Browsing by Author "Yilmaz N."

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A combined electrochemical and theoretical study into the effect of 2-((thiazole-2-ylimino)methyl)phenol as a corrosion inhibitor for mild steel in a highly acidic environment
(2016-10-01) Yilmaz N.; Fitoz A.; Ergun Ü.; Emregül K.
2-((Thiazole-2-ylimino)methyl)phenol (THYMP) was studied as a corrosion inhibitor for the protection of mild steel in 2 M HCl solution by means of weight loss, polarization, electrochemical impedance spectroscopy and scanning electron microscopy. The potential of zero charge (Epzc), was also determined for evaluation of the adsorption mechanism. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (μ) etc. were calculated using density functional theory (DFT) at B3LYP/6-31G(d,p) level. Theoretical and experimental results were in fairly good agreement.
A study of short- and long-term mRNA levels of the retn, iapp, and Drd5 genes in obese mice induced with high-fat diet
(2018-07-01) Timirci-Kahraman O.; Yilmaz U.; Yilmaz N.; Cevik A.; Horozoglu C.; Celik F.; Oguz Gokce M.; Ergen A.; Melekoglu A.; Zeybek U.
Background/Aim: Adipocyte gene expression is altered in obese individuals through multiple metabolic and biochemical pathways. In this study, we aimed to examine the expression of resistin (Retn), amylin (Iapp), and dopamine receptor domain 5 (Drd5) genes previously suggested to contribute to the pathogenesis of obesity, albeit controversially. We also aimed to determine the effects on short and long-term mRNA levels of these genes in obese mice, induced with high-fat diet (HFD). Materials and Methods: Two obesity models were created in our study: group T1 (20 mice) was fed with HFD (60% fat) for 3 months, and group T2 (20 mice) was fed with HFD (60% fat) for 6 months. The control group T0 (20 mice) was fed with a diet of 10% kcal fat supplement for 6 months. At the end of the experiment, their adipose tissues were dissected surgically. Tissue samples of each group were pooled for RNA isolation, cDNA synthesis was carried out and the mRNA levels were examined by quantitative real-time polymerase chain reaction. Serum resistin levels were measured using multiplex bead (luminex) technology for validation. Results: In T2 mice, the mRNA expression of Retn showed a moderate up-regulation (fold change=8.32; p=0.0019) in the adipose tissues. Iapp expression was also significantly up-regulated (fold change=9.78; p=0.012). Moreover, a 6.36-fold up-regulation for Drd5 was observed in the adipose tissues of T2 mice (p<0.001). At the same time, serum levels of resistin were found to be high in T1 and T2 mice compared to the control group (p<0.001 and p=0.024, respectively). Conclusion: Our study demonstrated that the mRNA levels of the genetic markers considered to play a role in adipogenesis were different in short- and long-term obesity models formed in C57BL/6J mice using HFD.
An experimental and theoretical study toward the synthesis, structure and thermal decomposition of some phenyl tetrazoles
(2015-01-01) Yilmaz N.; Öz S.; Atakol A.; Svoboda I.; Aydiner B.; Akay M.; Atakol O.
1-phenyl-1H-tetrazole (I), 1(2-chlorophenyl)-1H-tetrazole (II), 1(4-chlorophenyl)-1H-tetrazole (III), 1(4-hydroxyphenyl)-1H-tetrazole (IV), 1(4-methoxyphenyl)-1H-tetrazole (V), 1(4-nitrophenyl)-1H-tetrazole (VI), 1(2-pyridyl)-1H-tetrazole (VII), and bis-1,4-tetrazol-1-yl benzene (VIII) were prepared from aniline, 2-chloro aniline, 4-chloro aniline, 4-hydroxy aniline, 4-methoxy aniline, 4-nitro aniline, 2-aminopyridine, and 1,4-phenylendiamine and characterized by Infrared spectroscopy, elemental analysis, mass spectrometry, 1H Nuclear Magnetic Resonance, and 13C Nuclear Magnetic Resonance spectroscopy. Suitable crystals of compounds I, II, IV, V, and VI were obtained and their molecular structures were determined using single crystal X-ray Diffraction. All tetrazole compounds were also investigated using Thermogravimetry-Differential Thermal Analysis. At temperatures between 190-240 °C, the tetrazole ring decomposed exothermically. The decomposition products were estimated by relating the mass loss data and IR spectroscopy results of the residue with N2 release and isonitrile formation as outcome of thermal decomposition. The heat of the exothermic decomposition was measured by Differential Scanning Calorimetry. Optimizations and frequency analyses of all tetrazole compounds were performed at the B3LYP/cc-pVDZ level of theory which are DFT-based structures. The optimum geometries of tetrazole compounds were enlightened with the help of Gaussian 09 pocket program. The enthalpies of formation for solid state were calculated theoretically by CBS-4 M algorithm. The calculated results were compared with the experimental data obtained from DSC study. It was seen that the enthalpies of decomposition of compounds II, III, IV, and V were in good agreement with the theoretical values. However, decomposition of compounds I, VI, VII, and VIII showed significant variation from the theoretical calculations.
Flexible capacitive and piezoresistive pressure sensors based on screen-printed parylene C/polyurethane composites in low-pressure range
(2023) Kurnaz S.; Ozturk O.; Mehmet A.H.; Guduloglu U.; Yilmaz N.; Cicek O.
The use of polymers to fabricate flexible pressure sensors as an alternative to conventional pressure sensors has led to the development of physiological monitoring of human body and the electronic skin. In particular, the fabrication of flexible capacitive and piezoresistive sensors using a variety of materials and the investigation of their electromechanical properties are further developments in these fields. Herein, parylene C is synthesized via chemical vapor deposition method. Pressure-sensitive inks are prepared with a composite of parylene C, polyurethane, polymethylmethacrylate, and activated carbon at certain weight ratios. Flexible capacitive and piezoresistive pressure sensors are fabricated by the screen printing method. The sensitivity, detection limit, linearity range, and response/relaxation time, which define the capacitive and piezoresistive properties are investigated and presented in this paper. The sensitivities of the flexible capacitive and piezoresistive pressure sensors are 0.124 kPa−1 and 0.074 kPa−1 in the pressure range of 0.07-1.39 kPa. This study enables parylene C to be used in the composite structure and shows that it can be used not only as a protective layer but also in flexible pressure sensor applications. It also ensures that the design of the flexible capacitance pressure sensor can measure low pressure with high sensitivity compared to the flexible piezoresistive pressure sensor.
The parylene C as a flexible substrate and passivation layer: A promising candidate for a piezoelectric, piezoresistive, and capacitive pressure sensor in low-pressure range
(2023-01-01) Kurnaz S.; Ozturk O.; Yilmaz N.; Cicek O.
Variations in mineral element concentrations of poultry manure biochar obtained at different pyrolysis temperatures, and their effects on crop growth and mineral nutrition
(2015-12-01) Gunes A.; Inal A.; Sahin O.; Taskin M.B.; Atakol O.; Yilmaz N.
The effect of pyrolysis temperature on the nutritional quality of agricultural biochar is unclear, so better understanding of its properties and how it affects soil nutrient availability and plant growth is needed. Biochars obtained at different pyrolysis temperatures (250, 300, 350 and 400 °C) were characterized by thermogravimetric analyser and Fourier transform infrared spectroscopy. Biochars were applied at a rate of 10 g/kg to find out their effects on the mineral nutrition and growth of lettuce. The experimental results suggested that high biochar temperatures caused oxidation of the mineral elements, breaking of C-C and C-H bonds and removal of aliphatic and peptide groups from the pyrolysed materials. The total concentrations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn) and boron (B) were increased by increasing pyrolysis temperatures, although water-soluble concentrations of those elements were greatly reduced (with the exception of K and B). Compared to the control, dry weights of lettuce and maize crops were significantly increased by the biochar treatments obtained at 300 and 350 °C. Biochar treatments significantly increased the P and K concentrations of both plants compared to the control, while concentrations of Ca and Mg in lettuce plants were decreased. Iron, Mn and B concentration of the lettuce plants were reduced and Zn concentration of maize increased by the biochar treatments. It was concluded that in terms of an agricultural product, biochars produced at low temperature are better.