2,517 research outputs found
A multi-sensor system for robotics proximity operations
Robots without sensors can perform only simple repetitive tasks and cannot cope with unplanned events. A multi-sensor system is needed for a robot to locate a target, move into its neighborhood and perform operations in contact with the object. Systems that can be used for such tasks are described
A comprehensive analysis of interleukin-4 receptor polymorphisms and their association with atopy and IgE regulation in childhood
Background: The interleukin (IL) 4/IL13 pathway is involved in the regulation of IgE production associated with atopic diseases. Numerous polymorphisms have been identified in the coding region of the IL4 receptor alpha chain (IL4Ra) and previous association studies have shown conflicting results. Based on their putative functional role, polymorphisms A148G, T1432C and A1652G, located in the coding region of IL4Ra, were selected for association and haplotype studies in a large German population sample (n = 1,120). Methods: Genotyping was performed using allele-specific PCR and restriction-enzyme-based assays. Haplotypes were estimated, and population-derived IgE percentiles (50% IgE >60 IU/ml, 66% IgE >115 IU/ml and 90% IgE >457 IU/ml) were calculated as outcome variables in a haplotype trend regression analysis. Results: In our population, only polymorphism T1432C showed a trend for a protective effect against atopic rhinitis ( odds ratio, OR: 0.52, 95% confidence interval, CI: 0.26 - 1.02, p = 0.05). When haplotypes were calculated, one haplotype was significantly associated with elevated serum IgE levels at the 50th percentile ( OR 1.60, 95% CI 1.08 - 2.37, p = 0.02). Conclusions: These data indicate that IL4Ra polymorphisms, although suggested to be functionally relevant by in vitro studies, have only a minor influence on IgE regulation in our large population sample. Copyright (C) 2004 S. Karger AG, Basel
Interpretation of transverse tune spectra in a heavy-ion synchrotron at high intensities
Two different tune measurement systems have been installed in the GSI
heavy-ion synchrotron SIS-18. Tune spectra are obtained with high accuracy
using these fast and sensitive systems. Besides the machine tune, the spectra
contain information about the intensity dependent coherent tune shift and the
incoherent space charge tune shift. The space charge tune shift is derived from
a fit of the observed shifted positions of the synchrotron satellites to an
analytic expression for the head-tail eigenmodes with space charge.
Furthermore, the chromaticity is extracted from the measured head-tail mode
structure. The results of the measurements provide experimental evidence of the
importance of space charge effects and head-tail modes for the interpretation
of transverse beam signals at high intensity
Nonlinear Interactions Between Gravitational Radiation and Modified Alfven Modes in Astrophysical Dusty Plasmas
We present an investigation of nonlinear interactions between Gravitational
Radiation and modified Alfv\'{e}n modes in astrophysical dusty plasmas.
Assuming that stationary charged dust grains form neutralizing background in an
electron-ion-dust plasma, we obtain the three wave coupling coefficients, and
calculate the growth rates for parametrically coupled gravitational radiation
and modified Alfv\'{e}n-Rao modes. The threshold value of the gravitational
wave amplitude associated with convective stabilization is particularly small
if the gravitational frequency is close to twice the modified Alfv\'en
wave-frequency. The implication of our results to astrophysical dusty plasmas
is discussed.Comment: A few typos corrected. Published in Phys. Rev.
Nonlinear wave interaction and spin models in the MHD regime
Here we consider the influence on the electron spin in the MHD regime.
Recently developed models which include spin-velocity correlations are taken as
a starting point. A theoretical argument is presented, suggesting that in the
MHD regime a single fluid electron model with spin correlations is equivalent
to a model with spin-up and spin-down electrons constituting different fluids,
but where the spin-velocity correlations are omitted. Three wave interaction of
2 shear Alfven waves and a compressional Alfven wave is then taken as a model
problem to evaluate the asserted equivalence. The theoretical argument turns
out to be supported, as the predictions of the two models agree completely.
Furthermore, the three wave coupling coefficients obey the Manley-Rowe
relations, which give further support to the soundness of the models and the
validity of the assumptions made in the derivation. Finally we point out that
the proposed two-fluid model can be incorporated in standard Particle-In-Cell
schemes with only minor modifications.Comment: 8 page
- …