3,754 research outputs found

    Beam-Material Interaction

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    Th is paper is motivated by the growing importance of better understanding of the phenomena and consequences of high- intensity energetic particle beam interactions with accelerator, generic target , and detector components. It reviews the principal physical processes of fast-particle interactions with matter, effects in materials under irradiation, materials response, related to component lifetime and performance, simulation techniques, and methods of mitigating the impact of radiation on the components and envir onment in challenging current and future applicationComment: 28 pages, contribution to the 2014 Joint International Accelerator School: Beam Loss and Accelerator Protection, Newport Beach, CA, USA , 5-14 Nov 201

    Distribution of inorganic and organic nutrients in the South Pacific Ocean – evidence for long-term accumulation of organic matter in nitrogen-depleted waters

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    International audienceThe BIOSOPE cruise of the RV Atalante was devoted to study the biogeochemical properties in the South Pacific between the Marquesas Islands (141° W–8° S) and the Chilean upwelling (73° W–34° S). The 8000 km cruise had the opportunity to encounter different trophic situations, and especially strong oligotrophic conditions in the Central South Pacific Gyre (SPG, between 123° W and 101° W). In this isolated region, nitrate was undetectable between surface and 160–180 m, while regenerated nitrogen (nitrite and ammonium) only revealed some traces (-1), even in the subsurface maximum. Integrated nitrate over the photic layer, which reached 165 m, was close to zero. In spite of this severe nitrogen-depletion, phosphate was always present at significant concentrations (˜0.1 µmoles l-1), while silicate maintained at low but classical oceanic levels (˜1 µmoles l-1). In contrast, the Marquesas region (MAR) at west and Chilean upwelling (UPW) at east were characterized by large nutrient contents one hundred to one thousand fold higher than in the SPG. Distribution of surface chlorophyll concentration reflected this gradient of nitrate availability. The lowest value (0.023 nmoles l-1) was measured in the centre of the SPG, where integrated chlorophyll over the photic layer was very weak (˜10 mg m-2), since a great part (up to 50%) of the deep chlorophyll maximum (DCM) was located below the 1% light. But, because of the relative high concentration encountered in the DCM (0.2 µg l-1), chlorophyll a content over the photic layer varied much less (by a factor 2 to 5) than the nitrate content. In contrast to chlorophyll a, integrated content of particulate organic matter (POM) remained more or less constant along the investigated area (500 mmoles m-2, 60 mmoles m-2 and 3.5 mmoles m-2 for particulate organic carbon, particulate organic nitrogen and particulate organic phosphorus, respectively), except in the upwelling where values were two fold higher. Extensive comparison has shown that glass fiber GF/F filters efficiency collected particulate chlorophyll, while a significant fraction of POM (up to 50%) passed trough this filter and was retained by 0.2 µm Teflon membrane. The most striking feature was the large accumulation of dissolved organic matter (DOM) in the SPG relative to surrounding waters, especially dissolved organic carbon (DOC) where concentrations were at levels rarely measured in oceanic waters (>100 µmoles l-1). Due to this large pool of DOM over the whole photic layer of the SPG, integrated values followed an opposite geographical pattern than this of inorganic nutrients with a large accumulation within the centre of the SPG. While suspended particulate matter in the mixed layer had C/N ratio largely conform to Redfield stoichiometry (C/N˜6.6), marked deviations were observed in this excess DOM (C/N˜16 to 23). The existence of C-rich dissolved organic matter is recognized as a feature typical of oligotrophic waters, requiring the over consumption of carbon. Thus, in spite of strong nitrate-depletion leading to low chlorophyll biomass, the closed ecosystem of the SPG can produce a large amount of carbon. The implications of this finding are discussed, the conclusion being that, due to the lack of seasonal vertical mixing and weak lateral advection, the dissolved organic carbon biologically produced can be accumulated and stored in the photic layer for a very long period

    Internal water channel loss : Mendoza (Argentina)

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    Mendoza (Argentina) es una zona árida que se abastece de agua de los deshielos en las altas cuencas de los Andes. Su distribución se efectúa por una red semipública de 12 270 km de canales, de los cuales sólo 660 están impermeabilizados. La responsabilidad para mejorar dicha infraestructura -desde el dique hasta bocatoma de finca- recae sobre el Dpto. Gral. de Irrigación en la red primaria y las Inspecciones de Cauces, en la red secundaria y derivados. La distribución dentro de las fincas se realiza por cauces en tierra con pérdidas del 5 al 13 % en función de la textura de los suelos y el contenido de sedimentos de las aguas. Las aguas claras, cuando provengan del dique Potrerillos, incrementarán las pérdidas. Con el objeto de mejorar la eficiencia interna se determinó la relación entre longitud del cauce distribuidor y la superficie cultivada. Posteriormente se calcularon las pérdidas anuales de agua infiltrada por metro lineal. Para paliar estas pérdidas se confeccionaron tablas de uso práctico para revestimientos de pequeños cauces para las secciones rectangular y trapecial y para diferentes caudales, pendientes y materiales. Complementan esta acción la factibilidad de construcción de aforadores que posibiliten la recepción volumétrica, la reducción de jornales para riego y mantenimiento y el menor costo de mantenimiento de la red pública y privada de colectores de drenajes.The water distribution is done by means of an important semipublic net of ditches wich are 12 270 km. long. Only 660 of them are lined. Two sectors are responsible for carrying out the improvements in the understructures of the distribution net from the damn to the farm inlet gate. The official sector which is represented by the Gral. Dept. of Irrigation in the main net, and the Water Users Association in the secondary and derived nets. Both sectors are nowadays construccion and modernizing the irrigation nets. Land channel do the internal distribution of the water, the distance between the inlet gate and the head of the irrigation units. There are conveyance losses that can vary from the 5 % to the 13 % according to the land texture and the quality of the water. The aim of this work is to improve the internal efficiency. For this purpose the relation between the length of the distribution ditch and the cultivated area was determined. After that the annual losses of intake water by each lineal meter were calculated. In order to avoid the water losses practical dimension tables were made for different kinds of flow rates, slopes and materials. The complementary justification for this is: the feasability of the construction of flume that permit the volume reception, reduction of wages for irrigation time and a saving in the cost of maintenance of the public and private net of the collecting drains.Fil: Ortiz Maldonado, Gonzalo. Universidad Nacional de Cuyo. Facultad de Ciencias AgrariasFil: Tapia, Carlos F.. Universidad Nacional de Cuyo. Facultad de IngenieríaFil: Cerutti, Gustavo. Mendoza. Departamento General de Irrigació

    HBV vaccination with Fendrix is effective and safe in pre-dialysis CKD population

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    Background: Patients with chronic kidney disease have a poor response to hepatitis B vaccine due to the immunodeficiency conferred from chronic uremia. A recombinant HB vaccine containing an improved adjuvant system AS04 (HBV-AS04) has been manufactured but scarce evidence exists on HBV-AS04 use among patients with CKD. Aim: To assess efficacy and safety of an adjuvanted recombinant vaccine (HBV-AS04) in a large cohort of CKD patients at pre-dialysis stage (with susceptibility to HBV infection). Methods: Patients were prospectively enrolled to receive four 20-mcg doses of HBV-AS04 by intramuscular route (deltoid muscle) at months 1, 2, 3, and 4. Anti-HBs surface antibody concentrations were tested at intervals of 1, 2, 3, 4, and 12 months. Multivariate analyses were performed to assess the parameters, which predicted immunologic response to HBV-AS04 vaccine. Results: One hundred and seven patients were included and 102 completed the study. At completion of vaccine schedule, the frequency of responders (anti-HBs titers 65 10 mIU/mL) was 95% (97/102) (mean anti-HBs antibody titers, 688.9 \ub1 385 mIU/mL), according to per-protocol analysis. Serum haemoglobin levels were greater in responder than non- or low-responder patients to HBV-AS04 (P = 0.04) and this was confirmed by multivariate analysis. The seroprotection rate at month 50 was 88% (30/34) with lower anti-HBs antibody titers (218.5 \ub1 269.6 mIU/mL, P = 0.001). No major side effects were observed. Conclusions: Our prospective study performed in a real-world setting showed a high immunogenicity and safety of HBV-AS04 vaccine in patients with CKD not yet on maintenance dialysis. Studies provided with longer follow-ups are under way to assess the durability of seroprotection in responders

    The physics models of FLUKA: status and recent development

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    A description of the intermediate and high energy hadronic interaction models used in the FLUKA code is given. Benchmarking against experimental data is also reported in order to validate the model performances. Finally the most recent developments and perspectives for nucleus-nucleus interactions are described together with some comparisons with experimental data.Comment: talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 10 pages, p
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