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91.
(Na0.5K0.5)NbO3 (KNN)-modified nano-particulated powders, based on variations of sodium–potassium niobate, were synthesised by solid state
reaction from carbonate starting materials. The nanoparticles were attained by an optimization of the raw materials particle
size and particle refinement of the carbonates during their decomposition. Particle sizes between 50 and 200 nm have been
obtained as a function of calcination (decomposition) temperature. The obtained powders showed a co-existence between a tetragonal
phase and an orthorhombic phase. The optimization of the raw materials particle size and the particle refinement of the carbonates
during their decomposition play a key role in the formation of the KNN-modified nano particles. The developed method is well
suited for the production of KNN-modified nano powders at low cost for mass production. 相似文献
92.
Palladium-catalyzed [2 + 2 + 2] cycloaddition reactions of 3,4-didehydrophenanthrene (3,4-phenanthryne) and 1,2-didehydrotriphenylene (1,2-triphenylyne) afford sterically congested polycyclic aromatic hydrocarbons with novel structures. 相似文献
93.
J. Sanmartín M. R. Bermejo J. A. García-Vázquez J. Romero A. Sousa J. Strähle A. Brodbeck 《Transition Metal Chemistry》1993,18(2):187-190
Summary The electrochemical oxidation of anodic metal (nickel or cobalt) in MeCN solutions of 1-hydroxy-2-pyridinethione (HPT) gives [Ni(PT)2], [Co(PT)2] or [Co(PT)3]. When 1,10-phenanthroline (phen) or 2,2-bipyridine (bipy) are added to the electrolytic phase the product is a complex, [Ni(PT)2L] or [Co(PT)2L] (L = bipy or phen). The i.r., u.v. and 1H- and 13C-n.m.r. spectra of the complexes are discussed.This paper was presented at the 5th Inorganic Chemistry Meeting of the Royal Spanish Chemical Society, Tossa de Mar, Girona, Spain, September 1991. 相似文献
94.
The osmotic coefficients of acetamide, propionamide and butyramide in water were measured at 293.15, 298.15 and 308.15 K using
the isopiestic method. The activity coefficients were calculated for the aliphatic amides and the pairwise free energy coefficients
for solute-solute interactions were determined according to the McMillan-Mayer theory. The osmotic and activity coefficients
of amides are discussed in terms of solute-solute interactions. 相似文献
95.
An anodic stripping voltammetric method was developed in order to determine copper in the water used to prepare haemodialysis solutions. The interference from organic matter was overcome by high-pressure bomb mineralization. The electrochemical results were compared with those obtained by using graphite furnace atomic absorption spectrometry and the correlation was excellent (r = 0.983, p < 0.001). The detection limit was 0.2 μg l?1 copper. 相似文献
96.
Claudia Giovagnoli-Vicua Vilbett Briones-Labarca María Soledad Romero Ady Giordano Sebastin Pizarro 《Molecules (Basel, Switzerland)》2022,27(13)
The extraction of bioactive compounds from fruits, such as lemon, has gained relevance because these compounds have beneficial properties for health, such as antioxidant and anticancer properties; however, the extraction method can significantly affect these properties. High hydrostatic pressure and ultrasound, as emerging extraction methods, constitute an alternative to conventional extraction, improving extractability and obtaining extracts rich in bioactive compounds. Therefore, lemon extracts (LEs) were obtained by conventional (orbital shaking), ultrasound-assisted, and high-hydrostatic-pressure extraction. Extracts were then microencapsulated with maltodextrin at 10% (M10), 20% (M20), and 30% (M30). The impact of microencapsulation on LEs physicochemical properties, phenolics (TPC), flavonoids (TFC) and relative bio-accessibility (RB) was evaluated. M30 promoted a higher microencapsulation efficiency for TPC and TFC, and a longer time required for microcapsules to dissolve in water, as moisture content, water activity and hygroscopicity decreased. The RBs of TPC and TFC were higher in microcapsules with M30, and lower when conventional extraction was used. The data suggest that microencapsulated LE is promising as it protects the bioactivity of phenolic compounds. In addition, this freeze-dried product can be utilized as a functional ingredient for food or supplement formulations. 相似文献
97.
A binary relation R does not always possess the desirable property of transitivity. Consequently, this needs to be imposed artificially by deviating
as little as possible from R. In this paper, three approaches to transitive approximation are analyzed within a common distance-based framework: exterior
(transitive closure), interior (openings or maximal transitive sub-relations contained in R) and mixed (transitive fittings) approximation. Additionally, we propose a method for obtaining all these transitive approximations.
The method is based on a distance function optimization framework that leads to straightforward goal programming models. 相似文献
98.
We present a complete analysis of the set of homogeneous and isotropic cosmological solutions generated by a vector field coupled nonminimally to gravity. As a consequence of this analysis we can interpret our universe as (classical) fluctuations in the infinite past of unstable Minkowskian space-time. 相似文献
99.
Tarun Gheyi Logan Rodgers Richard Romero J. Michael Sauder Stephen K. Burley 《Journal of the American Society for Mass Spectrometry》2010,21(10):1795-1801
A strategy for increasing the efficiency of protein crystallization/structure determination with mass spectrometry has been
developed. This approach combines insights from limited proteolysis/mass spectrometry and crystallization via in situ proteolysis.
The procedure seeks to identify protease-resistant polypeptide chain segments from purified proteins on the time-scale of
crystal formation, and subsequently crystallizing the target protein in the presence of the optimal protease at the right
relative concentration. We report our experience with 10 proteins of unknown structure, two of which yielded high-resolution
X-ray structures. The advantage of this approach comes from its ability to select only those structure determination candidates
that are likely to benefit from application of in situ proteolysis, using conditions most likely to result in formation of
a stable proteolytic digestion product suitable for crystallization. 相似文献
100.
E. T. Romero Guzmán M. V. Esteller Alberich E. Ordoñez Regil 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(3):509-517
Phosphate fertilizers contain approximately 200 mg.kg-1 of uranium. The uranium and phosphate can move through the vadose zone and reach groundwater. Therefore, the knowledge of the ways in which these two elements are distributed, their partition relationships and their mobility behavior is of great interest. In order to study the latter, suction cup samplers, intended to collect soil water at different depths, were installed in an experimental site in a high plain of Mexico, where corn is cultivated and phosphate fertilizers are systematically applied. It was observed that the vadose zone contains high concentrations of uranium (1-50 mg.kg-1) and phosphates (22-33 mg.kg-1), which decrease at greater depths. Uranium concentration in the soil water varies between 10 and 3 mg.l-1 and phosphates between 1 and 0.3 mg.l-1. Their evolution throughout the profile of the vadose zone is determined by the decrease in concentrations, due to the physico-chemical processes involved. 相似文献