127 research outputs found

    Growth of total productivity of the factors, innovation and spillovers from advanced business services

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    Advanced business services (ABS) are seen as generators and disseminators of innovation among their client companies, and their use by client companies can improve efficiency and productivity. However, one question that has not been addressed is whether ABS provision can be an explanatory factor for the total productivity of the factors (TPF). This paper aims to determine whether the innovation generated and/or transmitted by ABS companies is reflected in the TPF growth in the manufacturing sector. For this purpose, a Cobb-Douglas function was estimated using panel data analysis on data of ten OECD countries in the period 1977-1996. ABS labour was considered the proxy variable for the provision of these types of services and treated as a separate factor in the production process. The quantitative study shows that the contribution of labour endowment in ABS to the efficiency and productivity of manufacturing industry is significant, that it generates spillovers and that it is an explanatory factor for the TPF

    Study of colloidal behaviour and rheology of Al2O3-TiO2 nanosuspensions to obtain free-flowing spray-dried granules for atmospheric plasma spraying

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    This work deals with the dispersion and stabilisation of nanosized Al2O3 and TiO2 particles in aqueous medium. The dispersing conditions were studied as a function of pH, dispersant content, solid loading and ageing. Well-dispersed nanosuspensions of Al2O3 with solids contents up to 15 vol.% and TiO2 with solids contents up to 30 vol.% were obtained by dispersing each type of nanoparticles with 4 wt% of polyacrylic acid-based polyelectrolyte. In order to obtain a concentrated 87 wt% Al2O3–13 wt% TiO2 suspension, a 15 vol.% homogeneous nanosuspension, composed by alumina and titania nanopowders, was prepared and then reconstituted by spray-drying into free-flowing powders. This spray-dried powder showed an adequate granule size distribution, a very high flowability and a reasonable density for diverse purposes, such as to be used in atmospheric plasma spraying as a feedstock to obtain nanostructured coatings

    Temperature dependence of dynamic, tunnelling and kinetic isotope effects in formate dehydrogenase

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    The origin of the catalytic power of enzymes has been a question of debate for a long time. In this regard, the possible contribution of protein dynamics in enzymatic catalysis has become one of the most controversial topics. In the present work, the hydride transfer step in the formate dehydrogenase (FDH EC 1.2.1.2) enzyme is studied by means of molecular dynamic (MD) simulations with quantum mechanics/molecular mechanics (QM/MM) potentials in order to explore any correlation between dynamics, tunnelling effects and the rate constant. The temperature dependence of the kinetic isotope effects (KIEs), which is one of the few tests that can be studied by experiments and simulations to shed light on this debate, has been computed and the results have been compared with previous experimental data. The classical mechanical free energy barrier and the number of recrossing trajectories seem to be temperature-independent while the quantum vibrational corrections and the tunnelling effects are slightly temperature-dependent over the interval of 5–45 °C. The computed primary KIEs are in very good agreement with previous experimental data, being almost temperature-independent within the standard deviations. The modest dependence on the temperature is due to just the quantum vibrational correction contribution. These results, together with the analysis of the evolution of the collective variables such as the electrostatic potential or the electric field created by the protein on the key atoms involved in the reaction, confirm that while the protein is well preorganised, some changes take place along the reaction that favour the hydride transfer and the product release. Coordinates defining these movements are, in fact, part of the real reaction coordinate

    Hierarchical mesoporous NanoMUV-2 for the selective delivery of macromolecular drugs

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    Although Metal-organic frameworks (MOFs) have received attention as drug delivery systems, their application in the delivery of macromolecules is limited by their pore size and opening. Herein, we present the synthesis of nanostructured MUV-2, a hierarchical mesoporous iron-based MOF that can store high payloads of the macromolecular drug paclitaxel (ca. 23% w/w), increasing its selectivity towards HeLa cancer cells over HEK non-cancerous cells. Moreover, this NanoMUV-2 permits full degradation under simulated physiological conditions while maintaining biocompatibility, and is amenable to specific surface modifications that increase its cell permeation, efficient cytosol delivery and cancer-targeting effect, further intensifying the cancer selectivity of paclitaxel

    Atmospheric plasma spraying coatings from alumina titania feedstockcomprising bimodal particle size distributions

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    In this work, Al2O3 13 wt% TiO2 submicron-nanostructured powders were deposited using atmospheric plasma spraying. The feedstocks were obtained by spray drying two starting suspensions of different solids content, prepared by adding nanosized TiO2 and submicron-sized Al2O3 powders to water. The spray-dried granules were heat-treated to reduce their porosity and the powders were fully characterised in both untreated and thermally treated state. Comparison with two commercial feedstocks was carried out. Characterisation allowed a temperature for the thermal treatment to be chosen on the basis of the sprayability of the feedstock and the preservation as much as possible of the submicron-sized structure of the unfired agglomerates. Optimisation of the deposition conditions enabled the reconstituted powdrs to be successfully deposited, yielding coatings that were well bonded to the substrate. The coating microstructure, characterised by SEM, was mostly formed by a matrix of fully molten particles where the presence of semi-molten feedstock agglomerates was also observed. Moreover, microhardness, toughness, adhesion and tribological behaviours were determined, and the impact of the granule characteristics on these properties was studied. It was found that changing the feedstock characteristics allows controlling the coating quality and properties. In general, good mechanical properties were obtained using a feedstock comprising a binary mixture of submicrometric Al2O3 and nanometric TiO2 particles in the spray-dried powderThis work has been supported by Spanish Ministry of Economy and Competitiveness (MAT2009-14144-C03 and MAT2012-38364-C03).Vicent, M.; Bannier, E.; Moreno, R.; Salvador Moya, MD.; Sanchez, E. (2013). Atmospheric plasma spraying coatings from alumina titania feedstockcomprising bimodal particle size distributions. Journal of the European Ceramic Society. 33:3313-3324. doi:10.1016/j.jeurceramsoc.2013.05.009S331333243

    A bonding evolution theory study of the reaction between methylidyne radical, CH(X2Π), and cyclopentadiene, C5H6

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    In the present work, bonding evolution theory (BET) is applied to gain insight about the complex reaction between methylidyne radical, CH (X2 Π) and cyclopentadiene, C5H6. The novelty of this work is that all reaction pathways take place in the doublet electronic state and an unpaired electron is always present. Therefore, taking the aforementioned reaction as explicative example, we have shown how to apply the BET tool to these kinds of open-shell systems, by splitting the wavefunctions into the corresponding alpha and beta parts. As an added value, we have included a point-by-point description of the algorithm we use to make it available for the readers. Hence, a complete analysis of bond breaking/forming and charge redistribution along the multi-channels connecting reactants to products via the transition states and intermediates is presented. We show how the BET brings about the representation of the electronic flow in complex molecular rearrangements like the one herein studied, yielding a transparent rationalization based on the electron density redistribution. The present study allows us to conclude that along the different processes giving rise to the benzene product, the breaking of a C C sigma bond initiates the electronic rearrangement in two cases, but not in the third one. The last step in these processes can be described as an initial weakening of the C H bond with a quasi-hydride formation and a final retro-transfer of electrons from the quasi-hydride to the C H bond. On the other hand, in the way to the fulvene product, the breaking of the C C sigma bond takes place after previous electronic redistribution. Neither the last step of the fulvene formation process nor the interesting H transfer described in the second one, can be explaiFunding for open access charge: CRUE-Universitat Jaume

    Bioactive glass coatings by suspension plasma spraying from glycoletherbased solvent feedstock

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    Bioactive glasses are emerging as a substitute of hydroxyapatite in the development of bioactive coatings for biomedical applications. The deposition of these coatings is carried out by a wide range of methods, being atmospheric plasma spraying the most employed technique. However, the research on the deposition of these coatings from suspension feedstocks by thermal spraying is still incipient, therefore more research about this topic is needed. Thus, a bioactive glass suspension, composed of fine glass particles, was prepared and stabilised through rheological and sedimentation tests to be used as a feedstock in plasma spraying. The solvent used in the suspension preparation was dipropylene glycol methyl ether in order to develop a new type of bioactive suspension. Consequently, as a new type of solvent was used, its effect on the plasma torch properties was determined. On other hand, the rheological behaviour of the suspension feedstock was assessed by means of a simple viscosity model. This suspension was deposited onto metallic substrates by plasma spraying, employing several spraying distances. All coatings displayed a suitable adherence and similar thickness. However, the microstructure of the obtained coatings is highly affected by the spraying distance as it can be seen in coatings surface and cross-section field emission gun environmental scanning electron microscopy examination. Thus, a relation between the spraying distance and coatings microstructure was found. On the other hand, X-ray diffraction confirmed the amorphous nature of the obtained coatings

    Activación alcalina de metacaolín. Efecto de la adición de silicato soluble y de la temperatura de curado

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    El objetivo del presente trabajo es determinar el efecto que la cantidad de sílice soluble presente en la disolución activadora (relación molar SiO2/Na2O entre 0 y 0.69) y la temperatura de curado (85ºC, 150ºC y 200ºC) ejercen sobre las propiedades físico-mecánicas y las características mineralógicas y microestructurales de los productos formados por activación alcalina de metacaolín. Para ello se determinaron los valores de resistencia mecánica a compresión de los materiales objeto de estudio y se realizó un estudio mineralógico y microestructural de los mismos por DRX, SEM-EDX, 29Si RMN-MAS y porosimetría de mercurio. Los resultados obtenidos muestran que la resistencia mecánica del material guarda una estrecha relación con la naturaleza, microestructura y composición química de los productos de reacción así como con las condiciones de curado. En todos los casos se genera, como principal producto de reacción, un polímero inorgánico alcalino con propiedades cementantes (gel N-A-S-H) responsable, en mayor medida, de las propiedades mecánicas del material. Como productos secundarios se forman algunas zeolitas cuya proporción y tipo (sodalita, zeolita A, faujasita, …) dependen tanto de la naturaleza del activador como de las condiciones de curado. La presencia de sílice soluble en la disolución activadora conduce a la formación de geles con una mayor relación Si/Al y a la ralentización de la zeolitización, factores, ambos, con un efecto positivo sobre la resistencia mecánica. Con respecto a la temperatura de curado, existe un valor umbral, en función de la composición del material, a partir del cual un incremento en dicha temperatura deja de tener efectos positivos sobre la evolución de la resistencia mecánicaThis study has been undertaken to determine the effect that the soluble silica content in the activating solution (molar ratio SiO2/Na2O between 0 and 0.69) and curing temperature (85ºC, 150ºC, and 200ºC) have on the physico-mechanical properties and mineralogical and microstructural characteristics of products formed by alkaline activation of metakaolin. The compression strength of the materials obtained was determined and a mineralogical and microstructural study of these materials was conducted by XRD, SEM-EDX, 29Si MAS-NMR, and mercury porosimetry. The results show that the mechanical strength of the material is closely related to the nature, microstructure, and chemical composition of the reaction products, as well as to the curing conditions. In all cases, the main reaction product that forms is an inorganic alkaline polymer with cementing properties (N-A-S-H gel), which is largely responsible for the mechanical properties of the material. Some zeolites form as by-products, whose quantity and type (sodalite, zeolite A, faujasite, etc.) depend on the nature of the activator and the curing conditions. The presence of soluble silica in the activating solution leads to the formation of gels with a larger Si/Al ratio and slower zeolitisation, these both being factors with a positive effect on mechanical strength. The curing temperature exhibits a threshold value that depends on the composition of the material, beyond which an increase in curing temperature ceases to positively affect the evolution of the material’s mechanical strengt

    GOOGLE-DOCS COMO HERRAMIENTA PARA LA DIRECCIÓN ONLINE DE PROYECTOS FINALES EN LAS TITULACIONES DEL EEES

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    The purpose of the present paper is to share our first assessments of an experience using the software Google-Docs as a monitoring tool for guiding various final degree / master projects. This innovative practice meets one of the challenges of implementation of the European Higher Education Area, namely, in the design of degree and master qualifications, the accomplishment of a final project is included as part of the 240 and 60 ECTS, respectively.La finalidad del presente trabajo es compartir nuestras primeras valoraciones sobre una experiencia de utilización del software GoogleDocs como herramienta de seguimiento para la dirección de distintos trabajos final de carrera/máster. Esta práctica innovadora responde a uno de los retos que plantea la implantación del Espacio Europeo de Educación Superior: en la estructura de las titulaciones de Grado y Máster se incluye la realización de un proyecto final formando parte de los 240 y 60 créditos ECTS, respectivament

    On the catalytic transfer hydrogenation of nitroarenes by a cubane-type Mo3S4 cluster hydride: disentangling the nature of the reaction mechanism

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    Cubane-type Mo3S4 cluster hydrides decorated with phosphine ligands are active catalysts for the transfer hydrogenation of nitroarenes to aniline derivatives in the presence of formic acid (HCOOH) and triethylamine (Et3N). The process is highly selective and most of the cluster species involved in the catalytic cycle have been identified through reaction monitoring. Formation of a dihydrogen cluster intermediate has also been postulated based on previous kinetic and theoretical studies. However, the different steps involved in the transfer hydrogenation from the cluster to the nitroarene to finally produce aniline remain unclear. Herein, we report an in-depth computational investigation into this mechanism. Et3N reduces the activation barrier associated with the formation of Mo–HHOOCH dihydrogen species. The global catalytic process is highly exergonic and occurs in three consecutive steps with nitrosobenzene and N-phenylhydroxylamine as reaction intermediates. Our computational findings explain how hydrogen is transferred from these Mo–HHOOCH dihydrogen adducts to nitrobenzene with the concomitant formation of nitrosobenzene and the formate substituted cluster. Then, a b-hydride elimination reaction accompanied by CO2 release regenerates the cluster hydride. Two additional steps are needed for hydrogen transfer from the dihydrogen cluster to nitrosobenzene and N-phenylhydroxylamine to finally produce aniline. Our results show that the three metal centres in the Mo3S4 unit act independently, so the cluster can exist in up to ten different forms that are capable of opening a wide range of reaction paths. This behaviour reveals the outstanding catalytic possibilities of this kind of cluster complexes, which work as highly efficient catalytic machines
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