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31.
Determinations of the aqueous iron species Fe(II) and Fe(III) are essential for a fully-informed understanding of redox processes involving iron. Most previous methods for speciation of iron have been based on the calorimetric determination of Fe(II) followed by reduction of Fe(III) and analysis for total iron. The indirect determination of Fe(III) and the consumption of relatively large sample volumes have limited the accuracy and utility of such methods. A method based on ion-chromatography has been developed for simultaneous direct determination of Fe(II) and Fe(III). Sample pretreatment involves only conventional filtration and acidification. No interferences with the iron(II) determination were found; in determination of iron(III) the only interference observed was an artifact peak (of unknown origin) that occurred only when iron(II) was present, and had an area that was a function of the iron(II) concentration and could hence be corrected for. Solutions of iron(II) free from iron(III) can be prepared by treatment with a mixture of hydrogen and nitrogen in the presence of palladium black as catalyst, to reduce the iron(III). Photoreduction of iron(III) in acidified samples increases the Fe(II)/Fe(III) ratio; no means of circumventing this effect is known, other than storing the samples in the dark and analysing them as soon as possible. 相似文献
32.
Lynch CL Hale JJ Budhu RJ Gentry AL Finke PE Caldwell CG Mills SG MacCoss M Shen DM Chapman KT Malkowitz L Springer MS Gould SL DeMartino JA Siciliano SJ Cascieri MA Carella A Carver G Holmes K Schleif WA Danzeisen R Hazuda D Kessler J Lineberger J Miller M Emini E 《Organic letters》2003,5(14):2473-2475
[reaction: see text] A novel approach to alpha,alpha-disubstituted-beta-amino acids (beta(2,2)-amino acids) was employed in the synthesis of a series of 3-(pyrrolidin-1-yl)propionic acids possessing high affinity for the CCR5 receptor and potent anti-HIV activity. The rat pharmacokinetics for these new analogues featured higher bioavailabilities and lower rates of clearance as compared to cyclopentane 1. 相似文献
33.
G. A. Gaddy J. L. McLain E. S. Steigerwalt R. Broughton B. L. Slaten G. Mills 《Journal of Cluster Science》2001,12(3):457-471
Fibers and films prepared from blends of poly(vinyl alcohol) and poly(acrylic acid) were found to be suitable matrices for the solid-state photoreduction of silver ions in the presence of air. Fast generation of nanometer-sized silver crystallites was observed when fibers of polymer blends crosslinked with dimethyl sulfoxide were irradiated with 350nm light. Optical determinations of the formation kinetics were carried out using thin films of noncrosslinked as well as lightly and heavily crosslinked polymer blends. Small Ag clusters were detected initially, which were stable in the dark but transformed into larger metal particles upon further illumination. Both formation processes occurred only under high light intensity illumination and the kinetic data were inconsistent with monophotonic mechanisms. 相似文献
34.
Basil I. Swanson Lucia M. Babcock David Schiferl David C. Moody Robert L. Mills Robert R. Ryan 《Chemical physics letters》1982,91(5):393-395
We report Raman measurements made on SO2 in a diamond cell up to 75 kbar showing two new phases, solid II and solid III, which differ from known, zero-pressure solid I. Spectra indicate that SO2 molecules aggregate in solid III to possibly form a cyclical trimer; solid III is shown to be photochemically active to blue radiation. 相似文献
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Allison M. Mills Daniel Brunling Michael Ruck 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):i70-i72
A redetermination of the structure of `La32.66Fe11S60' in the trigonal space group Rm led to the new formula La52Fe12S90 and to a redefinition of the structure type. In the structure, the Fe2+ cations occur in Fe2S9 dimers of face‐sharing octahedra (with 3m symmetry). The dimers are linked by face‐ and vertex‐sharing bi‐ and tricapped LaS6 trigonal prisms (with m symmetry) to form a three‐dimensional network containing two types of cuboctahedral cavities. The larger cavities remain empty, while the smaller ones accommodate alternative sites for disordered La3+ cations. 相似文献