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21.
M. Mihalik J. Pospíšil A. Rudajevová X. Marti D. Wallacher A. Hoser T. Hofmann M. Diviš V. Sechovský 《Intermetallics》2011,19(10):1622-1626
REIr2Si2 (RE = La, Ce, Pr and Nd) were found to be polymorphic compounds which can crystallize in two different tetragonal types of crystallographic structures (β-phase: CaBe2Ge2-type; α-phase: ThCr2Si2-type). Here we study the structural phase transitions (α- to β- and β- to α-) using thermal expansion, differential thermal analysis and neutron diffraction. Both phase transitions occur at temperatures lower than 1300 °C, have a hysteresis up to 300 °C, do not show any intermediate steps and are accompanied with the absorption/release of the latent heat. We conclude that these structural phase transitions are of the first order. 相似文献
22.
23.
Abbott AP Barker GW Davies DL Griffiths GA Walter AJ Kocovský P 《Analytical chemistry》2002,74(16):4002-4006
The use of ephedrine-substituted quaternary ammonium binaphthyl salts as molecular receptors is demonstrated. The electrochemical oxidation of the receptor is affected by the binding of an analyte in solution. The binding site on the binaphthyl salt has been determined using computer modeling and confirmed using 1D and 2D NMR studies. It is shown that the sensitivity of the receptor is related to the size of the analyte. Axially chiral binaphthyl salts are shown to bind chiral analytes in a different manner and this is demonstrated using lactic and mandelic acid. The presence of a polar functional group on the analyte is also shown to have an effect on the guest-host interaction. 相似文献
24.
Palkosková P Hlavata H Dvorák P Novotný J Novotný J 《Radiation protection dosimetry》2002,101(1-4):597-599
An improvement in the clinical results obtained using total body irradiation (TBI) with photon beams requires precise TBI treatment planning, reproducible irradiation, precise in vivo dosimetry, accurate documentation and careful evaluation. In vivo dosimetry using LiF Harshaw TLD-100 chips was used during the TBI treatments performed in our department. The results of in vivo thermoluminescence dosimetry (TLD) show that using TLD measurements and interactive adjustment of some treatment parameters based on these measurements, like monitor unit calculations, lung shielding thickness and patient positioning, it is possible to achieve high precision in absorbed dose delivery (less than 0.5%) as well as in homogeneity of irradiation (less than 6%). 相似文献
25.
Radiation fields on board aircraft contain particles with energies up to a few hundred MeV. Many instruments have been tested to characterise these fields. This paper presents the results of studies on the use of an Si diode spectrometer to characterise these fields. The spectrometer has been in use since spring 2000 on more than 130 return flights to monitor and characterise the on-board field. During a Czech Airlines flight from Prague to New York it was possible to register the effects of an intense solar flare, (ground level event, GLE 60), which occurred on 15 April 2001. It was found that the number of deposition events registered was increased by about 70% and the dose in Si by a factor of 2.0 when compared with the presence of galactic cosmic rays alone. Directly measured data are interpreted with respect to on-earth reference field calibration (photons, CERN high-energy particles): it was found that this approach leads to encouraging results and should be followed up. 相似文献
26.
Jaroslav Hamerský 《Thin solid films》1976,38(1):101-107
CdSe films prepared in vacuum by sublimation from the compound at oxygen partial pressures in the residual atmosphere from 2.8 × 10?5 to 3.2 × 10?4 Torr and at substrate temperatures of 295 and 523 K were subjected to X-ray structural analysis. The results obtained are analysed and discussed in terms of some structures different from those of CdSe, e.g. CdSeO3 and CdSeO3.SeO2. 相似文献
27.
Chemical oxygen demands of fourteen nitrogenous compounds were determined by the dichromate method. Only pyridine and its derivatives were resistant to oxidation. Heterocyclic compounds containing one atom of nitrogen in a molecule, e.g. quinoline, pyrrole, proline, and indole were 90–100 per cent oxidized. Nitrogen is split off these compounds as NH3. Heterocyclic compounds containing two or more atoms of nitrogen in a molecule are also easily oxidized. However, only a part of the nitrogen is split off as NH3. On the basis of the results obtained it is possible to make the following generalization: nitrogen in amino groups is split off mostly as NH3; quinoline, pyrrole, pyrrolidine, and indole nitrogen is split off as NH3; from imidazole and pyrimidine rings, one atom of nitrogen is split off as NH3 and one as N2; from the purine configuration, two atoms of nitrogen are split off as NH3 and two atoms as N2; from isoalloxazine, three atoms of nitrogen are split off as NH3 and one as N2. 相似文献
28.
The chlorine and oxygen overpotential in dependence on the current density i (A cm?2) and on the temperature in the range of 15–75°C was measured at γ-MnO2 and β-PbO2 electrodes in concentrated water solutions of sodium chloride and perchlorate. From the measured values the experimental activation energy in dependence on overpotential was calculated and, for the temperature of 25°C, the constants of Tafel's equation (a,b) (α, io respectively) were evaluated. 相似文献
29.
The Isw2p-Itc1p chromatin remodelling complex of Saccharomyces cerevisiae is a member of the ISWI class of ATPases with a nucleosome spacing activity, involved in regulation of expression of a broad spectrum of genes. Its absence causes derepression of a-specific genes and aberrant morphology in alpha-mating type cells. We report here that the deletion of the ISW2 gene in the originally non-invasive BY strain induces mating type-specific invasive growth strongly affected by nitrogen starvation. Although the Flo11 protein was postulated to be critical for haploid invasive growth, we showed that the invasive growth caused by the isw2 and itc1 deletions in alpha-mating type cells was Flo11p-independent. This type of invasive growth was proved to be a consequence of the activation of the pheromone response pathway. Our results suggest that Isw2 and Itc1 proteins do not have the same impact on the described phenomenon. 相似文献
30.
Separation of H(2)SO(4) + CuSO(4) mixture by diffusion dialysis 总被引:1,自引:0,他引:1
Diffusion dialysis of aqueous solution of H(2)SO(4) + CuSO(4) has been investigated in a two-compartment cell with an anion-exchange membrane Neosepta-AFN. The experiments have proved that sulfuric acid permeates well through the membrane used, while cupric sulfate is efficiently rejected. This operation is very effective at high acid concentrations and low concentrations of cupric sulfate. Furthermore, it has been found that even at the highest concentration of CuSO(4), the rejection coefficient is higher than 0.965. The flux of CuSO(4) calculated from the time dependences of the CuSO(4) concentration is negatively influenced by increasing acid concentration. 相似文献