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A high-speed spectrograph shutter
Device can operate in close-open-close mode. Beam splitter placed behind static-slit assembly allows use of more than one camera. Each frame in particular series may be conveniently varied in exposure time and spacing. This can be done independent of other frames in the series. In ''open'' position, shutter transmits light over wide wavelength range
Mobility of Dislocations in Aluminum
The velocities of individual dislocations of edge and mixed types in pure aluminum single crystals were determined as a function of appliedâresolved shear stress and temperature. The dislocation velocities were determined from measurements of the displacements of individual dislocations produced by stress pulses of known duration. The BergâBarrett xâray technique was employed to observe the dislocations, and stress pulses of 15 to 108 ÎŒsec duration were applied by propagating torsional waves along the axes of [111]âoriented cylindrical crystals. Resolved shear stresses up to 16Ă10^6 dynesâcm^2 were applied at temperatures ranging from â150° to +70°C, and dislocation velocities were found to vary from 10 to 2800 cmâsec over these ranges of stress and temperature. The experimental conditions were such that the dislocation velocities were not significantly influenced by impurities, dislocation curvature, dislocationâdislocation interactions, or longârange internal stress fields in the crystals. The velocity of dislocations is found to be linearly proportional to the appliedâresolved shear stress, and to decrease with increasing temperature. Qualitative comparison of these results with existing theories leads to the conclusion that the mobility of individual dislocations in pure aluminum is governed by dislocationâphonon interactions. The phononâviscosity theory of dislocation mobility can be brought into agreement with the experimental results by reasonable choices of the values of certain constants appearing in the theory
Mobility of Edge Dislocations in the BasalâSlip System of Zinc
This paper presents the results of measurements of the velocities of ă1210ă (0001) edge dislocations in zinc as a function of applied shear stress. All tests were conducted at room temperature on 99.999% pure zinc monocrystals. Dislocations were revealed by means of the BergâBarrett xâray technique. Stress pulses of microsecond duration were applied to the test specimens by means of a torsion testing machine. Applied resolved shear stresses ranged from 0 to 17.2Ă10^6 dynâcm^2 and measured dislocation velocities ranged from 40â700 cmâsec. The results of this study indicate that the velocity of edge dislocations in the basal slip system of zinc is linearly proportional to the applied resolved shear stress. These results are analyzed in terms of the phonon drag theory. Agreement between this theory and the results reported here is quite good
Community education as a multi-system operation
When I think of a community, I think of people
Computer Library Literature Review on Effectiveness of Antimotion Sickness Drugs
Physiological responses to antimotion sickness drugs - antihistamines, belladonnas, and phenothiazine
Underuse of coronary revascularization procedures in patients considered appropriate candidates for revascularization.
Background: Ratings by an expert panel of the appropriateness of treatments may offer better guidance for clinical practice than the variable decisions of individual clinicians, yet there have been no prospective studies of clinical outcomes. We compared the clinical outcomes of patients treated medically after angiography with those of patients who underwent revascularization, within groups defined by ratings of the degree of appropriateness of revascularization in varying clinical circumstances.Methods: This was a prospective study of consecutive patients undergoing coronary angiography at three London hospitals. Before patients were recruited, a nine-member expert panel rated the appropriateness of percutaneous transluminal coronary angioplasty (PTCA) and coronary-artery bypass grafting (CABG) on a nine-point scale (with 1 denoting highly inappropriate and 9 denoting highly appropriate) for specific clinical indications. These ratings were then applied to a population of patients with coronary artery disease. However, the patients were treated without regard to the ratings. A total of 2552 patients were followed for a median of 30 months after angiography.Results: Of 908 patients with indications for which PTCA was rated appropriate (score, 7 to 9), 34 percent were treated medically; these patients were more likely to have angina at follow-up than those who underwent PTCA (odds ratio, 1.97; 95 percent confidence interval, 1.29 to 3.00). Of 1353 patients with indications for which CABG was considered appropriate, 26 percent were treated medically; they were more likely than those who underwent CABG to die or have a nonfatal myocardial infarction - the composite primary outcome (hazard ratio, 4.08; 95 percent confidence interval, 2.82 to 5.93) - and to have angina (odds ratio, 3.03; 95 percent confidence interval, 2.08 to 4.42). Furthermore, there was a graded relation between rating and outcome over the entire scale of appropriateness (P for linear trend = 0.002).Conclusions: On the basis of the ratings of the expert panel, we identified substantial underuse of coronary revascularization among patients who were considered appropriate candidates for these procedures. Underuse was associated with adverse clinical outcomes. (N Engl J Med 2001;344:645-54.) Copyright (C) 2001 Massachusetts Medical Society
Machine for Producing Square Torsion Pulses of Microsecond Duration
A dynamic torsion testing machine has been built for the purpose of applying a known constant shear stress to a 12.7-mm-diam cylindrical test specimen for very short periods of time. The shear stress at the surface of the specimen rises from zero to any desired value in the range 0 to 3000 psi, within a period of 4 to 6 ÎŒsec. The time at constant stress varies linearly with axial position from the free end of the specimen ranging from 0 to about 500 ÎŒsec. The stress is removed within a period of 4 to 6 ÎŒsec and for short specimens it remains essentially zero thereafter. This machine has been developed for the measurement of dislocation velocities up to 25 m/sec in metal single crystals
Dislocation Mobility in Copper
The velocity of dislocations of mixed edge-screw type in copper crystals of 99.999% purity has been measured as a function of stress at room temperature. Dislocation displacements produced by torsion stress pulses of microsecond duration were detected by etch pitting {100} surfaces. A nearly linear relationship between dislocation velocity and resolved shear stress was found. Stresses from 2.8Ă10^6 to 23.1Ă10^6 dyn/cm^2 produced velocities from 160 to 710 cm/sec. These data give a value of the damping constant for high-velocity dislocations of 7Ă10^(-4) dyn·sec/cm^2, in good agreement with the values deduced from internalfriction measurements. The results also agree, within experimental and theoretical uncertainties, with the phonon viscosity model for the mobility of dislocations
Influence of Aerobic Exercise on Ghrelin-o-Acyltransferase in Normal Weight and Obese Adults: A Pilot Study
Please see the pdf version of the abstract
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