Showing papers by "University of New South Wales published in 1970"

On closed categories of functors

Abstract: Brian Day Received November 7, 19~9 The purpose of the present paper is to develop in further detail the remarks, concerning the relationship of Kan functor extensions to closed structures on functor categories, made in "Enriched functor categories" | 1] §9. It is assumed that the reader is familiar with the basic results of closed category theory, including the representation theorem. Apart from some minor changes mentioned below, the terminology and notation employed are those of |i], |3], and |5].

An extremal problem in graph theory

Abstract: G(n;l) will denote a graph of n vertices and l edges. Let f0(n, k) be the smallest integer such that there is a G (n;f0(n, k)) in which for every set of k vertices there is a vertex joined to each of these. Thus for example fo = 3 since in a triangle each pair of vertices is joined to a third. It can readily be checked that fo = 5 (the extremal graph consists of a complete 4-gon with one edge removed). In general we will prove: Let n > k, andthen f0(n, k) = f(n, k).

On topological quotient maps preserved by pullbacks or products

Abstract: We are concerned with the category of topological spaces and continuous maps. A surjection f: X → Y in this category is called a quotient map if G is open in Y whenever f−1G is open in X. Our purpose is to answer the following three questions:Question 1. For which continuous surjections f: X → Y is every pullback of f a quotient map?Question 2. For which continuous surjections f: X → Y is f × lz: X × Z → Y × Z a quotient map for every topological space Z? (These include all those f answering to Question 1, since f × lz is the pullback of f by the projection map Y ×Z → Y.)Question 3. For which topological spaces Z is f × 1Z: X × Z → Y × Z a qiptoent map for every quotient map f?

The founder effect and response to artificial selection

Abstract: The response to selection in any line depends on the size of the initial sample by which the line is founded. For a single locus with additive gene action the effects of number of founders on early rate of response and on final limits are studied in relation to selection intensity and number of parents in the selected line. The reduction in total response caused by a small number of founders is greatest for large populations under intense selection, especially when the desirable alleles are rare in the base population. If these alleles are at high frequencies it is possible that a line which has gone through a bottleneck may be more sensitive to a reduced population size during subsequent selection than a line which has not. Under some conditions replicate selection lines founded with small samples are likely to be less variable in response than lines founded with moderately large samples.

Determination of the Néel Temperature of Face-Centered-Cubic Iron

Abstract: The N\'eel temperature of face-centered-cubic iron precipitated in a copper single-crystal matrix has been determined by neutron diffraction as approximately 67\ifmmode^\circ\else\textdegree\fi{}K. This disagrees with a previous determination of 8\ifmmode^\circ\else\textdegree\fi{}K, but is in good agreement with a value of 60\ifmmode^\circ\else\textdegree\fi{}K predicted by extrapolation of results obtained with iron-manganese alloys.

Chromosome Pairing: Effect of Colchicine on an Isochromosome

Abstract: Two separable stages in the process of chromosome pairing have been demonstrated. The first results in a close spatial relationship of homologs, and the second results in synapsis and formation of chiasmata. Colchicine reduces chiasma formation in conventional bivalents but not in an isochromosome. Thus, colchicine affects only the first stage of pairing.

Management of chronic psychiatric patients by a token reinforcement system1

Abstract: A token reinforcement system for the reduction of institutionalized behavior in a chronic psychiatric ward is described. Quantitative assessments were made of the effects of the system on five types of positively reinforced behavior, two types of unreinforced behavior, and two types of fined behavior. To assess whether these effects were a function of the token procedures, three experiments were carried out, the first removing tokens for a brief period, the second making tokens non-contingent on behavior, and the third removing fines in one area while maintaining them in another. The token procedures were found to be the source of the observed improvements.

The trigeminal mesencephalic nucleus. II. Electron microscopy

Abstract: The fine structure of cells in the trigeminal mesencephalic nucleus was examined in adult mouse and cat. Cell surfaces were studed with small spinous processes which were free of synaptic contacts. Some cells in soma-soma and axosomatic contact were joined by maculae and membrane fusions resembling in cross section the zonula adherens and macula occludens of epithelial cells. Synapses containing three distinct morphological types of vesicles contacted the cell soma. The possible functions of synapses and membrane fusions were discussed.

A Theoretical Analysis of the Plain-Knitted Structure

Abstract: A theoretical analysis was made of the relaxed plain-knitted structure. The analysis differs from previous ones in that no arbitrary geometrical loop shape is assumed and no empirical methods are used. The loop configuration is de rived from consideration of the reaction forces and couples acting within the structure, their magnitude being determined by the yarn displacement necessary for loop interlocking. A minimum-energy structure is shown to exist; this structure is fairly independent of fabric tightness and yarn properties. The actual energy minimum is fairly shallow, so that in practice some difficulty could be expected in obtaining a perfectly relaxed fabric; this would lead to a corresponding spread in experimental values of plain-knitted fabric shape and dimensions. The numerical values of fabric dimensions obtained from the analysis show good agreement with the experimental data reported by other workers.

A lock exchange flow

Abstract: In this paper the interchange flow between two reservoirs connected by a contraction and containing fluid of different densities is considered. The effect of the boundary layers on the floor and walls of the contraction on the depth of flow in the contraction is discussed for the case of single layer flowing from one reservoir to the other. Next the theory for a denser layer plunging under a stationary layer is developed. In this case there is a discontinuity at the point of intersection of the surfaces of the flowing and the stationary fluids and there are three possible flow regimes depending on whether this discontinuity occurs at, downstream of, or upstream of the contraction.Finally, the case where there is an interchange flow with fluid flowing from each reservoir into the other is introduced. This latter theory parallels that developed by Wood (1968) for the case of two layers flowing from one reservoir through a contraction into another reservoir and as in this case there are two points of control, one at the position of minimum width and one (the virtual point of control) away from this position of minimum width.Experiments are described for a single layer flowing through the contraction and the results of these are used to obtain an indication of the accuracy that could be expected from the experiments with the more complicated exchange flow. The experiments with the exchange flow verified the major elements of the theory.

The life cycles and ecology of Australian lampreys of the genus Mordacia

Abstract: The life cycles and ecology of two closely related species of lampreys of the genus Mordacia were studied in various rivers in south-eastern Australia. In the Moruya River in southern New South Wales, the anadromous parasitic species, M. mordax (Richardson), has a larval life of three and a half years with metamorphosis occurring in late February or early March. The nonparasitic species, M. praecox Potter, metamorphoses at a different time (late October or November) and at a significantly longer length than M. mordax. The latter probably reflects a longer larval life in M. praecox, an estimate of which could not be obtained from the available data. Thus an extension of the larval phase, as well as a reduction in the post-metamorphic stages, may have occurred in the evolution of nonparasitic lampreys from parasitic forms. Evidence is presented to show that seasonal differences in temperature influence the pattern of ammocoete growth throughout the year, while local differences in the density of food are responsible for differences in growth rates in different areas. The effect of flooding and reduction in the water levels on the distribution of ammocoetes is discussed. A description is given of the behaviour of metamorphosing and transformed M. mordax prior to their migration out to sea. The above data is collated with that obtained from other studies to produce an overall picture of the life cycles of the two species of Mordacia.

An Experimental Investigation of the Influence of Strain-Rate and Temperature on the Flow Stress Properties of a Low Carbon Steel Using a Machining Test:

Abstract: Results obtained from machining and conventional slow-speed compression tests are used to calculate the constants σ1 and n in the empirical stress/strain equation σ = σ1***enover a range of strain-rates (10-3to 2·8 times 104/s) and temperatures (room temperature to 200°C) for a low carbon, free machining steel. The results are consistent with those obtained for a similar material using high-speed tension tests. Some results showing the influence of higher temperatures (up to 800°C) on the flow stress are also obtained from the machining tests by considering the flow along the tool-chip interface. These results show a dynamic strain-ageing effect similar to that found in high-speed tension and compression tests on similar materials.

Effect of tensile prestrain on the yield locus of 1100-f aluminium

Abstract: A series of combined stress tests in torsion-tension space is carried out on thin-walled tubes of 1100-F commercially pure aluminium. One initial and four subsequent yield loci are established to a maximum prestrain level of 14 per cent tensile plastic strain.The results are analysed in terms of a proposed, rationally based, yield criterion constructed according to statistical reasoning.It is shown that during prestrain a significant degree of geometrical distortion is undergone by the yield loci, accompanied by a strong Bauschinger effect and a flattening of part of the locus opposite to the loading point.It is found that the yield locus does not rotate during prestrain and, contrary to the case for torsion prestrain, exhibits evidence of a sharply rounded corner developing at the loading point.The proposed criterion is shown to fit the experimental results extremely well and the mechanism of distortion is explained in terms of a statistical model for work-hardening materials.

Maximizing Human Power Output by Suitable Selection of Motion Cycle and Load

Abstract: In this paper various factors affecting human power output are discussed, including the mechanical properties of muscle, the geometry of the input motion and the kinematics of the input motion. A mulitpurpose ergometer, designed and built to take account of these factors is described. Two basic motions are possible on the ergometer: cycling and rowing. The rowing motions may be made with any combination of seat and feet either sliding or fixed. In the rowing motions, during a single to and fro cycle, prescribed variations in velocity of the input links can be forced on a subject. Experimental work, which is described, showed that there are considerable differences in the effectiveness of the various ways of working, and that one in particular, a modified rowing motion, allowed the production of greater average amounts of power for periods up to two minutes than have so far been recorded and published (to the author's knowledge).

Chlorophyll degradation and lipid oxidation in frozen unblanched peas.

Abstract: Storage of hand-podded unblanched frozen peas for 20 months at –9·4° resulted in considerable conversion of chlorophylls to pheophytins, the formation of phytol-free derivatives, a decrease in total pigment and the formation of peroxides and TBA-reactive materials. Greater storage stability was found in samples blanched prior to storage, and to a lesser extent in unblanched peas stored in nitrogen or at –23·3°. Lipoxygenase and chlorophyll bleaching activities of extracts from frozen unblanched peas decreased during storage, lipoxygenase being the more stable. Model system studies with pea and soya extracts indicated that chlorophyll loss and lipid oxidation during storage were most likely caused by lipoxygenase and a lipohydroperoxide breakdown factor shown to be present in crude extracts.

Primary lactase deficiency: Genetic or acquired?

Abstract: From a critical review of the literature, it would appear that, in animals, intestinal lactase is an adaptive enzyme, with adaptation occurring in 5–8 weeks. In man, short-term attempts at adaptation have not been successful, although a fall in lactase activity or lactose absorption has been found after substrate withdrawal in some subjects. The expression of any biologic phenomenon is related to the sum of the effects of numerous genetic or environmental factors. It would seem that in the Chinese, at least, and presumably in other ethnic groups, the major factor influencing lactase activity is the dietary content of lactose. Adaptation of intestinal lactase occurs, provided milk intake continues at the high level found in most Western European populations, beyond the normal age of weaning. If lactose intake is reduced at or shortly after weaning, then lactase activity appears to decline over a period of years. This is analogous to the postweaning decline in lactase activity found in animals.