The effect of etching time on the statistical properties of hydrophilic surfaces of SiO2/TiO2/glass nano bilayers has been studied using atomic force microscopy (AFM) and a stochastic approach based on a level crossing analysis. We have created rough surfaces of the hydrophilic SiO2/TiO2 nano bilayer system by using 26% potassium hydroxide (KOH) solution. Measuring the average apparent contact angle allowed us to assess the degree of hydrophilicity, and the optimum condition was determined to be 10 min etching time. A level crossing analysis based on AFM images provided deeper insight into the microscopic details of the surface topography. With different etching times, it has been shown that the average frequency of visiting a height with positive slope behaves in a Gaussian manner for heights near the mean value and obeys a power law for heights far away from the mean value. Finally, by applying the generalized total number of crossings with positive slope, it was found that the both high heights and deep valleys of the surface have a great effect on the hydrophilic degree of the SiO2/TiO2/glass nano bilayer investigated system. 相似文献
An unsteady-state model is developed for primary and secondary stages of freeze drying process of skim milk. The results are compared with those obtained from a quasi-steady-state (QSS) formulation. The QSS formulation is not valid where the applied heat load is high. The applied heat load affects on the drying time the most compared to other parameters like chamber pressure and the radiation surface temperature. 相似文献
Based on the transfer matrix method, we theoretically analyze the transmission spectra of electromagnetic waves through one-dimensional self-similar fractal structures composed of lossy and dispersive single-negative materials. Multiple double-positive defects layers are introduced into the proposed structure, and some interesting properties are obtained. We find that the loss factor decreases the transmission peaks of defect modes, but the main properties of transmission spectra do not destroy. We believe that the introduction of loss is essential in order to obtain correct results on the performance of the structures. 相似文献
An effective approach of one‐pot catalytic Strecker reaction between aromatic aldehydes, aniline or toluidine and trimethylsilyl cyanide in the presence of amine‐functionalized Fe3O4@SiO2 nanoparticles grafted with gallic acid (GA) as a powerful catalyst was developed. The fabricated reusable catalyst demonstrated high efficiency in the synthesis of α‐aminonitriles along with facile work‐up procedure. Fe3O4@SiO2‐NH2‐GA was characterized by Fourier transform‐infrared spectroscopy, scanning electron microscopy image, vibrating‐sample magnetometer curve, energy‐dispersive X‐ray analysis and thermogravimetric analysis. 相似文献
This paper considers the problem of the two-dimensional mixed convection stagnation-point flow of a magnetohydrodynamic non-Newtonian nanofluid bounded by a vertical stretching sheet. Convective surface boundary and zero surface nanoparticle mass flux conditions are employed. The effects of buoyancy, radiation, Brownian motion, thermophoresis, and viscous dissipation are taken into account. The stretching velocity is assumed to vary linearly with the distance from the stagnation point. The fluid is electrically conducted with uniform magnetic field, and the work done due to deformation is taken into consideration. The three-coupled partial differential boundary layer equations are reduced to ordinary differential equations by using proper similarity transformations. Analytical solution by homotopy analysis method is obtained. Effects of different physical parameters on the dynamics of the problem are analyzed and discussed.
Russian Journal of Electrochemistry - The activity of PtCu/C catalysts in methanol electrooxidation is studied in HClO4 solution. The electrochemical behavior of catalysts is compared for samples... 相似文献
The objective of this research project is to investigate the biocompatibility of N-isopropylacrylamide (NIPAAm) monomers and poly(N-isopropylacrylamide) (PNIPAAm) nanoparticles in vitro. PNIPAAm nanoparticles of different sizes were synthesized and characterized
by transmission electron microscopy and dynamic light scattering. Cytotoxicity studies using MTS assays were conducted on
fibroblasts, smooth muscle cells, and endothelial cells. In addition, the concentration of NIPAAm monomers remaining on PNIPAAm
nanoparticles was determined using bromination and spectrophotometry. The cytotoxicity results did not show a significant
difference in cell survival when cells were exposed to different particle sizes (100, 300, and 500 nm). Dose studies showed
that all three cell types exposed to 100 nm PNIPAAm nanoparticles at concentrations less than or equal to 5 mg/mL were compatible,
while cells exposed to NIPAAm monomers exhibited toxicity even at very low concentrations. We also found that 1 mg/mL concentration
of 100 nm PNIPAAm nanoparticles was cytocompatible for 4 days, whereas NIPAAm monomers were cytotoxic after 24 h of exposure.
Photomicrographs showed altered morphology in cells exposed to NIPAAm monomers, while cells exposed to PNIPAAm nanoparticles
maintained their normal morphology. Finally, a very low concentration of NIPAAm monomers remained on the PNIPAAm nanoparticles
after synthesis and dialysis. Our results demonstrate that NIPAAm monomers are cytotoxic, whereas PNIPAAm nanoparticles are
compatible at 5 mg/mL concentration or below for fibrobasts, smooth muscle cells, and endothelial cells. 相似文献
An efficient approach for the synthesis of N-alkyl-2-aryl-2-(6-oxo-4H-benzo[f][1,2,3]triazolo[1,5-a][1,4]diazepin-5(6H)-yl)acetamides is described. The protocol involves Ugi four-component reaction of 2-bromobenzoic acid, propargylamine, aldehydes and isocyanides followed by in situ sequential click reaction of azide ion with triple bond and N-arylation reaction to afford desired products in good to excellent yields. 相似文献
The lattice Boltzmann simulation of nanofluid flow and heat transfer during natural convection within a dumbbell-shaped heat exchanger is carried out. The heat exchanger is filled with CuO–water. The KKL model is employed to predict the thermo-physical properties of nanofluid. In order to perform a comprehensive hydrothermal investigation, different post-processing approaches such as heatline visualization, total entropy generation, local entropy generation based on local fluid friction irreversibility and heat transfer irreversibility, average and local Nusselt variation are employed. In the present investigation, it is tried to present the impact of different influential parameters like Rayleigh number, solid volume fraction of nanofluid and thermal arrangement of internal fins-bodies on the fluid flow, heat transfer rate and entropy generation. 相似文献
Given that it has been possible to successfully cryopreserve human ovarian tissue by direct plunging into liquid nitrogen, this study was designed to establish the future direction to be taken in this line of research. Bovine oviductal epithelial fragments (as a tissue model) and large biopsy fragments (approximately 2.0 cubic mm) of human ovarian tissue were used for cryopreservation. Two protocols were tested: with permeable cryoprotectants (dimethyl sulphoxide, propylene glycol, glycerol) + egg yolk + sucrose or trehalose + a synthetic blocker of ice nucleation, Supercool X-1000; and using only permeable cryoprotectants (glycerol and ethylene glycol) + egg yolk + Supercool X-1000. The cryopreserved tissue specimens were subsequently thawed and the cryoprotectants removed by dilution in graded sucrose solutions. Both the dynamic growth and hormonal activity of the ovarian tissue pieces, vitrified using only permeable cryoprotectants, were greater than after vitrification in a mixture of permeable cryoprotectants and sucrose. Unlike the case for other reproductive tissue (spermatozoa, oocytes, embryos), these findings suggest that the cryopreservation of ovarian tissue by direct plunging into liquid nitrogen must be achieved by vitrification using only permeable cryoprotectants and agents that prevention ice formation. 相似文献