Showing papers by "University of Newcastle published in 1998"
TL;DR: In this article, a technique for exploring this phenomenon, geographically weighted regression, is introduced, and a related Monte Carlo significance test for spatial non-stationarity is also considered, using limiting long-term illness data from the 1991 UK census.
Abstract: In regression models where the cases are geographical locations, sometimes regression coefficients do not remain fixed over space. A technique for exploring this phenomenon, geographically weighted regression is introduced. A related Monte Carlo significance test for spatial non-stationarity is also considered. Finally, an example of the method is given, using limiting long-term illness data from the 1991 UK census.
1,442 citations
TL;DR: In this article, a sediment-based calibration of the U37K′ paleotemperature index is presented, based on the analysis of 149 surface sediments from the eastern South Atlantic in order to define the most suitable calibration for this region.
975 citations
TL;DR: Geographically weighted regression and the expansion method are two statistical techniques which can be used to examine the spatial variability of regression results across a region and so inform on the presence of spatial nonstationarity as discussed by the authors.
Abstract: Geographically weighted regression and the expansion method are two statistical techniques which can be used to examine the spatial variability of regression results across a region and so inform on the presence of spatial nonstationarity. Rather than accept one set of 'global' regression results, both techniques allow the possibility of producing 'local' regression results from any point within the region so that the output from the analysis is a set of mappable statistics which denote local relation ships. Within the paper, the application of each technique to a set of health data from northeast England is compared. Geographically weighted regression is shown to produce more informative results regarding parameter variation over space. 1 Spatial nonstationarity A frequent aim of data analysis is to identify relationships between pairs of variables, often after negating the effects of other variables. By far the most common type of analysis used to achieve this aim is that of regression, in which relationships between one or more independent variables and a single dependent variable are estimated. In spatial analysis the data are drawn from geographical units and a single regression equation is estimated. This has the effect of producing 'average' or 'global' parameter estimates which are assumed to apply equally over the whole region. That is, the relationships being measured are assumed to be stationary over space. Relationships which are not stationary, and which are said to exhibit spatial nonstationarity, create problems for the interpretation of parameter estimates from a regression model. It is the intention of this paper to compare the results of two statistical techniques, Geographically weighted regression (GWR) and the expansion method (EM), which can be used both to account for and to examine the presence of spatial nonstationarity in relationships .
899 citations
Book•
03 Aug 1998TL;DR: The Brauer group and group actions The spectrum Tensor products of $C^*$-algebras The imprimitivity theorem Miscellany Index Bibliography as mentioned in this paper The algebra of compact operators Hilbert $C *$-modules Morita equivalence Sheaves, cohomology, and bundles Continuous trace
Abstract: The algebra of compact operators Hilbert $C^*$-modules Morita equivalence Sheaves, cohomology, and bundles Continuous-trace $C^*$-algebras Applications Epilogue: The Brauer group and group actions The spectrum Tensor products of $C^*$-algebras The imprimitivity theorem Miscellany Index Bibliography.
875 citations
TL;DR: The Metropolis algorithm provides a quantum advance in the capability to deal with parameter uncertainty in hydrologic models by using a random walk that adapts to the true probability distribution describing parameter uncertainty.
809 citations
01 Jan 1998
TL;DR: A multiple attribute decision making problem usually comprises a finite number of explicitly given alternative designs and a set of performance attributes and design selection involves either choosing the most favourable design from the alternative set or ranking all the alternative designs with regard to all attributes.
Abstract: A multiple attribute decision making (simply MADM) problem usually comprises a finite number of explicitly given alternative designs and a set of performance attributes. Design selection involves either choosing the most favourable design from the alternative set or ranking all the alternative designs with regard to all attributes. A MADM problem may have either qualitative or quantitative data. More generally, MADM problems may involve both types of data, and approaches for dealing with these will be investigated in Section 3.4.
746 citations
TL;DR: Factors such as breeding density, genetic variation in the population and the intensity of sexual conflicts determine the costs and benefits to males and females of engaging in extra-pair copulations, and therefore contribute to the variation among populations.
Abstract: Molecular techniques used to assign paternity have revealed previously unknown incidences of extra-pair paternity in socially monogamous bird species. DNA fingerprinting has now been used sufficiently often for mating-system biologists to appreciate the natural variation in the frequency of broods showing extra-pair young. The variation between species and between populations of the same species is surprisingly marked. Explaining this variation may help us to understand the factors promoting sexual selection. Recent comparative studies and detailed behavioural studies suggest that factors such as breeding density, genetic variation in the population and the intensity of sexual conflicts determine the costs and benefits to males and females of engaging in extra-pair copulations, and therefore contribute to the variation among populations.
595 citations
TL;DR: In this article, the hardness of a number of coated systems has been measured using a variety of experimental techniques ranging from traditional macro-Vickers indentation to ultra-low-load depth-sensing nanoindentation.
Abstract: The hardness of a number of coated systems has been measured using a variety of experimental techniques ranging from traditional macro-Vickers indentation to ultra-low-load depth-sensing nanoindentation. This has allowed the hardness response to be measured over scales ranging from those less than the coating thickness, where a coating-dominated response is expected, to much more macroscopic scales where system behaviour is dominated by the substrate. The objective has been to construct a mathematical description of the hardness performance of coated systems which well describes the behaviour over this wide range of scales. Previous attempts at such quantitative descriptions have usually involved models focusing on some particular deformation mechanism (e.g. plasticity, elastic response or fracture). In contrast, this paper presents a new approach to analysing hardness data essentially using dimensionless parameters containing descriptors equally applicable to either plasticity- or fracture-dominated behaviour with all scales measured relative to the coating thickness. The model shows an excellent fit to a wide range of experimental data. Furthermore, once the fit has been made, not only can some deductions be made regarding dominant deformation mechanisms, but the model allows predictions of the contact response of other coated systems to be made.
539 citations
TL;DR: This paper points out the precise domain-specific knowledge required by each method, such as the explicit intentions of the guideline designer, and presents a machine-readable language, called Asbru, to represent and to annotate guidelines based on the task-specific ontology.
473 citations
TL;DR: Impaired individuals in a multiplex pedigree with MRX (MRX30), previously mapped to Xq22, show a point mutation in the PAK3 (p21-activated kinase) gene, which encodes a serine-threonine kinase, which is critical for human cognitive function.
Abstract: Nonsyndromic X-linked mental retardation (MRX) syndromes are clinically homogeneous but genetically heterogeneous disorders, whose genetic bases are largely unknown. Affected individuals in a multiplex pedigree with MRX (MRX30), previously mapped to Xq22, show a point mutation in the PAK3 (p21-activated kinase) gene, which encodes a serine-threonine kinase. PAK proteins are crucial effectors linking Rho GTPases to cytoskeletal reorganization and to nuclear signalling. The mutation produces premature termination, disrupting kinase function. MRI analysis showed no gross defects in brain development. Immunofluorescence analysis showed that PAK3 protein is highly expressed in postmitotic neurons of the developing and postnatal cerebral cortex and hippocampus. Signal transduction through Rho GTPases and PAK3 may be critical for human cognitive function.
467 citations
TL;DR: In this paper, it was shown that the magnetic field along the line of sight strongly affects the observable radio polarization patterns, and that random fluctuations in the degree of polarization caused by Faraday dispersion are expected to become significantly larger than the mean value of p at λ −≳−20 −−30 cm.
Abstract: Faraday rotation and depolarization of synchrotron radio emission are considered in a consistent general approach, under conditions typical of spiral galaxies, i.e. when the magneto-ionic medium and relativistic electrons are non-uniformly distributed in a layer containing both regular and fluctuating components of magnetic field, thermal electron density and synchrotron emissivity. We demonstrate that non-uniformity of the magneto-ionic medium along the line of sight strongly affects the observable polarization patterns. The degree of polarization p and the observed Faraday rotation measure RM are very sensitive to whether or not the source is symmetric along the line of sight. The RM may change sign in a certain wavelength range in an asymmetric slab even when the line-of-sight magnetic field has no reversals. Faraday depolarization in a purely regular magnetic field can be much stronger than suggested by the low observed rotation measures. A twisted regular magnetic field may result in p increasing with λ— a behaviour detected in several galaxies. We derive expressions for statistical fluctuations in complex polarization and show that random fluctuations in the degree of polarization caused by Faraday dispersion are expected to become significantly larger than the mean value of p at λ ≳ 20 − 30 cm. We also discuss depolarization arising from a gradient of Faraday rotation measure across the beam, both in the source and in an external Faraday screen. We briefly discuss applications of the above results to radio polarization observations. We discuss how the degree of polarization is affected by the scaling of synchrotron emissivity ɛ with the total magnetic field strength B. We derive formulae for the complex polarization at λ 0 under the assumption that ɛ ∝ B2B2⊥, which may arise under energy equipartition or pressure balance between cosmic rays and magnetic fields. The resulting degree of polarization is systematically larger than for the usually adopted scaling ɛ ∝ B2⊥; the difference may reach a factor of 1.5.
TL;DR: The hypothesis that endogenously-produced nitric oxide (NO • ) gas is a natural plant growth regulator was experimentally tested in this paper, where a wide spectrum of both climacteric and non-climacteric varieties of fruits, flowers, vegetables and legume sprout species were investigated.
TL;DR: The dissociation observed in the performance of dyslexic individuals on different auditory tasks suggests a sub-modality division similar to that already described in the visual system, which may provide a non-linguistic means of identifying children at risk of reading failure.
TL;DR: The relationship between information technologies and space and place is explored in a broad swathe of recent writings and discourses on the geographies of 'cyberspace' and information technologies.
Abstract: This article critically explores how the relations between information technologies and space and place are being conceptualized in a broad swathe of recent writings and discourses on the geographies of 'cyberspace' and information technologies. After analysing the powerful role of spatial and territorial metaphors in anchoring current discourses about information tech- nologies and society, the article goes on to identify three broad, dominating perspectives. These I label the perspective of 'substitution and transcendence' (dominated by technological Utopian- ists), the 'co-evolution' perspective (drawing from political economy and cultural studies) and the 'recombination' perspective (derived from recent work in actor-network theory). The discussion turns to each in turn, extracting the geographical dimensions and implications of each. The article concludes by considering the implications of the discussion for spatial treatments of society- technology relations and for broader debates about the nature of space and place.
TL;DR: This paper considers some of the key developments in camera calibration for aerial mapping and attempts to put them into perspective and the driving forces behind each improvement have been highlighted.
Abstract: Corriger les images de la distorsion des chambres de prises de vues a ete une preoccupation importante des usagers, aussi longtemps qu'ils ont voulu utiliser ou reconstituer fidelement les informations observees. La cartographie a ete initialement la principale application. Tandis que cette tâche se poursuit de nos jours, d'autres applications necessitent egalement un etalonnage precis des chambres, telles que les determinations tridimensionnelles a courte distance et de nombreuses autres mesures a deux dimensions. Dans le passe, les chambres utilisees etaient peu nombreuses et tres onereuses tandis qu'aujourdhui une grande societe industrielle aura normalement de nombreuses cameras bon marche qu'il utilisera pour des travaux de mesures tres importants. On se sert de nos jours de cameras beaucoup plus qu'on ne le fit jamais, mais l'âge d'or de l'etalonnage des chambres de prises de vues aeriennes pour la cartographie est desormais termine. On examine dans cet article quelques uns des essais et des developpements-cles et on les remet en perspective. On y met en particulier en evidence les forces sous-jacentes qui ont preside a chaque amelioration.
TL;DR: It is demonstrated that excitatory synapses onto interneurons within a fear conditioning circuit show NMDA-receptor independent long-term potentiation, which might underlie the increased synchronization of activity between neurons in the basolateral amygdala after fear conditioning.
Abstract: Fear conditioning is a paradigm that has been used as a model for emotional learning in animals. The cellular correlate of fear conditioning is thought to be associative N-methyl-D-aspartate (NMDA) receptor-dependent synaptic plasticity within the amygdala. Here we show that glutamatergic synaptic transmission to inhibitory interneurons in the basolateral amygdala is mediated solely by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. In contrast to AMPA receptors at inputs to pyramidal neurons, these receptors have an inwardly rectifying current-voltage relationship, indicative of a high permeability to calcium. Tetanic stimulation of inputs to interneurons caused an immediate and sustained increase in the efficacy of these synapses. This potentiation required a rise in postsynaptic calcium, but was independent of NMDA receptor activation. The potentiation of excitatory inputs to interneurons was reflected as an increase in the amplitude of the GABA(A)-mediated inhibitory synaptic current in pyramidal neurons. These results demonstrate that excitatory synapses onto interneurons within a fear conditioning circuit show NMDA-receptor independent long-term potentiation. This plasticity might underlie the increased synchronization of activity between neurons in the basolateral amygdala after fear conditioning.
TL;DR: In this article, a structural deterioration reliability model is developed to calculate probabilities of structural failure (flexure) for a typical reinforced concrete continuous slab bridge, assuming that corrosion will lead to a reduction in the cross-sectional area of the reinforcing steel.
TL;DR: The molecular genetics of the ice plant are characterized, emphasizing selected genes and their products and an analysis of the multiple stages of growth as an ecological adaptation to progressive stress.
Abstract: This review describes the life cycle of Mesembryantheum crystallinum L. (the common ice plant, Aizoaceae, Caryophyllales), a halophyte with a developmentally programmed switch from C3 photosynthesis to Crassulacean acid metabolism (CAM) which is accelerated by salinity and drought. Since there has been controversy regarding the interplay between genes and environmental stimuli during the development of M. crystallinum, it is timely to summarize the life cycle for a defined set of conditions. We seek to establish the framework whereby five stages of development can be described in terms of morphology, physiology, and molecular biology. Stages 1 and 2, representing germination and growth of a juvenile form, show a determinate pattern of growth. Although specific genes for salt tolerance can be induced at these stages, stress early in development prevents progression to the mature form (stages 3-5) in which the plants advance to mature growth, flowering, and seed development. Growth in stage 3 is indeterminate in the absence of stress, but development and flowering are accelerated by environmental stresses, and CAM is constitutively expressed. Depending on the severity of the stress, plants start to flower (stage 4) and then die from the roots, ultimately with only seed capsules remaining viable, with salt sequestered into large epidermal bladder cells (stage 5). We highlight responses to salinity leading to compartmentation of ions and compatible solutes, turgor maintenance, and CAM. Finally, the molecular genetics of the ice plant are characterized, emphasizing selected genes and their products. We conclude with an analysis of the multiple stages of growth as an ecological adaptation to progressive stress. The initial determinate and inflexible juvenile phase provides a critical mass of plant material which supports the indeterminate, mature phase. Depending on the degree of stress, the mature form is then propelled towards flowering and seedset. CONTENTS Summary 171 I. Introduction 172 II. Standardizing methodology 173 III. Growth and development 175 IV. Effects of salt stress on developmental physiology 176 V. Ionic composition of cells during development 179 VI. Water transport within the plant 179 VII. The switch from C3 to Crassulacean Acid Metabolism 181 VIII. Stress and plant-growth regulators 182 IX. Molecular biology 183 X. Genetics, ploidy and mutants 184 XI. Conclusions and future directions 185 Acknowledgements 187 References 187.
TL;DR: In this article, it was suggested that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber, and the present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of replenishment.
TL;DR: Results on a self-report measure showed that vitamin D3 significantly enhanced positive affect and there was some evidence of a reduction in negative affect, which has implications for seasonality, SAD, serotonin, food preference, sleep, and circadian rhythms.
Abstract: Mood changes synchronised to the seasons exist on a continuum between individuals, with anxiety and depression increasing during the winter months. An extreme form of seasonality is manifested as the clinical syndrome of seasonal affective disorder (SAD) with carbohydrate craving, hypersomnia, lethargy, and changes in circadian rhythms also evident. It has been suggested that seasonality and the symptoms of SAD may be due to changing levels of vitamin D3, the hormone of sunlight, leading to changes in brain serotonin. Forty-four healthy subjects were given 400 IU, 800 IU, or no vitamin D3 for 5 days during late winter in a random double-blind study. Results on a self-report measure showed that vitamin D3 significantly enhanced positive affect and there was some evidence of a reduction in negative affect. Results are discussed in terms of their implications for seasonality, SAD, serotonin, food preference, sleep, and circadian rhythms.
TL;DR: In this paper, the SIBERIA catchment evolution model was used to explore linkages between catchment process and hypsometry, and it was shown that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve.
Abstract: Hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms. Yet there has been little work aimed at relating hypsometry to landform process and scale. This paper uses the SIBERIA catchment evolution model to explore linkages between catchment process and hypsometry. SIBERIA generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters. However, we show that not only does the hypsometry reflect landscape runoff and erosion process, but it is strongly dependent on channel network and catchment geometry. We show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve, though little on the hypsometric integral. For landforms dominated by fluvial sediment transport, the classic Strahler ‘mature’ hypsometric curve is only generated for catchments with roughly equal width and length. Narrow catchments show a hypsometric curve more similar to Strahler's ‘monadnock’ form. For landscapes dominated by diffusive transport, the simulated hypsometric curve is concave-down everywhere, this being consistent with curves reported for some example catchments in France. Because the transition between diffusive dominance to fluvial is scale-dependent, with larger catchments exhibiting greater fluvial dominance, then the hypsometric curve is a scale-dependent descriptor of landforms. Experimental results for simulated landforms from a small-scale rainfall-erosion simulator are reported. It is shown that SIBERIA yields satisfactory fits to the data, confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes. © 1998 John Wiley & Sons, Ltd.
TL;DR: In this paper, the effects of ozone on wild species posed by ozone on growth and resource allocation are discussed. But the authors focus on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities.
Abstract: Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting/grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems.
TL;DR: The role of perceived location is explored by recording the walking trajectories of people wearing displacing prism glasses to suggest that perceived location, rather than optic or retinal flow, is the predominant cue that guides locomotion on foot.
TL;DR: In this article, a simple, unified critical state constitutive model for both clay and sand is presented, which is formulated in terms of the state parameter that is defined as the vertical distance between current state (v, p′) and the critical state line in v−ln p′ space.
Abstract: The purpose of this paper is to present a simple, unified critical state constitutive model for both clay and sand. The model, called CASM (Clay And Sand Model), is formulated in terms of the state parameter that is defined as the vertical distance between current state (v, p′) and the critical state line in v–ln p′ space. The paper first shows that the standard Cam-clay models (i.e. the original and modified Cam-clay models) can be reformulated in terms of the state parameter. Although the standard Cam-clay models prove to be successful in modelling normally consolidated clays, it is well known that they cannot predict many important features of the behavior of sands and overconsolidated clays. By adopting a general stress ratio-state parameter relation to describe the state boundary surface of soils, it is shown that a simple, unified constitutive model (CASM) can be developed for both clay and sand. It is also demonstrated that the standard Cam-clay yield surfaces can be either recovered or approximated as special cases of the yield locus assumed in CASM.
The main feature of the proposed model is that a single set of yield and plastic potential functions has been used to model the behaviour of clay and sand under both drained and undrained loading conditions. In addition, it is shown that the behaviour of overconsolidated clays can also be satisfactorily modelled. Simplicity is a major advantage of the present state parameter model, as only two new material constants need to be introduced when compared with the standard Cam-clay models. © 1998 John Wiley & Sons, Ltd.
TL;DR: In this paper, the TOPMODEL parameterizations are conditioned on discharges, and then further conditioned on estimates of saturated areas derived from ERS-I synthetic aperture radar (SAR) images combined with the In (α/tan β) topographic index, and compared to ground truth saturation measurements made in one small subcatchment.
Abstract: Distributed hydrological models are generally overparameterized, resulting in the possibility of multiple parameterizations from many areas of the parameter space providing acceptable fits to observed data. In this study, TOPMODEL parameterizations are conditioned on discharges, and then further conditioned on estimates of saturated areas derived from ERS-I synthetic aperture radar (SAR) images combined with the In (α/tan β) topographic index, and compared to ground truth saturation measurements made in one small subcatchment. The uncertainty associated with the catchment-wide predictions of saturated area is explicitly incorporated into the conditioning through the weighting of estimates within a fuzzy set framework. The predictive uncertainty associated with the parameterizations is then assessed using the generalized likelihood uncertainty estimation (GLUE) methodology. It is shown that despite the uncertainty in the predictions of saturated area the methodology can reject many previously acceptable parameterizations with the consequence of a marked reduction in the acceptable range of a catchment average transmissivity parameter and of improved predictions of some discharge events.
TL;DR: This work reviews the research on DNA topoisomerase IIβ over the last 10 years and suggests that the role of the β isoform is not yet clear.
Abstract: Type II DNA topoisomerase activity is required to change DNA topology. It is important in the relaxation of DNA supercoils generated by cellular processes, such as transcription and replication, and it is essential for the condensation of chromosomes and their segregation during mitosis. In mammals this activity is derived from at least two isoforms, termed DNA topoisomerase II alpha and beta. The alpha isoform is involved in chromosome condensation and segregation, whereas the role of the beta isoform is not yet clear. DNA topoisomerase II beta was first reported in 1987. Here we review the research on DNA topoisomerase II beta over the last 10 years.
TL;DR: The authors examined available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM), and concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere.
Abstract: This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.
TL;DR: In this paper, it was shown that deformation was initiated by sinking of greenstones, which rapidly subsided; the domes then rose passively as accommodation structures, and the resulting deformation is part of a larger process involving partial convective overturn of the crust.