Characterization and evaluation of Ni/SiO catalysts for hydrogen production and tar reduction from catalytic steam pyrolysis-reforming of refuse derived fuel

A series of Ni/SiO catalysts have been prepared and investigated for their suitability for hydrogen production and tar reduction in a two-stage pyrolysis-reforming system, using refuse derived fuel (RDF) as the raw material. Experiments were conducted at a pyrolysis temperature of 600°C, and a reforming temperature of 800°C. The product gases were analysed by gas chromatography (GC) and the condensed fraction was collected and quantified using gas chromatography-mass spectrometry (GC-MS). The effects of the catalyst preparation method, nickel content and the addition of metal promoters (Ce, Mg, Al), were investigated. Catalysts were characterised using BET surface area analysis, temperature programmed oxidation (TPO), and scanning electron microscopy (SEM). The TPO and SEM analysis of the reacted catalysts showed that amorphous type carbons tended to be deposited over the Ni/SiO catalysts prepared by impregnation, while filamentous type carbons were favoured with the sol-gel prepared catalysts. The influence of catalyst promoters (Ce, Mg, Al) added to the Ni/SiO catalyst prepared by the sol-gel method was found not to be significant, as the H production was not increased and the tar formation was not reduced with the metal-added catalyst. The highest H concentration of 57.9vol.% and lower tar amount produced of 0.24mg/g; were obtained using the 20wt.% Ni/SiO catalyst prepared by sol-gel. On the other hand a low catalytic activity for H production and higher tar produced were found for the impregnated series of catalysts, which might be due to the smaller surface area, pore size and due to the formation of amorphous carbons on the catalyst surface. Alkenes and alcohol functional groups were mainly found in the analysed tar samples, with major concentrations of styrene, phenol, indene, cresols, naphthalene, fluorene, and phenanthrene

Volume modulus inflation and a low scale of SUSY breaking

The relation between the Hubble constant and the scale of supersymmetry breaking is investigated in models of inflation dominated by a string modulus. Usually in this kind of models the gravitino mass is of the same order of magnitude as the Hubble constant which is not desirable from the phenomenological point of view. It is shown that slow-roll saddle point inflation may be compatible with a low scale of supersymmetry breaking only if some corrections to the lowest order Kahler potential are taken into account. However, choosing an appropriate Kahler potential is not enough. There are also conditions for the superpotential, and e.g. the popular racetrack superpotential turns out to be not suitable. A model is proposed in which slow-roll inflation and a light gravitino are compatible. It is based on a superpotential with a triple gaugino condensation and the Kahler potential with the leading string corrections. The problem of fine tuning and experimental constraints are discussed for that model.Comment: 28 pages, 8 figures, comments and references added, minor change in notation, version to be publishe

Cosmic D-Strings and Vortons in Supergravity

Recent developments in string inspired models of inflation suggest that D-strings are formed at the end of inflation. Within the supergravity model of D-strings there are 2(n-1) chiral fermion zero modes for a D-string of winding n. Using the bounds on the relic vorton density, we show that D-strings with winding number n>1 are more strongly constrained than cosmic strings arising in cosmological phase transitions. The D-string tension of such vortons, if they survive until the present, has to satisfy 8\pi G_N \mu \lesssim p 10^{-26} where p is the intercommutation probability. Similarly, D-strings coupled with spectator fermions carry currents and also need to respect the above bound. D-strings with n=1 do not carry currents and evade the bound. We discuss the coupling of D-strings to supersymmetry breaking. When a single U(1) gauge group is present, we show that there is an incompatibility between spontaneous supersymmetry breaking and cosmic D-strings. We propose an alternative mechanism for supersymmetry breaking, which includes an additional U(1), and might alleviate the problem. We conjecture what effect this would have on the fermion zero modes.Comment: 11 page

The Robustness of n_s < 0.95 in Racetrack Inflation

A spectral index n_s < 0.95 appears to be a generic prediction of racetrack inflation models. Reducing a general racetrack model to a single-field inflation model with a simple potential, we obtain an analytic expression for the spectral index, which explains this result. By considering the limits of validity of the derivation, possible ways to achieve higher values of the spectral index are described, although these require further fine-tuning of the potential.Comment: 7 pages, 2 figure

PRIMER ACERCAMIENTO A LOS RESTOS ARQUEOLÓGICOS DEL BALNEARIO ROMANO

Se expone el estado de la cuestión en el estudio del termalismo de la Región de Murcia con particular atención a la época romana. Se centra el tema en la investigación del balneario de Fortuna y en las nuevas perspectivas que para el tema ha ofrecido el descubrimiento de una parte interesante del yacimiento romano del lugar cuyas excavaciones se describen: se trata de un edificio de considerable entidad cuya estructura todavía apenas queda especificada, pero que se espera aclarar con el avance de las investigaciones arqueológicas. Se plantean los nuevos horizontes que este descubrimiento crea para la interpretación del conjunto epigráfico de la Cueva Negra, cuyos tituli picti adquieren consistencia y se sitúan en una nueva dimensión intelectual al ponerlos en relación con la vida del balneario

PRIMER ACERCAMIENTO A LOS RESTOS ARQUEOLÓGICOS DEL BALNEARIO ROMANO

The situation of the research on thermalism in the Region of Murcia, with particular attention paid to the Roman period, are set forth in this article. The exposition centers on the research carried out in the baths of Fortuna and on the new perspectives opened by the discovery, in the Roman part of the site, of a large building which structure only dates partly determined. The authors explain the new horizon which this discovery offers towards the interpretation of the epigraphical collection found in the Cueva Negra, whose tituli picti acquire consistency and they are situated in a new intelectual dimension when they are related to the livelihood of the Roman Baths.Se expone el estado de la cuestión en el estudio del termalismo de la Región de Murcia con particular atención a la época romana. Se centra el tema en la investigación del balneario de Fortuna y en las nuevas perspectivas que para el tema ha ofrecido el descubrimiento de una parte interesante del yacimiento romano del lugar cuyas excavaciones se describen: se trata de un edificio de considerable entidad cuya estructura todavía apenas queda especificada, pero que se espera aclarar con el avance de las investigaciones arqueológicas. Se plantean los nuevos horizontes que este descubrimiento crea para la interpretación del conjunto epigráfico de la Cueva Negra, cuyos tituli picti adquieren consistencia y se sitúan en una nueva dimensión intelectual al ponerlos en relación con la vida del balneario

El balneario de Fortuna y la Cueva Negra (Fortuna, Murcia)

Se expone el estado de la cuestión en el estudio del termalismo de la Región de IVIurcia con particular atención a la época romana. Se centra el tema en la investigación del balneario de Fortuna y en las nuevas perspectivas que para el tema lia ofrecido el descubrimiento de una parte interesante del yacimiento romano del lugar cuyas excavaciones se describen: se trata de un edificio de considerable entidad cuya estructura todavía apenas queda especificada, pero que se espera aclarar con el avance de las investigaciones arqueológicas. Se plantean los nuevos horizontes que este descubrimiento crea para la interpretación del conjunto epigráfico de la Cueva Negra, cuyos tituli picti adquieren consistencia y se sitúan en una nueva dimensión intelectual al ponerlos en relación con la vida del balneario.The situation of the research on thermalism in the Región of Murcia, with particular attention paid to the Román period, are set forth in this article. The exposition centers on the research carried out in the baths of Fortuna and on the new perspectivas oponed by the discovery, in the Román part of the site, of a large building which structure only dates partly determined. The authors explain the new horizon which this discovery offers towards the interpretation of the epigraphical collection found in the Cueva Negra, whose tituli picti acquire consistency and they are situated in a new intelectual dimensión when they are related to the livelihood of the Román Baths

GYES, a multifibre spectrograph for the CFHT

We have chosen the name of GYES, one of the mythological giants with one hundred arms, offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph for the prime focus of the Canada-France-Hawaii Telescope. Such an instrument could provide an excellent ground-based complement for the Gaia mission and a northern complement to the HERMES project on the AAT. The CFHT is well known for providing a stable prime focus environment, with a large field of view, which has hosted several imaging instruments, but has never hosted a multifibre spectrograph. Building upon the experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are investigating the feasibility of a high multiplex spectrograph (about 500 fibres) over a field of view 1 degree in diameter. We are investigating an instrument with resolution in the range 15000 to 30000, which should provide accurate chemical abundances for stars down to 16th magnitude and radial velocities, accurate to 1 km/s for fainter stars. The study is led by GEPI-Observatoire de Paris with a contribution from Oxford for the study of the positioner. The financing for the study comes from INSU CSAA and Observatoire de Paris. The conceptual study will be delivered to CFHT for review by October 1st 2010.Comment: Contributed talk at the Gaia ELSA conference 2010, S\`evres 7-11 June 2010, to be published on the EAS Series, Editors: C. Turon, F. Arenou & F. Meynadie

Accidental Inflation in String Theory

We show that inflation in type IIB string theory driven by the volume modulus can be realized in the context of the racetrack-based Kallosh-Linde model (KL) of moduli stabilization. Inflation here arises through the volume modulus slow-rolling down from a flat hill-top or inflection point of the scalar potential. This situation can be quite generic in the landscape, where by uplifting one of the two adjacent minima one can turn the barrier either to a flat saddle point or to an inflection point supporting eternal inflation. The resulting spectral index is tunable in the range of 0.93 < n_s < 1, and there is only negligible production of primordial gravitational waves r < 10^{-6}. The flatness of the potential in this scenario requires fine-tuning, which may be justified taking into account the exponential reward by volume factors preferring the regions of the universe with the maximal amount of slow-roll inflation. This consideration leads to a tentative prediction of the spectral index $n_s\approx 0.95$ or $n_s \approx 0.93$ depending on whether the potential has a symmetry phi -> - phi or not.Comment: 15 pages, 6 figures, LaTeX, uses RevTex

Models of Modular Inflation and Their Phenomenological Consequences

We study models of modular inflation of the form expected to arise from low energy effective actions of superstring theories. We argue on general grounds that the most likely models of modular slow-roll inflation are small field models in which the inflaton moves about a Planck distance from an extremum of the potential. We then focus on models in which the inflaton is the bosonic component of a single (complex) chiral superfield and explain the generic difficulties in designing small field models of modular inflation. We then show that if the Kaehler potential (KP) of the inflaton is logarithmic as in perturbative string theories, then it is not possible to satisfy the slow-roll conditions for any superpotential. We find that if the corrections to the KP are large enough so it can be approximated by a canonical KP in the vicinity of the extremum, then viable slow-roll inflation is possible. In this case, several parameters have to be tuned to a fraction of a percent. We give a prescription for designing successful small field supergravity models of inflation when the KP is canonical and calculate the slow-roll parameters from the superpotential parameters. Our results strengthen the case for models in which the moduli slowly roll about a Planck distance from a relatively high scale extremum that is located in the vicinity of the central region of moduli space units. Generic models of this class predict a red spectrum of scalar perturbations and negligible spectral index running. They also predict a characteristic suppression of tensor perturbations despite the high scale of inflation. Consequently, a detection of primordial tensor anisotropies or spectral index running in cosmic microwave background observations in the foreseeable future will rule out this entire class of modular inflation models.Comment: 35 pages, 1 figur