Irradiation enhanced creep in LMFBR fuel element cladding

Rate changes observed in irradiation enhanced creep and swelling in stainless steel cladding are ascribed to the precipitation of carbide. Empirical equations modified according to precipitation kinetics are consistent with results from fuel element irradiation and in particular describe the “second peak” phenomenon.     

Low temperature electroplated Au?SnNi?Au ohmic contacts on n type GaAs

A method is described for fabricating ohmic contacts on n type GaAs by alloying electroplated layers of Au-SnNi-Au at 300°C, resulting in a contact resistance of approximately 3 × 10?5 ? cm2. In applications for which this resistance is adequate, the technique has the advantage of requiring low-temperature alloying for short times.     

Analysis of polymer membrane formation through spinodal decomposition. III: Two-dimensional simulations of early-stage behavior

A nonlinear diffusion equation is used to study early-stage spinodal decomposition of polymer solutions, in relation to the membrane formation, in two dimensions. The effects of overall polymer composition and composition-dependent mobility and diffusivity are included in our simulations. Our results show a kinetically stable structure is established during the early stages, which corresponds to a circular range of peaks in the two-dimensional frequency spectrum. Such a spectrum is found to result in an interconnected cell structure in the two-dimensional real space. A decrease in the level of polymer interdomain interconnectedness is obtained as time increases, which indicates the influence of interfacial tension. As the overall polymer composition is increased, an increase in interdomain distances is observed, although the same early stage morphological structure is obtained. Finally, calculated interdomain distances from the two-dimensional simulation are larger than those obtained in equivalent one-dimensional model systems.     

A study of the complexing properties of a hydrosoluble polymer based on modified polyacrylamide containing diethanolamine functions

The grafting addition of diethanolamine functional groups on polyacrylamide was carried out by a Mannich reaction. The polymer obtained includes amino alcohol functions as well as carboxylate functions due to partial hydrolysis. The complexing power of this polymer toward Cu²⁺ ions shows an increased stability of the complexes compared to those obtained with diethanolamine. The range of existence is similarly extended for the complexes with a high degree of coordination due to the proximity of the complexing sites in the macromolecular chain.     

Polarized liquid3He in a4He circulating dilution refrigerator

We have used a⁴He circulating dilution refrigerator to produce cold liquid³He with a steady state out-of-equilibrium nuclear spin polarization. Polarizations on the order of 15% (more than 7 times higher than the equilibrium polarization in the external field of 6.6 T) have been obtained in the mixing chamber of the refrigerator at temperatures between 10 and 15 mK. The polarization is enhanced at high pressure because the molar susceptibility of concentrated³He is larger than that of the dilute phase. The polarization exchange between the dilute and concentrated phases (in direct contact in the heat exchanger of the refrigerator) amplifies the enhancement. The polarization diminishes below a pressure of 2.6 bar. This allows us to scale and reinterpret susceptibility data of the dilute phase¹ in combination with the effective mass deduced from osmotic pressure measurements². We find 1+F ₀ ^a = 0.89±1% on the phase separation line in the pressure range 0–20 bar.We would like to thank Profs. D.M. Lee and M.S. Tagirov for the many discussions during their visits.     

Electron-transfer coupling in microbial fuel cells: 1. comparison of redox-mediator reduction rates and respiratory rates of bacteria

Redox mediators promote electron transfer in microbial fuel cells. The reduction of a range of redox mediators by bacteria was studied in some detail in order to identify effective mediator—organism combinations. Rates of reduction of mediator dyes by bacteria were measured spectrophotometrically at 30°C under anaerobic conditions for standardised concentrations of organism, substrate and dye. The kinetics of dye reduction showed two general patterns: a simple, exponential curve or a complex curve with an initial linear rate followed by a faster exponential rate of reduction. Dye-reduction rates were greater than rates of oxygen consumption (Q_O2) for several combinations of organism and redox dye. Thionine, brilliant cresyl blue, methylene blue and benzyl viologen were tested in combination with Alcaligenes eutrophus, Azotobacter chroococcum, Bacillus subtilis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa and Pseudomonas putida, using glucose and succinate as substrates. Rates of reduction of alizarin brilliant blue, 2,6-dichlorophenolindophenol, gallocyanine, new methylene blue, N,N-dimethyl-disulphonated thionine, phenazine ethosulphate, resorufin, safranine-O, phenothiazinone and toluidine blue-O were also measured with Pr. vulgaris only. For E. coli, both Q_O2 and the rate of thionine reduction increased with increasing temperature in the range 25 to 37°C, but for Pr. vulgaris thionine reduction rates did not correlate with temperature in this way. Dye-reduction rates and Q_O2 for Az. chroococcum were dependent on the components of the washing solution and/or the temperature at which cell suspensions were prepared. The results are discussed in relation to the use of these dyes as electron-transfer mediators in microbial fuel cells.     

Diffusion creep by dislocation climb in beryllium and Be-Cu single crystals

High temperature creep of beryllium and Be-Cu alloy (10 wt pct Cu) single crystals com-pressed along the -c axis was shown to proceed by pure climb of -c dislocations (Burgers vector [0001]). Experimental results can be explained if we assume that -c dislocation loops grow in the basal planes. The activation energy for the climb of the -c dislocations is found to exceed the activation energy for self diffusion by 10 ±5 kcal/mole for both beryllium and Be-Cu. This leads us to think that thec dislocation climb rate is controlled by the processes of vacancy emission or absorption at jogs rather than by lattice diffusion.