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espanolEn este trabajo se estudia la posibilidad de preparar aleaciones de alta entropia del sistema Al-Sc-Ti-V-Cr. Para ello se han seleccionado los elementos y la composicion utilizando los criterios conocidos y disponibles en la literatura y se han preparado mediante fusion por arco tres aleaciones con contenidos que varian entre el 10 y 35 at.%. Las tres aleaciones tienen una microestructura dendritica bifasica similar, siendo las dendritas una solucion solida bcc enriquecida en Ti, V o Cr. El escandio aparece unicamente en el espacio interdendritico formando el intermetalico Al2Sc. La dureza de las dendritas crece con el contenido en Ti y se hace menor a medida que es mayor el contenido en Cr. Ademas, la tenacidad de las aleaciones depende de la dureza de las dendritas siendo esta mayor cuanto mas blandas son las dendritas. Los resultados obtenidos demuestran que ni los criterios empiricos utilizados ni los calculos mediante THERMOCALC permiten predecir la formacion de una unica solucion solida ni la naturaleza de las fases observadas experimentalmente. EnglishThe feasibility of preparing high entropy alloys in the Al-Sc-Ti-V-Cr system has been evaluated taking into account the different criteria reported in the literature. Based on such criteria, three Al-Sc-Ti-V-Cr alloys were chosen with contents of each element varying from 10 to 35 at. %, and prepared by arc melting. All alloys exhibit a two-phase dendritic microstructure, with the major dendritic phase being a bcc solid solution enriched in Ti, V, or Cr. Scandium is strongly rejected from the dendrites towards the interdendritic regions to form Al2Sc in the three alloys. The bcc solid solution dendrites become harder with high Ti content and lower with high Cr content. The toughness of the alloys depends on the hardness of the dendrites, with alloys with harder dendrites becoming more brittle. The results indicate that neither empirical criteria used nor THERMOCALC calculus tool can predict properly the formation of a single solid solution nor the nature of the existing phases respectively.

We describe a novel approach for simultaneously determining regional differences in action potential (AP) morphology and tissue electrophysiological properties in isolated atria. The epicardial surface of rat atrial preparations was placed in contact with a multi-electrode array (9 × 10 silver chloride electrodes, 0.1 mm diameter and 0.1 mm pitch). A glass microelectrode (100 MΩ) was simultaneously inserted into the endocardial surface to record intracellular AP from either of 2 regions (A, B) during pacing from 2 opposite corners of the tissue. AP duration at 80% of repolarisation and its restitution curve was significantly different only in region A (p < 0.01) when AP was initiated at different stimulation sites. Alternans in AP duration and AP amplitude, and in conduction velocity were observed during 2 separate arrhythmic episodes. This approach of combining microelectrode array and intracellular membrane potential recording may provide new insights into arrhythmogenic mechanisms in animal models of cardiovascular disease.

The creep behaviour of some oxide-dispersion-hardened Fe-Al-Cr iron aluminides has been examined at 700-750°C and compared with similar dispersion-hardened steels and commercial Fe-Cr alloys. Very fine oxide particles form during material processing, which are generally fcc Y2O3 phase with a thin disk morphology, and partially coherent with the ordered FeAl matrix. The materials show excellent creep strength at the tested temperatures which may be related to the oxide particles being barriers opposing dislocation motion. Precise details of dislocation-particle interactions are not clear, but it is suggested that the fine particles are cut relatively easily by the dislocations. © 2014 Elsevier B.V.

An aluminium matrix composite was prepared by mixing commercial aluminium powders and 15 vol % of FeAlCr powders and consolidation by hot extrusion. The extruded composite was subjected to severe plastic deformation by equal channel angular pressing (ECAP) at room temperature and at 150°C. The extruded composite presents a uniform distribution of particles although some defects are observed such as residual pores and particle agglomerates. The particle distribution does not show a significant change due to ECAP. The extruded composite exhibits a relatively fine grain size of the order of 1-2 μm that was refined to 550 nm after three ECAP passes at room temperature by route A and to 636 nm after four passes at 150°C by route Bc. The yield stress of the composites was increased by 140 to 180% after ECAP as compared with the extruded condition.

The large number of missions associated with ESA’s Copernicus program has necessitated several new image sensor designs for earth observation (or living planet) applications as each instrument needs to be highly optimized. Whilst the majority of these sensors have utilised CCD technology, the use of CMOS is starting to increase. New CCD designs and technology trends for hyperspectral applications such as Sentinel 4, Sentinel 5, Sentinel 5 precursor (TropOMI), Flex and 3MI are described. In these the sensor design has been optimized to provide highest possible signal levels with lowest possible noise in combination with higher frame rates and reduced image smear. CMOS sensors for MTG (Meteosat Third Generation) and METImage are then described. Both use extremely large pixels, up to 250μm square, at high line rates. Radiation test data and key performance measurements are shown for MTG and for a test device that has been made for METImage. Finally, newer developments including back-illumination and means for achieving a TDI function in standard-processed CMOS are briefly described.

Many important metallic alloys are characterised by the chemical ordering of their atomic component elements. Examples are beta brass (βCuZn - one of the components of common brass), many of the gold-base alloys used in dentistry, Nickel-Titanium shape memory alloys with superelastic properties (great stretchability, as used for orthodontic wires) and Nickel-Aluminium gamma-prime phase which strengthens superalloys for high-temperature turbines. The figure shown below (Fig. 1) represents such an ordered arrangement of two atomic species (could be copper and gold, or nickel and aluminium) on a face centred cubic lattice. The disordered lattice would have the yellow and blue atoms randomly distributed. While such important materials, the realisation that these crystals are chemically ordered (in contrast to chemically-disordered alloys, such as alpha brass (αCuZn), steels, aluminium alloys, and most other metallic alloys) is a relatively new understanding, being just now one century old. It had been understood for a long time before that crystals contained spatially-ordered atoms, but not that there was chemical order hidden inside. It was only with the development of methods of diffraction of x-rays by crystals that it became possible to recognise and quantify such chemical order.

A CuCrZr alloy has been processed by equal channel angular pressing and annealing. Changes of microstructure have been analysed using thermoelectric power measurements, which are very sensitive to the amount of solute as well as other defects introduced during processing. Severe plastic deformation of solutionized material leads to significant increases in the amount of solute, which leads to significantly more precipitation on ageing. Such factors must be taken into account in any interpretation of final microstructures and mechanical properties. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Severe plastic deformation has been used over the last decades as a method for processing ductile materials to obtain fine microstructures. Typically, the microstructure obtained has a submicron size, and only rarely is the formation of nanostructures described. The present short paper examines the nature of the substructures produced during deformation in the strain range about 1–10, when dislocations accumulate to produce cell and sub-boundary structures, and considers the variation of both microstructural size and the typical misorientation across boundaries present as the strain level increases. Some examples of severe plastic deformation carried out on bulk samples of iron aluminide alloys and composites are described, where conventional processing techniques have been used to impose the high strain levels. An advantage of such conventional processes over the special techniques commonly used to impose high strain is that upscaling to large material volumes may be envisaged. The effect of such microstructural refinement on the room temperature strength and ductility of these intermetallics will be demonstrated. The high dislocation density leads to good strength, but many high angle boundaries are required to improve ductility. High-temperature creep resistance in suitable iron aluminide alloys and composites has been obtained for cases when severe plastic deformation leads to a refinement and redistibution of second phase particles.

Severe plastic deformation has been carried out in some iron aluminide alloys by repeated high-temperature forging and used to refine the dispersion of cast-in second phase particles. The second phases considered range from brittle Laves phases to tougher boride phases, with both apparently refined in the same way by the forging. It appears that refinement is mostly determined by the initial morphology of the second phase particles, with elongated particles being broken towards an equiaxed shape. A relatively uniform distribution of fine second phase particles, such as would be needed for good high-temperature creep resistance, requires very high levels of imposed plastic strain on initially fine elongated particles.

A directionally cast Cu-Fe composite has been deformation processed both by Equal Channel Angular Pressing (ECAP) followed by rod rolling and by rod rolling alone, and the microstructural evolution and resulting mechanical behaviour examined. Material processed by rod rolling alone shows higher strength and slightly better ductility. Matrix microstructure is characterised by elongated dislocation cells/subgrains, which are finer with higher boundary misorientations after rod rolling alone. The initial Fe dendrites transform slowly to thin ribbons with a narrower range of crystal orientations after rolling alone than after preliminary ECAP. Strengthening here is principally due to matrix microstructural refinement, with contributions due to dislocations in cell boundaries and within the cells and due to grain/subgrain boundaries. Fe in solid solution as well as in the form of precipitate particles leads to additional matrix hardening, with the coarse precipitates producing locally harder regions of finer microstructures due to deformation incompatibility with the matrix. The use of ECAP as an initial stage of processing has not led to the expected microstructural refinement and improved mechanical behaviour. © 2011 Elsevier B.V.

Iron aluminides are of interest for applications in power generation from fossil fuels because of excellent high temperature oxidation-corrosion resistance in aggressive environments and are potential replacements for high temperature steels. The Fe-base composition ensures relative cheapness, while the high Al content leads to significant density reduction over commercial steels. Problems of low ductility/toughness at room temperature and poor high temperature (creep) strength, however, have prevented significant commercial use. After studies led by Oak Ridge National Laboratory (USA) from about 1980 to 2000, research has continued in Europe both as pan-European efforts and as national efforts in countries such as the Czech Republic, France, Germany and Spain. An overview of such recent activities is presented, indicating the research strategies involved, and the progress toward making iron aluminides useful engineering materials. Recent activities have targeted microstructural refinement through novel processing to improve room temperature ductility or attempted alloying additions to improve high temperature strength. Achieving the required properties remains difficult, and has led to developments of iron aluminides as cast components and as coatings. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fe–Al alloys, both those based on Fe3Al and those based on FeAl, show an anomalous increase in flow stress for temperatures in the range about 500–900 K. Some of the important characteristics of the experimental results collected over decades of study are reviewed, concentrating here on FeAl alloys with B2 order. Particular attention is given to the influence of vacancy concentration and the stress orientation when testing single crystal samples. Recent analyses deduce that the stress anomaly is caused by the high concentration of vacancies present at these temperatures. Re-analysis here of the hardening suggests that vacancies may annihilate at the dislocation cores and the new jogs may be suitable sites for subsequent dislocation decomposition into less mobile segments.

14 pages, 8 figures., [EN] Nanostructured metals and alloys have a variety of chemical and physical properties that are greatly modified by the nano-scale of their microstructure. At the same time, these materials generally show very high strength, although ductility or toughness may not be good. Strength increases as the microstructure scale reduces from the macro-micro level and even finer, but sometimes the strength appears to fall as the structure scale approaches the nano level. These strength variations are examined here, and the mechanisms responsible for both strengthening and weakening are discussed. The fall in ductility and toughness as materials become nanostructured is a complex topic that requires extensive analysis, but this will not be treated in the present overview., [ES] Los metales y aleaciones nanoestructuradas muestran una serie de propiedades químicas y físicas fuertemente modificadas cuando su microestructura entra en la escala nano. A la vez, estos materiales muestran generalmente alta resistencia pero mediocre ductilidad o tenacidad. La resistencia aumenta cuando baja la escala de la microestructura desde el nivel micro hacia el nivel nano, pero a veces la resistencia parece reducir por las microestructuras mas finas. Se examinan aquí todas estas variaciones y se discuten los mecanismos responsables del endurecimiento y ablandamiento. Los cambios de ductilidad o tenacidad cuando la microestructura entra en la escala nano necesitan un análisis detallado que no se trata en este articulo.

An Al-Cu-Li alloy has been severely deformed by rolling over a wide range of temperatures and the evolution of deformation substructure and precipitation examined. A high dislocation density is retained at all temperatures, with dislocations forming cell and subgrain arrangements. There is a greater extent of recovery and coarsening at the higher temperatures. Much finer precipitate particles are seen after rolling than after simple ageing, and grain boundary precipitation is much less extensive. Particle size is reduced both by extensive precipitation on dislocations and by the breakage of previously formed precipitates by the subsequent high strain. Material strength is increased by the presence of the deformation substructure and the fine precipitates, while ductility is improved only when extensive recovery has taken place. More severe deformation, controlling the extent of precipitation, is necessary to refine structures further. © 2008 Elsevier B.V. All rights reserved.

Microstructure evolution of a Fe–Ni–Al alloy has been examined during annealing at temperatures between about 700 and 800 °C. This material is brittle in the cast state but shows good strength with ductility after a stabilising anneal at 1100 °C when it has a duplex microstructure of B2 dendrites with fcc interdendritic phase. The 700–800 °C ageing leads to the formation of metastable bcc precipitates within the dendrites with less change within the interdendritic regions. The long-term coarsening of these precipitates is controlled by diffusion within the B2 phase. The composition of the B2 phase changes with annealing temperature, which is believed to modify the diffusion rate and, correspondingly, the rate of particle coarsening. The present coarsening study serves to define annealing conditions for preparation of optimum microstructure before material testing, as well as define upper temperature limits for possible long-term application, where stable microstructures are required.

Surfactant lines the alveolar surface and prevents alveolar collapse. Derangements of surfactant cause respiratory failure and interstitial lung diseases. The collectins, surfactant proteins A and D, are also important in innate host defense. However, surfactant regulation in the postnatal lung is poorly understood. We found that the epithelial integrin, alphavbeta6, regulates surfactant homeostasis in vivo by activating latent transforming growth factor (TGF)-beta. Adult mice lacking the beta-subunit of alphavbeta6 (Itgb6-/-) developed increased bronchoalveolar lavage phospholipids and surfactant proteins A and D, and demonstrated abnormal-appearing alveolar macrophages, reminiscent of the human disease pulmonary alveolar proteinosis. Using lung-specific expression of constitutively active TGF-beta1 in Itgb6-/- mice, we found that TGF-beta1 was sufficient to normalize these abnormalities. Tgfbeta1-deficient mice also demonstrated increased phospholipids and surfactant proteins A and D, but mice lacking the key TGF-beta signaling molecule, SMAD3, did not. Therefore, integrin-mediated activation of latent TGF-beta1 regulates surfactant constituents independent of intracellular SMAD3. In vivo increases in surfactant protein A and D were not associated with increases in mRNA for these proteins in alveolar tissue from Itgb6-/- mice. On the other hand, isolated alveolar macrophages from Itgb6-/- mice were defective in processing phospholipids in vitro, suggesting that reduced surfactant clearance contributes to altered surfactant homeostasis in these mice in vivo. These findings show that alphavbeta6 and TGF-beta1 regulate homeostasis of phospholipids and collectins in adult mouse lungs and may have implications for anti-fibrotic therapeutics that inhibit active TGF-beta in the lung.

Most studies of creep resistance in Fe-Al intermetallics are oriented at typical applications of 500-650 °C in competition with conventional stainless steels. These intermetallics show excellent oxidation and corrosion resistances even above 1000 °C, where conventional steels are no longer sufficiently resistant. This overview considers attempts at the development of good creep resistance for temperatures intermediate between these two temperature regimes. A variety of cast Fe3Al-based alloys containing solution or precipitate/dispersoid-forming additions will be reported. These alloys show good room temperature strength but weaken above 500 °C due to thermally activated deformation processes. It is shown to be difficult to improve creep strength by changing matrix diffusivity. Solution additions only slightly improve creep strength above 700 °C. Hardening in some alloys containing Fe2Nb Laves precipitates will be discussed. These materials show good strength to 700 °C, but the fine precipitates coarsen rapidly at higher temperatures. Carbide and boride additions generally show poor strengthening due coarse dispersoid distributions, but excellent thermal stability allows good strength retention to very low strain rates. As well as such alloying and structural factors, the importance of processing control to obtain the desired stable microstructures will be considered. © 2006 Elsevier B.V. All rights reserved.

Work hardening in polycrystalline Fe-Al alloys has been examined for alloys containing from nearly no Al up to about 40 at.% Al. A sharp maximum in work hardening is seen for alloys containing 26-30% Al. Examination of dislocation structures with increasing Al content over the region of the maximum shows that the most important change, apart from the formation of superdislocation dipoles instead of single dislocation dipoles, is the predominance of straight screw dislocations and the formation of sessile dislocation segments by reactions of mobile dislocations. The peak in work hardening rate coincides with increased elastic anisotropy, but this is believed to reflect the importance of core/Peierls effects rather than to be a direct cause of high work hardening. © 2007 Elsevier B.V. All rights reserved.

An Al-7%Si alloy was severely deformed by equal channel angular pressing (ECAP) to study the refinement of the microstructure and associated changes of mechanical properties. The initial coarse dendritic structure was broken into an elongated sub-micron grain/subgrain structure, with high dislocation density, and distributed fine Si particles. The Si particles in the composite are seen to induce a high dislocation density during deformation and lead to faster structural refinement than in a monolithic alloy with the same composition as the matrix. The additional strengthening of the composite relative to the monolithic alloy is due to both the finer grain size and the high retained dislocation density. Severe plastic deformation leads also to an improvement of the ductility of the strong material due to the refinement of both matrix microstructure and the Si particles, We should like to acknowledge financial support of the Spanish Ministry of Education and Science under project number MAT2003-01540, as well as the award of a Juan de la Cierva post-doctoral fellowship for one of the authors (I.G.)

© 2015 Elsevier Inc. All rights reserved. Abstract The chemical composition of nanosized oxides has been analysed in a mechanically-alloyed (MA) iron-chromium-aluminium intermetallic containing yttria additions using an aberration-corrected, high-resolution scanning transmission electron microscope (STEM). The oxide particles are seen to contain yttrium and oxygen only, but very little of the matrix metallic elements, while the matrix in the immediate vicinity shows a very low iron content. Possible reasons for the change of matrix composition outside the particle-matrix interface are discussed., We would like to acknowledge financial support of the Spanish Ministry of Education and Science under project number MAT2009-07342.

The evolution of mechanical properties between room temperature and 573 K (300 °C) has been studied in a Mg-Y-Zn-Gd alloy under different heat treated and thermomechanically processed conditions. The different distributions of longperiodstackingordered phase and precipitation of lamellar Gd-rich phase, modified by severe deformation processing, lead to strengths ranging between 112 and 175 MPa at 573 K (300 °C). Microstructures have been evaluated under different processing conditions and comparison made with a similar alloy without Gd previously studied. Although the alloys can achieve similar room temperature strengths, only the Gd-containing alloy can retain sufficient high strength at temperatures above 473 K (200 °C). This is due to the strengthening effect of the lamellar Gd-rich precipitates that are broken and redistributed during the severe deformation processing., We would like to acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness under project number MAT2012-34135.

© 2014 Elsevier Ltd. Concentrated solar power systems are receiving increasing attention as electricity generating systems, whereby the sun's heat is focused onto a receiver heated to high temperatures. Systems operating today are generally limited to temperatures below about 600. °C, but there is considerable interest in increasing operating temperatures, with heat receivers generally constructed using refractory metallic alloys or ceramics. The present study compares the behaviour of a range of metallic or ceramic materials with advanced intermetallic alloys which have been developed for high-temperature aeronautic or power-generating systems. A few experiments are reported using intense solar heating to demonstrate the damage that may be sustained, depending on the material that is considered. Accelerated cyclic oxidation experiments further emphasize the sensitivity of the various materials to oxidation and thermal damage accumulation. The important characteristics required of the material to be used for the receiver are described and used to generate property maps where the suitability of different classes of materials (metal, intermetallic, ceramic) may be compared. Depending on the precise conditions of where the receiver will operate, and whether creep, fracture or oxidation/spalling is the most important damaging process, either refractory Ni-base alloys, Mo-silicides, or ceramics may be the best material for the application.

Methods of severe plastic deformation of ductile metals and alloys offer the possibility of processing engineering materials to very high strength with good ductility. After typical amounts of processing strain, a submicrocrystalline material is obtained, with boundaries of rather low misorientation angles and grains containing a high density of dislocations. In the present study, an Al-Mg-Si alloy was severely plastically deformed by equal channel angular pressing (ECAP) to produce such a material. The material was subsequently annealed for dislocation recovery and grain growth. The strength of materials in various deformed and annealed states is examined and the respective contributions of loosely-arranged dislocations, many grain boundaries, as well as dispersed particles are deduced. It is shown that dislocation strengthening is significant in as-deformed, as well as lightly annealed materials, with grain boundary strengthening providing the major contribution thereafter. © Springer Science+Business Media, LLC 2007.

The addition of Nb to Fe3Al-base alloys has been shown to improve strength for temperatures below about 700 °C, but thereafter the strength gains are minimal. Changes of order and precipitation occur on annealing of quenched Fe-Al-Nb alloys at temperatures in the range of about 600-800 °C, and these are responsible for the changes of mechanical properties. Factors responsible for the poor precipitate stability and loss of strength are examined, which include the role of interface structure on destabilizing precipitates of the intermediate phase which forms, promoting its transition to the stable Laves phase, as well as allowing rapid coarsening of Laves precipitates. © 2006.

The microstructure and mechanical behaviour of Al-based composites reinforced with TiAl intermetallic particles has been examined in the as-extruded state and after processing by equal channel angular pressing (ECAP). The latter produces a grain size reduction in the aluminium matrix to values of 500 nm, using route A, and 750 nm, using route C. The ECAP produces up to a 75% increase in the yield stress of the composites, being more rapid when route A is used. The strengthening effect by ECAP is much larger than that obtained by increasing the volume fraction of reinforcement particles from 25 to 50% in these composites, Thanks to the Spanish Ministry of Education and Science for financing this study under project number MAT2003-01540.

The anomalous stress peak observed near 500–600 °C in Fe–Al alloys has now been convincingly explained using a model of hardening by immobile thermal vacancies on the lower temperature side of the peak and the loss of hardening as these vacancies become mobile at higher temperatures. The large numbers of vacancies required for such hardening are associated with compositions close to stoichiometry, i.e. 40–50%Al, raising the question of whether such a vacancy hardening model can be adopted for Fe3Al alloys, which show a similar stress peak anomaly. Examination of data on vacancy formation over the entire range of composition, Fe–Fe3Al–FeAl, shows that, indeed, a vacancy hardening model appears capable of explaining the stress anomaly for both FeAl and Fe3Al.

Severe deformation by equal channel angular pressing (ECAP) of extruded Al-TiAl composites have been studied to understand the influence on the microstructure and mechanical properties as a function of reinforcement particle size and distribution. Microstructure refinement to submicron grain size was already observed in the aluminium matrix after the first ECAP pass, with saturation occurring after four passes. The number of ECAP passes that the composites can sustain before fracturing decreases with the decrease of interparticle spacing, i.e, with an increase in volume fraction of reinforcement particles and/or the decrease in their size. The strength of the composites increases and the ductility decreases after processing by ECAP. The reduction of ductility occurs by weakening of the Al-TiAl interface due to stress concentrations accumulated by the severe deformation of the aluminium matrix. © 2005 Elsevier B.V. All rights reserved.

The sub-micrometer microstructure developed during severe plastic deformation by equal channel angular pressing in an Al alloy containing a small amount of dispersed intermetallic particles has been examined in material in a variety of solutionised and precipitated states. Microstructural refinement, and corresponding strengthening, occurs faster in these particle-containing materials than in particle-free equivalents. Coarse precipitate and dispersoid particles remain mostly unaffected by the severe deformation, and appear to help stabilise a finer deformation microstructure, while fine precipitates are sheared and apparently dissolved. The extent of microstructural refinement and strengthening depends more on solute content than on particle distributions. The limited effect of dispersoid and precipitate particles may be due, in part, to their presence in only small volume fractions, less than 1% by volume each. Strengthening depends more on dislocation arrangements and densities than on the nuber of boundaries present. © 2004 Elsevier B.V. All rights reserved.

Nanoindentation has been used to study Young's modulus and hardness of Fe-Al alloys with Al contents from 22 to 47 at%, and the influence of Cr additions to near Fe3Al alloys. Materials are examined in the quenched state and the well-annealed state with, respectively, relatively poor order with retained thermal vacancies, and good order with few vacancies. Significant changes occur in both modulus and hardness, affected by Al content, Cr addition and heat treatment. These changes are discussed in terms of state of order, possible role of magnetisation, and vacancies. © 2013 Elsevier Masson SAS. All rights reserved.

On the basis of single crystal diffraction analyses it is shown that conversion of 13H-dibenzo(a,i)fluoren-13-one into its oxime causes distortion of the aromatic framework because of steric crowding. The oxime is, in consequence, chiral.Key words: oxime, crystal structure, chirality.

The crystal structure of trimethylammonio n-hexadecylsulfonamidate contains antiparallel monolayers stabilized by strong C−H···O bonds (C···O 3.22 A). There are also significant C−H···X (X = N, O) bonds linking adjacent layers. The structure suggests that nitrogen ylides have potential as amphoteric surfactants. The crystallography of paraffinic monolayers is discussed and the crystal structures of n-C16H33X compounds are shown to belong to three distinct types.

T cell antigen recognition involves the formation of a structured interface between antigen-presenting and T cells that facilitates the specific transmission of activating and desensitizing stimuli. The molecular machinery that organizes the signaling molecules and controls their disposition in response to activation remains poorly understood. We show here that in T cells Discs large (Dlg1), a PDZ domain-containing protein, is recruited upon activation to cortical actin and forms complexes with early participants in T cell activation. Transient overexpression of Dlg1 attenuates basal and Vav1-induced NFAT reporter activation. Reduction of Dlg1 expression by RNA interference enhances both CD3- and superantigen-mediated NFAT activation. Attenuation of antigen receptor signaling appears to be a complex, highly orchestrated event that involves the mutual segregation of important elements of the early signaling complex.

Iron aluminides have been examined over many years, especially since the 1960s with renewed attention since the 1980s. Several clear characteristics of these materials have been demonstrated, some good and some less attractive. Properties seen are those such as reasonable strength from room temperature to about 500 °C; acceptable but not good ductility at room temperature dependent in part on environmental sensitivity; poor creep and high temperature strength above 500 °C; excellent oxidation and corrosion resistance; cheap constituent elements but difficult thermomechanical forming. This article reviews advances in strengthening and improving ductility of FeAl over the last decade or so, concentrating especially on activities of the authors' groups, and reviews also possibilities for exploiting the excellent oxidation/corrosion resistance at high temperatures by improving the high temperature creep behaviour.

The high-temperature strength of a Fe-25%Al-2%Nb alloy in both a solutionised state and a precipitated state has been determined for temperatures up to 900 °C and compared with that of a solution hardened Fe3Al alloy. Some comparisons of these materials with previously reported Fe 3Al-based materials are also made. The Fe-25%Al-2%Nb material is capable of retaining good strength to temperatures above 800 °C, but rapid coarsening of the Laves precipitate particles at higher temperatures leads to strength loss at such temperatures. The presence of stable dispersed particles at the intermediate temperatures means that good strength can be retained to very low strain rates. © 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The diynol ester PhC(O)OCH2CC–CCCH2OH readily forms very long (4 cm) needle-shaped crystals. The crystal structure in the range 100–293 K contains strong O–H⋯O hydrogen bonds which link molecules related by the operation of a 21 screw axis into chains which are parallel to the long axis of the needle. Coefficients of linear expansion suggest that attractive intermolecular forces are strongest in the direction of the needle axis.

The goal of the Complex Trait Consortium is to promote the development of resources that can be used to understand, treat and ultimately prevent pervasive human diseases. Existing and proposed mouse resources that are optimized to study the actions of isolated genetic loci on a fixed background are less effective for studying intact potygenic networks and interactions among genes, environments, pathogens and other factors. The Collaborative Cross will provide a common reference panel specifically designed for the integrative analysis of complex systems and will change the way we approach human health and disease.

Iron aluminides do not generally show good aqueous corrosion resistance. The present study attempts to improve their corrosion resistance by prior surface oxidation. While good corrosion resistance can indeed be obtained, it is found to be difficult to ensure that the oxide layer is continuous and defect free. © 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

The coarsening of oxide particles and grains in an ODS FeAl intermetallic has been examined during annealing at high temperatures under conditions where recrystallization does not yet occur. Coarsening of the yttria particles is shown to be controlled by the diffusion of the metallic species through the intermetallic matrix, while the increases of grain size by grain growth are determined by the pinning action of the large number of yttria particles. Hardness falls during the annealing and is seen to depend on both particle size increases and grain size increases.

Integrins are heterodimeric cell-surface proteins that regulate cell growth, migration and survival. We have shown previously that the epithelial-restricted integrin αvβ6 has another critical function; that is, it binds and activates latent transforming growth factor-β (TGF-β)1,2. Through a global analysis of pulmonary gene expression in the lungs of mice lacking this integrin (Itgb6 null mice) we have identified a marked induction of macrophage metalloelastase (Mmp12)—a metalloproteinase that preferentially degrades elastin and has been implicated in the chronic lung disease emphysema3. Here we report that Itgb6-null mice develop age-related emphysema that is completely abrogated either by transgenic expression of versions of the β6 integrin subunit that support TGF-β activation, or by the loss of Mmp12. Furthermore, we show that the effects of Itgb6 deletion are overcome by simultaneous transgenic expression of active TGF-β1. We have uncovered a pathway in which the loss of integrin-mediated activation of latent TGF-β causes age-dependent pulmonary emphysema through alterations of macrophage Mmp12 expression. Furthermore, we show that a functional alteration in the TGF-β activation pathway affects susceptibility to this disease.

The mechanical behaviour of equal channel angular pressing (ECAP) processed Al-3Mg was examined by compression testing in a direction normal to the processing directions. ECAP-processed materials showed no initial yield plateau and needed significant straining before dynamic strain ageing appeared. The results showed that annealed materials had fewer dislocations that were easily locked by solute.

Specific methods of mechanical ventilation management reduce mortality and lower health care costs. However, in the face of a predicted deficit of intensivists, it is unclear whether residency programs are training internists to provide effective care for patients who require mechanical ventilation. To evaluate these educational outcomes, we administered a validated 19-item case-based test and survey to resident physicians at 31 diverse U.S. internal medicine residency programs nationwide. Of 347 senior residents, 259 (75%) responded. The mean test score was 74% correct (SD, 14%; range, 37 to 100%). Important items representing evidence-based standards of critical care answered incorrectly were as follows: use of appropriate tidal volume in the acute respiratory distress syndrome (48% incorrect), identifying a patient ready for a weaning trial (38% incorrect), and recognizing indication for noninvasive ventilation (27% incorrect). Most accurately identified pneumothorax (86% correct) and increased intrathoracic positive end-expiratory pressure (93% correct). Better scores were associated with "closed" versus "open" intensive care unit organization (76 versus 71% correct, p = 0.001), resident perception of greater versus lesser ventilator knowledge (79 versus 71% correct, p = 0.001), and graduation from a U.S. versus international medical school (75 versus 69% correct, p = 0.033). Although overall training satisfaction correlated strongly with program use of learning objectives (r = 0.89, p < 0.0001), only 46% reported being satisfied with their mechanical ventilation training. We conclude that senior residents may not be gaining essential evidence-based knowledge needed to provide effective care for patients who require mechanical ventilation. Residency programs should emphasize evidence-based learning objectives to guide mechanical ventilation instruction.

Born at Renfrew on 8 October 1900, Thomas Stevens Stevens (‘TSS’) was the only child of John and Jane Stevens. His father, a draughtsman and engineer, was production director of William Simons and Company Ltd of Renfrew, shipbuilders specializing in dredger construction. Before her marriage in 1898, his mother Jane (née Irving) was a schoolteacher. His upbringing was typically middle-class, and both parents gave every encouragement for their son to study. However, as a delicate asthmatic youngster Tom's early education was given, until the age of eight, at home by his mother—a fact held by many to be responsible for the seeds that brought forth his great love of language and his sensitive and wide-ranging intellect. Thereafter he attended Paisley Grammar School (1909–15) and the Glasgow Academy (1915–17). At Paisley Grammar School his attention was drawn by Joseph Towers, a teacher of English, and at the Glasgow Academy he delighted in the sardonic humour of G.L. Moffatt, who taught mathematics. Physics and chemistry had nevertheless captured his imagination and in the Academy he enjoyed the extensive opportunities that were provided for practical chemistry. It was a love and a boyish enthusiasm that he retained and continued to practise throughout his professional career. In a popular lecture that he gave in the 1950s, ‘The anatomy of the chemist’, Tommy includes the account given by the famous American teacher, Ira Remsen, of the most impressive experiment he had ever performed: ‘nitric acid acts upon copper’. The story ends, ‘… I drew my fingers across my trousers and another fact was discovered. Nitric acid acts on trousers…’. With its smells, fizzes and bangs it is surely a portrait of the young Stevens himself.

Crystals of 9-methylfluoren-9-ol, C(14)H(12)O, undergo a reversible phase transition at 176 (2) K. The structure of the high-temperature alpha form at 200 K is compared with that of the low-temperature beta form at 100 K. Both polymorphs crystallize in space group P1 with Z = 4 and contain discrete hydrogen-bonded R(4)(4)(8) ring tetramers arranged around crystallographic inversion centres. The most obvious changes observed on cooling the crystals to below 176 K are an abrupt increase of ca 0.5 A in the shortest lattice translation, and a thermal transition with deltaH = 1 kJ mol(-1).

The submicron microstructure developed here after heavy deformation of Al-3Mg by equal channel angular pressing (ECAP) is shown to consist of an elongated grain and cell structure of width 70-80 nm and 300-400 nm length. There is also a high dislocation density inside these grains with some tendency to dislocation arrangement as a cell structure. Many of the grain boundaries are shown to be of low-medium angle and are not the randomly misoriented, high-angle boundaries generally assumed to be present. Annealing at low temperatures leads to a reduction of dislocation density, some reduction of grain length as transverse boundaries form in the elongated grains, and grain coarsening. At higher temperatures a duplex structure forms as some regions show localized recrystallization. The relationship of grain boundary misorientation and high-temperature coarsening and recrystallization to the applied heavy strain and alloy composition is discussed. © 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

The crystalline state and mechanical properties of several rapidly solidified Al-Ni-Ce alloys have been examined in both as-solidified materials and after low temperature annealing to crystallise initially amorphous materials. Significant changes in mechanical properties occur due to changes of both chemical composition and of crystalline structure. Further detailed examinations of deformation mechanisms are necessary. © 2002 Published by Elsevier Science Ltd. on behalf of Acta Materialia Inc.

The influence of a variety of machining conditions on the tensile behaviour of a mechanically alloyed FeAl intermetallic has been examined. Yield behaviour is hardly affected by machining conditions, and ductility is only weakly sensitive to machining speed or cutting depth. This behaviour seems to be related more with the extent of subsurface damage or work hardening than with the roughness of the machined samples. © 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Groundwater contamination by fuel spills from aboveground and underground storage tanks has been of growing concern in recent years. This problem has been magnified by the addition of oxygenates, such as ethanol and methyl-tertiary-butyl ether (MTBE) to fuels to reduce vehicular emissions to the atmosphere. These additives, although beneficial in reducing atmospheric pollution, may, however, increase groundwater contamination due to the co-solvency of petroleum hydrocarbons and by the provision of a preferential substrate for microbial utilisation. With the introduction of ethanol to diesel fuel imminent and the move away from MTBE use in many states of the USA, the environmental implications associated with ethanol additive fuels must be thoroughly investigated. Diesel fuel movement was followed in a 1-m soil column and the effect of ethanol addition to diesel fuel on this movement determined. The addition of 5% ethanol to diesel fuel was found to enhance the downward migration of the diesel fuel components, thus increasing the risk of groundwater contamination. A novel method using soil packed HPLC columns allowed the influence of ethanol on individual aromatic hydrocarbon movement to be studied. The levels of ethanol addition investigated were at the current additive level (approx. 25%) for ethanol additive fuels in Brazil and values above (50%) and below (10%) this level. An aqueous ethanol concentration above 10% was required for any movement to occur. At 25% aqueous ethanol, the majority of hydrocarbons were mobilised and the retention behaviour of the soil column lessened. At 50% aqueous ethanol, all the hydrocarbons were found to move unimpeded through the columns. The retention behaviour of the soil was found to change significantly when both organic matter content and silt/clay content was reduced. Unexpectedly, sandy soil with low organic matter and low silt/clay was found to have a retentive behaviour similar to sandy subsoil with moderate silt/clay, but little organic matter. It was concluded that sand grains might have a more important role in the adsorption of petroleum hydrocarbons than first realised. This method has shown that soil packed HPLC columns can be used to provide a quick estimate of petroleum hydrocarbon, and possibly other organic contaminant, movement in a variety of different soil types.