Experimental Design of Bioassays for Screening and Low Dose Extrapolation

Relatively high doses of chemicals generally are employed in animal bioassays to detect potential carcinogens with relatively small numbers of animals. The problem investigated here is the development of experimental designs which are effective for high to low dose extrapolation for tumor incidence as well as for screening (detecting) carcinogens. Several experimental designs are compared over a wide range of different dose response curves. Linear extrapolation is used below the experimental data range to establish an upper bound on carcinogenic risk at low doses. The goal is to find experimental designs which minimize the upper bound on low dose risk estimates (i.e., maximize the allowable dose for a given level of risk). The maximum tolerated dose (MTD) is employed for screening purposes. Among the designs investigated, experiments with doses at the MTD, 1/2 MTD, 1/4 MTD, and controls generally provide relatively good data for low dose extrapolation with relatively good power for detecting carcinogens. For this design, equal numbers of animals per dose level perform as well as unequal allocations.     

Portfolio optimization: New capabilities and future methods

Summary  This paper addresses the problem of portfolio selection in finance. In many cases, currently available software to compute the efficient frontier runs into difficulty in problems with more than about 600 securities. To proceed beyond this size, it is often necessary to modify the problem in which case there is typically a loss of information. In this paper, we discuss a computer capability that can exactly compute mean-variance efficient frontiers of problems with up to 2,000 securities in very reasonable time (even if a problem’s covariance matrix is 100% dense). The paper also discusses an augmentation to the theory of portfolio selection that allows multiple objectives (such as dividends, liquidity, social responsibility, amount invested in R&D, and so forth) to be incorporated into the portfolio selection process. In such problems, the efficient set is no longer a “frontier,” but is now best described as a “surface” with the interesting property that it is composed of platelets (like on the back of a turtle). Moreover, the computer capability that can compute the exact efficient frontier of a mean-variance problem with up to 2,000 securities also has, after additional coding, the ability to compute exactly all platelets of the efficient surface of a tri-criterion portfolio problem with up to 400 securities.

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Zusammenfassung  In dieser Arbeit stellen wir einen leistungsf?higen Rechenalgorithmus vor, um den effizienten Rand (die nichtdominierten Alternativen) von Portfolio-Auswahlproblemen in der Finanzierung zu bestimmen. Wir bezeichnen den Berechnungsalgorithmus, der in Java programmiert ist, mit MPQ (multi-parametric quadratic programming). MPQ weist gegenüber bisherigen Berechnungsverfahren eine Reihe von Vorteilen auf: Es kann für umfangreiche Anwendungsf?lle genutzt werden, ist durch passable Rechenzeiten charakterisiert und kann die Menge effizienter Alternativen in einem Bruchteil bisher üblicher Rechenzeiten bestimmen.

     

Is There a Quest for Identity?*

It is widely assumed that people today experience an imperative quest for identity, and that altruism and work have been displaced as credible routes to self-discovery by the abandonment of inhibition and the attainment of intimacy. A preliminary examination of these premises is made through questions included in a survey of adults in the Los Angeles metropolitan area and in questionnaires administered to students at UCLA, two Australian universities, and one British university. Very few adults in Los Angeles, even in the youngest and most highly educated brackets, acknowledge any preoccupation with the question, “Who am I really?,”though most university students in the four samples do. Both adults and students endorse altruism most frequently, impulse-release least frequently, and intimacy with intermediate frequency as routes to self-discovery. They differ most in their evaluation of work as a medium for self-discovery. All observations apply only to a self-conscious search for identity.     

Cultural determinants of jealousy

I disagree with the practice of defining romantic jealousy in terms of other emotions, on the grounds that it is circular and redundant. Moreover, it appears implausible to me that the variety of private motives for protecting a relationship against an interloper can be accounted for by a unitary source of motivation, such as an emotion of romantic jealousy. I propose that the words romantic jealousy, instead of identifying an emotion of jealousy, refer to the situation characterized by the potential, or actual, loss of a loved one, or a mate, to a real or imagined rival. Reactions in such a situation, whatever they may be, are labeled as jealousy. On the basis of the assumption that individuals create culture to satisfy personal goals and are, in turn, affected by their cultural creations, I identify particular cultural factors as increasing the likelihood that an individual will be threatened by a jealousy event. The individual makes use of culturally sanctioned coping strategies for dealing with the threat. These concepts are discussed in the context of appraisal processes.     

Organizational Careers: An Interactionist Perspective*

The concept of career is both useful and necessary for the study of organizations. Through members' constructions of organizational careers, an organization becomes real and capable of action. Organizational careers intermediate between the programmatic and the symbolic elements of organizational situations. Careers, through their objective and subjective dualism, penetrate both the organization's symbolic order and its objective activity and order, constituting a third and essential element in organizational structure. Careers are highly interdependent upon communication processes, notably as negotiation of joint plans of action and of identity, role and status. Careers, work, and identity are seen as interrelated aspects of the self as a social object. Events and interactions in organizational situations lead to shifts in the moral definitions of the self and others, and to behavior which serves to protect the self from becoming profaned.