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- SourceAvailable from: Khalida Akhtar[Show abstract] [Hide abstract]
ABSTRACT: Monodispersed powders of copper oxide precursor were produced in spherical and bipyramidal particle morphologies by the urea-based homogenous precipitation method. Composition of the starting reactant mixtures and synthesis conditions had significant effect on the morphology of the precipitated particles. Extensive optimization of these parameters was thus performed, in order to explore the key factors responsible for the production of monodispersed systems of the precipitated powders. It was observed that the particles obtained from the copper nitrate urea system were spherical and amorphous copper (II) basic carbonate, while those produced in copper chloride urea solution were bi-pyramidal and crystalline copper (II) basic chloride. On controlled calcination at the elevated temperatures both of these compounds transformed into crystalline copper oxide powders with identical crystal structures, though with different crystallite sizes. In both cases, the particles retained their original shape integrity to a maximum extent and showed no sign of sintering. (C) 2014 Published by Elsevier Ltd.Materials Research Bulletin 09/2014; 57:121–126. DOI:10.1016/j.materresbull.2014.05.028
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ABSTRACT: A simple and sensitive chemiluminescence (CL) method was developed for the determination of citalopram in pharmaceutical preparations and human plasma. The method is based on the enhancement of the weak CL signal of the luminol-H2 O2 system. It was found that the CL signal arising from the reaction between alkaline luminol and H2 O2 was greatly increased by the addition of silver nanoparticles in the presence of citalopram. Prepared silver nanoparticles (AgNPs) were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM). Various experimental parameters affecting CL intensity were studied and optimized for the determination of citalopram. Under optimized experimental conditions, CL intensity was found to be proportional to the concentration of citalopram in the range 40-2500 ng/mL, with a correlation coefficient of 0.9997. The limit of detection (LOD) and limit of quantification (LOQ) of the devised method were 3.78 and 12.62 ng/mL, respectively. Furthermore, the developed method was found to have excellent reproducibility with a relative standard deviation (RSD) of 3.65% (n = 7). Potential interference by common excipients was also studied. The method was validated statistically using recovery studies and was successfully applied to the determination of citalopram in the pure form, in pharmaceutical preparations and in spiked human plasma samples. Percentage recoveries were found to range from 97.71 to 101.99% for the pure form, from 97.84 to 102.78% for pharmaceutical preparations and from 95.65 to 100.35% for spiked human plasma. Copyright © 2013 John Wiley & Sons, Ltd.Luminescence 05/2014; 29(3). DOI:10.1002/bio.2539
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ABSTRACT: Aerosol optical and radiative properties have, for the first time, been retrieved from ground-based measurements in Karachi, Pakistan. Ground-based aerosol measurements were obtained using a GRIMM Model 1.109 optical particle counter (OPC). The optical and radiative properties of aerosols were retrieved from these measurements using the Aerosol Robotic Network (AERONET) inversion algorithm. The volumetric size distribution obtained from the OPC measurements shows three distinct modes, one fine and two coarse, with a fine mode particle diameter of about 0.29 mu m and coarse mode particle diameters of about 7 mu m and 22.5 mu m. An overlap in between the size range of 0.25 mu m to 7 mu m has been carried out by using OPC data together with data obtained from AERONET. The obtained OPC-transposed data set (OPCAOD) was compared with those obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and AERONET Sunphotometer. The analysis revealed a moderate correlation of 0.57 between OPCAOD and MODISAOD data but only low correlations between OPCAOD and AERONET(AOD) data (0.21), and between MODISAOD and AERONET(AOD) data (0.26). The Single Scattering Albedo (SSA) for the measurement days, calculated at a wavelength of 676 nm, ranged from 0.83 +/- 0.01 to 0.90 +/- 0.02, showing slight variations in magnitude between the different measurement days. The asymmetry parameter (ASY), a wavelength-dependent quantity, was calculated for the same wavelength yielding values that ranged from 0.59 +/- 0.01 to 0.68 +/- 0.02. The aerosol radiative forcing (ARF) values measured for the period of observation at the top of the atmosphere, at the earth's surface, and within the atmosphere ranged from 31.2 W/m(2) to -28.27 W/m(2), from -69.76 W/m(2) to -73.57 W/m(2), and from 38.56 W/m(2) to 45.3 W/m(2), respectively.Aerosol and Air Quality Research 04/2014; 14(3-3):686-696. DOI:10.4209/aaqr.2013.09.0294
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