Polyploidy in the common tree toad Hyla versicolor Le Conte

A karyotype of the first known naturally occurring anuran polyploid in North America is described. Hyla versicolor, the common tree toad, is tetraploid (2n-->4n=48). Individual chromosmes representing, each set of four of the Hyla versicolor karyotype correspond closely with those of the diploid (2n = 24) Hyla andersonii karyotype.     

大蟾蜍卵孵化的温度效应研究

为了解大蟾蜍卵的孵化率、发育起点温度、发育有效积温和蝌蚪成活率,将产出当天的大蟾蜍卵采集回实验室,分别置于5个不同温度(10℃、15℃、20℃、25℃和30℃)下孵化,观察和测量记录卵的孵化率、孵化后3 d蝌蚪的成活率、体长及每个温度下卵的发育历期。光照周期设为14L∶10D。结果表明:温度对大蟾蜍卵的孵化率影响显著;孵化后3 d蝌蚪的成活率随着温度的升高而降低,30℃下孵化的蝌蚪在2 d之内全部死亡;温度对大蟾蜍卵孵化后3 d蝌蚪全长的影响极显著(F=55.592,df=4,N=50,p<0.000 1),大蟾蜍的卵孵化后3 d蝌蚪的全长随着温度的升高而增加;应用直线回归法和直接最优化法算得的大蟾蜍卵的发育起点温度和有效积温分别为0.35℃、68.64℃/d和0.15℃、69.29℃/d。     

Contributions of the visual ventral pathway to long-range apparent motion

Objects displaced intermittently across the visual field will nonetheless give an illusion of continuous motion [called apparent motion (AM)] under many common conditions. It is believed that form perception is of minor importance in determining AM, and that AM is mediated by motion-sensitive areas in the "where" pathway of the cortex. However, form and motion typically interact in specific ways when natural objects move through the environment. We used functional magnetic resonance imaging to measure cortical activation to long-range AM, compared to short-range AM and flicker, while we varied stability of structural differences between forms. Long-range AM activated the anterior-temporal lobe in the visual ventral pathway, and the response varied according to the form stability. The results suggest that long-range AM is associated with neural systems for form perception.     

Correspondence matching in apparent motion: evidence for three-dimensional spatial representation

The path of an object in apparent motion depends on correspondence matching, the decision that images seen at different places and at different times represent the same object. One determinant of correspondence is proximity. Still debated, however, is whether proximity is defined in a two- or three-dimensional spatial representation. Observers judged the motion path taken by an object with two neighbors of different apparent depth. Given similar two-dimensional distances, objects moved toward the neighbor of the same apparent depth. This is evidence that correspondence operates in a three-dimensional spatial representation.     

Optomotor response in human infants to apparent motion: evidence of innateness

Human infants were placed inside a stationary cylinder containing a columnar pattern like that used to elicit the optokinetic reflex. By sequential illumnination of the columns, the pattern was made to appear to rotate. Optokinetic nystagmus was clearly evoked in 64.7 percent of the subjects, with a weak-positive response in an additional 11.8 percent.     

不同发育期大蟾蜍幼体的热适应

为了解大蟾蜍幼体的热适应特性,并验证最适性模型,应用温度梯度槽对不同发育期大蟾蜍幼体的最适温度、最高逃避温度和最高致死温度进行了研究。大蟾蜍蝌蚪期的最适温度为(15.77±2.21)℃,变态期为(24.26±2.88)℃,幼体期为(27.62±2.58)℃。在每一个发育期,幼体都有2个最适温度峰值,这一结果与最适性模型的预测完全一致。不同发育期大蟾蜍幼体的最适温度存在显著性差异(F=282.521,P<0.001,df=2,N=150)。蝌蚪期的最高逃避温度为(32.45±1.25)℃,变态期为(35.11±1.29)℃,幼体期为(37.83±1.72)℃。不同发育期大蟾蜍幼体的最高逃避温度间存在显著差异(F=119.585,P<0.001,df=2,N=90)。蝌蚪期的最高致死温度为(36.56±1.3)℃,变态期为(38.45±1.53)℃,幼体期为(39.96±1.39)℃。不同发育期大蟾蜍幼体的最高致死温度存在显著差异(F=35.372,P<0.001,df=2;N=60)。     

Aldosterone-induced protein in toad urinary bladder

Simultaneous electrophysiological and biochemical experiments demonstrated a specific aldosterone-induced protein in paired urinary hemibladders isolated from the toad Bufo marinus. Whenever aldosterone stinlmulated short-circuit current, aldosterone specifically increased [(35)S] methionine incorporation into a low-molecular-weight protein (about 12,000). Comparative studies with dexamethasone and insulin and inhibitory studies with spironolactone and actinomycin D suggest mineralocorticoid specificity.     

Glutamate uptake by the isolated toad brain

The isolated toad brain accumulates L-glutamate against strong concentration gradients until a tissue-to-medium concentration ratio of about 3000 : 1 is attained. The accumulated glutamate does not equilibrate with most of the endogenous tissue glutamate but is converted rapidly to glutamine and released into the medium. This mechanism may be involved in the preservation of low extracellular levels of cerebral glutamate.     

Perception of risk

Studies of risk perception examine the judgements people make when they are asked to characterize and evaluate hazardous activities and technologies. This research aims to aid risk analysis and policy-making by providing a basis for understanding and anticipating public responses to hazards and improving the communication of risk information among lay people, technical experts, and decision-makers. This work assumes that those who promote and regulate health and safety need to understand how people think about and respond to risk. Without such understanding, well-intended policies may be ineffective.     

氨酪酸对离体蟾蜍心脏活动的影响

采用常规离体蟾蜍心脏灌流法 ,通过生理记录仪经张力换能器系统描记心脏活动 ,探讨氨酪酸(GABA)对离体蟾蜍心脏活动的影响 ;结果表明 ,GABA明显增强了蟾蜍离体心脏收缩和舒张活动 ,并在一定范围内存在剂量依赖性 ;GABAA 受体阻断剂印防己毒素和GABAB 受体激动剂巴氯酚对心脏的收缩和舒张均有抑制作用 ;GABA能够加强肾上腺素对离体蟾蜍心脏的增强作用 ,而逆转乙酰胆碱的抑制作用 ;在酚妥拉明存在的条件下 ,GABA的正性肌力作用受到抑制 ;而在普萘洛尔和阿托品分别存在的条件下 ,GABA能够逆转普萘洛尔对离体蟾蜍心脏的抑制作用 ,而加强阿托品对离体蟾蜍心脏的增强作用 ;以上这些药品对心率均无明显影响。GABA对离体蟾蜍心脏的增强作用是通过GABAA 受体正性肌力作用和GABAB 受体负性肌力作用共同调节的 ,在生理状态下 ,以GABAA 受体作用为主 ,GABA的正性肌力作用可能是通过肾上腺素能系统中的α1 受体介导来完成的 ,而与胆碱能系统可能无关     

Perception of Ultrasound

Ultrasonic vibrations can be perceived as audible sounds when a piezoelectric transducer is pressed against certain areas of the human body. In the range of frequencies investigated (20 to 108 kcy/sec), the threshold of perception seemed to lie near the threshold of feeling (about 10(-4) watt/cm(2)), and the perceived audible sound appeared to be between 8 and 9 kcy/sec, as judged by six test subjects. The threshold of perception and the perceived frequency appear to be dependent upon the hearing characteristics of the individual.     

Timing of the apparent effects of cloud seeding

The average hourly precipitation amounts, on 96 experimental days without cloud seeding in the Whitetop experiment, show a marked maximum between 4 and 7 o'clock in the afternoon, presumably reflecting the convection activity caused by heating of the ground occurring during an earlier period. No such maximum is observed on the 102 days with seeding. The hypothetical explanation presupposes that seeding with silver iodide creates early general cloudiness, which prevents ground temperatures from rising to levels usually attained on days without seeding. This hypothesis may explain not only the mechanism of the loss in rain in the Whitetop experiment, apparently induced by seeding, but also may explain certain phenomena noticed in the Grossversuch III experiment.     

乡村居民灾害感知分析

[研究目的]为政府减灾战略的制定和实施及新农村建设提供科学依据.[方法]采用问卷调查和入户访谈的方法,对宝鸡市陈仓区桥镇4个自然村居民的灾害感知状况进行了分析.[结果]76.47%被访者表示担心暴雨,55.88%的表示担心洪水;14.71%的被调查者平时不会准备防灾补给品,17.65%的被调查者很少会注意灾害预报信息;在灾害信息获取方面,94.12%的被调查者通过电视新闻或节目获取,55.88%的通过广播或村委会通知获取;灾害发生时,79.41%的被调查者第一时间选择到附近安全点避难,2.94%的人选择等待政府安排;灾害发生后,90%的被调查者会向家人求助,50%的向外地亲友和村委会求助.[结论]当地居民主要担心暴雨和洪水灾害;居民多采用传统防灾措施应对灾害;.灾害信息获取以大众传媒为主,渠道单一;居民灾后寻求帮助的可能性随着社会距离(社会关系的疏远度)的增加呈现衰减趋势.     

Curvilinear motion in the absence of external forces: naive beliefs about the motion of objects

University students were asked to draw the path a moving object would follow in several different situations. Over half of the students, including many who had taken physics courses, evidenced striking misconceptions about the motion of objects. In particular, many students believed that even in the absence of external forces, objects would move in curved paths.     

美国英语与美国人的时间观

语言作为文化的一部分，是文化的重要表达形式，透过一个民族的语言层面，可以窥见这个民族的文化形态。本文试图通过分析美国英语与时间有关的用语，来探讨美国人支配、利用时间的方式，以及时间这一无声的语言在美国文化中所蕴含的意义     

Moving visual scenes influence the apparent direction of gravity

When an observer views a wide-angled display rotating around his line of sight, he both feels his body tilted and sees a vertical straight edge tilted opposite to the moving stimulus. Displacement of the perceived vertical increases with stimulus speed to reach a maximum (averaging 15 degrees) at 30 degrees per second.