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981.
A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5–25.0 μg mL?1 with a linear regression equation of A = 9.85 × 10?4 + 4.90 × 10?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 104L mol?1 cm?1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL?1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%. 相似文献
982.
983.
SHAH Syed Mazhar 《高等学校化学研究》2011,(3):366-370
A new method based on the cloud point extraction(CPE) for separation and preconcentration of nickel(Ⅱ) and its subsequent determination by graphite furnace atomic absorption spectrometry(GFAAS) was proposed, 8-hydroxyquinoline and Triton X-100 were used as the ligand and surfactant respectively. Nickel(Ⅱ) can form a hy-drophobic complex with 8-hydroxyquinoline, the complex can be extracted into the small volume surfactant rich phase at the cloud point temperature(CPT) for GFAAS determination. The factors af... 相似文献
984.
In this paper a formula for the coefficient of λ
n-gh+g-1 in the chromatic polynomial of a linear h-uniform hypergraph H of order n and girth g is proposed provided (g, h) ≠ (3, 3). This formula involves 13 types of spanning subhypergraphs of H for 3 ≤ h ≤ 5. 相似文献
985.
A. Lopez-Martens K. Hauschild A. V. Yeremin O. Dorvaux A. V. Belozerov Ch. Briançon M. L. Chelnokov V. I. Chepigin D. Curien P. Désesquelles B. Gall V. A. Gorshkov M. Guttormsen F. Hanappe A. P. Kabachenko F. Khalfallah A. Korichi A. C. Larsen O. N. Malyshev A. Minkova Yu. Ts. Oganessian A. G. Popeko M. Rousseau N. Rowley R. N. Sagaidak S. Sharo A. V. Shutov S. Siem L. Stuttgé A. I. Svirikhin N. U. H. Syed Ch. Theisen 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):245-250
Isomeric states in 253No have been investigated by conversion electron and γ -ray spectroscopy with the GABRIELA detection system. The 31μs isomer
reported more than 30 years ago is found to decay to the ground state of 253No by the emission of a 167keV M2 transition. The spin and parity of this low-lying isomeric state are established to be 5/2+ . The presence of another longer-lived isomeric state is also discussed. 相似文献
986.
Syed Masood Husain Marie Theres Heim Dirk Schepmann Bernhard Wünsch 《Tetrahedron: Asymmetry》2009,20(12):1383-1392
A very short (three steps) asymmetric synthesis of enantiomerically pure 1,4-disubstituted tetrahydro-1H-3-benzazepines 14 has been elaborated upon, starting from the trans- and cis-configured 11a-substituted 3-phenyl-2,3,11,11a-tetrahydro[1,3]oxazolo[2,3-b]-[3]-benzazepin-5(6H)-ones 6 and 7. The stereoisomerically pure lactams 6 and 7 were benzylated to give 6-benzyl-substituted products 8 and 9. NOE experiments showed a trans-configuration of the benzyl residue and the residue in the 11a-position indicated that the stereochemistry of the benzylation reaction was controlled by the stereocenter at the 11a-position. Reduction of the benzylated tricyclic benzolactams 8 and 9 with AlCl3/LiAlH4 (1/3) yielded the 1,3,4-trisubstituted 3-benzazepines 12 and 13, which were formed stereoselectively with the retention of configuration. Finally, removal of the N-(2-hydroxy-1-phenylethyl) residue by hydrogenolytic cleavage resulted in the formation of enantiomerically pure 1,4-disubstituted 3-benzazepines 14. The σ1, σ2, and NMDA receptor affinities of the enantiomerically pure 3-benzazepines 14 and ent-14 were investigated in competitive receptor binding studies. The butyl derivative ent-14c showed a high affinity towards σ1 and σ2 receptors, with Ki-values of 26 nM and 41 nM, respectively. 相似文献
987.
Syed Azer Reza 《Optics Communications》2009,282(7):1298-1303
To the best of our knowledge, proposed is the first variable fiber optical attenuator (VFOA) using an electronically controlled variable focus liquid lens. The approach uses the changes in the radius of curvature of the liquid lens edge to enable an electronically controlled optical wedge that produces a varying beam tilt angle. In effect, changing beam tilt within a single mode fiber (SMF) lens free space coupling assembly leads to a polarization independent broadband VFOA design. The demonstrated VFOA experiment shows broadband operation over the 1530-1560 nm C-Band with a 40 dB dynamic range, <0.5 dB resolution, 0.3 dB polarization dependant loss, 4.3 dB fiber-to-fiber optical loss, 3 dB optical bandwidth from 1510 nm to 1700 nm, and switching time of <100 ms. Applications for this VFOA include use in hand held test and measurement equipment. 相似文献
988.
Nasim Baimani Parviz Aberoomand Azar Syed Waqif Husain Homayon Ahmad Panahi Ali Mehramizi 《Journal of separation science》2019,42(7):1468-1476
We developed an approach for the use of polyester dendrimer during the imprinting process to raise the number of recognized sites in the polymer matrix and improve its identification ability. Photoresponsive molecularly imprinted polymers were synthesized on modified magnetic nanoparticles involving polyester dendrimer which uses the reactivity between allyl glycidyl ether and acrylic acid for the high‐yielding assembly by surface polymerization. The photoresponsive molecularly imprinted polymers were constructed using methylprednisoloneacetate as the template, water‐soluble azobenzene involving 5‐[(4, 3‐(methacryloyloxy) phenyl) diazenyl] dihydroxy aniline as the novel functional monomer, and ethylene glycol dimethacrylate as the cross‐linker. Through the evaluation of a series of features of spectroscopic and nano‐structural, this sorbent showed excellent selective adsorption, recognition for the template, and provided a highly selective and sensitive strategy for determining the methylprednisoloneacetate in real and pharmaceutical samples. In addition, this sorbent according to good photo‐responsive features and specific affinity to methylprednisoloneacetate with high recognition ability, represented higher binding capacity, a more extensive specific area, and faster mass transfer rate than its corresponding surface molecularly imprinted polymer. 相似文献
989.
Syed Pavel Afrose Subhajit Bal Ayan Chatterjee Krishnendu Das Dibyendu Das 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(44):15930-15934
Highly dynamic and complex systems of microtubules undergo a substrate‐induced change of conformation that leads to polymerization. Owing to the augmented catalytic potential at the polymerized state, rapid hydrolysis of the substrate is observed, leading to catastrophe, thus realizing the out‐of‐equilibrium state. A simple synthetic mimic of these dynamic natural systems is presented, where similar substrate induced conformational change is observed and a transient helical morphology is accessed. Further, augmented catalytic potential of these helical nanostructures leads to rapid hydrolysis of the substrate providing negative feedback on the stability of the nanostructures and realization of an out‐of‐equilibrium state. This simple system, made from amino acid functionalized lipids, demonstrates a substrate‐induced self‐assembled state, where the fuel‐to‐waste conversion leads to the temporal presence of helical nanostructures. 相似文献
990.
Saeed Ullah Jan Sami Ul Haq Syed Inayat Ali Shah Ilyas Khan Muhammad Atif Khan 《理论物理通讯》2019,71(6):647-657
This work is focused on the effect of heat and mass transfer with unsteady natural convection flow of viscous fluid along with ramped wall temperature under the assumption of the slip wall condition at the boundary. Analytical solutions are obtained by using Laplace transformation to the non-dimensional set of governing equations containing velocity, temperature and concentration. Moreover, the expression for skin-friction is derived by differentiating the analytical solutions of fluid velocity. Numerical tables for Skin-friction, Sherwood number and Nusselt-number are examined. For the physical aspects of the flow, we use various values of involved physical parameters such as Prandtl number (Pr), slip parameter ($\eta$), Schmidt number (Sc), buoyancy ratio parameter ($N$), Sherwood number (Sh), and time $(t)$. Additionally, the general solutions are plotted graphically and a comprehensive theoretical section of numerical discussions is included. 相似文献