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111.
Gregory B. Kharas Wellington M. B. Barros Amira Affaneh Lujain A. Alyahya Aamir S. Ansari Matthew J. Asztalos 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(11):664-668
Novel trisubstituted ethylenes, alkyl and alkoxy ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH?C(CN)CO2C3H7 (where R is 2,3-dimethyl, 2,5-dimethyl, 2,6-dimethyl, 3,4-dimethyl, 2,3-dimethoxy, 2,4-dimethoxy, 2,5-dimethoxy, 2,6-dimethoxy 3,4-dimethoxy, 3,5-dimethoxy) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and propyl cyanoacetate and characterized by CHN elemental analysis, IR, 1H- and 13C-NMR. All the ethylenes were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR, GPC, DSC, and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (0.6–5.0% wt.), which then decomposed in the 500–800°C range. 相似文献
112.
A. Stute B. Casabone B. Brandstätter D. Habicher H. G. Barros P. O. Schmidt T. E. Northup R. Blatt 《Applied physics. B, Lasers and optics》2012,107(4):1145-1157
We demonstrate several building blocks for an ion–photon interface based on a trapped 40Ca+ ion in an optical cavity. We identify a favorable experimental configuration and measure system parameters, including relative motion of the trapped ion and the resonator mode. A complete spectrum of cavity-assisted Raman transitions between the 42S1/2 and 32D5/2 manifolds is obtained. On two of these transitions, we generate orthogonally polarized cavity photons, and we demonstrate coherent manipulation of the corresponding pair of atomic states. Possible implementations of atom-photon entanglement and state mapping within the ion-cavity system are discussed. 相似文献
113.
114.
A Michael addition reaction of cyclic ketones and piperidones to a vinyl phosphonate is described. The reaction, catalyzed by chiral diamines, produced geminal γ-oxobisphosphonates in high yields (up to 92%) and very high ees (up to >99%). Disubstituted ketones gave drs of up to 8?:?92. The synthesis and characterization of several new compounds with potential biological activity is described. 相似文献
115.
ET da Costa CA Neves GM Hotta DT Vidal MF Barros AA Ayon CD Garcia CL do Lago 《Electrophoresis》2012,33(17):2650-2659
This paper describes a long-range remotely controlled CE system built on an all-terrain vehicle. A four-stroke engine and a set of 12-V batteries were used to provide power to a series of subsystems that include drivers, communication, computers, and a capillary electrophoresis module. This dedicated instrument allows air sampling using a polypropylene porous tube, coupled to a flow system that transports the sample to the inlet of a fused-silica capillary. A hybrid approach was used for the construction of the analytical subsystem combining a conventional fused-silica capillary (used for separation) and a laser machined microfluidic block, made of PMMA. A solid-state cooling approach was also integrated in the CE module to enable controlling the temperature and therefore increasing the useful range of the robot. Although ultimately intended for detection of chemical warfare agents, the proposed system was used to analyze a series of volatile organic acids. As such, the system allowed the separation and detection of formic, acetic, and propionic acids with signal-to-noise ratios of 414, 150, and 115, respectively, after sampling by only 30 s and performing an electrokinetic injection during 2.0 s at 1.0 kV. 相似文献
116.
A direct boundary element method (BEM) implementation for the dynamic interaction analysis in the frequency domain of 2D rigid structures with elastic orthotropic media is presented. The BEM implementation is based on non-singular full-space influence functions. The rigid structure response is obtained by applying equilibrium and kinetic compatibility conditions. The method is applied to the analysis of the dynamic response of a rigid tunnel in a half-space with various elasticity principal axes inclinations and to the analysis of two rigid rectangular galleries in a half space with various distances between them. 相似文献
117.
M. Alves Marques M. I. de Barros Marques M. Isabel Cabao A. M. Gaspar M. L. de Almeida 《Journal of Molecular Liquids》2004,110(1-3):23-31
Concentrated aqueous solutions of copper nitrate of different concentrations (0.66 mol dm−3 up to 4.84 mol dm−3) have been investigated by X-ray diffraction at room temperature. In these solutions a maximum of intensity (prepeak) is observed at low values of Q (approx. 0.6 to 1 Å−1) suggesting the existence of an intermediate range order in their structure, in agreement with previous investigations on different electrolytes. In order to get information on the solvation shell of the copper cation, Raman spectroscopy experiments have been performed for the more concentrated solution. Polarization observations, isotopic substitution of the solvent and the comparison with a Raman spectrum of a concentrated aqueous solution of aluminum nitrate were performed in order to improve the interpretation of the obtained results with these convergent observations. 相似文献
118.
The influence of pre-adsorbed H and O on the adsorption and decomposition of methanol-d4 on Ru(0 0 1) surfaces is analysed by RAIRS. It is shown that the reactivity of CD3OD at 90 K is not determined by the nature of the modifying atom nor by the structure of the pre-adsorbed layer: a low dose of CD3OD (0.1 L) undergoes O-D bond breaking, yielding CD3O-, both on Ru(0 0 1)-H (0.5 ? θH < 1 ML) and on Ru(0 0 1)-O (0.25 ? θO ? 0.6 ML) surfaces. At 90 K, methoxide-d3 acquires a tilted configuration on all these surfaces, despite the fact that oxygen forms ordered phases whereas hydrogen (adsorbed at this temperature) does not. A fraction of the methoxide-d3 undergoes C-D bond breaking at 110 K on all the modified surfaces, in a lower extent than on clean Ru(0 0 1). The stabilizing effect is more pronounced on the O modified layers, and is coverage dependent. The chemical nature of the pre-adsorbed atom is determinant of the unreacted methoxide geometry, as only oxygen is capable of inducing a reorientation of this species towards C3v local symmetry. Confirmation of the adsorption geometries, both at 90 and 110 K, was obtained from the RAIR spectra of the selectively labelled CHD2OH, adsorbed on the same surfaces. The long-range repulsive interactions between the pre-adsorbed atom and the final decomposition product at 130 K (carbon monoxide) are more evident on the denser O layer (0.6 ML), since this species does not remain on the surface. No partially hydrogenated intermediates were detected on the H modified surfaces, suggesting that, in case exchange reactions occur, they yield only gaseous products. On the contrary, direct evidence for the participation of pre-adsorbed O was supplied by the detection of deuterated formate (DCOO) for θO = 0.6 ML. 相似文献
119.
C. C. Barros Jr. M. R. Robilotta 《The European Physical Journal C - Particles and Fields》2006,45(2):445-450
We estimate, by means of a model, the long-range part of the hyperon scalar form factors and their contribution to the pion-hyperon
sigma term. 相似文献
120.
A. M. Gaspar M. Alves Marques M. I. Cabao M. I. de Barros Marques T. Buslaps V. Honkimaki 《Journal of Molecular Liquids》2004,110(1-3):15-22
Concentrated aqueous solutions of calcium chloride and calcium bromide have been investigated by X-ray diffraction. In the diffraction patterns of aqueous chloride solutions of different concentrations, a maximum of intensity is observed in the region 0.6–1.1 Å−1, while in the investigated aqueous bromide solution no maximum is observed in that region. This pre-peak suggests the existence of positional correlations in solution beyond direct contact. The interpretation is similar to the one proposed by the authors in previous investigations, and is supported by the calculations based on ad hoc molecular models. The influence of the anion is discussed. 相似文献