高速色散补偿系统中喇曼放大器性能研究

利用喇曼放大器的非线性偏微分耦合方程组,对带喇曼放大器的色散补偿系统进行了仿真,并与传统的仿真方法进行了比较.结果表明:在色散完全补偿系统中,当传输速率较高时,忽略色散后的传统仿真方法的结果,与采用色散补偿技术后使整个系统色散为零的仿真结果有一定偏差,此时不能忽略色散的作用.还对前补偿系统和后补偿系统进行了研究,利用Q值性能判别法,分别得到了信号光脉冲的最佳占空比和最佳脉冲阶数.     

Total surface areas of Group IVA organometallic compounds: Predictors of toxicity to algae and bacteria

There is a high correlation between molecular surface area (TSA) of triorganotin and triorganolead compounds and their toxicity towards a bacterium (Escherichia coli) and an alga (Selenastrum capricornutum). Parallel attempts to correlate other Group IVA organometals incorporating silicon or germanium were unsuccessful. It was further demonstrated, however, that a high correlation was obtainable between certain series of compounds with the same organic substituent but different metal centers involving all Group IVA elements. In both instances, the inability to obtain a quantitative structure-activity relationship (QSAR) for all systems studied appears to be a function of the solubility of the compounds. While organotin TSA values have been found to correlate well with their toxicities toward various organisms, this study clearly suggests that this type of QSAR can be readily extended to include other organometal systems, provided that there is no solubility problem and the toxicity is a function of the hydrophobicity of the organometal compounds.     

R?ntgenspektrometrische Elementbestimmung in Abwasser: Probenvorbereitung und Matrixkorrekturverfahren

Zusammenfassung Für Elementbestimmungen in Abwasser wird ein Röntgenfluorescenzverfahren beschrieben. Zur Probenvorbereitung werden die Elemente durch Gefriertrocknung auf einem inerten Träger angereichert. Diese Anreicherung ist nicht selektiv und erfaßt praktisch alle in Abwasser gelösten und suspendierten Verunreinigungen. Für die Berechnung der Elementkonzentrationen aus den gemessenen Fluorescenzintensitäten wird ein Matrixkorrekturverfahren angegeben, welches dem unterschiedlichen Absorptionsverhalten der Probenmatrix Rechnung trägt. Die Massenabsorptionskoeffizienten werden durch Messung der diffus gestreuten Bremsstrahlung bzw. der Comptonstreustrahlung ermittelt. Die Selbstabsorption des zu bestimmenden Elementes wird rechnerisch berücksichtigt. Das Korrekturverfahren kann auf alle mit Röntgenfluorescenzanalyse bestimmbaren Elemente angewendet werden.

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Determination of elements in waste water by x-ray fluorescence analysis: Sample preparation and matrix correction method

Summary For sample preparation the elements are enriched upon an inert carrier by freeze-drying. This enriching procedure is not selective and collects all dissolved and suspended contaminations from the waste water. In order to calculate the element concentrations from the measured fluorescence intensities a matrix correction method is given which considers the different absorption behaviour of the matrix. The mass absorption coefficients are obtained by measuring the scattered X-ray tube spectrum or a Compton scattered X-ray tube line, respectively. The self-absorption of the element to be determined is taken into account. The correction method is applicable to all elements detectable by X-ray fluorescence.

Herrn Dr. H. Wagner danken wir für das stete Interesse, die zahlreichen konstruktiven Diskussionen und die Hilfe beim Abfassen des Manuskripts.     

Pressurized hot water extraction of berberine, baicalein and glycyrrhizin in medicinal plants

Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC.     

An alternative sampling algorithm for use in liquid chromatography/tandem mass spectrometry experiments

In liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses of complex peptide mixtures, dynamic exclusion functions are used to minimize repeat selections of identical precursors for collision induced dissociation (CID). We describe a new algorithm for the dynamic exclusion of m/z values during LC/MS/MS. Full-scan based peak exclusion (Fulspec) uses a simplified model of chromatographic peak formation to detect and exclude contaminants present throughout the run or that lead to broad peaks. Therefore, instead of excluding peptides from fragment analysis according to a rigidly predefined time window, the chromatographic properties of the detected analytes are used. The algorithm was tested on two datasets derived from previously published experiments. Fulspec achieves a distribution of CID spectra with minimal tailing on the retention time axis, without resorting to rigid exclusion of m/z values. The procedure further excludes intensities with a bias towards low-quality CID spectra. This combination frees up valuable analytical capacity. The underlying intensity vs. quality analyses challenge the assumption that abundant precursors automatically give the best identifications. Further validation of the algorithm will require its incorporation by equipment manufacturers into the instrument control programs.     

Cell docking inside microwells within reversibly sealed microfluidic channels for fabricating multiphenotype cell arrays

We present a soft lithographic method to fabricate multiphenotype cell arrays by capturing cells within an array of reversibly sealed microfluidic channels. The technique uses reversible sealing of elastomeric polydimethylsiloxane (PDMS) molds on surfaces to sequentially deliver various fluids or cells onto specific locations on a substrate. Microwells on the substrate were used to capture and immobilize cells within low shear stress regions inside channels. By using an array of channels it was possible to deposit multiple cell types, such as hepatocytes, fibroblasts, and embryonic stem cells, on the substrates. Upon formation of the cell arrays on the substrate, the PDMS mold could be removed, generating a multiphenotype array of cells. In addition, the orthogonal alignment and subsequent attachment of a secondary array of channels on the patterned substrates could be used to deliver fluids to the patterned cells. The ability to position many cell types on particular regions within a two dimensional substrate could potentially lead to improved high-throughput methods applicable to drug screening and tissue engineering.