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31.
A simple and miniaturized approach based on ultrasound-assisted emulsification-derivatization is proposed for the determination of nitrite in cosmetic samples by UV-vis micro-spectrophotometry. Oil/water emulsions were formed using 15 mg of cosmetic sample and 1 mL of an aqueous medium containing 0.5% w/v SDS and 1% v/v acetic acid. When powerful sonication systems were used to make emulsions, i.e. probe or cup-horn sonoreactor, stable and transparent emulsions were obtained in one or half minute per sample, respectively. The Griess reaction in these special conditions (i.e. sonication and the presence of an organized medium) was investigated. The absence of matrix effects allows external calibration with aqueous standards for nitrite quantification. Analytical features were compared to those of the European official method 82/434/EEC. Detection limit, sample throughput and reagent consumption were significantly improved. 相似文献
32.
Casitas A Poater A Solà M Stahl SS Costas M Ribas X 《Dalton transactions (Cambridge, England : 2003)》2010,39(43):10458-10463
Well-defined aryl-Cu(III)-halide species undergo reductive elimination upon acid addition resulting in the formation of strong aryl-halide bonds. The computationally studied mechanism points towards ligand protonation as the rate-determining step, in agreement with previous experimental data. 相似文献
33.
Shen NH Massaouti M Gokkavas M Manceau JM Ozbay E Kafesaki M Koschny T Tzortzakis S Soukoulis CM 《Physical review letters》2011,106(3):037403
We experimentally demonstrate, for the first time, an optically implemented blueshift tunable metamaterial in the terahertz (THz) regime. The design implies two potential resonance states, and the photoconductive semiconductor (silicon) settled in the critical region plays the role of intermediary for switching the resonator from mode 1 to mode 2. The observed tuning range of the fabricated device is as high as 26% (from 0.76 THz to 0.96 THz) through optical control to silicon. The realization of broadband blueshift tunable metamaterial offers opportunities for achieving switchable metamaterials with simultaneous redshift and blueshift tunability and cascade tunable devices. Our experimental approach is compatible with semiconductor technologies and can be used for other applications in the THz regime. 相似文献
34.
Benjamin Assel Kyriakos Christodoulides Alon E. Faraggi Costas Kounnas John Rizos 《Nuclear Physics B》2011
We extend the classification of free fermionic heterotic-string models to vacua in which the SO(10) GUT symmetry is broken at the string level to the Pati–Salam subgroup. Using our classification method we recently presented the first example of a quasi-realistic heterotic-string vacuum that is free of massless exotic states. Within this method we are able to derive algebraic expressions for the Generalised GSO (GGSO) projections for all sectors that appear in the models. This facilitates the programming of the entire spectrum analysis in a computer code. The total number of vacua in the class of models that we classify is 251∼1015. We perform a statistical sampling in this space of models and extract 1011 GGSO configurations with Pati–Salam gauge group. Our results demonstrate that one in every 106 vacua correspond to a three generation exophobic model with the required Higgs states, needed to induce spontaneous breaking to the Standard Model. 相似文献
35.
Kyriaki S. Pafiti Costas S. Patrickios Clarissa Abetz Volker Abetz 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):4957-4965
High‐molecular‐weight (MW) symmetrical multiblock copolymers, based on the hydrophobic monomers styrene (Sty) and methyl methacrylate (MMA), and the more polar monomer, 2‐vinyl pyridine (2VPy), were prepared using stepwise reversible addition‐fragmentation chain transfer polymerization. All copolymers shared a common poly(ethylene glycol) (PEG) midblock, introduced as a bifunctional macromolecular chain transfer agent. In total, five ABA triblock copolymers, five ABCBA pentablock terpolymers, and two ABCDCBA heptablock quaterpolymers (comprising four different monomer types) were synthesized. The MWs of the multiblock polymers were determined using gel permeation chromatography (GPC) and proton nuclear magnetic resonance (1H NMR) spectroscopy, with the latter values being closer to the theoretically expected, whereas GPC MW distributions were relatively narrow, broadening with the number of blocks. The compositions of the synthesized polymers, as determined by 1H NMR spectroscopy, were also close to the expected values. Finally, films cast from chloroform solutions of the pentablock terpolymers P2VPy‐b‐PSty‐b‐PEG‐b‐PSty‐b‐P2VPy, PSty‐b‐PMMA‐b‐PEG‐b‐PMMA‐b‐PSty, and P2VPy‐b‐PMMA‐b‐PEG‐b‐PMMA‐b‐P2VPy examined using transmission electron microscopy exhibited PSty and PMMA cylinders (first two) and lamellae (third terpolymer). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4957–4965 相似文献
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Farooq A. Khanday Costas Psychalinos Nisar A. Shah 《Circuits, Systems, and Signal Processing》2013,32(3):959-978
Square-root-domain (SRD) CMOS analog realization of a single cell architecture of the complex Temporal Derivative Cellular Neural Networks (TDCNNs) is introduced in this paper. TDCNN initiates time derivative ‘diffusion’ between CNN cells for non-separable spatiotemporal filtering applications, where the input to the CNN is an image that changes over time. The evaluation of the performance of the complex SRD TDCNN cell has been done using the Cadence Orcad software with TSMC 0.18-μm CMOS process model parameters. The provided simulated results confirm the validity of the theory. 相似文献
39.
Francesco dellIsola Emilio Turco Anil Misra Zacharias Vangelatos Costas Grigoropoulos Vasileia Melissinaki Maria Farsari 《Comptes Rendus Mecanique》2019,347(5):397-405
In this paper, we reveal that the mathematical discrete model of Hencky type, introduced in [1], is appropriate for describing the mechanical behavior of micro-metric pantographic elementary modules. This behavior does not differ remarkably from what has been observed for milli-metric modules, as we prove with suitably designed experiments. Therefore, we conclude that the concept of pantographic microstructure seems feasible for micro-metrically architected microstructured (meta)materials as well. These results are particularly indicative of the possibility of fabricating materials that can have an underlying pantographic microstructure at micrometric scale, so that its unique behavior can be exploited in a larger range of technological applications. 相似文献
40.
Georgiadis C Moultos O Gergidis LN Vlahos C 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):835-842
The micellization behavior of hybrid dendritic-star copolymers with solvophilic dendritic units is studied by means of Brownian dynamics simulations. The critical micelle concentration and the micelle size and shape are examined for different solvophobic/solvophilic ratios r as a function of the number of the dendritic and linear arms. Hybrid dendritic-star copolymers with one dendritic and up to three solvophobic linear branches form spherical micelles with preferential aggregation number. Those with two dendritic arms and three solvophobic branches form micelles with wide aggregation numbers only for small values of r. For hybrid dendritic-star copolymers with three dendritic arms and two or three solvophobic linear arms, micelles with wide aggregation numbers are also formed but for slightly higher values of r. Our results for the aggregation number are compared with existing results of other architectures obtained at the same temperature, and an inequality for the aggregation number is proposed. 相似文献