Showing papers by "University of Newcastle published in 1986"

Improved finite word length characteristics in digital control using delta operators

Abstract: This paper examines some of the consequences of finite word lengths in digital control. It is shown that, in many cases of practical importance, the usual shift operator formulation is inferior to an alternative formulation which we designate the delta operator approach. This latter approach is shown to give better coefficient representation and less roundoff noise in many cases. We thus argue that the shift operator and its associated Z -transform can be replaced by delta operators and their associated transform which we designate a Δ-transform. An added advantage of this approach is that discrete designs and transforms converge to their continuous-time counterparts as the sampling rate is increased.

The approaches to learning of students in a traditional and in an innovative problem‐based medical school

Abstract: The way in which students approach their learning is dependent on a variety of factors including the characteristics of the departments and teaching to which they are exposed. These factors appear to influence whether the students adopt a surface, deep or strategic approach. In order to explore further the relationship between educational context and approach to learning, a comparison was made between students attending a traditional medical school and those attending a problem-based medical school. The results showed marked differences, with the problem-based school being higher on deep approach and lower on surface approach than the traditional school. This study provides one of the first pieces of evidence of a difference between students in the two types of medical school which can be directly attributed to the educational environment. Students in the problem-based school appear to have an approach to learning which more closely approximates the aims of most medical schools. The results provide support for the philosophies and strategies of the problem-based schools.

Preliminary conclusions of the Royal Society and Academia Sinica 1985 geotraverse of Tibet

Abstract: The 1985 Chinese/British expedition to the Tibetan Plateau attempted to solve the question of the origin of the very thick crustal rocks in this region. Continuing northwards movement of the Indian plate over the past 38 Myr has given rise to severe folding and thrust faulting, causing crustal thickening by internal deformation. Previous collisions of microplate terranes derived from Gondwanaland occurred during Mesozoic times but the Kun Lun terrane of northern Tibet was already part of Laurasia by the Carboniferous

Comparison of theoretical and empirical interatomic potentials

Abstract: Despite a wealth of theoretical and experimental research on interatomic potentials, there has been only limited guidance on how well each compares to all others. In this report, many popular theoretical potentials are compared to a large range of experimental potentials to gauge the accuracy of the various theoretical models. From this comparison it is found that the “ Universal Potential” of Biersack and Ziegler agrees best with the available measurements. Correction factors are derived which give similar agreement for the other potentials, but some systematic deviations still persist at the low or high energy end for most other potentials, as demonstrated for the Moliere potential.

Theories of migration: a review*

Abstract: A general review of the literature on migration theory is presented. Some basic concepts and themes in migration analysis are first described. Sections are included on early economic perspectives on migration analysis; the human capital approach; issues of rationality information and stress; random utility models and the treatment of the error term; the search theory perspective on migration; gravity models and the aggregation problem; basic properties of the gravity model; and search theory and the gravity model. Sections also deal with heterogeneity and the process of search in migration decisions; temporal aspects of migration behavior; and migration commuting and the interaction between local labor and housing markets.

Adaptive computed torque control for rigid link manipulators

Abstract: In this paper we shall examine the adaptive control of rigid link manipulator systems. We give a parameterization of a genereal rigid body which yields dynamic equations that are linear in the unknown parameters. Standard linear estimation techniques together with an adaptive computed torque control law are shown to give a globally convergent adaptive system which does not require measurements of accelerations or additional torques.

An algorithm for profile and wavefront reduction of sparse matrices

Abstract: SUMMARY An algorithm for reducing the profile and wavefront of a sparse matrix is described. The scheme is applicable to any sparse matrix which has a symmetric pattern of zeros and may be used to generate efficient labellings for finite element grids. In particular, it is suitable for generating efficient labellings for profile and frontal solution schemes. Empirical evidence, obtained from analysis of the 30 test problems collected by Everstine, suggests that the new algorithm is superior to existing methods for profile and wavefront reduction. It is fast, requires only a small amount of memory, and is simple to program.

Riccati equations in optimal filtering of nonstabilizable systems having singular state transition matrices

Abstract: Until recently, it was believed that a necessary and sufficient condition for convergence of the Riccati difference equation of optimal filtering was that the system be both delectable and stabilizable. Recently, it has been shown that the stabilizability condition can be removed but convergence has only established under restrictive assumptions including the requirement that the state transition matrix be nonsingular. The present paper generalizes these results in several directions. First, properties of the algebraic Riccati equation are established for the case of singular state transition matrix. Second, several assumptions previously imposed in establishing convergence of the Riccati difference equation for systems with unreachable modes on the unit circle are relaxed including replacing observability by detectability, weakening the conditions on the initial covariance, and allowing the state transition matrix to be singular. Third, results on the convergence and properties of the Riccati equations are expressed as both necessary and sufficient conditions, whereas previous results were only sufficient. These extensions mean that the results have wider applicability, including fixed-lag smoothing problems and filtering for systems with time delays. The implications of the results in the dual problem of optimal control are also studied.

Bend loss measurements on high numerical aperture single-mode fibers as a function of wavelength and bend radius

Abstract: The results of an investigation into the bend loss as a function of wavelength for single-radius bends in monomode fibers are given. The fibers considered have a high numerical aperture and a protective coating which has a refractive index greater than that of the cladding. For these fibers the pure bend loss is shown to be the dominant loss mechanism over the wavelength range 633-1152 nm. In addition, oscillations in the loss are observed as the bend radius is varied at the longer wavelengths. These oscillations are shown to result from the coupling of light under weak coupling conditions from a whispering gallery mode in the cladding formed by the pure bend loss, to the fundamental mode in the core. An expression is derived which relates the bend radius at which the minima in the oscillations occur to the fiber parameters and a qualitative explanation is given for the reduction in the oscillation amplitude as the bend radius and wavelength are decreased. A criterion is identified for assessing the strength of the coupling between the whispering gallery mode and fundamental mode. Using this criterion the attenuation coefficient of the pure bend loss at which a transition from weak to strong coupling occurs is determined and is found to agree with observations. The effect of the coupling strength between the whispering gallery mode and the fundamental mode on the characteristics of the pure bend loss is discussed. Finally, possible applications arising from the results of this work are identified.

The isolation and nucleotide sequence of the complex AROM locus of Aspergillus nidulans.

Abstract: The AROM locus of A. nidulans, which governs five consecutive steps in pre-chorismate aromatic amino acid biosynthesis, has been cloned in a bacteriophage vector. The nucleotide sequence of the locus reveals a single, open reading-frame of 4,812 base-pairs, apparently without introns. An internal segment of the A. nidulans AROM sequence has extensive homology with the E. coli aroA gene that encodes the 5-enolpyruvylshikimate 3-phosphate synthase.

Detection of patients with high alcohol intake by general practitioners.

Abstract: General practitioners have the potential to treat patients with alcohol problems effectively. Despite the medical implications of excessive alcohol intake, it appears that general practitioners are not sufficiently aware of the drinking habits of their patients. The aim of the study was to investigate the accuracy of 56 randomly chosen general practitioners in detecting which of their patients had a high alcohol intake. Altogether, 2081 patients were recruited in general practitioners9 waiting rooms, where they answered questions about their drinking habits. After the consultations general practitioners were asked to indicate the patients9 levels of alcohol intake. The results showed that general practitioners correctly identified only 27.5% of patients who were classified as "high risk" drinkers, using Australian Medical Association criteria. They correctly identified only 45.2% of patients who were classified as "moderate to heavy" drinkers, defined by them as drinkers who consume four or more standard drinks a day. These findings have important implications for clinical practice since they indicate that general practitioners are failing to perform adequately in an important area of preventive medicine. This issue needs to be addressed in undergraduate and postgraduate medical education.

Removal of singularities in tresca and mohr–coulomb yield functions

Abstract: The Tresca and Mohr–Coulomb yield functions are used widely in metal and soil plasticity computations. Both of these criteria, however, possess angular vertices at which the gradient with respect to the stresses, and hence the elastoplastic constitutive law, is undefined. This paper describes a modified yield function which may be used to ‘round-off’ these vertices. When used in conjunction with the parent yield function, the modified yield function results in a yield surface which is continuous and differentiable for all values of the stresses. The modified yield function is used in the vicinity of the vertices and is given in a form suitable for finite element programming.

Organized structures in a turbulent plane jet: topology and contribution to momentum and heat transport

Abstract: In the self-preserving region of a slightly heated turbulent plane jet, conventional isocorrelation contours of velocity and temperature fluctuations support the existence of organized large-scale structures. Temperature fronts associated with these structures were visually detected using a spanwise rake of cold wires. This method of detection was then used to condition velocity and temperature fluctuations and products of these fluctuations. Ensemble-averaged velocity vectors, constructed in the plane of main shear, suggest a topology for the organized motion in which the temperature front is identified with the diverging separatrix connecting adjacent structures on the same side of the centreline. Coherent stresses and heat fluxes are particularly significant near the diverging separatrix. Contributions by the coherent and random motions to the averaged momentum and heat transports are generally of the same order of magnitude.

Assessment of local isotropy using measurements in a turbulent plane jet

Abstract: Following a review of the difficulties associated with the measurement and interpretation of statistics of the small-scale motion, the evidence for and against local isotropy is assessed in the light of measurements in a turbulent plane jet at moderate values of the Reynolds and Peclet numbers. These measurements include spatial derivatives with respect to different spatial directions of the longitudinal velocity fluctuation and of the temperature fluctuation. Relations between mean-square values of these derivatives suggest strong departures from local isotropy for both velocity and temperature. In contrast, the locally isotropic forms of the vorticity and temperature dissipation budgets are approximately satisfied. Possible contamination of the fine-scale measurements by the anisotropic large-scale motion is assessed in the context of the measured structure functions of temperature and of the measured skewness of the streamwise derivative of temperature. Structure functions are, within the framework of local isotropy, consistent with the average frequency and amplitude of temperature signatures that characterize the quasi-organized large-scale motion. Conditional averages associated with this motion account, in an approximate way, for the skewness of the temperature derivative but make negligible contributions to the skewness of velocity derivatives. The degree of spatial organization of the fine structure is inferred from conditional statistics of temperature derivatives.

Growth Regulators Have Rapid Effects on Photosynthate Unloading from Seed Coats of Phaseolus vulgaris L.

Abstract: Of nine plant growth regulators (indoleacetic acid, 1-naphthalene acetic acid, gibberellic acid, giberellin 4/7, 6-benzylaminopurine, 6-furfurylaminopurine, abscisic acid, and 1-aminocyclopropane carboxylic acid) tested, only 6-benzylaminopurine and abscisic acid affected 14C-photosynthate unloading from excised seed coats of Phaseolus vulgaris L. Unloading, in the presence of KCl, was stimulated by 25 to 40%. Stimulation occurred immediately for 6-benzylaminopurine and for abscisic acid within 10 to 12 minutes of application.

Students' approaches to learning in an innovative medical school: a cross-sectional study.

Abstract: Summary. A slightly modified version of Entwistle and Ramsden's Approaches to Studying Inventory was administered to first-, third- and final-year students in an innovative medical school (response rate 84 per cent), to see whether the Inventory's constructs also apply to medical students, to see whether they might constitute a helpful framework for counselling students in academic difficulty, and to see whether the students' responses reflected the educational philosophy of the school. The psychometric robustness of the instrument was confirmed, and its applicability to these groups of medical students was established. The instrument was not highly predictive of academic success, but seemed to offer a useful framework for student counselling. Student responses to the inventory were consistent with the school's educational philosophy.

Postmortem neurochemical studies in depression.

Abstract: The delineation of monoamine neurotransmitter systems in the brain and the observation that drugs affecting these systems can alter both pathological and normal mood represent circumstantial evidence suggesting a disturbance of neurotransmitter function in the major affective disorders. Current neurochemical hypotheses of major affective illnesses are based on the observation that reserpine, which depletes brain serotonin (5-HT),' noradrenaline (NA)? and dopamine (DA),' is associated with the development of depression in a substantial number of subjects? These observations, together with some data on the neurochemical effects of antidepressants, have led to the noradrenaline deficit5 and serotonin deficit6 hypotheses of depression. More recently, the clinical observation of a delayed response to antidepressant therapy has led to the suggestion that an alteration in receptor function leads to depression' and may account for the therapeutic effect of antidepressant treatments: Indirect evidence that supports these various hypotheses has been found in a series of studies of monoaminas and metabolites in urine and cerebrospinal fluid (CSW and in some neuroendocrine studies,\" but results are not always consistent and are open to various interpretations. More direct evidence of a putative neurochemical disturbance in depression may be provided by studies of postmortem tissue (which have proved valuable in the case of some neuropsychiatric conditions, e.g., Parkinson's disease, Alzheimer's disease). This paper describes such a study and also discusses some of the problems associated with autopsy studies.

Costs, severity of illness and outcome in intensive care.

Abstract: Severity of illness (Therapeutic Index Severity Score, Classes 1-4) and direct clinical costs (labour costs, diagnostic costs, drugs, disposables, etc.) were determined for 100 consecutive patients admitted to Royal Newcastle Hospital Intensive Care Unit over six weeks. Outcome was assessed using mortality, quality of life, functional status, productivity and mental status one month after separation from the Unit. The mean total admission cost was $1,357 (Class 4 mean = $3,706) but for over 70% of patients costs were less than $1,000. The main component of cost was labour (about 60% for all classes). TISS proved a strong predictor (P less than 0.001) of total admission costs. Survival to one month was 89% and optimal association between cost and survival was found with those with low costs more likely to survive (P less than 0.001). On the other hand, no association was found between total admission cost and resulting quality of life. However, there was an association between pre-admission and follow-up quality of life (P less than 0.0005).

Burnout and professional depression: related concepts?

Abstract: In 1978 Oswin documented a process of 'professional depression' affecting some nursing staff in long-stay hospitals. This study tested the hypothesis that 'professional depression' in long-stay nursing and 'emotional exhaustion' as a component of burnout describe a similar phenomenon. This hypothesis was supported. The results are consistent with Cherniss' characterization of burnout, which appears to show considerable similarities to the concept of depression. In this study professional depression demonstrated a substantial correlation with depressed mood. Personality demonstrated significant relationships with burnout variables, extrapunitive hostility correlating with hardening toward others, intropunitiveness with avoidance as a coping response. These findings, although confined to hospital nurses, support the usefulness of approaches stressing the interaction between the work environment and the individual.

Complete nucleotide sequence of the Escherichia coli recB gene

Abstract: The complete nucleotide sequence of the Escherichia coli recB gene which encodes a subunit of the ATP-dependent DNase, Exonuclease V, has been determined. The proposed coding region for the RecB protein is 3543 nucleotides long and would encode a polypeptide of 1180 amino acids with a calculated molecular weight of 133,973. The start of the recB coding sequence overlaps the 3' end of the upstream ptr gene, and the recB termination codon overlaps the initiation codon of the downstream recD gene, suggesting that these genes may form an operon. No sequences which reasonably fit the consensus for an E. coli promoter could be identified upstream of the proposed recB translational start. The predicted RecB amino acid sequence contains regions of homology with ATPases, DNA binding proteins and DNA repair enzymes.

Complete nucleotide sequence of recD, the structural gene for the α subunit of Exonuclease V of Escherichia coli

Abstract: Intracellular amplification of the Escherichia coli RecB and RecC proteins does not result in an increase in Exonuclease V activity unless the level of a third protein, encoded between the recB and argA genes, is also amplified. Nucleotide sequence analysis of this region reveals a 1,824 nucleotide open reading frame which would encode a protein of 608 amino acids with a calculated molecular weight of 66,973. This is assumed to be the structural gene for the alpha subunit of Exonuclease V, recently designated recD. The proposed initiation codon of the recD gene overlaps the termination codon of the upstream recB gene by one nucleotide, suggesting that these genes may form an operon. The deduced amino acid sequence of the RecD protein contains a region which is homologous to highly conserved sequences in adenine nucleotide binding proteins.

Chapter 22 Depolarization-dependent protein phosphorylation in synaptosomes: mechanisms and significance

Abstract: Publisher Summary This chapter reviews the methods used to study synaptosomal protein phosphorylatio to evaluate the limitations of the procedures and the likelihood of introducing in vitro artefacts. It describes the major synaptosomal phosphoproteins and the effect of depolarization on their labeling with 32Pi. The chapter focuses on phosphoproteins having molecular weights between 40 and 90 kDa because these proteins have been extensively investigated in disrupted synaptic tissue. The chapter describes mechanisms of protein kinase activation and control, which account for the observed phosphorylation of proteins before and after depolarization, and outlines the possible functions of the major synaptosomal phosphoproteins in relation to neurotransmitter release. A number of experimental systems have been used to investigate the role(s) of protein phosphorylation in neurotransmitter release and, out of these, synaptosome preparations constitute an excellent model. These subcellular organelles have the particular advantage of being an in vitro nerve terminal preparation that retains the capacity to release neurotransmitters in a physiologically relevant manner. They are relatively homogeneous compared to neuronal cell cultures containing axons, cell bodies, dendrites and nuclei, and brain slices, which contain nonneuronal cells.

Patient satisfaction with primary-care consultations.

Abstract: This study examines patients' perceptions of their latest consultation with a primary-care physician. A new questionnaire measured patients' views on their “ideal” physician prior to the visit and their satisfaction on similar dimensions immediately afterward. Ratings by the 503 eligible patients (87% response rate) showed that all 43 items were relevant and that a shortened version could also be used successfully. Patients held high expectations for, but were also quite satisfied with, their physicians' actual behavior during the consultation. Factor analysis of perceptions supported other research findings and raised some anomalies in relation to overordering of investigations and waiting time. Other analyses showed which characteristics of physicians and patients were most influential on satisfaction and which dimensions of care were common or distinct to the 22 physicians involved in this study.