Showing papers by "Australian National University published in 1975"
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01 Jan 1975TL;DR: Feyman and Wing as discussed by the authors introduced the simplicity of the invariant imbedding method to tackle various problems of interest to engineers, physicists, applied mathematicians, and numerical analysts.
Abstract: sprightly style and is interesting from cover to cover. The comments, critiques, and summaries that accompany the chapters are very helpful in crystalizing the ideas and answering questions that may arise, particularly to the self-learner. The transparency in the presentation of the material in the book equips the reader to proceed quickly to a wealth of problems included at the end of each chapter. These problems ranging from elementary to research-level are very valuable in that a solid working knowledge of the invariant imbedding techniques is acquired as well as good insight in attacking problems in various applied areas. Furthermore, a useful selection of references is given at the end of each chapter. This book may not appeal to those mathematicians who are interested primarily in the sophistication of mathematical theory, because the authors have deliberately avoided all pseudo-sophistication in attaining transparency of exposition. Precisely for the same reason the majority of the intended readers who are applications-oriented and are eager to use the techniques quickly in their own fields will welcome and appreciate the efforts put into writing this book. From a purely mathematical point of view, some of the invariant imbedding results may be considered to be generalizations of the classical theory of first-order partial differential equations, and a part of the analysis of invariant imbedding is still at a somewhat heuristic stage despite successes in many computational applications. However, those who are concerned with mathematical rigor will find opportunities to explore the foundations of the invariant imbedding method. In conclusion, let me quote the following: "What is the best method to obtain the solution to a problem'? The answer is, any way that works." (Richard P. Feyman, Engineering and Science, March 1965, Vol. XXVIII, no. 6, p. 9.) In this well-written book, Bellman and Wing have indeed accomplished the task of introducing the simplicity of the invariant imbedding method to tackle various problems of interest to engineers, physicists, applied mathematicians, and numerical analysts.
3,249 citations
TL;DR: Complementarity relationships between this sequence and a purine-rich tract in the ribosome binding site of different bacterial mRNAs suggest that the 3′-end of 16S RNA determines the intrinsic capacity of ribosomes to translate a particular cistron.
Abstract: The sequence of the 3'-terminus of 16S RNA from different bacteria has been determined. Complementarity relationships between this sequence and a purine-rich tract in the ribosome binding site of different bacterial mRNAs suggest that the 3'-end of 16S RNA determines the intrinsic capacity of ribosomes to translate a particular cistron.
1,323 citations
TL;DR: The method employs a discontinuous salt gradient and separates VLDL, LDL, and HDL as verified by cellulose acetate- and immuno-electrophoresis and offers some advantages for research applications.
1,054 citations
TL;DR: This work proposes a possible selective mechanism, based on the realisation that immunological surveillance function (defined here as recognition and elimination of modified host cells by sensitised thymus-derived lymphocytes (T-cells) may be considerably enhanced in mice heterozygous at the H-2 gene complex), which may benefit heterozygotes in the HL-A system for man.
Abstract: THE major histocompatibility (H) antigens of higher animals show extreme genetic polymorphism equalled, in higher vertebrates, only by that associated with the immunoglobulins1. Maintenance of such a high rate of variability implies evolutionary advantage for heterozygotes in the HL-A system for man, or at the H-2 gene complex in mice2,3. We propose a possible selective mechanism, based on the realisation that immunological surveillance function (defined here as recognition and elimination of modified host cells by sensitised thymus-derived lymphocytes (T-cells) may be considerably enhanced in mice heterozygous at the H-2 gene complex.
717 citations
TL;DR: A model of cell interaction is produced which will account for reactivity is much higher between different strains within a species than between species, in spite of the much greater antigenic disparity in the second case, and a very high proportion of cells may respond to allogeneic stimuli.
Abstract: Allogeneic reactions have conventionally been considered as typical immune responses by one population of cells to antigens present on the other. This view is inadequate, since it does not explain many features of these reactions, among which are: (1) reactivity is much higher between different strains within a species than between species, in spite of the much greater antigenic disparity in the second case; (2) a very high proportion of cells may respond to allogeneic stimuli; (3) major histocompatibility differences are not essential for vigorous allogeneic reactions; (4) the responding population need not be immunologically competent to respond to antigens of the stimulating population; (5) the stimulating population must be both metabolically active and immunocompetent. We have tried to produce a model of cell interaction which will account for these and other anomalies, which at the same time explaining both normal antigenic stimulation (through cell-cell cooperation) and allogeneic interactions as examples of the same basic mechanisms. The model is based on the Bretscher-Cohn scheme of cell interaction. An allogeneic reaction is seen as having two stages: (1) Cells come together when antibody receptors on cells of one population combine with antigens on cells of the other. To this extent, our model is the same as the conventional one. It need not be the responding population which has the receptors, however. (2) A species-specific proliferation signal passes between the cells. This is the same signal as is involved in normal antibody induction. Even antigen-receptor bonds which are very weak may result in effective stimulation of one or both partners because of enhancing effect of this signal, and because the antigens involved are probably repeated over the cell surface, enabling multipoint binding. This explains the very proportions of cells which proliferate. The exact outcome of any allogeneic interaction will depend on which of the two populations have antibody receptors for antigens on the other, which can produce the proliferative stimulus, and which can respond to either the proliferative signal alone or to this stimulus plus antigen.
569 citations
TL;DR: In this article, a set of three parametric earth models (PEM) are presented, where radial variations of the density and velocities are represented by piecewise continuous analytical functions of radius (polynomials of order not higher than the third).
493 citations
TL;DR: A central function of the major histo-compatibility (H) antigens may be to signal changes in self to the immune system, with extreme genetic polymorphism found in the major H antigen systems of higher vertebrates reflecting evolutionary pressure exerted by this immunological surveillance mechanism.
464 citations
TL;DR: The need for making planned experiments explicitly aimed at testing theoretical models, such as those proposed in this article, is emphasized, as it has proved to be particularly useful in this respect.
Abstract: Although a considerable body of data exists on the parametrization of the ground-state splittings of S-state ions in crystals, relatively little progress has been made in obtaining a quantitative understanding of the mechanisms which determine these parameters. In the course of summarizing our present understanding, we emphasize the need for making planned experiments explicitly aimed at testing theoretical models, such as those proposed in this article. The variable frequency E.P.R. technique is described in some detail, as it has proved to be particularly useful in this respect.
461 citations
TL;DR: It is inferred that “prestige” scores for occupations are fallible estimates of the socioeconomic statuses of occupation, within the context of mobility processes in (at least) the U.S. and Australia.
358 citations
TL;DR: Structural‐activity studies led to the findings that nipecotic acid (piperidine‐3‐carboxylic acid) is a powerful non‐competitive inhibitor of GABA uptake, and that perhydro‐1,2‐oxazine‐6‐car boxylic Acid is a relatively weak competitive inhibitor ofGA uptake.
Abstract: —A variety of isoxazoles structurally related to muscimol (3-hydroxy-5-aminomethylisoxazole) were tested as inhibitors of the uptake of GABA and some other amino acids in rat brain slices, and of the activity of the GABA-metabolizing enzymes l-glutamate 1-carboxylyase and GABA:2-oxo-glutarate aminotransferase A bicyclic derivative, 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol, proved to be a more potent inhibitor of GABA uptake than muscimol Structure-activity studies on this derivative, which appeared to be a competitive inhibitor of GABA uptake, led to the findings that nipecotic acid (piperidine-3-carboxylic acid) is a powerful non-competitive inhibitor of GABA uptake, and that perhydro-1,2-oxazine-6-carboxylic acid is a relatively weak competitive inhibitor of GABA uptake
316 citations
TL;DR: The technique very efficiently removed red cells from a wide range of lymphoid cell suspensions and eliminated lymphocytes killed by mechanical stress, by antibody and complement and by prolonged tissue culture.
TL;DR: A retinal ganglion cell distribution map has been prepared for the cresyl violet stained cat retina and it differs from previously published maps in revealing the visual streak to be more substantial and in showing a higher peak density at the presumed visual pole.
Abstract: A retinal ganglion cell distribution map has been prepared for the cresyl violet stained cat retina. It differs from previously published maps in revealing the visual streak to be more substantial and in showing a higher peak density of 9-10,000 ganglion cells/mm2 at the presumed visual pole. The map was used to obtain a minimum estimate of the retinal ganglion cell population as 217,000 cells, more than double the total previously reported. The problem of classifying the cells of the ganglion cell layer is discussed in detail and examples of criterion cells illustrated. The paper also includes an account of retinal mensuration (dimensions, area, etc.) and a discussion of the visual streak orientation.
TL;DR: In this article, a model of peridotitic komatiite magma was developed in which selective removal of garnet during ascent produces CaO/Al 2 O 3 > 1 and heavy rare-earth element depletion in the resultant peridoteitic or mafic extrusions.
Abstract: The experimentally determined extrusion temperature (1650° ± 20°C) for Archean peridotitic komatiite magma implies diapirism of upper mantle peridotite from a depth of at least 200 km. Models of magma genesis are developed in which selective removal of garnet during ascent produces CaO/Al 2 O 3 > 1 and heavy rare-earth element depletion in the resultant peridotitic or mafic extrusions. Magma genesis can be interpreted with a model of the Archean geotherm, lithosphere, and plate tectonics processes resembling the modern Earth, but this does not account for the distinctive preservation and character of Archean greenstone belts. A preferred model of a steeper Archean geotherm, thin lithosphere (≃50 km), and asthenosphere with approximately 5 percent melting does not allow eclogitization and subduction of basaltic oceanic crust, but it postulates scraping off of such crust against and between primitive sialic nucleii. This model may account for the distinctive characteristics of the Archean greenstone and “granite” terranes.
TL;DR: In this article, the potential of odd alternant hydrocarbons (OAHs) in the design of organic metals and superconductors was discussed, which gives reason to suppose that they may prove equal or even superior to present systems.
Abstract: I WISH to draw attention to the potential of odd alternant hydrocarbons (OAHs) in the design of organic metals and superconductors which gives reason to suppose that they may prove equal or even superior to present systems. There is now strong evidence for the existence of the metallic state in certain organic charge transfer salts, and a suggestion of low temperature superconducting fluctuations in the case of tetrathiofulvalene–tetracyanoquinodimethane (TTF–TCNQ); present interest is now focused on the stabilisation of these states at greater (critical) temperatures1. In contrast to the molecular crystals usually formed by conjugated organic molecules (which are held together by van der Waals' forces and characterised by a relatively weak intermolecular interaction), these salts crystallise as segregated one-dimensional stacks of cation and/or anion radicals in which the charge transfer process and thus the electronic mobility within a stack is greatly enhanced by the abnormally high overlap of the π-electron wave functions of nearest neighbours in the stack and by the ability of the constituent molecules to stabilise an ionic fluctuation.
TL;DR: Microelectrophoretic methods were used to study the effects on spinal neurones of a series of conformationally restricted analogues of GABA, most of which are structurally related to musci‐mol (3‐hydroxy‐5‐aminomethylisoxazole).
Abstract: —Microelectrophoretic methods were used to study the effects on spinal neurones of a series of conformationally restricted analogues of GABA, most of which are structurally related to musci-mol (3-hydroxy-5-aminomethylisoxazole). 3-Hydroxy-5-(l-aminoethyl)isoxazole and 3-hydroxy-5-(2-aminoethyl)isoxazole were GABA-like depressants comparable in effectiveness with GABA. The inhibitors of GABA uptake 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol and nipecotic acid (piperidine-3-carboxylic acid) reversibly enhanced the depressant action of GABA. 3-Hydroxy-5-dimethylaminomethly-isoxazole, 5,6,7,8-tetrahydro-4H-isoxazolo[4,5-d]azepm-3-ol, 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol, and nipecotic acid reversibly antagonized the postsynaptic action of glycine.
A structure-activity correlation was made in an indirect attempt to elucidate some comformational requirements for interaction of GABA with its postsynaptic receptor and the binding site of its uptake system. The results seem to indicate that different conformations of GABA are required for these interactions.
TL;DR: Measurements of perikaryal size and its variation with eccentricity from the central area support the indetification of the large cells with the class of alpha cells previously defined in Golgi‐stained preparations.
Abstract: There is a distinct class of large ganglion cell bodies observable in whole-mount preparations of the cat's retina stained with cresyl violet. Measurements of perikaryal size and its variation with eccentricity from the central area support the identification of the large cells with the class of alpha cells previously defined in Golgi-stained preparations. A complete enumeration of alpha cells in one retina yielded a total of 6212. They were encountered in all parts of the retina and had a peak density within the central area ( 200/mm2). The retinal distribution was displayed as a contour map of alpha-cell density. Away from the central area, the lines of iso-density had the form of a 4-pointed star with rather blunt points corresponding to horizontal and vertical ridges of augmented density. Along horizontal, vertical and oblique strips through the central area, alpha-cell density was an approximately constant fraction of total ganglion cell-density. The average value of the fraction was 3.3% from which it has been calculated that the cat's retina may contain as many as 190,000 ganglion cells.
TL;DR: The "condensing" effect of cholesterol in mixed phospholipid-cholesterol films is seen as a taper-fray accommodation and the lipid distribution in erythrocyte membrane is shown to be conducive to a stable strain-free membrane.
TL;DR: In this paper, a cubic perovskite-type 3olymorph of CaSiO 3 has been obtained from synthetic crystalline (wollastonite) and glass forms of the material and has been compressed to loading pressures above 160 kbar and heated to about 1500° C by a laser in a diamond anvil cell.
TL;DR: The survival time of mouse thyroid, transplanted under the kidney capsule of an H-2 incompatible recipient, is extended by holding the thyroid in organ culture for 12 days prior to transplantation.
Abstract: The survival time of mouse thyroid, transplanted under the kidney capsule of an H-2 incompatible recipient, is extended by holding the thyroid in organ culture for 12 days prior to transplantation.
TL;DR: Measurement of cytotoxicity of T cells from donors immunised with either lymphocytic choriomeningitis (LCM) or ectromelia virus using target cells infected with the homologus virus shows that in mice, certain specific immunological effector functions of thymus-derived lymphocytes are efficient only when donors of T cell and the cells with which they interact have at least a part of the H-2 gene complex in common.
Abstract: EVIDENCE is mounting that in mice, certain specific immunological effector functions of thymus-derived (T) lymphocytes are efficient only when donors of T cells and the cells with which they interact have at least a part of the H-2 gene complex in common1–8. Examples include T helper function in vivo and in vitro1–3, cytotoxicity mediated by T cells against virus-infected4–6 or TNP-modified7 target cells in vitro, immunopathology mediated by T cells4, or protection against bacterial8 and viral infection6 in vivo. This requirement for H-2 compatibility has been studied in detail by measuring the cytotoxicity of T cells from donors immunised with either lymphocytic choriomeningitis (LCM) or ectromelia virus using target cells infected with the homologus virus.
TL;DR: Trans‐4‐aminocrotonic acid, an analogue of GABA in an extended conformation, acts as efficiently as GABA with respect to each of the above systems, indicating that extended rather than folded conformations of GABA are likely to be important in the interaction of GABA with the specific macromolecules concerned.
Abstract: —
Cis-4-aminocrotonic acid, an analogue of GABA in a folded conformation, appears not to act as a GABA analogue with respect to bicuculline-sensitive postsynaptic receptors, ‘high affinity’ GABA uptake and GABA: 2-oxoglutarate aminotransferase in the mammalian central nervous system. On the other hand, trans-4-aminocrotonic acid, an analogue of GABA in an extended conformation, acts as efficiently as GABA with respect to each of the above systems, indicating that extended rather than folded conformations of GABA are likely to be important in the interaction of GABA with the specific macromolecules concerned.
TL;DR: In this paper, the maximum likelihood estimation for rectangular lattice autonormal schemes is discussed and the efficiency of the coding technique in testing for randomness on various types of lattice is assessed.
Abstract: SUMMARY Maximum likelihood estimation for rectangular lattice autonormal schemes is discussed. Explicit results for the first-order isotropic scheme are given and compared with those obtained using a simple coding technique. The efficiency of the coding technique in testing for randomness on various types of lattice is assessed.
TL;DR: In this article, the effect of soil water potential on the respiration of microorganisms in soil was studied and it was shown that the sensitivity of bacteria to relatively small negative potentials was probably due to their restricted movement as the soil pores drained.
Abstract: The effect of soil water potential on the respiration of microorganisms in soil was studied. Bacterial respiration decreased rapidly below −3 bar; at -20 bar it was very slight. The most rapid decline occurred above − 6 bar. The respiration of a mixed population of microorganisms, however, was maintained at a fairly high level between −8 and −30 bar but subsequently declined until at −50 bar it became negligible. At potentials below −50 bar, additions of glucose caused no increase in respiration. The sensitivity of bacteria to relatively small negative potentials was probably due to their restricted movement as the soil pores drained.
TL;DR: Two central problems are dealt with in the paper: How is it possible for the binocular visual system to detect the correct disparity in repeating patterns such as computer-generated random-dot stereograms?
TL;DR: The cell death occurring normally, and the cell death resulting from axotomy, can both be prevented by NGF treatment leading to an hypertrophy of both superior cervical ganglia and axotomised SCG consistent with the hypothesis than NGF is the retrograde trophic agent for the sympathetic nervous system in the developing animal.
TL;DR: It is found that arecaidine and guvacine are competitive inhibitors of GABA uptake in rat brain slices and it is proposed that some of the psychic effects of betel nut consumption may be the result of inhibition of GABA absorption.
Abstract: THE pharmacological properties of betel nut, the dried seed of Areca catechu which is consumed in immense quantities in the East as a masticatory, are usually interpreted in terms of the cholinomimetic effects of the major alkaloid component, arecoline. Betel nut contains lesser amounts of the related alkaloid guvacoline and the amino acids arecaidine and guvacine. According to popular tradition, a mixture of crushed betel nut and lime is enveloped in leaves of Piper betle before chewing. This treatment with lime has been shown to hydrolyse almost quantitatively arecoline to arecaidine1, a well tolerated substance which lacks the typical parasympathomimetic effects of arecoline, including tremor and salivation1,2. Studies on the effects of arecaidine on the behaviour of mice indicate that this substance participates in producing some of the psychic changes ascribed to the betel mixture1,2. These betel constituents are tetrahydronicotinic acid derivatives (Fig. 1) and we have shown that nipecotic acid, ‘hexahydronicotinic acid’, is a potent inhibitor of the uptake of the central inhibitory transmitter γ-aminobutyric acid (GABA) in rat brain slices3. Nipecotic acid potentiates the depressant action of microelectrophoretically administered GABA on the firing of feline spinal neurones4. As the uptake of GABA is likely to be concerned with the inactivation of this transmitter, interference with GABA uptake could result in behavioural changes. The structural similarities between nipecotic acid and the betel nut constituents together with the above mentioned findings prompted us to examine the influence of these compounds on GABA uptake. We have found that arecaidine and guvacine are competitive inhibitors of GABA uptake in rat brain slices and we propose that some of the psychic effects of betel nut consumption may be the result of inhibition of GABA uptake.
TL;DR: In this paper, the ages of lead-lead mineral isochrons were determined for eight intrusive bodies in the Kalgoorlie-Norseman area of Western Australia, ranging from 2630 to 2760 m.y.
01 Jul 1975
TL;DR: In this paper, the authors considered methods for finding high-precision approximations to simple zeros of smooth functions, and gave fast methods for evaluating the elementary functions log(x), exp(x), sin (x) etc. to high precision.
Abstract: : The author considers methods for finding high-precision approximations to simple zeros of smooth functions. As an application, the author gives fast methods for evaluating the elementary functions log(x), exp(x) , sin(x) etc. to high precision. For example, if x is a positive floating-point number with an n-bit fraction, then (under rather weak assumptions) an n-bit approximation to log(x) or exp(x) may be computed in time asymptotically equal to 13M(n) log of n to the base 2 as n approaches infinity, where M(n) is the time required to multiply floating-point numbers with n-bit fractions. Similar results are given for the other elementary functions, and some analogies with operations on formal power series are mentioned.