Photoactivity tests of TiO2-based inorganic sunscreens. Part 1: Non-aqueous dispersions

A new method of measuring photoactivity of a major group of inorganic sunscreens (coated titanium dioxide) is presented based on the photobleaching of the radical 1,1-diphenyl-2-picrylhydrazyl.     

Localization of carboxyl groups at surface layer of carboxylated polymer emulsion particles by alkali treatment

For the purpose of localizing carboxyl groups from inside to particle surface, styrene — butyl acrylate — methacrylic acid (74.3/17.0/8.7, mol ratio) terpolymer emulsion was kept under pH 9 at different temperatures. The amount of carboxyl groups at the particle surface, As, was remarkably increased by the alkali-treatment above 35 °C. On the other hand, As value of the alkalitreated emulsion was decreased by keeping under ph 3 above 45 °C, although in the case of the original emulsion without the alkalitreatment, it was not changed by the acid-treatment. These results suggest that a part of polymer segments which have ionized carboxyl groups is dragged out at the surface by an increase in the affinity of the groups against water, and the dragged segments turn back into the inside again when the carboxyl groups are deionized.Part 97 of the series Studies on Suspension and Emulsion.     

Determination of resonance couplings and high energy amplitudes in γN → πN using fixed-t dispersion relations

The real parts of the amplitudes are generated entirely from their imaginary parts via d.rs., and essentially all available data is included at all energies with momentum transfer |t| < 1 GeV². A total of 46 resonance couplings and 50 high energy parameters are varied to fit all the data simultaneously with a χ² of 4.8 per data point.     

Skeletons and Central Sets

Let be an open proper subset of Rⁿ. Its skeleton is the setof points with more than one nearest neighbour in the complementof its central set is the set of centres in maximal open ballsincluded in . Intuitively, if we think of as a land mass inwhich height is proportional to distance from the sea, its skeletonand central set can be thought of as corresponding to ridgesin the mountains of . In this note I discuss the metric andtopological properties of such sets. I show that any skeletonin Rⁿ is F, and has dimension at most n – 1, by any ofthe usual measures of dimension; that if is bounded and connected,its skeleton and central set are connected; and that separatesRⁿ iff its skeleton does iff its central set does. Any centralset in Rⁿ is a G set of topological dimension at most n –1. In the plane, I show that both skeletons and central setsare locally path-connected, and indeed include many paths offinite length. For any , its central set includes its skeleton;I give examples to show that the central set can be significantlylarger than the skeleton. 1991 Mathematics Subject Classification:54F99.     

Limits on a long range pion nucleon interaction from pionic atom and πN scattering data

Experimental limits are obtained on any non-electromagnetic long range pion nucleon interaction, from accurate π⁺p scattering data and from pionic atom energy levels. Such an interaction is effectively ruled out in the regionr?100 fm unless its potential falls off faster thanr ^?4.     

The equivalent polarised-photon approximation

The equivalent photon approximation is studied for the case where the scattered electron is detected. The equivalent photon is then polarised. The region of validity is found to depend on the virtual photon scattering angle, rather than on the electron scattering angle, and this distinction is important. A discrepancy concerning the dependence on beam energy of the total cross section for $\text{e}\text{e}\text{?}\text{→}\text{e}\text{e}\text{?}\text{+}$ hadrons which was noted by Bonneau et al. is resolved.