Showing papers by "University of Auckland published in 1998"

The International Study of Asthma and Allergies in Childhood (ISAAC). ISAAC Steering Committee.

Abstract: Despite considerable research, the aetiology of asthma and allergic disease remains poorly understood. The International Study of Asthma and Allergies In Childhood (ISAAC), was founded to maximize the value of epidemiological research into asthma and allergic disease by establishing a standardized methodology and facilitating international collaboration. It has achieved its specific aims which are to describe the prevalence and severity of asthma, rhinitis and eczema in children living in different centres and to make comparisons within and between countries; to obtain baseline measures for assessment of future trends in the prevalence and severity of these diseases; and to provide a framework for further aetiological research into genetic, lifestyle, environmental and medical care factors affecting these diseases. The ISAAC design comprises three phases. Phase One used simple core written questionnaires for two age groups, and was completed in 156 collaborating centres in 56 countries and a total of 721 601 children participated. In the 13–14 years age group 155 centres from 56 countries participated, of which 99 centres completed a video questionnaire. For the 6–7 years age group there were 91 collaborating centres in 38 countries. ISAAC Phase One has demonstrated a large variation in the prevalence of asthma symptoms in children throughout the world including hitherto unstudied populations. It is likely that environmental factors were responsible for major differences between countries. The results provide a framework for studies between populations in contrasting environ-ments which are likely to yield new clues about the aetiology of asthma. ISAAC Phase Two will investigate possible aetiological factors, particularly those suggested by the findings of Phase One. ISAAC Phase Three will be a repetition of Phase One in the year 2000 to assess trends in prevalence.

Overview of spatial channel models for antenna array communication systems

Abstract: Spatial antenna diversity has been important in improving the radio link between wireless users. Historically, microscopic antenna diversity has been used to reduce the fading seen by a radio receiver, whereas macroscopic diversity provides multiple listening posts to ensure that mobile communication links remain intact over a wide geographic area. In later years, the concepts of spatial diversity have been expanded to build foundations for emerging technologies, such as smart (adaptive) antennas and position location systems. Smart antennas hold great promise for increasing the capacity of wireless communications because they radiate and receive energy only in the intended directions, thereby greatly reducing interference. To properly design, analyze, and implement smart antennas and to exploit spatial processing in emerging wireless systems, accurate radio channel models that incorporate spatial characteristics are necessary. In this tutorial, we review the key concepts in spatial channel modeling and present emerging approaches. We also review the research issues in developing and using spatial channel models for adaptive antennas.

Manufacturing cheap, resilient, and stealthy opaque constructs

Abstract: It has become common to distribute software in forms that are isomorphic to the original source code. An important example is Java bytecode. Since such codes are easy to decompile, they increase the risk of malicious reverse engineering attacks.In this paper we describe the design of a Java code obfuscator, a tool which - through the application of code transformations - converts a Java program into an equivalent one that is more difficult to reverse engineer.We describe a number of transformations which obfuscate control-flow. Transformations are evaluated with respect to potency (To what degree is a human reader confused?), resilience (How well are automatic deobfuscation attacks resisted?), cost (How much time/space overhead is added?), and stealth (How well does obfuscated code blend in with the original code?).The resilience of many control-altering transformations rely on the resilience of opaque predicates. These are boolean valued expressions whose values are known to the obfuscator but difficult to determine for an automatic deobfuscator. We show how to construct resilient, cheap, and stealthy opaque predicates based on the intractability of certain static analysis problems such as alias analysis.

Data Mining Methods for Knowledge Discovery

Abstract: Foreword. Preface. 1. Data Mining and Knowledge Discovery. 2. Rough Sets. 3. Fuzzy Sets. 4. Bayesian Methods. 5. Evolutionary Computing. 6. Machine Learning. 7. Neural Networks. 8. Clustering. 9. Preprocessing. Index.

Rat models of hypertension, cardiac hypertrophy and failure.

Abstract: Time for primary review 24 days. Animals have been used by humans for centuries to understand their own biology. In cardiovascular research, animal models have allowed the study of cardiovascular disease in the early stages, as well as the investigation of the mechanisms of the pathogenesis of cardiovascular disease and the effects of drug intervention. The aim of these studies is to provide clear concepts for selected investigations in humans. An ideal animal model for any cardiovascular disease in humans should have five characteristics: (i) mimic the human disease, (ii) allow studies in chronic, stable disease, (iii) produce symptoms which are predictable and controllable, (iv) satisfy economical, technical and animal welfare considerations, and (v) allow measurement of relevant cardiac, biochemical and haemodynamic parameters. The use of rats as animal models is rational from the economic viewpoint and many techniques have been developed to measure relevant functional parameters. However, there is often insufficient consideration as to whether the other criteria, especially the mimicry of human disease, are satisfied with the choice of rat models of cardiovascular disease. Three examples illustrate the problems. Firstly, cardiovascular diseases such as hypertension and heart failure in humans are usually slowly developing with wide-ranging neurohumoral adaptations in contrast to the acute onset of symptoms in many surgical or drug-induced rat models of these important diseases. Secondly, cardiovascular disease is uncommon in young humans but markedly increases with age [1]yet most models of hypertension and heart failure only use young adult rats. Animal models of ageing have been recently reviewed [2]. Thirdly, the development of atherosclerosis is very unusual in most strains of rats, even in the presence of sustained high blood lipid levels, in contrast to humans where atherosclerosis is common and an important risk factor in hypertension and heart failure. Although this review … * Corresponding author. Tel.: +64 (9) 373 7599 ext. 6418; Fax: +64 (9) 373 7556.

Modelling the mechanical properties of cardiac muscle

Abstract: A model of passive and active cardiac muscle mechanics is presented, suitable for use in continuum mechanics models of the whole heart. The model is based on an extensive review of experimental data from a variety of preparations (intact trabeculae, skinned fibres and myofibrils) and species (mainly rat and ferret) at temperatures from 20 to 27 degrees C. Experimental tests include isometric tension development, isotonic loading, quick-release/restretch, length step and sinusoidal perturbations. We show that all of these experiments can be interpreted with a four state variable model which includes (i) the passive elasticity of myocardial tissue, (ii) the rapid binding of Ca2+ to troponin C and its slower tension-dependent release, (iii) the kinetics of tropomyosin movement and availability of crossbridge binding sites and the length dependence of this process and (iv) the kinetics of crossbridge tension development under perturbations of myofilament length.

Selective head cooling in newborn infants after perinatal asphyxia : A safety study

Abstract: Aims. To determine the practicality and safety of head cooling with mild or minimal systemic hypothermia in term neonates with moderate to severe hypoxic-ischemic encephalopathy. Methods. Study group infants ≥37 weeks9 gestation, who had an umbilical artery pH ≤7.09 or Apgars ≤6 at 5 minutes, plus evidence of encephalopathy. Infants with major congenital abnormalities were excluded. Trial Design. Infants were randomized to either no cooling (controls; rectal temperature = 37.0 ± 0.2°C,n = 10) or sequentially, either minimal systemic cooling (rectal temperature = 36.3 ± 0.2°C,n = 6) or mild systemic cooling (rectal temperature = 35.7 ± 0.2°C, n = 6). Head cooling was accomplished by circulating water at 10°C through a coil of tubing wrapped around the head for up to 72 hours. All infants were warmed by servo-controlled overhead heaters to maintain the allocated rectal temperature. The rectal, fontanelle, and nasopharyngeal temperatures were continuously monitored. Results. From January 1996 to October 1997, 22 term infants were randomized from 2 to 5 hours after birth. All infants showed a metabolic acidosis at delivery, with similar umbilical artery pH in the control group (mean ± standard deviation, 6.79 ± 0.25), minimal cooling group (6.98 ± 0.21), and mild cooling group (6.93 ± 0.11), and depressed Apgar scores at 5 minutes in the control group (4.5 ± 2), minimal cooling group, (4.7 ± 2) and mild cooling group (6.0 ± 1). In the mild-cooled infants, the nasopharyngeal temperature was 34.5°C during cooling, 1.2°C lower than the rectal temperature. This gradient narrowed to 0.5°C after cooling was stopped. No adverse effects because of cooling were observed. No infants developed cardiac arrhythmias, hypotension, or bradycardia during cooling. Thrombocytopenia occurred in 2 out of 10 controls, 2 out of 6 minimal cooling infants, and 1 out of 6 mild cooling infants. Hypoglycemia (glucose Conclusions. Mild selective head cooling combined with mild systemic hypothermia in term newborn infants after perinatal asphyxia is a safe and convenient method of quickly reducing cerebral temperature with an increased gradient between the surface of the scalp and core temperature. The safety of mild hypothermia with selective head cooling is in contrast with the historical evidence of adverse effects with greater depths of whole-body hypothermia. This safety study and the strong experimental evidence for improved cerebral outcome justify a multicenter trial of selective head cooling for neonatal encephalopathy in term infants.

Magnetic resonance imaging of the wrist in early rheumatoid arthritis reveals a high prevalence of erosions at four months after symptom onset

Abstract: OBJECTIVES To evaluate the role of magnetic resonance imaging (MRI) of the wrist in detecting early joint damage in patients with rheumatoid arthritis (RA). METHODS MRI was performed on 42 patients with early RA (median symptom duration of four months). Scans were scored separately by two musculoskeletal radiologists using a newly devised scoring system, which was validated. MRI findings were compared with plain radiography, clinical measures, and HLA-DRB*01/04 genotyping. RESULTS Interobserver reliability for the overall MRI score was high ( r = 0.81) as was intraobserver reliability ( r = 0.94 for observer 1 and 0.81 for observer 2). There was more variation in scoring synovitis (interobserver reliability: r = 0.74). Erosions were detected in 45% of scans (19 of 42), compared with 15% of plain radiographs. The most common site for erosions was the capitate (39%), for synovitis the ulnar aspect of the radiocarpal joint, and for tendonitis, the extensor carpi ulnaris tendon. The total MRI score and MRI synovitis score correlated most significantly with C reactive protein ( r = 0.40 and 0.42 respectively, p r = 0.83) as well as the Ritchie score and disease activity score ( r = 0.32, p CONCLUSIONS A high proportion of RA patients develop MRI erosions very early in their disease, when plain radiography is frequently normal. MRI of the dominant wrist may identify those requiring early aggressive treatment.

A dual process model of perfectionism based on reinforcement theory

Abstract: This article begins with a brief review of the current literature on the structure and measurement of perfectionism. It is concluded from this review that two major types can be distinguished, a normal/healthy form and a pathological form. These two forms are then defined as positive and negative perfectionism and related directly to Skinnerian concepts of positive and negative reinforcement. The positive/negative distinction is then further elaborated on in terms of approach/avoidance behavior, goal differences, self-concept involvement, emotional correlates, and the promoting environment. Finally, some of the more obvious theoretical and practical implications are briefly explored.

Aluminum Induces Oxidative Stress Genes in Arabidopsis thaliana

Abstract: Changes in gene expression induced by toxic levels of Al were characterized to investigate the nature of Al stress. A cDNA library was constructed from Arabidopsis thaliana seedlings treated with Al for 2 h. We identified five cDNA clones that showed a transient induction of their mRNA levels, four cDNA clones that showed a longer induction period, and two down-regulated genes. Expression of the four long-term-induced genes remained at elevated levels for at least 48 h. The genes encoded peroxidase, glutathione-S-transferase, blue copper-binding protein, and a protein homologous to the reticuline:oxygen oxidoreductase enzyme. Three of these genes are known to be induced by oxidative stresses and the fourth is induced by pathogen treatment. Another oxidative stress gene, superoxide dismutase, and a gene for Bowman-Birk protease inhibitor were also induced by Al in A. thaliana. These results suggested that Al treatment of Arabidopsis induces oxidative stress. In confirmation of this hypothesis, three of four genes induced by Al stress in A. thaliana were also shown to be induced by ozone. Our results demonstrate that oxidative stress is an important component of the plant's reaction to toxic levels of Al.

Dynamical quantum noise in trapped bose-einstein condensates

Abstract: We introduce the study of dynamical quantum noise in Bose-Einstein condensates through numerical simulation of stochastic partial differential equations obtained using phase-space representations. We derive evolution equations for a single trapped condensate in both the positive-P and Wigner representations and perform simulations to compare the predictions of the two methods. The positive-P approach is found to be highly susceptible to the stability problems that have been observed in other strongly nonlinear, weakly damped systems. Using the Wigner representation, we examine the evolution of several quantities of interest using from a variety of choices of initial stare for the condensate and compare results to those for single-mode models. [S1050-2947(98)06612-8].

Influence of prenatal mercury exposure upon scholastic and psychological test performance: benchmark analysis of a New Zealand Cohort

Abstract: This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7-year-old New Zealand children were correlated with the mercury concentration in their mothers' hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.

The immunological effects of thought suppression.

Abstract: Individuals often suppress emotional thoughts, particularly thoughts that arouse negative emotions, as a way of regulating mood and reducing distress. However, recent work has highlighted the complexities and unexpected cognitive and physiological effects of thought suppression. In a study designed to examine the short-term immunological effects of thought suppression, participants wrote about either emotional or nonemotional topics with or without thought suppression. Blood was drawn before and after each experimental session on 3 consecutive days. Results showed a significant increase in circulating total lymphocytes and CD4 (helper) T lymphocyte levels in the emotional writing groups. Thought suppression resulted in a significant decrease in CD3 T lymphocyte levels. The implications of the results for the role of the expression and suppression of emotion in health are discussed.

Neuroprotection With Prolonged Head Cooling Started Before Postischemic Seizures in Fetal Sheep

Abstract: Objective Cerebral hypothermia has been shown to reduce damage from experimental hy-poxia-ischemia if started shortly after reperfusion However, in the newborn infant it may not be feasible to determine prognosis so soon after exposure to asphyxia The aim of this study was to determine whether head cooling, delayed until shortly before the onset of postasphyxial seizure activity, is neuroprotective Methods Unanesthetized near-term fetal sheep in utero were subjected to 30 minutes of cerebral ischemia Later, at 55 hours, they were randomized to either cooling (n = 7) or sham cooling (n = 10) for 72 hours Intrauterine cooling was induced by circulating cold water through a coil around the fetal head The water temperature was titrated to reduce fetal extradural temperature from 391 ± 01°C to between 30°C and 33°C, while maintaining esophageal temperature >37°C Results Cerebral cooling suppressed the secondary rise in cortical impedance (a measure of cytotoxic edema), but did not prevent delayed seizures, 8 to 30 hours after ischemia Transient metabolic changes including increased plasma lactate and glucose levels were seen with a moderate sustained rise in blood pressure This severe cerebral insult resulted in depressed residual parietal electroencephalographic activity after 5 days recovery (−142 ± 15 decibels), associated with a watershed distribution of neuronal loss (eg, 94 ± 4% in parasagittal cortex and 77 ± 4% in the lateral cortex) Hypothermia was associated with better recovery of electroencephalographic activity (−89% ± 18 decibels) and substantially reduced neuronal loss in the parasagittal cortex (46 ± 13%), the lateral cortex (9 ± 4%), and other regions except the cornu ammonis sectors 1 and 2 of the hippocampus Conclusions Delayed selective head cooling begun before the onset of postischemic seizures and continued for 3 days may have potential to significantly improve the outcome of moderate to severe hypoxic-ischemic encephalopathy

The green prescription study : A randomized controlled trial of written exercise advice provided by general practitioners

Abstract: OBJECTIVES: The purpose of this study was to determine whether written advice from general practitioners increases physical activity among sedentary people more than verbal advice alone. METHODS: Sedentary patients (n = 456) received verbal advice on increasing physical activity and were then randomized to an exercise prescription (green prescription) group or a verbal advice group. RESULTS: The number of people engaging in any recreational physical activity at 6 weeks increased substantially, but significantly more so in the green prescription group. Also, more participants in the green prescription group increased their activity over the period. CONCLUSIONS: A written goal-oriented exercise prescription, in addition to verbal advice, is a useful tool for general practitioners in motivating their parents to increase physical activity.

Effects of Lowering Average or Below-Average Cholesterol Levels on the Progression of Carotid Atherosclerosis Results of the LIPID Atherosclerosis Substudy

Abstract: Background—Cholesterol lowering in patients with above-average cholesterol levels has been shown to reduce the progression of atherosclerosis and lower the risk of coronary heart disease events. However, there has been uncertainty about the effects of cholesterol lowering in patients with average or below-average cholesterol levels. Methods and Results—In this study, 522 patients with a history of myocardial infarction or unstable angina and with baseline levels of total cholesterol between 4 and 7 mmol/L (mean, 5.7 mmol/L) were randomized to treatment with a low fat diet plus pravastatin (40 mg daily) or to a low fat diet plus placebo. Treatment with pravastatin reduced the levels of total cholesterol by 19%, LDL cholesterol by 27%, apolipoprotein B by 19%, and triglycerides by 13% (all 2P<.0001) and increased apolipoprotein A1 and HDL cholesterol levels by 4% (both 2P<.0005), in comparison with placebo. Carotid atherosclerosis was assessed from B-mode ultrasound measurements of the common carotid artery...

Sequential changes in the metabolic response in severely septic patients during the first 23 days after the onset of peritonitis

Abstract: OBJECTIVE: To quantify the sequential changes in metabolic response occurring in patients with severe sepsis after the onset of peritonitis. SUMMARY BACKGROUND DATA: Understanding the changes in energy expenditure and body composition is essential for the optimal management of severely septic patients; however, they have not been quantified in the context of modern surgical care. METHODS: Twelve patients with severe sepsis secondary to peritonitis (median APACHE II score = 21.5) had measurements of energy expenditure and body composition as soon as they were hemodynamically stable and 5, 10, and 21 days later. Sequential measurements of acute-phase proteins and cytokine responses were also made. RESULTS: Resting energy expenditure rose to 49% above predicted and remained elevated throughout the study period. Total energy expenditure was 1.25 x resting energy expenditure. Body fat was oxidized when energy intake was insufficient to achieve energy balance. There was a positive fluid balance of 12.5 1 over the first 2 days after onset of sepsis; thereafter, body water changes closely paralleled body weight changes and were largely accounted for by changes in extracellular water. During the 21 -day study period, there was a loss of 1.21 kg (13%) of total body protein. During the first 10 days, 67% of the protein lost came from skeletal muscle, but after this time it was predominantly from viscera. Intracellular potassium levels were low but did not deteriorate further after hemodynamic stability had been reached. There was a reprioritization of hepatic protein synthesis that was obligatory and independent of changes in total body protein. The cytokine responses demonstrated the complexity, redundancy, and overlap of mediators. CONCLUSIONS: The period of hypermetabolism in severely septic patients is similar to that previously described, but the fluid changes are larger and the protein loss is greater. Protein loss early on is predominantly from muscle, thereafter from viscera. Fat loss can be prevented and cell function preserved once hemodynamic stability is achieved.

Optimal protein requirements during the first 2 weeks after the onset of critical illness

Abstract: ObjectiveTo obtain optimal protein requirements in critically ill sepsis or trauma patients during the first 2 wks after admission to the intensive care unit.DesignRetrospective study.SettingDepartment of critical care medicine at a teaching hospital.PatientsImmediate posttrauma patients or severely

Multinational Corporate Evolution and Subsidiary Development

Abstract: The book “Multinational Corporate Evolution and Subsidiary Development,” edited by Julian Birkinshaw and Neil Hood, sets out to bring together a good sample of contemporary research on multinational subsidiary management (or “development”) and, thus, remedy a gap in the literature. Birkinshaw and Hood position the subsidiary as a viable unit of analysis for researchers and provide an important resource for researchers and managers in the field.

Melanin-concentrating hormone: a functional melanocortin antagonist in the hypothalamus

Abstract: Melanin-concentrating hormone (MCH) and α-melanocyte-stimulating hormone (α-MSH) demonstrate opposite actions on skin coloration in teleost fish. Both peptides are present in the mammalian brain, a...