7,690 research outputs found
System design and performance of earth/lunar horizon sensor BEC project 3744
An infrared horizon sensor system has been designed which is capable of searching over a wide field for the edges of a planet and, upon locating such edges, stations itself in a position which provides signals which identify the local vertical to the planet. In this fixed attitude it requires no continuous mechanical movement and operates with a minimum utilization of power. The system is thus capable of providing a high degree of accuracy when used for local vertical determination in orbits around the earth, the moon, or other planets. A detailed description of the design and operating features of the horizon scanner is given and the evaluation test data which have been completed are presented
Excited Heavy Mesons Beyond Leading Order in the Heavy Quark Expansion
We examine the decays of excited heavy mesons, including the leading power
corrections to the heavy quark limit. We find a new and natural explanation for
the large deviation of the width of the from the heavy quark
symmetry prediction. Our formalism leads to detailed predictions for the
properties of the excited bottom mesons, some of which recently have been
observed. Finally, we present a detailed analysis of the effect of power
corrections and finite meson widths on the angular distributions which may be
measured in heavy meson decays.Comment: Uses REVTeX, 19 pages, 6 EPS figures embedded with epsf.st
B Meson Transitions into Higher Mass Charmed Resonances
We use QCD sum rules to estimate the universal form factors describing the
semileptonic B decays into excited charmed resonances, such as the and
states and belonging to the heavy
quark doublet, and the and states and
belonging to the s_\ell^P={5\2}^- doublet.Comment: LaTex, 14 pages, 1 figur
Modeling inflammation and oxidative stress in gastrointestinal disease development using novel organotypic culture systems.
Gastroesophageal reflux disease (GERD), Barrett's esophagus (BE), graft-versus-host disease (GVHD), and inflammatory bowel diseases such as ulcerative colitis and Crohn's disease are common human gastrointestinal diseases that share inflammation as a key driver for their development. A general outcome resulting from these chronic inflammatory conditions is increased oxidative stress. Oxidative stress is caused by the generation of reactive oxygen and nitrogen species that are part of the normal inflammatory response, but are also capable of damaging cellular DNA, protein, and organelles. Damage to DNA can include DNA strand breaks, point mutations due to DNA adducts, as well as alterations in methylation patterns leading to activation of oncogenes or inactivation of tumor suppressors. There are a number of significant long-term consequences associated with chronic oxidative stress, most notably cancer. Infiltrating immune cells and stromal components of tissue including fibroblasts contribute to dynamic changes occurring in tissue related to disease development. Immune cells can potentiate oxidative stress, and fibroblasts have the capacity to contribute to advanced growth and proliferation of the epithelium and any resultant cancers. Disease models for GERD, BE, GVHD, and ulcerative colitis based on three-dimensional human cell and tissue culture systems that recapitulate in vivo growth and differentiation in inflammatory-associated microphysiological environments would enhance our understanding of disease progression and improve our ability to test for disease-prevention strategies. The development of physiologically relevant, human cell-based culture systems is therefore a major focus of our research. These novel models will be of enormous value, allowing us to test hypotheses and advance our understanding of these disorders, and will have a translational impact allowing us to more rapidly develop therapeutic and chemopreventive agents. In summary, this work to develop advanced human cell-based models of inflammatory conditions will greatly improve our ability to study, prevent, and treat GERD, BE, GVHD, and inflammatory bowel disease. The work will also foster the development of novel therapeutic and preventive strategies that will improve patient care for these important clinical conditions
Higher Order Corrections at Zero Recoil
The general structure of the corrections at zero recoil is studied. The
relevant matrix elements are forward matrix elements of local higher
dimensional operators and their time ordered products with higher order terms
from the Lagrangian. These matrix elements may be classified in a simple way
and the analysis at the non recoil point for the form factor of heavy quark
currents simplifies drastically. The second order recoil corrections to the
form factor of the axial vector current, relevant for the
determination from decays, are estimated to be .Comment: LaTeX, 25 pages, one figure, appended after \end{document} as
uu-encoded and compressed eps file, uses epsf, CERN-TH.7162/9
Retention of mouth-to-mouth, mouth-to-mask and mouth-to-face shield ventilation
Background: Retention of mouth-to-mouth, mouth-to-mask and mouth-to-face shield ventilation techniques is poorly understood.Methods: A prospective randomised clinical trial was undertaken in January 2004 in 70 candidates randomly assigned to training in mouth-to-mouth, mouth-to-mask or mouth-to-face shield ventilation. Each candidate was trained for 10 min, after which tidal volume, respiratory rate, minute volume, peak airway pressure and the presence or absence of stomach inflation were measured. 58 subjects were reassessed 1 year later and study parameters were recorded again. Data were analysed with ANOVA, \textgreekq2 and McNemar tests.Results: Tidal volume, minute volume, peak airway pressure, ventilation rate and stomach inflation rate increased significantly at reassessment with all ventilation techniques compared with the initial assessment. However, at reassessment, mean (SD) tidal volume (960 (446) vs 1008 (366) vs 1402 (302) ml; p<0.05), minute volume (12 (5) vs 13 (7) vs 18 (3) l/min; p<0.05), peak airway pressure (14 (8) vs 17 (13) vs 25 (8) cm H2O; p<0.05) and stomach inflation rate (63% vs 58% vs 100%; p<0.05) were significantly lower with mouth-to-mask and mouth-to-face shield ventilation than with mouth-to-mouth ventilation. The ventilation rate at reassessment did not differ significantly between the ventilation techniques.Conclusions: One year after a single episode of ventilation training, lay persons tended to hyperventilate; however, the degree of hyperventilation and resulting stomach inflation were lower when a mouth-to-mask or a face shield device was employed. Regular training is therefore required to retain ventilation skills; retention of skills may be better with ventilation devices
More on Symmetries in Heavy Quark Effective Theory
We present a general classification of all normal and ``chiral" symmetries of
heavy quark effective theories. Some peculiarities and conondrums associated
with the ``chiral" symmetries are discussed.Comment: 15 pages, preprint UR-1320, ER40685-77
Strong Decays of Strange Charmed P-Wave Mesons
Goldstone boson decays of P-wave mesons are studied within the
framework of Heavy Hadron Chiral Perturbation Theory. We first analyze the
simplest single kaon decays of these strange charmed mesons. We derive a model
independent prediction for the width of and use experimental
information on to constrain the S-wave contribution to decay.
Single and double pion decay modes are then discussed and shown to be
significantly restricted by isospin conservation. We conclude that the pion
channels may offer the best hope for detecting one strange member of an
otherwise invisible P-wave flavor multiplet.Comment: 16 pages, 2 updated figures not included but available upon request,
CALT-68-1902. (Revised estimates for error on width and for isospin
violating neutral pion decay of .
Binary Reactive Adsorbate on a Random Catalytic Substrate
We study the equilibrium properties of a model for a binary mixture of
catalytically-reactive monomers adsorbed on a two-dimensional substrate
decorated by randomly placed catalytic bonds. The interacting and
monomer species undergo continuous exchanges with particle reservoirs and react
() as soon as a pair of unlike particles appears on sites
connected by a catalytic bond.
For the case of annealed disorder in the placement of the catalytic bonds
this model can be mapped onto a classical spin model with spin values , with effective couplings dependent on the temperature and on the mean
density of catalytic bonds. This allows us to exploit the mean-field theory
developed for the latter to determine the phase diagram as a function of in
the (symmetric) case in which the chemical potentials of the particle
reservoirs, as well as the and interactions are equal.Comment: 12 pages, 4 figure
Lymphoepithelial Cyst of the Pancreas: Serum Markers do not Help
We report a case of lymphoepithelial cyst of the
pancreas with non-specific elevation of CA 19.9 and
CEA. Pre-operative diagnosis by conventional means
proved elusive, and only surgical resection and
histopathology revealed the diagnosis. The origin
and diagnosis are discussed by literature review
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