Influencia del homogeneizado previo al laminado en frío en la microestructura del AA3003

The aluminum alloy AA3003 produced by a direct chill continuous casting process has a microstructure that significantly affects its potential use in engineering applications. This work studies the effects of the homogenizing heat treatment on the microstructure of AA3003 with cold working. Six conditions were studied, combining the variables initial condition (with and without homogenizing) and amount of cold working. All conditions were evaluated by means of optical and scanning electron microscopy, in combination with backscattered electrons and energy dispersive X ray spectroscopy techniques. Results suggest that for both initial conditions, the secondary phases present are Al6(Mn,Fe) and ?-Al(Mn,Fe)Si, which vary in number, size, and shape. The homogenization caused the dissolution and precipitation of dispersoids, in addition to the spheroidization of primary particles, and minor variation of the size of secondary particles during cold working. Secondary phases are composed of primary and secondary particles, which differ in their Fe and Mn content, resulting in a lower Mn/Fe ratio for the primary particles (0,57 for the as?received condition and 0,80 for the homogenized condition), whereas the dispersoids have a higher Mn/Fe ratio (1,56 after the homogenization). Homogenization increased ductility and reduced the likelihood of cracking during cold working. This was evidenced by the results obtained for strength, hardness, and ductility.La aleación de aluminio AA3003 proveniente de colada continua posee una microestructura que afecta significativamente su uso potencial en aplicaciones de ingeniería. Este trabajo estudia los efectos de la homogeneización sobre la microestructura del AA3003 con trabajo en frío. Se estudiaron seis condiciones combinando las variables: condición inicial (con y sin homogeneizado) y cantidad de trabajo en frío. Se evaluaron todas las condiciones mediante microscopía óptica y electrónica de barrido, combinadas con técnicas de electrones retrodispersados y espectroscopía de dispersión de rayos X. Los resultados sugieren que, para ambas condiciones iniciales, las fases secundarias presentes son Al6(Mn,Fe) y ?-Al(Mn,Fe)Si. La homogeneización causó la disolución y precipitación de los dispersoides, la esferoidización de las partículas primarias y permitió que la variación del tamaño de las partículas secundarias fuese mínima durante el trabajo en frío. Además, se obtuvo que las fases secundarias están compuestas de partículas primarias y secundarias, que difieren en su contenido de Fe y Mn, lo que resulta en una relación Mn/Fe más baja para las partículas primarias (0,57 para la condición recibida y 0,80 para la condición homogeneizada), mientras que los dispersoides tienen una mayor relación Mn/Fe (1,56 después de la homogeneización). La homogenización aumentó la ductilidad y redujo la probabilidad de agrietamiento del material durante el trabajo en frío, lo cual se evidenció en los resultados obtenidos de resistencia, dureza y ductilidad

The beta function of the multichannel Kondo model

The beta function of the multichannel Kondo model is calculated exactly in the limit of large spin N and channel number M=gamma*N, with constant gamma. There are no corrections in any finite order of 1/N. One zero is found at a finite coupling strength, showing directly the Non--Fermi liquid behavior of the model. This renormalization group flow allows to introduce a variational principle for the entropy, to obtain the low temperature thermodynamics. Such in particular the low temperature thermodynamics of the non--crossing approximation to the Kondo model becomes accessible.Comment: 4 page

Problème du rajeunissement des sols issus de l'altération de roches volcaniques, par des éruptions récentes de cendres, aux Nouvelles-Hébrides et aux îles Canaries

Abstract. - Two soils, one from Aoba (New Hebrides), the other from Tenerife (Canarian Islands), the rejuvenation of which by a fall of volcanic ashes has been dated (by 14 C), show that, in a humid tropical or subtropical environment, the recent rejuvenation leads to pedological forms relatively less maturated than the normal soils type. In Aoba, they are one thousand years old, saturated and slighty evoluted andosols, in Tenerife appear andic brown earths that are less than 9000 years old and bury tropical paleosols. It is noteworthy in Aoba, that only one thousand years has been enough to form halloysite, whereas Aomine and Miyauchi (1963) estimated tah 8000 years have been necessary in the case of the Japanese andosols.Résumé. - Deux sols, l'un situé à Aoba (Nouvelles Hébrides), l'autre à Tenerife (Iles Canaries), dont le rajeunissement par un recouvrement de cendres volcaniques a été daté en âge absolu (par 14 C), montrent qu'en milieu tropical ou subtropical humide, le rajeunissement conduit à des formations pédologiques relativement moins évoluées que la normale. Dans le cas d'Aoba, il s'agit d'andosols saturés datant de mille ans environ ; dans celui de Tenerife, ce sont des sols bruns andiques âgés de moins de 9000 ans, recouvrant des paléosols tropicaux. Il est remarquable à Aoba, qu'un millier d'années a suffi, en milieu tropical humide pour l'apparition d'halloysite, alors qu'Aomine et Miyauchi (1963) estimaient qu'un laps de temps de 8000 ans était nécessaire dans le cas des andosols du Japon.Quantin Patrick, Fernandez-Caldas E., Guttierrez-Jerez F., Tejedor M.L., Delibrias G. Problème du rajeunissement des sols issus de l'altération de roches volcaniques par des éruptions récentes de cendres, aux Nouvelles-Hébrides et aux îles Canaries. In: Bulletin de l'Association de géographes français, N°426, 52e année, mai 1975. pp. 211-217

Smearing of charge fluctuations in a grain by spin-flip assisted tunneling

We investigate the charge fluctuations of a grain (large dot) coupled to a lead via a small quantum dot in the Kondo regime. We show that the strong entanglement of charge and spin flips in this setup can result in a stable SU(4) Kondo fixed point, which considerably smears out the Coulomb staircase behavior already in the weak tunneling limit. This behavior is robust enough to be experimentally observable.Comment: 4 pages, 1 figure, final version for PRB Rapid Com

Assessing the Influence of Salmon Farming through Total Lipids, Fatty Acids, and Trace Elements in the Liver and Muscle of Wild Saithe Pollachius virens

Saithe Pollachius virens are attracted to uneaten salmon feed underneath cages at open-cage salmon farms in Norway. The aggregated Saithe have modified their feeding habits as they have switched from wild prey to uneaten food pellets, which could lead to physiological and biochemical changes in the Saithe. Variations in profiles of total lipids, fatty acids, and trace elements in Saithe liver and muscle were measured to evaluate the influence of fish feed from salmon farms on wild Saithe populations. Farm-aggregated Saithe had higher fat content in liver tissues than did individuals captured more than 25 km away from farms, but no clear differences were found in muscle tissues. High proportions of fatty acids of terrestrial origin, such as oleic, linoleic, and linolenic acids, in liver and muscle tissues of farm-aggregated Saithe reflected the presence of wild Saithe at farms. Accordingly, low proportions of arachidonic, eicosapentaenoic, and docosahexaenoic acids in Saithe tissues mirrored the feeding activity at farms. Variations in specific trace element signatures among fish groups also revealed the farming influence on wild Saithe. High levels of Fe, As, Se, Zn, and B in liver, but also As, B, Li, Hg, and Sr in muscle of Saithe captured away from farms indicated the absence of feeding at farms.This study was part of the project “Evaluation of actions to promote sustainable coexistence between salmon culture and coastal fisheries – ProCoEx” funded by The Norwegian Seafood Research Fund (FHF). The study was also supported by the Norwegian Research Council through the EcoCoast project

Cobertura y composición especifica de los matorrales mesomediterráneos silicícolas, intervenidos con practicas preparatorias de repoblación por decapado total, seguido de subsolado pleno, en el Andévalo de la provincia de Huelva

Has been studied the influence of the laboured, bulldocer scalping plus full subsoiling, in the presence of characteristic species of the mesomediterranean siliceous soils shrubs of “the Andévalo” in Huelva. The study is set in the Council “Cabezas Rubias”, province of Huelva, on a Pinus pinea reforestation, eight years after the bulldocer scalping and subsoiling previous plantation labours, were done, the total shrub cover has been estimated and compared as the addiction of its specific covers in the situations: 1) Grown shrubs after the considered preparatory treatment; 2) Shrubs presence in close areas without reforestation, therefore without any preparatory practice for reforestation. From the statistical analysis, no relation was obtained in the total cover variable with the applied treatment, it can be concluded that the only species which reduces its presence (in a 65.56%) is Cistus ladanifer. The specific cover average representation increases in Erica australis (33.90%), Erica umbellata (84.01%) and in all the flora components from the “Other species” group, composed by Halimium ocymoides, Genista triacanthos and Lavandula stoechas. In this group, Genista triacanthos and Lavandula stoechas didn’t appeared in the testigo shrub, appearing with low representation after the reforestation labours studied.Se ha estudiado la influencia que las prácticas preparatorias de repoblación consistentes en decapado total, seguido de subsolado pleno, tienen en la presencia de las especies características de los matorrales mesomediterráneos silicícolas del Andévalo onubense. El estudio se desarrolla en el término municipal de Cabezas Rubias, provincia de Huelva, sobre una repoblación de Pinus pinea y transcurridos ocho años tras la aplicación de las labores de decapado y subsolado que precedieron a la plantación donde se ha estimado y comparado la cobertura total del matorral, como suma de sus coberturas específicas, en dos situaciones: 1) matorral desarrollado tras ser intervenido con el tratamiento preparatorio considerado; 2) matorral presente en rodales contiguos no repoblados y por lo tanto no sometido a ninguna práctica preparatoria de repoblación. En el análisis estadístico realizado, no se verificó relación entre la variable cobertura total y la aplicación de las labores conjuntas de decapado total y subsolado pleno. Sin embargo, las mismas prácticas influyeron de forma significativa en las coberturas específicas de las especies integrantes del matorral muestreado. De la comparación sobre la variable cobertura específica respecto del tratamiento ensayado, se deduce que la única especie que disminuye su presencia es Cistus ladanifer, - 65,56%. La representatividad media de la cobertura específica aumenta en Erica australis, 33,90% ; en Erica umbellata, 84,01% y en todos los componentes florísticos que integran el grupo denominado Otras especies, constituido por Halimium ocymoides, Genista triacanthos y Lavandula stoechas. En este grupo, Genista triacanthos y Lavandula stoechas permanecieron ausentes en el matorral testigo, apareciendo con baja representatividad tras las labores de repoblación estudiadas

Hatchery production of the greater amberjack (Seriola dumerili)

DIVERSIF

The role of genetically engineered soybean and Amaranthus weeds on biological and reproductive parameters of Spodoptera cosmioides (Lepidoptera: Noctuidae)

BACKGROUND: In soybean fields containing insecticide- and herbicide-resistant genetically engineered varieties, some weed species have increasingly become difficult to manage and may favor the population growth of secondary pests like Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae). To test this hypothesis, we measured life-history traits, population growth parameters and adult nutrient content of S. cosmioides reared on foliage from four Amaranthus species, from Cry1Ac Bt and non-Bt soybean varieties, and on meridic artificial diet. RESULTS: Larvae reared on A. palmeri and A. spinosus had a shorter development time (5–7 days) than larvae raised on the soybean varieties and A. hybridus. Armyworm survival probability was zero on A. viridis and highest (80% and 71%) on soybeans and A. palmeri. The latter and the artificial diet produced the heaviest larvae and pupae, in contrast to the non-Bt soybean variety. Body nutrient content diverged mostly for adults reared on artificial diet compared with those raised on the soybean varieties. The intrinsic rate of population increase (overall fitness) was 27.88% higher for the armyworms on A. palmeri, Cry1Ac Bt soybean and artificial diet compared with those on non-Bt soybean, A. spinosus and A. hybridus. CONCLUSIONS: Cry1Ac soybean fields infested by some Amaranthus weeds, especially A. palmeri, are conducive to the population growth of S. cosmioides. Integrated pest management programs may be needed to properly manage S. cosmioides in soybean fields, with surveillance for population peaks and judicious control measures when needed.Fil: Páez Jerez, Paula Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia. Cátedra Terapéutica Vegetal; ArgentinaFil: Hill, Jorge Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia. Cátedra Terapéutica Vegetal; ArgentinaFil: Pereira, Eliseu J. G.. Universidade Federal de Viçosa.; BrasilFil: Medina Pereyra, Pilar. Fundación Miguel Lillo; ArgentinaFil: Vera, María Teresa. Universidad Nacional de Tucumán. Facultad de Agronomía y Zootecnia. Cátedra Terapéutica Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentin

Biofilm formation of Flavobacterium psychrophilum on various substrates

The ability of Flavobacterium psychrophilum to adhere to and form biofilms on different types of materials used on rainbow trout (Oncorhynchus mykiss) farms was evaluated in this study. F. psychrophilum NCIMB 1947T, was inoculated onto a variety of different surfaces, including stainless steel, plastic, glass, wood, and zinc pyrithione encapsulated antibacterial plastic. The samples were then cultured in a humidified chamber or transferred into fish tanks containing either (1) freshwater or (2) filtered lake water. The formation of biofilms was quantified by fluorescent microscopy. F. psychrophilum formed biofilms on all of the surfaces tested; however, the adherence of the bacterium to the antibacterial plastic was much lower than the attachment observed on the other surfaces, illustrating the bacteriostatic properties of this material for F. psychrophilum. Moreover, bacterial numbers were greater on the surfaces maintained in lake water compared with those maintained in freshwater. The mineral composition of the lake water may have been responsible for the increased bacterial adherence observed between the two types of water. Treatment of the water, regular cleaning of equipment and the use of antimicrobial material to house the fish may help reduce biofilm formation by F. psychrophilum in fish farming systems

Structure of Alluvial Valleys from 3-D Gravity Inversion: The Low Andarax Valley (Almería, Spain) Test Case

This paper presents a gravimetric study (based on 382 gravimetric stations in an area about 32 km2) of a nearly flat basin: the Low Andarax valley. This alluvial basin, close to its river mouth, is located in the extreme south of the province of Almería and coincides with one of the existing depressions in the Betic Cordillera. The paper presents new methodological work to adapt a published inversion approach (GROWTH method) to the case of an alluvial valley (sedimentary stratification, with density increase downward). The adjusted 3D density model reveals several features in the topography of the discontinuity layers between the calcareous basement (2,700 kg/m3) and two sedimentary layers (2,400 and 2,250 kg/m3). We interpret several low density alignments as corresponding to SE faults striking about N140?145°E. Some detected basement elevations (such as the one, previously known by boreholes, in Viator village) are apparently connected with the fault pattern. The outcomes of this work are: (1) new gravimetric data, (2) new methodological options, and (3) the resulting structural conclusions