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811.
812.
813.
Jo?o Carlos de Andrade Aline R Coscione Ronei J Poppi Cesar Mello 《Analytical sciences》2008,24(9):1147-1150
An artificial neural network (ANN) calibration model was developed to determine aluminum in the presence of iron in soil extracts, using xylenol orange as chromogenic reagent. The spectral data of synthetic mixtures of Al(3+) and Fe(3+) as well as of the soil extracts, were recorded in the range between 410 and 580 nm. Method validation was carried out using 18 soil extracts. The results gave good linear correlations between the ANN model and the ICP OES measurements for both species. 相似文献
814.
A series of imines was synthesized by an ultrasound-assisted reaction of aldehydes and primary amines using silica as the promoter. Products were obtained in high yields even in large scale synthesis. 相似文献
815.
Swimming, i.e., being able to advance in the absence of external forces by performing cyclic shape changes, is particularly
demanding at low Reynolds numbers. This is the regime of interest for micro-organisms and micro- or nano-robots. We focus
in this paper on a simple yet representative example: the three-sphere swimmer of Najafi and Golestanian (Phys. Rev. E, 69, 062901–062904, 2004). For this system, we show how to cast the problem of swimming in the language of control theory, prove global controllability
(which implies that the three-sphere swimmer can indeed swim), and propose a numerical algorithm to compute optimal strokes
(which turn out to be suitably defined sub-Riemannian geodesics).
相似文献
816.
Stille reactions between halobenzenes and other substituted (hetero)arenes and tributylphenyltin were carried out in ethanol-water solution using Pd/CaCO3 as catalyst in a ligand-free system. The catalyst could be recycled three times without any loss of activity. The ethanol-water solution, after removal of the catalyst and extraction of the product, was found to have catalytic activity, thus showing the presence of soluble Pd(0)/Pd(II) species that can be regarded as the true catalysts. 相似文献
817.
Ultrasonic excitation affects friction interactions between food materials and cutting tools 总被引:1,自引:0,他引:1
In the food industry, ultrasonic cutting is used to improve separation by a reduction of the cutting force. This reduction can be attributed to the modification of tool–workpiece interactions at the cutting edge and along the tool flanks because of the superposition of the cutting movement with ultrasonic vibration of the cutting tool. In this study, model experiments were used to analyze friction between the flanks of a cutting tool and the material to be cut. Friction force at a commercial cutting sonotrode was quantified using combined cutting–friction experiments, and sliding friction tests were carried out by adapting a standard draw-off assembly and using an ultrasonic welding sonotrode as sliding surface. The impact of material parameters, ultrasonic amplitude, and the texture of the contacting food surface on friction force was investigated. The results show that ultrasonic vibration significantly reduces the sliding friction force. While the amplitude showed no influence within the tested range, the texture of the contact surface of the food affects the intensity of ultrasonic transportation effects. These effects are a result of mechanical interactions and of changes in material properties of the contact layer, which are induced by the deformation of contact points, friction heating and absorption heating because of the dissipation of mechanical vibration energy. 相似文献
818.
We present a theoretical model for the evolution of mixture concentrations in a micro-pervaporation device, similar to those
recently presented experimentally. The described device makes use of the pervaporation of water through a thin PDMS membrane
to build up a solute concentration profile inside a long microfluidic channel. We simplify the evolution of this profile in
binary mixtures to a one-dimensional model which comprises two concentration-dependent coefficients. The model then provides
a link between directly accessible experimental observations, such as the widths of dense phases or their growth velocity,
and the underlying chemical potentials and phenomenological coefficients. It shall thus be useful for quantifying the thermodynamic
and dynamic properties of dilute and dense binary mixtures. 相似文献
819.
Sara Nasiri Sovari Isabelle Kolly Kevin Schindler Youri Cortat Shing-Chi Liu Aurelien Crochet Aleksandar Pavic Fabio Zobi 《Molecules (Basel, Switzerland)》2021,26(17)
The reaction of rhenium α-diimine (N-N) tricarbonyl complexes with nitrosonium tetrafluoroborate yields the corresponding dicarbonyl-nitrosyl [Re(CO)2(NO)(N-N)X]+ species (where X = halide). The complexes, accessible in a single step in good yield, are structurally nearly identical higher charge congeners of the tricarbonyl molecules. Substitution chemistry aimed at the realization of equivalent dicationic species (intended for applications as potential antimicrobial agents), revealed that the reactivity of metal ion in [Re(CO)2(NO)(N-N)X]+ is that of a hard Re acid, probably due to the stronger π-acceptor properties of NO+ as compared to those of CO. The metal ion thus shows great affinity for π-basic ligands, which are consequently difficult to replace by, e.g., σ-donor or weak π-acids like pyridine. Attempts of direct nitrosylation of α-diimine fac-[Re(CO)3]+ complexes bearing π-basic OR-type ligands gave the [Re(CO)2(NO)(N-N)(BF4)][BF4] salt as the only product in good yield, featuring a stable Re-FBF3 bond. The solid state crystal structure of nearly all molecules presented could be elucidated. A fundamental consequence of the chemistry of [Re(CO)2(NO)(N-N)X]+ complexes, it that the same can be photo-activated towards CO release and represent an entirely new class of photoCORMs. 相似文献
820.