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Trond E. Jentoftsen Odd-Arne Lorentsen Ernest W. Dewing Geir M. Haarberg Jomar Thonstad 《Metallurgical and Materials Transactions B》2002,33(6):909-913
The solubility of TiO2 in cryolite-alumina melts at 1020 °C was measured; it decreased with increasing alumina concentration up to ∼3.5 wt pct total
oxide and then increased at higher alumina concentrations. The solubility was found to be 3.1 wt pct Ti in cryolite, and 2.7
wt pct Ti in an alumina-saturated melt. Modeling indicated that the most probable titanium species are TiOF2 and Na2TiO3, which coexist in the solution; the former dominates at low alumina concentrations and the latter at high alumina concentrations.
Additional unknown amounts of fluoride may also be associated with these species. Determination of the solubility of TiO2 in alumina-saturated melts as a function of temperature showed that the solubility increased from 1.9 wt pct Ti at 975 °C
to 2.8 wt pct Ti at 1035 °C, the apparent partial molar enthalpy of dissolution of TiO2 being 88±4 kJ mol−1. 相似文献
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BM Jenssen JU Skaare M Ekker D Vongraven SH Lorentsen 《Canadian Metallurgical Quarterly》1996,32(11):2115-2125
The present study focuses on the distribution and accumulation of persistent organochlorine compounds in different tissues and organs of grey seal (Halichoerus grypus) pups. Thus, levels of drins (aldrin, dieldrin, endrin), chlordanes (heptachlor, heptachlorepoxide, oxychlordane, transnonachlor), DDTs (p,p'-DDE, o,p'-DDD, p,p'-DDD, o,p'-DDT, p,p'-DDT) and 22 PCB congeners were determined in samples of brain, fat, and liver of 0-10 days old grey seal pups from the species' main breeding site in Norway. Whereas 10 different compounds were detected in the blubber, 8 compounds were detected in the liver. The concentrations of the two major classes of OCs (PCBs and DDTs) in liver were both about 75% of that in blubber. In cerebral tissue, only two PCB congeners were detected, and sigma PCB was only about 1% of that measured in the blubber. The distribution pattern of PCB-congeners in liver and brain differed significantly from that in blood and blubber tissue, indicating that the physico-chemical properties of the individual congeners and the lipid composition of the tissue are decisive for the tissue-specific pattern of congener distribution. A significant increase of the sigma DDT/sigma PCB-ratio as a function of blubber thickness indicates that DDT compounds are more readily accumulated in older pups. 相似文献
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Trond E. Jentoftsen Ernest W. Dewing Odd-Arne Lorentsen Geir M. Haarberg Jomar Thonstad 《Metallurgical and Materials Transactions B》2012,43(4):869-874
Chronopotentiometric studies were made on a cryolite melt containing 3.0 wt pct Al2O3 and 0.466 wt pct Fe(II) at 1293 K (1020 °C). The diffusion coefficient calculated from the time of the principal chronopotentiometric transition decreased as the current density was increased, and at the same time, a second subsequent transition appeared. The diffusion coefficient calculated from this second transition was constant at 5.44 × 10?5 cm2 s?1. The results were interpreted to show that Fe(II) in the solution exists in two forms. Fe is deposited reversibly from an active form; its exchange current density must be >1 A cm?2. Deposition from the other form is irreversible, and it occurs directly only at high overpotentials, leading to the second transition. The equilibrium constant [active]/[inactive] = 5.4. When the equilibrium is displaced by electrolysis of the active form, the inactive form decomposes to replenish it with a rate constant of 0.9 s?1. The Tafel curve for the direct deposition of the inactive form shows a slope of 113 mV/decade, which is interpreted as n = 2 and a symmetry factor ≈1. The exchange current density is approximately 0.3 μA cm?2. The active and inactive forms are identified tentatively as FeF 3 ? and FeF 5 3? , respectively. 相似文献
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JH Graversen RH Lorentsen C Jacobsen SK Moestrup BW Sigurskjold HC Thogersen M Etzerodt 《Canadian Metallurgical Quarterly》1998,273(44):29241-29246
Tetranectin, a homotrimeric protein belonging to the family of C-type lectins and structurally highly related to corresponding regions of the mannose-binding proteins, is known specifically to bind the plasminogen kringle 4 protein domain, an interaction sensitive to lysine. Surface plasmon resonance and isothermal calorimetry binding analyses using single-residue and deletion mutant tetranectin derivatives produced in Escherichia coli showed that the kringle 4 binding site resides in the carbohydrate recognition domain and includes residues of the putative carbohydrate binding site. Furthermore, the binding analysis revealed that the interaction is sensitive to calcium in addition to lysine. 相似文献
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Trond E. Jentoftsen Odd-Arne Lorentsen Ernest W. Dewing Geir M. Haarberg Jomar Thonstad 《Metallurgical and Materials Transactions B》2002,33(6):901-908
The solubilities of FeO, FeAl2O4, NiO, and NiAl2O4 were measured in cryolite-alumina melts at 1020 °C. FeO was found to be the stable solid phase at alumina concentrations
below 5.0 wt pct, while FeAl2O4 was stable above that. The corresponding figure for the nickel system was 3.0 wt pct Al2O3. These values correspond to Gibbs energies of formation of the aluminates (from the constituent oxides) of −17.6 and −29
kJ/mol, respectively. In alumina-saturated melts in the range 980 to 1050 °C, the solubilities of both aluminates increased
with increasing temperature, the apparent enthalpies of solution being 65 kJ/mol for FeAl2O4, and 249 kJ/mol for NiAl2O4. Investigation of the solubilities of the aluminates as a function of the NaF/AlF3 ratio in alumina-saturated melts at 1020 °C showed maxima at a molar ratio of around 5. The results are discussed in terms
of the species apparently existing in the solution, and are consistent with the solute species being fluorides, not oxyfluorides.
The activity coefficients of FeF2 (liquid) and NiF2 (solid) in dilute solution in cryolite are found to be 0.22 and 1.2, respectively. 相似文献
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Ernest W. Dewing Trond E. Jentoftsen Odd-Arne Lorentsen Geir M. Haarberg Jomar Thonstad 《Metallurgical and Materials Transactions B》2012,43(6):1241-1242
In chronopotentiometric work on Fe2+ in a cryolite melt (Jentoftsen et al. in Metall. Mater. Trans. B, 2012, vol. 43B, pp. 869?C74), after depletion of Fe2+ at the surface of the iron cathode was complete, continuing electrolysis produced a solution of Al in cryolite, provided that the time was less than a few hundred milliseconds. Potential?Ctime curves indicate a diffusion-controlled, 2-electron reduction to form monovalent aluminum. 相似文献
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