Showing papers by "University of Queensland published in 1990"

An introduction to generalized linear models

Abstract: Part 1 Background scope notation distributions derived from normal distribution. Part 2 Model fitting: plant growth sample birthweight sample notation for linear models exercises. Part 3 Exponential family of distributions and generalized linear models: exponential family of distributions generalized linear models. Part 4 Estimation: method of maximum likelihood method of least squares estimation for generalized linear models example of simple linear regression for Poisson responses MINITAB program for simple linear regression with Poisson responses GLIM. Part 5 Inference: sampling introduction for scores sampling distribution for maximum likelihood estimators confidence intervals for the model parameters adequacy of a model sampling distribution for the log-likelihood statistic log-likelihood ratio statistic (deviance) assessing goodness of fit hypothesis testing residuals. Part 6 Multiple regression: maximum likelihood estimation least squares estimation log-likelihood ratio statistic multiple correlation coefficient and R numerical example residual plots orthogonality collinearity model selection non-linear regression. Part 7 Analysis of variance and covariance: basic results one-factor ANOVA two-factor ANOVA with replication crossed and nested factors more complicated models choice of constraint equations and dummy variables analysis of covariance. Part 8 Binary variables and logistic regression: probability distributions generalized linear models dose response models general logistic regression maximum likelihood estimation and the log-likelihood ratio statistic other criteria for goodness of fit least squares methods remarks. Part 9 Contingency tables and log-linear models: probability distributions log-linear models maximum likelihood estimation hypothesis testing and goodness of fit numerical examples remarks. Appendices: conventional parametrizations with sum-to-zero constraints corner-point parametrizations three response variables two response variables and one explanatory variable one response variable and two explanatory variables.

An ontological model of an information system

Abstract: An ontological model of an information system that provides precise definitions of fundamental concepts like system, subsystem, and coupling is proposed. This model is used to analyze some static and dynamic properties of an information system and to examine the question of what constitutes a good decomposition of an information system. Some of the major types of information system formalisms that bear on the authors' goals and their respective strengths and weaknesses relative to the model are briefly reviewed. Also articulated are some of the fundamental notions that underlie the model. Those basic notions are then used to examine the nature and some dynamics of system decomposition. The model's predictive power is discussed. >

Bacterial flora of fishes: a review

Abstract: Bacterial floras isolated from eggs, skin, gills, and intestines have been described for a limited number of fish species. Generally, the range of bacterial genera isolated is related to the aquatic habitat of the fish and varies with factors such as the salinity of the habitat and the bacterial load in the water. In many investigations, identification of isolates to the genus level only makes it difficult to determine the precise relationships of aquatic and fish microfloras. Bacteria recovered from the skin and gills may be transient rather than resident on the fish surfaces. Microfloras of fish intestines appear to vary with the complexity of the fish digestive system. The genera present in the gut generally seem to be those from the environment or diet which can survive and multiply in the intestinal tract, although there is evidence for a distinct intestinal microflora in some species. While obligate anaerobes have been recovered from carp and tilapia intestines, low ambient temperatures may prevent colonization by anaerobes in species such as rainbow trout.

Cell death induced in a murine mastocytoma by 42-47°C heating in vitro: Evidence that the form of death changes from apoptosis to necrosis above a critical heat load

Abstract: SummaryThe pathogenesis of heat-induced cell death is controversial. Categorizing the death occurring after various heat loads as either apoptosis or necrosis might help to elucidate this problem, since it has been shown that these two processes differ in their mode of initiation as well as in their morphological and biochemical features. Log-phase cultures of mastocytoma P-815 × 2·1 were heated at temperatures ranging from 42 to 47°C for 30 min. After 42°C heating a slight increase in apoptosis was observed morphologically. However, after heating at 43, 43.5 and 44°C, there was marked enhancement of apoptosis, and electrophoresis of DNA showed characteristic internucleosomal cleavage. With heating at 45°C both apoptosis and necrosis were enhanced, whereas at 46 and 47°C only necrosis was produced. DNA extracted from the 46 and 47°C cultures showed virtually no degradation, which contrasts with the random DNA breakdown observed in necrosis produced by other types of injury; lysosomal enzymes released duri...

Expertise, visual search, and information pick-up in squash.

Abstract: The visual search characteristics of expert and novice squash players were compared in two experiments In the first experiment subjects were required to predict the forthcoming direction and force of an opponent's stroke from a film display This film display was designed to simulate the normal display available to the defending player in squash and involved the use of variable temporal cut-offs to force the subjects to use advance cues in their prediction Systematic differences in the information pick-up of the experts and novices were observed on the film task but these differences were achieved with only relatively minor between-group variations in visual search strategy In the second experiment, set in the natural field setting, no expert-novice differences in either fixation distribution, order, or duration were observed on a comparable prediction task This provided further support for the conclusion that the limiting factor in the perceptual performance of the novices is not an inappropriate search strategy but rather an inability to make full use of the information available from fixated display features Some practical implications of these findings for the squash coach and player are considered

Anticipation in squash: Differences in advance cue utilization between expert and novice players

Abstract: The time of occurrence and spatial location of the advance cues used to anticipate the direction and force of an opponent's stroke in squash were examined using a film task. This task, designed to simulate the normal perceptual display of the defensive player, consisted of two discrete parts, each containing 160 individual stroke sequences (trials). In the first part of the film task, the display was occluded at different time intervals throughout the development of the opponent's stroke and the 16 expert and 20 novice subjects had to predict both the direction (down‐wall or cross‐court) and force (drive or drop shot) of the opponent's stroke. In the second part of the film task, visibility to selected advance cues was occluded by placing opaque mats on the film surface. Across all of the film task conditions experts were superior to novices in predicting the event outcome from the information available, highlighting the important contribution anticipatory skills make to expert performance in thi...

Adolescents' perceptions of the nature of their communication with parents.

Abstract: This study examines the effects of the age and sex of adolescent and the sex of parent upon adolescents' perceptions of the nature of their communication with each parent Two hundred and ninety-six adolescents aged 13-17 years completed a communication schedule, rating 14 content areas along six process dimensions: frequency of conversation, initiator, levels of recognition of adolescents' opinion, self-disclosure, domination, and levels of satisfaction Multivariate analyses of variance were conducted separately for each process dimension Frequency ratings revealed that adolescent females of all ages reported talking more often with mothers than did adolescent males Adolescent males, however, believed they talked more often than did females with fathers about interests, sexual issues, and general problems Mothers were seen to initiate more conversations than fathers on a wide range of topics Mothers were also perceived as more likely to recognize and accept the adolescents' opinions Adolescent females believed they disclosed more to mothers than fathers, but males believed they disclosed equally to both parents Males disclosed more to fathers than did females about their sexual or other problems, while females disclosed more often overall to their mothers than did males Adolescent males were equally satisfied with their discussions with both parents, but females were more satisfied about conversations with mothers rather than fathers In sum, the results suggest that mothers' more frequent initiation of discussions with their younger adolescents and their greater recognition of their opinions lead to older adolescents interacting more with mothers than fathers

British cultural studies

Abstract: One of the markers of contemporary studies in the humanities and social sciences is the close, critical attention directed onto the mass media and popular culture. British cultural studies, emerging out of the expanded English university system in the 1970s, were among the first to develop and broadly disseminate the methodologies and approaches which made such attention possible. Focusing initially on the relations between language and ideology through the close analysis of media texts, before diversifying into a broad range of interdisciplinary activities - cultural theory, cultural history, ethnography, media studies, and the analysis of the social construction of gender, race and identity - British cultural studies has played a fundamental role in establishing the conceptual and theoretical agenda for studies of popular cultural forms and practices.

Efficiency, effectiveness, and duration of stroke rehabilitation.

Abstract: This prospective multicenter study identifies the variables significant in the prediction of rehabilitation efficiency, achievement of rehabilitation potential and duration of rehabilitation stay in 258 persons with a first stroke admitted to comprehensive inpatient rehabilitation in Brisbane, Australia, during 1984. All three dependent variables were poorly predicted, with only 17% of the variance in rehabilitation efficiency, only 30% of the variance in achievement of rehabilitation potential, and only 22% of the variance in duration of rehabilitation stay explained. Unlike other reports, we considered most of the major medical (side of paralysis, stroke etiology, site of the lesion, arterial distribution affected, etc.), rehabilitative (initial Barthel Index score, interval from stroke onset to acute-care hospital admission, interval from hospital admission to rehabilitation commencement, neurologic measures, etc.), and demographic (age, years of education, occupation, ethnicity, etc.) variables. The high proportion of unexplained variance is likely to be due to nonmedical factors influencing the selection of patients for rehabilitation.

Bistability and optical switching of spatial patterns in a laser

Abstract: Bistability of the transverse configuration of the optical field is found for a helium–neon laser oscillating in the TEM01* hybrid optical-resonator mode. Optically induced switching between the mirror-symmetric field patterns occurs when a fraction of the spatially rotated output field is reinjected into the laser resonator. These phenomena are described theoretically with laser equations modeling the mutual interaction of the two first-order transverse modes of the optical resonator. The experimentally observed bistability and switching of the field patterns is in full qualitative agreement with the theoretical results.

Prevalence and course of depressive disorders in hospitalized stroke patients.

Abstract: In a sample of ninety-nine patients seen two months post-stroke, 18 percent were diagnosed as having minor depression and 14 percent major depression. At follow-up, fifteen months later, the prevalence of depressive disorder had declined substantially, to 12 percent overall. Major depression was characterized by an average duration of thirty-nine weeks, a mortality rate of 23 percent and was associated with positive family history of affective or anxiety disorder. Among patients with left hemisphere lesions, major depression was associated with cognitive impairment. Minor depression had a shorter average duration (twelve weeks) and was more common in males. These two syndromes may define distinct types of post-stroke depression with implications for treatment interventions.

Immunopathogenesis of oral lichen planus.

Abstract: Oral lichen planus (LP) is a common mucosal disorder in which cell mediated immunity is thought to play a major role. In this paper, a unifying hypothesis which attempts to integrate cellular and molecular signals in the local immune response in oral LP is presented. In this model, modified keratinocyte surface antigens are the target for the cytotoxic cell response which characterizes oral LP, whereas mast cells and antigen presenting Langerhans cells are key cellular elements in the evolving lesion. It has been established that mast cell degranulation induces adhesion molecule expression on endothelium which facilitates lymphocyte homing to the tissues. These adhesive interactions between lymphocytes and keratinocytes are postulated to be important determinants in the effector phase of the lesion. Cytokines produced by both lymphocytes and keratinocytes which influence the local immune response could promote chronicity. Accordingly, modulation of immunologic events is a potential therapeutic approach for oral LP.

Factors affecting the concentrations of ferritin in serum in a healthy Australian population.

Abstract: We measured by different techniques the ferritin concentration in serum in two large asymptomatic Australian population samples: 1367 bank employees and 601 insurance corporation employees. Ethanol intake, diet, the frequency of blood donation, smoking and exercise habits, and past medical history were documented. The median concentration of ferritin in serum varied according to age and sex, but was generally higher than in previously reported populations under age 65 years. Results for the two population samples were in close agreement. Apart from the blood donation status, the most important factors influencing the concentration of ferritin in serum were ethanol intake in men and diet in women. Heavy ethanol intake was associated with increased values, even among men without evidence of liver disease. We conclude that the reference range for ferritin concentration in serum in the Australian population should be significantly increased and should be related to age as well as sex. This study emphasizes the need to determine local reference ranges for ferritin concentrations in serum.

Interhemispheric transfer of plasticity in the cerebral cortex

Abstract: Each half of the body surface is represented topographically in the contralateral cerebral hemisphere. Physiological data are presented showing that homotopic regions of primary somatosensory cortex are linked such that plasticity induced in one hemisphere, in the form of receptive field expansion brought about by a small peripheral denervation, is immediately mirrored in the other hemisphere. Neurons which display the plasticity show no responsiveness to stimulation of the ipsilateral body surface. This suggests that the pathways and mechanisms mediating this transfer are specific to the role of maintaining balance, or integration, between corresponding cortical fields.

Deposition of manganese in a drinking water distribution system.

Abstract: The deposition of manganese in a water distribution system with manganese-related "dirty water" problems was studied over a 1-year period. Four monitoring laboratories with Robbins biofilm sampling devices fitted to the water mains were used to correlate the relationship among manganese deposition, the level of manganese in the water, and the chlorination conditions. Manganese deposition occurred by both chemical and microbial processes. Chemical deposition occurred when Mn(II) not removed during water treatment penetrated the filters and entered the distribution system, where it was oxidized by chlorine and chlorine dioxide used for disinfection. Microbial deposition occurred in areas with insufficient chlorination to control the growth of manganese-depositing biofilm. At 0.05 mg of Mn(II) per liter, the chemical deposition rate was much greater than microbial deposition. Significant deposition occurred at 0.03 mg of manganese per liter, and dirty water complaints were not eliminated until manganese levels were continuously less than 0.02 mg/liter and chlorination levels were greater than 0.2 mg/liter. A guideline level of 0.01 mg of manganese per liter is recommended.

Prevalence of haemochromatosis amongst asymptomatic Australians

Abstract: We determined the prevalence of iron overload due to homozygous haemochromatosis in an asymptomatic Australian (predominantly Caucasian) population by surveying 1968 employees of two large corporations. Subjects were screened by measurement of transferrin saturation and serum ferritin concentration and, in all subjects with elevation of both indices, percutaneous liver biopsy was performed to establish whether significant iron overload was present. The prevalence of iron overload due to haemochromatosis in this population was 0.36%. The prevalence rate was not significantly different between males and females, suggesting that this autosomal recessive disease is expressed equally in females given an adequate dietary iron supply. The positive predictive value of a transferrin saturation consistently greater than 45% together with an elevated serum ferritin concentration was 64%. It is concluded that the prevalence of significant iron overload due to homozygous haemochromatosis warranting treatment is approximately 1:300 and that transferrin saturation should be included in existing adult health screening programmes.

Construct validity of eight tests of attention : comparison of normal and closed head injured samples

Abstract: Attentional problems are common symptoms of brain impairment and are generally assessed by a number of psychological tests. However, clinicians do not always agree on the processes measured by these tests and validation of the tests is often inadequate. The present study used factor-analytic techniques to examine the construct validity of eight attention tests (Letter Cancellation, Serial Subtraction, Digit Span, Digit Symbol, Stroop Colour-Word, Trail Making, Symbol Digit Modality, and Knox Cube). These tests were administered to 125 university controls, 45 normal controls from the community, and 37 closed-head-injured patients. Each of the 13 measures from the eight tests were found to load on one of three components/factors (identified as visuo-motor scanning, sustained selective processing, and visual/auditory spanning) for the normal as well as the patient group. Comparison of the mean performances of the patients and their matched controls suggested that: (a) severe short-term patients were...

Growth hormone receptor expression in the rat gastrointestinal tract.

Abstract: We have used immunohistochemistry to define the cellular distribution of GH receptors in the gastrointestinal tract (GIT) and its derivatives. Immunohistochemistry was performed in the adult rat GIT with a panel of characterized monoclonal antibodies to the GH receptor. The most intense and heterogeneous immunoreactivity was observed in epithelial cell subpopulations of GIT mucosa. Mesenchymal elements of the GIT were homogenously and moderately immunoreactive. Intense immunoreactivity was observed in the ductal epithelium of the sublingual gland, scattered basal epidermal cells of the esophageal mucosa, zymogen cells of the gastric glands, scattered surface epithelial cells of the stomach, and scattered peripheral pancreatic acinar groups. Scattered enteroendocrine cells and parietal cells, crypt and villous columnar cells of the small intestine, surface columnar cells of the cecum/colon, crypt base columnar cells of the colon, and contiguous peripheral cords of pancreatic islet cells displayed strong im...

Regulation of growth hormone (GH) bioactivity by a recombinant human GH-binding protein.

Abstract: The in vitro biological effects of serum GH-binding protein (GHBP) were measured in the mouse 3T3-F442A preadipocyte adipogenesis assay during GH stimulation. Coincubation of increasing concentrations of human (h) GH (0.14-4.5 nM) with 4.2 nM recombinant hGHBP-(1-247) in serum-free medium shifted the hGH dose-response curve to the right over the range 0.14-0.9 nM. When the hGH concentration was fixed at 0.45 nM, a dose-dependent inhibition of GH bioactivity was seen over the range of 0.1-11.3 nM GHBP, with an ED50 of 3 nM. The presence of serum had no effect on the inhibitory properties of GHBP. When 2% pooled human serum was added to incubation medium containing 0.45 nM hGH and GHBP (0.6 nM-5.7 nM), the effect of GHBP was again inhibitory, with an ED50 of 1.2 nM. Two percent serum alone was adipogenic, but at this low serum concentration it is likely that some factor other than GH is responsible. In a homologous receptor assay, the binding of [125I]hGH to IM-9 lymphocytes was inhibited in a dose-dependent manner by increasing concentrations of hGHBP in the physiological range, providing further support for the idea that GHBP can regulate the bioactivity of GH by blocking the binding of free GH to target tissues in vivo. Our results suggest that one function of GHBP is to dampen the biological effects of pulsatile GH secretion by reducing free GH during secretory pulses. This effect combined with an increased half-life of circulating GH would have the effect of flattening the hormone secretory profile at the target tissue level.

Utility and validity of the STAI with anxiety disorder patients

Abstract: Factor analytic studies of the State-Trait Anxiety Inventory (STAI) have provided support for the concepts of state and trait anxiety. This article reports the factor structure of the STAI (Form X) using 205 panic-disordered patients with and without agoraphobia. Results show that a two-factor oblique solution is the most appropriate, accounting for 41.1 per cent of the variance. Eighteen of the A-State items had salient loadings on factor 1 (state anxiety) and all 20 of the A-Trait items had salient loadings on factor 2 (trait anxiety). This study demonstrates the utility of the STAI in measuring anxiety in clinical populations and further supports the theoretical distinction between state and trait anxiety.

Insulin increases the cell number of the inner cell mass and stimulates morphological development of mouse blastocysts in vitro

Abstract: Previous studies showed that insulin promotes cell proliferation and morphological development of preimplantation mouse embryos. In this report, the receptor responsible for these actions and the cell populations that are affected were investigated. Insulin's 9% stimulation of blastocyst cell number was entirely due to a 23% increase in ICM cell number with an EC50 of 0.54 pM. This and the similar degrees of stimulation of immunosurgically isolated ICMs by both physiological and supraphysiological insulin concentrations suggest that insulin receptors are present on the ICM and respond to exogenous insulin transcytosed through the TE to promote expansion of the ICM cell numbers. In morphological studies, insulin increased the number of blastocysts and decreased the number of morulae by 10% after 54 h culture from 2-cell embryos with EC50s of about 0.95 pM. The equivalence of these EC50s suggests mediation of insulin's stimulation of blastocyst formation via insulin receptors which are functionally expressed around the time of compaction at the 8-cell stage. These results support our hypothesis that insulin has an important role in the regulation of growth during preimplantation development.