解读病毒性传染病的六大特点

病毒性传染病具有普遍性、依赖性、适应性、恶毒性、顽固性和难预防等六大特点.病毒性传染病分布广泛,种类繁多,病毒可以引起全身各个组织器官的病变;病毒必须依赖于宿主细胞,在其中复制和增殖,病毒具有"嗜袭性",进入人体后,各得其所,赖以生存.病毒具有高度变异性,变异株可以适应各种环境,有益于自身的延续;病毒可以引起全身各系统的病变,其中对于中枢神经系统的损害往往是致命性的;病毒具有不同的变种,随时可能发生不同的变异,难以研制出普遍有效的疫苗.     

大流行性流感:古老的疾病,人类的灾难

300年来,有10次全球性流感大流行。流感大流行有一定的周期性、不可预见性、灾害性、持久性,至今人类依然没有找到准确预见、避免一场新的流感大流行的良策。2003年末以来,高致病性H5N1禽流感呈现前所未有的暴发,席卷整个亚洲、部分欧洲国家,尽管人类采取积极的控制措施,但H5N1在亚洲已经顽固地存在下来,成为地方病,并且病毒不断进化(宿主范围扩大、病毒致病性增强、环境中耐受力增强)、人类病例不断出现,已使世界比1968年以来任何时刻都更加靠近一场流感大流行。因此,人类紧迫地需要通力合作、全力准备、从容应对,延缓、减弱或避免这场大浩劫。     

Altered patterns of word associations in dementia and aphasia

The word associations of 38 demented, 17 aphasic, and 22 normal subjects were studied. Both normal and brain-injured subjects appear to make judgments about the grammatical class of the word stimulus. Certain stimulus words (especially nouns and adjectives) elicit paradigmatic responses whereas other words (especially verbs and adverbs) elicit syntagmatic responses. The mechanism producing syntagmatic responses seems relatively resistant to deterioration in dementia or aphasia. However, in dementia the mechanism that generates paradigmatic responses becomes progressively less efficient (possibly due to a loss of semantic markers) and consequently more random (idiosyncratic) responses emerge. Perseverative responses, inhibited in normal subjects, are more prevalent in dementia. Anomic aphasics show a pattern of word associations similar to that of subjects with mild dementia. Broca's aphasics, while making fewer paradigmatic associations than normals, retain enough self-monitoring mechanisms so that few idiosyncratic and perseverative responses are made while more null responses occur. Wernicke's aphasics show a marked shift away from a paradigmatic word association strategy, possibly due to an inability to access semantic markers or a true loss of these markers. Metalinguistic deficits (i.e., a failure to adopt an appropriate strategy) may also contribute to this shift away from paradigmatic associations. Furthermore, a disruption of self-monitoring mechanisms in Wernicke's aphasia leads to an increase in perseverative and idiosyncratic responses.     

Utility of extension of functional equations—when possible

Jean-Claude Falmagne observed in 1981 [On a recurrent misuse of classical functional equation result. Journal of Mathematical Psychology, 23, 190-193] that, even under regularity assumptions, not all solutions of the functional equation k(s+t)=k(s)+k(t), important in many fields, also in the theory of choice, are of the form k(s)=Cs. This is certainly so when the domain of the equation (the set of (s,t) for which the equation is satisfied) is finite. We mention an example showing that this can happen even on some infinite, open, connected sets (open regions). The more general equations k(s+t)=?(s)+n(t) and k(s+t)=m(s)n(t), called Pexider equations, have been completely solved on R². In case they are assumed valid only on an open region, they have been extended to R² and solved that way (the latter if k is not constant). In this paper their common generalization

k(s+t)=?(s)+m(s)n(t)     

Individual differences in preschool children's knowledge of superordinate categories

The present study assesses intensional knowledge of superordinate categories in preschool children. This assessment is part of a larger programmatic research effort aimed at the development of a cognitive preschool screening test to detect learning problems prior to their manifestation in school failure. Necessary prerequisites for including intensional superordinate category knowledge as a potential component of this screening test are addressed: (a) Are there substantial variations in this knowledge across preschool children? (b) Can the knowledge be measured reliably using game-like picture tasks? (c) Do individual differences in this knowledge relate to the child's current level of intellectual functioning? An underlying assumption for the development of this screening test is that assessing gradually emerging abstract knowledge that develops through active, ongoing processing is more likely to predict learning problems than assessing knowledge that develops through rote associative learning. Consistent with this approach was the prediction that one component of intension, knowledge of differences, would be a better predictor of current functioning than knowledge of similarities. The data support this contention. Although both knowledge of similarities and differences was stable within an individual, variable among individuals and highly correlated with each other, only knowledge of differences related to the child's concurrent level of intellectual functioning.     

Stimulus control of defensive burying in the rat

Rats shocked once through a wire-wrapped stationary prod mounted on the wall of a test chamber incorporated the bedding material covering the chamber floor into a defensive reaction. When tested 1 min later, they approached the prod and buried it. Evidence was provided by three separate studies of this burying response that rats had learned about the association of both the position and brightness of the prod with shock after this single conditioning trial. In Experiment 1, the amount of burying decreased if either the position or brightness of the prod had been changed prior to the test. In Experiments 2 and 3, rats were shocked through one of two prods (white or black) mounted on opposite walls of the test chamber. When the positions of the prods were unchanged for the test, almost every subject buried the prod through which it had been shocked, even when the conditioning-test interval was 24 hr; whereas, each rat directed substantial amounts of bedding material at both prods when the positions of the two prods were reversed. Thus, discriminated “avoidance” learning can be rapid, reliable, and enduring when shock is administered “by” a clearly defined stimulus object, i.e., when cue and consequence are spatially contiguous.     

The Political Universe of Lyndon B. Johnson and His Advisors: Diagnostic and Strategic Propensities in Their Operational Codes

This study uses the Verbs in Context System (VICS) to analyze and compare the operational codes of President Lyndon Johnson and his advisors during the Vietnam conflict. The initial focus is on changes in Johnson's general operational code as revealed in public statements during the period leading to the decisions to bomb North Vietnam and to intervene with ground forces in South Vietnam. Johnson's public operational codes for the domestic, foreign, and Vietnam domains are then compared, and his public operational code for the Vietnam conflict is contrasted with the private operational code of his Vietnam advisors (as expressed in private memoranda). Period effects, domain effects, and other differences are revealed between the views of Johnson and those of his advisors.