2,075 research outputs found

    The formation of planetary disks and winds: an ultraviolet view

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    Planetary systems are angular momentum reservoirs generated during star formation. This accretion process produces very powerful engines able to drive the optical jets and the molecular outflows. A fraction of the engine energy is released into heating thus the temperature of the engine ranges from the 3000K of the inner disk material to the 10MK in the areas where magnetic reconnection occurs. There are important unsolved problems concerning the nature of the engine, its evolution and the impact of the engine in the chemical evolution of the inner disk. Of special relevance is the understanding of the shear layer between the stellar photosphere and the disk; this layer controls a significant fraction of the magnetic field building up and the subsequent dissipative processes ougth to be studied in the UV. This contribution focus on describing the connections between 1 Myr old suns and the Sun and the requirements for new UV instrumentation to address their evolution during this period. Two types of observations are shown to be needed: monitoring programmes and high resolution imaging down to, at least, milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure

    A robust model for rapidly varying flows over movable bottom with suspended and bedload transport: modelling and numerical approach

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    We propose a coupled model for suspended and bedload sediment transport in the shallow water framework. The model is deduced under hydrostatic pressure assumptions and will not assume any Bossinesq hypothesis. The numerical resolution is carried out in a segregated way. First the underlying system of conservation laws is solved by using a first order path-conservative Riemann solver. Then, the source terms corresponding with the erosion and depositions rates are approximated in a semi-implicit way. The final scheme preserves the positivity of the density. Several numerical experiments were carried out in order to validate the model and the numerical scheme. The results obtained are in good agreement with the experimental data

    Crystal Structure and Physical Properties of U3T3Sn4 (T = Ni, Cu) Single-Crystals

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    Heat capacity experiments, crystal structure determination and transmission electron microscopy have been carried out on U3Cu3Sn4 single-crystals. U3Cu3Sn4 was confirmed to be a heavy-fermion antiferromagnet (TN=13(1) K) with a low temperature electronic heat capacity coefficient gamma=390 mJ/molUK2. Low temperature heat capacity experiments on a U3Ni3Sn4 single-crystal indicate that below 0.4 K there is a crossover between the previously observed non-Fermi liquid behavior and a Fermi liquid state.Comment: 12 pages (incl. 2 tables & 4 figures), to appear in Physica

    In-hospital mortality of non-st segment elevation myocardial infarction in a Puerto Rican population

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    Introduction: Currently, there is limited published information on in-hospital mortality regarding ST segment elevation and non-ST segment elevation myocardial infarction. This information is even scarcer on the Hispanic population. We aim to study if there is a difference on in-hospital mortality between ST elevation myocardial infarction (STEMI) and non-ST elevation myocardial infarction (NSTEMI) in a mostly Hispanic population. Methods: A secondary data analysis of a non-concurrent prospective study was performed using the Puerto Rican Heart Attack study database. Dependent variable was in-hospital mortality and independent variable was type of myocardial infarction (STEMI or NSTEMI). We conducted, sequentially, a descriptive, bivariate and multivariate analysis. The chi-squared test was used to compare categorical variables and t-test for continuous variables. Finally, a logistic regression model was used to perform the multivariate analysis. Results: From the 838 Puerto Rican patients hospitalized with ST classification, 310 (37%) were diagnosed with STEMI. Patients with STEMI were younger (65 years vs 68 years; p=0.008), more likely to receive invasive treatment (47.9% vs 27.5%, p<0.001), and less likely to have a history of hypertension (72.5% vs 79.0%, p=0.033) compared to NSTEMI patients. For every 1- year increase in age, there is a 4% increase in in-hospital mortality. Patients with hyperlipidemia were approximately two times more likely to die in the hospital compared to patients without hyperlipidemia. In the unadjusted analysis, there was no significant association between STEMI and NSTEMI patients and in-hospital mortality. After adjusting for confounders, patients with STEMI had twice the risk of dying than those with NSTEMI. Conclusions: Findings from this study suggest that Puerto Ricans with STEMI have double the risk of in-hospital mortality than NSTEMI patients. Our findings were similar to those reported in the literature. A timely recognition of at-risk patients, especially among STEMI patients, may help reduce short-term morality among patients hospitalized with acute myocardial infarction in Puerto Rico

    Assessing the responses of exploited marine populations in a context of rapid climate change: the case of blackspot seabream from Strait of Gibraltar.

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    Assessing the response of exploited marine populations in a context of rapid climate change: the case of blackspot seabream from the Strait of Gibraltar.— There is a growing concern over the decline of fisheries and the possibility of the decline becoming worse due to climate change. Studies on small–scale fisheries could help to improve our understanding of the effect of climate on the ecology of exploited stocks. The Strait of Gibraltar is an important fishery ground for artisanal fleets. In this area, b lackspot seabream ( Pagellus bogaraveo ) is the main species targeted by artisanal fisheries in view of its relevance in landed weight. The aims of this study were to explore the possible effects of two atmospheric oscillations, the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO), on the capture of blackspot seabream in the Strait of Gibraltar, to determine their association with oceanographic conditions, and to improve our knowledge about the possible effects of climate change on fisheries ecology so that fishery management can be improved. We used two types of data from different sources: (i) landings per unit of effort reported from a second working group between Morocco and Spain on Pagellus bogaraveo in the Gibraltar Strait area, for the period 1983–2011 , and (ii) the recorded blackspot seabream landings obtained from the annual fisheries statistics published by the Junta de Andalucía (Andalusian Regional Government). Our results indicate that the long–term landing of blackspot seabream in the Strait of Gibraltar is closely associated with atmospheric oscillations. Thus, prolonged periods of positive trends in the NAO and AO could favour high fishery yields. In contrast, negative trends in NAO and AO could drastically reduce yield.Postprint0,000

    Analysis of the effect of atmospheric oscillations on physical condition of pre–reproductive bluefin tuna from the Strait of Gibraltar

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    Analysis of the effect of atmospheric oscillations on physical condition of pre–reproductive bluefin tuna from the Strait of Gibraltar .— The aim of this study was to explore the possible effects of atmospheric oscillations: North Atlantic Oscillation (NAO) and Arctic Oscillation (AO), on the physical condition of bluefin tuna ( Thunnus thynnus ). We estimated a fitness ratio from 3,501 pairs of length–weight data based on bluefin tuna caught in bait–boat fisheries before the spawning season (January, February and March), for each length class and year. In order to obtain a single fitness ratio (K–mean) per year we determined the average for all length classes. We also evaluated Le Cren’s condition index (K LC ). We observed significant positive correlations between the atmospheric oscillations and both physical condition indexes. In the case of K–mean, the AO explained 75% of the observed variability. Regarding K LC , the NAO explained approximately 73% of the observed variability, while the AO explained 70% of the observed variability. The increase in physical conditions of bluefin tuna in association with positive atmospheric oscillations could be mediated by the increase in the prevalence of strong trade winds. We concluded that the increase in the prevalence of strong westerly winds, mediated by a positive AO or NAO, favours the trip from the Atlantic to the Mediterranean by reducing energy costs due to migration and by increasing the supply of nutrients at the surface by the mixing of deep water and surface water in local areas such as the Strait of Gibraltar.Postprin

    Sub-terahertz, microwaves and high energy emissions during the December 6, 2006 flare, at 18:40 UT

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    The presence of a solar burst spectral component with flux density increasing with frequency in the sub-terahertz range, spectrally separated from the well-known microwave spectral component, bring new possibilities to explore the flaring physical processes, both observational and theoretical. The solar event of 6 December 2006, starting at about 18:30 UT, exhibited a particularly well-defined double spectral structure, with the sub-THz spectral component detected at 212 and 405 GHz by SST and microwaves (1-18 GHz) observed by the Owens Valley Solar Array (OVSA). Emissions obtained by instruments in satellites are discussed with emphasis to ultra-violet (UV) obtained by the Transition Region And Coronal Explorer (TRACE), soft X-rays from the Geostationary Operational Environmental Satellites (GOES) and X- and gamma-rays from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz impulsive component had its closer temporal counterpart only in the higher energy X- and gamma-rays ranges. The spatial positions of the centers of emission at 212 GHz for the first flux enhancement were clearly displaced by more than one arc-minute from positions at the following phases. The observed sub-THz fluxes and burst source plasma parameters were found difficult to be reconciled to a purely thermal emission component. We discuss possible mechanisms to explain the double spectral components at microwaves and in the THz ranges.Comment: Accepted version for publication in Solar Physic

    Skin diseases in cetaceans. Scientific Committee document SC/60/DW8, International Whaling Commission, June 2008, Santiago, Chile

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    Micro-organisms that are known or suspected to cause skin diseases in cetaceans are briefly reviewed. Viruses belonging to four families i.e. Caliciviridae, Herpesviridae, Papillomaviridae and Poxviridae were detected by electron microscopy, histology and molecular techniques in vesicular skin lesions, black dots perceptible by the touch, warts and tattoos in several species of odontocetes and mysticetes. Herpesviruses, poxviruses and likely a cutaneous papillomavirus are cetacean specific. Among bacteria, Dermatophilus spp., Erysipelothrix rhusiopathiae, Mycobacterium marinum, Pseudomonas spp., Streptococcus iniae and Vibrio spp. were isolated from ulcerative dermatitis, pyogranulomatous dermatitis and panniculitis, diamond skin disease and slow-healing ulcers and abscesses. Aeremonas spp., Mycobacterium marinum, Pseudomonas spp. and Vibrio spp. are normally present in the marine environment while Erysipelothrix rhusiopathiae and Streptococcus iniae are fish pathogens that may also infect captive dolphins. Most seem to be opportunistic pathogens, exploiting some break-down in the host’s defenses to initiate an infection. Selection of antibiotic-resistant bacteria through the prophylactic use of antibiotics in aquaculture is suggested to be a growing problem in South America and may account for the emergence of unusual cutaneous conditions. At least four groups of fungi i.e. Candida albicans, Fusarium spp., Trichophyton spp. and Lacazia loboi cause skin diseases. Candidiasis occurs predominantly in captive odontocetes. The lesions are often localized around the body orifices and may become extensive, granulating and ulcerated. Fusariosis is characterized by firm, erythematous, cutaneous nodules. Trichophyton spp. was isolated from widespread superficial nodules in an Atlantic T. truncates kept in captivity in Japan. Lobomycosis or lacaziosis is distinguished by grayish, whitish to slightly pink, verrucuous lesions, often in pronounced relief that may ulcerate. While initially described only in Tursiops truncates and Sotalia guianensis from the Americas, lobomycosis seems to be expanding to other continents. The role of ballast water in transporting fungi worldwide should be investigated. Finally, ciliated protozoans, likely Kyaroikeus cetarius, caused invasive dermatitis in small cetaceans from the USA and Korea. The aquatic environment of cetaceans is naturally home to bacteria and fungi but cetacean skin has several mechanisms to impede invasion. Chemical contaminants may affect natural skin barriers and depress the immune system. Wounds and specific viral infection (poxvirus, herpesvirus) may provide routes of entry
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