Showing papers by "University of New South Wales published in 1983"

Natural convection of air in a square cavity: A bench mark numerical solution

Abstract: Details are given of the computational method used to obtain an accurate solution of the equations describing two-dimensional natural convection in a square cavity with differentially heated side walls. Second-order, central difference approximations were used. Mesh refnement and extrapolation led to solutions for 103⩽Ra⩽10 6 which are believed to be accurate to better than 1 per cent at the highest Rayleigh number and down to one-tenth of that at the lowest value.

The afferent volleys responsible for spinal proprioceptive reflexes in man

Abstract: 1. To define the neural volleys responsible for the Achilles tendon jerk and the H reflex, muscle afferent activity was recorded using micro-electrodes inserted percutaneously into appropriate fascicles of the tibial nerve in the popliteal fossa.2. The response of soleus muscle afferents to tendon percussion consisted of a dispersed volley, starting 3.5-7.0 ms after percussion, increasing to a peak over 6.5-11.0 ms, and lasting 25-30 ms, depending on the strength of percussion. Electrical stimuli to the sciatic nerve at a level adequate to evoke an H reflex but subthreshold for the M wave produced a more synchronized volley, the fastest fibres of which had conduction velocities of 62-67 m/s, and the slowest 36-45 m/s.3. The wave of acceleration produced by percussion subthreshold for the ankle jerk spread along the skin at over 150 m/s. Midway between the bellies of the gastrocnemii it consisted of a damped oscillation with four to five separate phases and maximum amplitude approximately one-twentieth of that recorded on the Achilles tendon.4. With ten primary spindle endings, tendon percussion subthreshold for the ankle jerk elicited two to five spike discharges per tap, the shortest interspike intervals being 4-7 ms. Tendon percussion elicited single discharges from two Golgi tendon organs, and altered the discharge pattern of a single secondary spindle ending. The degree of dispersion of the multi-unit muscle afferent volley can be explained by the pattern of discharge of primary spindle endings.5. Percussion on the Achilles tendon evoked crisp afferent volleys in recordings from nerve fascicles innervating flexor hallucis longus, tibialis posterior, the intrinsic muscles of the foot and the skin of the foot. Electrical stimuli delivered to the tibial nerve in the popliteal fossa at a level sufficient for the H reflex of soleus produced either a volley in muscle afferents from the intrinsic muscles of the foot or a volley in cutaneous afferents from the foot.6. For comparable stimuli in the two positions, the H reflex was inhibited but the Achilles tendon jerk enhanced when the ankle was dorsiflexed from 105 degrees to 90 degrees .7. The duration of the rise times of the excitatory post-synaptic potentials (e.p.s.p.s) produced in soleus motoneurones by electrical stimulation, and by tendon percussion subthreshold for the H reflex and the ankle jerk respectively, was estimated from post-stimulus time histograms of the discharge of voluntarily activated single motor units in soleus. The mean e.p.s.p. rise times were 1.9 ms for electrical stimulation and 6.6 ms for tendon percussion. There was evidence that the duration of the electrically evoked e.p.s.p. was curtailed by an inhibitory post-synaptic potential (i.p.s.p.) of only slightly longer latency than the e.p.s.p.8. The mechanically induced and electrically induced afferent volleys are not homogeneous volleys in group I a afferents from triceps surae. The afferent volleys differ in so many respects that it is probably invalid to compare the H reflex and tendon jerk as a measure of fusimotor activity. It is suggested that neither reflex can be considered a purely monosynaptic reflex.

Patterns of Interpersonal Information Seeking for the Purchase of a Symbolic Product

Abstract: The author extends the research on consumer prepurchase information seeking to a product which is essentially socially symbolic rather than utilitarian. A survey of the purchasers of a fashion item...

Brainstem Influences on the Cephalic Circulation: Experimental Data From Cat and Monkey of Relevance to the Mechanism of Migraine

Abstract: SYNOPSIS Stimulation of the locus ceruleus produces vasoconstriction in the intracerebral circulation and vasodilatation in the extracerebral circulation. The latter is mediated by the seventh cranial nerve, involving a non-cholinergic transmitter. These vascular changes are reminiscent of those occurring in migraine. Stimulation of the trigeminal ganglion or of the trigeminal divisions produces a reflex dilatation in the external carotid territory also mediated by non-cholinergic fibers in the seventh nerve. It is postulated that, in migraine, activation of the locus ceruleus would produce vasoconstriction in the cerebral circulation and dilatation extracerebrally. Such an effect would account for both the neurological symptoms of migraine and the observed changes in blood flow and vascular reactivity. Dilatation in the external carotid territory could lead to further reflex changes by activation of the central pathways described. Changes in locus ceruleus activity could be responsible for the pain of the headache phase of migraine, by disrupting a descending pain control system.

Initial phases of starvation and activity of bacteria at surfaces.

Abstract: The activity of the hydrophilic Vibrio sp. strain DW1 and the hydrophobic Pseudomonas sp. strain S9, which both undergo starvation-induced responses, was examined at nutrient-enriched and nutrient-deficient interfaces. The initial period of response to a starvation regime (“dwarfing” phase) is a sequence of two processes: fragmentation and continuous size reduction of the fragmented cells. This dwarfing phase is also one of intense metabolic activity as supported by O2 uptake measurements of the endogenous metabolism and the use of inhibitors of the proton flow, the electron transport chain, and membrane-bound ATPase. Hydrophilic bacteria become even smaller at nutrient-deficient surfaces than in the liquid phase upon starvation, and this is reflected in a higher endogenous metabolism exhibited by surface-associated cells compared with those in the liquid phase. On the other hand, hydrophobic bacteria dwarfing at surfaces did not exhibit a greater size reduction and exhibited an endogenous metabolism that was only slightly higher than that of cells in the liquid phase. Bacterial scavenging of surface-localized nutrients is related to the degree of irreversible binding of dwarf and starved bacteria, which in turn may be related to the degree of cell surface hydrophobicity.

Sensory effects of pulling or vibrating exposed tendons in man.

Abstract: The role of muscle receptors in proprioception has been demonstrated in a variety of ways (for review see McCloskey, 1978) but is still doubted by some. One simple but critical experiment has produced conflicting results: when a tendon of a conscious subject is exposed at operation under local anaesthesia, and pulled so as to stretch its muscle while the joint at which the muscle acts is held still, the subject is claimed by some to perceive nothing (Gelfan and Carter, 1967; Moberg, 1972), while others claim that the subject feels that the joint seems to move (Matthews and Simmonds, 1974). In the present study 4 patients were studied while undergoing surgery at the wrist or hand under local anaesthesia, and a more extensive study was carried out in the laboratory on the exposed, transected tendon of extensor hallucis longus of one of the authors (D.I.McC.). All 4 patients and the experimental subject detected stretches imposed on their muscles, and reported them as rotations of the joint or joints to which those muscles attach. In all cases the movements reported were in the direction of joint rotation that would normally stretch the muscle tested. In the experimental subject it was shown that stretches were detected with comparable acuity to that demonstrable for the detection of movements imposed on the intact toe. Also, the subject was able to detect, as joint movements, sinusoidal stretches of less than 1 mm imposed on the tendon at 1 or 5 Hz. The experimental subject experienced illusory movements of plantar flexion of the big toe when longitudinal vibration at 100 Hz, 20 to 100 microns amplitude was applied. These were sometimes partly masked by spread of the vibration through the foot. These vibration-induced illusions correspond to those reported by Goodwin et al. (1972) for transverse vibration applied through the skin. The subject could maintain a constant tension through the tendon in a contraction in which his effort was held constant. If, during such an effort, a downward movement was imposed on the toe to which the tendon normally connects, or the skin on the bottom of the toe was scratched, achieved tension fell.

Reviving the problem of acquiescent response bias.

Abstract: Summary Rorer's claim that meaningless acquiescence to attitude and personality scale items does not generalize and hence cannot be a souce of artifactual relationships is critically examined. Rorer excepts ambiguous scales from his own generalizations without providing or suggesting any test to tell which scales are ambiguous to a problematical degree; thus his generalizations are of unknown applicability. Three studies are reported in which balanced scales are scored for acquiescence only—i.e., scored without any reverse-scoring. Many high correlations between such scores were found—in direct contradiction of the findings used by Rorer. Correlations between acquiescence scores derived from balanced attitude scales and balanced personality scales were, however, generally low. It is concluded that meaningless acquiescence may be evinced by respondents to any scale if they find its items ambiguous and that such acquiescence will generalize from scale to scale. Meaningless acquiescence could then create man...

Leadership style, budgetary participation and managerial behavior

Abstract: This paper reports the results of a study of the effects of leadership style and budgetary participation on performance and job satisfaction. The first two variables have been given much attention in the organizational behavior and management accounting literatures, respectively, while litte consideration has been given to both jointly. The most important results of the study reveal that the two variables interact in their effects on the criterion variables. Under certain leadership conditions, budgetary participation was found to have strong positive effects on performance and job satisfaction. Under other conditions, the reverse was true. The implications of the results for control system design and personnel management are considered.

Extracranial vascular changes and the source of pain in migraine headache

Abstract: The extracranial circulation of 66 migrainous patients was assessed during unilateral headache by recording the pulse amplitude of the superficial temporal artery and its main frontal branch, by facial thermography, and by changes in the intensity of headache when temporal or carotid arteries were compressed. Amplitude of pulsation of the superficial temporal artery did not differ between headache and headache-free sides but the amplitude of its frontal branch was increased on the headache side, specifically in a subgroup of patients whose headache was relieved by compressing the superficial temporal artery ("extracranial vascular" group). Facial thermograms demonstrated significant differences in heat loss from the temples and orbits between migrainous patients and controls, frontotemporal changes being more conspicuous in the extracranial vascular group. It was concluded that dilatation of the superficial temporal artery and its branches contributes substantially to migraine headache in only a minority of patients.

Homocysteinemia, ischemic heart disease, and the carrier state for homocystinuria

Abstract: Precocious atherosclerosis occurs in homocystinuria due to cystathionine β-synthase deficiency and there is evidence that homocysteine may produce endothelial damage. Mild homocysteinemia has been reported in heterozygotes after methionine loads and it has been suggested that they could have an increased risk of atherogenesis. We measured plasma amino acids before and after a methionine load (100 mg per kg) in 17 obligatory heterozygotes, in 20 men under 50 yr with established ischemic heart disease, and in matched controls, to determine whether methionine loading allows identification of heterozygotes, and whether there is an altered rate of methionine metabolism in patients with premature coronary artery disease. The obligate heterozygotes had higher mean plasma concentrations of methionine and total homocysteine at 4, 8 and 12 hours after the load than their controls, and lower concentrations of total cysteine and taurine in fasting and all post load samples; however, there was considerable overlap of measurements in heterozygotes and their controls even when differential weightings were applied. There were no differences in mean plasma concentrations of methionine, total homocysteine or total cysteine between the patients with ischemic heart disease and their controls at any measurement point. However, two patients with premature coronary artery disease, identical twins, had persistent elevation of total plasma homocysteine and an exaggerated homocysteine response to methionine. Oral folate restored homocysteine concentrations before and after methionine to normal. We conclude that heterozygotes for cystathionine β-synthase deficiency have a reduced ability to metabolise methionine but that under normal western dietary conditions they are unlikely to have elevated plasma homocysteine concentrations, presumably because of enhanced homocysteine remethylation; because of this they are unlikely to have an increased risk of atherogenesis. With these small numbers we could show no evidence for a predominance of heterozygotes among patients with established premature coronary vascular disease, but two patients, identical twins, had persistent mild homocysteinemia responsive to folic acid which could have constituted an additional risk factor for atherogenesis.

Localization of Two Brominated Metabolites, Aerothionin and Homoaerothionin, in Spherulous Cells of the Marine Sponge Aplysina fistularis (=Verongia thiona)

Abstract: Energy dispersive X-ray microanalysis was used to localize the two brominated natural products (aerothinonin and homoaerothionin) in the tissues of a marine demosponge, Aplysina fistularis. Virtually all of these compounds were localized within the spherules of the spherulous cells in the mesohyl. This is the first localization of any secondary metabolite at the cellular or sub-cellular level in any marine invertebrate. In Aplysina fistularis, as in other species of the same genus studied by Vacelet, the spherulous cells are concentrated just beneath the exopinacoderm and just beneath the endopinacoderm of the excurrent canals. Moreover, there is electron microscopic evidence for degeneration of some spherulous cells throughout the mesohyl. Presumably, this degeneration can release some aerothionin and homoaerothionin, which are known to have antibiotic properties. After release from the spherulous cells, these brominated natural products could function (1) within the mesohyl to exclude some types of bacteria or to aggregate ingested bacteria and/or (2) within the boundary layer of the surrounding seawater for defense or offense, as considered in the discussion section.

Responses of marine bacteria under starvation conditions at a solid-water interface.

Abstract: Size changes during starvation of 17 marine bacterial isolates at a solid-water interface and in the liquid phase were examined. Twelve rod-shaped, hydrophilic bacteria decreased in size more rapidly at the solid surface than in the liquid phase, a result parallel to that observed previously for one of the strains at an air-water interface. On the other hand, three rod-shaped, hydrophobic bacteria diminished in size more rapidly in the liquid phase than at the solid-water interface. The rapid size decrease (defined here as the dwarfing phase) in either situation appeared to be an active process which occurred more rapidly when the cells were in an early stage of logarithmic growth at the onset of starvation. Dwarfing was reversibly inhibited by low temperature and low pH but was not inhibited by chloramphenicol. Three coccoidal bacteria showed little tendency to become smaller upon starvation in the liquid phase or at a surface.

Nutrient composition of stone fruit (Prunus spp.) cultivars: apricot, cherry, nectarine, peach and plum.

Abstract: A total of 23 cultivars of apricot, cherry, nectarine, peach and plum available on the retail market in Sydney, Australia during the summer of 1981–82 were analysed and data are presented for water, protein, fat, sugars (fructose, glucose and sucrose), starch, dietary fibre, organic acids (malic, citric, quinic, shikimic and oxalic acids), ash, sodium, potassium, calcium, magnesium, iron, zinc, vitamin C, α-carotene, β-carotene, thiamin, riboflavin niacin, soluble solids, respiration rate and titratable acidity Edible weight and energy were calculated Data were compared with various national food composition tables

Observations of nodule growth during the oxidation of pure binary iron-aluminum alloys

Abstract: Oxidation studies were carried out in oxygen at 800°C, on a series of pure binary iron-based alloys with between 1.9 and 9.8 wt. % aluminum. The results are presented in conjunction with the existing literature and these permit the development of a classification of scale morphologies based on alloy composition. Alloys with less than about 2.4 wt. % aluminum form bulky stratified scales composed of Fe2O3 and Fe3O4 with FeAl2O4 and Al2O3 at the scale-metal interface. Alloys with between 2.4 and 6.9 wt. % form an external Al2O3 scale but this is interspersed with iron oxide nodules that penetrate the alloy substrate. Only alloys with greater than 6.9 wt. % aluminum form completely protective Al2O3 scales. Models based on oxide nucleation are presented for the growth of bulky scales and also the iron oxide nodules.

Theory of Fatigue for Brittle Flaws Originating from Residual Stress Concentrations

Abstract: A theory is formulated for the general fatigue response of brittle flaws which experience residual stress concentrations. The indentation crack is taken as a model flaw system for the purpose of setting up the basic fracture mechanics equations, but the essential results are expected to have a wider range of applicability in the strength characterization of ceramics. A starting fatigue differential equation is first set up by combining an appropriate stress intensity factor for point- or line-contact flaws with a power-law crack velocity function. Analytical solutions are then obtained for the case of static fatigue. The resulting relation between lifetime and failure stress is shown to have exactly the same power-law form as the conventional solution for Griffith (residual-stress-free) flaws. This “equivalence” is used as a basis for extending the results to dynamic fatigue. A comparison of these analytical solutions with numerical counterparts defines the limits of accuracy of the theoretical procedure. However, while the form of the lifetime relation remains invariant, the values of the exponent and coefficient differ significantly for flaws with and without residual stress. Accordingly, the application of conventional fatigue theory to evaluate crack velocity parameters, without due regard for the nature of the critical flaw, can lead to serious errors. Explicit conversion formulas are given for transforming “apparent” velocity parameters for indentation flaws directly into “true” parameters. The implications of these results concerning the use of the indentation method for materials evaluation are discussed.

Convergence in the somatosensory pathway between cutaneous afferents from the index and middle fingers in man.

Abstract: Average short-latency cerebral potentials were recorded from the parietal scalp to mechanical stimulation of the index and middle fingers and to electrical stimulation of the digital nerves in normal subjects. The early components of the cerebral potential, representing the arrival of the afferent volley at the sensorimotor cortex, were studied during stimulation of the fingers separately and together. When strong or moderate stimuli were used there was a suppressive interaction between the afferent input from the two fingers with either electrical or mechanical stimulation. During simultaneous stimulation of both fingers the size of the early component of the cerebral potential was less than predicted by simple addition of the potentials produced by stimulation of the fingers individually. When very weak stimuli, close to the level necessary for detection by the subject, the input from the two fingers produced additive or facilitatory interactions in the early components of the cerebral potential. These results suggest that there is convergence between the afferent inputs from the index and middle fingers along the somatosensory pathway. At levels of stimulation comparable to those which produced facilitation in the electrophysiological studies, simultaneous stimulation to both fingers was detected significantly more frequently than would be expected from the detection of stimulation to individual fingers.

Comparative efficacy of behavioral and cognitive treatments of depression

Abstract: Twenty-five depressed subjects were allocated to either behavioral treatment, cognitive treatment, or no-treatment conditions for an 8-week period. Measures of depressive-related symptomatology and treatment-related target areas were administered prior to treatment, at midtreatment, and immediately following treatment. Depression was also assessed at a 5-month follow-up. Marked improvement was observed on most measures across the treatment period in both treatment conditions but not in the notreatment condition. Cognitive and behavioral treatments were found to be equally effective in alleviating depression. Treatment effects were maintained at the follow-up. At all but the midtreatment assessment, the two treatments were found to have an equivalent impact on treatment-related target areas. Various explanations of the results are offered, including the role of nonspecific treatment factors.

Surgical availability of the plantaris tendon

Abstract: The plantaris tendon is valuable as a donor tendon in hand surgery, but its presence is difficult to predict. Dissection of 658 cadavers showed that the tendon was present in 81.8% of limbs dissected and that there was no significant difference in the availability of plantaris between the two sexes or the sides. The incidence of bilateral absence shows that when the plantaris is absent on one side, the chance of finding it on the other is 1 in 3. There is no significant relationship between the condition of palmaris longus and the presence or usefulness of plantaris.

Agency Contracts, Institutional Modes, and the Transition to Foreign Direct Investment by British Manufacturing Multinationals Before 1939

Abstract: This paper analyzes the transition from agents to branch selling as alternative institutional modes for transacting abroad by pre-1939 British manufacturing multinationals. A model to explain the shift between alternative modes is specified in terms of transaction costs. Agent opportunism and contract monitoring costs are the major transaction costs. Besides transaction costs, the frequency of transactions and the accumulation of market-specific knowledge by the principal were found to be important variables.