Showing papers by "University of Melbourne published in 1996"

Surface Plasmon Spectroscopy of Nanosized Metal Particles

Abstract: The use of optical measurements to monitor electrochemical changes on the surface of nanosized metal particles is discussed within the Drude model. The absorption spectrum of a metal sol in water is shown to be strongly affected by cathodic or anodic polarization, chemisorption, metal adatom deposition, and alloying. Anion adsorption leads to strong damping of the free electron absorption. Cathodic polarization leads to anion desorption. Underpotential deposition (upd) of electropositive metal layers results in dramatic blue-shifts of the surface plasmon band of the substrate. The deposition of just 0.1 monolayer can be readily detected by eye. In some cases alloying occurs spontaneously during upd. Alloy formation can be ascertained from the optical absorption spectrum in the case of gold deposition onto silver sols. The underpotential deposition of silver adatoms onto palladium leads to the formation of a homogeneous silver shell, but the mean free path is less than predicted, due to lattice strain in t...

Mathematical Programs with Equilibrium Constraints

Abstract: This book provides a solid foundation and an extensive study for an important class of constrained optimization problems known as Mathematical Programs with Equilibrium Constraints (MPEC), which are extensions of bilevel optimization problems. The book begins with the description of many source problems arising from engineering and economics that are amenable to treatment by the MPEC methodology. Error bounds and parametric analysis are the main tools to establish a theory of exact penalisation, a set of MPEC constraint qualifications and the first-order and second-order optimality conditions. The book also describes several iterative algorithms such as a penalty-based interior point algorithm, an implicit programming algorithm and a piecewise sequential quadratic programming algorithm for MPECs. Results in the book are expected to have significant impacts in such disciplines as engineering design, economics and game equilibria, and transportation planning, within all of which MPEC has a central role to play in the modelling of many practical problems.

Synthesis of Nanosized Gold−Silica Core−Shell Particles

Abstract: Gold colloids have been homogeneously coated with silica using the silane coupling agent (3-aminopropyl)trimethoxysilane as a primer to render the gold surface vitreophilic. After the formation of a thin silica layer in aqueous solution, the particles can be transferred into ethanol for further growth using the Stober method. The thickness of the silica layer can be completely controlled, and (after surface modification) the particles can be transferred into practically any solvent. Varying the silica shell thickness and the refractive index of the solvent allows control over the optical properties of the dispersions. The optical spectra of the coated particles are in good agreement with calculations using Mie's theory for core−shell particles.

Principles of bone biology

Abstract: Basic principles - cell biology biochemistry bone re-modelling and mineral homeostasis the hormones of bone other systemic hormones that influence bone metabolism local regulators of bone molecular mechanisms of metabolic bone diseases pharmacological mechanisms of therapeutics methods in bone research.

LOGIT MODELS AND LOGISTIC REGRESSIONS FOR SOCIAL NETWORKS: I. AN INTRODUCTION TO MARKOV GRAPHS AND p*

Abstract: Spanning nearly sixty years of research, statistical network analysis has passed through (at least) two generations of researchers and models. Beginning in the late 1930's, the first generation of research dealt with the distribution of various network statistics, under a variety of null models. The second generation, beginning in the 1970's and continuing into the 1980's, concerned models, usually for probabilities of relational ties among very small subsets of actors, in which various simple substantive tendencies were parameterized. Much of this research, most of which utilized log linear models, first appeared in applied statistics publications. But recent developments in social network analysis promise to bring us into a third generation. The Markov random graphs of Frank and Strauss (1986) and especially the estimation strategy for these models developed by Strauss and Ikeda (1990; described in brief in Strauss, 1992), are very recent and promising contributions to this field. Here we describe a large class of models that can be used to investigate structure in social networks. These models include several generalizations of stochastic blockmodels, as well as models parameterizing global tendencies towards clustering and centralization, and individual differences in such tendencies. Approximate model fits are obtained using Strauss and Ikeda's (1990) estimation strategy. In this paper we describe and extend these models and demonstrate how they can be used to address a variety of substantive questions about structure in social networks.

The Prodromal Phase of First-episode Psychosis: Past and Current Conceptualizations

Abstract: The initial prodrome in psychosis is potentially important for early intervention, identification of biological markers, and understanding the process of becoming psychotic. This article reviews the previous literature on prodrome, including descriptions of symptoms and signs, and patterns and durations of prodromes in both schizophrenic and affective psychoses. Early detailed descriptions, achieved through mainly anecdotal reports, are compared with current conceptualizations, such as the DSM-III-R checklist of mainly behavioral items, which seeks to enhance reliability of measurement but at the expense of adequately describing the full range of phenomena. Current confusion about the nature of prodromal features and concerns regarding the reliability of their measurement are highlighted. This article proposes an alternative model for conceptualizing prodromal changes (the hybrid/interactive model) and discusses the different ways to view this phase. The need for a more systematic evaluation of the prodromal phase in first-episode psychosis is emphasized.

Osteoporosis in men.

Abstract: Hip fractures in men account for one third of all hip fractures and have a higher mortality than in women. The public health burden will increase as the increase in the numbers of elderly men in the community increases. In addition, the age-specific incidence of hip fractures may be increasing in some, but not all, countries. Vertebral fractures may be a public health problem as recent studies suggest that the prevalence in the community is 20-30%, similar to that reported in women. Forearm fractures should probably not be regarded as a public health problem. Peak bone mass is higher in men than women because men have bigger bones. Peak bone mineral density is the same. The amount of trabecular bone lost at the spine and iliac crest during ageing is similar in men and women. Cortical bone loss is less in men because endocortical resorption is less and periosteal formation is greater. Bone loss accelerates in elderly men because endocortical resorption and increasing cortical porosity increase the surface available for resorption. Bone fragility is less in men than women because: (a) the cross-sectional surface of the bone is larger; (b) trabecular bone loss is less as a percentage of the higher peak bone mass; (c) trabecular bone loss occurs by thinning rather than perforation; and (d) periosteal appositional growth compensates for endocortical resorption by maintaining the bending strength of bone. Reduced BMD in men with fractures may be due to reduced peak bone size and mass, and bone loss. Bone loss occurs by reduced bone formation. Whether men with fractures have increased bone fragility due to reduced periosteal appositional growth during ageing is unknown. The age-related decline in testosterone, adrenal androgens, growth hormone, and insulin-like growth factor 1 may contribute to reduced bone formation and bone loss. Men with vertebral fractures often have hypogonadism or illnesses with few clinical features that should be considered with a high index of suspicion (alcoholism, myeloma, malabsorption, primary hyperparathyroidism, haemochromatosis, Cushing's disease). Secondary hyperparathyroidism may contribute to bone loss by activating bone turnover and so increasing the number of bone remodelling units with impaired bone formation in each. There is no proven treatment for osteoporosis in men because there have been no trials using anti-fracture efficacy as an end point. Testosterone replacement should be considered in men with proven hypogonadism and vitamin D deficiency should be corrected if present. Calcium supplements and bisphosphonates are reasonable options given the lack of information.

An experimental study of round jets in cross-flow

Abstract: The structure of round jets in cross-flow was studied using flow visualization techniques and flying-hot-wire measurements. The study was restricted to jet to freestream velocity ratios ranging from 2.0 to 6.0 and Reynolds numbers based on the jet diameter and free-stream velocity in the range of 440 to 6200.Flow visualization studies, together with time-averaged flying-hot-wire measurements in both vertical and horizontal sectional planes, have allowed the mean topological features of the jet in cross-flow to be identified using critical point theory. These features include the horseshoe (or necklace) vortex system originating just upstream of the jet, a separation region inside the pipe upstream of the pipe exit, the roll-up of the jet shear layer which initiates the counter-rotating vortex pair and the separation of the flat-wall boundary layer leading to the formation of the wake vortex system beneath the downstream side of the jet.The topology of the vortex ring roll-up of the jet shear layer was studied in detail using phase-averaged flying-hot-wire measurements of the velocity field when the roll-up was forced. From these data it is possible to examine the evolution of the shear layer topology. These results are supported by the flow visualization studies which also aid in their interpretation.The study also shows that, for velocity ratios ranging from 4.0 to 6.0, the unsteady upright vortices in the wake may form by different mechanisms, depending on the Reynolds number. It is found that at high Reynolds numbers, the upright vortex orientation in the wake may change intermittently from one configuration of vortex street to another. Three mechanisms are proposed to explain these observations.

Borrowing Others' Words: Text, Ownership, Memory, and Plagiarism

Abstract: In this article, I attempt to deal with some of the complexities of text, ownership, memorization, and plagiarism. Arguing that plagiarism cannot be cast as a simple black-and-white issue, the prevention of which can be achieved via threats, warnings, and admonitions, I suggest that it needs to be understood in terms of complex relationships between text, memory, and learning. This is part of an attempt to explore more generally different relationships between learning, literacy, and cultural difference. I look first at the background to the notion of authorship and ownership of text, arguing that the way ownership and creativity are understood within European and U.S. contexts needs to be seen as a very particular cultural and historical development. By looking at shifting premodern, modern, and postmodern understandings of text and authorship, I show how the dominant modernist paradigm has always been filled with tensions and ambiguities. Then I discuss how these confusions around plagiarism lead to difficulties and hypocrisies in how textual borrowing is understood. I follow this examination of the development of the Western notion of textual ownership with a consideration of what it means to impose this view in a context where understandings of texts, ownership, and learning may be very different. By looking at learning in a Chinese context and also at the particularities of studying in Hong Kong, I show why we need much more subtle appreciations of the relationships between different approaches to texts. Finally, I discuss some general implications for understanding text, ownership, and learning.

Quantitative Phase Imaging Using Hard X Rays.

Abstract: The quantitative imaging of a phase object using 16 keV x rays is reported. The theoretical basis of the techniques is presented along with its implementation using a synchrotron x-ray source. We find that our phase image is in quantitative agreement with independent measurements of the object.

The Amyloid Precursor Protein of Alzheimer's Disease in the Reduction of Copper(II) to Copper(I)

Abstract: The transition metal ion copper(II) has a critical role in chronic neurologic diseases. The amyloid precursor protein (APP) of Alzheimer's disease or a synthetic peptide representing its copper-binding site reduced bound copper(II) to copper(I). This copper ion-mediated redox reaction led to disulfide bond formation in APP, which indicated that free sulfhydryl groups of APP were involved. Neither superoxide nor hydrogen peroxide had an effect on the kinetics of copper(II) reduction. The reduction of copper(II) to copper(I) by APP involves an electron-transfer reaction and could enhance the production of hydroxyl radicals, which could then attack nearby sites. Thus, copper-mediated toxicity may contribute to neurodegeneration in Alzheimer's disease.

Prediction of Milling Force Coefficients From Orthogonal Cutting Data

Abstract: The mechanistic and unified mechanics of cutting approaches to the prediction of forces in milling operations are briefly described and compared. The mechanistic approach is shown to depend on milling force coefficients determined from milling tests for each cutter geometry. By contrast the unified mechanics of cutting approach relies on an experimentally determined orthogonal cutting data base (i.e., shear angle, friction coefficient and shear stress), incorporating the tool geometrical variables, and milling models based on a generic oblique cutting analysis. It is shown that the milling force coefficients for all force components and cutter geometrical designs can be predicted from an orthogonal cutting data base and the generic oblique cutting analysis for use in the predictive mechanistic milling models. This method eliminates the need for the experimental calibration of each milling cutter geometry for the mechanistic approach to force prediction and can be applied to more complex cutter designs. This method of milling force coefficient prediction has been experimentally verified when milling Ti 6 Al 4 V titanium alloy for a range of chatter, eccentricity and run-out free cutting conditions and cutter geometrical specifications.

Ligand-regulated transport of the Menkes copper P-type ATPase efflux pump from the Golgi apparatus to the plasma membrane: a novel mechanism of regulated trafficking.

Abstract: The Menkes P-type ATPase (MNK), encoded by the Menkes gene (MNK; ATP7A), is a transmembrane copper-translocating pump which is defective in the human disorder of copper metabolism, Menkes disease Recent evidence that the MNK P-type ATPase has a role in copper efflux has come from studies using copper-resistant variants of cultured Chinese hamster ovary (CHO) cells These variants have MNK gene amplification and consequently overexpress MNK, the extents of which correlate with the degree of elevated copper efflux Here, we report on the localization of MNK in these copper-resistant CHO cells when cultured in different levels of copper Immunofluorescence studies demonstrated that MNK is predominantly localized to the Golgi apparatus of cells in basal medium In elevated copper conditions there was a rapid trafficking of MNK from the Golgi to the plasma membrane This shift in steady-state distribution of MNK was reversible and not dependent on new protein synthesis In media containing basal copper, MNK accumulated in cytoplasmic vesicles after treatment of cells with a variety of agents that inhibit endosomal recycling We suggest that MNK continuously recycles between the Golgi and the plasma membrane and elevated copper shifts the steady-state distribution from the Golgi to the plasma membrane These data reveal a novel system of regulated protein trafficking which ultimately leads to the efflux of an essential yet potentially toxic ligand, where the ligand itself appears directly and specifically to stimulate the trafficking of its own transporter

A Field Study of Control System “Redesign”: The Impact of Institutional Processes on Strategic Choice*

Abstract: . This paper studies the role of an organization's accounting control system (ACS) as part of an interrelated control “package,” in which other control systems function either as substitutes or complements. Drawing on resource dependence and institutional theories, it argues that this control mix is not only contingent on the organization's technical environment but also on its institutional environment. In addition, the paper draws on empirical evidence to demonstrate how the design of the “package” is actively shaped by the strategic choices of its dominant coalition. The empirics are based on a longitudinal field study of one large, public teaching hospital in Australia that underwent material changes in its governance structure, culture, and accounting control system. Resume. Les auteurs etudient le role du systeme de contole comptable d'une organisation, a titre d'element d'une « famille » de systemes de controle relies entre eux a l'interieur de Iaquelle les autres systemes de controle jouent le role de substituts ou de complements. S'inspirant de la theorie de la dependance des ressources et de la theorie institutionnelle, ils affirment que cette combinaison de systemes n'est pas seulement tributaire de l'environnement technique de l'organisation, mais de son environnement institutionnel. Ils se fondent, en outre, sur des constatations empiriques pour demontrer comment la structure de la « famille » de systemes est activement faconnee par les choix strategiques du groupe dominant. Les donnees empiriques proviennent d'une etude longitudinale sur le terrain, menee aupres d'un important hopital public universitaire australien dont la structure de regie, la culture et le systeme de controle comptable ont connu des transformations majeures.

Ecological modernisation, ecological modernities

Abstract: The concept of ecological modernisation is increasingly being used in policy analysis to indicate deeply embedded and ecologically self‐conscious forms of cultural transformation. Its meaning varies significantly depending on author and context. Without further clarification, there is a danger that the term may serve to legitimise the continuing instrumental domination and destruction of the environment. The normative dimensions of different uses of the concept call for greater attention. These may be weak or strong, and they raise issues relating to the relationship of the term to its ecological and modernist references.

An evaluation of volatility forecasting techniques

Abstract: The existing literature contains conflicting evidence regarding the relative quality of stock market volatility forecasts. Evidence can be found supporting the superiority of relatively complex models (including ARCH class models), while there is also evidence supporting the superiority of more simple alternatives. These inconsistencies are of particular concern because of the use of, and reliance on, volatility forecasts in key economic decision-making and analysis, and in asset/option pricing. This paper employs daily Australian data to examine this issue. The results suggest that the ARCH class of models and a simple regression model provide superior forecasts of volatility. However, the various model rankings are shown to be sensitive to the error statistic used to assess the accuracy of the forecasts. Nevertheless, a clear message is that volatility forecasting is a notoriously difficult task.

Validation of Questionnaire and Bronchial Hyperresponsiveness against Respiratory Physician Assessment in the Diagnosis of Asthma

Abstract: Background. The Tasmanian Asthma Survey (TAS) and the International Study of Asthma and Allergies in Childhood (ISAAC) have used questionnaires to measure the prevalence of asthma in adults and children. We have investigated the validity of these questionnaires by comparing response to questionnaire with a physician assessment of asthma status in the past 12 months. Methods. Ninety-three adults were given the TAS questionnaire to complete and 361 children were given the ISAAC questionnaire. Ninety-one adults and 168 children completed bronchial challenge with hypertonic saline. A consultation with a respiratory physician blinded to the results of the questionnaire and bronchial challenge was given to all subjects. Results. In both adults and children, questionnaires showed high agreement with respiratory physician diagnosis with respect to asthma symptoms in the past 12 months. For the TAS questionnaire the positive and negative predictive values (95% confidence limits) for physician diagnosis for adults were 0.89 (0.68-0.98) and 0.94 (0.86-0.98) respectively. The instrument was also sensitive 0.80 (0.58-0.93) and highly specific 0.97 (0.90-0.99). For the ISAAC questionnaire the positive and negative predictive values for physician diagnosis of asthma in children were 0.61 (0.50-0.71) and 0.94 (0.88-0.98) respectively. Sensitivity and specificity were 0.85 (0.73-0.93) and 0.81 (0.76-0.86) respectively. Compared to the physician diagnosis, the sensitivity of bronchial hyperresponsiveness (BHR) for asthma was low for adults 0.39 (0.21-0.61) and children 0.54 (0.48-0.67) as were the positive predictive values : 0.55 (0.31-0.79) for adults and 0.64 (0.49-0.77) for children. A definition of asthma requiring both a positive questionnaire response and BHR was highly specific but not sensitive for adults 0.37 (0.20-0.59) or children 0.47 (0.35-0.60). Conclusion. Both the TAS and ISAAC questionnaires are valid instruments for the determination of asthma symptoms in the past 12 months.

Risk Factors for Stress Fractures in Track and Field Athletes A Twelve-Month Prospective Study

Abstract: The aim of this 12-month prospective study was to investigate risk factors for stress fractures in a cohort of 53 female and 58 male track and field athletes, aged 17 to 26 years. Total bone mineral content, regional bone density, and soft tissue composition were measured using dual-energy x-ray absorptiometry and anthropometric techniques. Menstrual characteristics, current dietary intake, and training were assessed using questionnaires. A clinical biomechanical assessment was performed by a physical therapist. The incidence of stress fractures during the study was 21.1% with most injuries located in the tibia. Of the risk factors evaluated, none was able to predict the occurrence of stress fractures in men. However, in female athletes, significant risk factors included lower bone density, a history of menstrual disturbance, less lean mass in the lower limb, a discrepancy in leg length, and a lower fat diet. Multiple logistic regression revealed that age of menarche and calf girth were the best independent predictors of stress fractures in women. This bivariate model correctly assigned 80% of the female athletes into their respective stress fracture or nonstress fracture groups. These results suggest that it may be possible to identify female athletes most at risk for this overuse bone injury.

Caring for relatives with serious mental illness: the development of the Experience of Caregiving Inventory.

Abstract: The aim of this study was to develop a practical, comprehensive, and valid self-report measure of the experience of caring for a relative with a serious mental illness. The notion of caregiver "burden' was rejected; instead caregiving was conceptualised within a 'stress-appraisal-coping' framework. A 66-item version of the Experience of Caregiving Inventory (ECI) was derived from analyses of responses from 626 caregivers, and then tested on an independent sample of 63 relatives of patients with schizophrenia recently in acute care. The extent to which the ECI complied with the stress-coping model was tested, especially the degree to which it, in association with coping, predicted psychological morbidity in carers. Ten sub-scales with good internal consistency resulted from our analyses, eight negative (difficult behaviours; negative symptoms; stigma; problems with services; effects on the family; the need to provide backup; dependency; loss) and two positive (rewarding personal experiences; good aspects of the relationship with the patient). The ECI, in conjunction with coping style, predicted a large proportion of the variance in the General Health Questionnaire (GHQ). We concluded that the ECI taps salient dimensions of caregiving distinct from, although linked with, coping and psychological morbidity. It has potential as a useful outcome measure for interventions aimed at promoting caregiver well-being.

Thermodynamics of order-disorder in minerals. II: symmetric formalism applied to solid solutions.

Abstract: The thermodynamics of order-disorder in mineral solid solutions are handled with symmetric formalism, whereby the mineral is treated as a solid solution between an independent set of end-members with which the range of composition and states of ordering of the phase can be represented. An n-component mineral, requiring s independent order parameters to represent the state of order in the mineral, involves an independent set of n + s end-members. Symmetric formalism involves ideal mixing-on-sites with regular-solution activity coefficients. It is applied to omphacite, orthopyroxene, ferromagnesian clinoamphibole, and alkali feldspar. The model for omphacite, with a single order parameter, successfully produces the topology of paired miscibility gaps with tricritical points at their apices and with a critical curve connecting them. Ferromagnesian orthopyroxene is shown to behave effectively as an ideal solution at all geologically relevant temperatures. Cummingtonite-grunerite solid solutions are slightly positively nonideal in either a two-site or a three-site model. Na-K alkali feldspars with order-parameter coupling involving tetrahedral site occupancies can show the essential topologic relationships in this system, with only one independent binary interaction energy. The power of symmetric formalism comes from the simplicity of its representation of the thermodynamics of minerals and its flexibility with few adjustable parameters.

Self-indexing inverted files for fast text retrieval

Abstract: Query-processing costs on large text databases are dominated by the need to retrieve and scan the inverted list of each query term. Retrieval time for inverted lists can be greatly reduced by the use of compression, but this adds to the CPU time required. Here we show that the CPU component of query response time for conjunctive Boolean queries and for informal ranked queries can be similarly reduced, at little cost in terms of storage, by the inclusion of an internal index in each compressed inverted list. This method has been applied in a retrieval system for a collection of nearly two million short documents. Our experimental results show that the self-indexing strategy adds less than 20% to the size of the compressed inverted file, which itself occupies less than 10% of the indexed text, yet can reduce processing time for Boolean queries of 5-10 terms to under one fifth of the previous cost. Similarly, ranked queries of 40-50 terms can be evaluated in as little as 25% of the previous time, with little or no loss of retrieval effectiveness.

A hitchhiker's guide to the human Hsp70 family

Abstract: The human Hsp70 family encompasses at least 11 genes which encode a group of highly related proteins. These proteins include both cognate and highly inducible members, at least some of which act as molecular chaperones. The location of cognate Hsp70s within all the major subcellular compartments is an indication of the importance of these proteins. The expression of several inducible Hsp70 genes is also an indication of the importance of these proteins in the stres response. The existence of multiple genes and protein isoforms has created confusion in the identification and naming of particular family members. We have compiled, from the literature, a list of genes and genetic loci and produced a two-dimensional protein map of the known human Hsp70 family members. This will enable researchers in the field to quickly and reliably identify human Hsp70s. We have also devised a more rational nomenclature for these genes and gene products which, subject to general acceptance, could be extended to Hsp70 families from other species.

Factors Affecting Auditory Performance of Postlinguistically Deaf Adults Using Cochlear Implants

Abstract: A model of auditory performance and a model of ganglion cell survival in postlinguistically deafened adult cochlear implant users are suggested to describe the effects of aetiology, duration of deafness, age at implantation, age at onset of deafness, and duration of implant use. The models were compared with published data and a composite data set including 808 implant users. Qualitative agreement with the model of auditory performance was found. Duration of deafness had a strong negative effect on performance. Age at implantation had a slight negative effect on performance, increasing after age 60 years. Age at onset of deafness had little effect on performance up to age 60. Duration of implant use had a positive effect on performance. Aetiology had a relatively weak effect on performance.

The execution algorithm of mercury, an efficient purely declarative logic programming language

Abstract: We introduce Mercury, a new purely declarative logic programming language designed to provide the support that groups of application programmers need when building large programs. Mercury's strong type, mode, and determinism systems improve program reliability by catching many errors at compile time. We present a new and relatively simple execution model that takes advantage of the information these systems provide, yielding very efficient code. The Mercury compiler uses this execution model to generate portable C code. Our benchmarking shows that the code generated by our implementation is significantly faster than the code generated by mature optimizing implementations of other logic programming languages.