128 research outputs found
Stress-energy tensor in the Bel-Szekeres space-time
In a recent work an approximation procedure was introduced to calculate the
vacuum expectation value of the stress-energy tensor for a conformal massless
scalar field in the classical background determined by a particular colliding
plane wave space-time. This approximation procedure consists in appropriately
modifying the space-time geometry throughout the causal past of the collision
center. This modification in the geometry allows to simplify the boundary
conditions involved in the calculation of the Hadamard function for the quantum
state which represents the vacuum in the flat region before the arrival of the
waves. In the present work this approximation procedure is applied to the
non-singular Bel-Szekeres solution, which describes the head on collision of
two electromagnetic plane waves. It is shown that the stress-energy tensor is
unbounded as the killing-Cauchy horizon of the interaction is approached and
its behavior coincides with a previous calculation in another example of
non-singular colliding plane wave space-time.Comment: 17 pages, LaTex file, 2 PostScript figure
Application of an energy-like stability metric for axial compressor design
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003.Includes bibliographical references (p. 125-126 ).by Josep M. Dorca Luque.S.M
Addition of hyaluronic acid improves tlerance to 7% hypertonic saline solution in bronchiectasis patients.
Background: The excessive retention of sputum in the airways, leading to pulmonary infections, is a common consequence of bronchiectasis. Although inhalation of 7% hypertonic saline (HS) has proven an effective method to help remove the mucus, many patients are intolerant of this treatment. The addition of 0.1% hyaluronic acid to HS (HS+HA) could increase tolerance to HS in these patients. The main objective of this study was to evaluate the tolerability of HS+HA in bronchiectasis patients who are intolerant to HS. Methods: This prospective, observational, open-label study analysed the outcomes of two groups of bronchiectasis patients previously scheduled to start HS therapy. Patients were assessed for tolerance to HS by a questionnaire, spirometry and clinical evaluation. Patients who were intolerant were evaluated for tolerance to HS+HA approximately one week later. All patients were evaluated for their tolerance to HS or HS+HA 4 weeks after the start of their treatment. Patients were also assessed with quality-of-life and adherence questionnaires, and all adverse events were registered. Results: A total of 137 bronchiectasis patients were enrolled in the study (age = 63.0 ± 14.7 years; 63.5% women). Of these, 92 patients (67.1%) were tolerant and 45 patients (32.9%) were intolerant to HS. Of the 45 patients intolerant to HS, 31 patients (68.9%) were tolerant and 14 patients (31.1%) intolerant to HS+HA. Of these 31 tolerant patients, 26 (83.9%) could complete the 4-week treatment with HS+HA. Conclusions: Two-thirds of bronchiectasis patients that presented intolerance to inhaled HS alone are tolerant to inhaled HS+HA, suggesting that HA improves tolerance to HS therapy
Braneworld Tensor Anisotropies in the CMB
Cosmic microwave background (CMB) observations provide in principle a
high-precision test of models which are motivated by M theory. We set out the
framework of a program to compute the tensor anisotropies in the CMB that are
generated in braneworld models. In the simplest approximation, we show the
braneworld imprint as a correction to the power spectra for standard
temperature and polarization anisotropies.Comment: Minor corrections and references added. Accepted for publication in
Phys. Rev.
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