7,111 research outputs found
Contrapuntos vitales y lecturas múltiples en Las dos ventanas de Esteban Valentino y Marina Aizen
Cells of the synovium in rheumatoid arthritis. Chondrocytes
Rheumatoid arthritis (RA) is one of the inflammatory joint diseases in a heterogeneous group of disorders that share features of destruction of the extracellular matrices of articular cartilage and bone. The underlying disturbance in immune regulation that is responsible for the localized joint pathology results in the release of inflammatory mediators in the synovial fluid and synovium that directly and indirectly influence cartilage homeostasis. Analysis of the breakdown products of the matrix components of joint cartilage in body fluids and quantitative imaging techniques have been used to assess the effects of the inflammatory joint disease on the local remodeling of joint structures. The role of the chondrocyte itself in cartilage destruction in the human rheumatoid joint has been difficult to address but has been inferred from studies in vitro and in animal models. This review covers current knowledge about the specific cellular and biochemical mechanisms that account for the disruption of the integrity of the cartilage matrix in RA
Diferentes técnicas de integración paisajística en carreteras. Análisis de eficacia a través de la percepción de observadores.
En el trabajo que se expone en este artículo se planteó como objetivo realizar un análisis de las diferentes medidas de integración paisajística que se utilizan en las autopistas y autovías españolas. Para ello, se ha realizado una revisión bibliográfica de la normativa, la documentación científica, las guías y demás recomendaciones en este ámbito, y se ha efectuado un inventario fotográfico que recoge las medidas de restauración observadas en las diferentes vías. Gracias a una encuesta fotográfica y al posterior análisis de la percepción del público de las diferentes medidas de integración, se han identificado las variables medioambientales clave en la integración de las autopistas en el paisaje, los aspectos de diseño más adecuados y las medidas de integración paisajística más efectivas
Alternating direction implicit time integrations for finite difference acoustic wave propagation: Parallelization and convergence
This work studies the parallelization and empirical convergence of two finite
difference acoustic wave propagation methods on 2-D rectangular grids, that use
the same alternating direction implicit (ADI) time integration. This ADI
integration is based on a second-order implicit Crank-Nicolson temporal
discretization that is factored out by a Peaceman-Rachford decomposition of the
time and space equation terms. In space, these methods highly diverge and apply
different fourth-order accurate differentiation techniques. The first method
uses compact finite differences (CFD) on nodal meshes that requires solving
tridiagonal linear systems along each grid line, while the second one employs
staggered-grid mimetic finite differences (MFD). For each method, we implement
three parallel versions: (i) a multithreaded code in Octave, (ii) a C++ code
that exploits OpenMP loop parallelization, and (iii) a CUDA kernel for a NVIDIA
GTX 960 Maxwell card. In these implementations, the main source of parallelism
is the simultaneous ADI updating of each wave field matrix, either column-wise
or row-wise, according to the differentiation direction. In our numerical
applications, the highest performances are displayed by the CFD and MFD CUDA
codes that achieve speedups of 7.21x and 15.81x, respectively, relative to
their C++ sequential counterparts with optimal compilation flags. Our test
cases also allow to assess the numerical convergence and accuracy of both
methods. In a problem with exact harmonic solution, both methods exhibit
convergence rates close to 4 and the MDF accuracy is practically higher.
Alternatively, both convergences decay to second order on smooth problems with
severe gradients at boundaries, and the MDF rates degrade in highly-resolved
grids leading to larger inaccuracies. This transition of empirical convergences
agrees with the nominal truncation errors in space and time.Comment: 20 pages, 5 figure
Systematic search for gamma-ray periodicity in active galactic nuclei detected by the Fermi Large Area Telescope
We use nine years of gamma-ray data provided by the Fermi Large Area
Telescope (LAT) to systematically study the light curves of more than two
thousand active galactic nuclei (AGN) included in recent Fermi-LAT catalogs.
Ten different techniques are used, which are organized in an automatic
periodicity-search pipeline, in order to search for evidence of periodic
emission in gamma rays. Understanding the processes behind this puzzling
phenomenon will provide a better view about the astrophysical nature of these
extragalactic sources. However, the observation of temporal patterns in
gamma-ray light curves of AGN is still challenging. Despite the fact that there
have been efforts on characterizing the temporal emission of some individual
sources, a systematic search for periodicities by means of a full likelihood
analysis applied to large samples of sources was missing. Our analysis finds 11
AGN, of which 9 are identified for the first time, showing periodicity at more
than 4sigma in at least four algorithms. These findings will help in solving
questions related to the astrophysical origin of this periodic behavior.Comment: 16 pages, 5 figures, 4 tables. Accepted by Ap
Bird flight behavior, collision risk and mitigation options at high-speed railway viaducts
High-speed railway (HSR) networks are rapidly expanding and are predicted to continue to grow over coming decades. However, there is scant knowledge of their environmental impacts. Their possible effects on bird mortality, particularly at viaducts, gives especial cause for concern. This work presents the results of a nine-month monitoring of bird activity in the vicinity of three HSR viaducts in Central Spain. The study focused on the effects of the infrastructure regarding bird frequentation of the site and on bird flight activity in the danger zone for collision with passing trains. The findings show (i) that bird communities may differ markedly between sites and (ii) that bird activity increases near the railway together with changes in relative species abundances. Furthermore, (iii) birds show a significant tendency to avoid flying across the danger zone, but (iv) all kinds of birds are at a real risk of collisions with trains at viaducts. The greatest danger is at viaduct extremes rather than in their central section, particularly during gusts of wind and for small or medium-sized birds. It also appears that relatively low viaducts might pose greater risk. In practical terms, these results (i) emphasise the need for thorough prior prospection of bird species present, and their flight patterns, where new viaducts are to be built, (ii) show that there is a real risk of bird collisions with trains at viaducts, which should be mitigated, with particular attention due to viaduct extremes and areas where their height is not much above the surrounding vegetation and (iii) strongly indicate the need to minimise viaduct features that may attract birds to them, for example as potential nest sitesThis study is derived from research into the ecology and mortality of
birds at highspeed railways done under project EU LIFE+ Impacto Cero
(LIFE 12 BIO/ES/000660). JEM and JH form part of the REMEDINAL
TE-CM research network, funded by the Comunidad de Madrid (P2018/
EMT-4338). Comments by two anonymous reviewers improved the final
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