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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4601-4616 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the effects of laser radiation on cloud drops and of the possibility of producing a clear optical channel in a cloud is presented. In order to produce a model that is appropriate to a realistic cloud with a distribution of drop sizes it is first necessary to study what happens to a single water drop subjected to laser radiation of different intensities. Various heating regimes are mapped out as a function of laser flux and fluence at the 10.6 μm wavelength. It is found that typical cloud drops can superheat until they become unstable and explode from the center. For a long laser pulse the boundary for this to occur is found to be 50(5/r)2 kW/cm2, where r is the drop radius in microns. Using these results a model that is spatially one-dimensional through the cloud is constructed for a distribution of drop sizes. Laser beam intensity as the light penetrates a cloud is calculated from Mie scattering and absorption cross sections for a beam diameter that is small in the sense that light scattered once is assumed lost. The internal temperature distribution of the drops is calculated and a phenomenological drop explosion model is given for drops that reach the unstable 305 °C spinodal temperature at their center. Energy and water mass content are conserved as the cloud background is modified in an average sense by drop evaporation or recondensation. Recondensation is treated in the diffusion regime according to the Kohler model, with vapor pressure over a drop modified by surface tension and dissolved nonwater content. Comparison with experimental data for a laboratory produced cloud is given and good agreement, particularly with respect to the predicted onset of drop explosion, is found. Results are also presented for hypothetical cloud conditions and laser intensities. The possibility of clearing a thin cloud with low fluence to the 3.8 μm is considered, as well as the passive evaporation of melted ice crystal clouds.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 784-795 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fluid model is presented for the purpose of calculating numerically the structures of surface plasmas with neutrals returning from the surface, in collision-dominated parameter regimes. Limiting corrections to thermal conduction and viscous pressure are obtained through comparisons with previous Fokker–Planck transport calculations. The model includes removal by pumping, as well as by ionization, of some of the returning neutrals, and solutions are obtained for different relative strengths of pumping. Increasing velocities of plasma flow toward the surface and increasing plasma temperatures near the surface are seen with increased pumping. In the asymptotic region, far from the surface, agreement is found between these families of numerical model solutions and two classes of analytic solutions. Applications to other fundamental and applied problems are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 353-370 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stationary flow model of spherical ablation is extended to shells, solutions with a density discontinuity at the critical surface, and charged-particle-beam-driven ablation. Parameter studies of the shell solutions show the relationship between shell aspect ratio, relative ablative mass removal or burnthrough, laser power, and shell material type. The discontinuous solutions are shown to occur when the critical surface and sonic surface coalesce. The relationship of these discontinuous solutions to particular physical situations is shown to be ambiguous in a way that must be resolved by microscopic transport calculations. Charged-particle-driven ablative implosion processes are shown to resemble laser-driven ablation. However, qualitatively different ablation processes occur in different regimes of the power and particle range of the incident beam. Procedures are described by which stationary solutions can be used to predict and interpret the results of experiments and numerical simulations.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 353 (1991), S. 331-333 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Neutrinos would be detected by the standard technique of observing the Cerenkov light emitted by upward-moving muons, produced by neutrinos interacting in or below the detector. At these high energies, the direction of the muon produced is within 1° of the direction of the parent neutrino, so ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2568
    Keywords: duodenal ulcer ; acute therapy ; substituted benzimidazole ; omeprazole ; H2-antagonist ; ranitidine ; gastrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To assess the comparative efficacy of omeprazole 20 mg, a proton pump inhibitor, versus ranitidine 150 mg twice a day, an H2-receptor antagonist, in healing duodenal ulcers we performed a randomized, double-blind, multicenter trial in 309 patients with endoscopically diagnosed ulcers. Patients were treated for up to four weeks and were seen at week 2 and at week 4, if unhealed at week 2, for determination of ulcer status by endoscopy, review of daily self-assessment symptom diaries, and clinical laboratory including fasting serum gastrin. Gastrin levels were repeated two weeks after cessation of study medication. Evaluation of baseline demographic and laboratory parameters demonstrated no significant differences between the two groups at entry. At week 2, 42% of the omeprazole and 34% of the ranitidine-treated patients were healed (P=NS). At week 4, there was a 19% advantage in ulcer healing for the omeprazole-treated patients in comparison to those treated with ranitidine (82% vs 63%, respectively,P〈0.05). Healing of ulcers ≥1.0 cm occurred in 83% of those treated with omeprazole versus 37% treated with ranitidine (P〈0.01). There were no significant differences in rate of pain relief or incidence of clinical laboratory abnormalities. Mean fasting serum gastrin value during treatment increased over the baseline in both groups, (P〈0.05). The percent change was significantly greater with omeprazole but few patients had elevations above the upper limit of normal for the assay. Both drugs were well tolerated. Omeprazole 20 mg demonstrated superiority in healing duodenal ulcers at four weeks in comparison to ranitidine 150 mg twice daily and was more effective in healing ulcers 〉-1.0 cm.
    Type of Medium: Electronic Resource
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