Interaction of Hawking radiation with static sources in deSitter and Schwarzschild-deSitter spacetimes

We study and look for similarities between the response rates $R^{\rm dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ of a static scalar source with constant proper acceleration $a_0$ interacting with a massless, conformally coupled Klein-Gordon field in (i) deSitter spacetime, in the Euclidean vacuum, which describes a thermal flux of radiation emanating from the deSitter cosmological horizon, and in (ii) Schwarzschild-deSitter spacetime, in the Gibbons-Hawking vacuum, which describes thermal fluxes of radiation emanating from both the hole and the cosmological horizons, respectively, where $\Lambda$ is the cosmological constant and $M$ is the black hole mass. After performing the field quantization in each of the above spacetimes, we obtain the response rates at the tree level in terms of an infinite sum of zero-energy field modes possessing all possible angular momentum quantum numbers. In the case of deSitter spacetime, this formula is worked out and a closed, analytical form is obtained. In the case of Schwarzschild-deSitter spacetime such a closed formula could not be obtained, and a numerical analysis is performed. We conclude, in particular, that $R^{\rm dS}(a_0, \Lambda)$ and $R^{\rm SdS}(a_0, \Lambda, M)$ do not coincide in general, but tend to each other when $\Lambda \to 0$ or $a_0 \to \infty$. Our results are also contrasted and shown to agree (in the proper limits) with related ones in the literature.Comment: ReVTeX4 file, 9 pages, 5 figure

Clergue o laic? Algunes reflexions sobre l'estatus de l'artista i la qüestió de l'autoria a l'Europa romànica

Contribució al I Simposi Científic de l'IEM (Reial Acadèmia de Bones Lletres de Barcelona, 3 de juliol de 2012

Do static sources respond to massive scalar particles from the Hawking radiation as uniformly accelerated ones do in the inertial vacuum?

We revisit the recently found equivalence for the response of a static scalar source interacting with a {\em massless} Klein-Gordon field when the source is (i) static in Schwarzschild spacetime, in the Unruh vacuum associated with the Hawking radiation and (ii) uniformly accelerated in Minkowski spacetime, in the inertial vacuum, provided that the source's proper acceleration is the same in both cases. It is shown that this equivalence is broken when the massless Klein-Gordon field is replaced by a {\em massive} one.Comment: 4 pages, 2 figure

Synthesis, structure, properties and biological behaviour of the complex [RuIV (H2L) CI2] 2H2O (H4L- 1,2-cyclohexanediamminetetraacetic acid)

The highly water-soluble ruthenium complex [Ru(H2L)Cl 2]·2H2O, in which H4L is the sequestering ligand trans-l,2-cyclohexanediamminetetraacetic acid (cdta) has been synthesized, structurally characterized and its properties studied. The X-ray crystallographic study shows that the chelating coordinated ligand is tetradentate while the ruthenium environment is octahedral and slightly distorted, with two chloride anions coordinated in cis positions. Potentiometric, conductimetric and infrared studies confirm the presence of two free carboxylic groups, while electronic and voltammetric studies show that the central ion is Ru(IV). The testing of the cytotoxic activity of this complex against three different human cancer cell lines indicates that [Ru(H 2L)Cl2]·2H2O shows a remarkable and selective antiproliferative effect against the human uterine neck carcinoma HeLa and the malign adenocarcinoma ADLD, showing only a discrete turnout cell inhibition activity against colon adenocarcinoma HT-29. The important antiprotiferative behaviour of complex against the human adenocarcinoma ADLD, indicates that [Ru(H2L)Cl2]·2H2O might be considered as potential antineoplastic compound.Ministerio de Ciencias y Tecnología PPQ2000-0035-P4 BQU2001-245

Modelo didáctico de profesores de enseñanza media de química : análisis de casos en el desarrollo del tema disoluciones (Santa Fe – Argentina)

La presente investigación se realizó en tres aulas de Química de Enseñanza Media (Argentina) durante el año 2008, en el marco del proyecto AECI/7510/07 entre las universidades del Litoral (Argentina) y de Santiago de Compostela (España). El propósito fue caracterizar los modelos didácticos que se ponen de manifiesto al desarrollar los docentes, una propuesta de tipo constructivista de secuencias de enseñanza para el tema Disoluciones. Con los aportes del análisis de opinión de las actividades (pre y post) realizadas por los docentes y la observación directa de las clases, se infiere que los profesores desarrollan sus clases en forma tradicional -probablemente la metodología propuesta no ha sido asimilada debido al tipo de instrucción al que están habituados el profesorado y el alumnado- aunque se observan intentos de aproximarse a modelos más constructivistas

Compostela, Bari y Jerusalén: tras las huellas de una cultura figurativa en los Caminos de Peregrinación

El apogeo de las peregrinaciones a Santiago de Compostela desde finales del siglo XI coincide con la aparición del culto de san Nicolás en Bari y con el fenómeno de la Primera Cruzada. Compostela y Bari, en su condición de ciudades de llegada y partida de peregrinos, se convierten, asimismo, en centros privilegiados con la aparición de un nuevo estilo internacional: el Románico, que propone una nueva y revolucionaria cultura figurativa monumental caracterizada por los intercambios, en la que la dedicación de las capillas, las reliquias –cruces patriarcales–, los símbolos de peregrinación –la concha de Santiago–, o los sujetos iconográficos de la épica caballeresca se encuentran a lo largo de todos los Caminos, terrestres y marítimos, del Mediterráneo. De este modo, se desarrolla una peregrinación “circular” entre Compostela, Roma, Bari, Monte Sant’Angelo y Jerusalén, lo que supone una competencia entre los santuarios, en la que estos intentan ofrecer a los peregrinos una cultura figurativa adaptada a sus vicisitudes

Un nuevo testimonio de la iconografía jacobea: Los relieves pintados de Santiago de Turégano (Segovia) y su relación con el altar mayor de la Catedral de Santiago

Una reciente restauración llevada a cabo en la iglesia parroquial de Santiago de Turégano (Segovia) ha puesto al descubierto una de las más curiosas representaciones del culto jacobeo en el siglo XIII. Detrás del un altar barroco había permanecido oculto un peculiar muro absidal decorado con relieves. Éste está formado por un conjunto de lastras que representan un grupo de peregrinos que están de pie o de rodillas delante de la estatua del apóstol Santiago. Resulta muy probable que esta memorable composición se hiciese eco del nuevo escenario consagrado en 1211 en el altar mayor de la Catedral de Santiago así como de los nuevos ritos de peregrinación relacionados con él. Además, los relieves conservan una capa de pintura original que permite replantearnos la cuestión de la policromía en la escultura románica así como su comparación con los también relieves pintados del Pórtico de la Gloria

Semiclassical approach to black hole absorption of electromagnetic radiation emitted by a rotating charge

We consider an electric charge, minimally coupled to the Maxwell field, rotating around a Schwarzschild black hole. We investigate how much of the radiation emitted from the swirling charge is absorbed by the black hole and show that most of the photons escape to infinity. For this purpose we use the Gupta-Bleuler quantization of the electromagnetic field in the modified Feynman gauge developed in the context of quantum field theory in Schwarzschild spacetime. We obtain that the two photon polarizations contribute quite differently to the emitted power. In addition, we discuss the accurateness of the results obtained in a full general relativistic approach in comparison with the ones obtained when the electric charge is assumed to be orbiting a massive object due to a Newtonian force.Comment: 8 pages (revtex), 8 figure

Bacteriological conversion in twenty urinary tuberculosis patients treated with ofloxacin, rifampin and isoniazid: a 10-year follow-up study

Twenty patients withuri nary tuberculosis were treated withofloxac in (200 mg/day, 6 months), rifampin (600 mg/day, 3 months) and isoniazid (300 mg/day, 3 months) between 1989 and 1990. All patients were new cases, diagnosed by observation and/or isolation of Mycobacterium tuberculosis in one of the three morning urine samples. Bacteriological culture conversion (negativization) was assessed as a clinical guide of efficacy, comparing it, as the only parameter, against a control group (150 patients) withurina ry tuberculosis who received conventional therapy. Bacteriological follow-up studies were performed in bothgroups monthly for 6 months, then again 6 months later and then every year for 10 years after completion of treatment. In the 20 patients, the initial culture was positive with over 100 colonies per culture (>50%); the smear was positive in 45% of the patients (most were 2+). All strains were susceptible to rifampin, isoniazid and ofloxacin. Two patients discontinued treatment. Beginning withth e first monthof treatment, the bacteriological conversion was 100%, 89.5% and 100% in the remaining controls. In the control group, which received conventional treatment, the conversion was: 90%, 87%, 93% and 100% in the remaining controls. Treatment withofloxacin resulted in a bacteriological conversion similar to that following conventional treatment (p>0.05, Fisher’s exact test). After 10 years of patient follow-up, we conclude that ofloxacin, in combination withrifampin and isoniazid (bothfor 3 months only is effective against M. tuberculosis, providing satisfactory bacteriological and clinical efficacy