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31.
Sabiha-Javied S. Waheed N. Siddique M. Tufail M. M. Chaudhry N. Irfan 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(1):17-24
The concentration of 32 elements was determined in phosphate rock samples from the Hazara phosphate deposits of Pakistan using
instrumental neutron activation analysis (INAA) technique employing different irradiation protocols. These included 23 major,
minor and trace elements (Al, As, Ba, Br, Co, Cr, Cs, Fe, Ga, Hf, K, Mn, Na, Rb, Sb, Sc, Sn, Ta, Th, U, V, Zn and Zr) and
9 rare earth elements (REEs) namely Ce, Eu, Ho, La, Lu, Nd, Sm, Tb and Yb. The results have been compared with the global
values of these elements. The concentrations for most of the elements studied are lower than the concentrations reported in
the literature whereas the concentrations of As, Co, Fe, K, Mn, Na and Sb are comparable. Two samples namely HR-4 and HR-5
have the highest concentrations for majority of the REFs with high enrichment factors. The quality assurance of data was performed
through the concurrent use of Lake Sediment (SL-1) and GSJ-JR-1 (Rhyolite) reference materials. The acquired data will serve
as a reference for the follow-up studies to assess the agronomic effectiveness of the Hazara phosphate rocks. 相似文献
32.
S. Waheed N. Siddique M. Arif I. Fatima N. Khalid S. Rahman M. Daud M. Wasim 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):539-548
This paper presents the results of the proficiency test exercise conducted in Pakistan for the determination of trace elements
in mushroom reference material. Thirteen laboratories from different organizations of the country submitted trace elemental
data on Al, As, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Fe, Hg, K, Li, Mg, Mn, Na, P, Pb, Rb Sc, Si, Sm, Sr, Th, Zn. Results for
Al, As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb Sc, and Zn, in the mushroom material were reported by two or
more participating laboratories and could be subjected to statistical evaluation. The original data of these trace elements
was subjected to a computer program “Histo Version 2.1” provided by IAEA. The four outlier tests, i.e., Dixon, Grubbs, skewness
and kurtosis were applied to the data sets. Consensus (overall) mean values, absolute standard deviation, relative standard
deviation, standard error, median and range of values for these elements have been reported at a significance level of 0.05. 相似文献
33.
M. Siddique Rao Tahir Ali Khan M. Shafi 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):531-537
Mössbauer effect technique has been used for the comparative study of Cu1?x Zn x Fe2O4 and Cu1?x Cd x Fe2O4 ( x = 0.0?1.0) ferrites. Both Zn2+ and Cd2+ cations are divalent, non-magnetic ions with different ionic radii. With the substitution of these non-magnetic cations the average internal magnetic field decreases and paramagnetic behavior is dominated at x = 0.7 in both series. It is observed that the occupancy of Cu2+ ions for tetrahedral site is not constant for all compositions but fluctuate between 8–15%. It is also found that Cu2+ ions have more preference for tetrahedral site in Cu-Zn system as compared to the Cu-Cd system. Zn2+ and Cd2+ both ions occupy tetrahedral site completely and form normal spinels for x = 1.0. 相似文献
34.
Manoj Kr. Paul Y. Dilipkumar Singh Abhijit Dey Sandip Kr. Saha Siddique Anwar Asoke. P Chattopadhyay 《Liquid crystals》2016,43(3):343-360
New homologous series of coumarin Schiff base derived from 6-aminocoumarin and their zinc(II) complexes have been synthesised. The spectroscopic characterisations, photophysical properties, phase transition temperature, characterisation of phase and gelation behaviour are reported. The ligand is non-mesogenic at lower 4-n-alkoxy chain length (n = 4) and mesogenic for longer chains (n > 4). For small chains (n = 5, 7, 8), ligand displays monotropic nematic or nematic-smectic A phase sequences, whereas longer homologues (n = 12, 14, 16 and 18) display only enantiotropic smectic A phase. The ligands and their Zn(II) complexes are fluorescent in nature. Interestingly, ligands exhibit gelation property only in polar solvents, whereas Zn(II) complexes discourage gelation. The effect of 4-n-alkoxy chain length on the gelation properties was also discussed. Density functional theory calculations show broad agreement with observed molecular conformation, dipole moment, molecular orbitals and polarisability of the coumarin Schiff base molecules and their Zn(II) complexes. 相似文献
35.
This comment points out to a mistake in the main equation of Solteiro Pires et al. (Nonlinear Dyn. 61:295–301, 2010) concerning the fractional velocity in particle swarm optimization. The correct fractional velocity equation is provided and simulation experiments are redone in the comment. 相似文献
36.
ZrOCl2·8H2O catalyzed environmentally benign synthesis of isobenzofuran-1(3H)-ones are described.ZrOCl2·8H2O appeared to be an excellent catalyst for the condensation and reactions.Reaction of phthalaldehydic acid(2-carboxybenzaldehyde) with methylaryl and cyclic ketones was initiated by condensation and occurred in one step providing excellent yields(90-98%). 相似文献
37.
Khan SJ Sorensen CM Chakrabarti A 《Langmuir : the ACS journal of surfaces and colloids》2012,28(13):5570-5579
This paper presents simulation studies of nanoparticle supercluster (NPSC) nucleation from a temperature quenched system. The nanoparticles are represented as 5 nm, spherical gold nanoparticles ligated with alkane thiols. The pair potential accounts for the van der Waals interaction between the metallic cores and ligand-ligand and ligand-solvent interactions. Phenomena well-known for molecular systems are observed including a prenucleation induction period, fluctuating prenucleation clusters that predominately add monomers one at a time, a critical nucleus size, and growth of NPSCs from solution in the presence of an equilibrium supernatant, all consistent with classical nucleation theory. However, only the largest prenucleating clusters are dense, and the cluster size can occasionally range greater than the critical size in the prenucleation regime until a cluster with low enough energy occurs, then nucleation ensues. Late in the nucleation process, the clusters display a crystalline structure that is a random mix of face-centered cubic (fcc) and hexagonal close-packed (hcp) lattices and indistinguishable from a randomized icosahedra structure. 相似文献
38.
The International Atomic Energy Agency Marine Environmental Laboratory (IAEA-MEL) conducted an intercomparison exercise for
the “Trace elements and methyl mercury in fish scallop: IAEA-452” in 2009. The Neutron Activation Analysis (NAA) laboratory
at PINSTECH, Pakistan took part in this exercise. Comparison with the IAEA results showed that of the 18 elements reported
to the IAEA 7 had unacceptable z-scores while the data for two elements was questionable (2< |z-score| <3). Upon investigation it was discovered that the large number of elements having unacceptable z-scores was due to human error and the greater difficulty in analyzing biological samples which have low amounts of trace
elements. Therefore selection of values corresponding to matrix matched reference materials (RMs), such as IAEA-436 and IAEA-407,
and to non-interfering peaks the results obtained became comparable to the IAEA results with only the result for As having
|z-score|> 3. 相似文献
39.
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