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11.
Monosized poly(styrene/N-[3-(dimethylamino)propyl]methacrylamide/poly(ethylene glycol) ethyl ether methacrylate) [poly(St/PEG-EEM/DMAPM)] cationic nanoparticles were synthesized by emulsifier-free emulsion polymerization conducted in the presence of a cationic initiator, 2,2-azobis(2-methylpropionamidine) dihydrochloride (APDH or V-50). Particle sizes and surface charge densities were measured with a Zeta Sizer. The structure of the terpolymers was determined by Fourier transform IR and 1H NMR spectroscopies. The amounts of the main monomer (St), cationic comonomer (DMAPM), stabilizer (PEG-EEM), and initiator (APDH), and the water-to-monomer phase ratio were all effective on both the average size and the surface charge of the nanoparicles. The average particle size was in the range 75–400 nm depending on the recipe applied; it decreased on increasing the amount of DMAP or PEG-EEM or the water-to-monomer phase ratio in the feed, while it increased with increasing St or APDH content. These nanoparticles were quite monodisperse with a polydispersity index of 1.008–1.14. 相似文献
12.
Two sensitive, simple and rapid UV and second order derivative spectrophotometric methods were developed for the determination of nizatidine and ranitidine hydrochloride in pure form and pharmaceutical preparations. For the first method, UV spectrophotometic method, nizatidine was determined at 325 nm and ranitidine at 325.5 nm with detection limits of 0.07 and 0.04 μg/mL, respectively. For the second method, the distances between two extremum values (peak-to-peak amplitudes), 328/356.5 nm for nizatidine and 326/357 nm for ranitidine were measured in the second order derivative-spectra. The detection limits were found to be 0.02 μg/mL for nizatidine and 0.016 μg/mL for ranitidine, respectively. The thermal analysis of the two drugs was studied by Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) techniques. Enthalpy changes were obtained 121.9 and 124.15 J/g for nizatidine and ranitidine, respectively. The proposed method was successfully applied to the analysis of pharmaceutical preparations. The results were in good agreement with those obtained using the reference method; no significant difference were found in the accuracy and precision as revealed by the accepted values of t- and F-tests. 相似文献
13.
U. Kürüm R. M. Öksüzoğlu M. Yüksek H. G. Yaglioglu H. Çınar Ayhan Elmali 《Applied Physics A: Materials Science & Processing》2011,104(4):1025-1030
We studied the nonlinear absorptive characteristics (saturation intensity threshold and effective nonlinear absorption coefficients)
and nonlinear refraction in a 50-nm-thick VO
x
thin amorphous film prepared by pulsed DC magnetron reactive sputtering. The absorptive and refractive nonlinearities were
investigated by pump–probe and Z-scan techniques. The closed-aperture Z-scan results reveal self-defocussing characteristics
of the amorphous VO
x
thin film for both nanosecond and picosecond pulse durations. Experimental results show that a phase transition does not
occur in the range of intensities used for the experiments and the investigated sample can be treated as an amorphous semiconductor
structure. The open-aperture Z-scan curves with nanosecond pulses exhibit saturable absorption for all input intensities.
On the other hand, the open-aperture Z-scan curves with picosecond pulses exhibit nonlinear absorption/saturable absorption
for low/high input intensities, respectively. Saturation intensity thresholds were found to be 15.3 MW/cm2 for 4-ns pulse duration and 586 MW/cm2 for 65-ps pulse duration. 相似文献
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A rapid and specific proton magnetic resonance spectroscopic method was developed for determining acetazolamide in tablets. Maleic acid was used as the internal standard and DMSO-d6 served as the NMR solvent. the concentration of drug per unit dose was calculated from the integration values for the resonance signals of acetazolamide at 2.14 ppm and maleic acid at 6.20 ppm. the method using commercial products gave comparable results of those obtained by the method of USP XXIII. 相似文献
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