Investigation of a Spin Transition in a LaCoO<Subscript>3</Subscript> Single Crystal by the Method of X-Ray Magnetic Circular Dichroism at the Cobalt <Emphasis Type="Italic">K</Emphasis>- and <Emphasis Type="Italic">L</Emphasis><Subscript>2,3</Subscript>-Edges

Spin transitions of cobalt ions in LaCoO₃ single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K- and L_2,3-edges of Co³⁺ ions. The orbital momentum of cobalt ions obtained for the K-edge at the 3d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor of approximately 1.6, whereas the slope of the magnetization curve value in the same temperature range and magnetic field increases by a factor of more than 10. XMCD experiments at the cobalt L_2,3-edges demonstrate gradual growth of the ratio of the orbital momentum to the spin one L/S from 0.48 to 0.53 in the temperature range from 60 K to 120 K.     

Dynamic response of composite plates with cut-outs,part I: Simply-supported plates

The effect of square cut-outs on the natural frequencies of square, simply-supported composite plates is investigated. The forced and free dynamic response of plates with cut-outs is formulated. Laminations are assumed to be symmetric about the mid-plane and the plates are considered analytically as homogeneous anisotropic plates. In the method of solution it is assumed that the effect of the cut-out is equivalent to an external loading on the plate. For free vibration, the method leads to an infinite system of frequency equations. Depending upon the accuracy required, a suitable size of the system of frequency equations is selected. Results are given for square, simply-supported composite plates with centrally located square cut-outs for different modulus ratios. A comparison of results obtained from this method for isotropic plates with cut-outs with available literature is made and excellent agreement is obtained.     

APPLICATION OF STRAIN GAGES TO MEASURE ADHESIVE STRAINS THROUGH THE THICKNESS OF AN ADHESIVELY -BONDED STIFFENED STRIP

Small strain gages were used to measure the through-the-thickness extensional strain distribution in an adhesively-bonded stiffened strip subjected to four-point bending. A comparison between experiment and analysis was conducted. The results show good correlation of the experimental and analytical trends of the through-the-thickness extensional strain distribution in the adhesive layer.     

Internal conical refraction of elastic waves in orthorhombic crystals

The elastic wave propagation in orthorhombic crystals has been studied and a condition has been derived for the existence of internal conical refraction for crystals belonging to this class. It is shown that the direction in which ICR occurs is given by the roots of a quadratic equation. Expressions have been derived for the angle of the cone and other parameters relating to the cone for the three principal planes, and these have been numerically evaluated for Barytes, Celestites, and lodic acid.     

Extension of oblique-incidence method to photo-orthotropic elasticity

With the interpretation of isochromatic and isoclinic fringes in transparent, birefringent, orthotropic composites established, efforts have been in progress to determine the-individual values of the principal stresses or strains. Several methods have recently been proposed. Some of them utilize the photoelastic results only partially and rely on numerical procedures. Others have attempted to obtain the required information based entirely on experimental data. In this paper, the classical oblique-incidence technique is applied to transversely isotropic-birefringent composites. The proposed extension is verified by applying it to the problem of an orthotropic half-plane subjected to an edge-load.     

Nonconventional carbon additions to azomethines. aryl amination/indoline synthesis by direct aryl radical addition to azomethine nitrogen

[reaction: see text]. The generality of a new method for aryl amination has been defined. Ketimines derived from o-bromophenethylamine cyclize to the N-substituted indoline when treated with nBu3SnH and a radical initiator. The pH-neutral conditions tolerate base- and acid-sensitive functionality. The observed regioselectivity is nonconventional for addition reactions involving carbon radicals and carbon-heteroatom pi-bonds.     

Synthesis and characterization of chemically bonded stationary phases on hydride surfaces by hydrosilation of alkynes and dienes

A hydrosilation reaction was used to bind four compounds with one or more alkyne groups or two alkene functionalities. The diffuse reflectance infrared Fourier transform, the 29Si cross-polarization magic-angle spinning (CP-MAS) NMR, and the 13C CP-MAS NMR spectra were used to characterize the various bonded materials. The bonded phase density was determined from carbon elemental analysis. The two ten-carbon hydrophobic stationary phases were characterized chromatographically and static stability tests were run in acidic and basic solutions.     

Peaceful pyrolysis-a novel method for the decomposition of metal-perchlorate complexes of organic ligands

Perchlorate complexes of vanadium(IV), iron(III), dysprosium, yttrium, copper(II) and nickel with the organic ligands dimethyl sulphoxide, antipyrine, 4-aminoantipyrine, 4-(2-hydroxynaphthyl)-azoantipyrine, and 4-(2,4-dihydroxyphenyl)azoantipyrine have been prepared and analysed for their metal content after decomposition by a non-explosive pyrolytic technique, viz. heating with ammonium chloride. The results obtained agree with those obtained by the standard methods. This pyrolytic technique is found to be very convenient, rapid and accurate.