1.48 and 1.84 µm thulium emissions in monoclinic KGd(WO4)2 single crystals

By exciting at 788 nm, we have characterized the near infrared emissions of trivalent thulium ions in monoclinic KGd(WO4)2 single crystals at 1.48 and 1.84 mm as a function of dopant concentration from 0.1% to 10% and temperature from 10 K to room temperature. We used the reciprocity method to calculate the maximum emission cross-section of 3.0310220 cm2 at 1.838 mm for the polarization parallel to the Nm principal optical direction. These results agrees well with the experimental data. Experimental decay times of the 3H4!3F4 and 3F4!3H6 transitions have been measured as a function of thulium concentration.

Assessing changes in Cd phytoavailability to tomato in amended calcareous soils.

A plot study was conducted to assess changes in Cd phytoavailability to a tomato cultivar in an agricultural soil in Southeastern Spain amended in two different ways (A and B), under controlled conditions. The experimental soil corresponded to a fine-loamy carbonatic thermic Calcidic Haploxeroll (Soil Survey Staff, 1998). A) Soil was amended with a single application of sewage sludge from a municipal source that had a total Cd concentration of 0.5 mg kg-1 at a rate that represented a final average concentration in the mixture of soil and sludge of less than 50 µg Cd kg-1. B) The amendment consisted of the addition of a mineral fertiliser with the same amount of NPK as in the sewage sludge application. The final levels of Cd were supposed to be negligible. A plot series without amendments was also performed (C). DTPA plus triethanolamine, and ammonium acetate extractable fractions in soils were analysed for all the plots. The time-dependent Cd accumulation in different parts of the tomato plants was studied by means of a Cd salt treatment. For each block (A, B, and C) four levels of Cd (0, 3, 30, 100 mg kg-1) were added as CdCl2. There was a significant increase in plant Cd after the initial cropping. Tomato stems, leaves and fruits were analysed separately for Cd determination. Differential Cd distribution and accumulation in tomato parts was detected.

Structural factors impacting carrier transport and electroluminescence from Si nanocluster-sensitized Er ions.

We present an analysis of factors influencing carrier transport and electroluminescence (EL) at 1.5 µm from erbium-doped silicon-rich silica (SiOx) layers. The effects of both the active layer thickness and the Si excess content on the electrical excitation of erbium are studied. We demonstrate that when the thickness is decreased from a few hundred to tens of nanometers the conductivity is greatly enhanced. Carrier transport is well described in all cases by a Poole-Frenkel mechanism, while the thickness-dependent current density suggests an evolution of both density and distribution of trapping states induced by Si nanoinclusions. We ascribe this observation to stress-induced effects prevailing in thin films, which inhibit the agglomeration of Si atoms, resulting in a high density of sub-nm Si inclusions that induce traps much shallower than those generated by Si nanoclusters (Si-ncs) formed in thicker films. There is no direct correlation between high conductivity and optimized EL intensity at 1.5 µm. Our results suggest that the main excitation mechanism governing the EL signal is impact excitation, which gradually becomes more efficient as film thickness increases, thanks to the increased segregation of Si-ncs, which in turn allows more efficient injection of hot electrons into the oxide matrix. Optimization of the EL signal is thus found to be a compromise between conductivity and both number and degree of segregation of Si-ncs, all of which are governed by a combination of excess Si content and sample thickness. This material study has strong implications for many electrically driven devices using Si-ncs or Si-excess mediated EL.

Metal dealing at the origin of the Chordata phylum: The metallothionein system and metal overload response in Amphioxus.

Non-vertebrate chordates, specifically amphioxus, are considered of the utmost interest for gaining insight into the evolutionary trends, i.e. differentiation and specialization, of gene/protein systems. In this work, MTs (metallothioneins), the most important metal binding proteins, are characterized for the first time in the cephalochordate subphylum at both gene and protein level, together with the main features defining the amphioxus response to cadmium and copper overload. Two MT genes (BfMT1 and BfMT2) have been identified in a contiguous region of the genome, as well as several ARE (antioxidant response element) and MRE (metal response element) located upstream the transcribed region. Their corresponding cDNAs exhibit identical sequence in the two lancelet species (B. floridae and B. lanceolatum), BfMT2 cDNA resulting from an alternative splicing event. BfMT1 is a polyvalent metal binding peptide that coordinates any of the studied metal ions (Zn, Cd or Cu) rendering complexes stable enough to last in physiological environments, which is fully concordant with the constitutive expression of its gene, and therefore, with a metal homeostasis housekeeping role. On the contrary, BfMT2 exhibits a clear ability to coordinate Cd(II) ions, while it is absolutely unable to fold into stable Cu (I) complexes, even as mixed species. This identifies it as an essential detoxification agent, which is consequently only induced in emergency situations. The cephalochordate MTs are not directly related to vertebrate MTs, neither by gene structure, protein similarity nor metal-binding behavior of the encoded peptides. The closest relative is the echinoderm MT, which confirm proposed phylogenetic relationships between these two groups. The current findings support the existence in most organisms of two types of MTs as for their metal binding preferences, devoted to different biological functions: multivalent MTs for housekeeping roles, and specialized MTs that evolve either as Cd-thioneins or Cu-thioneins, according to the ecophysiological needs of each kind of organisms.

Recollida i emmagatzematge d'aigües al mas Sanmartí de Serraïma (Bages). Gestió sostenible de l'aigua per a usos domèstics, agrícoles i ramaders en relació al gènere

L'article exposa la racionalització i la sostenibilitat en la captació, l'emmagatzematge i el posterior ús de les aigües d'un mas de la Catalunya central. L'estructuració d'una xarxa de recollida d'aigües d'escolament superficial a l'entorn d'un turó proper al mas va permetre l'acumulació de volums d'aigua renovables en una bassa, malgrat l'aridesa climàtica i la pràctica absència de recursos hídrics subterranis. D'altra banda, la recollida de les aigües pluvials es complementava amb les aigües de les teulades connetades a una cisterna interior i amb un pou obert situat al mateix coll del mas. Aquests recursos hídrics permetien uns usos diversificats en relació a les activitats domèstiques, ramaderes i agrícoles que es realitzaven en el mas. Les dones s'ocupaven de les labors de neteja, de l'elaboració del menjar, de la higiene i de l'aviram, mentre que els homes s'encarregavem del bestiar, l'hort i els conreus. El mas Sanmartí constitueix un exemple reeixit d'aquest emmagatzematge divers i dispers d'aigües lligat a un ús sostenible.

Domain matched epitaxial growth of Bi1.5Zn1Nb1.5O7 thin films by pulsed laser deposition

Bi1.5Zn1Nb1.5O7 (BZN) epitaxial thin films were grown by pulsed laser deposition on Al2O3 with a double ZnO buffer layer through domain matching epitaxy (DME) mechanism. The pole figure analysis and reciprocal space mapping revealed the single crystalline nature of the thin film. The pole figure analysis also shows a 60º twinning for the (222) oriented crystals. Sharp intense spots in the SAED pattern also indicate the high crystalline nature of BZN thin film. The Fourier filtered HRTEM images of the BZN-ZnO interface confirms the domain matched epitaxy of BZN with ZnO buffer. An electric field dependent dielectric tunability of 68% was obtained for the BZN thin films with inter digital capacitors patterned over the film.

Adsorption energy and spin state of first-row transition metals adsorbed on MgO(100)

Slab and cluster model spin-polarized calculations have been carried out to study various properties of isolated first-row transition metal atoms adsorbed on the anionic sites of the regular MgO(100) surface. The calculated adsorption energies follow the trend of the metal cohesive energies, indicating that the changes in the metal-support and metal-metal interactions along the series are dominated by atomic properties. In all cases, except for Ni at the generalized gradient approximation level, the number of unpaired electron is maintained as in the isolated metal atom. The energy required to change the atomic state from high to low spin has been computed using the PW91 and B3LYP density-functional-theory-based methods. PW91 fails to predict the proper ground state of V and Ni, but the results for the isolated and adsorbed atom are consistent within the method. B3LYP properly predicts the ground state of all first-row transition atom the high- to low-spin transition considered is comparable to experiment. In all cases, the interaction with the surface results in a reduced high- to low-spin transition energy.

First principles analysis of the stability and diffusion of oxygen vacancies in meetal oxides

Oxygen vacancies in metal oxides are known to determine their chemistry and physics. The properties of neutral oxygen vacancies in metal oxides of increasing complexity (MgO, CaO, alpha-Al2O3, and ZnO) have been studied using density functional theory. Vacancy formation energies, vacancy-vacancy interaction, and the barriers for vacancy migration are determined and rationalized in terms of the ionicity, the Madelung potential, and lattice relaxation. It is found that the Madelung potential controls the oxygen vacancy properties of highly ionic oxides whereas a more complex picture arises for covalent ZnO.

Oxygen vacancies as active sites for water dissociation on rutile TiO2(110)

Through an interplay between scanning tunneling microscopy experiments and density functional theory calculations, we determine unambiguously the active surface site responsible for the dissociation of water molecules adsorbed on rutile TiO2(110). Oxygen vacancies in the surface layer are shown to dissociate H2O through the transfer of one proton to a nearby oxygen atom, forming two hydroxyl groups for every vacancy. The amount of water dissociation is limited by the density of oxygen vacancies present on the clean surface exclusively. The dissociation process sets in as soon as molecular water is able to diffuse to the active site.

Bonding of gold nanoclusters to oxygen vacancies on rutile TiO2(110)

Through an interplay between scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we show that bridging oxygen vacancies are the active nucleation sites for Au clusters on the rutile TiO2(110) surface. We find that a direct correlation exists between a decrease in density of vacancies and the amount of Au deposited. From the DFT calculations we find that the oxygen vacancy is indeed the strongest Au binding site. We show both experimentally and theoretically that a single oxygen vacancy can bind 3 Au atoms on average. In view of the presented results, a new growth model for the TiO2(110) system involving vacancy-cluster complex diffusion is presented.

1.84 micron emission of Tm3+ sensitized by Yb3+ ions in monoclinic KGd(WO4)2 single crystals

By exciting at 940 nm, we have characterized the 1.84 m near infrared emission of trivalent thulium ions in Yb3+, Tm3+:KGd WO4 2 single crystals as a function of the dopant concentration and temperature, from 10 K to room temperature. An overall 3H6 Stark splitting of 470 cm−1 for the Tm3+ ions in the Yb3+, Tm3+:KGd WO4 2 was obtained. We also studied the blue emission at 476 nm Tm3+ and the near infrared emissions at 1.48 m Tm3+ and 1 m Yb3+ as a function of the dopant concentration. Experimental decay times of the 1G4, 3H4, and 3F4 Tm3+ and 2F5/2 Yb3+ excited states have been measured as a function of Yb3+ and Tm3+ ion concentrations. For the 3F4 →3H6 transition of Tm3+ ions, we used the reciprocity method to calculate the maximum emission cross section of 3.07 10−20 cm2 at 1.84 m for the polarization parallel to the Nm principal optical direction.

Gestió integral del manteniment : fonaments i aplicació de la metodologia RCM

El Manteniment entès com a tal té pocs anys d'existència. Els automatismes, la robotització, la complexitat de les màquines, la seva informatització i control, i la millora tecnològica dels materials i dels equips fins a límits desconeguts, entre d'altres, han anat dotant a aquest servei d'una importància cada vegada més creixent en el món empresarial. La Gestió òptima del Manteniment, l'objectiu principal d'aquest treball, és el conjunt de tècniques i sistemes que permeten prevenir les averies, efectuar revisions programades, lubricacions i reparacions efucaces, donant al mateix temps normes i procediements de funcionament als usuaris del sistema productiu, per tal de contribuir i aportar riquesa a l'empresa. Aquest òrgan busca el més convenient per a les màquines, amb l'objectiu d'allargar la seva vida útil de la forma més rendible possible.

Implantació d’una nau industrial destinada a la fabricació de contenidors de reciclatge

El projecte s’ha realitzat a CONSTRUCCIÓ TÈCNICA INDUSTRIAL DEL TERSLU, empresa situada a Aiguaviva, municipi de Girona. Aquesta empresa es dedica a la construcció metàl•lica, però sobretot a la construcción d’estructures metàl•liques lleugeres i pesades, caldereria i manteniment industrial. L’objecte del projecte és buscar un mètode per la reducció del temps de fabricació imillorar la distribució en planta. Per a això s’han d’investigar diferents alternatives icomparar-les entre si per arribar a un resultat final satisfactori. La implantació de la nova distribució en planta com a objectiu final vol aconseguiraugmentar els beneficis globals de l’empresa. Això s.aconsegueix analitzant diferentsdistribucions, l’aplicació de diferents processos de fabricació i muntatge i augmentant lacoordinació entre el departament tècnic i el taller

Las mujeres en paro de larga duración en el Vallès Occidental

Aquest document recull les principals conclusions de l'estudi "Les dones en atur de llarga durada al Vallès Occidental". La perspectiva teòrica que orienta la investigació és la que considera el treball en la seva doble vessant productiva i reproductiva, entenent que la càrrega de treball reproductiu que acostumen a suportar les dones condiciona no només les seves possibilitats reals de treballar en el mercat sinó també les seves actituds davant d'aquest. Per tal de copsar la diversitat de situacions laborals i familiars de les dones en atur s'ha construit una tipologia d'oportunitats davant el mercat en la qual es consideren conjuntament la trajectòria sòcio-laboral i la trajectòria familiar de les treballadores. Els perfils tipus que n'han resultat han estat contrastats amb els resultats d'una anàlisi del mercat de treball de la comarca - dades d'oferta i demanda d'ocupació i entrevistes semi-dirigides als principals actors sòcio-econòmics. Les conclusions de l'estudi mostren l'existència d'un comportament laboral femení mitjançant per conductes pròpies de l'àmbit domèstic, per la qual cosa les estratègies de demanda d'ocupació de le dones se situen a l'entorn de la definició de le seves possibilitats professionals segons la magnitud i les característiques de la seva càrrega domèstica i la seva situació familiar. Això provoca l'acumulació de dones en el que podem anomenar una feble posició de mercat.

Excavacions arqueologiques al jaciment d'Abasiya. Recerca, interpretació i projecte de conservació d'un conjunt arqueológic a Karima, Sudan

Remuntant el riu Nil es troba la muntanya sagrada de Dyebel Bar kal identificada pels egipcis i pels nubis com el lloc on va néixer el déu Aman. Els fa raons egipcis durant la XVIII dinastia van construir un temple dedicat a aquesta divinitat ¡ van fer d'aquesta zona (coneguda a I'antiguitat amb el nomde Napata) un dels principals centres religiosos de I'antiga Núbia. La historia compartida entre Núbiai Egipte compren segles de relacions i va culminar amb la conquesta egípcia que va suposar una egiptizació dels costums nubis. Tant es així que després d'alguns segles, els reis nubis van unificarels territoris i es van proclamar faraons de les dues terres.El jaciment arqueològic d'Abasiya que pertany a I'àrea arqueològica de Dyebel Barkal (Figura 1)es troba en la actual ciutat de Karima, a uns 400km de Khartum la capital de Sudan. És avuien dia una plac;a urbana de Karima a només700m de I'àrea arqueològica de DyebelBarkal, on simultàniament estan treballantequips arqueològics de diferents països.Abasiya compren, fins el moment, quatresectors que corresponen a I'acumulació derestes arquitectòniques. Durant 5 campanyes s'han excavat totalment els sectors A, CiD, i parcialment el Sector B, que encara esta en procés d'excavació.