Fission Dynamics: The Quest of a Temperature Dependent Nuclear Viscosity

oai:ojs2.jnp.chitkara.edu.in:article/2This paper presents a journey within some open questions about the current use of a temperature dependent nuclear viscosity in models of nuclear fission and proposes an alternative experimental approach by using systems of intermediate fissility. This study is particularly relevant because: i) systems of intermediate fissility offer a suitable frame-work since the intervals between the compound nucleus and scission point temperatures with increasing excitation energy are much smaller than in the case of heavier systems, ii) the dependence of viscosity on the temperature may change with the fissility of the composite system; iii) the opportunity to measure also observables in the evaporation residues channel translates into a larger set of effective constraints for the models

Measuring Kinetic Performance of Monolithic and Fused-Core Columns Using Packed-Capillary Liquid-, Ultrahigh-Performance- and Supercritical Fluid Chromatography

The high temperature and pressure capabilities of the newest LC instruments and the improvements in column technology that resulted in small particle columns and new morphologies like fused-core and monolithic columns imposed the need for methods that enable the selection of chromatographic conditions and columns to achieve the best tradeoff between efficiency and analysis time. Desmet’s kinetic plot method (KPM) can be used to choose optimal column and instrument conditions. The KPM method can be used for both isocratic and gradient elution and is useful in the comparison of different types of chromatographies (HPLC, GC, CEC, SFC). The KPM was used to compare the performance of packed-capillary (0.2 and 0.3 mm) and microbore (2.0 and 2.1 mm) superficially porous and monolithic C18 columns in packed-capillary liquid (isocratic elution), ultrahigh-pressure liquid (isocratic and gradient elution) and supercritical fluid (isobaric elution) chromatography. The goal of this study is to determine which silica substrate (fused-core, monolithic) is more suitable for high efficiency and speed in packed-capillary liquid and ultrahigh-pressure liquid chromatography and to compare the performance obtained in ultrahigh-pressure chromatography using isocratic and gradient elution modes. In SFC, the goal was to determine the kinetic performance parameters that can be obtained using an open tubular capillary column and an alkylphenone as an analyte. The monolithic column was found to outperform the fused-core column for slow separations (using packed-capillary LC in 0.46-2.70 mm/s linear velocity range), but did not provide better performance than the fused-core column at high-speed separations (using UPLC in 0.67-6.76 mm/s linear velocity range). The kinetic performance parameters (minimal plate height, Hmin; maximal plate number, Nmax; optimal plate number, Nopt and optimal velocity, uopt) found for heptanophenone (C7) in packedcapillary LC were for the monolithic column: Hmin=17.58 μm, Nmax=550,000, Nopt=150,000 and uopt=0.98 mm/s and for the fused-core column Hmin=18.08 μm, Nmax=120,000, Nopt=41,000 and uopt=1.05 mm/s and in UPLC were for the monolithic column Hmin=12.17 μm, Nmax=100,000, Nopt=19,000 and uopt=2.56 mm/s and for the fused-core Hmin=5.58 μm, Nmax=120,000, Nopt=52,000 and uopt=3.23 mm/s. In UPLC with isocratic elution, the monolithic column yielded similar Nmax as the fused-core column at pressures that can be obtained using a conventional HPLC. Nevertheless shorter analysis times and higher plate numbers can be obtained with the fused-core column. The Nopt value found for the microbore monolith was significantly lower than that found for the capillary monolith. The open-tubular capillary SFC column provided similar performance to the microbore monolithic and fused-core columns. In UPLC with gradient elution, the monolithic column was found to be less powerful in the gradient mode. The fused-core column allowed maximum throughput and resolution in the gradient mode

Viscosity, Fission Time Scale and Deformation of 156Dy.

In the fusion-fission reaction 40Ar +116Cd - 156Dy* - fission, atEb=216 MeVand238 MeV.gamma rays were measured in coincidence with fission fragments.JRC.D-Institute for Reference Materials and Measurements (Geel