Showing papers by "University of New South Wales published in 1973"

Energetic Cost of Locomotion in Kangaroos

Abstract: THE hopping of kangaroos is reminiscent of a bouncing ball or the action of a pogo stick. This suggests a significant storage and recovery of energy in elastic elements. One might surmise that the kangaroo's first hop would require a large amount of energy whereas subsequent hops could rely extensively on elastic rebound. If this were the case, then the kangaroo's unusual saltatory mode of locomotion should be an energetically inexpensive way to move.

Polyhedral decompositions of cubic graphs

Abstract: A polyhedral decomposition of a finite trivalent graph G is defined as a set of circuits = {C1, C2, … Cm} with the property that every edge of G occurs exactly twice as an edge of some Ck. The decomposition is called even if every Ck is a simple circuit of even length. If G has a Tait colouring by three colours a, b, c then the (a, b), (b, c) and (c, a) circuits obviously form an even polyhedral decomposition. It is shown that the converse is also true: if G has an even polyhedral decomposition then it also has a Tait colouring. This permits an equivalent formulation of the four colour conjecture (and a much stronger conjecture of Branko Grunbaum) in terms of polyhedral decompositions alone.

Differential equations in Banach spaces

Abstract: Let H be a fixed Hilbert space and B(H, H) be the Banach space of bounded linear operators from H to H with the uniform operator topology. Oscillation criteria are obtained for the operator differential equationwhere the coefficients A, C are linear operators from B(H, H) to B(H, H), for each t ≤ 0. A solution Y: R+ → B(H, H) is said to be oscillatory if there exists a sequence of points ti ∈ R+, so that ti → ∞ as i → ∞, and Y(ti) fails to have a bounded inverse. The main theorem states that a solution Y is oscillatory if an associated scalar differential equation is oscillatory.

Complex formation between sugars and metal ions

Abstract: Cyclitols and sugars containing an axial-equatorial-axial sequence of three hydroxyl groups in a six-membered ring, or a cis-cis sequence in a five-membered ring, form 1:1 complexes with metal cations in hydroxylic solvents. At least one of the hydroxyl groups can be replaced by a methoxy group without substantially affecting complex formation. Lanthanum(III) forms the strongest complexes (K about 10 mol−11 in water), followed by calcium and strontium. Complex formation causes downfield shifts of the signals in the p.m.r. spectrum, that of the hydrogen atom vicinal to the oxygen atom central in the ax-eq-ax sequence being the largest. Complex formation will change the conformational equilibrium of methyl β-D-ribopyranoside and β-D-lyxopyranose; it will change the anomeric equilibrium of allose, gulose, ribose, and lyxose. It will also alter the equilibrium in methanol between the methyl glycosides of the above-mentioned sugars; in the presence of calcium or strontium chlorides, methyl glycosides can be synthesized which normally are only minor products of methanolysis. Complex formation makes possible the separation of some sugars by electrophoresis and on ion-exchange columns.

Development and elimination of pigmented moles, and the anatomical distribution of primary malignant melanoma.

Abstract: In Sydney, Australia, the number of pigmented moles per person increases to age 15 in males and 20-29 in females, the most exposed parts of the body reaching peak values soonest. A decline then begins so that moles are almost absent in persons 80 years old. On each part of the body, depigmented spots and nevi with definite or faint halos are more common soon after the peak values have been reached. The delayed development of moles on sunlight-protected parts of the body may be related to the fact that in European pop ulations the frequency of malignant melanoma increases as the Equator is approached but many of the additional melanomas are found in anatomical sites minimally exposed to sunlight.

Comparative Studies on the Isolation of Membrane Lipoteichoic Acid from Lactobacillus fermenti

Abstract: Preparations of membrane lipoteichoic acid containing different amounts of protein were isolated from intact organisms of Lactobacillus fermenti NCTC 6991 by various procedures chosen for their ability to disrupt the hydrophobic interaction of lipoteichoic acid with other membrane components. The highest yield of lipoteichoic acid was obtained with hot aqueous phenol, and this preparation contained very little protein. Partial removal of cell lipids with chloroform-methanol followed by extraction with water at 100 C gave a lipoteichoic acid-protein complex that was a very effective immunogen; immunogenicity was shown to relate to protein content, though the specificity of the antibodies was directed against the teichoic acid component.

A test of consumer demand theory using observations of individual consumer purchases

Abstract: In this paper we report a test of consumer demand theory using price, quantity and expenditure data for individual consumer's entire expenditures in an ongoing economic system. In conducting the test major emphasis has been placed on controlling and calculating errors of observation in the data collected and explicitly incorporating the measures of errors of observation into the evaluation of the test results.) The analysis presented below demonstrates that efforts directed along these lines are essential to (I) obtain observations of sufficient accuracy to contradict the theory of consumer demand and (2) distinguish between actual contradictions between propositions of the theory and propositions describing observations, on the one hand, and the effects of measurement error, on the other. 0

The inhibitory effect of manganese on transmitter release at the neuromuscular junction of the toad

Abstract: Summary 1 Manganese, at low concentrations (0·5–2·0 mm), blocks neuromuscular transmission in toads. Endplate potentials (e.p.ps) are reduced in amplitude but the amplitude of miniature endplate potentials (m.e.p.ps) is, if anything, increased. 2 The release of transmitter by an action potential is reduced in solutions containing Mn, but is still well described by the Poisson equation. 3 Log-log plots of e.p.p. quantal content (m) against [Ca] have a mean gradient of 3·73, and a model based on the co-operative action of four calcium ions in excitation-secretion coupling, and competitive inhibition by Mn, was constructed. The model, with its exponent of 4, is shown in fact to predict gradients of less than four for log-log plots of m against [Ca]. 4 The assumption of competitive inhibition by Mn was supported by modified Lineweaver-Burk plots of m−¼ against 1 / [Ca]. The mean dissociation constants for Ca and Mn were 1·3 mm and 015 mm respectively. From the model, an upper estimate of the density of calcium* receptor sites' of 30 per square micron of nerve terminal was obtained. 5 In contrast to its inhibitory effect on evoked release, Mn increases the spontaneous release of transmitter. It is suggested that Mn may increase m.e.p.p. frequency by releasing Ca from an intracellular store.

Localization of bacteria in the gastrointestinal tract: a possible explanation of intestinal spirochaetosis.

Abstract: The large intestine of rats and dogs was examined by light and electron microscopy. In both species localization of bacteria in specific areas of the tissue was observed. Fusiform bacteria mixed with spirochaetes were seen at the opening of the crypts into the large bowel. However, at the base of the crypts homogeneous populations of spiral organisms were found; some crypts contained Borrelia-type spirochaetes, whereas others contained spiral bacteria with other morphology. Very few spiral bacteria, including those of the spirillum type, were seen in the lumen of the large intestine. Experiments in rats showed that mucosa-associated spiral organisms appeared in large numbers in the stools when diarrhea was induced with magnesium sulfate. These observations were taken as a basis for explaining intestinal spirochaetosis of dogs and other animals, a syndrome which has been frequently described and which, until now, has been considered to reflect pathogenicity of these organisms.

An analysis of a token economy in stuttering therapy

Abstract: A stuttering therapy program in which adult stutterers were hospitalized and treated in small groups (n = 4) under token economy conditions is described. The Token System reinforced reductions and penalized increases in stuttering during conversation. The therapy program was divided into three stages. Initially, subjects were treated by the token system, which was then integrated with a delayed auditory feedback schedule designed to instate and shape a prolonged speech pattern into normal fluent speech. Finally, subjects passed through a speech situation hierarchy while under token control conditions. Experiments conducted in the first two stages of treatment are described. The first-stage experiments examined the design of the token system; the second-stage experiment assessed the effect of a contingent punishment schedule integrated with the delayed auditory feedback procedure in order to shape rate of speaking as well as fluency.

Measurement of non-enzymic browning of dehydrated carrot

Abstract: Non-enzymic browning of sulphited dehydrated carrot is measured by extracting brown materials with 2% acetic acid containing 1% formaldehyde, followed by precipitation of interfering pigments absorbing at 420 nm with 10% lead acetate and ethyl alcohol. The presence of sulphur dioxide is shown to reduce the absorption at 420 nm of a glucose—glycine browning solution and an extract of dehydrated carrot, the effect depending on time of incubation and exposure to light. The use of formaldehyde in the extraction solvent overcomes the effect of sulphur dioxide at concentrations up to 19 200 parts/million. The presence of carotenoids is shown to increase the absorption of browning extracts at 420 nm leading to high results. The interference from pigment materials is overcome by precipitation with lead acetate and ethyl alcohol. The use of both formaldehyde and lead acetate has no additional effect on browning determinations. Comparative tests of the proposed lead-alcohol precipitation method with an alcohol precipitation method, using both a glucose-glycine browning mixture and an extract of dehydrated carrot, shows only the lead-alcohol precipitation method to overcome errors due to carotenoid pigments either originally present in the extract or added as β-carotene, while the additional use of formaldehyde during extraction is necessary to overcome errors due to sulphur dioxide. Browning of dehydrated sulphited carrot stored for up to 20 days at 50 °C decreased with time of storage when measured by the alcohol precipitation method and in dehydrated non-sulphited carrot, browning showed only a slight increase with storage time. When measured by the lead-alcohol precipitation method, browning showed only a slight increase in stored dehydrated sulphited carrot, but a marked increase in stored dehydrated non-sulphited carrot, in agreement with visual observations.

Bacterial associations in the teredo Bankia australis (Lamellibranchia: Mollusca)

Abstract: Electron microscope examination of the so-called “Gland of Deshayes” in the teredos Bankia australis and related species has revealed that this structure is not a glandular tissue, but represents associations of bacteria.

A study of the effect of non-collinear Zeeman, hyperfine and fine structure tensors on E.S.R. spectra

Abstract: Second order perturbation solutions are given to the general experimental hamiltonian : where the axes of the g, D and A tensors may be non-collinear. The effects of the non-collinearities are discussed in terms of the modifications of the E.S.R. parameters for both single crystal and polycrystalline samples. The principles are illustrated for the E.S.R. of the formyl radical from published single crystal and powder data.

An extension of predictor control for systems with control time-delays

Abstract: The control of systems having time-delays in their control paths is considered and feedback laws are developed. A linear system is proposed and a quadratic criterion is optimized over an infinite interval to obtain time-invariant laws. A particularly simple law obtained by the solution of a non-delayed problem can be developed when all controls are delayed by the same amount, but when each control is delayed by a different amount the solution becomes quite complicated. Nevertheless this paper shows how solutions can be obtained by solving a sequence of tracking problems. In contrast to the state-delayed problem, where non-linear partial differential equations need be solved, only ordinary differential equations with single-point boundary values need be solved for the control-delayed problem. The time-invariant feedback law obtained involves a knowledge of the time-delay storages and performs a linear operation on these. The kernels of this operation cannot in general be derived as impulse responses of lum...

Formation of nitric oxide in fuel-lean and fuel-rich flames

Abstract: The Zeldovich mechanism is found to predict the concentrations of nitric oxide downstreamof flat, premixed lean and moderately fuel-rich flames ( O + N 2 ⇄ k − 1 k 1 N O + N . ( 1 ) Oxygen-atom concentrations are calculated from Eq. (2), which is derived by assuming that Reactions (3) and (4) are equilibrated, [ O ] m = [ O ] e ( [ C O ] m / [ C O ] e ) ( [ C O 2 ] e / [ C O 2 ] m ) ( [ O 2 ] m / [ O 2 ] e ) , ( 2 ) where the subscript e refers to equilibrium, and m to measured values, C O + O H ⇄ C O 2 + H , ( 3 ) H + O 2 ⇄ O H + O . ( 4 ) When [O]eis used in place of [O]m, the agreement is not satisfactory. For fuel-rich hydrocarbon flames (>1.15), an initial rapid formation of nitric oxide is observedwhich would require a high oxygen-atom concentration if it were to be explained by the Zeldovich mechanism. Similarly, high oxygen-atom concentrations are required to account for the observed rate of formation of nitric oxide in the post-flame gases of very fuel-rich hydrocarbon flames (>1.5). The required [O] are orders-of-magnitude greater than the probable [O] estimated fromreported values of [H]/[H]e (via the relationship [O]/[O]e=([H]/[H]e)2, which applies in fuel-rich flames). An alternative path for nitric oxide formation, involving the production of nitrogen atoms by reaction of nitrogen with hydrocarbon fragments, and their subsequent reaction by Reaction (5), is investigated; N + O H ⇄ N O + H . ( 5 ) It is concluded that this path is a more-plausible mechanism, in very fuel-rich hydrocarbonflames, than that requiring unreasonably high oxygen-atom concentrations. Further, as suggested by Fenimore, the mechanism involving nitrogen atoms may explain the rapid formation of nitric oxide observed in the vicinity of the reaction zone of moderately fuel-rich flames.

Intrinsic contractility of lymphatics in sheep and in dogs.

Abstract: Intralymphatic pressures were monitored from plastic cannulas implanted in the thoracic, lumbar trunk and mesenteric lymphatics of conscious and anesthetized sheep, and in the thoracic duct of anaesthetized dogs. Extrinsic factors appeared to be important in the propulsion of lymph only in the thoracic duct of the dog. Intrinsic pulsatile pressure patterns were recorded from all lymphatics studied in sheep, and from the thoracic duct in one out of three dogs. The pulses ranged from about 1–15 mm Hg in amplitude and from about 2–20 pulses/min in frequency. A parameter of contractility was defined and used to establish the existence in sheep of a linear relationship between contractility and flow rate. This relationship was demonstrated when flow was increased by infusion into the lymphatic or into a vein, or, in the case of mesenteric lymphatics, by feeding fat. It was concluded that the intrinsic contractility is myogenic in origin and is the major factor responsible for lymph propulsion at least in sheep; the relationship between contractility and flow enables the rate of lymph flow to keep pace with the rate of lymph production.