172 research outputs found

    Chromatographic separations of niobium, tantalum, molybdenum, and tungsten

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    Castigo y responsabilidad: ensayos de filosofía del derecho

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    - Divulgação dos SUMÁRIOS das obras recentemente incorporadas ao acervo da Biblioteca Ministro Oscar Saraiva do STJ. Em respeito à Lei de Direitos Autorais, não disponibilizamos a obra na íntegra.- Localização na estante: 343:340.12 H325

    Super and massive AGB stars - IV. Final fates - Initial to final mass relation

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    We explore the final fates of massive intermediate-mass stars by computing detailed stellar models from the zero age main sequence until near the end of the thermally pulsing phase. These super-AGB and massive AGB star models are in the mass range between 5.0 and 10.0 Msun for metallicities spanning the range Z=0.02-0.0001. We probe the mass limits M_up, M_n and M_mass, the minimum masses for the onset of carbon burning, the formation of a neutron star, and the iron core-collapse supernovae respectively, to constrain the white dwarf/electron-capture supernova boundary. We provide a theoretical initial to final mass relation for the massive and ultra-massive white dwarfs and specify the mass range for the occurrence of hybrid CO(Ne) white dwarfs. We predict electron-capture supernova (EC-SN) rates for lower metallicities which are significantly lower than existing values from parametric studies in the literature. We conclude the EC-SN channel (for single stars and with the critical assumption being the choice of mass-loss rate) is very narrow in initial mass, at most approximately 0.2 Msun. This implies that between ~ 2-5 per cent of all gravitational collapse supernova are EC-SNe in the metallicity range Z=0.02 to 0.0001. With our choice for mass-loss prescription and computed core growth rates we find, within our metallicity range, that CO cores cannot grow sufficiently massive to undergo a Type 1.5 SN explosion.Comment: 15 pages, 7 figures, accepted for publication in MNRA

    Sulindac Enhances the Killing of Cancer Cells Exposed to Oxidative Stress

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    BACKGROUND:Sulindac is an FDA-approved non-steroidal anti-inflammatory drug (NSAID) that affects prostaglandin production by inhibiting cyclooxygenases (COX) 1 and 2. Sulindac has also been of interest for more than decade as a chemopreventive for adenomatous colorectal polyps and colon cancer. PRINCIPAL FINDINGS:Pretreatment of human colon and lung cancer cells with sulindac enhances killing by an oxidizing agent such as tert-butyl hydroperoxide (TBHP) or hydrogen peroxide. This effect does not involve cyclooxygenase (COX) inhibition. However, under the conditions used, there is a significant increase in reactive oxygen species (ROS) within the cancer cells and a loss of mitochondrial membrane potential, suggesting that cell death is due to apoptosis, which was confirmed by Tunel assay. In contrast, this enhanced killing was not observed with normal lung or colon cells. SIGNIFICANCE:These results indicate that normal and cancer cells handle oxidative stress in different ways and sulindac can enhance this difference. The combination of sulindac and an oxidizing agent could have therapeutic value

    Primordial to extremely metal-poor AGB and Super-AGB stars: White dwarf or supernova progenitors?

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    Getting a better understanding of the evolution and nucleosynthetic yields of the most metal-poor stars ( Z ¿ 10 ¿5 ) is critical because they are part of the big picture of the history of the primitive universe. Yet many of the remaining unknowns of stellar evolution lie in the birth, life, and death of these objects. We review stellar evolution of intermediate-mass Z = 10 ¿5 models existing in the literature, with a particular focus on the problem of their final fates. We emphasise the importance of the mixing episodes between the stellar envelope and the nuclearly processed core, which occur after stars exhaust their central He (second dredge-up and dredge-out episodes). The depth and efficiency of these episodes are critical to determine the mass limits for the formation of electron-capture SNe. Our knowledge of these phenomena is not complete because they are strongly affected by the choice of input physics. These uncertainties affect stars in all mass and metallicity ranges. However, difficulties in calibration pose additional challenges in the case of the most metal-poor stars. We also consider the alternative SN I1/2 channel to form SNe out of the most metal-poor intermediate-mass objects. In this case, it is critical to understand the thermally pulsing Asymptotic Giant Branch evolution until the late stages. Efficient second dredge-up and, later, third dredge-up episodes could be able to pollute stellar envelopes enough for the stars to undergo thermal pulses in a way very similar to that of higher initial Z objects. Inefficient second and/or third dredge-up may leave an almost pristine envelope, unable to sustain strong stellar winds. This may allow the H-exhausted core to grow to the Chandrasekhar mass before the envelope is completely lost, and thus let the star explode as an SN I1/2. After reviewing the information available on these two possible channels for the formation of SNe, we discuss existing nucleosynthetic yields of stars of metallicity Z = 10 ¿5 and present an example of nucleosynthetic calculations for a thermally pulsing Super-Asymptotic Giant Branch star of Z = 10 ¿5 . We compare theoretical predictions with observations of the lowest [Fe/H] objects detected. The review closes by discussing current open questions as well as possible fruitful avenues for future research.Peer ReviewedPostprint (author's final draft

    The depth of sewage filters and the degree of purification

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    "Bulletins of the state Water survey": 1 leaf at end.At head of title: State of Illinois. Department of registration and education. Division of the state Water survey. A.M. Buswell, chief...Bibliography: p. 78-80.Enumeration continues from preceding title

    Crop Updates 2006 - Katanning

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    This session covers sixteen papers from different authors 2006 SEASONAL OUTLOOK, David Stephens and Michael Meuleners, Department of Agriculture Review of climate model summaries reported in the Department of Agriculture’s growing season outlooks, Meredith Fairbanks, Department of Agriculture Farmers commodity outlook 2006, Thomas Schulz, Department of Agriculture Why is salinity such a difficult problem for plant breeders? T J Flowers, TD Colmer, University of Western Australia Matching nitrogen supply to wheat demand in 2005, Narelle Simpson, Ron McTaggart, Wal Anderson, Lionel Martin and Dave Allen, Department of Agriculture Wheat varieties in 2006, Brenda Shackley, Department of Agriculture Performance of dwarf potential milling oat varieties in Western Australian environments, Raj Malik and Kellie Winfield, Department of Agriculture Field pea lessons for 2006, Rodger Beermir, Department of Agriculture Better returns from Durum wheat, Shahahan Miyan, Department of Agriculture Summer weeds can reduce grain yield and protein, Dr. Abul Hashem, Department of Agriculture, Dr Shahab Pathan, Department of Agriculture, Vikki Osten, Queensland Department of Primary Industries and Fisheries Management of Summer Weeds, Alex Douglas, Department of Agriculture Frost or Friction, Garren Knell, Steve Curtin, Wade Longmuir, Consult Ag Pty Ltd PROFITING FROM MARGINAL LAND SEMINAR Producing Bio-Diesel and rubber from marginal land?? Dr Henry Brockman, Department of Agriculture SGSL Producer network – on ground implementation of saltbush based pastures, Justin Hardy, Arjen Ryder, John Paul Collins and Jessica Johns, Department of Agriculture Enhancing the profitability of “Edenia” using saltbush and perenials, SGSL Producer case study, John Pepall, Jinka’s Hill LCDC Investment in saltland pastures, Allan Herbert, Department of Agricultur

    Roadmap on Electronic Structure Codes in the Exascale Era

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    Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing.Comment: Submitted as a roadmap article to Modelling and Simulation in Materials Science and Engineering; Address any correspondence to Vikram Gavini ([email protected]) and Danny Perez ([email protected]
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