28,876 research outputs found
Microstructure, magneto-transport and magnetic properties of Gd-doped magnetron-sputtered amorphous carbon
The magnetic rare earth element gadolinium (Gd) was doped into thin films of
amorphous carbon (hydrogenated \textit{a}-C:H, or hydrogen-free \textit{a}-C)
using magnetron co-sputtering. The Gd acted as a magnetic as well as an
electrical dopant, resulting in an enormous negative magnetoresistance below a
temperature (). Hydrogen was introduced to control the amorphous carbon
bonding structure. High-resolution electron microscopy, ion-beam analysis and
Raman spectroscopy were used to characterize the influence of Gd doping on the
\textit{a-}GdC(:H) film morphology, composition, density and
bonding. The films were largely amorphous and homogeneous up to =22.0 at.%.
As the Gd doping increased, the -bonded carbon atoms evolved from
carbon chains to 6-member graphitic rings. Incorporation of H opened up the
graphitic rings and stabilized a -rich carbon-chain random network. The
transport properties not only depended on Gd doping, but were also very
sensitive to the ordering. Magnetic properties, such as the spin-glass
freezing temperature and susceptibility, scaled with the Gd concentration.Comment: 9 figure
Integrable dispersionless KdV hierarchy with sources
An integrable dispersionless KdV hierarchy with sources (dKdVHWS) is derived.
Lax pair equations and bi-Hamiltonian formulation for dKdVHWS are formulated.
Hodograph solution for the dispersionless KdV equation with sources (dKdVWS) is
obtained via hodograph transformation. Furthermore, the dispersionless
Gelfand-Dickey hierarchy with sources (dGDHWS) is presented.Comment: 15 pages, to be published in J. Phys. A: Math. Ge
Entanglement in the dispersive interaction of trapped ions with a quantized field
The mode-mode entanglement between trapped ions and cavity fields is
investigated in the dispersive regime. We show how a simple initial preparation
of Gaussian coherent states and a postselection may be used to generate
motional non-local mesoscopic states (NLMS) involving ions in different traps.
We also present a study of the entanglement induced by dynamical Stark-shifts
considering a cluster of N-trapped ions. In this case, all entanglement is due
to the dependence of the Stark-shifts on the ions' state of motion manifested
as a cross-Kerr interaction between each ion and the field.Comment: 10 pages, 5 figures, corrected typo
In vitro Anti-Gastric Tumor Activities and Possible Mechanisms of Action of Paederosidic Acid from Paederia scandens (Lour) Merrill
Purpose: To evaluate the anti-tumor activity and explore the possible mechanisms of action of paederosidic acid isolated from Paederia scandens (Lour.) Merrill.Methods: Paederosidic acid (PA) was isolated from P. scandens and identified by spectroscopic methods. The cytotoxic effects of PA in gastric cancer cell lines (MGC-803, BGC-823, and SGC-7901 cells) were assayed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). Apoptosis of PA in SGC-7901 cells was evaluated by DAPI staining. To investigate the possible mechanisms of apoptosis, the effect of PA on C-caspase-3, C-caspase-9, Bcl-2 and Bax expressions in SGC-7901 cells were assayed by Western blot analysis.Results: PA exerted significant inhibitory effects on MGC-803, BGC-823, and SGC-7901 cells with 50 % inhibitory concentration (IC50) values of 42.2, 43.7, and 30.5 μM, respectively, and in a concentration-dependent manner. Subsequently, SGC-7901 cells were selected for further studies. After treatment with PA, obvious condensation of the nucleus was observed in fluorescence photomicrographs, which is a characteristic of apoptosis. In addition, caspase-3, caspase-9 proteins and Bax were significantly up-regulated (p < 0.05), whereas Bcl-2 was significantly down-regulated (p < 0.05) by PA in a concentration-dependent manner.Conclusion: PA has significant anti-tumor activity on SGC-7901 cells in vitro, and the possible mechanism of action may be related to PA-induced apoptosis via mitochondria-mediated apoptosis pathway.Keywords: Paederosidic acid, Paederia scandens, Anti-tumor activity, Apoptosis, Gastric cance
On the Toda Lattice Equation with Self-Consistent Sources
The Toda lattice hierarchy with self-consistent sources and their Lax
representation are derived. We construct a forward Darboux transformation (FDT)
with arbitrary functions of time and a generalized forward Darboux
transformation (GFDT) for Toda lattice with self-consistent sources (TLSCS),
which can serve as a non-auto-Backlund transformation between TLSCS with
different degrees of sources. With the help of such DT, we can construct many
type of solutions to TLSCS, such as rational solution, solitons, positons,
negetons, and soliton-positons, soliton-negatons, positon-negatons etc., and
study properties and interactions of these solutions.Comment: 20 page
Nonequilibrium Green's function approach to mesoscopic thermal transport
We present a formulation of a nonequilibrium Green's function method for
thermal current in nanojunction atomic systems with nonlinear interactions.
This first-principle approach is applied to the calculation of the thermal
conductance in carbon nanotube junctions. It is shown that nonlinearity already
becomes important at low temperatures. Nonlinear interactions greatly suppress
phonon transmission at room temperature. The peak of thermal conductance is
found to be around 400K, in good agreement with experiments. High-order phonon
scattering processes are important for diffusive heat transport.Comment: 4 pages, 4 figure
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