Torsion nonminimally coupled to the electromagnetic field and birefringence

In conventional Maxwell--Lorentz electrodynamics, the propagation of light is influenced by the metric, not, however, by the possible presence of a torsion T. Still the light can feel torsion if the latter is coupled nonminimally to the electromagnetic field F by means of a supplementary Lagrangian of the type l^2 T^2 F^2 (l = coupling constant). Recently Preuss suggested a specific nonminimal term of this nature. We evaluate the spacetime relation of Preuss in the background of a general O(3)-symmetric torsion field and prove by specifying the optical metric of spacetime that this can yield birefringence in vacuum. Moreover, we show that the nonminimally coupled homogeneous and isotropic torsion field in a Friedmann cosmos affects the speed of light.Comment: Revtex, 12 pages, no figure

Massive motion in Brans-Dicke geometry and beyond

Gravity theories that can be viewed as dynamics for area metric manifolds, for which Brans-Dicke theory presents a recently studied example, require for their physical interpretation the identification of the distinguished curves that serve as the trajectories of light and massive matter. Complementing previous results on the propagation of light, we study effective massive point particle motion. We show that the relevant geometrical structure is a special Finsler norm determined by the area metric, and that massive point particles follow Finsler geodesics.Comment: 12 page

Effect of antioxidant and optimal antimicrobial mixtures of carvacrol, grape seed extract and chitosan on different spoilage microorganisms and their application as coatings on different food matrices

There is growing interest in the use of natural agents with antimicrobial (AM) and antioxidant (AOX) properties. Optimization of the AM capacity for mixtures containing carvacrol, grape seed extract (GSE) and chitosan, against gram-negative (Pseudomonas aeruginosa), gram-positive bacteria (Staphylococcus aureus, Listeria innocua and Enterococcus faecalis) and yeast (Saccharomyces cerevisiae) at 106 cfu mL−1 was studied. To observe the synergistic or antagonistic effect and find optimal combinations between the three agents, a simplex centroid mixture design was run for each microorganism, combining carvacrol (0-300 ppm, X1)X, GSE (0-2000 ppm, X2) and chitosan (0-2% w/v, X3). Results of the response surface analysis showed several synergistic effects for all microorganisms. Combinations of 60 ppm-400 ppm-1.2% w/v (carvacrol-GSE-chitosan; optimal AM combination 1, OAMC-1); 9.6 ppm-684 ppm-1.25% w/v (OAMC-2); 90 ppm-160 ppm-1.24% w/v (OAMC-3) were found to be the optimal mixtures for all microorganisms. Radical scavenging activity (RSA) of the same agents was then compared with a standard AOX (butylated hydroxytoluene; BHT) at different concentrations (25, 50 and 100 ppm; as well as the optimal AM concentrations) by the 1,1-diphenyl-2- picrylhydrazyl (DPPH) method. RSA increased in the following order: chitosan< carvacrol< BHT< GSE and for the OAMC: OAMC-2< OAMC-1< OAMC-3. The best RSA (OAMC-3) was applied as a coating in two different food matrices (strawberries and salmon). For strawberries, P. aeruginosa was more sensitive to the action of OAMC-3 than S. cerevisiae. For salmon, S. aureus was more resistant to the action of OAMC-3 than E. faecalis and L. innocua.info:eu-repo/semantics/publishedVersio

Why disease due to Mycobacterium tuberculosis is less common than expected in HIV-positive patients in Edinburgh

AbstractBy December 1993, only five cases of tuberculosis were observed in the 1030 HIV-positive patients in Edinburgh, U.K., although, on the basis of historical tuberculin skin test data, between four and eight new cases of tuberculosis were expected per year. Of 310 HIV-positive patients, none of the 19 (6·1%) who were tuberculin skin test positive had developed tuberculosis after 87 months (average) of follow-up. It is suggested that new or re-infection is a more common cause of tuberculosis in HIV-positive patients than reactivation. Restriction fragment length polymorphism typing of Mycobacterium tuberculosis strains could confirm this hypothesis and support currently suggested additional infection control procedures

Geographic Information Systems(GIS) and Virtual Reality Models (VRM) to Improve the Analysis of Genetic and Silvicultural Trials

GIS systems have become core tools for mapping needs in forestry. During the last decade software platforms have expanded the basic capabilities of data storage and retrieval in map formats. Complex overlay procedures, terrain analysis, 3D modeling, spatial and geostatistical tools, and remote sensing integration have increased the power of space related information. In addition, new VRM have emerged as improved tools for visualization, simulation and teaching. Research field trials in forestry are usually established to minimize spatial environmental variation, however exploring this assumption �ex ante� or �ex post� has been always tedious and uncertain and has lacked the power of visualization and analysis. Powerful spatial statistical analyses and interpolation analyses may be integrated to visualize site variability, remove environmental trends or integrate those to conventional statistical analyses. We investigated the �ex post� analysis of a research trial using ARCMAP/GIS and ARCScene VRM tools (ESRI, Inc) in order to explore their utility for trial analysis. Detailed sampling activities investigating specific physiological or ecological process may take full advantage of GIS and VRM tools capabilities to understand site variability and locate highly representative sampling points. That information may be used for modeling based on the same spatial information.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Combined microbiological test to assess changes in an organic matrix used to avoid agricultural soil contamination, exposed to an insecticide

Combined microbiological test (Biolog Ecoplate, denaturing gradient gel electrophoresis (DGGE) and Real Time PCR (qPCR)) were developed to evaluate the impact of repeated diazinon (DZN) applications at high concentration (40 mg kg-1) on microbial communities in a microcosm simulating the organic matrix (straw (50%): peat (25%): soil (25%) vv-1) of an pesticide biopurification system (PBS). Moreover, pesticide dissipation was also evaluated. After three successive exposition of DZN, dissipation efficiency was high; achieved 87%, 93% and 96% after each application, respectively showing a clear accelerated dissipation of this pesticide in the organic matrix. The results obtained with Biolog Ecoplate showed that community level physiological profiles were no affected by the addition of DZN. On the other hand, molecular assays (DGGE and QPCR) demonstrated that the microbial structure (bacteria and fungi) remained relatively stable over time with high DZN doses compared to control. Therefore, the results of the present study, clearly, demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.Fil: Tortella, G. R.. Universidad de la Frontera. Nucleo Cientifico y Tecnologico En Recursos Naturales (bioren-ufro). Departamento de Ciencias Quimicas y Recursos Naturales; ChileFil: Salgado, E.. Universidad de la Frontera. Nucleo Cientifico y Tecnológico En Recursos Naturales; ChileFil: Cuozzo, Sergio Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); ArgentinaFil: Mella Herrera, R. A.. Universidad de la Frontera. Nucleo Cientifico y Tecnológico En Recursos Naturales; ChileFil: Parra, L.. Universidad de la Frontera. Núcleo Científico y Tecnológico en Recursos Naturales; ChileFil: Diez, M. C.. Universidad de la Frontera. Nucleo Cientifico y Tecnológico En Recursos Naturales; ChileFil: Rubilar, O.. Universidad de la Frontera. Nucleo Cientifico y Tecnológico En Recursos Naturales; Chil

Dominance and Stand Structure Analyses of a GXE Interaction Trial

Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Carbendazim dissipation in the biomixture of on-farm biopurification systems and its effect on microbial communities

The impact of repeated carbendazim (CARB) applications on the extent of \CARB\ dissipation, the microbial diversity, the community level physiological profile (CLPP), and the enzymatic activity within the biomixture of an on-farm biopurification system was evaluated. After three successive \CARB\ applications, the \CARB\ dissipation efficiency was high; the efficiency of dissipation was 87%, 94% and 96% after each application, respectively. Although microbial enzymatic activity was affected significantly by \CARB\ application, it could recover after each \CARB\ pulse. Likewise, the numbers of cultivable bacteria, fungi and actinomycetes (as measured in CFUs) were slightly affected by the addition of CARB, but the inhibitory effect of the pesticide application was temporary. Denaturing gradient gel electrophoresis (DGGE) and Biolog Ecoplate assays demonstrated that the microbial populations remained relatively stable over time when compared to the control. The results obtained herein therefore demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.This work was supported by FONDECYT project No 11100236

Maxwell's field coupled nonminimally to quadratic torsion: Induced axion field and birefringence of the vacuum

We consider a possible (parity conserving) interaction between the electromagnetic field $F$ and a torsion field $T^\alpha$ of spacetime. For generic elementary torsion, gauge invariant coupling terms of lowest order fall into two classes that are both nonminimal and {\it quadratic} in torsion. These two classes are displayed explicitly. The first class of the type $\sim F T^2$ yields (undesirable) modifications of the Maxwell equations. The second class of the type $\sim F^2 T^2$ doesn't touch the Maxwell equations but rather modifies the constitutive tensor of spacetime. Such a modification can be completely described in the framework of metricfree electrodynamics. We recognize three physical effects generated by the torsion: (i) An axion field that induces an {\em optical activity} into spacetime, (ii) a modification of the light cone structure that yields {\em birefringence} of the vacuum, and (iii) a torsion dependence of the {\em velocity of light.} We study these effects in the background of a Friedmann universe with torsion. {\it File tor17.tex, 02 August 2003}Comment: 6 page