24,833 research outputs found
Almost sure exponential stability of numerical solutions for stochastic delay differential equations
Using techniques based on the continuous and discrete semimartingale convergence theorems, this paper investigates if numerical methods may reproduce the almost sure exponential stability of the exact solutions to stochastic delay differential equations (SDDEs). The important feature of this technique is that it enables us to study the almost sure exponential stability of numerical solutions of SDDEs directly. This is significantly different from most traditional methods by which the almost sure exponential stability is derived from the moment stability by the Chebyshev inequality and the Borel–Cantelli lemma
Polarity during tissue repair, a multiscale problem
Tissue repair is essential for all organisms, as it protects the
integrity and function of tissues and prevents infections and
diseases. It takes place at multiple scales, from macroscopic to
microscopic levels. Most mechanisms driving tissue repair rely
on the correct polarisation of collective cell behaviours, such as
migration and proliferation, and polarisation of cytoskeletal and
junctional components. Furthermore, re-establishment and
maintenance of cell polarity are fundamental for a tissue to be
fully repaired and for withstanding mechanical stress during
homeostasis and repair. Recent evidence highlights an
important role for the interplay between cell polarity and tissue
mechanics that are critical in tissue repair
Ferromagnetic semiconductor single wall carbon nanotube
Possibility of a ferromagnetic semiconductor single wall carbon nanotube
(SWCNT), where ferromagnetism is due to coupling between doped magnetic
impurity on a zigzag SWCNT and electrons spin, is investigate. We found, in the
weak impurity-spin couplings, at low impurity concentrations the spin up
electrons density of states remain semiconductor while the spin down electrons
density of states shows a metallic behavior. By increasing impurity
concentrations the semiconducting gap of spin up electrons in the density of
states is closed, hence a semiconductor to metallic phase transition is take
place. In contrast, for the case of strong coupling, spin up electrons density
of states remain semiconductor and spin down electron has metallic behavior.
Also by increasing impurity spin magnitude, the semiconducting gap of spin up
electrons is increased.Comment: 10 pages and 9 figure
Inhibitory Effects of Angelica Polysaccharide on Activation of Mast Cells
This study was designed to investigate the inhibitory effects of Angelica polysaccharide (AP) on activation of mast cells and its possible molecular mechanism. In our study, we determined the proinflammatory cytokines and allergic mediators in anti-DNP IgE stimulated RBL-2H3 cells and found that AP (50, 100, and 20
Star-forming regions of the Aquila rift cloud complex. I. NH3 tracers of dense molecular cores
(Abridged) Aims. In the present part of our survey we search for ammonia
emitters in the Aquila rift complex which trace the densest regions of
molecular clouds. Methods. From a CO survey carried out with the Delingha 14-m
telescope we selected ~150 targets for observations in other molecular lines.
Here we describe the mapping observations in the NH3(1,1) and (2,2) inversion
lines of the first 49 sources performed with the Effelsberg 100-m telescope.
Results. The NH3(1,1) and (2,2) emission lines are detected in 12 and 7
sources, respectively. Among the newly discovered NH3 sources, our sample
includes the following well-known clouds: the starless core L694-2, the Serpens
cloud Cluster B, the Serpens dark cloud L572, the filamentary dark cloud L673,
the isolated protostellar source B335, and the complex star-forming region
Serpens South. Angular sizes between 40" and 80" (~0.04-0.08 pc) are observed
for compact starless cores but as large as 9' (~0.5 pc) for filamentary dark
clouds. The measured kinetic temperatures of the clouds lie between 9K and 18K.
From NH3 excitation temperatures of 3-8K we determine H2 densities with typical
values of ~(0.4-4) 10^4 cm^-3. The masses of the mapped cores range between
~0.05 and ~0.5M_solar. The relative ammonia abundance, X= [NH3]/[H2], varies
from 10^-7 to 5 10^-7 with the mean = (2.7+/-0.6) 10^-7 (estimated from
spatially resolved cores assuming the filling factor eta = 1). In two clouds,
we observe kinematically split NH3 profiles separated by ~1 km/s. The splitting
is most likely due to bipolar molecular outflows for one of which we determine
an acceleration of <~ 0.03 km/s/yr. A starless core with significant rotational
energy is found to have a higher kinetic temperature than the other ones which
is probably caused by magnetic energy dissipation.Comment: 28 pages, 22 figures, 6 tables, accepted for publication in A&
Numerical simulation of a metro vehicle running over rail with fastening system failure using finite element method
In this paper, the dynamic responses of a moving vehicle traversing over railway track with fastening system failure were investigated using a vehicle/track coupling system model. In this model, the moving vehicle is developed by multi-body dynamics, and the direct fixation track is modeled by finite element method, where the rail is treated as an Euler-Bernoulli beam supported by fastening systems. An invalidation factor is used to determine the failure of the fastening system. The Hertzian spring is adapted to model the wheel/rail contact force between the moving wheel set and the rail. The proposed vehicle/track system model is verified with some field testing results in Zhengzhou subway. To solve the vehicle/track system model with nonlinear contact force, an iterative procedure is proposed. The effects of fastening system failure on the responses of the vehicle and track are investigated. It indicates that the wheel/rail contact force varies abruptly when the vehicle passing over the fastening system failure zone, which result in track deterioration
Linear Temperature Variation of the Penetration Depth in YBCO Thin Films
We have measured the penetration depth on thin films from transmission at 120, 330 and 510~GHz,
between 5 and 50~K. Our data yield simultaneously the absolute value and the
temperature dependence of . In high quality films
exhibits the same linear temperature dependence as single crystals, showing its
intrinsic nature, and . In a lower quality one, the
more usual dependence is found, and . This
suggests that the variation is of extrinsic origin. Our results put the
-wave like interpretation in a much better position.Comment: 12 pages, revtex, 4 uuencoded figure
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