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81.
82.
In a systematic study of the transfer process to sulphur dioxide, in seven different H2 + SO2 gas mixtures, the time spectra of the muonic sulphur X-rays yield muon transfer rates to the SO2 molecule, deduced from the lifetimes of the p atoms, which agree all well with each other. The muonic oxygen time spectra show an additional structure as if p atoms of another kind were present. Reduced transfer ratesO are reproducible if one uses the model of ephemeral p atoms. The intensity ratios between the different kinds of p atoms are also discussed in the framework of this model and the one of black and white p atoms. 相似文献
83.
Summary A high-performance liquid chromatographic method for the simultaneous determination of urinary organic acids and creatinine for following the metabolism of aromatic solvents is reported. After extraction of acidified, filtered urine with diethylether followed by evaporation, the dried residue is dissolved in mobile phase. Hydroxybenzoic acid is used as internal standard. A column of Nucleosil C18 is used with a precolumn of the same material. The mobile phase is acetonitrilephosphate buffer, pH 3.3 (1783). For determination of creatinine the sample is simply diluted 10-fold and the eluate monitored at 215 nm (UV). This technique gives highly reproducible results and is simple, reliable and useful for biological monitoring. 相似文献
84.
B. Vezin Ph. Dugourd D. Rayane P. Labastie J. Chevaleyre M. Broyer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(Z1):128-130
Ionization Potentials of LinHm clusters have been measured by photoionization. As in Lin, odd-even alternations and shell closing effects are observed. In a first approximation, we find that LinH clusters behave like Lin–1 and LinH2 like Lin–2. The results may be interpreted by assuming that the bonding of one hydrogen localizes one electron and that the other electrons remain delocalized. 相似文献
85.
We present a cellular automata model as a new approach to Bernoulli site percolation on the square lattice. A new macroscopic quantity is defined and numerically computed at each level step of the automata dynamics. Its limit manifests a critical behavior at a value of the site occupancy probability quite close to those obtained for site percolation on 2 with the best-known numerical methods. 相似文献
86.
Hubert Delange 《Monatshefte für Mathematik》1993,116(3-4):175-196
Let (n) be the number of prime divisors ofn, counted with multiplicity. We denote byS(x, k) the set of thenx for which (n)=k, and byV
p(n) the exponent of the primep in the factorization ofn. In a previous paper we proved a result which implies that, ify=x/2
k
tends to infinity withk>2loglogx where >1, then the distribution of the numbers
on the setS(x, k) converges to the normal distribution of Gauss. Here, besides a slight improvement of that result, we give, for the moment of orderq of the above mentioned distribution, a formula which holds uniformly for 2loglogxklog (x/3)/log2 where 1<<3/2. 相似文献
87.
Polyimide and SU-8 microfluidic devices manufactured by heat-depolymerizable sacrificial material technique 总被引:1,自引:0,他引:1
The following paper describes a sacrificial layer method for the manufacturing of microfluidic devices in polyimide and SU-8. The technique uses heat-depolymerizable polycarbonates embedded in polyimide or SU-8 for the generation of microchannels and sealed cavities. The volatile decomposition products originating from thermolysis of the sacrificial material escape out of the embedding material by diffusion through the cover layer. The fabrication process was studied experimentally and theoretically with a focus on the decomposition of the sacrificial materials and their diffusion through the polyimide or SU-8 cover layer. It is demonstrated that the sacrificial material removal process is independent of the actual channel geometry and advances linearly with time unlike conventional sacrificial layer techniques. The fabrication method provides a versatile and fast technique for the manufacturing of microfluidic devices for applications in the field of microTAS and Lab-on-a-Chip. 相似文献
88.
Jagoda M Warzeska S Pritzkow H Wadepohl H Imhof P Smith JC Krämer R 《Journal of the American Chemical Society》2005,127(43):15061-15070
For a number of phosphoryltransfer enzymes, including the exonuclease subunit of DNA polymerase I, a mechanism involving two-metal ions and double Lewis-acid activation of the substrate, combined with leaving group stabilization, has been proposed. Inspired by the active site structure of this enzyme, we have designed as a synthetic phosphoryl transfer catalyst the dicopper(II) macrocyclic complex LCu(2). Crystal structures of complexes [(L)Cu(2)(mu-NO(3))(NO(3))](NO(3))(2) (1), [(L)Cu(2)(mu-CO(3))(CH(3)OH)](BF(4))(2) (2), and [(L)Cu(2)(mu-O(2)P(OCH(3))(2))(NO(3))](NO(3))(2) (3) illustrate various possibilities for the interaction of oxoanions with the dicopper(II) site. 1 efficiently promotes the transesterification of dimethyl phosphate (DMP) in CD(3)OD, k(cat) = 2 x 10(-)(4) s(-)(1) at 55 degrees C. 1 is the only available catalyst for the smooth transesterification of highly inert simple dialkyl phosphates. From photometric titrations and the pH dependence of reactivity, we conclude that a complex [(L)Cu(2)(DMP)(OCH(3))](2+) is the reactive species. Steric bulk at the -OR substituents of phosphodiester substrates O(2)P(OR)(2)(-) drastically reduces the reactivity of 1. This is explained with -OR leaving group stabilization by Cu coordination, an interaction which is sensitive to steric crowding at the alpha-C-atom of substituent R. A proposed reaction mechanism related to that of the exonuclease unit of DNA polymerase I is supported by DFT calculations on reaction intermediates. The complex [(L)Cu(3)(mu(3)-OH)(mu-CH(3)O)(2)(CH(3)CN)(2)](ClO(4))(3) (4) incorporates a [Cu(OH)(OCH(3))(2)(CH(3)CN)(2)](-) complex anion, which might be considered as an analogue of the [PO(2)(OCH(3))(2)(OCD(3))](2)(-) transition state (or intermediate) of DMP transesterification catalyzed by LCu(2). 相似文献
89.
Cataldi TR Bianco G Frommberger M Schmitt-Kopplin P 《Rapid communications in mass spectrometry : RCM》2004,18(12):1341-1344
A rapid, simple and selective method involving direct separation by gas chromatography (GC) with electron ionization mass spectrometry (EI-MS) was employed to determine some N-acylhomoserine lactones (AHLs). Using GC/EI-MS, simultaneous separation and characterization of AHLs were possible without prior derivatization. Informative fragmentation patterns were obtained to identify the structures of N-acyl chains of AHLs. Electron ionization resulted in a common fragmentation pattern with the most abundant ion at m/z 143 and other minor peaks at m/z 71, 57, and 43. The presence of AHLs in extracts of Burkholderia cepacia strains was achieved in selected ion monitoring mode by using the prominent fragment at m/z 143. 相似文献
90.
The reaction of acetone-4-chlorophenylhydrazone (6) with bromine in the presence of acetamide yields 2-bromo-2-(4-chlorophenylazo)-propane (7) and 2,2-bis(4-chlorophenylazo)propane (8). The unstable heteroallylic bromide7 was subjected without isolation to nucleophilic displacements with a series of heteronucleophiles thereby affording the corresponding 2-(4-chlorophenylazo)-2-propane derivatives9 with the azo- and heteroelement-functions in a geminal position to each other.
Herrn Prof. Dr. Dr. h. c.K. Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet. 相似文献