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Ammoniacal thiosulfate has been used lately as an alternative lixiviant for leaching gold from sulfides ores which are not amenable for cyanidation. However, the oxidation of the sulfide minerals generates products that inhibit the dissolution of gold and can promote the degradation of the leaching solution. The complexity of the ammoniacal thiosulfate leaching system has prevented the unification and clarification of the mechanisms of oxidation of sulfide ores used for gold extraction. In this study, a method combining polarization curves, Electrochemical impedance spectroscopy (EIS), and in situ Raman spectroscopy was implemented to investigate the oxidation process of high-purity pyrite. Pyrite samples were dispersed in carbon paste electrode (CPE-Py). The polarization curves of CPE-Py exhibited an increase in current values for overpotentials greater than 0.1 V, indicating the initiation of mineral oxidation processes. Subsequently, a maximum current was observed initially, followed by subsequent decrease, indicating the occurrence of passivation processes on the electrode surface. Hydrodynamic polarization curves demonstrated that the overpotential at which the passivation process occurs is independent of mass transport, suggesting that the passivation products were formed through solid-state transformation. Impedance spectra revealed that at overpotentials below 0.1 V, a partially resolved capacitive semicircle was observed, which was associated with the resistance encountered when charge was transferred between the solution and the surface layer interface. This resistance decreased as the polarization overpotential increased, implying a decrease in charge transfer kinetics. At higher overpotentials (0.3 V-0.4 V), a second capacitive semicircle appeared, linked to the oxidation of one or several species present in the mineral. In situ Raman spectroscopy was utilized to identify the oxidation species of pyrite in ammonia-thiosulfate ((NH4)2S2O3) leaching solution at a pH = 10.2. The composition of the species varied depending on the applied anodic potential. At low anodic potentials (0.1 V), Fe(OH)2 and thiosulfate (S2O32-) were formed, while at high anodic potentials (0.4 V), iron products such as Fe3O4 and γ-FeOOH, as well as sulfide species including thiosulfate, tetrathionates and sulfates (S2O32-, S4O6-2 and SO42-) were formed.

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This work present structural, morphological, magnetic, and electrical properties of GaSb/Mn multilayer deposited via DC magnetron sputtering at room temperature and at 423 K. The samples are characterized by forming layers of 3, 6 and 12 periods of the GaSb/Mn structure. Through XRD patterns, it was possible to stablish the formation of GaSb, Mn3Ga, and Mn2Sb2 phases. FTIR measurements present an optical interference associated with periodicity and the homogenous thickness of the layers. HR-SEM shows the multilayer architecture with columnar microstructure in the formation of layers with grain nucleation on the surface. A ferromagnetic-like behavior was observed in the multilayers at room temperature related to the domains and interlayers interaction. Additionally, the hysteresis curves present shifts attributed to the effect of exchange bias coupling. I-V curves show RESET-SET states of the multilayer system with bipolar resistive behavior, which can be modified by external magnetic fields. The resistive switching evidenced corresponds to the conductive mechanism based on the capacitive conductance and the formation of conductive filaments in multilayer structure.

RESUMO

Due to the increased use of environmentally friendly fuels, it becomes imperative to evaluate the impact of biofuels on the performance of materials used in auto parts. The corrosive effects of biofuels are important in terms of durability of auto-parts since there is an evidence of the increasing deterioration in automobile parts with the long-term use of biofuels. In this research, the behavior of metals, used in the manufacturing of auto parts, in pure bioethanol (E100) and bioethanol-gasoline blends with 30% (E30), 50% (E50), and 85% (E85) of ethanol content were evaluated. Electrochemical impedance Spectroscopy (EIS) curves were done under static conditions at 45 °C. The metallic materials evaluated were stainless steel, tin, carbon steel and copper. The EIS diagrams showed two capacitive arcs for all materials. The high frequency arc was related to the dielectric response of the fuel blends, while the second one shows the characteristics and activity of the metal/fuel interface. According to the transfer resistance (Rt) obtained from the second arc of the EIS measurements, copper and carbon steel exhibited corrosion susceptibility in all fuel blends, while stainless steel and tin showed good anticorrosion behavior by showing high Rt values. The highest charge transfer resistance was showed by tin, followed by stainless steel, carbon steel and copper. Except for carbon steel and copper, the other set samples were compatible with the evaluated blends.

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RESUMEN Antecedentes: el carcinoma de células de Hürtlhe (CCH) de la glándula tiroides representa el 0,4-10% de los tumores diferenciados de tiroides. Se trataría de un carcinoma diferenciado de entidad propia. El tratamiento resulta controvertido dado que no existen estudios controlados prospectivos aleatorizados que validen la extensión de la tiroidectomía y la eficacia del tratamiento adyuvante con yodo radiactivo o radioterapia. Objetivo: analizar los factores pronósticos y de tratamiento que afectan la supervivencia del CCH. Material y métodos: se llevó a cabo una revisión sistemática de las bases MEDLINE, EMBASE COCHRANE y LILACS-BIREME con el objetivo de encontrar literatura relevante con respecto a los factores de riesgo y pronóstico que influyen en la supervivencia. Resultados: se identificaron el género masculino, tamaño tumoral > 4 cm, la invasión ganglionar y extratiroidea y las metástasis a distancia como factores de mal pronóstico. La tiroidectomía total muestra una tendencia favorable a la mayor supervivencia. Conclusión: el manejo de los pacientes con CCH continúa presentando aspectos controvertidos. Se requieren investigaciones a gran escala sobre tratamientos multimodales. El Registro Nacional abierto a todos los cirujanos por la AACCyC, cuyos resultados se conocerán en 2023, podrían aportar evidencias de mayor calidad. Los autores son conscientes de que esta presentación contiene fortalezas y debilidades. Entre las primeras, es el primer metanálisis que se realiza sobre factores pronóstico y de supervivencia del CCH; sin embargo, el grado de heterogeneidad de los trabajos resulta muy alto para algunas variables y no ha sido posible incluir otros factores de riesgo que puedan afectar el pronóstico.

ABSTRACT Background: Hürthle cell carcinoma (HCC) of the thyroid gland, which accounts for about 0.4-10% of all differentiated thyroid cancer, is considered differentiated carcinoma with a distinct entity. The treatment of this disease is controversial since there are no prospective randomized controlled trials validating the extent of thyroidectomy and the efficacy of adjuvant treatment with radioactive iodine or radiation therapy. Objective: The aim of this study is to analyze the prognostic factors affecting survival of patients with HCC. Material and methods: We performed an electronic search in MEDLINE, EMBASE, COCHRANE, and LILACS-BIREME databases to find relevant literature regarding risk and prognostic factors affecting survival. Results: Male sex, tumor size > 4 cm, lymph node involvement, extrathyroid extension and distant metastases were associated with adverse outcome. Total thyroidectomy showed a trend toward higher survival. Conclusions: The management of patients with HCC is still controversial. Large-scale research on multimodal treatments is required. The AACCyC national registry which is opened to all surgeons will provide high quality evidence on the matter. The authors are aware of the strengths and weaknesses of this presentation. This is the first meta-analysis on risk factors and survival of HCC; however, the degree of heterogeneity of the studies was very high for some variables and it was not possible to include in this analysis other risk factors that could affect the prognosis.

RESUMO

In this work, a detailed study of structural, electrical and magnetic characterization of (GaMn)Sb diluted magnetic semiconductors (DMS) is presented. (GaMn)Sb thin films were grown by DC magnetron co-sputtering method as an innovative procedure to fabricate III-V DMS. The presence of unusual Mn2Sb2 and Mn2Sb secondary phases, induced by substrate temperature and deposition time, were revealed through XRD measurements. Magnetization measurements allow determining crossover between a paramagnetic-like to a ferromagnetic-like behavior controlled by secondary phases. It was found that both, the magnetic remanence and magnetic coercivity, increases with substrate temperature. Interestingly, the magnetic response is paramagnetic at lower deposition times and substrate temperatures, and XRD measurements suggest the absence of Mn2Sb and Mn2Sb2 in secondary phases. For longer deposition times or higher substrate temperature, XRD shows the presence of Mn2Sb2 and Mn2Sb phases and ferromagnetic-like behavior. The DC resistivity of our samples was characterized and the carrier density was determined by Hall measurements and, in contrast with the reported in other studies, found them to be a p-type semiconductor with carrier densities as big as one order of magnitude larger than reported values. From the ferromagnetic-like samples, evidence of an anomalous Hall-effect in the sample was found, with higher magnetic saturation and a anomalous Hall conductivity of 2380 S/cm. All the results point to a contribution of the secondary phases to the overall magnetic response of the samples used, and suggest the importance of studying the formation of secondary phases in the growth of DMS, especially, for the case of (GaMn)Sb where Mn ion can have multiple oxidation states.

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RESUMO

The aim of the present work is to evaluate the impact of pure palm biodiesel fuel (B100) and biodiesel blends with 0.32% oleic, palmitic, acetic, myristic, and stearic acids on the properties of some polymeric materials used commonly in the manufacture of auto parts such as the polyamide 66 (PA66), polyoxymethylene (POM), and high-density polyethylene (HDPE). The effects of the B100 and B100⁻acid blends on polymeric materials were examined by comparing changes in the gain/loss of mass and by measuring the hardness, the impact strength, and the tensile strength of the materials at the end of the exposure. The characterization of the polymers was carried out before and after exposure by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). After the immersion in B100⁻acids blends, the HDPE exhibited an increase in mass of 5%, which was very similar in all blends. The PA66 showed a small decrease in weight (2% approx.) in all mixtures. The POM presented an increase in the percentage of weight in the mixture of B100 with acetic acid of 0.3%. A decrease was observed in the crystallinity of the HDPE when exposed to blends of B100⁻acids. This behavior may be associated with a plasticizing effect in the HDPE exposed to the blends. The mechanical properties of POM and HDPE showed no significant changes after immersion in the fuels. On the other hand, PA66 exhibited a significant decrease in maximum stress value after immersion in B100, B100⁻oleic acid and B100⁻palmitic acid blends. The variation of the mechanical properties of the PA66 after exposure to B100 was potentiated by addition of organic acids. The assessed polymers did not undergo appreciable changes in the chemical structure of the samples after immersion in the fuels, so the variation in the mechanical properties could be explained by physical absorption of the fuel into the polymers.

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OBJECTIVE:: Sedation/somnolence are major side effects of pharmacotherapies for depression, and negatively affect long-term treatment compliance in depressed patients. Use of mirtazapine (MIR), an atypical antidepressant approved for the treatment of moderate to severe depression with comorbid anxiety disorders, is associated with significant sedation/somnolence, especially in short-term therapy. Nonetheless, studies with human subjects suggest that MIR-induced sedation is transient, especially when high and repeated doses are used. The purpose of this study was to explore the effects of acute and chronic administration of different doses of MIR on sedation in the rat. METHODS:: Assessment of sedation was carried out behaviorally using the rotarod, spontaneous locomotor activity, and fixed-bar tests. RESULTS:: A 15-mg/kg dose of MIR induced sedative effects for up to 60 minutes, whereas 30 mg/kg or more produced sedation within minutes and only in the first few days of administration. CONCLUSION:: These results suggest that 30 mg/kg is a safe, well-tolerated dose of MIR which generates only temporary sedative effects.

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Se fabricaron películas del compuesto cuaternario Cu2ZnSnSe4 por el método de co-evaporación de los precursores cobre, estaño y seleniuro de zinc en presencia de una atmosfera de selenio. Las muestras fueron depositadas sobre sustratos de vidrio tipo soda lime. A partir de las medidas de difracción de rayos X se estableció, que la fase que caracteriza el compuesto es sensible a cambios en los parámetros de síntesis afectando la estructura del material. Se detallaron propiedades estructurales como distancia interplanar, planos cristalinos, tamaños del cristalito y posiciones atómicas de los elementos del compuesto; a través de la comparación de las estructuras estannita y kesterita asociadas al crecimiento del Cu2ZnSnSe4. El análisis comparativo entre las estructuras, permitió determinar la tipo estannita como la que cristaliza el material. Usando el método Rietveld y programas de cómputo se logró simular la estructura estannita obtenida; evidenciando diferencias sutiles con la estructura kesterita.

We fabricated quaternary compound, Cu2ZnSnSe4, films by co-evaporation of copper, tin and zinc selenide precursors in a selenium atmosphere and deposited the samples on soda-lime glass substrates. From the x-ray diffraction data, we established that the phase that characterizes the compound is sensitive to changes in the synthesis parameters and affects the structure of the material. Through a comparison of stannite and kesterite structures associated with Cu2ZnSnSe4 growth, we detailed structural properties such as interplanar distance, crystal planes, crystallite size and the atomic position of the elements of the compound. A comparative analysis of the structures revealed that the stannite is the crystallizing material. Using the Rietveld method and software we were able to simulate the stannite structure establishing subtle differences with the kesterite structure.

Fabricaram-se filmes do composto Cu2ZnSnSe4 pelo método de co-evaporação dos percursores cobre, estanho e seleneto de zinco na presença de uma atmosfera de selênio. As amostras foram depositadas sobre substratos de vidro tipo soda lime. A partir das medidas de difração de raios X se estabeleceu que a fase que caracteriza o composto é sensível a alterações nos parâmetros de síntese afetando a estrutura do material. Detalharam-se propriedades estruturais como distancia interplanar, planos cristalinos, tamanhos do cristalito e posições atómicas dos elementos do composto; através da comparação das estruturas estannita e kesterita associadas ao crescimento do Cu2ZnSnSe4. A análise comparativa entre as estruturas, permitiu determinar o tipo Estannita como a que cristaliza o material. Utilizando o método Rietveld e programas de computação conseguiu-se simular a estrutura estannita obtida; mostrando diferenças subtis com a estrutura kesterita.

RESUMO

El presente trabajo pretende hacer un aporte al conocimiento del comportamiento electroquímico de recipientes de hojalata en medio del ion citrato, y al papel que juega la concentración de dicho ion en la estabilidad de los recipientes. Todo ello, a través del estudio electroquímico individual de los materiales con los cuales son fabricados los recipientes de hojalata, acero y estaño. El estudio se llevó acabo mediante medidas de polarización potenciodinámica e impedancia electroquímica sobre electrodos fabricados con ambos materiales e inmersos en soluciones de diferentes concentraciones de citrato a un valor de pH de 3,0. Se evidencia que a este valor de pH, el ion citrato ejerce un notable efecto de despolarización anódica sobre el estaño, por la formación de complejos solubles y estables. Esto hace que el estaño se torne anódico respecto al acero pudiendo otorgar una protección anticorrosiva al sustrato de acero de los recipientes de hojalata.

The present work tries to do a contribution to the knowledge of the electrochemical behavior of tinplate containers in citrate ion medium and the role that citrate ion concentration plays on the stability of the containers; all that, through the individual electrochemical study of the materials of which the tinplate is made, steel and tin. The study was done by potentiodynamic polarization and electrochemical impedance on electrodes made with both materials, immersed in solutions of different citrate concentrations at pH 3,0. It was evidenced that the citrate ion has a remarkable effect of anodic depolarization on tin with the formation of soluble and stable complexes. This causes that tin becomes anodic with respect to the steel being able to grant an anticorrosive protection to the steel substrate of the tinplate containers.

O presente trabalho tem como objetivo contribuir com o conhecimento do comportamento eletroquímico da folha de flandes em meios contendo íons citrato, bem como o papel que a concentração de íon citrato desempenha na estabilidade dos recipientes. Os estudos eletroquímicos foram conduzidos a partir dos materiais individuais que constituem o ferro estanhado, ou seja, o aço e o estanho. Os experimentos foram realizados utilizando- se técnicas de polarização potenciodinâmica e de impedância eletroquímica em eletrodos formados, separadamente, por aço e estanho que permaneceram imersos em soluções de citrato, a pH 3,0 com diferentes concentrações. Foi evidenciado que o íon citrato apresenta um efeito notável de depolarização anódica no estanho pela formação de complexos estáveis e solúveis. Consequentemente, o estanho se torna anódico em relação ao aço e oferece uma proteção anticorrosiva aos substratos de aço que constituem os recipientes de ferro estanhado.