Arenas de dragado marino como nueva fuente para materiales de construcción

This work deals with the use of dredged marine sand (DMS) in pastes and mortars as construction material. Different materials from two Spanish ports were used: DMS-0 from Sant Carles de la Ràpita and DMS-A, DMS-B and DMS-C from Barcelona. The aim of the study was to assess DMS as addition (its influence on cohesion and fluidity) or as a fine granular corrector (its influence on compressive strength) in different mixes of cement paste and mortars, respectively. Two experimental stages were carried out: firstly, DMS-0 material was used on the production of pastes and mortars (partial substitution of raw sand 0/2 mm); secondly, DMS-A, DMS-B and DMS-C were used on mortar production (partial substitution of raw sand 0/5 mm). The fresh and hardened properties obtained were compared to those of the control mixes; the results revealed 25 % as an optimum substitution ratio of raw sands for DMS.Este trabajo propone el uso de arenas de dragado marino (DMS) en pastas y morteros como material constructivo. Se utilizaron materiales de dos puertos españoles: DMS-0 del puerto de Sant Carles de la Ràpita, y DMS-A, DMS-B y DMS-C del puerto de Barcelona. El objetivo del estudio era evaluar el material DMS como adición (influencia sobre cohesión y fluidez) o como corrector granular (influencia sobre resistencia a la compresión) en diferentes mezclas de pasta y morteros de cemento, respectivamente. Se realizaron dos fases experimentales: primero, se empleó el DMS-0 en la producción de pastas y morteros (sustitución parcial de arena natural 0/2 mm); a continuación, se emplearon DMS-A, DMS-B y DMS-C en la producción de morteros (sustitución parcial de arena natural 0/5 mm). Los resultados obtenidos fueron comparados con las mezclas de control y revelaron que la proporción óptima de sustitución de arenas naturales por DMS era del 25 %

Electronic damage in quartz (c-SiO2) by MeV ion irradiations: Potentiality for optical waveguiding applications

The damage induced on quartz (c-SiO2) by heavy ions (F, O, Br) at MeV energies, where electronic stopping is dominant, has been investigated by RBS/C and optical methods. The two techniques indicate the formation of amorphous layers with an isotropic refractive index (n = 1.475) at fluences around 1014 cm−2 that are associated to electronic mechanisms. The kinetics of the process can be described as the superposition of linear (possibly initial Poisson curve) and sigmoidal (Avrami-type) contributions. The coexistence of the two kinetic regimes may be associated to the differential roles of the amorphous track cores and preamorphous halos. By using ions and energies whose maximum stopping power lies inside the crystal (O at 13 MeV, F at 15 MeV and F at 30 MeV) buried amorphous layer are formed and optical waveguides at the sample surface have been generated

Black hole radiance, short distances, and TeV gravity

Using a derivation of black hole radiance in terms of two-point functions one can provide a quantitative estimate of the contribution of short distances to the spectrum. Thermality is preserved for black holes with $\kappa l_P <<1$. However, deviations from the Planckian spectrum can be found for mini black holes in TeV gravity scenarios, even before reaching the Planck phase.Comment: LaTeX, 4 pages, 1 figure. Misprints correcte

Nuevos datos sobre Otiorhynchus (Lixorrhynchus) zariquieyi (Clermont, 1949) (Coleoptera, Curculionidae)

En este artículo se da a conocer el hallazgo de nuevos ejemplares de Otiorhynchus (Lixorrhynchus) zariquieyi (Clermont, 1949). Hasta ahora, la especie era conocida por su espécimen tipo, un macho capturado en medio endogeo en 1928. Cuatro machos y ocho hembras capturados vivos, además de algunos restos, fueron recolectados en dos nuevas localidades de España, las cuevas Tassana y de la Bora Major (Alt Empordà, Girona). Se redescribe la especie, aportándose nuevos detalles de su morfología, en particular, la genitalia de ambos sexos. También se comentan algunos aspectos relativos a su ecologia y distribución. Es la primera vez que se documenta la presencia de la especie en hábitat cavernícola. Palabras clave: Otiorhynchus zariquieyi, Curculionidae, Nuevas citas, Hábitat cavernícola, Descripción, España.This paper discusses the discovery of new specimens of Otiorhynchus (Lixorrhynchus) zariquieyi (Clermont, 1949). Until now, the species was known by its type specimen, a male captured in an endogean environment in 1928. Four live males, eight live females and some remains were collected from two further localities in Spain, the Tassana and the Bora Major caves (Alt Empordà, Girona). The species is redescribed, giving new details of its morphology, in particular the genitalia of both sexes. Some remarks about the ecology and distribution are also provided. It is the first time this species has been found in a cave habitat. Key words: Otiorhynchus zariquieyi, Curculionidae, New records, Cave habitat, Description, Spain.En este artículo se da a conocer el hallazgo de nuevos ejemplares de Otiorhynchus (Lixorrhynchus) zariquieyi (Clermont, 1949). Hasta ahora, la especie era conocida por su espécimen tipo, un macho capturado en medio endogeo en 1928. Cuatro machos y ocho hembras capturados vivos, además de algunos restos, fueron recolectados en dos nuevas localidades de España, las cuevas Tassana y de la Bora Major (Alt Empordà, Girona). Se redescribe la especie, aportándose nuevos detalles de su morfología, en particular, la genitalia de ambos sexos. También se comentan algunos aspectos relativos a su ecologia y distribución. Es la primera vez que se documenta la presencia de la especie en hábitat cavernícola. Palabras clave: Otiorhynchus zariquieyi, Curculionidae, Nuevas citas, Hábitat cavernícola, Descripción, España

Short-distance contribution to the spectrum of Hawking radiation

The Hawking effect can be rederived in terms of two-point functions and in such a way that it makes it possible to estimate, within the conventional semiclassical theory, the contribution of ultrashort distances at I+ to the Planckian spectrum. The analysis shows that, for Schwarzschild astrophysical black holes, the Hawking radiation (for both bosons and fermions) is very robust up to very high frequencies (typically two orders above Hawking\u27s temperature). Below this scale, the contribution of ultrashort distances to the spectrum is negligible. We argue, using a simple model with modified two-point functions, that the above result seems to have a general validity and that it is related to the observer independence of the short-distance behavior of the corresponding two-point function. The above suggests that only at high emission frequencies could an underlying quantum theory of gravity potentially predict significant deviations from Hawking\u27s semiclassical result. © 2007 The American Physical Society

Swift heavy ion damage to sodium chloride: synergy between excitation and thermal spikes

Systematic data on the effect of irradiation with swift ions (Zn at 735 MeV and Xe at 929 MeV) on NaCl single crystals have been analysed in terms of a synergetic two-spike approach (thermal and excitation spikes). The coupling of the two spikes, simultaneously generated by the irradiation, contributes to the operation of a non-radiative exciton decay model as proposed for purely ionization damage. Using this scheme, we have accounted for the π-emission yield of self-trapped excitons and its temperature dependence under ion-beam irradiation. Moreover, the initial production rates of F-centre growth have also been reasonably simulated for irradiation at low temperatures ( < 100 K), where colour centre annealing and aggregation can be neglected

Use of SEVIRI images and derived products in a WMO Sand and Dust Storm Warning System

The Visible/IR images of SEVIRI (Spinning Enhanced Visible and Infrared Imager), on board Meteosat Second Generation (MSG) satellites, are used to monitor dust events. Satellite-based detection of dust is a difficult problem due in part to the observing-system limitations. The main difficulty is that the dust can be confused with water/ice clouds. SEVIRI is not as optimal for the viewing of dust as SEAWIFS or MODIS, due to the fact that both of them count with additional short-wavelength channels. However, the SEVIRI 15-minute loop images can detect small dust plumes as well as subtle changes from one image to the next. A description of how the AEMET, former INM, is developing the environment to support MSG satellite imagery to the WMO/GEO Sand and Dust Storm Warning System (SDS WS) for Europe, Africa and Middle East Regional Centre will be briefly presented, together with some on-going operational developments to best monitor dust events

Revising the observable consequences of slow-roll inflation

We study the generation of primordial perturbations in a (single-field) slow-roll inflationary universe. In momentum space, these (Gaussian) perturbations are characterized by a zero mean and a non-zero variance $\Delta^2(k, t)$. However, in position space the variance diverges in the ultraviolet. The requirement of a finite variance in position space forces one to regularize $\Delta^2(k, t)$. This can (and should) be achieved by proper renormalization in an expanding universe in a unique way. This affects the predicted scalar and tensorial power spectra (evaluated when the modes acquire classical properties) for wavelengths that today are at observable scales. As a consequence, the imprint of slow-roll inflation on the CMB anisotropies is significantly altered. We find a non-trivial change in the consistency condition that relates the tensor-to-scalar ratio $r$ to the spectral indices. For instance, an exact scale-invariant tensorial power spectrum, $n_t=0$, is now compatible with a non-zero ratio $r\approx 0.12\pm0.06$, which is forbidden by the standard prediction ($r=-8n_t$). The influence of relic gravitational waves on the CMB may soon come within the range of planned measurements, offering a non-trivial test of the new predictions.Comment: 24 page

Inflation, quantum field renormalization, and cmb anisotropies

We point out that if quantum field renormalization is taken into account the predictions of slow-roll inflation for both the scalar and tensorial power spectra change significantly for wavelengths that today are at observable scales. Copyright © 2012 by World Scientific Publishing Co. Pte. Ltd