Isotopic effects on non-linearity, molecular radius and intermolecular free length

Computation of non-linearity parameter (B/A), molecular radius (r _m) and intermolecular free length (L _f) for H₂O, C₆H₆, C₆H₁₂, CH₃OH, C₂H₅OH and their deuterium-substituted compounds have been carried out at four different temperatures, viz., 293.15, 303.15, 313.15 and 323.15 K. The aim of the investigation is an attempt to study the isotopic effects on the non-linearity parameter and the physicochemical properties of the liquids, which in turn has been used to study their effect on the intermolecular interactions produced thereof.     

Weak reciprocal continuity and fixed point theorems

The aim of the present paper is to introduce the notion of weak reciprocal continuity and obtain fixed point theorems by employing the new notion. The new notion is a proper generalization of reciprocal continuity and is applicable to compatible mappings as well as noncompatible mappings. Our results generalize several fixed point theorems.     

Anomalous magnetic behavior of CuO nanoparticles

We report studies on temperature, field and time dependence of magnetization on cupric oxide nanoparticles of sizes 9 nm, 13 nm and 16 nm. The nanoparticles show unusual features in comparison to other antiferromagnetic nanoparticle systems. The field cooled (FC) and zero field cooled (ZFC) magnetization curves bifurcate well above the Néel temperature and the usual peak in the ZFC magnetization curve is absent. The system does not show any memory effects which is in sharp contrast to the usual behavior shown by other antiferromagnetic nanoparticles. It turns out that the non-equilibrium behavior of CuO nanoparticles is very strange and is neither superparamagnetic nor spin glass like.     

Effect of donor-acceptor interaction strength on excitation energy migration and diffusion at high donor concentrations

The migration and diffusion modulated excitation energy transfer has been studied in a new dye pair 7-diethylamino-4-methylcoumarin (donor) to 3,3'-dimethyloxacarbocyanine iodide (acceptor) by steady-state and picosecond time-resolved spectroscopy. To reduce the artifact of self-absorption, at high donor concentrations, the time-resolved studies have been carried out in thin films of polyvinyl alcohol (solid matrix) and in methanol (liquid phase) at front-face geometry of excitation. The Forster-type (nonradiative) energy transfer [Discuss. Faraday Soc. 27, 7 (1959)] takes place directly from donor to acceptor in case of solid matrix, while Yokota-Tanimoto model [J. Phys. Soc. Jpn. 22, 779 (1967)] for diffusion has been found to be operating in the liquid phase. It has been found here that the high interaction strength between donor and acceptor molecules as compared to that among donors masks the effect of energy migration and diffusion at high donor concentrations. The rate and efficiency of energy transfer increase with increasing the acceptor concentration. This has been confirmed by the study of acceptor kinetics.     

Ab-initio study of AlN in zinc-blende and rock-salt phases

Group III-nitrides are of great interest in both fundamental sciences and technical application. Most of the common nitrides are well known as hard and wide band gap semiconductor materials. In general they have been studied in zinc-blende and wurtzite phases. In this paper, we focus our attention to structural, electronic, phase transition and elastic properties of aluminum nitride (AlN) in zinc-blende and rock-salt phases. A little work has been reported either theoretically or experimentally on elastic and electronic properties of AlN; especially in RS phase. All the calculations are performed using the full-potential linearized augmented plane-wave approach plus local orbitals within the framework of density functional theory as implemented in the Wien2k code. The generalized gradient approximation based on the Perdew–Burke–Ernzerhof is used for the exchange and correlation functional. We determine the full set of first order elastic constants, C₁₁, C₁₂ and C₄₄ at zero pressure to confirm the mechanical stability and hardness, which have not been established either experimentally or theoretically for RS phase. In the study obvious phase transition from ZB phase to RS phase due to pressure effect has been obtained at 12.75 GPa.     

Vanishing pseudo–Schur complements,reverse order laws,absorption laws and inheritance properties

The problem of vanishing of a (generalized) Schur complement of a block matrix (corresponding to the leading principal subblock) implying that the other (generalized) Schur complement (corresponding to the trailing principal subblock) is zero, is revisited. Absorption laws for two important classes of generalized inverses are considered next. Inheritance properties of the generalized Schur complements in relation to the absorption laws are derived. Inheritance by the generalized principal pivot transform is also studied.     

Static fluid spheres admitting Karmarkar condition

We explore a new relativistic anisotropic solution of the Einstein field equations for compact stars based on embedding class one condition.For this purpose,we use the embedding class one methodology by employing the Karmarkar condition.Employing this methodology,we obtain a particular differential equation that connects both the gravitational potentials e^λ and e^ν.We solve this particular differential equation choosing a simple form of generalized gravitational potential grr to describe a complete structure of the space-time within the stellar configuration.After determining this space-time geometry for the stellar models,we discuss thermodynamical observables including radial and tangential pressures,matter density,red-shift,velocity of sound,etc.,in the stellar models.We also perform a complete graphical analysis,which shows that our models satisfy all the physical and mathematical requirements of ultra-high dense collapsed structures.Further,we discuss the moment of inertia and M-R curve for rotating and non-rotating stars.     

Diffraction-induced spectral anomalies for information encoding and information hiding - Possibilities and limitations

It has been shown both theoretically and experimentally that drastic spectral changes take place around phase singularity and the shift in the spectral lines gives rise to the phenomenon called spectral switching. The shift of spectral lines towards the blue end or towards the red end of the spectrum might perhaps be used in free space communication applications. In more recent investigations, the possibility of information encoding with spectral anomalies have been discussed for two different optical systems. In this paper, we present schemes of information encoding and information hiding in the Airy pattern formed by diffraction of spatially coherent light after passing through a circular aperture. We propose a communication system that might be used to realize a new communication technique.     

Volumetric method for the estimation of persulphate in aqueous solution

Summary A rapid volumetric method for the estimation of persulphate using the persulphate-thiosulphate reaction catalysed by cupric ions has been proposed. The method consists in adding a known excess of standardised sodium thiosulphate solution to the persulphate solution containing 5 ml of 0.01 M copper sulphate solution and after the completion of the reduction of persulphate, titrating the remaining sodium thiosulphate against a standard solution of iodine.

---

Zusammenfassung Die durch Kupfer(II)-ionen katalysierte Reaktion zwischen Persulfat und Thiosulfat wird zur raschen, volumetrischen Persulfatbestimmung benutzt. Bei dem Verfahren gibt man zur Persulfatlösung, die 5 ml 0,01 m Kupfersulfatlösung enthält, einen Überschuß an Thiosulfatlösung und titriert nach Beendigung der Reaktion mit Jodlösung zurück.