Jaumann transport in relativistic continuum mechanics

We define the Jaumann derivative of a tensor field in relativity by a formal generalization of a stress rate in viscoelasticity. A tensor field is said to be Jaumann transported iff its Jaumann derivative vanishes. It is found that the gravitational potentials are Jaumann transported identically. The concept of a complete rotation tensor has been introduced to study the Jaumann derivative with respect to a null vector field. This provides a characterization of the integrability of a hypersurface orthogonal congruence. A perfect fluid collapsing by neutrino emission and undergoing Jaumann transport with respect to the neutrino flow is found to be compatible with that of a catastrophic collapse. The circumstances leading to the existence of ghost neutrinos are cited. The degeneracy of the Kerr-Newman black hole into the Reissner-Nordstrom black hole is expressed in terms of the Jaumann propagation.     

Estimation of trace elements in water matrix from photon attenuation coefficients

The method of elemental analysis based on the measurement of attenuation coefficient has been used to estimate the impurity introduced in a water matrix using a scintillation detector with a single channel analyser. For a 2% change in the mass attenuation coefficient the minimum detectable fractions of impurities were estimated to be of the order of 625–1250 μg/g for uranium and thorium compounds at photon energies 32.1 and 59.5 keV.     

Carrier-free separation of Sn113 from indium

A procedure for the separation of carrier-free Sn¹¹³ from deuteron bombarded indium is described. The method employed depends on the extraction of stannic cupferrate from mineral acid solution using carbon tetrachloride, followed by ignition of the complex.     

Synthesis of inductors and gyrators with voltage-controlled voltage sources

Inductors are synthetised using voltage-controlled voltage sources and RC elements. Wherever possible, unity-gain amplifiers are used. Practical circuits are presented. Some of these also realise gyrators.     

Raman spectra of irradiated NaClO3 and KClO3 crystals

Pure undamaged NaClO₃ and KClO₃ crystals show four Raman lines arising from the internal oscillations in the ClO₃ ion, besides a few other Raman lines due to lattice oscillations. On radiation damage by X-rays or γ-rays some new lines are observed in each crystal. In particular, two lines at ～ 680 and ～ 930 are assigned to the ozonide ion (O₃ ^?) in these lattices. It is postulated that by radiation damage a certain number of ClO₃ ions, which initially have a pyramidal structure, loose the chlorine atom leaving the three oxygen atoms at the corners of an equilateral tri-angle. Since an equilateral triangular structure should exhibit two normal oscillations, both of which are Raman active, such a postulate satisfactorily explains experimental results.     

Orientational (EPR) study of vanadyl ion in potassium hydrogen oxalate lattice

The EPR spectra of VO²⁺ doped KHC₂O₄ crystals revealed two sites with intensity ratio 2:1 and indicated two nearly parallel orientations of the ion in the lattice. On the basis of comparison of the experimentally determined and the calculated direction cosines, only one of the sites could be identified as the substitutional. The other site is suggested to be due to the interstitial occupation of VO²⁺ in the lattice. While the g? tensor is axially symmetric, the à tensor does not show such perfect axial character. The features are explained in terms of the covalency effects arising from hydrogen bonding in the lattice.     

A simple molecular theory for photo-induced smectic phase

The response of liquid crystals to light is very important for applications of liquid crystals in display and memory devices. Recently experiments have been carried out on liquid crystals doped with photoactive azo compounds. It is seen that UV rays incident on such systems can lower the nematic isotropic transition temperature T _NI . Also, in some mixtures, a photo-induced smectic phase is observed. This is attributed to the change in the trans (longer) isomer to cis (shorter) isomer of the photoactive dopant. We have earlier developed a molecular mean-field model assuming the medium to consist of inter-converting anti-parallel and parallel pairs to explain the molecular origin of “two lengths”. The model was used to explain double re-entrance, the effect of electric field on T _NI , etc. This model is modified to include the change of trans to cis isomer which is equivalent to an increase of fraction of parallel (shorter) pairs. The calculated phase diagram with respect to incident UV radiation energy shows an induced smectic phase. This is in qualitative agreement with experimental trends.