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991.
Carmen Ibáñez-Palomino J. Fermín López-Sánchez 《International journal of environmental analytical chemistry》2013,93(7):909-921
A systematic study of Hg2+ and CH3Hg+ (MeHg+) speciation using hyphenated techniques, was performed for high-performance liquid chromatography coupled to on-line UV irradiation and cold-vapour atomic fluorescence spectroscopy (HPLC-UV-CV-AFS). First, a comparative study of the behaviour of three mobile phase compositions (using tetrabutylammonium bromide (TBAB), L-cysteine and ammonium pyrrolidinedithiocarbamate (APDC)) is presented. The separation and detection system was optimised by considering factors that modify fluorescence signal and the separation such as, the addition of different percentages of an organic modifier (methanol (MeOH) and acetonitrile (ACN)) to the mobile phase, the type of reducing agent used (SnCl2 and NaBH4) and the potential memory effects of the material of which the injection system is made (stainless steel, PEEK). The mobile phase selected for its sensitivity was a mixture 80?:?20 MeOH?:?0.0015?mol?l–1 APDC and 0.01?mol?l–1 NH4CH3COO (pH 5.5). The detection and quantification limits were close to 1.5 and 5?µg?l?1 for both species (as Hg), respectively. Recoveries obtained using fortified water samples of distinct origin (soft mineral, tap, river, seawater, and wastewater), ranged from 90 to 115% for concentrations about 2 and 20 times over quantification limits. Good repeatability was obtained (about 5%) independently of the concentrations, with reproducibility values about 20% at low concentrations and 5–10% at higher concentrations. Our proposed method proved to be straightforward for use by environmental laboratories for routine Hg2+ and MeHg+ determinations in polluted water samples. 相似文献
992.
993.
Collective behaviours can be observed in both natural and man-made systems composed of a large number of elemental subsystems. Typically, each elemental subsystem has its own dynamics but, whenever interaction between individuals occurs, the individual behaviours tend to be relaxed, and collective behaviours emerge. In this paper, the collective behaviour of a large-scale system composed of several coupled elemental particles is analysed. The dynamics of the particles are governed by the same type of equations but having different parameter values and initial conditions. Coupling between particles is based on statistical feedback, which means that each particle is affected by the average behaviour of its neighbours. It is shown that the global system may unveil several types of collective behaviours, corresponding to partial synchronisation, characterised by the existence of several clusters of synchronised subsystems, and global synchronisation between particles, where all the elemental particles synchronise completely. 相似文献
994.
O. Pottiez Author Vitae B. Ibarra-Escamilla Author Vitae Author Vitae R. Grajales-Coutiño Author Vitae Author Vitae 《Optics & Laser Technology》2010,42(2):403-408
In this paper we study theoretically and experimentally a wavelength-tuneable Sagnac birefringence filter. The device is a Sagnac interferometer including a symmetric fibre coupler and a length of high-birefringence fibre in the loop. A wave retarder is inserted at each end of the birefringent fibre for absolute wavelength tuning. We show theoretically that wavelength tuning through wave plate orientation ensuring constant amplitude of the filtering function is possible only if a minimum of two wave retarders are included in the setup. The position of the transmission peaks then varies linearly with the angle of one of the retarders and can be adjusted over one entire channel spacing. This happens only when a quarter-wave retarder and a half-wave retarder are used, if the former is oriented at 45° with respect to the fibre birefringence axes, while the orientation of the latter serves as the adjustment parameter. The theoretical predictions are confirmed by the experimental results. 相似文献
995.
A.?Spad?o E.?Otón R.?D?browski M.??urowska J.?M.?Otón N.?Bennis 《Opto-Electronics Review》2010,18(2):219-222
Electrooptical properties of several new orthoconic antiferroelectric liquid crystal mixtures with partially fluorinated alkoxyalkoxy
terminal chains have been investigated in order to select the best mixture for display applications. Electrooptical studies
have been performed on these orthoconic materials aiming at evaluating their static and dynamic performance under passive
multiplexing conditions. A number of parameters have been evaluated, static and dynamic contrast, driving scheme for passive
multiplexing, rise and fall response times, dynamic range, and dynamic greyscale. 相似文献
996.
Physical phantoms used for the calibration of in vivo measurement equipments represent an approximate geometry of the body and usually contain a uniform distribution of radionuclides in the organ of interest. Numerical voxel phantoms allow an improvement of the calibration method by means of a more realistic definition of the phantom and the source. The distribution of the activity in the tissues evolves with time and it can be estimated by solving the specific biokinetic model of the radionuclide. Those results of predicted activity retained in the compartments of the model can be translated into the organs of a voxel phantom to be used as the source of radiation for a Monte Carlo radiation transport code. In this way, different patterns of contamination, according to different times after the intake, can be modelled and appropriate detection efficiencies can be obtained. In particular, it is studied the influence of the skeletal contribution in lung measurements in the in vivo assessment of 241Am. 相似文献
997.
998.
K. Esquivel Ma. G. García J. F. J. Rodríguez M. Vega González L. Escobar-Alarcón Luis Ortiz-Frade Luis A. Godínez 《Journal of nanoparticle research》2011,13(8):3313-3325
This study presents the synthesis of TiO2 doped with different amounts of Co and Ni, starting from a simple metallic titanium powder. A successful electrophoretic
deposition of these materials on ITO electrodes was achieved for its potential application as photoanodes. EDX, diffuse reflectance
UV–Vis spectroscopy, and XRD measurements gave information on the chemical composition of the material and the location of
the Ni or Co within the crystal structure of TiO2. Raman spectroscopy suggests that for a higher content of doping metal above a defined percentage, the formation of metal
oxide is promoted. A preliminary study of photoelectrocatalytic orange dye degradation shows higher color removal efficiency
as compared to the commercial TiO2 material. 相似文献
999.
New cyclic 2,3‐sulfite ester derivatives of poststerone—Discriminating diastereomers and probing spatial proximities by NMR and DFT calculations 下载免费PDF全文
1000.
Alejandro J. González Fá Isabella Cerutti Valeria Springer Stefano Girotti María E. Centurión María S. Di Nezio Marcelo F. Pistonesi 《Chromatographia》2017,80(9):1459-1466
The development of methodologies for the characterization of silver nanoparticles (AgNPs) synthesized using natural products has received increasing attention, especially to monitoring its stability and size for further application. In this paper, a capillary electrophoretic (CE) method is presented for characterization of AgNPs synthesized using honey or glucose as reducing agents. A simple electrolyte solution composed of 20 mM sodium borate and 20 mM sodium dodecylsulfate (SDS) at pH 8.5 was used for separation of AgNPs within a short analysis time (<12 min). The obtained results were compared with the traditional characterization techniques, such as transmission electron microscopy (TEM) and dynamic light scattering (DLS), showing satisfactory correlation in terms of size distribution. In addition, valuable information about electrophoretic mobility and zeta potential values of AgNPs was obtained by applying the CE-UV/Vis method. Thus, the proposed methodology represents a straightforward tool for the fast and cost-effective characterization of AgNPs within a single analysis, employing minimal amounts of reagents and samples. 相似文献