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51.
József Tamás Svidró Attila Diószegi Judit Tóth 《Journal of Thermal Analysis and Calorimetry》2014,115(1):331-338
The process of casting in sand moulds is used for a large volume of castings manufactured in the world. Internal channels and complex geometries of these products are formed by the placement of cores within the mould cavity. Resin-bound sand mixtures are essential ingredients in engine component manufacturing. In this study, a state-of-the-art application of Fourier thermal analysis in foundry technologies is presented. Investigation of decomposition phenomena of resin-bound moulding materials during casting production is a brand new area to use the potential of thermal sciences. Temperature measurements in test samples of standard types of moulding mixtures were performed. The registered cooling curves were processed by a numerical iteration algorithm to determine the amount of heat absorbed during degradation of the moulding material. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) of sand mixtures were carried out to compare the results of the Fourier thermal analysis with TG and DTA curves. 相似文献
52.
New cyclic 2,3‐sulfite ester derivatives of poststerone—Discriminating diastereomers and probing spatial proximities by NMR and DFT calculations 下载免费PDF全文
53.
D. A. Vasilevskii V. G. Petushok G. V. Kalechits R. A. Zheldakova V. K. Ol’khovik 《Russian Journal of General Chemistry》2013,83(9):1698-1702
A series of novel double quaternary ammonium salts based on 5,5-dioxo-5H-dibenzo[b,d]thiophene has been prepared via quaternization of the corresponding 3,7-bis(chloromethyl)dibenzothiophene-5,5-diones with various N,N-dimethylalkylamines. Pronounced fungicidal activity of the C1-substituted quaternary ammonium salts has been observed. 相似文献
54.
The electronic spectra of neutral PaO and PaO2 and their mono- (PaO+, PaO2 +) and dications (PaO2+, PaO2 2+) were studied by performing multiconfigurational quantum chemical calculations at the CASSCF/CASPT2 level of theory taking into account spin–orbit coupling. Including the protactinium 7s, 6d, and 5f orbitals as well as selected orbitals of oxygen in the active space, the vertical excitation energies at the ground-state geometries have been computed up to ca. 36,000 cm?1. The gas-phase electronic spectra at 298 and 3,000 K were evaluated on the basis of the computed oscillator strengths. 相似文献
55.
Attila Sipos Antal Udvardy Attila C. Bényei Sándor Berényi 《Central European Journal of Chemistry》2013,11(8):1278-1285
The synthesis of 3-deoxyoripavine (7) was realized as a novel and promising intermediate towards the synthesis of the important class of dopaminergic and/or serotonergic 10-deoxyaporphines and the special pharmacological tool µ opioid antagonist cyprodime. Generally, the preparation of these valuable biologically active compounds was achieved in remarkable yields. 相似文献
56.
Regioselective synthesis of haloaromatic tertiary alcohols can be achieved by ortho deprotonation/electrophilic reactions of (η6- fluoroarene)Cr(CO)3 complexes with halobenzophenones and metal removal. The coexistence of different halogens in the aromatic rings of these molecules make them unique within the group of tertiary alcohols. 相似文献
57.
58.
The OPAL research reactor in Australia has been used to determine k 0 values for 134mCs, 134Cs, 192Ir and 194Ir. Values for 24Na have also been measured for quality control. The neutron flux at the irradiation positions was very highly thermalised (f > 2,000), resulting in almost negligible activation by epithermal neutrons. As a consequence, the contribution to the total uncertainty of the k 0 values from epithermal-related factors such as Q 0 and $ \bar{E}_{\text{r}} $ was very small. The measured caesium k 0 values have been compared with the library values as well as with recent measurements by St Pierre et al. and Farina Arboccò et al. While there are k 0 values for 194Ir in the library, no 192Ir values have been measured previously. Despite 192Ir having a higher sensitivity than 194Ir, k 0 values were not measured during the establishment of the k 0-method because the nuclear data available at the time indicated that the activation cross-section of 191Ir deviated significantly from 1/v behaviour (g(T n ) ≠ 1), which would result in unacceptable errors if k 0 analysis were to be carried out using the Høgdahl convention. However later nuclear data compilations showed that 191Ir has better 1/v behaviour than previously reported, making it suitable for k 0 analysis using the Høgdahl convention. For completeness, k 0 values have been determined using both the Høgdahl and modified-Westcott conventions and these have been compared with library (194Ir) and calculated values. 相似文献
59.
Enantioselective organocatalytic Michael additions affords useful building blocks for many biologically and medicinally relevant compounds. Ionically-tagged diphenylprolinol silyl ether efficiently catalyzes several Michael additions of aldehydes to nitroalkenes in ionic liquids. The Michael additions work well in ionic liquids; yields up to 95% and enantioselectivities up to 95% ee were achieved. Furthermore, in some cases, the catalytic system was reusable. 相似文献
60.
We determine the proton affinity (PA) and gas-phase basicity (GB) of amino acid α-alanine at a chemically accurate level by performing explicitly-correlated CCSD(T)-F12b/aug-cc-pVDZ geometry optimizations and normal mode vibrational frequency calculations as well as CCSD(T)-F12b/aug-cc-pVTZ energy computations at the possible neutral and protonated geometries. Temperature effects at 298.15 K considering translational, rotational, and vibrational enthalpy and entropy corrections are obtained via standard statistical mechanics utilizing the molecular geometries and the harmonic vibrational energy levels. Both the amino nitrogen (N) and the carbonyl oxygen (O) atoms are proven to be potential protonation sites and a systematic conformational search reveals 3 N- and 9 O-protonated conformers in the 0.00–7.88 and 25.43–30.43 kcal/mol energy ranges at 0 K, respectively. The final computed PA and GB values at (0)298.15 K in case of N-protonation are (214.47)216.80 and 207.07 kcal/mol, respectively, whereas the corresponding values for O-protonation are (189.04)190.63 and 182.31 kcal/mol. The results of the benchmark high-level coupled-cluster computations are utilized to assess the accuracy of several lower-level cost-effective methods such as MP2 and density functional theory with various functionals (SOGGA11-X, M06-2X, PBE0, B3LYP, M06, TPSS). 相似文献