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971.
M. B. Alamin A. A. Mhapes A. M. Bejey A. Sadek R. H. Atweer K. Dubali Daw M. Saad 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):247-250
Since there is no database in Libya defining the intake of the individuals from different essential (minor and trace) and
toxic elements provided through food, drinking water and aerosol, a project has been proposed with the cooperation of IAEA
to determine the concentration of a number of elements such as Cs, Fe, Cr, Rb, Sc, Se, Co, Zn in the three mentioned sources.
Emphasis was placed on the use of nuclear and nuclear-related techniques. In this paper, the primary results are presented
for the concentration of minor and trace elements in some vegetables, spices and other foods which are widely used in the
Libyan meals. Instrumental neutron activation analysis utilizing a 10 MW water pool reactor and a γ-ray spectroscopy facility
was employed. For quality control, certified reference materials were analyzed simultaneosly with the samples which show good
agreements compared with the certified data. Emphasis was given to both elements iron and zinc for their importance. 相似文献
972.
A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic
spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets.
Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four
possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction
in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency,
form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided. 相似文献
973.
The adsorption of a surfactant mixture, based on an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS) and a nonionic
surfactant (Triton X-100, or TX100), on alumina nanoparticles was determined by solution depletion method combined with spectrometric
measurement. It is shown that the light scattering, originated from the residual adsorbent alumina particles in the supernatant
after centrifugation separation, interferes with the measurements of absorbance of the surfactant molecules, and therefore
constitutes an error source for determination of the surfactant concentration in the supernatant by spectrometric means. The
intensity of this light scattering, namely the influence of the residual alumina nanoparticles upon the surfactant adsorption,
was related to the surfactant adsorption and its equilibrium concentration and varied among a batch. In this paper we report
a Kalman filter method in order to eliminate the variational scattering background caused by non-separated residual alumina
nanoparticles in each supernatant. This method is of interest as it is simple, easy to carry out and of high precision. 相似文献
974.
H. -W. Sun W. -J. Kang J. Ha S. -X. Liang S. -G. Shen 《Journal of the Iranian Chemical Society》2004,1(1):40-46
The species of Cr(III) and Cr(VI) in water samples were determined by flow injection on-line preconcentration and separation on two-microcolumn system-derivative flame atomic absorption spectrometry during a collaborative analysis for certification. The Cr(III) and Cr(VI) in water samples were retained on two microcolumns with ion exchange resin and were eluted directly to nebulizer by 15% HNO3 and 8% NH4NO3, respectively. The characteristic concentration (at the sensitivity grade of 2 mV min?1 for 1 min of preconcentration time) for Cr(III) and Cr(VI) were 0.130 and 0.0985 μg l?1, in the order which were 332- and 431-fold better than those of FAAS, and 45- and 47-fold better than those of FI-FAAS, respectively. The relative standard deviations were 3.27% and 3.66% with corresponding detection limits (3σ) of 0.244 and 0.235 μg l?1, respectively. The linear ranges of determinations for Cr(III) and Cr(VI) were 0~100 μgm l?1 with correlation coefficients of 0.9984 to 0.9996. The satisfactory recovery of 94.4%~106% for Cr(III) and Cr(VI) could be obtained from water samples. 相似文献
975.
用过渡金属络合催化剂聚合环氧氯丙烷能获高分子量的聚合物。稀土络合催化剂对环氧乙烷,环氧丙烷及环硫丙烷的开环聚合具有明显效果。本文选用Y(acac)_3-H_2O-Al(i-Bu)_3催化剂,考察环氧氯丙烷的均聚合及其与环氧乙烷,环氧丙烷的共聚合,并用核 相似文献
976.
Mircho Georgiev Tatiana Popova Zhorro S. Nickolov Nikolay Goutev Georgi Georgiev Hiroatsu Matsuura 《Central European Journal of Chemistry》2004,2(4):617-626
The hypothesis that the degree of hydration of poly(oxyethylene) (POE) in aqueous solution depends on the mole ratio of water
molecules to ether oxygen atoms in the molecule has been verified by studying the isotropic Raman spectra in the O−H stretching
region for four short-chain POEs (C 1E
n
C 1 withn=1−4). Excellent coincidence of the O−H stretching Raman band for all four POEs studied in the range of mole ratio H2O/O
ether
from 25 to 0.6 was observed, thus confirming the assumption stated above. A conclusion that all ether oxygen atoms in the
POE molecule participate in hydrogen bonding with water molecules has been made. 相似文献
977.
A series of spiropyrans with a polyaromatic or heteroaromatic pendant was synthesized conveniently.Their photochromic behaviors were investigated with the aid of absorption spectral measurements.The results indicated that the compounds with the same parent spiropyran but different aromatic pendant show significantly different photochromic properties.This may be due to the π-π orbital interaction between the polyaromatic pendant and the open photomerocyanine form of spiropyran.The results obtained are very useful in the molecule design area. 相似文献
978.
Novel dense composite adsorbents for expanded bed adsorption of protein have been fabricated by coating 4% agarose gel onto Nd-Fe-B alloy powder by a water-in-oil emulsification method. Two composite matrices, namely Nd-Fe-B alloy-densified agarose (NFBA) gels with different size distributions and densities, NFBA-S (50-165 microm, 1.88 g/ml) and NFBA-L (140-300 microm, 2.04 g/ml), were produced. Lysozyme was used as a model protein to test the adsorption capacity and kinetics for the NFBA gels modified by Cibacron blue 3GA (CB-NFBA gels). Liquid-phase dispersion behavior in the expanded beds was examined by measurements of residence time distributions, and compared with that of Streamline SP (Amersham-Pharmacia Biotech, Sweden). The dependence of axial mixing in the expanded beds on flow velocity, bed expansion degree. settled bed height, and viscosity of liquid phase was investigated. Breakthrough curves of lysozyme in the expanded beds of the CB-NFBA gels were also examined. The dynamic binding capacity at 5% breakthrough was 23.3 mg/ml matrix for the CB-NFBA-S gels, and 16.7 mg/ml matrix for the CB-NFBA-L, at a flow velocity of 220 cm/h. The results indicate that the NFBA gels are promising for expanded bed adsorption of proteins. 相似文献
979.
L. F. Brum Malta Marta Eloisa Medeiros 《Journal of Thermal Analysis and Calorimetry》2005,81(1):149-152
Summary This work reports the room-temperature stabilization of the Bi4V2-xFexIIO11-1.5x γ ‘ phase, a promising ionic conductive material that finds application in solid oxide fuel cell and oxygen sensor devices. The Fe(II) cation proved to be a better stabilizer than Fe(III), which was previously used, since a lower substitution degree of V5+ is needed for the former. Powder X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry were used in these experiments. 相似文献
980.
H. R. Veenendaal P. M. van Berkel G. de Jong P. K. Baggelaar 《Accreditation and quality assurance》2007,12(7):365-368
Due to the relatively large spread in the results of microbiological proficiency tests, the z-scores are often not able to detect zero or low results as being ‘bad’ results. This paper describes an adapted z-score based on the average or the standard deviation of the 50% ‘highest’ results. The combination of the adapted z-scores of four samples enables a better judgement of the performance of each laboratory.
Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board or the Publisher. 相似文献