[en] The structures of two manganese(II) complexes of 1,3,5-triaza-7-phosphaadamantane (PTA) reveal the first transition-metal complexes of PTA in which the metal preferentially coordinates to a nitrogen and not the phosphorus of PTA. The coordination environment about the manganese was probed using X-ray crystallography (solid state) and EXAFS spectroscopy (solution)

[en] The TMX-Upgrade experiment was described, and the manner in which various plasma parameters could be affected was discussed. The initial analysis of the MHD stability of the tandem mirror was also discussed, with emphasis on the negative tandem configuration

[en] The distal nickel site of acetyl-CoA synthase (Ni_d-ACS) and reduced nickel superoxide dismutase (Ni-SOD) display similar square-planar Ni^IIN₂S₂ coordination environments. One difference between these two sites, however, is that the nickel ion in Ni-SOD contains a mixed amine/amidate coordination motif while the Ni_d site in Ni-ACS contains a bisamidate coordination motif. To provide insight into the consequences of the different coordination environments on the properties of the Ni ions, we systematically examined two square-planar Ni^IIN₂S₂ complexes, one with bisthiolate-bisamidate ligation (Et₄N)₂(Ni(L1))·2H₂O (2) (H₄L1 = N-(2-mercaptoacetyl)-N(prime)-(2-mercaptoethyl)glycinamide) and another with bisthiolate-amine/amidate ligation K(Ni(HL2)) (3) (H₄L2 = N-(2(double_prime)-mercaptoethyl)-2- ((2(prime)-mercaptoethyl)amino)acetamide). Although these two complexes differ only by a single amine versus amidate ligand, their chemical properties are quite different. The stronger in-plane ligand field in the bisamidate complex (Ni^II(L1))^2- (2) results in an increase in the energies of the d → d transitions and a considerably more negative oxidation potential. Furthermore, while the bisamidate complex (Ni^II(L1))^2- (2) readily forms a trinuclear species (Et₄N)₂({Ni(L1)}₂Ni)·H₂O (1) and reacts rapidly with O₂, presumably via sulfoxidation, the mixed amine/amidate complex (Ni^II(HL2))^- (3) remains monomeric and is stable for days in air. Interestingly, the Ni^III species of the bisamidate complex formed by chemical oxidation with I₂ can be detected by electron paramagnetic resonance (EPR) spectroscopy while the mixed amine/amidate complex immediately decomposes upon oxidation. To explain these experimentally observed properties, we performed S K-edge X-ray absorption spectroscopy and low-temperature (77 K) electronic absorption measurements as well as both hybrid density functional theory (hybrid-DFT) and spectroscopy oriented configuration interaction (SORCI) calculations. These studies demonstrate that the highest occupied molecular orbital (HOMO) of the bisamidate complex (Ni^II(L1))^2- (2) has more Ni character and is significantly destabilized relative to the mixed amine/amidate complex (Ni^II(HL2))^- (3) by 6.2 kcal mol^-1. The consequence of this destabilization is manifested in the nucleophilic activation of the doubly filled HOMO, which makes (Ni^II(L1))^2- (2) significantly more reactive toward electrophiles such as O₂.

[en] The delta¹⁸O and delta¹⁷O values of olivine from Kenna are 7.6 and 3.0 parts per thousand respectively, relative to SMOW. These values are typical of ureilites which form a unique group on a delta¹⁷O- delta¹⁸O graph. The ureilites are related to, but not directly derived from, the anhydrous phases of C2 and C3 meteorites. The ¹⁸O/¹⁶O fractionation between pyroxene and olivine is 0.60, indicating a temperature of last equilibration of 1000 +- 100⁰C. (author)

[en] Full text: For nuclear medicine patients who are breast feeding an infant, special radiation safety precautions may need to be taken. An estimate of the potential radiation dose to the child from ingested milk must be made, and breast-feeding may need to be suspended until levels of radioactivity in the breast-milk have fallen to acceptable levels. The risk of radiation to the child must be weighed against the benefits of breast-feeding and the possible trauma to both mother and child arising from interruption or cessation of the milk supply. In the United States, the Nuclear Regulatory Commission (NRC) has already published regulations which will necessitate an estimate of the infant's dose from breast milk to be made, in principle, for every breast-feeding patient. There is obviously, therefore, a need to provide a rapid and reliable means of estimating such doses. A spreadsheet template which automatically calculates the cumulative dose to breast feeding infants based on any multi-exponential clearance of activity from the breast milk, and any pattern of feeding, has been developed by the authors. The time (post administration) for which breast-feeding should be interrupted in order to constrain the radiation dose to a selected limit is also calculated along with the concentration of activity in breast milk at which feeding can resume. The effect of changing dose limits, feeding patterns and using individually derived breast milk clearance rates may be readily modelled using this spreadsheet template. Data has been included for many of the most commonly used radiopharmaceuticals and new data can readily be incorporated as it becomes available. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc

[en] Full text: This paper describes a spreadsheet program developed at Flinders Medical Centre to facilitate the interpretation of routine bone densitometry measurements obtained from a DEXA scanner. This program (written in EXCEL for PC or Macintosh platforms) may be used with any bone densitometer, and maintains a database of patients scanned along with all results obtained for each patient. Ancillary charts for T-Score and Z-Score analysis, based on World Health Organisation recommendations, are generated from selected measurements on a given patient - these provide an extremely useful visual aid to the interpretation of the results. A complete statistical trend analysis, including the generation of graphs appropriately scaled to visually reflect rates of bone loss relative to a specified reference rate, can also be carried out. As part of this analysis, changes in bone density are calculated and classified in terms of their statistical significance, along with a recommended time interval and date for follow-up measurements. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc

[en] Short communication

[en] Spreadsheet templates have been developed by the authors to calculate radiation exposures to others from patients to whom radioactive materials have been administered (or, indeed, from any source of radiation exposure) to be readily calculated. The time during which contact should be avoided, along with the residual activity at resumption of contact is also calculated using an iterative technique. These spreadsheets allow a great deal of flexibility in the specification of clearance rates and close contact patterns for individual patients. Estimates of doses, restriction times and residual activities for ¹³¹l thyrotoxic therapy, for various contact patterns and group of patients, were calculated. The spreadsheets are implemented using Microsoft EXCEL for both PC and Macintosh computers, and are readily available from the authors

[en] Full text: Radiation exposure of other persons from patients to whom radioactive materials have been administered is often a concern in nuclear medicine. This is particularly so in cases where patients are returning to young families after administration of relatively large activities of ¹³¹l iodide for therapeutic purposes; also, on occasion, some diagnostic radiopharmaceuticals (e.g. ¹¹¹ln leucocytes in activities exceeding 30 MBq) may also result in significant external exposures. Total radiation exposure depends critically on the clearance rate of the radioactive material from the body (effective half-life), external exposure rate per unit activity, the amount of radioactive material administered and the close contact exposure pattern. In order to limit the exposure to acceptable levels, it may be necessary to alter or restrict exposure patterns and/or avoid close contact altogether for a designated time after administration of the radioactive material. Spreadsheet templates which automatically calculate cumulative exposures from patients based on any single, bi- or tri-exponential whole body clearance rate and any diurnal (or any other periodic) exposure pattern have been developed at by the authors. The method used is an adaptation of that originally described by Mountford et al. The time (post-administration) during which contact should be avoided in order to constrain the radiation exposure to a selected maximum is also calculated using an iterative technique (Newton's method). These templates find particular application in the calculation of exposures to persons who are in contact with patients who have received ¹³¹l iodide for therapeutic purposes. In thyrotoxic patients for example, using typical retention data, avoidance of close contact with very young children is indicated for 25 days post administration if radiation exposure is to be limited to 1 mGy, and 10 days if radiation exposure is to be limited to 5 mGy (assuming an administered activity of 555 MBq). The effect of changing dose limits, exposure patterns and using individually derived clearance rates may be readily modelled using the spreadsheet templates

[en] Wounding with λ-carrageenan results in a marked decrease in the intracellular-free glutamine content of rat skeletal muscle. The potential mechanisms for this finding, including alterations in glutamine release, glutamine utilization, and glutamine synthesis, were investigated in rats under pentobarbitol anesthesia. Wounding did not increase glutamine release from muscle during incubation or isolated hindlimb perfusion. Wounded muscle utilized more glutamine than nonwounded muscle, as measured both by the production of [¹⁴C]O₂ and of -glutamate from labeled glutamine. Maximal glutamine synthetase activity was increased by wounding. The increase in glutamine synthetase activity in wounded muscle was prevented by adrenalectomy and restored by replacement doses of corticosterone in wounded adrenalectomized animals. The decrease in muscle free glutamine induced by wounding is therefore not mediated by an increase in the release of this amino acid, nor by a reduction in the tissue capacity for glutamine synthesis, but by an increase in glutamine utilization at the site of injury. This difference is apparently determined by the utilization of glutamine by the cellular components of the inflammatory infiltrate, which were shown to be capable of active glutaminolysis