Soil compaction and vegetation cover in a Scots pine stand at the Mediterranean rangelands

Right development of ROOT SYSTEMS is essential to ensure seedling survival in the initial stages of natural regeneration processes. Soil compaction determines this development both because of its influence on soil T�� & moisture dynamics and for its direct effect on soil mechanical impedance to root growth. All this effects can be assessed as a whole through soil penetration resistance (Soil Strength) measurements. SOIL STRENGTH has been usually evaluated in forest research in connection with severe disturbances derived from heavy machinery works during forest operations. Nevertheless, undisturbed soils are also expected to show different levels of compaction for root development. Organic matter modifies soil structure and so on porosity, compaction and resultant soil resistance to penetration. Its concentration in surface layers is rather related to vegetation cover composition and density. So within forest stands, a relationship is expected to be found between VEGETATION COVER density and compaction measured as resistance to penetration (soil strength)

Assessment of oral bioaccessibility of arsenic in playground soil in Madrid (Spain): A three-method comparison and implications for risk assessment

Three methodologies to assess As bioaccessibility were evaluated using playgroundsoil collected from 16 playgrounds in Madrid, Spain: two (Simplified Bioaccessibility Extraction Test: SBET, and hydrochloric acid-extraction: HCl) assess gastric-only bioaccessibility and the third (Physiologically Based Extraction Test: PBET) evaluates mouth–gastric–intestinal bioaccessibility. Aqua regia-extractable (pseudo total) As contents, which are routinely employed in riskassessments, were used as the reference to establish the following percentages of bioaccessibility: SBET – 63.1; HCl – 51.8; PBET – 41.6, the highest values associated with the gastric-only extractions. For Madridplaygroundsoils – characterised by a very uniform, weakly alkaline pH, and low Fe oxide and organic matter contents – the statistical analysis of the results indicates that, in contrast with other studies, the highest percentage of As in the samples was bound to carbonates and/or present as calcium arsenate. As opposed to the As bound to Fe oxides, this As is readily released in the gastric environment as the carbonate matrix is decomposed and calcium arsenate is dissolved, but some of it is subsequently sequestered in unavailable forms as the pH is raised to 5.5 to mimic intestinal conditions. The HCl extraction can be used as a simple and reliable (i.e. low residual standard error) proxy for the more expensive, time consuming, and error-prone PBET methodology. The HCl method would essentially halve the estimate of carcinogenic risk for children playing in Madridplaygroundsoils, providing a more representative value of associated risk than the pseudo-total concentrations used at present

Spectral-analysis-surface-waves-method in ground characterization

The prediction of train induced vibration levels in structures close to railway tracks before track construction starts is important in order to avoid having to implement costly mitigation measures afterwards. The used models require an accurate characterization of the propagation medium i.e. the soil layers. To this end the spectral analysis of surface waves (SASW) method has been chosen among the active surface waves techniques available. As dynamic source a modal sledge hammer has been used. The generated vibrations have been measured at known offsets by means of several accelerometers. There are many parameters involved in estimating the experimental dispersion curve and, later on, thickness and propagation velocities of the different layers. Tests have been carried out at the Segovia railway station. Its main building covers some of the railway tracks and vibration problems in the building should be avoided. In the paper these tests as well as the influence of several parameters on the estimated soil profile will be detailed.

Community Structure in Soil Porous System

Diffusion controls the gaseous transport process in soils when advective transport is almost null. Knowledge of the soil structure and pore connectivity are critical issues to understand and modelling soil aeration, sequestration or emission of greenhouse gasses, volatilization of volatile organic chemicals among other phenomena. In the last decades these issues increased our attention as scientist have realize that soil is one of the most complex materials on the earth, within which many biological, physical and chemical processes that support life and affect climate change take place. A quantitative and explicit characterization of soil structure is difficult because of the complexity of the pore space. This is the main reason why most theoretical approaches to soil porosity are idealizations to simplify this system. In this work, we proposed a more realistic attempt to capture the complexity of the system developing a model that considers the size and location of pores in order to relate them into a network. In the model we interpret porous soils as heterogeneous networks where pores are represented by nodes, characterized by their size and spatial location, and the links representing flows between them. In this work we perform an analysis of the community structure of porous media of soils represented as networks. For different real soils samples, modelled as heterogeneous complex networks, spatial communities of pores have been detected depending on the values of the parameters of the porous soil model used. These types of models are named as Heterogeneous Preferential Attachment (HPA). Developing an exhaustive analysis of the model, analytical solutions are obtained for the degree densities and degree distribution of the pore networks generated by the model in the thermodynamic limit and shown that the networks exhibit similar properties to those observed in other complex networks. With the aim to study in more detail topological properties of these networks, the presence of soil pore community structures is studied. The detection of communities of pores, as groups densely connected with only sparser connections between groups, could contribute to understand the mechanisms of the diffusion phenomena in soils.

The relationship between soil geochemistry and the bioaccessibility of trace elements in playground soil

A total of 32 samples of surficial soil were collected from 16 playground areas in Madrid (Spain), in order to investigate the importance of the geochemistry of the soil on subsequent bioaccessibility of trace elements. The in vitro bioaccessibility of As, Co, Cr, Cu, Ni, Pb and Zn was evaluated by means of two extraction processes that simulate the gastric environment and one that reproduces a gastric + intestinal digestion sequence. The results of the in vitro bioaccessibility were compared against aqua regia extractions (���total��� concentration), and it was found that total concentrations of As, Cu, Pb and Zn were double those of bioaccessible values, whilst that of Cr was ten times higher. Whereas the results of the gastric + intestinal extraction were affected by a high uncertainty, both gastric methods offered very similar and consistent results, with bioaccessibilities following the order: As = Cu = Pb = Zn > Co > Ni > Cr, and ranging from 63 to 7 %. Selected soil properties including pH, organic matter, Fe and CaCO3 content were determined to assess their influence on trace element bioaccessibility, and it was found that Cu, Pb and Zn were predominantly bound to organic matter and, to a lesser extent, Fe oxides. The former fraction was readily accessible in the gastric solution, whereas Fe oxides seemed to recapture negatively charged chloride complexes of these elements in the gastric solution, lowering their bioaccessibility. The homogeneous pH of the playground soils included in the study does not influence trace element bioaccessibility to any significant extent except for Cr, where the very low gastric accessibility seems to be related to the strongly pH-dependent formation of complexes with organic matter. The results for As, which have been previously described and discussed in detail in Mingot et al. (Chemosphere 84: 1386–1391, 2011), indicate a high gastric bioaccessibility for this element as a consequence of its strong association with calcium carbonate and the ease with which these bonds are broken in the gastric solution. The calculation of risk assessments are therefore dependant on the methodology used and the specific environment they address. This has impacts on management strategies formulated to ensure that the most vulnerable of society, children, can live and play without adverse consequences to their health.

Seismic Hazard and Ground Motion Characterization at the Itoiz Dam (Northern Spain).

This paper presents a new hazard-consistent ground motion characterization of the Itoiz dam site, located in Northern Spain. Firstly, we propose a methodology with different approximation levels to the expected ground motion at the dam site. Secondly, we apply this methodology taking into account the particular characteristics of the site and of the dam. Hazard calculations were performed following the Probabilistic Seismic Hazard Assessment method using a logic tree, which accounts for different seismic source zonings and different ground-motion attenuation relationships. The study was done in terms of peak ground acceleration and several spectral accelerations of periods coinciding with the fundamental vibration periods of the dam. In order to estimate these ground motions we consider two different dam conditions: when the dam is empty (T = 0.1 s) and when it is filled with water to its maximum capacity (T = 0.22 s). Additionally, seismic hazard analysis is done for two return periods: 975 years, related to the project earthquake, and 4,975 years, identified with an extreme event. Soil conditions were also taken into account at the site of the dam. Through the proposed methodology we deal with different forms of characterizing ground motion at the study site. In a first step, we obtain the uniform hazard response spectra for the two return periods. In a second step, a disaggregation analysis is done in order to obtain the controlling earthquakes that can affect the dam. Subsequently, we characterize the ground motion at the dam site in terms of specific response spectra for target motions defined by the expected values SA (T) of T = 0.1 and 0.22 s for the return periods of 975 and 4,975 years, respectively. Finally, synthetic acceleration time histories for earthquake events matching the controlling parameters are generated using the discrete wave-number method and subsequently analyzed. Because of the short relative distances between the controlling earthquakes and the dam site we considered finite sources in these computations. We conclude that directivity effects should be taken into account as an important variable in this kind of studies for ground motion characteristics.

Physical characterization of laser interaction and shock generation in laser shock processing: coupled theoretical-experimental analysis

Laser Shock Processing is developing as a key technology for the improvement of surface mechanical and corrosion resistance properties of metals due to its ability to introduce intense compressive residual stresses fields into high elastic limit materials by means of an intense laser driven shock wave generated by laser with intensities exceeding the 109 W/cm2 threshold, pulse energies in the range of 1 Joule and interaction times in the range of several ns. However, because of the relatively difficult-to-describe physics of shock wave formation in plasma following laser-matter interaction in solid state, only limited knowledge is available in the way of full comprehension and predictive assessment of the characteristic physical processes and material transformations with a specific consideration of real material properties. In the present paper, an account of the physical issues dominating the development of LSP processes from a moderately high intensity laser-matter interaction point of view is presented along with the theoretical and computational methods developed by the authors for their predictive assessment and new experimental contrast results obtained at laboratory scale.

Physical characterization of growing media using standard methods (CEN)- Limitations of Applicability for pine bark and vermiculite

CEN standards have helped to harmonize analytical methods for substrate analysis.Though, for special substrates or constituents the applicability might be Iimited. In this paper a comparative study of implementation of CEN standards to samples of pine bark and vermiculite has been carried out. For composted pine bark, an elongation of the equilibrium period up to 72 instead of 48 hours might increase the accuracy of determinations physical parameters according to EN 13041. For vermiculite, we suggest pycnometry as a feasible technique for the determination of particle density (PD), as the determination of organic matter (OM) as requested by EN 13041 for the calculation of the PD seems not to be applicable for this kind of material.

Uncertainties in the design of support structures and foundations for offshore wind turbines

Offshore wind industry has exponentially grown in the last years. Despite this growth, there are still many uncertainties in this field. This paper analyzes some current uncertainties in the offshore wind market, with the aim of going one step further in the development of this sector. To do this, some already identified uncertainties compromising offshore wind farm structural design have been identified and described in the paper. Examples of these identified uncertainties are the design of the transition piece and the difficulties for the soil properties characterization. Furthermore, this paper deals with other uncertainties not identified yet due to the limited experience in the sector. To do that, current and most used offshore wind standards and recommendations related to the design of foundation and support structures (IEC 61400-1, 2005; IEC 61400-3, 2009; DNV-OS-J101, Design of Offshore Wind Turbine, 2013 and Rules and Guidelines Germanischer Lloyd, WindEnergie, 2005) have been analyzed. These new identified uncertainties are related to the lifetime and return period, loads combination, scour phenomenon and its protection, Morison e Froude Krilov and diffraction regimes, wave theory, different scale and liquefaction. In fact, there are a lot of improvements to make in this field. Some of them are mentioned in this paper, but the future experience in the matter will make it possible to detect more issues to be solved and improved.

MEG networks organization is related to white matter integrity

Many studies have assessed the characterization of anatomical or functional connectivity in mild cognitive impairment (MCI), however it is still unknown how they are related in the course of the pathology. Here we integrate the analysis of magnetoencephalographic (MEG) data with white matter (WM) integrity quantification from diffusion weighted imaging (DWI), to asses whether the damage in the WM tracts disrupt the organization of the functional networks.

Caracterizaci��n de los par��metros de resistencia al corte y erosionabilidad del suelo para su aplicaci��n en los problemas de estabilidad de taludes en obras lineales

La tesis se organiza en un volumen de Memoria integrada por once cap��tulos que constituyen el cuerpo de la tesis y otro volumen de Ap��ndices titulado ���Caracterizaci��n geot��cnica de Base de los suelos de Espa��a��� que re��ne en forma de cuadros las caracter��sticas de textura, permeabilidad, humedad-succi��n, erosionabilidad y resistencia al corte de los cuarenta y dos perfiles de suelos representativos de los tipos del Mapa de suelos De Espa��a. Estos cuadros han sido elaborados originalmente por la doctorando durante sus estudios para la obtenci��n del DEA de la Suficiencia Investigadora, excepto los de resistencia al corte que lo han sido tambi��n por la doctorando de forma original, pero ya en la etapa de redacci��n de la tesis. En el Cap��tulo 1 ���Introducci��n��� se describe la motivaci��n, antecedentes, alcance y contenido de la tesis, ordenado seg��n el ��ndice que en ��l se incluye. Los Cap��tulos 2 ���Meteorizaci��n, 3 ���Balance H��drico��� y 4 ���Humedades caracter��sticas��� constituyen el ���estado del arte��� en el momento actual de los temas de geotecnia ambiental relacionados con la degradaci��n de la superficie terrestre y la estabilidad de taludes. El Cap��tulo 2, tras matizar algunas generalidades, aporta elementos para la cuantificaci��n de la alteraci��n de rocas como el �����ndice clim��tico de Weinert��� y de la erosi��n de suelos como la ���ecuaci��n universal de p��rdida de suelo (U.S.L.E.)��� El Cap��tulo 3, partiendo de los fen��menos de precipitaci��n y evapotranspiraci��n, plantea el balance h��drico en vertientes con instrumentos para evaluar la infiltraci��n y la escorrent��a, conceptos imprescindibles para adentrarse en los de resistencia y erosionabilidad del conjunto suelo-agua. En los Ap��ndices A1 y A2, se recogen valores de coeficientes de infiltraci��n en condiciones saturadas y no saturadas de los perfiles de suelos del Mapa de Espa��a. El Cap��tulo 4 se dedica al estudio de este conjunto suelo-agua con la definici��n de conceptos que lo caracterizan, basados en la relaci��n entre los contenidos de ambos elementos o ���humedad���, sus valores m��ximos y m��nimos y la forma en la que es retenida el agua por el suelo. Este cap��tulo acaba con el concepto de ���Curva caracter��stica Suelo-Agua/Soil Water Characteristic curve (SWCC)���, que liga el contenido de agua de un suelo con la tensi��n a la que est�� retenida (uauw) ���succi��n��� o con su expresi��n m��s usual ���pF���. En el Ap��ndice A 3 se adjuntan las SWCC de los perfiles de suelos del Mapa de suelos de Espa��a. En el Cap��tulo 5 ���Resistencia al corte de los suelos���, se detalla la influencia que tienen sobre la resistencia de los suelos factores como el paso del tiempo, el contenido de humedad y la presencia y tipo de vegetaci��n en la superficie del suelo estudiado. El Cap��tulo 6 ���Evaluaci��n de la erosi��n���, analiza el factor de erosionabilidad del suelo ���factor K��� de la U.S.L.E., su evaluaci��n en funci��n de la textura, estructura y permeabilidad del suelo, con la estimaci��n hecha para los cuarenta y dos perfiles de suelos del Mapa de Espa��a, contenida en el Ap��ndice 4. En el Cap��tulo 7 ���Metodolog��a de dise��o��� se hacen en su primera parte unas consideraciones geoambientales de dise��o aplicables al estudio de los problemas de inestabilidades en taludes. La segunda parte constituye el n��cleo de la tesis con la propuesta de ���estimaci��n de los par��metros de resistencia al corte del suelo���, consecuente con las teor��as y metodolog��a de an��lisis expuesta en los cap��tulos anteriores. En el Ap��ndice A 5 se presentan los valores de los par��metros coulombianos de resistencia al corte, ���c y ����� estimados seg��n la caracterizaci��n clim��tica a partir del ��ndice de Thornthwaite, en condicionesde dise��o para humedades naturales m��xima y m��nima de los cuarenta y dos perfiles de suelos del Mapa de suelos de Espa��a. El Cap��tulo 8 ���Aplicaci��n a casos reales��� se considera de gran inter��s al constituir una aut��ntica continuaci��n de la segunda parte del cap��tulo anterior, desarrollando la metodolog��a expuesta en ��l a cuatro problem��ticas de infraestructuras de obras lineales, relacionadas con problemas de erosi��n y deslizamientos en taludes. El Cap��tulo 9 ���Ensayos de referencia��� se incluye como punto de apoyo (referencia) a las teor��as expuestas, valorando la idoneidad de los tipos de ensayos y tipos de suelos seleccionados (Laboratorio de Geotecnia del CEDEX y Laboratorio Hong-Kong University of Science and Technology), utilizados para la obtenci��n, por correlaciones deducidas, de las curvas SWCC de los perfiles de suelos del Mapa de Espa��a, inclu��das en el Ap��ndice A 3, como se ha citado antes. En el Cap��tulo 10 ���Conclusiones y Futuras L��neas de Investigaci��n���se apuntan en primer lugar unas conclusiones que, a juicio de la doctorando, se pueden extraer con inter��s de esta tesis y a continuaci��n se esbozan unas posibles l��neas de investigaci��n, fundamentalmente de tipo experimental, que complementar��an los avances derivados de esta tesis o podr��an esclarecer y abrir nuevas interpretaciones de los fen��menos naturales de erosi��n y estabilidad de taludes en los que ��sta se ha centrado. Finalmente, en el Cap��tulo 11 ���Bibliograf��a��� se han reunido 328 referencias que reflejan una visi��n amplia y bastante completa del tema tratado, obtenida complementando las de tesis anteriores sobre esta singular materia (���Efecto estabilizador de la vegetaci��n en taludes���, L Fort 1975 y ���Determinaci��n de las caracter��sticas de fricci��n en el contacto suelo-geotextil a diferentes succiones, mediante equipos de laboratorio singulares���, E Asanza 2009), con propias de la doctorando (9) y las consideradas de mayor inter��s de los ��ltimos Congresos sobre Suelos no saturados,���Unsat 95���, ���Unsat 2002��� y ���Unsat 2011��� entre otros. ABSTRACT The thesis is organized in a volume of Memory composed of eleven chapters that make up the body of the thesis and other Appendices volume entitled "Geotechnical characterization of basis of the soils of Spain" that combines the characteristics of texture, permeability, moisture-suction, erosionability, and shear strength of forty-two profiles of soils representative of the types of the soil of Spain map in the form of pictures. These pictures have been produced originally by the student during their studies to obtain the DEA of the research, except those of the shear strength, also been done by the PhD student in an original way, but already at the stage of drafting of the thesis. Chapter 1 "Introducci��n" describes the motivation, background, scope and content of the thesis, ordered according to the index that is included. The Chapters: 2 "Weathering, 3 ���Water Balance��� and 4 ���moisture characteristics" are the "State of the art" at the present time of geotechnical environmental issues related to the degradation of the Earth's surface and the slope stability. Chapter 2 after clarify some general information, provides elements for the quantification of the alteration of rocks as "Weinert climate index" and soil erosion as the "universal equation of loss of soil (U.S.L.E.)" Chapter 3, on the basis of the phenomena of precipitation and evapotranspiration, raises the water balance in sheds with instruments to evaluate infiltration and runoff, essential concepts into the resistance and erosionability water-soil joint. Values of soils coefficients of infiltration in saturated and unsaturated conditions from the Spain map of profiles are collected in the Appendices A1 and A2. Chapter 4 is dedicated to the study of this joint ���soil-water���, with the definition of concepts that characterize it, based on the relationship between the contents of both elements or ���moisture���, their maximum and minimum values and the way in which water is retained by the soil. This chapter ends with the concept of ���Soil Water Characteristic curve (SWCC)", which linked the water content of a soil with the stress that it is retained (ua-uw) "suction" or its expression more usual "pF". The SWCC of the profiles of soils of the Spain soils Map are attached in the Appendix 3. In Chapter 5 ���Soils shear strength���,is detailed the influence that they have on the resistance of soils factors such as the passage of time, the content of moisture and the presence and type of vegetation on the surface of the studied soil. Chapter 6 "Assessment of erosion", analyses the soil erodibility factor "Kfactor" of the U.S.L.E., its evaluation based on texture, structure and permeability of the soil, with the estimate for forty-two profiles of soils on the Spain Soils Map, contained in Appendix 4. Chapter 7 "Design methodology" some considerations are made in the first part geo-environmental design applicable to the study of the problems of instabilities in slopes. The second part constitutes the core of the thesis with the proposal of ���estimation of parameters of shear strength���, of the soils consistent with theories and analytical methodology outlined in the previous chapters. Appendix A 5 presents the values of the coulombians parameters of shear strength, "c and ��" according to the characterization of climate from the index of Thornthwaite, in design for natural moisture conditions maximum and minimum of forty-two profils of Spain Soils Map Chapter 8 "Application to real cases" is considered of great interest to constitute a true continuation of the second part of the previous chapter, developing the methodology exposed it to four problems of civil-works infrastructure, related to problems of erosion and landslides in slopes. Chapter 9 "Tests of reference" is included as point of support (reference) to the theories exposed, assessing the suitability of the types of tests and types of selected soils (Geotechnical laboratory of CEDEX and laboratory Hongkong University of Science and Technology), used to obtain, by deduced correlations, of curves SWCC of soils profiles on the Spain Soils Map, included in Appendix A. 3, as it was mentioned before. Chapter 10 "Conclusions and future research lines" are running first conclusions which, in the opinion of the candidate, can be extracted with interest of this thesis, and then, it outlines some possible lines of research, mainly experimental, which would complement the advances arising from this thesis or could clarify and open new interpretations of natural phenomena of erosion and slope stability in which it has focused. Finally, in Chapter 11 "Bibliography" 328 references have been included which reflect a broad and fairly comprehensive view of the subject matter, obtained complementing those of the previous theses on this singular issue ("Vegetation stabilizing effect on slopes", L Fort 1975, and "Determination of the characteristics of friction in the contact soil-geotextile to different-suctions, through special laboratory equipment", E Asanza 2009) with some of them from of the candidate (9) and the others from of the considered as the most interesting of recent conferences on unsaturated soils, "Unsat 95", "Unsat2002" and "Unsat 2011" among others.

Multimodal integration of functional and structural brain connectivity. An application to the characterization of Mild Cognitive Impairment

La investigaci��n para el conocimiento del cerebro es una ciencia joven, su inicio se remonta a Santiago Ram��n y Cajal en 1888. Desde esta fecha a nuestro tiempo la neurociencia ha avanzado mucho en el desarrollo de t��cnicas que permiten su estudio. Desde la neurociencia cognitiva hoy se explican muchos modelos que nos permiten acercar a nuestro entendimiento a capacidades cognitivas complejas. Aun as�� hablamos de una ciencia casi en pa��ales que tiene un lago recorrido por delante. Una de las claves del ��xito en los estudios de la funci��n cerebral ha sido convertirse en una disciplina que combina conocimientos de diversas ��reas: de la f��sica, de las matem��ticas, de la estad��stica y de la psicolog��a. Esta es la raz��n por la que a lo largo de este trabajo se entremezclan conceptos de diferentes campos con el objetivo de avanzar en el conocimiento de un tema tan complejo como el que nos ocupa: el entendimiento de la mente humana. Concretamente, esta tesis ha estado dirigida a la integraci��n multimodal de la magnetoencefalograf��a (MEG) y la resonancia magn��tica ponderada en difusi��n (dMRI). Estas t��cnicas son sensibles, respectivamente, a los campos magn��ticos emitidos por las corrientes neuronales, y a la microestructura de la materia blanca cerebral. A lo largo de este trabajo hemos visto que la combinaci��n de estas t��cnicas permiten descubrir sinergias estructurofuncionales en el procesamiento de la informaci��n en el cerebro sano y en el curso de patolog��as neurol��gicas. M��s espec��ficamente en este trabajo se ha estudiado la relaci��n entre la conectividad funcional y estructural y en c��mo fusionarlas. Para ello, se ha cuantificado la conectividad funcional mediante el estudio de la sincronizaci��n de fase o la correlaci��n de amplitudes entre series temporales, de esta forma se ha conseguido un ��ndice que mide la similitud entre grupos neuronales o regiones cerebrales. Adicionalmente, la cuantificaci��n de la conectividad estructural a partir de im��genes de resonancia magn��tica ponderadas en difusi��n, ha permitido hallar ��ndices de la integridad de materia blanca o de la fuerza de las conexiones estructurales entre regiones. Estas medidas fueron combinadas en los cap��tulos 3, 4 y 5 de este trabajo siguiendo tres aproximaciones que iban desde el nivel m��s bajo al m��s alto de integraci��n. Finalmente se utiliz�� la informaci��n fusionada de MEG y dMRI para la caracterizaci��n de grupos de sujetos con deterioro cognitivo leve, la detecci��n de esta patolog��a resulta relevante en la identificaci��n precoz de la enfermedad de Alzheimer. Esta tesis est�� dividida en seis cap��tulos. En el cap��tulos 1 se establece un contexto para la introducci��n de la connect��mica dentro de los campos de la neuroimagen y la neurociencia. Posteriormente en este cap��tulo se describen los objetivos de la tesis, y los objetivos espec��ficos de cada una de las publicaciones cient��ficas que resultaron de este trabajo. En el cap��tulo 2 se describen los m��todos para cada t��cnica que fue empleada: conectividad estructural, conectividad funcional en resting state, redes cerebrales complejas y teor��a de grafos y finalmente se describe la condici��n de deterioro cognitivo leve y el estado actual en la b��squeda de nuevos biomarcadores diagn��sticos. En los cap��tulos 3, 4 y 5 se han incluido los art��culos cient��ficos que fueron producidos a lo largo de esta tesis. Estos han sido incluidos en el formato de la revista en que fueron publicados, estando divididos en introducci��n, materiales y m��todos, resultados y discusi��n. Todos los m��todos que fueron empleados en los art��culos est��n descritos en el cap��tulo 2 de la tesis. Finalmente, en el cap��tulo 6 se concluyen los resultados generales de la tesis y se discuten de forma espec��fica los resultados de cada art��culo. ABSTRACT In this thesis I apply concepts from mathematics, physics and statistics to the neurosciences. This field benefits from the collaborative work of multidisciplinary teams where physicians, psychologists, engineers and other specialists fight for a common well: the understanding of the brain. Research on this field is still in its early years, being its birth attributed to the neuronal theory of Santiago Ramo��n y Cajal in 1888. In more than one hundred years only a very little percentage of the brain functioning has been discovered, and still much more needs to be explored. Isolated techniques aim at unraveling the system that supports our cognition, nevertheless in order to provide solid evidence in such a field multimodal techniques have arisen, with them we will be able to improve current knowledge about human cognition. Here we focus on the multimodal integration of magnetoencephalography (MEG) and diffusion weighted magnetic resonance imaging. These techniques are sensitive to the magnetic fields emitted by the neuronal currents and to the white matter microstructure, respectively. The combination of such techniques could bring up evidences about structural-functional synergies in the brain information processing and which part of this synergy fails in specific neurological pathologies. In particular, we are interested in the relationship between functional and structural connectivity, and how two integrate this information. We quantify the functional connectivity by studying the phase synchronization or the amplitude correlation between time series obtained by MEG, and so we get an index indicating similarity between neuronal entities, i.e. brain regions. In addition we quantify structural connectivity by performing diffusion tensor estimation from the diffusion weighted images, thus obtaining an indicator of the integrity of the white matter or, if preferred, the strength of the structural connections between regions. These quantifications are then combined following three different approaches, from the lowest to the highest level of integration, in chapters 3, 4 and 5. We finally apply the fused information to the characterization or prediction of mild cognitive impairment, a clinical entity which is considered as an early step in the continuum pathological process of dementia. The dissertation is divided in six chapters. In chapter 1 I introduce connectomics within the fields of neuroimaging and neuroscience. Later in this chapter we describe the objectives of this thesis, and the specific objectives of each of the scientific publications that were produced as result of this work. In chapter 2 I describe the methods for each of the techniques that were employed, namely structural connectivity, resting state functional connectivity, complex brain networks and graph theory, and finally, I describe the clinical condition of mild cognitive impairment and the current state of the art in the search for early biomarkers. In chapters 3, 4 and 5 I have included the scientific publications that were generated along this work. They have been included in in their original format and they contain introduction, materials and methods, results and discussion. All methods that were employed in these papers have been described in chapter 2. Finally, in chapter 6 I summarize all the results from this thesis, both locally for each of the scientific publications and globally for the whole work.

Effects of soil management in vineyard on soil physical and chemical characteristics

Cover crops in Mediterranean vineyards are scarcely used due to water competition between the cover crop and the grapevine; however, bare soil management through tillage or herbicides tends to have negative effects on the soil over time (organic matter decrease, soil structure and soil fertility degradation, compaction, etc). The objective of this study was to understand how soil management affects soil fertility, compaction and infiltration over time. To this end, two bare soil techniques were compared, tillage (TT) and total herbicide (HT) with two cover crops; annual cereal (CT) and annual grass (AGT), established for 8 years. CT treatment showed the highest organic matter content, having the biggest amount of biomass incorporated into the soil. The annual adventitious vegetation in TT treatment (568 kg dry matter ha-1) that was incorporated into the soil, kept the organic matter content higher than HT levels and close to AGT level, in spite of the greater aboveground annual biomass production of this treatment (3632 kg dry matter ha-1) whereas only its roots were incorporated into the soil. TT presented the highest bulk density under the tractor track lines and a greatest resistance to penetration (at 0.2 m depth). AGT presented bulk density values (upper 0.4 m) lower than TT and penetration resistance in CT lower (at 0.20 m depth) than TT too. Effects of soil management in vineyard on soil physical and chemical characteristics - ResearchGate. Available from: http://www.researchgate.net/publication/268520480_Effects_of_soil_management_in_vineyard_on_soil_physical_and_chemical_characteristics [accessed May 20, 2015].

Factors driving the carbon mineralization priming effect in a sandy loam soil amended with different types of biochar

The effect of biochar on the soil carbon mineral- ization priming effect depends on the characteristics of the raw materials, production method and pyrolysis conditions. The goal of the present study is to evaluate the impact of three different types of biochar on physicochemical properties and CO2 emissions of a sandy loam soil. For this purpose, soil was amended with three different biochars (BI, BII and BIII) at a rate of 8 wt % and soil CO2 emissions were measured for 45 days. BI is produced from a mixed wood sieving from wood chip production, BII from a mixture of paper sludge and wheat husks and BIII from sewage sludge. Cumulative CO2 emissions of biochars, soil and amended soil were well fit to a simple first-order kinetic model with correlation coef- ficients (r 2 ) greater than 0.97. Results show a negative prim- ing effect in the soil after addition of BI and a positive prim- ing effect in the case of soil amended with BII and BIII. These results can be related to different biochar properties such as carbon content, carbon aromaticity, volatile matter, fixed carbon, easily oxidized organic carbon or metal and phenolic substance content in addition to surface biochar properties. Three biochars increased the values of soil field capacity and wilting point, while effects over pH and cation exchange capacity were not observed.

Identificaci��n de ��reas prioritarias para la conservaci��n de razas de ma��z en la sierra de Ecuador

En Ecuador el ma��z es el cultivo m��s importante en superficie y es base de la alimentaci��n para la poblaci��n rural que vive en los Andes. A diferencia de lo que sucede en la Costa, en la regi��n Sierra todav��a se cultivan numerosas variedades tradicionales que se agrupan en veinticuatro razas. Mantener esta diversidad es, pues, de gran importancia no solo para la seguridad alimentaria, sino tambi��n como fuente de genes para tolerancia a factores abi��ticos que podr��an ser incorporados a las variedades modernas. Si bien parte de esta diversidad fue recolectada a mediados del siglo pasado y est�� siendo conservada en distintos bancos de germoplasma, es deseable que su conservaci��n in situ tambi��n est�� asegurada, entre otras razones, porque de esta manera el cultivo puede seguir evolucionando. Para poder implementar un plan de conservaci��n en finca que contribuya a preservar este patrimonio, resulta imprescindible identificar ��reas id��neas donde concentrar los recursos y conocer las caracter��sticas y tipolog��as de los agricultores que manejan la diversidad actual. Generar esta informaci��n es el objetivo principal de esta investigaci��n y para lograrlo se han llevado a cabo cuatro estudios: (1) An��lisis de la diversidad a nivel de razas e identificaci��n de ��reas de alta riqueza de razas, alta diversidad morfol��gica y/o alta diversidad ecogeogr��fica en la Sierra de Ecuador, (2) Identificaci��n del perfil y las caracter��sticas de los agricultores que conservan y manejan las variedades tradicionales de ma��z en la Sierra de Ecuador, (3) An��lisis del conocimiento local, manejo y usos de variedades tradicionales de ma��z en la Sierra de Ecuador, y (4) Identificaci��n de ��reas de alta diversidad y bajo riesgo de p��rdida para la conservaci��n en finca de ma��z en la Sierra de Ecuador. Para el primer estudio se visitaron 303 fincas distribuidas a lo largo de la Sierra y se recolectaron 636 muestras que fueron caracterizadas morfol��gicamente mediante 14 variables: 8 relacionadas con la mazorca (forma, longitud y di��metro de la mazorca, color y di��metro de olote y n��mero y disposici��n de hileras) y 7 referidas el grano (n��mero total de granos, color, forma, longitud, anchura y grosor de grano y tipo de endospermo). Adicionalmente, las fincas donde se tomaron las muestras fueron caracterizadas ecogeogr��ficamente mediante 5 variables clim��ticas (temperatura media estacional, rango de temperatura media anual, temperatura m��nima de diciembre, precipitaci��n estacional y precipitaci��n de octubre), 2 geof��sicas (altitud y pendiente) y 5 ed��ficas (textura principal del suelo, profundidad a roca, pH, contenido en materia org��nica y fertilidad). A partir de esta informaci��n y mediante t��cnicas de sistemas de informaci��n geogr��fica (SIG), se generaron mapas de distribuci��n por raza en formato vectorial y un mapa de riqueza de razas, un mapa de diversidad morfol��gica y un mapa de diversidad ecogeogr��fica en formato r��ster con celdas de 10 km x 10 km. Los resultados permitieron constatar que, en los ��ltimos 60 a��os, no se ha perdido ninguna raza. Sin embargo, Canguil, Chaucho y Clavito han dejado de cultivarse en algunas provincias con la consiguiente erosi��n gen��tica del cultivo. La caracterizaci��n morfol��gica detect�� diferencias en el grado de variabilidad intra-raza, siendo Patillo Ecuatoriano, Racimo de Uva y Uchima las razas m��s heterog��neas tanto para los caracteres cualitativos como cuantitativos. A nivel clim��tico y geof��sico, tambi��n se detectaron diferencias en el grado de variaci��n intra-raza; Cuzco Ecuatoriano, Kcello Ecuatoriano y Monta��a Ecuatoriana fueron las razas que en promedio presentaron mayores rangos y coeficientes de variaci��n para estas variables ecogeogr��ficas. En cuanto a las condiciones ed��ficas todas las razas, excepto C��nico Dentado, presentaron una gran heterogeneidad, pudiendo crecer tanto en suelos ricos como pobres, con valores de pH entre ��cido y moderadamente alcalino. La comparaci��n entre razas revel�� diferencias significativas en los rangos ambientales de algunas razas como C��nico Dentado, que tiende a cultivarse a menor altitud y, por tanto, en ambientes menos fr��os y de mayor precipitaci��n que Blanco Blandito, Patillo Ecuatoriano, Sabanero Ecuatoriano, Uchima y Zhima. Para la mayor��a de las razas se encontraron materiales potencialmente adaptados a condiciones de estr��s (precipitaci��n estacional inferior a 500 mm y suelos con pH entre 4.5 y 5.5). Finalmente, los mapas de riqueza, de diversidad morfol��gica y de diversidad ecogeogr��fica mostraron 36 celdas de alta diversidad repartidas en las 10 provincias de la Sierra: 11 celdas en las provincias del norte, 11 en las provincias del centro y 14 en las provincias del sur. Para la caracterizaci��n e identificaci��n de las tipolog��as de los agricultores que cultivan ma��z en la Sierra de Ecuador y el an��lisis de los posibles factores de riesgo de p��rdida de diversidad, se realizaron entrevistas individuales y semiestructuradas a los agricultores due��os de las fincas donde se recolectaron las muestras para el estudio de diversidad (254 en total). Las preguntas que se formularon (11 abiertas y 5 cerradas) estuvieron organizadas en seis bloques: datos del agricultor, caracter��sticas de la finca, diversidad y conocimiento del cultivo, manejo del cultivo, usos y flujo de semillas. Los resultados indicaron que la diversidad de ma��z que hay en la Sierra de Ecuador es manejada mayoritariamente por agricultores mestizos, de entre 30 y 55 a��os, que cultivan una o dos variedades tradicionales para autoconsumo, en parcelas de menos de 0.5 ha y en asocio con fr��jol. El an��lisis de segmentaci��n mediante el algoritmo Chi-square automatic interaction detection (CHAID) permiti�� identificar un peque��o grupo de agricultores ind��genas con parcelas medianas (entre 0.5 ha y 1.5 ha) que conservan un mayor n��mero de variedades tradicionales por finca que el agricultor promedio. Los an��lisis estad��sticos no detectaron diferencias significativas entre etnias (mestizo vs. ind��gena), g��neros (hombre vs. mujer) y grupos de edad (j��venes menores de 30 a��os, adultos entre 30 y 55 a��os y adultos mayores de 55 a��os) en lo que respecta al conocimiento del cultivo (criterios de reconocimiento y razones de preferencia) y manejo (tipo de cultivo), pero s�� detectaron diferencias entre regiones, principalmente en el modo de cultivar el ma��z; mientras que en el norte y sur tienden a sembrarlo en asocio y con un mayor n��mero de especies, en el centro acostumbran a cultivarlo preferentemente solo. En cuanto a los usos, se recopilaron hasta 39 modos diferentes de consumir ma��z, siendo Kcello Ecuatoriano y Zhima las razas para las que se registr�� un mayor n��mero de usos. La comparaci��n del n��mero medio de usos por variedad entre etnias evidenci�� que los agricultores mestizos utilizan sus variedades tradicionales de forma m��s variada que los ind��genas. Entre los factores de riesgo que se analizaron, el bajo porcentaje de j��venes agricultores que se ocupan de las fincas podr��a suponer una amenaza a medio plazo por falta de relevo generacional. Adicionalmente, las numerosas sinonimias y homonimias que se detectaron y el bajo intercambio de semillas tambi��n podr��an ser causa de p��rdida de diversidad, bien por reemplazo o por envejecimiento de la semilla. Finalmente, se concluy�� que las razas Chaucho, Complejo Chillo-Huandango, Complejo Mishca-Huandango, C��nico Dentado, Monta��a Ecuatoriana y Sabanero Ecuatoriano son particularmente vulnerables, no solo por su baja presencia, sino tambi��n por el color de grano que tienen (los mismos que la mayor��a de las razas m��s comunes) y carecer de nombres y usos espec��ficos. Finalmente, para la priorizaci��n de ��reas de conservaci��n en finca para ma��z en la Sierra de Ecuador, se utilizaron 13 criterios de diferente naturaleza: 2 ecogeogr��ficos (precipitaci��n, diversidad ecogeogr��fica), 6 biol��gicos (grado de presencia del cultivo, riqueza de razas, diversidad morfol��gica, presencia de mezclas, presencia de razas locales y riesgo de erosi��n gen��tica), 3 culturales (abundancia de variedades por finca, diversidad de usos y frecuencia de intercambio) y 2 demogr��ficos (tama��o de la poblaci��n y distancia a n��cleos urbanos). Mediante t��cnicas SIG y de evaluaci��n multicriterio, los valores originales de las capas-criterio fueron transformados a una escala de 0 a 100. Posteriormente, las capas-criterio normalizadas fueron sumadas utilizando tres m��todos de ponderaci��n: (1) mismo peso, (2) diferente peso seg��n la puntuaci��n otorgada por 72 expertos, y (3) diferente peso seg��n el m��todo de comparaci��n entre pares de criterios. Los resultados permitieron identificar ocho celdas de 10 km x 10 km con alta puntuaci��n (> 65): tres celdas en el norte (una en cada una de las provincias), una celda en el centro (en la provincia de Cotopaxi), y cuatro celdas en la regi��n sur (dos en Azuay y otras dos en Loja). ABSTRACT In Ecuador, the maize is the most important cultivation in surface and it is a base of the feeding for the rural population who lives in the Andes. In contrast to what it happens on the Coast, in the Sierra region still there are cultivated numerous traditional varieties that are grouped into twenty-four races. Maintaining this diversity is, therefore, of great importance not only for food security, but also as a source of genes for tolerance to abiotic factors could be incorporated into modern varieties. Although part of this diversity was collected in the middle of the last century and is still preserved in various germplasm banks, it is desirable for the in situ conservation also is assured, among other reasons, because in this way the crop can continue to evolve. To be able to implement a conservation plan on farm that contribute to preserving this heritage, it is essential to identify suitable areas where to concentrate resources and know the characteristics and typology of farmer who managed the current diversity. To generate this information is the main target of this investigation and to achieve this, four studies have been carried out: (1) Analysis of the diversity at races and identification of areas of high richness of races, high morphological diversity and / or ecogeographical high diversity in the Sierra of Ecuador, (2) Identification of the profile and characteristics of farmers who conserve and manage traditional varieties of maize in the Sierra of Ecuador, (3) Analysis of local knowledge, management and use of traditional varieties of maize in the Sierra of Ecuador, and (4) Identification of areas of high diversity and low risk of loss for the conservation of maize in the Sierra of Ecuador. For the first study were visited 303 farms distributed along the Sierra and collected 636 samples that were characterized morphologically by 14 variables: 8 related to the ear (shape, length and diameter of the cob, colour, and diameter of cob and number and arrangement of rows) and 7 referred to the grain (total number of grain, colour, shape, length, width, and thickness and type of grain endosperm). In addition, the farms where the samples were taken were characterized ecogeographically through 5 climatic variables (seasonal average temperature, range of average annual temperature, minimum temperature for December, seasonal precipitation and precipitation of October), 2 geophysical (altitude and slope) and edaphic 5 (main texture of the soil, deep rock, pH, content of organic matter and fertility). From this information and techniques of geographic information systems (GIS), maps were generated for distribution by race in vector format and a map of richness of races, a map of morphological diversity and a map of ecogeographical diversity in raster format with cells of 10 km x 10 km. The results allowed observing that, over the past 60 years, it has not lost any race. Nevertheless, Canguil, Chaucho and Clavito have stopped being cultivated in some provinces with the consequent genetic erosion of the cultivation. The morphological characterization detected differences in the degree of variability intra-race, being Patillo Ecuatoriano, Racimo de Uva and Uchima races more heterogeneous both for the qualitative and quantitative characters. At climate and geophysical level, also detected differences in the degree of variation intra-race; Cuzco Ecuatoriano, Kcello Ecuatoriano and Monta��a Ecuatoriana were races that, on average, showed higher ranges and coefficients of variation for these geographical characters. In terms of the edaphic conditions, all races, except C��nico Dentado, showed a great heterogeneity, and can grow both in rich and poor soils, with pH values between acid and moderately alkaline. The comparison between races revealed significant differences in the environmental ranges in some races as C��nico Dentado, which tends to be grown at lower elevations and, therefore, in environments less cold and greater precipitation than Blanco Blandito, Patillo Ecuatoriano, Sabanero Ecuatoriano, Uchima and Zhima. For most of the races were found materials potentially adapted to stress conditions (seasonal precipitation less than 500 mm and soil with a pH between 4.5 and 5.5). Finally, the maps of richness, morphologic diversity and ecogeographical diversity showed 36 cells high diversity distributed in 10 provinces of the Sierra: 11 cells in the northern provinces, 11 in the central provinces and 14 in the southern provinces. For the characterization and identification of the typology of the farmers who cultivate corn in the Sierra of Ecuador and the analysis of the possible factors of risk of loss of diversity, there were realized interviews individual and semistructured to the farmers��� owners of the farms where the samples were gathered for the study of diversity (254 in whole). The questions that were formulated (11 opened ones and 5 closed ones) were organized in six blocks: data of the farmer, characteristics of the farm, diversity and knowledge of the crop, crop management, uses and seed flow. The results indicated that the maize diversity that exist in the Sierra of Ecuador is managed mainly by mestizo farmers, aged between 30 and 55, who cultivate one or two traditional varieties for self-consumption, on plots of less than 0.5 has and in associated with beans. The segmentation analysis algorithm using the Chi-square automatic interaction detection (CHAID technique), allowed to identify a small group of indigenous farmers with medium-sized plots (between 0.5 there is and 1.5 it is) that a major number of traditional varieties preserves for farm that the average farmer. The statistical analysis did not detect significant differences between ethnic groups (mestizos vs. indigenous), genres (man vs. women) and age groups (young people under 30 years of age, adults between 30 and 55 years and adults over 55 years old) in regards to the knowledge of the cultivation (recognition criteria and reasons of preference) and management (type of crop), but if detected differences between regions, mainly on the mode of cultivating the maize; while in the north and south they tend to sow in associate and with a greater number of species, in the center accustomed to cultivate it preferably only. In regards to the uses, they were compiled up to 39 different ways of consuming maize, being Kcello Ecuatoriano and Zhima the races for which a major number of uses registered. The comparison of the average number of uses per variety between ethnic groups showed that the mestizo farmers used their traditional varieties of form more varied than the indigenous people. Between the factors of risk that were analyzed, the low percentage of young farmers who deal with the farms might suppose a medium-term threat for lack of generational relief. In addition, the numerous synonyms and homonyms that were detected and the low seed exchange could also be a cause of loss of diversity, either by replacement or by aging of the seed. Finally, it was concluded that the races Chaucho, Complex Chillo-Huandango, Complex Mishca-Huandango, C��nico Dentado, Monta��a Ecuatoriana and Sabanero Ecuatoriano are particularly vulnerable, not only because of their low presence, but also by the grain color they have (the same as the majority of races more common) and lack of names and specific uses. Finally, for the prioritization of maize conservation areas on farm in the Sierra of Ecuador, used 13 criteria of different nature: 2 ecogeographic (precipitation, diversity ecogeographical), 6 biological (degree of presence of the crop, races richness, morphological diversity, the presence of mixtures, presence of local races and risk of genetic erosion), 3 cultural (abundance of varieties per farm, diversity of uses and frequency of exchange) and 2 demographic (population size and distance to urban centers). Using GIS techniques and multicriteria evaluation, the original values of the layers-criterion were transformed to a scale of 0 to 100. Later, the normalized layers - criteria were added using three weighting methods: (1) the same weight, (2) different weight according to the score given by 72 experts, and (3) different weight according to the method of comparison between pairs of criteria. The results allowed to identify eight 10 km cells x 10 km with high punctuation (> 65): three cells in the north (one in each of the provinces), a cell in the center (in the Cotopaxi province), and four cells in the south region (two in Azuay and other two in Loja).