Tan D. E. Koh 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(1):37-46
We theoretically study the spin-polarized transport
through double barrier magnetic tunnel junction (DBMTJ) consisting
of the quantum dot sandwiched by two ferromagnetic (FM) leads. The
tunneling current through the DBMTJ is evaluated based on the
Keldysh nonequilibrium Green’s function approach. The self-energy
and Green’s function of the dot are analytically obtained via the
equation of motion method, by systematically incorporating two
spin-flip phenomena, namely, intra-dot spin-flip, and spin-flip
coupling between the lead and the central dot region. The effects of
both spin-flip processes on the spectral functions, tunneling
current and tunnel magnetoresistance (TMR) are analyzed. The
spin-flip effects result in spin mixing, thus contributing to the
spectral function of the off-diagonal Green’s function components ( Gs[`(s)] r )\left( {G_{\sigma \bar \sigma }^r } \right). Interestingly, the spin-flip coupling
between the lead and dot enhances both the tunneling current and the
TMR for applied bias above the threshold voltage V
th
. On the
other hand, the intra-dot spin-flip results in an additional step in
the I-V characteristics near V
th
. Additionally, it
suppresses the tunneling current but enhances the TMR. The opposing
effects of the two types of spin-flip on the tunneling current means
that one spin-flip mechanism can be engineered to counteract the
other, so as to maintain the tunneling current without reducing the
TMR. Their additive effect on the TMR enables the DBMTJ to attain a
large tunneling current and high TMR for above threshold bias
values. 相似文献
110.
New substituted 2‐ferrocenylbenzimidazole derivatives are prepared by the oxidation of corresponding Schiff's bases in situ, generated from corresponding 1,2‐diamino‐4‐fluoro‐5‐(1‐piperazinyl)benzenes and 2‐ferrocenecarboxaldehyde using nitrobenzene. 相似文献