Heavy Metal Contamination in Sediments of Lake Nahuel Huapi,Nahuel Huapi National Park,Northern Patagonia,Argentina     

Ribeiro Guevara  Sergio  Massaferro  Julieta  Villarosa  Gustavo  Arribére  María  Rizzo  Andrea 《Water, air, and soil pollution》2002,137(1-4):21-44

Trace metals (Sb, As, Br, Cs, Co, Cr, Ag and Hg), rare earth elements (Ce, Eu, La, Lu, Sm, Tb and Yb), and Sc. were analysed in suspended load and in two sediment cores from Lake Nahuel Huapi, Nahuel Huapi National Park, Patagonia, Argentina, by using Instrumental Neutron Activation Analysis. The core activity profiles of ²¹⁰Pb and ¹³⁷Cs were measured to estimate the age of the sediments. Silver was enriched in the upper layers of both cores, and correlated with the strong growthof the population of Bariloche City in the last 50 yr. Concentrations are higher in the core sampled near Bariloche, andindicate some transport in the water body. Silver concentrationsmeasured in the suspended load were 4.58±0.36 and 3.46±0.40 μg g^-1 in the southern margin of the lake, near San Carlos de Bariloche City, whereas in the northern margin the concentrations were 1.68±0.18 and 1.88±0.23 μg g^-1. Concentration ratio for silver in suspended load and upper core layers were equal in both sampling points. These facts suggest that Ag contents correspond to inputs associated with human activities. Bromine concentrations show a strong increase abovebase line values, similar to silver. In contrast, caesium, chromium, and cobalt concentrations do not differ from base linevalues. The metalloids antimony and arsenic show little variationwith regard to base line concentration. Noticeable, the mercurycontents found in the suspended load.  相似文献   

Indigenous soil and water management in Senegambian rice farming systems     

Judith Carney 《Agriculture and Human Values》1991,8(1-2):37-48

Considerable attention has focussed on the potential of indigenous agricultural knowledge for sustainable development. Drawing upon fieldwork on the soil and water management principles of rice farming systems in Senegambia, this paper examines the potential of the traditional system for a sustainable food security strategy. Problems with pumpirrigation are reviewed as well as previous efforts in swamp rice development. It is argued that sustainability depends on more than ecological factors and in particular, requires sensitivity to socio-economic parameters such as the labor demands of the food security strategy, the sexual division of labor, and food pricing policies.  相似文献   

THE STRATIGRAPHIC POSITION OF THE JUDITH RIVER BEDS AND THEIR CORRELATION WITH THE BELLY RIVER BEDS     

Judith M 《Science (New York, N.Y.)》1903,18(450):211-212

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Sterilization regulations: debate not quelled by HEW document     

Coburn J 《Science (New York, N.Y.)》1974,183(4128):935-939

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Virology. Alzheimer's risk factor also aids HIV     

Youngsteadt E 《Science (New York, N.Y.)》2008,320(5883):1577

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Statement on scientific publication and security     

Atlas R  Campbell P  Cozzarelli NR  Curfman G  Enquist L  Fink G  Flanagin A  Fletcher J  George E  Hammes G  Heyman D  Inglesby T  Kaplan S  Kennedy D  Krug J  Levinson R  Marcus E  Metzger H  Morse SS  O'Brien A  Onderdonk A  Poste G  Renault B  Rich R  Rosengard A  Salzburg S  Scanlan M  Shenk T  Tabor H  Varmus H  Wimmer E  Yamamoto K;Journal Editors  Authors Group 《Science (New York, N.Y.)》2003,299(5610):1149

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Applied physics. Testing the limits for resists     

Reichmanis E  Nalamasu O 《Science (New York, N.Y.)》2002,297(5580):349-350

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Cuba and the dilemma of modern agriculture     

John Vandermeer  Judith Carney  Paul Gersper  Ivette Perfecto  Peter Rosset 《Agriculture and Human Values》1993,10(3):3-8

Having lost 73% of its purchasing power and 42% of it gross national product since the fall of the Soviet Union, Cuba faces a crisis with the modern agricultural system it had developed over the past 30 years. The response has been to put an alternative model into practice. The successes and problems associated with this model are discussed.  相似文献   

Constraints on neon and argon isotopic fractionation in solar wind     

Meshik A  Mabry J  Hohenberg C  Marrocchi Y  Pravdivtseva O  Burnett D  Olinger C  Wiens R  Reisenfeld D  Allton J  McNamara K  Stansbery E  Jurewicz AJ 《Science (New York, N.Y.)》2007,318(5849):433-435

To evaluate the isotopic composition of the solar nebula from which the planets formed, the relation between isotopes measured in the solar wind and on the Sun's surface needs to be known. The Genesis Discovery mission returned independent samples of three types of solar wind produced by different solar processes that provide a check on possible isotopic variations, or fractionation, between the solar-wind and solar-surface material. At a high level of precision, we observed no significant inter-regime differences in 20Ne/22Ne or 36Ar/38Ar values. For 20Ne/22Ne, the difference between low- and high-speed wind components is 0.24 +/- 0.37%; for 36Ar/38Ar, it is 0.11 +/- 0.26%. Our measured 36Ar/38Ar ratio in the solar wind of 5.501 +/- 0.005 is 3.42 +/- 0.09% higher than that of the terrestrial atmosphere, which may reflect atmospheric losses early in Earth's history.  相似文献   

Mutations in U4atac snRNA, a component of the minor spliceosome, in the developmental disorder MOPD I     

He H  Liyanarachchi S  Akagi K  Nagy R  Li J  Dietrich RC  Li W  Sebastian N  Wen B  Xin B  Singh J  Yan P  Alder H  Haan E  Wieczorek D  Albrecht B  Puffenberger E  Wang H  Westman JA  Padgett RA  Symer DE  de la Chapelle A 《Science (New York, N.Y.)》2011,332(6026):238-240

Small nuclear RNAs (snRNAs) are essential factors in messenger RNA splicing. By means of homozygosity mapping and deep sequencing, we show that a gene encoding U4atac snRNA, a component of the minor U12-dependent spliceosome, is mutated in individuals with microcephalic osteodysplastic primordial dwarfism type I (MOPD I), a severe developmental disorder characterized by extreme intrauterine growth retardation and multiple organ abnormalities. Functional assays showed that mutations (30G>A, 51G>A, 55G>A, and 111G>A) associated with MOPD I cause defective U12-dependent splicing. Endogenous U12-dependent but not U2-dependent introns were found to be poorly spliced in MOPD I patient fibroblast cells. The introduction of wild-type U4atac snRNA into MOPD I cells enhanced U12-dependent splicing. These results illustrate the critical role of minor intron splicing in human development.  相似文献