Research papers

Graph theory with applications to engineering and computer science

N.R. Malik

GRAPH THEORY WITH APPLICATIONS TO ENGINEERING AND COMPUTER SCIENCE

Narsingh Deo

Aspects of the biology of Tilapia mossambica Peters (Pisces: Cichlidae) in a natural freshwater lake (Lake Sibaya, South Africa)

Michael N. Bruton, R. E. Boltt

An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1–7 m deep. Adult fishes (over 8 cm standard length) are usually absent from water deeper than 12m and shallower than 0–5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral and sublittoral in the warm and transition periods (August–April) but moves into deep water in the cool season (May–July). Exposed and sheltered areas are utilized for different purposes by adult fishes, the former for nesting, and latter for feeding and mouth–brooding. Habitat selection by males is governed by the availability of suitable nest sites. Nests are most common in sparsely–vegetated sheltered areas. Brooding females preferred sheltered littoral areas but ventured onto the terrace to release the fry. Juveniles and fry inhabited exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour is described. The biology of T. mossambica in Lake Sibaya is compared to data on the same, and similar species, in other systems. The utilization of available resources in the lake by T. mossambica is discussed and reference is made to the importance of the retention of generalized characters for the successful habitation of the cyclically–renewed habitat of the littoral.

Some aspects of the biology of Dermestes maculatus Degeer (Coleoptera, Dermestidae) in dried fish

FABIAN N. C. OSUJI

Ion Mobility in Superfluid 3He

T. Soda

Progress of Theoretical Physics Vol. 58 No. 4 (1977) pp. 1096-1101 The Motion and Mobility of Ions in Superfluid 3 He Toshio Soda

Colonialism and the Two Publics in Africa: A Theoretical Statement

Peter P. Ekeh

This paper argues that the experiences of colonialism in Africa have led to the emergence of a unique historical configuration in modern postcolonial Africa: the existence of two publics instead of one public, as in the West. Many of Africa's political problems are due to the dialectical relationships between the two publics. I shall characterize these two publics and attempt to explain some of Africa's political features within the matrix of these publics. In order to give some empirical content to the distinction drawn here, I shall illustrate the issues raised with examples from Nigeria.

A new look at the statistical model identification

Hirotugu Akaike

The history of the development of statistical hypothesis testing in time series analysis is reviewed briefly and it is pointed out that the hypothesis testing procedure is not adequately defined as the procedure for statistical model identification. The classical maximum likelihood estimation procedure is reviewed and a new estimate minimum information theoretical criterion (AIC) estimate (MAICE) which is designed for the purpose of statistical identification is introduced. When there are several competing models the MAICE is defined by the model and the maximum likelihood estimates of the parameters which give the minimum of AIC defined by AIC = (-2)log-(maximum likelihood) + 2(number of independently adjusted parameters within the model). MAICE provides a versatile procedure for statistical model identification which is free from the ambiguities inherent in the application of conventional hypothesis testing procedure. The practical utility of MAICE in time series analysis is demonstrated with some numerical examples.

Historical Origins of the Health Belief Model

Irwin M. Rosenstock

Estudio de caso

Physics of liquid crystals

Michael J. Stephen, Joseph P. Straley

This review discusses the physical properties of nematic, cholesteric, and smectic liquid crystals. Molecular theories of the liquid crystal phases are discussed and the molecular field theories of the phase transitions between the various liquid crystal phases are presented. The elastic theory and hydrodynamics of liquid crystals is developed. A wide variety of phenomena in liquid crystals, including elastic distortions, disclinations, flow properties, fluctuations, light scattering, wave propagation, nuclear magnetic resonance, effects of magnetic and electric fields, electrohydrodynamics, and optical properties, is discussed.

Principles of Plasma Physics

N. A. Krall, A. W. Trivelpiece, K. Symon

Mass: still a fascinating concept in physics

D. Yeboah-Amankwah

The subject matter of this article is MASS, a common word indeed to all scientists who have to deal with matter in one form or another. It is probably also a familiar word to the modem housewife, although here I suspect, that we meet the first example of confusion of for weight, a point to which we return later. The commonness, or the seemingly commonplace nature of the term, hides a profound and, in some ways, as yet unresolved conceptual difficulty that is not at all obvious or apparent to the uninitiated. It is my intention in what follows to bring to the reader some of these deep meanings that go with the seemingly simple term mass and, in the process, obliquely make an incidental, but important point, namely, that even in the traditional aspects of physics, our ideas about concepts like are still very much alive and subject to further development.

<i>Principles of Environmental Physics</i>

J. L. Monteith, William E. Reifsnyder

PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX

Biology, immature stages and rearing of cocoa-capsids (Miridae: Heteroptera)

Raj Kumar, Ashika Ansari

Some aspects of the biology of four West African capsid pests of Cocoa, Distantiella theobroma (Distant), Sahlbergella singularis Haglund, Bryocoropsis laticollis Schumacher and Helopeltis corbisieri Schmitz (Miridae: Heteroptera) are briefly summarized. Their immature stages are described and sketched in detail. Keys to distinguish all the larval stages are given and the techniques for rearing them reviewed. The systematics of Bryocorinae is discussed.

The Strength of Weak Ties

Mark Granovetter

Analysis of social networks is suggested as a tool for linking micro and macro levels of sociological theory. The procedure is illustrated by elaboration of the macro implications of one aspect of small-scale interaction: the strength of dyadic ties. It is argued that the degree of overlap of two individuals' friendship networks varies directly with the strength of their tie to one another. The impact of this principle on diffusion of influence and information, mobility opportunity, and community organization is explored. Stress is laid on the cohesive power of weak ties. Most network models deal, implicitly, with strong ties, thus confining their applicability to small, well-defined groups. Emphasis on weak ties lends itself to discussion of relations between groups and to analysis of segments of social structure not easily defined in terms of primary groups.

Review of research in education

Lee S. Shulman, Susan Mowry, David C. Berliner

Introduction: Rethinking Learning: What Counts as Learning and What Learning Counts - Judith Green and Allan Luke Chapter 1: Redefining Disciplinary Learning in Classroom Contexts - Michael J. Ford and Ellice A. Forman Chapter 2: Cross-National Explorations of Sociocultural Research on Learning - Olga A. Vasquez Chapter 3: Learning in Inclusive Education Research: Re-mediating Theory and Methods With a Transformative Agenda - Alfredo J. Artiles, Elizabeth B. Kozleski, Sherman Dorn, and Carol Christensen Chapter 4: Validity in Educational Assessment - Pamela A. Moss, Brian J. Girard, and Laura C. Haniford Chapter 5: Social, Methodological, and Theoretical Issues Regarding Assessment: Lessons From a Secondary Analysis of PISA 2000 Literacy Tests - Jean-Yves Rochex Chapter 6: Culture and Learning in the Context of Globalization: Research Directions - Wan Shun Eva Lam Chapter 7: Engaging Young People: Learning in Informal Contexts - Jennifer A. Vadeboncoeur Chapter 8: Youth, Technology, and Media Cultures - Julian Sefton-Green

An Application of Programmed Instruction to Laboratory Work in a Preliminary Physics Course

Tamara Powell, Sally French

The physical sciences have received more than their fair share of attention from researchers in the field of educational technology. The new teaching aids and programmed instruction have been applied to both the theoretical and practical sides of all the major science subjects, but invariably these applications have concentrated on the communication of knowledge in the form of facts or procedures to the exclusion of the more subjective and attitudinal aspects of science training. This paper describes an experimental approach to the teaching of a practical physics course to the preliminary year students of a Ghanaian university. The whole course has been re‐orientated so that the practical work is approached in a somewhat unusual way in which particular emphasis is placed on ideas of accuracy. The student is led to develop an appreciation of the errors which occur in the taking of readings and in the calculation of results from those readings. The development of the course, in which extensive use is made of programmed instruction, is described and some of the problems involved in the programming of subjective material such as this are discussed. The results of pre‐ and post‐testing are presented, and gain scores are related to attitude scores as well as other achievement measures.

The biology of the West African shad <i>Ethmalosa fimbriata (Bowdich)</i> in the Lagos Lagoon, Nigeria

S. O. Facade, C. I. O. Olaniyan

The biology of the population of Ethmalosa fimbriata occurring in the Lagos lagoon was investigated. Three size groups, 35–69 mm (Yoyo), 70–169 mm (Efolo) and 170 mm and above (Agbodo) occur in the lagoon and the spatial distribution of these size groups and the length frequency distribution of the species is given. The relationship between length, weight, age and growth is discussed and the food and feeding intra‐relationship of the size groups is shown. Information on the fecundity and possible spawning periods is discussed.

Photo-Neutral Vector Meson Couplings in the Relativistic Extended Quark Model

Tsunehiro Kobayashi

Progress of Theoretical Physics Vol. 49 No. 1 (1973) pp. 282-292 High Energy Photo-Reactions and Generalized Vector Meson Dominance Model in the Relativistically Extended Quark Model Tsunehiro Kobayashi Progress of Theoretical Physics Vol. 52 No. 4 (1974) pp. 1355-1368 Gauge Freedom in Dual Feynman-Like Rules and Its Relation to the Massless Yang-Mills Field Theory Tamiaki Yoneya

Estimation of the Concentration of Low-Density Lipoprotein Cholesterol in Plasma, Without Use of the Preparative Ultracentrifuge

William T. Friedewald, Robert I. Levy, Donald S. Fredrickson

Abstract A method for estimating the cholesterol content of the serum low-density lipoprotein fraction (Sf0-20) is presented. The method involves measurements of fasting plasma total cholesterol, triglyceride, and high-density lipoprotein cholesterol concentrations, none of which requires the use of the preparative ultracentrifuge. Comparison of this suggested procedure with the more direct procedure, in which the ultracentrifuge is used, yielded correlation coefficients of .94 to .99, depending on the patient population compared.

Impurity Problem in the Ising Model

K. Sawada, Takeo Osawa

Progress of Theoretical Physics Vol. 49 No. 1 (1973) pp. 83-88 Critical Properties of Ising Models Containing Dilute Impurities Takeo Osawa and Katuro Sawada Progress of Theoretical Physics Vol. 50 No. 4 (1973) pp. 1232-1239 Critical Properties of Ising Models Containing Dilute Impurities. II Katuro Sawada and Takeo Osawa

Regge Pole Model and Hadron Physics

Yasuo Hara

The Regge pole model of hadron physics is surveyed. Kinematical properties of helicity amplitudes (symmetry properties, crossing relations and analyticity properties), Reggeization of helicity amplitudes, the MacDowell symmetry and the factorization of Regge residues are discussed. We also study the Pomeron, the vector- and tensor-trajectories and the pseudoscalar trajectories. Inclusive reactions in the Regge pole model are briefly discussed.

The Fluid Mosaic Model of the Structure of Cell Membranes

Sherwin J. Singer, Garth L. Nicolson

A fluid mosaic model is presented for the gross organization and structure of the proteins and lipids of biological membranes. The model is consistent with the restrictions imposed by thermodynamics. In this model, the proteins that are integral to the membrane are a heterogeneous set of globular molecules, each arranged in an amphipathic structure, that is, with the ionic and highly polar groups protruding from the membrane into the aqueous phase, and the nonpolar groups largely buried in the hydrophobic interior of the membrane. These globular molecules are partially embedded in a matrix of phospholipid. The bulk of the phospholipid is organized as a discontinuous, fluid bilayer, although a small fraction of the lipid may interact specifically with the membrane proteins. The fluid mosaic structure is therefore formally analogous to a two-dimensional oriented solution of integral proteins (or lipoproteins) in the viscous phospholipid bilayer solvent. Recent experiments with a wide variety of techniqes and several different membrane systems are described, all of which abet consistent with, and add much detail to, the fluid mosaic model. It therefore seems appropriate to suggest possible mechanisms for various membrane functions and membrane-mediated phenomena in the light of the model. As examples, experimentally testable mechanisms are suggested for cell surface changes in malignant transformation, and for cooperative effects exhibited in the interactions of membranes with some specific ligands. Note added in proof: Since this article was written, we have obtained electron microscopic evidence (69) that the concanavalin A binding sites on the membranes of SV40 virus-transformed mouse fibroblasts (3T3 cells) are more clustered than the sites on the membranes of normal cells, as predicted by the hypothesis represented in Fig. 7B. T-here has also appeared a study by Taylor et al. (70) showing the remarkable effects produced on lymphocytes by the addition of antibodies directed to their surface immunoglobulin molecules. The antibodies induce a redistribution and pinocytosis of these surface immunoglobulins, so that within about 30 minutes at 37 degrees C the surface immunoglobulins are completely swept out of the membrane. These effects do not occur, however, if the bivalent antibodies are replaced by their univalent Fab fragments or if the antibody experiments are carried out at 0 degrees C instead of 37 degrees C. These and related results strongly indicate that the bivalent antibodies produce an aggregation of the surface immunoglobulin molecules in the plane of the membrane, which can occur only if the immunoglobulin molecules are free to diffuse in the membrane. This aggregation then appears to trigger off the pinocytosis of the membrane components by some unknown mechanism. Such membrane transformations may be of crucial importance in the induction of an antibody response to an antigen, as well as iv other processes of cell differentiation.

Regression Models and Life-Tables

D. R. Cox

Summary The analysis of censored failure times is considered. It is assumed that on each individual are available values of one or more explanatory variables. The hazard function (age-specific failure rate) is taken to be a function of the explanatory variables and unknown regression coefficients multiplied by an arbitrary and unknown function of time. A conditional likelihood is obtained, leading to inferences about the unknown regression coefficients. Some generalizations are outlined.

Generalized Linear Models

J. A. Nelder, R. W. M. Wedderburn