25,029 research outputs found

    An ion probe study of the sulphur isotopic composition of Fe-Ni sulphides in CM carbonaceous chondrites

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    From the Introduction: The CM chondrites have endured variable degrees of aqueous alteration [1] which has changed their original mineralogy. A detailed study of the petrology and mineralogy of the sulphides in a suite of increasingly aqueously altered CMs, combined with sulphur isotope data measured in situ, can provide clues as to whether differences in the CM group are a result of different degrees of aqueous alteration, or whether they are the result of nebular heterogeneity

    Modified sorting technique to mitigate the collateral mortality of trawled school prawns (Metapenaeus macleayi)

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    The potential for changes to onboard handling practices in order to improve the fate of juvenile school prawns (Metapenaeus macleayi) discarded during trawling were investigated in two Australian rivers (Clarence and Hunter) by comparing a purpose-built, water-filled sorting tray against a conventional dry tray across various conditions, including the range of typical delays before the start of sorting the catch (2 min vs. 15 min). Juvenile school prawns (n= 5760), caught during 32 and 16 deployments in each river, were caged and sacrificed at four times: immediately (T0), and at 24 (T24), 72 (T72), and 120 (T12 0) hours after having been discarded. In both rivers, most mortalities occurred between T0 and T24 and, after adjusting for control deaths (<12%), were greatest for the 15-min conventional treatment (up to 41% at T120). Mixed-effects logistic models revealed that in addition to the sampling time, method of sorting, and delay in sorting, the weight of the catch, salinity, and percentage cloud cover were significant predictors of mortality. Although trawling caused some mortalities and comparable stress (measured as L -lactate) in all school prawns, use of the water tray lessened the negative impacts of some of the above factors across both the 2-min and 15-min delays in sorting so that the overall discard mortality was reduced by more than a third. When used in conjunction with selective trawls, widespread application of the water tray should help to improve the sustainability of trawling for school prawns

    On the Optical -- X-ray correlation from outburst to quiescence in Low Mass X-ray Binaries: the representative cases of V404 Cyg and Cen X-4

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    Low mass X-ray binaries (LMXBs) show evidence of a global correlation of debated origin between X-ray and optical luminosity. We study for the first time this correlation in two transient LMXBs, the black hole V404 Cyg and the neutron star Cen X-4, over 6 orders of magnitude in X-ray luminosity, from outburst to quiescence. After subtracting the contribution from the companion star, the Cen X-4 data can be described by a single power law correlation of the form LoptLX0.44L_{opt}\propto\,L_{X}^{0.44}, consistent with disk reprocessing. We find a similar correlation slope for V404 Cyg in quiescence (0.46) and a steeper one (0.56) in the outburst hard state of 1989. However, V404 Cyg is about 160280160-280 times optically brighter, at a given 393-9 keV X-ray luminosity, compared to Cen X-4. This ratio is a factor of 10 smaller in quiescence, where the normalization of the V404 Cyg correlation also changes. We show that once the bolometric X-ray emission is considered and the known main differences between V404 Cyg and Cen X-4 are taken into account (a larger compact object mass, accretion disk size, and the presence of a strong jet contribution in the hard state for the black hole system) the two systems lie on the same correlation. In V404 Cyg, the jet dominates spectrally at optical-infrared frequencies during the hard state, but makes a negligible contribution in quiescence, which may account for the change in its correlation slope and normalization. These results provide a benchmark to compare with data from the 2015 outburst of V404 Cyg and, potentially, other transient LMXBs as well.Comment: Accepted on ApJ, 12 pages, 4 figures, 4 table

    Tourist Shopping Activities and Development of Travel Sophistication

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    An ethnographic research approach was used to investigate shopping and consumption behavior of international tourists. This research informed a model that positions a tourist\u27s market-place activity as an evolving process that parallels and supports their advance in travel sophistication. The model illustrates that shopping and consumption may originate as a leisure-recreational pursuit for tourists but is transformed into a learning activity that facilitates their assimilation of a host culture. This, in turn, plays an important role in the tourist\u27s development of travel self-efficacy, as well as their motivation for return trips

    Embracing the power of belongingness: A descriptive mixed method research study

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    Background: Clinical placements should provide nursing students with a positive environment for learning in which they develop a framework for future practice. The literature articulates that this is not always the case. The objective of this research was to develop, implement and evaluate a new education seminar for nursing staff—The Art of Clinical Supervision (ACS), designed for nurses to provide a toolbox of strategies to better support students whilst on clinical placement. The ACS was presented in Western Australia, in both metropolitan and regional health services, in both the public and private health sector. This sample consisted of 199 registered nurses working in areas that actively placed nursing students. A mixed method approach incorporated surveys, online reflections and interviews. This article will outline the qualitative phase of this mixed method research. Analysis of the qualitative data determined that participants perceived the seminar as a helpful strategy for improving nursing practice in relation to student supervision. In particular, the concept of belongingness was viewed as an important component to improving attitudes and placement learning, the focus of this article. The implications of belongingness and how this can be promoted is an important concept that nursing leaders, education providers and clinical supervisors need to consider

    Repetitive Segmental Structure of the Transducin β Subunit: Homology with the CDC4 Gene and Identification of Related mRNAs

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    Retinal transducin, a guanine nucleotide regulatory protein (referred to as a G protein) that activates a cGMP phosphodiesterase in photoreceptor cells, is comprised of three subunits. We have identified and analyzed cDNA clones of the bovine transducin β subunit that may be highly conserved or identical to that in other G proteins. From the cDNA nucleotide sequence of the entire coding region, the primary structure of a 340-amino acid protein was deduced. The encoded β subunit has a Mr of 37,375 and is comprised of repetitive homologous segments arranged in tandem. Furthermore, significant homology in primary structure and segmental sequence exists between the β subunit and the yeast CDC4 gene product. The Mr 37,375 β subunit polypeptide is encoded by a 2.9-kilobase (kb) mRNA. However, there exists in retina other β-related mRNAs that are divergent from the 2.9-kb mRNA on the basis of oligonucleotide and primer-extended probe hybridizations. All mammalian tissues and clonal cell lines that have been examined contain at least two β-related mRNAs, usually 1.8 and 2.9 kb in length. These results suggest that the mRNAs are the processed products of a small number of closely related genes or of a single highly complex β gene

    Future climate stimulates population out-breaks by relaxing constraints on reproduction

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    When conditions are stressful, reproduction and population growth are reduced, but when favourable, reproduction and population size can boom. Theory suggests climate change is an increasingly stressful environment, predicting extinctions or decreased abundances. However, if favourable conditions align, such as an increase in resources or release from competition and predation, future climate can fuel population growth. Tests of such population growth models and the mechanisms by which they are enabled are rare. We tested whether intergenerational increases in population size might be facilitated by adjustments in reproductive success to favourable environmental conditions in a large-scale mesocosm experiment. Herbivorous amphipod populations responded to future climate by increasing 20 fold, suggesting that future climate might relax environmental constraints on fecundity. We then assessed whether future climate reduces variation in mating success, boosting population fecundity and size. The proportion of gravid females doubled, and variance in phenotypic variation of male secondary sexual characters (i.e. gnathopods) was significantly reduced. While future climate can enhance individual growth and survival, it may also reduce constraints on mechanisms of reproduction such that enhanced intra-generational productivity and reproductive success transfers to subsequent generations. Where both intra and intergenerational production is enhanced, population sizes might boom.Katherine A. Heldt, Sean D. Connell, Kathryn Anderson, Bayden D. Russell, Pablo Mungui
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