13,803 research outputs found
New Aspects of Thromboangiitis obliterans (von Winiwarter-Buerger's Disease)
The existence of thromboangiitis obliterans as a clinical entity has been a matter of debate for many years. In contrast to other immunovasculitides there is no organ involvement while peripheral vessels are affected. Heavy smokers under 40 years of age have a high predisposition for the disease. The cerebral form shows relapsing brain infarctions which can be visualized in CCT while panarteriography remains negative. Apart from unspecific inflammatory signs in blood and CSF there are distinctive laboratory findings proving the autoimmunological character of von Winiwarter-Buerger's disease. In the serum anti-elastin antibodies, IgE and anticollagen antibody activity are detectable. In 3 patients the authors detected specific immunohistochemical findings in a biopsy specimen of the temporal artery. In addition to platelet-inhibiting substances corticoids in acute and azathioprine in chronic treatment becomes necessary
Fluctuation Induced Instabilities in Front Propagation up a Co-Moving Reaction Gradient in Two Dimensions
We study 2D fronts propagating up a co-moving reaction rate gradient in
finite number reaction-diffusion systems. We show that in a 2D rectangular
channel, planar solutions to the deterministic mean-field equation are stable
with respect to deviations from planarity. We argue that planar fronts in the
corresponding stochastic system, on the other hand, are unstable if the channel
width exceeds a critical value. Furthermore, the velocity of the stochastic
fronts is shown to depend on the channel width in a simple and interesting way,
in contrast to fronts in the deterministic MFE. Thus, fluctuations alter the
behavior of these fronts in an essential way. These affects are shown to be
partially captured by introducing a density cutoff in the reaction rate. Some
of the predictions of the cutoff mean-field approach are shown to be in
quantitative accord with the stochastic results
Mapping the spin-dependent electron reflectivity of Fe and Co ferromagnetic thin films
Spin Polarized Low Energy Electron Microscopy is used as a spin dependent
spectroscopic probe to study the spin dependent specular reflection of a
polarized electron beam from two different magnetic thin film systems:
Fe/W(110) and Co/W(110). The reflectivity and spin-dependent
exchange-scattering asymmetry are studied as a function of electron kinetic
energy and film thickness, as well as the time dependence. The largest value of
the figure of merit for spin polarimetry is observed for a 5 monolayer thick
film of Co/W(110) at an electron kinetic energy of 2eV. This value is 2 orders
of magnitude higher than previously obtained with state of the art Mini-Mott
polarimeter. We discuss implications of our results for the development of an
electron-spin-polarimeter using the exchange-interaction at low energy.Comment: 5 pages, 4 figure
Precision Measurement of the 29Si, 33S, and 36Cl Binding Energies
The binding energies of 29Si, 33S, and 36Cl have been measured with a
relative uncertainty using a flat-crystal spectrometer.
The unique features of these measurements are 1) nearly perfect crystals whose
lattice spacing is known in meters, 2) a highly precise angle scale that is
derived from first principles, and 3) a gamma-ray measurement facility that is
coupled to a high flux reactor with near-core source capability. The binding
energy is obtained by measuring all gamma-rays in a cascade scheme connecting
the capture and ground states. The measurements require the extension of
precision flat-crystal diffraction techniques to the 5 to 6 MeV energy region,
a significant precision measurement challenge. The binding energies determined
from these gamma-ray measurements are consistent with recent highly accurate
atomic mass measurements within a relative uncertainty of .
The gamma-ray measurement uncertainties are the dominant contributors to the
uncertainty of this consistency test. The measured gamma-ray energies are in
agreement with earlier precision gamma-ray measurements.Comment: 13 pages, 4 figure
Application of wavelets to singular integral scattering equations
The use of orthonormal wavelet basis functions for solving singular integral
scattering equations is investigated. It is shown that these basis functions
lead to sparse matrix equations which can be solved by iterative techniques.
The scaling properties of wavelets are used to derive an efficient method for
evaluating the singular integrals. The accuracy and efficiency of the wavelet
transforms is demonstrated by solving the two-body T-matrix equation without
partial wave projection. The resulting matrix equation which is characteristic
of multiparticle integral scattering equations is found to provide an efficient
method for obtaining accurate approximate solutions to the integral equation.
These results indicate that wavelet transforms may provide a useful tool for
studying few-body systems.Comment: 11 pages, 4 figure
Two-finger selection theory in the Saffman-Taylor problem
We find that solvability theory selects a set of stationary solutions of the
Saffman-Taylor problem with coexistence of two \it unequal \rm fingers
advancing with the same velocity but with different relative widths
and and different tip positions. For vanishingly small
dimensionless surface tension , an infinite discrete set of values of the
total filling fraction and of the relative
individual finger width are selected out of a
two-parameter continuous degeneracy. They scale as
and . The selected values of differ from
those of the single finger case. Explicit approximate expressions for both
spectra are given.Comment: 4 pages, 3 figure
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