957 research outputs found
MS 223 Guide to Charles T. L. Huang, PhD Papers, 1973-2002
The Charles T. L. Huang, PhD papers contain notebooks, experiment lab data, professional papers of Dr. Huang that detail his career at Baylor College of Medicine and Texas Children\u27s Hospital. The collection consists of 5 boxes and loose materials (binders, notebooks) equaling 5 cubic feet. See more at https://archives.library.tmc.edu/ms-223
Instabilities in a Two-Component, Species Conserving Condensate
We consider a system of two species of bosons of equal mass, with
interactions and for bosons of the same and different
species respectively. We present a rigorous proof -- valid when the Hamiltonian
does not include a species switching term -- showing that, when
, the ground state is fully "polarized" (consists of
atoms of one kind only). In the unpolarized phase the low energy excitation
spectrum corresponds to two linearly dispersing modes that are even a nd odd
under species exchange. The polarization instability is signaled by the vani
shing of the velocity of the odd modes.Comment: To appear in Phys. Rev.
Anti-Helicobacter pylori activity of Plumbago zeylanica L
It has been shown that the presence of infection by Helicobacter pylori is strongly associated with gastric cancer and peptic ulceration. In western medicine, a 3-fold therapeutic regimen, emphasizing the use of antibiotics,,is typically used to suppress H. pylori activity. However, antibiotic drug resistance frequently develops as a consequence of such treatment. In our previous study, 50 Taiwanese folk medicinal plants were screened for their anti-H. pylori activities. The results revealed that Plumbago zeylanica L. had the highest inhibitory effects against H. pylori. In this study, therefore, we have focused on establishing the anti-H. pylori activities of P. zeylanica L. Water and the organic solvents ethanol, ethyl acetate and acetone were used for P. zeylanica L. extraction, obtaining yields of 1.66-6.84% (w/w). Excluding the water extract, higher anti-H. pylori activity was demonstrated for all the extracts, both using the agar diffusion and dilution methods. The ethyl acetate extract exhibited the lowest minimum inhibitory concentrations against five H. pylori strains, of which ranged from 0.32 to 1.28 mg ml(-1), followed, in ascending order, by the acetone, ethanol and water analogs. Bactericidal activity was determined for P. zeylanica L. extracts, with the lowest minimum bactericidal concentrations (5.12-20.48 mg ml(-1)) demonstrated for the ethyl acetate, followed, in ascending order, by the acetone and ethanol analogs. Bactericidal activity appeared to be in a dose-dependent manner. Through a broad pH range (2-7), bactericidal activity was not affected when extract concentrations were greater than or equal to the minimum bactericidal concentration. High stability was demonstrated for the ethyl acetate P. zeylanica L. extract within pH range of 1-7, exhibiting all pH treatments bactericidal activity. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved
Extraction of Step-Repulsion Strengths from Terrace Width Distributions: Statistical and Analytic Considerations
Recently it has been recognized that the so-called generalized Wigner
distribution may provide at least as good a description of terrace width
distributions (TWDs) on vicinal surfaces as the standard Gaussian fit and is
particularly applicable for weak repulsions between steps, where the latter
fails. Subsequent applications to vicinal copper surfaces at various
temperatures confirmed the serviceability of the new analysis procedure but
raised some theoretical questions. Here we address these issues using
analytical, numerical, and statistical methods. We propose an extension of the
generalized Wigner distribution to a two-parameter fit that allows the terrace
widths to be scaled by an optimal effective mean width. We discuss
quantitatively the approach of a Wigner distribution to a Gaussian form for
strong repulsions, how errors in normalization or mean affect the deduced
interaction, and how optimally to extract the interaction from the variance and
mean of the TWD. We show that correlations reduce by two orders of magnitude
the number of {\em independent} measurements in a typical STM image. We also
discuss the effect of the discreteness ("quantization") of terrace widths,
finding that for high misorientation (small mean width) the standard continuum
analysis gives faulty estimates of step interactions.Comment: 13 pages, 7 figures; info added on # ind. measurements/STM imag
An Improved Shashlyk Calorimeter
Shashlyk electromagnetic calorimeter modules with an energy resolution of
about 3%/sqrt{E (GeV)} for 50-1000 MeV photons has been developed, and a
prototype tested. Details of these improved modules, including mechanical
construction, selection of wave shifting fibers and photo-detectors, and
development of a new scintillator with improved optical and mechanical
properties are described. How the modules will perform in a large calorimeter
was determined from prototype measurements. The experimentally determined
characteristics of the calorimeter prototype show energy resolution of
sigma_E/E=(1.96+-0.1)% \oplus (2.74+-0.05)%/sqrt{E}, time resolution of sigma_T
= (72+-4)/sqrt{E} \oplus (14+-2)/E (ps), where photon energy E is given in GeV
units and \oplus means a quadratic summation. A punch-through inefficiency of
photon detection was measured to be \epsilon = 5*10^{-5} (\Theta >5 mrad).Comment: 29 pages, 21 figure
Dark solitons in ferromagnetic chains with first- and second-neighbor interactions
We study the ferromagnetic spin chain with both first- and second-neighbor
interactions. We obtained the condition for the appearance and stability of
bright and dark solitons for arbitrary wave number inside the Brillouin zone.
The influence of the second-neighbor interaction and the anisotropy on the
soliton properties is considered. The scattering of dark solitons from point
defects in the discrete spin chain is investigated numerically.Comment: 7 pages,5 figure
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