Design of the road versus the behaviour of the drivers. Overtaking, Speed and Sight Distance.

La tesina se compone de dos grandes bloques. En un primer bloque se analiza la casuística del Eix Transversal, con el objeto de averiguar si realmente el Eix es una vía tan peligrosa como los medios de comunicación parecen decir, por ello se inicia la tesina estudiando la accidentalidad en vías interurbanas tanto en España como en Catalunya, para poder comparar seguidamente los datos obtenidos con los del Eix. Para ello ha sido necesario analizar la casuística de cada uno de los accidentes que se produjeron en el Eix entre los años 1998 y 2000. La conclusión del estudio es rotunda: el Eix presenta globalmente, unos índices de siniestralidad notablemente inferiores al resto de las vías, sin embargo, tiene un tanto por ciento muy elevado de accidentes frontales. El tanto por ciento de accidentes frontales del Eix dobla a la media del resto de las vías. Por ello se decidió investigar el porqué de este hecho, realizándose un análisis más detallado de los accidentes frontales del Eix, tratando de averiguar si existen curvas, tramos, condiciones atmosféricas, franjas horarias... que propicien los accidentes. No se han detectado tramos con una especial concentración de accidentes (TCA), tal y como se verá, la casuística de los accidentes es muy dispar. Quedaba, por tanto, analizar la normativa empleada en el diseño de las zonas de adelantamiento, tema que se ha abordado en el segundo bloque de la tesina. Así mismo, con el objetivo de eliminar los accidentes frontales del Eix, se ha contemplado la posibilidad del desdoblamiento, opción que ha sido analizada tanto desde un punto de vista técnico como desde un punto de vista económico. La accidentalidad mejoraría enormemente, sin embargo, el coste económico de realizar el desdoblamiento sería inasumible. En un segundo bloque se incide en los principales factores que pueden ocasionar un accidente frontal. De este modo, en una primera parte se analizan de un modo general los factores que intervienen en un accidente de tráfico, haciendo especial hincapié en el factor humano y en la vía. En una segunda parte, se trata el tema que da sentido a la tesina: la distancia de visibilidad de adelantamiento. En esta parte se analiza en primer lugar las metodologías utilizadas en diferentes partes del mundo para obtener la distancia de visibilidad de adelantamiento que luego se aplica en las carreteras. Así se analizan y compararan los métodos empleados por la AASHTO y por Wang y Cartmell. Así mismo, se toca de un modo superficial los factores de seguridad de los parámetros de diseño. Seguidamente, se estudian las normativas empleadas en España y en el Reino Unido, con el objetivo de estudiar como se trata el tema de la distancia de visibilidad de adelantamiento en territorio europeo, que como se verá arroja una disparidad de criterios y de resultados muy notable. Una vez comparadas las diferentes metodologías y las diferentes normativas, se desarrolla un programa en EXCEL que permite calcular, en función de diferentes parámetros, el tanto por ciento de los adelantamientos que se producirían con éxito en función de la distancia de visibilidad de adelantamiento que se elija. Tal y como se verá en el análisis realizado a las diferentes metodologías, la aceleración es el parámetro que más discrepancias presenta entre los diferentes métodos. Según los expertos consultados, un valor de aceleración medio representativo del parque automovilístico europeo rondaría los 4-5 Km/h/s, valor que está en medio de los valores utilizados por la AASHTO y por la MUTCD. De todos modos, en la tesina se realiza un pequeño estudio con el objetivo de determinar una aceleración representativa de los vehículos de gama media. Con este resultado se determina el tanto por ciento de los adelantamientos que se producirían con éxito para cada distancia de adelantamiento

Caracterización de la función de la amenopeptidasa MPA1 en la meiosis de Arabidopsis Thaliana

Las proteasas son enzimas esenciales para la regulación del ciclo celular, especialmente las aminopeptidasas. En el caso de Arabidopsis thaliana, especie modelo en genética vegetal, estas proteínas son mayoritariamente metaloenzimas y su función es el corte de enlaces peptídicos localizados en los extremos N-terminales, afectando a una región clave para las modificaciones postraduccionales. Las metalopeptidasas de la familia M1 se encuentran en todos los eucariotas y son imprescindibles para su correcto crecimiento y desarrollo. En plantas se ha descrito además su implicación en la división meiótica, la división celular especializada que conduce a la formación de los gametos. En A. thaliana, la ausencia de función de la aminopeptidasa MPA1 (MEIOTIC PROPHASE AMINOPEPTIDASE 1), metalopeptidasa sensible al antibiótico puromicina, produce problemas de fertilidad como consecuencia de la formación de un elevado porcentaje de granos de polen inviables. El análisis de la meiosis masculina en el mutante nulo mpa1-1 ha revelado deficiencias en la formación de los quiasmas, las conexiones debidas a intercambios recíprocos de ADN entre los cromosomas homólogos que permiten su correcta segregación en anafase I. En el presente estudio se han caracterizado diferentes alelos mutantes producidos por inserciones de T-DNA localizadas en distintas regiones del gen. Aunque no se han encontrado problemas de viabilidad de polen en las correspondientes líneas, la caracterización citológica de la meiosis ha puesto de manifiesto un descenso en la frecuencia media de quiasmas con respecto al genotipo silvestre. Los resultados obtenidos permiten profundizar en el análisis de la función de MPA1 en la meiosis de A. thaliana, para tratar de dilucidar su papel en el proceso de recombinación homóloga, responsable de la formación de los quiasmas

Transport of fungal RAB11 secretory vesicles involves myosin-5, dynein/dynactin/p25, and kinesin-1 and is independent of kinesin-3

15 p.-8 fig.Hyphal tip cells of the fungus Aspergillus nidulans are useful for studying long-range intracellular traffic. Post-Golgi secretory vesicles (SVs) containing the RAB11 orthologue RabE engage myosin-5 as well as plus end– and minus end–directed microtubule motors, providing an experimental system with which to investigate the interplay between microtubule and actin motors acting on the same cargo. By exploiting the fact that depolymerization of F-actin unleashes SVs focused at the apex by myosin-5 to microtubule-dependent motors, we establish that the minus end–directed transport of SVs requires the dynein/dynactin supercomplex. This minus end–directed transport is largely unaffected by genetic ablation of the Hook complex adapting early endosomes (EEs) to dynein but absolutely requires p25 in dynactin. Thus dynein recruitment to two different membranous cargoes, namely EEs and SVs, requires p25, highlighting the importance of the dynactin pointed-end complex to scaffold cargoes. Finally, by studying the behavior of SVs and EEs in null and rigor mutants of kinesin-3 and kinesin-1 (UncA and KinA, respectively), we demonstrate that KinA is the major kinesin mediating the anterograde transport of SVs. Therefore SVs arrive at the apex of A. nidulans by anterograde transport involving cooperation of kinesin-1 with myosin-5 and can move away from the apex powered by dynein.This work was funded by grants from the Spanish Ministerio de Economía y Competitividad (BIO2012-30965 and BIO2015-65090-R) and the Comunidad de Madrid (Grant S2010/ BMD-2414) to M.A.P. and from the National Institutes of Health (RO1 GM097580) and the Uniformed Services University (intramural grant BIO-71-1972) to X.X.Peer reviewe

Cisternal maturation within the Aspergillus nidulans golgi visualized in vivo

3 p.Peer reviewe

Regulation of snares in the endovacuolar system of aspergillus nidulans

3 p.Peer reviewe

Analysis of 222Rn Surface Concentrations in the Basque Country (Spain): A Case Study of Heat Waves

The objective of this study was to characterize radon concentrations registered in the Radiological Surveillance Network of the Basque country in relation to local meteorological parameters, and to determine its behaviour under heatwave events. For this purpose, radon measurements and meteorological parameters from June 2012 to June 2015 were analysed at two sites, Bilbao and Vitoria (northern Spain), in a region characterized by complex orography, causing large temporal and spatial variability in meteorological conditions. Yearly, seasonal, and diurnal cycle differences and similarities were investigated at both sites. The temporal evolution of radon concentration was analysed at both sites during the two heatwave periods officially identified by the State Meteorological Agency (8–11 August 2012 and 17–23 August 2012). The analysis revealed two different patterns of radon concentrations, in terms of both time and intensity, under this synoptic pattern, making it also possible to identify regional transport channels of radon concentrations between the two sites. This set of results evidences the adequate position of both stations to represent the spatial and temporal evolution of radiological variables continuously in this region

Fracture mechanics analysis of hardmetals by using artificial small-scale flaws machined at the surface through short-pulse laser ablation

Laser ablation has become an innovative treatment for cemented carbides, regarding edge rounding and surface modification, aiming to improve their tribomechanical performance. Meanwhile, the precision offered for this technique has also positioned it as an effective mean to generate micronotches used for evaluation of mechanical properties in structural materials. However, similar approach has not been attempted for hardmetals; thus, it becomes the main objective of this work. Dimple-like and elongated micronotches are introduced in one fine-grained WC-11%wtCo grade. In doing so, laser processing parameters are first optimized to attain micronotches with appropriated geometry and size, i.e. similar to critical flaws identified in broken pristine specimens. Success of the implemented approach is then validated through subsequent flexural testing, fractographic inspection and fracture mechanics analysis of the results attained on samples containing surface micronotches, as far as laser-induced residual stresses are taken into consideration. In this regard, elongated micronotches are found to exhibit lower residual stresses, and postulate themselves as the optimal option of the two micronotch types studied. The suitability of laser ablation for shaping artificial small-scale flaws opens a new route for introducing controlled defects, alike those intrinsic to processing or induced during service, key aspect for further understanding damage tolerance issues in cemented carbides.Peer ReviewedPostprint (published version

Testing length-scale considerations in mechanical characterization of WC-Co hardmetal produced via binder jetting 3D printing

The extreme versatility of additive manufacturing (AM) as processing technology results in “AMed pieces” with intrinsic characteristics linked to the shaping route followed, which are also key for defining mechanical integrity. The latter requires validation by measuring the mechanical properties, at both macroscopic (global) and microscopic (local) levels; and thus, consideration of specific testing length-scale aspects. This work aims to study the correlation between microstructure and mechanical properties for a WC-12%wt.Co hardmetal grade produced via binder jetting 3D printing (BJT) and subsequent sintering. In doing so, macro- and micro- Vickers hardness as well as scratch tests, using different loads and indenter tips, are conducted. It is found that studied samples processed by means of BJT exhibit a microstructure consisting of a relatively wide carbide size distribution, including a significant volume fraction (higher than 15%) of carbides larger than 3 µm. This is a direct consequence of the relatively high sintering temperature needed for getting full dense specimens, when manufactured following this AM route. Meanwhile, mechanical properties are found to be isotropic, with hardness and scratch resistance values falling within ranges of those expected for hardmetals with similar binder content and mean carbide grain size. Very interesting, length-scale effects on testing are observed in terms of dispersion of measured hardness value as applied load decreases. These findings, together with similar ones linked to length-scale influence on scratch response, point out that effective selection of mechanical testing parameters become critical for studying and understanding phenomena such as elastic/plastic and deformation/fracture transitions in AMed hardmetals.Peer ReviewedPostprint (published version

Corrosion evaluation of austenitic and duplex stainless steels in molten carbonate salts at 600 °C for thermal energy storage

Next-generation concentrated solar power (CSP) plants are required to operate at temperatures as high as possible to reach a better energy efficiency. This means significant challenges for the construction materials in terms of corrosion resistance, among others. In the present work, the corrosion behavior in a molten eutectic ternary Li2CO3-Na2CO3-K2CO3 mixture at 600 °C was studied for three stainless steels: an austenitic grade AISI 301LN (SS301) and two duplex grades, namely 2205 (DS2205) and 2507 (DS2507). Corrosion tests combined with complementary microscopy, microanalysis and mechanical characterization techniques were employed to determine the corrosion kinetics of the steels and the oxide scales formed on the surface. The results showed that all three materials exhibited a corrosion kinetics close to a parabolic law, and their corrosion rates increased in the following order: DS2507 < SS301 < DS2205. The analyses of the oxide scales evidenced an arranged multilayer system with LiFeO2, LiCrO2, FeCr2O4 and NiO as the main compounds. While the Ni-rich inner layer of the scales presented a good adhesion to the metallic substrate, the outer layer formed by LiFeO2 exhibited a higher concentration of porosity and voids. Both the Cr and Ni contents at the inner layer and the defects at the outer layer were crucial for the corrosion resistance for each steel. Among the studied materials, super duplex stainless steel 2507 is found to be the most promising alternative for thermal energy storage of those structural components for CSP plants.Peer ReviewedPostprint (published version

Micromechanical properties of yttria-doped zirconia ceramics manufactured by direct ink writing

Yttria-doped zirconia ceramics have many applications in a wide range of industries mainly due to their excellent mechanical properties, corrosion resistance and biocompatibility. In this study, micromechanical properties of yttria-doped zirconia produced by Direct-Ink Writing (DIW) were investigated and compared to the ones produced by Cold Isostatic Pressing (CIP). In doing so, mechanical response was assessed at different length scales, from macro- up to submicrometric-, by means of Vickers hardness, nanoindentation, and nanoscratch tests. Microstructure was also characterized by determining grain size, crystal structure and phase tetragonal to monoclinic phase transformation. Results revealed that printed samples displayed 20–25% lower hardness values compared to those exhibited by the respective CIP pairs. Differences in hardness between 3 and 8 mol% yttria content evaluated for CIP samples were slight for printed samples, due to the effect of microstructural defects like porosity, resulting from the processing parameters used. At the local level, such an effect was found to be lower. In this sense, hardness and elastic modulus achieved by nanoindentation were closer, when comparing printed and CIP samples. Scratch tests carried out from 0 to 250 mN revealed that 3 mol% Y2O3 samples developed micro-fracture events in the track length, being the printed samples the ones heavily deformed.Peer ReviewedPostprint (author's final draft