The end point energies of nuclear $beta$ decays have been measured with a segmented planar Ge LEPS detector using both singles and coincidence techniques. The $beta - gamma$ coincidence has been performed with a segmented planar Ge LEPS and a single
10$%$ HPGe detector. The $gamma$ ray and $beta$ particle responses of the Segmented planer Ge LEPS detector were studied using monte carlo simulation code GEANT3. The experimentally obtained $beta$ spectrum was in reasonably good agreement with the simulation results. The experimental end point energies are determined with substantial accuracy for some of the known $beta$ decays in $^{106}$Rh, $^{210}$Bi and $^{90}$Y. The end point energies corresponding to three weak branches in $^{106}$Rh $rightarrow$ $^{106}$Pd decay has been measured for the first time.
Electron Capture (EC) decay of $^{146}$Gd($it{t_{1/2}}$ = 48d) to the low lying states of $^{146}$Eu has been studied using high-resolution $gamma$ ray spectroscopy. The $^{146}$Gd activity was produced by ($alpha$, 2n) reaction at E$_{alpha}$ = 32 M
eV using 93.8% enriched $^{144}$Sm target. The level structure has been considerably modified from the measurement of $gamma$ ray singles, $gammagamma$ coincidences and decay half lives. Lifetime measurement has been performed for the 3$^-$ (114.06 keV) and 2$^-$ (229.4 keV) levels of $^{146}$Eu using Mirror Symmetric Centroid Difference (MSCD) method with LaBr$_3$ (Ce) detectors. The lifetimes for these two states have been found to be 5.38 $pm$ 2.36 ps and 8.38 $pm$ 2.19 ps respectively. Shell model calculation has been performed using OXBASH code in order to interpret the results.
We study the excess free energy due to phase coexistence of fluids by Monte Carlo simulations using successive umbrella sampling in finite LxLxL boxes with periodic boundary conditions. Both the vapor-liquid phase coexistence of a simple Lennard-Jone
s fluid and the coexistence between A-rich and B-rich phases of a symmetric binary (AB) Lennard-Jones mixture are studied, varying the density rho in the simple fluid or the relative concentration x_A of A in the binary mixture, respectively. The character of phase coexistence changes from a spherical droplet (or bubble) of the minority phase (near the coexistence curve) to a cylindrical droplet (or bubble) and finally (in the center of the miscibility gap) to a slab-like configuration of two parallel flat interfaces. Extending the analysis of M. Schrader, P. Virnau, and K. Binder [Phys. Rev. E 79, 061104 (2009)], we extract the surface free energy gamma (R) of both spherical and cylindrical droplets and bubbles in the vapor-liquid case, and present evidence that for R -> Infinity the leading order (Tolman) correction for droplets has sign opposite to the case of bubbles, consistent with the Tolman length being independent on the sign of curvature. For the symmetric binary mixture the expected non-existence of the Tolman length is confirmed. In all cases {and for a range of radii} R relevant for nucleation theory, gamma(R) deviates strongly from gamma (Infinity) which can be accounted for by a term of order gamma(Infinity)/gamma(R)-1 ~ 1/R^2. Our results for the simple Lennard-Jones fluid are also compared to results from density functional theory and we find qualitative agreement in the behavior of gamma(R) as well as in the sign and magnitude of the Tolman length.
Measurements of the critical current density (Jc) by magnetization and the upper critical field (Hc2) by magnetoresistance have been performed for hafnium-doped MgB2. There has been a remarkable enhancement of Jc as compared to that by ion irradiatio
n without any appreciable decrease in Tc, which is beneficial from the point of view of applications. The irreversibility line extracted from Jc shows an upward shift. In addition, there has been an increase in the upper critical field which indicates that Hf partially substitutes for Mg. Hyperfine interaction parameters obtained from time differential perturbed angular correlation (TDPAC) measurements revealed the formation of HfB and HfB2 phases along with the substitution of Hf. A possible explanation is given for the role of these species in the enhancement of Jc in MgB2 superconductor.
