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排序方式: 共有477条查询结果,搜索用时 15 毫秒
1.
The phase diagram of the nematic mesophase present in the tetradecyltrimethylammonium bromide/sodium bromide/water ternary system was determined. A calamitic nematic mesophase (NC) was observed which extends to very high concentrations of electrolyte. The order parameters of the surfactant head group in the mesophases were studied by the NMR quadrupolar splitting of the deuterated surfactant. On increasing the temperature of nematic mesophases with low electrolyte concentrations, a phase separation occurs with the formation of a more highly ordered hexagonal phase and an isotropic phase. Diffusion measurements of the isotropic micellar solution by the NMR PFG method were used to estimate hydrodynamic radii at low surfactant concentrations and to study micelle diffusion as the concentration of the surfactant was increased to the liquid crystalline region. At higher surfactant concentrations, the diffusion coefficient reached a limiting value. The calamitic nematic mesophase in this surfactant/electrolyte/water system appears to be formed by long wormlike micelles. 相似文献
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Mohammed Alqarni Nader Ibrahim Namazi Sameer Alshehri Ibrahim A. Naguib Amal M. Alsubaiyel Kumar Venkatesan Eman Mohamed Elmokadem Mahboubeh Pishnamazi Mohammed A. S. Abourehab 《Molecules (Basel, Switzerland)》2022,27(14)
Industrial-based application of supercritical CO2 (SCCO2) has emerged as a promising technology in numerous scientific fields due to offering brilliant advantages, such as simplicity of application, eco-friendliness, and high performance. Loxoprofen sodium (chemical formula C15H18O3) is known as an efficient nonsteroidal anti-inflammatory drug (NSAID), which has been long propounded as an effective alleviator for various painful disorders like musculoskeletal conditions. Although experimental research plays an important role in obtaining drug solubility in SCCO2, the emergence of operational disadvantages such as high cost and long-time process duration has motivated the researchers to develop mathematical models based on artificial intelligence (AI) to predict this important parameter. Three distinct models have been used on the data in this work, all of which were based on decision trees: K-nearest neighbors (KNN), NU support vector machine (NU-SVR), and Gaussian process regression (GPR). The data set has two input characteristics, P (pressure) and T (temperature), and a single output, Y = solubility. After implementing and fine-tuning to the hyperparameters of these ensemble models, their performance has been evaluated using a variety of measures. The R-squared scores of all three models are greater than 0.9, however, the RMSE error rates are 1.879 × 10−4, 7.814 × 10−5, and 1.664 × 10−4 for the KNN, NU-SVR, and GPR models, respectively. MAE metrics of 1.116 × 10−4, 6.197 × 10−5, and 8.777 × 10−5errors were also discovered for the KNN, NU-SVR, and GPR models, respectively. A study was also carried out to determine the best quantity of solubility, which can be referred to as the (x1 = 40.0, x2 = 338.0, Y = 1.27 × 10−3) vector. 相似文献
4.
Ch. Zgheib E. Nassar M. Hamad R. Nader P. Masri J. Pezoldt G. Ferro 《Superlattices and Microstructures》2006,40(4-6):638
The effect of the germanium coverage prior to the epitaxial growth of 5 μm thick 3C-SiC on Si(100) substrates were evaluated with Atomic Force Microscopy and μ-Raman spectroscopy. The 3C-SiC layers were grown by atmospheric pressure chemical vapor deposition via a special procedure leading to layers with compressive instead of tensile stress. The Ge amount was varied from 0 up to 2 ML. The obtained results showed that the residual stress inside the layers is shifted in the compressive direction; the crystalline quality is improved with the Ge introduction but on the account of the surface roughness. These results open the route for the use of Ge-modified Si(100) as a potential substrate in order to improve the heteroepitaxial growth of 3C-SiC on silicon substrates. 相似文献
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Martynov S Kostson E Saffari N Stride E 《The Journal of the Acoustical Society of America》2011,130(5):2700-2708
There is increasing demand for accurate characterization of the in vivo behavior of microbubble agents used for ultrasound imaging and therapy. This study examines bubble-vessel interaction, in particular the propagation of disturbances along the vessel wall. Finite element simulations of a 3 μm radius microbubble suspended in a viscous liquid and enclosed in a 4 μm radius elastic vessel were performed, and the results compared with existing analytical results for wave propagation in elastic liquid-filled tubes. The vessel wall was shown to have a significant effect upon the amplitude of bubble oscillation and hence acoustic radiation from it, as well as distension of the vessel wall. It was found that the most important factor was the ratio of the excitation frequency to the natural "ring" frequency of the vessel which in turn depends upon its dimensions and mechanical properties. As this ratio increases, the motion of the vessel wall becomes increasingly localized to the site of the bubble. It was also shown that the validity of the results obtained using the applied model of vessel elasticity is limited to frequencies below the ring frequency, and this should be taken into account in the development of protocols for ultrasound safety and/or therapeutic procedures. 相似文献
7.
It is shown how to identify potential signatures of noncommutative geometry within the decay spectrum of a muon in orbit near
the event horizon of a microscopic Schwarzschild black hole. This possibility follows from a re-interpretation of Moffat’s
nonsymmetric theory of gravity, first published in Phys. Rev. D 19:3554, 1979, where the antisymmetric part of the metric tensor manifests the hypothesized noncommutative geometric structure throughout
the manifold. It is further shown that for a given sign convention, the predicted signatures counteract the effects of curvature-induced
muon stabilization predicted by Singh and Mobed in Phys. Rev. D 79:024026, 2009. While it is unclear whether evidence for noncommutative geometry may become observable anytime soon, this approach at least
provides a useful direction for future quantum gravity research based on the ideas presented here. 相似文献
8.
Here we show, analytically and numerically, that in a TiO(2) double-groove grating with two different groove widths per period attached on the SiO(2) substrate, the normally incident light couples to the +1st-order transmission with 96.9% efficiency and with a 50° diffraction angle that is larger than the SiO(2)-air interface critical angle. Modal analysis reveals that three propagating modes for the +1st diffraction order reach the grating back end in phase, while the corresponding propagating modes for the -1st and zeroth orders are added destructively at the grating end. Four optical devices based on this grating characteristic are numerically demonstrated. 相似文献
9.
The in-plane and out-of-plane resistivities of both 2H-TaSe2 and 2H-NbSe2 were determined down to 10 K. For both compounds, the resistivity anisotropy shows notably a slope change at temperatures where a CDW transition is expected to occur. On the other hand, for both compounds the resistivity anisotropy at the lowest temperature of measurement is much greater than expected by the Lawrence–Doniach model, which relates the critical magnetic field anisotropy to the normal state resistivity anisotropy for 3D-anisotropic superconductors. 相似文献
10.
The thermophoretic motion of a charged spherical colloidal particle and its accompanying cloud of counterions and coions in a temperature gradient is studied theoretically. Using the Debye-Hückel approximation, the Soret drift velocity of a weakly charged colloid is calculated analytically. For highly charged colloids, the nonlinear system of electrokinetic equations is solved numerically, and the effects of high surface potential, dielectrophoresis, and convection are examined. Our results are in good agreement with some of the recent experiments on highly charged colloids without using adjustable parameters. 相似文献