Showing papers by "University of New South Wales published in 1978"

Large-scale linearly constrained optimization

Abstract: An algorithm for solving large-scale nonlinear programs with linear constraints is presented. The method combines efficient sparse-matrix techniques as in the revised simplex method with stable quasi-Newton methods for handling the nonlinearities. A general-purpose production code (MINOS) is described, along with computational experience on a wide variety of problems.

Evidence for a long Leu-enkephalin striopallidal pathway in rat brain.

Abstract: THE pentapeptides leucine (Leu-) enkephalin and methionine (Met-) enkephalin were isolated from brain and shown to be endogenous opiates1. These peptides bind to the brain opiate receptor2, and their biological actions are blocked by the morphine antagonist naloxone3. The availability of synthetic enkephalins has led to the development of radioimmunoassays (refs 2, 4, and R. Miller, personal communication) and immunohistochemical techniques. Preliminary immunohistochemical studies5,6 have shown the distribution of enkephalin-containing fibres to coincide with the regional distribution of opiate receptors as determined by biochemical techniques and autoradiography6–8. The highest density of enkephalin-positive fibres6,8 was located in the globus pallidus. We have now confirmed the presence of enkephalin-immunoreactive fibres in the globus pallidus, and using specific lesions have shown this immunoreactivity to be abolished by destruction of the neural connections between the globus pallidus and the caudoputamen.

Tension Stiffening in Reinforced Concrete Slabs

Abstract: A nonlinear finite element model is used to predict the short-term behavior of reinforced concrete slabs under transverse service loads. The model is based on small deflection plate bending theory and uses a layered 16-degree-of-freedom rectangular plate bending element. The sources of material nonlinearity in reinforced concrete slabs are examined and accounted for in an incremental nonlinear solution procedure. Various methods are considered for treating the tension stiffening effect that occurs between the cracks in the tensile concrete in regions close to the reinforcement. Numerical calculations are used to assess the relative merits of these methods and to test the validity of the model. A simple treatment of the tension stiffening effect is proposed in which a modification is made to the tensile stress-strain diagram for the reinforcing steel. This produces accurate results with relatively economic use of computer time.

Low fat, low cholesterol diet in secondary prevention of coronary heart disease.

Abstract: Four hundred fifty-eight men with coronary heart disease participated in a trial of secondary prevention for 2 to 7 years. Overall five year survival was 81%. For those with first heart attacks it was 86%.

Secondary electron emission in the scanning electron microscope

Abstract: The secondary electron emission induced by electrons in the energy range 2.5–25 keV was measured in a SEM. Values of the emission coefficient for C, Al, Cu, Mo, Ag and Au are presented showing that it varies systematically with atomic number. The coefficient is still appreciable at 25 keV beam energy. The signal from the secondary electron collector in the SEM includes large contributions from sources other than secondary electron emission from the specimen. These contributions are discussed and their relative importance measured. Physics Abstracts classification numbers: 0.690, 8.900

Water Binding Capacity of Commercial Produced Native and Modified Starches

Abstract: The water binding capacities of five cereal and three tuberous starches, as well as fourteen modified wheat starches were determined using a Differential Scanning Calorimetry technique. Of the native starches, the tuberous ones had the highest moisture binding capacities. The influence of amylose/amylopectin ratio on water binding capacity was examined using waxy maize, normal maize and high amylose maize starches and increases in amylose level were found to result in reduced water binding. Chemical modification caused a reduction in the water binding capacity of wheat starch presumably as a result of blocking water binding sites on the starch molecules. Pregelatinized wheat starch showed a higher water binding capacity than wheat starch as a consequence of the disruption of the internal structure of the granule.

A controlled trial of cervical manipulation of migraine.

Abstract: The efficacy of cervical manipulation for migraine was evaluated. In a six-month trial, 85 volunteers suffering from migraine were randomly allocated to three treatment groups. One group received cervical manipulation performed by a medical practitioner or by a physiotherapist, another received cervical manipulation performed by a chiropractor, while the control group received mobilization performed by a medical practitioner or by a physiotherapist. For the whole sample, migraine symptoms were significantly reduced. No difference in outcome was found between those who received cervical manipulation, performed by chiropractor or orthodox therapist, and those who received the control treatment. Chiropractic treatment was no more effective than the other two treatments in reducing frequency, duration or induced disability of migraine attacks, but chiropractic patients did report a greater reduction in pain associated with their attacks.

Water dissociation in bipolar membranes: Experiments and theory

Abstract: Experimental results are given for the net rate of water dissociation in a bipolar membrane formed from a single polyolephine sheet for reverse biases of up to 60 volts and temperatures in the range 10–60°C. It is deduced that the membrane possesses a thin (600–10,000A) neutral layer between the charged regions. The water dissociation occurs in one or both of the interior surfaces of the charged regions, adjacent to the neutral region, in very narrow regions, with width of the order of 10 A, where there is uncompensated fixed charge. In the reaction layer the rate constant for dissociation of water is about 107 times its free solution value.

Recruitment order of human spindle endings in isometric voluntary contractions.

Abstract: 1. The responses of twenty-two spindle endings in the anterior tibial and toe extensor muscles of human subjects were studied during isometric voluntary contractions of the receptor-bearing muscle with the ankle joint fixed in 25° plantar flexion. 2. The discharge of eighteen endings accelerated in voluntary contractions when the contraction strength exceeded a threshold level which differed for different endings but was reproducible for the same ending. 3. With contractions of slow onset the latency to spindle acceleration varied with the speed of onset of the contraction. Endings with a background discharge were often unloaded by contractions until the contraction strength exceeded the threshold for activation of the ending. 4. No correlation was found between the sensitivity of a spindle to external length changes and its ease of activation in a voluntary contraction. For two spindle endings with a background discharge there was no change in either discharge frequency or the regularity of spindle discharge during contractions which were below the threshold for activation of the endings. It is concluded that the threshold for activation of a spindle ending in an isometric voluntary contraction is determined by its fusimotor innervation, and that fusimotor neurones probably have a recruitment order, much as do skeletomotor neurones. 5. Once activated, the discharge of spindle endings fluctuated with changes in skeletomotor activity but the relationship for some endings contained non-linearities. Such non-linearities were not as apparent in multi-unit recordings from a number of spindle endings in the contracting muscle. It is concluded that the fusimotor drive to a muscle is proportional to the skeletomotor drive to the muscle, and that skeletomotor and fusimotor neurones are subjected to similar if not identical descending command signals. From the work of Evarts (1968), it seems likely that these command signals are related more to desired muscle force than to desired muscle length.

Cleavages in deformed psammitic rocks from southeastern Australia: Their nature and origin

Abstract: Cleavages in deformed psammitic rocks from southeastern Australia range from spaced rough cleavages (morphological equivalents of slaty cleavage in psammites) to crenulation cleavages. The microstructure of these cleavages suggests that solution transfer processes play an important part in their development, and that their morphology is dependent on features of the pre-existing fabric (the fabric existing prior to cleavage formation). Former mechanical hypotheses (Leith, 1905; Wilson, 1946) do not explain the observed cleavage microfabrics. There is a general lack of cataclastic textures and of any significant internal deformation of shape-modified grains. These grains, however, have corroded, irregular boundaries typical of dissolution. Rough cleavage development requires dissolution about individual grains, whereas the development of “zonal” and “discrete” crenulation cleavages requires dissolution on existing rough cleavage seams along the limbs of developing microfolds. Cleavage differentiation in each case is due to the dissolution of quartz and feldspar and the passive concentration of phyllosilicates, opaques, and iron oxides along the cleavages. However, crystallization and/or recrystallization of mica may also contribute to the final cleavage fabric, particularly in rough cleavage fabrics where mica beards are well developed.

The inheritance of tibial dyschondroplasia in broilers

Abstract: 1. A breeding programme to develop a line of chickens with a high incidence of tibial dyschondroplasia (TD) from Australian broiler stock is described. 2. Despite the absence of a control flock, this programme has demonstrated that selection in a broiler population can rapidly increase the incidence of TD. 3. There was consistent circumstantial evidence of the presence of a major sex‐linked gene, the recessive allele of which is associated with an increased incidence of TD. 4. The realised heritability estimates (obtained in the absence of a control flock) consistently exceeded 1.00, suggesting the presence of an environmental trend favourable to the onset of TD over the four generations of this investigation. 5. There was a high maternal component or dominance genetic component, or both, for the inheritance of TD in the final generation, suggesting that environmental factors associated with the female parent line may influence the incidence of TD in broilers.

The number and distribution of ganglion cells in the retina of the brush-tailed possum, Trichosurus vulpecula.

Abstract: The distribution of ganglion cells in the retina of the adult brush-tailed possum was determined by light microscopy of Nissl stained retinal whole mounts. Qualitatively, the distribution in this marsupial retina shows features, such as an area centralis and a visual streak, which are found separately or together in eutherian mammals. The possum retina is avascular and the eye has a weak tapetum in the superior fundus.The retinal area is 260 mm2 and there are about 280,000 ganglion cells. The diameters of the ganglion cell somas range from 5 micrometer to 26 micrometer and the frequency distribution of soma size classes is skewed and unimodal (mean" 12.8 micrometer) with 62% of the cells falling in the class of diameters 7-13 micrometer. Maps of ganglion cell density were made for five retinae. These maps show that there is a band of high ganglion cell density (greater 2,000 cells mm-2) which extends across the retina about 0.6 mm above the optic disc in the tapetal region of the fundus and which lies in the plane of the animal's horizon when the eyes are in their primary position. By analogy with other species, this band is termed the visual streak. Near the temporal end of the visual streak, 2.9 mm from the optic disc, the ganglion cell density reaches a localized maximum of approximately 5,000 cells mm-2 thereby defining the centre of an area centralis (greater than 3,000 cells mm-2). The posterior nodal distance of the possum eye was estimated at 7.8 mm, which corresponds to a retinal magnification of 136 micrometer per degree of visual field. There are up to 30,000 glial cells which lie in, or slightly vitread to, the layer of the retinal ganglion cells.

Dangling bonds on silicon

Abstract: The electron-paramagnetic-resonance signal that appears when Si is crushed, cleaved, or abraded is shown to be proportional to the areas of microcracks induced in the specimen. These are shown to be more prevalent than previously realized. Detailed consideration shows that a wide variety of previously inexplicable data can now be understood. These include some effects of oxygen and hydrogen, variability of signal width, effects of abrasive particle size, and kind of cleavage. The origin of the unpaired electrons is considered and it is concluded that they may be in localized states on the surfaces of the microcracks, such states being apparently a case of Anderson localization. The atoms on the crack surfaces are subject to spatially varying overlap forces and stress fields whose energy range exceeds the normal bandwidth, thus inducing localization. The temperature dependence of the paramagnetism of such states is discussed, including correlation corrections, and shown to yield approximately ${T}^{\ensuremath{-}1}$ as observed experimentally. A similar explanation applies to Ge. Cleancleaved Si surfaces display negligible surface paramagnetism due to pairing of surface electrons on alternate atom sites. The results suggest that for amorphous Si and Ge, localized states on the surfaces of small atom aggregates should be considered as a possible source of the observed paramagnetism.

A General Energy Analysis of Fabric Mechanics Using Optimal Control Theory

Abstract: A general energy analysis has been formulated and applied to the study of fabric mechanics with the aid of computer programs. The analysis is chiefly concerned with the elastic or recoverable mechanisms of fabric rheology. The com puter programs can be readily adapted to provide a solution for various fabric structures and deformations simply changing the boundary conditions.The energy analysis is based on the fundamental principle that elastic structures alway s assume a confguration of minimum strain energy, regardless of the deformation applied. The resulting minimization problem is solved with the use of a specific optimization technique -i.e., it is treated as an optimal control problem. In particular, the total yarn strain encrgy (consisting of the sum of the individual yarn bending. torsion, lateral compression, and longitudinal extension strain energies) is minimized, subject to certain constraints which give rise to internal forces and couples acting within the fabric structure itself. The constr...

Epidermolysis bullosa—new therapeutic approaches

Abstract: Summary Drug therapy of epidermolysis bullosa dystrophica (E.B.D.) for the past forty years is reviewed. A reproducible method for the direct extraction of collagenase and collagen peptidase from skin homogenates is described. Markedly elevated collagenase and collagen peptidase activity is demonstrated in skin of dystrophic E.B. patients. Diphenylhydantoin in pharmacological doses is shown to cause significant inhibition of the collagenolytic system both in vitro and in vivo. Diphenylhydantoin was used parenterally in two children with proven E.B.D. and was found to have a beneficial effect on skin fragility.

Retinal abnormalities in the Siamese cat

Abstract: Ganglion cell density maps of the retinas of Siamese cats show the same major features of ganglion cell distribution as are found in normally pigmented cats, in particular the area centralis and visual streak. In the retinas of the seven Siamese cats investigated, however, the areas centralis was "underdeveloped" when compared with the normally pigmented cat. The peak ganglion cell density was lower and the ganglion cells usually larger than at the area centralis of the normally pigmented cat, and the characteristic blood vessel pattern around the area centralis was less developed. One animal showed a marked blood vessel abnormality, a vessel crossing the area centralis in each retina. In another animal, the distribution of ganglion cells appeared abnormal throughout the retina. Medium-sized, possibly X-type ganglion cells were lacking from all retinal areas, overall cell numbers were low and the distribution of ganglion cells showed a prominent visual streak.

Product-integration with the Clenshaw-Curtis and related points

Abstract: This paper is concerned with the theoretical properties of a productintegration method for the integral $$\int\limits_{ - 1}^1 {k(x)f(x)dx}$$ , wherek is absolutely integrable andf is continuous. The integral is approximated by $$\sum\limits_{i = 0}^n {w_{ni} f(x_{ni} )}$$ , where the points are given byx ni =cos(i?/n, 0?i?n, and where the weightsw ni are chosen to make the rule exact iff is any polynomial of degree ?n. The principal result is that ifk?L p [?1, 1] for somep>1, then the rule converges to the exact result asn?? for all continuous (or indeed R-integrable) functionsf, and moreover that the sum of the absolute values of the weights converges to the least possible value, namely $$\int\limits_{ - 1}^1 {|k(x)|dx}$$ . A limiting expression for the individual weights is also obtained, under certain assumptions. The results are exteded to other point sets of a similar kind, including the classical Chebyshev points.

Wave forces on pipeline buried in permeable seabed

Abstract: The wave-induced seepage force on buried pipelines has been evaluated theoretically. The seepage force is shown to be large enough to warrant inclusion in future engineering design calculations for pipeline stablity. The pore-water pressure field at a pipeline buried in a permeable seabed has been determined from potential theory and the pressure at the pipe integrated to give a net seepage force. This force, of constant magnitude, rotates as the waves pass, thereby tending to force the pipe against the surrounding soil in a cyclic manner. As each wave trough passes over the pipeline the seepage force acts vertically upwards and when combined with the total bouyant force it increases the likelihood of pipeline flotation.

Mathematical modeling of lag phases in microbial growth.

Abstract: This paper describes a mathematical method of the lap phases of Saccharomyces cerevisiae that incorporates the basic concepts previously presented in a two-stage deterministic model for the growth of this organism under conditions of oxygen excess with a sugar as the growth-limiting substrate. The model structure was suggested by an extensive investigation of the causes of the lap phases of S. cerevisiae which found that, in contrast to the traditionally accepted trends, the length of the lap phase was not inoculum-size dependent. This was consistent with other previously published work which suggested that a major factor in the length of the lag phases in S. cerevisiae was the need to synthesize adequate levels of glycolytic and respiratory enzymes. These suggestions were confirmed experimentally with lag-age data. Based on this conclusion a mathematical model was developed incorporating a description of the levels of glycolytic and respiratory enzymes and their effect on the growth rate and metabolism. This model was tested experimentally and the initial results indicate that many aspects of the lag phase of this organism may be described mathematically. The experimental findings further support the concept of primary regulatory control proposed by Bijkerk and Hall.

Sri Lanka in Gondwanaland and the evolution of the Indian Ocean

Abstract: The present position of Sri Lanka and its past fit in Gondwanaland are investigated in relation to the development of the Indian Ocean. The 3 stages in the evolution of the Indian Ocean are shown to be controlled by fundamental NW, NS, and NE Precambrian lineament directions in Sri Lanka and South India. These older lineaments were rejuvenated in the Mesozoic–Tertiary to form oceanic transform faults which determined the phases of Indian Ocean floor spreading.