The tricyanomercurate(II) ion

The tricyanomercurate(II) ion, [Hg(CN)₃]^?, is isolated in the form of its solid caesium salt from a 1:1:1 ethanolic solution of CsF, KCN and Hg(CN)₂, and characterised by IR and Raman vibrational spectroscopy. Assignments are made for the CN and HgC stretching vibrations and the HgCN bending vibrations. The spectra are consistent with the [Hg(CN)₃]^? ion occupying a site of C₁ symmetry.     

An EXAFS study of dopant substitution in LiNbO3 and LiTaO3

Abstract

We report an EXAFS study of Co and Fe doped LiNbO₃ and LiTaO₃. Our results show that the dopant ions occupy Li sites in both materials.     

Surface and interfacial waves of arbitrary form in isotropic elastic media

A method due to Friedlander of accommodating disturbances of arbitrary form into the theory of surface waves in a semi-infinite isotropic elastic body is extended and shown to yield a simple closed form solution for the displacement field. An analogous treatment of interfacial waves of arbitrary form at a plane contact discontinuity separating different isotropic elastic materials is also given.

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Résumé On développe une méthode, conçue par Friedlander, qui fait entrer les perturbations de forme arbitraire dans la théorie des ondes de surface dans un corps élastique isotropique semi-infini, et on montre qu'elle permet d'obtenir une solution simple et exacte pour le champ de déplacement. Les ondes de forme arbitraire qui existent dans le plan à la frontière de materiaux élastiques isotropiques differents sont traitées de façon analogue.

     

Concavities on the zonal slowness section of a transversely isotropic elastic material

The section of the slowness surface of a transversely isotropic elastic material in a zonal plane consists of an ellipse and a quartic curve with two nested branches, the inner of which is convex. Concavities can therefore occur only on the outer branch S and five possibilities arise: (I) S is convex; (II) S has two axial concavities (centred on the points of intersection of S with the axis of transverse isotropy); (III) S has two basal concavities (centred on the points of intersection of S with the basal plane); (IV) S has two axial and two basal concavities; (V) S has four oblique concavities, neither axial nor basal. The first and last of these are commonly realized in actual materials, the others only rarely. A unified treatment of stationary points and concavities on S is given in the course of which some previous results are simplified and their relationship clarified.     

Distinguishing nanocrystalline solids from fine-particle ensembles using Mössbauer spectroscopy

Nanocrystalline solids, formed by compacting fine powders, have been proclaimed to possess a new structure. Specific characteristics have been reported from Mössbauer studies, and these appear to confirm and reinforce a model of crystalline cores isolated by disordered, low-density grain boundaries. In measurements of three compacted samples, we were unable to reproduce the characteristics expected. Reasons are suggested as to why the results differ between similarly-prepared samples. It is pertinent to enquire whether any of the previously reported Mössbauer characteristics of fine-particle compacts require a new structural model, or whether all the results can be simply understood in terms of particle agglomerates. Reference to the literature reveals that there is no distinction.     

Elasticity and active force generation of cochlear outer hair cells.

The cochlear outer hair cell is described by a cylindrical membrane model, characterized by area and shear moduli for a passive elastic element and an active tension element dependent on the membrane potential. In passive experiments, these moduli are determined from the pressure-strain relations. The area modulus obtained is 0.07 N m-1, similar to a lipid bilayer and the shear modulus is 0.007 N m-1. These moduli combined with previous active experiments show that the active tension is nearly isotropic and is about 1.6 x 10(-2) N m-1 V-1, resulting in a 0.5 nN/mV force per cell. This implies that the receptor potential for acoustical stimulation produces an active force comparable to the acoustic force applied to the basilar membrane per outer hair cell. This finding supports the hypothesis that the outer hair cell acts as feedback motor in the fine tuning mechanism of the mammalian ear.