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31.
Bogusław Buszewski Agnieszka Ulanowska Tomasz Ligor Natalia Denderz Anton Amann 《Biomedical chromatography : BMC》2009,23(5):551-556
In this study, 38 samples of expired air were collected and analyzed from 20 non‐smoking volunteers, four passive smokers and 14 smokers (21 women and 17 men). Measurements were carried out using solid‐phase microextraction (SPME) as an isolation and preconcentration technique. The determination and identification were accomplished by gas chromatography coupled with mass spectrometry (GC/MS). Our data showed that ca 32% of all identified compounds in the breath of healthy non‐smokers were saturated hydrocarbons. In the breath of smoking and passive smoking volunteers hydrocarbons were predominant, but also present were more exogenous analytes such as furan, acetonitrile and benzene than in the breath of non‐smokers. Acetonitrile, furan, 3‐methylfuran, 2,5‐dimethylfuran, 2‐butanone, octane and decane were identified in breath of smoking and passive smoking persons. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
32.
The aim of this work was construction of the new wavelet function and verification that a continuous wavelet transform with a specially defined dedicated mother wavelet is a useful tool for precise detection of end-point in a potentiometric titration. The proposed algorithm does not require any initial information about the nature or the type of analyte and/or the shape of the titration curve. The signal imperfection, as well as random noise or spikes has no influence on the operation of the procedure.The optimization of the new algorithm was done using simulated curves and next experimental data were considered. In the case of well-shaped and noise-free titration data, the proposed method gives the same accuracy and precision as commonly used algorithms. But, in the case of noisy or badly shaped curves, the presented approach works good (relative error mainly below 2% and coefficients of variability below 5%) while traditional procedures fail. Therefore, the proposed algorithm may be useful in interpretation of the experimental data and also in automation of the typical titration analysis, specially in the case when random noise interfere with analytical signal. 相似文献
33.
34.
Ciesielski W Kassassir H Potrzebowski MJ 《Solid state nuclear magnetic resonance》2011,39(3-4):151-157
O-phospho-L-threonine is a convenient sample to setup a (1)H-(31)P-(13)C double cross-polarization (DCP) Hartmann-Hahn match. The (1)H-(31)P-(13)C technique is extremely sensitive to the rate of the sample spinning. Both zero-quantum (ZQ) and double-quantum (DQ) cross-polarization operate at an average spinning rate (6-7 kHz). At higher spinning rates (10 kHz), the DQCP mechanism dominates and leads to a reduction of signal intensity, in particular for lower (31)P RF field strength. The application of two shape pulses during the second cross-polarization greatly improves the signal to noise ratio allowing the recording of better quality spectra. (31)P-(13)C spectrally induced filtering in combination with cross-polarization (SPECIFIC-CP) experiments can be carried out under ZQCP and DQCP conditions if careful attention is paid to the choice of RF field amplitudes and carriers Ω. Application of 1D and 2D (1)H-(31)P-(13)C experiments is demonstrated on model samples; disodium ATP hydrate and O-phospho-L-tyrosine. 相似文献
35.
An efficient and stereoselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles is described by the intramolecular Pd(0)-catalysed cyclisation of amino allylic carbonates. The use of chiral ligands gave the corresponding heterocyclic derivatives having er values that were from moderate to good. 相似文献
36.
37.
Wlodzimierz Szwarc 《Journal of Global Optimization》1996,9(3-4):345-356
This paper deals with flow-shop models where n items are grouped in fixed sequences, called clusters. The clusters are to be processed on m machines in the same technological order. Each machine handles the clusters in the same order. Each completed item is available for processing on the next machine. The question is how to arrange the clusters to minimize the completion time. Models that include setup times for clusters with identical items are also examined. Approximate solutions along with new lower bounds are presented. Those solutions are optimal for the two machine case. 相似文献
38.
Piotr Bogus?aw Mucha Wojciech M. Zaj?czkowski 《Journal of Differential Equations》2002,186(2):377-393
In this paper a special Lp-estimate for the linearized compressible Navier-Stokes in the Lagrangian coordinates for the Dirichlet boundary conditions is obtained. The constant in the estimate does not depend on the length of time interval [0,T]. The result is essential to obtain an existence for regular solutions for the nonlinear problem with the lowest class of regularity in Lp-spaces. 相似文献
39.
Ralph E. Schlief Wlodzimierz Jarzeba Khalid A. M. Thakur Joseph C. Alfano Alan E. Johnson Paul F. Barbara 《Journal of Molecular Liquids》1994,60(1-3):201-220
Ultrafast pump - probe measurements have been made on the benzene - bromine atom charge transfer (CT) complex in CCl4 and cyclohexane solutions. Ultrafast optical excitation of the CT band of the complex yields an ion pair, which is comprised of a benzene cation and a bromide anion. The rate of charge recombination between the bromide and the benzene cation in the ion pair has been observed to be much faster than the rate of diffusion apart. The charge recombination rate is accelerated at high benzene concentrations as a result of the formation of a benzene dimer cation - bromide ion pair which undergoes much faster charge recombination than the benzene cation - bromide ion pair. 相似文献
40.
Wlodzimierz M. Tulczyjew 《Annali di Matematica Pura ed Applicata》1982,130(1):177-195
Summary
A framework for linear field theories based on the geometry of Lagrangian subspaces of symplectic spaces is formulated. Fields defined on finite compact domains and infinitesimal limits are treated in terms of de Rham currents. Field sources are included in the formulation. No distinction between elliptic and hyperbolic field equations is made. 相似文献