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  • 1
    Digitale Medien
    Digitale Medien
    Aluminum oxide adherence on Fe-Cr-Al alloys modified with group IIIB, IVB, VB, and VIB elements (1989)
    Springer
    Oxidation of metals 32 (1989), S. 337-355 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe-Cr-Al ; aluminum oxide ; adherence ; sulfur ; reactive elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A recent theory, explaining the effect of reactive elements on oxide adherence, states that sulfur adversely affects adherence and that reactive elements improve adherence by tying up sulfur as refractory sulfides. This theory is supported by work presented here, which correlates adherence behavior of Fe-Cr-Al alloys containing group IIIB through VIB elements with the stability of the sulfides that these elements form. Results show that poor adherence is produced by elements that form sulfides less stable than Al2S3 (VB and VIB elements), while good adherence is produced by elements which form sulfides more stable than Al2S3 (IIIB and IVB elements). In addition, the relative stability of sulfides, oxides, nitrides, and carbides must be considered. For example, group-IIIB elements are effective at much lower concentrations than group-IVB elements, because they react preferentially with S while group IVB elements react with C, N, and O before S.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00665442
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  • 2
    Digitale Medien
    Digitale Medien
    The influence of sulfur on adherence of Al2O3 grown on Fe-Cr-Al alloys (1988)
    Springer
    Oxidation of metals 29 (1988), S. 23-43 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe-Cr-Al ; aluminum oxide ; adherence ; sulfur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Recently a new theory was proposed to explain the effect that reactive elements have on oxide adherence. Based on data obtained on Ni-Cr-Al-Y material, this theory stated that trace quantities of sulfur in the alloy degrade adherence by weakening the metal-Al2O3 bond. The work presented here extends this concept to Fe-Cr-Al alloys by examining Al2O3 adherence on foil samples with various bulk sulfur levels obtained using high-temperature vacuum anneals. Results show that long-time vacuum anneals dramatically increase the adherence of the subsequently grown aluminum oxide, concurrent with removal of sulfur from the matrix. This evidence shows that the Al2O3-metal bond is intrinsically strong without the presence of reactive elements such as Y or rare earths in the alloy. Sulfur in the alloy, and not void formation, was found responsible for oxide spalling. In addition, voids were eliminated by reducing the sulfur concentration near the oxide-metal interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00656348
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  • 3
    Digitale Medien
    Digitale Medien
    Oxidation behavior of Fe-20Cr-5Al rare earth alloys in air and synthetic exhaust gas (1991)
    Springer
    Oxidation of metals 36 (1991), S. 57-80 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe-Cr-Al ; oxidation ; aluminum oxide ; air ; exhaust gas
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Fe-20Cr-5Al alloy foils are used in automotive catalytic converters. This work examines oxidation behavior of four production-processed alloy foils in both air and synthetic exhaust gas environments. Oxidation tests were performed between 750° C and 1150° C for times to 96 hrs. Weight gain results in both atmospheres were similar, an indication that the same mechanism controls oxidation in both environments. At high temperatures (〉-950° C) both atmospheres produce weight gains consistent with α-alumina growth. Activation energies of 323 kJ/gmole and 271 kJ/gmole were calculated for oxidation in air and synthetic exhaust gas, respectively. At lower temperatures (〈-850° C), accelerated weight gains can occur from growth of transition alumina. Despite similar weight gain results, the two atmospheres produce different oxide morphologies: at 950° C and above, air produces a rounded, porous oxide while synthetic exhaust produces a more compact, angular oxide. Unexpectedly, oxide spalling occurred on foils oxidized in synthetic exhaust at 1050° C and above.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00938456
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  • 4
    Digitale Medien
    Digitale Medien
    Adherence behavior of oxide grown in air and synthetic exhaust gas on Fe-Cr-Al alloys containing strong sulfide-forming elements: Ca, Mg, Y, Ce, La, Ti, and Zr (1993)
    Springer
    Oxidation of metals 40 (1993), S. 555-583 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Fe-Cr-Al ; oxidation ; air ; exhaust gas ; aluminum oxide ; oxide adherence ; reactive elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This work evaluated the adherence of oxide grown in air and synthetic exhaust gas on Fe-20Cr-5Al alloys containing strong sulfide-forming elements: Ca, Mg, Y, Ce, La, Ti, and Zr. Results support the theory that reactive elements provide good oxide adherence on alumina-forming materials primarily by tying up sulfur as stable Sulfides; however, other influences on adherence were found. Highly volatile elements, such as Ca and Mg, lose their sulfur-controlling ability by diffusing out of the matrix and into the growing oxide scale. Zirconium results in the growth of an extensive network of oxide pegs into the substrate which improves adherence. Titanium segregates to the alumina scale and acts as a sink for S in the matrix. In synthetic exhaust gas (N2+CO2+H2O), local oxide spalling was observed and was shown to be caused by H2O in the atmosphere. The added benefits of Ti and Zr, i.e., forming oxide pegs and sinks for S, improve adherence in this environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00666391
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  • 5
    Digitale Medien
    Digitale Medien
    Oxidation resistance of aluminum-coated Fe-20Cr alloys containing rare earths or yttrium (1993)
    Springer
    Oxidation of metals 40 (1993), S. 295-320 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Al-coating ; aluminum oxide ; Fe-Cr alloy ; oxidation resistance ; rare earths ; yttrium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Aluminum-coated Fe-20Cr-(rare earth or yttrium) alloy foils were developed with oxidation resistance equivalent or superior to Fe-20Cr-5Al-(rare earth or yttrium) alloy foils. The coated foils were made by dipping Fe-20Cr sheet into a salt-covered aluminum bath and then rolling the sheet to foil. Oxidation resistance of the coated foil was enhanced by adding rare earths or yttrium to the Fe-20Cr substrate alloys to insure oxide adherence. Test results indicate that only sufficient addition to tie up sulfur as a stable sulfide is needed in the Fe-20Cr alloy. Aluminum-coated foils show lower oxide growth rates than similar Fe-Cr-Al alloys, most likely the result of fewer impurities (particularly Fe) is the coated foils' growing oxide scale.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00664495
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  • 6
    Digitale Medien
    Digitale Medien
    Proton and phosphorus nmr investigation of the conformational states of acid polyadenylic double helix (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 803-816 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proton and phosphorus nmr have been used to investigate the double-helical structures of polyriboadenylic acid [poly(A)] formed in acidic solutions (pH 〈 6). The results obtained at low pH (∼4.5) are consistent with the model for the acid poly(A) double helix proposed by Rich [Rich, A., Davies, D. R., Crick, F. H. C. & Watson, J. D. (1961) J. Mol. Biol. 3, 71-86]. Other models that have been proposed are inconsistent with the nmr data. The nmr measurements have also been used to examine the conformation of poly(A) helix in the half-protonated state. Although the base-stacking arrangement of this state is similar to that observed in the more extensively protonated low-pH state, the phosphate backbone conformation is different from that found in either the neutral or low-pH structures.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1981.360200412
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  • 7
    Digitale Medien
    Digitale Medien
    Interactions of DNA with divalent metal ions. II. Proton relaxation enhancement studies (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 203-218 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The extent and modes of binding of the divalent metal ions Mn2+ and Co2+ to DNA and the effects of salt on the binding have been studied by measurements of the effects of these paramagnetic metal ions on the longitudinal and transverse relaxation rates of the protons of the solvent water molecules, a technique that is sensitive to overall binding. The number of water molecules coordinated to the DNA-bound Mn2+ and Co2+ is found to be between five and six, and the electron spin relaxation times and the electron-nuclear hyperfine constants associated with Mn2+ and Co2+ are little or not affected by the binding. These observations indicate little disturbance of the hydration sphere of Mn2+ and Co2+ upon binding to DNA. An average 2-3-fold reduction in the exchange rate of the water of hydration of the bound metal ions and an order-of-magnitude increase in their rotational correlation time are attributed to hydrogen-bond formation with the DNA. The binding constants of Mn2+ to DNA, at metal concentrations approaching zero, are found to be inversely proportional to the second power of the salt concentration, in agreement with the predictions of Manning's polyelectrolyte theory. A remarkable quantitative agreement with the polyelectrolyte theory is also obtained for the anticooperativity in the binding of Mn2+ to DNA, although the experimental results can be well accounted for by another simple electrostatic model. The various modes of binding of divalent metal ions to DNA are discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210116
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  • 8
    Digitale Medien
    Digitale Medien
    Distribution of Mn2+ ions around poly(rI)·poly(rC) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1283-1297 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The distribution of bound Mn2+ ions about poly(rI)·poly(rC) has been studied by measuring the effect of this paramagnetic metal ion on the relaxation behavior of poly(rI)·poly(rC) protons. By combining selective spin - lattice and spin - spin relaxation rates for various protons, some of the principle regions of ion association can be identified. The relaxation data on the CH6 proton are consistent with a 〈 10% occupancy of phosphate inner-sphere binding sites. The broadening of the imino proton resonance requires a substantial occupancy of sites located in the major groove, possibly near IN7. This would also be consistent with the observation that IH8 resonance is the proton most susceptible to relaxation by Mn2+. The relaxation data for the IH2 proton indicate a relatively low occupancy of minor-groove binding sites (e.g., IN3).
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360250709
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  • 9
    Digitale Medien
    Digitale Medien
    A 2H-nmr study of the DNA hydration water in solid li-DNA assemblies (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 717-732 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High-resolution 2H-nmr is employed to monitor the D2O in hydrated solids of Li-DNA prepared from solution by three different methods: lyophilization, slow evaporation of the water, and wet spinning in alcohol. From the spectral shapes and spin-spin relaxation measurements, the DNA in the lyophilized samples is found to be locally ordered with a domain size of ∼ 0.4 μm. Much longer range macrosopic ordering is found in samples prepared by slow evaporation of the water. Here the DNA spontaneously assembles into a structure that is probably cholesteric, in which the pitch axis is perpendicular to the plane on which the DNA dried. The wet-spinning method produces macroscopically, uniaxially oriented DNA molecules with a maximum helix axis disorder of 12°. To aid in the comparison between calculated and experimental line shapes, a two-dimensional technique is employed to separate the contributions to the line width arising from DNA static disorder, magnetic inhomogeneities, and spin-spin relaxation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270502
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  • 10
    Digitale Medien
    Digitale Medien
    Investigation of the thermal unfolding of secondary and tertiary structure in E. coli tRNAfMet by high-resolution nmrThe results presented here were taken from the Ph.D. Thesis of K.L.W., submitted December, 1973. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 749-762 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The high-resolution (300 MHz) proton nmr spectrum of E. coli tRNAfMet has been examined in 0.17M NaCl, with and without Mg2+, and at various temperatures. In light of recent studies of other E. coli tRNA and fragments of tRNAfMet, some low field (11-15 ppm) resonances previously assigned to secondary structure base pairs are reassigned to a tertiary structure A14-S4U8 base pair and a protected uridine residue in the anticodon loop. These two resonances and other low field resonances which are assigned to secondary structure base pairs are used to monitor the thermal unfolding of the molecule. In the absence of Mg2+ the tertiary structure base pair is present only to ∼45°C, but in the presence of Mg2+ it remains until at least 70°C. Analysis of the temperature dependence of other low field resonances indicates that the melting of the dihydrouridine stem occurs more or less simultaneously with the loss of tertiary structure. The observation of the resonance from the A14-S4U8 base pair proves that tertiary structure is present in this molecule below 40°C, even in the absence of Mg2+.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1975.360140407
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