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排序方式: 共有753条查询结果,搜索用时 15 毫秒
741.
HH Hassan SG El-Banna AF Elhusseiny el-SM Mansour 《Molecules (Basel, Switzerland)》2012,17(7):8255-8275
We report the synthesis of aramide nanoparticles containing a chiral N-phthaloyl valine moiety and their antioxidant activities on hepatic contents of cytochrome P???, amidopyrene N-demethylase, aniline-4-hyroxylase and induced the hepatic content of cytochrome b5 and nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C-reductase. Polymers were obtained as well-separated spherical nanoparticles while highly aggregated particles via H-bonding organization of the aramide-containing pyridine led to a thin layer formation. The effects of the nanoparticles and CCl? on enzyme activities and thiobarbituric acid reactive substances (TBARS) levels of male rat liver were studied. Pretreatments of rats with the polyamides prior to the administration of CCl? decreased the hepatic content of the tested enzymes. Doses reduced the toxic effects exerted by (?CCl?) upon the liver through inhibition of the cytochrome P??? system. Inhibition of such metabolizing enzymes could reduce the carcinogenic effects of chemical carcinogens. 相似文献
742.
E. Mansour 《Journal of Non》2012,358(3):454-460
A series of glass of the molar formula xAl2O3-(50-x)PbO-25B2O3-25SiO2 with x:2.5–17.5 with step of 2.5 mol.% was prepared and measured for, density, molar volume and infrared absorption. A semiquantitative analysis of the IR spectra was performed. It was found that each oxide would contribute in density with a specific factor. The density factor related to PbO is markedly higher than that of the other two oxides represent the glass skeleton which means that the content of PbO is the main factor affecting the density. The depolymerization of the whole glass skeleton increases with increasing the content of Al2O3. There is a competition between the role of PbO and Al2O3 in changing the value of N4 and the crosslinking of the glass network. The silicate network tends to be distinguished from the reminder of the whole glass network with increasing alumina. The IR band located near 700 cm? 1 was suggested to be due to the vibrations of bridging oxygens between trigonal boron atoms. An essential change in the role of PbO in these glasses from glass modifier to glass former occurred around 12 mol.% Al2O3. 相似文献
743.
In this paper we introduce three sampling theorems for transformations defined in terms of Jackson q-integration when the kernel of the transformation is a solution or the Green’s function of singular q-Sturm–Liouville problems. We consider the problem when the q-Sturm–Liouville problem is singular either at infinity or at zero with detailed investigations when the singular point is infinity. This approach allows the derivation of sampling representations for transforms whose kernels are linear combinations of q-Bessel functions, not just a single one as previously established. 相似文献
744.
Y.M. Abbas S.A. Mansour M.H. Ibrahim Shehab.E. Ali 《Journal of magnetism and magnetic materials》2012
The structural and magnetic properties of the spinel ferrite system Co1+xFe2−2xSnxO4 (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm−1 and 425 cm−1, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. 相似文献
745.
Khaled. Elsayed Hisham Imam Amro Harfoosh Yasser Hassebo Yasser Elbaz Mouayed Aziz Mohy Mansour 《Optics & Laser Technology》2012,44(1):130-135
A passive, Q-switched pulsed, Nd:YAG laser system was designed and built, which can provide a potential compact robust laser source for portable laser induced breakdown spectroscopy systems.The developed laser system operates at 1064 nm. Each laser shot contains a train of pulses having maximum total output energy of 170 mJ. The number of pulses varies from 1–6 pulses in each laser shot depending on the pump energy. The pulse width of each pulse ranges from 20 to 30 ns. The total duration of the output pulse train is within 300 μs. The multi-pulse nature of the laser shots was employed to enhance the LIBS signal. To validate the system, LIBS measurements and analysis were performed on ancient ceramic samples collected from Al-Fustat excavation in Old Cairo. The samples belong to different Islamic periods in Egypt history. The results obtained are highly indicative that useful information can be provided to archeologists for use in restoring and repairing of precious archeological objects. 相似文献
746.
Ceramic compositions of a complex perovskite CaXPb(1?X)TiO3 (CPT) systems with x=0.6, 0.7 and 0.8 were prepared by mechanical mixing of their oxides (CaTiO3 and PbTiO3). The structure of the (CPT) ceramics was characterized by X-ray diffraction (XRD) The ceramics transform gradually from orthorhombic phase (pseudo cubic phase) to cubic phase by increasing pb content percent. The dc resistivity ρ(t) versus temperature (range 300–525 K) for x=0.6, 0.7 and 0.8. The ρ.T/curves reveal that samples exhibit a metallic behaviour at low temperature and undergo a metal-semiconductor transition with increasing temperature at Tp=373 K, 343 K and 333 K, for x=0.6, 0.7 and 0.8, respectively. The nature of conduction mechanism is studied in semiconductor region by studying the current–voltage temperature characteristics. The current–voltage characteristics were interpreted in terms of Poole–Frenkel type of conduction mechanism. 相似文献
747.
The ground state degeneracy of an SU(N)
k
topological phase with n quasiparticle excitations is a relevant quantity for quantum computation, condensed matter physics, and knot theory. It is
an open question to find a closed formula for this degeneracy for any N >2. Here we present the problem in an explicit combinatorial way and analyze the case N = 3. While not finding a complete closed-form solution, we obtain generating functions and solve some special cases. 相似文献
748.
749.
Quantum groups are used to define q-special functions. The Casimir operatorsof a variation of SU
q(2) and E
q(2) are derived. The proposed q-associated Legendreand q-Bessel functions are the eigenfunctions of the Casimirs. The results differfrom ordinary q-special functions, but this is expected since the q-generalizationis not unique. 相似文献
750.
A novel method for the determination of cobalt(II) by stripping voltammetry is described. It involves an adsorptive accumulation
of the cobalt(II)-2-aminocyclopentene-1-dithiocarboxylic acid complex on a hanging mercury drop electrode, followed by a stripping
voltammetric measurement of the catalytic reduction current of the complex at –1.4 V at pH = 9 (vs. Ag/AgCl). The effects
of various experimental parameters on the catalytic current were investigated. An accumulation time of 60 s results in a low
experimental limit of detection of 0.1 ng/mL of Co(II), and 0.50 to 40.0 ng/mL of cobalt can be determined. The relative
standard deviation at 0.50 ng/mL is 2.8%. Possible interferences from co-existing ions were also investigated.
Received: 17 August 1998 / Revised: 16 November 1998 / Accepted: 20 November 1998 相似文献