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51.
Antonia María Rojano‐Delgado José Ruiz‐Jiménez María Dolores Luque de Castro Rafael De Prado 《Electrophoresis》2010,31(8):1423-1430
A simple CE method for simultaneous determination of glyphosate and its metabolites (i.e. aminomethylphosphonic acid, glyoxylate, sarcosine and formaldehyde) in plants is reported here. A BGE of pH 7.5, 10% ACN, 7.5 mM phthalate, containing 0.75 mM hexadecyltrimethylammonium bromide as an electro‐osmotic flow modifier, an applied voltage of –20 kV and absorptiometric monitoring at 220 nm were the optimal chemical and instrumental parameters. The method, with development time 20 min, shows linear calibrations within the range 5–500 μg/mL (for all target analytes) with correlation coefficients between 0.999 and 0.998. It has been validated by application to samples of Lolium spp. The electroinjection mode hinders most interferents to enter the capillary, thus providing a clean electropherogram and making unnecessary long sample‐preparation steps. 相似文献
52.
Antonia M. Delgado Jeffrey S. Geronimo Plamen Iliev Yuan Xu 《Constructive Approximation》2009,30(1):71-91
The one-variable Bernstein–Szegő theory for orthogonal polynomials on the real line is extended to a class of two-variable
measures. The polynomials orthonormal in the total degree ordering and the lexicographical ordering are constructed and their
recurrence coefficients discussed.
相似文献
53.
Antonia Wilson Bluher 《Inventiones Mathematicae》1990,102(1):335-376
Oblatum 1-IV-1989 &; 27-IX-1989 相似文献
54.
A useful experimental check of the accuracy of measured lateral vorticity components is provided by comparing the vorticity-velocity cross products with the lateral derivative of the Reynolds shear stress. The check has been carried out in the self-preserving turbulent wake of a cylinder. 相似文献
55.
Measurements of the lateral components
j
(j=2 and 3) of the vorticity fluctuation vector have been made, using a vorticity probe consisting of two X-wires, in the intermediate wake of a circular cylinder. The effect of the spatial resolution of the probe on the measurement of
j has been studied. As the spatial resolution impairs, the variance and flatness factor of
j decrease whereas the skewness of
j increases. Reasonably accurate values of
j
2
can be obtained by applying spectral corrections for the spatial resolution effect.Near the beginning of the intermediate wake, the variance of
2 is larger than that of
3 due to the significant contribution from ribs which connect consecutive spanwise roll vortices. This difference decreases with downstream distance. Also, the presence of the rolls is reflected by a local extremum in the skewness of
3 on each side of the wake centerline. The magnitude of the extremum decreases with downstream distance.The support of the Australian Research Council is gratefully acknowledged. 相似文献
56.
Velocity measurements were made in two jet flows, the first exiting from a smooth contraction nozzle and the second from a long pipe with a fully developed pipe flow profile. The Reynolds number, based on nozzle diameter and exit bulk velocity, was the same (䏪,000) in each flow. The smooth contraction jet flow developed much more rapidly and approached self-preservation more rapidly than the pipe jet. These differences were associated with differences in the turbulence structure in both the near and far fields between the two jets. Throughout the shear layer for x<3d, the peak in the v spectrum occurred at a lower frequency in the pipe jet than in the contraction jet. For x́d, the peaks in the two jets appeared to be nearly at the same frequency. In the pipe jet, the near-field distributions of f(r) and g(r), the longitudinal and transverse velocity correlation functions, differed significantly from the contraction jet. The integral length scale Lu was greater in the pipe jet, whereas Lv was smaller. In the far field, the distributions of f(r) and g(r) were nearly similar in the two flows. The larger initial shear layer thickness of the pipe jet produced a dimensionally lower frequency instability, resulting in longer wavelength structures, which developed and paired at larger downstream distances. The regular vortex formation and pairing were disrupted in the shear layer of the pipe jet. The streamwise vortices, which enhance entrainment and turbulent mixing, were absent in the shear layer of the pipe jet. The formation of large-scale structures should occur much farther downstream in the pipe jet than in the contraction jet. 相似文献
57.
The effect of Reynolds number on a turbulent far-wake 总被引:1,自引:0,他引:1
The turbulent far-waked generated by a circular cylinder is investigated for two values (1350 and 4600) of the Reynolds number Re θ (based on the free stream velocity and the momentum thickness). Two arrays of sixteen X-wires, eight in the (x,?y)-plane and eight in the (x,?z)-plane, are used to capture the main features of the large-scale motion in two orthogonal planes. Both the magnitude of the measured Reynolds stresses and the size of the two-point velocity and vorticity correlation contours increase with Reynolds number. The probability density function and spectra of the velocity signals also exhibit differences with Re θ. A comparison of centerline turbulence intensities with those in the literature suggests that the Reynolds number dependence may disappear for Re θ?5000. 相似文献
58.
José Luis Martínez Vidal Antonia Garrido Frenich María M. Aguilera-Luiz Roberto Romero-González 《Analytical and bioanalytical chemistry》2010,397(7):2777-2790
Two rapid multi-residue screening methods for the determination of 21 veterinary drugs in milk by ultra-high-performance liquid
chromatography-tandem mass spectrometry (UHPLC-MS/MS) have been developed and compared. For both methods, veterinary drugs
were extracted from milk samples using a rapid extraction procedure based on the modification of the well-known QuEChERS (Quick,
Easy, Cheap, Effective, Rugged, and Safe) method, and no further clean-up steps were necessary. One screening method was based
on the selection of a characteristic neutral loss or product ion of the various families of compounds, whereas another one
was based on the choice of a selected reaction monitoring (SRM) for each compound. These methods were compared with regards
to false negatives, cut-off values and the unreliability region. The total run time for both methods was 3 min, allowing quick
selection of samples that contained veterinary drugs. Non-negative samples were re-analyzed by the UHPLC-MS/MS confirmation/quantification
method, which consisted in the monitoring of two SRM for each compound. The methods were validated according to international
guides. The proposed analytical methods allow for the identification and confirmation of the target veterinary drugs at trace
levels employing quick analysis time. 相似文献
59.
Juan Antonio Padilla-Sánchez Patricia Plaza-Bolaños Roberto Romero-González Antonia Garrido-Frenich José Luis Martínez Vidal 《Journal of chromatography. A》2010,1217(36):5724-5731
Due to the different physico-chemical properties of phenols, the development of a methodology for the simultaneous extraction and determination of phenolic compounds belonging to several families, such as chlorophenols (CPs), alkylphenols (APs), nitrophenols (NTPs) and cresols is difficult. This study shows the development and validation of a method for the analysis of 13 phenolic compounds (including CPs, APs, NTPs and cresols) in agricultural soils. For this purpose, a quick, easy, cheap, effective, rugged and safe (QuEChERS)-based procedure was developed, validated and applied to the analysis of real samples. A derivatization step prior to the final determination by gas chromatography (GC) coupled to a triple quadrupole analyzer operating in tandem mass spectrometry (QqQ-MS/MS) was performed by using acetic acid anhydride (AAA) and pyridine (Py). The optimized procedure was validated, obtaining average extraction recoveries in the range 69–103% (10 μg kg−1), 65–98% (50 μg kg−1), 76–112% (100 μg kg−1) and 76–112% (300 μg kg−1), with precision values (expressed as relative standard deviation, RSD) ≤ 22% (except for 4-chlorophenol) involving intra-day and inter-day studies. Furthermore, 15 real soil samples were analyzed by the proposed method in order to assess its applicability. Some phenolic compounds (e.g. 2,4,6-trichlorophenol or 4-tert-octylphenol) were found in the samples at trace levels (<10 μg kg−1). 相似文献
60.
Antonia Wachter-Zeh Alexander Zeh Martin Bossert 《Designs, Codes and Cryptography》2014,71(2):261-281
A new probabilistic decoding algorithm for low-rate interleaved Reed–Solomon (IRS) codes is presented. This approach increases the error correcting capability of IRS codes compared to other known approaches (e.g. joint decoding) with high probability. It is a generalization of well-known decoding approaches and its complexity is quadratic with the length of the code. Asymptotic parameters of the new approach are calculated and simulation results are shown to illustrate its performance. Moreover, an upper bound on the failure probability is derived. 相似文献