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排序方式: 共有431条查询结果,搜索用时 15 毫秒
71.
EC Dreaden SC Mwakwari LA Austin MJ Kieffer AK Oyelere MA El-Sayed 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(18):2819-2822
Gold nanoparticles are known to activate anti-tumor potential in macrophage immune cells; however, the subsequent effects of these cells on others nearby are poorly understood. A novel gold-nanoparticle conjugate that selectively targets and induces cytotoxic activity of tumor-associated macrophages towards breast cancer cells in co-culture is synthesized. These constructs are promising new tools for studying fundamental biological interactions with nanoscale materials and candidates for emerging macrophage-mediated delivery applications. 相似文献
72.
Rajeh Z. Al-Zaid Abdulaziz I. Al-Negheimish Mohammed A. Al-Saawani Ahmed K. El-Sayed 《Composites Part B》2012,43(2):129-141
This paper presents analytical study on reinforced concrete (RC) beams strengthened for flexure with externally bonded fiber reinforced polymer (FRP) reinforcement. A simple yet rational numerical model is developed and proposed for this purpose. The model is based on cross-sectional analysis satisfying strain compatibility and equilibrium conditions. The moment–curvature relationship can be generated for an RC beam section using an incremental strain technique. The model can also generate the load–deflection relationship of the beam with respect to its configuration, loading system, and preloading conditions. The model can predict the flexural capacity of FRP-strengthened section based on full composite action and IC debonding failure modes. This also allows for designing the FRP strengthening area according to the desired failure mode. Various IC debonding criteria were adopted in the model and compared with test results from the literature. The result of comparison indicated that the accuracy of the model is dependent on the adopted IC debonding criterion. Furthermore, the model was verified against test data related to full composite action failure mode and good agreement was found. 相似文献
73.
Abdel-Rahman El-Sayed Hossnia S. Mohran Hany M. Abd El-Lateef 《Metallurgical and Materials Transactions A》2012,43(2):619-632
The article describes the use of Tafel plot and electrochemical impedance spectroscopy (EIS) techniques, in order to study
the corrosion process of pure zinc, nickel, and synthetic Zn-Ni alloys in various concentrations (0.25 to 1 M) of KOH solution
in a temperature range 298 K to 328 K (25 °C to 55 °C). The corrosion rate increases with increasing both concentration of
KOH and temperature for all investigated electrodes. The results showed that the increase in Ni content improves the corrosion
resistance and increases the barrier of activation energy, and the higher value of corrosion resistance is obtained at 10 pct Ni.
The electrochemical measurements using two mentioned techniques are in good agreement with the results of microhardness in
that the microhardness gradually increases with increasing Ni content in the alloy. Thus, the corrosion rate of these alloys
is significantly reduced compared with that of pure zinc. It is observed that the Warburg tail at low frequency completely
disappears at the applied potentials in the case of alloy IV (10 pct Ni) only. This indicates that the diffusion of Zn ion
species is strongly reduced. Therefore, addition of Ni to Zn has a beneficial effect, because it leads to lower loss of anode
material. The results obtained at certain positive potential (+420 mV vs SCE) exhibited that the semicircle diameter in the case of alloys is lower compared with that of pure zinc. This result means
that the values of the charge transfer resistance (R
ct
) in the case of alloys are decreased, due to the breakdown of the oxide layer at this potential. This behavior can be considered
as an important criterion for a good battery anode, due to reactivation of the alloy surface at certain positive potential
(+0.420 V vs SCE) and suppression of hydrogen gas compared with those of pure zinc. 相似文献
74.
We formulate a constitutive framework for biodegradable polymers that accounts for nonlinear viscous behavior under regimes with large deformation. The generalized Maxwell model is used to represent the degraded viscoelastic response of a polymer. The large-deformation, time-dependent behavior of viscoelastic solids is described using an Ogden-type hyperviscoelastic model. A deformation-induced degradation mechanism is assumed in which a scalar field depicts the local state of the degradation, which is responsible for the changes in the material’s properties. The degradation process introduces another timescale (the intrinsic material clock) and an entropy production mechanism. Examples of the degradation of a polymer under various loading conditions, including creep, relaxation and cyclic loading, are presented. Results from parametric studies to determine the effects of various parameters on the process of degradation are reported. Finally, degradation of an annular cylinder subjected to pressure is also presented to mimic the effects of viscoelastic arterial walls (the outer cylinder) on the degradation response of a biodegradable stent (the inner cylinder). A general contact analysis is performed. As the stiffness of the biodegradable stent decreases, stress reduction in the stented viscoelastic arterial wall is observed. The integration of the proposed constitutive model with finite element software could help a designer to predict the time-dependent response of a biodegradable stent exhibiting finite deformation and under complex mechanical loading conditions. 相似文献
75.
M. Eid M. B. El-Arnaouty M. Salah El-Sayed Soliman El-Sayed A. Hegazy 《Journal of Polymer Research》2012,19(3):9835
A series of PVA/PVP based hydrogels at different compositions were prepared by gamma irradiation. The gel fraction degree
of swelling were investigated. Highly stable and uniformly distributed silver nanoparticles have been obtained onto hydrogel
networks. The morphology and structure of (PVA/PVP) hydrogel and dispersion of the silver nanoparticles in the polymeric matrix
were examined by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), respectively. The formation of silver
nanoparticles has been confirmed by ultraviolet visible (UV–vis) spectroscopy. A strong characteristic absorption peak was
found to be around 420 nm for the silver nanoparticles in the hydrogel nanocomposite. The X-ray diffraction pattern confirmed
the formation of silver nanoparticles with average particle size of 12 nm. The diameter distribution of silver nanoparticles
was determined by dynamic light scattering DLS. Transmission electron microscope (TEM) showed almost spherical and uniform
distribution of silver nanoparticles through the hydrogel network and the mean size of silver nanoparticles ranging is 23 nm.
The good swelling properties and antibacterial of PVA/PVP-Ag hydrogel suggest that it can be a good candidate as wound dressing. 相似文献
76.
Hesabi ZR Allam NK Dahmen K Garmestani H A El-Sayed M 《ACS applied materials & interfaces》2011,3(4):952-955
In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 °C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses. 相似文献
77.
Emad El-Sayed Etman 《Canadian Metallurgical Quarterly》2011,15(1):2-8
The capacity and ductility of RC slabs are affected by the use of fiber-reinforced polymer (FRP) as their main reinforcement for repair and rehabilitation. The balance between increasing the capacity and reducing the ductility of flexural members reinforced with FRP was always a matter of discussion. In this research, innovative hybrid reinforcement system (HRS) was introduced to provide the required increase in capacity while keeping the ductility within an acceptable range. Ten RC one-way slabs were tested in this investigation. They included a control slab which was reinforced with ordinary steel, while the rest of the slabs were reinforced internally with HRS with nine different profiles. The main variables considered in this study were the type of core or perimeter reinforcement and the number of perimeter reinforcing layers. It was revealed that the use of the innovative HRS resulted in remarkable increases in section ultimate load capacity as well as ductility. 相似文献
78.
Manar El-Sayed Abdul-Raouf Abdul-Raheim Mahmoud Abdul-Raheim Nermine El-Sayed Maysour Hamed Mohamed 《Journal of surfactants and detergents》2011,14(2):185-193
Trimeric-type nonionic surfactants based on tris(2-aminoethyl)amine were prepared. N-alkyl chloride (namely, octanoyl chloride,
n-decanoyl chloride, n-dodecanoyl chloride) was reacted with tris(2-aminoethyl)amine in the presence of toluene and triethylamine. The products
were partially reduced and then ethoxylated by poly(ethylene glycol) of molecular weights 400, 1,000, and 2,000 g mol−1. The structures were confirmed by infrared (IR) and 1HNMR spectroscopy. The molecular weights of the surfactants were measured by gel permeation chromatography (GPC). The properties
of the prepared compounds were investigated by the surface tension, interfacial tension, and cloud point. The emulsification
power of the prepared surfactants for oil-in-water emulsions was also studied and the emulsion stability was monitored by
an optical microscope and the bottle testing method. Some factors affecting the emulsion stability were investigated 相似文献
79.
Manar El-Sayed Abdel-Raouf Abdul-Raheim Mahmoud Abdul-Raheim Abdel-Azim Ahmed Abdel-Azim 《Journal of surfactants and detergents》2011,14(1):113-121
Several ethoxylated sugar-based amine surfactants have been synthesized and characterized by IR and 1HNMR spectroscopy. The surface activity of the prepared compounds has been thoroughly studied and some of their surface properties
(such as CMC, Γmax, and A
min) have been calculated. The surface properties of the prepared compounds were correlated to their chemical structure. It was
found that CMC decreases when increasing the molecular weight of polyethylene glycols, whereas A
min increases. Furthermore, the thermodynamic parameters of adsorption and micellization were also calculated. They include ΔG, ΔH, and ΔS of micellization and adsorption. The data show that the synthesized surfactants favor adsorption, so that they can be used
as demulsifiers for crude oil emulsions. In this respect, the demulsification test was carried out and the results of demulsification
efficiency were correlated to the chemical composition of the investigated compounds. Some factors that affect the demulsification
efficiency were also considered. 相似文献
80.
El-Sayed M. Sherif 《Journal of Industrial and Engineering Chemistry》2013,19(6):1884-1889
The corrosion behavior of aluminum and its inhibition by 3-amino-1,2,4-triazole-5-thiol (ATAT) in naturally aerated stagnant Arabian Gulf water was reported. The work was carried out using electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarization (CPP), and potentiostatic current–time (CCT) measurements. EIS data indicated that ATAT decreased the corrosion of Al by increasing the solution and polarization resistances, the impedance of the interface and the maximum degree of phase angle. ATAT was also found to decrease the cathodic, anodic, and corrosion currents and corrosion rate as well as increase the polarization resistance of Al as confirmed by the CPP and CCT measurements. 相似文献