Synthesis of block copolymers based on oxyethylene chains and their use as polymer electrolytes

High-molecular-weight copolymers were prepared consisting predominantly of oxyethylene and oxymethylene-oligo(oxyethylene) blocks with a small 1-phenylethylene block. Ionic conductivities of mixtures of the copolymers with CF₃SO₃Li were measured.     

Rates of Trace Mineral-Catalyzed Decomposition of Hydrogen Peroxide

Rapid hydrogen peroxide (H2O2) decomposition is a significant limitation of catalyzed H2O2 propagations (i.e., modified Fenton’s reagent) for the remediation of contaminated soil and groundwater by in situ chemical oxidation. Rates of H2O2 decomposition mediated by seven trace minerals and four iron and manganese oxides were evaluated in batch reactors containing slurries of H2O2 and each of 11 minerals. At pH 3, the dominant catalysts in the decomposition of H2O2 on a per surface area basis were the manganese and iron oxides pyrolusite, goethite, and hematite, while decomposition rates in the presence of the manganese oxyhydroxide manganite and the trace mineral siderite were one to two orders of magnitude lower. At pH 7, the dominant catalysts were hematite and pyrolusite, and decomposition rates were one to two orders of magnitude lower in the presence of goethite, manganite, and siderite. The trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, and willemite provided the least activity for decomposing H2O2 at both pH regimes. The results of this study document that the trace minerals anatase, bauxite, cuprite, ilmenite, magnesite, siderite, and willemite do not provide a significant pathway for H2O2 decomposition in the subsurface, and efforts to stabilize H2O2 for ISCO should focus on reactions occurring on the surfaces of iron and manganese oxides.     

Attenuation and depolarisation data obtained on 12 GHz satellite-Earth paths at four Canadian locations

A preliminary result of the Communication Technology Satellite (CTS) propagation experiment carried out in Canada is presented. These results of 11.7 GHz band were obtained in 1978 while the CTS was located at 116 degrees W longitude.     

Crack propagation near cylindrical voids

Stress intensity factorsK _I andK _II are presented for a planar, sharp-ended crack subjected to nearby line forces and line force doublets. The resulting near crack tip stress field is used to predict the influence of such singularities upon the crack propagation direction. The concept of the criticality of the angle of crack departure from symmetric propagation is introduced and used to compare computer predictions with experiments performed on double cantilever beam (DCB) specimens of 7075 aluminum alloy. The form of the near crack tip elastic equations and the criticality are verified. The critical angle parameter is found to be a material and experimental constant, independent of the strength of the centers of stress.     

Calculating Dislocation Spacings in Pile-Ups at Grain Boundaries

Dislocation pile-ups near planar grain boundaries have been analyzed employing full anisotropic elastic solutions, single-crystal anisotropic approximations, and isotropic approximations. The calculations were performed for a series of iron-silicon bicrystal configurations and results from the various methods compared. Three of the bicrystal/slip system combinations exhibited repulsive image forces, allowing elastically self-consistent position calculations. Based on these results, either linear elastic or nonlinear effects can dominate the behavior of these pile-ups, depending on specific boundary conditions.     

A Measurement of the Energy Resolution and Related Properties of an SCG1-C Scintillation Glass Shower Counter Array for 1-25 GeV Positrons

We report the measurement of the energy resolution of a 4×4 array of SCG1-C scintillation glass counters (Ohara Optical Glass Manufacturing Co., Ltd.) exposed to positrons in the energy range of 1 to 25 GeV. Each element of the array was 20.5 radiation lengths long. The resolution of the array was measured both with and without a 3.5 radiation length SCG1-C scintillation glass active converter and 0.2 radiation length hodoscopes used to measure shower position. We obtained an energy resolution ?/E = (1.63 + 1.46/?E)% without the active converter and ?/E = (0.64 + 3.94/?E)% with the active converter. Performing a partial correction for the average energy loss in the 0.2 radiation length hodoscopes resulted in an energy resolution of ?/E = (0.50 + 3.43/?/E)% for the active converter measurement. We also report on the measurement of the absolute number of photons produced by 1 GeV showers, the optical attenuation length for the light produced by showers, the fraction of the total light output that is due to Cerenkov light relative to scintillation light for showers, and the radiation darkening sensitivity of the scintillation glass.     

Electron-transfer coupling in microbial fuel cells. 2. performance of fuel cells containing selected microorganism—mediator—substrate combinations

Various phenoxazine, phenothiazine, phenazine, indophenol and bipyridilium derivatives were tested for their effectiveness as redox mediators in microbial fuel cells containing Alcaligenes eutrophus, Bacillus subtilis, Escherichia coli, or Proteus vulgaris as the active biological agent, and glucose or succinate as the oxidisable substrate. A ferricyanide-Pt cathode was used. The open-circuit cell e.m.f.′s increased in the order of increasing negative formal redox potentials at pH 7(E⁷_m) of the redox compounds. Several of the redox agents worked well as mediators, maintaining steady currents over several hours, and thionine was found to be particularly effective in maintaining relatively high cell voltages when current was drawn from the cell. A number of the compounds tested did not function well, either because they were incompletely or slowly reduced by the microorganisms or because of their instability. P. vulgaris, with thionine as mediator and glucose as substrate, showed the best performance in a fuel cell. This system was examined in some detail under various conditions of external load to establish the effects of organism concentration, mediator concentration, and substrate addition. Coulombic outputs from these cells were calculated by integration of the current-time plots. Coulombic yields of 30–60% were obtained, on the basis of (theoretical) complete oxidation of added substrate to CO₂ and water.     

Potential and limitations of Sr/Ca ratios in coccolith carbonate: new perspectives from cultures and monospecific samples from sediments

The Sr/Ca ratio of coccoliths was recently proposed as a potential indicator of past growth rates of coccolithophorids, marine algae, which play key roles in both the global carbonate and carbon cycles. We synthesize calibrations of this proxy through laboratory culture studies and analysis of monospecific coccolith assemblages from surface sediments. Cultures of coccolithophorids Helicosphaera carteri, Syracosphaera pulchra and Algirospira robusta confirm a 1-2% increase in Sr/Ca per degrees C previously identified in Emiliania huxleyi and Gephyrocapsa oceanica. This effect is not due merely to increases in growth rate with temperature and must be considered in palaeoceanographic studies. In light-limited cultures of E. huxleyi, Calcidiscus leptoporus and G. oceanica at constant temperature, coccolith Sr/Ca ratios vary by 10% across the range of possible growth and calcification rates for a given species. Among different species under similar culture conditions, Sr/Ca ratios vary by 30%. Although the highest ratios are in the cells with highest calcification and organic carbon fixation rates, at lower rates there is much scatter, indicating that different mechanisms control interspecific and intraspecific coccolith Sr/Ca variations. In field studies in the Equatorial Pacific and Somalia coastal region, coccolith Sr/Ca correlates with upwelling intensity and productivity. A more dynamic response is observed in larger coccoliths like C. leptoporus (23-55% variation in Sr/Ca) than in smaller coccoliths of G. oceanica or Florisphaera profunda (6-15% variation in Sr/Ca). This response suggests that, despite temperature effects, coccolith Sr/Ca has potential as an indicator of coccolithophorid productivity. If the variable Sr/Ca response of different species accurately reflects their variable productivity response to upwelling (and not different slopes of Sr/Ca with productivity), coccolith Sr/Ca could provide useful data on past changes in coccolith ecology. The mechanism of coccolith Sr/Ca variations remains poorly understood but is probably more closely tied to biochemical cycles during carbon acquisition than to chemical kinetic effects on Sr incorporation in the calcite coccolith crystals.     

The metabolic cost of operating a bicycle generator light

The purpose of the study was to determine the metabolic cost of operating a bicycle generator (dynamo) light. Nineteen subjects (12 males, 7 females) volunteered to participate in the study. All tests were conducted using a multigeared road bicycle mounted on a Velodyne computer-controlled, electromagnetically-braked bicycle training simulator. A tyre sidewall-driven 6V 3W bicycle generator was attached to the bicycle frame. Tyre pressure was maintained at 6.12 atm. Gears were prescribed to produce simulated riding speeds of approximately 13 and 21 km h(-1) at 62 rpm. Subjects rode four, 5-min stages during the test session to evaluate riding under conditions of generator OFF or ON at each speed. Oxygen consumption, heart rate, and rating of perceived exertion (RPE) were recorded at the end of each minute. Paired samples t tests revealed significant differences between generator OFF and ON conditions for both the metabolic cost of cycling and heart rate at each of the speeds tested. There were no significant differences found between conditions for RPE. Bicycling with the generator ON increased oxygen consumption by 8.4% at 13 km h(-1) and 9.6% at 21 km h(-1).