U.V. absorption spectra of 8-oxyquinoline and its copper chelate

From a comparison of the U.V. absorption spectra of the copper chelate of 8-oxyquinoline in ethyl alcoholic solution with those of the ligand itself in the same medium and in the presence of 0.l N HClO₄ and 0.1N NaOH respectively, a probable structure for the former has been suggested. The structure presupposes a planar configuration for the complex and a metal-ligand double bonding.     

Spectral properties and emission efficiencies of GdVO4 phosphors

GdVO₄ with activators Eu, Dy, Sm and Bi has been synthesised by a solid-state reaction. GdVO₄:Eu³⁺ (3%) yielded the highest quantum efficiency of 95%. Interesting energy-transfer properties have been revealed in the mixed-activator phosphor (GdVO₄:Eu³⁺, Sm³⁺) when excited in the 4f shell of Sm³⁺ at 408 nm. Bismuth-activated GdVO₄ gives rise to a broad-band emission peaking at 525 nm in comparison to YVO₄:Bi³⁺, which gives an emission peak at 570 nm under UV excitation. The quantum efficiency of GdVO₄:Bi³⁺ increases gradually with bismuth concentration and reaches a maximum of 80% for a bismuth concentration of ≈0.5%. There is a shift in the excitation band of GdVO₄:Bi³⁺ towards longer wavelengths with increasing concentration of bismuth, which can lead to energy transfer from bismuth to europium in a phosphor with both these activators. Heat treatment of GdVO₄:Bi³⁺ at 1500 °C for 3–3.5 h resulted in a large percentage of bismuth being lost from the lattice as evaluated by X-ray fluorescence. However, if a large percentage of bismuth (of the order of 3% or more) is initially added, a sufficient quantity of bismuth can still be retained after heat treatment, which can lead to the development of ceramic scintillators for X-ray tomographic applications. Addition of 3–5% boron gives a white GdVO₄ phosphor without any chemical treatment. Received: 27 Feruary 2001 / Accepted: 1 August 2001 / Published online: 30 October 2001     

Enhancement of the Peierls gap by a radiation field

The stability of the Peierls phase is investigated in the presence of a radiation with frequency less than that for inter-band transitions. It is observed that such an external radiation enhances the gap. This result is in contrast with the case when the external radiation has a frequency higher than that for inter-band transitions.     

Dual band multi-branch lasing from a hybrid CO2 laser

By judicious imposition of longitudinal mode control onto a resonator cavity, the Q-value of which increases with decreasing wavelength in the 11 to 9 μm region, simultaneous oscillation was obtained on all the four branches from a hybrid CO2 laser when its low pressure section operates in the sub-threshold condition. In the above threshold operation of this section, the hybrid laser lases simultaneously only on 9P, 9R, and 10P branch lines. This revised version was published online in November 2006 with corrections to the Cover Date.     

Estimation of the film thickness from the cohesive pressure at the air water interface

Summary The pressure-area curves for neutral monolayers of butyric, valeric, caproic and caprylic acids at the airwater interface were obtained from the surface tension concentration data. Similar curves for the charged monolayers of sodium octanoate and sodium lauryl sulphate in the presence and absence of excess neutral salts were constructed on the basis of the results on surface tension. From the comparison of the pressure area curves of each of these monolayers at air-water and oil-water interfaces under identical conditions, the cohesive pressures of the monolayer at the air-water interface were calculated for different areas per adsorbed molecule using the equation ofDavies. The cohesive pressure was observed to vary linearly with the square of the reciprocal area per adsorbed molecule or ion. From the slope of such linear plot, magnitude of the two-dimensionalvan der Waals constant in each case was estimated. The thickness of the interfacial film was estimated from the comparison of the values of two- and three-dimensionalvan der Waals constants. This is, however, found to be considerably greater than the length of the stretched molecules adsorbed at the interface. When correction for entropy, as suggested byGershfeld is introduced, the film thickness becomes identical with the length of the molecule. Based in part upon the thesis submitted byA. K. Chatterjee for the Ph. D. degree of the Jadavpur University (1966).     

On backflow in two and three dimensions

The interaction between the backflow patterns generated by two slowly-moving impurities in an arbitrary liquid is examined in both three- and two-dimensional systems. It is concluded that this interaction becomes more important as the dimensionality is reduced.     

Boundary effects on the soliton mass in (1+1)-dimensional supersymmetric theories

A proper incorporation of boundary effects, in terms of a surface term contribution to the one-loop soliton mass in (1+1)-dimensional supersymmetric theories, is shown to resolve the problem of renormalizability in the soliton sector, which otherwise arises in a finite space calculation of the soliton mass using a modified version of a set of boundary conditions proposed by Rouhani. The saturation of the Witten-Olive bound for such boundary conditions follows immediately.     

Adsorption der organischen zweibasischen Säuren an flüssigen Grenzflächen. I. Neutrale Einzelschichten der nichtionisierten Säuren

Ohne Zusammenfassung     

The calculation of fractional parentage coefficients for many-boson systems

A second quantised operator approach has been used to calculate formulae for one-body fractional parentage coefficients (fpc) for a system of many spinless bosons. A number of examples have been discussed and compared with some of those already calculated by a different technique when used to simplify Jahn-Teller problems in atomic physics. It has been shown explicitly that this procedure may be generalised to find two-boson fpc which are useful when calculating matrix elements of two-body boson operators.     

The stress field in the neighborhood of a branched crack in an infinite elastic sheet

The problem of a branched crack consisting of a main crack and a straight branch starting from one of its tip located in an infinite elastic sheet is considered under the assumptions of two-dimensional theory of Elasticity. Employing Kolosov-Muskhelishvili representation of the stress function and other well known techniques the problem is reduced to the solution of an integral equation. The nature of the stress singularity at the re-entrant corner, where the two branches of the crack meet, is discussed. Based upon a numerical solution of the integral equation the stress intensity factors at the two tips are computed for two types of prescribed traction at infinity and various geometric configurations of the branched crack.