Showing papers on "Population published in 1974"

Labor and Monopoly Capital

Abstract: This book first took shape in my mind as little more than a study of occupational shifts in the United States. I was interested in the structure of the working class, and the manner in which it had changed. That portion of the population employed in manufacturing and associated industries—the so-called industrial working class—had apparently been shrinking for some time, if not in absolute numbers at any rate in relative terms. Since the details of this process, especially its historical turning points and the shape of the new employment that was taking the place of the old, were not clear to me, I undertook to find out more about them. And since, as I soon discovered, these things had not yet been clarified in any comprehensive fashion, I decided that there was a need for a more substantial historical description and analysis of the process of occupational change than had yet been presented in print.This article can also be found at the Monthly Review website, where most recent articles are published in full.Click here to purchase a PDF version of this article at the Monthly Review website.

The hitch-hiking effect of a favourable gene.

Abstract: SUMMARY When a selectively favourable gene substitution occurs in a population, changes in gene frequencies will occur at closely linked loci. In the case of a neutral polymorphism, average heterozygosity will be reduced to an extent which varies with distance from the substituted locus. The aggregate eifect of substitution on neutral polymorphism is estimated; in populations of total size 10 6 or more (and perhaps of 10 4 or more), this eifect will be more important than that of random fixation. This may explain why the extent of polymorphism in natural populations does not vary as much as one would expect from a consideration of the equilibrium between mutation and random fixation in populations of different sizes. For a selectively maintained polymorphism at a linked locus, this process will only be important in the long run if it leads to complete fixation. If the selective coefficients at the linked locus are small compared to those at the substituted locus, it is shown that the probability of complete fixation at the linked locus is approximately exp (— Nc), where c is the recombinant fraction and N the population size. It follows that in a large population a selective substitution can occur in a cistron without eliminating a selectively maintained polymorphism in the same cistron.

A framework for the study of access to medical care.

Abstract: Definitions and aspects of the concept of access to medical care are reviewed and integrated into a framework that views health policy as designed to affect characteristics of the health care delivery system and of the population at risk in order to bring about changes in the utilization of health care services and in the satisfaction of consumers with those services. Indicators are suggested for the measurement of the various relevant aspects of access, with the system and population descriptors seen as process indicators and utilization and satisfaction as outcome indicators in a theoretical model of the access concept.

Morbidity and Mortality in Diabetics In the Framingham Population: Sixteen Year Follow-up Study

Abstract: In a sixteen year follow-up study in Framingham, it was found that diabetics in general show an increased morbidity and mortality from all cardiovascular causes. Insulin-treated diabetic women showed the greatest relative mortality from coronary heart disease. Diabetics were found to have higher lipid values, more hypertension and more obesity, even prior to diagnosis. When all the associated risk factors, individually or together, were taken into consideration their presence could not entirely explain the increase in cardiovascular morbidity and mortality experienced by the diabetic. An as yet unknown factor appears to be present in diabetics that could be responsible for much of the higher incidence of cardiovascular complications in diabetics.

The evolutionary advantage of recombination

Abstract: The controversy over the evolutionary advantage of recombination initially discovered by Fisher and by Muller is reviewed. Those authors whose models had finite-population effects found an advantage of recombination, and those whose models had infinite populations found none. The advantage of recombination is that it breaks down random linkage disequilibrium generated by genetic drift. Hill and Robertson found that the average effect of this randomly-generated linkage disequilibrium was to cause linked loci to interfere with each other's response to selection, even where there was no gene interaction between the loci. This effect is shown to be identical to the original argument of Fisher and Muller. It also predicts the "ratchet mechanism" discovered by Muller, who pointed out that deleterious mutants would more readily increase in a population without recombination. Computer simulations of substitution of favorable mutants and of the long-term increase of deleterious mutants verified the essential correctness of the original Fisher-Muller argument and the reality of the Muller ratchet mechanism. It is argued that these constitute an intrinsic advantage of recombination capable of accounting for its persistence in the face of selection for tighter linkage between interacting polymorphisms, and possibly capable of accounting for its origin.

Biological Populations with Nonoverlapping Generations: Stable Points, Stable Cycles, and Chaos

Abstract: Some of the simplest nonlinear difference equations describing the growth of biological populations with nonoverlapping generations can exhibit a remarkable spectrum of dynamical behavior, from stable equilibrium points, to stable cyclic oscillations between 2 population points, to stable cycles with 4, 8, 16, . . . points, through to a chaotic regime in which (depending on the initial population value) cycles of any period, or even totally aperiodic but boundedpopulation fluctuations, can occur. This rich dynamical structure is overlooked in conventional linearized analyses; its existence in such fully deterministic nonlinear difference equations is a fact of considerable mathematical and ecological interest.

Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset.

Abstract: Weight loss causes loss of menstrual function (amenorrhea) and weight gain restores menstrual cycles. A minimal weight for height necessary for the onset of or the restoration of menstrual cycles in cases of primary or secondary amenorrhea due to undernutrition is indicated by an index of fatness of normal girls at menarche and at age 18 years, respectively. Amenorrheic patients of ages 16 years and over resume menstrual cycles after weight gain at a heavier weight for a particular height than is found at menarche. Girls become relatively and absolutely fatter from menarche to age 18 years. The data suggest that a minimum level of stored, easily mobilized energy is necessary for ovulation and menstrual cycles in the human female.

Dispersion and Population Interactions

Abstract: The spatial component of environment, often neglected in modeling of ecological interactions, in general operates to increase species diversity. This arises due to the heterogeneity of the environment, but such heterogeneity can arise in an initially homogeneous environment due to what may be random initial events (e.g., colonization patterns), effects of which are magnified by species interactions. In this way, homogeneous environments may become heterogeneous and heterogeneous environments even more so. In patchy environments, distinct patches are likely to be colonized initially by different species, and thereby a kind of founder effect results whereby individual patches evolve along different paths simply as a consequence of initial colonization patterns. Species which would be unable to invade may nevertheless survive by establishing themselves early and will moreover be found in lower densities in other areas as overflow from their "safe" areas. Spatially continuous environments may evolve toward es...

Niche Overlap and Diffuse Competition

Abstract: Current theory predicts a distinct upper limit on the permissible degree of niche overlap; moreover, theory suggests that maximal tolerable overlap should be relatively insensitive to environmental variability. Data presented here demonstrate that, within the lizard subset of natural desert communities, niche overlap decreases both with increasing environmental variability and with increasing numbers of lizard species. The latter two factors are themselves positively correlated. A partial correlation analysis is interpreted as indicating that the extent of tolerable niche overlap does not necessarily decrease due to environmental variability, but rather that overlap is probably more closely related to the number of potential interspecific competitors in a community, or what has been termed "diffuse competition." This result lends support to the "niche overlap hypothesis," which asserts that maximal tolerable overlap should vary inversely with the intensity of competition. Moreover, this empirical discovery indicates that niche overlap theory could be profitably expanded to incorporate the number of competing species. Although the average amount of overlap between pairs of species decreases with the intensity of diffuse competition, the overall degree of competitive inhibition tolerated by individuals comprising an average species could nevertheless remain relatively constant, provided that extensive niche overlap with a few competitors is roughly equivalent to lower average overlap with a greater number of competitors.

Gene Flow in Seed Plants

Abstract: Gene dispersal (flow, or migration) within and between plant populations has been of continuous interest to plant breeders and seed producers for many decades. Economic considerations have stimulated studies of gene flow as a function of distance, breeding system, pollinating agent, and planting design in numerous domestic plants. Only during the past two decades have a large body of plant evolutionists become interested in information accruing from these studies, and in the rates of gene flow in wild populations. Their efforts have concentrated primarily on related problems such as adaptations for and mechanics of pollen and seed (or fruit) dispersal, plant-pollinator coevolution, adaptive radiation in pollination and seed dispersal mechanisms, and colonization and the alteration of species boundaries. Early in this century, anecdoctal evidence on the movement of pollen and seed vectors, dispersal of pollen by wind, and the range extensions of weed species led to the casual assumption that gene flow must be extensive, and that it must play a major role in the cohesion of populations and population systems. This view eroded as more information became available and was more critically interpreted (e.g., Grant, 1958, 1971; Ehrlich and Raven, 1969; Stebbins, 1970a; Bradshaw, 1972).

Effectiveness of linear prediction characteristics of the speech wave for automatic speaker identification and verification

Abstract: Several different parametric representations of speech derived from the linear prediction model are examined for their effectiveness for automatic recognition of speakers from their voices. Twelve predictor coefficients were determined approximately once every 50 msec from speech sampled at 10 kHz. The predictor coefficients and other speech parameters derived from them, such as the impulse response function, the autocorrelation function, the area function, and the cepstrum function were used as input to an automatic speaker‐recognition system. The speech data consisted of 60 utterances, consisting of six repetitions of the same sentence spoken by 10 speakers. The identification decision was based on the distance of the test sample vector from the reference vector for different speakers in the population; the speaker corresponding to the reference vector with the smallest distance was judged to be the unknown speaker. In verification, the speaker was verified if the distance between the test sample vector and the reference vector for the claimed speaker was less than a fixed threshold. Among all the parameters investigated, the cepstrum was found to be the most effective, providing an identification accuracy of 70% for speech 50 msec in duration, which increased to more than 98% for a duration of 0.5 sec. Using the same speech data, the verification accuracy was found to be approximately 83% for a duration of 50 msec, increasing to 98% for a duration of 1 sec. In a separate study to determine the feasibility of text‐independent speaker identification, an identification accuracy of 93% was achieved for speech 2 sec in duration even though the texts of the test and reference samples were different.

Identification of a novel cell type in peripheral lymphoid organs of mice

Abstract: Several properties of lymphoid dendritic cells in situ have been determined, and contrasted to information previously established for lymphocytes and mononuclear phagocytes. Dendritic cells are not found in newborn mice, and their concentration in both spleen and mesenteric lymph node does not reach adult levels until 3–4 wk of age. Dendritic cells largely disappear from adherent populations following administration of steroids (2.5 mg hydrocortisone acetate s.c.) and ionizing radiation (Do of 100 rads for Co60). Splenic dendritic cells can originate from precursors located in both bone marrow and spleen itself, probably the red pulp. The mature splenic population does not actively divide (pulse labeling index with [3H]thymidine of 1.5–2.5%), but does turnover at substantial rate, 10+% of the total pool per day. The influx of new cells appears to be derived from a proliferating precursor compartment, but the mechanism for efflux or turnover is not known. Dendritic cells in spleen and node undergo little or moderate increase in numbers during development of a primary immune response. These in vivo characteristics, taken together, further distinguish dendritic cells as a novel cell type, distinct from mononuclear phagocytes and lymphocytes.

Growth with Exhaustible Natural Resources: Efficient and Optimal Growth Paths

Abstract: The proposition that limited natural resources provide a limit to growth and to the sustainable size of population is an old one. The natural resource that was the centre of the discussion in Malthus' day was land; more recently, some concern has been expressed over the limitations imposed by the supplies of oil, or more generally, energy sources, of phosphorus, and of other materials required for production. Those who predicted imminent doom in the nineteenth century were obviously wrong. Were they simply wrong about the immediacy of catastrophe, or did they leave out something fundamental from their calculations? There are at least three economic forces offsetting the limitations imposed by natural resources: technical change, the substitution of man-made factors of production (capital) for natural resources, and returns to scale. This study is an attempt to determine more precisely under what conditions a sustainable level of per capita consumption is feasible, to characterize steady state paths in economies with natural resources, and to describe the optimal growth path of the economy, in particular to derive the optimal rate of extraction and the optimal savings rate in the presence of exhaustible natural resouces. One of the interesting problems posed by the presence of exhaustible natural resources is that some of the basic concepts of growth theory, such as " steady state " and " natural rate of growth ", need to be re-examined. If, for instance, there are two unproduced factors, labour and natural resources, one of which is growing exponentially, the other of which is not growing at all, what is the " natural rate of growth "? In conventional economic discussions, the long-run growth rate of the economy is determined simply by the natural rate of growth and is independent of the savings rate. We shall show that in economies with natural resources, efficient growth paths which differ with respect to savings rate also differ, even asymptotically, with respect to the rate of growth. The analysis of optimal growth paths presents certain technical difficulties, because there are two state variables (the stock of capital per man and the stock of natural resources per man) and two control variables (the rate of extraction of natural resources and the savings rate). Fortunately, by the appropriate choice of variables, the qualitative properties of the path can be completely described. Optimal growth paths for economies with only capital or with just natural resources have been examined elsewhere. Typically, a country begins with little capital and hence, in the former models, optimal growth is characterized by increasing consumption per capita. On the other hand, natural resources act much like a capital good; since the stock

Proportion of disease caused or prevented by a given exposure, trait or intervention

Abstract: Miettinen, O. S. (Harvard School of Public Health, Boston. Mass. 02115). Proportion of disease caused or prevented by a given exposure, trait or intervention. Am J Epidemiol 99: 325-332, 1974.—The structures of two epidemiologic parameters are explored. One, the \"etiologic fraction.\" relates to markers of increased risk, and it is the proportion of disease attributable to the marker and/or to factors associated with it. The other, the \"prevented fraction,\" is the equivalent of this for a marker of reduced risk. It is shown that both parameters depend—in different ways—on the frequency of the marker among cases of the disease, and on the \"standardized morbidity ratio\" for those with the marker. Point estimation of these parameters is often straight-forward, particularly in case-control studies.

Pathologic changes in the peripheral airways of young cigarette smokers.

Abstract: The lungs of young smokers and controls of comparable age from a population of sudden non-hospital deaths were systematically studied to determine the relation between cigarette smoking and pathologic changes in peripheral airways. The characteristic lesion observed was a respiratory bronchiolitis associated with clusters of pigmented alveolar macrophages and was present in the lungs of all smokers studied but rarely seen in nonsmokers (p<0.002). The lungs of smokers also showed small but significant increases in mural inflammatory cells and denuded epithelium in the membranous bronchioles as compared to controls (p<0.05). We postulate that this respiratory bronchiolitis is a precursor of centriacinar emphysema and may be responsible for the subtle functional abnormalities observed in young smokers. (N Engl J Med 291: 755–758, 1974)

Competition and the structure of bird communities.

Abstract: Professor Cody's monograph emphasizes the role of competition at levels above single species populations, and describes how competition, by way of the niche concept, determines the structure of communities. Communities may be understood in terms of resource gradients, or niche dimensions, along which species become segregated through competitive interactions. Most communities appear to exist in three or four such dimensions. The first three chapters describe the resource gradients (habitat types, foraging sites, food types), show what factors restrict species to certain parts of the resource gradients and so determine niche breadths, and illustrate the important role of resource predictability in niche overlap between species for resources they share. Most examples are drawn from eleven North and South American bird communities, although the concepts and methodology are far more general. Next, the optimality of community structure is tested through parallel and convergent evolution on different continents with similar climates and habitats, and the direct influence of competitors on resource use is investigated by comparisons of species--poor island communities to species-rich mainland ones. Finally, the author discusses those sorts of environments in which the evolution of one species--one resource set is not achieved, and where alternative schemes of resource allocation, often involving several species that act ecologically as one, must be followed.

Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine. II. Mucous cells

Abstract: The mucous cell population of duodenum, jejunum and ileum was investigated in the light and electron microscopes with the help of radioautography in mice sacrificed at various times after single injection or continuous infusion of 3H-thymidine. Mucous cells are characterized by globules of mucus and by dilated cisternae of rough endoplasmic reticulum. Two subgroups of mucous cells, one called common and the other granular, may be identified. The granular mucous cells differ from the common ones by the presence of small dense granules embedded within the mucous globules. Each subgroup is further divided into immature oligomucous cells containing few mucous globules, and mature goblet cells with a large accumulation of mucous globules. Common and granular oligomucous cells are found exclusively in the crypt, mainly within the lower mid-crypt, whereas the corresponding two types of goblet cells are present in the upper part of the crypts and in the lower part of the villi. Only common mucous cells are observed in the upper part of the villi. The two types of oligomucous cells, but not goblet cells, have the ability to take up 3H-thymidine and divide. Electron microscopic radioautography demonstrates that, as oligomucous cells migrate upwards, they transform into goblet cells. The latter then migrate to the villus epithelium. In the case of granular mucous cells, this migration is associated with a gradual loss of the characteristic dense granules, so that the granular goblet cells reaching the upper part of the villi become common goblet cells. The goblet cells in the villus epithelium, regardless of their origin, ascend towards the villus tips where they are lost through the extrusion zones. The turnover time of common mucous cells is about three days, as for columnar cells; and that of granular mucous cells, somewhat shorter. In both cases, the divisions of oligomucous cells account only for the production of about half the mucous cells present. Hence, the other half must be derived from precursors other than oligomucous cells. Since a few crypt-base columnar cells contain the odd mucous globule, they are suspected of being the precursors of the two types of oligomucous cells and, through them, of the entire mucous cell population.

Model of brain rhythmic activity. The alpha-rhythm of the thalamus.

Abstract: 1. A model of a neuronal network has been set up in a digital computer based on histological and biophysical data experimentally obtained from the thalamus; the model includes two populations of neurons interconnected by means of negative feedback; in the model allowance is also made for other sort of interactions. 2. To test the hypothesis that the alpha-rhythm (8–13 Hz rhythmic activity characteristic of the EEG) is a filtered noise signal the simulated neuronal network was stimulated by random trains of pulses with a Poisson distribution. The density of pulses fired by the simulated neurons was computed as well as the oscillations of the mean membrane potential of the population of simulated neurons. The latter was found to be equivalent to the experimentally obtained alpha rhythms. 3. In order to test the hypothesis that several noise sources are responsible for thalamo-cortical coherences three simulated neuronal networks were coupled together using several noise sources as secondary inputs. It was shown that although all the networks produced simulated alpha signals with identical spectra they could have significantly different values of coherence depending on the relation between correlated and uncorrelated input signals. 4. The model was analysed by means of linear systems analysis after introducing the necessary simplifications and approximations. In this way it was possible to evaluate the influence of different physiological or histological parameters upon the statistical properties of the resulting rhythmic activity in an analytical form. 5. By changing the model parameters it was shown that a family of spectral curves could be obtained which simulated the development of the EEG as function of age from a predominantly low frequency to a clearly rhythmic type of signal. This was shown to depend mainly on the feedback coupling parameters.

Biological Accommodation in the Benthic Community at McMurdo Sound, Antarctica

Abstract: Studies of the benthos between 30 and 60 m at Cape Armitage, McMurdo Sound. Antarctica, reveal an epifaunal community in which sponges and their asteroid and nudibranch predators predominate. Field experiments demonstrated that, with the exception of Mycale accrata, the growth rates of the sponges are too slow to measure in one year. Mycale, however, was observed to increase its mass as much as 67%. Because of its more rapid growth rate, Mycale appears to be the potential dominant in competition for substratum space, the resource potentially limiting to the sessile species. This conclusion is supported by observations of Mycale growing over and, in some cases, apparently having smothered many other sessile species representing at least three phyla. The densities and size frequency distributions of all the predators were measured; numerous feeding observations allowed an accurate appraisal of dietary compositions. Because of the predators' very slow consumption rates, however, direct measures of ingestion and its impact on prey populations were not possible. Estimates of the ingestion rates were derived from measurements of predator respiration rates, growth rates, and gonad growth. Data from the field surveys and the energetics studies suggest that Mycale is prevented from dominating the space resource by the predation of two asteroids. Perknaster fuscus antarcticus and Acodontaster conspicuus. Adult Perknaster specialize on Mycale, and the sponge provides a small proportion of the diet of A. conspicuus. Acodontaster conspicuus and the dorid nudibranch Austrodoris memurdensis are the most important predators on three species of rossellid sponges (Rossella racovitzae, R. nuda, and Scolymastra joubini). Despite this relatively heavy consumption and despite the fact that none of these sponges has a refuge in growth from potential mortality from A. conspicuus, very large standing crops of the rossellid sponges have accumulated. This accumulation appears to result from predation on larval and young A. conspicuus and Austrodoris by Odontaster validus, which is primarily a detrital feeder and apparently acts as a filter against the settlement and survival of the A. conspicuus and Austrodoris larvae. In addition, predation upon adult A. conspicuus by O. validus and the actinian urticinopsis antarcticus annually kills approximately 3.5% of the A. conspicuus population. This mortality exceeds the apparent rate at which A. conspicuus escape the larval filter.

Suicidal feelings in the general population: a prevalence study.

Abstract: Seven hundred and twenty subjects from a general population survey were interviewed as to the occurrence of suicidal feelings of five different degrees. A total of 8.9 per cent reported suicidal feelings of some degree in the past year. Responses ranged along a continuum such that subjects reporting more intense feelings also reported the less intense. For 3.5 per cent the maximum intensity consisted only of feelings that life was not worth while; 2.8 per cent reached the point of wishing themselves dead, 1 per cent the point of having thought of taking their lives, 1 per cent seriously considered suicide or made plans, and 0.6 per cent made an actual suicide attempt. Subjects experiencing suicidal feelings in the last year reported more minor psychiatric symptoms, particularly of depression, were more socially isolated, less religious, and to a lesser extent had experienced more stressful events and more somatic illness. In these respects they resembled descriptions of completed suicides. Unlike suicides, however, they were more likely to be female and did not show any other specific demographic characteristics.

Optimal Reproductive Effort in Fluctuating Environments

Abstract: When the life history functions B (E) and P (E)-fecundity and postbreeding survival-are subject to environmentally induced fluctuations, one of two patterns is selected for: If the functions are concave (iteroparity in constant environments), the optimal population is monomorphic. Variation in B (E) selects for reduced effort in all individuals; variation in P (E) for increased breeding. If functions are convex (semelparity in constant environments) and fecundity is the parameter at issue, the optimal population can be polymorphic, with only a fraction of the population reproducing annually. Increasing the severity of fluctuations reduces the optimal value of this proportion, even if the average rate of reproductive success is not changed.

Conditioned Behavior in Drosophila melanogaster

Abstract: Populations of Drosophila were trained by alternately exposing them to two odorants, one coupled with electric shock. On testing, the flies avoided the shock-associated odor. Pseudoconditioning, excitatory states, odor preference, sensitization, habituation, and subjective bias have been eliminated as explanations. The selective avoidance can be extinguished by retraining. All flies in the population have equal probability of expressing this behavior. Memory persists for 24 hr. Another paradigm has been developed in which flies learn to discriminate between light sources of different color.

Estimation of linkage disequilibrium in randomly mating populations

Abstract: The degree of linkage disequilibrium, D, between two loci can be estimated by maximum likelihood from the frequency of diploid genotypes in a sample from a random-mating population. Haploid genotypes can be identified directly in some species from a sample of chromosomes extracted from the population and made homozygous, or by test crossing. The maximum likelihood estimators of D are described, with examples, for both methods, including the cases where both loci are codominant and one or both are dominant. The efficiencies of the methods are compared when D = 0: If both loci are codominant the estimate of D has the same variance V(D) = p(1 − p)q(1 − q)/N, from a sample of N identified diploids as from N identified haploid types, where p and q are the gene frequencies; therefore the diploid method is more efficient in practice since less labour is required. With dominance at either locus V(D) is lower for samples of the same size using the haploid method if the dominant alleles are at high frequency.

Non-linear age-dependent population dynamics

Abstract: where P( t ) is the total population at time t and 5 is the growth modulus. This law is clearly inapplicable to situations in which the population competes for resources (e.g., space and food), for in these situations 5 should depend on the size of the population: the larger the population, the slower should be its rate of growth. To overcome this deficiency in the Malthusian law, VERHULST [1845, 1847] assumed that f i= (6o-co0 P ) P (5o, COo=constant). (1.2)

Membrane proteins related to anion permeability of human red blood cells. I. Localization of disulfonic stilbene binding sites in proteins involved in permeation.

Abstract: (3H)DIDS (4,4′-diisothiocyano-2,2′-ditritiostilbene-disulfonate) was used as a convalent label for membrane sites involved in anion permeability. The label binds to a small, superficially located population of sites, about 300,000 per cell, resulting in almost complete inhibition of anion exchange. The relationship of biding to inhibition is linear suggesting that binding renders each site nonfunctional. In the inhibitory range less than 1% of the label is associated with lipids but at higher concentrations of DIDS, the fraction may be as high as 4%. In ghosts, however, treatment with (3H)DIDS results in extensive labeling of lipids. In cells, a protein fraction that behavens on SDS acrylamide gels as thought its molecular weight is 95,000 daltons (95K) is predominatly labeled by (3H)DIDS. The only other labeled protein is the major sialoglycoprotein which contains less than, 5% of the total bound (3H)DIDS. Because of the linear relationship of binding to inhibition and the unique architecture of the site, it is suggested that the (3H)DIDS-binding site of the 95K protein is the substrate binding site of the anion transport system. The 95K protein is asymmetrically arranged in the membrane with the sites arranged on the outer face accessible to agent in the medium. In “leaky” ghost, only a few additional binding sites can be reached from the inside of the membrane in the 95K protein, in contrast to the extensive labeling of other membrane proteins in ghosts as compared to cells.

The Small Sample Behavior of Some Statistics Which Test the Equality of Several Means

Abstract: Four statistics which may be used to test the equality of population means are com-pared with respect to their robustness under heteroscedasticity, their power, and the overlap of their critical regions. The four are: the ANOVA F-statistic; a modified F which has the same numerator as the ANOVA but an altered denominator; and two similar statistics proposed by Welch and James which differ primarily in their approximations for their critical values. The critical values proposed by Welch are a better approximation for small sample sizes than that proposed by James. Both Welch's statistic and the modified F are robust under the inequality of variances. The choice between them depends upon the magnitude of the means and their standard errors. When the population variances are equal, the critical region of the modified F more closely approximates that of the ANOVA than does Welch's.

Epidemiology;: An introductory text

Abstract: This classic text presents the basic principles of epidemiology. It includes coverage of epidemiologic concepts, measurements of morbidity and mortality, sources of data on community health, selected indices of health, descriptive epidemiology, analytic studies, prophylactic and therapeutic trials, screening in the detection of disease, population dynamics and health, epidemiologic aspects of infectious disease, occupational epidemiology, selected statistical topics, and more.