Circannual Variations of the Bleeding Time in the Rat

This study was carried out to determine the annual fluctuations of the tail bleeding time in the rat. Bleeding time was determined by transection of the tail of pentobarbital-anesthetized rats. Over a 6-year period, monthly measurement of the tail bleeding time revealed highly reproducible circannual fluctuations. Bleeding times were shortened in the summer (414 ± 18 s in July), being almost half that observed during the winter span (886 ± 32 s in January). The difference between these two time points was highly significant (p > 0.001). This study reports for the first time circannual variations of the bleeding time in the rat.     

时间序列的相似性测度

时间序列（time series）是指按时间顺序排列的观测值集合,在生物信息学研究领域中,DNA序列和基因表达数据都可以视为时间序列数据。时间序列分析中很重要的环节就是刻划两个时间序列或者时间子序列的相似性,用于序列比对等。时间序列的相似性测度是时间序列研究中的基础和重点,直接影响查询、聚类等后续计算的效率和精度,在高通量基因芯片数据分析、基因网络构建等研究中,具有重要的应用,目前已引起了众多研究人员的关注,在欧氏距离的基础上进行了大量的研究,本文综述了基于欧式距离和时间弯曲的时间序列相似性测度及其相关领域的研究进展,可作为进一步研究的参考。     

孵育时间在二氧化钛选择性富集磷酸化肽中的影响

目的:旨在探索孵育时间在二氧化钛选择性富集磷酸化肽中的影响。方法:以大肠杆菌BL21(DE3)为材料,预实验确定二氧化钛磁珠与肽段之间的最适比例,之后在此比例下继续探究不同孵育时间条件下的富集效果,以观察孵育时间在二氧化钛富集体系中的影响。结果:预实验确定磁珠与肽段之间最适比例为3 :1,在此比例下发现随着孵育时间的增加其富集效率会逐渐降低,最后确定大肠杆菌中最适孵育时间为5min。结论:孵育时间在大肠杆菌二氧化钛富集体系中对富集效果有明显的影响,并且呈负相关。推测不同样品的最佳孵育时间与样品种属有关。     

物质、能量在生态网络中的滞留时间及其灵敏度的解析表达

物质、能量在生态网络中的总滞留时间（TRT）是反映物质、能量在生态网络中流动特征的一个整体指标．本文在分析生态网络中物质、能量滞留时间的基础上,给出了总滞留时间关于流动参量和状态参量的灵敏度解析形式．     

First Passage Time Analysis of Animal Movement and Insights into the Functional Response

Movement plays a role in structuring the interactions between individuals, their environment, and other species. Although movement models coupled with empirical data are widely used to study animal distribution, they have seldom been used to study search time. This paper proposes first passage time as a novel approach for understanding the effect of the landscape on animal movement and search time. In the context of animal movement, first passage time is the time taken for an animal to reach a specified site for the first time. We synthesize current first passage time theory and derive a general first passage time equation for animal movement. This equation is related to the Fokker–Planck equation, which is used to describe the distribution of animals in the landscape. We illustrate the first passage time method by analyzing the effect of territorial behavior on the time required for a red fox to locate prey throughout its home range. Using first passage time to compute search times, we consider the effect of two different searching modes on a functional response. We show that random searching leads to a Holling type III functional response. First passage time analysis provides a new tool for studying how animal movement may influence ecological processes.     

Time to fixation in the presence of recombination

We study the evolutionary dynamics of a haploid population of infinite size recombining with a probability r in a two locus model. Starting from a low fitness locus, the population is evolved under mutation, selection and recombination until a finite fraction of the population reaches the fittest locus. An analytical method is developed to calculate the fixation time T to the fittest locus for various choices of epistasis. We find that: (1) for negative epistasis, T decreases slowly for small r but decays fast at larger r; (2) for positive epistasis, T increases linearly for small r and mildly for large r; (3) for compensatory mutation, T diverges as a power law with logarithmic corrections as the recombination fraction approaches a critical value. Our calculations are seen to be in good agreement with the exact numerical results.     

EEG Activity in the Process of Measuring-off of Time Intervals by Humans

We recorded EEG from sites C3 and C4 in an experimental situation with internal counting-off of a 20-sec-long time interval, whose beginning and end were limited by the tested subject by pushing a button; 65 adult men and women took part in the tests. In the first experimental series, the subject obtained no real information on the accuracy in production of the interval. In the second series, such information was displayed by feedback visual signals. We calculated means of the measured intervals ( ), coefficient of variation of the realizations (CV), and, in the series with the real feedback, successfulness of measuring-off (normalized number of fits within an acceptable range of the standard interval, 19 to 21 sec). Analysis of the data obtained in the first experimental series for the entire tested group demonstrated the existence of a reverse dependence between the modal frequency of EEG beta rhythm recorded from the left hemisphere in the course of measuring-off of the interval and the value. In the second series, we found significant negative correlation between the beta rhythm power in both hemispheres and CV, that between the alpha rhythm power in the left hemisphere and , and positive correlation between the alpha rhythm frequency in the left hemisphere and successfulness of the interval counting-off. Analysis of the dynamics of EEG of each tested subject demonstrated the existence of mostly reverse dependences between the powers of a few EEG rhythms and duration of the produced interval. We hypothesize that the frequencies of the alpha and beta EEG oscillations play the role of significant indices reflecting the speed of the internal clock of the individual. We also emphasize the complex nature and the high individual variability of the EEG pattern in the course of measuring-off of time intervals.     

An Estimate of the Variance of Estimators for Lead Time and Screening Benefit Time in Randomized Cancer Screening Trials

Variance estimators are derived for estimators of the average lead time and average benefit time due to screening in a randomized screening trial via influence functions. The influence functions demonstrate that these estimators are asymptotically equivalent to the mean difference, between the study and control case groups, in the appropriate survival times. For estimating benefit time, the survival time is measured since start of study; for estimating lead time, the survival time is measured since time of diagnosis. Asymptotic variances of these estimators can be calculated in a straightforward manner from the influence functions, and these variances can be estimated from actual trial data. The performance of the variance estimators is assessed via a simulated screening trial. The situation involving censored data is also discussed.     

Time Horizon and Dominance in Dynamic Life Cycle Assessment

Temporal aspects have traditionally not been recognized adequately in life cycle assessment (LCA). The dynamic LCA model recently proposed offers a significant step forward in the dynamic assessment of global warming impacts. The results obtained with dynamic LCA are highly sensitive to the choice of a time horizon. Therefore, decision making between alternative systems can be critical because conclusions are dependent on the specific time horizon. In this article, we develop a decision‐making methodology based on the concept of time dominance. We introduce instantaneous and cumulative time dominance criteria to the dynamic LCA context and argue why the dominance of an alternative should also imply preference. Our approach allows for the rejection of certain alternatives without the determination of a specific time horizon. The number of decision‐relevant alternatives can thereby be reduced and the decision problem facilitated. We demonstrate our methodology by means of a case study of end‐of‐life alternatives for a wooden chair derived from the original authors of dynamic LCA and discuss the implications and limitations of the approach. The methodology based on time dominance criteria is supplementary to the dynamic LCA model, but does not substitute it. The overall value of this article stretches beyond LCA onto more general assessments of global warming, for example, in policy where the choice of a time horizon is equally significant.     

拟南芥开花时间调控的分子基础

在合适的时间开花对大多数植物的生存和成功繁衍极为重要。开花时间受错综复杂的环境因素和植物自身的遗传因子影响,由开花调控因子所构成的光周期、春化、温度、赤霉素、自主以及年龄等至少6条既相互独立又相互联系的遗传途径调控。该文综述了有关拟南芥(Arabidopsis thaliana)开花时间调控的分子机制的最新研究进展,并对今后的研究进行了展望。     

半圈养条件下白唇鹿行为时间分配及活动规律的研究

白唇鹿 (Cervus albirostris)是我国青藏高原特有种 ,在鹿类进化史上极其重要。因其药用价值很高 ,几十年来捕杀现象严重 ,数量大为减少 ,濒于灭绝 ,1 988年被列为国家一级保护动物 [13 ] 。目前白唇鹿分布在 2 9°～ 40°N,92°～ 1 0 2°E的区域内[1] 。它们主要活动于海拔 350 0～ 50 0 0 m之间的高寒半荒漠草原 ,高山草甸草原和亚高山灌丛草原 [7] 。国内对白唇鹿的研究 ,涉及到食性[7,11] 、繁殖[3～ 5] 、形态、生态地理分布[6] 等 ,而对白唇鹿非发情期行为时间分配尚无报道。 1 998年 3～ 4月我们在上海野生动物园对其进行了专题研…     

时间减影在静脉肾盂造影中的应用价值研究

目的探讨数字X线机(DFR)时间减影对静脉肾盂造影的诊断价值,并与常规单纯DFR静脉肾盂造影比较。方法对38例运用数字(DFR)静脉肾盂造影的检查者,同时采用时间减影进行分析。检查结果正常16例,肾盂积水、肾结石、输尿管畸形、输尿管结石等22例。结论数字静脉肾盂造影检查 时间减影检查,较好地克服了传统造影方法的不足,为泌尿系统的诊断和治疗提供了更全面和确切的依据,取得了较好的临床效果。     

半自然状态下鳄蜥活动时间分配的初步研究

在半自然的条件下采用瞬时扫描法对鳄蜥活动时间分配进行了初步的研究,结果表明:在池养鳄蜥的活动时间分配中,静栖占69·09%,在穴占28·82%,移动占0·80%,捕食占0·28%,晒太阳占0·44%,其它占0·58%;比较了不同性别鳄蜥的活动时间分配,其中雄性鳄蜥用在移动的时间占1·15±1·22%,雌性为0·45±1·00%,经过单因素检验显示其差异显著(P<0·01),其它行为活动时间分配差异不显著;初步比较了不同生境中鳄蜥的行为差异,结果显示鳄蜥在池养的条件下弹性行为的表现频次正在下降。     

内皮抑素抗黑色素瘤血管新生时间窗及最佳剂量的研究

目的:获取不同黑色素瘤发展阶段的荷瘤鼠的最佳治疗时间以及最佳用药量。方法:将肿瘤大小不等的雄性黑色素瘤荷瘤鼠进行内皮抑素分组对比治疗,在用药3、5、7天后处死荷瘤鼠,剥离瘤体,称瘤重,分析生长趋势,做病理切片并进行HE染色和免疫组化。在与对照组进行对照后,根据肿瘤的大小、恶性化的程度以及CD31和VEGF的表达情况,找出内皮抑素的用药最有效的治疗时间窗。然后通过进一步实验,在已经检测出的不同肿瘤大小的荷瘤鼠的恩度作用时间窗内,给荷瘤鼠使用用不同浓度梯度的药物,在不同肿瘤发展大小之后剥离瘤体,做与上述类似的操作并分析,确定在治疗时间窗时的恩度使用的最佳剂量。结论:5天为内皮抑素抗黑色素瘤血管新生时间窗,两个实验组中,中等剂量即15 mg/kg和20 mg/kg为恩度作用最佳剂量。     

Equidirection: A Measure of Similarity Among Time Series

In the present paper we investigate the concept of equidirection, i.e. similarity in the direction of variation, or parallelism in the broader sense, among m (m ≧ 2) times series, especially under the assumption that the time series are realizations of processes with independent increments. However, the processes need not be stationary. Furthermore, the probabilities for the direction of variation may be unstable, in which case only upper and lower bounds are known. A measure based on the concept of equidirection was developed that enables identification of clusters of similar time series and analysis of relationships among variables.     

Variables Aggregation in Time Varying Discrete Systems

In this work we extend approximate aggregation methods in time discrete linear models to the case of time varying environments. Approximate aggregation consists in describing some features of the dynamics of a general system involving many coupled variables in terms of the dynamics of a reduced system with a few number of variables. We present a time discrete time varying model in which we distinguish two time scales. By using perturbation methods we transform the system to make the global variables appear and build up the aggregated system. The asymptotic relationships between the general and aggregated systems are explored in the cases of a cyclically varying environment and a changing environment in process of stabilization. We show that under quite general conditions the knowledge of the behavior of the aggregated system characterizes that of the general system. The general method is also applied to aggregate a multiregional time dependent Leslie model showing that the aggregated model has demographic rates depending on the equilibrium proportions of individuals in the different patches.     

生川乌中生物碱成分含量随煎煮时间变化的研究

本文研究乌头中生物碱成分的含量随煎煮时间变化的趋势,为考查乌头类中药的毒性,提供定量指标.按不同时间水煎提取样品;分别采用容量法、比色法和薄层扫描法测定总生物碱、双酯性生物碱和乌头碱的含量.生川乌醇水双提总生物碱含量最高,水提样品中以煎煮4 h较高;生川乌醇水双提酯性生物碱含量最高,水提样品中以煎煮2 h为最高,比双提酯性生物碱含量低;生川乌醇水双提乌头碱含量最高,水提样品中以煎煮2h为最高,比双提乌头碱含量低.为乌头类中药的毒性研究提供了详细的参考指标.     

Time budget and activity patterns of the lion-tailed macaque (Macaca silenus)

We studied time budgeting of lion-tailed macaques in the Anamalai Wildlife Sanctuary, Tamil Nadu, India, with regard to seven activity categories. Groups spent >50% of their time feeding and foraging, 33% of the time resting, and 15% moving. More energetic activities were spread uniformly through the day. Feeding had two annual peaks: one closely following the northeast monsoon and the other corresponding to the southwest monsoon. These also coincided with peaks of food availability and mating. Time saved in feeding was spent mostly on resting. Ranging showed a pattern contrary to that of time spent moving and was related more to weather than to food availability; it increased during cooler periods. The middle and upper stories of the canopy were used >93% of the time. The ground was used rarely. Time budgeting characteristics of the lion-tailed macaque are primarily frugiinsectivorous adaptations to a wet evergreen forest habitat.     

Exploration of Reaction Time: Ideas for an Inquiry Investigation in Physics Education

Reaction time, the time between a stimulus and a person's reaction to it, is a concept familiar to most teenagers, particularly in the context of driving. We describe a simple inexpensive activity that utilizes students’ creativity and invokes the scientific method in order to explore reaction time. The goal of the activity is to give students a realistic understanding of their reaction time and to challenge them to consider the implications of this for driving scenarios.     

三种笼养灵长类活动时间分配的比较研究

采用焦点动物法和连续记录法对3种笼养灵长类活动时间分配进行比较研究。结果表明,川金丝猴Rhi-nopithecus roxellanae和熊猴Macaca assamensis用于休息的时间多于猕猴Macaca mulatta,移动时间则相反;川金丝猴和猕猴用于理毛的时间多于熊猴。不同性别年龄组之间的活动时间分配有差异,主要表现在川金丝猴母亲用于理毛的时间明显多于成年儿子,用于玩耍的时间则相反;猕猴成年雄性的移动时间和理毛时间多于成年雌性,玩耍时间则少于成年雌性;熊猴成年雌性的移动时间多于成年雄性,与成年个体相比,幼体花更多的时间用于玩耍,而相应的减少了其休息时间。