Showing papers by "University of Wollongong published in 2002"

Use of Ionic Liquids for π-Conjugated Polymer Electrochemical Devices

Abstract: π-Conjugated polymers that are electrochemically cycled in ionic liquids have enhanced lifetimes without failure (up to 1 million cycles) and fast cycle switching speeds (100 ms). We report results for electrochemical mechanical actuators, electrochromic windows, and numeric displays made from three types of π-conjugated polymers: polyaniline, polypyrrole, and polythiophene. Experiments were performed under ambient conditions, yet the polymers showed negligible loss in electroactivity. These performance advantages were obtained by using environmentally stable, room-temperature ionic liquids composed of 1-butyl-3-methyl imidazolium cations together with anions such as tetrafluoroborate or hexafluorophosphate.

Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping

Abstract: Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2−x(SiC)x/2 with x=0, 0.2, and 0.3 and for 10 wt % nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing Jc and Hirr. Compared to the undoped sample, Jc for the 10 wt % doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, and 14 at 30 K and 2 T. At 20 K and 2 T, the Jc for the doped sample was 2.4×105 A/cm2, which is comparable to Jc values for the best Ag/Bi-2223 tapes. At 20 K and 4 T, Jc was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. The magnetic Jc is consistent with the transport Jc which remains at 20 000 A/cm2 even at 10 T and 5 K for the doped sample, an order of magnitude higher than the undoped one. Because o...

Cognitive functioning of long-term heavy cannabis users seeking treatment.

Abstract: ContextCognitive impairments are associated with long-term cannabis use, but the parameters of use that contribute to impairments and the nature and endurance of cognitive dysfunction remain uncertain.ObjectiveTo examine the effects of duration of cannabis use on specific areas of cognitive functioning among users seeking treatment for cannabis dependence.Design, Setting, and ParticipantsMultisite retrospective cross-sectional neuropsychological study conducted in the United States (Seattle, Wash; Farmington, Conn; and Miami, Fla) between 1997 and 2000 among 102 near-daily cannabis users (51 long-term users: mean, 23.9 years of use; 51 shorter-term users: mean, 10.2 years of use) compared with 33 nonuser controls.Main Outcome MeasuresMeasures from 9 standard neuropsychological tests that assessed attention, memory, and executive functioning, and were administered prior to entry to a treatment program and following a median 17-hour abstinence.ResultsLong-term cannabis users performed significantly less well than shorter-term users and controls on tests of memory and attention. On the Rey Auditory Verbal Learning Test, long-term users recalled significantly fewer words than either shorter-term users (P = .001) or controls (P = .005); there was no difference between shorter-term users and controls. Long-term users showed impaired learning (P = .007), retention (P = .003), and retrieval (P = .002) compared with controls. Both user groups performed poorly on a time estimation task (P<.001 vs controls). Performance measures often correlated significantly with the duration of cannabis use, being worse with increasing years of use, but were unrelated to withdrawal symptoms and persisted after controlling for recent cannabis use and other drug use.ConclusionsThese results confirm that long-term heavy cannabis users show impairments in memory and attention that endure beyond the period of intoxication and worsen with increasing years of regular cannabis use.

Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping

Abstract: Doping of MgB2 by nano-SiC and its potential for improvement of flux pinning was studied for MgB2-x(SiC)x/2 with x = 0, 0.2 and 0.3 and a 10wt% nano-SiC doped MgB2 samples. Co-substitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5K, introducing pinning centres effective at high fields and temperatures and enhancing Jc and Hirr significantly. Compared to the non-doped sample, Jc for the 10wt% doped sample increased by a factor of 32 at 5K and 8T, 42 at 20K and 5T, and 14 at 30K and 2T. At 20K, which is considered to be a benchmark operating temperature for MgB2, the best Jc for the doped sample was 2.4x10^5A/cm2 at 2T, which is comparable to Jc of the best Ag/Bi-2223 tapes. At 20K and 4T, Jc was 36,000A/cm2, which was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. Because of such high performance, it is anticipated that the future MgB2 conductors will be made using the formula of MgBxSiyCz instead of the pure MgB2.

Electroactive conducting polymers for corrosion control

Abstract: This paper reviews the literature describing the effects of conducting polymer coatings on the corrosion rate of ferrous alloys (iron, steel and stainless steel). The literature is interpreted in terms of the proposed mechanisms of corrosion protection: barrier, inhibitor, anodic protection and the mediation of oxygen reduction. The most intriguing aspect of the reported literature are the studies demonstrating corrosion protection when deliberate defects were introduced into the coating to expose the bare metal. These studies show that protection afforded by conducting polymer coatings is not due to simple barrier protection or inhibition alone. Many studies illustrate that the polymer/metal interface is modified to produce passivating oxide layers and that charge transfer reactions occur between the metal and polymer. These studies support the proposed anodic protection mechanism, as do the reports of significant ennoblism. On the other hand, there is considerable variation in the reported shift in corrosion potential and these highlight the influence of substrate preparation, coating composition and mode of application and the nature of the electrolyte on the corrosion protection provided by the conducting polymer. For example, the evidence suggests that the emeraldine base form of polyaniline is superior to the emeraldine salt in terms of corrosion protection for steel. However, the number of direct comparisons is small and the reasons for the differences are not well understood. Also not well understood are the role of the counterion release and local pH changes on pinhole protection. It is also argued that the conducting polymer reduces the likelihood of large increases in pH at the polymer/metal interface and so stabilizes the coating against cathodic disbondment. Further work is clearly needed to increase the protection period by further studies on the corrosion protection mechanism so that the polymer composition and processing methods may be optimized.

Coasts: Form, Process and Evolution

Abstract: Coasts are some of the most rapidly changing places on earth. Understanding the natural adjustments that occur between coastal landforms and the processes that influence them is essential for the better management of coastal resources. Coasts provides a necessary background in geomorphology for those studying coastal systems. It describes the landforms that occur on the coast, their responses to the processes that shape them, and the pattern of evolution that can be determined for different types of coast over thousands of years. Numerous examples from around the world are used to illustrate the variety of environments. Particular attention is paid to coastal morphodynamics, the co-adjustment of process and form, on rocky, reef, sandy, deltaic-estuarine and muddy coasts. This valuable text for advanced undergraduate and graduate students is well illustrated and contains an extensive reference section. It will also be of great interest to environmental scientists, geologists, coastal managers and planners.

Communication loads on clinical staff in the emergency department.

Abstract: SEVERAL STUDIES quantifying the impact of poor communication on clinical work suggest that communication is a likely cause of systematic error in the health system. In Australia, inadequate communication has been associated with 17% of system problems, and, of these, 84% were deemed potentially preventable. 1 About 50% of all adverse events detected by general practitioners were associated with communication difficulties. 2 Within intensive care units, 2% of the activity consists of verbal communication between nurses and doctors, but accounts for 37% of error reports. 3 Thus, the evidence strongly suggests that poor communication wastes time, threatens patient care and may be one of the chief culprits behind preventable adverse events in clinical practice. 4 The research reported here extends work begun in the United Kingdom in the mid-1990s, 5,6 in which it was found that physician teams in hospital were subject to high levels of interruption. Clinical staff also appeared to bear a higher communication load than necessary, considering the many tasks that could be accomplished by accessing information sources rather than asking questions of people. It has since been hypothesised that such interruptions impose cognitive loads on clinical staff and have a negative impact on memory, leading to clinical error. 7 As a continuation of this research, we measured communication load more precisely and studied communication patterns in a high-workload clinical setting. METHODS 1.Methods

Duration of life-threatening antecedents prior to intensive care admission

Abstract: Objective: To document the characteristics and incidence of serious abnormalities in patients pri- or to admission to intensive care units. Design and setting: Prospec- tive follow-up study of all patients admitted to intensive care in three acute-care hospitals. Patients: The study population totalled 551 pa- tients admitted to intensive care: 90 from the general ward, 239 from op- erating rooms (OR) and 222 from the Emergency Department (ED). Measurements and results: Patients from the general wards had greater severity of illness (APACHE II me- dian 21) than those from the OR (15) or ED (19). A greater percentage of patients from the general wards (47.6%) died than from OR (19.3%) and ED (31.5%). Patients from the general wards had a greater number of serious antecedents before admis- sion to intensive care 43 (72%) than those from OR 150 (64.4%) or ED 126 (61.8%). Of the 551 patients 62 had antecedents during the period 8-48 h before admission to intensive care, and 53 had antecedents both within 8 and 48 h before their admis- sion. The most common antecedents during the 8 h before admission were hypotension (n=199), tachycardia (n=73), tachypnoea (n=64), and sud- den change in level of consciousness (n=42). Concern was expressed in the clinical notes by attending staff in 70% of patients admitted from the general wards. Conclusions: In over 60% of patients admitted to intensive care potentially life-threatening ab- normalities were documented during the 8 h before their admission. This may represent a patient population who could benefit from improved re- suscitation and care at an earlier stage.

P300 amplitude is determined by target‐to‐target interval

Abstract: P300 event-related brain potential (ERP) measures are affected by target stimulus probability, the number of nontargets preceding the target in the stimulus sequence structure, and interstimulus interval (ISI). Each of these factors contributes to the target-to-target interval (TTI), which also has been found to affect P300. The present study employed a variant of the oddball paradigm and manipulated the number of preceding nontarget stimuli (0, 1, 2, 3) and ISI (1, 2, 4 s) in order to systematically assess TTI effects on P300 values from auditory and visual stimuli. Number of preceding nontargets generally produced stronger effects than ISI in a manner suggesting that TTI determined P300 measures: Amplitude increased as TTI increased for both auditory and visual stimulus conditions, whereas latency tended to decrease with increased TTI. The finding that TTI is a critical determinant of P300 responsivity is discussed within a resource allocation theoretical framework.

Effects of dietary fat types on body fatness, leptin, and ARC leptin receptor, NPY, and AgRP mRNA expression.

Abstract: Some, but not all, fats are obesogenic. The aim of the present studies was to investigate the effects of changing type and amount of dietary fats on energy balance, fat deposition, leptin, and lept...

Understanding voluntary simplifiers.

Abstract: Most of the literature on the voluntary simplicity (VS) lifestyle has come from the popular press and environmental activists, who tend to take a rather philosophical and moralistic stance. Although several academics have discussed the concept, it has had little mention in the marketing literature. Recently, a detailed commentary has considered the VS lifestyle from a social-science perspective. Although this lifestyle type has been gaining attention, the literature reveals there is no clear understanding of this way of life. Different authors have different opinions about what should be at the essence of what constitutes VS lifestyle behavior. Our research seeks to address this problem by gaining a fuller understanding of voluntary simplifiers in relation to nonvoluntary simplifiers. Thus, this article reports on a study of 53 one-hour interviews that contrasts and compares these two groups. From the findings, it was revealed that there are indeed certain differences across groups that could be of particular interest to marketers and academics. © 2002 John Wiley & Sons, Inc.

The biomechanics of adiposity--structural and functional limitations of obesity and implications for movement.

Abstract: Obesity is a significant health problem and the incidence of the condition is increasing at an alarming rate worldwide. Despite significant advances in the knowledge and understanding of the multifactorial nature of the condition, many questions regarding the specific consequences of the disease remain unanswered. For example, there is a dearth of information pertaining to the structural and functional limitations imposed by overweight and obesity. A limited number of studies to date have considered plantar pressures under the feet of obese vs. non-obese, the influence of foot structure on performance, gait characteristics of obese children and adults, and relationships between obesity and osteoarthritis. A better appreciation of the implications of increased levels of body weight and/or body fat on movement capabilities of the obese would provide an enhanced opportunity to offer more meaningful support in the prevention, treatment and management of the condition.

Response inhibition deficits in obsessive-compulsive disorder.

Abstract: Difficulty inhibiting irrelevant information may play a central role in the aetiology of obsessive-compulsive disorder (OCD). The aim of the present study was to determine whether OCD subjects (n=20) exhibit deficits in behavioural and cognitive inhibition compared with a clinical control group diagnosed with panic disorder (n=20). All subjects were administered a Go/Nogo task (a measure of behavioural inhibition) and a Stroop test (a measure of cognitive inhibition). OCD subjects made more commission errors on the Go/Nogo task, and they made more errors and displayed longer reaction times on the interference trial of the Stroop task. Trends towards correlations were observed between OCD severity scores and Stroop reaction time, where the more severe the OCD symptoms the faster was the response. No correlations between clinical symptomatology or subject demographics and the Go/Nogo task were observed. It was demonstrated that OCD subjects exhibit deficits in behavioural and cognitive inhibition, which together may underlie the repetitive symptomatic behaviours of the disorder, such as compulsions and obsessions.

Self-Concept, Attributional Style and Self-Efficacy Beliefs of Students with Learning Disabilities with and without Attention Deficit Hyperactivity Disorder

Abstract: A considerable comorbidity, ranging from 40% to 80%, has been reported in the literature between learning disabilities (LD) and attention deficit hyperactivity disorder (ADHD). This study examined how students with LD and students with comorbid ADHD (LD/ADHD) differ from typically achieving peers in self-concept, self-efficacy beliefs and attributional style. The study also explored the relationship between academic self-concept, academic self-efficacy beliefs and academic-attributional style. Both students with LD and students with LD/ADHD reported significantly lower scores on academic self-concept, academic attributional style and academic self-efficacy beliefs than typically achieving peers. No significant differences were found between students with LD and with LD/ADHD on these variables. However, the LD/ADHD group reported significantly lower scores on peer-relation self-concept than the other two groups. Results revealed that the academic self-perceptions of students with learning disabilities were...

Cardiac Membrane Fatty Acid Composition Modulates Myocardial Oxygen Consumption and Postischemic Recovery of Contractile Function

Abstract: Background— Regular fish consumption is associated with low cardiovascular disease morbidity and mortality. Fish oils modify cardiac membrane phospholipid fatty acid composition with potent antiarrhythmic effects. We tested the effects of dietary fish oil on ventricular hemodynamics and myocardial oxygen consumption (MVO2). Methods and Results— Male Wistar rats were fed for 16 weeks on a reference diet rich in n-6 polyunsaturated fatty acids (PUFA), a diet rich in saturated animal fat (SAT), or a diet rich in n-3 PUFA from fish oil. Isolated working hearts were perfused with porcine erythrocytes (40% hematocrit) at 75 mm Hg afterload with variable preload (5 to 20 mm Hg) or with low coronary flow ischemia with maintained afterload, preload, and heart rate, then reperfused. MVO2 was low and coronary perfusion reserve high in n-3 PUFA hearts, and cardiac output increased with workload. The n-3 PUFA reduced ischemic markers—acidosis, K+, lactate, and creatine kinase—and increased contractile recovery during ...

Chandra Observations of NGC 4636-an Elliptical Galaxy in Turmoil

Abstract: Chandra images show symmetric, 8 kpc long, armlike features in the X-ray halo surrounding NGC 4636. The leading edges of these features are sharp and are accompanied by temperature increases of ~30%. These properties suggest that the armlike structures are produced by shocks, driven by symmetric off-center outbursts. We interpret these observations as part of a cycle in which the cooling gas originally fueled a nuclear outburst about 3 × 106 yr ago that led to shocks reheating the cooling gas and thus preventing the accumulation of significant amounts of cooled gas in the galaxy center and temporarily starving the central active galactic nucleus.

Strain Response from Polypyrrole Actuators under Load

Abstract: The strain generated by an actuator material when subjected to an external force is a key performance parameter. However, very little is known about the performance of polymer actuator materials when subjected to external loads. Increasing external loads were applied to polypyrrole films and the actuator response was found to decrease linearly. Analysis of the effects of the applied load on actuator strain showed that the rate of strain decrease with increasing load depended upon the difference in the Young’s modulus of the polymer in the doped and undoped states. A simple analytical model shows good agreement with the experimental data.

Increased Congruence Does Not Necessarily Indicate Increased Phylogenetic Accuracy—The Behavior of the Incongruence Length Difference Test in Mixed-Model Analyses

Abstract: Comprehensive phylogenetic analyses utilize data from distinct sources, including nuclear, mitochondrial, and plastid molecular sequences and morphology. Such heterogeneous datasets are likely to require distinct models of analysis, given the different histories of mutational biases operating on these characters. The incongruence length difference (ILD) test is increasingly being used to arbitrate between competing models of phylogenetic analysis in cases where multiple data partitions have been collected. Our work suggests that the ILD test is unlikely to be an effective measure of congruence when two datasets differ markedly in size. We show that models that increase the contribution of one data partition over another are likely to increase congruence, as measured by this test. More alarmingly, for many bipartition comparisons, character congruence increases bimodally - either increasing or decreasing the contribution of one data partition will increase congruence - making it impossible to arrive at a single optimally congruent model of analysis.

Specificity of quantitative EEG analysis in adults with attention deficit hyperactivity disorder.

Abstract: Attention deficit hyperactivity disorder (ADHD) in children and adolescents is characterised by excessive restlessness and an extremely poor concentration span, resulting in impulsive and disruptive behaviour. Clinical observation of ADHD in adults suggests that the early hyperactivity is diminished in terms of its impact on social and academic function, while impulsive-type behaviours remain unchanged. EEG studies in children and adolescents with ADHD have reported significantly more low-frequency power (predominantly theta) and less high-frequency power (predominantly beta) than in normal subjects. In normal children and adolescents, a decrease in theta power and an increase in beta power are found with increasing age, leading some researchers to interpret the EEG anomalies in ADHD as evidence of developmental delay. Studies of adults with ADHD compared with normal adult control subjects have found a reduction in the difference between the two groups, suggesting that the reduced beta activity apparent in ADHD children and adolescents changes with age. Adults with ADHD thus appear to have elevated low-frequency power as their predominant EEG difference from normal control subjects. The present study examined whether this EEG profile was specific to adult ADHD patients. Quantitative EEGs were recorded at rest in an eyes-open condition and used to compare 50 adult patients diagnosed with ADHD with 50 non-ADHD subjects (who presented for ADHD assessment but failed to meet the diagnostic criteria) and 50 control subjects. The ADHD group differed from both the non-ADHD and the control groups on the basis of elevated theta activity. The ADHD and control groups did not differ in beta activity, but relative theta was reduced and relative beta power was elevated in the non-ADHD group compared with both the ADHD and control groups. These results suggest that quantitative EEG may be used to differentiate ADHD adults from both normal adults and adults who display some of the symptoms of ADHD, but fail to meet the diagnostic criteria of ADHD.

Dietary n-3 and n-6 fatty acids alter avian metabolism: metabolism and abdominal fat deposition

Abstract: The effects of dietary saturated fatty acids and polyunsaturated fatty acids (PUFA) of the n-3 and n-6 series on weight gain, body composition and substrate oxidation were investigated in broiler chickens. At 3 weeks of age three groups of chickens (n 30; ten birds per group) were fed the fat-enriched experimental diets for 5 weeks. These diets were isonitrogenous, isoenergetic and contained 208 g protein/kg and 80 g edible tallow, fish oil or sunflower oil/kg; the dietary fatty acid profiles were thus dominated by saturated fatty acids, n-3 PUFA or n-6 PUFA respectively. Resting RQ was measured in five birds from each treatment group during weeks 4 and 5 of the experiment. There were no significant differences between treatments in total feed intake or final body mass. Birds fed the PUFA diets had lower RQ and significantly reduced abdominal fat pad weights (P<0.01) compared with those fed tallow. The dietary lipid profile changes resulted in significantly greater partitioning of energy into lean tissue than into fat tissue (calculated as breast lean tissue weight:abdominal fat mass) in the PUFA groups compared with the saturated fat group (P<0.01; with no difference between the n-3 and n-6 PUFA groups). In addition, the PUFA-rich diets lowered plasma concentrations of serum triacylglycerols and cholesterol. The findings indicate that dietary fatty acid profile influences nutrient partitioning in broiler chickens.

Pleistocene coastal stratigraphy, sea‐level highstands and neotectonism of the southern Australian passive continental margin—a review

Abstract: Located in a tectonically stable, intraplate setting and in the far field of former ice sheets, the southern Australian passive continental margin represents a globally important region for quantifying sea level during Pleistocene highstands. The stratigraphical record of the southern Australian margin is dominated by geographically extensive coastal barrier, estuarine and peritidal landforms of bioclastic, temperate carbonate affinity, a function of regional aridity. Siliciclastic successions dominate the eastern Australian coastline. Despite the generally high level of tectonic stability, regional contrasts are evident in the elevation of Pleistocene shoreline deposits that largely relate to pre-Quaternary geotectonic setting. The most complete record of Pleistocene highstand deposits occurs in the Murray Basin–Coorong Coastal Plain region, and indicates that interglacial sea-level highstands, for at least the past 11 interglacials, did not deviate by more than 6 m from present sea-level. The Pleistocene marginal marine record of southern Australia is dominantly represented by coastal successions deposited during marine oxygen isotope stages 5e and 7, equating with relative sea-level maxima of 2–6 m and greater than 1 m above present sea-level (APSL) respectively. Intertidal facies of Late Pleistocene interstadial successions rarely occur above present sea level. The most reliable record of glacio-eustatic (ice equivalent) sea level is registered on coastlines developed on stable Precambrian cratons such as the Gawler Craton (Eyre Peninsula), where a consistent elevation of 2 m APSL is registered for over 500 km for the last interglacial shoreline (125 ka). Copyright © 2002 John Wiley & Sons, Ltd.