AC impedance study of degradation of porous nickel battery electrodes

AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low

Effect of Hydrostatic Compression on the Energy of the 14.4-kev Gamma Ray from Fe^(57) in Iron

The energy of the recoil-free fraction of they rays emitted by nuclei bound in solids1 has been found to be affected by temperature and by electronic configuration. The latter effect has been named the "isomeric" shift. Compression of a solid should influence the energy through both of these mechanisms. We have measured the effect of hydrostatic compression at 295°K on the energy hν of the recoil-free 14.4-kev γ rays emitted by 0.1-μsec Fe^(57) bound in metallic iron

Formation of Pillars at the Boundaries between H II Regions and Molecular Clouds

We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ratio of the initial amplitude to wavelength is greater than 0.02, portions of the IF temporarily separate from the molecular cloud surface, locally decreasing the ablation pressure. This causes the appearance of a large, warm HI region and triggers nonlinear dynamics of the IF. The local difference of the ablation pressure and acceleration enhances the appearance and growth of a multimode perturbation. The stabilization usually seen at the IF in the linear regimes does not work due to the mismatch of the modes of the perturbations at the cloud surface and in density in HII region above the cloud surface. Molecular pillars are observed in the late stages of the large amplitude perturbation case. The velocity gradient in the pillars is in reasonably good agreement with that observed in the Eagle Nebula. The initial perturbation is imposed in three different ways: in density, in incident photon number flux, and in the surface shape. All cases show both stabilization for a small initial perturbation and large growth of the second harmonic by increasing amplitude of the initial perturbation above a critical value.Comment: 21 pages, 8 figures, accepted for publication in ApJ. high resolution figures available upon reques

Principles and practical implementation of farming systems research and farmer participatory research. Including Vulindlela District and Sobantu Village case studies

This publication integrates theory and practical work arising from courses in Farming Systems and Farmer Participatory Research held at the Institute of Natural Resources and associated institutions in KwaZulu-Natal during 1996 and 1997. The courses were conducted as part of a project supported by the UK. Government's Department for International Development and managed by the UK Natural Resources Institute (NRI). Objectives of this publication are 1) to provide reference material in Farming Systems and Farmer Participatory Research for interested audiences in KwaZulu-Natal and elsewhere; 2) by integrating theory and practice, to demonstrate how the principles, approaches and methods of FSRJFPR can be applied to real situations; 3) to record the situation, suggestions and priorities of rural and peri-urban families in Vulindlela District, as recorded by course participants; 4) to provide a springboard of information for further development initiatives in Vulindlela and elsewhere in KwaZulu-Natal; 5) to present the Urban Agriculture workshop held in Sobantu Village as a case study of participatory workshop methods

Waves on the surface of the Orion molecular cloud

Massive stars influence their parental molecular cloud, and it has long been suspected that the development of hydrodynamical instabilities can compress or fragment the cloud. Identifying such instabilities has proved difficult. It has been suggested that elongated structures (such as the `pillars of creation') and other shapes arise because of instabilities, but alternative explanations are available. One key signature of an instability is a wave-like structure in the gas, which has hitherto not been seen. Here we report the presence of `waves' at the surface of the Orion molecular cloud near where massive stars are forming. The waves seem to be a Kelvin-Helmholtz instability that arises during the expansion of the nebula as gas heated and ionized by massive stars is blown over pre-existing molecular gas.Comment: Preprint of publication in Natur

Palaeoenvironment, palaeoclimate and age of the Brassington Formation (Miocene) of Derbyshire, UK

he Brassington Formation is the most extensive Miocene sedimentary succession onshore in the UK. Because of its unique position at the margin of NW Europe, the pollen from this lithostratigraphical unit provides evidence on the development of vegetation affected by North Atlantic currents and hypothesized atmospheric circulation changes during the Middle to Late Miocene climate cooling. Palynostratigraphy suggests that the uppermost Kenslow Member of the Brassington Formation is not coeval. Previously, all occurrences of the Kenslow Member were assumed to be contemporary. The oldest pollen assemblage is from the more southern Bees Nest Pit, which represents a subtropical conifer-dominated forest of late Serravallian age (c. 12 Ma). A younger assemblage was observed from the more northern Kenslow Top Pit; this indicates that a subtropical mixed forest was present during the early Tortonian (11.6–9 Ma). The shift from a conifer-dominated to a mixed forest was related to precipitation. Although the total precipitation did not change between the two assemblages, the younger assemblage had more uniform rainfall throughout the year. The diachronous nature of the Kenslow Member means that the depositional model of the Brassington Formation needs revising, and this will have implications for Neogene to recent uplift of the southern Pennines. Supplementary material: All valid formally defined palynomorph taxa below the generic level that are mentioned in this paper, with full author citations, are available at http://www.geolsoc.org.uk/SUP18889

Country-wide extension of integrated crop management of chickpea in Nepal

This paper discusses lessons that have been learned both from discussions at the present meeting and those distilled from experiences of project partners during the collaborative activities of NARC, ICRISAT and NRI under the Crop Protection Programme's (DFID) project to rehabilitate chickpea in Nepal (DFID R7885). Chickpea is a crop that can compete with alternatives; it is highly profitable when grown with appropriate technology and improves livelihoods for poor farmers. Markets per se are not a limiting step for the nationwide expansion of improved chickpea production in Nepal (most chickpea consumed in Nepal is still imported), but aspects of marketing are, and need addressing to ensure trouble free expansion of chickpea production. Aspects of infrastructure also need addressing, especially the connectivity between research and extension organizations in Nepal, to enable joined-up extension services and technology support. Seed storage has too low a priority for both farmers and extension services and needs greater focus. Pesticide quality and insecticide resistance need monitoring and infrastructure and policy/legislation to support biological alternatives such as NPV needs attention. Farmers' past experiences with particular management tools (eg, familiarity with insecticides from vegetable p r o d u c t i o n ) often coincided with success, and finally skills of diagnosis and timing for applications of technology needs particular attention across all farmers. Because chickpea is self-fertilizing, farmers can produce and maintain their own seed stock negating the long-term role of seed production enterprises in up-scaling. The project also encouraged low cost inputs, which are less financially rewarding for Small and Medium Entrepreneurs (SMEs). There is, however, always a need for technology inputs and seed provision for new farmers so there is still a role for the private sector. Self-help groups increasingly need to take on the role of seed producers. Agriculture holds a position of low priority in popular media such as newspapers and television, so alternatives need to be exploited to ensure widespread knowledge dissemination

A Resolved Ring of Debris Dust around the Solar Analog HD 107146

We present resolved images of the dust continuum emission from the debris disk around the young (80-200 Myr) solar-type star HD 107146 with CARMA at λ = 1.3 mm and the CSO at λ = 350 μ. Both images show that the dust emission extends over an approximately 10" diameter region. The high-resolution (3") CARMA image further reveals that the dust is distributed in a partial ring with significant decrease in a flux inward of 97 AU. Two prominent emission peaks appear within the ring separated by ~140° in the position angle. The morphology of the dust emission is suggestive of dust captured into a mean motion resonance, which would imply the presence of a planet at an orbital radius of ~45-75 AU