Greener Selective Cycloalkane Oxidations with Hydrogen Peroxide Catalyzed by Copper-5-(4-pyridyl)tetrazolate Metal-Organic Frameworks

Microwave assisted synthesis of the Cu(I) compound [Cu(µ4-4-ptz)]n [1, 4-ptz = 5-(4-pyridyl)tetrazolate] has been performed by employing a relatively easy method and within a shorter period of time compared to its sister compounds. The syntheses of the Cu(II) compounds [Cu3(µ3-4-ptz)4(µ2-N3)2(DMF)2]n∙(DMF)2n (2) and [Cu(µ2-4-ptz)2(H2O)2]n (3) using a similar method were reported previously by us. MOFs 1-3 revealed high catalytic activity toward oxidation of cyclic alkanes (cyclopentane, -hexane and -octane) with aqueous hydrogen peroxide, under very mild conditions (at room temperature), without any added solvent or additive. The most efficient system (2/H2O2) showed, for the oxidation of cyclohexane, a turnover number (TON) of 396 (TOF of 40 h−1), with an overall product yield (cyclohexanol and cyclohexanone) of 40% relative to the substrate. Moreover, the heterogeneous catalytic systems 1–3 allowed an easy catalyst recovery and reuse, at least for four consecutive cycles, maintaining ca. 90% of the initial high activity and concomitant high selectivity.

Nickel Contact Dermatitis in Fortaleza, Ceará, Brazil: 1993-1994

This work consists in an evaluation of the occurrence of nickel contact dermatitis, its distribution between sexes and in which parts of the body the dermatitis usually occurs. It was accomplished a two year (1994-1995) retrospective study of 404 patch-tested patients which had previous clinical diagnosis of contact dermatitis. The occurrence of nickel sensitisation was 19,8%. 88,8% of these 19,8% were women and the rest, 11,2%, were men. The lesions were present predominantly on hands, forearms, earlobes and feet. The authors comment about possible variations of occurrence of nickel contact dermatitis in rural areas and/or tropical countries

Development of copper and nickel based oxide thin-films: design and fabrication of thin-film transistors

Dissertação para obtenção do Grau de Doutor em Nanotecnologia e Nanociência

Assessment of hydrogen sulfide removal from biogas using a field scale anoxic biotrickling filter.

Hydrogen sulphide is one of the most toxic and corrosive compound present in swine-derived biogas streams.In this study, afield scale biotrickling filter for the removal of hydrogen sulfide was investigated.A Biofilter packed with supporting biofilm materials was fed continuously with a proprietary nutrient solution and operatedfor over 73days. The system has been operating with a H2S inlet concentrations ranging from 1,000to 3,000 ppm.Significant removal efficiencies >95% was demonstrated. pH of the stock feeding solution decreased from 6.2 to as low as 3.5within couple days.The resulting drop in pH provided circumstantial evidence to support biological H2 Soxidation to sulphuric acid by sulfide-oxidizers. Sulfur precipitation was also observed to occur. The results suggested that H2S removal from biogas stream can be efficiently achieved using portable, low cost and maintenance free biotrickling filters.

Hydrogen permeation in parabolic trough receivers

The continued economic and population development puts additional pressure on the already scarce energetic sources. Thus there is a growing urge to adopt a sustainable plan able to meet the present and future energetic demands. Since the last two decades, solar trough technology has been demonstrating to be a reliable alternative to fossil fuels. Currently, the trough industry seeks, by optimizing energy conversion, to drive the cost of electricity down and therefore to place itself as main player in the next energetic age. One of the issues that lately have gained considerable relevance came from the observation of significant heat losses in a large number of receiver modules. These heat losses were attributed to slow permeation of traces of hydrogen gas through the steel tube wall into the vacuum annulus. The presence of hydrogen gas in the absorber tube results from the decomposition of heat transfer fluid due to the long-term exposure to 400°C. The permeated hydrogen acts as heat conduction mean leading to a decrease in the receivers performance and thus its lifetime. In order to prevent hydrogen accumulation, it has been common practice to incorporate hydrogen getters in the vacuum annulus of the receivers. Nevertheless these materials are not only expensive but their gas absorbing capacity can be insufficient to assure the required level of vacuum for the receivers to function. In this work the building of a permeation measurement device, vulnerabilities detected in the construction process and its overcome are described. Furthermore an experimental procedure was optimized and the obtained permeability results, of different samples were evaluated. The data was compared to measurements performed by an external entity. The reliability of the comparative data was also addressed. In the end conclusions on the permeability results for the different samples characteristics, feasibility of the measurement device are drawn and recommendations on future line of work were made.

Development of bio-batteries based on electrospun membranes

Fundação para a Ciência e a Tecnologia (FCT-MCTES) under the grant SFRH/BD/69306/2010

Glutathione levels in and total antioxidant capacity of Candida sp. cells exposed to oxidative stress caused by hydrogen peroxide

INTRODUCTION: The capacity to overcome the oxidative stress imposed by phagocytes seems to be critical for Candida species to cause invasive candidiasis. METHODS: To better characterize the oxidative stress response (OSR) of 8 clinically relevant Candida sp., glutathione, a vital component of the intracellular redox balance, was measured using the 5,5'-dithiobis-(2-nitrobenzoic acid (DTNB)-glutathione disulfide (GSSG) reductase reconversion method; the total antioxidant capacity (TAC) was measured using a modified method based on the decolorization of the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic) acid radical cation (ABTS*+). Both methods were used with cellular Candida sp. extracts treated or not with hydrogen peroxide (0.5 mM). RESULTS: Oxidative stress induced by hydrogen peroxide clearly reduced intracellular glutathione levels. This depletion was stronger in Candida albicans and the levels of glutathione in untreated cells were also higher in this species. The TAC demonstrated intra-specific variation. CONCLUSIONS: Glutathione levels did not correlate with the measured TAC values, despite this being the most important non-enzymatic intracellular antioxidant molecule. The results indicate that the isolated measurement of TAC does not give a clear picture of the ability of a given Candida sp. to respond to oxidative stress.

Historic and potential technology transition paths of grid battery storage: Co-evolution of energy grid, electric mobility and batteries

Scarcity of fuels, changes in environmental policy and in society increased the interest in generating electric energy from renewable energy sources (RES) for a sustainable energy supply in the future. The main problem of RES as solar and wind energy, which represent a main pillar of this transition, is that they cannot supply constant power output. This results inter alia in an increased demand of backup technologies as batteries to assure electricity system safety. The diffusion of energy storage technologies is highly dependent on the energy system and transport transition pathways which might lead to a replacement or reconfiguration of embedded socio-technical practices and regimes (by creating new standards or dominant designs, changing regulations, infrastructure and user patterns). The success of this technology is dependent on hardly predictable future technical advances, actor preferences, development of competing technologies and designs, diverging interests of actors, future cost efficiencies, environmental performance, the evolution of market demand and design and evolution of our society.

Smart platform towards batteries analysis based on internet-of-things

This paper presents a new approach of pre-defined profiles, based in different voltage and current values, to control the charging and discharging processes of batteries in order to assess their performance. This new approach was implemented in a prototype that was specially developed for such purpose. This prototype is a smart power electronics platform that allows to perform batteries analysis and to control the charging and discharging processes through a web application using pre-defined profiles. This platform was developed aiming to test different batteries technologies. Considering the relevance of the energy storage area based in batteries, especially for the batteries applied to electric mobility systems, this platform allows to perform controlled tests to the batteries, in order to analyze the batteries performance under different scenarios of operation. Besides the results obtained with the batteries, this work also intends to produce results that can contribute to an involvement in the strengthening of the Internet-of-Things.

Advances and future challenges in printed batteries

There is an increasing interest in thin and flexible energy storage devices to meet modern society needs for applications such as, radio frequency sensing, interactive packaging and other consumer products. Printed batteries comply these requirements and are an excellent alternative to conventional batteries for many applications. Flexible and micro-batteries are also included in the area of printed batteries whenever fabricated by printing technologies. The main characteristics, advantages, disadvantages, developments, and printing techniques of printed batteries are presented and discussed in this review. The state-of-art takes into account both the research and industrial levels. In the academic one, the research progress of printed batteries is summarized divided in lithium-ion battery (Li-ion), zinc-manganese dioxide (Zn-MnO2), and other battery types with emphasis on the different materials for anode, cathode and separator as well as in the battery design. With respect to the industrial state-of-art, materials, device formulations and manufacturing techniques are presented. Finally, the prospects and challenges of printed batteries are discussed.

Lithium ion rechargeable batteries: State of the art and future needs of microscopic theoretical models and simulations

This review deals with the recent developments and present status of the theoretical models for the simulation of the performance of lithium ion batteries. Preceded by a description of the main materials used for each of the components of a battery -anode, cathode and separator- and how material characteristics affect battery performance, a description of the main theoretical models describing the operation and performance of a battery are presented. The influence of the most relevant parameters of the models, such as boundary conditions, geometry and material characteristics are discussed. Finally, suggestions for future work are proposed.

Silicon nanowire arrays coupled with cobalt phosphide spheres as low-cost photocathodes for efficient solar hydrogen evolution

We demonstrate the first example of silicon nanowire array photocathodes coupled with hollow spheres of the emerging earth-abundant cobalt phosphide catalysts. Compared to bare silicon nanowire arrays, the hybrid electrodes exhibit significantly improved photoelectrochemical performance toward the solar-driven H2 evolution reaction.

Nickel(II) complexes of bidentate N-N′ ligands containing mixed pyrazole, pyrimidine and pyridine aromatic rings as catalysts for ethylene polymerisation

This work describes the synthesis and characterisation of Ni(II) complexes of the following neutral bidentate nitrogen ligands containing pyrazole (pz), pyrimidine (pm) and pyridine (py) aromatic rings: 2-pyrazol-1-yl-pyrimidine (pzpm), 2-(4-methyl-pyrazol-1-yl)-pyrimidine (4-Mepzpm), 2-(4-bromo-pyrazol-1-yl)-pyrimidine (4-Brpzpm), 2-(3,5-dimethyl-pyrazol-1-yl)-pyrimidine (pz*pm), 2-pyrazol-1-yl-pyridine (pzpy) and bis(3,5-dimethylpyrazol-1-yl)phenylmethane (bpz*mph). The complexes [NiBr2(pzpm)] (1), [NiBr2(4-Mepzpm)] (2), [NiBr2(4-Brpzpm)] (3), [NiBr2(pz*pm)] (4), [NiBr2(pzpy)] (5) and [NiBr2(bpz*mph)] (6) were tested as catalysts for ethylene polymerisation, in the presence of the cocatalysts methylaluminoxane (MAO) or diethylaluminium chloride (AlEt2Cl), the catalyst systems 1-3/MAO showing moderate to high activities up to the temperature of 20 °C only in the presence of MAO, whereas 4-6/MAO revealed to be inactive. Other related Pd(II) complexes, already reported in previous works, such as [PdClMe(pzpm)], [PdClMe(pz*pm)], [PdClMe(pzpy)] and [PdClMe(bpz*mph)], also showed to be inactive in the polymerisation of ethylene, when activated by MAO or AlEt2Cl. Selected samples of polyethylene products were characterised by GPC/SEC, 1H and 13C NMR and DSC, showing to be low molecular weight polymers with Mn values ranging from ca. 550 to 1500 g mol−1 and unusually low dispersities of 1.2–1.7, with total branching degrees generally varying between 2 and 12%, melting temperatures from 40 to 120 °C and crystallinities from 40 to 70%.

Energía Eólica en Argentina: una cuestión estratégica hacia la Economía del Hidrógeno. Wind Energy in Argentina: a strategic subject towards the Hydrogen Economy.

Identificación/caracterización del problema: El abastecimiento energético en base a fuentes no tradicionales o recursos no renovables es un tema altamente estratégico en las agendas de los Estados. El petróleo se está agotando y las existencias no alcanzarán para abastecer el consumo mundial.Esto ha llevado a Gobiernos a implementar alternativas de producción energética basadas en fuentes no tradicionales, tales como el Hidrógeno (H2), lo cual creará una Economía basada en el Hidrógeno.Argentina cuenta con una matriz energética dependiente en un 90 por ciento del petróleo y con reservas certificadas de petróleo y gas natural para 8,6 y 9,4 años respectivamente. Sin duda, los desafíos próximos serán: a) crear las herramientas necesarias para minimizar una potencial crisis energética en el corto plazo, y b) desarrollar políticas energéticas que articulen su autoabastecimiento e inserción en la Economía del Hidrógeno. Dado que Argentina cuenta con uno de los recursos renovables más importantes del mundo, "el viento", tiene condiciones inmejorables para obtener Hidrógeno (H2) por electrólisis del agua, utilizando energía eléctrica proveniente de fuentes renovables como la eólica (EE). Es por ello que apostar al desarrollo local del H2 basado en la EE nos ofrecerá como país, un rol estratégico en la futura Economía del Hidrógeno.Objetivo General: Identificar la actual Matriz Energética Argentina y reconocer los factores limitantes y oportunidades para la diversificación de la misma, utilizando la Energía Eólica (EE) como pilar hacia la Economía del Hidrógeno (Econo-H2). El fin último será esbozar herramientas de política energética e instrumentos regulatorios pertinentes, que sirvan de base para la formulación de una macro política energética.Metodología de Investigación: Se utilizarán técnicas de análisis de la siguiente información:a) Documental (textos, artículos, información periodística)b) Técnica, Legal y administrativa) Oral (Declaraciones oficiales-privadas y entrevistas)d) Visual (imágenes, gráficos y mapas)e) Datos (cronológicos, estadísticos y geográficos)Resultados esperados: La formulación de herramientas de política energética y de instrumentos regulatorios pertinentes, que sirvan de base para la formulación de una macro política energética que considere la Energía Eólica (EE) como un pilar fundamental para la diversificación de la matriz energética actual. Asimismo se reflexionará sobre la importancia de asociar la EE a la producción masiva del hidrógeno (H2) para la inserción y proyección futura de la Argentina hacia la Economía del Hidrógeno.Importancia del Proyecto: Argentina ha ratificado el protocolo de Kioto y forma parte de la Johannesburg Renewable Energy Coalition (JREC), por la cual ha asumido compromisos para fijar políticas nacionales de incentivo para el desarrollo de uso de energías renovables.Sin embargo, y a pesar de una serie de iniciativas y leyes promulgadas relacionadas a uso de energías renovables, hasta la fecha, no se ha logrado cumplir con metas concretas.Consideramos que uno de los factores fundamentales que ha dificultado esto, se basa en la ausencia de una política de Estado de mediano y largo plazo que incluya a las energías renovables como un objetivo concreto y un sistema de instrumentos y planes complementarios que acompañen dicha política.

Entwicklung neuer Modellkatalysatoren auf Porenbetonbasis : Untersuchung von Porenbetonabfällen, Herstellung, Charakterisierung und katalytische Testversuche der Nickel-, Kupferoxid-, Nickeloxid- und Chromocen-Porenbetonkatalysatoren

Kupferoxid-Katalysator, Nickeloxid-Katalysator, Nickel-Katalysator, Chromocen-Katalysator, Porenbeton, Porenbetonabfälle