293 research outputs found

    Academic citizenship and wellbeing: An exploratory cross-cultural study of South African and Swedish academic perceptions

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    Academic citizenship is, conceptually speaking, closely related to organisational citizenship behaviour, as both concepts can be regarded as consisting essentially of personal co-worker and organisational support behaviours. Academics across the world operate in widely divergent settings in different socioeconomic and political situations and higher education environments. Such differing circumstances might be expected to have a bearing on the priorities that academics face in different countries and the ways academic citizenship is understood. This paper uses a mixed methods approach to analyse perceptions of academic citizenship and employee well-being in one Swedish and one South African university which operate in starkly different socioeconomic circumstances. The findings of the exploratory study suggest that despite wide-ranging differences in socioeconomic environments between the two countries, there is a high degree of common understanding of the form and substance of academic citizenship and its bearing on well-being. Key words Academic citizenship, organisational citizenship behaviour, South African and Swedish universities, well-bein

    The human insulin receptor mRNA contains a functional internal ribosome entry segment.

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    Regulation of mRNA translation is an important mechanism determining the level of expression of proteins in eukaryotic cells. Translation is most commonly initiated by cap-dependent scanning, but many eukaryotic mRNAs contain internal ribosome entry segments (IRESs), providing an alternative means of initiation capable of independent regulation. Here, we show by using dicistronic luciferase reporter vectors that the 5'-UTR of the mRNA encoding human insulin receptor (hIR) contains a functional IRES. RNAi-mediated knockdown showed that the protein PTB was required for maximum IRES activity. Electrophoretic mobility shift assays confirmed that PTB1, PTB2 and nPTB, but not unr or PTB4, bound to hIR mRNA, and deletion mapping implicated a CCU motif 448 nt upstream of the initiator AUG in PTB binding. The IR-IRES was functional in a number of cell lines, and most active in cells of neuronal origin, as assessed by luciferase reporter assays. The IRES was more active in confluent than sub-confluent cells, but activity did not change during differentiation of 3T3-L1 fibroblasts to adipocytes. IRES activity was stimulated by insulin in sub-confluent cells. The IRES may function to maintain expression of IR protein in tissues such as the brain where mRNA translation by cap-dependent scanning is less effective

    SMART precision interferometry at 794 nm

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    Single-mode fibers have been used in the near-infrared to dramatically reduce calibration error for long-baseline interferometry. We have begun an effort to apply the advantages of spatial filtering at visible wavelengths for precision measurements of pulsating Cepheids using the IOTA interferometer. Rather than employing photometric taps to calibrate fluctuating coupling efficiency, we are using an "asymmetric" coupler which allows this calibration to be done without losing photons. The Single-Mode Asymmetric Recombination Technique (SMART) experiment has finished lab-testing, and has been installed at IOTA for full commissioning in Summer 2002. We report the results of lab characterization and first sky tests, as well as first fringes on a star using a visible-wavelength single-mode coupler. With both lab and sky experience using unpolarized light, we have found that circular silica fibers are quite practical for precision interferometric measurements. We conclude that circular fibers (as opposed to polarization maintaining fibers) have an undeserved poor reputation and that birefringence effects pose no significant difficulty

    Green Plants in the Red: A Baseline Global Assessment for the IUCN Sampled Red List Index for Plants

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    Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question ‘How threatened are plants?’ is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the world’s plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed

    Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using Data from the Second, Third, and Fourth LIGO Runs

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    We present the results of a search for short-duration gravitational-wave bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray satellite experiments during LIGO's S2, S3, and S4 science runs. The search involves calculating the crosscorrelation between two interferometer data streams surrounding the GRB trigger time. We search for associated gravitational radiation from single GRBs, and also apply statistical tests to search for a gravitational-wave signature associated with the whole sample. For the sample examined, we find no evidence for the association of gravitational radiation with GRBs, either on a single-GRB basis or on a statistical basis. Simulating gravitational-wave bursts with sine-gaussian waveforms, we set upper limits on the root-sum-square of the gravitational-wave strain amplitude of such waveforms at the times of the GRB triggers. We also demonstrate how a sample of several GRBs can be used collectively to set constraints on population models. The small number of GRBs and the significant change in sensitivity of the detectors over the three runs, however, limits the usefulness of a population study for the S2, S3, and S4 runs. Finally, we discuss prospects for the search sensitivity for the ongoing S5 run, and beyond for the next generation of detectors.Comment: 24 pages, 10 figures, 14 tables; minor changes to text and Fig. 2; accepted by Phys. Rev.

    Linear perturbative theory of the discrete cosmological N-body problem

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    We present a perturbative treatment of the evolution under their mutual self-gravity of particles displaced off an infinite perfect lattice, both for a static space and for a homogeneously expanding space as in cosmological N-body simulations. The treatment, analogous to that of perturbations to a crystal in solid state physics, can be seen as a discrete (i.e. particle) generalization of the perturbative solution in the Lagrangian formalism of a self-gravitating fluid. Working to linear order, we show explicitly that this fluid evolution is recovered in the limit that the initial perturbations are restricted to modes of wavelength much larger than the lattice spacing. The full spectrum of eigenvalues of the simple cubic lattice contains both oscillatory modes and unstable modes which grow slightly faster than in the fluid limit. A detailed comparison of our perturbative treatment, at linear order, with full numerical simulations is presented, for two very different classes of initial perturbation spectra. We find that the range of validity is similar to that of the perturbative fluid approximation (i.e. up to close to ``shell-crossing''), but that the accuracy in tracing the evolution is superior. The formalism provides a powerful tool to systematically calculate discreteness effects at early times in cosmological N-body simulations.Comment: 25 pages, 21 figure

    Search for gravitational waves from binary inspirals in S3 and S4 LIGO data

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    We report on a search for gravitational waves from the coalescence of compact binaries during the third and fourth LIGO science runs. The search focused on gravitational waves generated during the inspiral phase of the binary evolution. In our analysis, we considered three categories of compact binary systems, ordered by mass: (i) primordial black hole binaries with masses in the range 0.35 M(sun) < m1, m2 < 1.0 M(sun), (ii) binary neutron stars with masses in the range 1.0 M(sun) < m1, m2 < 3.0 M(sun), and (iii) binary black holes with masses in the range 3.0 M(sun)< m1, m2 < m_(max) with the additional constraint m1+ m2 < m_(max), where m_(max) was set to 40.0 M(sun) and 80.0 M(sun) in the third and fourth science runs, respectively. Although the detectors could probe to distances as far as tens of Mpc, no gravitational-wave signals were identified in the 1364 hours of data we analyzed. Assuming a binary population with a Gaussian distribution around 0.75-0.75 M(sun), 1.4-1.4 M(sun), and 5.0-5.0 M(sun), we derived 90%-confidence upper limit rates of 4.9 yr^(-1) L10^(-1) for primordial black hole binaries, 1.2 yr^(-1) L10^(-1) for binary neutron stars, and 0.5 yr^(-1) L10^(-1) for stellar mass binary black holes, where L10 is 10^(10) times the blue light luminosity of the Sun.Comment: 12 pages, 11 figure

    A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO

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    The first simultaneous operation of the AURIGA detector and the LIGO observatory was an opportunity to explore real data, joint analysis methods between two very different types of gravitational wave detectors: resonant bars and interferometers. This paper describes a coincident gravitational wave burst search, where data from the LIGO interferometers are cross-correlated at the time of AURIGA candidate events to identify coherent transients. The analysis pipeline is tuned with two thresholds, on the signal-to-noise ratio of AURIGA candidate events and on the significance of the cross-correlation test in LIGO. The false alarm rate is estimated by introducing time shifts between data sets and the network detection efficiency is measured with simulated signals with power in the narrower AURIGA band. In the absence of a detection, we discuss how to set an upper limit on the rate of gravitational waves and to interpret it according to different source models. Due to the short amount of analyzed data and to the high rate of non-Gaussian transients in the detectors noise at the time, the relevance of this study is methodological: this was the first joint search for gravitational wave bursts among detectors with such different spectral sensitivity and the first opportunity for the resonant and interferometric communities to unify languages and techniques in the pursuit of their common goal.Comment: 18 pages, IOP, 12 EPS figure
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