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1.
Eggenhffner R. Masini R. Bellingeri E. Cimberle M. R. Ferdeghini C. Costa G. A. Kaiser E. Signorelli E. 《Il Nuovo Cimento D》1994,16(10):1659-1664
Il Nuovo Cimento D - The formation of Hg-based HTSC materials was investigated through the development of non-conventional techniques. The former was based on a singlestep synthesis at temperatures... 相似文献
2.
Data about the existence of native HO? CH2? CH2? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C4) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc. 相似文献
3.
The 29th PME research forum on theories included only one European perspective on mathematics education. In order to convey trends in theory usage in Europe we compile, survey and analyze a large subset of the research papers from the 4th European Congress on Mathematics Education (CERME4). That is, this paper includes a discussion of trends seen within CERME4 reports1 on theory usage by European researchers inseven of the fourteen working groups and (a) Outlines similarities and differences in theory usage and (b) takes a futuristic stance on ways in which researchers from different traditions could understand each other. Such an enterprise would further Hans-Georg Steiner's vision of bridging theoretical traditions which are independently formulated in different regions of the world. 相似文献
4.
Uwe Bandelow Mindaugas Radziunas Andrei Vladimirov Bernd Hüttl Ronald Kaiser 《Optical and Quantum Electronics》2006,38(4-6):495-512
We study both theoretically and experimentally typical operation regimes of 40 GHz monolithic mode-locked lasers. The underlying
Traveling Wave Equation model reveals quantitative agreement for characteristics of the fundamental mode-locking as pulse
width and repetition frequency tuning, as well as qualitative agreement with the experiments for other dynamic regimes. Especially
the appearance of stable harmonic mode-locking at 80 GHz has been predicted theoretically and confirmed by measurements. Furthermore,
we derive and apply a simplified Delay-Differential-Equation model which guides us to a qualitative analysis of bifurcations
responsible for the appearance and the breakup of different mode-locking regimes. Higher harmonics of mode-locking are predicted
by this model as well. 相似文献
5.
6.
Zepeck F Gräwert T Kaiser J Schramek N Eisenreich W Bacher A Rohdich F 《The Journal of organic chemistry》2005,70(23):9168-9174
[Structure: see text]. The IspG protein is known to catalyze the transformation of 2-C-methyl-d-erythritol 2,4-cyclodiphosphate into 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate in the nonmevalonate pathway of isoprenoid biosynthesis. We have found that the apparent IspG activity in the cell extracts of recombinant Escherichia coli cells as observed by a radiochemical assay can be enhanced severalfold by coexpression of the isc operon which is involved in the assembly of iron-sulfur clusters. The recombinant protein was isolated by affinity chromatography under anaerobic conditions. With a mixture of flavodoxin, flavodoxin reductase, and NADPH as the reducing agent, stringent assay methods based on photometry or on 13C NMR detection of multiply 13C-labeled substrate/product ratios afforded catalytic activities greater than 60 nmol mg(-1) min(-1) for the protein "as isolated" (i.e., without reconstitution of any kind). Lower apparent activities were found using photoreduced deazaflavin as an artifactual electron donor, whereas dithionite was unable to serve as an artificial electron donor. The apparent Michaelis constant for 2-C-methyl-D-erythritol 2,4-cyclodiphosphate was 700 microM. The enzyme was inactivated by EDTA and could be reactivated by Mn2+. The pH optimum was at 9.0. The protein contained 2.4 iron ions and 4.4 sulfide ions per subunit. The replacement of any of the three conserved cysteine residues afforded mutant proteins which were devoid of catalytic activity and contained less than 6% of Fe2+ and less than 23% of S2- as compared to the wild-type protein. Sequence comparison indicates that putative IspG proteins of plants, the apicomplexan protozoan Plasmodium falciparum, and bacteria from the Bacteroidetes/Chlorobi group contain an insert of about 170-320 amino acid residues as compared with eubacterial enzymes. 相似文献
7.
Methods have been developed to allow applications of membrane introduction mass spectrometry (MIMS) to monitor solution phase components of fermentation broths using electron ionization. The solutions are transported by flow injection analysis (FIA) through a direct insertion membrane probe, fitted with a silicone membrane in the sheet configuration. Analytes of interest pass through the membrane and are ionized by electron implant ionization. The compounds monitored are ammonia, acetic acid, and ethanol, with ammonia being detected as the monochloramine derivative which is generated at pH 10 upon addition of hypochlorite. Quantitation is achieved using external standard solutions. The dynamic range for the quantification of ammonia is 2-8000 ppm, and for ethanol and acetic acid 10-1000 ppm. This method provides rapid detection of analytes of interest, on-line monitoring capabilities, and the advantage of electron ionization. The introduction of samples into the mass spectrometer is achieved readily and automatically, the response time is a few seconds, and there are no memory effects. 相似文献
8.
The40Ar/39Ar technique is an analytical variation of the K–Ar dating method. A known fraction of the39K in a sample is converted to39Ar by irradiation with fast neutrons. In an incremental heating experiment, the argon is released from the sample fractionally by stepwise heating. The result is a series of apparent ages.40Ar/39Ar age spectrum was determined for the sample Oase Vestfold. The minimum of the saddle-shaped age spectrum gives 1.0 billion years. 相似文献
9.
S. Jakobs Ulrike Schulz Angela Duparré Norbert Kaiser 《Analytical and bioanalytical chemistry》1997,358(1-2):242-244
SiO2 protective coatings have been deposited on polycarbonate substrates by plasma ion assisted deposition. The influence of ion energy on the water permeability and the surface topography of the coatings was studied by infrared spectroscopy and atomic force microscopy. Coatings deposited at sufficiently high ion energies show a barrier effect against moisture uptake and considerably reduced film roughness. Both effects are attributed to an increase of the packing densities of the coatings. 相似文献
10.
Robert Weis Marcel Kaiser Reto Brun Robert Saf Werner Seebacher 《Monatshefte für Chemie / Chemical Monthly》2006,137(10):1365-1374
Summary. 4-Aminobicyclo[2.2.2]octan-2-ones and -ols showed activity against the causative organisms of East African sleeping sickness
and Malaria tropica. Several imino derivatives of the ketones were more active. Now hydrazono analogues and 3-hydroximino
derivatives of the ketones and alcohols were synthesized. The structures of the obtained isomers were elucidated by NMR spectroscopy.
A single phenylhydrazone exhibited quite good antitrypanosomal activity in the range of already known imino analogues. 相似文献