Determinació de la ubicació estructural dels ions Yb3+ i Nb3+ en Yb:RTP, Nb:RTP i (Nb,Yb):RTP

Estudi elaborat a partir d’una estada al Stony Brook University al juliol del 2006. El RbTiOPO4 (RTP) monocristal•lí és un material d' òptica no lineal molt rellevant i utilitzat en la tecnologia làser actual, químicament molt estable i amb unes propietats físiques molt destacades, entre elles destaquen els alts coeficients electro-òptics i l'alt llindar de dany òptic que presenta. En els últims anys s’està utilitzant tecnològicament en aplicacions d'òptica no lineal en general i electro-òptiques en particular. En alguns casos ja ha substituït, millorant prestacions, a materials tals com el KTP o el LNB(1). Dopant RTP amb ions lantànids (Ln3+) (2-4), el material es converteix en un material làser auto-doblador de freqüència, combinant les seves propietats no lineals amb les de matriu làser. El RTP genera radiació de segon harmònic (SHG) a partir d’un feix fonamental amb longituds d’ona inferiors a 990 nm, que és el límit que presenta el KTP.La determinació de la ubicació estructural i l’estudi de l'entorn local del ions actius làser és de fonamental importància per a la correcta interpretació de les propietats espectroscòpiques d’aquest material. Mesures de difracció de neutrons sobre mostra de pols cristal•lí mostren que els ions Nb5+ i Ln3+ només substitueixin posicions de Ti4+ (8-9). Estudis molt recents d'EPR (electron paramagnetic resonance) semblen indicar que quan la concentració d'ió Ln3+ es baixa, aquest ió presenta la tendència a substituir l'ió alcalí present a l'estructura (10).Després dels resultats obtinguts en el present treball a partir de la tècnica EXAFS a la instal•lació sincrotò del Brookhaven National Laboratory/State University of New York (Stony Brook) es pot concloure definitivament que els ions Nb s’ubiquen en la posició Ti (1) i que els ions Yb3+ es distribueixen paritariament en les dues posicions del Ti (1 i 2). Aquests resultats aporten una valuosa informació per a la correcta interpretació dels espectres, tant d’absorció com d’emissió, del material i per la avaluació dels paràmetres del seu comportament durant l'acció làser.

Chronic murine myocarditis due to Trypanosoma cruzi: an ultrastructural study and immunochemical characterization of cardiac interstitial matrix

In an attempt to define the mouse-model for chronic Chagas' disease, a serological, histopathological and ultrastructural study as well as immunotyping of myocardium collagenic matrix were performed on Swiss mice, chronically infected with Trypanosoma cruzi strains: 21 SF and mambaí (Type II); PMN and Bolivia (Type III), spontaneously surviving after 154 to 468 days of infection. Haemagglutination and indirect immunofluorescence tests showed high titres of specific antibodies. The ultrastructural study disclosed the cellular constitution of the inflammatory infiltrate showing the predominance of monocytes, macrophages with intense phagocytic activity, fibroblasts, myofibroblasts and abundant collagen matrix suggesting the association of the inflammatory process with fibrogenesis in chronic chagasic cardiomyopathy. Artertolar and blood capillary alterations together with dissociation of cardiac cells from the capillary wall by edema and inflammation were related to ultrastructural lesions of myocardial cells. Rupture of parasitized cardiac myocells contribute to intensify the inflammatory process in focal areas. Collagen immunotyping showed the predominance of Types III and IV collagen. Collagen degradation and phagocytosis were present suggesting a reversibility of the fibrous process. The mouse model seems to be valuable in the study of the pathogenetic mechanisms in Chagas cardiomyopathy, providing that T. cruzi strains of low virulence and high pathogenecity are used.

Codificación a nivel de paquete para comunicaciones móviles por satélite

Una de les opcions que es contemplen per transmetre continguts multimèdia i proporcionar accés a Internet a grups de usuaris mòbils és fer servir satèl·lits. Les condiciones de propagació del canal mòbil impliquen que d'una manera o altra haurem de garantir la qualitat de servei. Això té fins i tot més importància si tenim en compte que, en el cas d'accés a Internet, no es té la capacitat d'assumir cert percentatge de pèrdua de dades que tenim, per exemple, en la transmissió de so o vídeo (rebaixant la qualitat). Entre les principals alternatives per a aquesta classe d’entorns es troba la inclusió de codificacions a nivell de paquet. El funcionament d'aquesta tècnica es basa en incloure a la transmissió paquets redundants, obtinguts mitjançant un determinat algoritme. El receptor podrà recuperar la informació original que es volia enviar, sempre que hagi rebut una certa quantitat de paquets, similar a la quantitat de paquets originals. A aquest mecanisme se'l coneix com Forward Error Correction (FEC) a nivell de paquet. En aquesta memòria es valoren breument les alternatives existents i s'expliquen algunes de les codificacions per a FEC més importants. A continuació es realitza un estudi compartiu d’algunes d'elles: les variants de LDPC (Low Density Parity Check) conegudes com LDGM (Low Density Generator Matrix), i la codificació Raptor

Effects of selection and drift on G matrix evolution in a heterogeneous environment: a multivariate Qst-Fst Test with the freshwater snail Galba truncatula.

Unraveling the effect of selection vs. drift on the evolution of quantitative traits is commonly achieved by one of two methods. Either one contrasts population differentiation estimates for genetic markers and quantitative traits (the Q(st)-F(st) contrast) or multivariate methods are used to study the covariance between sets of traits. In particular, many studies have focused on the genetic variance-covariance matrix (the G matrix). However, both drift and selection can cause changes in G. To understand their joint effects, we recently combined the two methods into a single test (accompanying article by Martin et al.), which we apply here to a network of 16 natural populations of the freshwater snail Galba truncatula. Using this new neutrality test, extended to hierarchical population structures, we studied the multivariate equivalent of the Q(st)-F(st) contrast for several life-history traits of G. truncatula. We found strong evidence of selection acting on multivariate phenotypes. Selection was homogeneous among populations within each habitat and heterogeneous between habitats. We found that the G matrices were relatively stable within each habitat, with proportionality between the among-populations (D) and the within-populations (G) covariance matrices. The effect of habitat heterogeneity is to break this proportionality because of selection for habitat-dependent optima. Individual-based simulations mimicking our empirical system confirmed that these patterns are expected under the selective regime inferred. We show that homogenizing selection can mimic some effect of drift on the G matrix (G and D almost proportional), but that incorporating information from molecular markers (multivariate Q(st)-F(st)) allows disentangling the two effects.

Euclidean geometric invariant of framed knots in manifolds

We present an invariant of a three dimensional manifold with a framed knot in it based on the Reidemeister torsion of an acyclic complex of Euclidean geometric origin. To show its nontriviality, we calculate the invariant for some framed (un)knots in lens spaces. An important feature of our work is that we are not using any nontrivial representation of the manifold fundamental group or knot group.

Cell-matrix interactions in Schistosomal portal fibrosis: a dynamic event

In recent years, one of the most significant progress in the understanding of liver diseases was the demonstration that liver fibrosis is a dynamic process resulting from a balance between synthesis and degradation of several matrix components, collagen in particular. Thus, fibrosis has been found to be a very early event during liver diseases, be it of toxic, viral or parasitic origin, and to be spontaneously reversible, either partially or totally. In liver fibrosis cell matrix interactions are dependent on the existence of the many factors (sometimes acting in combination) which produce the same events at the cellular and molecular levels. These events are: (i) the recruitment of fiber-producing cells, (ii) their proliferation, (iii) the secretion of matrix constituents of the extracellular matrix, and (iv) the remodeling and degradation of the newly formed matrix. All these events represent, at least in principle, a target for a therapeutic intervention aimed at influencing the experimentally induced hepatic fibrosis. In this context, hepatosplenic schistosomiasis is of particular interest, being an immune cell-mediated granulomatous disease and a model of liver fibrosis allowing extensive studies in human and animals as well as providing original in vitro models.

Studies on survival, biological activities and behavior of Biomphalaria glabrata, the host snail of Schistosomiasis, submitted to increased hydrostatic pressure: a technique

To study changes in survival, in biological activities and behavior of planorbids submitted to increased hydrostatic pressure, we developed a technique using two transparent chambers and a hydraulic piston. The apparatus permitted renewal of the liquid medium without substantial variations in pressure, thus eliminating excretion products and maintaining the desired O2 level and thereby permitting us to evaluate the effects of pressure independently of the occurrence of anoxia. Pressure was maintained without any contact of the liquid medium with compressed air, a situation which reproduced with relative fidelity what occurs in nature and assured the presence of the same amounts of gases in the two observation chambers (Control and Experimental). Biomphalaria glabrata was found to be able to survive at least 48 hours when submitted to 49.02 x 10**4 Pa (equivalent to a water depth of 48.8 m), continuing to day egg masses and showing few behavioral changes when compared with the control group.

Extracellular matrix components in peripheral nerve repair: how to affect neural cellular response and nerve regeneration?

Peripheral nerve injury is a serious problem affecting significantly patients' life. Autografts are the "gold standard" used to repair the injury gap, however, only 50% of patients fully recover from the trauma. Artificial conduits are a valid alternative to repairing peripheral nerve. They aim at confining the nerve environment throughout the regeneration process, and providing guidance to axon outgrowth. Biocompatible materials have been carefully designed to reduce inflammation and scar tissue formation, but modifications of the inner lumen are still required in order to optimise the scaffolds. Biomicking the native neural tissue with extracellular matrix fillers or coatings showed great promises in repairing longer gaps and extending cell survival. In addition, extracellular matrix molecules provide a platform to further bind growth factors that can be released in the system over time. Alternatively, conduit fillers can be used for cell transplantation at the injury site, reducing the lag time required for endogenous Schwann cells to proliferate and take part in the regeneration process. This review provides an overview on the importance of extracellular matrix molecules in peripheral nerve repair.

Evaluation of cumulative PCB exposure estimated by a job exposure matrix versus PCB serum concentrations.

Although polychlorinated biphenyls (PCBs) have been banned in many countries for more than three decades, exposures to PCBs continue to be of concern due to their long half-lives and carcinogenic effects. In National Institute for Occupational Safety and Health studies, we are using semiquantitative plant-specific job exposure matrices (JEMs) to estimate historical PCB exposures for workers (n = 24,865) exposed to PCBs from 1938 to 1978 at three capacitor manufacturing plants. A subcohort of these workers (n = 410) employed in two of these plants had serum PCB concentrations measured at up to four times between 1976 and 1989. Our objectives were to evaluate the strength of association between an individual worker's measured serum PCB levels and the same worker's cumulative exposure estimated through 1977 with the (1) JEM and (2) duration of employment, and to calculate the explained variance the JEM provides for serum PCB levels using (3) simple linear regression. Consistent strong and statistically significant associations were observed between the cumulative exposures estimated with the JEM and serum PCB concentrations for all years. The strength of association between duration of employment and serum PCBs was good for highly chlorinated (Aroclor 1254/HPCB) but not less chlorinated (Aroclor 1242/LPCB) PCBs. In the simple regression models, cumulative occupational exposure estimated using the JEMs explained 14-24% of the variance of the Aroclor 1242/LPCB and 22-39% for Aroclor 1254/HPCB serum concentrations. We regard the cumulative exposure estimated with the JEM as a better estimate of PCB body burdens than serum concentrations quantified as Aroclor 1242/LPCB and Aroclor 1254/HPCB.

The Importance of Revenue Sharing for the Local Economic Impacts of a Renewable Energy Project: A Social Accounting Matrix Approach

As demand for electricity from renewable energy sources grows, there is increasing interest, and public and financial support, for local communities to become involved in the development of renewable energy projects. In the UK, “Community Benefit” payments are the most common financial link between renewable energy projects and local communities. These are “goodwill” payments from the project developer for the community to spend as it wishes. However, if an ownership stake in the renewable energy project were possible, receipts to the local community would potentially be considerably higher. The local economic impacts of these receipts are difficult to quantify using traditional Input-Output techniques, but can be more appropriately handled within a Social Accounting Matrix (SAM) framework where income flows between agents can be traced in detail. We use a SAM for the Shetland Islands to evaluate the potential local economic and employment impact of a large onshore wind energy project proposed for the Islands. Sensitivity analysis is used to show how the local impact varies with: the level of Community Benefit payments; the portion of intermediate inputs being sourced from within the local economy; and the level of any local community ownership of the project. By a substantial margin, local ownership confers the greatest economic impacts for the local community.

Constructing a Social Accounting Matrix for Libya

In this paper a Social Accounting Matrix is constructed for Libya for the year 2000. The procedure was divided into three steps. First, a macro SAM was constructed to consistently capture and represent the macroeconomic framework of the Libyan economy in 2000. Second, that macro SAM was disaggregated into a micro SAM incorporating the accounts for individual activities, primary factors and the main economic institutions. But the SAM obtained in this way was not balanced. So in thE final step we balanced the SAM using a cross-entropy procedure in General Algebraic Modelling System (GAMS). This SAM integrates national income, inputoutput, flow-of-funds, and foreign trade statistics into a comprehensive and consistent dataset. The lack of coherent time series data for Libya is a serious obstacle for applied research that uses econometric analysis. Our main intension in constructing this SAM has been one of providing benchmark data for economy-wide analysis using CGE modelling for Libya.

Disaggregating the Household Sector in a 2004 UK Input Output Table and Social Accounting Matrix by Income Quintiles

This paper disaggregates a UK Input-Output (IO) table for 2004 based on household income quintiles from published survey data. In addition to the Input-Output disaggregation, the household components of a UK Income Expenditure (I-E) account used to inform a Social Accounting Matrix (SAM),have also been disaggregated by household income quintile. The focus of this paper is on household expenditure on the UK energy sector.

Analytic approximation of matrix functions in Lp

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