Isolamento de bactérias associadas a plantas do bioma caatinga no semiárido nordestino.

A Caatinga é um bioma exclusivamente brasileiro e corresponde a 70% do território nordestino. Esse bioma caracteriza-se pela distribuição irregular das chuvas e pelas características sazonais de sua vegetação, que apresenta forte endemismo. Atrelada a essa rica vegetação e adaptada às condições peculiares desta região, está a microbiota, em especial as rizobactérias. Este trabalho teve por objetivo isolar bactérias e avaliar a densidade destes micro-organismos associados à raiz e rizosfera de plantas de cinco famílias botânicas da Caatinga. As amostras foram separadas em solo da rizosfera e raiz, sendo as amostras de tecido radicular submetidas a um processo de desinfecção superficial. As bactérias associadas à raiz e da rizosfera foram isoladas em meio TSA acrescido de 5% de NaCl. A densidade populacional bacteriana associada à raiz variou de 9,3 X 103 (Cobretum sp.) a 1,9 X 108 (Terminalia sp.) UCF/g TVF e da rizosfera a variação foi de 3,3 X 108 (Schinus sp.) e 8,3 X 104 (Cobretum sp.) UCF/g TVF. A variabilidade morfológica encontrada neste trabalho sugere uma ampla diversidade de genótipos bacterianos associados à rizosfera e raízes de plantas destes gêneros encontrados na Caatinga

Temporal build-up of electromagnetically induced transparency and absorption resonances in degenerate two-level transitions

The temporal evolution of electromagnetically induced transparency (EIT) and absorption (EIA) coherence resonances in pump-probe spectroscopy of degenerate two-level atomic transition is studied for light intensities below saturation. Analytical expression for the transient absorption spectra are given for simple model systems and a model for the calculation of the time dependent response of realistic atomic transitions, where the Zeeman degeneracy is fully accounted for, is presented. EIT and EIA resonances have a similar (opposite sign) time dependent lineshape, however, the EIA evolution is slower and thus narrower lines are observed for long interaction time. Qualitative agreement with the theoretical predictions is obtained for the transient probe absorption on the $^{85}Rb$ $D_{2}$ line in an atomic beam experiment.Comment: 10 pages, 9 figures. Submitted to Phys. Rev.

Bactérias associadas a plantas do bioma caatinga: fixação de nitrogênio X salinidade.

A Caatinga é um bioma com alto grau de endemismo, típico do Semiárido do Nordeste brasileiro, e enfrenta problemas de salinidade, principalmente nas áreas com agricultura irrigada. A fixação biológica de nitrogênio (FBN) é o principal processo responsável pela entrada de nitrogênio de forma assimilável pelas plantas nos ecossistemas. Neste contexto, este trabalho teve como objetivo selecionar bactérias fixadoras de nitrogênio, isoladas de plantas da Caatinga, e avaliar a influência da salinidade sobre esse processo. As bactérias foram inoculadas em meio semisólido NFb, livre de nitrogênio, e para avaliação da salinidade sobre a FBN foram inoculadas em NFb com o acréscimo de 0,01%; 0,1%; 1%; 2,5%; e 5% de NaCl. Foi observado que 65% das bactérias foram capazes de fixar nitrogênio in vitro, apresentando maior frequência entre as linhagens isoladas da raiz. A estimativa da distância entre o halo de crescimento e a superfície do meio apresentou diferenças entre as bactérias, podendo-se inferir diferenças de tolerância ao oxigênio. Quanto à influência da salinidade sobre a FBN, foi observado que a concentração de 5% inibiu a FBN em todas as linhagens avaliadas. Além disso, as bactérias apresentaram diferentes limites de tolerância quanto à capacidade de fixar nitrogênio in vitro

Adiabatic following criterion, estimation of the nonadiabatic excitation fraction and quantum jumps

An accurate theory describing adiabatic following of the dark, nonabsorbing state in the three-level system is developed. An analytical solution for the wave function of the particle experiencing Raman excitation is found as an expansion in terms of the time varying nonadiabatic perturbation parameter. The solution can be presented as a sum of adiabatic and nonadiabatic parts. Both are estimated quantitatively. It is shown that the limiting value to which the amplitude of the nonadiabatic part tends is equal to the Fourier component of the nonadiabatic perturbation parameter taken at the Rabi frequency of the Raman excitation. The time scale of the variation of both parts is found. While the adiabatic part of the solution varies slowly and follows the change of the nonadiabatic perturbation parameter, the nonadiabatic part appears almost instantly, revealing a jumpwise transition between the dark and bright states. This jump happens when the nonadiabatic perturbation parameter takes its maximum value.Comment: 33 pages, 8 figures, submitted to PRA on 28 Oct. 200

Biocontrol of Rhizoctonia solani damping-off and promotion of tomato plant growth by endophytic actinomycetes isolated from native plants of Algerian Sahara

Thirty-four endophytic actinomycetes were isolated from the roots of native plants of the Algerian Sahara. Morphological and chemical studies showed that twenty-nine isolates belonged to the Streptomycesgenus and five were non-Streptomyces. All isolates were screened for their in vitro antifungal activityagainst Rhizoctonia solani. The six that had the greatest pathogen inhibitory capacities were subsequentlytested for their in vivo biocontrol potential on R. solani damping-off in sterilized and non-sterilized soils,and for their plant-growth promoting activities on tomato seedlings. In both soils, coating tomato seedswith antagonistic isolates significantly reduced (P < 0.05) the severity of damping-off of tomato seedlings.Among the isolates tested, the strains CA-2 and AA-2 exhibited the same disease incidence reduction asthioperoxydicarbonic diamide, tetramethylthiram (TMTD) and no significant differences (P < 0.05) wereobserved. Furthermore, they resulted in a significant increase in the seedling fresh weight, the seedling length and the root length of the seed-treated seedlings compared to the control. The taxonomic positionbased on 16S rDNA sequence analysis and phylogenetic studies indicated that the strains CA-2 AA-2were related to Streptomyces mutabilis NBRC 12800ᵀ(100% of similarity) and Streptomyces cyaneofuscatus JCM 4364ᵀ(100% of similarity), respectively

Character Recognition Based on Phenomenological Attributes

A theoretical approach is suggested for describing upper-case letters not in terms of the physical attributes of their archetypes but in terms of more general descriptions of their underlying representations. A method is presented for finding these general descriptions through the study of ambiguous characters. Functional attributes are the describers of the underlying representations of letters. The relations between the physical attributes of the input character and the functional attributes that specify its identity are given in part by graphical context rules which incorporate the stylistic consistency within the character itself and its neighbors. The implications of our theory of characters to the areas of computerized character recognition and type design are noted

BIOPROSPECÇÃO E DIVERSIDADE GENÉTICA DE BACTÉRIAS ENDOFÍTICAS ASSOCIADAS A PLANTAS DE MANDIOCA

Cassava is mostly planted in sandy soils which are usually of low fertility, thereby making it necessary to perform beneficial associations with microorganisms that can promote their growth. In this perspective, the possibility of selecting bacterial isolates efficient in promoting the growth of the culture is evident, which can provide subsidies for future inoculants. The objective of this study was to isolate, identify, select and evaluate the genetic diversity of endophytic bacteria in roots and stems of cassava grown in Garanhuns - PE, with features involved in promoting plant growth. The isolation was performed on culture medium semisolid LGI-P. The selected isolates were evaluated for the potential to fix N2, as the ability to produce indole acetic acid, for their ability to solubilize inorganic phosphate and produce exopolysaccharides. Some bacterial isolates had their 16S rRNA gene sequenced by the Sanger method. A total of 52 endophytic bacteria isolates were obtained from cassava. Regarding the potential to fix N2, 15% of the isolates were positive. As for the production of IAA, 78% of the isolates produced this phytohormone in a medium with increased L-tryptophan. Approximately 31% of the isolates were able to solubilize inorganic phosphate and 60% had exopolysaccharide. The identification of 19 isolates allowed the grouping into six bacterial genera, namely: Achromobacter, Bacillus, Burkholderia, Enterobacter, Pantoea and Pseudomonas. Cassava plants grown in Garanhuns - PE present interaction with different groups of endophytic bacteria and there are bacterial groups with several characteristics involved in promoting plant growth.A mandioca é, geralmente, plantada em solos arenosos e de baixa fertilidade, tornando eminente a necessidade da mesma em realizar associações benéficas com micro-organismos que possam auxiliar seu crescimento. Nessa ótica, é evidente a possibilidade de seleção de isolados bacterianos eficientes em promover o crescimento da cultura, os quais podem fornecer subsídios para futuros inoculantes. O objetivo deste trabalho foi isolar, identificar, selecionar e avaliar a diversidade genética de bactérias endofíticas de raízes e caules de mandioca, cultivada em Garanhuns - PE, com características envolvidas na promoção de crescimento vegetal. O isolamento foi realizado em meio de cultura semissólido LGI-P. Os isolados selecionados foram avaliados quanto ao potencial de fixar N2, quanto à capacidade de produzir ácido indol acético, quanto à capacidade de solubilizar fosfato inorgânico e produzir exopolissacarídeos. Alguns isolados bacterianos tiveram o gene 16S rRNA sequenciados pelo método de Sanger. No total, foram obtidos 52 isolados de bactérias endofíticas de mandioca. Em relação ao potencial para fixar N2, 15% dos isolados foram positivos. Quanto à produção de AIA, 78% dos isolados produziram este fitohormônio em meio com o acréscimo de L-triptofano. Cerca de 31% dos isolados foram capazes de solubilizar fosfato inorgânico e 60% apresentaram produção de exopolissacarídeos. A identificação de 19 isolados possibilitou o agrupamento em seis gêneros bacterianos, sendo eles: Achromobacter, Bacillus, Burkholderia, Enterobacter, Pantoea e Pseudomonas. Plantas de mandioca cultivadas em Garanhuns - PE apresentam interação com diferentes grupos de bactérias endofíticas e há grupos bacterianos com diversas características envolvidas na promoção de crescimento vegetal

Un Modelo de aplicación web institucional universitaria : el caso de los webcom: webs de facultades de comunicación de Iberoamérica /

Consultable des del TDXTítol obtingut de la portada digitalitzadaDesde su inicio, la tesis doctoral perseguía un objetivo prioritario: el diseño de un modelo de aplicación web institucional universitaria. Para ello se fueron estableciendo categorías específicas que, bajo parámetros de calidad, sirvieron como referencia para el análisis de los productos institucionales hoy existentes. La investigación se inició en 2002 con una percepción del investigador: facultades que enseñan comunicación no suelen tener una efectiva política de comunicación institucional en diversos frentes o, en peor caso, carecen de ella. Esta percepción se repetía en los sitios web institucionales de las carreras, estudios o facultades de comunicación ya conocidos y visitados, que distaban demasiado de ser productos profesionales de técnicos universitarios. La conclusión más relevante extraída de la investigación es que de 64 sitios web observados y analizados, menos de una decena estén en condiciones de considerarse productos eficientes de comunicación y gestión. Esta realidad no puede entenderse, simplemente, como producto de la casualidad. A partir de esta experiencia, los actores implicados deberían entender que en la última década se ha dado un cambio muy significativo en el modo de gestionar la información en las organizaciones. Se tiene la tecnología a disposición para utilizarla en pos de la eficacia de la misión institucional, y aunque no es la panacea que solucionará todas las dificultades, es una herramienta que, bien utilizada, genera mayor productividad y eficiencia en la gestión global. La construcción de un modelo teórico-práctico que funcione como el verdadero punto de partida para el desarrollo de aplicaciones webs universitarios institucionales es el principal resultado de esta investigación. Las conclusiones que aquí se sintetizan refuerzan el diseño del propio modelo, a partir de una percepción bien acabada de cómo los públicos abordan y consumen el producto. Además, como un espiral de conocimiento, tanto el modelo final como las conclusiones sobre el consumo serán útiles como antecedentes en futuras investigaciones y proyectos de comunicación institucional universitaria.From their beginning, the doctoral thesis persecuted a high-priority objective: the design of a model of university application institutional web. For it, we were establishing specific categories that, under quality parameters, served like reference for the analisis of already existing institutional products. The investigation began in 2002 with a perception of the investigador: faculties that teach communication usually do not have an effective policy of institutional communication in diverse fronts or, in worse case, they lack her. This perception repeated in the institutional websites of the degrees, studies or faculties of communication already known and visited, that were far from being professional products of university technicians. The most important conclusion extracted of the investigation is that of 64 observed and analyzed websites, less than a ten they can consider efficient products of communication and management. This reality can not be understood simply, like product of the chance. From this experience, the implied actors would have to understand that in the last decade a very significant change in the way has ocurred to manage the information in the organizations. The technology to disposition must to use it after the effectiveness of the institutional mission, and, although it is not the panacea that will solve all the dificulties, it is a tool that, used well, generates greater productivity and efficiency in the global management. The construction of a theorical-practical model that it works as a true departure point for the development of institutional university applications webs is the main result of this investigation. The conclusions that are synthesized here reinforce the design of the own model, from a finished affluent perception of how the public approach and consume the product. In adittion, like a knowledge spiral, as much the final model as the conclusions on the consumption will be usefull like antecedents in future investigations and projects of university institutional communication