Clinical trials. Planned Ritalin trial for tots heads into uncharted waters

U.S. scientists are gearing up for a major clinical trial intended to measure the effects of a popular but controversial drug used to treat attention deficit hyperactivity disorder, methylphenidate (Ritalin), on a previously untested population--children aged 3 to 6. But in doing so, they are running up against ethical concerns about using young subjects in clinical trials. The scientists involved in the study admit that they are concerned about the drug's effect on the children's still-developing personalities and brains, as well as their inability to give informed consent. But they believe that such trials are the only way to answer concerns about rising use of the drug among this population.     

Assumptions in tests for meiotic drive

Recent claims for the existence of meiotic drive in the ABO blood groups require the assumption of equal fertility (if there is no other selection operating) for the various mating types. There is evidence that does not support this assumption, and there are no convincing a priori grounds for making it.     

In quest of virtual tests for structural composites

The difficult challenge of simulating diffuse and complex fracture patterns in tough structural composites is at last beginning to yield to conceptual and computational advances in fracture modeling. Contributing successes include the refinement of cohesive models of fracture and the formulation of hybrid stress-strain and traction-displacement models that combine continuum (spatially averaged) and discrete damage representations in a single calculation. Emerging hierarchical formulations add the potential of tracing the damage mechanisms down through all scales to the atomic. As the models near the fidelity required for their use as virtual experiments, opportunities arise for reducing the number of costly tests needed to certify safety and extending the design space to include material configurations that are too complex to certify by purely empirical methods.     

篇章类英语试题的考点效度验证

在我国大规模英语考试试卷中基于篇章类的试题占相对比较高的比例,其考点效度关乎整份试卷的效度。本文通过对篇章类英语试题考点所属构念效度的例析,说明从考点层面所获取的相关效验证据对基于篇章类试题的考点效度进行了有效验证。     

Breath tests for determining alcohol in the blood

The "drunk driver" represents one social problem that medicine and the exact sciences have been asked to help solve. Once the decision to employ the criminal justice system for that purpose was made, they were asked to provide both a more precise measure of intoxication, in order that criminal sanctions might be brought into play, and means of determining that measure in individual defendants. The use of breath tests in the courtroom to determine alcohol in the blood, along with evidence of related scientific issues, thus serves well to illustrate the mechanisms by which these scientific contributions may enter into the social scheme.     

Osmotic pressure influence in germination tests for antibiosis

A common test for the presence of toxic organic substances in plant tissues, and therefore of the potential role of antibiosis (specifically allelopathy) in native plant cozmmunities, has been to apply a water extract of the tissues in germination tests of cultivated annuals. The observed osmotic pressure of the extracts can be high, and sucrose solutions of similar osmotic pressure result in a depression of germnination and early development. Thus in the aforementioned type of test, extracts must be diluted to an osmotic pressure no greater than 0.5 atmopheres.     

Mothers' transitions from welfare to work and the well-being of preschoolers and adolescents

Results from a longitudinal study of 2402 low-income families during the recent unprecedented era of welfare reform suggest that mothers' transitions off welfare and into employment are not associated with negative outcomes for preschoolers (ages 2 to 4 years) or young adolescents (ages 10 to 14 years). Indeed, no significant associations with mothers' welfare and employment transitions were found for preschoolers, and the dominant pattern was also of few statistically significant associations for adolescents. The associations that did occur provided slight evidence that mothers' entry into the labor force was related to improvements in adolescents' mental health, whereas exits from employment were linked with teenagers' increased behavior problems.     

利用油菜花瓣实验检测油菜菌核病

摘要：油菜菌核病是由Sclerotinia sclerotiorum (Lib) de Bary引起的,是世界范围内造成损失最严重的病害之一。该病害主要通过感染了核盘菌子囊孢子的花瓣落在植株茎、叶上来侵染植株。本实验采用添加了两种不同PH指示剂的改良型Steadman’s培养基检测被子囊孢子感染的花瓣,样品采自合肥的两块不同试验田,在油菜花期（3月下旬～4月中旬）每天采摘新鲜花瓣在室温下培养,结果表明整个花期,除1块田1天没有检测出外,其余每天都有被子囊孢子感染的花瓣出现（感染子囊孢子的花瓣接种后培养基变色）。油菜初花期被子囊孢子感染的花瓣较少,而盛花期和终花期被感染的花瓣较多,第一块田被感染的花瓣数在两种培养基上出现的百分率分别为32.0％和40.2％,第二块田分别为27.3％和35.7％。第一块田油菜菌核病的发病率和病指分别为2.7％和1.8,第二块田分别为1.5％和0.4。子囊孢子感染的花瓣数与后期油菜菌核病的发病率呈显著正相关（r=0.829,r0.05=0.811）。研究被感染的花瓣数可以帮助决定最适宜的病害防治时期。     

晚稻种子包衣对比试验

推广种子包衣技术是种子工程建设的重要内容.我县属油-稻两熟制农区,油菜种子包衣技术已在生产中普遍应用,取得了良好效果,晚稻种子包衣仍处在试验示范阶段.为明确晚稻种子包衣的应用效果.2000年进行了大区对比试验. 1 材料与方法