Tracer diffusion of cobalt ions in some alkali metal chlorides

The concentration dependence of experimental diffusion coefficients of cobalt ions in presence of some alkali metal chlorides is examined in the light of the Onsager theory. The diffusion coefficients are measured in 1% agar gel using the zone-diffusion technique. The positive and negative deviations observed at higher and lower concentrations, respectively, are explained in terms of relative contributions of various types of effects occurring in the diffusion medium.     

A simple extrapolation method for clustered eigenvalues

Numerical Algorithms - This paper introduces a simple variant of the power method. It is shown analytically and numerically to accelerate convergence to the dominant eigenvalue/eigenvector pair,...     

Instrumental neutron activation analysis of some ancient punchmark coins from India

A nondestructive instrumental neutron activation analysis technique is applied for the analysis of precious ancient punchmark coins. Coins ranging between 8th century B.C. to 2nd century B.C. were irradiated with thermal neutrons in a²⁵²Cf neutron source facility and analyzed by comparator method of instrumental neutron activation analysis, using high purity germanium detector coupled to a multichannel analyzer, the activities being measured at photopeak energies of the corresponding radioisotopes. It is observed that punchmark coins are mainly of two types: copper or silver based. Other elements present in varying proportions are gold, arsenic and antimony.     

Determination of Activation Energy for the Diffusion of Fe<Superscript>3+</Superscript> Ions in Agar Gel Medium Containing Various Transition Metal Sulfates

The study of the diffusion of ferric ions in agar gel containing transition metal sulfates was carried out. The effect of gel concentration, electrolyte concentration and temperature on the diffusion of Fe³⁺ ions in various transition metal sulfates was studied with a view to verify Wang’s model of diffusion and the applicability of transition state theory to diffusion in a gel medium. The diffusion coefficients were measured using the zone diffusion technique. For a given concentration of electrolyte the activation energy (E) is found to decrease with an increase in the charge density of the cation of the supporting electrolyte and for a given system it is found to decrease with increasing electrolyte concentration in agreement with Wang’s model. This observation is explained on the basis of the distortion in the water structure caused by ions and agar molecules. At a given electrolyte concentration the magnitude of the Arrhenius parameters, E and D _o, is found to decrease with increasing gel concentration in agreement with the transition state theory of diffusion.     

Study of J-T effect on the self-energy of electrons in manganite systems

We present here a theoretical study of the effect of Jahn-Teller(J-T) distortion on the self-energy of electrons in the CMR manganites. The model consists of the itinerant e _g electrons distorted by J-T effect and the localized t _2g core electrons carrying strong ferromagnetism due to Hund’s rule. The phonon interacts with the e _g electrons as well as the J-T distorted e _g band. The electron Green’s functions are calculated by Zubarev’s technique. The electron self-energy which carries all the information of the model is calculated from the Green’s function. The effect of J-T distortion, magnetism on the frequency and temperature dependent dynamic self-energy is presented in this paper. The results are discussed.     

The influence of band Jahn-Teller effect and magnetic order on the magneto-resistance in manganite systems

A model calculation is presented in order to study the magneto-resistivity through the interplay between magnetic and structural transitions for the manganite systems. The model consists of an orbitally doubly degenerate conduction band and a periodic array of local moments of the t_2g electrons. The band electrons interact with the local t_2g electrons via the s-f hybridization. The phonons interact with the band electrons through static and dynamic band Jahn-Teller (J-T) interaction. The model Hamiltonian including the above terms is solved for the single particle Green's functions and the imaginary part of the self-energy gives the electron relaxation time. Thus the magneto-resistivity (MR) is calculated from the Drude formula. The MR effect is explained near the magnetic and structural transition temperatures.     

Effect of gamma irradiation on antioxidant activity of Amoora rohitaka

The effect of a medium dose of gamma radiation on antioxidant activity of Amoora rohitaka was studied. Radiation doses were 0, 1, 3 and 5?kGy. Antioxidant activity was screened by using different assay. With increasing dose the formation of Maillard reaction products (MRPs) contributes to the increase in the antioxidant activity. MRPs are formed as a result of Maillard reaction. In ABTS [2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid di-ammonium salt] assay, ethanol extract showed increase in scavenging activity. It also showed a marked increase in polyphenolic contents. The present study reveals that gamma irradiation can be an efficient process to increase antioxidant activity of Amoora rohitaka.     

An integral representation of the Green function for a linear array of acoustic point sources

We present a new algorithm for the evaluation of the quasi-periodic Green function for a linear array of acoustic point sources such as those arising in the analysis of line array loudspeakers. A variety of classical algorithms (based on spatial and spectral representations, Ewald transformation, etc.) have been implemented in the past to evaluate these acoustic fields. However as we show, these methods become unstable and/or impractically expensive as the frequency of use of the sources increases. Here we introduce a new numerical scheme that overcomes some of these limitations allowing for simulations at unprecedentedly large frequencies. The method is based on a new integral representation derived from the classic spatial form, and on suitable further manipulations of the relevant integrands to render the integrals amenable to efficient and accurate approximations through standard quadrature formulas. We include a variety of numerical results that demonstrate that our algorithm compares favorably with several classical methods both for points close to the line where the poles are located and at high-frequencies while remaining competitive with them in every other instance.     

Diffusion of Cesium Ions Labeled with 134 Cs in Agar Gel Containing Alkali Metal Iodides: Obstruction Effect and Activation Energy

The effect of some alkali metal iodides on the obstruction effect and activation energy for tracer-diffusion of cesium ions in an agar gel medium was studied using the zone-diffusion technique. It to be observed that both the extent of obstruction (α) and the activation energy (E) decrease with the increasing charge density of the cation of the supporting electrolyte. These trends are explained on the basis of competitive hydration between ions and agar molecules and the relative distortion in the water structure that is brought about by these different ions and agar molecules, respectively.     

Dissociation of 1P states in hot QCD Medium Using Quasi-Particle Model

We extend the analysis of a very recent work [1] to study the dissociation phenomenon of 1P states of the charmonium and bottomonium spectra (χ_c and χ_b) in a hot QCD medium using Quasi-Particle Model. This study employed a medium modified heavy quark potential which has quite different form in the sense that it has a lomg range Coulombic tail in addition to the Yukawa term even above the deconfinement temperature. Then we study the flavor dependence of their binding energies and explore the nature of dissociation temperatures by employing the Quasi-Particle debye mass for pure gluonic and full QCD case. Interestingly, the dissociation temperatures obtained by employing EoS1 and EoS2 with the Γ criterion, is closer to the upper bound of the dissociation temperatures which are obtained by the dissolution of a given quarkonia state by the mean thermal energy of the quasi-partons in the hot QCD/QGP medium.