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41.
42.
Omar Ramadan 《International Journal of Infrared and Millimeter Waves》2005,26(12):1757-1770
Unconditionally stable formulations of the anisotropic perfectly matched layer (APML) are presented for truncating double
negative (DNG) meta-material finite difference time domain (FDTD) grids. In the proposed formulations, the Z-transform theory
is employed in the alternating direction implicit FDTD (ADI-FDTD) scheme to obtain update equations for the field components
in the DNG meta-material domains. Numerical examples carried out in one dimensional Lorentzian type DNG meta-material domains
are included to show the validity of the proposed formulations. 相似文献
43.
Mohamad Sh. Ramadan Nabila M. El-Mallah Sherif M. Abd-Elmenem 《Journal of Dispersion Science and Technology》2013,34(8):1110-1120
AbstractThe interaction between anionic dyes [Reactive Orange 122 (R.O 122), Reactive Blue 19 (R.B 19), Reactive Violet 5 (R.V 5) and Acid Green 20 (A.G 20)] with cationic surfactant cetyltrimethylammoniun bromide (CTAB) has been investigated by spectrophotometry and conductance technique. The used dyes are characterized by tautomeric behavior which affects the mechanism of the interaction. Various parameters such as dye structure, surfactant composition, solvent composition, temperature and pH of the medium were studied. The spectral data were applied for calculating the binding constant between dye and surfactant (Kb), fraction of micellization (?mic), and standard free energy change of binding (ΔG°b) in 0,10,20 and 30 v/v % acetonitile (AN). Conductance technique was constructed to estimate the ion pairing constant (Ka) at different temperatures and v/v % AN. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for ion pair formation were evaluated. The role of hydrophobic and electrostatic effect on dye-surfactant interaction was discussed. 相似文献
44.
The consecutive stepwise formation constants of 1:1 and 1:2 chelate species formed by the interaction of DC-2-CPHD and DC-3-CPHD anions with tripositive lanthanon and divalent copper, nickel, cobalt, zinc, manganese, and cadmium cations were determined potentiometrically at ionic strengh of 0.1 (KNO3) and 30°C. The results indicate that two different coordination modes, one tridentate (DC-2-CPHD), and one bidentate (DC-3-CPHD), are in evidence. 相似文献
45.
Ramadan El Sayed 《中国化学》2010,28(4):594-600
Benzaldehyde [4‐(4‐bromophenyl)thiazol‐2‐yl]hydrazones 5a – 5d were prepared by reacting the thiosemicarbazones 2a – 2d with 2,4′‐dibromoacetophenone ( 1 ) in absolute ethanol. Acetylation of 5a and 5b with Ac2O/Py at room temperature gave the N‐acetyl derivatives 6a and 6b . 4‐Methyl‐2‐pentanone/cyclopentanone [4‐(4‐bromo‐phenyl)thiazol‐2‐yl]hydrazones ( 8a ) and ( 8b ) were similarly obtained from the reaction of 1 with the thiosemicarbazones 7a and 7b , respectively. Cyclization of D‐galactose thiosemicarbazone ( 9 ) and its tautomers 10 and 11 with 1 afforded an equilibrium mixture of the acyclic 2‐thiazolylhydrazone 12 , together with its respective cyclic galactosyl derivatives 13 and 14 , whose structures were studied by using 1H and 13C NMR spectra. The antimicrobial activity of the synthesized thiazole derivatives was evaluated in vitro by using an agar diffusion technique, and some of these compounds showed potential activity against Candida albicans. 相似文献
46.
Mohamed M. Ibrahim Abd El-Motaleb. M. Ramadan 《Journal of inclusion phenomena and macrocyclic chemistry》2010,68(3-4):287-296
Two new artificial peptides with histidine side chains, namely N-methyl N,N′-bis(Im-bzl-l-histidylmethylestermethyl)amine L1 and N,N′,N″,N?-tetrakis(Im-bzl-l-histidylmethyl-estermethyl)ethylene diamine L2 have been synthesized and were shown to form stable zinc complexes [L1Zn(H2O)2](ClO4)2 1 and [L2Zn2(H2O)3](ClO4)4 2, respectively. Solution studies (pH–1NMR titrations) of the ligand L2 in the presence of zinc ions were also reported. The catalytic activity of zinc complex species 1 and 2 as structural phosphotriestrase models were tested on the hydrolysis/detoxification of p-nitrohenl diphenylphosphate (p-NPDPP). From the correlation between the pH-rate profiles and the species distribution curves, the catalytically active species could be identified. On the basis of R-dependence as well as the rate acceleration of each complex, the possibility of cooperative action of zincs in dinuclear zinc complex is debated. 相似文献
47.
A neutral hydroxylated octadecyl monolith (ODM-OH) for reversed-phase capillary electrochromatography has been developed. The ODM-OH was prepared by the in situ polymerization of octadecyl acrylate and pentaerythritol triacrylate (PETA) in a ternary porogenic solvent. Pentaerythritol triacrylate possesses a hydroxyl functional group, which imparts the monolith with a hydrophilic group, thus the acronym ODM-OH. The ODM-OH column exhibited cathodal EOF over a wide range of pH and ACN concentration in the mobile phase despite the fact that it was devoid of any fixed charges. This ODM-OH monolith exhibited stronger EOF than its counterpart the ODM made from the in situ polymerization of octadecyl acrylate and trimethylolpropane trimethacrylate. Similar to ODM, it is believed that the EOF was due to the adsorption of ions from the mobile phase onto the surface of the monolith thus imparting the neutral monolithic column the zeta potential necessary to support the EOF. The higher EOF exhibited by ODM-OH was due to the presence of polar OH groups on its surface, which would favor stronger adsorption of ions from the mobile phase. The wide applications of the neutral ODM-OH column were demonstrated in the separation of a wide range of small and large solutes. As a typical result, the ODM-OH was able to separate proteins quite rapidly yielding 200,000 plates/m. 相似文献
48.
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50.
Simultaneous washing and concentration of functionalized magnetic beads in a complex sample solution were demonstrated by applying a rotational magnetic actuation system to a microfluidic chip under continuous flow conditions. The rotation of periodically arranged small permanent magnets close to the fluidic channel carrying a magnetic bead suspension allows trapping and releasing of the beads along the fluidic channel in a periodical manner. Each trapping and releasing event resembles one washing cycle. A purification efficiency of magnetic beads out of a mixed magnetic and non-magnetic bead sample solution of 83±4% at a flow rate of 0.5 μL min(-1), and a magnetic bead recovery or concentration efficiency of 91±5% were achieved using a flow rate of 0.2 μL min(-1). The detection performance of the device was experimentally evaluated with two different bioassays, using either streptavidin-coated magnetic beads in combination with biotinylated fluorescent isothiocyanate (FITC), or a mouse antigen (Ag)-antibody (Ab) system. 相似文献