Suchergebnisse

The modern military industry demands the most innovative and high-quality metals and alloys, as well as processing technologies. Iron and its alloys are a common material used for different types of weapons and military equipment. Lasers have been widely used in the metal surface processing, but the changes that occur on laser treated metal surfaces have not yet been sufficiently investigated. A study of morphological and chemical changes on the metal surface induced by Nd:YAG laser treatment in ambient air is presented. A pulsed Nd:YAG laser (1064 nm, Gaussian spatial profile, FWHM 8 ns, energy up to 525 mJ, beam diameter of 1-10 mm and fluence up to 3.5 J/cm 2 ) was used. Micro-morphological analyses of sample surfaces before and after laser treatment process were performed by optical and SEM microscopies. EDX method was used for chemical analyses and Spectra colorimeter for investigation of induced color changes. The laser irradiation effects were studied as a function of two laser parameters, number of laser pulses and laser fluencies, around and over the damage threshold. The results show that there are significant differences depending on these laser parameters.

Bentonite is a key barrier for the isolation of high-level radioactive waste within Deep Geological Repository. However, bentonite may be altered by contact with cementitious materials and their alkaline pore fluids. This study offers an extensive morphological and semi-quantitative characterization of the bentonite surface exposed to three types of alkaline pore fluids released by different cement-based materials. The bentonite surfaces were studied using a thorough scanning electron microscopy exploration and analysed using an energy-dispersive ꭕ-ray detector (SEM-EDX). In addition, statistical, element mappings, ꭕ-ray diffraction and infrared spectroscopy analyses were performed. The aim was to have a picture of the morphological and chemical alterations of bentonite at very early stages in accordance with the integrated approach necessary to address bentonite stability in the long-term. As a consequence of the reactivity, two types of morphologies stood out in the matrix of bentonite: platelets and coatings-like crusts characterized by their high Mg and Ca content. These alterations presented a different scope depending on the type of alkaline pore solution involved and suggested the precipitation of authigenic magnesium silicate hydrates (M-S-H) and/or trioctahedral clay minerals and Ca‑carbonates. The knowledge of the performance of bentonite subjected to these alkaline solutions can help in the evaluation of the most suitable cement-based materials to be used next to bentonite ; The experimental work was supported by funding from the European Union's Horizon 2020 Research and Training programme from EURATOM [H2020-NFRP 2014, 2015] under grant agreement n◦662147; CEBAMA

10 páginas, 8 figuras, 21 referencias. ; [EN]: The present paper shows an interesting Optical Microscopy (OM) and Scanning Electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX) application to study degradation crust formation processes in Fort San Pedro, a historical building located at the colonial City of San Francisco de Campeche, México; and the Cathedral of Seville, at Seville, Spain. The results show that while in Seville the crusts are consequence of sulfur dioxide reaction whit calcareous stone, leading to gypsum crystal formation (CaSO4.2H2O), in San Francisco de Campeche, deterioration crust are consequence of natural recrystallization processes of CaCO3 induced by excessive environmental humidity. ; [ES]: En este trabajo se presenta una interesante aplicación de técnicas microscópicas, como microscopía óptica y la microscopía electrónica de barrido acoplada a un sistema de detección de Rayos X (SEM/EDX), para estudiar los procesos de formación de costras de deterioro del Baluarte de San Carlos en la ciudad de San Francisco de Campeche, México y la Catedral de la ciudad de Sevilla, España. Los resultados indican que mientras en la ciudad de Sevilla, las costras se componen principalmente de cristales de yeso (CaSO4.2H2O), como consecuencia de la reacción del dióxido de azufre atmosférico emitido por vehículos automotores con los componentes calcáreos de la piedra, en la ciudad de San Francisco de Campeche, son producto de procesos de disolución y recristalización de CaCO3, inducido por la excesiva humedad ambiental característica de climas tropicales. ; Este trabajo se desarrolló con apoyo del proyecto "Influencia del entorno urbano en los procesos de degradación de edificios militares y religiosos de la época colonial en la ciudad de Campeche", Clave Camp-C05-028, financiado por el Fondo Mixto CONACYT-Gobierno del Estado de Campeche y la oficina de colaboración Internacional del CONACYT, a través de una acción concertada con el CSIC-España. También se agradece el apoyo de CONACYT mediante el proyecto 59998 y las facilidades prestadas por el Centro INAH-Campeche a través de la arqueóloga Helena Barba Meinecke. ; Peer reviewed

Background: Illegal gold mining activities around Kayeli Bay have led to increased heavy metal contamination that has the potential to impair water quality and growth of Enhalus acoroides, an important seaweed species. This study aimed to investigate the distribution and concentration of heavy metals Pb and Hg in Enhalus acoroides organs (roots, rhizomes, and leaves) using SEM-EDX techniques and evaluate the impact of mining activities on the surface microstructure of these organs. Methods: Enhalus acoroides samples were collected from ten sampling points in Kayeli Bay, which were selected based on potential heavy metal contamination. SEM-EDX analysis was performed to assess the surface microstructure and distribution of heavy metals in the seaweed samples. Results: Results showed significant differences in Pb and Hg concentrations among samples from different locations, with Hg content consistently higher than Pb. Surface microstructure analysis showed morphological changes in roots, rhizomes, and leaves exposed to heavy metals, indicating environmental stress in Enhalus acoroides. Conclusion: This study confirmed the negative impact of heavy metal contamination on Enhalus acoroides in Kayeli Bay due to illegal gold mining activities. High concentrations of heavy metals, especially Hg, in seaweed organs indicate potential risks to marine ecosystem health and the sustainability of fisheries resources. These findings emphasize the need for stricter environmental monitoring and management to protect this important marine habitat from heavy metal pollution.

Abstract. A PM1 geochemical and mineralogical study using Scanning Electron Microscopy (SEM) was performed on a pilot site in the Agri Valley which is close to the oil pre-treatment plant (C.O.V.A) of Europe's largest on-shore hydrocarbon reservoir. The study identified PM1 geochemical and mineralogical characters in the period before, during and immediately after a burning torch flare event. The finer fraction (DFe < 0.7 μm) consisted mainly of secondary particles and soot. In the coarser fraction (DFe ≥ 0.7 μm), natural particles originating from crustal erosion and soot were abundant. Fine quartz particles and lower Al / Si ratios are markers for desert dust origin, proving that a Saharan dust episode which occurred during the observation period played a significant role in supplying geogenic aerosol components to the PM1. Largest amounts of ≥ 0.7 μm fraction particles observed on the day of flare event may be due to a greater supply of Saharan geogenic particles. Soot had been significantly increasing long before the flare event, suggesting that this increase is also related to other causes, although we cannot exclude a contribution from flaring. S-rich aerosol consisted mainly of mixed particles originating from deposition and heterogeneous nucleation of secondary sulfates on mineral dust. Only-S particles were identified in the ≥ 0.7 μm fraction following the flare event. These particles may be indicators of larger amounts of sulphur in the atmosphere.

Este trabalho é um dos desdobramentos da busca por uma maneira de apresentar as idéias geradas pela apropriação dasformas do conjunto de algumas taças de cristal quebradas. É um dos resultados de uma vasta experimentação de ações quevisam ressignificar estes objetos que perderam sua função utilitária, mas ganharam grande potencial artístico. Na verdade o trabalho consiste em estabelecer novas relações a estes objetos que saíram das suas significações, das suas relações de uso ehábito cotidiano.

The university reform of 1918 institutes a democratic university when it demands a "strictly democratic government" and that the students might express their "own thought in university bodies through their representatives". This foundational act is potent: it privileges the freedom to learn over corporate interests, establishes the autonomy, and anticipates the recognition of higher education as a common good. Reclaiming the critical spirit of the 1918 reformists, we show in this work that the agreement signed in 2017 by the rector Hugo Juri whereby UNC becomes associated with edX constitutes a counter-reformation that (i) seeks to build an international brand, (ii) makes higher education more precarious, and (iii) brings about a weakening of the democracy at the university. ; La reforma universitaria de 1918 instituye una universidad democrática al exigir un "gobierno estrictamente democrático" y que los estudiantes puedan expresar su "pensamiento propio en los cuerpos universitarios por medio de sus representantes". Ese acto fundacional es potente: antepone la libertad de aprender sobre los intereses corporativos, establece la autonomía y anticipa el reconocimiento de la educación superior como un bien público. Reivindicando el espíritu crítico de los reformistas de 1918, en este trabajo mostramos que el acuerdo firmado en el año 2017 por el rector Hugo Juri mediante el cual la UNC pasa a formar parte del consorcio edX constituye una contrarreforma que (i) busca construir una marca internacional, (ii) precariza la educación y (iii) conlleva también una pérdida de la democracia universitaria.

Here are the ten courses that have been chosen by https://mashable.com/uk/deals/best-free-online-courses-stanford-university as the best Stanford University courses to take online. And Economics 1 at Stanford https://www.edx.org/course/principles-of-economics is on the list. They are all on edX. As they say: “All products … Continue reading →

La Universidad Nacional de Córdoba -bajo el rectorado de Hugo Juri- es la primera universidad del país, y una de las primeras en Latinoamérica, que se incorpora al consorcio edX, una plataforma de educación a distancia masiva (MOOC) creada por Harvard y el MIT (Massachusetts Institute of Technology). Dicho consorcio está compuesto por alrededor de 100 instituciones, entre universidades de distintas partes del mundo, empresas (como Microsoft) y organismos internacionales (FMI, Banco Mundial, BID). Bajo el lema "Educación de calidad para todos, en cualquier lugar" promovido por edX, se justifica el lucro, la mercantilización y la precarización de la educación universitaria. Este trabajo se propone presentar algunos aspectos claves de este acuerdo que supone la neoliberalización de la universidad pública. Entre ellos podemos mencionar: la creación de una marca internacional y la comercialización de datos y la precarización de la educación y la pérdida de gratuidad. Esto afecta directamente la democracia universitaria, restringiendo el cogobierno y la actividad gremial de estudiantes y docentes.