喜树碱类药物四十年研发的回顾与反思

通过对喜树碱类药物研发过程的历史回顾,探讨其存在的哲学意义和对其它植物药研发的价值。     

Stimulus control depends on the subjective value of the outcome

Stimuli that provide information about likely future reinforcers tend to shift behavior, provided a reliable relation between the stimulus and the reinforcer can be discriminated. Stimuli that are apparently more reliable exert greater control over behavior. We asked how the subjective value (measured in terms of preference) of reinforcers associated with stimuli influences stimulus control. Five pigeons worked on a concurrent chains procedure in which half of all trials ended in a smaller reinforcer sooner, and the other half in a larger reinforcer later. In Signaled trials, the color and flash duration on the keys in the initial link signaled the outcome of the trial. In Conflicting probe trials, the color and the flash duration signaled conflicting information about the outcome of the trial. Choice in Signaled trials shifted toward the signaled outcome, but was never exclusive. In Conflicting probe trials, control was divided idiosyncratically between the 2 stimulus dimensions, but still favored the outcome with the higher subjective value. Thus, stimulus control depends not only on the perceived reliability of stimuli, but also on the subjective value of the outcome.     

On the measurement of time allocation on multiple variable-interval schedules

Six pigeons were trained on a modified multiple-schedule procedure. In a three-key chamber, the center key was lighted red or green, depending upon which component schedule was in effect. A response on this key transferred this color to each of two side keys, and responses on one of those keys produced reinforcers according to the component schedule. After 2 s, the side-key lights were extinguished, the center key was reilluminated, and a further center-key response was required to give access, as before, to the component schedules. Components alternated every 3 min. This limited-access procedure allowed both times spent switched into the side keys and time spent not switched in to be measured in the two components. Component reinforcer rates were varied over eight experimental conditions. Both component response rate and component time allocation were increasing functions of relative component reinforcer rate, and these functions were not significantly different. This finding implies that local response rates (responses divided by time switched in) were unaffected by changing component reinforcer rates on multiple schedules. Because a similar result was recently obtained for concurrent schedules, models of multiple and concurrent-schedule performance may need to consider only the time allocation of behavior emitted at equal tempo in the component schedules.     

Diminishing marginal value as delay discounting.

The fundamental law underlying economic demand and exchange is the tendency for value of marginal units to diminish with increasing amounts of a commodity. The present paper demonstrates that this law follows from three still-more-basic psychological assumptions: (a) limited consumption rate, (b) delay discounting, and (c) choice of highest valued alternative. Cases of diminishing marginal value apparently due to pure intensity of reward may plausibly be attributed to the above three factors. The further assumption that maximum consumption rate may vary within and across individuals implies that some substances may be unusually addictive and that some individual animals may be unusually susceptible to addiction.     

Influence in canonical correlation analysis

The perturbation theory of the generalized eigenproblem is used to derive influence functions of each squared canonical correlation coefficient and the corresponding canonical vector pair. Three sample versions of these functions are described and some properties are noted. As particular applications, the influence function of the squared multiple correlation coefficient and influence functions of eigenvalues and eigenvectors in correspondence analysis are obtained. Three numerical examples are briefly discussed.We thank the Editor and the anonymous reviewers for their helpful comments. This research was carried out with the financial support of the Italian Ministry of the University and the National Research Council.     

INTERRELATING NATURE, HUMANITY, AND THE WORK OF GOD: SOME ISSUES FOR FUTURE REFLECTION

Abstract. This essay suggests some future items for an agenda about human viability, defined as survivability with meaning and purpose, by exploring interrelations between nature, humanity, and the work of God. It argues for intrinsic and creative value in nature, so there is a value kinship, as well as a factual kinship, between humans, nature, and God-working. It considers humans as "webs of culture, life, and cosmos" and suggests some implications of this notion of human nature for viability. And it asks what human fulfillment can be in light of the awesome creative-destroying-recreative activity that seems to be the ground of an evolving universe.     

Diagnosticity,confidence, and the need for information

Recent research has suggested that people prefer to use the most diagnostic available information as the basis for their choices and decisions, and are most confident in those decisions when information is highly diagnostic. However, the effect of information diagnosticity on the need for additional information has yet to be investigated; that is, in an optional stopping task, will the amount of information requested depend upon information diagnosticity? Three models of the role of diagnosticity in information use were examined; expected value, a confidence criterion, and information cost. Subjects attempted to categorize stimuli with the aid of information of varying costs and diagnosticity levels. They requested more information when it was obtained at a low cost. More importantly, across cost conditions, subjects consistently requested greater amounts of information when that information was of a low diagnosticity. These data seem most consistent with use of a confidence criterion that is adjusted for information costs.     

See the devil and tame him

Born in 1921, professor of philosophy at the University of Warsaw and art theory in the Polish Academy of Sciences; has published twelve books and more than three hundred articles (bibliography in volume 14 of A. Mercier (ed.).Philosophers on Their Own Work. Bern: 1990) ranging over the history of aesthetics, Marxist and Soviet aesthetics, and issues related to the status of the arts in contemporary Western culture.     

Stimulus Effects On Behavior Allocation In Three-alternative Choice

Six pigeons were trained on three-alternative concurrent variable-interval schedules that were available through a switching response and were signaled by colored stimuli. The discriminative stimuli for two of the schedules were always 560 nm and 630 nm, but the stimulus signaling the third alternative was varied across conditions over seven levels between these colors. For each third-alternative stimulus condition, the relative frequency of reinforcers was varied over three conditions with 4:1 and 16:1 reinforcer ratios between each pair of alternatives. The distribution of responses between the alternatives was dependent jointly on the third-alternative reinforcer rate and on the disparity between the stimulus signaling the third alternative and those signaling the other alternatives. A generalized matching approach was unable to provide invariant measures of the discriminability between constant stimuli, but a contingency-discriminability approach provided excellent fits and sensible and invariant stimulus discriminability measures.     

Maximization of sums of quotients of quadratic forms and some generalizations

Monotonically convergent algorithms are described for maximizing six (constrained) functions of vectors x, or matricesX with columns x₁, ..., x _r . These functions are h₁(x)= _k (xA _kx)(xC _kx)^–1, H₁(X)= _k tr (XA _k X)(XC _k X)^–1, h₁(X)= _{k l} (x _l A _kx _l ) (x _l C _kx _l )^–1 withX constrained to be columnwise orthonormal, h₂(x)= _k (xA _kx)²(xC _kx)^–1 subject to xx=1, H₂(X)= _k tr(XA _kX)(XA_kX)(XC_kX)^–1 subject toXX=I, and h₂(X)= _{k l} (x _l A _kx _l )² (x _l C _kX _l )^–1 subject toXX=I. In these functions the matricesC _k are assumed to be positive definite. The matricesA _k can be arbitrary square matrices. The general formulation of the functions and the algorithms allows for application of the algorithms in various problems that arise in multivariate analysis. Several applications of the general algorithms are given. Specifically, algorithms are given for reciprocal principal components analysis, binormamin rotation, generalized discriminant analysis, variants of generalized principal components analysis, simple structure rotation for one of the latter variants, and set component analysis. For most of these methods the algorithms appear to be new, for the others the existing algorithms turn out to be special cases of the newly derived general algorithms.This research has been made possible by a fellowship from the Royal Netherlands Academy of Arts and Sciences to the author. The author is obliged to Jos ten Berge for stimulating this research and for helpful comments on an earlier version of this paper.