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TG Index, its Graphical Matrix Representation and Application on Polyenes
Selçuk Gümüş,Lemi Türker 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.5
A novel topological index (TG Index) has been introduced. The graphical matrix representation of the TG index includes the use of directed subgraphs for the first time in graph theory literature. The application of the TG index on certain properties of polyenes yielded very well correlation data.
Structural and Molecular Orbital Properties of Some Boroxine Derivatives-A Theoretical Study
Lemi Türker,Selçuk Gümüş,Taner Atalar 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10
In the present study, firstly, the variations of the geometric parameters induced by different substituents on boroxine skeleton (symmetrically H, CH3, Cl, F, NO2 substituted boroxines) are investigated by using B3LYP/6-31G(d,p), RHF/6-31G(d,p), and MP2/6-31G(d,p) levels of the theory. The second objective is to estimate the substituent effect on the molecular aromaticity of boroxine derivatives using energetic and NICS criteria. Moreover, the effects of different theoretical levels on NICS values have been investigated in a systematic approach. Lastly, a rotational analysis has been performed to investigate the effect of rotation around the B-Me and B-NO2 bonds on total energy of the system. It has been found that electron withdrawing substituents contribute the aromaticity of boroxine affirmatively. Conversely, electron donors make the system less aromatic. Also, the theoretical vibrational spectra for these boroxine derivatives are presented and compared with the experimental data from the literature.
Synthesis of Some Novel Pyrimidine Derivatives and Investigation of their Electrochemical Behavior
Esvet Akbas,Abdulkadir Levent,Selçuk Gümüş,Mehmet Rauf Sümer,İnci Akyazı 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.12
2-Iminopyrimidines (1a-e) and 2-thioxopyrimidine (2) were synthesized using the Biginelli three component cyclocondensation reaction of an appropriate β-diketone, arylaldehyde, and guanidine (for 1a-e) or thiourea (for 2). The electrochemical properties of the novel systems were investigated by CV and DPV. Moreover, B3LYP/6-31G(d,p) method was applied to the present structures in order to gather some structural and physicochemical data.
Kwang Yeon Hwang,Meltem Tan,Selçuk Gümüş,Nurettin Mengeş,İshak Bildirici,Ahmet Şener 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.9
3-Acetyl-5-benzoyl-6-methyl-2-phenyl-4H-pyran-4-one has been subjected to condensation with a series of primary amines (ethylamine – octylamine) to clarify the proposed mechanism in our previous study. The reactions of the shorter amines of the series (ethylamine – butylamine) yielded unsymmetric pyridinone products, whereas the other amines (pentylamine – octylamine) yielded symmetrical pyridinones. The starting material and the products as well as the intermediates have been subjected to theoretical analysis by quantum chemical calculations at B3LYP/6-31G(d,p)level, which provided supporting data for the experimental findings.
Effects of metal surface grinding at the porcelain try-in stage of fixed dental prostheses
Halil İbrahim Kılınç,Bülent Kesim,Hasan Önder Gümüş,Mehmet Dinçel,Selçuk Erkaya 대한치과보철학회 2014 The Journal of Advanced Prosthodontics Vol.6 No.4
PURPOSE. This study was to evaluate the effect of grinding of the inner metal surface during the porcelain try-in stage on metal-porcelain bonding considering the maximum temperature and the vibration of samples. MATERIALS AND METHODS. Ninety-one square prism-shaped (1 × 1 × 1.5 mm) nickel-chrome cast frameworks 0.3 mm thick were prepared. Porcelain was applied on two opposite outer axial surfaces of the frameworks. The grinding was performed from the opposite axial sides of the inner metal surfaces with a low-speed handpiece with two types of burs (diamond, tungsten-carbide) under three grinding forces (3.5 N, 7 N, 14 N) and at two durations (5 seconds, 10 seconds). The shear bond strength (SBS) test was performed with universal testing machine. Statistical analyzes were performed at 5% significance level. RESULTS. The samples subjected to grinding under 3.5 N showed higher SBS values than those exposed to grinding under 7 N and 14 N (P<.05). SBS values of none of the groups differed from those of the control group (P>.05). The types of bur (P=.965) and the duration (P=.679) did not affect the SBS values. On the other hand, type of bur, force applied, and duration of the grinding affected the maximum temperatures of the samples, whereas the maximum vibration was affected only by the type of bur (P<.05). CONCLUSION. Grinding the inner metal surface did not affect the metalporcelain bond strength. Although the grinding affected the maximum temperature and the vibration values of the samples, these did not influence the bonding strength.