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61.
J. Ren H. -D. Ließ R. Mäckel H. Baumgärtner 《Fresenius' Journal of Analytical Chemistry》1995,353(3-4):303-306
Based on the well known Kelvin probe for work function measurements a new microstructure analysis system – the Scanning Kelvin Microscope – has been developed. It allows to measure simultaneously with high lateral resolution the distribution of the contact potential difference (CPD) between a conductive sample and a reference probe together with the topographical structure of the sample surface. The measurement is contact free and non-destructive and can be carried out in natural environments. At present the lateral resolution of the measurement approaches 5 m. The results can be displayed on a computer in three dimensional colour pictures. 相似文献
62.
Based on the well known Kelvin probe for work function measurements a new microstructure analysis system - the Scanning Kelvin Microscope - has been developed. It allows to measure simultaneously with high lateral resolution the distribution of the contact potential difference (CPD) between a conductive sample and a reference probe together with the topographical structure of the sample surface. The measurement is contact free and non-destructive and can be carried out in natural environments. At present the lateral resolution of the measurement approaches 5 microm. The results can be displayed on a computer in three dimensional colour pictures. 相似文献
63.
In this paper three Banach spacesA
0(),A
andA
1() of functions holomorphic in the unit ballB of
n
are defined. We exhibit bounded projections fromC
0(B) ontoA
0(), fromL
1(B) ontoA
1(), and fromL(B) ontoA(). Using these projections, we show thatA
0()* A
1() andA
1()* A().Supported in part by the National Natural Science Foundation of China. 相似文献
64.
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
65.
The reaction of tungstate ions with the gamma-10-tungstosilicate in mixed water-ethanol (v/v) yields the corresponding isomer of the 12-tungstosilicate isolated as its tetrabutylammonium salt. It was characterized by means of (183)W NMR, infrared, Raman, and UV spectroscopies and was identified with the isomer resulting from the Keggin structure (alpha-isomer) by rotation of two tritungstic groups by pi/3. Cyclic voltammetry shows that the reducibility increases in the sequence alpha-beta-gamma as the number of rotated tritungstic groups. Whereas the gamma-12-tungstosilicate anion is unstable in pure aqueous solution whatever the pH value, it is stable in mixed aqueous-organic or pure organic solvents, even at boiling temperatures. In contrast, the two- and four-electron-reduced blue species are stable in aqueous media but not the one-electron-reduced blue. Study of the (183)W NMR spectrum of the two-electron-reduced species showed that the two spin-paired electrons are delocalized on all the W atoms on the NMR time scale but have a larger residency time on one group of four atoms. 相似文献
66.
67.
Henriksen T Juhler RK Svensmark B Cech NB 《Journal of the American Society for Mass Spectrometry》2005,16(4):446-455
The purpose of the work presented here was to evaluate the influence of solution composition and analyte characteristics on responsiveness to analysis with negative ion electrospray ionization mass spectrometry. The responses of a series of structurally diverse acidic molecules were compared in various solvents. Response was generally observed to be higher in methanol than acetonitrile and response for all analytes was poorer when water was mixed with the organic solvent. A positive correlation between negative ion ESI-MS response and log P was observed when either acetonitrile or methanol was used as the electrospray solvent. This result was expected because analytes with significant nonpolar character should be particularly responsive to ESI-MS analysis due to their higher affinity for electrospray droplet surfaces. It was also predicted that highly acidic analytes would be most responsive to analysis with negative ion ESI-MS due to their tendency to form negative ions. However, for the analytes studied here, acidity was found not to have a consistent influence on ESI-MS response. Many of the highly acidic molecules were quite polar and, consequently, were poorly responsive. Furthermore, the deprotonated molecular ion was detected for a number of molecules with very high pKa values, which would not be expected to form negative ions in the bulk solution. Ultimately, these results indicate that acidity is not a conclusive parameter for prediction of the relative magnitudes of negative ion ESI-MS response among a diverse series of analytes. Analyte polarity does; however, appear to be useful for this purpose. 相似文献
68.
The exchange of the PPh3 ligand in the complex [1,3-bis(2,6-dimethylphenyl)4,5-dihydroimidazol-2-ylidene](PPh3)(Cl)2Ru=CHPh (7) for a pyridine ligand at ambient temperature leads to the formation of the stable phosphine-free carbene ruthenium complex [1,3-bis(2,6-dimethylphenyl)4,5-dihydroimidazol-2-ylidene](C5H5N)2(Cl)2 Ru=CHPh (8). The resulted ruthenium complex exhibits highly catalytic activity for the cross metathesis of acrylonitrile with various functionalized olefins under mild conditions, and its activity can be further improved by the addition of a Lewis acid such as Ti(OiPr)4. In the mixture products, the Z-isomer predominates. 相似文献
69.
示差脉冲伏安法测定黄酒中的酪氨酸 总被引:3,自引:0,他引:3
本文研究了硼砂介质中镍与酪氨酸络合物的示差脉冲吸附伏安特性,实验了仪器参数对示差脉冲阴极吸附伏安法的影响,在最佳条件下络合物峰电流与酪氨酸浓度在2.0×10^-7~4.0×10^-5mol.L^-1范围内有线性关系,并以此法测定了黄酒中酪氨酸的含量。 相似文献
70.
Alfaya RV Fujiwara ST Gushikem Y Kholin YV 《Journal of colloid and interface science》2004,269(1):32-36
3-n-propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M=Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl-+ MClz <=> (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. 相似文献