Magmatic processes at the volcanic front of Central Mexican volcanic belt: Sierra de Chichinautzin volcanic field (Mexico)

The Sierra de Chichinautzin (SCN) volcanic field is considered one of the key areas to understand the complex petrogenetic processes at the volcanic front of the Mexican Volcanic Belt (MVB). New as well as published major- and trace-element and Sr and Nd isotopic data are used to constrain the magma generation and evolution processes in the SCN. From inverse and direct modelling, combined 87Sr/86Sr and 143Nd/144Nd data, and use of multi-dimensional log-ratio discriminant function based diagrams and other geological and geophysical considerations, we infer that mafic magmas from the SCN were generated by partial melting of continental lithospheric mantle in an extensional setting. Inverse modelling of primary magmas from the SCN further indicates that the source region is not depleted in high-field strength elements (HFSE) compared to large ion lithophile elements (LILE) and rare-earth elements (REE). The petrogenesis of evolved magmas from the SCN is consistent with the partial melting of the continental crust facilitated by influx of mantle-derived magmas. Generally, an extensional setting is indicated for the SCN despite continuing subduction at the Middle America Trench

Geothermal systems simulation: A case study

Geothermal reservoir simulation is a key step for developing sustainable and efficient strategies for the exploitation of geothermal resources. It is applied in the assessment of several areas of reservoir engineering, such as reservoir performance and re-injection programs, pressure decline in depletion, phase transition conditions, and natural evolution of hydrothermal convection systems. Fluid flow and heat transfer in rock masses, fluid-rock chemical interaction and rock mass deformation are some of the processes addressed in reservoir modelling. The case study of the Las Tres Virgenes (LTV) geothermal field (10 MWe), Baja California Sur, Mexico is presented. Three dimensional (3D) natural state simulations were carried out from emplacement and cooling of two spherical magma chambers using a conductive approach. A conceptual model of the volcanic system was developed on a lithostratigraphic and geochronological basis. Magma chamber volumes were established from eruptive volumes estimations. The thermophysical properties of the medium were assumed to correspond to the dominant rock in each lithological unit as an initial value, and further calibration was made considering histograms of experimentally obtained thermophysical properties of rocks. As the boundaries of the model lie far from the thermal anomaly, we assumed specified temperature boundaries. A Finite Volume (FV) numerical scheme was implemented in a Fortran 90 code to solve the heat equation. Static formation temperatures from well logs were used for validation of the numerical results. Good agreement was observed in those geothermal wells dominated by conductive heat transfer. For other wells, however, it is clear that conduction alone cannot explain observed behaviour, three-dimensional convective models are being implemented for future multiphysics simulations

Review of the field, analytical and statistical methods used in the determination and handling of rare-earth elements in soil-plant system

El presente artículo es una revisión detallada de estudios científicos publicados que tratan el tema relacionado con la determinación de los elementos de las tierras raras (REEs) en el sistema suelo-planta. Los estudios han sido llevados a cabo principalmente en países europeos y asiáticos. Cabe señalar que la investigación en los países latinoamericanos es muy escasa; sin embargo, es creciente el interés de analizar la aportación de estos elementos al suelo y la planta, lo cual se debe a la aplicación de fertilizantes que contienen dosis elevadas de estos elementos en su composición. Diversas técnicas de muestreo, experimentación y análisis han sido empleadas para la determinación de los REEs. No obstante, se considera que el manejo de los datos ha sido incorrecto estadísticamente. El contenido del presente artículo aborda: (i) las generalidades de los REEs; (ii) el análisis de la bibliografía disponible con el fin de conocer las metodologías de muestreo y análisis más utilizadas en 37 artículos en total, señalando algunos puntos que se consideran todavía deficientes; (iii) dos ejemplos de la aplicación de técnicas estadísticas (intervalo de confianza de la media y pruebas de significancia de la relación F de Fisher y t de Student) utilizando datos reportados en dos artículos. Los resultados mostraron, con los datos del primer artículo analizado, que: a) no se aplicó una metodología estadística para evaluar la calidad de datos; b) al aplicar estadística se encontró que existen diferencias sistemáticas entre los datos determinados en el laboratorio y los certificados. En el segundo artículo analizado se demostró, mediante pruebas de significancia, que existen diferencias significativas en las medias de Ce y Eu (los dos elementos tomados como ejemplos) en las plantas de un sitio a otro.This study concerns a detailed review of published papers on rare-earth elements (REEs) in soil-plant system. Such studies have been carried out mainly in Europe and Asia and are relatively scarse in Latin American countries. Nevertheless, the interest in evaluating the uptake of REEs in soil-plant system is continually increasing. This is due to the fact that fertilizers contain high concentrations of these elements. Different techniques have been used for sampling, experimental work and REE determinations. However, we consider that the data handling has been rather statistically deficient. This review elaborates on the following points: (i) general characteristics of the REEs; (ii) bibliographical review of sampling and analytical techniques actually used in 37 papers with an emphasis on the statistical deficiencies; (iii) examples of the application of statistical methods (confidence interval of the mean and significance tests of Fisher F and Student t) based on two of the compiled papers. The first application showed that the original authors did not apply any statistical methodology to evaluate their data quality and that there are systematic differences between the data analyzed in their laboratory and the certified values of the reference material. The application of significance tests to the data from the second paper demonstrated that there are significant differences in the mean values of Ce and Eu (only these two elements were exemplified) in plants from different sites.Fil: Hernández-Martínez, J. Lucero. Universidad Nacional Autónoma de México. Instituto de GeofísicaFil: Verma, Surendra P.. Universidad Nacional Autónoma de México. Centro de Investigación de Energí

Evaluation of GSJ instrusive rocks JG1, JG2, JG1a, and JGb1 by an objective outlier rejection statistical procedure

An objective procedure involving fourteen statistical tests (a total of thirty-four variants) for detection and rejection of outliers in a univariate sample was applied to five geochemical Reference Material (RM) databases of intrusive rocks from the Geological Survey of Japan (GSJ). All available concentration data for JG1, JG1a, and JG3 granodiorites, JG2 granite, and JGb1 gabbro were first grouped in eight general analytical methods. These groups were tested for systematic differences using analysis of variance (ANOVA). After this process, the databases were evaluated by means of statistical tests for detection of possible outliers at a strict confidence level of 99%, minimizing the danger of rejecting a valid observation as an outlier. New concentration mean values and other statistical parameters were computed from final normal distributions. Although 23% of mean concentration values were practically identical to those reported in earlier literature, 67% differ by about 1% to 20%. The present statistical scheme provides a better perspective to evaluate existing geochemical databases than probably erroneous two-standard deviation method involving prior subjective judgments used by the U.S. and Japanese scientists. The present mean values with generally lower %RSD may contribute to a better estimation of precision, accuracy, and sensitivity of routine analysis for intrusive rock samples

Evaluation of the odd-even effect in limits of detection for electron microprobe analysis of natural minerals

Limit of detection (LOD), being a fundamental quality parameter for analytical techniques, has been recently investigated and a systematic behavior has been observed for most odd–even element pairs for many techniques. However, to the best of our knowledge very few LOD data are available in published literature for electron microprobe analysis; these consist of three papers, two being on rare-earth elements and the third covering a large number of elements of atomic number between 21 and 92. These data confirm the systematic behavior of LODs for many odd–even pairs. To initiate to full this gap, we determined LODs for several major rock-forming chemical elements from Na to Fe with atomic numbers between 11 and 26, during the microprobe analysis of common minerals (olivine, plagioclase, pyroxene, amphibole, quartz, and opaques) in volcanic rocks. The odd–even effect of nuclear stability seems to be present in LOD data for most odd–even pairs investigated. Nevertheless, the experimental strategy concerning the reference materials, calibration procedure, and blank measurements, should be substantially modified to better evaluate the systematic behavior of LOD values in microprobe analysis

Antikonvulzivno djelovanje Schiffovih baza- derivata isatina

Schiff bases of N-methyl and N-acetyl isatin derivatives with different aryl amines have been synthesized and screened for anticonvulsant activities against maximal electroshock (MES) and subcutaneous metrazole (ScMet). N-methyl-5-bromo-3-(p-chlorophenylimino) isatin 2 exhibited anticonvulsant activity in MES and ScMet with LD50 > 600 mg kg-1, showing better activity than the standard drugs phenytoin, carbamazepine and valproic acid. Thus, compound 2 may be chosen as a prototype for development of new anticonvulsants.Schiffove baze N-metil i N-acetil derivata izatina s različitim aromatskim aminima sintetizirane su i ispitane na sposobnost suzbijanja konvulzija uzrokovanih elektrošokom (MES) i subkutanom primjenom metrazola (ScMet). N-metil-5-bromo-3-(p-klorofenilimino) izatin 2 pokazao je nisku neurotoksičnost i jače antikonvulzivno djelovanje nego standardni antikonvulzivi fenitoin, karbamazepin i valproična kiselina. Zbog toga se spoj 2 može smatrati prototipom za razvoj novih antikonvulziva

Antikonvulzivno djelovanje Schiffovih baza- derivata isatina

Schiff bases of N-methyl and N-acetyl isatin derivatives with different aryl amines have been synthesized and screened for anticonvulsant activities against maximal electroshock (MES) and subcutaneous metrazole (ScMet). N-methyl-5-bromo-3-(p-chlorophenylimino) isatin 2 exhibited anticonvulsant activity in MES and ScMet with LD50 > 600 mg kg-1, showing better activity than the standard drugs phenytoin, carbamazepine and valproic acid. Thus, compound 2 may be chosen as a prototype for development of new anticonvulsants.Schiffove baze N-metil i N-acetil derivata izatina s različitim aromatskim aminima sintetizirane su i ispitane na sposobnost suzbijanja konvulzija uzrokovanih elektrošokom (MES) i subkutanom primjenom metrazola (ScMet). N-metil-5-bromo-3-(p-klorofenilimino) izatin 2 pokazao je nisku neurotoksičnost i jače antikonvulzivno djelovanje nego standardni antikonvulzivi fenitoin, karbamazepin i valproična kiselina. Zbog toga se spoj 2 može smatrati prototipom za razvoj novih antikonvulziva

Comparative Performance of Four Single Extreme Outlier Discordancy Tests from Monte Carlo Simulations

Using highly precise and accurate Monte Carlo simulations of 20,000,000 replications and 102 independent simulation experiments with extremely low simulation errors and total uncertainties, we evaluated the performance of four single outlier discordancy tests (Grubbs test N2, Dixon test N8, skewness test N14, and kurtosis test N15) for normal samples of sizes 5 to 20. Statistical contaminations of a single observation resulting from parameters called δ from ±0.1 up to ±20 for modeling the slippage of central tendency or ε from ±1.1 up to ±200 for slippage of dispersion, as well as no contamination (δ=0 and ε=±1), were simulated. Because of the use of precise and accurate random and normally distributed simulated data, very large replications, and a large number of independent experiments, this paper presents a novel approach for precise and accurate estimations of power functions of four popular discordancy tests and, therefore, should not be considered as a simple simulation exercise unrelated to probability and statistics. From both criteria of the Power of Test proposed by Hayes and Kinsella and the Test Performance Criterion of Barnett and Lewis, Dixon test N8 performs less well than the other three tests. The overall performance of these four tests could be summarized as N2≅N15>N14>N8

Allelic dimorphism of Plasmodium vivax gam-1 in the Indian subcontinent

BACKGROUND: Genetic polymorphism is an inevitable component of a complex organism especially in multistage infectious organisms such as malaria parasites. Understanding the population genetic structure of the parasites would provide valuable information for effective malaria control strategies. Recently, the development of molecular tools like PCR has made analysis of field samples possible and easier and research on Plasmodium vivax has also been strengthened. Not many reports are available on the genetic polymorphism of P. vivax from the Indian sub-continent. This study evaluates the extent of diversity in field isolates of India with respect to Pvgam-1. METHODS: A study was designed to assess the diversity of Pvgam-1 among field isolates from India, using a nested PCR assay. Field isolates were collected from different regions of the country and the observed variability was confirmed by sequencing data. RESULTS: Both Belem and Chesson type alleles were present either exclusively or in mixed form among isolates of all 10 study sites. The Belem type allele was predominant, occurring in 67% of isolates. The proportion of isolates showing the mixed form (both Belem and Chesson type alleles occurring together in the same isolate) was about 13 overall (up to 38.5% in some isolates). Sequencing of the PCR-amplified Belem and Chesson type alleles confirmed the PCR results. Among the 10 study sequences, 11 polymorphic sites and four singleton variations were observed. All the nucleotide substitutions were non-synonymous. CONCLUSION: Study shows limited diversity of Pvgam-1 marker in Indian isolates with well representation of both Belem and Chesson type alleles