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51.
RE Droleskey PJ Holman KA Waldrup DE Corrier GG Wagner 《Canadian Metallurgical Quarterly》1993,79(3):424-434
Babesia odocoilei continuously cultured in white-tailed deer (Odocoileus virginianus) erythrocytes was examined by transmission and scanning electron microscopy. Merozoites, trophozoites, intermediate-stage forms, and dividing forms were observed. Merozoites possessed a single nucleus, inner membrane complex, rhoptries, free ribosomes, rough endoplasmic reticulum, and single membrane-bound vesicles. Trophozoites lacked an inner membrane complex and rhoptries. Intermediate stages were characterized by distinct segments of inner membrane complex. Dividing forms ranged from cells with an elongated nucleus to mature daughter cells joined by a ringlike structure. Babesia odocoilei was characterized by its close proximity to the erythrocyte membrane, membranous structures resembling feeding organelles, and reproduction via a method resembling budding sensu stricto. 相似文献
52.
A perturbation expansion technique for approximating the three dimensional anisotropic elastic Green's function is presented. The method employs the usual series for the matrix (I–A)-1 to obtain an expansion in which the zeroth order term is an isotropic fundamental solution. The higher order contributions are expressed as contour integrals of matrix products, and can be directly evaluated with a symbolic manipulation program. A convergence condition is established for cubic crystals, and it is shown that convergence is enhanced by employing Voigt averaged isotropic constants to define the expansion point. Example calculations demonstrate that, for moderately anisotropic materials, employing the first few terms in the series provides an accurate solution and a fast computational algorithm. However, for strongly anisotropic solids, this approach will most likely not be competitive with the Wilson-Cruse interpolation algorithm.This research was sponsored by the Exploratory Studies Program of Oak Ridge National Laboratory and the Division of Materials Science, U. S. Department of Energy, under contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc. 相似文献
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54.
TM H?ltt? KA R?nnholm H Jalanko M Ala-Houhala M Antikainen C Holmberg 《Canadian Metallurgical Quarterly》1997,17(6):573-580
The aim of this study was to examine the effect of intensive practice in table tennis on perceptual coincident timing. The main question was whether the perceptual demands encountered in fast ball sports produce modifications of the perceptual visual system. Expert table tennis players and novices were compared in a perceptual task which consisted of estimating, by pressing a key, the arrival of a moving stimulus at a target. The stimulus, which was presented either at constant velocity or at constant deceleration, reproduced as closely as possible the natural visual demands encountered in table tennis. The difference between the time of response and the time of arrival of the stimulus at a target position was measured over 40 trials for each of the 16 participants. The results showed no effect of expertise under the constant-velocity condition but an effect under the decelerative condition, indicating that experts were less trajectory-dependent than novices. This result was interpreted as reflecting a better adaptation of the perceptual system of experts to the constraints encountered during table tennis and specifically to the perceptual demands resulting from varied and decelerated ball trajectories. Finally, some limitations of the coincidence anticipation procedure are highlighted, concerning its use in practical settings for evaluating athletes or detecting sport talents, and the need for the simulation conditions during testing to reproduce as closely as possible the perceptual demands of real life is discussed. 相似文献
55.
A fast parasitic-insensitive continuous-time filter and equalizer integrated circuit that uses an active integrator is described. Circuit techniques for excess-phase cancellation and for setting the corner-frequency of the filter and equalizer are also described. These techniques result in a filter and equalizer chip with performance independent of process, supply, and temperature without employing phase-lock loops. The 20-MHz sixth-order Bessel filter and second-order equalizer operate from 5 V and generate only 0.24% (-52 dB) of total harmonic distortion when processing 2-Vpp differential output signals. The device is optimized to limit high-frequency noise and to amplitude equalize the data pulses in hard disk read-channel systems. The device supports data rates of up to 36 Mb/s and is built in a 1.5-μm, 4-GHz BiCMOS technology 相似文献
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57.
Recently theories of vortex fluctuations in two-dimensional superconducting films have been compared to the experimentally determined power law dependence of voltage on current and to the temperature-dependent resistance in small applied fields. Here an alternative interpretation of the power law and a practical difficulty of flux pinning for measurements in small fields are pointed out. To illustrate these points, experimental examples are presented for very homogeneous granular aluminum films. 相似文献
58.
A Maillet J Titze V Gushin I Nichiporuk KA Kirsch C Gharib G Gauquelin-Koch 《Canadian Metallurgical Quarterly》1998,69(11):1045-1051
BACKGROUND: When the European Space Agency planned the EUROMIR'95 long-duration flight with a European astronaut on board the Russian orbital MIR station, it organized simultaneously a ground simulation, called the Human Behaviour Study, of this manned space mission. The ground simulation was a confinement experiment, and this paper describes the changes in volume-regulating hormones that occurred during and after 20 weeks of confinement. METHODS: In a normobaric diving chamber, 3 subjects were confined for 135 d. Arterial pressure, plasma concentrations of blood volume-regulating hormones (active renin and arginine-vasopressin), and urinary variables (aldosterone, arginine-vasopressin, and metabolites of catecholamines) were measured before, during, and after confinement. RESULTS: Arterial pressure was increased from week 1 until week 15 of confinement, while heart rate was elevated from week 6 until the end of the simulation. Plasma active renin was elevated throughout the confinement (after week 6). Urine volume increased transitively on the first 2 d of confinement. CONCLUSIONS: The results obtained during this long-term confinement experiment have major importance regarding concerns about spaceflight and bed rest data, because we observed hormonal changes during the experiment that normally are assigned to the fluid shift that occurs in weightlessness or in the head-down tilt position (i.e., an increase of renin, an increase of urinary volume during the first two days, and a decreased urinary cyclic guanosine monophosphate. 相似文献
59.
JS Plummer KA Berryman C Cai WL Cody J DiMaio AM Doherty JJ Edmunds JX He DR Holland S Levesque DR Kent LS Narasimhan JR Rubin ST Rapundalo MA Siddiqui AJ Susser Y St-Denis PD Winocour 《Canadian Metallurgical Quarterly》1998,8(23):3409-3414
The synthesis and antithrombotic activity of a series of nonpeptide bicyclic thrombin inhibitors is described. We have explored the SAR with modifications to the P1 site. The introduction of arginine mimetics at the P1 site led to potent and selective thrombin inhibitors. 相似文献
60.