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排序方式: 共有1278条查询结果,搜索用时 15 毫秒
1.
Frizzell LA 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1988,35(5):578-581
The threshold dosages for high-intensity focal lesion production were determined at 3 MHz in the cat liver for exposure durations covering the range 0.003-35 s. The liver threshold was found to parallel that for the brain over the range of exposure durations 0.1 to 10 s, but to be more than twice the intensity level, approximately following the relation IT 0.5=460 W-cm2/s2, where I is the peak intensity and T is the exposure duration. At shorter exposure durations the threshold curve deviates from this relation, probably due to a change to a transient cavitation mechanism of damage 相似文献
2.
Effects of early-postmortem glycolytic rate on beef tenderness 总被引:1,自引:0,他引:1
Electrical stimulation (ES) was applied at 500 V to one side from each of 60 beef carcasses at 30 to 40 min postmortem. Wide ranges of early-postmortem glycolytic and cooling rates were produced in the musculature by use of three different forms of ES (in addition to non-ES treatment of the contralateral sides) and application of chilling routines of four different degrees of severity. Panel and Warner-Bratzler shear evaluations of loin steaks from all 120 sides showed that tenderness was highest when glycolysis had proceeded at an intermediate rate (corresponding to the attainment of a 3-h pH of about 6·1) and was appreciably lower on both sides of this mid-value. The toughening effect of rapid glycolysis (relative to that of a moderately increased glycolytic rate) persisted through 14 days of aging at 2°C.
These observations appear to be incompatible with the view that lysosomal enzymes contribute significantly to ES-induced tenderization. They also indicate that the effect of ES on tenderness is highly dependent on the subsequent cooling rate, very slow chilling sometimes accelerating the already high rate of pH fall to such an extent that the tissue is significantly toughened. Finally, they suggest that the goal of maximizing the early-postmortem rate of pH decline in bovine muscle is misguided and, if attained, will cause sub-optimal tenderness. 相似文献
3.
Limited Angle Reconstruction in Tomography via Squashing 总被引:3,自引:0,他引:3
We give a new algorithm for reconstructing a density f in the plane from its projections along those lines making an angle greater than a fixed delta > 0 with the x axis. Of course, the performance of the algorithm depends on delta and on the smoothness of f, but it appears to give a practical and simple solution to the problem whenever one exists. The basic idea, which seems to be new, is to make an affine (squashing) scale change of f to g for which the projections are then known at n equally spaced angles, so that we know how to find g, and then we obtain f from g by inverting the scale change. 相似文献
4.
Recursive algorithms for implementing digital image filters 总被引:1,自引:0,他引:1
Ferrari LA Sankar PV Shinnaka S Sklansky J 《IEEE transactions on pattern analysis and machine intelligence》1987,(3):461-466
The B-spline functions are used to develop recursive algorithms for the efficient implementation of two-dimensional linear digital image filters. These filters may be spatially varying. The B-splines are used in a representation of the desired point spread function. We show that this leads to recursive algorithms and hardware implementations which are more efficient than either direct spatial domain filter realizations or FFT implementations. The Z-transform is used to develop a discrete version of Duhamel's theorem. A computer architecture for B-spline image filters is proposed and a complexity analysis and comparison to other approaches is provided. 相似文献
5.
Effects of hyperlipemia on circulating leukocytes and erythrocytes were studied in dogs which were given repeated, intravenous
injections of a nonionic detergent, Triton WR-1339.
Erythrocyte lipid concentrations increased from 3.6±0.9 mg/1010 cells in control animals to 9.3±1.5 mg in the hyperlipemic group. This increase was accompanied by a shift in the distribution
of total fatty acids toward a higher percentage of saturated and monounsaturated acids. In contrast to the changes observed
in erythrocytes, the leukocyte lipid content remained unaltered in dogs with serum cholesterol levels ranging from 500 to
more than 2,000 mg/100 ml. Leukocyte counts rose whereas hematocrit values, hemoglobin concentrations, and erythrocyte counts
decreased. Oxygen utilization studies showed no significant metabolic differences between leukocytes which were isolated from
hyperlipemic or control animals. Circulating leukocytes in dogs with an endogenously induced hyperlipemia were shown therefore
to maintain normal lipid concentrations and did not participate in lipophage formation, as reported for certain diet-induced
lipemias. 相似文献
6.
A study of the dependence of the gain-switched laser operation of chromium forsterite on crystal parameters is presented. Results are reported for a wide range of chromium (IV) ion concentration: 0.02-0.12 at. % and 12-41 figure of merit, with emphasis on performance of the recently developed material with a dopant level of >0.10 at. %. Threshold and slope efficiency calculations are compared with measured performance for all crystals, with variation of pump polarization and output coupling. With 3% output coupling, the lowest threshold of 1.8 mJ, and highest slope efficiency of 13% were measured for a short, high-dopant-level crystal. With 33% output coupling a slope efficiency of 44% was measured for this crystal. Results demonstrate the considerable potential of short, high-dopant-level crystals for applications such as amplification, diode pumping, and narrow-bandwidth operation. 相似文献
7.
Favre M Chtcheglova LA Lapshin DA Sekatskii SK Valle F Dietler G 《Ultramicroscopy》2007,107(10-11):882-886
We have recently developed a new method for directly measuring the spring constant of single molecules and molecular complexes on a real-time basis [L.A. Chtcheglova, G.T. Shubeita, S.K. Sekatskii, G. Dietler, Biophys. J. 86 (2004) 1177]. The technique combines standard force spectroscopy with a small dithering of tip. Changes in the amplitude of the oscillations are measured as a function of the pulling-off force to yield the spring constant of the complex. In this report, we present the first results of combination of this approach with the force-clamp spectroscopy. The standard atomic-force microscope has been supplemented with an electronic unit, which is capable of realizing an arbitrary force function, and permits the force-loading regime to be interrupted at any time. Using this method, the time needed to rupture a single bond can be measured as a function of the force that is required to maintain the complex in a stretched condition. The energy landscape of the avidin-biotin complex is explored and discussed. 相似文献
8.
Fluorescent additives which allow the determination of droplet temperatures in hydrocarbon fuel sprays have been developed. These systems, which exploit the chemistry of organic exciplexes; should make possible the determination of droplet temperatures within 1 degree C. Two specific systems are described: 3,10-dicyanophenanthrene/diethylaniline over the 20-135 degrees C range, and naphthalene/tetramethyl-p-phenylene diamine over the 140-265 degrees C range. These additives should allow 2-D real-time nonintrusive visualization of the droplet temperatures in an evolving fuel spray. 相似文献
9.
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