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1.
Alfred Kreutzberger Elfriede Kreutzberger Hans-Joachim Saltler Hayriye Aml Aysel Gürsoy 《Journal of heterocyclic chemistry》1982,19(4):753-755
The three-component reaction comprising the interaction of 2-amino-4-antipyrinyl-5-ethylthiazole (1) with s-triazine (2) and pyrrolidine leads to 4-anitpyrinyl-5-ethyl-2-[(4-pyrrolidinyl)methyleneamino]thiazole (5). Structure 5 is supported by 1H- and 13C-NMR spectroscopy. 相似文献
2.
In this paper, we study conharmonic curvature tensor in Kenmotsu manifolds with respect to semi-symmetric metric connection and also characterize conharmonically flat, conharmonically semi-symmetric and φ-conharmonically flat Kenmotsu manifolds with respect to semi-symmetric metric connection. 相似文献
3.
Mehmet Burçin Pişkin Aysel Kantürk Figen Hatice Ergüven 《Research on Chemical Intermediates》2013,39(2):569-583
In this study, the solid-state reaction mechanism and kinetics were investigated for production of anhydrous sodium metaborate (NaBO2), an industrially and technologically important boron compound. To assess the kinetics of solid-state production of NaBO2, the chemical reaction between borax (Na2B4O7) and sodium hydroxide (NaOH) was investigated by use of the thermal analysis techniques thermogravimetry (TG) and differential thermal analysis (DTA). DTA curves obtained under non-isothermal conditions at different heating rates (5, 10 and 20 °C/min), revealed five endothermic peaks corresponding to five solid-state reactions occurring at 70, 130, 295, 463, and 595 °C. The stages of the solid-state reaction used for production NaBO2 were also analyzed by XRD, which showed that at 70 and 130 °C, Na2B4O7 and NaOH particles contacted between the grains, and diffusion was initiated at the interface. However, there was not yet any observable formation of NaBO2. Formation of NaBO2 was initiated and sustained from 295 to 463 °C, and then completed at 595 °C; the product was anhydrous NaBO2. Activation energies (E a) of the solid-state reactions were calculated from the weight loss based on the Arrhenius model; it was found that in the initial stages of the solid-state reaction E a values were lower than in the last three steps. 相似文献
4.
Aysel Kantürk Figen Pınar Yilmaz Atali Mehmet Burçin Pişkin 《Journal of Thermal Analysis and Calorimetry》2014,118(1):31-42
In this study, the thermal behavior in terms of glass transition (T g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min?1) during DSC. The results show that the Xtrabase composite displayed the highest T g (120 °C at a 5 °C min?1 heating rate) and E a (157.64 kJ mol?1) values associated with thermal degradation from the main chain of the polymer. 相似文献
5.
Eymen Akşener Aysel Kantürk Figen Sabriye Pişkin 《Research on Chemical Intermediates》2014,40(5):2103-2117
In this study, the synthesis of barium metaborate powder (BaB2O4) was carried out by ultrasound-assisted precipitation using different borate solutions. Different solutions such as borax (Na2B4O7, BD), boric acid (H3BO3, BA), and sodium metaborate (NaBO2, SMB) were used in the synthesis and an ultrasonic immersion horn probe was used as the major source of ultrasound. The effect of reaction temperature and time, pH, and crystallization time on the BaB2O4 yield (%) was investigated. The ultrasound-assisted synthesis up to 90 % yield could be achieved using a 0.2 M BD solution at 80 °C, reacting for 5 min at pH 13 followed by 2 h of crystallization. Following crystallization, the obtained powder was heated up to 140, 250, 650, and 750 °C for 2.5 h, and it was shown that β-BaB2O4 nanometric powders were obtained after the 750 °C heat treatment. 相似文献
6.
Ümmühan Ocak Miraç Ocak Aysel Başoğlu Semanur Parlayan Dilek Başaran Hakan Alp Halit Kantekin 《Polyhedron》2010
A series of crown ethers carrying an anthracene group with nitrogen–sulfur donor atom, which differ in having three, four and five sulfur atoms in the macrocycle was designed and synthesized by the reaction of the corresponding macrocyclic compound and 9-chloromethyl-anthracene. The influence of metal cations such as Al3+, Zn2+, Fe2+, Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Cd2+, Hg2+ and Pb2+ on the spectroscopic properties of the ligands was investigated in acetonitrile–dichloromethane (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Al3+, Zn2+, Fe2+, Fe3+, Cu2+, Hg2+ and Pb2+ the results of which disclosed the complexation compositions and complex stability constants of the novel ligands with these cations. The monoazapentathia crown ether showed sensitivity for Al3+ with linear range and detection limit of 2.6 × 10−6 M–2.6 × 10−5 M and 8.1 × 10−7 M, respectively. 相似文献
7.
We consider the equilibrium configurations for static spherically symmetric self-gravitating perfect fluids in general relativity. The fluid obeys an equation of state which is the extreme limit allowed by Hawking's strong energy condition. The new solutions we have found are generalized Einstein static universes which have a Killing horizon similar to the one we are familiar with from the vacuum Schwarzschild solution. 相似文献
8.
In this paper, we show that the Boothby-Wang fibration of the Iwasawa manifold
is an unstable critical point for the energy of a distribution.
The work of the first author is partially supported by TBAG-?G/2. 相似文献
9.
Fatih Güleç Aysel Niftaliyeva Ali Karaduman 《Research on Chemical Intermediates》2018,44(12):7205-7218
2,6-Dimethylnaphthalene (2,6-DMN) is one of the crucial intermediates for the synthesis of polybutylenenaphthalate and polyethylene naphthalate (PEN). The complex synthesis procedure and the high cost of 2,6-DMN production significantly reduce the commercialisation of PEN even though PEN demonstrates superior properties compared with polyethylene terephthalate. 2,6-DMN can be produced by methylation of 2-methylnaphthalene (2-MN) and/or naphthalene, disproportionation of 2-MN, and/or isomerisation of dimethylnaphthalenes (DMNs). In this study, synthesis of 2,6-triad DMN isomers consisting of 2,6-DMN, 1,6-DMN, and 1,5-DMN have been investigated with the disproportionation of 2-MN over unmodified and Zr-modified mesoporous MCM-41 zeolite catalysts. In contrast to other DMN isomers, both 1,5-DMN and 1,6-DMN can be effectively isomerised to be profitable 2,6-DMN. The disproportionation of 2-MN experiments were carried out in a catalytic fixed-bed reactor in the presence of 1 g of catalyst at a temperature range of 350–500 °C and weight hourly space velocity between 1 to 3 h?1. The results demonstrated that mesoporous MCM-41 zeolite catalyst has a selective pore shape for 2,6-triad DMN isomers, which may allow a decrease in the production cost of 2,6-DMN. Additionally, 2,6-DMN was successfully synthesised by the disproportionation of 2-MN over MCM-41 zeolite catalyst. Furthermore, both the conversion of 2-MN and the selectivity of 2,6-DMN were considerably enhanced by the Zr impregnation on MCM-41. 相似文献
10.