Showing papers on "Population published in 1988"

An Ecological Perspective on Health Promotion Programs

Abstract: During the past 20 years there has been a dramatic increase in societal interest in preventing disability and death in the United States by changing individual behaviors linked to the risk of contracting chronic diseases. This renewed interest in health promotion and disease prevention has not been without its critics. Some critics have accused proponents of life-style interventions of promoting a victim-blaming ideology by neglecting the importance of social influences on health and disease. This article proposes an ecological model for health promotion which focuses attention on both individual and social environmental factors as targets for health promotion interventions. It addresses the importance of interventions directed at changing interpersonal, organizational, community, and public policy, factors which support and maintain unhealthy behaviors. The model assumes that appropriate changes in the social environment will produce changes in individuals, and that the support of individuals in the population is essential for implementing environmental changes.

Sources, Sinks, and Population Regulation

Abstract: Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive success fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capita deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats a...

Models for longitudinal data: a generalized estimating equation approach.

Abstract: This article discusses extensions of generalized linear models for the analysis of longitudinal data. Two approaches are considered: subject-specific (SS) models in which heterogeneity in regression parameters is explicitly modelled; and population-averaged (PA) models in which the aggregate response for the population is the focus. We use a generalized estimating equation approach to fit both classes of models for discrete and continuous outcomes. When the subject-specific parameters are assumed to follow a Gaussian distribution, simple relationships between the PA and SS parameters are available. The methods are illustrated with an analysis of data on mother's smoking and children's respiratory disease.

Specification of cerebral cortical areas

Abstract: How the immense population of neurons that constitute the human cerebral neocortex is generated from progenitors lining the cerebral ventricle and then distributed to appropriate layers of distinctive cytoarchitectonic areas can be explained by the radial unit hypothesis. According to this hypothesis, the ependymal layer of the embryonic cerebral ventricle consists of proliferative units that provide a proto-map of prospective cytoarchitectonic areas. The output of the proliferative units is translated via glial guides to the expanding cortex in the form of ontogenetic columns, whose final number for each area can be modified through interaction with afferent input. Data obtained through various advanced neurobiological techniques, including electron microscopy, immunocytochemistry, [3H]thymidine and receptor autoradiography, retrovirus gene transfer, neural transplants, and surgical or genetic manipulation of cortical development, furnish new details about the kinetics of cell proliferation, their lineage relationships, and phenotypic expression that favor this hypothesis. The radial unit model provides a framework for understanding cerebral evolution, epigenetic regulation of the parcellation of cytoarchitectonic areas, and insight into the pathogenesis of certain cortical disorders in humans.

The Dimensions of Residential Segregation

Abstract: This paper conceives of residential segregation as a multidimensional phenomenon varying along 5 distinct axes of measurement: evenness exposure concentration centralization and clustering. 20 indices of segregation are surveyed and related conceptually to 1 of the 5 dimensions. Using data from a large set of US metropolitan areas the indices are intercorrelated and factor analyzed. Orthogonal and oblique rotations produce pattern matrices consistent with the postulated dimensional structure. Based on the factor analyses and other information 1 index was chosen to represent each of the 5 dimensions and these selections were confirmed with a principal components analysis. The paper recommends adopting these indices as standard indicators in future studies of segregation. (authors)

The economy as an evolving complex system II

Abstract: * Introduction W.B. Arthur, S.N., Durlauf, and D. Lane * Asset Pricing Under Endogenous Expectations in an Artificial Stock Market W.B. Arthur, J.H. Holland, B. LeBaron, R. Palmer, and P. Tayler * Natural Rationality V.M. Darley and S.A. Kauffman * Statistical Mechanics Approaches to Socioeconomic Behavior S.N. Durlauf * Is What Is Good for Each Best for All? Learning From Others in the Information Contagion Model D. Lane * Evolution of Trading Structures Y.M. Ioannides * Foresight, Complexity, and Strategy D. Lane and R. Maxfield * The Emergence of Simple Ecologies of Skill J.F. Padgett * Some Fundamental Puzzles in Economic History/Development D.C. North * How the Economy Organizes Itself in Space: A Survey of the New Economic Geography P. Krugman * Time and Money P. Shubik * Promises Promises J. Geanakoplos * Macroeconomics and Complexity: Inflation Theory A. Leijonhufvud * Evolutionary Dynamics in Game-Theoretic Models K. Lindgren * Identification of Anonymous Endogenous Interactions C.F. Manski * Asset Price Behavior in Complex Environments W.A. Brock * Population Games L.E. Blume * Computational Political Economy K. Kollman, J. H. Miller, and S. Page * The Economy as an Interactive System A.P. Kirman * How Economists Can Get A Life L. Tesfatsion * Some Thoughts About Distribution in Economics P.W. Anderson

Introduction to the Theory and Practice of Econometrics

Abstract: This book interweaves inferential approaches and theory and practice in econometrics. Basic statistical and linear algebra concepts are introduced as they are needed to give life to the statistical model under study. Most econometric applications start with a tentative theory or hypothesis a sample of data and the goal of learning something about the phenomena under study from the limited set of observations. Therefore a sample of data that may be used to investigate a particular economic hypothesis is presented to motivate the analysis of each of the statistical models presented. This linkage between the economic process that is thought to have generated the data and a particular statistical model is a unifying theme throughout the book. It progresses from the special case of investigating the possibilities for determining the location and scale parameters for a population from a sample of observations to investigating a complex simultaneous system of structural equations under general stochastic assumptions. To ensure that the reader understands the basic concepts and conclusions as they relate to linear statistical models simple special case models are evaluated and then the analysis is repeated for the general case. The 1st half of book gives the student a solid introduction to the formulation and use of linear statistical models. The 2nd half introduces the student to the econometric problems that arise when it is taken into account that economic data are stochastic dynamic and simultaneous and that the optimal statistical procedure sometimes changes as we change the statistical model the amount and type of information used and the measure of performance.

Genetics and demography in biological conservation

Abstract: Predicting the extinction of single populations or species requires ecological and evolutionary information. Primary demographic factors affecting population dynamics include social structure, life history variation caused by environmental fluctuation, dispersal in spatially heterogeneous environments, and local extinction and colonization. In small populations, inbreeding can greatly reduce the average individual fitness, and loss of genetic variability from random genetic drift can diminish future adaptability to a changing environment. Theory and empirical examples suggest that demography is usually of more immediate importance than population genetics in determining the minimum viable sizes of wild populations. The practical need in biological conservation for understanding the interaction of demographic and genetic factors in extinction may provide a focus for fundamental advances at the interface of ecology and evolution.

The Evolution of Ecological Specialization

Abstract: The evolution of "niche breadth," or "niche width," was a more popular topic in the evolutionary ecological literature of the 1960s and 1970s than it has been recently (109, 118, 120, 134, 155, 156). This review summarizes current hypotheses on the evolution of specialization and generalization and suggests areas in which future research might be rewarding. The topic is so broad that every area of biology bears on it. We cannot hope to offer an exhaustive review of evidence and in particular have slighted much of the ecological literature to emphasize genetic and evolutionary perspectives. We limit our discussion almost entirely to animals. We adopt Hutchinson's (86) representation of a population's ecological niche as an n-dimensional hypervolume, the axes of which are environmental variables or resources. Along each of these, the population displays a wide or narrow tolerance or pattern of utilization, relative to other populations or species. Specialization and generalization must be defined with reference to particular axes (e.g. temperature, range of food particle sizes). Brown (9) suggests that niche breadth along different axes is positively correlated and that this explains positive correlations across species between local abundance and breadth of geographic range. Multidimensional specialization might be expected if species arise in localized regions that differ in several ecological respects from those occupied by parent species. Cody (20), however, suggested that the breadth of habitat is negatively correlated with diet breadth among certain bird species. In practice, quantitative measurement of niche breadth can be difficult (22,

International statistical classification of diseases and related health problems. Tenth revision.

Abstract: The International Classification of Diseases has, under various names, been for many decades the essential tool for national and international comparability in public health. This statistical tool has been customarily revised every 10 years in order to keep up with the advances of medicine. At first intended primarily for the classification of causes of death, its scope has been progressively widening to include coding and tabulation of causes of morbidity as well as medical record indexing and retrieval. The ability to exchange comparable data from region to region and from country to country, to allow comparison from one population to another and to permit study of diseases over long periods, is one of the strengths of the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD). WHO has been responsible for the organization, coordination and execution of activities related to ICD since 1948 (Sixth Revision of the ICD) and is now proceeding with the Tenth Revision. For the first time in its history the ICD will be based on an alphanumeric coding scheme and will have to function as a core classification from which a series of modules can be derived, each reaching a different degree of specificity and adapted to a particular specialty or type of user. It is proposed that the chapters on external causes of injury and poisoning, and factors influencing health status and contact with health services, which were supplementary classifications in ICD-9, should form an integral part of ICD-10. The title of ICD has been amended to "International Statistical Classification of Diseases and Related Health Problems"', but the abbreviation "ICD" will be retained.(ABSTRACT TRUNCATED AT 250 WORDS)

Learning to read and write: A longitudinal study of 54 children from first through fourth grades.

Abstract: My research focused on literacy development in children through fourth grade and followed an earlier study (Juel, Griffith, & Gough, 1986). The Simple View of reading and writing received support in this earlier study and was examined in my current research. Of particular concern were these questions: Do the same children remain poor readers year after year? Do the same children remain poor writers year after year? What skills do the poor readers lack? What skills do the poor writers lack? What factors seem to keep poor readers from improving? What factors seem to keep poor writers from improving? The probability that a child would remain a poor reader at the end of fourth grade if the child was a poor reader at the end of first grade was .88. Early writing skill did not predict later writing skill as well as early reading ability predicted later reading ability. Children who became poor readers entered first grade with little phonemic awareness. By the end of fourth grade, the poor readers had still not achieved the level of decoding skill that the good readers had achieved at the beginning of second grade. Good readers read considerably more than the poor readers both in and out of school, which appeared to contribute to the good readers' growth in some reading and writing skills (e.g., in ideas for stories). Poor readers tended to become poor writers. The Simple View received support in accounting for reading and writing development through fourth grade. This study examined the development of literacy in one elementary school with a large minority, low socioeconomic status population. The reading and writing development of 54 children was followed as they progressed from first through fourth grade. This in-depth examination of literacy acquisition in a microcosm of at-risk children attempted to answer the following questions: Do the same children remain poor readers year after year? Do the same children remain poor writers year after year? What skills do the poor readers lack?

Smoking and Drinking in Relation to Oral and Pharyngeal Cancer

Abstract: A case-control study of oral and pharyngeal cancer conducted in four areas of the United States provided information on the tobacco and alcohol use of 1114 patients and 1268 population-based controls. Because of the large study size, it could be shown that the risks of these cancers among nondrinkers increased with amount smoked, and conversely that the risks among nonsmokers increased with the level of alcohol intake. Among consumers of both products, risks of oropharyngeal cancer tended to combine more in a multiplicative than additive fashion and were increased more than 35-fold among those who consumed two or more packs of cigarettes and more than four alcoholic drinks/day. Cigarette, cigar, and pipe smoking were separately implicated, although it was shown for the first time that risk was not as high among male lifelong filter cigarette smokers. Cessation of smoking was associated with a sharply reduced risk of this cancer, with no excess detected among those having quit for 10 or more years, suggesting that smoking affects primarily a late stage in the process of oropharyngeal carcinogenesis. The risks varied by type of alcoholic beverage, being higher among those consuming hard liquor or beer than wine. The relative risk patterns were generally similar among whites and blacks, and among males and females, and showed little difference when oral and pharyngeal cancers were analyzed separately. From calculations of attributable risk, we estimate that tobacco smoking and alcohol drinking combine to account for approximately three-fourths of all oral and pharyngeal cancers in the United States.

One-month prevalence of mental disorders in the United States. Based on five Epidemiologic Catchment Area sites.

Abstract: • One-month prevalence results were determined from 18571 persons interviewed in the first-wave community samples of all five sites that constituted the National Institute of Mental Health Epidemilogic Catchment Area Program. US population estimates, based on combined site data, were that 15.4% of the population 18 years of age and over fulfilled criteria for at least one alcohol, drug abuse, or other mental disorder during the period one month before interview. Higher prevalence rates of most mental disorders were found among younger people (

Prevalence of Patent Foramen Ovale in Patients with Stroke

Abstract: The cause of ischemic stroke in younger adults is undefined in as many as 35 percent of patients. We studied the prevalence of patent foramen ovale as detected by contrast echocardiography in a population of 60 adults under 55 years old with ischemic stroke and a normal cardiac examination. We compared the results with those in a control group of 100 patients. The prevalence of patent foramen ovale was significantly higher in the patients with stroke (40 percent) than in the control group (10 percent, P less than 0.001). Among the patients with stroke, the prevalence of patent foramen ovale was 21 percent in 19 patients with an identifiable cause of their stroke, 40 percent in 15 patients with no identifiable cause but a risk factor for stroke, such as mitral valve prolapse, migraine, or use of contraceptive agents, and 54 percent in 26 patients with no identifiable cause (P less than 0.10). These results suggest that because of the high prevalence of clinically latent venous thrombosis, paradoxical embolism through a patent foramen ovale may be responsible for stroke more often than is usually suspected.

Modern Planktonic Foraminifera

Abstract: 1. Introduction.- 2. Taxonomy and Species Features.- 2.1 Introduction.- 2.2 Species List.- 2.2.1 Spinose Planktonic Foraminifera.- 2.2.2 Non-spinose Planktonic Foraminifera.- 3. Collecting and Culture Methods.- 3.1 Introduction.- 3.2 Collection for Ecological Studies.- 3.3 Fixation and Storing of Samples.- 3.4 Laboratory Preparations.- 3.5 Collection for Physiological and Ecological Studies.- 3.5.1 Net Collection.- 3.5.2 SCUBA Collection.- 3.6 Isolation and Preparation for Maintenance Culture.- 3.7 Maintenance Cultures.- 3.8 Monitoring Vitality and Growth of the Cultures.- 3.9 Feeding Techniques.- 3.9.1 Algal Prey.- 3.9.2 Animal Prey.- 3.10 Cataloguing and Storing Shells.- 3.11 Summary.- 4. Cellular Ultrastructure.- 4.1 Introduction.- 4.2 Fixation of Planktonic Foraminifera for Fine Structure Analysis.- 4.3 Cytoplasmic Streaming.- 4.4 Peripheral Cytoplasm and Rhizopodial Morphology.- 4.4.1 Cytoskeletal Structures.- 4.4.2 Filaments.- 4.5 Fine Structure of Cytoplasmic Organelles.- 4.5.1 Nucleus.- 4.5.2 Mitochondria.- 4.5.3 Peroxisomes.- 4.5.4 Endoplasmic Reticulum, Golgi Complex, and Vacuolar System.- 4.5.5 Fibrillar Bodies.- 4.5.6 Lipids and Various Cytoplasmic Inclusions.- 4.6 Comparative Fine Structure Data of Benthic and Planktonic Species.- 4.7 Comparative Fine Structure of Planktonic Foraminifera and Radiolaria.- 4.8 Summary.- 5. Host and Symbiont Relationships.- 5.1 Introduction.- 5.2 Symbiosis, Commensalism and Parasitism.- 5.3 Symbiont Morphology and Structural Association with Host.- 5.3.1 Dinoflagellate Symbiont Fine Structure.- 5.3.2 Chrysophycophyte Symbiont Fine Structure.- 5.4 Symbiont and Host Physiological Interactions.- 5.5 Origin of Symbionts.- 5.6 Major Features of Algal Symbionts.- 5.7 Summary.- 6. Trophic Activity and Nutrition.- 6.1 Introduction.- 6.2 Natural Prey.- 6.3 Laboratory Studies of Trophic Activity.- 6.3.1 Prey Acceptance and Rate of Digestion.- 6.3.2 Cannibalism.- 6.3.3 Fine Structure Studies of Prey Capture and Digestion.- 6.3.4 Trophic Activity and Longevity.- 6.3.5 Laboratory Studies of Omnivorous Feeding.- 6.4 Prey Abundance and Foraminiferal Distribution.- 6.5 Predators on Planktonic Foraminifera.- 6.6 Comparative Data with Benthic Foraminifera and Radiolaria.- 6.7 Summary.- 7. Reproduction.- 7.1 Introduction.- 7.2 Gametogenesis.- 7.2.1 Light Microscopic Data.- 7.2.2 Fine Structure Data.- 7.3 Morphological Changes during Gametogenesis.- 7.4 Reproductive Cycles.- 7.5 Comparisons with Benthic Foraminifera and Radiolaria.- 7.6 Summary.- 8. Shell Ontogeny.- 8.1 Introduction.- 8.2 Ontogenetic Concept for Spinose Species.- 8.2.1 Five Stage Concept.- 8.2.2 Ontogeny of Globigerinoides sacculifer.- 8.3 Variations in Developmental Morphology of Spinose Species.- 8.4 Variations in Developmental Morphology of Non-spinose Species.- 8.5 Quantitative Ontogeny.- 8.6 Coiling Directions.- 8.7 Taxonomic Applications.- 8.8 Summary.- 9. Shell Architecture.- 9.1 Introduction.- 9.2 Chamber Deposition and Pore Formation.- 9.2.1 Chamber Formation in Non-spinose Species.- 9.2.2 Pore Formation and Wall Thickening.- 9.2.3 Keel Development.- 9.2.4 Pustule Formation.- 9.3 Chamber Formation in Spinose Species.- 9.3.1 Spine Types.- 9.4 Wall Thickening and Gametogenic Calcification.- 9.5 Physiological Mechanism and Rates of Calcification.- 9.6 Organic Composition of the Calcitic Wall.- 9.7 Resorption and Repair Processes.- 9.8 Abnormal Shell Growth.- 9.9 Summary.- 10. Ecology.- 10.1 Introduction.- 10.2 Statistical Treatment and the Transfer Function.- 10.3 Stable Isotopes.- 10.4 Distributional Pattern of Planktonic Foraminifera.- 10.4.1 Horizontal Distribution.- 10.4.2 Seasonal Distribution.- 10.4.3 Vertical Distribution.- 10.4.4 Patchiness and Daily Vertical Migration.- 10.4.5 General Sea Surface Temperature in the Past.- 10.5 Population Dynamics.- 10.5.1 Reproductive Strategies.- 10.5.1.1 Lunar Periodicity.- 10.5.1.2 Annual Periodicity.- 10.5.2 Water Mass Boundary Effects.- 10.6 Experimental Studies.- 10.7 Summary.- 11. Sedimentation - Settlement of Shells.- 11.1 Introduction.- 11.2 Shells Released by Reproduction and Juvenile Mortality.- 11.3 Aggregates - Sedimentation.- 11.4 Predation.- 11.5 Residence Time and Sinking Velocity.- 11.6 Seasonal Fluctuations in the Settlement.- 11.7 Dissolution in the Deep Water.- 11.8 Summary.- 12. Concluding Remarks.- 12.1 Effects Influencing the Isotopic Signal.- 12.1.1 Temperature Effect.- 12.1.2 GlacialEffect.- 12.1.3 Water Mass Effect.- 12.1.4 VitalEffect.- 12.1.5 Selective Production.- 12.1.6 Differential Dissolution.- 12.2 Carbon Isotopes.- 12.3 Summative Perspective.- 13. References.- 14. Glossary.- 15. Index.

A Theory of Marriage Timing

Abstract: With the use of a midified job-search theory, a conceptual framework is developed to show that some factors influence marriage timing by either facilitating or impeding assortative mating. Transiti...

Citizen participation, perceived control, and psychological empowerment.

Abstract: The research integrates the citizen participation literature with research on perceived control in an effort to further our understanding of psychological empowerment. Eleven indices of empowerment representing personality, cognitive, and motivational measures were identified to represent the construct. Three studies examined the relationship between empowerment and participation. The first study examined differences among groups identified by a laboratory manipulation as willing to participate in personally relevant or community relevant situations. Study II examined differences for groups defined by actual involvement in community activities and organizations. Study III replicated Study II with a different population. In each study, individuals reporting a greater amount of participation scored higher on indices of empowerment. Psychological empowerment could be described as the connection between a sense of personal competence, a desire for, and a willingness to take action in the public domain. Discriminant function analyses resulted in one significant dimension, identified as pyschological empowerment, that was positively correlated with leadership and negatively correlated with alienation.

Equivalence scales, well‐being, inequality, and poverty: sensitivity estimates across ten countries using the luxembourg income study (lis) database

Abstract: The Luxembourg Income Study (LIS) database on which this article is based offers researchers exciting new possibilities for international comparisons based on household income microdata. Among the choices the LIS microdata allows a researcher, e.g. income definition, income accounting unit, etc., is the choice of family equivalence scale, a method for estimating economic well-being by adjusting income for measurable differences in need. The range of potential equivalence scales that can and are being used in the ten LIS countries and elsewhere to adjust incomes for size and related differences in need span a wide spectrum. The purpose of this paper is to review the available equivalence scales and to test the sensitivity of various income inequality and poverty measures to choice of equivalence scale using the LIS database. The results of our analysis indicate that choice of equivalence scale can sometimes systematically affect absolute and relative levels of poverty; and inequality and therefore rankings of countries (or population subgroups within countries). Because of these sensitivities, one must carefully consider summary statements and policy implications derived from cross-national comparisons of poverty and/or inequality.

Recruitment dynamics in complex life cycles

Abstract: Organisms living in the marine rocky intertidal zone compete for space This, together with predation, physical disruption, and differing species tolerances to physiological stress, explains the structure of the ecological communities at some sites At other sites the supply of larvae is limiting, and events in the offshore waters, such as wind-driven upwelling, explain the composition of intertidal communities Whether the community ecology at a site is governed by adult-adult interactions within the site, or by limitations to the supply of larvae reaching the site, is determined by the regional pattern of circulation in the coastal waters Models combining larval circulation with adult interactions can potentially forecast population fluctuations These findings illustrate how processes in different ecological habitats are coupled

The Duke-UNC Functional Social Support Questionnaire. Measurement of social support in family medicine patients.

Abstract: A 14-item, self-administered, multidimensional, functional social support questionnaire was designed and evaluated on 401 patients attending a family medicine clinic. Patients were selected from randomized time-frame sampling blocks during regular office hours. The population was predominantly white, female, married, and under age 45. Eleven items remained after test-retest reliability was assessed over a 1- to 4-week follow-up period. Factor analysis and item remainder analysis reduced the remaining 11 items to a brief and easy-to-complete two-scale, eight-item functional social support instrument. Construct validity, concurrent validity, and discriminant validity are demonstrated for the two scales (confidant support--five items and affective support--three items). Factor analysis and correlations with other measures of social support suggest that the three remaining items (visits, instrumental support, and praise) are distinct entities that may need further study.

A new set of international comparisons of real product and price levels estimates for 130 countries, 1950–1985

Abstract: A new set of international comparisons covering the period 1950–85 is developed here for 121 market and 9 centrally planned economies. This new so-called Penn World Table (Mark 4), a completely revised and updated expansion of an equivalent table published by the authors in 1984, draws on the data of two previously unavailable international comparison benchmark studies. This article presents a detailed description of all estimation procedures, and excerpts from the overall DATA TABLE covering two years, 1980 and 1985. Three computer diskettes accompanying this article (and also available from the authors) contain the complete 36–year, 60,000 entry DATA TABLE in a form that economizes on scarce journal space and is immediately machine-readable. For the 121 market economies, the DATA TABLE gives annually, in addition to population and exchange rates, real product and price level estimates for four different national income concepts, and for the major subaggregates, consumption, investment, and government. Only population and real gross domestic product estimates are given for the nine centrally planned economies, however. This new table is one more step toward the goal of establishing a new worldwide System of Real National Accounts.

Absence of backscattering in the quantum Hall effect in multiprobe conductors

Abstract: Under certain conditions, high magnetic fields in a two-dimensional conductor lead to a suppression of both elastic and inelastic backscattering. This, together with the formation of edge states, is used to develop a picture of the integer quantum Hall effect in open multiprobe conductors. We consider both ideal contacts without elastic scattering and also disordered contacts. Ideal contacts populate edge states equally whereas disordered contacts lead to an initial nonequilibrium population of the edge states. In Hall samples much larger than an inelastic length, and in the presence of disordered contacts, the sample edges become equipotential lines only an inelastic scattering length away from the current source and current drain contacts. Samples so small that the carriers can travel from one contact to the other without inelastic relaxation do not exhibit exact quantization if the contacts are disordered. In all cases we find that the quantum Hall effect occurs only if the sample exhibits at least two sets of equilibrated edge states which do not interact via elastic or inelastic scattering. The onset of interaction between the two sets of edge states leads to deviations from exact quantization and eventually to a breakdown of the quantum Hall effect.

How common is white coat hypertension

Abstract: Twenty-one percent of 292 patients with untreated borderline hypertension (clinic diastolic blood pressures persistently between 90 and 104 mm Hg) were found to have normal daytime ambulatory pressures (defined from a population of normotensive subjects). These patients were defined as having "white coat" hypertension, and they were more likely to be female and younger, to weigh less, and to be more recently diagnosed than patients whose pressure was elevated both in the clinic and during ambulatory monitoring. Patients with white coat hypertension did not show a generalized increase of blood pressure lability, nor an exaggerated pressor response while at work. The phenomenon is more pronounced when blood pressure is measured by a physician than by a technician. In such patients, the pressor response may be relatively specific to the physician's office and lead to significant misclassification of hypertension.

Allozyme electrophoresis: A handbook for animal systematics and population studies [Book Review]

Abstract: Review(s) of: Allozyme electrophoresis: A handbook for animal systematics and population studies by B.J. Richardson , P.R. Baverstock and M. Adams. Academic Press: Sydney, Florida, London 1986 ISBN 0125878400 Pp. 401 ; R.R.P.: $60.00 (hard cover)

The Hispanic Population of the United States

Abstract: This Census Bureau study examines the social demographic and ethnic diversity among the Hispanic groups in the US. Chapter 1 considers the meaning of Hispanic ethnicity with brief historical vignettes on the incorporation of each of the 3 major groups into US society. Chapter 2 is devoted to defining the population and to providing a critical discussion of the data used to portray changes in the characteristics of Hispanic origin peoples. While this discussion is based largely on data from the 1980 census attention is also given to 1960 and 1970 census data to identify the strengths and limitations of the items used to enumerate the Spanish origin population over time. It also considers how changes in enumeration practices and in definitions of specific items limit the accuracy of measurement and especially the representation of temporal change. The remainder of the book is dedicated to compiling a comprehensive profile of the demographic and socioeconomic characteristics of the Hispanic origin populations emphasizing the vast diversity among them through comparisons of Mexicans Puerto Ricans and Cubans; Central/South Americans; and where appropriate blacks and non-Hispanic whites. The book is organized by subject matter rather than by nationality. The analyses begin with a demographic profile in chapter 3 which considers the size of the population as well as its changing age and sex composition rates of growth and residential distribution. Since the rapid growth of the population has resulted from both high fertility and high rates of immigration during the 1960s and 1970s separate chapters are devoted to each of these topics. Another chapter considers the marriage patterns and living arrangements of Hispanic origin groups. 3 additional chapters examine the educational labor market and economic well-being of the population. Other topics of special importance to Hispanic origin groups such as linguistic practices are not covered in extensive detail as separate chapters but rather are discussed in conjunction with the topics considered above. A final brief chapter reiterates in synopsis form the major conclusions of the study.

Restless bandits: activity allocation in a changing world

Abstract: We consider a population of n projects which in general continue to evolve whether in operation or not (although by different rules). It is desired to choose the projects in operation at each instant of time so as to maximise the expected rate of reward, under a constraint upon the expected number of projects in operation. The Lagrange multiplier associated with this constraint defines an index which reduces to the Gittins index when projects not being operated are static. If one is constrained to operate m projects exactly then arguments are advanced to support the conjecture that, for m and n large in constant ratio, the policy of operating the m projects of largest current index is nearly optimal. The index is evaluated for some particular projects.

Obesity and knee osteoarthritis. The Framingham Study.

Abstract: Study objective To determine whether obesity preceded knee osteoarthritis and was thus a possible cause. Design Cohort study with weight and other important variables measured in 1948 to 1951 (mean age of subjects, 37 years) and knee arthritis evaluated in 1983 to 1985 (mean age of subjects, 73 years). Setting Population-based participants; a subset (n = 1420) of the Framingham Heart Study cohort. Methods For those subjects in the Framingham Study having knee radiographs taken as part of the 18th biennial examination (1983 to 1985), we examined Metropolitan Relative Weight, a measure of weight adjusted for height at the onset of the study (1948 to 1951). Relative risks were computed as the cumulative incidence rate of radiographic knee osteoarthritis in the heaviest weight groups at examination 1 divided by the cumulative rate in the lightest 60% weight groups at examination 1. Relative risks were adjusted for age, physical activity level, and uric acid level. Results In 1983 to 1985, 468 subjects (33%) had radiographic knee osteoarthritis. For men, the risk of knee osteoarthritis was increased in those in the heaviest quintile of weight at examination 1 compared with those in the lightest three quintiles (age-adjusted relative risk, 1.51; 95% confidence interval [CI], 1.14 to 1.98); risk was not increased for those in the second heaviest quintile (relative risk, 1.0). The association between weight and knee osteoarthritis was stronger in women than in men; for women in the most overweight quintile at examination 1, relative risk was 2.07 (95% CI, 1.67 to 2.55), and for those in the second heaviest group, relative risk was 1.44 (95% CI, 1.11 to 1.86). This link between obesity and subsequent osteoarthritis persisted after controlling for serum uric acid level and physical activity level, and was strongest for persons with severest radiographic disease. Obesity at examination 1 was associated with the risk of developing both symptomatic and asymptomatic osteoarthritis. Conclusions These results and other corroborative cross-sectional data show that obesity or as yet unknown factors associated with obesity cause knee osteoarthritis.

The co-occurrence of alcoholism with other psychiatric disorders in the general population and its impact on treatment.

Abstract: It is apparent from previous studies in clinical populations that there is a high comorbidity rate between alcoholism and other psychiatric diagnoses. However, this may simply be an expression of Berkson's bias (i.e., an increased tendency for persons with multiple diagnoses to seek and receive treatment and thus fall into study populations drawn from treatment sources). In this article, we use data from the Epidemiologic Catchment Area survey to examine the comorbidity between alcohol abuse and dependence, other substances of abuse and nonsubstance psychiatric disorders in a sample of approximately 20,000 persons drawn from the general population. We also examine the effect of comorbidity on psychiatric treatment. Every one of the psychiatric diagnoses we examined was more likely to occur in alcoholics than in nonalcoholics. Associations were particularly strong with antisocial personality disorder, other substance use and mania. The association between alcoholism and depressive disorders was positive but not very strong. The presence of other illnesses increased the likelihood of utilization of treatment services by alcoholics but did not increase the likelihood that drinking problems would be communicated to a doctor. The findings confirm prior studies of comorbidity in clinical samples and suggest the need for increased vigilance toward alcoholism by physicians.