Finite Temperature Effective Potential for Gauge Models in de Sitter Space

The one-loop effective potential for gauge models in static de Sitter space at finite temperatures is computed by means of the $\zeta$--function method. We found a simple relation which links the effective potentials of gauge and scalar fields at all temperatures. In the de Sitter invariant and zero-temperature states the potential for the scalar electrodynamics is explicitly obtained, and its properties in these two vacua are compared. In this theory the two states are shown to behave similarly in the regimes of very large and very small radii a of the background space. For the gauge symmetry broken in the flat limit ($a \to \infty$) there is a critical value of a for which the symmetry is restored in both quantum states. Moreover, the phase transitions which occur at large or at small a are of the first or of the second order, respectively, regardless the vacuum considered. The analytical and numerical analysis of the critical parameters of the above theory is performed. We also established a class of models for which the kind of phase transition occurring depends on the choice of the vacuum.Comment: 23 pages, LaTeX, 5 figure.ep

Implementation of two data bases on biosafety of biocontrol agents.

Since 1994, two data bases are being developed at the National Research Center for Monitoring and Environmental Impact Assessment - (CNPMA/EMBRAPA), under a project entitled "Risk Analysis and Environmental Impact of the Use of Biocontrol Agents". The first, "Who is Who on Risk Assessment of Biocontrol Agents" is an international data base and stores information on researchers, institutions and laboratories involved in such studies. It is presently available on the Internet for on-line search. Over 300 specialists from around the world are currently included in the data base. The second, "Risk Assessment of Biocontrol Agents", stores information collected from scientific papers about methodologies for risk assessment of the use of biocontrol agents. Over 100 papers have been processed and available for consultation at CNPMA/EMBRAPA's library. These data bases are being developed under a research project, conducted at CNPMA. The contribution of this work is to identify researchers and institutions that work with this issue and provide fast communication among them to faster exchange of experiences, and also to facilitate the selection of methodologies that could be used in different studies

Urokinase-type plasminogen activator and arthritis progression: contrasting roles in systemic and monoarticular arthritis models

INTRODUCTION: Urokinase-type plasminogen activator (u-PA) has been implicated in tissue destruction/remodeling. The absence of u-PA results in resistance of mice to systemic immune complex-driven arthritis models; monoarticular arthritis models involving an intra-articular (i.a.) antigen injection, on the other hand, develop more severe arthritis in its absence. The aims of the current study are to investigate further these contrasting roles that u-PA can play in the pathogenesis of inflammatory arthritis and to determine whether u-PA is required for the cartilage and bone destruction associated with disease progression. METHODS: To determine how the different pathogenic mechanisms leading to arthritis development in the different models may explain the contrasting requirement for u-PA, the systemic, polyarticular, immune complex-driven K/BxN arthritis model was modified to include an i.a. injection of saline as a local trauma in u-PA-/- mice. This modified model and the antigen-induced arthritis (AIA) model were also used in u-PA-/- mice to determine the requirement for u-PA in joint destruction. Disease severity was determined by clinical and histologic scoring. Fibrin(ogen) staining and the matrix metalloproteinase (MMP)-generated neoepitope DIPEN staining were performed by immunohistochemistry. Gene expression of inflammatory and destructive mediators was measured in joint tissue by quantitative PCR. RESULTS: In our modified arthritis model, u-PA-/- mice went from being resistant to arthritis development following K/BxN serum transfer to being susceptible following the addition of an i.a. injection of saline. u-PA-/- mice also developed more sustained AIA compared with C57BL/6 mice, including reduced proteoglycan levels and increased bone erosions, fibrin(ogen) deposition and DIPEN expression. Synovial gene expression of the proinflammatory mediators (TNF and IL-1β), aggrecanases (ADAMTS-4 and -5) and MMPs (MMP3 and MMP13) were all sustained over time following AIA induction in u-PA-/- mice compared with C57BL/6 mice. CONCLUSIONS: We propose that u-PA has a protective role in arthritis models with 'wound healing-like' processes following local trauma, possibly through u-PA/plasmin-mediated fibrinolysis, but a deleterious role in systemic models that are critically dependent on immune complex formation and complement activation. Given that cartilage proteoglycan loss and bone erosions were present and sustained in u-PA-/- mice with monoarticular arthritis, it is unlikely that u-PA/plasmin-mediated proteolysis is contributing directly to this tissue destruction/remodeling

Atrial natriuretic peptide effects on intracellular pH changes and ROS production in HEPG2 cells: Role of p38 MAPK and phospholipase D

Aims: The present study was performed to evaluate Atrial Natriuretic Peptide ( ANP) effects on intracellular pH, phospholipase D and ROS production and the possible relationship among them in HepG2 cells. Cancer extracellular microenvironment is more acidic than normal tissues and the activation of NHE- 1, the only system able to regulate pHi homeostasis in this condition, can represent an important event in cell proliferation and malignant transformation. Methods: The ANP effects on pHi were evaluated by fluorescence spectrometry. The effects on p38 MAPK and ROS production were evaluated by immunoblots and analysis of DCF- DA fluorescence, respectively. RT- PCR analysis and Western blotting were used to determine the ANP effect on mRNA NHE- 1 expression and protein levels. PLD- catalyzed conversion of phosphatidylcholine to phosphatydilethanol ( PetOH), in the presence of ethanol, was monitored by thin layer chromatography. Results: A significant pHi decrease was observed in ANP- treated HepG2 cells and this effect was paralleled by the enhancement of PLD activity and ROS production. The ANP effect on pHi was coupled to an increased p38 MAPK phosphorylation and a down- regulation of mRNA NHE- 1 expression and protein levels. Moreover, the relationship between PLD and ROS production was demonstrated by calphostin- c, a potent inhibitor of PLD. At the same time, all assessed ANP- effects were mediated by NPR- C receptors. Conclusion: Our results indicate that ANP recruits a signal pathway associated with p38 MAPK, NHE- 1 and PLD responsible for ROS production, suggesting a possible role for ANP as novel modulator of ROS generation in HepG2 cells. Copyright (C) 2005 S. Karger AG, Basel

Left hemispatial neglect and overt orienting in naturalistic conditions: Role of high-level and stimulus-driven signals

Deficits of visuospatial orienting in brain-damaged patients affected by hemispatial neglect have been extensively investigated. Nonetheless, spontaneous spatial orienting in naturalistic conditions is still poorly understood. Here, we investigated the role played by top-down and stimulus-driven signals in overt spatial orienting of neglect patients during free-viewing of short videos portraying everyday life situations. In Experiment 1, we assessed orienting when meaningful visual events competed on the left and right side of space, and tested whether sensory salience on the two sides biased orienting. In Experiment 2, we examined whether the spatial alignment of visual and auditory signals modulates orienting. The results of Experiment 1 showed that in neglect patients severe deficits in contralesional orienting were restricted to viewing conditions with bilateral visual events competing for attentional capture. In contrast, orienting towards the contralesional side was largely spared when the videos contained a single event on the left side. In neglect patients the processing of stimulus-driven salience was relatively spared and helped orienting towards the left side when multiple events were present. Experiment 2 showed that sounds spatially aligned with visual events on the left side improved orienting towards the otherwise neglected hemispace. Anatomical scans indicated that neglect patients suffered grey and white matter damages primarily in the ventral frontoparietal cortex. This suggests that the improvement of contralesional orienting associated with visual salience and audiovisual spatial alignment may be due to processing in the relatively intact dorsal frontoparietal areas. Our data show that in naturalistic environments, the presence of multiple meaningful events is a major determinant of spatial orienting deficits in neglect patients, whereas the salience of visual signals and the spatial alignment between auditory and visual signals can counteract spatial orienting deficits. These results open new perspectives to develop novel rehabilitation strategies based on the use of naturalistic stimuli

Heat-kernel Coefficients and Spectra of the Vector Laplacians on Spherical Domains with Conical Singularities

The spherical domains $S^d_\beta$ with conical singularities are a convenient arena for studying the properties of tensor Laplacians on arbitrary manifolds with such a kind of singular points. In this paper the vector Laplacian on $S^d_\beta$ is considered and its spectrum is calculated exactly for any dimension $d$. This enables one to find the Schwinger-DeWitt coefficients of this operator by using the residues of the $\zeta$-function. In particular, the second coefficient, defining the conformal anomaly, is explicitly calculated on $S^d_\beta$ and its generalization to arbitrary manifolds is found. As an application of this result, the standard renormalization of the one-loop effective action of gauge fields is demonstrated to be sufficient to remove the ultraviolet divergences up to the first order in the conical deficit angle.Comment: plain LaTeX, 23 pp., revised version, a misprint in expressions (1.8) and (4.38) of the second heat coefficient for the vector Laplacian is corrected. No other change

Avaliação ecotoxicologica de agentes microbianos de controle de pragas.

A concessão de registro comercial de produtos fitossanitários contendo agentes microbianos de controle de pragas (AMCs), os biopesticidas, pelos órgãos federais registrantes esta sujeita a previa apresentação de dados que indiquem conclusivamente que o produto, quando usado de acordo com as prescrições, não causará efeitos significativamente adversos a seres humanos ou ao ambiente. Esta avaliação dos riscos potenciais de um AMC e parte importante tanto no processo de desenvolvimento do produto como na sua regulamentação (registro comercial). Esse processo é necessário para assegurar que o agente microbiano a ser utilizado ofereça riscos mínimos ao ambiente e aos organismos não-visados. No Brasil, os documentos básicos relativos ao registro de produtos fitossanitários contendo AMCs são regulamentações do Ministério da Agricultura - MA, Lei n.7.802, de 11/7/89 e Decreto n.98.816, de 11/1/90 (Brasil, 1995) e do Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis - IBAMA (Portaria 131 de 3/11/97) (Brasil, 1997), esta ultima especifica para o registro de biopesticidas para uso em florestas e ecossistemas hídricos. No âmbito da região do Cone Sul também existe uma regulamentação harmonizada entre Argentina, Brasil, Chile, Paraguai e Uruguai, a ser implementada na região a partir de janeiro de 1998 (COSAVE, 1997), bastante semelhante aquela aprovada pelo IBAMA, uma vez que a proposta aprovada no Cone Sul foi apresentada pelo Brasil. Como forma de defesa do ambiente e dos consumidores, compete aos órgãos públicos estabelecer os critérios para a avaliação de riscos, dentro de normas especificas, compatíveis com os padrões internacionais que regulamentam o mesmo assunto. Estas normas devem levar em consideração as características especificas dos produtos biológicos quanto a composição, forma de ação e comportamento no ambiente. Os testes de segurança geralmente exigidos incluem uma avaliação toxicológica em mamíferos e uma ecotoxicologica sobre organismos benéficos não-visados do ambiente, além de uma identificação completa do microrganismo e seu processamento e componentes da formulação. Esse documento abordará apenas o processo de avaliação ecotoxicologica de biopesticidas sobre organismos benéficos não-visados

Aspectos de risco e impacto ambiental dos agentes microbianos.

Recentemente se observa que os procedimentos para controle de pragas estão mudando no mundo todo, com velocidade maior ou menor dependendo do estágio de desenvolvimento econômico e social de cada país. Vários fatores fazem esta mudança inevitável, entre eles o custo elevado para se desenvolver novas moléculas químicas, o aumento do rigor na legislação de alguns países quanto a presença de resíduos químicos em alimentos, e a preocupação do publico quanto a efeitos adversos dos pesticidas químicos. Assim, o numero de novos produtos químicos no mercado diminuiu ao longo dos últimos anos. Por outro lado e crescente a necessidade de novos produtos ou formas de controle, motivada pelo aparecimento de resistência de pragas a pesticidas químicos e pelo surgimento de novas pragas. E este desbalanceamento entre a necessidade e a disponibilidade de alternativas e que tem impulsionado o desenvolvimentos de técnicas que podemos denominar, de forma geral, de "biológicas": controle biológico clássico, que envolve principalmente a utilização de inimigos naturais; controle microbiano, que utiliza microrganismos (vírus, bactérias, fungos e protozoários), formulados ou não, capazes de causar doenças em insetos ou prevenir o estabelecimento de microrganismos causadores de doenças em plantas; modificadores de comportamento da praga, que exploram comportamentos específicos das pragas de forma a confundi-las ou altera-las, conseguindo assim o seu controle (ex. feromônios); manipulação genética: técnica esta que tem seu alcance pela interferência na reprodução do inseto, na imunização da planta ao ataque de insetos selecionados ou no aumento da atividade microbiana de controle da praga. Entretanto, qualquer que seja a técnica biológica utilizada para uso no controle de pragas, ela não será livre de risco

Thermal Fields, Entropy, and Black Holes

In this review we describe statistical mechanics of quantum systems in the presence of a Killing horizon and compare statistical-mechanical and one-loop contributions to black hole entropy. Studying these questions was motivated by attempts to explain the entropy of black holes as a statistical-mechanical entropy of quantum fields propagating near the black hole horizon. We provide an introduction to this field of research and review its results. In particular, we discuss the relation between the statistical-mechanical entropy of quantum fields and the Bekenstein-Hawking entropy in the standard scheme with renormalization of gravitational coupling constants and in the theories of induced gravity.Comment: 44 pages, LaTeX fil