The importance of the reinforcer as a time marker

Shifts in the psychometric function in the Free Operant Psychophysical Procedure (FOPP) have traditionally been explained by suggesting the pacemaker rate is proportional to the reinforcement rate (Behavioral Theory of Timing; BeT), or by direct associative competition between the two responses (Learning to Time; LeT). The application of these models assumes that the stimulus onset is the relevant time marker. Head-entries were reinforced in the second half of a stimulus (s1) and in the first half of a different stimulus (s2). During extinction, response times shifted earlier in s2 only, contrary to BeT. Competition between responses is an unlikely cause of the shift, contrary to LeT. We found a single-cycle correlation between the last food delivery and the time the rat stopped responding on s2. This correlation was also present in FOPP data. These results are consistent with the interpretation that the reinforcer, more than the stimulus onset, acted as the relevant time marker on this task.     

Comparison of Scalar Expectancy Theory (SET) and the Learning-to-Time (LeT) model in a successive temporal bisection task

The present research tested the generality of the "context effect" previously reported in experiments using temporal double bisection tasks [e.g., Arantes, J., Machado, A. Context effects in a temporal discrimination task: Further tests of the Scalar Expectancy Theory and Learning-to-Time models. J. Exp. Anal. Behav., in press]. Pigeons learned two temporal discriminations in which all the stimuli appear successively: 1s (red) vs. 4s (green) and 4s (blue) vs. 16s (yellow). Then, two tests were conducted to compare predictions of two timing models, Scalar Expectancy Theory (SET) and the Learning-to-Time (LeT) model. In one test, two psychometric functions were obtained by presenting pigeons with intermediate signal durations (1-4s and 4-16s). Results were mixed. In the critical test, pigeons were exposed to signals ranging from 1 to 16s and followed by the green or the blue key. Whereas SET predicted that the relative response rate to each of these keys should be independent of the signal duration, LeT predicted that the relative response rate to the green key (compared with the blue key) should increase with the signal duration. Results were consistent with LeT's predictions, showing that the context effect is obtained even when subjects do not need to make a choice between two keys presented simultaneously.     

Length of survival of patients with acquired immune deficiency syndrome in the United Kingdom.

An analysis of the lengths of survival of patients with the acquired immune deficiency syndrome presenting with different opportunistic diseases was performed using epidemiological data routinely collected at the PHLS Communicable Disease Surveillance Centre. The overall crude case fatality rate was 55.4% (93/168). The median survival times were: 21.2 months for Kaposi''s sarcoma, 12.5 months for Pneumocystis carinii pneumonia, and 13.3 months for other opportunistic infections. The shortest median survival time (6.6 months) was found for those with both Kaposi''s sarcoma and P carinii pneumonia. There were significant differences between durations of survival of patients with Kaposi''s sarcoma and those with all other diseases, which indicated impaired cellular immunity apart from opportunistic infections. This analysis shows that those with Kaposi''s sarcoma alone have the most favourable prognosis.     

The Regulation of Ant Colony Foraging Activity without Spatial Information

Many dynamical networks, such as the ones that produce the collective behavior of social insects, operate without any central control, instead arising from local interactions among individuals. A well-studied example is the formation of recruitment trails in ant colonies, but many ant species do not use pheromone trails. We present a model of the regulation of foraging by harvester ant (Pogonomyrmex barbatus) colonies. This species forages for scattered seeds that one ant can retrieve on its own, so there is no need for spatial information such as pheromone trails that lead ants to specific locations. Previous work shows that colony foraging activity, the rate at which ants go out to search individually for seeds, is regulated in response to current food availability throughout the colony's foraging area. Ants use the rate of brief antennal contacts inside the nest between foragers returning with food and outgoing foragers available to leave the nest on the next foraging trip. Here we present a feedback-based algorithm that captures the main features of data from field experiments in which the rate of returning foragers was manipulated. The algorithm draws on our finding that the distribution of intervals between successive ants returning to the nest is a Poisson process. We fitted the parameter that estimates the effect of each returning forager on the rate at which outgoing foragers leave the nest. We found that correlations between observed rates of returning foragers and simulated rates of outgoing foragers, using our model, were similar to those in the data. Our simple stochastic model shows how the regulation of ant colony foraging can operate without spatial information, describing a process at the level of individual ants that predicts the overall foraging activity of the colony.     

卵龄和脉冲持续时间对小鼠卵母细胞电活化效果的影响

实验研究了相同电场强度，一次脉冲条件下，不同脉冲持续时间和不同卵龄对小鼠卵母细胞电活化效果的影响，结果说明：（１）在场强０．４５ＫＶ／ｃｍ，一次脉冲持续时间为１０、２０和４０μｓ时，卵母细胞活化率很低，仅为９．８％，５．５％和１２％，当脉冲持续８０、１６０、３２０、６４０和２８０μｓ时，活化率明显升高，分别为３６．５％、５３．３％，５９．７％，５１．２％和３９．４％，脉冲持续时间对卵线细胞碎裂率影     

Reduction of variability of EEG occipital,parietal, and central alpha rhythms by visual feedback stimulation

Two experiments, each with 24 normal right-handed adults, examined variability of the response of EEG alpha rhythms during repeated visual stimulations that were contingent on the occurrence of those rhythms. Within-trial variability of alpha durations and no-alpha (alpha blocking) durations were recorded from bipolar derivations along two bilateral posterior-anterior lines. Variability was significantly lower for: (1) the contingent EEG connected to the stimulus compared to the contralateral EEG, which was recorded simultaneously but was not connected to the stimulus; (2) occipitoparietal EEGs compared to parietocentral EEGs; (3) alpha durations compared to no-alpha durations. Differences in variability among the four EEG locations on the left or the right side were significant for contingent EEGs but not for contralateral nonconnected EEGs. The results were interpreted to be a demonstration that feedback EEG method can be applied to research on the functional topography of an EEG response to sensory stimuli in terms of the reduction of variability of the response that can be achieved with feedback.     

A Spiking Neuron Model for Binocular Rivalry

We present a biologically plausible model of binocular rivalry consisting of a network of Hodgkin-Huxley type neurons. Our model accounts for the experimentally and psychophysically observed phenomena: (1) it reproduces the distribution of dominance durations seen in both humans and primates, (2) it exhibits a lack of correlation between lengths of successive dominance durations, (3) variation of stimulus strength to one eye influences only the mean dominance duration of the contralateral eye, not the mean dominance duration of the ipsilateral eye, (4) increasing both stimuli strengths in parallel decreases the mean dominance durations. We have also derived a reduced population rate model from our spiking model from which explicit expressions for the dependence of the dominance durations on input strengths are analytically calculated. We also use this reduced model to derive an expression for the distribution of dominance durations seen within an individual.     

北京石灰性草甸土冬小麦营养元素生物循环的特点与锰、锌肥效应

 本文用盆钵试验研究京郊石灰性草甸土冬小麦养分生物循环的结果表明：小麦对不同养分吸收、携出和归还数量的差异很大。根据随籽粒携出和以根茬归还的比例特点,可将养分划分为三种类型：1)低归还高携出型(N、P、K);2)低携出高归还型(Ca、Fe);3)中归还中携出型(Mg、Mn、Cu、Zn)。施锰增加植株对氮和锰的吸收及钾和锰随籽粒的携出;施锌则降低植株对锰的吸收和随籽粒携出的钾、钙、镁、铁、锰量。锰肥和锌肥有拮抗作用。     

秸秆还田对耕作黑土中小型土壤动物群落的影响

为了考察秸秆还田对耕作黑土中土壤动物群落结构的影响,2009年到2011年在黑龙江省海伦市进行了定点实验,调查了样地A(17kg秸秆+含高浓度催腐剂还田)、样地B(8.5kg秸秆+含低浓度催腐剂还田)、样地C(对照样地),样地D(8.5kg秸秆还田),样地E(17kg秸秆还田)的中小型土壤动物群落结构。共获取中小型土壤动物21779只,分别隶属于58个类群。其中,甲螨亚目、姬跳虫科、棘跳虫科与驼跳科4个类群土壤动物在本地区是最适应环境变化的土壤动物类群。土壤动物群落结构分析表明,对照样地C中土壤动物密度最高(46591.67只/m~2),土壤动物类群最多(17.17),土壤动物优势度指数最大(0.37),样地D中土壤动物丰富度指数最多(2.63),样地A中土壤动物多样性指数最高(1.72),样地B中土壤动物均匀性最高(0.64)。同时,各样地土壤动物基本都具有表聚性,样地A中土壤动物更趋于生存于上层土壤。综合比较分析表明,样地A秸秆还田方式相对来说最利于土壤动物生存。主成分分析表明,不同秸秆还田方式对土壤动物密度、甲螨亚目动物类群、节跳虫科类群、前气门亚目类群影响较大,是耕作黑土中对秸秆还田方式反应敏感的土壤动物指标,今后可以作为考察耕作黑土秸秆还田肥力效应的评价指标。另外,CAA分析表明:受土壤环境因子影响较大的土壤动物类群多为研究区域内优势类群与常见类群,土壤动物的密度与土壤中有机质、有机碳、碳氮比与全磷的含量关系最为密切。     

Foraging,Delayed Maturation,and Advantages of Cooperative Breeding in White-winged Choughs,Corcorax melanorhamphos

White-winged choughs live in groups which cooperate in all aspects of rearing young, affording an opportunity to examine the influence of cooperation on foraging behavior. The amount of food choughs forage for themselves and feed to young increases with age, supporting the idea that individuals which dispersed to breed would have difficulty in rearing young. When feeding nestlings, individuals in the two larger groups returned to the nest less often and with larger loads than the individuals in the smallest group. Choughs in the smallest group also consumed less food at the beginning of each trip from the nest than those in the larger groups. We suggest that these measures indicate the greater efficiency allowed to individuals in larger groups when foraging from the nest. In all groups, individuals returning to the nest simultaneously with other group members carried smaller loads than those returning alone. We propose that returning in groups enables all nestlings of asynchronously hatched broods to obtain sufficient food.     

Speciation durations and Pleistocene effects on vertebrate phylogeography.

An approach applied previously to avian biotas is extended in this paper to other vertebrate classes to evaluate Pleistocene phylogeographic effects and to estimate temporal spans of the speciation process (speciation durations) from mitochondrial (mt) DNA data on extant taxa. Provisional molecular clocks are used to date population separations and to bracket estimates of speciation durations between minimum and maximum values inferred from genetic distances between, respectively, extant pairs of intraspecific phylogroups and sister species. Comparisons of genetic-distance trends across the vertebrate classes reveal the following: (i) speciation durations normally entail at least two million years on average; (ii) for mammals and birds, Pleistocene conditions played an important role in initiating phylogeographic differentiation among now-extant conspecific populations as well as in further sculpting pre-existing phylogeographic variety into many of today''s sister species; and (iii) for herpetofauna and fishes, inferred Pleistocene biogeographic influences on present-day taxa differ depending on alternative but currently plausible mtDNA rate calibrations.     

The Troms? heart study: coffee consumption and serum lipid concentrations in men with hypercholesterolaemia: an randomised intervention study.

In a 10 week trial to assess the effects of coffee consumption and coffee brewing methods on serum cholesterol concentrations 33 men with hypercholesterolaemia were randomly assigned to: continue with their usual coffee intake; stop drinking coffee altogether; or stop drinking coffee for five weeks, thereafter drinking either boiled or filter coffee. Cholesterol concentrations fell significantly in all subjects abstaining for the first five weeks compared with subjects not giving up and continued to fall in those abstaining for 10 weeks. Cholesterol concentrations rose again in subjects returning to boiled coffee but remained the same in those returning to filter coffee. Abstention from heavy coffee drinking is an efficient way of reducing serum cholesterol concentrations in men with hypercholesterolaemia. The extent to which the brewing method affects this relation requires further study.     

雄安新区上游白洋淀流域水质净化提升目标下的生态恢复格局优化

白洋淀流域是雄安新区重要的淡水来源之一,流域内退耕政策在改善水质同时大幅降低了农田面积。如何通过退耕空间规则的优化权衡水质净化效率与农田面积是亟待解决的问题。通过设置基于不同退耕规则的情景,并与实际情景对比,提出了退耕规则的优化方案。结果表明：相同面积下,河岸带退耕的水质净化效率高于坡耕地退耕;相同退耕规则下,退耕还林驱动的水质净化效率高于还灌,还草;单位面积河岸带退耕的水质净化效率随缓冲区距离增加而降低;300m河岸带退耕还林情景下的水质净化率提升高于其他所有模拟情景,也比实际退耕情景（2015）高,同时农田面积降幅也低于实际情景。研究表明通过对退耕规则进行空间优化不仅能够满足区域水质净化提升的目标,还有利于保障区域农田面积,减少生态系统服务间的权衡。     

Effects of pulse ultrasonic irradiation on the lag phase of Saccharomyces cerevisiae growth

Aims: This paper presents an analysis of lag phase phenomena in Saccharomyces cerevisiae growth as a function of ultrasonic irradiation. Methods and Results: Pulse irradiation treatments were performed by a 20 kHz ultrasonic transducer with different durations and energies. Data obtained from experiments were then employed to estimate growth parameters by specific transfer function. The significance of the different lag times in response to ultrasonic irradiation was analysed. The results showed that the yeast growth in lag phase responded to the irradiated ultrasonic of 20 min more than the 10 min. The ultrasonic energies between 330 and 360 W s m^?3 could decrease lag time up to 1 h compared to the sample without ultrasonic irradiation. Conversely, the treatments with energies higher than 850 W s m^?3 were able to extend the lag time and decrease the yeast growth. Conclusions: The lag durations of S. cerevisiae were changed significantly by different ultrasonic irradiations, energies and durations. In particular, sufficient irradiation energies reduced the lag time, resulting in accelerated yeast growth. In contrast, high energy could inactivate growth by increasing the lag time. Significance and Impact of the Study: This work provides an alternative technique to either accelerate or inactivate the S. cerevisiae lag phase. The approach can be developed in experiment designed to control the yeast growth by ultrasonic irradiation as assistance in the environments.     

Cell responses to single pheromone molecules may reflect the activation kinetics of olfactory receptor molecules

Olfactory receptor cells of the silkmoth Bombyx mori respond to single pheromone molecules with "elementary" electrical events that appear as discrete "bumps" a few milliseconds in duration, or bursts of bumps. As revealed by simulation, one bump may result from a series of random openings of one or several ion channels, producing an average inward membrane current of 1.5 pA. The distributions of durations of bumps and of gaps between bumps in a burst can be fitted by single exponentials with time constants of 10.2 ms and 40.5 ms, respectively. The distribution of burst durations is a sum of two exponentials; the number of bumps per burst obeyed a geometric distribution (mean 3.2 bumps per burst). Accordingly the elementary events could reflect transitions among three states of the pheromone receptor molecule: the vacant receptor (state 1), the pheromone-receptor complex (state 2), and the activated complex (state 3). The calculated rate constants of the transitions between states are k(21)=7.7 s(-1), k(23)=16.8 s(-1), and k(32)=98 s(-1).     

Dyar's Rule and the Investment Principle: optimal moulting strategies if feeding rate is size-dependent and growth is discontinuous

We consider animals whose feeding rate depends on the size of structures that grow only by moulting (e.g. spiders'' legs). Our Investment Principle predicts optimum size increases at each moult; under simplifying assumptions these are a function of the scaling of feeding rate with size, the efficiency of moulting and the optimum size increase at the preceding moult. We show how to test this quantitatively, and make the qualitative prediction that size increases and instar durations change monotonically through development. Thus, this version of the model does not predict that proportional size increases necessarily remain constant, which is the pattern described by Dyar''s Rule. A literature survey shows that in nature size increases tend to decline and instar durations to increase, but exceptions to monotonicity occur frequently: we consider how relaxing certain assumptions of the model could explain this. Having specified various functions relating fitness to adult size and time of emergence, we calculate (using dynamic programming) the effect of manipulating food availability, time of hatching and size of the initial (or some intermediate) instar. The associated norms of reaction depend on the fitness function and differ from those when growth follows Dyar''s Rule or is continuous. We go on to consider optimization of the number of instars. The Investment Principle then predicts upper and lower limits to observed size increases and explains why increases usually change little or decline through development. This is thus a new adaptive explanation for Dyar''s Rule and for the most common deviation from the Rule.     

Weddell seals do not lengthen calls in response to conspecific masking

Some mammalian and avian species alter their vocal communication signals to reduce masking by background noises (including conspecific calls). A preliminary study suggested that Weddell seals (Leptonychotes weddellii) increase the durations of some underwater call types when overlapped by another calling seal. The present study examined the durations and overlapping sequences of Weddell seal calls recorded in Eastern Antarctica. The calling rate, call type (13 major categories), total duration, numbers of elements per call and overlapping order of 100–200 consecutive calls per recording location were measured. In response to increased conspecific calling rates, the call durations and numbers of elements (within repeated-element call types) did not change or became shorter. Calls that were not overlapped were 3.8?±?6.1 s long, the first call in a series of overlapped calls was 14.4?±?15.7 s and subsequent calls in an overlapping series were 6.5?±?10.3 s. The mean durations of non-overlapped and overlapped calls matched random distributions. Weddell seals do not appear to be adjusting the durations or timing of their calls to purposefully avoid masking each other’s calls. The longer a call is, the more likely it is to overlap another call by chance. An implication of this is that Weddell seals may not have the behavioural flexibility to reduce masking by altering the temporal aspects of their calls or calling behaviours as background noises (natural and from shipping) increase.     

持续低温弱光对黄瓜叶片气体交换、叶绿素荧光猝灭和吸收光能分配的影响

持续常温弱光(25℃/18℃,l00umol m-2 s-1)、低温弱光(12℃/12℃,100 umol m-2 s-1和7℃/7℃,l00μmolm-2s-1)均导致黄瓜生长减慢或停滞、叶绿素含量、气孔导度和净光合速率、光合电子传递速率下降以及胞间CO2浓度上升.常温弱光和12℃弱光处理对光系统II的最大光化学效率Fv/Fm无显著影响,而7℃弱光处理导致Fv/Fm的可逆性下降.常温弱光和7℃、12℃弱光处理均导致了光化学反应速率的降低以及天线热耗散和反应中心过剩能量的增加.在胁迫后,12℃弱光0比7℃弱光更有利于植株光合功能的恢复.     

Mental Summation of Temporal Duration within and across Senses

Perceiving, memorizing, and estimating temporal durations are key cognitive functions in everyday life. In this study, a duration summation paradigm was used to examine whether summation of temporal durations introduces an underestimation or overestimation bias, and whether this bias is common to visual and auditory modalities. Two within- or across-modality stimuli were presented sequentially for variable durations. Participants were asked to reproduce the sum of the two durations (0.6–1.1 s). We found that the sum of two durations was overestimated regardless of stimulus modalities. A subsequent control experiment indicated that the overestimation bias arose from the summation process, not perceptual or memory processes. Furthermore, we observed strong positive correlations between the overestimation bias for different sensory modalities within participants. These results suggest that the sum of two durations is overestimated, and that supra-modal processes may be responsible for this overestimation bias.