1,721,073 research outputs found
Hongos micorrícicos arbusculares en asociación con Lotus tenuis en ambientes halomórficos de la Cuenca del río Salado
Full text linkFil: García, Ileana. Museo Argentino de Ciencias Naturales Bernardino Rivadavia; ArgentinaFil: Cabello, Marta Noemi. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Instituto Spegazzini; ArgentinaFil: Fernández-López, Carolina. INTA; ArgentinaFil: Chippano, Tomás. Museo Argentino de Ciencias Naturales Bernardino Rivadavia; ArgentinaFil: Mendoza, Rodolfo. Museo Argentino de Ciencias Naturales Bernardino Rivadavia; Argentin
Phosphorus nutrition and mycorrhizal growth response of broadleaf and narrowleaf birdsfoot trefoils
No full textIn Argentina narrowleaf trefoil (Lotus glaber) predominates over broadleaf trefoil (Lotus corniculatus). Researchers have suggested this predominance occurs because L. glaber grows better at low levels of P availability. I studied the effect of increasing phosphorus (P) nutrition and mycorrhizal growth response of Lotus corniculatus and Lotus glaber in a soil of low available P. L. corniculatus was more efficient in P utilization than L. glaber and produced larger yields of shoot tissue per unit of P. The critical P concentration, measured as a percentage of P in the shoot required to achieve 90% of maximum shoot yield, was 0.22 in L. corniculatus and 0.28 in L. glaber. The roots of both two species were heavily infected by arbuscular micorrhizae (AM), and both mycorrhizal and nonmycorrhizal plants responded strongly to added P in soil. This suggests that both species are at no advantage or disadvantage whether mycorrhizal or nonmicorrhizal. The fraction of roots colonized by AM fungi differed between species at low levels of added P but was similar at high levels of added P. The specific root length (cm g-1) of mycorrhizal plants was greatest in L. corniculatus when P was insufficient to achieve maximum growth. The lower critical P concentration and the higher specific root length at low levels of P nutrition may be why L. corniculatus is superior to L. glaber in soils low in P. Therefore, the predominance of L. glaber compared with L. corniculatus in Argentinean soils is not due to ability of L. glaber to grow better in soil at low levels of P availability.Fil: Mendoza, Rodolfo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Mendoza-san Juan. Estación Experimental Agropecuaria Mendoza. Laboratorio Ecofisiología Vegetal; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Lotus tenuis seedlings subjected to drought or waterlogging in a saline sodic soil
Full text linkThe growth response of Lotus tenuis seedlings to drought and waterlogging in a saline-sodic soil, themobilization of Na+ in tissue, and the association with native AM fungi and Rhizobium bacteria werestudied by means of two experiments under controlled conditions.In the first experiment, we tested the effect of the duration of waterlogging on seedlings very early aftersowing, when they had the two cotyledons totally expanded and, in the second experiment, we tested theeffect of water stress on seedlings of different growth stages, at a wide range of water availability in thesoil, from deficit to water excess L. tenuis seedlings were able to deal with the intensity of water stress atvery early growth stages. They established symbiotic associations with AM fungi and Rhizobium bacteriaand regulated Na+ concentration in plant tissue to prevent leaf injury. The seedling strategy consistedin decreasing the shoot:root ratio under water deficit and increasing the shoot:root ratio under waterexcess.Lotus seedlings are highly tolerant to the combination of water and salt stress from early stages in theirdevelopment and early plant establishment in adverse soil conditions is an important ability of L. tenuisseedlings to grow and survive longer within a grassland ecosystem.Fil: García, Ileana Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia"; ArgentinaFil: Mendoza, Rodolfo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia"; Argentin
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Landfarming of petroleum wastes in a cold dry climate of Tierra del Fuego: Effect on soil and vegetation
Full text linkThe effect of adding organic oily wastes on plant cover and on soil water content was studied in a soil covered by a community of low forage value in Tierra del Fuego (Argentina). Oily wastes were mixed with the top 3 cm of the soil in May 1993 at rates of 1.51 and 3.03 % (w/w basis). In December 1993, half of each plot was fertilized with N and P, and changes in species abundance and total cover were evaluated in December of 1994 and 1995. Soil samples at 0-3, 3-6 and 6-9 cm depths were taken in December of 1993-1995, and analyzed for pH, water content, and total petro- leum hydrocarbon (TPH). The oily wastes increased water content and pH in the soil. Fertilization increased plant growth but both fertilization and oily waste increased plant cover. TPH in soil decreased from 3 % to 0.18 % during the experimental period, but fertilization did not affect the decrease in TPH with time. The results, combined with the annual rainfall and the water table elevation at the site, suggests that the risk of contaminating the water table is relatively low. It is concluded that landfarming could be applied as a remedial action in soils of Tierra del Fuego. In addition, amending the soil with oily waste in dry heath ecosystems increased water conservation and this effect promoted plant growth.Fil: Mendoza, Rodolfo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Ecofisiología Vegetal (i); ArgentinaFil: Portal, R.. Total Austral; Argentin
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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