Showing papers by "University of Western Australia published in 1976"

Black-hole evaporation in the Klein-Sauter-Heisenberg-Euler formalism

Abstract: A generalization of the classical approach of barrier penetration introduced by Klein, Sauter, Heisenberg, and Euler to curved spaces endowed with future horizons is given. This technique allows one to recover most directly results obtained by Hawking recently. The treatment here presented encompasses, as special cases, the works of Deruelle and Ruffini, of Damour and Ruffini, and of Nakamura and Sato.

THE SPECIFIC ADSORPTION OF DIVALENT Cd, Co, Cu, Pb, AND Zn ON GOETHITE

Abstract: Summary The specific adsorption of divalent Cd, Co, Cu, Pb, and Zn on goethite is measured as a function of pH. For each mole of heavy metal adsorbed approximately two moles of H+ ions are displaced from the interface. Using these results the heavy metal adsorption data are expressed as functions of the solution concentrations of both H+ and metal ions, and the interfacial reaction is described by the equation, 2SH+M2+= S2M+2H+. The adsorption data are consistent with an electrochemical model of the simultaneous adsorption of H+ ions and divalent metal ions on to the oxide. The intrinsic affinities of the metal ions for the oxide surface increase in the order, Cd < Co < Zn < Pb < Cu. However, besides the affinity of the metal ion for the surface, the adsorption curves are considered to be influenced by surface charge, the adsorption density of the metal ions and their size. The analysis of the data in terms of H+ and M2+ ion adsorption is considered to be complementary to the hydrolysis model for heavy metal adsorption.

Comparative vertebrate endocrinology

Abstract: The third edition of this popular textbook retains the successful format of previous editions, dealing with the nature, actions and roles of hormones among vertebrate animals. Special emphasis is placed on the evolution and origins of hormones and their receptors, on the role of hormones in the physiological coordination of vertebrates, and on dealing with each endocrine process in the context of the organism's physiology, ecology and evolution. Comparative Vertebrate Endocrinology discusses the intimate physiology of the endocrine system and the pivotal role of hormones in coordinating basic body processes such as nutrition, reproduction, calcium metabolism and osmoregulation, as well as their contributions to animal coloration, molting and development. The species included range from lower chordates through to mammals, including marsupials.

THE CAT LUNG STRIP AS AN in vitro PREPARATION OF PERIPHERAL AIRWAYS: A COMPARISON OF β-ADRENOCEPTOR AGONISTS, AUTACOIDS AND ANAPHYLACTIC CHALLENGE ON THE LUNG STRIP AND TRACHEA

Abstract: 1 A new in vitro preparation, the isolated lung strip of the cat, is described for investigating the direct effect of drugs on the smooth muscle of the peripheral airways of the lung. The preparation comprises a thin strip of lung parenchyma which can be mounted in a conventional organ bath for isometric tension recording. Its pharmacological responses have been characterized and compared with the isolated tracheal preparation of the cat. 2 The lung strip exhibited an intrinsic tone which was relaxed by catecholamines, aminophylline and flufenamate. It was contracted strongly by histamine, prostaglandin F2alpha, acetylcholine, compound 48/80, potassium depolarizing solution and alternating current field stimulation. In contrast, the cat trachea was unresponsive to histamine and prostaglandin F2alpha and did not exhibit an intrinsic tone. 3 (-)-Isoprenaline and (-)-adrenaline were much more potent in relaxing the lung strip than the trachea. The potency order of relaxation responses to isoprenaline, adrenaline and (+/-)-noradrenaline in the lung strip was isoprenaline greater than adrenaline greater than noradrenaline but in the trachea was isoprenaline greater than noradrenaline greater than or equal to adrenaline. 4 beta2-Adrenoceptor selective agonists salbutamol and terbutaline were more potent in the lung strip than the trachea, suggesting beta2-adrenoceptors predominated in the lung strip. Propranolol was equipotent in inhibiting isoprenaline relexations of the lung strip and trachea, whereas practolol was much less effective in inhibiting lung strip than trachea, further supporting a predominance of beta2-adrenoceptors in lung strip and beta1-adrenoceptors in trachea. 5 Strong Schultz-Dale type contractions were elicited in both lung strips and trachea by Ascaris lumbricoides antigen in actively sensitized cats. The initial phase of the contractile response of the lung strip following challenge was shown to be due to histamine release and was absent in the trachea. The delayed phase of the contraction which took several minutes to develop in both the mepyramine-treated lung strip and trachea was not due to prostaglandins E1, F2alpha or bradykinin, the probable mediator being slow reacting substance of anaphylaxis (SRS-A). 6 It is concluded that the isolated lung strip of the cat is useful as an in vitro model for investigating the effect of drugs on the smooth muscle of the peripheral airways of the lungs.

Darwin's finches: population variation and natural selection

Abstract: Van Valen's model, which relates morphological variation to ecological variation in an adaptive scheme, was investigated with individually marked and measured Darwin's finches on two adjacent Galapagos islands, Santa Cruz and Daphne Major. Results show that environmental heterogeneity is correlated with large continuous, morphological variation: variation in bill dimensions of Geospiza fortis is greater on Santa Cruz than on Daphne, as is environmental heterogeneity. Within populations of this species, different phenotypes distribute themselves in different habitat patches, select foods of different sizes and hardness, and exploit them with efficiencies that are phenotype- (bill size) dependent. These data constitute indirect evidence that natural selection has a controlling influence over the level of phenotypic variation exhibited by a population. Further evidence is that phenotypes did not survive equally well during the study period; on Daphne island G. fortis was apparently subjected to directional selection on bill tip length and G. scandens to normalizing selection on body weight and bill depth. Other factors which may have contributed to the establishment of a difference in variation between Santa Cruz and Daphne populations are the founder effect, genetic drift, and assortative mating. Annual climatic unpredictability is considered a source of environmental heterogeneity which, through its effect upon food supply, favors large morphological variation. It is predicted that species of large individual size are more influenced by this than are small species, and consequently exhibit greater size-corrected variation. The prediction is tested with data from six Geospiza species, and found to be correct.

Taylor-vortex instability and annulus-length effects

Abstract: Critical speeds for the onset of Taylor vortices and for the later development of wavy vortices have been determined from torque measurements and visual observations on concentric cylinders of radius ratios R1/R2 = 0·894–0·954 for a range of values of the clearance c and length L: c/R1 = 0·0478–0·119 and L/c = 1–107. Effectively zero variation of the Taylor critical speed with annulus length was observed. The speed at the onset of wavy vortices was found to increase considerably as the annulus length was reduced and theoretical predictions are realistic only for L/c values exceeding say 40. The results were similar for all four clearance ratios examined. Preliminary measurements on eccentrically positioned cylinders with c/R1 = 0·119 showed corresponding effects.

Global stability in two species interactions.

Abstract: It is proved that sufficient conditions for global stability in a Lotka-Volterra model of a two species interactions are (i) the equilibrium is feasible, (ii) the equilibrium is locally stable and (iii) at the equilibrium each species sustains density dependent mortalities due to intraspecific interactions.

Factors affecting the reduction of acetylene by root nodules of lupinus species

Abstract: SUMMARY A number of parameters affecting acetylene reduction by root nodules of Lupinus angustifolius, L. cosentinii and L. luteus have been studied. Acetylene reduction could be satisfactorily measured in air provided a sufficiently high pC2H2 was used. However, evacuation of air from containers was not harmful to the nodule system. The maximal rate of acetylene reduction occurred at 23°C but the rate was hardly less at 33°C. Plant age had a marked effect upon the rate of acetylene reduction in its nodules. Rates of acetylene reduction in nodules were maintained at high levels after the onset of flowering but rapid reduction in nodule activity occurred after pods were filled. Decapitation of plants had little or no effect on acetylene reduction by the nodules, but removal of the nodules reduced their activity by 70–85%. Brief rinsing of the nodules and rapid drying with blotting paper had little effect on their acetylene reducing activity, but prolonged wetting markedly decreased it. Nodulated roots and whole plants responded similarly to pO2. Acetylene reduction was zero in the absence of oxygen, increased to a maximum rate by 0.2–0.25 atm O2, remained constant up to 0.4–0.5 atm O2, and then declined sharply to nearly zero at 0.9 atm. We detected no diurnal rhythm, attributable to effects of light on supply of photosynthate, with any of the three species.

Phosphate adsorption on goethite (α-FeOOOH)

Abstract: SYNTHETIC goethite has been extensively studied as a model adsorbent in the search for a precise description of the chemical reactions involved in phosphate adsorption by soil minerals. Infrared studies1,2 have now firmly established that phosphate on goethite and other iron oxides results in a bridging binuclear complex of the type Fe–O–P–O–Fe. The infrared studies were, however, carried out on dried samples of phosphated goethite. We now report infrared studies on wet goethite films which confirm that the binuclear complex exists in the presence of water.

Selective withdrawal from a finite rectangular tank

Abstract: The time development of two-dimensional fluid motion induced by a line sink in a rectangular, density stratified reservoir with a free surface is given. It is shown that the initiation of such a sink gives birth to a spectrum of internal expanding shear fronts with a progressively decreasing vertical wavelength. These fronts move out from the sink and travel towards the far wall, where they are reflected. This process ceases once the front with a vertical wavelength equal to the steady withdrawal-layer thickness has reached the end wall. The fronts so introduced continue to move back and forth, expanding to standing waves if the viscosity of the fluid is small enough. The evolution and nature of the withdrawal layer are shown to depend critically on the relative magnitude of the convective inertia and viscous forces, the number of reflexions from the rear wall and the Prandtl number.

Crystal structure of the copper(I) iodide–pyridine (1/1 ) tetramer

Abstract: The crystal structure of the copper(I) iodide pyridine adduct has been determined by X-ray diffraction at 295 K and refined by least squares to R 0.057 for 2 710 ‘observed’ reflections. Crystals are orthorhombic, space group P212121, with a= 16.032(6), b= 15.510(2), and c= 11.756(3)A. The asymmetric unit is Cu4I4py4, based on the well-known tetrahedral tetrameric Cu4I4 unit, with Cu–N 2.04, Cu–I 2.70, and Cu–Cu 2.69 A; the latter distance is much shorter than in the analogous complexes formed with phosphine and arsine ligands.

Characterization of partially neutralized ferric chloride solutions

Abstract: Ferric hydroxy polycations formed in a range of partially neutralized ferric nitrate solutions have been characterized using electron microscope and density gradient ultracentrifugation techniques. In all solutions the initial polycations were discrete spheres 1.5–3.0 nm diameter. From these spheres, rods composed of 2–5 spheres were formed during ageing. These rods aged by two distinct processes which depended on the solution conditions. In one the rods remained the same length and aggregated with time to form extensive raft-like arrays of rods. The spheres within the rods slowly coalesced and goethite was formed. In the other process the rods increased in length but not width and did not form “rafts” Goethite was formed during this increase in length. On extended ageing, some of the rods linked and coalesced to give lath shaped goethite crystals. The first process was favored by high ionic strength and/or high ferric concentrations and the second by a lower ionic strength and/or concentration.

The acetylene reduction assay as a means of studying nitrogen fixation in white clover under sward and laboratory conditions

Abstract: The acetylene reduction assay was used to follow seasonal changes in nitrogen fixation activity in a white clover-perennial ryegrass ley in Northern Ireland. The annual estimate for fixation by the ley was 268 kg ha−1 (239 lb/acre) nitrogen virtually all of which was fixed during March to October. Nitrogen fixation was curtailed drastically after the ley was cut but recovered as new foliage expanded on the clover. Glasshouse experiments described the effects of temperature, shading and defoliation on nitrogen fixation by white clover, and indicated that these factors might be important in modifying symbiosis under field conditions.

Effect of anaerobiosis on activities of alcohol dehydrogenase and pyruvate decarboxylase in roots of zea mays

Abstract: Summary Flushing of nitrogen gas through culture solutions, for periods between 4 and 15 h, increased activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) in roots of intact maize plants (activities expressed as μmol mg protein−1 min−1). The activity of ADH was six to nine times greater than the activity of PDC. Under root anaerobiosis of intact maize plants, activities of both ADH and PDC were similar in all root segments taken between o and 37 mm behind the apex, but lower activities were found in the older root segments. These differences in enzyme levels between younger and older root tissues were affected neither by the light regime of the shoots nor by imposing anaerobiosis of the shoots as well as the roots; i.e. the differences in ADH and PDC activities found in root segments of different ages were not due to a superior oxygen supply from the shoots to the tissues near the shoot-root junction. Roots of intact maize plants were also exposed to a range of oxygen concentrations, by flushing the nutrient solution with gases of different composition. ADH activities in the roots were highest with gas mixtures containing 8–13% oxygen, intermediate with pure nitrogen, and lowest when the solution was flushed with gas containing 20% oxygen. It is concluded that ADH activity cannot be used to diagnose the degree of oxygen deficiency to which maize roots have been exposed.

Pathogenicity of 203 isolates of Rhynchosporium secalis on 21 barley cultivars

Abstract: Twenty-one cultivars of barley were each inoculated with 203 isolates of Rhynchosporium secalis from barley-growing areas of southern Australia. The isolates were differentiated into 35 distinct pathotypes (designated Aust. 1 to 35) on the basis of the reactions of the barley cultivars. Each cultivars appeared to have distinctive resistance since no two reacted identically to all pathotypes or isolates. Only one cultivar, Atlas 46, was resistant to all of the isolates used.

Development of bauxite in relation to parent material near Jarrahdale, Western Australia

Abstract: The relationship between well‐exposed bedrock materials and lateritic bauxite developed over them was investigated in a deep railway cutting, located within the Jarrahdale bauxite mining area in southwestern Australia Observations in the field and chemical and quantitative mineralogical analysis indicate that the bauxite developed by lateritization in place of the underlying gneissic‐granite/meta‐quartz dolerite basement complex in a leaching environment

Effect of waterlogging on growth and activity of alcohol dehydrogenase in barley and rice

Abstract: Summary Flooding usually reduced shoot and root growth of barley. In addition, root growth was inhibited much more in flooding-sensitive than flooding-tolerant cultivars. Prolonged flooding resulted in larger increases in activity of alcohol dehydrogenase (ADH) in roots of flooding-tolerant than flooding-sensitive cultivars. Barley and rice were also grown in solutions flushed with gases of different oxygen concentration. In rice roots, high activities of ADH and pyruvate decarboxylase (PDC) were found only when the solutions were flushed with pure N2 gas. In barley roots, activities of ADH and PDC were highest using gases between 3 and 13% O2, lower with pure N2, and very low when using 20% O2. These results indicate that the level of ADH occurring in plant roots will be very dependent on experimental conditions, as for example root density. Species differences in activity of ADH might be mainly related to different oxygen tensions inside the roots, due in turn to differences in volume of aerenchyma and morphology of roots.

A Feedback Receive Amplifier for Optical Transmission Systems

Abstract: We consider the design and implementation of a lownoise feedback receive amplifier for use in optical communication systems. The feedback amplifier configuration is advantageous in that it offers a wide bandwidth with good signal to noise ratio.