Teabags: Computer programs for instrumental neutron activation analysis

Described is a series of INAA data reduction programs collectively known as TEABAGS (Trace Element Analysis By Automated Gamma-ray Spectrometry). The programs are written in FORTRAN and run on a Nuclear Data ND-6620 computer system, but should be adaptable to any medium-sized minicomputer. They are designed to monitor the status of all spectra obtained from samples and comparison standards irradiated together and to do all pending calculations without operator intervention. Major emphasis is placed on finding all peaks in the spectrum, properly identifying all nuclides present and all contributors to each peak, determining accurate estimates of the background continua under peaks, and producing realistic uncertainties on peak areas and final abundances.     

The apparent molal volumes of 1:1 electrolytes in urea solution. II. Variation of apparent molal volume with salt concentration

The apparent molal volumes of NaCl, NaBr, KCl, KBr, LiCl, and CsCl were measured as a function of salt concentration in 1m and 8m aqueous urea at 25°C. It was found that equations of the form $$\phi = \phi _0 + S\prime \surd \bar C + b\prime C$$ where the limiting slopeS′ is the same for all the salts in a given concentration of urea, accurately describe the data for salt concentrations less than 1M. The values found forS′ were 1.52 in 1m urea and 1.00 in 8m urea. These are in good agreement with estimated values of the Debye-Hückel limiting slope.     

Rotation of Cellulose Ribbons During Degradation with Fungal Cellulase

Degradation of bacterial cellulose with a commercial cellulase, Celluclast 1.5L (Novo Nordisk), from the fungus Trichoderma reesei, causes a rotational movement of the cellulose microfibrils. Purified cellulases (CBH I, CBH II, and EG II) do not induce rotation of bacterial cellulose, however, ratios of CBH I and EG II do cause rotation of bacterial cellulose. Equimolar amounts of CBH I or CBH II and EG II do not result in motion during degradation. Based on these observations, we provide further evidence supporting, at least on theoretical grounds, the hypothesis that cellulose chains have intrinsic chirality. As the cellulase enzymes interact with and degrade the cellulose fibrils, the crystalline structure of the cellulose is altered, allowing the linear cellulose polymers to relax into a lower energy state, thus relieving the strain induced by crystallization of the nascent -glucan chains during the biogenesis of the microfibril. This conversion of crystalline bacterial ribbons into more relaxed conformations produces the rotation observed during the treatment of bacterial cellulose with cellulase.     

An improved radiochemical neutron activation analysis procedure for trace mercury

Summary Radiochemical neutron activation analysis has proven to be a powerful tool for measuring trace mercury in a variety of materials. In a modification of an established NIST method, selenium interfering with the ²⁰³Hg indicator is removed by precipitating mercury as periodate, and the chemical yield is measured gravimetrically. The current method is better suited to multiple samples, less subject to explosion during the combustion step, provides a measurement of the yield for each sample, and involves less radiation exposure to personnel. The procedure has been applied to the certification of mercury in SRMs 1575a Pine Needles, 1632c Bituminous Coal, and 2702 Marine Sediment.     

Instrumental neutron activation analysis: A valuable link in chemical metrology

Summary Prompt gamma activation analysis (PGAA) is a common technique for the identification of hydrogen and the measurement of hydrogen concentrations within a material. Carbon fiber reinforced epoxy matrix composites are materials that are known to absorb water. The experiments described herein demonstrate the feasibility of using PGAA to detect water absorption and desorption and show that PGAA measurements of hydrogen concentration are more sensitive to water absorption than gravimetric measurements. Hydrogen concentration measurements are made using PGAA after calibration with a boric acid solution sample. Relative changes in PGAA measurements generally agree with values expected based on gravimetric measurements.     

Grothendieck Spaces and Duals of Injective Tensor Products

Let E and F be Fréchet spaces. We prove that if E isreflexive, then the strong bidual is a topological subspace of . We also prove that if, moreover, E is Montel and F has the Grothendieckproperty, then has the Grothendieck property whenever either E or has the approximation property. A similar result is obtainedfor the property of containing no complemented copy of c₀.     

Determination of Burnup Effects in 197Au(n,γ)198Au Prior to Reactor Neutron Field Characterisation

A simple and accurate method is presented to evaluate the burnup effects involved in the neutron activation of ¹⁹⁷Au prior to any neutron flux characterisation, based on the spectrometry of the ¹⁹⁸Au and ¹⁹⁹Au decay gammas. The obtained burnup factor can be used as input for reactor neutron field characterisation techniques using ¹⁹⁷Au(n,)¹⁹⁸Au as a monitor. This way an iterative procedure is avoided.     

Neutron irradiation in activation analysis: A new rabbit for the NBSR

Two radiochemical separation methods were developed for the separation of ⁸⁸Y from a SrS target (3.2 g, pressed into a 19 mm disc) and Al (2.5 g, the capsule contained the target). The first method was based on solvent extraction technique using undiluted TBP/HNO₃ system and the second was an extraction chromatography using a column packed with TBP-impregnated Amberlite XAD-4 resin. A simple procedure was used for the impregnation of the XAD-4 resin with TBP. For both methods concentrated nitric acid was used for extraction/adsorption and 2M HCl for back extraction/elution of ⁸⁸Y. In terms of recovery of ⁸⁸Y, the solvent (TBP)-impregnated resin showed better results (average 91.2% compared to 88.9% with extraction).