Nuclear decay studies of rare-earth fission-product nuclides using fast radiochemical separation techniques

A facility for the rapid radiochemical separation of individual rare-earth fission product nuclides from mixed fission products has been developed at the Idaho National Engineering Laboratory (INEL). This facility, called the INEL ESOL (elemental separation on-line) facility, includes an electroplated spontaneously fissioning²⁵²Cf source, a He jet transport system to deliver short half-life fission products from the²⁵²Cf hot cell to the radiochemistry laboratory, and a high pressure liquid chromatograph for the individual separation of rare-earth radioelemental fractions. The fission product collection and separation instrumentation is interfaced to a microprocessor that controls valves, motors and other devices and monitoring instrumentation. The data acquistion instrumentation can be controlled from a signal originating from the microprocessor or initiated manually. The results of some recent decay scheme studies on¹⁵³Pm and¹⁵⁴Pm are reported.     

New half-life measurement of 182Hf: improved chronometer for the early solar system

The decay of 182Hf, now extinct, into stable 182W has developed into an important chronometer for studying early solar system processes such as the accretion and differentiation of planetesimals and the formation of the Earth and the Moon. The only 182Hf half-life measurements available were performed 40 years ago and resulted in an imprecise half-life of (9+/-2)x10(6) yr. We redetermined the half-life by measuring the specific activity of 182Hf based on two independent methods, resulting in a value of t(1/2)(182Hf)=(8.90+/-0.09)x10(6) yr, in good agreement with the previous value, but with a 20 times smaller uncertainty. The greatly improved precision of this half-life now permits very precise intercalibration of the 182Hf-182W isotopic system with other chronometers.     

Order parameters from U.V. spectra with incompletely polarized absorption bands

A new method is developed for the determination of Saupe's order parameters S* and D* from I.R. or U.V. spectra and the temperature dependence of their degree of anisotropy R. This method can be applied to molecules with one uniformly polarized band and another band of mixed polarization if all bands concerned are polarized in the same plane. For that a relation D* = f(S*) between the order parameters as a function of temperature is necessary, which can be obtained from the lines of constant entropy in the order triangle. These isentropics are calculated from the orientational distribution function of the ordered system. The resulting function D* = f(S*) is equal to that of the mean field theory given by Luckhurst et al., but can be derived here in a very easy way. The method is applied to diaminoanthraquinones with a point symmetry C_2v.     

Synthesis and characterization of poly(N‐vinyl formamide) hydrogels—A potential alternative to polyacrylamide hydrogels

The synthesis and characterization of solution‐cast, molded gels of N‐vinyl formamide (NVF) has not been previously reported even though NVF is an isomer of acrylamide (AAm) and polyacrylamide (PAAm) hydrogels have many commercial applications. Aqueous NVF solutions were cross‐linked into gels using a novel cross‐linker, 2‐(N‐vinylformamido)ethylether, and the thermally‐activated initiator VA‐044. For a given formulation, PNVF gels swell up to twice that of PAAm gels cross‐linked with N,N′‐methylenebisacrylamide. From swelling and compression measurements, PNVF gels were found to be more hydrophilic than PAAm gels. Flory‐Huggins solubility parameters were χ = 0.38?₂ + 0.48 for PNVF and χ = 0.31?₂ + 0.49 for PAAm, where ?₂ is the polymer volume fraction. The shear moduli for PNVF and PAAm scale with ? and ? respectively, consistent with good solvent behavior, also suggesting PNVF is more hydrophilic than PAAm. Similarity of mechanical properties for both gels as a function of ?₂ suggests that network structures of PNVF and PAAm gels are similar. Fracture strains of both gels declined with ?₂ by the same linear function while fracture stresses were about 500 kPa regardless of formulation. Since NVF is a liquid monomer, less toxic than AAm and can be hydrolyzed to a cationic form, PNVF gels could become technologically significant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013