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It was derived theoretically that a sharp end-point of this spectrophotometrical titration is defined, in order of importance, by: 1. *KC ? *KI (numerically speaking, log should be at least 4); 2. *KI being large (numerically e.g. 104-105); this is already reached by choosing a high pH; 3. it being low; 4. mt being as high as possible. 相似文献
4.
Gründler P 《Talanta》1983,30(11):870-872
Anodic-stripping voltammetry is used to perform automatic complexometric titrations of metal ions, with high precision. The stripping peaks are converted into corresponding titrant volume increments which are added consecutively during stripping. In analysis of samples containing about 1 mmole, each of lead, indium and gallium, relative standard deviations of 0.008-0.03% were attained. 相似文献
5.
Composition and hydrolysis products of a biotechnical available complex of macrolides were analyzed by HPLC and ESI-CID-MSn. Major components are leucomycin-type antibiotics (leucomycins A1 (5), A7 (3), A9 (2), 9-desoxy-9-oxo-turimycin H3 (4) and niddamycin B (6). Hydrolysis of the complex mixture yielded 9-, 13-isoforocidins (7, 8, 9, 11) and 9-oxo-forocidin (10). A preparative separation procedure was elaborated furnishing compounds 3 - 11 for semisynthetic experiments.Prof. Dr. Udo Gräfe deceased on 14.2.2003. For obituarity see: Schlegel B (2003) J Peptide Sci 9: 661–661. 相似文献
6.
Karlheinz Gröchenig 《Monatshefte für Mathematik》1985,100(3):171-182
We study the properties of sequences (c
n
) in a compact groupG such that (x
n
) being (weakly) well-distributed implies (c
n
x
n
) being (weakly) well-distributed and give a complete characterisation in terms of almost constant sequences as well as a generalisation to non-compact locally compact groups. 相似文献
7.
[reaction: see text] The enzymatic degradation of starch can be monitored electronically using single-walled carbon nanotubes (SWNTs) as semiconducting probes in field-effect transistors (FETs). Incubation of these devices in aqueous buffer solutions of amyloglucosidase (AMG) results in the removal of the starch from both the silicon surfaces and the side walls of the SWNTs in the FETs, as evidenced by direct imaging and electronic measurements. 相似文献
8.
Christian C. Van de Sande Syed Zahoor Ahmad Friedrich Borchers Karsten Levsen 《Journal of mass spectrometry : JMS》1978,13(11):666-670
Gaseous protonated aziridine ions are produced at the threshold from β-phenoxyethylamine molecular ions. The evidence for this is collisional activation spectra, using various precursors (including labelled analogues) under electron impact and field ionization conditions. Partial conversion to the acyclic \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^ + {\rm H}_{\rm 2} $\end{document} isomer occurs at higher electron energies and is rationalized by means of a potential energy surface constructed from energetic data. 相似文献
9.
For the first time, the nuclear magnetic resonance (NMR) spin-spin coupling mechanism is decomposed into one-electron and electron-electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin-spin coupling constants result from totally different Fermi contact coupling mechanisms. (1)J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas (2)J(H,H) spin-spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of (1)J(C,H) and (2)J(H,H), respectively, for hydrocarbons. 相似文献
10.
Karsten Lebelt 《manuscripta mathematica》1977,21(4):341-355
Let R be a commutative noetherian ring with identity. To a finite free resolution F of an R-module M and every integer p1 we associate finite free complexes C
*
p
F. C
*
p
F is a free resolution of PM-the p-th exterior power of M if the degree of torsionfreeness of M is large enough. Using C
*
p
F we further study the degree of torsionfreeness of PM. As an application we prove a special case of a conjecture of P. Hackman concerning a connection between rank and torsionfreeness of a module. 相似文献