两种群均具有常收获率或常投放率的Lotka-Volterra系统可以存在三个极限环

证明了两种群均具有常收获率或常投放率的Lotka-Volterra系统可以存在三个极限环。     

植物种群具有常收获率的一类植物-食植者微分模型

讨论植物种群具有常收获率的一类植物－－食植者微分方程模型。分析了此系统当对植物种群的常收获率逐渐增大的过程中，在第一象限内轨线拓扑结构的变化规律，从而获知对植物种群不同程度的常收获率将对食植生态环境所产生影响的程度。     

具常投放率的反应扩散系统的渐近性质

本文研究一类具常投放率的人口动力学中反应扩散系统的Neumann初边值问题,应用比较函数讨论其解的渐近性态,给出稳态解的存在条件．     

一类食饵具有常数投放率系统的恢复率

在现实的生态系统中,特别当捕食者的密度大或捕食能力强时,人们常采用食饵补充的方式来控制捕食者和食饵种群数量的稳定,以达到生态平衡．本文在Chisholm,R．A．和Filotas,E．研究的捕食-食饵模型基础上,定义了食饵具有常数投放率的捕食系统,讨论了此系统的恢复率与食饵最大容量之间的关系以及投放率对恢复率和预警长度的影响．最后通过算例分析了递减的恢复率作为系统转移的指示器与投放率与食饵最大容量的关系,说明食饵的投放率可增强预警效果．     

具有放牧率的某些周期生态模型

§1.引言对生态数学中的logistic模型以及Lotka-Volterra模型的研究已从常系数转向变系数,例如,[1-3]讨论了周期系数的情形,[4]讨论了概周期系数的情形。文[8]指出,当这些模型具有放牧率时,尚待研究。本文所讨论的是有周期放牧率的几种周期模型。§2讨论有放牧率的logistic模型,     

人类性染色体拟常染色体区的研究进展

拟常染色体区是性染色体上的重要区域,对于维持性染色体结构与功能、保证性染色体在减数分裂过程中正常配对与分离具有重要意义。拟常染色体区与常染色体结构与功能的异同点也为了解性染色体的起源与进化提供了很好的材料。人类的拟常染色体区由PAR1和PAR2两个区域组成,这两个区域在结构上有明显不同。位于其上的基因虽然不多,但与许多遗传疾病相关,详细研究该区的基因与疾病的关系还有助于尽早诊断并防治与之相关的遗传疾病。本文全面综述了人类性染色体拟常染色体区的最新研究进展。     

常乐康佐治婴幼儿急性腹泻疗效观察

目的:为探讨微生态制剂"常乐康"对婴幼儿急性腹泻作用,减少过多静脉输液及滥用抗生素.方法:对180例急性腹泻患儿,随机分为治疗组和对照组,两组均用消化道黏膜保护剂,治疗组在此基础上加用微生态制剂"常乐康",用药后分别记录两组症状体征消失时间,显效率、总有率比较.结果:治疗组在粪便性状、便次正常,发热及呕吐消失时间均比对照组短,治疗组显效率明显高于对照组,总有效率94.5%(87/92)P＜0.01.结论:微生态制剂"常乐康"治疗婴幼儿急性腹泻不但缩短病程,而且提高治愈率,无副作用,可作为佐治婴幼儿急性腹泻病重建肠道微生态屏障的主要药物.     

具小扩散率种群的生长和灭绝行为

本文研究一类由反应扩散系统的初边问题描述的具常投放率的捕食食饵种群的生长模型,应用上、下解理论分析其解的长时间性态和具小扩散率种群的灭绝行为,给出参数环境．     

具有函数放养率或捕获率天敌有种内竞争系统的稳定性

本文讨论具有函数放养率或捕获率且天敌有种内竞争系统的稳定性．具体研究雌寄生蜂与寄主生态系统．进行了稳定性分析,种群灭绝分析,指出了理论上和实践意义．     

乳果糖联合美常安治疗成人功能性便秘的临床疗效观察

目的 观察乳果糖联合美常安(枯草杆菌肠球菌二联活菌)治疗成人功能性便秘的疗效及安全性.方法 采用随机分组、平行对照试验.按入选标准选择成人便秘患者64例,随机进入试验组和对照组,每组均为32例.试验组服用乳果糖15 mL bid和美常安500 mg tid;对照组服用乳果糖15 mL bid,疗程2周.观察排便次数、大便性状及便秘伴随症状的变化.结果 试验组48 h首次排便率(78.12％)明显高于对照组(53.33％)(P＜0.05);试验组平均每周排便次数明显高于对照组(P＜0.01);治疗后试验组和对照组大便恢复正常率分别为87.50％和60.00％(P＜0.05),试验组腹胀缓解率(84.00％)及排便困难缓解率(92.59％)均明显高于对照组(56.52％和65.38％)(均为P ＜0.05);试验组总有效率(93.75％)明显高于对照组(73.33％)(P＜0.05);两组均无严重不良反应发生.结论 乳果糖联合美常安治疗成人功能性便秘比单纯应用乳果糖治疗症状改善快、效果好、安全.     

一类食饵种群具有常数存放率的Kolmogorov系统的定性分析

本文对一类食饵种群具有常数存放率的Kolmogorov系统进行了定性分析,研究了系统平衡点的性态,证明了极限环的存在和唯一性．     

REPEATED ASSESSMENT OF THE ENDOGENOUS 24-HOUR PROFILE OF BLOOD PRESSURE UNDER CONSTANT ROUTINE*

The impact of environmental and behavioral factors on the 24-h profile of blood pressure (BP) has been well established. Various attempts have been made to control these exogenous factors, in order to investigate a possible endogenous circadian variation of BP. Recently, we reported the results of the first environmentally and behaviorally controlled laboratory study with 24-h recordings of BP and heart rate (HR) during maintained wakefulness. In this constant-routine study, a pronounced endogenous circadian rhythm of HR was found, but circadian variation of BP was absent. This result suggested that the circadian rhythm of BP observed in earlier controlled studies, with sleep allowed, was evoked by the sleep–wake cycle as opposed to the endogenous circadian pacemaker. In order to verify our previous finding during maintained wakefulness, we repeated the experiment five times with six normotensive, healthy young subjects. Statistical analyses of the hourly measurements of BP and HR confirmed the replicable presence of an endogenous circadian rhythm of HR, as well as the consistent absence of an endogenous circadian variation of BP. Thus, this study provided additional evidence that the 24-h profile of BP—as observed under normal circumstances—is the sole result of environmental and behavioral factors such as the occurrence of sleep, and has no endogenous circadian component. (Chronobiology International, 18(1), 85–98, 2001)     

DEVELOPMENT OF THE EGG OF THE MACKEREL AT DIFFERENT CONSTANT TEMPERATURES

1. Mackerel egg development was followed to hatching at constant temperatures of 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, and 24°C. Experiment showed that typical development could be realized only between 11° and 21°. 2. The length of the developmental period increases from 49.5 hours to 207 hours when the temperature is lowered from 21° to 10°C. 3. The calculated µ for the development of the mackerel egg is about 19,000 at temperatures above 15° and approximately 24,900 for temperatures below 15°C. 15° is, apparently, a critical temperature for this process. 4. The calculated values of µ for eight stages of development preceding hatching, i.e. 6 somites, 12 somites, 18 somites, 24 somites, three-quarters circles, four-fifths circles, five-sixths circles, and full circles, are essentially the same as the µ''s for hatching, indicating that the rate of differentiation up to hatching is governed by one process throughout. Critical temperatures for these stages approximate 15°. 5. The total mortality during the incubation period was least at 16°C. where it amounted to 43 per cent. At temperatures above and below this there was a steady increase in the percentage of mortality which reached 100 per cent at 10° and 21°.     

桃蚜、萝卜蚜发育速率在恒温和变温下的变化规律研究

本文报道桃蚜(Myzus persicae)萝卜蚜(Lipaphis erysimi)在一系列恒温、变温下的发育速率,结果表明:(1)恒温下发育速率与温度关系遵循有下上限的logistic曲线;(2)除了在恒温下随温度升高死亡率急剧增加、发育速率迅速下降的高温区(桃蚜:>28℃,萝卜蚜:>30℃)外,温度波动不改变发育速率与温度的函数关系;(3)变温下,在上述高温区内的发育速率仍基本按经典的logistic曲线随温度升高而上升,但在一温度下的发育速度又随停留时间延长而逐渐下降;在恒温下只能完成部分虫期发育的低温区,变温下发育速率亦接近经典的logistic曲线。文中根据上述结果提出了一个昆虫发育率在恒温和变温下变化规律的初步模型,并发现文献中有大量的基本符合这一模型例证的。     

THE EFFECT OF 40 HOURS OF CONSTANT WAKEFULNESS ON NUMBER COMPARISON PERFORMANCE

We investigated the effects of sleep loss and circadian rhythm on number comparison performance. Magnitude comparison of single-digits is robustly characterized by a distance effect: Close numbers (e.g., 5 versus 6) produce longer reaction times than numbers further apart (e.g., 2 versus 8). This distance effect is assumed to reflect the difficulty of a comparison process based on an analogous representation of general magnitude. Twelve male participants were required to stay awake for 40?h in a quasi-constant-routine protocol. Response speed and accuracy deteriorated between 00:00 and 06:00?h but recovered afterwards during the next day, indicating a circadian rhythm of elementary cognitive function (i.e., attention and speed of mental processing). The symbolic distance effect, however, did not increase during the nighttime, indicating that neither cumulative sleep loss nor the circadian clock prolongs numerical comparison processes. The present findings provide first evidence for a relative insensitivity of symbolic magnitude processing against the temporal variation in energy state. (Author correspondence: michael.steinborn@uni-tuebingen.de)     

THE EFFECT OF CONSTANT TEMPERATURES ON THE HATCHING OF EGGS AND SURVIVAL OF THE FRESHWATER SNAIL BIOMPHALARIA GLABRATA (SAY)

SUMMARY

The incubation period and percentage hatching of eggs of pigmented and unpigmented Biomphalaria glabrata at constant temperatures were investigated in the range 14 °C to 34 °C. In order to determine the influence of extreme temperatures on adult snails, specimens of the same species were exposed to 0 °C and 40 °C for selected time periods. The results indicate that sustained temperatures below 16 °C and above 32 °C are detrimental to the development and hatching of B. glabrata embryos. The optimum temperatures for incubation period and hatching differ from each other. As far as temperature is concerned, this foreign snail species should be capable of successfully colonizing the warmer parts of southern Africa.