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[en] Volume 13a of the 'Chemical Thermodynamics' (TDB) series, is the first of two volumes describing the selection of chemical thermodynamic data for species of iron. Because of the voluminous information in the literature, it has been more efficient to prepare the review in two (unequal) parts. This larger first part contains assessments of data for the metal, simple ions, aqueous hydroxido, chlorido, sulfido, sulfato and carbonato complexes, and for solid oxides and hydroxides, halides, sulfates, carbonates and simple silicates. The second part will provide assessments of data for other aqueous halido species, sulfide solids, and solid and solution species with nitrate, phosphate and arsenate, as well as some aspects of solid solutions in iron-oxide and iron-sulfide systems. The database system developed at the OECD/NEA Data Bank ensures consistency not only within the recommended data sets of iron, but also among all the data sets published in the series. This volume will be of particular interest to scientists carrying out performance assessments of deep geological disposal sites for radioactive waste
[en] A stack of Lexan detectors from the Apollo 17 mission has been analyzed to obtain Z measurements of sufficient accuracy to resolve the iron peak into its isotopic components. Within this distribution several peaks are present. With the centrally located, most populated peak assumed to be 56Fe, our measurements imply that the abundances of 54Fe and 58Fe are appreciable fractions of the 56Fe abundance. (orig./BJ)
[de]Ein Stapel von Lexan-Detektoren der Apollo 17 Mission wurde im Hinblick auf hinreichend genaue Ladungsmessungen untersucht, die es gestatten, den Eisenpeak hinsichtlich der Isotope aufzuloesen. Im Rahmen der entsprechenden Verteilung treten mehrere peaks auf. Unter der Annahme, dass es sich bei dem am haeufigsten besetzten peak um 56Fe handelt, zeigen diese Messungen dass die 54Fe- und 58Fe-Haeufigkeit nur ungefaehr 25 bzw. 50% niedriger ist als diejenige von 56Fe. (orig./BJ)
[en] We have computed magnetic dipole strength distributions for iron isotopes within shell-model calculations based on model spaces with 40Ca and 48Ca cores, respectively. These distributions have been incorporated into statistical model calculations of neutron capture cross-sections. We find significant differences if the cross-sections are compared to those obtained with empirical parametrizations of the M1 strength distributions, the latter being commonly used in applications of the statistical model to astrophysically important capture reactions. As this is traditionally done, these studies are based on the hypothesis that the strength functions for all excited states are the same as for the ground state. Using neutron capture on 68Fe as an example we investigate the validity of this hypothesis and calculate the capture cross-section on the basis of individual strength distributions calculated within the shell model for the lowest 30 states in the compound nucleus 69Fe. Finally we explore which effect the scissors mode, a fundamental orbital M1 excitation observed in deformed nuclei at rather low excitation energies, might have on capture cross-sections for nuclei with low neutron thresholds, a situation which typically occurs for r-process nuclei. The appendix compares the spin- and parity-dependent level densities for 69Fe with those obtained with other models. (orig.)
[en] Based on the theory of relativity in superstrong magnetic fields (SMFs), we have carried out an estimation on electron capture (EC) rates of nuclides 52,53,54,55,56Fe in the SMFs in magnetars. The rates of change of electronic fraction (RCEF) in the EC process are also discussed. The results show that the EC rates increase greatly and even exceeds by 4 orders of magnitude (e.g. 54Fe, 55Fe and 56Fe) in SMF. On the contrary, the RCEF decreases largely and even exceeds by 5 orders of magnitude in the SMF. (authors)
[en] The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (α-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of α-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe2+ + α-FeOOH and the system of DIRB + α-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of α-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments. - This is the first case reporting the reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide.
[en] Variations in coordination states of extra-framework iron are studied in low iron content ferrisilicates (Si57Fe ∼ 200) during various in situ treatments. In Fe-LTA complete Fe3+ ↔ Fe2+ reversibility is observed. In Fe-MFI extra-framework iron can be stabilized in Fe2+ state in spite of ambient oxidizing conditions (N2O, 620 K). Further, in Fe-MFI simultaneous stabilization of Fe2+ and Fe3+ may take place providing centres for redox catalytic processes.
[en] The absorption from iron tablets given with 5 types of meals was studied in 153 subjects. The meals were: a hamburger meal with beans and potatoes, a simple breakfast meal, a Latin American meal composed of black beans, rice and maize and two Southeast Asian meals composed of rice, vegetables, and spices served with and without fish. The groups were directly compared by relating the absorption from the iron tablets to the absorption from a standardized reference dose of iron given on an empty stomach. The composition of meals with respect to content of meat or fish or the presence of large amounts of phytates seemed to have no influence on the absorption of iron from tablets. The absorption from iron tablets was about 40% higher when they were given with rice meals than when they were given with the other meals studied. The average decrease in absorption by meals was about 50-60% based on a comparison when tablets were given on an empty stomach. When tablets from which the iron was released more slowly were used, the absorption increased by about 30% except when they were given with rice meals, where the absorption was unchanged. The differences among the meals in their effect on the absorption of iron from tablets thus disappeared when the slow-release tablets were given. (author)
[en] Some L-chondrite meteorites found in the arid desert region of Roosevelt County in New Mexico, USA, and 14C dated to determine the terrestrial age have been examined by 57Fe Moessbauer spectroscopy. The preliminary results reported here suggest that the initial weathering processes involve oxidation of iron in the iron-nickel alloy. After prolonged exposure to terrestrial weathering for approximately 36 000 years, the iron(II)-sulphide and -silicate phases are also oxidised. The corrosion products are complex and include paramagnetic Fe3+ species and macroscopic iron(III) oxide and/or oxyhydroxide phases. A meteorite which fell approximately 16 500 years ago at the end of the last glaciation showed extensive corrosion despite its relatively short terrestrial age. The result is associated with climatic changes which occurred at that time. (orig.)