Showing papers by "Deakin University published in 1999"

Issues in stacked generalization

Abstract: Stacked generalization is a general method of using a high-level model to combine lower-level models to achieve greater predictive accuracy In this paper we address two crucial issues which have been considered to be a 'black art' in classification tasks ever since the introduction of stacked generalization in 1992 by Wolpert: the type of generalizer that is suitable to derive the higher-level model, and the kind of attributes that should be used as its input We find that best results are obtained when the higher-level model combines the confidence (and not just the predictions) of the lower-level ones We demonstrate the effectiveness of stacked generalization for combining three different types of learning algorithms for classification tasks We also compare the performance of stacked generalization with majority vote and published results of arcing and bagging

Logit models and logistic regressions for social networks: III. Valued relations

Abstract: This paper generalizes thep* model for dichotomous social network data (Wasserman & Pattison, 1996) to the polytomous case. The generalization is achieved by transforming valued social networks into three-way binary arrays. This data transformation requires a modification of the Hammersley-Clifford theorem that underpins thep* class of models. We demonstrate that, provided that certain (non-observed) data patterns are excluded from consideration, a suitable version of the theorem can be developed. We also show that the approach amounts to a model for multiple logits derived from a pseudo-likelihood function. Estimation within this model is analogous to the separate fitting of multinomial baseline logits, except that the Hammersley-Clifford theorem requires the equating of certain parameters across logits. The paper describes how to convert a valued network into a data array suitable for fitting the model and provides some illustrative empirical examples.

The Relationship between Organizational Climate and Employee Perceptions of Involvement: The Importance of Support

Abstract: One of the key factors that may influence employees’ perceptions of involvement is organizational climate. This article examines the relationship between employee perceptions of involvement and org...

Collaborative Learning in an Online Environment

Abstract: The study described in this article researched the process of collaborative learning that occurred when postgraduate students studying a Master of Business Administration (MBA) program used computer-mediated communication (CMC) as a means of small-group and large-group communication It reports a largely qualitative study of groups of students learning collaboratively while living remotely from their university campus The main objective of the research was to observe and document the effects of the use of the computer-mediated group conferences on the group interaction of the students and to record their use and perceptions of the effects of the use of computer-mediated communication in their learning process Cet article decrit une recherche qui porte sur le processus d’apprentissage collaboratif observe chez des etudiants inscrits a un programme de maitrise en administration des affaires (MBA), qui ont utilise la communication mediatisee par ordinateur comme moyen de communication en petit groupe et en grand groupe Il decrit une etude qualitative menee aupres de groupes d’etudiants qui, pendant une periode ou ils ne se presentent pas sur le campus universitaire, doivent mener a distance une demarche d’apprentissage collaboratif L’objectif principal de la recherche consistait a observer et a documenter les effets des forums de discussion sur l’interaction d’un groupe d’etudiants, a rapporter leur maniere de l’utiliser et a definir leurs perceptions quant aux incidences de la communication mediatisee par ordinateur sur le processus d’apprentissage

Etiology of the Metabolic Syndrome: Potential Role of Insulin Resistance, Leptin Resistance, and Other Players

Abstract: Obesity and Type 2 diabetes are now major public health issues in developed nations and have reached epidemic proportions in many developing nations, as well as disadvantaged groups in developed countries, e.g., Mexican-Americans, African-Americans, and Australian Aborigines. These groups all show hyperinsulinemia and insulin resistance, which have been demonstrated to be future predictors of Type 2 diabetes and have also been suggested as key factors in the etiology of the Metabolic Syndrome. It is now increasingly recognized that Type 2 diabetes is part of a cluster of cardiovascular disease (CVD) risk factors comprising the Metabolic Syndrome. This group is at very high risk of atherosclerosis because each of the risk factors in the Metabolic Syndrome cluster in its own right is an important CVD risk factor. They also contribute cumulatively to atherosclerosis. A key strategy in reducing macrovascular disease lies in the better understanding of the Metabolic Syndrome--glucose intolerance, hypertension, hyperlipidemia, and central obesity. Although it has been suggested that hyperinsulinemia/insulin resistance is the central etiological factor for the Metabolic Syndrome, epidemiological data do not support the idea that this can account for all of the cluster abnormalities. We have animal and human data suggesting that hyperleptinemia rather than, or synergistically with, hyperinsulinemia may play a central role in the genesis of the CVD risk factor cluster that constitutes the syndrome. Studies in Psammomys obesus (the Israeli sand rat) suggest hyperinsulinemia/insulin resistance is an early metabolic lesion in the development of obesity and Type 2 diabetes. This animal also develops other features of the Metabolic Syndrome, making it an excellent model to investigate etiology. Psammomys, when placed on an ad libitum laboratory diet, develops hyperinsulinemia, insulin resistance, impaired glucose tolerance, diabetes, and dyslipidemia. It also develops hyperleptinemia and leptin insensitivity, and hyperleptinemia is correlated with insulin resistance independent of changes in body weight. It is likely that a similar sequence occurs in the transition from the prediabetic state to Type 2 diabetes in humans. More recently, other potential players in the etiology of the Metabolic Syndrome have been suggested including endothelial dysfunction and acetylation-stimulating protein (ASP). It has been suggested that endothelial dysfunction may be an antecedent for both Type 2 diabetes and the Metabolic Syndrome. In addition, ASP is a serious new candidate for an important role in insulin resistance. The ASP pathway plays a critical role in fatty acid metabolism and storage, and it has been suggested that ineffective storage of fatty acids by adipocytes due to a defect in the ASP pathway may lead to insulin resistance and Type 2 diabetes.

The opportunities and effectiveness of the health promoting primary school in improving child health— a review of the claims and evidence

Abstract: School health programs have been part of schooling for most of this century. The health promoting school is a recently developed concept which seeks to provide a multifaceted approach to school health. Will it provide a better frame-work to assist schools address the health issues of their students? This paper examines the development of the health promoting school and identifies its structural components. It reviews the claims and evidence which have emerged from the school health research literature which focus on primary schools. Findings indicate health gains for primary school students are difficult to assess, and will most likely occur if a well-designed program is implemented which links the curriculum with other health promoting school actions, contains substantial professional development for teachers and is underpinned by a theoretical model. The paper concludes by discussing how improvements can be made in more accurately assessing the effectiveness of the health promoting primary school in improving school health.

The Relative Age Effect in Soccer: Cross-Cultural Evidence for a Systematic Discrimination against Children Born Late in the Competition Year

Abstract: Previous findings of skewed birth date distributions among sports professionals have been interpreted as evidence for a systematic discrimination against children born shortly before the cut-off date for each age grouping. Alternative explanations for these findings exist, however. This research therefore attempted to replicate the effect in a cross-cultural comparison. A strong relative age effect in professional soccer was found in Germany, Japan, Brazil, and Australia, showing that the effect is independent of different cut-off dates and a variety of climatic and sociocultural factors. A shifted peak in the birth date distribution of Australian soccer professionals paralleling a corresponding change in the cut-off date in Australian soccer in 1989 was also established. This pattern of results provides strong evidence for the cut-off date in youth soccer as the main cause for the relative age effect in professional soccer.

Sexual Knowledge, Experience and Feelings Among People with Disability

Abstract: The current study was designed to evaluate the sexual knowledge, experience, feelings and needs of people with intellectual disability or physical disability, and compare them to people from the general population. Sixty people with mild intellectual disability (28 males, 32 females, mean age=27.62 years), 60 people with physical disability (33 males, 27 females, mean age=28.65 years) and 100 people from the general population (40 males, 60 females, mean age=30.10 years) participated in the study. Each respondent completed the Sexual Knowledge, Experience and Needs Scale (SexKen). This scale assesses levels of knowledge, experience, feelings and needs in 12 different areas of sexuality. The results demonstrated that people with intellectual disability experienced lower levels of sexual knowledge and experience, more negative attitudes to sex and stronger sexual needs than people with physical disability, in all areas of sexuality. People with physical disability demonstrated these same trends when they were compared to people from the general population. An interpretation of these results as they relate to the sexuality of people with intellectual or physical disability is provided.

Significant Life Experiences and Formative Influences on the Development of Adults’ Environmental Awareness in the UK, Australia and Canada

Abstract: Summary Environmental educators in Australia (n = 82), and Canada (n = 48) wrote autobiographical statements describing the formative influences and significant life experiences (SLE) which led to their concern for the environment. Content analysis identified the influences/experiences mentioned most often, both as single factors, e.g. ‘close family’, and as groups of logically related factors, e.g. ‘people’, a group composed of the factors ‘close family’, ‘older friends'’, ‘friends'’, and ‘having children’. The final lists of single factors were similar but not identical in the two countries, and both differed slightly from the list already derived from a sample of environmental educators in the UK (n = 233). Here we present the single and grouped factors named most often in Australia, then do the same for Canada, and then compare the principal factors in all three nations.

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs

Abstract: BACKGROUND Recent studies suggest that resistant starch (effective in producing butyrate and lowering possibly toxic ammonia) is rapidly fermented in the proximal colon; the distal colon especially would, however, benefit from these properties of resistant starch. AIMS To determine whether wheat bran (a rich source of insoluble non-starch polysaccharides), known to hasten gastrointestinal transit, could carry resistant starch through to the distal colon and thus shift its site of fermentation. METHODS Twenty four pigs were fed four human type diets: a control diet, or control diet supplemented with resistant starch, wheat bran, or both. Intestinal contents and faeces were collected after two weeks. RESULTS Without wheat bran, resistant starch was rapidly fermented in the caecum and proximal colon. Supplementation with wheat bran inhibited the caecal fermentation of resistant starch, resulting in an almost twofold increase (from 12.9 (2.5) to 20.5 (2.1) g/day, p CONCLUSIONS Wheat bran can shift the fermentation of resistant starch further distally, thereby improving the luminal conditions in the distal colonic regions where tumours most commonly occur. Therefore, the combined consumption of resistant starch and insoluble non-starch polysaccharides may contribute to the dietary modulation of colon cancer risk.

Leptin is released from the human brain: influence of adiposity and gender.

Abstract: Leptin, a 16-kDa circulating protein primarily derived from adipocytes, is an important factor in the regulation of appetite and energy expenditure. Using simultaneous arterio-venous blood sampling, several organs were assessed with regard to their individual roles in leptin metabolism in healthy male and female subjects constituting a range of body mass indices. Plasma leptin levels were unchanged after passage through the hepatosplanchnic and forearm circulations. In contrast, concentrations in the renal vein were consistently lower than those in the renal artery (-15%; P 28 kg/m2), but not lean (change, 2.3+/-2.3 vs. 0.1+/-0.1 ng/mL, respectively; P<0.05), indicating a probable influence of both gender and adiposity on brain leptin release. An attempt to grossly localize the site of brain release by using cerebral venous scans to distinguish between jugular venous drainage from cortical and subcortical brain areas revealed no region-specific secretion. These data raise the possibility that the brain is a nonadipose source of leptin. In addition, the higher level of brain release observed in females may contribute to the well documented gender differences in overall plasma leptin levels.

Effects of regular walking on cardiovascular risk factors and body composition in normoglycemic women and women with type 2 diabetes.

Abstract: OBJECTIVE: To examine the impact of a 12-week walking program on body composition and risk factors for cardiovascular disease in women with type 2 diabetes and in normoglycemic women with first-degree diabetic relatives. RESEARCH DESIGN AND METHODS: There were 11 postmenopausal women with type 2 diabetes and 20 normoglycemic women of similar age and BMI who were asked to walk 1 h per day on 5 days each week for 12 weeks. Fitness (estimated VO2max) was assessed with a 1.6-km walking test; body composition was measured by dual-energy X-ray absorptiometry; and sex hormone, metabolic, and lipid concentrations were measured in serum. RESULTS: After 12 weeks, estimated VO2max improved in both groups (P

Recognition of facial emotional expressions from moving and static displays by individuals with mental retardation.

Abstract: Moving and static videotaped and photographic displays of posed emotional expressions were presented to 12 adults with mental retardation and 12 without mental retardation to investigate the role of movement in the recognition of facial expressions of emotion Participants chose the corresponding emotion portrayed by the displays from among six written and pictorial labels of the emotions Results indicated that individuals with mental retardation were significantly poorer at identifying anger, fear, disgust, and surprise Both groups performed significantly better on the moving as opposed to the static videotaped displays of the emotions sad and angry Visual-perceptual limitations are likely contributors to the poorer performance of the group with mental retardation in recognizing moving and static facial expressions of emotion

Sports participation, sports injuries and osteoarthritis: implications for prevention.

Abstract: There is increasing concern that too much physical activity may lead to osteoarthritis. The continuous stress that physical activity places on the joints can result in microtrauma and degeneration of the articular cartilage. However, the onset of osteoarthritis appears to depend on the frequency, intensity and duration of physical activity. Research has shown that individuals of all ages can tolerate moderate amounts of exercise without adverse consequences or accelerated development of osteoarthritis. However, excessive participation in high impact sports, particularly over a long period of time and at an elite level, can increase the risk of developing osteoarthritis. Participants may also be at risk if they have abnormal joint anatomy or alignment, joint instability, underlying muscle weakness or imbalance, or if they are overweight and engage in significant amounts of exercise.

State of environment indicators of ‘river health’: exploring the metaphor

Abstract: Summary 1. Indicators are crucial to many socio-political schemes for portraying environmental influences of society. For example, the OECD model for State of the Environment Reporting uses three different sorts of indicators (pressure, condition, response) to differentiate the present condition of the environment from the anthropogenic pressures upon it and from any societal responses made to alleviate those pressures (thereby improving aspects of the overall condition). 2. These sorts of indicators have a fundamental technical basis in the science supporting their exposition and usage. However, the criteria used in interpreting the indicator values are likely to be set by considerations that go beyond scientific grounds. That is, indicators are socially determined in the end. However, many scientists find it difficult to involve the public in such reporting. 3. Scientists who are uncomfortable with this non-technical use of their indicator constructs should recognize that it is merely another manifestation of the overall broadening of environmental concern termed ‘ecosystem health’. The emerging field of ecosystem health seeks to take our technical understanding of how the environment functions and combine it with socio-economic goals, using a human health metaphor and an ethical underpinning. 4. River health might be better served by adopting a veterinary approach rather than the model of human health. This is because, like animals, riverine environments come in many different forms and cannot complain of ill health. Desirable interventions will vary with the uses to which we wish to put a river and our reasons for being concerned about a river’s health. A framework for this diagnostic approach is presented. 5. An enormous challenge lies ahead in integrating the various measurements of riverine attributes that might together constitute ‘river health’. We need ways to cater for the pluralism of modern societies, and we need more dynamic assessments of river condition, possibly founded on studies of key ecological processes.

Decision tree grafting from the all-tests-but-one partition

Abstract: Decision tree grafting adds nodes to an existing decision tree with the objective of reducing prediction error. A new grafting algorithm is presented that considers one set of training data only for each leaf of the initial decision tree, the set of cases that fail at most one test on the path to the leaf. This new technique is demonstrated to retain the error reduction power of the original grafting algorithm while dramatically reducing compute time and the complexity of the inferred tree. Bias/variance analyses reveal that the original grafting technique operated primarily by variance reduction while the new technique reduces both bias and variance.

Creatine supplementation increases muscle total creatine but not maximal intermittent exercise performance

Abstract: This study investigated creatine supplementation (CrS) effects on muscle total creatine (TCr), creatine phosphate (CrP), and intermittent sprinting performance by using a design incorporating the t...

Effect of Temperature on Muscle Metabolism During Submaximal Exercise in Humans

Abstract: To study the effect of temperature on muscle metabolism during submaximal exercise, six endurance-trained men had one thigh warmed and the other cooled for 40 min prior to exercise using water-perfused cuffs. One cuff was perfused with water at 50-55 degrees C (HL) with the other being perfused with water at 0 degree C (CL). With the cuffs still in position, subjects performed cycling exercise for 20 min at a work load corresponding to 70% VO2,peak (where VO2,peak is peak pulmonary oxygen uptake) in comfortable ambient conditions (20-22 degrees C). Muscle biopsies were obtained prior to and following exercise and forearm venous blood was collected prior to and throughout the exercise period. Muscle temperature (Tmus) was not different prior to treatment, but treatment resulted in a large difference in pre-exercise Tmus (difference = 6.9 +/- 0.9 degrees C; P < 0.01). Although this difference was reduced following exercise; it was nonetheless significant (difference = 0.4 +/- 0.1 degree C; P < 0.05). Intramuscular [ATP] was not affected by either exercise or muscle temperature. [Phosphocreatine] decreased (P < 0.01) and [creatine] increased (P < 0.01) with exercise but were not different when comparing HL with CL. Muscle lactate concentration was not different prior to treatment nor following exercise when comparing HL with CL. Muscle glycogen concentration was not different when comparing the trials before treatment, but the post-exercise value was lower (P < 0.05) in HL compared with CL. Thus, net muscle glycogen use was greater during exercise with heating (208 +/- 23 vs. 118 +/- 22 mmol kg-1 for HL and CL, respectively; P < 0.05). These data demonstrate that muscle glycogen use is augmented by increases in intramuscular temperature despite no differences in high energy phosphagen metabolism being observed when comparing treatments. This suggests that the increase in carbohydrate utilization occurred as a direct effect of an elevated muscle temperature and was not secondary to allosteric activation of enzymes mediated by a reduced ATP content.

The association of diet and thrombotic risk factors in healthy male vegetarians and meat-eaters.

Abstract: Objective: The aim of this study was to assess thrombosis tendency in subjects who were habitual meat-eaters compared with those who were habitual vegetarians. Design: Cross-sectional comparision of habitual meat-eaters and habitual vegetarians. Setting: Free living subjects. Subjects: One hundred and thirty-nine healthy male subjects (vegans n=18, ovolacto vegetarians n=43, moderate-meat-eaters n=60 and high-meat-eaters n=18) aged 20–55 y who were recruited in Melbourne. Outcome measures: Dietary intake was assessed using a semi-quantitative Food Frequency Questionnaire. The parameters of thrombosis were measured by standard methods. Results: Saturated fat and cholesterol intakes were significantly higher and polyunsaturated fat (PUFA) was significantly lower in the meat-eaters compared with vegetarians. In the meat-eaters, the platelet phospholipids AA levels were significantly higher than in the vegetarians, but there was no increase in ex vivo platelet aggregation and plasma 11-dehydro thromboxane B2 levels. Vegetarians, especially the vegans, had a significantly increased mean collagen and ADP stimulated ex vivo whole blood platelet aggregation compared with meat-eaters. The vegan group had a significantly higher mean platelet volume than the other three dietary groups. However, meat-eaters had a significantly higher cluster of cardiovascular risk factors compared with vegetarians, including increased body mass index, waist to hip ratio, plasma total cholesterol (TC), triacylglycerol and LDL-C levels, ratio of TC/HDL-C and LDL-C/HDL-C and plasma factor VII activity. Conclusions: Consumption of meat is not associated with an increased platelet aggregation compared with vegetarian subjects. Sponsorship: Meat Research Corporation, Australia.

Seasonal and annual foraging movements of little penguins from phillip island, victoria

Abstract: Little penguins, Eudyptula minor, from a breeding colony on Phillip Island, Victoria were radio-tracked at sea during incubation, chick-rearing and non-breeding periods from 1991 to 1993. Their locations, which we have assumed to reflect foraging movements, varied according to season and breeding activities, and there were marked differences from year to year. Duration and distance of trips ranged from single day-trips a few kilometres from Phillip Island, typically during the breeding season, to longer trips outside the breeding season up to 500 km away lasting more than a month, but 95% of all birds located were within 20 km of the coast. In the breeding season foraging trips averaged 4.4 days during incubation compared with 2.1 days when there were chicks in the nest; in the non-breeding period foraging trips took 5.2 days on average. The duration of trips for adults feeding chicks increased with the age of the chicks. Birds from nests on the north and south sides of Phillip Island differed in their use of areas close to the island, but showed a similar distribution on more distant trips. The location of foraging trips is discussed in relation to information on the abundance of prey species of fish within the foraging range of the birds.