Response of poly(vinyl chloride) electrodes based on the neutral carrier 1,4,7,10-tetraoxacyclododecane

Ion-selective electrodes based on the neutral carrier, 12-crown-4, in a poly(vinyl chloride) matrix were found to respond ideally, or almost ideally, to potassium, sodium, barium, strontium, magnesium, cobalt(II), nickel(II) and aluminum ions. The electrode showed good selectivity for Al³⁺ over Co²⁺ and Mg²⁺, and for Co²⁺ over Mg²⁺. Little selectivity was found for the other ions tested.     

Thermally enhanced neutralization in hyperthermal energy ion scattering

Neutralization probabilities are presented for hyperthermal energy Na+ ions scattered from a Cu(001) crystal as a function of surface temperature and scattered velocity. A large enhancement in neutralization is observed as the temperature is increased. Velocity-dependent charge transfer regimes are probed by varying the incident energy, with the most prominent surface temperature effects occurring at the lowest energies. The data agree well with results obtained from a model based on the Newns-Anderson Hamiltonian, where the effects of both temperature and velocity are incorporated.     

Physical and chemical analysis of elemental sulfur formation during galena surface oxidation

The surface oxidation of sulfide minerals, such as galena (PbS), in aqueous solutions is of critical importance in a number of applications. A comprehensive understanding of the formation of oxidation species at the galena surface is still lacking. Much controversy over the nature of these oxidation products exists. A number of oxidation pathways have been proposed, and experimental evidence for the formation of elemental sulfur, metal polysulfides, and metal-deficient lead sulfides in acidic conditions has been shown and argued. This paper provides further insight into the electrochemical behavior of galena at pH 4.5. Utilizing a novel experimental system that combines in situ electrochemical control and AC mode atomic force microscopy (AFM) surface imaging, the formation and growth of nanoscopic domains on the galena surface are detected and examined at anodic potentials. AFM phase images indicate that these domains have different material properties to the underlying galena. Continued oxidation results in nanoscopic pitting and the formation of microscopic surface domains, which are confirmed to be elemental sulfur by Raman spectroscopy. Further clarification of the presence of elemental sulfur is provided by Cryo-XPS. Polysulfide and metal-deficient sulfide could not be detected within this system.     

Circuit based graphs for renormalized perturbation theory

A generalization of graph theory is introduced and used to obtain Feynman parametric formulas relevant to renormalized amplitudes. The generalization of graph theory is based upon circuit coefficients instead of the usual incidence matrix. The parametric formulas presented are valid for amplitudes which have been renormalized, as in the Zimmermann formulation, by subtracting Taylor terms in momentum space.The research reported in this paper was supported in part by the Max-Planck-Institut für Physik, München, by the German and American Fulbright Commission in Bonn, and by the Department of Mathematics of the University of Virginia, Charlottesville.     

Temperature dependence of self-diffusion in adamantane

Radiotracer experiments show that self-diffusion in the rotator crystalline phase of adamantane proceeds by a vacancy mechanism. The results are in good agreement with those determined from NMR experiments.     

EFFECT OF SURFACE CONDITION AND PRIOR PLASTIC DEFORMATION ON X-RAY EFFECTIVE ELASTIC PARAMETERS IN A STEEL AND ITS WELD

The effective elastic parameter (EEP) was determined for three material and surface conditions of ASTM 516 grade 70 steel and found to differ by as much as 19 percent. This difference occurred between data for plate with a machined surface and that for a chemically milled surface.
In these tests, the same EEP appeared to apply for specimens both before and after exposure to yield level strains. This suggests that the X-ray calibration data may be used to determine stresses in welds exposed to yield-level residual strains as long as the appropriate EEP values are used for the weld material and surface condition.