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Wireless Personal Communications - Due to the widely spreading of fake news utilizing image manipulation and its bad effects, this paper investigates efficient image contents verification and...  相似文献   
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Theoretical analysis of heat transfer in laminar pulsating flow   总被引:2,自引:0,他引:2  
Pulsation effect on heat transfer in laminar incompressible flow, which led to contradictory results in previous studies, is theoretically investigated in this work starting from basic principles in an attempt to eliminate existing confusion at various levels. First, the analytical solution of the fully developed thermal and hydraulic profiles under constant wall heat flux is obtained. It eliminates the confusion resulting from a previously published erroneous solution. The physical implications of the solution are discussed. Also, a new time average heat transfer coefficient for pulsating flow is carefully defined such as to produce results that are both useful from the engineering point of view, and compliant with the energy balance. This rationally derived average is compared with intuitive averages used in the literature. New results are numerically obtained for the thermally developing region with a fully developed velocity profile. Different types of thermal boundary conditions are considered, including the effect of wall thermal inertia. The effects of Reynold and Prandtl numbers, as well as pulsation amplitude and frequency on heat transfer are investigated. The mechanism by which pulsation affects the developing region, by creating damped oscillations along the tube length of the time average Nusselt number, is explained.  相似文献   
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In this study 24 factorial design associated with surface response methodology was used to develop and optimize a reconstitutable suspension of rifampicin. The study illustrated the effect of the percentage of each of sucrose, avicel RC-591, hydrophilic aerosil, and aerosol-OT on the flowability and the bulk density of the dry mixture as well as the viscosity, the sedimentation volume, and the redispersibility of the suspension. An empirical equation developed for each of the above responses was used with the aid of computer software to plot a contour map of the most significant effects and interactions. Five replicates at the center of the design were used to independently calculate the experimental error and to detect any curvature in the response surface. Three formulas which are not included in the design were prepared to check the validity of the model equation.  相似文献   
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Infrared (IR) and optical absorption spectra were measured in order to study the structure of some tellurite glasses containing boric oxide. The compositions (mol%) were (100-X) TeO2,XB2O3 whereX=5, 10, 20, 25, 30. The optical spectra were measured at room temperature in the wavelength range 350–450 nm, and the results show that the fundamental absorption edge is a function of composition, with the optical absorption due to indirect transitions. The optical band gap increases with increasing B2O3 content. The validity of the Urbach rule was investigated. The IR results prove the distribution of the TeO4 polyhedra which determines the network and the basic oscillations of the building units in the tellurite glasses. The IR results also prove the distribution of the boroxal group. The electrical conductivity was measured as a function of temperature in the temperature range (300–573 K). Both the conductivity and activation energy were found to be a function of added oxide type.  相似文献   
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ZnO nanoparticles were synthesized by liquid-phase pulse laser ablation of a Zn foil target immersed in deionized water. Nanosecond Q-switched Nd:YAG laser pulses of 532 nm were applied to the Zn foil target at a perpendicular and inclined (θ = 45°) angles. X-ray diffraction analysis revealed that both cases feature a ZnO nanostructure with a hexagonal wurtzite structure and that the particle size increases with the inclined target angle. Field emission scanning electron microscopy results of a colloidal drop cast on a glass substrate showed the ZnO has a nanorod structure in the case of a perpendicular target angle and an interlaced tattered nanosheet structure in the case of an inclined target angle. Photoluminescence spectra showed emission peaks in the UV, violet, blue, and green spectral regions, which correspond to excitonic and various defects resulting in an enhancement of emissions at inclined target angle.  相似文献   
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The bacterial quality and safety of raw milk sources in Taif region (Western Saudi Arabia) were analyzed for the natural contamination of fecal coliform and Escherichia coli by standard most probable number method. The E. coli isolates were identified to species identity using API 20E and screened for markers of STEC (Stx1, Stx2), ETEC (ST, LT), (EaeA) and ExPEC (CNF1, CNF2, SfaS, PapA, CdtB, IutA, FyuA, TraT) using PCR assays. Thirty-three E. coli strains were recovered from raw milk sample sources, which were contaminated by fecal coliform. None of the investigated isolates reacted positively with the PapA, SfaS and CdtB, ST and LT-specific primers. Markers of STEC and EPEC were each detected in three strains. NTEC was detected in four strains. The most frequent virulence markers were TraT (17 strains), IutA (11 strains) and FyuA (8 strains). Results suggested a possibility of potential public health threat of E. coli originating from raw milk sources.  相似文献   
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In the present study, six families of sulfated polysaccharides were obtained from seaweed Dictyopteris delicatula by proteolytic digestion, followed by acetone fractionation and molecular sieving on Sephadex G-100. Chemical analyses demonstrated that all polysaccharides contain heterofucans composed mainly of fucose, xylose, glucose, galactose, uronic acid, and sulfate. The fucans F0.5v and F0.7v at 1.0 mg/mL showed high ferric chelating activity (~45%), whereas fucans F1.3v (0.5 mg/mL) showed considerable reducing power, about 53.2% of the activity of vitamin C. The fucan F1.5v presented the most prominent anticoagulant activity. The best antiproliferative activity was found with fucans F1.3v and F0.7v. However, F1.3v activity was much higher than F0.7v inhibiting almost 100% of HeLa cell proliferation. These fucans have been selected for further studies on structural characterization as well as in vivo experiments, which are already in progress.  相似文献   
10.
Juvenile rats are more susceptible to the acute toxicity of the phosphorothionate insecticides parathion and chlorpyrifos than are adult rats. Developmental changes in brain acetylcholinesterase and hepatic aliesterase (carboxylesterase), cytochrome P450, and the P450-mediated metabolism of these two phosphorothionate insecticides were investigated in male Sprague-Dawley rats. Specific activities of acetylcholinesterase in cerebral cortex, but not medulla oblongata, and of liver aliesterases increased with age, indicating the presence of both more target esterases and more protective esterases, respectively, in the adult compared to the juvenile animal. Sensitivity of the brain acetylcholinesterase to inhibition by paraoxon and chlorpyrifosoxon, as measured by IC50 values, did not change significantly with age, whereas the hepatic aliesterase sensitivity to inhibition decreased with age. Progressive increases in activities of P450-mediated activation (desulfuration) (6- to 14-fold) and detoxication (dearylation) (2- to 4-fold), as well as concentrations of P450 (7-fold) and protein (2-fold), were observed between neonate and adult hepatic microsomes. Microsomal pentoxyresorufin O-dealkylase activity followed a developmental pattern similar to desulfuration and dearylation, displaying a 16-fold increase between neonates and adults. However, microsomal ethoxyresorufin O-deethylase activity increased until 21 days of age, displaying a 16-fold increase, then decreased in adulthood to a level 10-fold higher than neonates. These results indicate that target enzyme sensitivity is not responsible for age-related toxicity differences, nor is the potential for hepatic bioactivation, whereas lower levels of hepatic aliesterase-mediated protection and P450-mediated dearylation probably contribute significantly to the greater sensitivity of juveniles to phosphorothionate toxicity.  相似文献   
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