Graphic sequences of trees and a problem of Frobenius

We give a necessary and sufficient condition for the existence of a tree of order n with a given degree set. We relate this to a well-known linear Diophantine problem of Frobenius.     

Angular momentum transfer in incomplete fusion

Isomeric cross-section ratios of evaporation residues formed in¹²C+⁹³Nb and¹⁶O+⁸⁹Y reactions were measured by recoil catcher technique followed by off-line γ-ray spectrometry in the beam energy range of 55.7–77.5 MeV for¹²C and 68–81 MeV for¹⁶O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical deexcitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.     

Diffusion of propylene adsorbed in Na-Y and Na-ZSM5 zeolites: Neutron scattering and FTIR studies

Here we report the quasielastic neutron scattering and FTIR studies on the dynamics of propylene adsorbed in Na-Y and Na-ZSM5 zeolites. QENS data show that although the mechanism of translational motion of propylene is jump diffusion in both the cases of Na-Y and Na-ZSM5 zeolites, the diffusivity is affected by the host size and is hindered in the case of Na-ZSM5. FTIR studies showed that guest-host interaction in Na-ZSM5 is stronger than that in Na-Y zeolite corroborating the QENS results.      

Thickness dependent magnetic and structural properties of Co films grown on GaAs (100)

The structural, magnetic and transport properties measurements carried out on Co thin films deposited by electron beam evaporation on GaAs substrate as a function of layer thickness ranging from 50 Å to 1000 Å are presented here. Structural measurements show the film to be amorphous in nature at lower thickness which becomes crystalline at higher thickness. Magnetic measurements show an increase in saturation magnetization (M_S) with film thickness. M_S values are found to vary from 521 emu/cm³ to 1180 emu/cm³ for thicknesses ranging from 50 Å to 1000 Å. The coercivity and saturation field value shows a systematic decrease up to 600 Å thickness and increase thereafter. Various microstructural parameters were also calculated using GIXRR technique. A clear grain growth is observed in AFM technique with film thickness and its influence on transport properties was also seen. Different surface morphology and magnetic domain structures were obtained on different thin film samples by AFM and MFM techniques, respectively. XPS measurements reveal formation of CoAs phase at the interface between Co and GaAs. All these results are discussed and interpreted in detail in this communication.     

Energy levels, oscillator strengths and lifetimes in Ar V

We have calculated the excitation energies, oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions among the 46 LS levels belonging to the configurations 3s ²3p ², 3s3p ³, 3s ²3p3d, 3p ⁴, 3s ²3p4s, 3s ²3p4p, 3s3p ²(² S)4s, 3s3p ²(² P)4s, 3s3p ²(⁴ P)4s, 3s3p ²(² D)4s, 3s ²3p4d and 3s ²3p4f of Si-like Argon. These states are represented by extensive Configuration-Interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. From our transition probabilities we have also calculated the radiative lifetimes of singlet and triplet states of Ar V. Our results are compared with other available theoretical calculations and experimental data. To assess the importance of relativistic effects on our calculated values, we have also carried out calculations in the intermediate-coupling scheme using the Breit-Pauli Hamiltonian. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimentally compiled energy values of the National Institute for standards and Technology (NIST). The energy splitting of 85 fine-structure levels, the oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions and the lifetimes of some fine-structure levels are presented and compared with available experimental and other theoretical values. In this calculation, we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.     

Estimate of etched tracks by optical method and spark counting

Solid State Nuclear Track Detectors (SSNTD) are commonly used for long term measurements of radon, thoron and progeny concentrations. In the present study, we compared the optical counting method and the spark counting technique for counting the alpha tracks on LR 115 track detector films. The paper discusses the various parameters that are innate in the process. More than 300 films were counted by both optical microscope and spark counter and the results are compared. The overall results show that the tracks obtained by spark counting are marginally less compared to the optical measurement. A linear fit of the data gives a slope less that one, which indicates that both the methods are almost in good agreement for counting the tracks when the track density is low. At higher track densities the spark counter gives an underestimation with respect to actual number of tracks formed, which could be corrected using a relation obtained between the tracks measured by optical method and spark counting.      

Optical properties of selenium-tellurium nanostructured thin film grown by thermal evaporation

Se-Te nanostructured thin films were deposited on glass substrates in the presence of oxygen and argon by thermal evaporation. The properties of Se-Te thin films strongly depend on the deposition method. During the process used, the substrate is cooled to a temperature of 77 K employing liquid nitrogen. The nanostructured thin films of Se_100−xTe_x (where x=4, 8 and 16) are deposited on glass substrate. The surface morphology of the deposited films was investigated through Scanning Electron Microscopy (SEM). The typical size of these nanostructures is in the range 40-100 nm and the length is of the order of several micrometers. The optical parameters i.e. optical gap (E_g), absorption coefficient (α), and extinction coefficient (k) are calculated in the wavelength range 190-1100 nm. It was found that the optical band gap decreased from 3.4 to 2.9 eV when Te concentration was increased in the Se_100−xTe_x nanostructured thin films. The large bandgap may be attributed to the decrease in particle size which clearly exhibits a quantum size effect. XRD analysis was performed to confirm glassy nature of the nanostructured thin films.     

RF breakdown by toroidal helicons

Bounded whistlers are well-known for their efficient plasma production capabilities in thin cylindrical tubes. In this paper we shall present their radio frequency (RF) breakdown and discharge sustaining capabilities in toroidal systems. Pulsed RF power in the electronmagnetohydrodynamic (EMHD) frequency regime is fed to the neutral background medium. After the breakdown stage, discharge is sustained by toroidal bounded whistlers. In these pulsed experiments the behaviour of the time evolution of the discharge could be studied in four distinct phases of RF breakdown, steady state attainment, decay and afterglow. In the steady state average electron density of ≈10¹² per cc and average electron temperature of ≈20 eV are obtained at 10⁻³ mbar of argon filling pressure. Experimental results on toroidal mode structure, background effects and time evolution of the electron distribution function will be presented and their implications in understanding the breakdown mechanism are discussed.     

Magnetic properties of undoped YBa 2 Cu 3 O 6 + x system

In the present paper, we study the magnetic properties of bilayer cuprate antiferromagnets. In order to evaluate the expressions for spin-wave dispersion, sublattice magnetization, Néel temperature and the magnetic contribution to the specific heat, the double time Green's function technique has been employed in the random phase approximation (RPA). The spin wave dispersion curve for a bilayer antiferromagnetic system is found to consist of one acoustic and one optic branch. The “optical magnon gap” has been attributed solely to the intra-bilayer exchange coupling (J _⊥ ) as its magnitude does not change significantly with the inter-bilayer exchange coupling (J_z). However J_z is essential to obtain the acoustic mode contribution to the magnetization. The numerical calculations show that the Néel temperature (T _N ) of the bilayer antiferromagnetic system increases with the J_z and a small change in J_z gives rise to a large change in the Néel temperature of the system. The magnetic specific heat of the system follows a T² behaviour but in the presence of J_z it varies faster than T². Received 13 July 2000 and Received in final form 14 May 2001     

New insight into the DNA binding studies,In-Vitro anti-cancer activity and molecular modelling of dioxo complexes of Molybdenum(VI) and Tungsten(VI) hydroxamic acids

The present study embodies the detail of interaction of Complex 1, Bis(N-phenyl-o-methoxybenzohydroxamato)Molybdenum(VI): [N-PMBHA-Mo(VI)] and Complex 2, Bis(N-phenylbenzohydroxamato)Tungsten(VI): [N-PBHA-W(VI)] with ct-DNA (Calf thymus-DNA) and its consequences by UV–Visible absorption spectroscopy, fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, viscosity measurements and molecular docking. The intrinsic binding constant, K_b of complexes were determined which follows the order as complex 1 > complex 2 along with variation in shift and intensity for the complexes. Fluorescence spectroscopy applied for the determination of Stern–Volmer quenching constant, binding constant and the number of binding sites which reveals groove mode of binding. Non-radiative energy transfer between donor and acceptor molecule exposed by Förster energy transference theory (FRET) studies. The increase in the relative viscosity of ct-DNA with increasing the concentration of the complex 1 and complex 2 is also revealed. FTIR analysis also revealed that both the complexes interacted positively with bases and phosphates of ct-DNA. The docking studies complemented the experimental results revealing minor groove mode of binding for both the complexes. Finally, the in-vitro cytotoxicity studies indicate that the complexes have excellent anticancer activity against the breast cancer cell line, MCF-7, which could be a constructive guideline to produce new generations of anticancer agents.