Population polygons of tektite specific gravity for various localities in australasia

Comparison of specific gravity of tektites from australia, asia, texas, and czechoslovaki

Electrochemical behavior of Sn-Zn alloys with different grain structures in chloride-containing solutions

In the present research the electrochemical behavior of the Sn-Zn alloys (Sn-1 wt.%Zn, Sn-4 wt.%Zn and 8.9 wt.%Zn) in 3% NaCl solution is analyzed using potentiodynamic cyclic polarization measurements and Electrochemical Impedance Spectroscopy (EIS) technique. Specimens were longitudinally solidified with simultaneous heat extraction in two opposite directions. Working electrodes were constructed using longitudinal and cross sections of the specimens with both types of structure: columnar and equiaxed. Results obtained from the polarization curves indicated that the two types of grain structures of Sn-Zn alloys (Sn-1 wt.%Zn, Sn-4 wt.%Zn and Sn-8.9 wt.%Zn) corresponding to longitudinal section present a pseudo passive zone. In the case of specimens from cross sections of the samples, the columnar and equiaxed zones of Sn-8.9 wt.%Zn are the only ones that do not have this pseudo passive region. In addition, the interdendritic zone of alloys is susceptible to corrosion by dealloying because this phase is zinc-rich. This type of corrosion also occurs in the zinc rich lamellar structure present in the eutectic. The percentage of zinc in the alloy increases with increasing susceptibility to pitting corrosion. The EIS values obtained revealed that the susceptibility to corrosion increases with increasing zinc content in alloys, for both the columnar and equiaxed zones. In addition, the columnar zones of Sn-4 wt.%Zn and Sn-8.9 wt.%Zn specimens are more resistant to corrosion than the equiaxed grain specimens. However, the equiaxed zone of Sn-1 wt.%Zn alloy is less susceptible to corrosion than the columnar zone. After adjustment by equivalent circuits it is revealed that the equiaxed zone of Sn-8.9 wt.%Zn alloy has a second porous layer composed of corrosion products on the electrode surface.Fil: Mendez, Claudia Marcela. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Scheiber, Verónica L.. Provincia de Misiones. Comité de Desarrollo e Innovación Tecnológica. Centro de Desarrollo e Innovación Tecnológica; ArgentinaFil: Rozicki, Roberto S.. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; ArgentinaFil: Kociubczyk, Alex Iván. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Ares, Alicia Esther. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Electrochemical characterization of Zn-Sn alloys

En el presente trabajo se analizó el comportamiento electroquímico de probetas de Zn y Sn puros y de aleaciones Zn-Sn con concentraciones en peso de Sn, esto es, Zn3%Sn, Zn10%Sn y Zn50%Sn. Las aleaciones preparadas fueronsolidificadas direccionalmente en forma horizontal con extracción calórica en dos sentidos opuestos, obteniéndose asíen cada una de las probetas la transición de estructura columnar a equiaxial. Los diferentes tipos de estructurasobtenidas, columnar y equiaxial, fueron utilizadas como electrodos de trabajo. El análisis a la resistencia a lacorrosión se realizó mediante ensayos de polarización potenciodinámica cíclica y mediante la técnica deespectroscopía de impedancia (EIS), empleando una celda convencional de tres electrodos, un electrodo de referenciade calomel saturado, un electrodo de platino como contraelectrodo y una solución deaereada de NaCl al 3%, atemperatura ambiente. A partir de las medidas potenciodinámicas cíclicas obtenidas se observó que los potenciales decorrosión de los materiales son ligeramente más nobles conforme el contenido de Sn aumenta en la aleación. Laobservación microscópica de las probetas luego de los ensayos denotó una mayor tendencia a la corrosión por picadocon el aumento del porcentaje en peso de Sn y la disminución de la corrosión generalizada frente al Zn puro. Losespectros de EIS obtenidos fueron ajustados de acuerdo a dos modelos de circuitos eléctricos equivalentes. Losparámetros hallados describen el comportamiento de la capa de óxido formada. Para la estructura columnar, lamuestra de Zn puro es la menos resistente a la corrosión generalizada, aumentando su resistencia con el agregado deSn en las probetas.In the present work was analyzed the electrochemical behavior of Zn 3 % Sn, Zn10 %Sn and Zn50 % Sn alloys (weight percentage), and Zn and Sn pures. The samples were obtained by the horizontally unidirectional solidification method, with extraction of heat in two opposite directions. From each of the samples were obtained the three zones: columnar, equiaxed and columnar-to-equiaxed transition (CET). The different types of structures obtained were cut longitudinally and used like work electrodes. The analysis to the corrosion resistance was realized through potentiodynamic cyclic polarization essays and the EIS technique. For the tests was used a conventional threeelectrode cell, a reference electrode saturated calomel, was used platinum as a counter electrode and a 3% NaCl solution, dereated, at room temperature. From the potentiodynamic measures obtained was observed that the corrosion potential is slightly more noble when in the alloy increases the Sn content. After the tests, the microscopic observation of the samples showed that whit the increase of Sn content, increases the susceptibility of pitting corrosion and decreases the generalized corrosion versus pure Zn. The EIS obtained spectrums were adjusted according two equivalent circuit models. The found parameters described the behavior of the oxide formed film on the top of the material. For the columnar structure, the pure Zn sample is the most susceptible to the corrosion, the resistance increases with the amount of Sn.Fil: Scheiber, V. L.. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mendez, Claudia Marcela. Universidad Nacional de Misiones; ArgentinaFil: Ares, Alicia Esther. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Cs.exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Groundwater-Gossan interaction and the genesis of the secondarysiderite rock at Las Cruces ore deposit (SW Spain)

Part of the Las Cruces secondary siderite deposit has sparked an interest in the scientific communitybecause of its unique mineralogy. The original gossan formed by goethite and hematite has been replacedby a siderite and galena rock. We postulate that this rock can be formed by the interaction of iron oxideswith groundwater similar in composition to that of the present day. Hydrochemical and isotopic charac-teristics of groundwater support this hypothesis. The negative Eh values, the existence of H2S and the ten-dency toward high sulfate isotope values indicate a reducing groundwater condition. The highammonium, boron and iodine concentrations as well as the low d13C values of dissolved inorganic carbon(DIC) confirm the organic matter oxidation. The reductive dissolution of Pb-bearing goethite at theexpense of Dissolved Organic Carbon (DOC) leads to the precipitation of Fe-sulfides, galena and siderite.The formation of siderite from this process is confirmed by the low amount of dissolved Fe in groundwa-ter (<10 ppb), its low d13C values and thermodynamic calculations. One-dimensional reactive transportmodeling demonstrated that the present-day groundwater flux and chemical composition could formthe siderite rock in less than 1 Ma with no external supply of reactants. Sensitivity analyses revealed thatthe time of formation depends on the structure of the groundwater flux (spaced fractures or pervasive),the flow rate and especially the DOC concentration. In fact, calculations with the highest DOC measuredconcentration resulted in a mineral zonation: one zone formed by Fe-sulfides and other zone formed bysiderite, with galena in both zones. Reactive transport calculations and the similarity of its high d34S val-ues indicate that the sulfur of galena came from the current groundwater. Reactive transport calculationsand the similarity of its high d34S values indicate that the sulfur of galena came from the currentgroundwater

Customization, extension and reuse of outdated hydrogeological software

Each scientist is specialized in his or her field of research and in the tools that he or she uses during the research in a specified site. Thus, he or she is the most suitable person for improving the tools by overcoming their limitations to realize faster and higher quality analysis. However, most scientists are not software developers. Hence, it is necessary to provide them with an easy approach that enables non-software developers to improve and customize their tools. This paper presents an approach for easily improving and customizing any hydrogeological software. It is the result of experiences with updating several interdisciplinary case studies. The main insights of this approachhave been demonstrated using four examples: MIX (FORTRAN-based), BrineMIX (C++-based), EasyQuim and EasyBal (both spreadsheet-based). The improved software has been proven to be a better tool for enhanced analysis by substantially reducing the computation time and the tedious processing of the input and output data files

Recent and old groundwater in the Niebla-Posadas regional aquifer (southern Spain): Implications for its management

The Niebla-Posadas (NP) aquifer in southern Spain is one of the main groundwater sources for the lower Guadalquivir Valley, a semiarid region supporting an important population, agriculture and industry. To contribute to the understanding of this aquifer the assessment of sustainable use of groundwater, the residence time of groundwater in the NP aquifer has been estimated using 3H, 14C and 36Cl. Along the flow paths, recharged groundwater mixes with NaCl-type waters and undergoes calcite dissolution and is further modified by cation exchange (Ca Na). Consequently, the water loses most of its calcium and the residual d13CDIC in the groundwater is isotopically enriched. Further modifications take place along the flow path in deeper zones, where depleted d13CDIC values are overprinted due to SO42 and iron oxide reduction, triggered by the presence of organic matter. Dating with 3H, 14C and 36Cl has allowed the differentiation of several zones: recharge zone (30 ky). An apparent link between the tectonic structure and the groundwater residence time zonation can be established. Regional faults clearly separates deep zone 1 from the distinctly older age (>30 ky) deep zone 2. From the estimated residence times, two groundwater areas of different behavior can be differentiated within the aquifer

The potential of open-access data for flood estimations: uncovering inundation hotspots in Ho Chi Minh City, Vietnam, through a normalized flood severity index

Hydro-numerical models are increasingly important to determine the adequacy and evaluate the effectiveness of potential flood protection measures. However, a significant obstacle in setting up hydro-numerical and associated flood damage models is the tedious and oftentimes prohibitively costly process of acquiring reliable input data, which particularly applies to coastal megacities in developing countries and emerging economies. To help alleviate this problem, this paper explores the usability and reliability of flood models built on open-access data in regions where highly resolved (geo)data are either unavailable or difficult to access yet where knowledge about elements at risk is crucial for mitigation planning. The example of Ho Chi Minh City, Vietnam, is taken to describe a comprehensive but generic methodology for obtaining, processing and applying the required open-access data. The overarching goal of this study is to produce preliminary flood hazard maps that provide first insights into potential flooding hotspots demanding closer attention in subsequent, more detailed risk analyses. As a key novelty, a normalized flood severity index (INFS), which combines flood depth and duration, is proposed to deliver key information in a preliminary flood hazard assessment. This index serves as an indicator that further narrows down the focus to areas where flood hazard is significant. Our approach is validated by a comparison with more than 300 flood samples locally observed during three heavy-rain events in 2010 and 2012 which correspond to INFS-based inundation hotspots in over 73 % of all cases. These findings corroborate the high potential of open-access data in hydro-numerical modeling and the robustness of the newly introduced flood severity index, which may significantly enhance the interpretation and trustworthiness of risk assessments in the future. The proposed approach and developed indicators are generic and may be replicated and adopted in other coastal megacities around the globe.</p

Effects of Methoxyisoflavone, Ecdysterone, and Sulfo-Polysaccharide Supplementation on Training Adaptations in Resistance-Trained Males

PURPOSE: Methoxyisoflavone (M), 20-hydroxyecdysone (E), and sulfo-polysaccharide (CSP3) have been marketed to athletes as dietary supplements that can increase strength and muscle mass during resistancetraining. However, little is known about their potential ergogenic value. The purpose of this study was to determine whether these supplements affect training adaptations and/or markers of muscle anabolism/catabolism in resistance-trained athletes. METHODS: Forty-five resistance-trained males (20.5±3 yrs; 179±7 cm, 84±16 kg, 17.3±9 % body fat) were matched according to FFM and randomly assigned to ingest in a double blind manner supplements containing either a placebo (P); 800 mg/day of M; 200 mg of E; or, 1,000 mg/day of CSP3 for 8-weeks during training. At 0, 4, and 8-weeks, subjects donated fasting blood samples and completed comprehensive muscular strength, muscular endurance, anaerobic capacity, and body composition analysis. Data were analyzed by repeated measures ANOVA. RESULTS: No significant differences (p&gt;0.05) were observed in training adaptations among groups in the variables FFM, percent body fat, bench press 1RM, leg press 1RM or sprint peak power. Anabolic/catabolic analysis revealed no significant differences among groups in active testosterone (AT), free testosterone (FT), cortisol, the AT to cortisol ratio, urea nitrogen, creatinine, the blood urea nitrogen to creatinine ratio. In addition, no significant differences were seen from pr

Pressure Dependence of Born Effective Charges, Dielectric Constant and Lattice Dynamics in SiC

The pressure dependence of the Born effective charge, dielectric constant and zone-center LO and TO phonons have been determined for $3C$-SiC by a linear response method based on the linearized augmented plane wave calculations within the local density approximation. The Born effective charges are found to increase nearly linearly with decreasing volume down to the smallest volume studied, $V/V_0=0.78$, corresponding to a pressure of about 0.8 Mbar. This seems to be in contradiction with the conclusion of the turnover behavior recently reported by Liu and Vohra [Phys.\ Rev.\ Lett.\ {\bf 72}, 4105 (1994)] for $6H$-SiC. Reanalyzing their procedure to extract the pressure dependence of the Born effective charges, we suggest that the turnover behavior they obtained is due to approximations in the assumed pressure dependence of the dielectric constant $\varepsilon_\infty$, the use of a singular set of experimental data for the equation of state, and the uncertainty in measured phonon frequencies, especially at high pressure.Comment: 25 pages, revtex, 5 postscript figures appended, to be published in Phys. Rev.