RELEVANCE OF REGRESSION TO THE MEAN TO EPIDEMIOLOGICAL AND CLINCAL STUDIES: A REVIEW OF THE LITERATURE

Investigation of the relative heights of pairs of fathers and sons led the famous 19th century scientist, Sir Francis Galton, to the concept known as "regression to the mean." Gallon observed that sons of extremely tall or extremely short fathers tended to be less extremely tall or short. The concept has since been - found to apply to virtually any experiment requiring a test-retest design. On the average, the bottom group on the first test will tend to increase, and the top group will on average decrease on the retest. For example, a clinical study requiring an initially high blood pressure baseline value (screening value), might decrease as a group on a subsequent retest, perhaps merely due to a regression effect. One way to account for possible bias due to regression effects is by using an appropriate control group. In the absence of a control group, James (1973) has developed some useful formulas for estimating the expected regression effect, when a truncated population is being sampled. Choice of an appropriate baseline value should also be guided by consideration of the potential effects of regression.     

昆虫对生物农药的抗性机制及对策

本文综述了昆虫对B.t等生物杀虫剂的抗性机制及延缓昆虫抗性发展所应采取的措施.昆虫通过下列不同机制产生抗生:1)昆虫的血淋巴对B.t等生物杀虫剂的营养细胞的抑制作用.2)各种来源的蛋白酶对毒素蛋白的过度降解作用.3)昆虫中肠沉淀蛋白对毒素蛋白的沉淀作用.4)中肠上皮修复能力增强.5)中肠的吸附位点对毒素蛋白的亲和力下降.通过加强对B.t菌株的选育,合理科学的用药方式及采用不同的模式进行植物基因操作以提高杀虫蛋白的表达和活性等综合措施,减缓和降低昆虫抗性的发展.     

THE DUTY TO DIE AND THE BURDENSOMENESS OF LIVING

This article addresses the question of whether the arguments for a duty to die given by John Hardwig, the most prominent philosophical advocate of such a duty, are sound. Hardwig believes that the duty to die is relatively widespread among those with burdensome illnesses, dependencies, or medical conditions. I argue that although there are rare circumstances in which individuals have a duty to die, the situations Hardwig describes are not among these. After reconstructing Hardwig's argument for such a duty, highlighting his central premise that ill, dependent, or aged individuals can impose unfair burdens upon others by continuing to live, I clarify precisely what Hardwig intends by his thesis that many of us have a duty to die. I then show that an important disanalogy exists between an uncontroversial example in which an individual has a duty to die and the situations in which Hardwig proposes individuals have a duty to die. More specifically, in situations where a duty to die exists, an individual's having a duty to die logically implies that those she burdens have a right to kill that individual in self‐defense. I then suggest that the burdens that ill, dependent, or aged individuals impose on their families, loved ones, or caregivers do not constitute the kind of threat that warrants the latter killing the former in self‐defense. Hence, the duty to die is much rarer than Hardwig supposes.