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排序方式: 共有2749条查询结果,搜索用时 15 毫秒
91.
Anwar A. Wassil Abd El-Ftaah Bastawy Farag Fatma A. Moukdad 《Drug development and industrial pharmacy》2013,39(1):57-62
ABSTRACTThe construction of PVC matrix-type β-blockers (sotalol, carvedilol, and betaxolol) ion selective electrodes and their use for direct potentiometry of their respective species are described. The proposed sensors are based on the complex ion associates of β-blockers with tungstophosphate (TP) and Ammonium Reineckate (Rein) ionophoris in poly vinyl chloride membrane (PVC) with Dioctylphthalate (DOP) plasticizer. The four electrodes (Beta-TP), (Sota-TP), (Carve-TP), and (Cave-Rein) show stable potential response with near Nernstian slope of 50.8, 33.7, 32.35, and 33 mv per decade, range of concentration 10?2–10?7 M β-blockers. Selectivity coefficients data obtained for 11 different organic and inorganic ions are presented. The electrodes have fast response time (30 and 40 s) and were used over wide range of pH 4.5–8.5. Validation of the method according to the quality assurance standers shows suitability of proposed sensors for use in the quality control assessment of these drugs. The results obtained for the determination of β-blockers with the proposed electrodes show average recoveries of 100.78% and a mean standard deviation of ±1.2. The nominal are obtained. The data agree well with those obtained by standard methods. 相似文献
92.
93.
94.
R. Awad M. Roumié A. I. Abou-Aly S. A. Mahmoud M. M. Barakat 《Journal of Superconductivity and Novel Magnetism》2012,25(2):273-291
Superconducting samples of type Bi1.8Pb0.4Sr2Ca2.1Cu3−x
Ru
x
O10+δ
, (Bi, Pb)-2223, with 0.0≤x≤0.4 and type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ
, (Tl, Pb)/Sr-1212, with 0.0≤x≤0.525 were synthesized using the standard solid-state reaction technique. The lattice parameters and the surface morphology
for these samples were determined using X-ray powder diffraction (XRD) and scanning electron microscope (SEM) measurements,
respectively. All element-contents of the samples prepared were estimated from the electron dispersive X-ray (EDX) technique,
and their results were compared with those obtained from particle-induced X-ray emission (PIXE). In addition, the oxygen-content
was determined using elastic Rutherford backscattering spectroscopy (RBS) technique at 3 MeV proton beam. The superconducting
transition temperature T
c and the hole carrier concentration P were determined from the electrical resistivity measurement. The data of both T
c and P for Bi1.8Pb0.4Sr2Ca2.1Cu3−x
Ru
x
O10+δ
and Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ
phases increased up to x=0.05 and 0.075, respectively and then they decreased as x increased. The superconductivity was completely destroyed around x=0.4 and 0.525 for (Bi, Pb)-2223 and (Tl, Pb)/Sr-1212 phases, respectively. The normal-state electrical resistivity data were
analyzed using the two and three dimensional variable range hopping (2D-VRH and 3D-VRH) and the Coulomb gab (CG). 相似文献
95.
Mahmoud KhazmaAdeline Goullieux Rose-Marie DheillyMichèle Quéneudec 《Cement and Concrete Composites》2012,34(2):223-230
Lignocellulosic lightweight concretes are a potential contributor to sustainable development. However, lignocellulosic aggregates are not always fully compatible with cement matrices leading to setting delays, significant dimensional variations and low mechanical strengths. An aggregate treatment, reducing water absorption and water-soluble molecule release, can avoid or reduce these drawbacks. In this study a coating treatment, using a pectin/polyethylenimin (PP) mixture, was applied to flax shives, which is a lignocellulosic by-product. Before shive coating, a dilution with distilled water or a micro-wave heating were conducted to decrease PP mixture viscosity.The PP treatment involved a decrease in shive water absorption. Compared to standard shive concrete, treated shive concrete exhibited a decrease in setting delay with an increase in cement hydration enthalpy, an increase in mechanical strengths and a significant reduction in dimensional variations. Although a slight increase in thermal conductivity and bulk density was measured, the cement-shive composite obtained still belongs to the insulating concrete category. 相似文献
96.
Transmission pricing has become a major issue in the discussions about the deregulated electricity markets.Conse-quently,open access to the transmission system is one of the basic topics to allow compe... 相似文献
97.
Nitrile butadiene rubber loaded with different concentrations of thin graphite nanosheets have been successfully prepared by using a two‐roll mill. The percolation concentration of the nanocomposites was 0.5 phr. The I–V characteristic curves showed that the nanocomposites exhibited ohmic behaviour at a certain voltage and then non‐linear behaviour. The Richardson–Schottky and Poole–Frenkel models were used to investigate the reason for the space charge. The experimental data fit the Schottky model well. The conductivity as a function of temperature was also studied and the data were fitted by using the Mott relation. The Mott relation showed that as the concentration of graphite nanosheets in the rubber composite increases, the hopping distance between the graphite nanosheet layers decreases, which enhances the conductivity of the nanocomposite at low concentrations. Copyright © 2011 Society of Chemical Industry 相似文献
98.
99.
Normal ultrasonic transducers of 0.5, 1, and 2 MHz are modified using delay lines which are made of Quartz. Such modification is to ameliorate the capability of the transducer to investigate Gd-doped ZnO thin films whose thickness is too thin. The normal transducers cannot test materials that have too thin thickness due to the near fields of these transducers. The near field is considered as blind area of the transducer. Therefore, the specimen under test must have thickness bigger than the near field of the used transducer, or instead delay lines can be used. Samples of Gd-doped ZnO thin films are prepared using sol gel technique. The ultrasonic pulse echo method is used at room temperature. Flaws are found in different prepared specimens. Results show that such delay lines are suitable to ameliorate the ultrasonic transducer to test Gd-doped ZnO thin films. 相似文献
100.
Mahmoud A. Hamad 《Journal of Superconductivity and Novel Magnetism》2014,27(7):1777-1780
Magnetocaloric effect in half-metallic double perovskite Sr0.4Ba1.6?x La x FeMoO6 (x = 0, 0.1, 0.2, 0.3) were investigated. It is shown that Sr0.4Ba1.6?x La x FeMoO6 exhibits the largest magnetic entropy change (ΔS M ) of 0.086 J/kg K upon 0.2 T magnetic field variation. Furthermore, ΔS M distribution of the Sr0.4Ba1.6?x La x FeMoO6 is much more uniform than that of gadolinium. Through these results, polycrystalline samples of Sr0.4Ba1.6?x La x FeMoO6 have some potential applications for magnetic refrigerants in a wide temperature range, including room temperature. 相似文献