Análisis molecular de sistemas génicos implicados en la homeostasis de níquel y eficiencia simbiótica en Rhizobium leguminosarum

Los suelos ultramáficos, que poseen elevadas concentraciones de níquel, cobalto y cromo de manera natural, son fuente de bacterias resistentes a altas concentraciones de metales. Se realizó la caracterización físico-química de seis suelos ultramáficos del suroeste europeo, seleccionándose un suelo de la región de Gorro, Italia, como el más adecuado para aislar bacterias endosimbióticas resistentes a metales. A partir de plantas-trampa de guisante y lenteja inoculados con suspensiones de ese suelo, se obtuvieron 58 aislados de Rhizobium leguminosarum bv. viciae (Rlv) que fueron clasificados en 13 grupos según análisis de PCR-RAPDs. Se determinó la resistencia a cationes metálicos [Ni(II), Co(II), Cu(II), Zn(II)] de una cepa representante de cada grupo, así como la secuencia de los genomas de las cepas que mostraron altos niveles (UPM1137 y UPM1280) y bajos niveles (UPM1131 y UPM1136) de tolerancia a metales. Para identificar mecanismos de resistencia a metales se realizó una mutagénesis al azar en dicha cepa mediante la inserción de un minitransposón. El análisis de 4313 transconjugantes permitió identificar 14 mutantes que mostraron una mayor sensibilidad a Ni(II) que la cepa silvestre. Se determinó el punto de inserción del minitransposón en todos ellos y se analizaron en más detalle dos de los mutantes (D2250 y D4239). En uno de los mutantes (D2250), el gen afectado codifica para una proteína que presenta un 44% de identidad con dmeF (divalent efflux protein) de Cupriavidus metallidurans. Cadena arriba de dmeF se identificó un gen que codifica una proteína con un 39% de identidad con el regulador RcnR de Escherichia coli. Se decidió nombrar a este sistema dmeRF, y se generó un mutante en ambos genes en la cepa Rlv SPF25 (Rlv D15). A partir de experimentos de análisis fenotípico y de regulación se pudo demostrar que el sistema dmeRF tiene un papel relevante en la resistencia a Ni(II) y sobre todo a Co(II) en células en vida libre y en simbiosis con plantas de guisante. Ambos genes forman un operón cuya expresión se induce en respuesta a la presencia de Ni(II) y Co(II). Este sistema se encuentra conservado en distintas especies del género Rhizobium como un mecanismo general de resistencia a níquel y cobalto. Otro de los mutantes identificados (D4239), tiene interrumpido un gen que codifica para un regulador transcripcional de la familia AraC. Aunque inicialmente fue identificado por su sensibilidad a níquel, experimentos posteriores demostraron que su elevada sensibilidad a metales era debida a su sensibilidad al medio TY, y más concretamente a la triptona presente en el medio. En otros medios de cultivo el mutante no está afectado específicamente en su tolerancia a metales. Este mutante presenta un fenotipo simbiótico inusual, siendo inefectivo en guisantes y efectivo en lentejas. Análisis de complementación y de mutagénesis dirigida sugieren que el fenotipo de la mutación podría depender de otros factores distintos del gen portador de la inserción del minitransposón. ABSTRACT Ultramafic soils, having naturally high concentrations of nickel, cobalt and chrome, are potential sources of highly metal-resistant bacteria. A physico-chemical characterization of six ultramafic soils from the European southwest was made. A soil from Gorro, Italy, was chosen as the most appropriated for the isolation of heavy-metal-resistant endosymbiotic bacteria. From pea and lentil trap plants inoculated with soil suspensions, 58 isolates of Rhizobium leguminosarum bv. viciae (Rlv) were obtained and classified into 13 groups based on PCR-RAPDs analysis. The resistance to metallic cations [Ni(II), Co(II), Cu(II), Zn(II)] was analyzed in a representative strain of each group. From the results obtained in the resistance assays, the Rlv UPM1137 strain was selected to identify metal resistance mechanism. A random mutagenesis was made in UPM1137 by using minitransposon insertion. Analysis of 4313 transconjugants allowed to identify 14 mutants with higher sensitivity to Ni(II) than the wild type strain. The insertion point of the minitransposon was determined in all of them, and two mutants (D2250 and D4239) were studied in more detail. In one of the mutants (D2250), the affected gene encodes a protein with 44% identity in compared with DmeF (divalent efflux protein) from Cupriavidus metallidurans. Upstream R. leguminosarum dmeF, a gene encoding a protein with 39% identity with RcnR regulator from E. coli was identified. This protein was named DmeR. A mutant with both genes in the dmeRF deleted was generated and characterized in Rlv SPF25 (Rlv D15). From phenotypic and regulation analysis it was concluded that the dmeRF system is relevant for Ni(II) and specially Co(II) tolerance in both free living and symbiotic forms of the bacteria. This system is conserved in different Rhizobium species like a general mechanism for nickel and cobalt resistance. Other of the identified mutants (D4239) contains the transposon insert on a gene that encodes for an AraC-like transcriptional regulator. Although initially this mutant was identified for its nickel sensitivity, futher experiments demonstrated that its high metal sensitivity is due to its sensitivity to the TY medium, specifically for the tryptone. In other media the mutant is not affected specifically in their tolerance to metals. This mutant showed an unusual symbiotic phenotype, being ineffective in pea and effective in lentil. Complementation analysis and directed mutagenesis suggest that the mutation phenotype could depend of other factors different from the insertion minitransposon gene.

Binary metal oxides for composite ultrafiltration membranes

A new ultrafiltration membrane was developed by the incorporation of binary metal oxides inside polyethersulfone. Physico-chemical characterization of the binary metal oxides demonstrated that the presence of Ti in the TiO2?ZrO2 system results in an increase of the size of the oxides, and also their dispersity. The crystalline phases of the synthesized binary metal oxides were identified as srilankite and zirconium titanium oxide. The effect of the addition of ZrO2 can be expressed in terms of the inhibition of crystal growth of anocrystalline TiO2 during the synthesis process. For photocatalytic applications the band gap of the synthesized semiconductors was determined, confirming a gradual increase (blue shift) in the band gap as the amount of Zr loading increases. Distinct distributions of binary metal oxides were found along the permeation axis for the synthesized membranes. Particles with Ti are more uniformly dispersed throughout the membrane cross-section. The physico-chemical characterization of membranes showed a strong correlation between some key membrane properties and the spatial particle distribution in the membrane structure. The proximity of metal oxide fillers to the membrane surface determines the hydrophilicity and porosity of modified membranes. Membranes incorporating binary metal oxides were found to be promising candidates for wastewater treatment by ultrafiltration, considering the observed improvement influx and anti-fouling properties of doped membranes. Multi-run fouling tests of doped membranes confirmed the stability of permeation through membranes embedded with binary TiO2?ZrO2 particles.

XPS as Characterization Tool for PV: From the Substrate to Complete III-V Multijunction Solar Cells

This contribution aims to illustrate the potential of the X-ray photoelectron spectroscopy (XPS) technique as a tool to analyze different parts of a solar cell (surface state, heterointerfaces, profile composition of ohmic contacts, etc). Here, the analysis is specifically applied to III-V multijunction solar cells used in concentrator systems. The information provided from such XPS analysis has helped to understand the physico-chemical nature of these surfaces and interfaces, and thus has guided the technological process in order to improve the solar cell performance.

Afectación de los agrosistemas de la zona del Caño San Miguel por la salinización de los suelos

La degradación por salinización de los suelos regados con aguas salobres viene aumentando a escala mundial. El problema de la concentración de sales más solubles que el yeso depende principalmente del agua de riego, la aridez climática y la ausencia de drenaje. Estas condiciones se dan en el aluvium del río Limón, que es un tributario del lago Maracaibo, sito en el estado de Zulia de Venezuela. La regulación del río Limón mediante el cierre de los embalses de Manuelote y Tulé ha disminuido los aportes de aguas y sedimentos de las avenidas de inundación, que tienen carácter diluyente. Por otro lado, el balance de sales solubles en el suelo ha registrado una acumulación neta en los años de extrema aridez anteriores al año 2006, dado que la mayor dilución de las aguas ombrogénicas embalsadas procedentes de las lluvias no ha sido suficiente para compensar la concentración por evapotranspiración “in situ” de las aguas retenidas en la cuenca baja, sobre todo en ausencia de desagüe superficial y drenaje profundo. Las inundaciones posteriores a 2006 fueron suficientes para disminuir la salinidad superficial hasta los valores encontrados en 2010. El estudio experimental de esta problemática en el sector del caño San Miguel ha sido abordado mediante el establecimiento del perfil de salinidad acoplado con el perfil hipotético de humedad usado en la taxonomía de suelos. Este perfil define la disponibilidad del agua del suelo para la vegetación en función de tres potenciales: 1) el potencial físico-químico o matricial, que depende de la energía de adsorción a la superficie de las partículas; 2) el potencial gravitatorio, que depende de la profundidad; y 3) el potencial osmótico, que depende de la concentración de la solución del suelo; lo que supone un avance respecto a tener en cuenta sólo el perfil de humedad, que solamente considera el potencial gravi-químico integrado por el matricial y el gravitatorio. El perfil normalizado de 200 mm de de agua útil, retenida entre 33 y 1500 kPa de succión, incluye ocho fases gravi-químicas de 25 mm. La presente investigación incluye el potencial osmótico estimado por la conductividad eléctrica del extracto de pasta saturada. Los experimentos de lavado de sales en columnas de suelo, simulando la distribución de las lluvias en cinco años representativos de los cuartiles estadísticos de la serie disponible de 38 años completos, han determinado el comportamiento de las sales solubles en un suelo sometido a drenaje. Los resultados han evidenciado que el balance de sales unido al balance de agua controla la degradación de los agrosistemas por salinización. La alternativa frutícola puede ser aumentada en estas condiciones, porque el balance de sales favorece el establecimiento de cultivos permanentes a costa de otros usos del suelo de menor interés económico, como el cultivo de forrajes en regadío y el aprovechamiento de los pastizales en secano durante el barbecho de desalinización, cuya caracterización se ha completado con el estudio de la vegetación indicadora del grado de salinidad. ABSTRACT Saline degradation of soils irrigated with brackish water is increasing worldwide. The problem of salts concentration more soluble than gypsum depends on irrigation water quality, climatic aridity, and drainage limitations. These conditions meet in Limón River alluvium, which is tributary to Maracaibo´s Lake in Zulia State, Venezuela. Limón River regulation by closing Manuelote and Tulé reservoirs has diminished the input of water and sediments from inundations, which exerted dilutive effects. On the other hand, the soil balance of soluble salts has registered a net accumulation during those extremely dry years before 2006 because the greater dilution of ombrogenic dammed water coming from rain has not been enough to compensate salt concentration by “in situ” evapotranspiration in middle basin water, mainly in the absence of superficial runoff and deep drainage. Floods after 2006 were enough to reduce the high superficial salinity figures to those addressed in 2010. The experimental study of this trouble in San Miguel´s pipe area has been addressed through of the establishment of its salinity profile together to the hypothetic moisture profile typically used in soil taxonomy. This salinity profile describes soil water availability for vegetation according to three potentials: 1) physico-chemical or matrix potential, which depends on the adsorption energy of the soil solution to the surface of soil particles; 2) gravitational potential, which depends on soil depth; and 3) osmotic potential, which depends on the concentration of the soil solution. This represents an advance from just using moisture regime, which only considers the matrix and gravitational components of a gravi-chemical potential. The standardized moisture profile of 200 mm useful water being retained between 33 and 1500 kPa includes eight gravi-chemical stages of 25 mm. This research also includes the osmotic component, which is estimated by the electric conductivity of the saturated paste extract. Salts leaching trials in soil columns simulating rain distribution along five model years, representing the statistical quartiles of the available series of 38 complete years, have determined the behaviour of soluble salts in a soil being subjected to drainage. Results have evidenced that salt and water balances considered together are able to control the agrosystem’s degradation by salinization. The fruit production alternative could be improved under these conditions because the salts balance favours the establishment of permanent crops to the detriment of other soil uses of lower economical interest such as irrigated forage and non-irrigated pasture during desalinization fallow, which characterization has been completed through assessing the presence of salinity-indicator vegetation.

MRI and Bidimensional relaxometry sequences for macro and microstructure assessment in food models.

Physico-chemical and organoleptic characteristics of food depend largely on the microscopic level distribution of gases and water, and connectivity and mobility through the pores. Microstructural characterization of food can be accomplished by Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Spectroscopy (NMR) combined with the application of methods of dissemination and multidimensional relaxometry. In this work, funded by the EC Project InsideFood, several artificial food models, based on foams and gels were studied using MRI and 2D relaxometry. Two different kinds of foams were used: a sugarless and a sugar foam. Then, a half of a syringe was filled with the sugarless foam and the other half with the sugar foam. Then, MRI and NMR experiments were performed and the sample evolution was observed along 3 days in order to quantify macrostructural changes through proton density images and microstructural ones using T1T2 maps, using an inversion CPMG sequence. On the proton density images it may be seen that after 16 hours it was possible to differentiate the macrostructural changes, as the apparition of free water due to a syneresis phenomenon. On the interface it can be seen a brighter area after 16 hours, due to the occurrence of free water. Moreover, thanks to the bidimensional relaxometry (T1-T2) it was possible to differentiate among microscopic changes. Differences between the pores size can be observed as well as the microstructure evolution after 30.5 hours, as a consequence differences are shown on free water redistribution through larger pores and capillarity phenomena between both foams.

Comportamiento frente a la durabilidad de morteros de reparación de cemento modificados con polímeros

El auge que ha surgido en los últimos años por la reparación de edificios y estructuras construidas con hormigón ha llevado al desarrollo de morteros de reparación cada vez más tecnológicos. En el desarrollo de estos morteros por parte de los fabricantes, surge la disyuntiva en el uso de los polímeros en sus formulaciones, por no encontrarse justificado en ocasiones el trinomio prestaciones/precio/aplicación. En esta tesis se ha realizado un estudio exhaustivo para la justificación de la utilización de estos morteros como morteros de reparación estructural como respuesta a la demanda actual disponiéndolo en tres partes: En la primera parte se realizó un estudio del arte de los morteros y sus constituyentes. El uso de los morteros se remonta a la antigüedad, utilizándose como componentes yeso y cal fundamentalmente. Los griegos y romanos desarrollaron el concepto de morteros de cal, introduciendo componentes como las puzolanas, cales hidraúlicas y áridos de polvo de mármol dando origen a morteros muy parecidos a los hormigones actuales. En la edad media y renacimiento se perdió la tecnología desarrollada por los romanos debido al extenso uso de la piedra en las construcciones civiles, defensivas y religiosas. Hubo que esperar hasta el siglo XIX para que J. Aspdin descubriese el actual cemento como el principal compuesto hidraúlico. Por último y ya en el siglo XX con la aparición de moléculas tales como estireno, melanina, cloruro de vinilo y poliésteres se comenzó a desarrollar la industria de los polímeros que se añadieron a los morteros dando lugar a los “composites”. El uso de polímeros en matrices cementantes dotan al mortero de propiedades tales como: adherencia, flexibilidad y trabajabilidad, como ya se tiene constancia desde los años 30 con el uso de caucho naturales. En la actualidad el uso de polímeros de síntesis (polivinialacetato, estireno-butadieno, viniacrílico y resinas epoxi) hacen que principalmente el mortero tenga mayor resistencia al ataque del agua y por lo tanto aumente su durabilidad ya que se minimizan todas las reacciones de deterioro (hielo, humedad, ataque biológico,…). En el presente estudio el polímero que se utilizó fue en estado polvo: polímero redispersable. Estos polímeros están encapsulados y cuando se ponen en contacto con el agua se liberan de la cápsula formando de nuevo el gel. En los morteros de reparación el único compuesto hidraúlico que hay es el cemento y es el principal constituyente hoy en día de los materiales de construcción. El cemento se obtiene por molienda conjunta de Clínker y yeso. El Clínker se obtiene por cocción de una mezcla de arcillas y calizas hasta una temperatura de 1450-1500º C por reacción en estado fundente. Para esta reacción se deben premachacar y homogeneizar las materias primas extraídas de la cantera. Son dosificadas en el horno con unas proporciones tales que cumplan con unas relación de óxidos tales que permitan formar las fases anhidras del Clínker C3S, C2S, C3A y C4AF. De la hidratación de las fases se obtiene el gel CSH que es el que proporciona al cemento de sus propiedades. Existe una norma (UNE-EN 197-1) que establece la composición, especificaciones y tipos de cementos que se fabrican en España. La tendencia actual en la fabricación del cemento pasa por el uso de cementos con mayores contenidos de adiciones (cal, puzolana, cenizas volantes, humo de sílice,…) con el objeto de obtener cementos más sostenibles. Otros componentes que influyen en las características de los morteros son: - Áridos. En el desarrollo de los morteros se suelen usar naturales, bien calizos o silícicos. Hacen la función de relleno y de cohesionantes de la matriz cementante. Deben ser inertes - Aditivos. Son aquellos componentes del mortero que son dosificados en una proporción menor al 5%. Los más usados son los superplastificantes por su acción de reductores de agua que revierte en una mayor durabilidad del mortero. Una vez analizada la composición de los morteros, la mejora tecnológica de los mismos está orientada al aumento de la durabilidad de su vida en obra. La durabilidad se define como la capacidad que éste tiene de resistir a la acción del ambiente, ataques químicos, físicos, biológicos o cualquier proceso que tienda a su destrucción. Estos procesos dependen de factores tales como la porosidad del hormigón y de la exposición al ambiente. En cuanto a la porosidad hay que tener en cuenta la distribución de macroporos, mesoporos y microporos de la estructura del hormigón, ya que no todos son susceptibles de que se produzca el transporte de agentes deteriorantes, provocando tensiones internas en las paredes de los mismos y destruyendo la matriz cementante Por otro lado los procesos de deterioro están relacionados con la acción del agua bien como agente directo o como vehículo de transporte del agente deteriorante. Un ambiente que resulta muy agresivo para los hormigones es el marino. En este caso los procesos de deterioro están relacionados con la presencia de cloruros y de sulfatos tanto en el agua de mar como en la atmosfera que en combinación con el CO2 y O2 forman la sal de Friedel. El deterioro de las estructuras en ambientes marinos se produce por la debilitación de la matriz cementante y posterior corrosión de las armaduras que provocan un aumento de volumen en el interior y rotura de la matriz cementante por tensiones capilares. Otras reacciones que pueden producir estos efectos son árido-álcali y difusión de iones cloruro. La durabilidad de un hormigón también depende del tipo de cemento y su composición química (cementos con altos contenidos de adición son más resistentes), relación agua/cemento y contenido de cemento. La Norma UNE-EN 1504 que consta de 10 partes, define los productos para la protección y reparación de estructuras de hormigón, el control de calidad de los productos, propiedades físico-químicas y durables que deben cumplir. En esta Norma se referencian otras 65 normas que ofrecen los métodos de ensayo para la evaluación de los sistemas de reparación. En la segunda parte de esta Tesis se hizo un diseño de experimentos con diferentes morteros poliméricos (con concentraciones de polímero entre 0 y 25%), tomando como referencia un mortero control sin polímero, y se estudiaron sus propiedades físico-químicas, mecánicas y durables. Para mortero con baja proporción de polímero se recurre a sistemas monocomponentes y para concentraciones altas bicomponentes en la que el polímero está en dispersión acuosa. Las propiedades mecánicas medidas fueron: resistencia a compresión, resistencia a flexión, módulo de elasticidad, adherencia por tracción directa y expansión-retracción, todas ellas bajo normas UNE. Como ensayos de caracterización de la durabilidad: absorción capilar, resistencia a carbonatación y adherencia a tracción después de ciclos hielo-deshielo. El objeto de este estudio es seleccionar el mortero con mejor resultado general para posteriormente hacer una comparativa entre un mortero con polímero (cantidad optimizada) y un mortero sin polímero. Para seleccionar esa cantidad óptima de polímero a usar se han tenido en cuenta los siguientes criterios: el mortero debe tener una clasificación R4 en cuanto a prestaciones mecánicas al igual que para evaluar sus propiedades durables frente a los ciclos realizados, siempre teniendo en cuenta que la adición de polímero no puede ser elevada para hacer el mortero competitivo. De este estudio se obtuvieron las siguientes conclusiones generales: - Un mortero normalizado no cumple con propiedades para ser clasificado como R3 o R4. - Sin necesidad de polímero se puede obtener un mortero que cumpliría con R4 para gran parte de las características medidas - Es necesario usar relaciones a:c< 0.5 para conseguir morteros R4, - La adición de polímero mejora siempre la adherencia, abrasión, absorción capilar y resistencia a carbonatación - Las diferentes proporciones de polímero usadas siempre suponen una mejora tecnológica en propiedades mecánicas y de durabilidad. - El polímero no influye sobre la expansión y retracción del mortero. - La adherencia se mejora notablemente con el uso del polímero. - La presencia de polímero en los morteros mejoran las propiedades relacionadas con la acción del agua, por aumento del poder cementante y por lo tanto de la cohesión. El poder cementante disminuye la porosidad. Como consecuencia final de este estudio se determinó que la cantidad óptima de polímero para la segunda parte del estudio es 2.0-3.5%. La tercera parte consistió en el estudio comparativo de dos morteros: uno sin polímero (mortero A) y otro con la cantidad optimizada de polímero, concluida en la parte anterior (mortero B). Una vez definido el porcentaje de polímeros que mejor se adapta a los resultados, se plantea un nuevo esqueleto granular mejorado, tomando una nueva dosificación de tamaños de áridos, tanto para el mortero de referencia, como para el mortero con polímeros, y se procede a realizar los ensayos para su caracterización física, microestructural y de durabilidad, realizándose, además de los ensayos de la parte 1, mediciones de las propiedades microestructurales que se estudiaron a través de las técnicas de porosimetría de mercurio y microscopia electrónica de barrido (SEM); así como propiedades del mortero en estado fresco (consistencia, contenido de aire ocluido y tiempo final de fraguado). El uso del polímero frente a la no incorporación en la formulación del mortero, proporcionó al mismo de las siguientes ventajas: - Respecto a sus propiedades en estado fresco: El mortero B presentó mayor consistencia y menor cantidad de aire ocluido lo cual hace un mortero más trabajable y más dúctil al igual que más resistente porque al endurecer dejará menos huecos en su estructura interna y aumentará su durabilidad. Al tener también mayor tiempo de fraguado, pero no excesivo permite que la manejabilidad para puesta en obra sea mayor, - Respecto a sus propiedades mecánicas: Destacar la mejora en la adherencia. Es una de las principales propiedades que confiere el polímero a los morteros. Esta mayor adherencia revierte en una mejora de la adherencia al soporte, minimización de las posibles reacciones en la interfase hormigón-mortero y por lo tanto un aumento en la durabilidad de la reparación ejecutada con el mortero y por consecuencia del hormigón. - Respecto a propiedades microestructurales: la porosidad del mortero con polímero es menor y menor tamaño de poro critico susceptible de ser atacado por agentes externos causantes de deterioro. De los datos obtenidos por SEM no se observaron grandes diferencias - En cuanto a abrasión y absorción capilar el mortero B presentó mejor comportamiento como consecuencia de su menor porosidad y su estructura microscópica. - Por último el comportamiento frente al ataque de sulfatos y agua de mar, así como al frente de carbonatación, fue más resistente en el mortero con polímero por su menor permeabilidad y su menor porosidad. Para completar el estudio de esta tesis, y debido a la gran importancia que están tomando en la actualidad factores como la sostenibilidad se ha realizado un análisis de ciclo de vida de los dos morteros objeto de estudio de la segunda parte experimental.In recent years, the extended use of repair materials for buildings and structures made the development of repair mortars more and more technical. In the development of these mortars by producers, the use of polymers in the formulations is a key point, because sometimes this use is not justified when looking to the performance/price/application as a whole. This thesis is an exhaustive study to justify the use of these mortars as a response to the current growing demand for structural repair. The thesis is classified in three parts:The first part is the study of the state of the art of mortars and their constituents.In ancient times, widely used mortars were based on lime and gypsum. The Greeks and Romans developed the concept of lime mortars, introducing components such as pozzolans, hydraulic limes and marble dust as aggregates, giving very similar concrete mortars to the ones used currently. In the middle Age and Renaissance, the technology developed by the Romans was lost, due to the extensive use of stone in the civil, religious and defensive constructions. It was not until the 19th century, when J. Aspdin discovered the current cement as the main hydraulic compound. Finally in the 20th century, with the appearance of molecules such as styrene, melanin, vinyl chloride and polyester, the industry began to develop polymers which were added to the binder to form special "composites".The use of polymers in cementitious matrixes give properties to the mortar such as adhesion, Currently, the result of the polymer synthesis (polivynilacetate, styrene-butadiene, vynilacrylic and epoxy resins) is that mortars have increased resistance to water attack and therefore, they increase their durability since all reactions of deterioration are minimised (ice, humidity, biological attack,...). In the present study the polymer used was redispersible polymer powder. These polymers are encapsulated and when in contact with water, they are released from the capsule forming a gel.In the repair mortars, the only hydraulic compound is the cement and nowadays, this is the main constituent of building materials. The current trend is centered in the use of higher contents of additions (lime, pozzolana, fly ash, silica, silica fume...) in order to obtain more sustainable cements. Once the composition of mortars is analyzed, the technological improvement is centred in increasing the durability of the working life. Durability is defined as the ability to resist the action of the environment, chemical, physical, and biological attacks or any process that tends to its destruction. These processes depend on factors such as the concrete porosity and the environmental exposure. In terms of porosity, it be considered, the distribution of Macropores and mesopores and pores of the concrete structure, since not all of them are capable of causing the transportation of damaging agents, causing internal stresses on the same walls and destroying the cementing matrix.In general, deterioration processes are related to the action of water, either as direct agent or as a transport vehicle. Concrete durability also depends on the type of cement and its chemical composition (cement with high addition amounts are more resistant), water/cement ratio and cement content. The standard UNE-EN 1504 consists of 10 parts and defines the products for the protection and repair of concrete, the quality control of products, physical-chemical properties and durability. Other 65 standards that provide the test methods for the evaluation of repair systems are referenced in this standard. In the second part of this thesis there is a design of experiments with different polymer mortars (with concentrations of polymer between 0 and 25%), taking a control mortar without polymer as a reference and its physico-chemical, mechanical and durable properties were studied. For mortars with low proportion of polymer, 1 component systems are used (powder polymer) and for high polymer concentrations, water dispersion polymers are used. The mechanical properties measured were: compressive strength, flexural strength, modulus of elasticity, adhesion by direct traction and expansion-shrinkage, all of them under standards UNE. As a characterization of the durability, following tests are carried out: capillary absorption, resistance to carbonation and pull out adhesion after freeze-thaw cycles. The target of this study is to select the best mortar to make a comparison between mortars with polymer (optimized amount) and mortars without polymer. To select the optimum amount of polymer the following criteria have been considered: the mortar must have a classification R4 in terms of mechanical performance as well as in durability properties against the performed cycles, always bearing in mind that the addition of polymer cannot be too high to make the mortar competitive in price. The following general conclusions were obtained from this study: - A standard mortar does not fulfill the properties to be classified as R3 or R4 - Without polymer, a mortar may fulfill R4 for most of the measured characteristics. - It is necessary to use relations w/c ratio < 0.5 to get R4 mortars - The addition of polymer always improves adhesion, abrasion, capillary absorption and carbonation resistance - The different proportions of polymer used always improve the mechanical properties and durability. - The polymer has no influence on the expansion and shrinkage of the mortar - Adhesion is improved significantly with the use of polymer. - The presence of polymer in mortars improves the properties related to the action of the water, by the increase of the cement power and therefore the cohesion. The cementitious properties decrease the porosity. As final result of this study, it was determined that the optimum amount of polymer for the second part of the study is 2.0 - 3.5%. The third part is the comparative study between two mortars: one without polymer (A mortar) and another with the optimized amount of polymer, completed in the previous part (mortar B). Once the percentage of polymer is defined, a new granular skeleton is defined, with a new dosing of aggregate sizes, for both the reference mortar, the mortar with polymers, and the tests for physical, microstructural characterization and durability, are performed, as well as trials of part 1, measurements of the microstructural properties that were studied by scanning electron microscopy (SEM) and mercury porosimetry techniques; as well as properties of the mortar in fresh State (consistency, content of entrained air and final setting time). The use of polymer versus non polymer mortar, provided the following advantages: - In fresh state: mortar with polymer presented higher consistency and least amount of entrained air, which makes a mortar more workable and more ductile as well as more resistant because hardening will leave fewer gaps in its internal structure and increase its durability. Also allow it allows a better workability because of the longer (not excessive) setting time. - Regarding the mechanical properties: improvement in adhesion. It is one of the main properties which give the polymer to mortars. This higher adhesion results in an improvement of adhesion to the substrate, minimization of possible reactions at the concrete-mortar interface and therefore an increase in the durability of the repair carried out with mortar and concrete. - Respect to microstructural properties: the porosity of mortar with polymer is less and with smaller pore size, critical to be attacked by external agents causing deterioration. No major differences were observed from the data obtained by SEM - In terms of abrasion and capillary absorption, polymer mortar presented better performance as a result of its lower porosity and its microscopic structure. - Finally behavior against attack by sulfates and seawater, as well as to carbonation, was better in the mortar with polymer because of its lower permeability and its lower porosity. To complete the study, due to the great importance of sustainability for future market facts, the life cycle of the two mortars studied was analysed.

Guidelines of natural zeolites characterization for acid mine drainage treatment. Case study Guayaquil, Ecuador

Zeolites constitute one of the less common groups of tectosilicates. Zeoli1es with pores between -2 to 10 A in their structures have strong sorption capacity and are widely used in industrial and municipal operations to eliminate toxic substances. One of the major environmental problems in the mining activity is the treating of acid mine drainage. In this context, it is very important to search alternatives to manage this challenge. One feasible alternative is using zeolitic tuffs. The results of the physical-chemical characterization of zeolitic tuffs are the c1ue lo continue or not with deeper analysis and tests 01 acid mine drainage treatments. The guidelines to reach this purpose are the main goal of this work. Zeolite 1uff samples (named as XB_01 and XB_02) studied in this work were laken rn the Late Cretaceous Coastal Cayo Arch Ecuador, specifically in the Guaraguao River, showing the most important characteristics of heulandite zeolitic tuffs. X-ray powder diffraction (XRD) tests were developed in order to confirm that the samples belong to the heulandite-type zeoli1ic tuffs. Additionally, Thermogravimetric analysis (TG), Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and X-ray fluorescence (XRF) of the samples was necessary in order to define the Si/Al ratio and the main mineralogical phases. The XB_01 sample shows a higher ratio Si/Al than XB_02 sample. The cation exchange capacity est was the fundamental step to define the potentiality of the zeolite to use in acid mine drainage treatment Three methodologies were employed to determine the cation exchange capacity. The Cuban standard 626 and the ammonium exchange methodologies reflect results more consistent with each other. This is the starting point to continue with deeper studies such as breakthrough curves for heavy metal ions found in acid mine waters.

ARXPS analysis of a GaAs/GaInP heterointerface with application in III-V multijunction solar cells

In this contribution, angle-resolved X-ray photoelectron spectroscopy is used to explore the extension and nature of a GaAs/GaInP heterointerface. This bilayer structure constitutes a very common interface in a multilayered III-V solar cell. Our results show a wide indium penetration into the GaAs layer, while phosphorous diffusion is much less important. The physico-chemical nature of such interface and its depth could deleteriously impact the solar cell performance. Our results probe the formation of spurious phases which may profoundly affect the interface behavior.

Long wave theory for experimental devices with compressed/expanded surfactant monolayers

Surfactant monolayers are of interest in a variety of phenomena, including thin film dynamics and the formation and dynamics of foams. Measurement of surface properties has received a continuous attention and requires good theoretical models to extract the relevant physico- chemical information from experimental data. A common experimental set up consists in a shallow liquid layer whose free surface is slowly com- pressed/expanded in periodic fashion by moving two slightly immersed solid barriers, which varies the free surface area and thus the surfactant concentration. The simplest theory ignores the fluid dynamics in the bulk fluid, assuming spatially uniform surfactant concentration, which requires quite small forcing frequencies and provides reversible dynamics in the compression/expansion cycles. Sometimes, it is not clear whether depar- ture from reversibility is due to non-equilibrium effects or to the ignored fluid dynamics. Here we present a long wave theory that takes the fluid dynamics and the symmetries of the problem into account. In particular, the validity of the spatially-uniform-surfactant-concentration assumption is established and a nonlinear diffusion equation is derived. This allows for calculating spatially nonuniform monolayer dynamics and uncovering the physical mechanisms involved in the surfactant behavior. Also, this analysis can be considered a good means for extracting more relevant information from each experimental run.

1H HR MAS NMR metabolomic and non-destructive 2D NMR relaxometry to assess internal quality in apples.

NMR can be considered a multi-scale multidimensional technology in the sense that it provides both spatial insight at macroscopic (MRI) or microscopic level (relaxometry), together with chemical characterization (HR-MAS). In this study 296 apples (from 4 cultivars) were MRI screened (20 slices per fruit) among which 7 fruits were used for metabolomic study by 1H HR MAS in order to assess various chemical shifts: malic acid, sucrose, glucose, fructose and ethanol. On the first season, tissue samples were taken from the sound and affected apples (near the core, centre and outer part of the mesocarp) belonging to sound and affected locations, while on the second season, tissue samples were focused on the comparison between sound and affected tissue. Beside, MRI and 2D non-destructive relaxometry (on whole fruits, and localized tissue) where performed on 72 and 12 apples respectively in order to compare features at macroscopic (tissue) and microscopic (subcellular) level. HR MAS shows higher content of ?-glucose, ?-glucose, malic acid and aromatic compounds in watercore affected tissues from both seasons, while sound tissue reflects higher sucrose. Microscopic (subcellular) degradation of tissue varies according to disorder development and is in good accordance with macroscopic characterization with MRI.

Capacidad y comportamiento de la adsorción de fenol en caolines naturales y modificados

En la actualidad las industrias químicas, farmacéuticas y clínicas, originan contaminantes en aguas superficiales, aguas subterráneas y suelos de nuestro país, como es el caso del fenol, contaminante orgánico común y altamente dañino para los organismos, incluso a bajas concentraciones. Existen en el mercado diferentes metodologías para minimizar la contaminación pero muchos de estos procesos tienen un alto coste, generación de contaminantes, etc. La adsorción de contaminantes por medio de arcillas es un método ampliamente utilizado, encontrándose eficaz y económico. Pero la dificultad de adsorber un contaminante orgánico como el fenol motiva la creación de un material llamado organoarcillas. Las organoarcillas son arcillas modificadas con un surfactante, a su vez, los surfactantes son moléculas orgánicas que confieren a la superficie de la arcilla carga catiónica en lugar de aniónica, haciendo más fácil la adsorción de fenol. Para esta tesis se ha elegido el caolín como material adsorbente, fácilmente disponible y relativamente de bajo coste. Se ha trabajado con: arenas de caolín, material directo de la extracción, y caolín lavado, originado del proceso de lavado de las arenas de caolín. Ambos grupos se diferencian fundamentalmente por su contenido en cuarzo, ampliamente mayor en las arenas de caolín. Con el objetivo de desarrollar un material a partir del caolín y arenas de éste con capacidad de retención de contaminates, en concreto, fenol, se procedió a modificar los materiales de partida mediante tratamientos térmicos, mecánicos y/o químicos, dando lugar a compuestos con mayor superficie química reactiva. Para ello se sometió el caolín y las arenas caoliníferas a temperaturas de 750ºC durante 3h, a moliendas hasta alcanzar su amorfización, y/o a activaciones con HCl 6M o con NaOH 5M durante 3h a 90ºC. En total se obtuvieron 18 muestras, en las que se estudiaron las características físico-químicas, mineralógicas y morfológicas de cada una de ellas con el fin de caracterizarlas después de haber sufrido los tratamientos y/o activaciones químicas. Los cambios producidos fueron estudiados mediante pH, capacidad de intercambio catiónico (CEC), capacidad de adsorción de agua (WCU y CWC), distribución de tamaño de partícula (PSD), área de superficie específica (SBET), difracción de rayos X (XRD), espectroscopía infrarroja por transformada de Fourier (FTIR), métodos térmicos (TG, DTG y DTA), y microscopía electrónica de transmisión y barrido (SEM y TEM). Además se analizó los cambios producidos por los tratamientos en función de las pérdidas de Al y Si que acontece en las 18 muestras. Los resultados para los materiales derivados de la arenas caoliníferas fueron similares a los obtenidos para los caolines lavados, la diferencia radica en la cantidad de contenido de caolinita en los diferente grupos de muestras. Apoyándonos en las técnicas de caracterización se puede observar que los tratamientos térmico y molienda produce materiales amorfos, este cambio en la estructura inicial sumado a las activaciones ácida y alcalina dan lugar a pérdidas de Si y Al, ocasionando que sus propiedades físico-químicas, mineralógicas y morfológicas se vean alteradas. Un fuerte aumento es observado en las áreas superficiales y en la CEC en determinadas muestras, además entre los cambios producidos se encuentra la producción de diferentes zeolitas en porcentajes distintos con el tratamiento alcalino. Para la obtención de las organoarcillas, las 18 muestras se sometieron a la surfactación con hexadeciltrimetil amonio (HDTMA) 20 mM durante 24h a 60ºC, esta concentración de tensioactivo fue más alta que la CEC de cada muestra. Los camext bios anteriormente producidos por los tratamientos y activaciones, afectan de forma diferente en la adsorción de HDTMA, variando por tanto la adsorción del surfactante en la superficie de las muestras. Se determinó el tensioactivo en superficie por FTIR, además se realizó un análisis de componentes principales (PCA) para examinar la dependencia entre las relaciones Si/Al de las muestras en la capacidad de adsorción de tensioactivo, y para el estudio de la adsorción de HDTMA en las muestras se realizaron además del análisis termogravimétrico, aproximaciones con los modelos de Freundllich y Langmuir. Se persigue conocer las diferentes formas y maneras que tiene el tensioactivo de fijarse en la superficie de las muestras. En las organoarcillas resultantes se cuantificó el fenol adsorbido cuando éstas fueron puestas en contacto con diferentes concentraciones de fenol: 50, 500, 1000, 2000, y 2500 mg/l durante 24h. El contaminante sorbido se calculó por medio de cromatografía de gases, y se realizaron aproximaciones con los modelos de Freundllich y Langmuir. El comportamiento de adsorción de fenol en arcillas orgánicas es regido por las características de las muestras. De forma general se puede decir que las muestras de caolines lavados tienen más capacidad de adsorción de fenol que las muestras de arenas de caolín y que la activación alcalina ha proporcionado una mejora en la adsorción de fenol en los dos grupos. En consecuencia se han obtenido materiales adsorbentes heterogéneos y por tanto, con propiedades diferentes. Se ha evaluado el comportamiento global de las arenas de caolín por un lado y del caolín lavado por otro. Las arenas de caolín presentan altos niveles de cuarzo y su uso para ciertos tipos de industrias no son recomendados en ocasiones por el alto costo que el proceso de limpieza y purificación implicaría. Por ello es importante reseñar en este proyecto las aplicaciones que ofrecen algunas muestras de este grupo. Los ensayos acontecidos en esta tesis han dado lugar a las siguientes publicaciones: • Pérdida de Al y Si en caolines modificados térmica- o mecánicamente y activados por tratamientos químicos. A. G. San Cristóbal, C Vizcayno, R. Castelló. Macla 9, 113-114. (2008). • Acid activation of mechanically and thermally modfied kaolins. A. G. San Cristóbal, R. Castelló, M. A. Martín Luengo, C Vizcayno. Mater. Res. Bull. 44 (2009) 2103-2111. • Zeolites prepared from calcined and mechanically modified kaolins. A comparative study. A. G San Cristóbal, R. Castelló, M. A. Martín Luengo, C Vizcayno. Applied Clay Science 49 (2010) 239-246. • Study comparative of the sorption of HDTMA on natural and modified kaolin. A. G San Cristóbal, R. Castelló, J. M. Castillejo, C Vizcayno. Aceptada en Clays and Clay minerals. • Capacity of modified kaolin sand and washed kaolin to adsorb phenol. A. G San Cristóbal, R. Castelló, C Vizcayno. Envío a revista sujeto a la publicación del artículo anterior. ABSTRACT Today’s chemical, pharmaceutical and clinical industries generate pollutants that affect the soils and surface and ground waters of our country. Among these, phenol is a common organic pollutant that is extremely harmful to living organisms, even at low concentrations. Several protocols exist to minimize the effects of pollutants, but most are costly procedures or even generate other pollutants. The adsorption of hazardous materials onto clays is perhaps the most used, efficient and cost-saving method available. However, organic compounds such as phenol are difficult to adsorb and this has led to the development of materials known as organoclays, which are much better at remediating organic compounds. Organoclays are clays that have been modified using a surfactant. In turn, surfactants are organic molecules that confer a cationic rather than anionic charge to the clay surface, improving it’s capacity to adsorb phenol. For this doctorate project, kaolin was selected as an adsorbent material for the removal of phenol given its easy sourcing and relatively low cost. The materials investigated were kaolin sand, a directly extracted material, and washed kaolin, which is the byproduct of the kaolin sand washing process. The main difference between the materials is their quartz content, which is much higher in the kaolin sands. To generate a product from kaolin or kaolin sand capable of retaining organic pollutants such as phenol, both materials were subjected to several heat, chemical and/or mechanical treatments to give rise to compounds with a greater reactive surface area. To this end the two starting materials underwent heating at 750ºC for 3 h, grinding to the point of amorphization and/or activation with HCl 6M or NaOH 5M for 3 h at 90ºC. These treatments gave rise to 18 processed samples, which were characterized in terms of their morphological, mineralogical, and physical-chemical properties. The behaviour of these new materials was examined in terms of their pH, cation exchange capacity (CEC), water adsorption capacity (WCU and WCC), particle size distribution (PSD), specific surface area (SBET), and their X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal (DTG, DTA) and scanning and transmission electron microscopy (SEM and TEM) properties. The changes conferred by the different treatments were also examined in terms of Al and Si losses. Results for the materials derived from kaolin sands and washed kaolin were similar, with differences attributable to the kaolinite contents of the samples. The treatments heat and grinding produced amorphous materials, which when subjected to acid or alkali activation gave rise to Si and Al losses. This in turn led to a change in physico- chemical, mineralogical and morphological properties. Some samples showed a highly increased surface area and CEC. Further, among the changes produced, alkali treatment led to the generation of zeolites in different proportions depending on the sample. To produce the organoclays, the 18 samples were surfacted with hexadecyltrimethylammonium (HDTMA) 20 mM for 24 h at 60ºC. This surfactant concentration is higher than the CEC of each sample. The amount of HDTMA adsorbed onto the surface of each sample determined by FTIR varied according to treatment. A principle components analysis (PCA) was performed to examine correlations between sample Si/Al ratios and surfactant adsorption capacity. In addition, to explore HDTMA adsorption by the samples, DTG and DTA data were fitted to Freundllich and Langmuir models. The mechanisms of surfactant attachment to the sample surface were also addressed. The amount of phenol adsorbed by the resultant organoclays was determined when exposed to different phenol concentrations: 50, 500, 1000, 2000, and 2500 mg/l for 24 h. The quantity of adsorbed pollutant was estimated by gas chromatography and the data fitted to the models of Freundllich and Langmuir. Results indicate that the phenol adsorption capacity of the surfacted samples is dependent on the sample’s characteristics. In general, the washed kaolin samples showed a greater phenol adsorption capacity than the kaolon sands and alkali activation improved this capacity in the two types of sample. In conclusion, the treatments used gave rise to adsorbent materials with varying properties. Kaolin sands showed high quartz levels and their use in some industries is not recommended due to the costs involved in their washing and purification. The applications suggested by the data obtained for some of the kaolin sand samples indicate the added value of this industrial by-product. The results of this research project have led to the following publications: • Pérdida de Al y Si en caolines modificados térmica- o mecánicamente y activados por tratamientos químicos. A. G. San Cristóbal, C Vizcayno, R. Castelló. Macla 9, 113-114. (2008). • Acid activation of mechanically and thermally modfied kaolins. A. G. San Cristóbal, R. Castelló, M. A. Martín Luengo, C Vizcayno. Mater. Res. Bull. 44 (2009) 2103-2111. • Zeolites prepared from calcined and mechanically modified kaolins. A comparative study. A. G. San Cristóbal, R. Castelló, M. A. Martín Luengo, C Vizcayno. Applied Clay Science 49 (2010) 239-246. • Study comparative of the sorption of HDTMA on natural and modified kaolin. A. G. San Cristóbal, R. Castelló, J. M. Castillejo, C Vizcayno Accepted in Clays and Clay minerals. • Capacity of modified kaolin sand and washed kaolin to adsorb phenol. A. G San Cristóbal, R. Castelló, C Vizcayno. Shipment postponed, subject to the publication of the previous article.

Ulmus laevis in the Iberian Peninsula: a review of its ecology and conservation

European white elm (Ulmus laevis Pallas) populations are scarce, small and fragmented in the Iberian Peninsula. Due to these characteristics the indigenous status of the species in the region has been questioned, whilst the species? role in Iberian riparian forest ecology has been neglected. Herein we review past studies regarding this species? distribution and ecology in the Iberian Peninsula, with special emphasis on the establishment of conservation priorities. We first present a collection of palaeogeographic, historic and genetic data suggesting that the Iberian Peninsula was a glacial refuge for U. laevis. Secondly, we analyse U. laevis distribution in relation to soil physico- chemical properties and water availability in Spain. Following this, we focus on the reproductive biology of the species, and investigate the effect of masting and empty seed production on predation and regeneration establishment. Finally, based on this knowledge, we propose conservation policies for U. laevis in the Iberian Peninsula.

Road Dust Emission Sources and Assessment of Street Washing Effect

Although previous studies report on the effect of street washing on ambient particulate matter levels, there is a lack of studies investigating the results of street washing on the emission strength of road dust. A sampling campaign was conducted in Madrid urban area during July 2009 where road dust samples were collected in two sites, namely Reference site (where the road surface was not washed) and Pelayo site (where street washing was performed daily during night). Following the chemical characterization of the road dust particles the emission sources were resolved by means of Positive Matrix Factorization, PMF (Multilinear Engine scripting) and the mass contribution of each source was calculated for the two sites. Mineral dust, brake wear, tire wear, carbonaceous emissions and construction dust were the main sources of road dust with mineral and construction dust being the major contributors to inhalable road dust load. To evaluate the effectiveness of street washing on the emission sources, the sources mass contributions between the two sites were compared. Although brake wear and tire wear had lower concentrations at the site where street washing was performed, these mass differences were not statistically significant and the temporal variation did not show the expected build-up after dust removal. It was concluded that the washing activities resulted merely in a road dust moistening, without effective removal and that mobilization of particles took place in a few hours between washing and sampling. The results also indicated that it is worth paying attention to the dust dispersed from the construction sites as they affect the emission strength in nearby streets.

Role of fibre in broiler diets - Firend or foe?

The fibrous fraction of the feeds encompasses a group of heterogeneous compounds differing in chemical composition and physical properties (Graham and Aman, 1991, Bach Knudsen, 2001). Dietary fiber is the most used term to define the fiber fraction of ingredients and feeds, and includes cell walls, stored non-starch polysaccharides (NSP), and lignin (Bach Knudsen, 2001). Based on their physico-chemical properties, DF can be divided into soluble and insoluble fractions with distinct effects on digestive physiology and animal metabolism. Consequently, the benefits of fiber inclusion in poultry diets will vary depending on factors such as characteristics of the fiber source, type of bird, and digestive health status.

Evaluation of the surface free energy of plant surfaces: toward standardizing the procedure

Plant surfaces have been found to have a major chemical and physical heterogeneity and play a key protecting role against multiple stress factors. During the last decade, there is a raising interest in examining plant surface properties for the development of biomimetic materials. Contact angle measurement of different liquids is a common tool for characterizing synthetic materials, which is just beginning to be applied to plant surfaces. However, some studies performed with polymers and other materials showed that for the same surface, different surface free energy values may be obtained depending on the number and nature of the test liquids analyzed, materials' properties, and surface free energy calculation methods employed. For 3 rough and 3 rather smooth plant materials, we calculated their surface free energy using 2 or 3 test liquids and 3 different calculation methods. Regardless of the degree of surface roughness, the methods based on 2 test liquids often led to the under- or over-estimation of surface free energies as compared to the results derived from the 3-Liquids method. Given the major chemical and structural diversity of plant surfaces, it is concluded that 3 different liquids must be considered for characterizing materials of unknown physico-chemical properties, which may significantly differ in terms of polar and dispersive interactions. Since there are just few surface free energy data of plant surfaces with the aim of standardizing the calculation procedure and interpretation of the results among for instance, different species, organs, or phenological states, we suggest the use of 3 liquids and the mean surface tension values provided in this study.