RF SQUID behaviour due to grain boundary weak links in a bulk YBCO is observed at 77 K using modified commercial rf electronics. Porous samples with lowI_c are found to show this characteristic whereas dense samples with higherI_c do not show SQUID behaviour.V-B modulation characteristic is found to be better when the rf pumping frequency is kept slightly higher than the resonance frequency of the tank circuit. Designing of coil for tank circuit with appropriateQ has been found to be very crucial for seeing the SQUID behaviour. Estimation of parameters such as coupling constant, mutual inductance, inductance and radius of the SQUID loop, have been made and their significance is discussed. Flux noise spectrum of the bulk rf SQUID in flux locked mode is also reported.

The fluctuating hydrodynamics theory of a fluid possessing internal rotation is set up following the Landau-Lifshitz approach.

The temperature dependence of shear viscosity of the system nitrobenzene-n-heptane has been studied near the critical concentration. The critical exponent of the shear viscosity Φ was calculated from the empirical formula$$\eta = \eta _{id} \varepsilon _{sp} ^{ - \Phi } $$ and compared with the theoretical and experimental results obtained for other critical systems. The shear viscosity satisfies scaling law relations similar to those previously established for equilibrium properties.

Using Green’s function method, microwave lossess were theoretically calculated for BaTiO₃, SrTiO₃ and KTaO₃ ferroelectric perovskites. In microwave range, an increase in frequency is followed by an increase in the dielectric loss. In the paraelectric phase, the dielectric loss decreases with increasing temperature showing the Curie-Weiss behaviour of the tangent loss.

Effect of incorporation of Sb in place of Bi in the bismuth cuprate superconductors has been examined. The nominal compositions studied are MCa_1·5Sr_1·5Cu₂O_8+δ and MCa₂Sr₂Cu₃O_10+δ, whereM=Bi_2−xSb_x or Bi_1·5−xSb_xPb_0·5. Different preparative routes such as the ceramic method, the matrix route as well as the melt route were employed to prepare the materials. No indication of either Sb entering the lattice or enhancement ofT_c is noted from resistivity, magnetic susceptibility and microwave absorption measurements.

The temperature dependence of magnetic susceptibility,x, of titanomagnetites (Fe_3−xTi_xO₄, 0⩽x⩽0.2) at different frequencies in the range of 13 Hz to 117 kHz is reported. Whereas the position of thex-peak of Fe₃O₄ at 120 K shows no significant shift over this frequency range, that of Fe_2.8Ti_0.2O₄ shifts from 70 K at 13 Hz to 115 K at 117 kHz. This seems to be the first observation of such large shift in the position of ax-peak observed at low-temperatures is attributed to the occurrence of an isotropic point (temperature at which first order anisotropy constantK₁=0) associated with change in crystal structure. In such a case a shift inx-peak with frequency is not expected normally. Thus, the observed large shift in the position ofx-peak with frequency is an unusual phenomenon and some of its repercussions are discussed.

The ionization energies and the polarizabilities of a donor in an isolated well of a quasi two dimensional (Q2D) GaAs/Ga_1−xAl_xAs heterostructure have been obtained for different well widths including electron-lattice coupling. A wave function that properly reduces to the hydrogenic function in the limiting case has been used. For fields of the order of 10⁵ V/m, the ionization energies decrease slightly with electric fields for all well widths (10 nm to 50 nm) studied. Also for a given electric field, as the well width increases, the ionization energy decreases. For fields of the order of 10⁷ V/m and for smaller well widths (<10 nm), the ionization energy generally increases with electric field. The results also show that for electric fields of this order, no donor bound state associated with the lowest subband is possible for well widths greater than 20 nm. The polarizabilities estimated using the expression for the dipole operator show that as the well width increases, the polarizability values also increase and do not show any abnormal behaviour.

The molecular charge-transfer absorption bands have been observed in solution of dimethyl sulphoxide (DMSO) and tetrachloro-p-benzoquinone (chloranil) in chloroform and cyclohexanone. The stability constant, the thermodynamic parameter of the complex and the extinction co-efficient of CT bands at 350 nm in chloroform and 360 nm in cylohexanone have been estimated on the assumption of the 1:1 complex formation. Detection of ESR signal of the solution of chloranil in pure DMSO (g ≈ 2) indicates the formation of chloranil radical anion, the precursor being the charge-transfer complex, which dissociates partly in high dielectric constant DMSO.

A new scale of electronegativity based on X-ray spectroscopic data was earlier presented by Mande and others for the elements₃Li to₅₄Xe. The present paper reports an extension of this scale carried out for most of the heavier elements lying between₅₅Cs and₉₂U. The present approach is based on the physical interpretation of electronegativity of an atom as the attractive electrostatic force it exerts at a distance equal to its covalent radius. To estimate this force, experimental spectroscopic data have been employed. The merits of such an approach have been pointed out recently by Mullay and may be of interest in the context of the intimate relation found between electronegativity and superconducting transition temperature.