Cambio de la estructura de la comunidad de colémbolos (Hexapoda: Collembola) en relación con el disturbio antrópico de los suelos

In order to evaluate the effects of the anthropic impact on the structure of de soil collembolan community, three different soil uses were researched: agricultural fields (AG) with 50 years of continuous farming, pastures entering the agricultural cycle (CG), and naturalized grasslands (NG). The study was carried out in fields of Chivilcoy (34°53'49 S, 60°01'09 W, elev. 60 m) and Navarro (34°51’30 S, 59°12’25 W, elev. 43 m), Buenos Aires Province, Argentina. For each of the three uses, three fields were selected as replicates, with three soil samples per replicate and sample date (10) for a total of 216 samples analyzed. Collembolans (Hexapoda: Collembola) were extracted and identified to family level. Five families were found: Hypogastruridae, Onychiuridae, Isotomidae, Entomobryidae, and Katiannidae. Soils were also characterized by means of physical and chemical analyses. The index of degree of change of collembolan diversity was calculated with the biological data. The results show that the biological index of degree of change can detect soil use effects on the collembolan community. Somewhat surprisingly, the index showed that the diversity of collembolans was higher in the high anthropic impact site AG, followed by CG and lowest in NG. The results also show that collembolan families respond differently to soil use. The families Hypogastruridae, Onychiuridae, and Isotomidae presented differences between systems. Therefore, collembolan community structure can be a useful tool to assess agricultural practices´ impacts on soil.Con el objetivo de evaluar el efecto que produce el impacto antrópico sobre la estructura de la comunidad de colémbolos, tres usos diferentes del suelo fueron investigados: campos de agricultura (AG) con 50 años de agricultura continua, pasturas ingresando al ciclo agrícola (CG) y campos naturalizados (NG). El estudio fue llevado a cabo en campos de los partidos de Chivilcoy (34°53'49 S, 60°01'09 W, elev. 60 m) y Navarro de la provincia de Buenos Aires, Argentina. Para cada uno de los tres usos del suelo, tres campos fueron seleccionados como réplicas. Cada muestreo consistió en tres muestras de suelo por réplica y por fecha de muestreo (10) para un total de 216 muestras recolectadas y analizadas. Los colémbolos fueron extraídos de las muestras e identificados a nivel de familia. Se identificaron cinco familias: Hypogastruridae, Onychiuridae, Isotomidae, Entomobryidae y Katiannidae. Los suelos fueron además caracterizados mediante análisis físicos y químicos. Con los datos biológicos se calculó el índice de grado de cambio de la diversidad de colémbolos. Los resultados muestran que el índice biológico del grado de cambio puede detectar los efectos del uso del suelo sobre la comunidad de colémbolos. Sorpresivamente, el índice muestra que la diversidad de colémbolos medida a través del índice de grado de cambio es más alta en los sitios de mayor impacto antrópico (AG), seguido de CG y la menor diversidad en el sitio de menor impacto (NG). Los resultados muestran además que las familias de colémbolos responden de manera diferente al uso del suelo. Las familias Hypogastruridae, Onychiuridae e Isotomidae presentaron diferencias entre los usos. En consecuencia, la estructura de la comunidad de colémbolos puede ser una herramienta útil para evaluar el impacto en el suelo de las prácticas agrícolas.Fil: Sandler, Rosana Veronica. Universidad Nacional de LujánFil: Falco, Liliana B.. Universidad Nacional de LujánFil: Di Ciocco, César A.. Universidad Nacional de LujánFil: Castro Huerta, Ricardo. Universidad Nacional de LujánFil: Coviella, Carlos E.. Universidad Nacional de Lujá

Use of coal liquefaction catalysts for coal/oil coprocessing and heavy oil upgrading

The catalytic hydrogenation of coal and model solvents using dispersed or supported catalysts at different pressures has been the focus of several recent studies at PETC. The effectiveness of these catalysts has been studied in coal liquefaction and coal-oil coprocessing. Coal-oil coprocessing involves the co-reaction of coal and petroleum-derived oil or resid. The results of these studies have indicated that both dispersed and supported catalysts are effective in these systems at elevated H{sub 2} pressures ({approximately}2,500 psig). Attempts to reduce pressure indicated that a combination of catalyst concentration and solvent quality could be used to compensate for reductions in H{sub 2} pressure. Comparison of the coal and coprocessing systems reveals many similarities in the catalytic requirements for both systems. Both hydrogenation and hydrogenolysis activities are required and the reactive environments are similar. Also, the use of catalysts in the two systems shares problems with similar types of inhibitors and poisons. The logical extension of this is that it may be reasonable to expect similar trends in catalyst activity for both systems. In fact, many of the catalysts selected for coal liquefaction were selected based on their effectiveness in petroleum systems. This study investigates the use of supported and dispersed coal liquefaction catalysts in coal-oil coprocessing and petroleum-only systems. The focus of the study was delineating the effects of coal concentration, pressure, and catalyst type

Preliminary analysis of the genetic variability of two natural beds of the Scallop Euvola ziczac (Linnaeus, 1758) in Brazil

Euvola ziczac (formerly Pecten ziczac), a simultaneous hermaphroditic scallop was heavily fished in Brazil between 1972 and 1980. The production peaked in 1980 with 8,800 tons and was followed by the total collapse of the resource. In order to investigate the possible loss of genetic variability of the stock associated to overfishing and self-fertilization, the polymorphism of phosphoglucomutase (PGM) and glucose phosphate isomerase (GPI) was analyzed by electrophoresis of the adductor muscle of scallops from São Francisco (26° 20.583S; 48° 16.507W) and Bom Abrigo (25° 28.735S; 47° 37.621W) beds; the southern and northern extremes of the scallop fishing ground, respectively. Animals from São Francisco showed a strong deficiency of heterozygosity for GPI and PGM. In addition, PGM showed *exclusive alleles for each bed. Such results coupled with other information about the species suggested the following hypothesis: a) the stock was a metapopulation with at least two populations; b) some reproductive isolation might be occurring which might be influenced by conditions of larval transport and by the extremely low densities of scallops; c) presently, the stock seemed to be mostly maintained through self-fertilization; d) São Francisco could constitute a source-area, contributing with larvae and recruits to Bom Abrigo and other areas; e) both beds were suffering a genetic homogenization more evident in São Francisco. Such hypothesis needed to be investigated in order to furnish guidelines for future programs of recovery and management of the resource.info:eu-repo/semantics/publishedVersio