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131.
提出了小型燃煤锅炉微机系统的一种设计方案 ,介绍了其实际应用效果 ,并对微机控制与常规仪表控制相比 ,在节能、保证锅炉安全运行、改善工作条件、提高管理水平增加经济效益等方面具有明显的优点 相似文献
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硬盘系统一般采用气体润滑,以提高使用寿命和写可靠性。本文讨论了多了聚脂流润滑的IBM3370磁头/磁盘系统,以期提高磁记录密度。模型中考虑了超薄流体润滑的剪薄薄效应,并用有限差分法对润滑方程进行求解。应用摄动理论建立了IBM3370磁头/磁盘系统的动力学模型,分别对气体润滑和液体润滑的两自由度磁头进行了动力学仿真。仿真结果表明:在相同磁头倾角条件下,液膜润滑的磁头/磁盘的动力稳定性优于气何不骨的磁 相似文献
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AP Sampath HR Matthews MC Cornwall J Bandarchi GL Fain 《Canadian Metallurgical Quarterly》1999,113(2):267-277
Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 +/- 2.4 and 640 +/- 55 ms (mean +/- SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 +/- 30 and 1,400 +/- 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 +/- 37 nM in the dark-adapted outer segment and 5.5 +/- 2.4 nM after saturating illumination (mean +/- SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current. 相似文献
136.
Schizophrenic patients are extremely heavy tobacco smokers. However, a lower incidence of lung cancer in schizophrenic patients has been observed in comparison to other heavy smokers. Nicotine increases the proliferation of pulmonary neuroendocrine tissue, causing the release of a bombesin-like peptide. Thus, bombesin-like peptide levels in urine may be an indicator of precancerous, cigarette-induced lung damage. Bombesin-like peptide levels of 10 schizophrenic smokers and 11 schizophrenic nonsmokers were compared to those of nonschizophrenic subjects matched for age and pack-years of smoking. The nonschizophrenic smokers showed the expected increase in urinary bombesin-like peptide levels, as compared to nonschizophrenic nonsmokers. Schizophrenic patients had lower bombesin-like peptide levels independent of smoking effects. The mechanism of the difference in bombesin-like peptide levels between schizophrenic patients and nonschizophrenic subjects is unknown, but one possibility involves alteration in the alpha 7-nicotinic acetylcholine receptor, which mediates the growth of some neuroendocrine cell lines in vitro. 相似文献
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138.
JF Watchko MJ Daood GC Sieck JJ LaBella BT Ameredes AP Koretsky B Wieringa 《Canadian Metallurgical Quarterly》1997,82(5):1416-1423
Creatine kinase (CK) is an enzyme central to cellular high-energy phosphate metabolism in muscle. To characterize the physiological role of CK in respiratory muscle during dynamic contractions, we compared the force-velocity relationships, power, and work output characteristics of the diaphragm (Dia) from mice with combined myofibrillar and sarcomeric mitochondrial CK deficiency (CK[-/-]) with CK-sufficient controls (Ctl). Maximum velocity of shortening was significantly lower in CK[-/-] Dia (14.1 +/- 0.9 Lo/s, where Lo is optimal fiber length) compared with Ctl Dia (17.5 +/- 1.1 Lo/s) (P < 0.01). Maximum power was obtained at 0.4-0.5 tetanic force in both groups; absolute maximum power (2,293 +/- 138 W/m2) and work (201 +/- 9 J/m2) were lower in CK[-/-] Dia compared with Ctl Dia (2,744 +/- 146 W/m2 and 284 +/- 26 J/m2, respectively) (P < 0.05). The ability of CK[-/-] Dia to sustain shortening during repetitive isotonic activation (75 Hz, 330-ms duration repeated each second at 0.4 tetanic force load) was markedly impaired, with CK[-/-] Dia power and work declining to zero by 37 +/- 4 s, compared with 61 +/- 5 s in Ctl Dia. We conclude that combined myofibrillar and sarcomeric mitochondrial CK deficiency profoundly impairs Dia power and work output, underscoring the functional importance of CK during dynamic contractions in skeletal muscle. 相似文献
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140.
MH Skiadopoulos S Surman JM Tatem M Paschalis SL Wu SA Udem AP Durbin PL Collins BR Murphy 《Canadian Metallurgical Quarterly》1999,73(2):1374-1381