Ore paragenesis of the Tajo Vein, Paramillos de Uspallata ore deposit, Mendoza Province, Argentina

La Veta Tajo forma par te del yacimiento Paramillos de Uspallata (32°28’29.6”S; 69°08’46”O), ubicado en la Precordillera Occidental de la provincia de Mendoza. Este yacimiento está formado por un conjunto de vetas con mineralización de Pb-Zn-Ag hospedadas en basaltos triásico-jurásicos y en sedimentitas triásicas. Los estudios mineraló- gicos (microscopía óptica convencional y SEM-EDX) realizados sobre muestras provenientes de la veta Tajo permitieron determinar que la paragénesis de mena está compuesta por galena argentífera, esfalerita, calcopirita, tetraedrita, freibergita, boulangerita, owyheeita, pirita, arsenopirita y marcasita así como la existencia de dos pulsos de mineralización, un primer pulso principalmente de Pb-Zn-Ag-(Cu) en ganga carbonática y un segundo pulso estéril en ganga de cuarzo. Por otra parte los análisis de química mineral permitieron determinar la composición de los minerales de mena y de esta forma establecer cuáles son aquellos portadores de Ag.The Tajo Vein is par t of the Paramillos de Uspallata ore deposit (32°28’29.6”S; 69°08’46”W) that is located in the Western Precordillera of Mendoza Province. This ore deposit consists of Pb-Zn-Ag veins hosted by Triassic-Jurassic basalts and Triassic sedimentary rocks. Mineralogical studies (optical microscopy and SEM-EDX analyses) carried out on samples from the Tajo Vein allowed the identification of an ore paragenesis consisting of Ag-galena, sphalerite, chalcopyrite, tetrahedrite, freibergite, boulangerite, owyheeite, pyrite, arsenopyrite and marcasite, occurring in two mineralization stages, the first consisting of Pb-Zn-Ag-(Cu) mineralization with a carbonate gangue and the barren second one with a quartz gangue. Chemical analyses allowed to determine the composition of the ore minerals and the Ag-bearing phases.Fil: Carrasquero, S. I.. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Rubinstein, Nora Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Bevins, R. E.. National Museum of Wales; Reino Unid

Sliding wear of a-C:H coatings against alumina in corrosive media

This paper reports the results obtained from the study of friction and sliding wear in two corrosive solutions of an a-C:H coating deposited on 316L stainless against an alumina ball, employed as static counter part. Calculations of the values of the von Mises stresses developed at the coating–substrate interface, as soon as the ball touches the coated sample, and how this state of stress influences the response of the coated system under the corrosion environment, are presented and discussed. The results obtained from these calculations, as well as from the experiments conducted in the present research, are compared with other experiments published in the literature, where a-C:H coatings deposited on different substrates and with different coating architectures were tested in similar corrosive media. It has been determined that in those systems, where the von Mises stress in the coating, found in the vicinity of the interface, exceeds the threshold value of approximately 370MPa, coating failure with spallation will take place, regardless of the substrate nature on which this coating has been deposited. From this analysis it has been concluded that the coating yield strength is of utmost importance in conferring the a-C:H coated system there quired stability in a corrosive solution

Ore paragenesis of the Tajo Vein, Paramillos de Uspallata ore deposit, Mendoza Province, Argentina

La Veta Tajo forma par te del yacimiento Paramillos de Uspallata (32°28’29.6”S; 69°08’46”O), ubicado en la Precordillera Occidental de la provincia de Mendoza. Este yacimiento está formado por un conjunto de vetas con mineralización de Pb-Zn-Ag hospedadas en basaltos triásico-jurásicos y en sedimentitas triásicas. Los estudios mineraló- gicos (microscopía óptica convencional y SEM-EDX) realizados sobre muestras provenientes de la veta Tajo permitieron determinar que la paragénesis de mena está compuesta por galena argentífera, esfalerita, calcopirita, tetraedrita, freibergita, boulangerita, owyheeita, pirita, arsenopirita y marcasita así como la existencia de dos pulsos de mineralización, un primer pulso principalmente de Pb-Zn-Ag-(Cu) en ganga carbonática y un segundo pulso estéril en ganga de cuarzo. Por otra parte los análisis de química mineral permitieron determinar la composición de los minerales de mena y de esta forma establecer cuáles son aquellos portadores de Ag.The Tajo Vein is part of the Paramillos de Uspallata ore deposit (32°28’29.6”S; 69°08’46”W) that is located in the Western Precordillera of Mendoza Province. This ore deposit consists of Pb-Zn-Ag veins hosted by Triassic-Jurassic basalts and Triassic sedimentary rocks. Mineralogical studies (optical microscopy and SEM-EDX analyses) carried out on samples from the Tajo Vein allowed the identification of an ore paragenesis consisting of Ag-galena, sphalerite, chalcopyrite, tetrahedrite, freibergite, boulangerite, owyheeite, pyrite, arsenopyrite and marcasite, occurring in two mineralization stages, the first consisting of Pb-Zn-Ag-(Cu) mineralization with a carbonate gangue and the barren second one with a quartz gangue. Chemical analyses allowed to determine the composition of the ore minerals and the Ag-bearing phases.Instituto de Recursos Minerale

The character of fracture of iron based thermal coating during fretting

The character of destruction of thermal coatings during fretting has been investigated. An iron based plasma coating has been tested with oscillation amplitude from 30 to 200 microns. The tests were conducted in air. It has been determined that the main factor influencing the rate of the wear of the coating during fretting corrosion is the size of the coating area involved into the wear process. The coating exhibits high wear resistance when the amplitude of the oscillation is commensurate with the size of the sprayed particles. During destruction of the coating the leading role belongs to fatigue-oxidation processes. The wear of the coating acquires a catastrophic character when coating macro defects - pores and interlayer boundaries - are involved into the wear process

ALMIDONES HIDRÓFOBOS

Polymers of natural origin such as starch have been seen by many authors as an attractive and viable alternative as substitutes for some synthetic polymers, since they and their derivatives are not very harmful to the environment and their use could reduce the pollution produced by polymers petroleum derivatives. However, due to its hydrophilic nature, its properties are compromised by the degree of humidity in the environment, which constitutes a very important limitation when developing products derived from it. It is for this reason that different chemical modification methods have been developed in order to convert it into a hydrophobic material, which makes it easier not only to obtain products resistant to humidity, but also to hydrolytic degradation. This, in addition, allows the obtaining of materials that are easier to mold and friendly to the environment and, therefore, useful for the manufacture of utensils. In this review, many of the advances obtained in the different routes of chemical modification directed towards the synthesis of hydrophobic starches are presented, especially the obtaining of etherified and esterified starches, emphasizing especially the influence of the means of synthesis and the conditions of reaction.Polímeros de origen natural como el almidón han sido vistos por muchos autores como una alternativa atractiva y viable como sustitutos de algunos polímeros sintéticos, ya que ellos y sus derivados resultan ser poco nocivos para el medio ambiente y su uso podría reducir la contaminación producida por polímeros derivados del petróleo. Sin embargo, debido a su carácter hidrófilo sus propiedades se ven comprometidas con el grado de humedad del ambiente, lo cual constituye una limitación muy importante a la hora de desarrollar productos derivados del mismo. Es por esta razón que se han desarrollado diferentes métodos de modificación química con la finalidad de convertirlo en un material hidrófobo, lo que facilita no solo obtener productos resistentes a la humedad, sino también a la degradación hidrolítica. Esto, además, permite la obtención de materiales más fáciles de moldear y amigables con el medio ambiente y, por lo tanto, útiles para la fabricación de utensilios. En esta revisión se presentan muchos de los avances obtenidos en las diferentes vías de modificación química dirigidas hacia la síntesis de almidones hidrófobos, en especial la obtención de almidones eterificados y esterificados, haciendo énfasis especialmente en la influencia de los medios de síntesis y las condiciones de reacción

Structural Basis of Teneurin-Latrophilin Interaction in Repulsive Guidance of Migrating Neurons

Teneurins are ancient metazoan cell adhesion receptors that control brain development and neuronal wiring in higher animals. The extracellular C terminus binds the adhesion GPCR Latrophilin, forming a trans-cellular complex with synaptogenic functions. However, Teneurins, Latrophilins, and FLRT proteins are also expressed during murine cortical cell migration at earlier developmental stages. Here, we present crystal structures of Teneurin-Latrophilin complexes that reveal how the lectin and olfactomedin domains of Latrophilin bind across a spiraling beta-barrel domain of Teneurin, the YD shell. We couple structure-based protein engineering to biophysical analysis, cell migration assays, and in utero electroporation experiments to probe the importance of the interaction in cortical neuron migration. We show that binding of Latrophilins to Teneurins and FLRTs directs the migration of neurons using a contact repulsion-dependent mechanism. The effect is observed with cell bodies and small neurites rather than their processes. The results exemplify how a structure-encoded synaptogenic protein complex is also used for repulsive cell guidance

Molecular dynamics in nanophase-separated comb-like poly(α- n-alkyl β-L-aspartate)s

A series of poly(α-n-alkyl β-L-aspartates) which are nanophase self-assembled comb-like polymers has been studied by dielectric spectroscopy in a broad frequency range ( 10-2≤ν≤3×106 Hz), with n-alkyls side chains of various lengths, 10≤n≤18. In every member of the series the same relaxations were identified after the decomposition of the experimental isothermal trace in up to three peaks with relaxation times distributions. The strength, width and average relaxation time for all the relaxation modes were determined for each material. Besides the local low temperature, Arrhenius modes, two relaxation modes, α and αPE, present a cooperative character whose dynamics are not affected by the side chains melting. The αPE relaxation is a polyethylene-like glass transition of the amorphous side chains and its dynamics is strongly dependent on the n value due to the increasing restrictions imposed by the self-assembled confinement. The strength of the αPE relaxation mode increases as the lateral chains loose their 2D order. The restricted chopstick motion of the rigid rods is thought to be the origin of the α mode; this motion is hindered at temperatures where the cage size decreases as a result of the increasing disorder with temperature

ESTUDIO DEL DETERIORO CORROSIVO DE COMPONENTES DE ENSAMBLAJE EN TORRES DE TRASMISIÓN DE ALTA TENSIÓN

The objective of this work was to characterize the corrosive deterioration of the galvanizedcomponents of assembly of the structure of an electrical power transmission tower. For this, a visualinspection accompanied by a metallographic analysis, thickness measurement of the galvanized,morphological analysis by scanning electron microscopy (SEM) with chemical microanalysisby dispersive energy (EDX) was carried out. The results obtained show that the metal components evaluated have two clearly differentiable zones in terms of surface tonality: a clear and a dark zone, which indicates the presence of a preferential corrosive deterioration of the coating. The microanalysis by EDX carried out in these zones shows that the damage by corrosion and the consequent loss of thickness of the zinc protective coating of the evaluated components is associated with the presence of atmospheric pollutants. It is concluded that the capacity of protection against corrosion of the galvanized remaining in function of the aggressiveness of the environment to which they are exposed by the proximity of an industrial zone, is one of the main causes of the deterioration. Keywords: Galvanized, transmission towers, corrosion, contaminants, industrial atmosphere. References [1]M. Morcillo, J. Alcántara, I. Díaz, B. Chico, J.Simancas and D. Fuente, “Marine atmospheric corrosion of carbon steels”, Revista de Metalurgia, Vol. 44, no 2, pp 045, 2015. [2].M. Morcillo, M. Almeida, F. Fragata and Z. Panossian, “Corrosión y Protección de los Metales en Atmosferas de Iberoamérica”, Tomo I, España, Ed. Proyecto CYTED, 2002, pp 779. [3].F. Cadena, L. Irusta b and M.J. Fernandez-Berridib, “Performance evaluation of alkyd coatings for corrosion protection in urban and industrial environments”, Progress in Organic Coatings, Vol.76, pp 1273- 1278, 2013. [4].L. Linares, “Evaluación de la corrosividad atmosférica y su efecto en los cables de transmisión eléctrica a 400kV de CVG EDELCA”, Tesis de Maestría. Universidad del Zulia. Maracaibo, Venezuela, 2007. [5].J. Guerra, A. Castañeda and J. Howland, “Estudio preliminar de la agresividad corrosiva de la atmósfera en el puente de los Caras, Manabí, Ecuador”, Revista CENIC Ciencias Químicas, Vol. 47, pp. 17-29, 2016. [6].D. J. Pazmiño, “Análisis y diseño estructural de una torre de transmisión eléctrica para el proyecto hidroeléctrico Angamarca-Sinde 32MW, Cantón Pangua, provincia de Cotopaxi”. Tesis de grado. Universidad Central del Ecuador, Ecuador, 2016. [7]Norma ISO 1463, 2003, “Metallic and oxide coatings-Measurement of coatings thickness-Microscopical Method”, ISO, Genève, Switzerland. [8]Norma ASTM E 45, 2005, “Standard Test Methods of Determining the Inclusion Content of Steel”, ASTM International, West Conshohocken, PA. [9]Norma ASTM A -36, 2003, “Standard Specification for Carbon Structural Steel”, ASTM International, West Conshohocken, PA. [10]Norma ASTM A 123/A, 2000, “Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products”, ASTM International, West Conshohocken, PA. [11]Norma ASTM A 153, 2003, “Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware”, ASTM International, West Conshohocken, PA. [12]Y. Rico and E. Carrasquero, “Efecto de la composición química en el comportamiento mecánico de recubrimientos galvanizados por inmersión en caliente: una revisión”, Ingenius, N°18, pp. 30-39, 2017. [13].M. Morcillo, M. Almeida, F. Fragata and Z. Panossian, “Corrosión y Protección de los Metales en Atmosferas de Iberoamérica”, Tomo II, España, Ed. Proyecto CYTED, pp 441-494. 2002.El objetivo del presente trabajo fue caracterizar el estado de deterioro corrosivo de los componentes galvanizados de ensamblaje de la estructura de una torre de transmisión de energía eléctrica. Para ello se realizó en primera instancia una inspección visual acompañado de un análisis metalográfico,medición de espesor del galvanizado, análisis morfológico por microscopia electrónica de barrido (MEB) con microanálisis químico por energía dispersiva (EDX). Los resultados obtenidos evidencian que los componentes metálicos evaluados presentan dos zonas claramente diferenciables en cuanto a tonalidad superficial: una zona clara y otra oscura, lo que indica la presencia de un deterioró corrosivo preferencial del recubrimiento. Los microanálisis químicos por EDX realizados en estas zonas reflejan que el daño por corrosión y la consecuente pérdida de espesor del recubrimiento protector de zinc de los componentes evaluados está asociado a la presencia de contaminantes atmosféricos. Se concluye que la capacidad de protección contra la corrosión del galvanizado remanente en función de la agresividad del ambiente al cual están expuesto por la cercanía de una zona industrial, es una de las principales causas del deterioro. Palabras Claves: Galvanizado, torres de trasmisión, corrosión, contaminantes, atmosfera industrial. Referencias [1]M. Morcillo, J. Alcántara, I. Díaz, B. Chico, J.Simancas y D. Fuente, “Marine atmospheric corrosion of carbon steels”, Revista de Metalurgia, Vol. 44, no 2, pp 045, 2015. [2].M. Morcillo, M. Almeida, F. Fragata y Z. Panossian, “Corrosión y Protección de los Metales en Atmosferas de Iberoamérica”, Tomo I, España, Ed. Proyecto CYTED, 2002, pp 779. [3].F. Cadena, L. Irusta b y M.J. Fernandez-Berridib, “Performance evaluation of alkyd coatings for corrosion protection in urban and industrial environments”, Progress in Organic Coatings, Vol.76, pp 1273- 1278, 2013. [4].L. Linares, “Evaluación de la corrosividad atmosférica y su efecto en los cables de transmisión eléctrica a 400kV de CVG EDELCA”, Tesis de Maestría. Universidad del Zulia. Maracaibo, Venezuela, 2007. [5].J. Guerra, A. Castañeda y J. Howland, “Estudio preliminar de la agresividad corrosiva de la atmósfera en el puente de los Caras, Manabí, Ecuador”, Revista CENIC Ciencias Químicas, Vol. 47, pp. 17-29, 2016. [6].D. J. Pazmiño, “Análisis y diseño estructural de una torre de transmisión eléctrica para el proyecto hidroeléctrico Angamarca-Sinde 32MW, Cantón Pangua, provincia de Cotopaxi”. Tesis de grado. Universidad Central del Ecuador, Ecuador, 2016. [7]Norma ISO 1463, 2003, “Metallic and oxide coatings-Measurement of coatings thickness-Microscopical Method”, ISO, Genève, Switzerland. [8]Norma ASTM E 45, 2005, “Standard Test Methods of Determining the Inclusion Content of Steel”, ASTM International, West Conshohocken, PA. [9]Norma ASTM A -36, 2003, “Standard Specification for Carbon Structural Steel”, ASTM International, West Conshohocken, PA. [10]Norma ASTM A 123/A, 2000, “Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products”, ASTM International, West Conshohocken, PA. [11]Norma ASTM A 153, 2003, “Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware”, ASTM International, West Conshohocken, PA. [12]Y. Rico y E. Carrasquero, “Efecto de la composición química en el comportamiento mecánico de recubrimientos galvanizados por inmersión en caliente: una revisión”, Ingenius, N°18, pp. 30-39, 2017. [13].M. Morcillo, M. Almeida, F. Fragata y Z. Panossian, “Corrosión y Protección de los Metales en Atmosferas de Iberoamérica”, Tomo II, España, Ed. Proyecto CYTED, pp 441-494. 2002