Showing papers by "University of New South Wales published in 1994"

On Gibbs sampling for state space models

Abstract: SUMMARY We show how to use the Gibbs sampler to carry out Bayesian inference on a linear state space model with errors that are a mixture of normals and coefficients that can switch over time. Our approach simultaneously generates the whole of the state vector given the mixture and coefficient indicator variables and simultaneously generates all the indicator variables conditional on the state vectors. The states are generated efficiently using the Kalman filter. We illustrate our approach by several examples and empirically compare its performance to another Gibbs sampler where the states are generated one at a time. The empirical results suggest that our approach is both practical to implement and dominates the Gibbs sampler that generates the states one at a time.

Why Some Material Is Difficult to Learn

Abstract: The experiments reported in this article flow from the following assumptions concerning our cognitive processes: (a) Schema acquisition and automation are major learning mechanisms when dealing with higher cognitive activities and are designed to circumvent our limited working memories and emphasize our highly effective long-term memories. (b) A limited working memory makes it difficult to assimilate multiple elements of information simultaneously. (c) Under conditions where multiple elements of information interact, they must be assimilated simultaneously. (d) As a consequence, a heavy cognitive load is imposed when dealing with material that has a high level of element interactivity. (e) High levels of element interactivity and their associated cognitive loads may be caused both by intrinsic nature of the material being learned and by the method of presentation. (f) If the intrinsic element interactivity and consequent cognitive load are low, the extraneous cognitive load is critical when dealing with i...

Lattice Methods for Multiple Integration

Abstract: This paper reviews the use of lattice methods for the approximate integration of smooth periodic functions over the unit cube in any number of dimensions.

Modeling Wave-Enhanced Turbulence in the Ocean Surface Layer

Abstract: Until recently, measurements below the ocean surface have tended to confirm “law of the wall” behavior, in which the velocity profile is logarithmic, and energy dissipation decays inversely with depth. Recent measurements, however, show a sublayer, within meters of the surface, in which turbulence is enhanced by the action of surface waves. In this layer, dissipation appears to decay with inverse depth raised to a power estimated between 3 and 4.6. The present study shows that a conventional model, employing a “level 2½” turbulence closure scheme predicts near-surface dissipation decaying as inverse depth to the power 3.4. The model shows agreement in detail with measured profiles of dissipation. This is despite the fact that empirical constants in the model are determined for situations very different from this near-surface application. The action of breaking waves is modeled by a turbulent kinetic energy input at the surface. In the wave-enhanced layer, the downward flux of turbulent kinetic en...

Power Distance, Individualism/Collectivism, and Job-Related Attitudes in a Culturally Diverse Work Group

Abstract: Hofstede's power distance (PD) and individualism (IDV) constructs were validated in the context of a single multicultural work setting. Two hundred sixty-three workers from 28 different countries employed in the information services branch of a large Australian bank completed a questionnaire the items of which measured some implications of the constructs, namely: superior-subordinate relationships, decision-making styles, the work ethic, task orientation, the psychological contract, and individual versus group achievement. On the basis of their Hofstede country index, the subjects were divided into high and low PD and IDV groups, respectively, and differences in their scores on theoretically relevant items provided support for both constructs. The questionnaire also included items stenming from the model about the nature and incidence of inteethnic work-related friction. As predicted, the out-group non-Anglo-Celt respondents reported a greater incidence of discrimination, regarded cultural diversity in th...

Fortnightly Review: Methadone maintenance treatment in opiate dependence: a review

Abstract: This paper examines the changes and advances in research and clinical practice and examines the role of treatment structure and programme characteristics in the delivery of methadone maintenance. Methadone prescribing has become much more available over the past decade, both in countries with a history of its use, such as the United Kingdom and Australia, and in countries around the world which previously had not endorsed substitute prescribing.1 There is a need to examine closely the framework in which this treatment is delivered to ensure that the modes of delivery most effective from both cost and benefit perspectives are utilised. This review focuses entirely on methadone maintenance because this is the most extensively evaluated and most used treatment, with about a quarter of a million drug misusers receiving methadone treatment globally. A small number of experimental diamorphine and buprenorphine substitute programmes are being evaluated in several countries. Most studies have come from the United States and focus on the long term use of methadone in a specific setting; in contrast, methadone treatment in the United Kingdom has received virtually no formal evaluation to date bar one study.2 There is concern that a considerable amount of the methadone prescribing could be having little impact on illicit drug use or risk taking behaviour,3 a recent study of drug users in police custody echoes this.4 The Advisory Council on the Misuse of Drugs has recommended a shift to a more structured approach for delivery of oral methadone maintenance. The organisation and regulation of methadone maintenance treatment varies widely, with explicit guidelines for programme operation in the United States and Australia and a virtual absence of structure and regulation in Britain. It is likely that policy analysts and treatment providers in countries with high levels of regulation and structured programmes …

Guiding the selection of human antibodies from phage display repertoires to a single epitope of an antigen.

Abstract: We have developed a strategy for guiding the selection of human antibody fragments from phage display repertoires to a single epitope of an antigen, using rodent monoclonal antibodies as a template. Thus the heavy chain of a rodent antibody (MAb32) directed against human tumor necrosis factor alpha (TNF alpha) was cloned and paired as a template chain with a repertoire of human light chains for display as Fab fragments on filamentous phage. The phage were selected by binding to the antigen. The selected human light chains were in turn paired with a repertoire of human heavy chains displayed on phage, and the phage selected again. The isolated phage displaying human antibody fragments binding to TNF alpha also bound to a peptide comprising the N-terminal region of TNF alpha as with MAb32. One of the human Fab fragments was recloned for expression as a glycosylated human antibody in mammalian cells: Binding to TNF alpha could be competed with MAb32 or with anti-serum to the peptide, indicating the same epitope. The human antibody was found to have a binding affinity (Kd = 15 nM) similar to MAb32 (Kd = 26 nM). The process contrasts with existing means of "humanizing" rodent monoclonal antibodies in that the antibodies derived are completely human.

Genetic variation of microsatellite loci in a bottlenecked species: the northern hairy‐nosed wombat Lasiorhinus krefftii

Abstract: We investigate the utility of hypervariable microsatellite loci to measure genetic variability remaining in the northern hairy-nosed wombat, one of Australia's rarest mammals. This species suffered a dramatic range and population reduction over the past 120 years and now exists as a single colony of about 70 individuals at Epping Forest National Park, central Queensland. Because our preliminary research on mitochondrial DNA and multilocus DNA fingerprints did not reveal informative variation in this population, we chose to examine variation in microsatellite repeats, a class of loci known to be highly polymorphic in mammals. To assess the suitability of various wombat populations as a reference for comparisons of genetic variability and subdivision we further analysed mitochondrial DNA cytochrome b sequence, using phylogenetic methods. Our results show that appreciable levels of variation still exist in the Epping Forest colony although it has only 41% of the heterozygosity shown in a population of a closely-related species. From museum specimens collected in 1884, we also assessed microsatellite variation in an extinct population of the northern hairy-nosed wombat, from Deniliquin, New South Wales, 2000 km to the south of the extant population. The apparent loss of variation in the Epping Forest colony is consistent with an extremely small effective population size throughout its 120-year decline.

Cross-Cultural Differences in the Self Concept A Test of Hofstede's Individualism/Collectivism Distinction

Abstract: Twenty-six Malaysian (Collectivist), 32 Australian, and 20 British (Individualist) subjects completed ten statements beginning with "I am." The responses were coded according to whether they were idiocentric, group, or allocentric self-references. The scores were then weighted according to the rank order in which they appeared on the questionnaire. As predicted by Hofstede's model, people from the collectivist culture produced significantly more group and fewer idiocentric self-descriptions than did people from the individualist cultures. The data support a pan-cultural model of the self in which cross-cultural variations in the self-concept are not treated as categorically different, but as reflecting the relative salience of the self's constituent components.

Sport and the maintenance of masculine hegemony.

Abstract: Sport is a crucial arena in which masculine hegemony is constructed and reconstructed. The effects of sporting activity are usefully analyzed in terms of two major dimensions. Those that relate directly to men, and those that serve dominant interests less directly, though no less effectively, through inferiorizing women and their activities. Processes through which sport directly supports male dominance are ones which associate males and maleness with valued skills and the sanctioned use of aggression/force/violence. Sport celebrates the dominant form of masculinity, though it must be noted that as well as women, some men are also excluded. This monopolization process is completed by a series of concrete processes which exclude women from the terrain completely, or if they do manage to pass through the barriers, effectively minimizes their achievements. Four concrete processes are considered and illustrated from the Australian sporting scene, those of definition, direct control, ignoring, and trivialization. It is necessary to understand these processes if we are to develop strategies to circumvent them. The mere fact that it is necessary for these processes to be continually invoked demonstrates that there are contradictions which can be exploited.

Species coexistence and self-organizing spatial dynamics

Abstract: IN a patchy environment, dispersal between neighbouring local populations can allow the total (regional) population to persist1–5; even where all patches are identical and the within-patch dynamics are unstable, the total population readily persists as a metapopulation. This persistence is associated with striking, self-organized spatial patterns in the densities of the subpopulations. In the case of hosts and parasitoids, these may form spiral waves, spatial chaos, or a so-called 'crystal lattice' with regularly spaced knots of high population density4,6. Here we extend earlier work on two species to three or more, showing that coexistence of competing species is usually associated with some degree of persistent spatial segregation, even when the environment is uniform. At its most extreme, this can confine one species to small, relatively static 'islands' within the habitat, giving the appearance of isolated pockets of favourable habitat. The distributions of interacting species may thus result from a trade-off between dispersal and competition within subpopulations, as much as from external factors.

Task-dependent reflex responses and movement illusions evoked by galvanic vestibular stimulation in standing humans.

Abstract: 1. To identify the vestibular contribution to human standing, responses in leg muscles evoked by galvanic vestibular stimulation were studied. Step impulses of current were applied between the mastoid processes of normal subjects and the effects on the soleus and tibialis anterior electromyograms (EMGs), ankle torque, and body sway were identified by post-stimulus averaging. The responses were measured when subjects stood on a stable platform or on an unstable platform and the effects of eye closure were also assessed. Responses were also recorded during voluntary contraction of the leg muscles and when subjects balanced a load equivalent to their own body in a situation where vestibular postural reflexes would not be useful. 2. At a mean post-stimulus latency of 56 ms, there were reciprocal changes in soleus and tibialis anterior muscle activity followed, at 105 ms, by larger responses of opposite sign. These were termed the short- and middle-latency responses, respectively. Both responses increased with stimulus intensity, but the short-latency response had a higher threshold. The early response had a similar latency to EMG responses evoked by rapid postural perturbations. Both responses were larger when the eyes were closed, but eye closure was associated with increased sway and EMG activity, and the responses were of similar magnitude when scaled to background EMG level. 3. Both short- and middle-latency EMG responses in soleus and tibialis anterior muscles produced small transient postural sways. The transient changes in EMG activity were followed by a larger prolonged sway which was not attributable to the activity in these muscles but rather to reflex or volitional adjustments to movements at other body segments. When subjects were prevented from swaying, the galvanic stimulus produced illusory movements in the opposite direction to the sway evoked when standing, and it is possible that the prolonged sway is a reaction to the illusion of sway. 4. The short- and middle-latency responses were modified during different postural tasks according to the dependence on vestibular reflexes. When the support platform was unstable, the EMG responses to galvanic stimulation were larger. There were no vestibular-evoked responses when seated subjects made voluntary contractions of the leg muscles or when they stood upright with the trunk supported, using the ankles to balance a body-like load.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanisms of Apoptosis: Integration of Genetic, Biochemical, and Cellular Indicators

Abstract: Apoptosis, or programmed cell death, is defined by morphologic change resulting in nonpathologic cell loss and is relevant to a wide spectrum of biology The process is best characterized in the nematode Caenorhabditis elegans where ced genes mediate the death of specific cells during development Some corresponding genes have been identified in mammalian cells Expression of the mammalian bcl-2 gene (homologous to ced-9) suppresses apoptosis in many systems The ced-3 gene is homologous to a mammalian protease Increased levels of the tumor suppressor p53 due to DNA damage may result in either blockage of the cell cycle at G1 or apoptosis Mutation of p53 is associated with decreased cell death from radiation and cytotoxic drugs Initiation of the apoptotic pathway may occur as a consequence of conflicting growth signals Hierarchical relationships variously between bcl-2, p53, myc, and other genes indicate a complex pattern of regulation Stimuli resulting in apoptosis may cause production of free radicals and increased intracellular calcium concentration The relationship of these changes to the hallmark of apoptosis, internucleosomal fragmentation of DNA, is unclear, and "laddering" of DNA is not always evident Apoptotic DNA degradation probably occurs sequentially, initially involving breakage into 50 kilobases or larger fragments The nuclease(s) responsible have not been identified, but deoxyribonuclease I is implicated The association between nuclease activation and chromatin condensation is complex, and programmed cell death may be subject to cytoplasmic regulation Available data suggest that clearer understanding of apoptosis will result in better cancer therapy

Interactive-activation as a framework for understanding morphological processing

Abstract: A description is given of the main experiments that have been taken as support for the view that, in reading, a prefixed word is stripped of its prefix and lexically accessed on the basis of its stem. Since one of the most important of those experiments had been poorly executed, a new version of the same study is presented with results that are entirely consistent with the previous one. However, logical problems exist with the view that says that stems act as access codes used to gain access to the lexicon, the main ones having to do with the fact that a prefix store is required. As a result, an alternative model is favoured, namely, an interactive-activation model. Prefixed words are represented in decomposed form in this model, but no prelexical prefix-stripping is required. A detailed examination is made of the manner in which this framework is able to incorporate the previous empirical results, as well as other aspects of morphological processing.

Radiation and the Lung: A Reevaluation of the Mechanisms Mediating Pulmonary Injury

Abstract: Recent data from several investigators, including our unit, have provided additional information on the etiology of radiation-induced lung damage. These data suggest that there are two quite separate and distinct mechanisms involved: (a) classical radiation pneumonitis, which ultimately leads to pulmonary fibrosis is primarily due to radiation-induced local cytokine production confined to the field of irradiation; and (b) sporadic radiation pneumonitis, which is an immunologically mediated process resulting in a bilateral lymphocytic alveolitis that results in an "out-of-field" response to localized pulmonary irradiation. Both animal experiments and human studies show that classical radiation pneumonitis has a threshold dose and a narrow sigmoid dose-response curve with increasing morbidity and mortality over a very small dose range. Clinical pneumonitis rarely causes death, whereas in the animal and human studies of classical radiation pneumonitis, all subjects will eventually suffer irreversible pulmonary damage and death. The description of classical radiation pneumonitis is that of an acute inflammatory response to lung irradiation, which is confined to the area of irradiation. Recent studies have also shown that irradiation induces gene transcription and results in the induction and release of proinflammatory cytokines and fibroblast mitogens in a similar fashion to other chronic inflammatory states, and which ultimately results in pulmonary fibrosis. The description of classical radiation pneumonitis does not adequately explain the following observed clinical characteristics: (a) the unpredictable and sporadic onset; (b) the occurrence in only a minority of patients; (c) the dyspnoea experienced, which is out of proportion to the volume of lung irradiated; and (d) the resolution of symptoms without sequelae in the majority of patients. We have demonstrated a bilateral lymphocytic alveolitis of activated T lymphocytes and a diffuse increase in gallium lung scan uptake in patients studied before and 4 to 6 weeks after strictly unilateral lung irradiation. This is suggestive of a hypersensitivity pneumonitis, which gives rise to an "out-of-field" response to localized lung irradiation and hence more accurately describes the clinical picture of radiation pneumonitis. Reevaluation of the mechanisms of pulmonary injury from irradiation suggest that (a) a new term, sporadic radiation pneumonitis, should be introduced to describe the clinical picture of radiation pneumonitis, which is not adequately explained by the classical description and is quite clearly an entirely different process; and (b) that the chronic response to localized lung irradiation that leads to pulmonary fibrosis is largely mediated through the induction and release of tissues cytokines.

The fifth domain of beta 2-glycoprotein I contains a phospholipid binding site (Cys281-Cys288) and a region recognized by anticardiolipin antibodies.

Abstract: We have identified a phospholipid binding site in the fifth domain of beta 2-glycoprotein I (beta 2-GPI). Using synthetic peptides spanning the fifth domain of beta 2-GPI, we have shown that the presence of the sequence Glu274-Cys288 caused a decrease in the binding of purified anticardiolipin (aCL) antibodies in a modified cardiolipin (CL)-ELISA by inhibiting the binding of beta 2-GPI to CL. This peptide bound to and could be eluted from a CL affinity column in a manner similar to native beta 2-GPI. Peptides corresponding to other regions of the fifth domain had no inhibitory effect. The inhibitory activity was restricted to the sequence Cys281-Lys-Asn-Lys-Glu-Lys-Lys-Cys288. Peptides in which the two flanking cysteine residues were deleted or substituted with serine residues possessed no inhibitory activity, indicating that the conformation of this highly positively charged sequence may be critical for phospholipid binding. aCL antibodies purified from patients with autoimmune disease were shown to bind directly to wells coated with native beta 2-GPI but not to wells coated with a preparation of beta 2-GPI cleaved between Lys317 and Thr318. The integrity of this sequence is therefore critical for these antibodies to recognize beta 2-GPI, and the putative epitope for aCL antibodies is most likely to be in this region.

Postural stability, falls and fractures in the elderly: results from the Dubbo Osteoporosis Epidemiology Study.

Abstract: OBJECTIVE: To assess measures of postural stability in a large population of persons aged over 60 years in order to compare performance between fallers and non-fallers and relate postural stability to fracture prevalence. METHODS: The sensorimotor, visual and balance functions were measured in 1762 ambulatory, community-dwelling patients aged between 60 and 100 years (mean age, 70.1 years) living in a large semi-urban Australian city. A history of recent falls and fractures was recorded at the time of assessment. RESULTS: The prevalence of impairment in all tests increased with age. Men performed significantly better than women in tests of muscle strength, visual field dependence, sway on the floor with eyes open and dynamic balance. In the 12 months before testing, 72.3% of the patients experienced no falls, 18.4% fell only once and 9.3% fell on two or more occasions. Multiple fallers had weaker quadriceps, poorer tactile sensitivity, greater visual field dependence and greater body sway than other patients. Test scores for once-only fallers were mostly between those for non-fallers and multiple fallers. Those who suffered recent fall-related fractures had significantly reduced tactile sensitivity and quadriceps strength and increased body sway. Postural stability was also impaired in patients taking psychoactive and/or anti-hypertensive medications. CONCLUSION: Tests of postural stability can identify, independently of age, individuals living in the community who are at risk of falls and fall-related fractures. Language: en

Fast Computation of Multivariate Kernel Estimators

Abstract: Multivariate extensions of binning techniques for fast computation of kernel estimators are described and examined. Several questions arising from this multivariate extension are addressed. The choice of binning rule is discussed, and it is demonstrated that linear binning leads to substantial accuracy improvements over simple binning. An investigation into the most appropriate means of computing the multivariate discrete convolutions required for binned kernel estimators is also given. The results of an empirical study indicate that, in multivariate settings, the fast Fourier transform offers considerable time savings compared to direct calculation of convolutions.

The Catalytic Hydrogenolysis of Esters to Alcohols

Abstract: The hydrogenolysis of esters to alcohols is a reaction between esters and hydrogen which selectively splits a C-0 bond adjacent to a carbonyl group (1). A well-known large-scale industrial process based on this reaction the production of fatty alcohols from natural fatty acid esters-has been operated commercially for more than 50 years. Several processes which include the hydrogenolysis of an ester have been proposed for the manufacture of basic chemicals such as methanol and ethanol. Furthermore, there has been continuous interest over the past two decades in replacing the existing, energy-intensive processes for the production of ethylene glycol and 1,4-butanedioI by more cost-effective routes involving ester hydrogenolysis. While particular aspects of the literature on hydrogenolysis of esters have been reviewed already [1–3], the objective of the present work is to give a more general summary with special emphasis on the present or possible industrial applications of ester hydrogenolysis.

Neuropeptides in Migraine and Cluster Headache

Abstract: The cerebral circulation is invested by a rich network of neuropeptide Y (NPY) and noradrenaline containing sympathetic nerve fibers in arteries, arterioles and veins. However, the nerve supply of vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP) containing fibers is sparse. While noradrenaline and NPY cause vasoconstriction, VIP, SP and CGRP are potent vasodilators. Stimulation of the trigeminal ganglion in cat and man elicits release of SP and CGRP. Subjects with spontaneous attacks of migraine show release of CGRP in parallel with headache. Cluster headache patients have release of CGRP and VIP during bouts. Treatment with sumatriptan aborts headache in migraine and cluster headache as well as the concomitant peptide release.

The provision of other services by auditors: Independence and pricing issues

Abstract: This research has three objectives: to identify the extent and level of other services provided by incumbent auditors in the Australian business environment; to examine pricing issues by investigating the relationship between fees for other services and audit fees; and to address the question of independence by (a) identifying whether the incidence of audit qualification is related to the level of other services purchased and (b) investigating whether there is a relationship between audit tenure and the level of other services provided. Information on audit fees, fees for other services, size, audit qualifications, industry and auditor (Big 8(6)/Non-Big 8(6)) was obtained from publicly available information for the majority of the top 500 Australian companies listed on the Australian stock exchange between 1986–1990. This study provides evidence that an increasing number of clients are purchasing other services from their auditor. A significant positive relationship between fees paid for other se...