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911.
V. A. Titov V. I. Rakhlin A. A. Titov F. A. Kuznetsov M. G. Voronkov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(12):1907-1910
The thermodynamic properties of several silicon-containing derivatives of asymmetric dimethylhydrazine were estimated by comparative methods. The CVD diagrams of the deposition of silicon nitride and dioxide from gas media containing these reagents were constructed. 相似文献
912.
913.
Montecchi M. Nichelatti E. Montereali R.M. Piccinini M. Somma F. 《Optical and Quantum Electronics》2004,36(1-3):43-56
An analytical expression of the complex permittivity is derived for absorbing centres featuring inhomogeneous absorption-line broadening. Such an expression gives the dispersion law of the real part of the permittivity when the imaginary part has a Gaussian lineshape. Our mathematical approach starts from an overlap integral of Lorentzian-type dielectric susceptibilities weighted by a Gaussian probability distribution of the resonance absorption energies. The analytical solution found is consistent with the Kramers–Kronig relation. We demonstrate that, like in the case of homogeneous absorption-line broadening, the refractive index increases at photon energies lower than the resonance absorption energy also for inhomogeneous absorption-line broadening; if the absorbing centres emit Stokes-shifted radiation, such an increase can be exploited for passive and active waveguiding applications. An example is reported regarding active waveguides based on colour centres in a lithium fluoride crystal. 相似文献
914.
J. L. Souza A. F. Santos L. Polese Marisa S. Crespi C. A. Ribeiro 《Journal of Thermal Analysis and Calorimetry》2007,87(3):673-677
Poly(3-hydroxybutyrate), PHB has been structurally
modified through reaction with maleic anhydride, MA. Transesterification reaction
was carried out fixing the PHB and MA and besides time and temperature the
concentration of the triethylamine (used as catalyst) was changed. Glass transition,
melting and crystallization temperature obtained from DSC curves and thermal
degradation temperatures obtained from TG traces were used to evaluate the
influence of the reaction conditions on the modification of PHB according
to factorial design. On the base of the results the optimum conditions are
to perform the PHB modification reaction with MA reaction at 110°C for
1 h with 5% v/v triethylamine. 相似文献
915.
T. Martinez M. Navarrete L. Cabrera F. Juárez A. Ramos K. Vazquez 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):569-572
Nine brands of tobacco cigarettes manufactured and distributed in the Mexican market were analyzed by γ-spectrometry to certify
their non-artificial radioactive contamination. Since natural occurring radioactive materials (NORM) 40K, 232Th, 235U, and 239U (and decay products from the latter three nuclides) are the main sources for human radiation exposure, the aim of this work
was to determine the activity of 40K and potassium concentration. Averages of 40K and potassium concentration were of 1.29±0.18 Bq·g−1, and 4.0±0.57%. The annual dose equivalents to the whole body from ingestion and inhalation of 26 Bq 40K were 0.23 μSv and 15.8 μSv, respectively. The corresponding 50 years committed dose equivalents was 0.23 μSv. The total
committed dose to the lungs due to inhalation of 40K in tobacco was 16 μSv. Potassium concentrations obtained in this work were in the same range of those obtained by INAA,
so showing that the used technique is acute, reproducible, and accessible to laboratories equipped with low background scintillation
detectors. 相似文献
916.
917.
A liquid chromatography-mass spectrometry method for the determination of the coccidiostats metronidazole, ronidazole, dimetridazole,
secnidazole, tinidazole and ipronidazole in feedstuff was developed. The 5-nitroimidazoles were extracted from animal feed
with a pH 2 phosphate buffer solution followed by a solid phase extraction procedure based on HLB cartridges. The liquid chromatographic
separation of the extracts was performed on a C18 bonded silica column applying a gradient of elution with pH 4.3 ammonium acetate buffer solution and acetonitrile. Quantification
for each 5-nitroimidazole was carried out monitoring its molecular ion [M + H]+ obtained by positive electrospray ionisation mode. A pool of feedstuffs was used to optimise and validate the method. Linearity,
quantification limit, intra-day and inter-day reproducibility and accuracy were estimated using this pool of feedstuffs spiked
with the drugs. For the confirmatory assay, several fragment ions from each 5-nitroimidazole were obtained and monitored.
The method was applied successfully to determine 5-nitroimidazoles in feedstuff at level of 0.05 mg kg−1. 相似文献
918.
Annali di Matematica Pura ed Applicata (1858-1865) - 相似文献
919.
920.
F. Ati S. El-Aoufi A. Chergui H. Y. Aboul-Enein B. Maouche 《Journal of the Iranian Chemical Society》2008,5(3):506-513
This paper describes khellin hydrolysis mechanism using semiemperical PM3 implemented in Gaussian 03 package. The calculations show that in the presence of an acidic media, an enolate molecular ion leads directly to ω-acetokhellinone while in the basic media it leads to khellinone. 相似文献