An application of a Theorem of Ash to finite covers

The technique of covers is now well established in semigroup theory. The idea is, given a semigroup S, to find a semigroup having a better understood structure than that of S, and an onto morphism of a specific kind from to S. With the right conditions on , the behaviour of S is closely linked to that of . If S is finite one aims to choose a finite . The celebrated results for inverse semigroups of McAlister in the 1970s form the flagship of this theory.Weakly left quasi-ample semigroups form a quasivariety (of algebras of type(2, 1)), properly containing the classes of groups, and of inverse, left ample, and weakly left ample semigroups. We show how the existence of finite proper covers for semigroups in this quasivariety is a consequence of Ashs powerful theorem for pointlike sets. Our approach is to obtain a cover of a weakly left quasi-ample semigroup S as a subalgebra of S × G, where G is a group. It follows immediately from the fact that weakly left quasi-ample semigroups form a quasivariety, that is weakly left quasi-ample. We can then specialise our covering results to the quasivarieties of weakly left ample, and left ample semigroups. The latter have natural representations as (2, 1)-subalgebras of partial (one-one) transformations, where the unary operation takes a transformation to the identity map in the domain of . In the final part of this paper we consider representations of weakly left quasi-ample semigroups.This work was supported by the London Mathematical Society, Fundação para a Ciência e a Tecnologia, Centro de Álgebra da Universidade de Lisboa, Centro de Matemática da Universidade do Porto and projects POCTI/32440/MAT/2000 and POCTI/32817/Mat/2000 of FEDER.Special issue of Studia Logica: Algebraic Theory of Quasivarieties Presented by M. E. Adams, K. V. Adaricheva, W. Dziobiak, and A. V. Kravchenko     

Ethical Issues in Cancer Genetics: 1) Whose Information Is It?

This article presents and discusses four clinical cases that exemplify the complexity of ethical dilemmas concerning the provider's obligation to disclose or withhold genetic information from patients. Case 1: What is the responsibility of the cancer genetics provider to ensure that a positive test results is shared with distant relatives? Case 2: To ensure that results go to at-risk relatives, do we have the right to ignore the wishes of the designated next-of-kin? Case 3: Do we have the right to reveal a familial BRCA1 mutation to a patient's relative, who is at 50% risk? Case 4: Do we have an obligation to reveal that a patient is not a blood relative and therefore, not at risk to have inherited a familial mutation? These cases form the basis for discussing the provider's dual obligations to keeping patient confidentiality and informing patients and families about risk (i.e. duty to warn). We also provide a summary of consensus points and additional discussion questions for each case.     

Psychopharmacology's debt to experimental psychology

The role of experimental psychology in the development of psychopharmacology has largely been ignored in recent historical accounts. In this article the authors attempt to redress that gap by outlining work in early experimental psychology that contributed significantly to the field. While psychiatrists focused on the therapeutic nature of drugs or their mimicry of psychopathology, experimental psychologists used psychoactive drugs as tools to study individual differences in normal behavior as well as to develop methodologies using behavior to study mechanisms of drug action. Experimental work by Kraepelin, Rivers, and Hollingworth was particularly important in establishing drug-screening protocols still used today. Research on nitrous oxide and on the effects of drug combinations is discussed to illustrate the importance of experimental psychology to psychopharmacology.     

Depressogenic cognitive styles: predictive validity, information processing and personality characteristics, and developmental origins.

Two of the major cognitive theories of depression, the theory of Beck [Beck, A. T. (1967). Depression: clinical, experimental and theoretical aspects. New York: Harper & Row. and Beck, A. T. (1987) Cognitive models of depression. Journal of Cognitive Psychotherapy: an International Quarterly, 1, 5-37] and the hopelessness theory [Abramson, Metalsky, & Alloy, (1989) Hopelessness depression: a theory-based subtype of depression. Psychological Review, 96, 358-372], include the hypothesis that particular negative cognitive styles increase individuals' likelihood of developing episodes of depression, in particular, a cognitively mediated subtype of depression, when they encounter negative life events. The Temple-Wisconsin Cognitive Vulnerability to Depression (CVD) project is a two-site, prospective longitudinal study designed to test this cognitive vulnerability hypothesis, as well as the other etiological hypotheses of Beck's and the hopelessness theories of depression. In this article, based on CVD project findings to date, we review evidence that the hypothesized depressogenic cognitive styles do indeed confer vulnerability for clinically significant depressive disorders and suicidality. In addition, we present evidence regarding moderators of these depressogenic cognitive styles, the information processing and personality correlates of these styles and the possible developmental antecedents of these styles. We end with a consideration of future research directions and the clinical implications of cognitive vulnerability to depression.     

Using psychodynamic concepts in strategic family therapy: A suicidal adolescent case

This paper describes the treatment of a suicidal adolescent with strategic family therapy. The cotherapists conceptualized the case psychoanalytically and systemically. They propose that their understanding of psychodynamics enhanced their ability to tailor their interventions to the family's unique style and capacities. Rather than dismiss psychodynamic concepts as irrelevant to strategic family therapy, they maintain that an appreciation of individual members' ego strengths, defenses, affects, and unacknowledged impulses leads to the construction of more effective metaphors and a set of interventions more isomorphic to family patterns.     

Human aggressive responses maintained by avoidance or escape from point loss.

During 50-min sessions, 6 male human subjects could press either Button A or Button B available as nonreversible options. Button A presses were nonaggressive responses and earned points according to a fixed-ratio 100 schedule. Prior to the experiment subjects were instructed that every 10 (fixed-ratio 10) Button B presses (aggressive responses) subtracted a point from a fictitious 2nd subject. A random-time schedule of point loss was used to engender aggressive responding. The instructions attributed these point losses to the Button B presses of the subject's fictitious partner. Aggressive responding either escaped or avoided point loss by initiating an interval free of point loss. The duration of the interval was varied systematically across sessions. Avoidance contingencies maintained a high rate of aggressive responding over 30 sessions in the absence of point loss. Escape contingencies also maintained aggressive responding across sessions, with rates of aggressive responding corresponding to rates of point loss.