Quenching of plasma oscillation by a low-frequency externally applied wave

It is shown that the electron plasma oscillation is also quenched by a low-frequency externally applied wave, with generation of plural side bands. The phenomenon is described by a coupled Van der Pol-Mathieu equation.     

Preparation and properties of molybdenum and tungsten dinitrogen complexes: XX. Reactions of a tungsten-dinitrogen complex with water or alcohols in the presence of ketones. Conversion of ligating dinitrogen into ketazines and isolation of a novel chelate diazo complex as an intermediate

Ammonia is formed by treatment of cis-[W(N₂)₂ (PMe₂ Ph)₄] with water (in THF) or alcohols at 50°C. Addition of KOH to the systems, especially those containing n-alcohols such as 1-butanol and 1-pentanol, remarkably increases the yields of ammonia. On the other hand, ketazines are produced in high yields when ketones such as acetone and butanone are added to the systems. The reaction of the dinitrogen complex with 2,4-pentanedione in methanol or ethanol gives a novel chelate diazo complex [$\text{W(NNC(Me)CHCO}$Me)(acac)(PMe₂Ph)₃]. Mechanisms of these reactions are discussed.     

The effect of molecular weight heterogeneity on the second virial coefficient of linear polymers in good solvents

The effect of molecular weight heterogeneity on the second virial coefficient A₂ in good solvents is studied for binary mixtures of monodisperse poly(α-methylstyrenes). It is concluded that A₂ for polymer mixtures passes through a maximum with variation of the mixing ration. From comparison with the data, it is concluded that no available theory quantitatively explains both the molecular weight dependence of A₂ of monodisperse polymer and the variation of A₂ of mixtures with the mixing ratio. The interpenetration function for two polymer coils with different molecular weights is discussed on the assumption that the thermodynamic interaction between two polymer coils in good solvents can be approximated by a hard-sphere model.     

Asymmetric problem of a semi-infinite body having a hemispherical pit under uniaxial tension

This paper presents an asymmetric solution for the stress distributions around a hemispherical pit at a plane surface of a semi-infinite body under uniaxial tension. In this analysis, eight stress functions were chosen so as to fulfill the boundary conditions automatically, both at the plane surface and at infinity. On the other hand, the remaining boundary conditions at the surface of the pit were satisfied with the aid of the half-range expansion technique. Numerical results are given for the variations around the pit and along the z-axis and compared with the corresponding results under biaxial tension.     

Growth of Bi-Sr-Ca-Cu-O based superconducting whiskers

Superconducting whiskers of the Bi system have been grown by heating a glassy melt-quenched plate in a stream of O₂ gas. We have examined the growing phase and superconductivity of the whiskers grown at the different heating and cooling conditions. The Bi₂Sr₂CaCu₂O₈ (2212 phase) whiskers are grown from a wide range of initial compositions when the melt-quenched plates are heated at 840°C. The Bi₂Sr₂CuO₆ (2201) phase is dominant in the whiskers grown at lower temperature, 820 and 810°C. The growing pure 2223 whiskers have not been obtained so far. For the superconductivity of the 2212 whiskers, high oxygen partial pressure (P_O2, rapid cooling and higher heating temperature are preferable. Low P_O2 and slow cooling are preferable for the 2223 phase contained in the 2212 whiskers as a minor part. Heating time does not give remarkable effects on the growing phase and superconductivity.     

A 3 × 6 arrayed CCD X‐ray detector for continuous rotation method in macromolecular crystallography

A 3 × 6 arrayed charge‐coupled device (CCD) X‐ray detector has been developed for the continuous‐rotation method in macromolecular crystallography at the Photon Factory. The detector has an area of 235.9 mm × 235.9 mm and a readout time of 1.9 s. The detector is made of a 3 × 6 array of identical modules, each module consisting of a fiber‐optic taper (FOT), a CCD sensor and a readout circuit. The outputs from 18 CCDs are read out in parallel and are then digitized by 16‐bit analog‐to‐digital converters. The advantage of this detector over conventional FOT‐coupled CCD detectors is the unique CCD readout scheme (frame transfer) which enables successive X‐ray exposures to be recorded without interruption of the sample crystal rotation. A full data set of a lysozyme crystal was continuously collected within 360 s (180° rotation, 3 s/1.5° frame). The duty‐cycle ratio of the X‐ray exposure to the data collection time was almost 100%. The combination of this detector and synchrotron radiation is well suited to rapid and continuous data collection in macromolecular crystallography.