Preparació de materials híbrids orgànico-inorgànics a partir de sals d'imidazoli

Estudi elaborat a partir d’una estada a l’ Ecole Nationale Supérieure de Chimie de Montpellier, França, durant 2006. S’han sintetitzat materials híbrids orgànico-inorgànics mitjançant el procés sol-gel i altres estratègies sintètiques. En alguns casos, s’ha intentat estructurar aquests materials, ja sigui per autoestructuració o per mitjà de tensioactius. Com a catalitzadors de les reaccions d'hidròlisi i policondensació s’han utilitzat àcids, bases i fluorurs. Els materials obtinguts s’han caracteritzat mitjançant diferents tècniques: BET (Brunauer-Emmett-Teller), TEM (microscopia electrònica de transmissió), SEM (microscòpia electrònica de rastreig), raigs X en pols , IR i RMN (ressonància magnètica nuclear) en estat sòlid. Amb aquests materials es pretén preparar catalitzadors heterogenis de Pd per reaccions d’acoblament creuat, i de Ru per reaccions de metàtesi. També s’han sintetitzat sals d'imidazoli amb cadenes hidrocarbonades llargues amb l'objectiu de preparar gels de sílice amb aquestes molècules atrapades dins la matriu inorgànica. Aquests materials s’utilitzaran com a organocatalitzadors i també es prepararan els corresponents catalitzadors de Pd per reaccions de Heck, Suzuki i Sonogashira. Les sals d’imidazoli s’han utilitzat com a tensioactius en la preparació de gels de sílice estructurats. Aquestes molècules han resultat ser cristalls líquids i s’han caracteritzar mitjançant DSC (differential scanning calorimetry), microscopia òptica i raigs X.

Creació de materials per a l'aprenentatge autònom i guiat de la interpretació de conferències a nivell inicial i intermedi

El desenvolupament del projecte ens ha permès de crear materials per a l´aprenentatge autònom de la interpretació de conferències així com d´un material d´acompanyament i suport del procés d´aprenentatge no presencial. Aquests materials s´integren en les assignatures d´interpretació del Grau en Traducció i Interpretació i serveixen perquè els estudiants continuïn fent un treball guiat fora de l´aula. Es pot considerar també un material de suport a les classes presencials. Els materials desenvolupats cobreixen les cinc llengües dels nostres estudis (català, castellà, anglès, alemany i francès) i estan organitzats en dos blocs diferenciats: itineraris d´aprenentatge i banc de discursos. Aquesta divisió permet a l´estudiant treballar seguint dues opcions diferenciades: a) a partir d´una seqüenciació guiada de tasques; b) abordant directament la interpretació d´un discurs oral. El projecte s'ha dut a terme entre les universitats Pompeu Fabra i Autònoma de Barcelona, durant el període 2007- 2009.

Calorimetry of dehydrogenation and dangling-bond recombination in several hydrogenated amorphous silicon materials

Differential scanning calorimetry (DSC) was used to study the dehydrogenation processes that take place in three hydrogenated amorphous silicon materials: nanoparticles, polymorphous silicon, and conventional device-quality amorphous silicon. Comparison of DSC thermograms with evolved gas analysis (EGA) has led to the identification of four dehydrogenation processes arising from polymeric chains (A), SiH groups at the surfaces of internal voids (A'), SiH groups at interfaces (B), and in the bulk (C). All of them are slightly exothermic with enthalpies below 50 meV/H atoms , indicating that, after dissociation of any SiH group, most dangling bonds recombine. The kinetics of the three low-temperature processes [with DSC peak temperatures at around 320 (A),360 (A'), and 430°C (B)] exhibit a kinetic-compensation effect characterized by a linea relationship between the activation entropy and enthalpy, which constitutes their signature. Their Si-H bond-dissociation energies have been determined to be E (Si-H)0=3.14 (A), 3.19 (A'), and 3.28 eV (B). In these cases it was possible to extract the formation energy E(DB) of the dangling bonds that recombine after Si-H bond breaking [0.97 (A), 1.05 (A'), and 1.12 (B)]. It is concluded that E(DB) increases with the degree of confinement and that E(DB)>1.10 eV for the isolated dangling bond in the bulk. After Si-H dissociation and for the low-temperature processes, hydrogen is transported in molecular form and a low relaxation of the silicon network is promoted. This is in contrast to the high-temperature process for which the diffusion of H in atomic form induces a substantial lattice relaxation that, for the conventional amorphous sample, releases energy of around 600 meV per H atom. It is argued that the density of sites in the Si network for H trapping diminishes during atomic diffusion

Síntesi i propietats de vidres metàl•lics massissos i materials nanocomposites basats en Fe per aplicacions com a materials magnètics tous

Estudi realitzat a partir d’una estada a l’ Institut für Komplexe Materialien, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, entre 2010 i 2011. S'ha explorat l'efecte de les condicions i influència dels elements d'aleació en la capacitat de formació de vidre, l'estructura i les propietats tèrmiques i magnètiques de vidres metàl•lics massissos i materials nanocristal•lins en base Fe. La producció d'aquests materials en forma de cintes de unes 20 micres de gruix ha estat àmpliament estudiada i s'ha vist que presenten unes propietats excel•lents com a materials magnètics tous. El propòsit general d'aquest projecte era l'obtenció de composicions òptimes amb alta capacitat de formar vidre i amb excel•lents propietats magnètiques com a materials magnètics tous combinat amb bones propietats mecàniques. El projecte prenia com a punt de partida l'aliatge [FeCoBSi]96Nb4 ja que és el que presenta millor capacitat de formar vidre i presenta una alta imantació de saturació i baix camp coercitiu. S'ha fet un estudi dels factors fonamentals que intervenen en la formació de l'estat vitri. La composició abans esmentada ha estat variada amb l'addició d'altres elements per estudiar com afecten aquests nous elements a les propietats, la formació de vidre i l'estructura dels aliatges resultants amb l'objectiu de millorar-ne les propietats magnètiques i la capacitat de formació de vidre. Entre altres s'ha usat el Zr, Mo, Y i el Gd per millorar la formació de vidre; i el Co i el Ni per millorar les propietats magnètiques a alta temperatura. S'han estudiat les relacions entre la capacitat de formació de vidre i la seva estabilitat tèrmica, la resistència a la cristal•lització i la estructura de l'aliatge resultant després del procés de solidificació. Per aquest estudi s'han determinat els mecanismes que controlen la transformació i la seva cinètica així com les fases que es formen durant el tractament tèrmic permetent la formulació de models predictius.

Development of a Mix Design Process for Cold-in-Place Rehabilitation Using Foamed Asphalt, December 2005

Report by Iowa Department of Transportation about pavements materials.

Validation of the New Mix Design Process for Cold In-Place Rehabilitation Using Foamed Asphalt, 2007

Asphalt pavement recycling has grown dramatically over the last few years as a viable technology to rehabilitate existing asphalt pavements. Iowa's current Cold In-place Recycling (CIR) practice utilizes a generic recipe specification to define the characteristics of the CIR mixture. As CIR continues to evolve, the desire to place CIR mixture with specific engineering properties requires the use of a mix design process. A new mix design procedure was developed for Cold In-place Recycling using foamed asphalt (CIR-foam) in consideration of its predicted field performance. The new laboratory mix design process was validated against various Reclaimed Asphalt Pavement (RAP) materials to determine its consistency over a wide range of RAP materials available throughout Iowa. The performance tests, which include dynamic modulus test, dynamic creep test and raveling test, were conducted to evaluate the consistency of a new CIR-foam mix design process to ensure reliable mixture performance over a wide range of traffic and climatic conditions. The “lab designed” CIR will allow the pavement designer to take the properties of the CIR into account when determining the overlay thickness.

DIGITAL LIBRARY FOR DIGITAL DIVIDE AND ENVIRONMENT OF SCARCE ACCESS TO PRINTED MATERIALS: THE CASE OF UNIVERSITY JEAN PIAGET OF CAPE VERDE

With the failure of the traditional mechanisms of distributing bibliographic materials into developing countries, digital libraries show up as a strong alternative in accomplishing such job, despite the challenges of the digital divide. This paper discusses the challenges of building a digital library (DL) in a developing country. The case of Cape Verde as a digital divide country is analyzed, in terms of current digital library usage and its potentiality for fighting the difficulties in accessing bibliographic resources in the country. The paper also introduces an undergoing project of building a digital library at the University Jean Piaget of Cape Verde.

Characterization of magmatic sulfur in the Aegean island arc by means of the δ34S values of fumarolic H2S, elemental S, and hydrothermal gypsum from Nisyros and Milos islands

A delta(34)S value of +6.3 +/- 1.5% was estimated for the rhyodacitic degassing magma present underneath the hydrothermal system of Nisyros, based on the S isotope ratios of H2S in fumarolic vapors. This value was estimated by modeling the irreversible water-rock mass transfers occurring during the generation of the hydrothermal liquid which separates these fumarolic vapors. The S isotope ratio of the rhyodacitic degassing magma of Nisyros is consistent with fractional crystallization of a parent basaltic magma with an initial delta(34)S value of +4% (+/-at least 1.5%). This positive value could be explained by mantle contamination due to by either transference of fluids derived from subducted materials or involvement of altered oceanic crust, whereas contribution of biogenic sulfides from sediments seems to be negligible or nil. This conclusion agrees with the lack of N-2 and CO2 from thermal decomposition of organic matter contained in subducted sediments, which is a characteristic of the whole Aegean arc system. Since hydrothermal S at Milos and Santorini has isotope ratios similar to those determined at Nisyros, it seems likely that common controlling processes are active throughout the Aegean island arc. (C) 2002 Elsevier, Science B.V. All rights reserved.

Surface states in template synthesized tin oxide nanoparticles

Tin-oxide nanoparticles with controlled narrow size distributions are synthesized while physically encapsulated inside silica mesoporous templates. By means of ultraviolet-visible spectroscopy, a redshift of the optical absorbance edge is observed. Photoluminescence measurements corroborate the existence of an optical transition at 3.2 eV. The associated band of states in the semiconductor gap is present even on template-synthesized nanopowders calcined at 800°C, which contrasts with the evolution of the gap states measured on materials obtained by other methods. The gap states are thus considered to be surface localized, disappearing with surface faceting or being hidden by the surface-to-bulk ratio decrease.

Dissociation of vertical semiconductor diatomic artificial molecules

We investigate the dissociation of few-electron circular vertical semiconductor double quantum dot artificial molecules at 0 T as a function of interdot distance. A slight mismatch introduced in the fabrication of the artificial molecules from nominally identical constituent quantum wells induces localization by offsetting the energy levels in the quantum dots by up to 2 meV, and this plays a crucial role in the appearance of the addition energy spectra as a function of coupling strength particularly in the weak coupling limit.

Laser-induced forward transfer of liquids: Study of the droplet ejection process

Laser-induced forward transfer (LIFT) is a laser direct-write technique that offers the possibility of printing patterns with a high spatial resolution from a wide range of materials in a solid or liquid state, such as conductors, dielectrics, and biomolecules in solution. This versatility has made LIFT a very promising alternative to lithography-based processes for the rapid prototyping of biomolecule microarrays. Here, we study the transfer process through the LIFT of droplets of a solution suitable for microarray preparation. The laser pulse energy and beam size were systematically varied, and the effect on the transferred droplets was evaluated. Controlled transfers in which the deposited droplets displayed optimal features could be obtained by varying these parameters. In addition, the transferred droplet volume displayed a linear dependence on the laser pulse energy. This dependence allowed determining a threshold energy density value, independent of the laser focusing conditions, which acted as necessary conditions for the transfer to occur. The corresponding sufficient condition was given by a different total energy threshold for each laser beam dimension. The threshold energy density was found to be the dimensional parameter that determined the amount of the transferred liquid per laser pulse, and there was no substantial loss of material due to liquid vaporization during the transfer.

Viral self-assembly as a thermodynamic process

The protein shells, or capsids, of nearly all spherelike viruses adopt icosahedral symmetry. In the present Letter, we propose a statistical thermodynamic model for viral self-assembly. We find that icosahedral symmetry is not expected for viral capsids constructed from structurally identical protein subunits and that this symmetry requires (at least) two internal switching configurations of the protein. Our results indicate that icosahedral symmetry is not a generic consequence of free energy minimization but requires optimization of internal structural parameters of the capsid proteins

Production of Asphalt Rubber Concrete by the Dry Process, HR-1062, 1994

Disposal of used tires has been a problem throughout the United States. The 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) requires the use of recycled rubber in asphalt concrete starting in FY94. A moratorium has delayed this requirement until FY95. The Iowa DOT has researched six projects using crumb rubber modifier in asphalt concrete using the wet process. This process involves using a blender-reactor to blend the asphalt cement and crumb rubber. Using the wet process the asphalt cement has to reach a hotter temperature, than is normally required, for reaction to occur. The wet process is also much more expensive than conventional asphalt. This research deals with using a dry process to incorporate crumb rubber into the asphalt concrete mix. The project was constructed by Western Engineering of Harlan, Iowa, on IA 37 between Earling, Iowa and US 59. It was completed in September 1993. Western Engineering used a double drum mixer to produce the crumb rubber modified asphalt concrete by the dry process. The production and construction went well with minor difficulty and the dry process is a less expensive procedure for producing crumb rubber modified asphalt concrete.

Treating Iowa's Marginal Aggregates and Soils by Foamix Process, HR-212, 1980

Quality granular materials suitable for building all-weather roads are not uniformly distributed throughout the state of Iowa. For this reason the Iowa Highway Research Board has sponsored a number of research programs for the purpose of developing new and effective methods for making use of whatever materials are locally available. This need is ever more pressing today due to the decreasing availability of road funds and quality materials, and the increasing costs of energy and all types of binder materials. In the 1950s, Professor L. H. Csanyi of Iowa State University had demonstrated both in the laboratory and in the field, in Iowa and in a number of foreign countries, the effectiveness of preparing low cost mixes by stabilizing ungraded local aggregates such as gravel, sand and loess with asphalt cements using the foamed asphalt process. In this process controlled foam was produced by introducing saturated steam at about 40 psi into heated asphalt cement at about 25 psi through a specially designed and properly adjusted nozzle. The reduced viscosity and the increased volume and surface energy in the foamed asphalt allowed intimate coating and mixing of cold, wet aggregates or soils. Through the use of asphalt cements in a foamed state, materials normally considered unsuitable could be used in the preparation of mixes for stabilized bases and surfaces for low traffic road construction. By attaching the desired number of foam nozzles, the foamed asphalt can be used in conjunction with any type of mixing plant, either stationary or mobile, batch or continuous, central plant or in-place soil stabilization.