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排序方式: 共有178条查询结果,搜索用时 15 毫秒
1.
H.G. Wiedemann 《Thermochimica Acta》1973,7(2):131-149
A combination of thermobalance and X-ray camera is described which allows simultaneous thermogravimetric (TG) and X-ray measurements under high vacuum. During these measurements the sample is positioned in the sample holder of the camera in the usual fashion and is X-raved while the temperature is varied. The molecular beam of the gaseous decomposition products flows through a connecting tube which acts as a molecular beam former between camera and thermobalance. The molecular beam is directed towards the empty balance pan. The orifice through which the beam exits as well as the pan have special shapes that allow transfer of the angular momentum of the decomposition beam to the balance. The exerted force is a function of time and corresponds to the first derivative of the TG curve. i.e. to the DTG curve. The integrated curve is directly proportional to the change in mass of the probe. A quantitative evaluation is possible if the molecular composition of the beam is known. The calibration of the molecular beam and the evaluation of the measurements will be discussed. The results show that simultaneous detection of X-ray scattering and indirect TG curves allows a better interpretation of decomposition reactions.An additional investigation shows that thermal synthesis of chemical com- pounds can also be studied by thermogravimetry. Based on the same compound as described in the analysis. the pyrosynthesis is demonstrated. The special instrumentation and the test conditions are discussed. 相似文献
2.
Werner H Wiedemann R Laubender M Windmüller B Wolf J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(9):1959-1967
A series of iodo- and hydroxorhodium(I) complexes of the general composition trans-[RhX(=C=C=CRR')(PiPr3)2] (X = I: 5-7; X = OH: 8-11) was prepared from the related chlororhodium(I) precursors. The hydroxo compounds behave as organometallic Br?nsted bases and react with acids like MeCO2H, PhCO2H, PhOH, or TsOH by elimination of water to give the substitution products trans-[RhX'(=C=C=CRR')(PiPr3)2] (X' = MeCO2: 12, 13; X' = PhCO2: 14; X' = PhO: 15, 16; X' = TsO: 17, 18) in good to excellent yields. In contrast to the tosylates 17, 18, which react with CO by cleavage of the allenylidene-metal bond to give trans-[Rh(OTs)(CO)(PiPr3)2] (19), treatment of the acetato and phenolato derivatives 12, 13 and 15, 16 with CO affords by migratory insertion of the allenylidene unit into the Rh-O bond the alkynyl complexes trans-[Rh[C(triple bond)CCR(R')X'](CO)(PiPr3)2] (X' = MeCO2: 20, 21; X' = OPh: 22, 23). Similarly, the reactions of the hydroxo compounds 8, 10, and 11 with CH2(CN)2 and either CO or CNMe yield the carbonyl and the isocyanide complexes trans-[Rh[C(triple bond)CCR(R')CH(CN)2](L')(PiPr3)2] (L' = CO: 25-27; L' = CNMe: 28-30), respectively. By protolytic cleavage of the Rh-C sigma bond the gamma-functionalized alkynes HC(triple bond)CCR(R')CH(CN)2 (31, 32) are generated from 25, 26 and HCl in benzene. The molecular structure of 22 was determined by X-ray crystallography. 相似文献
3.
L. Raith M. Wiedemann und H. J. Karl 《Fresenius' Journal of Analytical Chemistry》1970,252(4-5):290-293
Zusammenfassung Nach i.v. Injektion von 4–6 Ci14C-Testosteron und 7–8 Ci3H-Androstendion oder entsprechenden Mengen14C-Dehydroepiandrosteron und3H-Dehydroepiandrosteronsulfat wurden die Glucuronide von Testosteron, Androsteron, Ätiocholanolon und Dehydroepiandrosteron sowie Dehydroepiandrosteronsulfat säulen- (Al2O3), papier- (Bush A2) und dünnschicht-chromatographisch (Chloroform/Äthylacetat 41) aus Urin abgetrennt und gas-chromatographisch (1% XE-60, Flammenionisationsdetektor) bestimmt. Nach splitting des Trägergases und Kondensation der gasförmigen Steroide in einem wattegefüllten Glasröhrchen eines Gasfraktionskollektors wurde die14C- und3H-Aktivität der einzelnen Androgenmetaboliten mit einem Müssigkeitsszintillationszähler gemessen und aus der spezifischen Aktivität (Impulse/Mikrogramm) die Produktions- und Interkonversionsraten von Testosteron, DHEA und DHEA-Sulfat berechnet.
Die Arbeit wurde mit Mitteln des Bundesministeriums für Wissenschaftliche Forschung gefördert. 相似文献
Determination of the metabolism and production rates androstendione of testosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulphate
After the i.v. application of 4–6 Ci14C-testosterone and 7–8 Ci3H-androstendione or equivalent dosages of tritium dehydroepiandrosterone sulphate and dehydroepiandrosterone the gluouronides of testosterone, etiocholanolone, androsterone and dehydroepiandrosterone and dehydroepiandrosterone sulphate were separated from urine by column (Al2O3), paper (system Bush A2) and thin-layer (chloroform:ethylacetate=41) chromatography. After a final gas-liquid chromatography on 1% XE-60 the androgen metabolites were estimated quantitatively by flame-ionisation detector. The radioactivity (3H and14C impulses) of the compounds was measured after splitting the carrier gas and condensation of the steroids in a gas-fraction collector. From the specific activity (Imp/g) the production and interconversion rates of testosterone, dehydroepiandrosterone and dehydroepiandrosterone sulphate were calculated.
Die Arbeit wurde mit Mitteln des Bundesministeriums für Wissenschaftliche Forschung gefördert. 相似文献
4.
Considering the N = 1 supersymmetry transformations of supersymmetric nonlinear sigma models in 1 + 1 dimensions we construct explicitly conserved Noether currents associated with supersymmetry transformations and derive the associated conserved charges in terms of the basic fields. We compare this result with superspace calculations. Finally we review the connection between extended supersymmetry and the geometry of the target space and derive an explicit form of the supercharges for extended supersymmetry. 相似文献
5.
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7.
Far-infrared-absorption spectroscopy is used to investigate the low-frequency (相似文献
8.
M. Wiedemann A. Wirtz H. J. Karl L. Raith 《Analytical and bioanalytical chemistry》1974,272(3):195-198
The newly synthesized125I-testosterone-3-carboxy-methyloxime-tyramide was tested for its applicability in protein binding methods. The binding of the radioactive steroid derivative to sex hormone binding globulin (SHBG), albumins and testosterone antibodies was examined. Furthermore the adsorption to florisil, charcoal and amberlite was studied. The results show:
- 125I-testosterone is bound to antibodies obtained by immunization with testosterone-3-oxime-albumin conjugate similarly to3H-testosterone and unlabelled steroid.
- 125I-testosterone and3H-testosterone show identical binding to florisil, charcoal and amberlite.
9.
B. Wiedemann G. R?dlinger H. Ch. Alt K. G. Heumann K. Bethge 《Fresenius' Journal of Analytical Chemistry》1999,364(8):772-776
The residual or doped element concentration [E] in GaAs measured by SSMS is only accurate with respect to the relative sensitivity
coefficient RSCE. For a trace element concentration, the RSCE = [E]SSMS/[E]TRUE is set to unity, if no reference material or method is available to approximate the concentration to the true value. For
boron a relative sensitivity coefficient of RSCB = 0.94 ± 0.08 was obtained using TI-IDMS as a reference method. RSCN = 1 is used for nitrogen determinations. A boron and nitrogen detection limit of 4.4 × 1013 cm–3 is achieved. SSMS was used as reference method to calibrate the FTIR factor fE = [E] / Iα due to the integrated local vibrational mode absorption Iα of atomic boron and nitrogen in GaAs. A factor of fB = (12.0 × 2.7) × 1016 cm–1 (517 cm–1) and fN = (7.4 ± 0.1) × 1015 cm–1 (472 cm–1) was obtained for a boron and nine nitrogen containing GaAs samples at 77 K and 10 K, respectively.
Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999 相似文献
10.