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At least 667 records · Page 37Linked to original sources
PubMed1970

Use of Triton X-100 scintillant in a simple method for the simultaneous assay of 55Fe and 59Fe by liquid scintillation counting.

A method is described using Triton X-100 scintillant to simplify liquid scintillation counting of (55)Fe alone or in combination with (59)Fe. The Triton acts as an efficient solubilizing agent allowing small volumes of aqueous solutions of iron compounds in hydrochloric acid to be counted. The efficiencies achieved are comparable with those of previously described methods whilst the technique is less time-consuming and the scintillant-aqueous mixture is stable at low temperatures. Reproducible quantitative recovery of radioactivity has been obtained.

Ascorbic Acid↗
PubMed2006

Can we predict uranium bioavailability based on soil parameters? Part 1: effect of soil parameters on soil solution uranium concentration.

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for (238)U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K(d), L kg(-1)) and the organic matter content (R(2)=0.70) and amorphous Fe content (R(2)=0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH=6, log(K(d)) was linearly related with pH [log(K(d))=-1.18 pH+10.8, R(2)=0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex.

Adsorption↗
PubMed2005

The use of a high-FeO olivine rock as a redox buffer in a nuclear waste repository.

Due to the higher stability of the spent nuclear fuel (mainly composed of UO2) under reducing conditions, and in order to enhance the retention/retardation of some key radionuclides, the olivine rock from the Lovasjärvi intrusion has been proposed as a potential redox-active backfill-additive in deep high-level nuclear waste (HLNW) repositories. In this work, two different approaches have been undertaken in order to establish the redox buffer capacity of olivine rock: (1) The capacity of the rock to respond to changes in pH or pe has been demonstrated and the final (pH, pe) coordinates agree with the control exerted by the system Fe(II)/Fe(III). (2) The rate of consumption of oxygen has been determined at different pH values. These rates are higher than the ones reported in the literature for other solids, what would point to the possibility of using this rock as an additive to the backfill material in a HLNW.

Buffers↗
PubMed2000

Association of 210Po(210Pb), 239+240Pu and 241Am with different mineral fractions of a beach sand at Seascale, Cumbria, UK

The degree of association of 210Po (in secular equilibrium with 210Pb), 239+240Pu and 241Am with iron oxide minerals in beach sand has been assessed using samples collected by panning and selective magnetic extraction techniques. The samples were obtained from Seascale beach (Cumbria), close to the BNF reprocessing plant at Sellafield (UK) and physically and chemically characterised in terms of their grain-size distribution, radionuclide content and magnetic properties. Low frequency (0.46 kHz) susceptibility (X(LF)) and saturation isothermal remanent magnetisation (SIRM) measurements were used to determine the magnetic properties of the bulk samples and the grain size fractions. Samples were also subjected to magnetic extraction, to concentrate the iron oxide minerals, and thence determine their degree of association with the radionuclides of interest. The efficiency of the magnetic extraction technique was estimated from rock magnetic measurements, before and after the extraction procedure. The placer deposits, enriched in iron oxide grains by environmental sorting processes, were both finer grained and more magnetic than the bulk sand. The mean particle diameter of the bulk sand was largely (approximately 75%) greater than 200 microm, whereas for the placer material, > 88% of particles have mean diameters of < 200 microm. Whilst X(LF) and SIRM values of the 100-200 microm placer material were approximately 40-50-fold higher than those of the bulk sand of equivalent grain size, the radionuclide concentrations were approximately 4-13-fold higher. In terms of mass, the percentage of magnetic material extracted from samples of bulk sand (using a powerful, approximately 0.3 T, rare earth magnet), was small (approx. 1-3%). Nevertheless, > 70% of the magnetic signal was associated with these extracts. Concentrations of all three radionuclides in the magnetic extracts were enhanced relative to the weakly magnetic residue. The proportions of 210Po(210Pb), 239+240Pu and 241Am associated with the magnetic extracts were approximately 18%, approximately 12% and approximately 11%, respectively. Therefore, although the strongly magnetic iron oxide fraction contains measurably enhanced levels of these radionuclides, the majority of the alpha-radioactivity appears to be associated with the weakly magnetic residue.

Journal Article↗
PubMed2002

Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling.

Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe3O4), calcite (CaCO3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH)2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO2, V2O3), sulfides (As2S3, ZnS), iron minerals (FeSe2, FeMoO4) and carbonate (MnCO3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell.

Arsenic↗
PubMed2006

Uranium(VI) reduction by Anaeromyxobacter dehalogenans strain 2CP-C.

Previous studies demonstrated growth of Anaeromyxobacter dehalogenans strain 2CP-C with acetate or hydrogen as the electron donor and Fe(III), nitrate, nitrite, fumarate, oxygen, or ortho-substituted halophenols as electron acceptors. In this study, we explored and characterized U(VI) reduction by strain 2CP-C. Cell suspensions of fumarate-grown 2CP-C cells reduced U(VI) to U(IV). More-detailed growth studies demonstrated that hydrogen was the required electron donor for U(VI) reduction and could not be replaced by acetate. The addition of nitrate to U(VI)-reducing cultures resulted in a transitory increase in U(VI) concentration, apparently caused by the reoxidation of reduced U(IV), but U(VI) reduction resumed following the consumption of N-oxyanions. Inhibition of U(VI) reduction occurred in cultures amended with Fe(III) citrate, or citrate. In the presence of amorphous Fe(III) oxide, U(VI) reduction proceeded to completion but the U(VI) reduction rates decreased threefold compared to control cultures. Fumarate and 2-chlorophenol had no inhibitory effects on U(VI) reduction, and both electron acceptors were consumed concomitantly with U(VI). Since cocontaminants (e.g., nitrate, halogenated compounds) and bioavailable ferric iron are often encountered at uranium-impacted sites, the metabolic versatility makes Anaeromyxobacter dehalogenans a promising model organism for studying the complex interaction of multiple electron acceptors in U(VI) reduction and immobilization.

Chlorophenols↗
PubMed1985

A simplified optical model description of heavy ion fragmentation.

The fragmentation of 213 MeV/nucleon 40Ar ions by 12C targets is described within the context of a simple abrasion-ablation fragmentation model. The abrasion part of the theory utilizes a quantum-mechanical formalism based upon an optical model potential approximation to the exact nucleus-nucleus multiple-scattering series. The ablation stage of the fragmentation is treated as a compound nucleus evaporation. The decay probabilities for the various particle emission channels are computed using the EVAP-4 Monte Carlo computer program. Predictions for production cross sections for isotopes of sulfur, phosphorus, silicon, and aluminum are made and compared with experimental data. The model is also used to compare predicted and experimental element production cross sections for 1.88 GeV/nucleon 56Fe colliding with 12C and 208Pb targets.

Argon↗
PubMed1995

Iron absorption from the whole diet. Relation to meal composition, iron requirements and iron stores.

OBJECTIVE: To validate a new method of measuring iron absorption from the whole diet over several days, to compare iron absorption from two types of diets and to relate iron absorption to iron requirements and iron stores. DESIGN: Iron absorption from two diets was studied in 21 healthy young women. All non-haem iron in all meals was labelled to the same specific activity with an extrinsic radio-labelled iron tracer. Haem iron absorption was calculated from the amount of haem iron and absorption from a reference dose of iron. RESULTS: Iron absorption was concordant with individual iron requirements measured from menstrual blood losses and body weights. Total iron absorption from one diet designed to be highly bioavailable, would cover iron requirements in about 94% of menstruating women. Iron absorption was reduced by half from a diet with less meat, more phytate and more calcium with main meals. This type of diet would cover iron requirements in only 65% of adult menstruating women. For both diets there was a marked reduction in iron absorption with increasing serum ferritin. Iron balance was not positive above a serum ferritin of about 60 micrograms/l. CONCLUSIONS: Bioavailability of dietary iron is a key factor in iron nutrition. A diet with much lean meat, ascorbic acid and a low phytate content can cover iron requirements in most non-pregnant women. The powerful control of iron absorption implies that dietary iron overload cannot develop in normal subjects, even with diets having high iron content or high bioavailability.

Adult↗
PubMedDate not supplied

[EPR-spectroscopy of human blood preparations. Remote sequelae of the Chernobyl accident].

It was shown, that as a result of Chernobyl accident the intensity of the EPR-signal of hemoproteins and ferroporphyrins of people blood increased, that most probably connected with disturbing of ferroprotein metabolism. Maximum intensity values had people, irradiated with low doses (to 2 cGy), that corroborate the theory of danger these doses for the people organism.

Electron Spin Resonance Spectroscopy↗
PubMed1991

The effect of interleukin-1 on iron metabolism in rats.

The effect of interleukin-1 on iron metabolism in rats was evaluated. Plasma iron decreased from 184 +/- 16 micrograms/dl (mean +/- SE) to 24 +/- 12 at 6 hours after interleukin-1 intramuscular administration in non-fasting rats and 109 +/- 6 micrograms/dl to 12 +/- 1 micrograms/dl in fasting rats, which was significantly lower than in control rats. Ferrokinetic studies showed a more rapid disappearance rate and lower iron turnover in interleukin-1-injected rats. The release of iron from the mononuclear phagocyte system to plasma was studied at 3 h after interleukin-1 administration. Although the percent of radioactivity in plasma of the total injected dose was 3.2 +/- 0.6% in interleukin-1, which was significantly lower than in the control rats (5.4 +/- 0.6%) at 9 h after intravenous injection of 59Fe chondroitin ferrous sulfate, there was no difference between the amount of 59Fe released from the mononuclear phagocyte system over the first 9 h in interleukin-1 and control rats. These data appear to imply that iron release is unimpaired but that, for some reason, there is an enhanced rate of clearance of the 59Fe once it has been released from the mononuclear phagocyte system into the plasma.

Animals↗
PubMed1999

Study on the distribution of radioactive trace elements in vitamin D-overloaded rats using the multitracer technique.

The uptake and distribution of radioisotopes of beryllium, calcium, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, gallium, arsenic, strontium and barium in vitamin D (VD)-overloaded rats were investigated and compared with those in control rats, using the multitracer technique. Each element revealed its characteristic distribution among various organs in control and VD-overloaded rats. For some elements, such as cobalt and chromium, the distribution patterns in them were significantly different. These results are discussed in terms of the metabolism of the elements in rats.

Acid Phosphatase↗
PubMedDate not supplied

Ferrokinetic studies with stable isotopes as tracers.

A methodology for ferrokinetic studies based on the administration of iron stable isotopes was developed. Fractional plasma clearance and intestinal iron absorption in rabbits were determined using the double tracer technique. Three rabbits were given 58Fe solution intravenously and about 40 min later 57Fe solution orally. Blood samples were drawn at different times following administration. The analysis of the single iron isotopes content in plasma samples was made by proton nuclear activation. The results were compared with those obtained from the administration, to the same rabbits, of the radioactive isotopes 55Fe and 59Fe. The agreement was found to be satisfactory.

Animals↗
PubMed1992

Changes of erythropoietic and storage iron components in certain clinical situations as evaluated by ferrokinetic investigations.

A method is described for the quantitative analysis of in vivo organ measurements of 59Fe activity in ferrokinetic investigations. The time-activity curves obtained by sequential surface monitoring over sacrum, liver and spleen can be resolved quantitatively into their different components contributing to the recorded count rate. The analysis is performed in three steps: (1) Count rate contributions from activity in other organs and from scattered radiation from regions outside the organ under investigation are corrected. (2) Distinction is made between radioactivity uptake of the tissue and radioactivity contained in the perfusing blood. (3) The resulting net organ activity is then further resolved into an erythropoietic and a storage iron component by use of a computer program (SAAM-27) and assuming a compartmental model for internal iron exchange. The method was tested in three groups of patients with different haematological disorders and in normal controls. Characteristic patterns of the parameters are found for different diseases and the results correlated well with the clinical findings. It is concluded that in vivo organ measurements of 59Fe activity, when performed and analysed with sufficient care, can provide an insight into the dynamics of the iron exchange that is taking place in an organ. This analytical approach may improve the diagnostic predictions of ferrokinetic investigations.

Erythropoietin↗