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Smia Paiva de Oliveira Nilda Braga de Lacerda Susana Churka Blum Maria Eugenia Ortiz Escobar Tegenes Senna de Oliveira 《Land Degradation \u0026amp; Development》2015,26(1):9-21
The productivity of agricultural areas in semi‐arid regions can be improved through the use of irrigation. However, the intensive cropping of such soils can have detrimental effects, especially with regard to soil organic matter (SOM) pools. The goal of this work was to evaluate soil organic carbon and nitrogen stocks of different irrigated agricultural systems and compare these to preserved natural ecosystems adjacent to each of the cropping systems. We selected four cropping systems: banana, a maize/bean succession (MB), pasture (P) and guava (G), as well as areas covered by native vegetation. Stocks of total soil organic carbon (TOC), amounts of unprotected and protected soil organic carbon, carbon and nitrogen in microbial biomass and microbial respiration were quantified. Surface soil TOC stocks under banana, G and P grass were significantly greater than under native vegetation and MB system. The most intensive management system was the MB, and the least intensive systems were P and G. The least intensive cropping systems were grouped on the basis of similarities in TOC, POC, total soil nitrogen and N in microbial biomass stocks. These results show that the degree of soil degradation resulting from changes in land use systems increases with the intensity of the land use systems themselves. This confirms the established hypothesis that the extent of degradation of soil properties and changes in some SOM fractions depend on the intensity of soil use. Furthermore, the adoption of conservation practices may remediate soil degradation and increase SOM stocks, mainly at the soil's surface. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Braga ME Leal PF Carvalho JE Meireles MA 《Journal of agricultural and food chemistry》2003,51(22):6604-6611
Turmeric extracts were obtained from two lots of raw material (M and S) using various techniques: hydrodistillation, low pressure solvent extraction, Soxhlet, and supercritical extraction using carbon dioxide and cosolvents. The solvents and cosolvents tested were ethanol, isopropyl alcohol, and their mixture in equal proportions. The composition of the extracts was determined by gas chromatography-flame ionization detection (GC-FID) and UV. The largest yield (27%, weight) was obtained in the Soxhlet extraction (turmeric (S), ethanol = 1:100); the lowest yield was detected in the hydrodistillation process (2.1%). For the supercritical extraction, the best cosolvent was a mixture of ethanol and isopropyl alcohol. Sixty percent of the light fraction of the extracts consisted of ar-turmerone, (Z)-gamma-atlantone, and (E)-gamma-atlantone, except for the Soxhlet extracts (1:100, ethanol), for which only ar-turmeronol and (Z)-alpha-atlantone were detected. The maximum amount of curcuminoids (8.43%) was obtained using Soxhlet extraction (ethanol/isopropyl alcohol). The Soxhlet and low pressure extract exhibited the strongest antioxidant activities. 相似文献
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JB McClain DE Betts DA Canelas ET Samulski JM DeSimone JD Londono HD Cochran GD Wignall D Chillura-Martino R Triolo 《Science (New York, N.Y.)》1996,274(5295):2049-2052
Interfacially active block copolymer amphiphiles have been synthesized and their self-assembly into micelles in supercritical carbon dioxide (CO2) has been demonstrated with small-angle neutron scattering (SANS). These materials establish the design criteria for molecularly engineered surfactants that can stabilize and disperse otherwise insoluble matter into a CO2 continuous phase. Polystyrene-b-poly(1,1-dihydroperfluorooctyl acrylate) copolymers self-assembled into polydisperse core-shell-type micelles as a result of the disparate solubility characteristics of the different block segments in CO2. These nonionic surfactants for CO2 were shown by SANS to be capable of emulsifying up to 20 percent by weight of a CO2-insoluble hydrocarbon into CO2. This result demonstrates the efficacy of surfactant-modified CO2 in reducing the large volumes of organic and halogenated solvent waste streams released into our environment by solvent-intensive manufacturing and process industries. 相似文献
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Vera Lygia El Id Bárbara Vale da Costa Daiane Salete Broch Mignoni Marina Belloni Veronesi Kelly Simoes Marcia Regina Braga Nelson Augusto dos Santos Junior 《林业研究》2015,26(2):339-346
Sesbania virgata(Cav.) Pers.is a pioneer species native to South America able to release allelochemicals that affect germination and development of other plant species.The aim of this work was to evaluate the allelopathic effect of S.virgata on the germination and development of co-occurring species from gallery forest and on agronomic species.Two forest native species,Enterolobium contortisiliquum(Vell.) Morong and Sapindus saponaria L.,and two agronomic species(these as control),Oryza sativa L.and Solanum lycopersicum L.were used in the lab and greenhouse assays with seeds and leaf extracts of S.virgata.Agronomic species were more affected than native species when co-germinated with seeds of S.virgata.The germination percentage and speed germination index of the agronomic species were reduced in both in vitro and greenhouse assays.In the same assays,the seeds of native species showed no significant differences in the parameters mentioned.However,the initial growth of the four species assayed was affected,with reduction in plant length and shoot diameter followed by significant reduction in plantlet shoot and root weights.In the assays with irrigation of S.virgata leaf extracts,no significant inhibitory effects on germination were observed for all species.Height and shoot diameter of the native species were not affected by the leaf extracts,nor were fresh and dry weights.However,these parameters increased in the agronomic species as they were irrigated with leaf extracts.Based on our data we conclude that seed leachates of S.virgata affect germination and seedling development of other species,suggesting that its invasive behavior is due mainly to seed allelochemicals.Although with less pronounced effects on native species,allelopathy of S.virgata might also influence Interspecific competition in its natural environment. 相似文献
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Pereira SA Menezes RC Gremião ID Silva JN Honse Cde O Figueiredo FB da Silva DT Kitada AA dos Reis EG Schubach TM 《Journal of Feline Medicine and Surgery》2011,13(4):220-223
Sporotrichosis is caused by Sporothrix schenckii. The cat is the animal species most affected by this mycosis and plays an important role in the zoonotic transmission of this disease. The definitive diagnosis is made by isolation of the fungus in culture; however, cytopathological examination is frequently used in cats. Medical records from cats treated at Instituto de Pesquisa Clínica Evandro Chagas/Fiocruz, Rio de Janeiro, Brazil, between 2004 and 2006 were reviewed. Criteria for inclusion were a diagnosis by isolation of S schenckii in culture and cytopathological examination of the same lesion as that used for collection of the culture material. Eight hundred and six cats were included in the study. Yeast-like structures suggestive of S schenckii were observed in 636 cases. The sensitivity of the method was 78.9%. Its practicality, low cost and sensitivity validate cytopathology as a safe technique for the presumptive diagnosis of sporotrichosis in cats. 相似文献
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