The determination of fluorine in bones by non-destructive neutron activation analysis using 11.2 sec20F

A fast non-destructive determination of fluorine in bone samples by thermal neutron activation analysis using¹⁹F(n, γ)²⁰F reaction was developed. About 0.1–1 g samples is irradiated for 15 sec in TRIGA MARK II reactor at a thermal neutron flux of 5·10¹¹ n·cm⁻²·sec⁻¹. After 15–25 sec cooling, the 1633 KeV²⁰F activity (T=11.2 sec) is counted for 15 sec with a Ge(Li) spectrometer. A standard sample is prepared by mixing CaF₂ and CaCO₃ powders. The interference from²³Na(n, α)²⁰F is corrected by employing²⁴Na 2754 KeV double escape peak activities in samples and the²⁰F/²⁴Na peak area ratio observed previously for pure Na₂CO₃ powder. The precision is 7% for a bone sample containing 1020 ppm F and the sensitivity is about 10 ppm F.     

Effect of a tridentate ligand on the structure, electronic structure, and reactivity of the copper(I) nitrite complex: role of the conserved three-histidine ligand environment of the type-2 copper site in copper-containing nitrite reductases

It is postulated that the copper(I) nitrite complex is a key reaction intermediate of copper containing nitrite reductases (Cu-NiRs), which catalyze the reduction of nitrite to nitric oxide (NO) gas in bacterial denitrification. To investigate the structure-function relationship of Cu-NiR, we prepared five new copper(I) nitrite complexes with sterically hindered tris(4-imidazolyl)carbinols [Et-TIC = tris(1-methyl-2-ethyl-4-imidazolyl)carbinol and iPr-TIC = tris(1-methyl-2-isopropyl-4-imidazolyl)carbinol] or tris(1-pyrazolyl)methanes [Me-TPM = tris(3,5-dimethyl-1-pyrazolyl)methane; Et-TPM = tris(3,5-diethyl-1-pyrazolyl)methane; and iPr-TPM = tris(3,5-diisopropyl-1-pyrazolyl)methane]. The X-ray crystal structures of all of these copper(I) nitrite complexes were mononuclear eta(1)-N-bound nitrite complexes with a distorted tetrahedral geometry. The electronic structures of the complexes were investigated by absorption, magnetic circular dichroism (MCD), NMR, and vibrational spectroscopy. All of these complexes are good functional models of Cu-NiR that form NO and copper(II) acetate complexes well from reactions with acetic acid under anaerobic conditions. A comparison of the reactivity of these complexes, including previously reported (iPr-TACN)Cu(NO2) [iPr-TACN = 1,4,7-triisopropyl-1,4,7-triazacyclononane], clearly shows the drastic effects of the tridentate ligand on Cu-NiR activity. The copper(I) nitrite complex with the Et-TIC ligand, which is similar to the highly conserved three-histidine ((His)3) ligand environment in the catalytic site of Cu-NiR, had the highest Cu-NiR activity. This result suggests that the (His)3 ligand environment is essential for acceleration of the Cu-NiR reaction. The highest Cu-NiR activity for the Et-TIC complex can be explained by the structural and spectroscopic characterizations and the molecular orbital calculations presented in this paper. Based on these results, the functional role of the (His)3 ligand environment in Cu-NiR is discussed.     

Sorption behavior of selenide on montmorillonite

Batch sorption experiments were performed to investigate the sorption mechanism of Se on montmorillonite under reducing conditions in deep geological environments. Based on E_h–pH diagrams and ultraviolet–visible spectra, Se was dissolved as selenide (Se(–II)) anions under the experimental conditions. The distribution coefficients (K_d; m³ kg^?1) of Se(–II) indicated ionic strength independence and slight pH dependence. The K_d values of Se(–II) were higher than those of Se(IV), which also exists as an anionic species. X-ray absorption near edge spectroscopy showed that the oxidation state of Se-sorbed on montmorillonite was zero even though selenide remained in the solution. These results suggest that Se(–II) was oxidized and precipitated on the montmorillonite surface. Therefore, it is implied that a redox reaction on the montmorillonite surface contributed to high K_d values for Se(–II).

     

A rotational band in82Zr

The neutron deficient nucleus⁸²Zr has been studied through the reaction⁵⁸Ni(²⁸Si, 2p 2n)⁸²Zr with a calculated cross section of 0.3% of the total fusion cross section atE(²⁸Si)=128 MeV. Gamma rays from excited states of⁸²Zr were measured and identified using the NORDBALL escape-suppression array at the Niels Bohr Institute. Reaction channel selection was performed by use of neutron and charged particle detector arrays in conjunction with the germanium detectors. A rotational band in⁸²Zr has been identified with spins up to 20 ? by analysis of reaction channel selectedγ-γ coincidence matrices. Band crossings were identified at frequencies 0.57 and 0.69 MeV.     

Preparation and Structures of Dication Salts of Phenyl-Substituted TTF Vinylogues

Some TTF vinylogues 1 containing phenyl groups at the vinyl positions were synthesized. The redox properties were investigated by cyclic voltammograms, showing that they are strong electron donors and the Coulomb repulsion is decreased in the dication states. Some of the donors afforded their dication salts as single crystals by electrochemical oxidation or the reaction with CuCl₂. X-ray structure analysis has revealed that the dication molecules have structures with planar TTF vinylogue units and twisted phenyl groups. The crystal structures are unusual to avoid the steric interactions of the phenyl groups.     

Reaction of13N produced by recoil deuterons in pile-irradiated acetic acid-d4 and malonic acid-d4

The reaction of¹³N to form¹³N-labelled compounds was studied in acetic acid-d₄ as a function of the halogenoacetic acid concentration and in malonic acid-d₄ as a function of the intermolecular distance of target malonic acid-d₄ at 195 and 295±6 K. In both deuterated carboxylic acids,¹³N atoms were found in several forms in the order of radiochemical yields,¹³NH₃>H¹³NO₃>[¹³N]aminoacid>HC¹³N. The yield of [¹³N]glycine formed in acetic acid-d₄ were markedly enhanced by iodoacetic acid and slightly by chloroacetic acid. In malonic acid-d₄, the yield of¹³NH₃ was directly proportional to the cubic root of the molar ratio, {D₂O/CD₂ (COOD)₂}, while the yields of H¹³N₃, [¹³N]aminomalonic acid and HC¹³N were inversely proportional to the cubic root of the molar ratio. The mechanism of the formation of the¹³N-compounds are discussed.     

Rapid determination of dysprosium in rock samples by neutron activation analysis with a ge(li) detector after chemical separation

A neutron activation method for the rapid determination of dysprosium in rocks, based on simple chemical separation and γ-spectrometry with a lithiumdrifted germanium detector, is described. The 94.7-keV photopeak of dysprosium-165 (2.3 h half-life) was measured. Several geochemical standard rocks covering a variety of rock types were analyzed. The detection limit was 0.005 μg of dysprosium. A precision of ±4.7% was obtained on 7 separate analyses of a basalt standard rock. The accuracy of the method is discussed.     

The determination of copper in zinc materials by neutron activation analysis using the 65Cu(n,γ)66Cu reaction

The nondestructive and destructive determinations of copper in zinc materials by neutron activation using ⁶⁵Cu(n,γ)⁶⁶Cu reaction are described. Observed cross-sections of ⁶⁴Zn(n,p)⁶⁴Cu and ⁶⁶Zn(n,p)⁶⁶Cu reactions for fission spectrum neutrons were 28 and 0.51 mb respectively. A double irradiation technique with one sample wrapped in cadmium foil and another bare, was employed for the correction of the concurrent formation of ⁶⁶Cu by (n,p) reaction. 100 p.p.m. of copper in zinc sulfide was determined nondestructively by γ-ray spectrometry using a thermal flux of 5 · 10¹¹ n/cm²/sec, while 0.5 p.p.m. of copper in zinc was determined by a thermal flux of 2.5 · 10¹⁰ n/cm²/sec, and by a rapid chemical separation involving copper(I) thiocyanate precipitation. The proposed activation procedures were compared with the spectrophotometric dibenzyldithiocarbamate procedure.     

Multielement analysis of the hair of mining industry workers

Scalp hair samples were collected from 75 zinc mine workers at the Nakadatsu Mine in Fukui Prefecture and were subjected to instrumental neutron activation analysis for determination of Cu, Cl, Mn, Ca, Au, Br, As, Na, K, Hg, Zn and Co concentrations. For determination of Cd, atomic absorption spectrophotometry was applied to approximately a half of the samples. The results were compared with the data of inhabitants of Suginami Ward in the Tokyo Metropolitan Area. Excessive concentration in the mean values of Zn, Cu, Mn and Hg was observed in the hair of the miners as compared with the Suginami residents. On the other hand, the mean concentrations of K and Cl in the hair of the miners were lower than those of the Suginami inhabitants.