(Appendix A) Geochemical composition of snow and eolian mineral dust from Berkner Island ice sheet, Antarctica

The Sr and Nd isotopic composition of dust extracted from recent snow layers at the top of Berkner Island ice sheet (located within the Filchner-Ronne Ice Shelf at the southern end of the Weddell Sea) enables us, for the first time, to document dust provenance in Antarctica outside the East Antarctic Plateau (EAP) where all previous studies based on isotopic fingerprinting were carried out. Berkner dust displays an overall crust-like isotopic signature, characterized by more radiogenic 87Sr/86Sr and much less radiogenic 143Nd/144Nd compared to dust deposited on the EAP during glacial periods. Differences with EAP interglacial dust are not as marked but still significant, indicating that present-day Berkner dust provenance is distinct, at least to some extent, from that of the dust reaching the EAP. The fourteen snow-pit sub-seasonal samples that were obtained span a two-year period (2002-2003) and their dust Sr and Nd isotopic composition reveals that multiple sources are at play over a yearly time period. Southern South America, Patagonia in particular, likely accounts for part of the observed spring/summer dust deposition maxima, when isotopic composition is shifted towards 'younger' isotopic signatures. In the spring, possible additional inputs from Australian sources would also be supported by the data. Most of the year, however, the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in East Antarctica, which carry old-crust-like isotopic fingerprints. Whether the restricted East Antarctic ice-free areas produce sufficient eolian material has yet to be substantiated however. The fact that large (> 5 µm) particles represent a significant fraction of the samples throughout the entire time-series supports scenarios that involve contributions from proximal sources, either in Patagonia and/or Antarctica (possibly including snow-free areas in the Antarctic Peninsula and other areas as well). This also indicates that additional dust transport, which does not reach the EAP, must occur at low-tropospheric levels to this coastal sector of Antarctica.

Efecto del riego deficitario controlado sobre el crecimiento vegetativo en plantaciones jóvenes de cerezo (Prunus avium L.)

En cerezo, plantas con excesivo vigor son poco precoces, poco productivas y de difícil manejo. El exceso de vigor podría ser controlado con estrategias de riego deficitario controlado (RDC). Durante dos años se realizó un ensayo de RDC en un monte frutal comercial joven y de alto vigor de cerezos Bing, plantado en suelo árido poco profundo y regado por goteo. Se evaluó la respuesta a distintos regímenes de riego sobre el crecimiento de brotes terminales y vigorosos, área y peso seco foliar, y crecimiento de tronco. Los tratamientos de riego fueron: T1 = 100%, T2 = 75% y T3 = 50% de la evapotranspiración máxima (ETc full), respectivamente. Se midió periódicamente el estado hídrico de la planta a través del potencial agua del tallo a mediodía y el estado hídrico del suelo mediante gravimetría. En T3 disminuyó la longitud de brotes, número y longitud de entrenudos, número de hojas, área foliar y peso seco foliar, y área de tronco. En T2 disminuyó la longitud de brotes y entrenudos y el área de sección de tronco. El potencial hídrico del tallo a mediodía fue un buen indicador del estado hídrico de las plantas. En cerezos, un ajuste preciso del nivel de restricción hídrica puede ser una estrategia de manejo para controlar vigor y para ahorrar importantes cantidades de agua.

O subtexto do Chanceler Pero Lopez de Ayala na Crônica de D. João I de Fernão Lopes referente ao biênio de 1383-1384 : autoridade e desafio

El intento del artículo es percibir cómo el cronista portugués Fernão Lopes (1385-1460) se apropia, en el último texto suyo, del discurso del castellano Pero Lopez de Ayala (1332-1407) en la Crónica de D. Juan I. La parte elegida para el examen fue el bienio de 1383-1384, antes, por lo tanto, de la Batalla de Aljubarrota (1385). La comparación de las crónicas citadas todavía ya fue realizada por investigadores renombrados, sin embargo mi trabajo sigue el camino por la reducción de escala, o sea, por un análisis interpretativo de un bienio especifico, con la finalidad de iniciar un análisis más abarcador del rasgo de la crónica medieval ibérica medieval, objeto de mi presente pesquisa.

Heterogeneidad de trayectorias laborales y temporalidades juveniles

Las trayectorias laborales de los jóvenes se diversifican en función de las duraciones, las etapas y las edades en las que ocurren los acontecimientos y se alcanzan ciertos roles. Sin embargo, factores clásicos asociados al origen social o al mundo del trabajo no alcanzan para comprender la diferenciación en los modos de inserción. Este artículo propone la inclusión de las temporalidades juveniles como factor clave para la comprensión de trayectorias laborales de jóvenes. Las temporalidades juveniles sirven para observar conjuntamente los marcos temporales dominantes de la inserción y la manera en la que los mismos son vividos por los sujetos. Las mismas discuten las tesis que señalan que en Argentina los jóvenes son prisioneros de un presentismo sin proyecto o que se someten inevitablemente a un contexto laboral incierto. Cuatro tipo des temporalidades han emergido en el análisis cualitativo y longitudinal de las trayectorias : los "planificadores", los "ejecutantes", los "latentes" y los "oportunistas"

Heterogeneidad de trayectorias laborales y temporalidades juveniles

Las trayectorias laborales de los jóvenes se diversifican en función de las duraciones, las etapas y las edades en las que ocurren los acontecimientos y se alcanzan ciertos roles. Sin embargo, factores clásicos asociados al origen social o al mundo del trabajo no alcanzan para comprender la diferenciación en los modos de inserción. Este artículo propone la inclusión de las temporalidades juveniles como factor clave para la comprensión de trayectorias laborales de jóvenes. Las temporalidades juveniles sirven para observar conjuntamente los marcos temporales dominantes de la inserción y la manera en la que los mismos son vividos por los sujetos. Las mismas discuten las tesis que señalan que en Argentina los jóvenes son prisioneros de un presentismo sin proyecto o que se someten inevitablemente a un contexto laboral incierto. Cuatro tipo des temporalidades han emergido en el análisis cualitativo y longitudinal de las trayectorias : los "planificadores", los "ejecutantes", los "latentes" y los "oportunistas"

Heterogeneidad de trayectorias laborales y temporalidades juveniles

Las trayectorias laborales de los jóvenes se diversifican en función de las duraciones, las etapas y las edades en las que ocurren los acontecimientos y se alcanzan ciertos roles. Sin embargo, factores clásicos asociados al origen social o al mundo del trabajo no alcanzan para comprender la diferenciación en los modos de inserción. Este artículo propone la inclusión de las temporalidades juveniles como factor clave para la comprensión de trayectorias laborales de jóvenes. Las temporalidades juveniles sirven para observar conjuntamente los marcos temporales dominantes de la inserción y la manera en la que los mismos son vividos por los sujetos. Las mismas discuten las tesis que señalan que en Argentina los jóvenes son prisioneros de un presentismo sin proyecto o que se someten inevitablemente a un contexto laboral incierto. Cuatro tipo des temporalidades han emergido en el análisis cualitativo y longitudinal de las trayectorias : los "planificadores", los "ejecutantes", los "latentes" y los "oportunistas"

Light adsorption of phytoplankton and parameters of its biomass and cell biovolumes in the Black Sea in 1998-2000

Bio-optical characteristics of phytoplankton have been observed during two-year monitoring in the western Black Sea. High variability in light absorption coefficient of phytoplankton was due to change of pigment concentration and chlorophyll a specific absorption coefficient. A relationships between light absorption coefficients and chlorophyll a concentration have been found: for the blue maximum (a_ph(440) = 0.0413x**0.628; R**2 = 0.63) and for the red maximum (?_ph(678) = 0.0190x**0.843; R**2 = 0.83). Chlorophyll a specific absorption coefficients decreased while pigment concentration in the Sea increased. Observed variability in chlorophyll a specific absorption coefficient at chlorophyll a concentrations <1.0 mg/m**3 had seasonal features and was related with seasonal change of intracellular pigment concentration. Ratio between the blue and red maxima decreased with increasing chlorophyll a concentration (? = 2.14 x**-0.20; R**2 = 0.41). Variability of spectrally averaged absorption coefficient of phytoplankton (a'_ph ) on 95% depended on absorption coefficient at the blue maximum (y = 0.421x; R**2 = 0.95). Relation of a_ph with chlorophyll a concentration was described by a power function (y = 0.0173x**0.0709; R**2 = 0.65). Change of spectra shape was generally effected by seasonal dynamics of intracellular pigment concentration, and partly effected by taxonomic and cell-size structure of phytoplankton.

(Table 1) Snow and ice thickness and layering at observation points of the North Pole 34 drifting station

Variability of total alkalinity in sea ice of the high-latitudinal Arctic from November 2005 to May 2006 is considered. For the bulk of one- and two-year sea ice, alkalinity dependence on salinity is described as TA = k x Sal, where k is salinity/alkalinity ratio in under-ice water. The given relationship is valid within a wide range of salinity from 0.1 psu in desalinated fraction of two-year ice to 36 psu in snow on the young ice surface. Geochemically significant deviations from the relationship noted were observed exclusively in snow and the upper layer of one-year ice. In the upper layer of one-year ice, deficiency of alkalinity is observed ( delta TA ~= -0.07 mEq/kg, or -15%). In snow on the surface of the one-year ice, alkalinity excess is formed under desalination ( delta TA is as high as 1.3 mEq/kg, or 380%). Deviations registered are caused by possibility of carbonate precipitation in form of CaCO3 x 6H2O under seawater freezing. It is shown that ice formation and the following melting might cause losses of atmospheric CO2 of up to 3 x 10**12 gC/year.

Downward particle fluxes at the oligotrophic and mesotrophic site of the EUMELI program

A two year record of downward particle flux was obtained with moored sediment traps at several depths of the water column in two regions characterized by different primary production levels (mesotrophic and oligotrophic) of the eastern subtropical North Atlantic Ocean in the framework of the EUMELI program. Settling particles were collected with multisample conical sediment-traps moored at 1000 and 2500 depths in the water column. Time-series samples were obtained between February 1991 and November 1992. During this time, sampling intervals varied from 8 to 10 d and were synchronized at all depths and also between the oligotrophic and mesotrophic moorings. Sediment-trap sampling procedures were consistent with JGOF and described elsewhere. The data shown here are mass, particulate organic carbon (POC), particulate inorganic carbon (PIC), coccolithophore, opal, and lithogenic downward fluxes obtained during the entire sediment-trap deployments at both sites.

Structural Changes and Formation of Rusta-shahr in Post-Revolutionary Rural Society in Iran

The following paper is based on the author's two-year research and fieldwork in Iran and examines the process of political and social changes since the Iranian Revolution of 1979 and the subsequent impact of the Iran-Iraq War of 1980-88. This paper focuses on the transition of traditional, small villages into rusta-shahr or small rural cities and the first and second nation-wide elections of shoura or councils which were the first steps toward self-government. The author is guardedly optimistic regarding this democratic process but warns of possible future social unrest if changes are not more "balanced" between cities and rural areas and if the employment needs of the burgeoning younger generation are not met, political and social consequences may be catastrophic.

Coupled model of initiation and propagation of corrosion in reinforced concrete

Corrosion of reinforcing steel in concrete due to chloride ingress is one of the main causes of the deterioration of reinforced concrete structures. Structures most affected by such a corrosion are marine zone buildings and structures exposed to de-icing salts like highways and bridges. Such process is accompanied by an increase in volume of the corrosión products on the rebarsconcrete interface. Depending on the level of oxidation, iron can expand as much as six times its original volume. This increase in volume exerts tensile stresses in the surrounding concrete which result in cracking and spalling of the concrete cover if the concrete tensile strength is exceeded. The mechanism by which steel embedded in concrete corrodes in presence of chloride is the local breakdown of the passive layer formed in the highly alkaline condition of the concrete. It is assumed that corrosion initiates when a critical chloride content reaches the rebar surface. The mathematical formulation idealized the corrosion sequence as a two-stage process: an initiation stage, during which chloride ions penetrate to the reinforcing steel surface and depassivate it, and a propagation stage, in which active corrosion takes place until cracking of the concrete cover has occurred. The aim of this research is to develop computer tools to evaluate the duration of the service life of reinforced concrete structures, considering both the initiation and propagation periods. Such tools must offer a friendly interface to facilitate its use by the researchers even though their background is not in numerical simulation. For the evaluation of the initiation period different tools have been developed: Program TavProbabilidade: provides means to carry out a probability analysis of a chloride ingress model. Such a tool is necessary due to the lack of data and general uncertainties associated with the phenomenon of the chloride diffusion. It differs from the deterministic approach because it computes not just a chloride profile at a certain age, but a range of chloride profiles for each probability or occurrence. Program TavProbabilidade_Fiabilidade: carries out reliability analyses of the initiation period. It takes into account the critical value of the chloride concentration on the steel that causes breakdown of the passive layer and the beginning of the propagation stage. It differs from the deterministic analysis in that it does not predict if the corrosion is going to begin or not, but to quantifies the probability of corrosion initiation. Program TavDif_1D: was created to do a one dimension deterministic analysis of the chloride diffusion process by the finite element method (FEM) which numerically solves Fick’second Law. Despite of the different FEM solver already developed in one dimension, the decision to create a new code (TavDif_1D) was taken because of the need to have a solver with friendly interface for pre- and post-process according to the need of IETCC. An innovative tool was also developed with a systematic method devised to compare the ability of the different 1D models to predict the actual evolution of chloride ingress based on experimental measurements, and also to quantify the degree of agreement of the models with each others. For the evaluation of the entire service life of the structure: a computer program has been developed using finite elements method to do the coupling of both service life periods: initiation and propagation. The program for 2D (TavDif_2D) allows the complementary use of two external programs in a unique friendly interface: • GMSH - an finite element mesh generator and post-processing viewer • OOFEM – a finite element solver. This program (TavDif_2D) is responsible to decide in each time step when and where to start applying the boundary conditions of fracture mechanics module in function of the amount of chloride concentration and corrosion parameters (Icorr, etc). This program is also responsible to verify the presence and the degree of fracture in each element to send the Information of diffusion coefficient variation with the crack width. • GMSH - an finite element mesh generator and post-processing viewer • OOFEM – a finite element solver. The advantages of the FEM with the interface provided by the tool are: • the flexibility to input the data such as material property and boundary conditions as time dependent function. • the flexibility to predict the chloride concentration profile for different geometries. • the possibility to couple chloride diffusion (initiation stage) with chemical and mechanical behavior (propagation stage). The OOFEM code had to be modified to accept temperature, humidity and the time dependent values for the material properties, which is necessary to adequately describe the environmental variations. A 3-D simulation has been performed to simulate the behavior of the beam on both, action of the external load and the internal load caused by the corrosion products, using elements of imbedded fracture in order to plot the curve of the deflection of the central region of the beam versus the external load to compare with the experimental data.

Evaluation of cover crops based on characteristics of nitrogen use, and aerial and root growth

La caracterización de los cultivos cubierta (cover crops) puede permitir comparar la idoneidad de diferentes especies para proporcionar servicios ecológicos como el control de la erosión, el reciclado de nutrientes o la producción de forrajes. En este trabajo se estudiaron bajo condiciones de campo diferentes técnicas para caracterizar el dosel vegetal con objeto de establecer una metodología para medir y comparar las arquitecturas de los cultivos cubierta más comunes. Se estableció un ensayo de campo en Madrid (España central) para determinar la relación entre el índice de área foliar (LAI) y la cobertura del suelo (GC) para un cultivo de gramínea, uno de leguminosa y uno de crucífera. Para ello se sembraron doce parcelas con cebada (Hordeum vulgare L.), veza (Vicia sativa L.), y colza (Brassica napus L.). En 10 fechas de muestreo se midieron el LAI (con estimaciones directas y del LAI-2000), la fracción interceptada de la radiación fotosintéticamente activa (FIPAR) y la GC. Un experimento de campo de dos años (Octubre-Abril) se estableció en la misma localización para evaluar diferentes especies (Hordeum vulgare L., Secale cereale L., x Triticosecale Whim, Sinapis alba L., Vicia sativa L.) y cultivares (20) en relación con su idoneidad para ser usadas como cultivos cubierta. La GC se monitorizó mediante análisis de imágenes digitales con 21 y 22 muestreos, y la biomasa se midió 8 y 10 veces, respectivamente para cada año. Un modelo de Gompertz caracterizó la cobertura del suelo hasta el decaimiento observado tras las heladas, mientras que la biomasa se ajustó a ecuaciones de Gompertz, logísticas y lineales-exponenciales. Al final del experimento se determinaron el C, el N y el contenido en fibra (neutrodetergente, ácidodetergente y lignina), así como el N fijado por las leguminosas. Se aplicó el análisis de decisión multicriterio (MCDA) con objeto de obtener un ranking de especies y cultivares de acuerdo con su idoneidad para actuar como cultivos cubierta en cuatro modalidades diferentes: cultivo de cobertura, cultivo captura, abono verde y forraje. Las asociaciones de cultivos leguminosas con no leguminosas pueden afectar al crecimiento radicular y a la absorción de N de ambos componentes de la mezcla. El conocimiento de cómo los sistemas radiculares específicos afectan al crecimiento individual de las especies es útil para entender las interacciones en las asociaciones, así como para planificar estrategias de cultivos cubierta. En un tercer ensayo se combinaron estudios en rhizotrones con extracción de raíces e identificación de especies por microscopía, así como con estudios de crecimiento, absorción de N y 15N en capas profundas del suelo. Las interacciones entre raíces en su crecimiento y en el aprovisionamiento de N se estudiaron para dos de los cultivares mejor valorados en el estudio previo: uno de cebada (Hordeum vulgare L. cv. Hispanic) y otro de veza (Vicia sativa L. cv. Aitana). Se añadió N en dosis de 0 (N0), 50 (N1) y 150 (N2) kg N ha-1. Como resultados del primer estudio, se ajustaron correctamente modelos lineales y cuadráticos a la relación entre la GC y el LAI para todos los cultivos, pero en la gramínea alcanzaron una meseta para un LAI>4. Antes de alcanzar la cobertura total, la pendiente de la relación lineal entre ambas variables se situó en un rango entre 0.025 y 0.030. Las lecturas del LAI-2000 estuvieron correlacionadas linealmente con el LAI, aunque con tendencia a la sobreestimación. Las correcciones basadas en el efecto de aglutinación redujeron el error cuadrático medio del LAI estimado por el LAI-2000 desde 1.2 hasta 0.5 para la crucífera y la leguminosa, no siendo efectivas para la cebada. Esto determinó que para los siguientes estudios se midieran únicamente la GC y la biomasa. En el segundo experimento, las gramíneas alcanzaron la mayor cobertura del suelo (83-99%) y la mayor biomasa (1226-1928 g m-2) al final del mismo. Con la mayor relación C/N (27-39) y contenido en fibra digestible (53-60%) y la menor calidad de residuo (~68%). La mostaza presentó elevadas GC, biomasa y absorción de N en el año más templado en similitud con las gramíneas, aunque escasa calidad como forraje en ambos años. La veza presentó la menor absorción de N (2.4-0.7 g N m-2) debido a la fijación de N (9.8-1.6 g N m-2) y escasa acumulación de N. El tiempo térmico hasta alcanzar el 30% de GC constituyó un buen indicador de especies de rápida cubrición. La cuantificación de las variables permitió hallar variabilidad entre las especies y proporcionó información para posteriores decisiones sobre la selección y manejo de los cultivos cubierta. La agregación de dichas variables a través de funciones de utilidad permitió confeccionar rankings de especies y cultivares para cada uso. Las gramíneas fueron las más indicadas para los usos de cultivo de cobertura, cultivo captura y forraje, mientras que las vezas fueron las mejor como abono verde. La mostaza alcanzó altos valores como cultivo de cobertura y captura en el primer año, pero el segundo decayó debido a su pobre actuación en los inviernos fríos. Hispanic fue el mejor cultivar de cebada como cultivo de cobertura y captura, mientras que Albacete como forraje. El triticale Titania alcanzó la posición más alta como cultiva de cobertura, captura y forraje. Las vezas Aitana y BGE014897 mostraron buenas aptitudes como abono verde y cultivo captura. El MCDA permitió la comparación entre especies y cultivares proporcionando información relevante para la selección y manejo de cultivos cubierta. En el estudio en rhizotrones tanto la mezcla de especies como la cebada alcanzaron mayor intensidad de raíces (RI) y profundidad (RD) que la veza, con valores alrededor de 150 cruces m-1 y 1.4 m respectivamente, comparados con 50 cruces m-1 y 0.9 m para la veza. En las capas más profundas del suelo, la asociación de cultivos mostró valores de RI ligeramente mayores que la cebada en monocultivo. La cebada y la asociación obtuvieron mayores valores de densidad de raíces (RLD) (200-600 m m-3) que la veza (25-130) entre 0.8 y 1.2 m de profundidad. Los niveles de N no mostraron efectos claros en RI, RD ó RLD, sin embargo, el incremento de N favoreció la proliferación de raíces de veza en la asociación en capas profundas del suelo, con un ratio cebada/veza situado entre 25 a N0 y 5 a N2. La absorción de N de la cebada se incrementó en la asociación a expensas de la veza (de ~100 a 200 mg planta-1). Las raíces de cebada en la asociación absorbieron también más nitrógeno marcado de las capas profundas del suelo (0.6 mg 15N planta-1) que en el monocultivo (0.3 mg 15N planta-1). ABSTRACT Cover crop characterization may allow comparing the suitability of different species to provide ecological services such as erosion control, nutrient recycling or fodder production. Different techniques to characterize plant canopy were studied under field conditions in order to establish a methodology for measuring and comparing cover crops canopies. A field trial was established in Madrid (central Spain) to determine the relationship between leaf area index (LAI) and ground cover (GC) in a grass, a legume and a crucifer crop. Twelve plots were sown with either barley (Hordeum vulgare L.), vetch (Vicia sativa L.), or rape (Brassica napus L.). On 10 sampling dates the LAI (both direct and LAI-2000 estimations), fraction intercepted of photosynthetically active radiation (FIPAR) and GC were measured. A two-year field experiment (October-April) was established in the same location to evaluate different species (Hordeum vulgare L., Secale cereale L., x Triticosecale Whim, Sinapis alba L., Vicia sativa L.) and cultivars (20) according to their suitability to be used as cover crops. GC was monitored through digital image analysis with 21 and 22 samples, and biomass measured 8 and 10 times, respectively for each season. A Gompertz model characterized ground cover until the decay observed after frosts, while biomass was fitted to Gompertz, logistic and linear-exponential equations. At the end of the experiment C, N, and fiber (neutral detergent, acid and lignin) contents, and the N fixed by the legumes were determined. Multicriteria decision analysis (MCDA) was applied in order to rank the species and cultivars according to their suitability to perform as cover crops in four different modalities: cover crop, catch crop, green manure and fodder. Intercropping legumes and non-legumes may affect the root growth and N uptake of both components in the mixture. The knowledge of how specific root systems affect the growth of the individual species is useful for understanding the interactions in intercrops as well as for planning cover cropping strategies. In a third trial rhizotron studies were combined with root extraction and species identification by microscopy and with studies of growth, N uptake and 15N uptake from deeper soil layers. The root interactions of root growth and N foraging were studied for two of the best ranked cultivars in the previous study: a barley (Hordeum vulgare L. cv. Hispanic) and a vetch (Vicia sativa L. cv. Aitana). N was added at 0 (N0), 50 (N1) and 150 (N2) kg N ha-1. As a result, linear and quadratic models fitted to the relationship between the GC and LAI for all of the crops, but they reached a plateau in the grass when the LAI > 4. Before reaching full cover, the slope of the linear relationship between both variables was within the range of 0.025 to 0.030. The LAI-2000 readings were linearly correlated with the LAI but they tended to overestimation. Corrections based on the clumping effect reduced the root mean square error of the estimated LAI from the LAI-2000 readings from 1.2 to less than 0.50 for the crucifer and the legume, but were not effective for barley. This determined that in the following studies only the GC and biomass were measured. In the second experiment, the grasses reached the highest ground cover (83- 99%) and biomass (1226-1928 g/m2) at the end of the experiment. The grasses had the highest C/N ratio (27-39) and dietary fiber (53-60%) and the lowest residue quality (~68%). The mustard presented high GC, biomass and N uptake in the warmer year with similarity to grasses, but low fodder capability in both years. The vetch presented the lowest N uptake (2.4-0.7 g N/m2) due to N fixation (9.8-1.6 g N/m2) and low biomass accumulation. The thermal time until reaching 30% ground cover was a good indicator of early coverage species. Variable quantification allowed finding variability among the species and provided information for further decisions involving cover crops selection and management. Aggregation of these variables through utility functions allowed ranking species and cultivars for each usage. Grasses were the most suitable for the cover crop, catch crop and fodder uses, while the vetches were the best as green manures. The mustard attained high ranks as cover and catch crop the first season, but the second decayed due to low performance in cold winters. Hispanic was the most suitable barley cultivar as cover and catch crop, and Albacete as fodder. The triticale Titania attained the highest rank as cover and catch crop and fodder. Vetches Aitana and BGE014897 showed good aptitudes as green manures and catch crops. MCDA allowed comparison among species and cultivars and might provide relevant information for cover crops selection and management. In the rhizotron study the intercrop and the barley attained slightly higher root intensity (RI) and root depth (RD) than the vetch, with values around 150 crosses m-1 and 1.4 m respectively, compared to 50 crosses m-1 and 0.9 m for the vetch. At deep soil layers, intercropping showed slightly larger RI values compared to the sole cropped barley. The barley and the intercropping had larger root length density (RLD) values (200-600 m m-3) than the vetch (25-130) at 0.8-1.2 m depth. The topsoil N supply did not show a clear effect on the RI, RD or RLD; however increasing topsoil N favored the proliferation of vetch roots in the intercropping at deep soil layers, with the barley/vetch root ratio ranging from 25 at N0 to 5 at N2. The N uptake of the barley was enhanced in the intercropping at the expense of the vetch (from ~100 mg plant-1 to 200). The intercropped barley roots took up more labeled nitrogen (0.6 mg 15N plant-1) than the sole-cropped barley roots (0.3 mg 15N plant-1) from deep layers.

Evaluación de la distribución de riesgos en los distintos modelos de asociación público-privada para la provisión de infraestructura carretera en México

México es de los pocos países en el mundo que ha realizado dos grandes programas para la construcción de autopistas en colaboración con el sector privado. El primero, fue realizado entre 1989 y 1994, con resultados adversos por el mal diseño del esquema de concesiones; y, el segundo con mejores resultados, en operación desde 2003 mediante nuevos modelos de asociación público-privada (APP). El objetivo de la presente investigación es estudiar los modelos de asociación público-privada empleados en México para la provisión de infraestructura carretera, realizando el análisis y la evaluación de la distribución de riesgos entre el sector público y privado en cada uno de los modelos con el propósito de establecer una propuesta de reasignación de riesgos para disminuir el costo global y la incertidumbre de los proyectos. En la primera parte se describe el estado actual del conocimiento de las asociaciones público-privadas para desarrollar proyectos de infraestructura, incluyendo los antecedentes, la definición y las tipologías de los esquemas APP, así como la práctica internacional de programas como el modelo británico Private Finance Initiative (PFI), resultados de proyectos en la Unión Europea y programas APP en otros países. También, se destaca la participación del sector privado en el financiamiento de la infraestructura del transporte de México en la década de 1990. En los capítulos centrales se aborda el estudio de los modelos APP que se han utilizado en el país en la construcción de la red de carreteras de alta capacidad. Se presentan las características y los resultados del programa de autopistas 1989-94, así como el rescate financiero y las medidas de reestructuración de los proyectos concesionados, aspectos que obligaron a las autoridades mexicanas a cambiar la normatividad para la aprobación de los proyectos según su rentabilidad, modificar la legislación de caminos y diseñar nuevos esquemas de colaboración entre el gobierno y el sector privado. Los nuevos modelos APP vigentes desde 2003 son: nuevo modelo de concesiones para desarrollar autopistas de peaje, modelo de proyectos de prestación de servicios (peaje sombra) para modernizar carreteras existentes y modelo de aprovechamiento de activos para concesionar autopistas de peaje en operación a cambio de un pago. De estos modelos se realizaron estudios de caso en los que se determinan medidas de desempeño operativo (niveles de tráfico, costos y plazos de construcción) y rentabilidad financiera (tasa interna de retorno y valor presente neto). En la última parte se efectúa la identificación, análisis y evaluación de los riesgos que afectaron los costos, el tiempo de ejecución y la rentabilidad de los proyectos de ambos programas. Entre los factores de riesgo analizados se encontró que los más importantes fueron: las condiciones macroeconómicas del país (inflación, producto interno bruto, tipo de cambio y tasa de interés), deficiencias en la planificación de los proyectos (diseño, derecho de vía, tarifas, permisos y estimación del tránsito) y aportaciones públicas en forma de obra. Mexico is one of the few countries in the world that has developed two major programs for highway construction in collaboration with the private sector. The first one was carried out between 1989 and 1994 with adverse outcomes due to the wrong design of concession schemes; and, the second one, in operation since 2003, through new public-private partnership models (PPPs). The objective of this research is to study public-private partnership models used in Mexico for road infrastructure provision, performing the analysis and evaluation of risk’s distribution between the public and the private sector in each model in order to draw up a proposal for risk’s allocation to reduce the total cost and the uncertainty of projects. The first part describes the current state of knowledge in public-private partnership to develop infrastructure projects, including the history, definition and types of PPP models, as well as international practice of programs such as the British Private Finance Initiative (PFI) model, results in the European Union and PPP programs in other countries. Also, it stands out the private sector participation in financing of Mexico’s transport infrastructure in 1990s. The next chapters present the study of public-private partnerships models that have been used in the country in the construction of the high capacity road network. Characteristics and outcomes of the highway program 1989-94 are presented, as well as the financial bailout and restructuring measures of the concession projects, aspects that forced the Mexican authorities to change projects regulations, improve road’s legislation and design new schemes of cooperation between the Government and the private sector. The new PPP models since 2003 are: concession model to develop toll highways, private service contracts model (shadow toll) to modernize existing roads and highway assets model for the concession of toll roads in operation in exchange for a payment. These models were analyzed using case studies in which measures of operational performance (levels of traffic, costs and construction schedules) and financial profitability (internal rate of return and net present value) are determined. In the last part, the analysis and assessment of risks that affect costs, execution time and profitability of the projects are carried out, for both programs. Among the risk factors analyzed, the following ones were found to be the most important: country macroeconomic conditions (inflation, gross domestic product, exchange rate and interest rate), deficiencies in projects planning (design, right of way, tolls, permits and traffic estimation) and public contributions in the form of construction works.

Random exams using Sweave

The adaptation of the Spanish University to the European Higher Education Area (EEES in Spanish) demands the integration of new tools and skills that would make the teaching- learning process easier. This adaptation involves a change in the evaluation methods, which goes from a system where the student was evaluated with a final exam, to a new system where we include a continuous evaluation in which the final exam may represent at most 50% in the vast majority of the Universities. Devising a new and fair continuous evaluation system is not an easy task to do. That would mean a student’s’ learning process follow-up by the teachers, and as a consequence an additional workload on existing staff resources. Traditionally, the continuous evaluation is associated with the daily work of the student and a collection of the different marks partly or entirely based on the work they do during the academic year. Now, small groups of students and an attendance control are important aspects to take into account in order to get an adequate assessment of the students. However, most of the university degrees have groups with more than 70 students, and the attendance control is a complicated task to perform, mostly because it consumes significant amounts of staff time. Another problem found is that the attendance control would encourage not-interested students to be present at class, which might cause some troubles to their classmates. After a two year experience in the development of a continuous assessment in Statistics subjects in Social Science degrees, we think that individual and periodical tasks are the best way to assess results. These tasks or examinations must be done in classroom during regular lessons, so we need an efficient system to put together different and personal questions in order to prevent students from cheating. In this paper we provide an efficient and effective way to elaborate random examination papers by using Sweave, a tool that generates data, graphics and statistical calculus from the software R and shows results in PDF documents created by Latex. In this way, we will be able to design an exam template which could be compiled in order to generate as many PDF documents as it is required, and at the same time, solutions are provided to easily correct them.

Comparing Common Data Environment Platforms for Student Collaborative Working: A Case Study from Ulster University

PAS1192-2 (2013) outlines the “fundamental principles of Level 2 information modeling”, one of these principles is the use of what is commonly referred to as a Common Data Environment (CDE). A CDE could be described as an internet-enabled cloudhosting platform, accessible to all construction team members to access shared project information. For the construction sector to achieve increased productivity goals, the next generation of industry professionals will need to be educated in a way that provides them with an appreciation of Building Information Modelling (BIM) working methods, at all levels, including an understanding of how data in a CDE should be structured, managed, shared and published. This presents a challenge for educational institutions in terms of providing a CDE that addresses the requirements set out in PAS1192-2, and mirrors organisational and professional working practices without causing confusion due to over complexity. This paper presents the findings of a two-year study undertaken at Ulster University comparing the use of a leading industry CDE platform with one derived from the in-house Virtual Learning Environment (VLE), for the delivery of a student BIM project. The research methodology employed was a qualitative case study analysis, focusing on observations from the academics involved and feedback from students. The results of the study show advantages for both CDE platforms depending on the learning outcomes required.