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排序方式: 共有245条查询结果,搜索用时 15 毫秒
41.
Kovalchuk N Starov V Langston P Hilal N Zhdanov V 《Journal of colloid and interface science》2008,325(2):377-385
Computer simulations of colloidal suspensions are discussed. The simulations are based on the Langevin equations, pairwise interaction between colloidal particles and take into account Brownian, hydrodynamic and colloidal forces. Comparison of two models, one taking into account inertial term in Langevin equation and another based on diffusional approximation proposed in [D.L. Ermak, J.A. McCammon, J. Chem. Phys. 69 (1978) 1352], has shown that both models enable the prediction of the correct values of the diffusion coefficient and residence time of particle in a doublet and are therefore suitable to study the dynamics of formation and breakage of clusters in colloidal suspensions. It is shown that the appropriate selection of the time step and taking into account inertia of particles provides also the correct value of the average kinetic energy of each particle during the simulations, what allows to use the model based on full Langevin equations as a reference model to verify the validity of the numerical scheme for simulation using diffusion approximation. 相似文献
42.
A nanocomposite (Ho2O3NPs/BNT) was synthesized by decorating holmium(III)oxide nanoparticles (H2O3NPs) on bentonite (BNT) through a realizable sonochemical approach for the electrochemical detection of haloperidol (Hlp). A glassy carbon electrode was modified with this nanocomposite. The Ho2O3NPs/BNT modified electrode outperformed bare and other modified electrodes in terms of electrochemical performance for Hlp detection in a pH 8.0 phosphate buffer. The proposed electrochemical platform showed a wide linear range (0.01 μM–24 μM), low detection limit (2.4 nM), and high sensitivity by square wave voltammetry. In addition, the proposed electrochemical sensor met the clinical criteria in terms of stability, selectivity, and repeatability. 相似文献
43.
In recent years there has been an increase in use of botanicals with antioxidant properties as skin photoprotective agents. Pomegranate (Punica granatum L.) fruit possesses strong antioxidant and antiinflammatory properties. Recently, we have shown that pomegranate-derived products rich in anthocyanidins and ellagitannins inhibit UVB-mediated activation of nuclear factor kappa B and modulate UVA-mediated cell proliferation pathways in normal human epidermal keratinocytes. In this study, we evaluated the effect of polyphenol-rich pomegranate fruit extract (POMx) on UVB-induced oxidative stress and photoaging in human immortalized HaCaT keratinocytes. Our data show that pretreatment of HaCaT cells with POMx (10-40 microg mL(-1)) inhibited UVB (15-30 mJ cm(-2))-mediated (1) decrease in cell viability, (2) decrease in intracellular glutathione content and (3) increase in lipid peroxidation. Employing immunoblot analysis we found that pretreatment of HaCaT cells with POMx inhibited UVB-induced (1) upregulation of MMP-1, -2, -7 and -9, (2) decrease in TIMP-1, (3) phosphorylation of MAPKs and (iv) phosphorylation of c-jun, whereas no effect was observed on UVB-induced c-fos protein levels. These results suggest that POMx protects HaCaT cells against UVB-induced oxidative stress and markers of photoaging and could be a useful supplement in skin care products. 相似文献
44.
Ryan Furlong Mirvana Hilal Vincent OBrien Anne Humeau-Heurtier 《Entropy (Basel, Switzerland)》2021,23(10)
Two-dimensional fuzzy entropy, dispersion entropy, and their multiscale extensions ( and , respectively) have shown promising results for image classifications. However, these results rely on the selection of key parameters that may largely influence the entropy values obtained. Yet, the optimal choice for these parameters has not been studied thoroughly. We propose a study on the impact of these parameters in image classification. For this purpose, the entropy-based algorithms are applied to a variety of images from different datasets, each containing multiple image classes. Several parameter combinations are used to obtain the entropy values. These entropy values are then applied to a range of machine learning classifiers and the algorithm parameters are analyzed based on the classification results. By using specific parameters, we show that both and approach state-of-the-art in terms of image classification for multiple image types. They lead to an average maximum accuracy of more than 95% for all the datasets tested. Moreover, results in a better classification performance than that extracted by as a majority. Furthermore, the choice of classifier does not have a significant impact on the classification of the extracted features by both entropy algorithms. The results open new perspectives for these entropy-based measures in textural analysis. 相似文献
45.
A 2-D computer simulation of a coaxial plasma device depending on the conservation equations of electrons, ions and excited
atoms together with the Poisson equation for a plasma gun is carried out. Some characteristics of the plasma focus device
(PF) such as critical wave numbers a
c and voltages U
c in the cases of various pressures Pare estimated in order to satisfy the necessary conditions of traveling particle densities (i.e. plasma patterns) via a linear analysis. Oscillatory solutions are characterized by a nonzero imaginary part of the growth
rate (σ) for all cases. The model also predicts the minimal voltage ranges of the system for certain pressure intervals.
相似文献
46.
Spreading behaviour of aqueous trisiloxane solutions over hydrophobic polymer substrates 总被引:1,自引:0,他引:1
Caleb Chong Wei Ping N. A. Ivanova V. M. Starov N. Hilal D. Johnson 《Colloid Journal》2009,71(3):391-396
The kinetics of spreading of aqueous trisiloxane solutions over different solid hydrophobic substrates has been investigated
experimentally. Two pure trisiloxane surfactants with 6 and 8 oxyethylene groups at concentrations close to the critical aggregation
concentration and the critical wetting concentration were used in the spreading experiments. Three hydrophobic substrates
(Teflon AF, Parafilm, and polystyrene) having different surface properties were used. It was found that the spreading behaviour
depends on the hydrophobic/roughness properties of substrates. The rapid spreading and complete wetting were observed for
both trisiloxane surfactant solutions at the critical wetting concentration on a substrate with a moderate hydrophobicity.
For both highly hydrophobic Teflon AF and Parafilm substrates only partial wetting was found. The experiments have shown that
the spreading behaviour over all substrates proceeds at two stages. At the critical aggregation concentration for both trisiloxanes
on all substrates the time lag of the spreading was detected.
The article is published in the original. 相似文献
47.
Zaid M. Odibat 《Applied mathematics and computation》2009,215(8):3017-3028
Variational iteration method has been successfully implemented to handle linear and nonlinear differential equations. The main property of the method is its flexibility and ability to solve nonlinear equations accurately and conveniently. In this paper, first, a general framework of the variational iteration method is presented for analytic treatment of differential equations of fractional order where the fractional derivatives are described in Caputo sense. Second, the new framework is used to compute approximate eigenvalues and the corresponding eigenfunctions for boundary value problems with fractional derivatives. Numerical examples are tested to show the pertinent features of this method. This approach provides a new way to investigate eigenvalue problems with fractional order derivatives. 相似文献
48.
Söhretoğlu D Sakar MK Sabuncuoğlu SA Ozgüneş H Duman H Sterner O 《Natural product research》2012,26(13):1261-1264
Chromatographic studies on the EtOAc soluble portion of the MeOH extract of Geranium lasiopus led to the isolation of eight flavonoids (kaempferol (1), quercetin (2), quercetin 3-O-β-glucopyranoside (3), quercetin 3-O-β-galactopyranoside (4), kaempferol 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (5), quercetin 3-O-α-rhamnopyranosyl-(1?→?6)-β-glucopyranoside (6), kaempferol 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (7) and quercetin 3-O-α-rhamnopyranosyl-(1?→?2)-β-glucopyranoside (8)), two simple phenolic compounds (gallic acid (9) and its methyl ester (10)) and a hydrolysable tannin (pusilagin (11)). The structures of the compounds were elucidated by 1- and 2-dimensional NMR techniques ((1)H, (13)C, COSY, HMBC, HMQC) and ESI-TOF-MS spectrometry. Inhibitory effects on H(2)O(2)-induced lipid peroxidation in human red blood cells of the different extracts of G. lasiopus, as well as isolated compounds, were investigated. All tested compounds showed comparable or higher activity than that of ascorbic acid and trolox. 相似文献
49.
Nasim Ahmed Syed Alwee Aljunid R. Badlishah Ahmad Hilal A. Fadhil Mohd Abdur Rashid 《Optical Review》2012,19(1):1-6
The bit-error rate (BER) performance of the spectral amplitude coding-optical code division multiple access (SACOCDMA) system
has been investigated by using NAND subtraction detection technique with enhanced double weight (EDW) code. The EDW code is
the enhanced version of double weight (DW) code family where the code weight is any odd number and greater than one with ideal
cross-correlation. In order to evaluate the performance of the system, we used mathematical analysis extensively along with
the simulation experiment. The evaluation results obtained using the NAND subtraction detection technique was compared with
those obtained using the complementary detection technique for the same number of active users. The comparison results revealed
that the BER performance of the system using NAND subtraction detection technique has greatly been improved as compared to
the complementary technique. 相似文献
50.
Hassan Yousif Ahmed M. Almaleeh Hilal Fadhil S.A. Aljunid Ammar Elyass N.M. Saad 《Optik》2012,123(15):1352-1359
This paper investigates the performance of vector combinatorial (VC) code for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a newly proposed subtract exclusive OR detection (SED) technique. VC code is constructed using Euclidean vector and algebraic ways. One of the important properties of this code is that the maximum cross correlation is one, which means that multi-user interference (MUI) and phase induced intensity noise (PIIN) are reduced. The weight for the VC code can be any positive integer number. The system performance was evaluated by comparing the theoretical studies using related equations and simulation results taken from the commercial optical systems, “VPI? TransmissionMaker 7.1”. Significant improvement in system performances has been observed when the proposed SED technique employing VC code was applied compared to other codes that utilize conventional balance detection techniques for spectral amplitude coding. 相似文献