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991.
992.
Jens Totz Aad van den Boogaart Sabine Van Huffel Danielle Graveron-Demilly Ioannis Dologlou Ralf Heidler Dieter Michel 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,124(2):400-409
In this paper, it is shown how the advantages of continuous regularization (CR) can be exploited to achieve an improved, fully automated LPSVD analysis of MRS time-domain data. The main advantage of CR is its ability to determine the number of spectral components even at low signal-to-noise ratios, which suggested its use forin vivospectroscopy. Estimation of the spectral parameters is possible. Two alternatives of automated data-analysis schemes are thoroughly investigated by means of Monte Carlo studies. The results suggest the combination of CR for model-order estimation with other methods for more-accurate parameter estimation. Several possible combinations, including those with an improved enhancement procedure and a total-least-squares method for quantitation, are discussed. Recommendations are given for spectral analysis, and a new data-analysis protocol which performs significantly better than previously used protocols of the same type is proposed. 相似文献
993.
994.
995.
A. H. Sabine 《Fresenius' Journal of Analytical Chemistry》1891,30(1):681
Ohne Zusammenfassung 相似文献
996.
997.
The investigated new class of heparinoid mimetics are spaced persulfated carbohydrates designed to increase the success rate of angioplasty and bypass surgery by preventing restenosis without increasing the risk of bleeding. Due to the presence of sulfate groups, these compounds are highly charged and, for preclinical kinetic investigations only small sample volumes of rat plasma were available. Therefore, capillary electrophoresis (CE) was applied. A bioanalytical method based on micellar elektrokinetic chromatography (MEKC) with UV-detection was developed for the selective quantitation of heparinoid mimetics (e.g., Ro 48-0843, Ro 48-3151, Ro 47-6199 and Ro 48-8722) in plasma. Using this method, only small volumes of plasma were required, which could be introduced directly into the separation capillary after 1:1 dilution with 100 mM aqueous sodium dodecyl sulfate (SDS). For increased sample throughput, an additional ultrafiltration step was performed after SDS-dilution of the plasma sample, improving both reproducibility and robustness of the method considerably. The sensitivity of the new method (3 μg/ml) was sufficient to follow plasma levels in pharmacokinetic studies. The practicability of this easy and rapid assay was demonstrated by the analysis of more than 350 plasma samples from pharmacokinetic studies performed in rats. 相似文献
998.
Susanne Voigt Sabine Dreher Johannes Orphal John P. Burrows 《Journal of Molecular Spectroscopy》1996,180(2):359-364
N2broadening coefficients have been measured for 65 lines of the13C16O 2–0 band using a Fourier transform spectrometer. These lines are located in the spectral range 4011–4252 cm−1. The spectra were recorded with 99% isotopically pure13CO in a White-type cell at a resolution of 0.005 cm−1. Voigt profiles convolved with the FTS apparatus function were fitted to the experimental lineshapes using a nonlinear least-squares fit technique. From the fits the Lorentzian HWHM was determined as function of N2pressure. Pressure broadening coefficients formbetween −33 and +34 were obtained with uncertainties of 5.8%. The results are compared to earlier published N2broadening coefficients and our measurements in the 2–0 band of12C16O. To our knowledge this is the first investigation of13CO pressure broadening. 相似文献
999.
Given a sequence of random variables taking values in {?v,…,0,…,+u}, let's define the local score of the sequence by Hn=max1?i?j?n(∑k=ijXk). The local score is used to analyze biological sequences pointing out regions of the sequences with interesting biological properties. In order to separate randomly events from really interesting segments, we establish here the distribution of the local score of Hn when the sequence is a Markov chain of order 1. To cite this article: S. Mercier, C. Hassenforder, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
1000.
Over the past decade, RNA conformation has been shown to respond to external stimuli. Thus, dependent on the presence of a high affinity ligand, specifically designed ribozymes can be regulated in a classical allosteric way. In this scenario, a binding event in one part of the RNA structure induces conformational changes in a separated part, which constitutes the catalytic centre. As a result activity is switched on (positive regulation) or off (negative regulation). We have developed a hairpin aptazyme responding to flavine mononucleotide (FMN). Ribozyme activity is dependent on binding of FMN and thus is switched on in the presence of FMN in its oxidized form. Under reducing conditions, however, FMN changes its molecular geometry, which is associated with loss of binding and consequently down‐regulation of ribozyme activity. While in previous experiments sodium dithionite was used for reduction of FMN, we now present an assay for electrochemically induced activity switching. We have developed an electrochemical microcell that allows for iterative cycles of reduction/oxidation of FMN in an oxygen free atmosphere and thus for reversible switching of ribozyme activity. The reaction proceeds in droplets of 3 to 10 μL at micro‐ to nanomolar concentrations of the reaction components. 相似文献