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581.
Ragno G Risoli A De Luca M Ioele G Oliverio F 《Analytical and bioanalytical chemistry》2007,389(3):923-929
A novel analytical technique able to determine the anti-ischemic drug trapidil in human serum and urine is proposed. In order
to achieve satisfactory sensitivity and selectivity, an extraction procedure was required to isolate the drug from complex
matrixes such as serum and urine. A solid-phase extraction procedure was investigated to both increase the analyte concentration
and eliminate the interfering molecules present in large amounts in both matrixes. Optimization of the extraction step was
realized by selecting a new polymeric sorbent based on a surface-modified styrene–divinylbenzene polymer which provided fast
and efficient drug extraction. Drug quantification was performed by using the third-order derivative spectra of the SPE eluates.
Absorbance specific signals at 3D335,316 and 3D316 nm for urine and serum, respectively, were demonstrated to be directly proportional to drug concentration and barely affected
by residual matrix interferences. Under the optimized experimental conditions the calibration plots were linear over the concentration
range 0.2–50 μg mL−1. The method was validated by analysis of a series of spiked samples. Accuracy (recovery of 95 and 94% for serum and urine,
respectively) and precision (RSD below 4%) were good.
Figure Assay of Trapidil in biological fluids by SPE and derivative spectrophotometry 相似文献
582.
A homogenization procedure for finding the bending stiffness of a 2D regular lattice with random local interactions is proposed. The kinematic and static methods are used to provide explicit upper and lower bounds for the homogenized moduli. The proposed homogenization procedure is applied to a masonry obtained by a random perturbation of the periodic running bond masonry [Cecchi, A., Sab, K., 2009. Discrete and continuous models for in plane loaded random elastic brickwork. Eur. J. Mech. A 28, 610–625].A numerical evaluation of the scatter between the discrete models and the 2D Love–Kirchhoff model is performed on a test case, for various values of the random perturbation parameter and of the parameter that characterizes the heterogeneity of the wall. As expected, when the number of heterogeneities in the structure is large enough, the average response of the random discrete model converges to an asymptotic response. It is shown that this asymptotic response is very close to that of the periodic discrete model which is in turn very close to the response of the deterministic homogenized model. Similarly to the conclusion of Cecchi and Sab [Cecchi A., Sab K., 2009. Discrete and continuous models for in plane loaded random elastic brickwork. Eur. J. Mech. A. 28, 610–625.] dedicated to in-plane loading, the present results concerning out-of-plane loading show (both by means of a discrete model and a homogenized model) that the running bond pattern may be used successfully to analyze historical masonries with blocks having irregular widths in the horizontal direction. 相似文献
583.
584.
A complete 160 Gbit/s single-channel OTDM system experiment is presented. The OTDM system includes all-optical transmitter, 3R (Retiming, Reshaping, and Reamplification), and receiver. Performance measurements of the single subsystems are also reported. Finally Q-factor measures verify the effectiveness of the whole system. 相似文献
585.
Antonella Capperucci Alessandro Degl'InnocentiSimona Biondi Tiziano NocentiniGiuseppe Rinaudo 《Tetrahedron letters》2003,44(14):2831-2835
Treatment of different silylated allenes with hexamethyldisilathiane (HMDST) in the presence of CoCl2·6H2O affords an easy and high yielding access to α,β-unsaturated thioacylsilanes, which undergo a self-dimerization reaction to afford polyfunctionalized 1,2-dithiins as the major products. 相似文献
586.
587.
We present new, explicit, volume-preserving splitting methods for polynomial divergence-free vector fields of arbitrary degree (both positive and negative). The main idea is to decompose the divergence polynomial by means of an appropriate basis for polynomials: the monomial basis. For each monomial basis function, the split fields are then identified by collecting the appropriate terms in the vector field so that each split vector field is volume preserving. We show that each split field can be integrated exactly by analytical methods. Thus, the composition yields a volume preserving numerical method. Our numerical tests indicate that the methods compare favorably to standard integrators both in the quality of the numerical solution and the computational effort. 相似文献
588.
The aim of this paper is to establish the existence of at least two non-zero ho-moclinic solutions for a nonlinear Laplacian difference equation without using A... 相似文献
589.
Francesca Lionetto Antonella Tarzia Miriam Coluccia Alfonso Maffezzoli 《Macromolecular Symposia》2007,247(1):50-58
Air-coupled ultrasound in one-side transmission mode has been applied to monitor the curing process of an unsaturated polyester resin, commonly used as a matrix in glass reinforced composites. The evolution of the resin mechanical properties during cure has been measured from the variation of longitudinal velocity. The technique has demonstrated to be a very powerful tool for detecting the structural changes occurring at gelation and vitrification. The no-contact ultrasonic results have been compared with those obtained using conventional contact ultrasonic measurements, characterized by direct coupling between the transducer and the resin, and with the rheological measurements. The good agreement among the results of the different techniques demonstrates the reliability of air-coupled ultrasound in monitoring the changes of viscoelastic properties occurring during the cure of thermosetting polymers. A further advantage of the proposed one-side ultrasonic technique is the absence of physical contact between the transducers and the sample, which is relevant during composite manufacturing, where probe contact could adversely affect the part quality or access from both sides is not practicable. No-contact ultrasonic cure monitoring is suitable for both stationary and moving liquid or solid samples in several process conditions such as moulding, filament winding, etc., opening the way to new applications of ultrasound in the composite industry. 相似文献
590.
Solid-phase microextraction (SPME), using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber, interfaced with liquid chromatography-fluorescence detection (LC-FD) has been applied to the determination of Ochratoxin A (OTA) in wine samples. Compared to the most widely adopted extraction/clean-up procedure based on immunoaffinity columns (IAC), the solventless extraction is simpler and cost-effective, requiring the simple immersion of the fiber in diluted wine samples. Furthermore, a fast LC separation is achieved under isocratic conditions. The linear range investigated in wine was 0.25-8 ng/mL; at fortification levels of 0.5 and 2 ng/mL, within-day intra-laboratory precision (repeatability) values, expressed as RSD%, were 5.9 and 5.1, respectively, whereas between days (n = 4) precision was 8.5 and 7.1%, respectively. The limit of detection (LOD) at a signal-to-noise (S/N) ratio of 3 was 0.07 ng/mL; the limit of quantification (LOQ) calculated at S/N = 10 was 0.22 ng/mL, well below the European regulatory level of 2 ng/mL. The potential of the method has been demonstrated by the analysis of a number of different wine samples. 相似文献