Euler buckling in a wheelbarrow obstacle course: a catastrophe with complex lag

This article studies human physical work capacity under increasing load from a general systems theory perspective. There are several points of generalization between the structure of nonliving (building materials) and living systems (humans) with respect to stress, strain, and fatigue. A catastrophe model for Euler buckling was transposed and tested for human performance in a wheelbarrow obstacle course under varying loads. Subjects were 129 employees of a Midwest manufacturing plant. A cusp model was hypothesized and verified (R2 = .68, control R2 = .11) where vertical load was the asymmetry factor, and body balance, height, and sex-related differences all contributed to bifurcation. A catastrophe model in codimension 10 was also invoked to explain memory in the system. Principal control variables were exercise habits, weight, balance, and sex-related differences (R2 = .75). The core model of human load-to-failure was concluded to be similar to that for Euler buckling: additional complexities were discovered which were attributed in part to systemic memory. Discussion points included the use of large dimension catastrophe models for problems involving complex lag effects, and the transposability of the model to the organizational systemic level.     

It Is Not Just About Location: Infants Perseverate to Container Shape During Object Search

In searching for a toy hidden at a new location, infants will err by searching at the previously correct location. This study investigated the possibility that 8.5‐month‐old infants would perseverate on the basis of other visual features by which covers could be individuated. Infants saw a toy hidden under 1 of 2 distinctly shaped covers. Following successful retrievals from the Shape A cover, infants saw the toy hidden under the Shape B cover. On this B trial, the covers were at locations that had not been baited on the preceding trials, precluding location perseveration. The infants erred by choosing the unbaited Shape A cover more often than control infants presented with 1 type of cover throughout. The findings suggest that infants perseverate to cover shape and are form biases biased toward cover shape even when location information is sufficient to support retrieval.     

Preventing disruption of special needs adoptions

The incidence of adoption disruptions is much higher in special-needs adoptions than in infant adoptions. This article reports the results of an analysis of differences in functioning between families able to sustain special-needs placements and families in which they disrupted. The finding is that the father plays a pivotal role in maintaining these placements. If he is actively involved in parenting, and able to nurture and support the mother in her role, placements are more likely to be sustained.     

帝国之梦的幻灭历程——评析英国战后初期的外交政策

第二次世界大城改变了世界的格局,传统的以欧洲为中心的国际关系格局己被美苏两极格局所取代。战争所引起的新势态要求英国的外交政策做出适当的调整。但由于外交政策的连续性,英国政府在战后初期仍竭力维持自己"大英帝国"的地位,这就使得其在处理国际事务时常常感到力不从心。从"三环外交"方针、英国对欧政策和苏伊士危机这三个方面对英国战后初期的外交政策进行评析进而阐述英国帝国之梦的幻灭历程。     

Sociocultural Contexts of Time to First Sex Among Hispanic Adolescents

This investigation examines the sociocultural influences on risk of first sex among a representative sample of Hispanic (primarily of Mexican origin) teens living in Los Angeles County. Teen acculturation (measured as language of interview) moderates the effects of gender on risk of sex, with less acculturated teens exhibiting the greatest gender difference. Teens living with both biological parents have significantly lower risk of sex and the effect of family acculturation (measured as generational status) operates through teens' language of interview. Neither measure of parent‐youth relationship (socioemotional support, parental control) is significant. Hispanic teens living in low‐density Hispanic neighborhoods have significantly higher risk of sex than do teens living in neighborhoods with higher levels of ambient hazards. The results highlight the importance of characterizing sociocultural influences at multiple levels of aggregation.     

Refugees: Challenges to Protection

By the end of the year 2000, the Office of the United Nations High Commissioner for Refugees will have been in existence for 50 years – which is probably some sort of record for an organization originally set up with just a three‐year mandate. There were many reasons for so limiting the successor agency to the International Refugee Organization, but it is doubtful whether anyone seriously thought that refugee problems would be resolved so quickly, or indeed that UNHCR would develop into the highly operational, visible and extensively funded entity that we see today. Fifty years of experience nevertheless suggests that it is high time for an audit, for an evaluation of strengths, weaknesses and achievements, and a little strategic thinking about the future.     

The Correspondence Between Fertility Intentions and Behavior in the United States

Using data from the 1979 National Longitudinal Survey of Youth, we describe the correspondence between intended family size and observed fertility for US men and women in the 1957–64 birth cohorts. Mean fertility intentions calculated from reports given in the mid‐20s modestly overstate completed fertility. But discrepancies between stated intent and actual fertility are common—the stated intent at age 24 (for both women and men) is more likely to miss than to match completed fertility. We focus on factors that predict which women and men will have fewer or more children than intended. Consistent with life‐course arguments, those unmarried, childless, or (for women) still in school at approximately age 24 were most likely to underachieve their intended parity (i.e., had fewer children than intended at age 24). We discuss how such discrepancies between intentions and behavior may cumulate to produce sizable cross‐group fertility differences.