Loop quantum gravity and light propagation

Within loop quantum gravity we construct a coarse-grained approximation for the Einstein-Maxwell theory that yields effective Maxwell equations in flat spacetime comprising Planck scale corrections. The corresponding Hamiltonian is defined as the expectation value of the electromagnetic term in the Einstein-Maxwell Hamiltonian constraint, regularized a la Thiemann, with respect to a would-be semiclassical state. The resulting energy dispersion relations entail Planck scale corrections to those in flat spacetime. Both the helicity dependent contribution of Gambini and Pullin [GP] and, for a value of a parameter of our approximation, that of Ellis et. al. [ELLISETAL] are recovered. The electric/magnetic asymmetry in the regularization procedure yields nonlinearities only in the magnetic sector which are briefly discussed. Observations of cosmological Gamma Ray Bursts might eventually lead to the needed accuracy to study some of these quantum gravity effects.Comment: Latex, 45 pages, shorter abstract, additional reference

Systematics of the Neotropical Genus Leptodactylus Fitzinger, 1826 (Anura: Leptodactylidae): Phylogeny, the Relevance of Non-molecular Evidence, and Species Accounts

A phylogeny of the species-rich clade of the Neotropical frog genus Leptodactylus sensu stricto is presented on the basis of a total evidence analysis of molecular (mitochondrial and nuclear markers) and non-molecular (adult and larval morphological and behavioral characters) sampled from > 80% of the 75 currently recognized species. Our results support the monophyly of Leptodactylus sensu stricto, with Hydrolaetare placed as its sister group. The reciprocal monophyly of Hydrolaetare and Leptodactylus sensu stricto does not require that we consider Hydrolaetare as either a subgenus or synonym of Leptodactylus sensu lato. We recognize Leptodactylus sensu stricto, Hydrolaetare, Adenomera, and Lithodytes as valid monophyletic genera. Our results generally support the traditionally recognized Leptodactylus species groups, with exceptions involving only a few species that are easily accommodated without proposing new groups or significantly altering contents. The four groups form a pectinate tree, with the Leptodactylus fuscus group diverging first, followed by the L. pentadactylus group, which is sister to the L. latrans and L. melanonotus groups. To evaluate the impact of non-molecular evidence on our results, we compared our total evidence results with results obtained from analyses using only molecular data. Although non-molecular evidence comprised only 3.5% of the total evidence matrix, it had a strong impact on our total evidence results. Only one species group was monophyletic in the molecular-only analysis, and support differed in 86% of the 54 Leptodactylus clades that are shared by the results of the two analyses. Even though no non-molecular evidence was included for Hydrolaetare, exclusion of that data partition resulted in that genus being nested within Leptodactylus, demonstrating that the inclusion of a small amount of non-molecular evidence for a subset of species can alter not only the placement of those species, but also species that were not scored for those data. The evolution of several natural history and reproductive traits is considered in the light of our phylogenic framework. Invasion of rocky outcrops, larval oophagy, and use of underground reproductive chambers are restricted to species of the Leptodactylus fuscus and L. pentadactylus groups. In contrast, larval schooling, larval attendance, and more complex parental care are restricted to the L. latrans and L. melanonotus groups. Construction of foam nests is plesiomorphic in Leptodactylus but their placement varies extensively (e.g., underground chambers, surface of waterbodies, natural or excavated basins). Information on species synonymy, etymology, adult and larval morphology, advertisement call, and geographic distribution is summarized in species accounts for the 30 species of the Leptodactylus fuscus group, 17 species of the L. pentadactylus group, eight species of the L. latrans group, and 17 species of the L. melanonotus group, as well as the three species that are currently unassigned to any species group.Se presenta una filogenia del género Leptodactylus, un ciado neotropical rico en especies, basada en análises combinados de datos moleculares (marcadores nuclear y mitocondriales) y no moleculares (caracteres de la morfología de adultos y larvas así como de comportamiento) se muestrearon > 80% de las 75 especies reconocidas. Los resultados apoyan la monofília de Leptodactylus sensu stricto, con Hydrolaetare como su grupo hermano. La monofília recíproca de Hydrolaetare y Leptodactylus no requiere considerar a Hydrolaetare como un subgénero o sinónimo de Leptodactylus sensu lato. Se reconocen Leptodactylus sensu stricto, Hydrolaetare, Adenomera y Lithodytes como géneros monofiléticos válidos. Los resultados en general resuelven los grupos tradicionalmente reconocidos de Leptodactylus, con excepciones de algunas especies que son reasignadas sin la necesidad de proponer nuevos grupos o alterar significativamente el contenido de los grupos tradicionales. Los cuatro grupos de especies forman una topología pectinada donde el grupo de L. fuscus tiene una posición basal, seguido por el grupo de L. pentadactylus que es el grupo hermano al clado formado por los grupo de L. latrans y L. melanonotus. Se estimó el impacto de los datos no moleculares en los resultados, comparándose los resultados de evidencia total con los de los análises de datos moleculares solamente. Los datos no moleculares representan un 3.5% de la matriz de evidencia total, pero estos datos tuvieron un impacto significativo en los resultados del análisis de evidencia total. En el análisis estrictamente molecular solamente un grupo de especies resultó monofilético, y el apoyo difirió en 86% de los 54 ciados de Leptodactylus compartidos entre los dos análises. A pesar que datos no moleculares no fueron incluidos para Hydrolaetare, la exclusión de evidencia no molecular resultó en el género estar dentro de Leptodactylus, demostrando que la inclusión de evidencia no molecular pequeña para un subgrupo de especies altera no solamente la posición topológica de esas especies, sino tambien de las especies para las cuales dichos datos no fueron codificados. La evolución de patrones de historia natural y reprodución se evalúan en el contexto filogenético. La invasión de afloramientos rocosos y la construción de cámaras de reprodución subterraneas está limitada a los grupos de Leptodactylus fuscus y L. pentadactylus, mientras que la oofagia larval está restringida al grupo de L. pentadactylus. Por otro lado, los cárdumenes larvales, la proteción del cárdumen, y otros comportamientos parentales complejos carecterizan al clado formado por los grupos de especies de L. latrans y L. melanonotus. Los resúmenes de especies incluyen información de sinonimias, etimología, morfología de adultos y larvas, cantos, y distribución geográfica para las 30 especies del grupo de Leptodactylus fuscus, 17 especies del grupo L. pentadactylus, ocho especies del grupo de L. latrans, 17 especies del grupo de L. melanonotus, así como para las tres especies que actualmente no se encuentran asociadas a ninguno de los grupos de especies.Taran Grant was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico Proc. 307001/2011-3 and Fundação de Amparo à Pesquisa do Estado de São Paulo Proc. 2012/10000-5

Removal of heavy metals using different polymer matrixes as support for bacterial immobilisation

Great attention is focused on the microbial treatment of metal contaminated environments. Three bacterial strains, 1C2, 1ZP4 and EC30, belonging to genera Cupriavidus, Sphingobacterium and Alcaligenes, respectively, showing high tolerance to Zn and Cd, up to concentrations of 1000ppm, were isolated from a contaminated area in Northern Portugal. Their contribution to Zn and Cd removal from aqueous streams using immobilised alginate, pectate and a synthetic cross-linked polymer was assessed. In most cases, matrices with immobilised bacteria showed better metal removal than the non-inoculated material alone. For the immobilisation with all the polymers, 1C2 was the strain that increased the removal of Zn the most, whereas EC30 was the most promising for Cd removal, especially when combined with the synthetic polymer with up to a ca. 11-fold increase in metal removal when compared to the polymer alone. Removal of individual metals from binary mixtures showed that there was differential immobilisation. There was greater removal of Cd than Zn (removals up to 40% higher than those showed for Zn). The results show that metal contaminated environments constitute a reservoir of microorganisms resistant/tolerant to heavy metals that have the capacity to be exploited in bioremediation strategies.Capsule immobilisation of bacteria in the naturally occurring alginate and pectate and in a synthetic cross-linked polymer increased the Zn and Cd removal abilities from single and binary contaminated waters; the applications with the synthetic polymer were the most promising for Cd and Zn removal in single and binary mixtures

Paleomagnetic and magnetic fabric studies of the San Gaspar ignimbrite, western Mexico - Constraints on emplacement mode and source vents

Paleomagnetic and magnetic fabric data for the 4.8 Ma San Gaspar ignimbrite, one of the largest in western Mexico, are used to investigate the source vents, emplacement mechanism and tectonics. Rock magnetic properties from distant parts of the ignimbrite are similar, suggesting relatively homogeneous mineralogy of the unit. Isothermal remanence and continuous susceptibility-temperature experiments point to low to medium-Ti titanomagnetites as the main magnetic carriers. Hysteresis ratio parameters of most samples fall in the pseudo-single-domain grain size region; wasp-waisted hysteresis loops were identified corresponding to high Hcr/Hc values. Stepwise thermal and alternating field demagnetization shows that secondary components are completely removed below 20 mT or 400 �C. Thereafter, the characteristic component is isolated with small within-site dispersion of mean direction (?95 < 10� at 7 out of 10 sites). The within-site consistency of directional features of magnetic fabric supports that the ignimbrite welded and cooled in situ and was probably emplaced in a NW-SE rift zone from a single eruption center located south or east of a younger Pleistocene caldera in the area. Paleomagnetic, rock magnetic and ore microscopy data support the hypothesis that the extensive and widespread ignimbrite deposits in western Mexico correspond to a major explosive volcanic phase in the Pliocene. � 2005 Elsevier B.V. All rights reserved

Internal friction phenomena in composites based on PZT-type ferroelectric powder and ferrites

The aim of the work was to determine the phenomena of internal friction (mechanical losses) occurring in ferroelectric-ferromagnetic composites created based on PZT-type ferroelectric powder and ferrite. The composites were obtained using ceramic powders – multi-component PZT-type solid solutions with ferroelectric properties. Their magnetic component included zinc-nickel powder Ni0.64Zn0.36Fe2O4. 30 × 10 × 1 mm3 test specimens were obtained using free sintering. Temperature Q -1(T) and amplitude Q -1(ε) internal friction dependencies were determined. Wide high temperature maxima were observed with regard to the internal friction temperature dependencies obtained for the tested specimens. The conducted measurements of amplitude (isothermal) dependencies of internal friction Q -1(ε) for the tested composites have allowed for interpreting the previously observed maximum on the temperature dependencies of internal friction

Toxicidade aguda do nitrito em larvas do peixe-rei marinho Odontesthes argentinensis (Teleostei, Atherinopsidae) Acute toxicity of nitrite on larvae of the marine pejerrey Odontesthes argentinensis (Teleostei, Atherinopsidae)

Este trabalho visou a determinar o efeito tóxico do nitrito sobre larvas do peixe-rei marinho Odontesthes argentinensis através de testes agudos com 96h de duração. As larvas utilizadas neste experimento foram cultivadas no Laboratório de Maricultura da FURG (Rio Grande - RS). Foi utilizada água do mar filtrada na salinidade 35‰, na temperatura de 23&deg;C, com fotoperíodo de 14 horas de luz e aeração constante. Diariamente, as larvas mortas foram retiradas e, em seguida, 100% do meio experimental foi renovado. Não foi fornecido alimento durante a exposição ao nitrito. As larvas foram expostas a cinco concentrações de nitrito: 50, 150, 250, 350 e 450mg L-1 N-NO2-, mais um controle onde o nitrito não foi adicionado. A CL50-96h (concentração letal para 50% dos organismos após 96 horas) e seu intervalo de confiança (95%) foram de 199,3 (142,0-279,6)mg L-1 N-NO2-. Os resultados deste trabalho sugerem que, assim como outras espécies de peixes marinhos, o O. argentinensis é uma espécie tolerante a altas concentrações de nitrito e é pouco provável que este último seja um problema para o cultivo intensivo desta espécie.<br>This work evaluated the toxicity of nitrite on larvae of the marine pejerrey Odontesthes argentinensis through acute exposure during 96h. Larvae used in this experiment were cultivated in the Laboratory of Mariculture of the University of Rio Grande. During the tests temperature was 23&deg;C, salinity 35‰, and 14 hours of light were provided. Every day dead larvae were removed and the experimental media were completely renewed. Larvae were deprived of food during the test. Concentrations for the acute tests were 50, 150, 250, 350 and 450mg L-1 N-NO2-, plus a control with no nitrite added. Lethal concentration for 50% of the organisms (LC50-96h), and its confidence interval, was 199.3 (142.0-279.6)mg L-1 N-NO2-. The results of the acute tests suggest that, as other species of marine fish larvae, O. argentinensis is tolerant to high concentrations of nitrite, and it is unlikely that it would be a problem for the intensive culture of this species