游动的智能代理人

以蚂蚁和其它群居性昆虫为模型，计算机科学家开发了互相合作以解决复杂问题——例如在繁忙的通信网络中重新安排通信源——的软件代理人。     

当天空不是极限时

智利诗人聂鲁达用一句话概括了他的命运观，即“每次偶然的际遇都是早有安排”。而天体物理学家Neil deGrasse Tyson的观点与之类似，无论是他在思索银河系的演变过程还是在思索个人的人生经历时都持这样的观点。41岁的Tyson的人生际遇把他推到了现在的职位上——美国自然史博物馆海登天文馆(于今年2月重新开放)的罗斯馆长一职。     

Munchausen Syndrome by Proxy: medical diagnostic criteria

Medical diagnostic criteria for Munchausen Syndrome by Proxy are presented. The strength of the known facts may vary from case to case, and thus there may be different degrees of diagnostic conviction. Therefore, diagnostic criteria for a definitive diagnosis, and a possible diagnosis of Munchausen Syndrome by Proxy are provided. Because the gathering of evidence in a case may, ultimately, diminish or exclude the diagnosis of Munchausen Syndrome by Proxy, diagnostic criteria for the inconclusive determination and the definitely excluded diagnosis are also enunciated.     

Children's recall of medical experiences: the impact of stress

OBJECTIVE: The study compared children's reports of two medical events, to assess the effects of the type of event on children's recall. Additionally, the study examined the effect of props on children's event reports. METHOD: Twenty children between the ages of 37 and 67 months were interviewed following either a voiding cysto-urethrogram (VCUG) or a pediatric assessment (PA) at a hospital. Interviews were conducted between 6 and 8 days after the event and included a doll and prop items. RESULTS: Ratings of stress were significantly higher for children who underwent the VCUG than those who underwent the PA. Children who experienced the VCUG procedure reported more correct information than the children who experienced the PA. Age was correlated with the total amount of correct information reported. Stress levels were correlated with both errors and accuracy of information. CONCLUSIONS: Children who experienced a stressful medical procedure remembered more than children who experienced a neutral medical event, although this increase in amount recalled was at the expense of accuracy. These findings suggest that stress impacts negatively on recall: however, the unique and structured nature of the VCUG procedure compared to the PA, and the familiarity of the PA prop items to the children who experienced the VCUG procedure, may also have contributed to differences in recall of the two events.     

Toddlers' and Preschoolers' Experience in Family Day Care: Age Differences and Behavioral Correlates

One hundred and twelve children, 56 toddlers and 56 preschoolers, were observed in their family child care settings to determine whether toddlers cared for in settings that also included preschoolers were, relative to the preschoolers, receiving more or less high-quality care and/or whether their functioning at child care appeared to be more or less dependent on aspects of the care providers’ interactions with the children. Quality of care was analyzed along two dimensions: sensitive/supportive care and structured care. Four indices of child functioning at child care were examined: integration in social activities, attention, positive mood, and angry/aggressive behavior. Results indicate that toddlers received less sensitive, supportive care than preschoolers in these mixed-age settings and toddlers were less socially integrated and less engaged in activities in the child care setting. Preschoolers displayed increased levels of angry/aggressive behavior relative to toddlers. In addition, associations of care provider behaviors and child functioning were larger for toddlers than preschoolers, suggesting that toddlers were more dependent on caregiver support for more successful functioning in these family child care settings. For both toddlers and preschoolers, care provider behavior and child functioning was generally poorer in settings with more children.     

Human computers: the first pioneers of the information age

Before computers were machines, they were people. They were men and women, young and old, well educated and common. They were the workers who convinced scientists that large-scale calculation had value. Long before Presper Eckert and John Mauchly built the ENIAC at the Moore School of Electronics, Philadelphia, or Maurice Wilkes designed the EDSAC for Manchester University, human computers had created the discipline of computation. They developed numerical methodologies and proved them on practical problems. These human computers were not savants or calculating geniuses. Some knew little more than basic arithmetic. A few were near equals of the scientists they served and, in a different time or place, might have become practicing scientists had they not been barred from a scientific career by their class, education, gender or ethnicity.     

物理科学：宇宙新闻

超新星1987A、银河系中心、暗物质透镜等等。1989年1月，John Horgan出席了在波士顿举行的美国天文学会会议。下面是他对该会议上讨论的四个专题所作的报导：     

Non-exercise estimation of VO(2)max using the International Physical Activity Questionnaire

Non-exercise equations developed from self-reported physical activity can estimate maximal oxygen uptake (VO(2)max) as well as submaximal exercise testing. The International Physical Activity Questionnaire (IPAQ) is the most widely used and validated self-report measure of physical activity. This study aimed to develop and test a VO(2)max estimation equation derived from the IPAQ-Short Form (IPAQ-S). College-aged males and females (n = 80) completed the IPAQ-S and performed a maximal exercise test. The estimation equation was created with multivariate regression in a gender-balanced subsample of participants, equally representing five levels of fitness (n = 50) and validated in the remaining participants (n = 30). The resulting equation explained 43% of the variance in measured VO(2)max (SEE = 5.45 ml·kg(-1)·min(-1)). Estimated VO(2)max for 87% of individuals fell within acceptable limits of error observed with submaximal exercise testing (20% error). The IPAQ-S can be used to successfully estimate VO(2)max as well as submaximal exercise tests. Development of other population-specific estimation equations is warranted.     

Practicing a maximal performance task: a cooperative strategy for muscle activity

The effect of practice on predicting elbow flexion movement time was studied. Participants (N = 18) performed 400 elbow flexion trials to a target in the horizontal plane. The trials were distributed equally over four sessions. The goal was to decrease the movement time (MT) for the same degree of accuracy. The electromyographic (EMG) activity of the biceps and triceps brachii was monitored with standard Beckman Ag/AgCl surface electrodes. The EMG measures formed two variable sets within one prediction equation. One variable set was composed of the onset of muscle activity relative to the start of movement (motor time) and the duration of muscle activity. The other variable set consisted of the mean amplitude value of the entire burst and of the first 30 ms (Q30) of activity. As the maximal speed of limb movement increased, the duration of muscle activity (motor time and EMG duration) decreased, and the magnitude of muscle activity (MAV and Q30) increased. Most of the change in the duration of muscle activity occurred in Session 1, while the magnitude of muscle activity continued to increase until Session 3. Multiple regression analysis revealed a cooperative strategy between the magnitude and duration of muscle activity. Early in learning, participants adjusted the magnitude of muscle activity to increase limb movement speed. As practice continued, alterations in the duration of muscle activity became more important, while the magnitude changes were less involved. Late in learning, both dimensions of muscle activity were used to decrease MT. We suggest that the interplay between the magnitude and duration of muscle activity may be due to: (a) cognitive factors related to the division of attention in a motor skill, (b) an increase in the frequency of motor unit firing that affects both dimensions of muscle activity, or (c) some combination of (a) and (b).