Microstructure of Silicon Carbide Whiskers Synthesized by Carbothermal Reduction of Silicon Nitride

The microstructure of silicon carbide whiskers synthesized by carbothermal reduction of silicon nitride has been studied using transmission electron microscopy. All of the whiskers examined are single crystals, and grow in the (111) crystallographic direction. Two different forms of stacking faults and microtwins were observed; in one the planar defects are normal to the whisker growth direction, and the other has the defect planes at an angle of about 70° to the growth axis, while both forms of the defects are on the [111] closed-packed planes. Without the addition of catalyst, droplets containing metallic impurities were not found at the tips of the whiskers synthesized by the present process. A core and outer regions were observed in the single-crystal whiskers, which may be evidence that the whiskers were formed by a two-stage mechanism.     

Immunoregulatory functions of paf-acether. VI. Dual effect on human B cell proliferation

The role of paf-acether (paf), a phospholipid cytokine, in the modulation of human B cell function was investigated. Paf, from 1×10⁻⁵ M to 10⁻⁶ M, decreased B cell proliferation induced by both phorbol myristate acetate (PMA) and anti-IgM antibodies (anti-IgM Ab). By contrast, 1×10⁻⁷ M to 1×10⁻⁹ M paf enhanced PMA triggered, but not anti-IgM triggered B cell proliferation. B cell proliferation was modulated between 24 and 72 hr of culture indicating that the effect of paf did not merely reflect a shift in proliferation kinetics. Interestingly, paf also enhanced the spontaneous proliferation of a Burkitt lymphoma-derived B cell line, Raji, which suggests that paf can directly act on B cells. The modulatory effect of paf on peripheral blood B cells was independent of PMA concentration, yet the effect on Raji cells was dependent upon cell density. The data suggest that paf is a potent modulator of B cell function, and may be involved in the control of humoral immune response. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Technology to facilitate ethical action: a proposed design

As emerging technologies support new ways in which people relate, ethical discourse is important to help guide designers of new technologies. This article endeavors to do just that by presenting an ethical analysis and design of technology intended to gather and act upon information on behalf of its users. The article elaborates on socio-technological factors that affect the development of technology to support ethical action. Research and practice implications are outlined.     

Air-conditioning Australian households: The impact of dynamic peak pricing

International mandates for smart metering are enabling variable and real-time pricing regimes such as dynamic peak pricing (DPP), which charges 10–40 times the off-peak rate for electricity during short periods. This regime aims to reduce peak electricity demand (predominantly due to increase in residential air-conditioning usage) and curb greenhouse gas emissions. Although trials indicate that DPP can achieve significant demand reductions, particularly in summer, little is known about how or why households change their cooling practices in response to this strategy. This paper discusses the outcomes of a small qualitative study assessing the impact of a DPP trial on household cooling practices in the Australian state of New South Wales. The study challenges common assumptions about the necessity of air-conditioning and impact of price signals. It finds that DPP engages households as co-managers of their cooling practices through a series of notification signals (SMS, phone, in-home display, email, etc.). Further, by linking the price signal to air-conditioning, some householders consider this practice discretionary for short periods of time. The paper concludes by warning that policy makers and utilities may serve to legitimise air-conditioning usage and/or negate demand reductions by failing to acknowledge the non-rational dynamics of DPP and household cooling practices.     

Quantitative Elemental Analysis of a Single Cell by Using Inductively Coupled Plasma-Mass Spectrometry in Fast Time-Resolved Analysis Mode

The elemental composition of a single yeast, green alga, or red blood cell (RBC) was precisely determined by using inductively coupled plasma-mass spectrometry (ICP-MS) operating in fast time-resolved analysis (TRA) mode. The technique is known as single-cell (SC)-ICP-MS. Phosphorus, sulfur, magnesium, zinc, and iron were detected in the three types of cell. The elemental composition of yeast and green alga obtained by SC-ICP-MS was consistent with results obtained from conventional ICP-MS measurements following acid digestion of the cells. Slight differences were found in the measured values between SC-ICP-MS and the conventional ICP-MS results for RBC. However, the SC-ICP-MS results for S and Fe in RBC were closer to the estimated values for these elements that were calculated from the level of hemoglobin in RBCs. The data suggest that SC-ICP-MS is suitable for the analysis of various cell types, namely, fungus, plant, and animal cells.     

Glass–Crystal Transition in II-IV-V2 Semiconducting Compounds

The crystallization behavior of amorphous CdGe_xAs₂, where the x values were varied from 0 to 1.2, was studied in order to document the effect of germanium on the amorphous structure. The glass-forming tendency of amorphous CdGe_xAs₂ was evaluated by Hruby's criterion. The crystallization mechanism of each group was proposed, interpreting DSC, XRD, EDS, and TEM data, interactively. The crystallization behavior appeared as two distinct groups: those based on the CdAs₂ structure and those on the CdGeAs₂ structure (chalcopyrite), depending on Ge content. Ge atoms were found to suppress a glass-to-glass exothermic transformation to higher temperatures in the CdAs₂ group, and crystallization in both groups. Proposed models of amorphous structure from previous investigators, measuring the radial distribution function, magnetic susceptibility, and macroscopic density, were correlated to the crystallization studies herein. A model of the transformation of glass structure with increasing Ge content from a CdAs₂ to a CdGeAs₂-like structure was established by extrapolation of experimental results indicating this behavior in crystalline CdGe_xAs₂ compounds with varying x .     

Dwelling performance and adaptive summer comfort in low-income Australian households

Increasing reliance on air-conditioning to improve summertime comfort in dwellings results in higher energy bills, peak electricity demand and environmental issues. In pursuit of social equity, society needs to develop ways of improving cooling that are less reliant on air-conditioning. Designing homes to emphasize adaptive thermal comfort can reduce this reliance, particularly when combined with improved dwelling thermal performance. A multi-method evaluation of 10 low-income dwellings in the state of Victoria in Australia is presented, including low-energy and ‘standard-performance’ houses. The combination of performance monitoring and householder interviews reveals new insights for achieving summertime comfort. The low-energy houses without air-conditioning were both measured and perceived as more comfortable than the ‘standard-performance’ houses with air-conditioning. The low-energy households achieved improved personal thermal comfort through a combination of improved fabric performance augmented with adaptive comfort activities (e.g., opening/closing windows). This outcome reduces reliance on air-conditioning, reduces living costs and energy consumption, and improves environmental outcomes. There is a need to integrate lessons from adaptive thermal comfort theory and strategies into minimum building performance requirements and standards, as well as wider design strategies. It is evident that adaptive comfort has a role to play in a transition to a low-carbon housing future.     

Effects of Microwave on Drug Release Property of Poly(Methyl Vinyl Ether-co-Maleic Acid) Matrix

ABSTRACT

The drug release behavior of beads made of poly(methyl vinyl ether-co-maleic acid) was investigated with respect to the influence of microwave irradiation. The beads were prepared by an extrusion method with sodium diclofenac as a model water-soluble drug. The beads were subjected to microwave irradiation at 80 W for 5 and 20 min, and at 300 W for 1 min 20 s and 5 min 20 s. The profiles of drug dissolution, drug content, drug-polymer interaction, and polymer-polymer interaction were determined by using dissolution testing, drug content assay, differential scanning calorimetry, and Fourier transform infra-red spectroscopy. Keeping the level of supplied irradiation energy identical, treatment of beads by microwave at varying intensities of irradiation did not bring about similar drug release profiles. The extent and rate of drug released from beads were markedly enhanced through treating the samples by microwave at 80 W as a result of loss of polymer-polymer interaction via the (CH₂)_n moiety, but decreased upon treating the beads by microwave at 300 W following polymer-polymer interaction via the O-H, COOH, and COO^? moieties as well as drug-polymer interaction via the N-H, O-H, COO^?, and C-O moieties. The beads treated by microwave at 300 W exhibited a higher level of drug release retardation capacity than those that were treated by microwave at 80 W in spite of polymer-polymer interaction via the (CH₂)_n moiety was similarly reduced in the matrix. The mechanism of drug release of both microwave-treated and untreated beads tended to follow zero order kinetics. The drug release was markedly governed by the state of polymer relaxation of the matrix and was in turn affected by the state of polymer-polymer and/or drug-polymer interaction in beads.     

Effect of Bi2O3 on Impurity Ion Distribution and Electrical Resistivity of Li-Zn Ferrites

Preventing the incorporation of impurities in Li-Zn ferrite grains during sintering is essential for production of ceramics with reproducible magnetic and electrical properties. Li-Zn ferrites of composition Li_0.3Zn_0.4Mn_0.05Fe_2.25O₄ were prepared with Bi₂O₃ and borosilicate sintering additives. The distribution of impurity ions in the sintered ferrites was investigated using transmission electron microscopy (TEM) coupled with energy dispersive spectroscopy (EDS). Ceramics prepared with Bi₂O₃ contained Si, Ca, and S impurities, located at grain boundaries and triple point regions. The low viscosity and good wetting properties of the Bi₂O₃ and to a lesser extent the borosilicate liquid phase allowed impurities to be selectively removed from the growing ferrite phase during sintering, thus improving sample resistivities.