A minor-merger origin for inner disks and rings in early-type galaxies

Nuclear disks and rings are frequent galaxy substructures, for a wide range of morphological types (from S0 to Sc). We have investigated the possible minor-merger origin of inner disks and rings in spiral galaxies through collisionless N-body simulations. The models confirm that minor mergers can drive the formation of thin, kinematically-cold structures in the center of galaxies out of satellite material, without requiring the previous formation of a bar. Satellite core particles tend to be deposited in circular orbits in the central potential, due to the strong circularization experienced by the satellite orbit through dynamical friction. The material of the satellite core reaches the remnant center if satellites are dense or massive, building up a thin inner disk; whereas it is fully disrupted before reaching the center in the case of low-mass satellites, creating an inner ring instead.Comment: 2 pages, 2 figures, Proceedings of the conference "Hunting for the Dark: The Hidden Side of Galaxy Formation", held in Malta, 19-23 Oct. 2009, ed. V. Debattista and C. C. Popescu, AIP Conf. Ser., in pres

Modeling wave propagation through an analytical surface model

Nowadays there is a certain development in the use of railway, especially in the form of trams and underground lines in urban areas. Despite its many advantages, this kind of transport is a significant source of vibrations, which may affect residents and buildings near to the track. Wave transmission through the ground is therefore a phenomenon of particular interest. The object of this article is to formulate and test an analytical model of vibration propagation through the terrain surface. The model is based on the wave equation and takes into account wave scattering and reflection in the interfaces between different soil layers. A sensitivity analysis of its main parameters is carried out, and then a comprehensive set of simulations is made to test model performance and analyze factors such as load magnitude and velocity or soil configuration. The model has proved to be an interesting instrument to study the vibration phenomenon from a theoretical point of view and some improvements are proposed to turn it into a tool for engineers and designers

Design and validation of a railway inspection system to detect lateral track geometry defects based on axle-box accelerations registered from in-service trains

Metropolitan railway transport has become an efficient solution to the mobility necessities in urban areas. Railway track maintenance tasks have to be improved and adjusted to metropolitan requirements, in particular the few hours available to operate due to the high frequency service offered. This paper describes and proposes an inertial monitoring system to detect and estimate track irregularities by using in-service vehicles. A new maintenance strategy is established, based on the railway track conditions and continuous monitoring is provided to do so. The system proposed consists of at least two accelerometers mounted on the bogie axle-box and a GPS (Global Positioning System). Lateral accelerations have been analyzed to study gauge and lateral alignment deviations. Accelerations have been treated and processed by high-pass filtering and validation has been carried out by comparison with measurements provided by a track monitoring trolley. Measurements were made on Line 1 of the Alicante metropolitan and tram network (Spain)

Evolution along the sequence of S0 Hubble types induced by dry minor mergers. II - Bulge-disk coupling in the photometric relations through merger-induced internal secular evolution

Galaxy mergers are considered as questionable mechanisms for the evolution of lenticular galaxies (S0's), on the basis that even minor ones induce structural changes that are difficult to reconcile with the strong bulge-disk coupling observed in the photometric scaling relations of S0's. We check if the evolution induced onto S0's by dry intermediate and minor mergers can reproduce their photometric scaling relations, analysing the bulge-disk decompositions of the merger simulations presented in Eliche-Moral et al. (2012). The mergers induce an evolution in the photometric planes compatible with the data of S0's, even in those ones indicating a strong bulge-disk coupling. The mergers drive the formation of the observed photometric relation in some cases, whereas they induce a slight dispersion compatible with data in others. Therefore, this evolutionary mechanism tends to preserve these scaling relations. In those photometric planes where the morphological types segregate, the mergers always induce evolution towards the region populated by S0's. The structural coupling of the bulge and the disk is preserved or reinforced because the mergers trigger internal secular processes in the primary disk that induce significant bulge growth, even although these models do not induce bars. Intermediate and minor mergers can thus be considered as plausible mechanisms for the evolution of S0's attending to their photometric scaling relations, as they can preserve and even strengthen any pre-existing structural bulge-disk coupling, triggering significant internal secular evolution (even in the absence of bars or dissipational effects). This means that it may be difficult to isolate the effects of pure internal secular evolution from those of the merger-driven one in present-day early-type disks (abridged).Comment: Accepted for publication in Astronomy & Astrophysics, 13 pages, 8 figures. Definitive version after proofs. Added references and corrected typo

The use of pocket-size imaging devices: a position statement of the European Association of Echocardiography.

Pocket-size imaging devices are a completely new type of echo machines which have recently reached the market. They are very cheap, smartphone-size hand-held echo machines with limited technical capabilities. The aim of this European Association of Echocardiography (EAE) position paper is to provide recommendations on the use of pocket-size imaging devices in the clinical arena by profiling the educational needs of potential users other than cardiologists experts in echo. EAE recommendations about pocket-size imaging devices can be summarized in: (1) pocket-size imaging devices do not provide a complete diagnostic echocardiographic examination. The range of indications for their use is therefore limited. (2) Imaging assessment with pocket-size imaging devices should be reported as part of the physical examination of the patient. Image data should be stored according to the applicable national rules for technical examinations. (3) With the exception of cardiologists who are certified for transthoracic echocardiography according to national legislation, specific training and certification is recommended for all users. The certification should be limited to the clinical questions that can potentially be answered by pocket-size devices. (4) The patient has to be informed that an examination with the current generation of pocket-size imaging devices does not replace a complete echocardiogram.Peer reviewe

Railway traffic induced vibrations: comparison of analytical and finite element models

The recent increase in the use of the railway and the establishment of more restrictive policies of harmful environmental effects of railway transport highlights the need to investigate ground vibrations related to trains. Therefore models to evaluate how this phenomenon affects have been performed. This article aims to expose both analytical and 3D-FE models and to compare theoretical formulation and results. Models have been calibrated and validated with real data. Furthermore, a simulation of the acceleration level of different railway infrastructure elements has been achieved

A contribution to the selection of emission-line galaxies using narrow-band filters in the optical airglow windows

Emission line galaxies are an invaluable tool for our understanding of the evolution of galaxies in the Universe. Imaging of deep fields with narrow-band filters allows not only the selection of these objects, but also to infer the line flux and the equivalent width of the emission line with some assumptions. The narrow-band filter technique provides homogeneous samples of galaxies in small comoving volumes in the sky. We present an analysis of the selection of emission-line galaxies using narrow-band filters. Different methods of observation are considered: broad-band -- narrow-band filters and two broad-band and one narrow-band filters. We study also the effect of several lines entering simultaneously inside the filters (this is the case of Halpha). In each case the equations to obtain the equivalent width and line flux from the photometry are obtained. Candidates to emission-line objects are selected by their color excess in a magnitude-color diagram. For different narrow-band filters, we compute the mean colors of stars and galaxies, showing that, apart from galaxies, some types of stars could be selected with certain filter sets. We show how to compute the standard deviation of the colors of the objects even in the usual case when there are not enough objects to determine the standard deviation from the data. We present also helpful equations to compute the narrow-band and the broad-band exposure times in order to obtain minimum dispersion in the ratio of fluxes of both bands with minimum total exposure time.Comment: Accepted for publication in PASP 48 pages, 10 figures Corrected typos, fixed references. Updated reference to T

Combined effects of land use and hunting on distributions of tropical mammals

Land use and hunting are 2 major pressures on biodiversity in the tropics. Yet, their combined impacts have not been systematically quantified at a large scale. We estimated the effects of both pressures on the distributions of 1884 tropical mammal species by integrating species’ range maps, detailed land-use maps (1992 and 2015), species-specific habitat preference data, and a hunting pressure model. We further identified areas where the combined impacts were greatest (hotspots) and least (coolspots) to determine priority areas for mitigation or prevention of the pressures. Land use was the main driver of reduced distribution of all mammal species considered. Yet, hunting pressure caused additional reductions in large-bodied species’ distributions. Together, land use and hunting reduced distributions of species by 41% (SD 30) on average (year 2015). Overlap between impacts was only 2% on average. Land use contributed more to the loss of distribution (39% on average) than hunting (4% on average). However, hunting reduced the distribution of large mammals by 29% on average; hence, large mammals lost a disproportional amount of area due to the combination of both pressures. Gran Chaco, the Atlantic Forest, and Thailand had high levels of impact across the species (hotspots of area loss). In contrast, the Amazon and Congo Basins, the Guianas, and Borneo had relatively low levels of impact (coolspots of area loss). Overall, hunting pressure and human land use increased from 1992 to 2015 and corresponding losses in distribution increased from 38% to 41% on average across the species. To effectively protect tropical mammals, conservation policies should address both pressures simultaneously because their effects are highly complementary. Our spatially detailed and species-specific results may support future national and global conservation agendas, including the design of post-2020 protected area targets and strategies

Hidratación y microestructura de cemento Portland sustituido parcialmente con sílice ultrafina

Geothermal waste, a by-product of steam power plants that use geothermal underground resources, was studied as a possible replacement for Portland cement. This waste consists primarily in amorphous nanometric silica with traces of sodium and potassium chlorides. The replacement ratios studied were 0, 10 and 20% in cements cured at 20 and 60 ºC. X-ray diffraction analysis showed that clinker phase hydration took place earlier in the presence of the geothermal waste. Scanning electron microscopy, in turn, revealed a reduction in porosity and intense calcium hydroxide consumption as a result of the pozzolanic reaction. The pastes containing 20% waste, however, an intense cracking was observed due to the formation of alkali silica reaction gel and ettringite. Cracking was more prominent at 60 ºC but was not observed in either the neat cement or the blend with 10 % waste. The presence of these detrimental phases was attributed to the formation of Friedel’s salt in the initial hydration stages, induced by the chlorides in the geothermal material.Se investigaron pastas de cemento Portland sustituido con un desecho geotérmico, subproducto de la generación de electricidad en plantas que emplean recursos geotérmicos. El desecho está compuesto principalmente de sílice amorfa de tamaño nanométrico, con cloruros de sodio y potasio. Se investigaron cementos con niveles de substitución de 0, 10 y 20%, curados a 20 y 60 °C. En presencia del desecho geotérmico, se observó por Difracción de rayos X cuantitativa que la hidratación de las fases del clínker se aceleró; además mediante microscopía electrónica de barrido se encontró una disminución en la porosidad y un intenso consumo de hidróxido de calcio por la reacción puzolánica. Sin embargo, para pastas con 20% de desecho geotérmico, se observó agrietamiento con la presencia de gel de reacción álcali sílice y ettringita; fue más acentuado a 60 °C y no se observó para pastas de cemento puro y con 10% de desecho. La presencia de las fases nocivas se atribuye a la formación de sal de Friedel en las etapas iniciales de hidratación, promovida por los cloruros provenientes del desecho geotérmico