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81.
Mahmoud A. Abd El-Ghaffar Nivin M. Ahmed Elham A. Youssef 《Journal of Coatings Technology and Research》2010,7(6):703-713
This work presents a method of preparing single-, double-, and triple-cation ferrite pigments by employing simple chemical
techniques to study their corrosion protection properties. The prepared pigments were characterized using X-ray diffraction
and scanning electron microscopy. All prepared ferrite pigments were evaluated using ASTM methods. Anticorrosive paint formulations
were performed using different prepared pigment loadings. The physico-mechanical and corrosion properties of dry paint films
were examined. The tests revealed that the prepared ferrite pigments show excellent anticorrosive behavior, and that the best
among them in performance are zinc and zinc magnesium. Calcium, zinc–calcium, and zinc–magnesium–calcium ferrites show better
performance in high pigment loadings, while magnesium ferrite pigments show good results only in low pigment loading. 相似文献
82.
Mohammad A. Khanfar Diaa T. A. Youssef Prof. Khalid A. El Sayed Prof. 《ChemMedChem》2010,5(2):274-285
The microfilament cytoskeleton protein actin plays an important role in cell biology and affects cytokinesis, morphogenesis, and cell migration. These functions usually fail and become abnormal in cancer cells. The marine‐derived macrolides latrunculins A and B, from the Red Sea sponge Negombata magnifica, are known to reversibly bind actin monomers, forming 1:1 stoichiometric complexes with G‐actin, disrupting its polymerization. To identify novel therapeutic agents for effective treatment of metastatic breast cancer, several semisynthetic derivatives of latrunculin A with diverse steric, electrostatic, and hydrogen bond donor and acceptor properties were rationally prepared. Analogues were designed to modulate the binding affinity toward G‐actin. Examples of these reactions are esterification, acetylation, and N‐alkylation. Semisynthetic latrunculins were then tested for their ability to inhibit pyrene‐conjugated actin polymerization, and subsequently assayed for their antiproliferative and anti‐invasive properties against MCF7 and MDA‐MB‐231 cells using MTT and invasion assays, respectively. 相似文献
83.
M. A. Abdelkareem E. T. Kasem N. Nakagawa E. A. M. Abdelghani A. A. Elzatahry K. A. Khalil N. A. M. Barakat 《Fuel Cells》2014,14(4):607-613
Mass transfer is a key parameter affecting the performance of the passive direct methanol fuel cells (DMFCs), which work under natural convection. In this study, effect of carbon nanofibers (CNFs) addition to the cathode microporous layer (MPL) on the performance of the passive DMFCs was investigated. The results indicated that CNFs content has a significant influence on both of the mass transport and the electrochemical surface area (ECSA). Interestingly, addition of the CNFs (20 wt.%) leads to increase the power density of the passive DMFC to 160% compared to pristine carbon black MPL. At low current density, the CNFs content has no influence on the performance, while at high current density the maximum performance can be obtained at 20 wt.% CNFs then the performance decreases with further increase in the CNFs content. Although the highest catalyst utilization is observed at 40 wt.% CNFs, a maximum power density of 36 mW cm–2 can be obtained at 20 wt.% CNFs and this is related to the significant effect of the mass transfer resistance under the passive operation conditions. Overall, addition of CNFs to the MPL can be considered an effective strategy to modify the passive DMFCs performance. 相似文献
84.
The production of cationised cotton fabrics, via Sandene 8425, 1, 1-dimethyl-3-hydroxy azetidinium chloride and 1, 1-diethyl-3-hydroxy azetidinium chloride, greatly enhances the exhaustion and fixation of acid dyes. This paper shows that these dyes can be used in the absence of salt in a neutral medium. Wash fastness, light fastness and other properties were studied. 相似文献
85.
86.
H.M. Barakat Magdy E. El-Adll Amany E. Aly 《Computers & Mathematics with Applications》2011,61(5):1366-1378
In this paper we develop two pivotal quantities to construct exact predication intervals for future exponential lifetime based on a random number of lower generalized order statistics. The distribution functions of the two pivotal quantities, when the sample size is assumed to be integer-valued random variable, are derived. Three important special cases for the random sample size are presented. A simulation study is conducted for illustrative purposes. 相似文献
87.
Chen (Computers and Electrical Engineering, vol. 30, 2004) illustrated that Tseng et al.’s authenticated encryption schemes, with message linkages for message flows, do not achieve their claimed integrity and authenticity properties. Furthermore, Chen presented some modified schemes to repair these flaws. In this paper, we show that the modified schemes proposed by Chen are not secure. In particular, we present an attack that allows a dishonest referee, in case of a dispute, to decrypt all the future and past authenticated ciphertext between the contended parties. We also present a simple fix to prevent this attack. 相似文献
88.
H. Bahmanpour K. M. Youssef R. O. Scattergood C. C. Koch 《Journal of Materials Science》2011,46(19):6316-6322
Copper alloys with different amounts of zinc were synthesized via high energy ball milling at liquid nitrogen and room temperature.
Bulk samples were produced in situ by controlling the milling temperature. It is shown that temperature plays an important
role in formation of artifact-free consolidated samples via its effect on defect formation and annihilation during the milling
process. The mechanical behavior of Cu–Zn nanocrystalline alloys was examined using Vickers microhardness and tensile tests.
The nanostructure of the alloys was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The
hardness results of processed alloys vary as a function of the alloying elements. Considering typical low ductility of nanocrystalline
materials, the improved ductility with the high strength observed in these alloys suggests that they are artifact-free and
may have several deformation mechanisms, which may include dislocation activity and nano-twinning. 相似文献
89.
Hamdy M. Youssef 《热应力杂志》2013,36(12):1293-1309
A problem of thermoelastic interactions in an elastic infinite layer 0 ≤ x ≤ h with an elevated temperature field arising from ramp-type heating and loading has been constructed. The governing equations are written in a unified system from which the field equations for coupled thermoelasticity as well as for generalized thermoelasticity can be easily obtained as particular cases. Due attention has been paid to the finite rise times of temperature and stress. The problem has been solved analytically by using a state-space approach. Solutions from the derived analytical expressions have been computed for a specific situation. The solution for the half-space when (h → ∞) has been found also. Numerical results for the temperature distribution and thermal stress are represented graphically. A comparison was made among the results predicted by the theories. 相似文献
90.
The dynamic tensile strengths of E-glass composite/polyurea and polyurea/steel interfaces within the E-glass composite/polyurea/AL-6XN stainless steel joint were measured using a laser spallation technique. Values of 370?±?20?MPa were obtained for the polyurea/composite interface while a much higher value of 486?±?20?MPa was obtained for the steel/polyurea interface. Because of the transient nature of the stress pulse, the strain rate changes continuously as the interface stress builds up. A peak strain rate of 5?×?105?s?1 was estimated. The effect of moisture on the tensile strength of the E-glass/polyurea interface was also examined. The effect was found to be minimal, with the tensile strength stabilizing at 320?±?25?MPa after 30?days of exposure to a 90%RH, 50?°C environment. When comparing the strengths of corresponding interfaces in an epoxy-bonded joint from a previous study, it was concluded that polyurea results in a much stronger and durable joint. 相似文献