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Mössbauer measurements in a-(Fe0.765Mn0.235)78Sn2Si6B14 have been performed with57Fe and119Sn. Both hyperfine fields show a kink near 70 K, indicating a freezing of the transverse spins. The ratio of the two hyperfine fields contains information about the correlation of the transverse spins. The ratioB
hf(Sn)/B
hf(Fe) stays constant aboveT
xy
and rises belowT
xy
. This indicates an alignment of the transverse spins on a local scale, as was also found inAuFe and a-FeZr. 相似文献
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Complete double photoelectron spectra are presented for 18 small molecules where the location of charges in the cations and dications is relatively clearly defined. The data demonstrate the importance of a coulombic repulsion contribution to the double ionisation energies. Examination of data for a wide range of molecules leads to a new empirical rule to calculate double ionisation energies from the molecules’ single ionisation energies and maximum dimensions. Where single and double ionisation energies are known the rule allows the deduction of plausible intercharge distances. 相似文献
27.
The unique capabilities of a multiple wavelength spectrofluorometer based on an intensified diode array detector are used for diagnosis of matrix effects and for rapid sequential determination of two analytes. This system is used to investigate problems due to background fluorescence, blank reactions, and scattering for the determination of thiamine in cereal and urine samples by a fluorometric kinetic procedure. A novel determination of thiamine and riboflavin in vitamin pills is based on monitoring the native fluorescence of riboflavin over one wavelength region, and the rate of formation of fluorescent thiochrome from thiamine over another wavelength region, after a computer-controlled change in the pH of the reaction mixture. 相似文献
28.
The reaction scope of trifluoromethanesulfonyl azide in diazo transfer reactions was extended to include the preparation of α-cyano-α-diazo-carbonyls, phenyl sulfonyl diazoacetophenone and diethyl diazomalonate in high yields. The effect of the bases used in the diazo transfer reactions were found to have a dramatic influence on the success of the reaction with pyridine being the base of choice. 相似文献
29.
Ryan R. Burton 《Tetrahedron letters》2006,47(40):7185-7189
Ruthenium-catalyzed [2+2] cycloadditions between C1-substituted 7-oxanorbornadienes and alkynes were investigated. Most of the cycloadditions occurred smoothly at 65 °C, giving the cyclobutene cycloadducts in moderate to good yields. The C1 substituent showed strong effect on the regioselectivity (up to 110:1) of the cycloadditions. 相似文献
30.
The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal-NaF-epinephrine-, and glucagon-stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8-17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1-5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X-305. The detergent to membrane protein ratio used in these studies was 3:1. Criteria for solubilization included lack of sedimentation at 100,000 X g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cyclase activity in Sephadex G-200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X-305. The solubilized enzyme was stimulated 5-fold by NaF, 7-fold by glucagon, and 20-fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10-fold, 3.4-fold, and 4-fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at -60 degrees C. 相似文献