Circadian clock in photoperiodic time measurement: a test of the Bünning hypothesis

A technique has been developed for effectively separating the direct inductive effect of a light signal from its effect on the phase of the rhythm of sensitivity to photoperiodic induction. With this technique it has been shown that a 75-minute pulse of light per day, when appropriately positioned with respect to the circadian activity cycle of the sparrow Passer domesticus, is sufficient to produce a response normally produced only by long days. The results cannot be interpreted in terms of a requirement of an absolute amount of either darkness or light and offer strong confirmation of Bünning's hypothesis concerning the mechanism of photoperiodic time measurement.     

信息时代图书馆员信息素养教育探析

21世纪将是人类空前的信息化时代,作为当代图书馆事业的主体,图书馆员的素质是影响图书馆事业建设和发展的决定性因素。本文概述了图书馆员信息素养的涵义和内容。并结合对北华大学图书馆的实践调查结果分析提出了加强图书馆员综合信息素养教育的途径和方法。     

Temporal order judgement and reaction time

A model which predicts judgment of the temporal order of stimuli from simple reaction time is proposed. Visual data show covariation of the two measures with luminance changes, and suggest that (i) temporal order judgments reflect a biased response criterion and (ii) the motor component of reaction time has little variability relative to variance in receptor system latency.     

Mechanism of transmitter release: voltage hypothesis and calcium hypothesis

The calcium hypothesis of synaptic transmission has been challenged by experimental results using the crayfish neuromuscular junction that suggest that presynaptic depolarization can trigger transmitter release directly without calcium influx. Results from electrophysiological experiments using the same preparation do not support this voltage hypothesis, but are consistent with the calcium hypothesis. Voltage may modulate, but not elicit, transmitter release.     

Evoked potentials and auditory reaction time in monkeys

Monkeys with bipolar stimulating and recording electrodes in primary auditory cortex were trained to release a key to the onset of a pure tone. Substitution of direct cortical stimulation for the pure tone resulted in a reduction of 15 milliseconds In the latency of the behavioral response. This changed latency agreed with the latency of the primary evoked potential recorded from the animals. Systematic related changes in the amplitude of the central response and in the latency of the behavioral response followed changes in the intensity and frequency of the acoustic stimulus.     

Relationship between reaction time and electroencephalographic alpha phase

Demonstrations of a relationship between human 8 to 13 per second (alpha) electroencephalographic activity and simple visual reaction time can be made at reliable levels of confidence by (i) sampling reaction times to stimuli given at phases of the alpha cycle 10 msec apart, (ii) selecting the phase with the slowest reaction times, and (iii) collecting enough reaction times to stimuli at this and some other control phase for statistical comparison.     

Web2.0时代的信息传播与公共关系

Web2.0时代,信息传播有别于传统媒体的特点。人们在利用新的媒体进行公共关系工作时,需要对公共关系的特征进行针对性的解读,更需要制定相应的公共关系策略。     

信息时代专业图书馆建设与服务

针对信息社会的发展,对专业图书馆的建设与服务从整体布局、资源建设、人才队伍建设和服务模式等方面提出了自己的观点,旨在提升信息服务的及时性、准确性和全面性,进一步扩大资源共享。     

浅谈信息时代的教育方式

步入21世纪后,多媒体技术随着Internet的发展而日趋成熟,教育方式发生了很大的变化。计算机辅助教育是信息时代的现代化教学方式,也是当今教育技术发展的新趋向。本文针对信息时代的教育方式,论述了计算机辅助教育的内容、作用及意义。     

Reverse methanogenesis: testing the hypothesis with environmental genomics

Microbial methane consumption in anoxic sediments significantly impacts the global environment by reducing the flux of greenhouse gases from ocean to atmosphere. Despite its significance, the biological mechanisms controlling anaerobic methane oxidation are not well characterized. One current model suggests that relatives of methane-producing Archaea developed the capacity to reverse methanogenesis and thereby to consume methane to produce cellular carbon and energy. We report here a test of the "reverse-methanogenesis" hypothesis by genomic analyses of methane-oxidizing Archaea from deep-sea sediments. Our results show that nearly all genes typically associated with methane production are present in one specific group of archaeal methanotrophs. These genome-based observations support previous hypotheses and provide an informed foundation for metabolic modeling of anaerobic methane oxidation.     

Chemical messengers in development: a hypothesis

The hypothesis that physiological and developmental regulatory mechanisms are similar has been presented. Well-known developmental systems chosen illustrate the capability of the model to suggest a simple mechanism underlying the effects on development of a diverse group of chemicals. This hypothesis might be applied to other systems including the induction of the lens, limb regeneration, and the induction of the head of hydra (124). I have proposed this hypothesis not only because it permits consideration of a complex and varied array of experimental observations as reflections of a simple basic biochemical mechanism, but because recent technical advances in instrumentation and methods allow it to be directly tested. The fluorescent antibody method for the cytochemical measurement of cyclic nucleotides provides a means for investigating changes in the concentrations of cyclic nucleotides in developing cells and could also be used to detect neurotransmitters in developing cells. Similarly, the scanning electron microscope in the emitted x-ray mode provides a method for measuring changes in the content and distribution of cations within developing cells. The hypothesis presented here suggests pleasing asceticism on the part of eukaryotes. It suggests that simple derivatives of metabolites, including neurotransmitters and cyclic nucleotides, are linked together as regulatory molecules throughout the eukaryotes. The neurotransmitters are suggested to have a more general role in information transmission in eukaryotes than is generally accepted. They are hypothesized to have progressed during evolution from being intracellular messengers to a role as intercellular messengers for the relatively slow communication of developmental informatbn; and, finally, this process has culminated with their participation in the rapid intercellular communication mediated by nerves. The thought that the complex pictures of physiological regulation and of the construction of a complex multicellular organism like man might be painted with so few colors is quite satisfying.     

Depressive disorders: toward a unified hypothesis

Our scientific understanding of psychiatric syndromes, including the phenomena of depression, has been hampered because of: (i) the use of metapsychological concepts that are difficult to test; (ii) methodological and linguistic barriers that prevent communication among psychoanalysts, behaviorists, experimental psychologists, and psychiatrists; and (iii) the reluctance of psychiatrists to accept animal models as possible approximations of certain aspects of human psychopathology. We have attempted to demonstrate that the animal models simulate some of the central features of clinical depression (for example, helplessness and object loss), thereby allowing one to rigorously investigate them from developmental, behavioral, and biochemical perspectives. The object loss model, as a concrete version of a metapsychological-psychoanalytic concept, has enabled primatologists to study the disruption of an attachment bond. The behavioral model accommodates this concept to a broader generalization: loss of reinforcement or loss of control over reinforcement. We have reviewed the evidence that these processes involve the diencephalic centers of reward or reinforcement, thereby permitting integration of the psychoanalytical and behavioral formulations with the biochemical hypotheses. Also, we have presented data strongly suggesting that the breaking of an attachment bond in the primate represents significant loss of reinforcement that induces helplessness and disrupts motivated behavior. Finally, we have argued that the depressive syndrome could be caused by interactions of genetic, chemical, developmental, and interpersonal factors, all of which impinge on the diencephalic centers of reinforcement.     

Serial errors in human learning: a test of the McCrary-Hunter hypothesis

An experiment was conducted on 120 human subjects to test the hypothesis that the probability distribution of serial errors is an invariant property of rote memorization. Contrary to the hypothesis, the relative difficulty function was significantly affected by ability to learn. There was a systematic tendency (p < .05) for fast learners to commit proportionately more errors in the middle of the sequence.     

Erythropoietin: hypothesis of action tested by analog computer

The action of erythropoietin on the pool of undifferentiated bone marrow cells has been examined with the aid of a model tested with an analog computer. The model is consistent with reported experimental results. The essential aspects of the action are (i) the effect is exerted during the S phase of the cell's cycle; (ii) " effective " erythropoietin is present in the cell only during G(1) and part of S; and, (iii) hormone molecules survive in the cell for only a limited time in effective form and require a certain time to assume this form.