Search

AbstractThe CdO and modified CdO nanoparticles were synthesized using hydrothermal method. The absorption spectra, crystal phase, surface morphology, particle size, and surface area of CdO and modified CdO nanoparticles were studied by UV–DRS, FT-IR, XRD, SEM, TEM, TGA, PL, and BET surface area analysis. The present paper reports adsorption technique for the removal of chromium (VI) using CdO and modified CdO nanoparticles. The operating variables such as adsorbent dose, nature of adsorbent, adsorbate concentration, contact time, and pH were optimized. The technique was found to be highly useful and cost effective for removal of chromium (VI). The Langmuir and Freundlich models were evaluated using the experimental data and result showed that the Freundlich isotherm fit better than the Langmuir isotherm.

The CdO and modified CdO nanoparticles were synthesized using hydrothermal method. The absorption spectra, crystal phase, surface morphology, particle size, and surface area of CdO and modified CdO nanoparticles were studied by UV–DRS, FT-IR, XRD, SEM, TEM, TGA, PL, and BET surface area analysis. The present paper reports adsorption technique for the removal of chromium (VI) using CdO and modified CdO nanoparticles. The operating variables such as adsorbent dose, nature of adsorbent, adsorbate concentration, contact time, and pH were optimized. The technique was found to be highly useful and cost effective for removal of chromium (VI). The Langmuir and Freundlich models were evaluated using the experimental data and result showed that the Freundlich isotherm fit better than the Langmuir isotherm.

Abstract: Path integration of a Lagrangian related to an electron gas in a random potential is carried out within the framework of Feynman's polygonal approach. The integration is direct and does not require the knowledge of an auxiliary measure or the artificial coupling of the system to external forces.

We assume that currents induced by isothermal changes of magnetic field decay logarithmically with time. Incorporating this time dependence into the critical state model, we obtain logarithmic relaxation rate of magnetization as a function of field for the case of an infinite cylinder. We compare these calculations with our earlier calculations on infinite slab geometry.

We present exact solutions of Bean’s critical state model for some sample shapes having non-zero demagnetization factorN. Virgin and hysteresis magnetization curves are obtained for samples in the shape of (i) a sphere (ii) a spheroid (iii) a cylinder of circular cross-section with its axis perpendicular to the field and (iv) a cylinder of elliptical cross section with its axis perpendicular to the field. Some interesting features seen in these first solutions forN≠ 0 are discussed.

A point-defect model of structural phase transitions in YBa2Cu3O6 + x is proposed. The model treats the basal-plane oxygen atoms as point defects. The treatment parallels the work of Alefeld and coworkers on ferroelasticity due to hydrogen in metals. The model predicts that the tetragonal-to-orthorhombic phase transition should be accompanied by precipitation into regions of high and low oxygen density, as well as high and low oxygen ordering. This is in agreement with experiment, as well as with the predictions of Khachaturyan's concentration-wave model. A new feature of the present model is the prediction of two characteristic temperatures related, respectively, to Snoek-type and Gorsky-type diffusive relaxations. Practical implications of the high diffusivity of the basal-plane oxygens include the easy fabricability of a bicrystal of Y-Ba-Cu-O such that the two components of the bicrystal are rotated by 90° with respect to each other, and are separated by a non-superconducting layer. Such a bicrystal can find applications as a Josephson-tunneling device.

A simple algebraic proof of a theorem due to Wigner on the product of three positive matrices is given. It is shown that the theorem holds for four matrices under an additional condition. The proofs are valid in the more general case of operators in a Hilbert space.

In certain agricultural fields of Khambhat Taluka in Gujarat State, the salinity has increased considerably rendering the land completely infertile. The occurrence of salinity in this area can be attributed partly to subsurface sea-water ingress and partly to improper land and water management practices prior to implementation of irrigation. Landsat MSS or TM and IRS IA LISS II data was used to test the feasibility of delineating saline soils by both visual image interpretation and digital analysis. The study of saline soils using multi-temporal Landsat images of the year 1977, 1983, and 1987, indicated an evident increase in saline areas in past few years. The Soil Brightness Index (SBI) generated from the IRS-IA data by the application of MSS equivalent coefficients brought out different categories of soil degradation. The supervised classification scheme aided in generating various salinity levels. The analysis of the soil samples of the above area exhibited increasing values of Electrical Conductivity (ECe), and the soluble cations with increasing levels of salinity.

A ferroacoustogyrotropic crystal is an acoustically active crystal for which at least one direction exists such that the acoustical rotatory power along this direction undergoes either a switching of sign, or a finite discrete jump in magnitude, when a suitable driving force is applied. It has been argued recently by Wadhawan that the technologically important crystal α-quartz should exhibit this effect. This idea is confirmed and further clarified in the present paper. A new fourth-rank axial tensor, which is the exact equivalent of the fifth-rank acoustic gyrotropic tensor, is introduced. A discrepancy in the literature about the number and kind of crystal classes which should allow acoustical activity is resolved. It is also shown that, like in the case of optical ferrogyrotropy, changes in the stored enthalpy during ferroacoustogyrotropic state shifts do not involve any contribution from the linear wavevector-dependent term responsible for acoustical activity. Such state shifts can therefore occur in ferroic crystals only.

It is shown how a delta potential can be replaced by appropriate boundary conditions for the wave function for the one‐dimensional Dirac equation. This technique is used to derive en explicit expression for the transfer matrix in the case of a linear chain of such potentials. Luttinger's proof of the Saxon‐Hutner theorem on band gaps is extended to the relativistic case by introducing necessary modifications. [Russian Text Ignore]

Two theoretical formulations for explaining acoustical activity, namely the first-strain-gradient theory and the rotation-gradient theory, are described and compared. In the first-strain-gradient theory acoustical activity is determined by a fifth-rank tensor d, called the acoustic gyrotropic tensor. A new fourth-rank pseudotensor Ghas been defined by us which is completely equivalent to the tensor d. We also introduce the term "pure ferroacoustogyrotropy" to describe the effect in which the acoustic rotatory power of a crystal can be switched in sign (without change of magnitude) for transverse acoustic waves travelling along acoustic axes (axes of 3-fold or higher rotational symmetry). This effect can occur in ferroic crystals only. Twenty-nine Aizu species allowing it are identified. A number of crystals are predicted to exhibit this effect, the most convenient to study being lead germanate.