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991.
Z. Řanda M. Vobecký J. Kuncír J. Benada 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(1):95-107
The application of multielement standards (MES) in routine neutron activation analysis brings a whole range of advantages.
This paper deals with the experience obtained during many years of application of these MES. Nine of these MES contain a total
of 50 elements in suitable combinations and concentrations; thus, the determination of most of the common elements by NAA
can be carried out simultaneously. This refers to the following elements: Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni,
Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Ag, Cd, In, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf,
W, Re, Au, Hg, Th and U. For the determination of the remaining elements such as Zr, Ta, Ir etc., single element standards
(SES) are used. 相似文献
992.
Khan N Ansari MS Baber Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(10):2265-2269
1H NMR assignment of seven differently N-substituted-3-methyl-4,1-benzoxazepine-2,5-diones (I) revealed that with the exception of allyl, N-methylene protons of the substituents exhibit diastereotopy due to presence of a chiral centre in the heterocyclic ring at C-3. The significant finding is that the methylenes at C-2' in the substituents n-propyl and n-butyl (Id, Ie) also show diastereotopy. However, the one closer to the chiral centre (at C-1') exhibits greater non-equivalence of its protons. The diastereotopic methylene groups reported in this study correspond to the simplest system AB on one hand and as complex as ABMM'X2 or ABMM'X3 on the other. Calculated spectra obtained from assigned set of data for most of the coupled protons were in good agreement with the observed ones. 相似文献
993.
M. Šícha J. Glosík J. Pavlík Z. Němeček J. Šafránková M. Tichý 《Czechoslovak Journal of Physics》1983,33(11):1226-1229
Conclusion In the present report an attempt has been made to use the second derivative method for measurements of the electron distribution function in flowing afterglow plasma. It has been shown that using the cross-correlation technique, this method seems to be a useful tool for flowing afterglow plasma investigation. 相似文献
994.
Chen YW Liu YC Lu SX Xu CS Shao CL Wang C Zhang JY Lu YM Shen DZ Fan XW 《The Journal of chemical physics》2005,123(13):134701
Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394 nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37 eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples. 相似文献
995.
Z. M. Khakimov F. T. Umarova N. T. Sulaymonov A. E. Kiv A. A. Levin 《International journal of quantum chemistry》2003,93(5):351-359
New model of Si? H bond dissociation is proposed and tested in the cluster Si10H16 by the simulation approach that combines classic molecular dynamics method and the self‐consistent tight‐binding electronic and total energy calculation one. It is shown that the monohydride Si? H bond is unstable with respect to silicon dangling bond and bend‐bridge Si? H? Si bond formation when this cluster traps the single positive charge and that hydrogen migrates through a path involving rather rotation around the Si? Si bond than the center of this bond (the bond‐centered position). These results can be useful for understanding hydrogen‐related phenomena at surfaces, interfaces, and internal voids of various hydrogenated silicon systems: electronic devices, silicon solar cells, and nanocrystalline and porous silicon. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 351–359, 2003 相似文献
996.
Z. Pietrzak-Flis M. M. Suplinska L. Rosiak 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):189-193
Intake with food and water of the natural radionuclides of the uranium and thorium series was determined for adult population of the south-western region in Poland, where in the 1950-ies an exploration of uranium ore was conducted. Concentration of the radionuclides was determined in food products and drinking water and their annual intake was estimated on the basis of the average annual consumption. The intake of238U,234U and230Th occurred mainly with water (33% to 68%), whereas the intake of232Th,228Th and226Ra was mainly with vegetables, potatoes, milk and flour. From the intake and dose coefficients the annual effective doses from the ingested radionuclides were calculated. The total dose was 5.6 Sv, of which 74% originated from226Ra. 相似文献
997.
998.
Zusammenfassung Versuchsergebnisse über die Verteilung des bivariant gebundenen Wassers und von Wasserstoff- bzw. Hydroxylionen in den Kristallen bei kriechender Kristallisation, wie auch die hydrolytische Spaltung dieser Kristalle, werden dargelegt. Sie zeigen, daß der Gehalt an Wasser und die damit verbundene hydrolytische Spaltung bei den Kristallen in der Kristallkruste größer ist als bei den auf dem Boden des Gefäßes ausgeschiedenen Kristallen. Die Wasserstoff- bzw. Hydroxylionen verteilen sich so, daß, in Zusammenhang mit dem pH-Wert der Ausgangslösung, die Lösungen, bereitet aus den Kristallen der Kristallkruste, einen niedereren bzw. höheren pH-Wert besitzen, als die Lösungen, bereitet aus den Kristallen am Boden des Gefäßes. 相似文献
999.
V. Balek L. A. Pérez-Maqueda J. Poyato Z. Černý V. Ramírez-Valle I. M. Buntseva J. L. Pérez-Rodríguez 《Journal of Thermal Analysis and Calorimetry》2007,88(1):87-91
The effect of grinding
on thermal behavior of pyrophyllite and talc as commonly used ceramic clay
minerals was investigated by DTA, TG, emanation thermal analysis (ETA), B.E.T.
surface area (s.a.) measurements, X-ray diffraction (XRD) and scanning electron
microscopy (SEM).
A vibratory mill was used in this study, grinding
time was 5 min. It was found that the grinding caused an increase in surface
area and a grain size reduction of the samples. From TG and DTA results it
followed that grinding caused a decrease of the temperature at which the structure
bound OH groups released. The formation of high temperature phases was enhanced
with the ground samples. For the ground talc sample the crystallization of
non-crystalline phase into orthorhombic enstatite was observed in the range
of 800°C. For ground pyrophyllite a certain agglomeration of grains was
observed in the range above 950°C. Moreover, for both clays the ETA characterized
a closing up of subsurface irregularities caused by grinding as a decrease
of the emanation rate in the range 250–400°C. The comparison of
thermal analysis results with the results of other methods made it possible
to better understand the effect of grinding on the ceramic clays. 相似文献
1000.
E. Segal L. Maistriau E. G. Derouane Z. Gabelica 《Journal of Thermal Analysis and Calorimetry》1994,41(2-3):701-712
The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation
of VPI-5 to AlPO4-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state31P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete
dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration
effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating
rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned
fragments stemming from the destruction of the water triple helix assemblage.
The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating
rates.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献