Background-independent charges in Topologically Massive Gravity

We construct background-independent Noether charges in Topologically Massive Gravity with negative cosmological constant using its first-order formulation. The procedure is carried out by keeping track of the surface terms in the variation of the action, regardless the value of the gravitational Chern-Simons coupling $\mu$. In particular, this method provides a definition of conserved quantities for solutions at the chiral point $\mu l = 1$ ($l$ is the AdS radius) that contain logarithmic terms (Log Gravity). It is also shown that the charge formula gives a finite result for warped AdS black holes without the need for any background-substraction procedure.Comment: 23 pages; appendix and a few references added; final version for JHE

Synthesis, thermal behavior, and aggregation in aqueous solution of poly(methyl methacrylate)-b-poly(2-hydroxyethyl methacrylate)

Indexación: ScieloABSTRACT Amphiphilic block copolymers of poly(methyl methacrylate) PMMA and poly(2-hidroxyethyl methacrylate) PHEMA were synthesized by a two-step atom transfer radical polymerization (ATRP). Copolymers with various degrees of polymerization and different relative block sizes were obtained. The structure of the resulting polymers have been characterized and verified by FT-IR and 1H-NMR, molecular weight were determined by size exclusion chromatography analyses. The thermal properties of these polymers were investigated by differential scanning calorimetry DSC and thermogravimetric analysis TGA. The glass transition temperature of mono halogenated PMMA increases from 116 °C to 123 °C with increasing molecular weight, whereas the glass transition temperature of block copolymers depends slightly on polymer structure. The derivatives of TGA curves indicate that thermal degradation occurs in one stage. The self-assembly of PMMA-b-PHEMA in aqueous solution have been investigated by fluorescence probing methods. The critical micelle concentrations are in the range 10-6 - 10-7 M. The micropolarity sensed by pyrene is higher than in aggregates formed by block copolymers based on polystyrene. Keywords: Block copolymers, glass transition temperature, thermogravimetric analysis, critical micelle concentration, fluorescence probing methods

Star Wars Episode III: Revenge of the Sith

This is a review of Star Wars Episode III: Revenge of the Sith (2005)

Falso aneurisma tras fractura diafisaria de fémur: Tratamiento mediante embolización

Un falso aneurisma es una complicación rara de una fractura de la diáfisis femoral. Se presenta un caso que fue diagnosticado tardíamente debido a la ausencia de sintomatología típica. Se discuten la etiología, profilaxis, diagnóstico y posibilidades terapéuticas; destacándose la novedad del diagnóstico y tratamiento mediante arteriografía y embolización selectiva.A false aneurysm following a closed femoral-shaft fracture is a rare complication. The author report a case that was lately diagnosed because of the absence of typical symptomatology. Aetiology, prophylaxis, diagnosis and treatment are discussed, emphasizing the new method of diagnosis and treatment by arteriography and selective embolism

Hamilton-Jacobi Counterterms for Einstein-Gauss-Bonnet Gravity

The on-shell gravitational action and the boundary stress tensor are essential ingredients in the study of black hole thermodynamics. We employ the Hamilton-Jacobi method to calculate the boundary counterterms necessary to remove the divergences and allow the study of the thermodynamics of Einstein-Gauss-Bonnet black holes.Comment: 21 pages, LaTe

Quenching of excited carbonyl triplets by benzene derivatives

Se ha medido la velocidad de desactivación de tripletes carbonilicos (biacetilo, bencilo, benzofenona y 4-metil-2-pentanona) por una serie d,e derivados del benceno. Los resultados pueden ser interpretados por un mecanismo de transferencia de carga. Los compuestos con hidrógenos lábiles (i.e.cumeno) muestran una mayor reactividad. La abstracción de hidrógeno ocurre desde el complejo de transferencia de carga. La desactivación del triplete de la 4-metil-2-pentanona fue medida entre - 5 y 70°C. Las energias de activación obtenidas variaron entre 8.1 kcal (para el cumeno) y 10 kcal (para el benceno)