Fission-fragment energy correlation measurements for (nth, f) of 232U and 233U

Fission-fragment mass and kinetic energy distributions and their correlations have been measured for ²³²U and ²³³U. The results on these uranium isotopes and ²³⁵U are compared. The mass peak/valley ratio of 785 ± 68 for ²³²U is the highest of the three isotopes. The 〈E_K〉(μ_H) distributions show significant differences. The dip ΔE_K at symmetry is $\text{16.2 ± 1.0}\text{MeV}\text{(}{}^{232}\text{U}\text{)}$, $\text{17.0 ± 1.0}\text{MeV}\text{(}{}^{233}\text{U}\text{)}\text{and}\text{20.6 ± 1.1}\text{MeV}\text{(}{}^{235}\text{U}\text{)}$. In the yields for high-kinetic-energy-selected events, the mass 134 dominates for ²³³U and ²³⁵U, but for ²³²U it is μ_H≈144, which dominates. This complete reversal of profiles can be understood in terms of fragment shells.     

Percolation in short fibres epoxy resin composites: Conductivity behavior and finite size effects near threshold

The conductivity behavior near threshold in randomly oriented carbon fibers-polymer composites is analysed. A fit to a power law dependence gives the exponent t = 3.0 ± 0.6.The conductivity fluctuations exhibited by small size samples are evidenced and analysed for the first time in real materials. Their variations with sample size and fibers concentration are consistent with the universal correlation length exponent v = 0.88 for three dimensional percolating systems.     

Studies of the reaction of 1,2-dithiole-3-thiones with nucleophiles

Substituted 1,2-dithiole-3-thiones react with nucleophiles (alkoxides, thiolates) to give various reaction products depending on the nucleophiles and on the substituents on the 1,2-dithiole-3-thione ring. The mechanistic aspects of these reactions are discussed.     

Fission-fragment energy correlation measurements for 252Cf(sf) and structures in far-out asymmetric fission

Fragment-mass and kinetic-energy distribution measurements for ²⁵²Cf(sf) have been extended to the far-out asymmetric low-yield fission region of M_H = 190 compared with the existing data that go up to M_H ≈ 168. The mass yield Y(m) shows a shoulder for M_H ≈ 163 and an important enhancement for M_H ? 176. The 〈E_K〉(m), σ_EK(m) and, to a lesser extent, Y(m) distributions show strong and correlated amplitude fluctuations for M_H ? 170. These data indicate strong and rapid changes in deformation of the nascent fragments and the coexistence of more than one deformed-shell stabilized scission configuration for the same mass splits. These structures and those present in the relatively high-yield regions are discussed in terms of the static macro-microscopic potential-energy calculations.     

The level structure of 114Cd from (n, γ) and (d,p) studies

Gamma rays and conversion electrons have been measured following thermal neutron capture in ¹¹³Cd using the crystal spectrometers GAMS and the β-spectrometer BILL at the High Flux Reactor of the ILL at Grenoble. Primary γ-rays following thermal and average resonance neutron capture at E_n = 2 keV and 24 keV were recorded at the High Flux Beam Reactor at the Brookhaven National Laboratory. The ¹¹³Cd(d, p)¹¹⁴Cd reaction was studied with the Q3D spectrograph at the Munich tandem accelerator. Combining all these experimental results an almost complete level scheme of ¹¹⁴Cd was constructed up to 3.3 MeV including 48 excited levels with spin and parity information. The level scheme is discussed in terms of particle-hole excitations across the Z = 50 closed shell coupled to collective states, as well as in an interacting boson configuration mixing scheme.     

Direct and automatic capillary GC analysis for molecular weight determination and distribution in crude oils and condensates up to C20

A direct and automatic method has been developed for molecular weight (MW) determination and distribution in crude oils and condensates up to C₂₀ (340°C) by gas chromatography. Chromatographic separation has been achieved with a 50 m OV-1 fused silica capillary column, fitted with a pre-column to eliminate the fraction boiling above 340°C. The internal standard is added for quantification. Approximately 550 peaks have been identified by the use of GC/MS on different paraffinic, naphthenic, and aromatic crude oils or condensate samples. From identification and by correlation with MS group-type analysis, a carbon number and a hydrocarbon group are attributed to each peak or group of peaks. Further molecular weights have been calculated from these groups. A comparison between results from this GC method and cryometry of narrow and wide fractions shows good agreement, within the precision of cryometry. An automatic identification by computer using programmed temperature indices was used for the direct determination of molecular weight. The final report gives weight percentage, molar percentage, and molecular weight for every boiling range group and hydrocarbon group.