Showing papers by "University of Western Australia published in 1974"

Natural convection in a shallow cavity with differentially heated end walls. Part 1. Asymptotic theory

Abstract: The problem of natural convection in a cavity of small aspect ratio with differentially heated end walls is considered. It is shown by use of matched asymptotic expansions that the flow consists of two distinct regimes : a parallel flow in the core region and a second, non-parallel flow near the ends of the cavity. A solution valid at all orders in the aspect ratio A is found for the core region, while the first several terms of the appropriate asymptotic expansion are obtained for the end regions. Parametric limits of validity for the parallel flow structure are discussed. Asymptotic expressions for the Nusselt number and the single free parameter of the parallel flow solution, valid in the limit as A → 0, are derived.

Modality effects in word identification

Abstract: An experiment was designed to investigate the locus of persistence of information about presentation modality for verbal stimuli. Twenty-four Ss were presented with a continuous series of 672 letter sequences for word/nonword categorization. The sequences were divided equally between words and nonwords, and each item was presented twice in the series, either in the same or in a different modality. Repetition facilitation, the advantage resulting from a second presentation, was greatest in the intramodality conditions for both words (+re responses) and nonwords (−ve responses). Facilitation in these conditions declined from 170 msec at Lag 0 (4 sec) to approximately 40 msec at Lag 63. Facilitation was reduced in the cross-modality condition for words and was absent from the cross-modality condition for nonwords. The modality-specific component of the repetition effect found in the word/nonword categorization paradigm may be attributed to persistence in the nonlexical, as distinct from lexical, component of the word categorization process.

Programming the generalization of a greeting response in four retarded children.

Abstract: Reinforcement techniques of prompting and shaping were employed to develop handwaving, a useful social greeting response, in four institutionalized retarded subjects. A multiple-baseline design across subjects demonstrated the reliable functioning of the training procedures. Specifically, it showed that training and maintenance of the greeting response by one experimenter was not usually sufficient for generalization of the response to the more than 20 other members of the institution staff who had not participated in the training of the response. However, high levels of generalization to staff members were recorded for three subjects over periods ranging from one to six months after a second experimenter trained and maintained the response in conjunction with the first experimenter. The fourth subject, although never receiving training by a second experimenter, showed similar results following a second training by the first experimenter.

Natural convection in a shallow cavity with differentially heated end walls. Part 3. Experimental results

Abstract: The steady motion of water in an enclosed rectangular cavity with differentially heated vertical end walls was studied experimentally, and the results are compared with the findings of parts 1 and 2. The depth-to-length ratios of the cavities were 102 and 1·9 × 102, and the Rayleigh number was allowed to vary sufficiently to enable a study to be made of the transition from a flow driven by the vertical wall boundary layers to one sustained by a longitudinal temperature gradient in the central sections of the cavity.

Phloem bleeding from legume fruits-A technique for study of fruit nutrition.

Abstract: Bleeding from phloem of cut distal tips of attached fruits was demonstrated in the genera Spartium, Genista, Lupinus and Jacksonia. Bleeding occurred over a 2-25 min period enabling 0.5-10 μl of sap to be collected from a fruit. A detailed study of Lupinus albus L. showed that exudation rate declined exponentially after cutting, but without any change with time in solute levels in exudate. Bleeding resumed at its initial rate and solute concentration on recutting the fruit tip.Phloem exudates had a high pH (7.8-8.0), a sucrose content of 100-210 mg ml(-1) but only traces of monosaccharides. Surrounding pod tissues contained only 15-35 mg ml(-1) of sugars (tissue water basis) more than two thirds of this monosaccharide. Amino compounds were present in phloem exudates at 8-28 mg ml(-1), asparagine and glutamine predominating but a wide spectrum of other amino acids being also present. No significant differences in levels of organic solutes were observed in phloem exudates collected from tips of attached versus detached fruits, from phloem exudates collected from fruit tips versus pedicels, or from basal versus distal ends of a detached fruit.Potassium was the major cation (1.5-2.2 mg ml(-1)) of the phloem exudate, Ca(2+) was at a much lower level than either Mg(2+) or Na(+). Trace element levels in phloem exudates appeared to be influenced by availability to the plant from the rooting medium. Nitrate was absent though detectable in non-vascular tissues of the shoot. (14)C- labelled assimilates were detected in exudates of L. albus one hour after feeding a source leaf (14)CO2; sucrose, organic acids and certain amino compounds achieved high specific labelling. (14)CO2 feeding studies coupled with the phloem bleeding technique revealed highly specific source-sink relationships between foliar organs and fruits of the primary inflorescence.

The specific adsorption of inorganic Hg(II) species and Co(III) complex ions on goethite

Abstract: The specific adsorption of Hg(II), as Hg2+ and HgCl20, on goethite has been measured as a function of pH The results show that the mercuric ion is not a typical heavy metal cation since its adsorption is considerably less than for other cations at pH values near their respective p*K values Complexing the mercuric ion with chloride to give HgCl20 was found to reduce adsorption to negligible amounts It is concluded that hydroxo ligands are essential for Hg(II) adsorption and it is probable that two hydroxo bridges are formed between the oxide surface and the adsorbed Hg(II) atom Reduction of the positive charged surface The considerable covalency of the Hg-OH bonds is believed to cause the relatively low affinity of the mercuric ion for the oxide by polarizing the surface-OH-Hg bonds and therefore minimizing the strength of the surface-OH bonds The complex ions [Co(NH3)6]3+, [Co(NH3)5H2O]3+, and [Co(en)2(H2O)2]3+ were not specifically adsorbed even when the latter two were hydrolyzed to hydroxo species Their inability to adsorb is again attributed to the covalency of the Co(III)-OH bonds of the hydroxo ions which prevents the formation of stable hydroxo bridges between the oxide surface and the Co(III) species

Estrogen receptor concentration in normal and pathological human uterine tissues.

Abstract: The estrogen receptor concentration of the cytoplasmic fraction of human endometrial homogenates was estimated in 63 normal and 47 abnormal tissues. The receptor concentration was highest in the early proliferative phase of the menstrual cycle and decreased progressively throughout the cycle to reach lowest levels in tissues showing decidual reaction or disintegrating secretory changes. In the postmenopausal endometrium the concentration of estrogen receptors was similar to that seen in the proliferative endometrium. The level of receptors in the hyperplastic proliferative endometrium of presumed anovulatory cycles was significantly less than in normal proliferative endometrium. These tissues, unlike all others studied, bound more 3H-estradiol at 37 C than at 25 C. Estrogen receptor determinations in cystic hyperplasia revealed a wide range of values which did not follow a specific pattern. In endometrial carcinoma, on the other hand, the receptor cpncentration correlated with the stage of differ...

Some biological interactions affecting intertidal populations of the kelp Egregia laevigata

Abstract: Near Santa Barbara, California (USA), the large laminarian kelp Egregia laevigata (Setchell) occurred from the lower intertidal zone to subtidal depths. In the intertidal zone there was a large recruitment of E. laevigata in the spring. The kelp were largely excluded from a zone in the lowest intertidal zone where the surf grass Phyllospadix sp, grew, but were abundant on all other rock surfaces. Experiments demonstrated that, while neither grazers nor sessile organisms significantly reduced recruitment, E. laevigata of the previous year-class did so. There were also interactions among E. laevigata of the same year-class, expressed as a density-dependent mortality of very small algae, and as faster growth rates and greater number of branches of kelp at low densities. These processes tended to make both numbers and biomass of E. laevigata uniform. The mortality rates of large E. laevigata were so high that, in some locations, no kelp survived for more than 8 months. E. laevigata was, therefore, essentially an annual and opportunistic species in the intertidal zone.

Stereopsis by binocular delay.

Abstract: HERE I report results which reveal a new form of binocular stereopsis sensitive to delays between the arrival of common input to both eyes instead of retinal disparity.

Regression of Left Ventricular Dilation and Hypertrophy after Removal of Volume Overload: Morphological and Ultrastructural Study

Abstract: Gross and ultrastructural changes occurring in the left ventricle in response to chronic volume overload were studied in dogs. One group of dogs was examined 28-43 days after an aortocaval fistula had been created; congestive heart failure had developed at the time of the examination. Two other groups of dogs were investigated 78 ± 17 (SD) days and 178 ± 4 days after similar fistulas had been closed. A group of control dogs was also studied. Aortocaval fistulas produced significant left ventricular dilation and hypertrophy. Ultrastructural changes included enlargement and distortion of intercalated disks, increase in number but decrease in size and relative volume of mitochondria, and loss of lateral alignment of sarcomeres. Left ventricles, 78 days after the fistulas had been closed, were not different ultrastructurally or grossly from those in dogs with patent fistulas. After 178 days of closure, ventricular mass and volume had decreased; mass was still significantly greater than that in normal dogs, but cavity volume was not. Ultrastructural abnormalities in dogs after 178 days of closure were much less marked than those in dogs with patent fistulas, and ultrastructure was hardly distinguishable from normal. The findings in these experiments indicate that gross and ultrastructural abnormalities produced in the left ventricle by chronic volume overload are largely, if not completely, reversible.

Differential effects of ouabain and ethacrynic acid on the labyrinthine potentials.

Abstract: Intravenous injection of 20–45 mg/kg Ethacrynic acid reversibly reduced the endocochlear potential and increased endolymph sodium concentration from less than 1 mM to 5–8 mM 20 min after the injection.

Behavioural relationships between Merino ewes and lambs during the four weeks after birth

Abstract: The attachment between the ewe and her lamb, as assessed by estimating the distance between ewe and lamb and observing their behaviour, was studied for the 4 weeks after birth. The ewe and lamb kept in close contact throughout this period. They were within 10 metres of each other in 56% of all observations; only in 6% of all observations were they more than 50 metres from each other. With increasing age of lamb, the ewe spent more time grazing while the lamb also spent more time grazing and playing and less time sucking. The lambs showed independent forms of behaviour such as the formation of groups as they got older. The distinct dependent behaviour traits were that if bothewe and lamb were lying or walking, then they were usually close together.The mean distance between ewes and lambs remained constant for dependent forms of behaviour but gradually increased with age for independent forms of behaviour.

Evidence for an electrogenic potassium pump as the origin of the positive component of the endocochlear potential

Abstract: The endocochlear potential (EP) and endolymph potassium concentration [K+] e were measured in the first turn of the guinea pig cochlea. Liquid ion exchanger K+ specific microelectrodes were used for [K+] measurement. The resting value of the cochlea endolymph [K+] e was 140±8.6 mM. The [K+] e was then reduced by perfusing scale media with K+ substituted Ringers containing 5, 20 or 50 mM K+. EP fell rapidly after perfusion to steady values of 9–35 mV and the [K+] e returned to stable values of 62–130 mM. The K+ conductance [G K] was calculated assuming that EP was produced by K+ current to be 0.16×10−7 mMoles/min/mV/mm of scala media. Active K+ flux was calculated from the measured flux after perfusion and the passive flux was derived fromG K and the driving force for K+. It was concluded that the assumption that EP is generated by K+ current is justified and that the electrogenic K+ flux after perfusion was accompanied by an apparently electroneutral flux.

Gas Sorption in Clay Mineral Systems

Abstract: Sorption isotherms for four gases (N2, A, Kr and CO2) , commonly used in specific surface area and pore structure measurements, have been accurately determined on a number of clay mineral and oxide systems. Specific surface areas obtained by application of the BET theory to these isotherms illustrate the extent to which the apparent cross-sectional areas for these sorbed gases vary with surface structure, ex- changeable cation and microporosity. V-n plots for nitrogen adsorption on these materials using nitrogen adsorption on crystalline materials of large crystal size as a standard isotherm provide appreciable ranges of linearity in each case. The specific surface areas obtained from these straight line plots agree well with the corresponding BET values. The linearity of these plots for illite clays indicates the absence of capillary condensation and that adsorption in slit-shaped pores takes place largely by the formation of physically adsorbed layers on the surfaces. Much larger BET specific surface areas were obtained from carbon dioxide sorption at 196K on goethite, hematite and gibbsite than from nitrogen, argon and krypton sorption at 78"K. It is suggested that enhanced sorption of CO2 into microporous regions of the oxides, inaccessible to the other gases, occurs in a similar fashion to that frequently observed for coal and charcoal materials. V-n plots for CO2 sorption in these materials using that for an illite clay as a standard isotherm, support this conclusion. Considerably lower BET specific surface areas were obtained for CO 2 sorption on kaolinite than were obtained for nitrogen, argon and krypton sorption. The shape of the V-n plots for CO., sorption on kao- linite compared with illite suggest that an initial specific adsorption of CO2 on the kaolinite is followed by a change in state with the completion of this layer, allowing normal multilayer formation to proceed.

The effects of inhibitors of microtubule and microfilament function on transferrin and iron uptake by rabbit reticulocytes and bone marrow

Abstract: Summary. The possible involvement of microtubules and microfilaments in the uptake of transferrin and iron by rabbit reticulocytes and bone marrow cells was investigated by using agents which interfere with the functions of these cellular components. Colchicine, vinblastine, vincristine, strychnine, and heavy water, which inhibit microtubule function, all diminished transferrin and iron uptake by the cells. Vinblastine was also shown to inhibit transferrin release fiom reticulocytes and the uptake of both citrate-bound iron and leucine. Cellular ATP levels were not affected. Cytochalasin B which is believed to disrupt microfilaments did not affect transferrin or iron uptake by the cells. It is concluded that the inhibitory effects observed were due to alteration of structural components of the cell membranes, probably in the microtubules.

Transferrin and Iron Uptake by Rabbit Bone Marrow Cells in Vitro

Abstract: Summary. The interaction between rabbit transferrin and rabbit bone marrow cells and reticulocytes was investigated using transferrin labelled with 125I and 59Fe. The pattern of transferrin and iron uptake by bone marrow was found to be similar to that by reticulocytes and occurred in four stages, viz (1) adsorption of transferrin, (2) progressive uptake of transferrin, (3) release of the iron to the cell, (4) release of transferrin from the cell. Total transferrin uptake per bone marrow erythroid precursor cell was eight times that per reticulocyte, while the rate of iron uptake was at least twice as great with marrow cells. Transferrin uptake and release and iron uptake were temperature dependent. Transferrin and iron uptake were inhibited by metabolic inhbitors, particularly those affecting oxidative metabolism. The activation energies for the association and dissociation reaction of transferrin and the activation energy for iron uptake by bone marrow cells were higher than those reported for reticulocytes. A further difference between the two cell types was that at a constant iron concentration, iron uptake by bone marrow cells decreased with decreasing degrees of transferrin saturation with iron. Small increases in transferrin uptake by bone marrow cells were also obtained with increasing transferrin saturation. The data support the view that both iron and transferrin uptake are dependent upon cellular metabolism.

The biology of dauciform roots in the sedge cyathochaete avenacea

Abstract: Summary Small, carrot-shaped roots produced by Cyathochaete avenacea (Cyperaceae) were investigated. Quantitative data are given on their comparative morphology, anatomy and soil-plant relationships. While factors controlling their formation appear to have much in common with those controlling proteoid root formation, their origin and structure are quite different. The cyperaceous roots become endomycorrhizal late in their development. These root structures are essentially distinct from any described in other families, and the term ‘dauciform’ is proposed to distinguish them.

The effect of prostaglandin F2alpha on ovarian blood flow and corpora lutea regression in the rabbit.

Abstract: IN many species luteolysis is dependent upon the presence of the uterus and an intact utero-ovarian vasculature. The occurrence of prostaglandin F2α (PGF2α) in uterine tissue, its specific venoconstrictor properties and its ability to induce luteolysis exogenously, led to the hypothesis that, its release by the uterus might cause luteolysis by constricting the uterine and utero-ovarian veins and reducing ovarian bloood flow1. The observation that total ovarian venous outflow fell during infusions of PGF2α in rats and rabbits (after laparotomy and ovarian vein cannulation) supported this hypothesis. A subsequent investigation using similar methods failed to confirm this in rats2. Experiments in sheep with ovaries and uterus transplanted in toto to the neck produced no unequivocal evidence for a drop in ovarian blood flow following doses of PGF2α producing luteolysis, at least until oestrus ensued3. With increasing doses however, an immediate fall in ovarian blood flow occurred4.