Research papers

Population biology of infectious diseases: Part I

Roy M. Anderson, Robert M. May

The biology of filter feeding teleosts in Lake St Lucia, Zululand

Stephen J. M. Blaber

The biology of filter feeding teleosts in St Lucia, was studied for two years from 1976 to 1978. The three common species, Gilchristella aestuarius, Hilsa kelee and Thryssa vitrirostris were studied with the composition and cyclical nature of the zooplankton which formed their food. Stolephorus commersonii and Hepsetia breviceps which were rare were only briefly examined. The zooplankton was dominated by the calanoid Pseudodiaptomus stuhlmanni which formed > 70 % of the calorific value of the zooplankton for 70 % of the study period. The mysid Mesopodopsis africana was second in importance in terms of calorific contribution while the amphipod Grandidierella lignorum was relatively abundant. Larval forms, particularly post‐veligers of Assiminea bifasciata were also important. There was a close correlation between the zooplankton cycles, both diel and annual, and the feeding, reproduction and recruitment of the three common filter feeding teleosts. G. aestuarius spent its whole life‐cycle in the system and spawned in early summer when the resulting juveniles could feed on the summer zooplankton peaks. They grew at 0.5 cm month −1 and attained maximum size in one year. They were non‐selective taking mainly P. stuhlmanni and post‐veligers. H. kelee spawned in the sea and juveniles were common in St Lucia during 1978 when they fed non‐selectively, chiefly on P. stuhlmanning the summer before disappearing over the winter. The resulting offspring went through a sequence of dietary changes which were closely related to zooplankton cycles. The importance of P. stuhlmanni in the pelagic food web of St Lucia is illustrated. The species supports not only the filter feeding teleosts but indirectly the predatory fish Argyrosomus hololepidotus and Elops machnata which feed on G. aestuarius and T. vitrirostris .

Reproduction in Education, Society and Culture

Michael Erben, Pierre Bourdıeu, Jean-Claude Passeron

Preface to the Second Edition - Pierre Bourdieu Foreword - Tom Bottomore PART ONE: FOUNDATIONS OF A THEORY OF SYMBOLIC VIOLENCE PART TWO: KEEPING ORDER Cultural Capital and Pedagogic Communication The Literate Tradition and Social Conservation Exclusion and Selection Dependence through Independence Appendix The Changing Structure of Higher Education Opportunities Redistribution or Translation?

THE SCIENTIFIC REVOLUTIONS

Peter Heimann

The activity of science has dramatically transformed society; since 1850 applied science has become the basis of the means of economic production in Europe. While modern society depends on industrial production based on the application of scientific results, the spectacular achievements of science in the last century have led to a transformation in the nature of science itself. The organisation of scientific activity for the generation of useful, practical knowledge has acquired a new meaning and impulse in the twentieth century, a development which has been described as the emergence of ‘industrialised science’, science as an industry producing applicable knowledge. An understanding of the dominance of science in contemporary culture and society demands an analysis of the social and intellectual transformations which led to such striking confidence in the value of the investigation and control of nature and the emergence of science as a socially-organised activity. The profound conceptual changes in physics in the twentieth century, the abandonment of the doctrines of absolute space and time in Einstein's theory of relativity and of causality and determinism in quantum mechanics, has customarily led to a depiction of the development of science by means of a disjunction between ‘classical’ or ‘Newtonian’ and ‘modern’ science. This historiographic framework is unsatisfactory, for the development of science must be seen in a broader perspective, as a social and cultural phenomenon. The attainment by natural science of appropriate methods of enquiry and social institutions, its methods being viewed as trained and organised common sense and its aims customarily regarded as value-free, is a feature of its recent history.

A discrete numerical model for granular assemblies

Peter Cundall, Otto D. L. Strack

The distinct element method is a numerical model capable of describing the mechanical behaviour of assemblies of discs and spheres. The method is based on the use of an explicit numerical scheme in which the interaction of the particles is monitored contact by contact and the motion of the particles modelled particle by particle. The main features of the distinct element method are described. The method is validated by comparing force vector plots obtained from the computer program BALL with the corresponding plots obtained from a photoelastic analysis. The photoelastic analysis used for the comparison is the one applied to an assembly of discs by De Josselin de Jong and Verruijt (1969). The force vector diagrams obtained numerically closely resemble those obtained photoelastically. It is concluded from this comparison that the distinct element method and the program BALL are valid tools for research into the behaviour of granular assemblies. La méthode des éléments distincts est un modèle numérique capable de décrire le comportement mécanique de l'assemblage de disques et de sphères. La méthode est basée sur l'utilisation d'un système numérique explicite dans lequel l'interaction des particules est contrôlée contact par contact et le mouvement des particules simulé particule par particule. Les caracteristiques principales de la méthode des eléments distints sont décrites. La méthode est validée en comparant les tracés de vecteur de force obtenus par le programme sur ordicateur BALL avec les tracés correspondants obtanus a l'aide d'une analyse photo-élastique. L'analyse photo-élastique utilisée pour la comparaison est celle appliquée sur un assemblage de disques par De Josselin de Jong et Verruijt (1969). Les diagrammes de vecteur de force obtenus numériquement sont très voisins de ceux obtenus photo-élastiquement. Cette comparaison permet de conclure que la methode des éléments distincts et le programme BALL sont des instruments valables pour la recherche du comportement des assemblages granulaires.

A two-dimensional superfluid?

P. V. E. McClintock

Theoretical Nuclear Physics

John M. Blatt, Victor F. Weisskopf

Will detente kill millikelvin research?

P. V. E. McClintock

Measuring the efficiency of decision making units

A. Charnes, W. W. Cooper, Edwardo L. Rhodes

A nonlinear (nonconvex) programming model provides a new definition of efficiency for use in evaluating activities of not-for-profit entities participating in public programs. A scalar measure of the efficiency of each participating unit is thereby provided, along with methods for objectively determining weights by reference to the observational data for the multiple outputs and multiple inputs that characterize such programs. Equivalences are established to ordinary linear programming models for effecting computations. The duals to these linear programming models provide a new way for estimating extremal relations from observational data. Connections between engineering and economic approaches to efficiency are delineated along with new interpretations and ways of using them in evaluating and controlling managerial behavior in public programs.

Fundamental Patterns of Knowing in Nursing

Barbara A. Carper

Jen Pan, former host of the Jacobin Show, joins me to discuss YouTube political messaging, elite activist language and what social democracy can do for art. Stay tuned for her forthcoming book from Verso.\n

The reproductive biology of Pellonula afzeliusi Johnels, and Sierrathrissa leonensis thys Audenaerde in Lake Kainji, Nigeria

Fidelis O. Otobo

The Biology of Oxygen Radicals

Irwin Fridovich

The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen. An unusual family of enzymes, the superoxide dismutases, protect against the deleterious actions of this radical by catalyzing its dismutation to hydrogen peroxide plus oxygen.

Toward a model of text comprehension and production.

Walter Kintsch, Teun A. van Dijk

The semantic structure of texts can be described both at the local microlevel and at a more global macrolevel. A model for text comprehension based on this notion accounts for the formation of a coherent semantic text base in terms of a cyclical process constrained by limitations of working memory. Furthermore, the model includes macro-operators, whose purpose is to reduce the information in a text base to its gist, that is, the theoretical macrostructure. These opera-tions are under the control of a schema, which is a theoretical formulation of the comprehender's goals. The macroprocesses are predictable only when the control schema can be made explicit. On the production side, the model is con-cerned with the generation of recall and summarization protocols. This process is partly reproductive and partly constructive, involving the inverse operation of the macro-operators. The model is applied to a paragraph from a psycho-logical research report, and methods for the empirical testing of the model are developed. The main goal of this article is to describe the system of mental operations that underlie the processes occurring in text comprehension and in the production of recall and summariza-tion protocols. A processing model will be outlined that specifies three sets of operations. First, the meaning elements of a text become

Modeling by shortest data description

J. Rissanen

On a measure of lack of fit in time series models

Greta M. Ljung, George E. P. Box

The overall test for lack of fit in autoregressive-moving average models proposed by Box & Pierce (1970) is considered. It is shown that a substantially improved approximation results from a simple modification of this test. Some consideration is given to the power of such tests and their robustness when the innovations are nonnormal. Similar modifications in the overall tests used for transfer function-noise models are proposed

Topics in Applied Physics

Edward M. Eyring

"Topics in Applied Physics." Nuclear Technology, 39(3), pp. 327–328

Population Biology of Plants.

B. R. Trenbath, John L. Harper

Aspects of the biology of<i>Scomberomorus maculatus</i>(Mitchill) in Trinidad

Mark Sturm

A study was made of the biology of S. maculatus . Results of gonadal examination of 347 males and 409 females suggest spawning takes place from October to April, a period associated with low salinities. First spawning takes place at ages I1 and/or III for both sexes. Sex ratio results suggest spawning may be promiscuous, males outnumbering females. Egg counts from 12 ripe females ranged from 26 057 to 149 736. A period of abundance from May to September may be associated with a post‐spawning feeding migration encompassing the island, possibly in a clockwise direction. Otolith were used to age 817 fish. Opaque and translucent rings are formed yearly. The translucent ring, representing a period of slow growth, is laid down during the spawning season. The fish can live for nine years with females growing faster than males. Growth parameters are compared with those obtained for Brazilian and Florida fish. Mortality rates were investigated and gill nets effected higher mortality rates than beach seines. Full recruitment takes place at age III for gill nets, and ages II and III for beach seines.

Observations on the biology and nutritive value of the African giant snail <i>Archachatina marginata</i>

S. S. AJAYI, O. O. TEWET, C Moriarty, M. O. AWESU

Summary Food habits, growth rate, reproductive performance, carcass characteristics and nutritive value of the giant snail were investigated in the field and with captive snails. Food consumed included fresh plant material, livestock faeces and dead animals. Clutch sizes varied from six to twelve and incubation periods from 30 to 45 days. Weight gains of young snails of average weight 20 g fed on diets of single plant species ranged from 18% on Talinum triangulare leaves to 200% on pawpaw fruit. Best growth was shown on leaves of cassava and cocoyam, grain chaff of maize and fruit of pawpaw. Dressing‐out percentage of snails of 200 g weight was 37.8%. Nutrient composition of the edible portion compared closely with that of domestic livestock. Nitrogen‐free extractive content was high at 5% and fat low at 1.3%. Mineral analysis revealed a high iron content of 12.2 mg/100 g in the edible carcass. The experiments showed that the snail could thrive in captivity on a variety of locally produced feeds, many of them rejected as waste products. It shows great promise as a domestic animal capable of being reared with negligible capital outlay.

Models for the Specific Adhesion of Cells to Cells

George I. Bell

A theoretical framework is proposed for the analysis of adhesion between cells or of cells to surfaces when the adhesion is mediated by reversible bonds between specific molecules such as antigen and antibody, lectin and carbohydrate, or enzyme and substrate. From a knowledge of the reaction rates for reactants in solution and of their diffusion constants both in solution and on membranes, it is possible to estimate reaction rates for membrane-bound reactants. Two models are developed for predicting the rate of bond formation between cells and are compared with experiments. The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.

Reproduction in Education, Society and Culture

Tricia Broadfoot

Reproduction in Education, Society and Culture Pierre Bourdieu & Jean‐Claude Passeron, 1977 London & Beverly Hills, Sage Publications Pp. 254, Cloth £8.00, Paper £3.50

Physics for technicians

Joshua Amuzu

The recent article on the salaries of technical staff working in university physics departments ( Physics Bulletin October 1977 p451) highlighted one of the problems that beset any attempts at attracting and retaining the services of suitably qualified technical staff. There is no doubt that the quality of technical staff affects in no small measure the quality of work in physics departments in the universities.

Social Learning Theory.

Jackson Kytle, Albert Bandura

Una exploracion de los avances contemporaneos en la teoria del aprendizaje social, con especial enfasis en los importantes roles que cumplen los procesos cognitivos, indirectos, y autoregulatorios.

Longman dictionary of contemporary English

Paul Procter

Longman dictionary of contemporary English , Longman dictionary of contemporary English , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی