Showing papers by "University of Sussex published in 2002"

Ecological responses to recent climate change.

Abstract: There is now ample evidence of the ecological impacts of recent climate change, from polar terrestrial to tropical marine environments. The responses of both flora and fauna span an array of ecosystems and organizational hierarchies, from the species to the community levels. Despite continued uncertainty as to community and ecosystem trajectories under global change, our review exposes a coherent pattern of ecological change across systems. Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible.

Sloan digital sky survey: Early data release

Abstract: The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 A at R ≈ 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.

The genome sequence of Schizosaccharomyces pombe

Abstract: We have sequenced and annotated the genome of fission yeast (Schizosaccharomyces pombe), which contains the smallest number of protein-coding genes yet recorded for a eukaryote: 4,824. The centromeres are between 35 and 110 kilobases (kb) and contain related repeats including a highly conserved 1.8-kb element. Regions upstream of genes are longer than in budding yeast (Saccharomyces cerevisiae), possibly reflecting more-extended control regions. Some 43% of the genes contain introns, of which there are 4,730. Fifty genes have significant similarity with human disease genes; half of these are cancer related. We identify highly conserved genes important for eukaryotic cell organization including those required for the cytoskeleton, compartmentation, cell-cycle control, proteolysis, protein phosphorylation and RNA splicing. These genes may have originated with the appearance of eukaryotic life. Few similarly conserved genes that are important for multicellular organization were identified, suggesting that the transition from prokaryotes to eukaryotes required more new genes than did the transition from unicellular to multicellular organization.

A systematic review of psychological factors as predictors of chronicity/disability in prospective cohorts of low back pain.

Abstract: Study Design. A systematic review of prospective cohort studies in low back pain. Objectives. To evaluate the evidence implicating psychological factors in the development of chronicity in low back pain. Summary of Background Data. The biopsychosocial model is gaining acceptance in low back pain, and has provided a basis for screening measurements, guidelines and interventions; however, to date, the unique contribution of psychological factors in the transition from an acute presentation to chronicity has not been rigorously assessed. Methods. A systematic literature search was followed by the application of three sets of criteria to each study: methodologic quality, quality of measurement of psychological factors, and quality of statistical analysis. Two reviewers blindly coded each study, followed by independent assessment by a statistician. Studies were divided into three environments: primary care settings, pain clinics, and workplace. Results. Twenty-five publications (18 cohorts) included psychological factors at baseline. Six of these met acceptability criteria for methodology, psychological measurement, and statistical analysis. Increased risk of chronicity (persisting symptoms and/or disability) from psychological distress/depressive mood and, to a lesser extent, somatization emerged as the main findings. Acceptable evidence generally was not found for other psychological factors, although weak support emerged for the role of catastrophizing as a coping strategy. Conclusion. Psychological factors (notably distress, depressive mood, and somatization) are implicated in the transition to chronic low back pain. The development and testing of clinical interventions specifically targeting these factors is indicated. In view of the importance attributed to other psychological factors (particularly coping strategies and fear avoidance) there is a need to clarify their role in back-related disability through rigorous prospective studies

Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample

Abstract: We describe the algorithm for selecting quasar candidates for optical spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected via their nonstellar colors in ugriz broadband photometry and by matching unresolved sources to the FIRST radio catalogs. The automated algorithm is sensitive to quasars at all redshifts lower than z ~ 5.8. Extended sources are also targeted as low-redshift quasar candidates in order to investigate the evolution of active galactic nuclei (AGNs) at the faint end of the luminosity function. Nearly 95% of previously known quasars are recovered (based on 1540 quasars in 446 deg2). The overall completeness, estimated from simulated quasars, is expected to be over 90%, whereas the overall efficiency (quasars/quasar candidates) is better than 65%. The selection algorithm targets ultraviolet excess quasars to i* = 19.1 and higher redshift (z 3) quasars to i* = 20.2, yielding approximately 18 candidates deg-2. In addition to selecting "normal" quasars, the design of the algorithm makes it sensitive to atypical AGNs such as broad absorption line quasars and heavily reddened quasars.

The catalytic pathway of horseradish peroxidase at high resolution

Abstract: A molecular description of oxygen and peroxide activation in biological systems is difficult, because electrons liberated during X-ray data collection reduce the active centres of redox enzymes catalysing these reactions. Here we describe an effective strategy to obtain crystal structures for high-valency redox intermediates and present a three-dimensional movie of the X-ray-driven catalytic reduction of a bound dioxygen species in horseradish peroxidase (HRP). We also describe separate experiments in which high-resolution structures could be obtained for all five oxidation states of HRP, showing such structures with preserved redox states for the first time.

The relation between children's and mothers' mental state language and theory-of-mind understanding.

Abstract: This study investigated the relation between mothers' utterances and theory of mind in a longitudinal study involving three time points over 1 year. Mothers were asked to describe some pictures to 82 children at all three time points. Mothers' use of mental state utterances in these descriptions at early time points was consistently correlated with later theory-of-mind understanding. This was true even when a number of potential mediators were accounted for, including children's own use of mental state language, their earlier theory-of-mind understanding, their language ability, their age, mothers' education, and other types of mother utterances. Mothers' mental state utterances seemed genuinely causal because early theory-of-mind ability was not related to later mother mental state utterances (i.e., it was not a reciprocal relation). Results also showed that children's desire talk preceded their talk about beliefs.

Towards a new map of European migration

Abstract: Students of European migration have been hampered by the legacy of those established forms of migration which have been historically most important – settler migrations from Europe to the Americas, guest-worker migrations from the Mediterranean Basin to Northern Europe, and refugee migrations after the World Wars. We need to appreciate that many of the key questions that were asked to frame our understanding of the functioning of migration now have a very different array of answers from the largely economic ones which shaped our earlier analyses. Now, new mobility strategies are deployed to achieve economic and, importantly, non-economic objectives. In the new global and European map of migration, the old dichotomies of migration study – internal versus international, forced versus voluntary, temporary versus permanent, legal versus illegal – blur as both the motivations and modalities of migration become much more diverse. In offering an overview of the new typologies and geographies of international migration in Europe, this paper will be less a rigorous cartography than a qualitative exploration of a changing typology including migrations of crisis, independent female migration, migration of skilled and professional people, student migration, retirement migration and hybrid tourism–migration. These relatively new forms of migration derive from new motivations (the retreat from labour migrations linked to production), new space–time flexibilities, globalisation forces, and migrations of consumption and personal self-realisation. More than ever, this multiplex nature of human migration and spatial mobility demands an interdisciplinary approach, enriched wherever possible by comparative studies. Copyright © 2002 John Wiley & Sons, Ltd.

Adaptive protein evolution in Drosophila

Abstract: For over 30 years a central question in molecular evolution has been whether natural selection plays a substantial role in evolution at the DNA sequence level1, 2. Evidence has accumulated over the last decade that adaptive evolution does occur at the protein level3, 4, but it has remained unclear how prevalent adaptive evolution is. Here we present a simple method by which the number of adaptive substitutions can be estimated and apply it to data from Drosophila simulans and D. yakuba. We estimate that 45% of all amino-acid substitutions have been fixed by natural selection, and that on average one adaptive substitution occurs every 45 years in these species.

Galaxy clustering in early sloan digital sky survey redshift data

Abstract: We present the first measurements of clustering in the Sloan Digital Sky Survey (SDSS) galaxy redshift survey. Our sample consists of 29,300 galaxies with redshifts 5700 km s-1 ≤ cz ≤ 39,000 km s-1, distributed in several long but narrow (25-5°) segments, covering 690 deg2. For the full, flux-limited sample, the redshift-space correlation length is approximately 8 h-1 Mpc. The two-dimensional correlation function ξ(rp,π) shows clear signatures of both the small-scale, fingers-of-God distortion caused by velocity dispersions in collapsed objects and the large-scale compression caused by coherent flows, though the latter cannot be measured with high precision in the present sample. The inferred real-space correlation function is well described by a power law, ξ(r) = (r/6.1 ± 0.2 h-1 Mpc)-1.75±0.03, for 0.1 h-1 Mpc ≤ r ≤ 16 h-1 Mpc. The galaxy pairwise velocity dispersion is σ12 ≈ 600 ± 100 km s-1 for projected separations 0.15 h-1 Mpc ≤ rp ≤ 5 h-1 Mpc. When we divide the sample by color, the red galaxies exhibit a stronger and steeper real-space correlation function and a higher pairwise velocity dispersion than do the blue galaxies. The relative behavior of subsamples defined by high/low profile concentration or high/low surface brightness is qualitatively similar to that of the red/blue subsamples. Our most striking result is a clear measurement of scale-independent luminosity bias at r 10 h-1 Mpc: subsamples with absolute magnitude ranges centered on M* - 1.5, M*, and M* + 1.5 have real-space correlation functions that are parallel power laws of slope ≈-1.8 with correlation lengths of approximately 7.4, 6.3, and 4.7 h-1 Mpc, respectively.

Molecular Junctions by Joining Single-Walled Carbon Nanotubes

Abstract: Crossing single-walled carbon nanotubes can be joined by electron beam welding to form molecular junctions Stable junctions of various geometries are created in situ in a transmission electron microscope Electron beam exposure at high temperatures induces structural defects which promote the joining of tubes via cross-linking of dangling bonds The observations are supported by molecular dynamics simulations which show that the creation of vacancies and interstitials induces the formation of junctions involving seven- or eight-membered carbon rings at the surface between the tubes

Buffered tree population changes in a quaternary refugium: evolutionary implications.

Abstract: A high-resolution pollen record from western Greece shows that the amplitude of millennial-scale oscillations in tree abundance during the last glacial period was subdued, with temperate tree populations surviving throughout the interval. This provides evidence for the existence of an area of relative ecological stability, reflecting the influence of continued moisture availability and varied topography. Long-term buffering of populations from climatic extremes, together with genetic isolation at such refugial sites, may have allowed lineage divergence to proceed through the Quaternary. Such ecologically stable areas may be critical not only for the long-term survival of species, but also for the emergence of new ones.

Cultural Values, Sources of Guidance, and their Relevance to Managerial Behavior A 47-Nation Study

Abstract: Data are presented showing how middle managers in 47 countries report handling eight specific work events. The data are used to test the ability of cultural value dimensions derived from the work of Hofstede, Trompenaars, and Schwartz to predict the specific sources of guidance on which managers rely. Focusing on sources of guidance is expected to provide a more precise basis than do generalized measures of values for understanding the behaviors that prevail within different cultures. Values are strongly predictive of reliance on those sources of guidance that are relevant to vertical relationships within organizations. However, values are less successful in predicting reliance on peers and on more tacit sources of guidance. Explaining national differences in these neglected aspects of organizational processes will require greater sensitivity to the culture-specific contexts within which they occur.

Teaching and Learning in their Disciplinary Contexts: A conceptual analysis

Abstract: The growing literature on undergraduate teaching and learning currently lacks an organising framework. This article sets out to provide one, distinguishing between hard pure, soft pure, hard applied and soft applied fields of study, and hence making it possible to highlight generally unremarked similarities and differences between the various research findings. In doing so, it draws extensively on the relevant literature, offering separate analyses of knowledge-related and socially related studies. The former embody curriculum, assessment and cognitive purpose, while the latter encompass group characteristics of teachers, types of teaching method and student learning requirements. The concluding section draws out the main implications for policy and practice related to staff development, computer-based learning, assessment of student learning and quality measures.

Truth may hurt but deceit hurts more: communication in palliative care.

Abstract: Healthcare professionals often censor their information giving to patients in an attempt to protect them from potentially hurtful, sad or bad news. There is a commonly expressed belief that what people do not know does not harm them. Analysis of doctor and nurse/patient interactions reveals that this well-intentioned but misguided assumption about human behaviour is present at all stages of cancer care. Less than honest disclosure is seen from the moment that a patient reports symptoms, to the confirmation of diagnosis, during discussions about the therapeutic benefits of treatment, at relapse and terminal illness. This desire to shield patients from the reality of their situation usually creates even greater difficulties for patients, their relatives and friends and other members of the healthcare team. Although the motivation behind economy with the truth is often well meant, a conspiracy of silence usually results in a heightened state of fear, anxiety and confusion--not one of calm and equanimity. Ambiguous or deliberately misleading information may afford short-term benefits while things continue to go well, but denies individuals and their families opportunities to reorganize and adapt their lives towards the attainment of more achievable goals, realistic hopes and aspirations. In this paper, some examples and consequences of accidental, deliberate, if well-meaning, attempts to disguise the truth from patients, taken verbatim from interviews, are given, together with cases of unintentional deception or misunderstandings created by the use of ambiguous language. We also provide evidence from research studies showing that although truth hurts, deceit may well hurt more. 'I think the best physician is the one who has the providence to tell to the patients according to his knowledge the present situation, what has happened before, and what is going to happen in the future' (Hippocrates).

Myosin VIIa, harmonin and cadherin 23, three Usher I gene products that cooperate to shape the sensory hair cell bundle

Abstract: Deaf-blindness in three distinct genetic forms of Usher type I syndrome (USH1) is caused by defects in myosin VIIa, harmonin and cadherin 23. Despite being critical for hearing, the functions of these proteins in the inner ear remain elusive. Here we show that harmonin, a PDZ domain-containing protein, and cadherin 23 are both present in the growing stereocilia and that they bind to each other. Moreover, we demonstrate that harmonin b is an F-actin-bundling protein, which is thus likely to anchor cadherin 23 to the stereocilia microfilaments, thereby identifying a novel anchorage mode of the cadherins to the actin cytoskeleton. Moreover, harmonin b interacts directly with myosin VIIa, and is absent from the disorganized hair bundles of myosin VIIa mutant mice, suggesting that myosin VIIa conveys harmonin b along the actin core of the developing stereocilia. We propose that the shaping of the hair bundle relies on a functional unit composed of myosin VIIa, harmonin b and cadherin 23 that is essential to ensure the cohesion of the stereocilia.

Socio-economic futures in climate change impact assessment: using scenarios as ‘learning machines’

Abstract: Climate impact assessment needs to take account of two interrelated processes: socio-economic change and climate change. To date, future change in socio-economic systems has not been sufficiently integrated with an analysis of climate change impacts. Participative and synthetic scenario approaches offer a means for dealing with critical issues of indeterminacy, innovation, reflexivity and framing in analysing change in socio-economic systems, paving the way for a coherent way of handling of socio-economic futures in impact assessment. We argue that scenarios represent heuristic tools that encourage social learning in climate impact assessment. The advantages and disadvantages of a scenario-based approach are explored using examples from regional climate impact assessment in the UK.

Galaxy Clusters in Hubble Volume Simulations: Cosmological Constraints from Sky Survey Populations

Abstract: We use gigaparticle N-body simulations to study galaxy cluster populations in Hubble volumes of ΛCDM and ΓCDM world models.

The SCUBA 8-mJy survey - I. Submillimetre maps, sources and number counts

Abstract: We present maps, source lists and derived number counts from the largest, unbiased, extragalactic submillimetre (submm) survey so far undertaken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT). Our maps are located in two regions of sky (ELAIS N2 and Lockman-Hole E) and cover 260arcmin2 , to a typical rms noise level of sigma 850 ~=2.5mJybeam-1 . We have reduced the data using both the standard JCMT surf procedures, and our own IDL -based pipeline which produces zero-footprint maps and noise images. The uncorrelated noise maps produced by the latter approach have enabled us to apply a maximum likelihood method to measure the statistical significance of each peak in our maps, leading to properly quantified errors on the flux density of all potential sources. We detect 19 sources with signal-to-noise ratios (S/N)>4, and 38 with S/N>3.5. To assess both the completeness of this survey and the impact of source confusion as a function of flux density, we have applied our source-extraction algorithm to a series of simulated images. The result is a new estimate of the submm source counts over the flux-density range S 850 ~=5-15mJy, which we compare with estimates derived by other workers, and with the predictions of a number of models. Our best estimate of the cumulative source count at S 850 >8mJy is per square degree. Assuming that the majority of sources lie at z >1.5, this result implies that the comoving number density of high-redshift galaxies forming stars at a rate in excess of 1000Msolar yr-1 is ~=10-5 Mpc-3 , with only a weak dependence on the precise redshift distribution. This number density corresponds to the number density of massive ellipticals with L >3-4L * in the present-day Universe , and is also the same as the comoving number density of comparably massive, passively evolving objects in the redshift band 1

Synthesis of shell cross-linked micelles with pH-responsive cores using ABC triblock copolymers

Abstract: A series of well-defined poly[(ethylene oxide)-block-2-(dimethylamino)ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEO−DMA−DEA) triblocks were synthesized by successive ATRP polymerization of DMA and DEA monomers using PEO-based macroinitiators of different molecular weights. These triblock copolymers dissolved molecularly in aqueous solution at low pH; on addition of NaOH, micellization occurred at pH 7.1 to form three-layer “onionlike” micelles comprising DEA cores, DMA inner shells, and PEO coronas. Above pH 7.3, dynamic light scattering studies indicated unimodal, near-monodisperse populations, with mean micelle diameters of 27−84 nm depending on block compositions (for PEO113 triblock copolymers) and polydispersities typically less than 0.10. The average hydrodynamic diameter Dh of the micelles decreased as the solution pH was increased from pH 7.3 to pH 9.0, indicating that the micelles become more compact due to deprotonation of the tertiary amine residues in the DMA and DEA blocks. 1H NMR studies supported a three-layer micelle structure and also revealed changes in the hydrophilicity of the DMA chains in the inner shell during cross-linking, which was achieved by adding the bifunctional alkyl iodide, 1,2-bis(2-iodoethoxy)ethane (BIEE). Selective quaternization of the DMA residues by the BIEE leads to increased hydrophilicity and colloid stability for the shell cross-linked (SCL) micelles. The minimum amount of BIEE required to “lock-in” the micellar structure depended on the thickness of the PEO corona: shorter PEO chains led to enhanced cross-linking efficiency. At pH 8.5, the hydrodynamic diameter of un-cross-linked micelles increased rapidly above 40−50 °C due to the LCST behavior of the neutral DMA chains in the inner shell. In contrast, the dimensions of the SCL micelles in dilute aqueous solution are independent of temperature. These SCL micelles exhibit reversible swelling on varying the solution pH. At low pH, the DEA cores become protonated and hence hydrophilic. The effect of varying the block composition and the target degree of cross-linking on the structural stability and pH-dependent (de)swelling of the SCL micelles was systematically studied. Longer DEA blocks and lower target degrees of cross-linking led to increased swellability, as expected.

Measurement of the electron electric dipole moment using YbF molecules.

Abstract: The most sensitive measurements of the electron electric dipole moment ${d}_{e}$ have previously been made using heavy atoms. Heavy polar molecules offer a greater sensitivity to ${d}_{e}$ because the interaction energy to be measured is typically ${10}^{3}$ times larger than in a heavy atom. We have used YbF to make the first measurement of this kind. Together, the large interaction energy and the strong tensor polarizability of the molecule make our experiment essentially free of the systematic errors that currently limit ${d}_{e}$ measurements in atoms. Our first result ${d}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}0.2\ifmmode\pm\else\textpm\fi{}3.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}e\mathrm{cm}$ is less sensitive than the best atom measurement but is limited only by counting statistics and demonstrates the power of the method.

Memory use in insect visual navigation

Abstract: The navigational strategies that are used by foraging ants and bees to reach a goal are similar to those of birds and mammals. Species from all these groups use path integration and memories of visual landmarks to navigate through familiar terrain. Insects have far fewer neural resources than vertebrates, so data from insects might be useful in revealing the essential components of efficient navigation. Recent work on ants and bees has uncovered a major role for associative links between long-term memories. We emphasize the roles of these associations in the reliable recognition of visual landmarks and the reliable performance of learnt routes. It is unknown whether such associations also provide insects with a map-like representation of familiar terrain. We suggest, however, that landmarks act primarily as signposts that tell insects what particular action they need to perform, rather than telling them where they are.

Identification of a DNA Nonhomologous End-Joining Complex in Bacteria

Abstract: In eukaryotic cells, double-strand breaks (DSBs) in DNA are generally repaired by the pathway of homologous recombination or by DNA nonhomologous end joining (NHEJ). Both pathways have been highly conserved throughout eukaryotic evolution, but no equivalent NHEJ system has been identified in prokaryotes. The NHEJ pathway requires a DNA end-binding component called Ku. We have identified bacterial Ku homologs and show that these proteins retain the biochemical characteristics of the eukaryotic Ku heterodimer. Furthermore, we show that bacterial Ku specifically recruits DNA ligase to DNA ends and stimulates DNA ligation. Loss of these proteins leads to hypersensitivity to ionizing radiation in Bacillus subtilis. These data provide evidence that many bacteria possess a DNA DSB repair apparatus that shares many features with the NHEJ system of eukarya and suggest that this DNA repair pathway arose before the prokaryotic and eukaryotic lineages diverged.

Paradoxes and dilemmas for stakeholder responsive firms in the extractive sector: lessons from the case of Shell and the Ogoni

Abstract: This paper examines some of the paradoxes and dilemmas facing firms in the extractive sector when they attempt to take on a more stakeholder-responsive orientation towards issues of environmental and social responsibility We describe the case of Shell and the Ogoni and attempt to draw out some of the lessons of that case for more sustainable operations in the developing world We argue that firms such as Shell, Rio Tinto and others may well exhibit increasingly stakeholder-responsive behaviours at the corporate, strategic level However for reasons of strategy, lack of competency or institutional will this increasing level of corporate responsiveness may not be mirrored effectively in dealings between subsidiary business units and their most important direct stakeholders: for example local communities and in the developing world We contrast the struggles of Shell to replicate its corporate stakeholder-responsiveness at the local level in Nigeria with the experiences of other firms that seem to have developed managerial capabilities at a somewhat deeper level throughout the firm with consequent benefits both for stakeholders and the business

Nanotubes in a Flash--Ignition and Reconstruction

Abstract: Single-walled carbon nanotubes (SWNTs) exhibit a range of unusual mechanical and electronic properties because of their unique structure and dimensions. Here we report another unusual property. We accidentally discovered that SWNTs ignite when exposed to a conventional photographic flash. This

Networks of value, commodities and regions: reworking divisions of labour in macro-regional economies

Abstract: The final, definitive version of this article has been published in the Journal, Progress in Human Geography 26 (1) 2002, Copyright SAGE Publications Ltd at: http://phg.sagepub.com/ [Full text of this article is not available in the UHRA]