Abstract
LONDON Royal Society, Feb. 18.—D'Arcy W. Thompson: The geometry of the siliceous skeletons of the Radiolaria. The figures of equilibrium and minimal area which are assumed by soap-films in Plateau's experiments have proved helpful in explaining the configurations of various cells and simple tissues in plants and animals. Among the most curious and anomalous of cell-forms are those of certain Radiolaria. In some of these the skeleton resembles a minute spiked helmet with three curved lappets or straps below. Even such an anomalous configuration as this may be precisely imitated or reproduced by an artificial system of liquid films.—H. W. S. Massey and C. B. O. Mohr: The collision of slow electrons with atoms (1). The theory has been developed in which the zero approximation is not a plane wave but the wave representing the motion of the electron in the static field of the atom concerned. Exchange does not become very important until voltages lower than those obtained on Born's theory using the plane wave as first approximation. At lower voltages, strong interference effects occur between the incident and exchanged electron waves, giving peculiar angular distributions of the scattered electrons. These effects are observed experimentally.—H. C. Webster: The artificial production of nuclear γ-radiation. The production of nuclear γ-radiation by bombardment with α-particles has been observed for the elements Li, Be, B, F, Na, Mg, Al. Negative results were obtained with H, C, N, Ni, Cu, Sn. The absolute efficiencies of production of the various radiations range from about 0.5 quanta per million α-particles for magnesium to about 30 quanta for beryllium. In addition, the way in which the efficiency of production varies with the residual range of the α-particles was investigated. The processes probably responsible for the radiations are discussed: some appear to be due to the capture of an α-particle by a nucleus without proton emission, others are probably due to a secondary process following proton emission, others may arise from inelastic collisions without capture.
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Societies and Academies. Nature 129, 325–327 (1932). https://doi.org/10.1038/129325b0
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DOI: https://doi.org/10.1038/129325b0