自学单元程序教材介绍:化学键(二)

伸展在晶格内的离子键很强,因此从晶格中移走离子是困难的。由于这个原因,离子型化合物具有较高的熔点和沸点。存在于共价型固体或液体中的分子间的作用力没有这样强(除1～2例外),使分子聚集在一起的作用力布遍于固体中也是不强的。考虑下列的气化热:     

Diversity of Gram negative bacteria antagonistic against major pathogens of rice from rice seed in the tropic environment

INTRODUCTIONRiceseedharborsadozenofplantpathogen icbacteria (Gotoetal.,1 988;Xieetal.,1 998) .Thebacterialpathogenscausearangeofricediseases,someverydestructivewhileothershavenoeffectonricecropgrowth .Inthisstudy ,wefoundalargenumberofbacteriaasso ciatedw…     

Peer relations across contexts: individual-network homophily and network inclusion in and after school

Peer relations across 2 contexts (in school and after school) were examined for 577 participants, approximately 12 years old, from 3 middle schools in Milan, Italy. The primary research questions were: Do peer networks from different contexts uniquely contribute to explaining variance in individual behavior? Do measures of peer preference and peer network inclusion across contexts uniquely contribute to explaining individual depressive symptoms? Structural equation models showed that both the in-school and the after-school peer networks uniquely contributed to explaining variance in 2 types of individual problem behavior (in-school problem behavior, after-school delinquency), and that similarity with the 2 peer networks varied according to behaviors specific to each context and across gender. Finally, both in-school and after-school peer network inclusion contributed to explaining variance in depressive symptoms, after controlling for classroom peer preference.     

完美的溜冰

看台上的观众都被海蒂那完美的动作深深地吸引了,她为她的代表队赢得了最高的分数。很显然,这是海蒂表现得最好的一次,虽然她已经在癌魔的折磨下生活一年了。     

Parameters in television captioning for deaf and hard-of-hearing adults: effects of caption rate versus text reduction on comprehension

Caption rate and text reduction are factors that appear to affect the comprehension of captions by people who are deaf or hard of hearing. These 2 factors are confounded in everyday captioning; rate (in words per minute) is slowed by text reduction. In this study, caption rate and text reduction were manipulated independently in 2 experiments to assess any differential effects and possible benefits for comprehension by deaf and hard-of-hearing adults. Volunteers for the study included adults with a range of reading levels, self-reported hearing status, and different communication and language preferences. Results indicate that caption rate (at 130, 180, 230 words per minute) and text reduction (at 84%, 92%, and 100% original text) have different effects for different adult users, depending on hearing status, age, and reading level. In particular, reading level emerges as a dominant factor: more proficient readers show better comprehension than poor readers and are better able to benefit from caption rate and, to some extent, text reduction modifications.     

Correlates of parental differential treatment: parental and contextual factors during middle childhood

The current study examined whether parental and contextual risk factors contribute to mothers' and fathers' differential treatment (MDT/FDT) when accounting for sibling dyad characteristics. Also explored was whether family type (single mothers vs. 2 parents) moderated the links between the parental and contextual correlates and MDT. One hundred and seventy-two families with older (M= 7.4 years) and younger (M= 5.2 years) siblings were studied. Parents and children reported about the parent-child relationship, and parents reported about the children's characteristics, their own psychological resources, and contextual factors. Controlling for sibling dyad characteristics, FDT was predicted most consistently by household chaos. Furthermore, single mothers were not at risk per se for using more MDT but only when coupled with high maternal anger.     

西德尼.哈里斯漫画

砂秘辱如.诬西德尼.哈里斯漫画@西德尼.哈里斯~~     

Children's probability intuitions: understanding the expected value of complex gambles

Two experiments used Information Integration Theory to study how children judge expected value of complex gambles in which alternative outcomes have different prizes. Six-year-olds, 9-year-olds and adults (N = 73 in Study 1, N = 28 in Study 2) saw chance games that involved shaking a marble in a bicolored tube. One prize was won if the marble stopped on blue, another if it stopped on yellow. Children judged how happy a puppet playing the game would be, with the prizes and probability of the blue and yellow outcomes varied factorially. Three main results appeared in both studies: First, participants in all age groups used the normatively prescribed multiplication rule for integrating probability and value of each individual outcome--a striking finding because multiplicative reasoning does not usually appear before 8 years of age in other domains. Second, all age groups based judgment of overall expected value meaningfully on both alternative outcomes, but there were individual differences--many participants deviated from the normative addition rule, showing risk seeking and risk averse patterns of judgment similar to the risk attitudes often found with adults. Third, even the youngest children took probability to be an abstract rather than physical property of the game. Overall, in contrast to the traditional view, the present results demonstrate functional understanding of probability and expected value in children as young as 5 or 6. These results contribute to the growing evidence on children's intuitive reasoning competence. This intuition can, on the one hand, support surprisingly precocious performance in young children, but it may also contribute to the biases evident in adults' judgment and decision.     

我的科学经历

回想起来,在我成长过程中,既有与众不同的地方,也有许多很平凡的地方。在上高中以前,我完全没有机会接触科学,对于科学的作用几乎一无所知。就是上高中以后,我的主要精力