Responses of lung cells to realistic exposure of primary and aged carbonaceous aerosols

Diesel exhaust and wood burning are important sources of ambient atmospheric particles due to increasing numbers of diesel cars and the importance of wood as a source of renewable energy. Inhalation is the predominant route of entry and uptake for fine and ultrafine particles into the body. Health effects of atmospheric particles are still not completely understood. There is consistent evidence from epidemiology that particle exposure contributes to respiratory and cardiovascular diseases. This study aimed at examining acute responses of airway epithelial cells and luminal macrophages after exposure to freshly emitted and photochemically aged carbonaceous aerosols under realistic atmospheric conditions. In addition to a bronchial epithelial cell line advanced cell cultures namely fully differentiated respiratory epithelia and primary surface macrophages were used. Our results demonstrate that a single exposure of the cells to realistic particle doses of 0.3–3 ng diesel or 3–9 ng wood aerosol per cm2 cell surface induces small, particle-specific responses. The release of interleukin-6 and -8 was found to be decreased in differentiated airway epithelia but not in the other cell models studied. Aerosol exposure decreased macrophage phagocytic activity by 45–90%. Cell and tissue integrity remained unaffected. Overall, primary and aged particles from the same combustion induced similar responses in the cell models tested, whereby particles from diesel exhaust affected the cells more than those from wood combustion.

Tissue Crowding Induces Caspase-Dependent Competition for Space.

Regulation of tissue size requires fine tuning at the single-cell level of proliferation rate, cell volume, and cell death. Whereas the adjustment of proliferation and growth has been widely studied [1, 2, 3, 4 and 5], the contribution of cell death and its adjustment to tissue-scale parameters have been so far much less explored. Recently, it was shown that epithelial cells could be eliminated by live-cell delamination in response to an increase of cell density [6]. Cell delamination was supposed to occur independently of caspase activation and was suggested to be based on a gradual and spontaneous disappearance of junctions in the delaminating cells [6]. Studying the elimination of cells in the midline region of the Drosophila pupal notum, we found that, contrary to what was suggested before, Caspase 3 activation precedes and is required for cell delamination. Yet, using particle image velocimetry, genetics, and laser-induced perturbations, we confirmed [ 6] that local tissue crowding is necessary and sufficient to drive cell elimination and that cell elimination is independent of known fitness-dependent competition pathways [ 7, 8 and 9]. Accordingly, activation of the oncogene Ras in clones was sufficient to compress the neighboring tissue and eliminate cells up to several cell diameters away from the clones. Mechanical stress has been previously proposed to contribute to cell competition [ 10 and 11]. These results provide the first experimental evidences that crowding-induced death could be an alternative mode of super-competition, namely mechanical super-competition, independent of known fitness markers [ 7, 8 and 9], that could promote tumor growth.

Comparative exergy analysis of direct alcohol fuel cells using fuel mixtures

Within the last years there has been increasing interest in direct liquid fuel cells as power sources for portable devices and, in the future, power plants for electric vehicles and other transport media as ships will join those applications. Methanol is considerably more convenient and easy to use than gaseous hydrogen and a considerable work is devoted to the development of direct methanol fuel cells. But ethanol has much lower toxicity and from an ecological viewpoint ethanol is exceptional among all other types of fuel as is the only chemical fuel in renewable supply. The aim of this study is to investigate the possibility of using direct alcohol fuel cells fed with alcohol mixtures. For this purpose, a comparative exergy analysis of a direct alcohol fuel cell fed with alcohol mixtures against the same fuel cell fed with single alcohols is performed. The exergetic efficiency and the exergy loss and destruction are calculated and compared in each case. When alcohol mixtures are fed to the fuel cell, the contribution of each fuel to the fuel cell performance is weighted attending to their relative proportion in the aqueous solution. The optimum alcohol composition for methanol/ethanol mixtures has been determined.

Perspectives on the design and use of direct alcohol fuel cells fed by alcohol blends

The fast-growing power demand by portable electronic devices has promoted the increase of global production of portable PEM fuel cell, a quarter of them consist of direct methanol fuel cell (DMFC) units. These present the advantage of being fuelled directly with a liquid fuel, as well as direct ethanol fuel cells (DEFC) do.

Fuel Cells: A Real Option for Unmanned Aerial Vehicles Propulsion

The possibility of implementing fuel cell technology in Unmanned Aerial Vehicle (UAV) propulsion systems is considered. Potential advantages of the Proton Exchange Membrane or Polymer Electrolyte Membrane (PEMFC) and Direct Methanol Fuel Cells (DMFC), their fuels (hydrogen and methanol), and their storage systems are revised from technical and environmental standpoints. Some operating commercial applications are described. Main constraints for these kinds of fuel cells are analyzed in order to elucidate the viability of future developments. Since the low power density is the main problem of fuel cells, hybridization with electric batteries, necessary in most cases, is also explored.

How do Impurity Inclusions Influence the Mechanical Properties of Multicrystalline Silicon?

The purpose of this research is to characterise the mechanical properties of multicrystalline silicon for photovoltaic applications that was crystallised from silicon feedstock with a high content of several types of impurities. The mechanical strength, fracture toughness and elastic modulus were measured at different positions within a multicrystalline silicon block to quantify the effect of impurity segregation on these mechanical properties. The microstructure and fracture surfaces of the samples was exhaustively analysed with a scanning electron microscope in order to correlate the values of mechanical properties with material microstructure. Fracture stresses values were treated statistically via the Weibull statistics. The results of this research show that metals segregate to the top of the block, produce moderate microcracking and introduce high thermal stresses. Silicon oxide is produced at the bottom part of the silicon block, and its presence significantly reduces the mechanical strength and fracture toughness of multicrystalline silicon due to both thermal and elastic mismatch between silicon and the silicon oxide inclusions. Silicon carbide inclusions from the upper parts of the block increase the fracture toughness and elastic modulus of multicrystalline silicon. Additionally, the mechanical strength of multicrystalline silicon can increase when the radius of the silicon carbide inclusions is smaller than ~10 µm. The most damaging type of impurity inclusion for the multicrystalline silicon block studied in this work was amorphous silicon oxide. The oriented precipitation of silicon oxide at grain and twin boundaries eases the formation of radial cracks between inclusions and decreases significatively the mechanical strength of multicrystalline silicon. The second most influencing type of impurity inclusions were metals like aluminium and copper, that cause spontaneous microcracking in their surroundings after the crystallisation process, therefore reducing the mechanical response of multicrystalline silicon. Therefore, solar cell producers should pay attention to the content of metals and oxygen within the silicon feedstock in order to produce solar cells with reliable mechanical properties.

Estudo e desenvolvimento de catalisadores para células a combustível visando o aumento de escala e avaliação da distribuição de corrente

O trabalho visa o desenvolvimento do sistema para medidas de distribuição de corrente e ampliação de escala (50 cm²) buscando aperfeiçoar as condições de preparação do conjunto eletrodo membrana (MEA) quanto às condições de operação da célula e avaliar a melhor geometria. Foram realizados estudos de síntese de catalisadores de Pt-M e avaliação do desempenho desses materias e das rotas de síntese utilizadas com objetivo de aplicar estes materias em sistemas de maior escala. A insuficiência do desempenho e estabilidade dos catalisadores são fatores que ainda inviabilizam o uso em larga escala das células a combustível de eletrólito polimérico sólido, destacando-se as perdas associadas ao desempenho do cátodo. Os catalisadores preparados foram nanopartículas bimetálicas PtM/C (M = Fe, Co e Ni) suportadas em carbono de elevada área superficial, por duas rotas sintéticas. Foram utilizadas as rotas: ácido fórmico e etilenoglicol modificado (EG). Em ambas as rotas se buscou catalisadores com alto grau de incorporação do segundo metal, tamanho de partícula pequeno e bom desempenho catalítico do cátodo. Observou-se que pela rota do ácido fórmico com modificações no processo de síntese é possível obter a incorporação nominal do segundo metal no catalisador, porém há desvantagem de o tamanho de partícula ser elevado. Pela rota do EG obteve-se catalisadores com pequeno tamanho de partícula, porém a incorporação do segundo metal mostrou-se ineficiente. Os estudos de ampliação de escala foram realizados em células de 50 cm2 variando-se as condições de operação; i) diferentes placas de distribuição de gás, e ii) diferentes valores de fluxo dos gases reagentes. Foi observado que a baixos fluxos de gases a quantidade de reagente é insuficiente para ser difundida por todo eletrodo, o que ocasiona reação apenas na região de entrada de gases no sistema, ocasionando uma rápida limitação em obter-se densidades de corrente alta. Pode-se observar que a diferença de desempenho entre as placas é pequena, porém a placa serpentina 6 apresentou melhor desempenho. O desempenho dos cátodos preparados com catalisadores comerciais e os sintetizados no laboratório nas células de 50 cm² mostrou sofrer bastante influência das condições de operação comparada com as células de 4,6 cm².

Electrochemical analysis of the performance of carbon supported Pd nanoparticles for direct formic acid fuel cells: from gold supported electrodes to catalyst-coated membranes

In this work carbon supported Pd nanoparticles were prepared and used as electrocatalysts for formic acid electrooxidation fuel cells. The influence of some relevant parameters such as the nominal Pt loading, the Nafion/total solids ratio as well as the Pd loading towards formic acid electrooxidation was evaluated using gold supported catalytic layer electrodes which were prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes (CCM). The results obtained show that, for constant Pd loading, the nominal Pd loading and the Nafion percentage on the catalytic layer do not play an important role on the resulting electrocatalytic properties. The main parameter affecting the electrocatalytic activity of the electrodes seems to be the Pd loading, although the resulting activity is not directly proportional to the increased Pd loading. Thus, whereas the Pd loading is multiplied by a factor of 10, the activity is only twice which evidences an important decrease in the Pd utilization. In fact, the results obtained suggest the active layer is the outer one being clearly independent of the catalytic layer thickness. Finally, catalyst coated membranes with Pd catalyst loadings of 0.1, 0.5 and 1.2 mg cm-2 were also tested in a breathing direct formic acid fuel cell.

The Policy Framework for the Promotion of Hydrogen and Fuel Cells in Europe: a Critical Assessment. Bruges European Economic Policy (BEEP) Briefing 19/2008

This paper reviews the current EU policy framework in view of its impact on hydrogen and fuel cell development. It screens EU energy policies, EU regulatory policies and EU spending policies. Key questions addressed are as follows: To what extent is the current policy framework conducive to hydrogen and fuel cell development? What barriers and inconsistencies can be identified? How can policies potentially promote hydrogen and fuel cells in Europe, taking into account the complex evolution of such a disruptive technology? How should the EU policy framework be reformed in view of a strengthened and more coherent approach? The paper concludes that the current EU policy framework does not hinder hydrogen development. Yet it does not constitute a strong push factor either. EU energy policies have the strongest impact on hydrogen and fuel cell development even though their potential is still underexploited. Regulatory policies have a weak but positive impact on hydrogen. EU spending policies show some inconsistencies. However, the large scale market development of hydrogen and fuel cells will require a new policy approach which comprises technology specific support as well as a supportive policy framework with a special regional dimension.

Synthesis, characterization, and electrical conduction of 10 mol% Dy2O3 doped CeO2 ceramics

Well-densified 10 mol% Dy2O3-doped CeO2 (20DDC) ceramics with average grain sizes of similar to 0.12-1.5 mu m were fabricated by pressureless sintering at 950-1550 degrees C using a reactive powder thermally decomposed from a carbonate precursor, which was synthesized via a carbonate coprecipitation method employing nitrates as the starting salts and ammonium carbonate as the precipitant. Electrical conductivity of the ceramics, measured by the dc three-point impedance method, shows a V-shape curve against the average grain size. The sample with the smallest grain size of 0.12 mu m exhibits a high conductivity of similar to 10(-1.74) S/cm at the measurement temperature of 700 degrees C, which is about the same conduction level of the micro-grained 10 mol% Sm2O3- or Gd2O3-doped CeO2, two leading electrolyte materials. (c) 2004 Elsevier Ltd. All rights reserved.

Native grain refinement of magnesium alloys

High purity Mg-Al type alloys have a naturally fine grain size compared to commercial purity alloys with the same basic composition. This is referred to as native grain refinement. It is shown that native grain refinement occurs only in magnesium alloys containing aluminium. The mechanism is attributed to the Al4C3 particles existing in these alloys. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Molten carbonate fuel cells

Over the past 12 months, developments in both porous and non-porous materials for the molten carbonate fuel cell (MCFC) should lead to significantly increased stack lifetimes. Lithium-sodium carbonate is emerging as the material of choice for the electrolyte and has been tested in a 10 kW scale stack. Several new cathode materials, with lower dissolution rates in the electrolyte than state-of-the-art NiO, have been tested. However a significant finding is that the dissolution rate of NiO can also be reduced by an order of magnitude by preparing it as a functional nanomaterial. Although most developers continue to use nickel anodes, recent tests with ceramic oxides anodes open up the prospects of reduced carbon deposition and future cells running directly on dry methane. (c) 2004 Published by Elsevier Ltd.

Microbial Fuel Cells: Methodology and Technology

Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. DescribingMFCsystems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.

Operation of polymer electrolyte membrane fuel cells with dry feeds: Design and operating strategies

The operation of polymer electrolyte membrane fuel cells (PEMFCs) with dry feeds has been examined with different fuel cell flow channel designs as functions of pressure, temperature and flow rate. Auto-humidified (or self-humidifying) PEMFC operation is improved at higher pressures and low gas velocities where axial dispersion enhances back-mixing of the product water with the dry feed. We demonstrate auto-humidified operation of the channel-less, self-draining fuel cell, based on a stirred tank reactor; data is presented showing auto-humidified operation from 25 to 115 degrees C at 1 and 3 atm. Design and operating requirements are derived for the auto-humidified operation of the channel-less, self-draining fuel cell. The auto-humidified self-draining fuel cell outperforms a fully humidified serpentine flow channel fuel cell at high current densities. The new design offers substantial benefits for simplicity of operation and control including: the ability to self-drain reducing flooding, the ability to uniformly disperse water removing current gradients and the ability to operate on dry feeds eliminating the need for humidifiers. Additionally, the design lends itself well to a modular design concept. (c) 2005 Elsevier B.V. All rights reserved.