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Search Results: 1 - 10 of 3782 matches for " Marcela Doubkova "
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Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR)
Wolfgang Wagner,Carsten Pathe,Marcela Doubkova,Daniel Sabel
Sensors , 2008,
Abstract: The high spatio-temporal variability of soil moisture is the result of atmosphericforcing and redistribution processes related to terrain, soil, and vegetation characteristics.Despite this high variability, many field studies have shown that in the temporal domainsoil moisture measured at specific locations is correlated to the mean soil moisture contentover an area. Since the measurements taken by Synthetic Aperture Radar (SAR)instruments are very sensitive to soil moisture it is hypothesized that the temporally stablesoil moisture patterns are reflected in the radar backscatter measurements. To verify this hypothesis 73 Wide Swath (WS) images have been acquired by the ENVISAT AdvancedSynthetic Aperture Radar (ASAR) over the REMEDHUS soil moisture network located inthe Duero basin, Spain. It is found that a time-invariant linear relationship is well suited forrelating local scale (pixel) and regional scale (50 km) backscatter. The observed linearmodel coefficients can be estimated by considering the scattering properties of the terrainand vegetation and the soil moisture scaling properties. For both linear model coefficients,the relative error between observed and modelled values is less than 5 % and thecoefficient of determination (R2) is 86 %. The results are of relevance for interpreting anddownscaling coarse resolution soil moisture data retrieved from active (METOP ASCAT)and passive (SMOS, AMSR-E) instruments.
Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR)
Wolfgang Wagner,Carsten Pathe,Marcela Doubkova,Daniel Sabel,Annett Bartsch,Stefan Hasenauer,Günter Bl?schl,Klaus Scipal,José Martínez-Fernández,Alexander L?w
Sensors , 2008, DOI: 10.3390/s8021174
Abstract: The high spatio-temporal variability of soil moisture is the result of atmosphericforcing and redistribution processes related to terrain, soil, and vegetation characteristics.Despite this high variability, many field studies have shown that in the temporal domainsoil moisture measured at specific locations is correlated to the mean soil moisture contentover an area. Since the measurements taken by Synthetic Aperture Radar (SAR)instruments are very sensitive to soil moisture it is hypothesized that the temporally stablesoil moisture patterns are reflected in the radar backscatter measurements. To verify this hypothesis 73 Wide Swath (WS) images have been acquired by the ENVISAT AdvancedSynthetic Aperture Radar (ASAR) over the REMEDHUS soil moisture network located inthe Duero basin, Spain. It is found that a time-invariant linear relationship is well suited forrelating local scale (pixel) and regional scale (50 km) backscatter. The observed linearmodel coefficients can be estimated by considering the scattering properties of the terrainand vegetation and the soil moisture scaling properties. For both linear model coefficients,the relative error between observed and modelled values is less than 5 % and thecoefficient of determination (R2) is 86 %. The results are of relevance for interpreting anddownscaling coarse resolution soil moisture data retrieved from active (METOP ASCAT)and passive (SMOS, AMSR-E) instruments.
Relation between Antibacterial Activity against Food Transmitted Pathogens and Total Phenolic Compounds in Grape Pomace Extracts from Cabernet Sauvignon and Syrah Varieties  [PDF]
Loreto Sanhueza, Mario Tello, Marcela Vivanco, Leonora Mendoza, Marcela Wilkens
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.45029
Abstract:

Grape pomace is the main by-product of wine production that concentrates bioactive metabolites of polyphenolic nature with antibacterial activity. Since grape pomace composition varied depending on grape variety, climate, vineyard location, and winemaking technology, it is important to study the composition and antibacterial activity of each variety separately. In this study, antibacterial activity against different food pathogens was evaluated and its relation with polyphenols content was determined. Grape pomace from Cabernet Sauvignon and Syrah varieties was extracted with methanol/HCl 1% (v/v), followed by sequential extractions with hexane, chloroform and ethyl acetate. Ethyl acetate fraction had the highest antibacterial activity determined through the microdilution method, reaching over 90% of inhibition at 500 μg·ml-1 with the exception of Salmonella Typhi (70% of inhibition). Staphylococcus aureus and Escherichia coli were the most susceptible strains, exceeding 50% of inhibition at 62.5 μg·ml-1. Ethyl acetate fraction contains the highest phenolic concentration in both Cabernet Sauvignon (132.2 mg of GAE g-1) and Syrah (102.6 mg of GAE g-1) pomace, as determined by the Folin-Ciocalteau method. Antibacterial activity present in grape pomace extracts is in direct relation to the polar phenolic content, in particular that from Cabernet Sauvignon.

Effects of Conservation Tillage on Total and Aggregated Soil Organic Carbon in the Andes  [PDF]
Marcela Quintero, Nicholas B. Comerford
Open Journal of Soil Science (OJSS) , 2013, DOI: 10.4236/ojss.2013.38042
Abstract:

Many Andisols of the Andes have been disturbed by traditional potato-based rotation agriculture disrupting soil structure, water retention capacity and organic matter content. This study was undertaken to investigate the contribution of conservation farming technology or reduced tillage in potato-based rotations in the Colombian Andes in order to rehabilitate total and aggregated soil organic C in disturbed organic matter-rich Andisols. Soils were sampled from farms with 7-year of reduced tillage and farms with conventional farming practices. Ultrasound energy was applied to samples to disrupt aggregation and total soil C was determined in order to investigate the amount of carbon held inside the aggregates of different soil size classes. Results indicated that reduced tillage in potato-based crop rotations increased the soil C concentration and average C content in the whole profile (≈117 cm depth) by 50 and 33% (1636 t C ha?1 vs. 1224 t C ha?1), respectively, as compared to conventional farming practices. Carbon content increased 177% in the subsoil (A2 horizon, 78 -117 cm depth, from 215 to 596 t?ha?1), although most of the soil C was in the A1 horizon (between 0 -78 cm average thickness, 1097 t?ha?1). These increases show that reduced tillage enhances C stores in Andisols which are already high in organic matter. In addition, C in aggregates represented more than 80% of the total organic matter and it was positively affected by conservation practices. The C increase was preferential in the smaller macroaggregates (<2 mm). The aggregate dispersion energy curves further suggested that C increase was occurring in microaggregates within the smaller macroaggregate fraction. Data suggested that smaller macroaggregates can be used in these soils to evaluate the influence of field management practices on soil C sequestration.

La Naturaleza histórica de la biodiversidad: elementos conceptuales de una crisis
Pinillos,Marcela;
Interciencia , 2005,
Abstract: biodiversity is here considered both as a concept and as an ongoing problem. as a concept it expresses an entirely new form of seeing the world, being in the context of this new ontology where the associated crisis acquires its current social and political dimensions. the ontology of biodiversity responds to a new paradigm, the systemic paradigm, which sees reality as a complex and continuously mutating product of a netlike interaction among entities of different nature, which in turn, are the product of reticular interactions at a lower integration level. when reasoning regarding the implications of this paradigm for the understanding of living systems (organisms, ecological and socio-cultural systems), their ethical consequences are perceived, which are at the core of the discussion on how legitimate is the existing social project. it is concluded that biodiversity entails problems of a well defined historical nature: the cognitive schizophrenia of understanding the world in one manner and yet acting as if it were in an entirely different way, therefore building the foundations of a true existential crisis of humankind.
Ectoparasite occurrence associated with males and females of wild rodents Oligoryzomys flavescens (Waterhouse) and Akodon azarae (Fischer) (Rodentia: Cricetidae: Sigmodontinae) in the Punta Lara wetlands, Argentina
Lareschi, Marcela;
Neotropical Entomology , 2010, DOI: 10.1590/S1519-566X2010000500022
Abstract: the objective of this research was to study infestation parameters and indexes of ectoparasites associated with each sex of the wild rodents oligoryzomys flavescens (waterhouse) andakodon azarae (fischer) in the punta lara wetlands, argentina. a trend towards higher mean abundance (ma) and ectoparasite specific richness was observed in males of o. flavescens whereas those values were similar for both a. azarae sexes. the prevalence of the following ectoparasites was significantly higher on males (p < 0.05): mysolaelaps microspinosus fonseca (65.2%) and hoplopleura travassosi werneck (73.9%) on o. flavescens, and ixodes loricatus neumann (71.4%) on a. azarae. only h. travassosi mean abundance was significantly higher on males (ma = 44.1). since i. loricatus and hoplopleura spp. are involved in the transmission of pathogens that cause diseases in animals and humans, and whose reservoirs are rodent hosts, these results are epidemiologically important.
Varia??es da cor preta e negra na pintura de Eduardo Sued
Rangel, Marcela;
ARS (S?o Paulo) , 2009, DOI: 10.1590/S1678-53202009000200003
Abstract: eduardo sued transforms the black pigment of his physical palette in color fields on his paintings. he usually distinguishes black from "darkblack". he says black goes to "dark black" as darkness and intensity take hold of it. for him, the black works only on its surface, while "darkblack" is deep. "there are black nights and 'darkblack' nights!" in this interview sued talks about what promotes his pictorial production, in particular his use of black paint to create his black and darkblack fields.
Las políticas de reforma universitaria: la lógica global y la respuesta local el caso de la Argentina
Mollis, Marcela;
Interface - Comunica??o, Saúde, Educa??o , 1999, DOI: 10.1590/S1414-32831999000200008
Abstract: this paper intends to reconstruct the recent history of university policies in argentina, with particular reference to university evaluation. we expect to offer an account describing the origin and the development of said policies and the bodies that put them into practice in the nineties, based on a program for modernizing universities, suggested within an international context (agencies) and latter implemented at regional and national levels. the student movements, marches, strikes and other reactions of the university stakeholders highlight a renewed perception of the crisis of the institution in the region, which shows peculiarities and similarities relative to the globalization processes that are taking place at the closing of this millenium.
El peronismo en la historia reciente: Algunas interpretaciones
Ferrari,Marcela;
Estudios de filosof?-a pr??ctica e historia de las ideas , 2008,
Abstract: this article explores the deep renovation in the ideological-cultural field that accompanies the return to democracy in the country, as well as the processes that bring about the formation of a new "cultural atmosphere". besides, through the conceptual and methodological news in the field, it analyses the production that aims at revisiting peronism at that time. in so doing, it attempts to tackle the continuity of the lines of the debate that started in previous decades, as well as a whole new line that at the beginning of the 80s began with the analyses of the "cultural battle" between politicians and intellectuals brought about by peronism after its first decline. the magnetism of peronism over the historiographical field in the 60s and 70s acquires a renewed vigour in the 80s, due to the political and ideological disputes and controversies in the interior of this political tradition in the period of the democratic transition. this new production is undoubtedly a fundamental chapter in the historiography of peronism, which continues in the following decades and inspires new readings. in this sense, this article attempts to join old and new ideas in the historiographical field, modulated by the changes in peronism as a political force since its electoral defeat against radicalism in 1983.
Reflexiones críticas de los estudios sobre trabajo y trabajadores en América Latina
Emili,Marcela;
Trabajo y sociedad , 2011,
Abstract: systematic studies of sociology of work in latin america go back to a relatively recent times, the decade of the sixties. from early work until today topics and approaches have varied, according to the pulse of the socio-economic changes that occur in the region. in this paper we propose to perform a critical reflection of the theoretical and methodological becoming who has crossed this discipline. we consider as "satarting point" the systematization made by three latin american authors in the tratado latinoamericano de sociología del trabajo (coordinado por enrique de la garza toledo): francisco zapata, laís abramo and cecilia montero.
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