8,239 research outputs found

    Annotated bibliography on hypoxia and its effects on marine life, with emphasis on the Gulf of Mexico

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    This bibliography contains 73 annotated references from publications and reports concerning hypoxia, .,; 2.0 ppm dissolved oxygen concentration, in the Gulf of Mexico. Instances of hypoxia from similar habitats and the effects of low oxygen levels on marine or estuarine organisms are also included. (PDF file contains 15 pages.

    South-West extension of the hard X-ray emission from the Coma cluster

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    We explore the morphology of hard (18-30 keV) X-ray emission from the Coma cluster of galaxies. We analyze a deep (1.1 Ms) observation of the Coma cluster with the ISGRI imager on board the \emph{INTEGRAL} satellite. We show that the source extension in the North-East to South-West (SW) direction (17\sim 17') significantly exceeds the size of the point spread function of ISGRI, and that the centroid of the image of the source in the 18-30 keV band is displaced in the SW direction compared to the centroid in the 1-10 keV band. To test the nature of the SW extension we fit the data assuming different models of source morphology. The best fit is achieved with a diffuse source of elliptical shape, although an acceptable fit can be achieved assuming an additional point source SW of the cluster core. In the case of an elliptical source, the direction of extension of the source coincides with the direction toward the subcluster falling onto the Coma cluster. If the SW excess is due to the presence of a point source with a hard spectrum, we show that there is no obvious X-ray counterpart for this additional source, and that the closest X-ray source is the quasar EXO 1256+281, which is located 6.16.1' from the centroid of the excess. The observed morphology of the hard X-ray emission clarifies the nature of the hard X-ray "excess" emission from the Coma cluster, which is due to the presence of an extended hard X-ray source SW of the cluster core.Comment: 7pages, 10 figure

    Adaptive plasticity in the mouse mandible

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    BACKGROUND: Plasticity, i.e. non-heritable morphological variation, enables organisms to modify the shape of their skeletal tissues in response to varying environmental stimuli. Plastic variation may also allow individuals to survive in the face of new environmental conditions, enabling the evolution of heritable adaptive traits. However, it is uncertain whether such a plastic response of morphology constitutes an evolutionary adaption itself. Here we investigate whether shape differences due to plastic bone remodelling have functionally advantageous biomechanical consequences in mouse mandibles. Shape characteristics of mandibles from two groups of inbred laboratory mice fed either rodent pellets or ground pellets mixed with jelly were assessed using geometric morphometrics and mechanical advantage measurements of jaw adductor musculature. RESULTS: Mandibles raised on diets with differing food consistency showed significant differences in shape, which in turn altered their biomechanical profile. Mice raised on a soft food diet show a reduction in mechanical advantage relative to mice of the same inbred strain raised on a typical hard food diet. Further, the soft food eaters showed lower levels of integration between jaw regions, particularly between the molar and angular region relative to hard food eaters. CONCLUSIONS: Bone remodelling in mouse mandibles allows for significant shifts in biomechanical ability. Food consistency significantly influences this process in an adaptive direction, as mice raised on hard food develop jaws better suited to handle hard foods. This remodelling also affects the organisation of the mandible, as mice raised on soft food appear to be released from developmental constraints showing less overall integration than those raised on hard foods, but with a shift of integration towards the most solicited regions of the mandible facing such a food, namely the incisors. Our results illustrate how environmentally driven plasticity can lead to adaptive functional changes that increase biomechanical efficiency of food processing in the face of an increased solicitation. In contrast, decreased demand in terms of food processing seems to release developmental interactions between jaw parts involved in mastication, and may generate new patterns of co-variation, possibly opening new directions to subsequent selection. Overall, our results emphasize that mandible shape and integration evolved as parts of a complex system including mechanical loading food resource utilization and possibly foraging behaviour

    Decoherence and entropy of primordial fluctuations II. The entropy budget

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    We calculate the entropy of adiabatic perturbations associated with a truncation of the hierarchy of Green functions at the first non trivial level, i.e. in a self-consistent Gaussian approximation. We give the equation governing the entropy growth and discuss its phenomenology. It is parameterized by two model-dependent kernels. We then examine two particular inflationary models, one with isocurvature perturbations, the other with corrections due to loops of matter fields. In the first model the entropy grows rapidely, while in the second the state remains pure (at one loop).Comment: 28 page

    Is the distribution of Amblyomma variegatum influenced by interspecific competition with Amblyomma hebraeum? Preliminary study: distribution range in Mozambique

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    Widely spread in intertropical and subtropical areas of Africa, the southern distribution of Amblyomma variegatum in Mozambique seems to have its limit around the Save River, at the 22nd parallel South. This area also corresponds to the northern limit of another Amblyomma tick, A. hebraeum. Several authors use to explain the absence of A. variegatum more southwards by an interspecific competition with A. hebraeum. Whereas only A. variegatum is known to favor dermatophilosis, a skin disease that can cause important burden in ruminants, both species are good vectors of Ehrlichia ruminantium, the bacteria causing heartwater, a fatal disease of ruminants representing a major constraint for livestock development in Africa. However, their vector competence may be different and vary according to the strain of E. ruminantium. As a result, the bio-ecology and distribution of those vectors in the field may result in specific epidemiological patterns for the diseases they transmit and are important to understand to adopt proper sanitary control and prevention measures. Little information on current (last decade) Amblyomma distribution in Mozambique is available, and little is known on the factors influencing their distribution. More especially, the existence of a distribution overlap, as observed in Zimbabwe is not known in Mozambique. Indeed the extent of this overlap and the distribution of A. variegatum and A. hebraeum in this particular area represent useful information to assess potential interspecific competition. The objective of this study is to assess the current distribution of A. variegatum and A. hebraeum in this country and to better locate and characterize species limitation ranges around the Save River with a view to further identify the factors influencing their distribution. First, an exhaustive literature review was made to collect all published and unpublished data relating to the distribution of A. variegatum and A. hebraeum in Africa. A field entomological survey was then conducted in Mozambique between February and April 2012 to identify ticks collected on cattle, in the Inhambane, Manica and Sofala provinces, nearby the Save River. Sampling sites included dip-tanks and corridors, used for acaricides treatment by neighboring farmers, as well as farms which were selected by the local Veterinary Service. In each study site, about 60 animals were carefully examined for ticks presence and abundance, mostly in corridors and on 10 laid-down animals most heavily infested by ticks. Ticks, males and females, were collected to confirm species identification. Data on domestic ruminant population and movements as well as breeding practices including tick control were also collected through interviews with farmers and local and central veterinary services. The epidemiological unit is the sampling site. A site was considered positive for a given tick species if at least one animal was infested by at least one tick of that species, otherwise, it was considered negative. To better assess species presence in their limit of distribution, an attempt was made to interpret presence and absence data to distinguish well-established or occasionally present population and likely not detected or absent populations. This was done considering sampling method, tick abundance, study period against phenology, as well as other information: last acaricide treatment, animal introduction, etc. Data were entered in Access database and displayed on a Geographic Information System, ArcMap9.3 A map of the current A. variegatum and A. hebraeum distribution was produced and included 103 positive sites out of 113 sampled between 2000 and 2012. The field survey conducted in 30 study sites evidenced a distribution overlap of 30km (western side) to 100km (eastern side) width, along a slanting line northwest-southeast accross the Save River, where both species were found in three sites and coinfestation of few animals was observed. The current distribution o

    Assimilating SAR-derived water level data into a hydraulic model: a case study

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    Satellite-based active microwave sensors not only provide synoptic overviews of flooded areas, but also offer an effective way to estimate spatially distributed river water levels. If rapidly produced and processed, these data can be used for updating hydraulic models in near real-time. The usefulness of such approaches with real event data sets provided by currently existing sensors has yet to be demonstrated. In this case study, a Particle Filter-based assimilation scheme is used to integrate ERS-2 SAR and ENVISAT ASAR-derived water level data into a one-dimensional (1-D) hydraulic model of the Alzette River. Two variants of the Particle Filter assimilation scheme are proposed with a global and local particle weighting procedure. The first option finds the best water stage line across all cross sections, while the second option finds the best solution at individual cross sections. The variant that is to be preferred depends on the level of confidence that is attributed to the observations or to the model. The results show that the Particle Filter-based assimilation of remote sensing-derived water elevation data provides a significant reduction in the uncertainty at the analysis step. Moreover, it is shown that the periodical updating of hydraulic models through the proposed assimilation scheme leads to an improvement of model predictions over several time steps. However, the performance of the assimilation depends on the skill of the hydraulic model and the quality of the observation data

    High Expression of hTERT and Stemness Genes in BORIS/CTCFL Positive Cells Isolated from Embryonic Cancer Cells.

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    BORIS/CTCFL is a member of cancer testis antigen family normally expressed in germ cells. In tumors, it is aberrantly expressed although its functions are not completely well-defined. To better understand the functions of BORIS in cancer, we selected the embryonic cancer cells as a model. Using a molecular beacon, which specifically targets BORIS mRNA, we demonstrated that BORIS positive cells are a small subpopulation of tumor cells (3-5% of total). The BORIS-positive cells isolated using BORIS-molecular beacon, expressed higher telomerase hTERT, stem cell (NANOG, OCT4, SOX2) and cancer stem cell marker genes (CD44 and ALDH1) compared to the BORIS-negative tumor cells. In order to define the functional role of BORIS, stable BORIS-depleted embryonic cancer cells were generated. BORIS silencing strongly down-regulated the expression of hTERT, stem cell and cancer stem cell marker genes. Moreover, the BORIS knockdown increased cellular senescence in embryonic cancer cells, revealing a putative role of BORIS in the senescence biological program. Our data indicate an association of BORIS expressing cells subpopulation with the expression of stemness genes, highlighting the critical role played by BORIS in embryonic neoplastic disease
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