Synchrotron X-ray microdiffraction reveals rotational plastic deformation mechanisms in polycrystalline thin films

Understanding the mechanical response of polycrystalline materials on the mesoscopic scale remains a challenge as it is largely determined by grain-to-grain interactions and the discrete underlying microstructure. We conducted in situ synchrotron Laue microdiffraction experiments to map local strain tensors and orientations over polycrystalline thin gold films for different applied biaxial strain states. The experimental results demonstrate stress relaxation to be accompanied by cooperative transport of dislocation density leading to rotational plastic deformation heterogeneities. We propose a disclination model of closed dislocation walls and consider the geometry of transformations corresponding to a Burgers circuit enclosing the multipole disclination configuration. The observed stress-driven rotational deformation of the grain is shown to be described by the change in rotational closure failure associated with a Burgers circuit around the multipole disclination configuration. This concept is further advanced in a non-Euclidian geometry to demonstrate that the observed microrotation is captured by higher-order gradients in a micropolar continuum theory.     

Low-Temperature Densification of Lanthanum Strontium Manganite (La1−xSrxMnO3+δ), x=0.0–0.20

Intermediate-stage sintering of lanthanum strontium manganite (LSM, where Sr=0.00, 0.05, 0.10, 0.15, and 0.20) was shown in dilatometry studies to be accelerated when subjected to alternating flows of air and nitrogen. The extent of rate enhancement decreased with increased Sr content, and decreased with increased temperature, which coincides with diminished oxygen nonstoichiometry. Shrinkage rates were further shown to be sensitive to the difference in oxygen content in the alternating gas flows. Baseline air sintering rates were measured using stepwise isothermal dilatometry, from which kinetic parameters were calculated using the Makipirtti–Meng model. Activation energies for sintering in air were determined to be 255 ± 26, 258 ± 28, 308 ± 32, 373 ± 37, and 417 ± 41 kJ/mol for Sr=0.0, 0.05, 0.10, 0.15, and 0.20, respectively. A diffusion-based model is proposed that is consistent with trends in accelerated shrinkage versus temperature. Transient cation vacancy gradients, which lead to higher cation mobility, were calculated from established oxygen diffusivities and oxygen nonstoichiometry as a function of temperature and time. A potential application of this approach is the processing of LSM-based cathode-side contact pastes in solid oxide fuel cells.     

RRD1, a component of the TORC1 signalling pathway,affects anaesthetic response in Saccharomyces cerevisiae

The molecular mechanisms of action of volatile anaesthetics remain unknown despite clinical use for over 150 years. While many effects of these agents have been characterized, clear insight into how these effects relate to the physiological state of anaesthesia has not been established. Volatile anaesthetics arrest cell division in Saccharomyces cerevisiae in a manner that parallels the anaesthetic actions of these drugs in mammals. To gain additional insight into the cellular activities of these drugs, we isolated genes that, when present on multi‐copy plasmids, render S. cerevisiae resistant to the volatile anaesthetic isoflurane. One of these genes, RRD1, encodes a subunit of the Tap42p–Sit4p–Rrd1p phosphatase complex that functions in the target of rapamycin complex 1 (TORC1) signalling pathway. In addition, we show that mutations in two other genes encoding components of the TORC1 pathway, GLN3 and URE2, also affect yeast anaesthetic response. These findings suggest that TORC1‐mediated signalling is involved in cellular response to volatile anaesthetics in S. cerevisiae. Copyright © 2009 John Wiley & Sons, Ltd.     

Warm homes: Drivers of the demand for heating in the residential sector in New Zealand

New Zealand houses are large, often poorly constructed and heated, by OECD standards, and consequently are colder and damper indoors than recommended by the World Health Organisation. This affects both the energy consumption and the health of households. The traditional New Zealand household pattern of only heating one room of the house has been unchanged for decades, although there has been substantial market penetration of unflued gas heaters and more recently heat pumps. This paper describes the residential sector and the results of two community-based trials of housing and heating interventions that have been designed to measure the impact of (1) retrofitting insulation and (2) replacing unflued gas heaters and electric resistance heaters with heat pumps, wood pellet burners and flued gas heaters. The paper describes findings on the rebound effect or ‘take-back’—the extent to which households take the gains from insulation and heating improvements as comfort (higher temperatures) rather than energy savings, and compares energy-saving patterns with those suggested by an earlier study. Findings on these aspects of household space heating are discussed in the context of the New Zealand government's policy drive for a more sustainable energy system, and the implications for climate change policy.     

AIR PURIFICATION AND VAPOR RECOVERY BY PRESSURE SWING ADSORPTION: A COMPARISON OF SILICALITE AND ACTIVATED CARBON

Air purification and vapor recovery by pressure swing adsorption (PSA) were experimentally investigated using the silicalite-DMMP-air system. The results from several cyclic steady-state PSA runs were compared at constant throughput with those from a previous study on the BPL activated carbon-DMMP-air system. The performance of BPL activated carbon was superior to that of silicalite because it demonstrated complete cleanup of the product effluent when starting from a saturated column, whereas, at similar process conditions, silicalite was able to cleanup only a portion of the product effluent. Nevertheless, both silicalite and BPL activated carbon respectively demonstrated enrichments (Y_e/Y_f) of 12 and 15 using only moderate vacuum. However, there were significant differences in the shapes of the cyclic steady-state product and exhaust profiles which were attributed to differences in the 1) mass transfer rates, 2) adsorption capacities, or 3) possibly shapes of the adsorption isotherms.     

Raman spectra of Graphon carbon black

The Raman spectrum of Graphon carbon black has been recorded using rotating cell techniques. Angular dependence of scattering at 1360, 1580 and 2700 cm^?1 are reported and these data suggest that the 1360 cm^?1 line is associated with non-planar microstructure distortions. The excitation frequency dependence of the intensity ratio of the bands at 1360 (D) and 1580 cm^?1 (G) is interpreted in terms of resonance (vibronic) interaction. This dependence is primarily the result of an increase in the intensity of the 1360 cm ^?1 line. The disorder-associated line (D) exhibits a significant excitation-dependent shift from 1378 cm^i?1 (457.9 nm Ar⁺) to 1330 cm^?1 (647.1 nm Kr⁺). The “graphite” (G) line position is less sensitive to changes in excitation frequency. The spectral features are discussed in terms of factor group, C_6v⁴, and layer site symmetry, C_3v. Also the possible role of localized alkene-like structure in zones of structural distortion is considered.     

Coal volatiles combustion-coal pyrolysis analogy: Observation of “low” apparent global activation energies

An attempt is made to draw analogies between rapid coal pyrolysis and coal combustion in order to use a singular observation made on the latter to validate an important modelling assumption associated with the former. Identical kinetics for the two complex processes are not implied; rather, parallels between their global behaviour are highlighted. What has been experimentally validated via a set of novel combustion experiments on low-c.v. coal-derived syngas combustion is the observation that a set of overlapping independent parallel first-order reactions describing non-isothermal rapid coal pyrolysis can be analytically approximated by a single first-order Arrhenius expression having a lower activation energy than any of the reactions of the set.     

Physiological activity of water beetle defensive agents. II. Absorption of selected anesthetic steroids and norsesquiterpenes across gill membranes of the minnowPimephales promelas Raf.

The uptake of selected steroids and norsesquiterpenes by live minnows,Pimephales promelas, was studied when the compounds were administered externally in aqueous solution. The gills of minnows absorbed 80% of the steroid removed from solution. Steroid absorption across minnow gills is apparently a nonmediated process as rate saturation could not be demonstrated. Initial absorption rates of test compounds were inversely correlated with (1) the degree of oxygenation, (2) water solubility, and (3) polarity on silica gel thin-layer chromatography. These findings support the Stein model of non-mediated transport. The majority of compounds anesthetic and toxic to minnows exerted their effects at a similar internal concentration. Anesthesia occurred at ca. 10^–6–10^–5 M and death at 10^–4–10^–3 M. Since various agents causing membrane stabilization and lysis in in vitro systems act in an identical concentration range, it is proposed that the defensive steroids and norsesquiterpenes of water beetles act via membrane stabilization and lysis.     

A comparison of pyrrolidide and picolinyl ester derivatives for the identification of fatty acids in natural samples by gas chromatography-mass spectrometry

The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of both the numbers and positions of the double bonds.