52 research outputs found

    Dissipationless Disk Accretion

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    We consider disk accretion resulting purely from the loss of angular momentum due to the outflow of plasma from a magnetized disk. In this limiting case, the dissipation due to the viscosity and finite electrical conductivity of the plasma can be neglected. We have obtained self-consistent, self-similar solutions for dissipationless disk accretion. Such accretion may result in the formation of objects whose bolometric luminosities are lower than the flux of kinetic energy in the ejected material.Comment: 17 pages, 6 figures, published in Astronomy Reports, Vol.49, No.1, 2005, p.57 (submitted September 13, 2003). Unfortunately, we did not upload the paper to astro-ph before, but since the topic is now of interest we feel that the paper would benefit the communit

    Research is needed to inform environmental management of hydrothermally inactive and extinct polymetallic sulfide (PMS) deposits

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    Polymetallic sulfide (PMS) deposits produced at hydrothermal vents in the deep sea are of potential interest to miners. Hydrothermally active sulfide ecosystems are valued for the extraordinary chemosynthetic communities that they support. Many countries, including Canada, Portugal, and the United States, protect vent ecosystems in their Exclusive Economic Zones. When hydrothermal activity ceases temporarily (dormancy) or permanently (extinction), the habitat and associated ecosystem change dramatically. Until recently, so-called "inactive sulfide" habitats, either dormant or extinct, received little attention from biologists. However, the need for environmental management of deep-sea mining places new imperatives for building scientific understanding of the structure and function of inactive PMS deposits. This paper calls for actions of the scientific community and the emergent seabed mining industry to i) undertake fundamental ecological descriptions and study of ecosystem functions and services associated with hydrothermally inactive PMS deposits, ii) evaluate potential environmental risks to ecosystems of inactive PMS deposits through research, and iii) identify environmental management needs that may enable mining of inactive PMS deposits. Mining of some extinct PMS deposits may have reduced environmental risk compared to other seabed mining activities, but this must be validated through scientific research on a case-by-case basis.FCT: IF/00029/2014/CP1230/CT0002/ UID/05634/2020/ CEECIND005262017/ UID/MAR/00350/2019; Direcao-Geral de Politica do Mar (DGPM) Mining2/2017/005/ Mining2/2017/001info:eu-repo/semantics/publishedVersio

    Computer-aided evaluation of the cellulite therapy effectivness based on thermal imaging

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    Cellulit jest częstym defektem kosmetycznym, występującym u większości kobiet w krajach wysoko rozwiniętych. Szacuje się, iż dotyka około 85% dojrzałych kobiet. Ze względu na powszechność tego schorzenia, jak również jego negatywny wpływ na samopoczucie oraz jakość życia kobiet, w literaturze fachowej poświęca mu się w ostatnich latach coraz więcej uwagi. Wspomniane prace dotyczą zarówno nowych sposobów diagnozowania lipodystrofii, jak również jej leczenia. Celem niniejszego eksperymentu było sprawdzenie przydatności metod termograficznych do oceny skuteczności 4-tygodniowej terapii antycellulitowej, przeprowadzonej z użyciem preparatu Body Lotion ,,Metamorphose 24”. Badaniami objęto 20 kobiet w wieku od 19 do 21 lat (średnia wieku 20,5±0,8). W przypadku każdej pacjentki odnotowano spadek zarówno liczby zmian lipodystroficznych, jak i ich powierzchni. Wyniki te potwierdziło badanie wizualno-palpacyjne. W pracy dowiedziono, że pomiary termowizyjne mogą z powodzeniem być stosowane do oceny terapii antycellulitowych.Cellulite is a common cosmetic defect occurring mostly in women from developed countries. It is estimated that it affects approximately 85% of mature women. Because of the high prevalence of this afflict, as well as its negative influence on the wellbeing and quality of life, it is widely discussed in the literature in last years. Described papers deal with both, new lipodystrophy diagnostic tools and treatment methods. The purpose of this experiment was to check whether thermography can be used for the evaluation of effectiveness of 4-week anti-cellulite therapy, conducted with usage of Body Lotion ,,Metamorphose 24” preparation. The experiment involved 20 women aged 19−21 (mean age 20.5±0.8). In case of each patient decrease in number of lipodystrophic changes as well as their area was observed. These results were confirmed by visual-palpation examination. It was proven that thermography can be successfully used for the evaluation of anti-celullite therapy

    Phase relations and melting of nominally ‘dry’ residual eclogites with variable CaO/Na(2)O from 3 to 5 GPa and 1250 to 1500 °C; implications for refertilisation of upwelling heterogeneous mantle

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    This study investigates the phase and melting relations of nominally ‘dry’ residual eclogites (Res2 and Res3), with varying bulk CaO/Na2O ratios (4 and 12, respectively), from ~160 (5 GPa) to ~90 km (3 GPa) depth. Garnet, clinopyroxene and minor quartz/coesite are subsolidus phases in both compositions. In contrast to Res2, in Res3, the proportions of garnet always exceeding those of clinopyroxene. This also leads to higher modal quartz/coesite in Res3 relative to Res2. In modelling melting along a near-adiabatic upwelling path with a mantle potential temperature of ~1360 °C, at 5 GPa, near-solidus andesitic Res3 partial melts are much less siliceous and sodic, and are more calcic and magnesian than the incipient dacitic melts of Res2. Continuously self-fluxed melting increases considerably from 4 to 3 GPa due to the increased breakdown of Ca-Eskolaite solid solution component in clinopyroxene along the adiabat. This causes a steepening of the solidus, but more-so for Res2 than for Res3. At 3 GPa, the near exhaustion of residual clinopyroxene causes higher melt productivity for Res3 (~60%) than for Res2 (~30%), despite both melts being of basaltic-andesite composition. Resulting Res3 melts are therefore significantly more calcic and magnesian, and less sodic than those of Res2 melts. As Res3 undergoes a higher degree of melting relative to Res2 during adiabatic ascent, Res3 eclogitic residues become significantly more refractory; with relatively higher Mg# and grossular in garnet, higher Mg# and Ca-tschermaks, and lower jadeite components of clinopyroxene, and higher garnet/clinopyroxene ratios than eclogitic Res2 residuals. In upwelling heterogenous mantle domains, the siliceous eclogitic melts formed within a body of eclogite will react with encapsulating mantle peridotite, effectively refertilising it and producing hybrid pyroxene- and garnet-rich rocks. Subsequent melting of these sources may lead to compositionaly diverse primitive mantle-derived magmas, with high Ca/Al and low Na/Ca signatures indicators of preferential melting of a heterogeneous mantle, previously refertilised by recycled Ca-rich oceanic crustal material, and primitive magmas with low Ca/Al and high Na/Ca derived from melting of mantle with a ‘normal recycled crustal material signature’. Thus, compositional magma diversity may directly reflect precursor compositions of the mantle source region.Anja Rosenthal, Gregory M. Yaxley, Wilson A. Crichton, István J. Kovács, Carl Spandler, Joerg Hermann, Judit K. Sándorné, Estelle Rose-Koga, Anne-Aziliz Pellete

    Organic, gas, and element geochemistry of hydrothermal fluids of the newly discovered extensive hydrothermal area in the Wallis and Futuna Region (SW Pacific)

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    International audienceTwo newly discovered hydrothermal vent fields of the Wallis and Futuna region, Kulo Lasi and Fatu Kapa, were sampled for fluid geochemistry. A great geochemical diversity was observed and assigned to the diversity of lithologies as well as the occurrence of various processes. Kulo Lasi fluids likely formed by interaction with fresh volcanic rocks, phase separation, and mixing with magmatic fluid. Conversely, the geochemistry of the Fatu Kapa fluids would be mostly due to water/felsic lavas reactions. In terms of organic geochemistry, fluids from both fields were found to be enriched in formate, acetate, and semivolatile organic compounds (SVOCs): n-alkanes, n-fatty acids, and polyaromatic hydrocarbons (PAHs). Concentrations of SVOCs reached a few ppb at most. The distribution patterns of SVOCs indicated that several processes and sources, at once of biogenic, thermogenic, and abiogenic types, likely controlled organic geochemistry. Although the contribution of each process remains unknown, the mere presence of organics at the μM level has strong implications for metal dispersion (cycles), deposition (ore-forming), and bioavailability (ecosystems), especially as our fluxes estimations suggest that back-arc hosted vent fields could contribute as much as MOR to the global ocean heat and mass budget
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