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1.
Separate groups of mice standardized in an alternating 12-hour-light,12-hour-dark regimen were treated with lidocaine hydrochloride every 3 hours over a 24-hour period. The results indicate a quantitative circadian periodicity with maximal convulsant activity at 2100 hours which was approximately a fourteen fold increase over the values observed at 1500 hours. 相似文献
2.
哺乳仔猪生后７ｄ龄出现觅食行为，仔猪生后３～５ｄ龄有饮水表现。５７．４％的仔猪吃奶或拱奶后马上吃料。仔猪生后５～１４ｄ每昼夜睡眠时间平均为１０６５ｍｉｎ（１７．７５ｈ），间隔时间较短，２１～２幼龄每昼夜平均睡眠时间为８３７ｍｉｎ（１３．９５ｈ）．哺乳仔猪生后５～１０ｄ龄每昼夜平均吃奶次数达３０．７次，平均间隔时间为４９．１ｍｉｎ。到１４ｄ龄，吃奶次数明显减少，持续时间也缩短，而间隔时间延长到６７．６ｍｉｎ。从第２１ｄ龄到断奶（第３５ｄ龄）吃奶（或拱奶）次数一般都在３５次左右，间隔和持续时间无明显规律。 相似文献
3.
A procedure is presented for calculating 24-hour totals of evaporation from wet and drying soils. Its application requires a knowledge of the daily solar radiation and the maximum and minimum air temperatures (standard Weather Service measurements), moist surface albedo (readily estimated or obtainable from a one-time measurement), and maximum and minimum surface temperatures (obtainable from surface or airborne sensors). Tests of the technique on a bare field of Avondale loam at Phoenix, Arizona, have shown it to be independent of season. 相似文献
4.
The normal ovarian cycle of female rats is typically replaced by persistent estrus when these animals are housed under constant light. Evidence presented here shows that the maintenance of periodicity in the environment can at least delay (if not prevent) the photic induction of persistent vaginal estrus. Female rats in constant light were exposed to vaginal smearing at random times or at the same time every day. In another experiment, female rats were exposed to either constant bright light, constant dim light, or a 24-hour photic cycle of bright and dim light. The onset of persistent vaginal estrus was delayed in rats exposed to 24-hour time cues even though the light intensities were the same as or greater than those for the aperiodic control groups. The results suggest that the absence of 24-hour time cues in constant light contributes to the induction of persistent estrus. 相似文献
5.
Daily 20-hour encephalic photophases (DEPP), transmitted (hours 0 to 20) via chronically implanted light-conducting fibers to selected sites in the basal hypothalamus of male white-crowned sparrows, were superimposed on daily 8-hour (hours 0 to 8) external ambient photophases (DAPP). Initially the birds displayed motor activity only during the 8-hour DAPP. After a delay of at least 2 weeks, some of the birds became intensively active during hours 8 to 20. We postulate that this period of "nocturnal" activity is equivalent to the nocturnal Zugunruhe shown by caged individuals of many nocturnally migratory species subjected to long days; such activity is generally regarded as the expression of migratory behavior. 相似文献
6.
Quantitation of hepatic glycogenolysis and gluconeogenesis in fasting humans with 13C NMR 总被引：20，自引：0，他引：20
D L Rothman I Magnusson L D Katz R G Shulman G I Shulman 《Science (New York, N.Y.)》1991,254(5031):573-576
The rate of net hepatic glycogenolysis was assessed in humans by serially measuring hepatic glycogen concentration at 3- to 12-hour intervals during a 68-hour fast with 13C nuclear magnetic resonance spectroscopy. The net rate of gluconeogenesis was calculated by subtracting the rate of net hepatic glycogenolysis from the rate of glucose production in the whole body measured with tritiated glucose. Gluconeogenesis accounted for 64 +/- 5% (mean +/- standard error of the mean) of total glucose production during the first 22 hours of fasting. In the subsequent 14-hour and 18-hour periods of the fast, gluconeogenesis accounted for 82 +/- 5% and 96 +/- 1% of total glucose production, respectively. These data show that gluconeogenesis accounts for a substantial fraction of total glucose production even during the first 22 hours of a fast in humans. 相似文献
7.
利用巴楚县气象站1970～2000年6～8月逐日实测地面降水资料、水汽压、24h变压、气温、相对湿度、最高气温、最低气温资料,从中发现11：00水汽压、14：0024h变压、17：0024h变压、17：00气温、17：00相对湿度、17：00最高气温减最低气温与每次降水的出现有着极为密切的关系,并通过使用真值图预报方法来预报未来24h有无降水,经试报实践证明,预报准确率达75％。 相似文献
8.
Saunders DS 《Science (New York, N.Y.)》1970,168(3931):601-603
Night-interrluption experiments with the wasp Nasonia vitripennis maintained in 48- and 72-hour light: dark cycles reveal two and three peaks of light sensitivity (diapause inhibition), respectively. The first peak is 19 hours after lights-on in all regimes tested; the later peaks occlur at 24-hour intervals thereafter, providing evidence for the circadian nature of the photoperiodic clock in this insect. 相似文献
9.
R Ader 《Science (New York, N.Y.)》1969,163(872):1225-1226
Rats reared under 12-hour alternating periods of light and dark were killed at times corresponding to the times at which the maximum or minimum plasma corticosterone concentrations occur in mature animals. The characteristic 24-hour adrenocortical rhythm was first observed in rats 21 to 25 days old. In rats handled or stimulated with electric shock, the rhythm developed as early as 16 days. 相似文献
10.
A fluorometric-analysis procedure, used to quantitate indoles, confirmed the presence of 5-hydroxytryptamine (5-HT) in an arachnid; there was unimodal cyclic production of 5-HT in brain and intestinal tissues over a 24-hour period. The same tissues produced 5-HT after 80-day culture; bimodal cyclic output was indicated during continuous 24-hour study. One peak occurred at 0200 hours, at the same time as the peak in vivo, suggesting an endogenously controlled mechanism of secretion. The second peak occurred at midmorning, a time when production in vivo was lowest, suggesting that there is a possible feedback-control mechanism in the organism that inhibits the endogenous output of 5-HT. 相似文献
11.
Casellas R Shih TA Kleinewietfeld M Rakonjac J Nemazee D Rajewsky K Nussenzweig MC 《Science (New York, N.Y.)》2001,291(5508):1541-1544
Receptor editing, clonal deletion, and anergy are the mechanisms by which B cells maintain tolerance to self antigens. To determine the extent to which receptor editing shapes the normal antibody repertoire, we generated an immunoglobulin kappa polymorphism that facilitates the detection of editing of immunoglobulin light chains in vivo. We found that B cells are targeted for editing during a 2-hour delay in development at the pre-BII cell stage, and that about 25% of all antibody molecules are produced by gene replacement. These results suggest that receptor editing represents a major force in shaping the antibody repertoire. 相似文献
12.
在阐述了对课程的认识、课程改革的必要性、新形势对人才的要求之后,提出了我院课程存在的不足,由此提出了针对目前我国高等教育改革形式应采取的改革措施,如重新修订教学计划,编制大学学习指南,增加学生讨论和动手机会,实施教学内容和方法评价、及时反馈信息等. 相似文献
13.
中国式现代化新时代思想政治教育发展赋予了新使命。在价值维度,高校思想政治理论课要以"人的现代化"为核心,以"为党育人、为国育才"为根本,落实立德树人根本任务。在理论维度,中国式现代化丰富了高校思想政治理论课的教学内容,保证了高校思想政治理论课的育人方向,提高了高校思想政治理论课的育人水平。在实践维度,中国式现代化赋能高校思想政治理论课教学,有助于优化主干课程的现代化内容,提高教学效果,拓宽高校育人格局。因此,中国式现代化赋能高校思想政治理论课具有充分的理论科学性和实践科学性,从而切实推动思想政治理论课的高质量发展。 相似文献
14.
WOLFSON A 《Science (New York, N.Y.)》1959,129(3360):1425-1426
Light-dark cycles with 12-hour and 16-hour photoperiods are known to be effective in 24-hour cycles in inducing gonadal activity and fat deposition in migratory birds. Twenty-four-hour cycles with 16-hour dark periods are not effective. To test the role of the light periods and the dark periods in a given cycle, slate-colored juncos were subjected to light in cycles which combined stimulatory photoperiods (L) and inhibitory dark periods (D) as follows: 12L-16D; 12L-20D; 16L-16D; 16L-22D; 16L-32D. The results indicate that the photoperiod, not the dark period, determined the response. 相似文献
15.
[目的]研究重铬酸钾和3,5-二氯苯酚对羊角月牙藻和斜生栅藻的毒性效应。[方法]以羊角月牙藻和斜生栅藻为试验绿藻,进行了重铬酸钾和3,5-二氯苯酚为参比物的72 h毒性试验。[结果]重铬酸钾对羊角月牙藻的72 h Ey C_(50)为1.02 mg/L,95%置信区间为0.98~1.06 mg/L;Ery C_(50)为2.48 mg/L,95%置信区间为2.25~2.74 mg/L。3,5-二氯苯酚对羊角月牙藻的72 h Ey C_(50)为1.12 mg/L,95%置信区间为1.08~1.16 mg/L;Ery C_(50)为2.41 mg/L,95%置信区间为2.22~2.62 mg/L。重铬酸钾对斜生栅藻的72 h Ey C_(50)为0.43mg/L,95%置信区间为0.42~0.43 mg/L;Ery C_(50)为1.07 mg/L,95%置信区间为1.02~1.12 mg/L。添加不同初始藻浓度,初始量为0.5×10~4个/m L时,3,5-二氯苯酚对斜生栅藻的72 h Ey C_(50)为1.68 mg/L,95%置信区间为1.63~1.72 mg/L;Ery C_(50)为1.43 mg/L,95%置信区间为1.42~1.44 mg/L。初始量为1.0×10~4个/m L时,3,5-二氯苯酚对斜生栅藻的72 h Ey C_(50)为1.55 mg/L,95%置信区间为1.51~1.60 mg/L;Ery C_(50)为1.39 mg/L,95%置信区间为1.38~1.40 mg/L。[结论]重铬酸钾和3,5-二氯苯酚可以作为参比物来评价绿藻的敏感度。 相似文献
16.
本项目通过对2019——2021年锦州地区112个气象观测站的分钟级降水数据进行统计分析,分别计算每个时次上的12小时、6小时、3小时及1小时的累计降水量。假设以累计降水量20mm为起点,每增加1mm降水时,向上浮动5mm的降水区间内发布暴雨蓝色、黄色以及橙色预警信号,以50mm为起点,每增加1mm降水时,向上浮动5mm的降水区间内发布暴雨红色预警信号,计算每个累计降水区间内的平均TS评分办法所得分数、提前时间以及有效性评分办法所得分数。找出各级暴雨预警信号预警信号准确率达到90%时,所对应的累计降水区间作为发布各级暴雨预警信号的最优降水区间,各级暴雨预警信号有效性评分办法得分最高时所对应的累计降水区间为该评分办法下的最优累计降水量区间。 相似文献
17.
“绿色教育”理念引领下测绘类人才培养模式创新探讨——以扬州环境资源职业技术学院工程测量技术专业为例 总被引：1，自引：1，他引：0
＂绿色教育＂是一种和谐教育观,人本教育观,素质教育观。扬州环境资源职业技术学院工程测量技术专业在发展过程中以绿色教育理念为引领、＂校企联盟＂为平台、工学结合为内容、岗位能力培养为导向,开展了基本能力平台（职业素养及情境体验式课程）、专项能力平台（工作分解结构课程）、专业工作能力平台（模块化项目式课程）这三个平台和对应的三类课程的建设,实施了＂1＋0.5＋1＋0.5＂四段三层结合的人才培养方案,构建了符合测绘行业特点和高职学生身心发展规律的人才培养模式。 相似文献
18.
采用时辰生理学指标,对四川凉山半细毛羊进行了昼夜节律研究。结果表明,绵羊机体的时辰生理学指标,存在着昼夜节律的规律。即,最大时辰变化主要在辰、巳和午时。说明这段时间是生理功能活动的最佳时期。 相似文献
19.
Suspended particulates in Pittsburgh air were collected on glass-fiber filters. The specific surface areas of particulates brushed from the filter surface varied from 1.55 to 4.51 square meters per gram when measured by the Brunauer-Emmett-Teller (BET) method with nitrogen and krypton, after 8-hour degassing of the samples at 25 degrees C. Specific surfaces of the same samples varied from 4.3 to 8.00 square meters per gram after 4-hour degassing at 200 degrees C. Bulk densities and densities of samples were 0.49 to 0.64 and 2.0 to 2.6 grams per cubic centimeter, respectively. These data provide some basis for explanation of unpredictable responses reported after inhalation of mixtures of pollutant gases and particles by animals and man; they should also assist in interpretation of gas-solid phase reactions in the atmosphere. 相似文献
20.
Rats were given electrical stimulation to the midbrain reticular formation or to the hippocampus 4 seconds after they received shocks contingent on the animals' bar-press responses. They were retested for memory of the shocks 64 seconds or 24 hours after the shocks. The animals that received stimulation to the midbrain reticular formation showed amnesia at the 64-second retest and memory at the 24-hour retest. In contrast, animals that received stimulation to the hippocampus showed memory at the 64-second retest and amnesia at the 24-hour retest. The data support a dual, parallel-processing model of memory. 相似文献