Estudio de las funciones dieléctricas del semiconductor sulfuro de plomo

Hemos calculado la estructura electrónica con la formulación de la funcional densidad, del semiconductor PbS. A partir de ella, calculamos la variación en frecuencia de las funciones dieléctricas en el espectro comprendido entre 0 y 5 eV. Los picos obtenidos, así como la forma general de las curvas correspondientes a las partes real ε 1 e imaginaria ε2, resultan muy bien caracterizados y entendidos en base a los diagramas de bandas y densidades de estados calculados. El espectro dispersivo tiene su punto de inflexión en razonable acuerdo con la energía a la cual la absorción alcanza su máximo y comienza a disminuir, correspondiendo a un comportamiento metálico en el rango de las energías mayores a 3 eV. También presentamos resultados de la reflectividad de este material.Fil: Albanesi, Eduardo Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Repetto, G.H.. Universidad Nacional de Entre Ríos; ArgentinaFil: Peltzer y Blanca, Eitel Leopoldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Dominguez, F.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentin

Report and policy brief: 2nd Annual Conference on Social Aspects of HIV/AIDS Research, Cape Town, 9 - 12 May 2004

This report and policy brief summarises the overarching principles, key findings and suggested policy options that emerged from rapporteur reports of conference proceedings of the 2nd Annual Conference on Social Aspects of HIV/AIDS Research, Cape Town, 9 - 12 May 2004. SAHARA-J (2004) 1(2): 62-77 Keywords: SAHARA Network, Conference proceedings, Policy brief, HIV, AIDS, Sub-Saharan Africa, reseach, Social aspects. RÉSUMÉ Ce dossier de rapport et de politique présente un compte-rendu des principes dominants, des conclusions principales et des options d'une politique proposée qui font partie des communications présentées de la 2è Conférence Annuelle de Recherche sur les Aspects Sociaux du VIH/SIDA, le Cap, 9 - 12 mai 2004. SAHARA-J (2004) 1(2): 62-77 Mots clés: Réseau du SAHARA, démarches de conférence, dossier de politique, HIV/AIDS, Afrique Secondaire-Saharan, reseach, aspects sociaux

Estudio teórico de corrimientos isoméricos en compuestos intermetálicos

En el presente trabajo hemos calculado los corrimientos isoméricos de compuestos intermetálicos formados por Fe y un metal de la serie 3d, tales como: Ti, V, Cr. Mn y Co. Todos los materiales fueron tratados en la estructura B2 (CsCl). Los estudios se realizaron por medio de cálculos teóricos llevados a cabo con el Full Potential Linear Augmented Plañe Wave (FP-LAPW). También se determinaron parámetros propios de los materiales como modulo de bulk y constante de celda de equilibrio. Para el caso del FeV, se han realizado experimentos para comparar con nuestros datos teóricos.In the present work isomer shifts of intermetallic compounds of Fe and transition metal of 3d series, such as: Ti, V, Cr, Mn and Co has been calculated. The materials were treated in the B2(CsCl) structure. Calculation were done by mean of the FP-LAPW . Additionally we have calculated structural parameters, bulk modulus and lattice constant. Experiments on FeV were carried out.Grupo de Estudio de Materiales y Dispositivos ElectrónicosInstituto de Física de Líquidos y Sistemas BiológicosFacultad de Ciencias Exacta

First evaluation of novel potential synergistic effects of glyphosate and arsenic mixture on Rhinella arenarum (Anura: Bufonidae) tadpoles

The toxicity of glyphosate-based herbicide (GBH) and arsenite (As(III)) as individual toxicants and in mixture(50:50 v/v, GBH-As(III)) was determined in Rhinella arenarum tadpoles during acute (48 h) and chronic assays (22days). In both types of assays, the levels of enzymatic activity [Acetylcholinesterase (AChE), Carboxylesterase(CbE), and Glutathione S-transferase (GST)] and the levels of thyroid hormones (triiodothyronine; T3 andthyroxine; T4) were examined. Additionally, the mitotic index (MI) of red blood cells (RBCs) and DNA damageindex were calculated for the chronic assay. The results showed that the LC50 values at 48 h were 45.95 mg/L forGBH, 37.32 mg/L for As(III), and 30.31 mg/L for GBH-As(III) (with similar NOEC ¼ 10 mg/L and LOEC ¼ 20 mg/L between the three treatments). In the acute assay, Marking´s additive index (S ¼ 2.72) indicated synergistictoxicity for GBH-As(III). In larvae treated with GBH and As(III) at the NOEC-48h (10 mg/L), AChE activityincreased by 36.25% and 33.05% respectively, CbE activity increased by 22.25% and 39.05 % respectively, andGST activity increased by 46.75% with the individual treatment with GBH and by 131.65 % with the GBH-As(III)mixture. Larvae exposed to the GBH-As(III) mixture also showed increased levels of T4 (25.67 %). In the chronicassay at NOEC-48h/8 (1.25 mg/L), As(III) and GBH-As(III) inhibited AChE activity (by 39.46 % and 35.65%,respectively), but did not alter CbE activity. In addition, As(III) highly increased (93.7 %) GST activity. GBHAs(III)increased T3 (97.34%) and T4 (540.93%) levels. Finally, GBH-As(III) increased the MI of RBCs andDNA damage. This study demonstrated strong synergistic toxicity of the GBH-As(III) mixture, negatively alteringantioxidant systems and thyroid hormone levels, with consequences on RBC proliferation and DNA damage intreated R. arenarum tadpoles.Fil: Lajmanovich, Rafael Carlos. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Peltzer, Paola. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Attademo, Andres Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; ArgentinaFil: Martinuzzi, Candela Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; ArgentinaFil: Simoniello, María F.. Universidad Nacional del Litoral; ArgentinaFil: Colussi, Carlina Leila. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; ArgentinaFil: Cuzziol Boccioni, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Saneamiento Ambiental. Cátedra de Ecotoxicología; ArgentinaFil: Sigrist, Mirna. Universidad Nacional del Litoral; Argentin

LAPW frozen-phonon calculation, shell model lattice dynamics and specific-heat measurement of SnO

An ab-initio Linear Augmented Plane-Wave (LAPW) calculation of the zone-centered phonon frequencies of SnO has been performed. E$_g$ symmetry has been ascribed to the mode observed at 113 cm$^{-1}$ in Raman measurements, discarding a previous B$_{1g}$ assignement. The other phonon modes measured by Raman spectroscopy are also well reproduced. A new shell-model has also been developed, that gives good agreement of the zone-centered frequencies compared to the measured data and the LAPW results. Specific heat measurements have been performed between 5 K and 110 K. Computation of the specific heat and the M\"{o}ssbauer recoilless fraction with the improved shell-model shows a good agreement with the experimental data as a function of temperature.Comment: 11 pages, 1 figure. to appear in Phys. Rev. B (November 1999

Estudio de las funciones dieléctricas del semiconductor sulfuro de plomo

Hemos calculado la estructura electronica con la formulacion de Iii funcional densidad, del semiconductor PbS. A partir de ella, calculamos la variacion en frecuencia de las funciones dielectricas en el espectro comprendido entre 0 y 5 eV. Los picos obtenidos, asi como la forma general de las curvas correspondientes a las partes real epsilon1 e imaginaria epsilon2, resultan muy bien caracterizadas y entendidos en base a los diagram de bandas y densidades de estados calculados. El espectro dispersivo tiene su punto de inflexion en razonable acuerdo con la energia a la cual la absorcion aJcanza su maximo y comienza a disminuir, correspondiendo a un comportamiento metalico en el rango de las energfas mayores a 3 eV. Tambien presentamos resultados de la reflectividad de este material.We have performed a calculation of the electronic structure within the density functional formalism, of the semiconductor PbS. From it, the dependence in frecuency of the dielectric functions in the range between 0 and 5 eV, is calculated. The peaks, as well as the general shape of the curves corresponding to the real part Si and imaginary part s2, are very well described and understandable in terms of the calculated bands and density of states. The dispersive spectrum has its point of inflexion in reazonably agreement with the energy where the absorption is maximum, and starts decreasing in a metalic like behavior, for energies higher than 3 eV. Also we present results on the reflectivity of this material.Instituto de Física de Líquidos y Sistemas BiológicosFacultad de Ingenierí

Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements

Kinematics of divergent boundaries and Rift-Rift-Rift junctions are classically studied using long-term geodetic observations. Since significant magma-related displacements are expected, short-term deformation provides important constraints on the crustal mechanisms involved both in active rifting and in transfer of extensional deformation between spreading axes. Using InSAR and GPS data, we analyse the surface deformation in the whole Central Afar region in detail, focusing on both the extensional deformation across the Quaternary magmato-tectonic rift segments, and on the zones of deformation transfer between active segments and spreading axes. The largest deformation occurs across the two recently activated Asal-Ghoubbet (AG) and Manda Hararo-Dabbahu (MH-D) magmato-tectonic segments with very high strain rates, whereas the other Quaternary active segments do not concentrate any large strain, suggesting that these rifts are either sealed during interdyking periods or not mature enough to remain a plate boundary. Outside of these segments, the GPS horizontal velocity field shows a regular gradient following a clockwise rotation of the displacements from the Southeast to the East of Afar, with respect to Nubia. Very few shallow creeping structures can be identified as well in the InSAR data. However, using these data together with the strain rate tensor and the rotations rates deduced from GPS baselines, the present-day strain field over Central Afar is consistent with the main tectonic structures, and therefore with the long-term deformation. We investigate the current kinematics of the triple junction included in our GPS data set by building simple block models. The deformation in Central Afar can be described by adding a central microblock evolving separately from the three surrounding plates. In this model, the northern block boundary corresponds to a deep EW-trending trans-tensional dislocation, locked from the surface to 10–13 km and joining at depth the active spreading axes of the Red Sea and the Aden Ridge, from AG to MH-D rift segments. Over the long-term, this plate configuration could explain the presence of the en-échelon magmatic basins and subrifts. However, the transient behaviour of the spreading axes implies that the deformation in Central Afar evolves depending on the availability of magma supply within the well-established segments

Adherence to Tuberculosis Therapy among Patients Receiving Home-Based Directly Observed Treatment: Evidence from the United Republic of Tanzania.

\ud \ud Non-adherence to tuberculosis (TB) treatment is the leading contributor to the selection of drug-resistant strains of Mycobacterium tuberculosis and subsequent treatment failure. Tanzania introduced a TB Patient Centred Treatment (PCT) approach which gives new TB patients the choice between home-based treatment supervised by a treatment supporter of their own choice, and health facility-based treatment observed by a medical professional. The aim of this study was to assess the extent and determinants of adherence to anti-TB therapy in patients opting for home-based treatment under the novel PCT approach. In this cross-sectional study, the primary outcome was the percentage of patients adherent to TB therapy as detected by the presence of isoniazid in urine (IsoScreen assay). The primary analysis followed a non-inferiority approach in which adherence could not be lower than 75%. Logistic regression was used to examine the influence of potentially predictive factors. A total of 651 new TB patients were included. Of these, 645 (99.1%) provided urine for testing and 617 patients (95.7%; 90%CI 94.3-96.9) showed a positive result. This result was statistically non-inferior to the postulated adherence level of 75% (p<0.001). Adherence to TB therapy under home-based Directly Observed Treatment can be ensured in programmatic settings. A reliable supply of medication and the careful selection of treatment supporters, who preferably live very close to the patient, are crucial success factors. Finally, we recommend a cohort study to assess the rate of adherence throughout the full course of TB treatment

Lead exposure in adult males in urban Transvaal Province, South Africa during the apartheid era

Human exposure to lead is a substantial public health hazard worldwide and is particularly problematic in the Republic of South Africa given the country’s late cessation of leaded petrol. Lead exposure is associated with a number of serious health issues and diseases including developmental and cognitive deficiency, hypertension and heart disease. Understanding the distribution of lifetime lead burden within a given population is critical for reducing exposure rates. Femoral bone from 101 deceased adult males living in urban Transvaal Province (now Gauteng Province), South Africa between 1960 and 1998 were analyzed for lead concentration by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Of the 72 black and 29 white individuals sampled, chronic lead exposure was apparent in nearly all individuals. White males showed significantly higher median bone lead concentration (ME = 10.04 µg·g−1), than black males (ME = 3.80 µg·g−1) despite higher socioeconomic status. Bone lead concentration covaries significantly, though weakly, with individual age. There was no significant temporal trend in bone lead concentration. These results indicate that long-term low to moderate lead exposure is the historical norm among South African males. Unexpectedly, this research indicates that white males in the sample population were more highly exposed to lead