Showing papers by "University of California published in 1983"

Dietary carcinogens and anticarcinogens Oxygen radicals and degenerative diseases

Abstract: The human diet contains a great variety of natural mutagens and carcinogens, as well as many natural antimutagens and anticarcinogens. Many of these mutagens and carcinogens may act through the generation of oxygen radicals. Oxygen radicals may also play a major role as endogenous initiators of degenerative processes, such as DNA damage and mutation (and promotion), that may be related to cancer, heart disease, and aging. Dietary intake of natural antioxidants could be an important aspect of the body’s defense mechanism against these agents. Many antioxidants are being identified as anticarcinogens. Characterizing and optimizing such defense systems may be an important part of a strategy of minimizing cancer and other age-related diseases.

How Language Structures Space

Abstract: This chapter is concerned with the structure that is ascribed to space and the objects within it by linguistic “fine structure,” that subdivision of language which provides a fundamental conceptual framework. The primary aim of the chapter is to characterize the general properties of this structuring and the linguistic-cognitive system in which it participates.

T cell subsets and the recognition of MHC class.

Abstract: We have presented and/or briefly reviewed data which indicates that there are two T cell subsets which interact respectively with the two Classes (1 and 2) of MHC antigen and which can be identified by the Ly (mouse) or Leu (human) molecules that they express. This correlation, and the large body of (largely) circumstantial but still quite convincing data, suggests that these Ly and Leu molecules play a very important role in T cell responses by actually interacting with monomorphic MHC class specific determinants. We suggest that this interaction facilitates and possibly helps direct the binding of the T cell receptor to polymorphic MHC determinants and antigen. In this model T cell "recognition" of MHC and antigen consists of several independent but connected interactions of T cell surface structure with MHC molecules and antigen on antigen-presenting cells or targets.

Evaluation of methods for estimating population pharmacokinetic parameters. III. Monoexponential model: routine clinical pharmacokinetic data.

Abstract: Individual pharmacokinetic parameters quantify the pharmacokinetics of an individual, while population pharmacokinetic parameters quantify population mean kinetics, interindividual kinetic variability, and residual variability, including intraindividual variability and measurement error. Individual pharmacokinetics are estimated by fitting a pharmacokinetic model to individual data. Population pharmacokinetic parameters have traditionally been estimated by doing this separately for each individual, and then combining the individual parameter estimates, the Standard Two Stage (STS) approach. Another approach, NONMEM, appropriately pools data across individuals and is therefore less dependent on individual parameter estimates. This study provides further evidence of NONMEM's validity and usefulness by comparing both approaches on simulated routine-type pharmacokinetic data arising from a monoexponential model. The estimates of population parameters (notably those describing interindividual variability) provided by the STS method are poorer than those provided by NONMEM, especially when there is considerable residual error. Further, NONMEM's estimates of population parameters do not require that the data be restricted to special types of routine data such as those obtained only at steady state, or only at peak or trough, nor do the estimates improve with such data. NONMEM's estimates do improve, however, when a data set is enhanced by the addition of single-observation-per-individual type data. Thus, population parameters can be estimated efficiently from data that simulate real clinical pharmacokinetic conditions.

Principles and Biophysics of Dialysis

Abstract: Intermittent dialysis therapy is used in chronic uremia to re-establish body water solute concentrations that cannot be achieved by the natural organ. In this sense, the dialyzer becomes an artificial kidney and it is through the transport of substances by this device that chemical and biophysical control consistent with continued survival is achieved. This chapter is organized as shown in Figure 1 and consists of two basic lines of development: 1. Consideration of the dialyzer and its operating principles, 2. Application of mass balance principles to various solute systems and the effect of dialyzer use on solute control during intermittent dialysis therapy.

Management of Resistance in Arthropods

Abstract: Since the earliest days of their awareness of resistance, entomologists have been concerned with understanding the factors responsible for its development and with divising measures for its control. It is remarkable that in reporting the first case of resistance — in the San Jose scale toward lime sulfur — Melander (1914) recognized the role of incomplete coverage and genetic recessiveness and speculated that should the scale become resistant also to oil sprays “we might have to introduce a weak strain to cross with the immune and thus return to the normal susceptible population.” Melander and other early pioneers in studies of resistance (Quayle 1922, Woglum 1925) may have been ahead of their time, however, for in the subsequent 30 years or so, resistance evolved slowly, affecting only 12 species of arthropods (review by Babers 1949). Interest in resistance intensified with the introduction of DDT and with the rapid development in cases of resistance to organochlorine, organophos-phate, carbamate and most recently to pyrethroid insecticides. The phenomenon now involves at least 428 species of arthropods and every class of commonly available compound (Georghiou and Mellon, this volume).

The Determination of Clutch Size in Precocial Birds

Abstract: The evolution and regulation of clutch size has long been a central issue in ornithology. Early ornithologists realized that females of each species of bird lay a characteristic number of eggs, and we have been trying to determine ever since why this is so. In pursuit of the answer to this seemingly simple question, ornithologists have not only accumulated a wealth of egg data, but also have made important contributions to such diverse topics as life-history strategies, population regulation and group selection. Yet how clutch size is determined remains a controversial issue. The consensus that was once sought in the form of a central theory (Lack, 1968; Cody, 1966; Klomp, 1970; von Haartman, 1971) has disappeared in a sea of specific hypotheses. In this review we attempt to organize and summarize clutch size theories as they emerge in modified form from recent research and evaluate their ability to explain observed patterns in clutch size variation. We concentrate on the literature and concepts published since the review of Klomp (1970), but we incorporate earlier work when necessary.

The Interdependence of Individual Portfolio Decisions and the Demand for Insurance

Abstract: We analyze the individual’s demand for insurance as a special case of general portfolio hedging activity. The demand for insurance contracts is determined simultaneously with the demands for other assets in the portfolio. We demonstrate that when the payoffs of the policy are correlated with the payoffs to the individual’s other assets, the demand for insurance contracts is generally not a separable portfolio decision. We argue that this separability condition is not generally met because of significant interdependence of claims across different insurance policies. Furthermore, our generalizations can reverse the standard prediction that wealthier individuals will demand less insurance.

Biotic Interactions in Benthic Foraminifera

Abstract: Foraminif era have a long geologic record, extending back perhaps to the Cambrian, and they are both abundant and diverse during most of the Phanerozoic. Over 40,000 species now have been described, of which approximately 4000 are living today (Tappan, 1971). They occur in all modern marine communities, and have also been found living in brackish and fresh water (Arnal, 1958; Boltovskoy and Lena, 1971; Resig, 1974). Foraminifera are especially diverse and abundant in deep-sea, coral reef, and many soft-bottom, shallow-water habitats (Hessler, 1974; Smith et al., 1978; Thiel, 1975; Murray, 1973; Wefer and Lutze, 1976), making them one of the most important animal groups on earth. Yet little is known about their interactions with other organisms, although much has been published on their distributional patterns. Successful use of foraminifera in paleobiology and paleoenvironmental interpretations requires more detailed ecologic knowledge (Lipps, 1981).

Upstream Waves and Particles

Abstract: The region upstream from terrestrial, planetary, and interplanetary shocks in which the magnetic field lines are connected to the shock is filled with a variety of plasma waves, MHD waves, energetic electrons, and ions associated with the near presence of the shock. These upstream waves and particles present us with a natural plasma laboratory which is providing basic information on plasma instabilities and collisionless shock physics, as well as insight into how cosmic ray acceleration may occur in the interstellar medium. Much remains to be done, however, before our present empirical knowledge is woven into the stronger fabric of theoretical understanding.

The relationship between androgen levels and human spatial abilities

Abstract: Individual differences on spatial tasks were examined relative to differences in free-androgen levels. A spatial test battery was administered to 91 males and females who differed in free-androgen levels as determined by a radioimmunoassay. Polynomial regression analyses yielded significant curvilinear functions relating spatial scores and androgen levels. A second study, conducted with a group of 33 males and females, replicated the basic findings of the first experiment.

Pesticide Resistance in Time and Space

Abstract: Within the evolutionarily insignificant period of just 65 years, beginning when the first case of resistance to a pesticide was reported (Melander, 1914), the phenomenon of resistance has proliferated exponentially so as to constitute today an indispensable consideration in nearly every pest control program.

Economic Voting and the “Symbolic Politics” Argument: A Reinterpretation and Synthesis

Abstract: Economic voting is generally regarded as a straightforward political demand for the amelioration of economic grievances. This assumption about motives underlies the implicit theories of politicians and the imputations of interests to voters in aggregate time series models. Several recent articles have argued that voting is not self-interested but a manifestation of “symbolic” preferences at the level of the collectivity. This article places the dispute between personal and collective decision referents into the broader perspective of a multi-stage model of information processing and decision making. Personal and collective decision referents are shown to define the poles of a continuum, and several hypotheses are derived to predict the relative weights assigned to each in the voter's calculus. The model is used in analyses of both the public's evaluations of incumbent economic management and economic voting in different electoral arenas by varying issue publics. Designed to maximize comparability with aggregate studies, this research includes both objective and subjective measures of economic conditions and indexes changes in personal conditions over time from panel data.

Generalized Expected Utility Analysis and the Nature of Observed Violations of the Independence Axiom

Abstract: First expressed by Allais in the early fifties, dissatisfaction with the expected utility model of individual risk taking behavior has mushroomed in recent years, as the number of papers in this volume, its predecessor (Allais & Hagen(1979)), and elsewhere2 indicates The nature of the current debate, ie whether to reject a theoretically elegant and heretofore tremendously useful descriptive model in light of accumulating evidence against its underlying assumptions, is a classic one in science, and the spur to new theoretical and empirical research which it is offering cannot help but leave economists, psychologists, and others who study this area with a better understanding of individual behavior toward risk

Facing the headaches of early failures: A state-of-the-art review of burn-in decisions

Abstract: System screening during electronic equipment manufacturing often cost-effective opportunities to remove and replace defective items. Burn-in is an important screening method used in predicting, achieving, and enhancing field reliability. Based on a simple calculation, we would expect the number of failures in the field to be a decreasing function of burn-in period. Especially, the expected number of failures drops significantly in the first part of the curve. Thus only a few hours of burn-in greatly reduces the failure rate, hence enhancing reliability. Qualitative studies on electronics burn-in have been done. It is well known that burn-in is costly. However, a comprehensive quantitative approach is lacking in the determination of optimal burn-in periods. This paper thoroughly reviews the studies of burn-in screenings applied to industrial products. Papers published in the past have been critically commented and systematically classified. This state-of-the-art review can serve as a guide in studying the burn-in problems.

Failure to integrate visual information from successive fixations

Abstract: After a 200-msec exposure to 12 dots from a 5 × 5 array, subjects made 4-deg saccades during a 37-msec blank interval, and then saw another 12 dots from the array for 17 msec. Subjects failed to identify the location of the missing dot, contradicting the conclusions of Jonides, Irwin, and Yantis (1982). Performance was also at chance levels with a 2.25-deg saccade, eliminating the possible effect of saccadic suppression of displacement. Screen brightness (2 log units above threshold) eliminated the phosphor persistence that probably accounts for the success of Jonides et al.’ s subjects.

Steady-state pharmacokinetics of phenytoin from routinely collected patient data.

Abstract: Previously reported routine Phenytoin clinical pharmacokinetic data from Japan, England, and Germany were analysed to estimate population pharmacokinetic parameters. There were 780 steady-state phenytoin concentrations and associated dosage rates (mg/day) from 322 patients. The patient group spanned paediatric and adult ages, mean age being 18.4 ± 17.3 (SD) years; 53% were males. The data were analysed using NONMEM, a computer programme designed for population pharmacokinetic analysis. Estimates of the influence of age, gender, data source, height and weight on the maximum elimination rate (Vm) and Michaelis-Menten constant (Km) were obtained. The Vm and Km of a 70kg adult male European were estimated to be 415 mg/day and 5.7 mg/L, respectively. Vm is not influenced by gender, age or data source. The parameters of a power function of height and weight were estimated to adjust Vm for body size. The best function adjusts Vm in proportion to weight to the 0.6 power; height contains no useful information. Km is not influenced by gender. The Km for patients less than 15 years old is 43% less than that of older patients. The Km of Japanese patients appears to be 23% less than that for European patients. Even after adjustments for age, etc., apparent Vm and Km vary unpredictably among individuals with a coefficient of variation between 10 to 20%, and approximately 50% respectively.

Comparison of Two Pseudo-Random Number Generators

Abstract: What do we want from a pseudo-random sequence generator? Ideally, we would like a pseudo-random sequence generator to quickly produce, from short seeds, long sequences (of bits) that appear in every way to be generated by successive flips of a fair coin.

The General Case

Abstract: My object in this section is to present Blackwell’s (1958) example of a standard stochastic semigroup, all of whose states are instantaneous. For other examples of this phenomenon, see Sections 3.3 of ACM and Section 2.12 of B & D. To begin with, consider the matrix $$ Q = \left( {\begin{array}{*{20}{c}} { - \lambda } & \lambda \\ \mu & { - \mu } \\ \end{array} } \right) $$ on {0, 1}, with λ and μ nonnegative, λ + μ positive. There is exactly one standard stochastic semigroup P on {0, 1} with P′(0) = Q, namely: $$ P\left( {t,0,0} \right) = \frac{\mu }{{\mu + \lambda }} + \frac{\lambda }{{\mu + \lambda }}{e^{{ - \left( {\mu + \lambda } \right)t}}}P\left( {t,0,1} \right) = 1 - P\left( {t,0,0} \right)P\left( {t,1,1} \right) = \frac{\lambda }{{\mu + \lambda }} + \frac{\mu }{{\mu + \lambda }}{e^{{ - 1\left( {\mu + \lambda } \right)t}}}P\left( {t,1,0} \right) = 1 - P\left( {t,1,1} \right) $$ (1) One way to see this is to use (5.29): define P by (1); check P is continuous, P(0) is the identity, P′(0) = Q, and P(t + s) = P(t) · P(s). Dull computations in the last step can be avoided by thinking: it is enough to do μ + λ = 1 by rescaling time; since P(u) is 2 × 2 and stochastic when u is t or s or t + s, it is enough to check that P(t + s) = P(t) · P(s) on the diagonal; by interchanging μ and λ, so 0 and 1, it is enough to check the (0, 0) position. This is easy.

Measuring compositional change along gradients

Abstract: A new procedure for measuring compositional change along gradients is proposed. Given a matrix of species-by-samples and an initial ordering of samples on an axis, the ‘gradient rescaling’ method calculates 1) gradient length (beta diversity), 2) rates of species turnover as a function of position on the gradient, and 3) an ecologically meaningful spacing of samples along the gradient. A new unit of beta diversity, the gleason, is proposed. Gradient rescaling is evaluated with both simulated and field data and is shown to perform well under many ecological conditions. Applications to the study of succession, phenology, and niche relations are briefly discussed.

The role of language and the language of role in institutional decision making

Abstract: The relationship between linguistic processes, cognitive activities, and social structures is explored by examining the decision making of committees of educators as they decide to place students into special education programs or retain them in regular classrooms. Often, different committee members enter committee meetings with different views of the student's case and its disposition, e.g., classroom teachers and parents provide accounts of the student's performance that compete with the view of the psychologist or district representative. Yet by the meeting's end, the version of the student's case provided by the psychologist or the district representative prevails.

Neurospora crassa: A Unique System for Studying Circadian Rhythms

Abstract: Progress in a particular field of biology has often been the result of the development of an organism or system especially well suited to research on that problem. The value of E. coli to molecular biology, the mammalian red blood cell to membrane biochemistry, and the oat coleoptile to plant physiology has been well-documented.

The Problem of the Average Speed of the Simplex Method

Abstract: Our goal is to give an exposition of our work on the average speed of the simplex method. Detailed proofs are in Smale 1982. Here we concentrate on the main ideas, with concepts emphasized. Some new things are added.

Algal Symbiosis and Its Recognition in the Fossil Record

Abstract: Symbiosis describes an association between two organisms that is of benefit to both. The association is generally long-term rather than transitory, and one or both partners have structural and/or behavioral adaptations that foster the association. In extreme cases of symbiosis, the reproductive systems of the partners are linked, so that continuation of the symbiosis is almost automatic; in these cases there are strong analogies with the meiotic sexual cycle (Margulis, 1980; Knoll, this volume).

International Economic Structures and American Foreign Economic Policy, 1887–1934

Abstract: American foreign economic policy between 1887 and 1934 was shaped in important ways by the international economic structure and the position of the United States as a “supporter” within it. As Britain's hegemony declined, and particularly after it joined the United States as a supporter just prior to World War I, American foreign economic policy became more liberal and active. Once Britain was transformed from a supporter into a spoiler in the late 1920s, leaving the United States as the sole supporter within the IES, both the international economy and American policy became more unstable and protectionist. During the 1970s, the United States, West Germany, and France all emerged as supporters within the IES, indicating that a moderately stable and liberal international economy may continue to exist in the future.