53 research outputs found
Quantitative evaluation of motor function before and after engraftment of dopaminergic neurons in a rat model of Parkinson's disease
Although gait change is considered a useful indicator of severity in animal models of Parkinson's disease, systematic and extensive gait analysis in animal models of neurological deficits is not well established. The CatWalk-assisted automated gait analysis system provides a comprehensive way to assess a number of dynamic and static gait parameters simultaneously. In this study, we used the Catwalk system to investigate changes in gait parameters in adult rats with unilateral 6-OHDA-induced lesions and the rescue effect of dopaminergic neuron transplantation on gait function. Four weeks after 6-OHDA injection, the intensity and maximal area of contact were significantly decreased in the affected paws and the swing speed significantly decreased in all four paws. The relative distance between the hind paws also increased, suggesting that animals with unilateral 6-OHDA-induced lesions required all four paws to compensate for loss of balance function. At 8 weeks post-transplantation, engrafted dopaminergic neurons expressed tyrosine hydroxylase. In addition, the intensity, contact area, and swing speed of the four limbs increased and the distance between the hind paws decreased. Partial recovery of methamphetamine-induced rotational response was also noted
Structure of Si(114) determined by global optimization methods
In this article we report the results of global structural optimization of
the Si(114) surface, which is a stable high-index orientation of silicon. We
use two independent procedures recently developed for the determination of
surface reconstructions, the parallel-tempering Monte Carlo method and the
genetic algorithm. These procedures, coupled with the use of a highly-optimized
interatomic potential for silicon, lead to finding a set of possible models for
Si(114), whose energies are recalculated with ab-initio density functional
methods. The most stable structure obtained here without experimental input
coincides with the structure determined from scanning tunneling microscopy
experiments and density functional calculations by Erwin, Baski and Whitman
[Phys. Rev. Lett. 77, 687 (1996)].Comment: 19 pages, 5 figure
Finding the reconstructions of semiconductor surfaces via a genetic algorithm
In this article we show that the reconstructions of semiconductor surfaces
can be determined using a genetic procedure. Coupled with highly optimized
interatomic potentials, the present approach represents an efficient tool for
finding and sorting good structural candidates for further electronic structure
calculations and comparison with scanning tunnelling microscope (STM) images.
We illustrate the method for the case of Si(105), and build a database of
structures that includes the previously found low-energy models, as well as a
number of novel configurations.Comment: 4 figures, 1 tabl
Dynamics of orientational ordering in fluid membranes
We study the dynamics of orientational phase ordering in fluid membranes.
Through numerical simulation we find an unusually slow coarsening of
topological texture, which is limited by subdiffusive propagation of membrane
curvature. The growth of the orientational correlation length obeys a
power law with in the late stage. We also discuss
defect profiles and correlation patterns in terms of long-range interaction
mediated by curvature elasticity.Comment: 5 pages, 3 figures (1 in color); Eq.(9) correcte
Two-particle localization and antiresonance in disordered spin and qubit chains
We show that, in a system with defects, two-particle states may experience
destructive quantum interference, or antiresonance. It prevents an excitation
localized on a defect from decaying even where the decay is allowed by energy
conservation. The system studied is a qubit chain or an equivalent spin chain
with an anisotropic () exchange coupling in a magnetic field. The chain
has a defect with an excess on-site energy. It corresponds to a qubit with the
level spacing different from other qubits. We show that, because of the
interaction between excitations, a single defect may lead to multiple localized
states. The energy spectra and localization lengths are found for
two-excitation states. The localization of excitations facilitates the
operation of a quantum computer. Analytical results for strongly anisotropic
coupling are confirmed by numerical studies.Comment: Updated version, 13 pages, 5 figures To appear in Phys. Rev. B (2003
Gauging the Poisson sigma model
We show how to carry out the gauging of the Poisson sigma model in an AKSZ
inspired formulation by coupling it to the a generalization of the Weil model
worked out in ref. arXiv:0706.1289 [hep-th]. We call the resulting gauged field
theory, Poisson--Weil sigma model. We study the BV cohomology of the model and
show its relation to Hamiltonian basic and equivariant Poisson cohomology. As
an application, we carry out the gauge fixing of the pure Weil model and of the
Poisson--Weil model. In the first case, we obtain the 2--dimensional version of
Donaldson--Witten topological gauge theory, describing the moduli space of flat
connections on a closed surface. In the second case, we recover the gauged A
topological sigma model worked out by Baptista describing the moduli space of
solutions of the so--called vortex equations.Comment: 49 pages, no figures. Typos corrected. Presentation improve
Modeling the impact of climate variability on diarrhea-associated diseases in Taiwan (1996-2007)
Diarrhea is an important public health problem in Taiwan Climatic changes and an increase in extreme weather events (extreme heat drought or rainfalls) have been strongly linked to the incidence of diarrhea-associated disease This study investigated and quantified the relationship between climate variations and diarrhea-associated morbidity in subtropical Taiwan Specifically this study analyzed the local climatic variables and the number of diarrhea-associated infection cases from 1996 to 2007 This study applied a climate variation-guided Poisson regression model to predict the dynamics of diarrhea-associated morbidity The proposed model allows for climate factors (relative humidity maximum temperature and the numbers of extreme rainfall) autoregression long-term trends and seasonality and a lag-time effect Results indicated that the maximum temperature and extreme rainfall days were strongly related to diarrhea-associated morbidity The impact of maximum temperature on diarrhea-associated morbidity appeared primarily among children (0-14 years) and older adults (40-64 years) and had less of an effect on adults (15-39 years) Otherwise relative humidity and extreme rainfall days significantly contributed to the diarrhea-associated morbidity in adult This suggested that children and older adults were the most susceptible to diarrhea-associated morbidity caused by climatic variation Because climatic variation contributed to diarrhea morbidity in Taiwan it is necessary to develop an early warning system based on the climatic variation information for disease control management (C) 2010 Elsevier BV All rights reserve
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