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1.
Journal of Solid State Electrochemistry - UV/Vis absorption spectroelectrochemistry is a very promising analytical technique due to the complementary information that is simultaneously obtained... 相似文献
2.
Applications of capillary electrophoresis to the determination of antibiotics in food and environmental samples 总被引:1,自引:0,他引:1
Ana M. García-Campaña Laura Gámiz-Gracia Francisco J. Lara Monsalud del Olmo Iruela Carmen Cruces-Blanco 《Analytical and bioanalytical chemistry》2009,395(4):967-986
In this paper we review applications of capillary electrophoresis (CE) to the determination of antibiotic residues in food
derived from animals and in environmental samples. Although many CE methods have been used to determine antibiotics in the
pharmaceutical field (drug quality control or therapeutic monitoring in biological samples), food and environmental applications
have been increasing in recent years. Due to the maximum residue limits established by the EU, in Directive 2377/90/EEC, for
foodstuffs of animal origin and considering the low levels that can be found in environmental or waste waters or soils, different
strategies to increase sensitivity have been developed, including off-line preconcentration, on-line stacking modes to use
higher sample volumes, or in-line solid-phase extraction. Also, several detection techniques, such as fluorescence, laser-induced
fluorescence, electrochemical detection, or mass spectrometry have been used; the last of these also enables unequivocal identification
of the residues, required by Commission Decision 2002/657/EC. All these aspects will be discussed in this paper, in relation
to the main groups of antibiotics used in veterinary and human medicine, for which applications in food and environmental
samples have been developed by using CE as an efficient alternative to liquid chromatography. 相似文献
3.
We construct the induced representations of the null-plane quantum Poincaré and quantum kappa Galilei algebras in (1+1) dimensions. The induction procedure makes use of the concept of module and is based on the existence of a pair of Hopf algebras with a nondegenerate pairing and dual bases. 相似文献
4.
In this paper, we propose a two-phased local search for vertex coloring. The algorithm alternately executes two closely interacting functionalities, i.e., a stochastic and a deterministic local search. The stochastic phase is basically based on biased random sampling that, according to a probability matrix storing the probability a vertex can be assigned to a color, iteratively constructs feasible colorings. The deterministic phase, instead, consists in assigning sequentially, according to a given ordering, each vertex to the color which causes the lowest increase of the solution penalty, and then, when the schedule is constructed, swap operations are executed to improve the performance. The interaction between the two phases is implemented by tunnelling information of what happened during a phase to the successive ones. Beyond the algorithm scheme, the novelty of the approach stems from the fact that the objective function is not minimizing the number of colors but a new penalty function. The proposed approach is tested on known benchmarks for the studied problem available on the public domain. From a comparison to the state of the art it appears that the proposed approach is robust and is able to achieve best known results. 相似文献
5.
The discrete heat equation is worked out to illustrate the search of symmetries of difference equations. Special attention
it is paid to the Lie structure of these symmetries, as well as to their dependence on the derivative’s discretization. The
case ofq-symmetries for discrete equations in aq-lattice is briefly considered at the end.
Talk delivered by J. Negro at the DI-CRM Workshop held in Prague, 18–21 June 2000.
This work has been partially supported by DGES of the Ministerio de Educación y Cultura of Spain under Projects PB98-0360
and the Junta de Castilla y León (Spain). 相似文献
6.
We discuss a fundamental characteristic of orthogonal polynomials, like the existence of a Lie algebra behind them, which can be added to their other relevant aspects. At the basis of the complete framework for orthogonal polynomials we include thus–in addition to differential equations, recurrence relations, Hilbert spaces and square integrable functions–Lie algebra theory. 相似文献
7.
Jos María Miguel del Corral Marina Gordaliza Jos-Luis Lpez Esther Del Olmo M. Angeles Castro M. Luisa Lpez 《Helvetica chimica acta》1995,78(7):1793-1796
The configuration of several keto-cyclolignans related to podophyllotoxin has been reviewed. Under basic catalysis, the configuration at the C-atom in α-position to the lactone carbonyl group in podophyllotoxone is inverted instead of the C-atom in α-position to the ketone group, as it has been reported. 相似文献
8.
Bailón-Pérez MI García-Campaña AM Cruces-Blanco C Del Olmo Iruela M 《Electrophoresis》2007,28(22):4082-4090
A method for the simultaneous determination of eight beta-lactam antibiotics (nafcillin, cloxacillin, oxacillin, dicloxacillin, ampicillin, amoxicillin, and penicillin G) in fortified milk samples of different origins has been proposed by using CZE with diode-array detection (CZE-DAD). Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using 175 mM Tris buffer with 20% ethanol at pH 8.0. Methylparaben has been used as an internal standard (IS). Taking into account the lack of sensitivity of the UV-Vis detection, a solvent extraction/SPE method was applied for off-line preconcentration and sample cleanup, and also an on-line preconcentration methodology, such as large-volume sample stacking (LVSS) with polarity switching, was developed, providing LODs ranging from 2 to 10 microg/L. The method permits the quantification of these residues below the levels established in milk by the EU Regulation. Satisfactory recoveries ranging from 86 to 93% were also obtained in milk samples of different origins. 相似文献
9.
F.J. Olmo A. Quirantes A. Alcntara H. Lyamani L. Alados-Arboledas 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):305-314
There is experimental evidence that the non-sphericity of certain atmospheric particles can cause scattering properties different from those predicted by standard Mie theory. Numerous studies indicate the need to consider the presence of non-spherical particles in modeling the optical properties of atmospheric aerosols. On the other hand, natural aerosols show a great variety of shapes, making difficult a realistic choice of a particle shape (or shape mixture) model. In this paper, we test a parameterization of the particle shape in the retrieval of size distribution, phase function, single scattering albedo and asymmetry parameter from direct and sky-radiance measurements. For this purpose we have substituted the Kernel based on the Mie theory included in the model SKYRAD.PACK by one derived for non-spherical particles. The method is applied under different atmospheric conditions, including Saharan dust outbreak, polluted and local mineral episodes. We compare the results with those obtained by the well known spheroids algorithm used in the AERONET network. 相似文献
10.
The exponential blueshift associated with the event horizon of a black hole makes conformal symmetry play a fundamental role in accounting for its thermal properties. Using a derivation based on two-point functions, we show that the full spectrum of thermal radiation of scalar particles by Kerr black holes can be explicitly derived on the basis of a conformal symmetry arising in the wave equation near the horizon. The simplicity of our approach emphasizes the depth of the connection between conformal symmetry and black hole radiance. 相似文献