TR Dizin İndeksli Yayınlar / TR Dizin Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7149
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Article Citation - WoS: 17Citation - Scopus: 19Lebesgue-Stieltjes Measure on Time Scales(TUBITAK, 2009) Deniz, Aslı; Ufuktepe, ÜnalThe theory of time scales was introduced by Stefan Hilger in his Ph. D. thesis in 1988, supervised by Bernd Auldbach, in order to unify continuous and discrete analysis [5]. Measure theory on time scales was first constructed by Guseinov [4], then further studies were made by Guseinov-Bohner [1], Cabada-Vivero [2] and Rzezuchowski [6]. In this article, we adapt the concept of Lebesgue-Stieltjes measure to time scales. We define Lebesgue-Stieltjes Δ and ▶-measures and by using these measures, we define an integral adapted to time scales, specifically Lebesgue-Stieltjes Δ-integral. We also establish the relation between Lebesgue-Stieltjes measure and Lebesgue-Stieltjes Δ-measure, consequently between Lebesgue-Stieltjes integral and Lebesgue-Stieltjes Δ-integral.Article Reactions of the Solvent-Stabilized Compound [moocl2(thf)2] With Aromatic Nitrogen Donor Ligands: Spectroscopic Characterization and Semiempirical Am1* Calculations(TUBITAK, 2009) Kılıçkaya, Gülşah; Doğan, Başak; Acar, Nursel; Sözüer, Hikmet IşılReaction of the solvent-stabilized dioxo-molybdenum(VI) compound [MoO2 Cl2 (THF)2]withP Ph3 yielded the oxomolybdenum(IV) species [MoOCl2 (THF)2](1) by the removal of one oxygen atom as PPh3 O. The complexes [MoOCl2 (=NC6 H4 CN)] 2,[MoOCl2 (CNC6 H4 OH)] 3,[MoOCl2 (=NC6 H4 NH2)] 4,and [MoOCl2 (=NC6 H4 OCH3)] 5, were synthesized by the reactions of [MoOCl2 (THF)2]with XC6 H4 Y(X =NH2, Y = CN; X= CN, Y = OH; X = Y = NH2;X=NH2,Y=OCH3). All the new compounds were characterized by elemental analyses, and FTIR, UV-Vis, and 1 H and 13 C-NMR spectra. Geometrical parameters and molecular orbital calculations showed that compounds 2-5 are stabilized by a charge transfer between the Mo center and the phenyl ring.Article Citation - WoS: 9Citation - Scopus: 10Hydrogenation of Citral Over Ni and Ni-Sn Catalysts(TUBITAK, 2008) Aykaç, Hilal; Yılmaz, SelahattinLiquid phase citral hydrogenation over zeolite-supported monometallic Ni and bimetallic Ni-Sn catalysts was studied. The zeolite support materials were Na-Y, Na-mordenite, and clinoptilolite. Ni and Sn contents of the monometallic and bimetallic catalysts were 8.1-9.2 wt% and 0.46 wt%, respectively. The type of the zeolite support affected the activity and selectivity of the catalysts differently. The main product of the citral hydrogenation reaction was citronellal, for both monometallic (84.5% yield) and bimetallic (44.5% yield) catalysts. The addition of promoter increased the selectivity to unsaturated alcohols (geraniol+nerol), i.e. it changed from 0.9% to 6.3% over mordenite and from 0.9% to 2.1% over Na-Y-supported catalysts. Furthermore, activity of the Ni catalysts decreased while the quantity of acetal remained almost constant. Intimate contact between active metal, promoter, and support, and a catalyst with a high concentration of weak acid sites gave high selectivity to geraniol+nerol.Article Citation - WoS: 3Citation - Scopus: 3Hydrogenation of Citral Over Pt and Pt-Sn Catalysts(TUBITAK, 2008) Aykaç, Hilal; Yılmaz, SelahattinHydrogenation of citral on monometallic (Pt) and bimetallic (Pt-Sn) catalysts was investigated. It was found that the catalyst activities and product distributions were different over Na-Y and Clino supports. Among monometallic catalysts, Pt/Na-Y was more selective to citronellol (3.9%) and unsaturated alcohols, geraniol and nerol, (14.1%). Sn addition increased the catalyst activities. However, its effect on product distribution differed. Yield of geraniol+nerol changed from 5.1% to 19.7% over Clino. However, selectivity to unsaturated alcohols over Na-Y decreased when it was prepared as a bimetallic catalyst support. Unsaturated alcohol formation was favored when there was a metal support interaction over monometallic catalysts, and metal-promoter interaction over bimetallic catalyst.Article Citation - WoS: 1Citation - Scopus: 1Casimir energies for some single cavities(TUBITAK, 2006) Ahmedov, Hacı; Duru, İsmail HakkıCasimir energies for some single cavities. Casimir energies are discussed for some cavities.Article Evidence for the Presence of a Second Electron Donor for the Cytoplasmic Thioredoxins in the Yeast Saccharomyces Cerevisiae(TUBITAK, 2006) Koç, Ahmet; Karakaya, Hüseyin Çağlar; Ünlü, Ercan SelçukIn yeast, the cytoplasmic thioredoxin system is composed of NADPH, thioredoxin reductase-1 (TRR1) and 2 thioredoxin genes (TRX1, TRX2). In this study, using yeast knockout mutants for TRR1, TRX1 and TRX2 genes, the role of the thioredoxin system in methionine sulfoxide reduction was investigated. Cells lacking both TRX1 and TRX2 genes simultaneously were not able to reduce methionine sulfoxides to methionine; however, mutants missing the TRR1 gene were able to reduce methionine sulfoxides to methionine, which showed that electrons could be transferred from NADPH to thioredoxins in the absence of TRR1. Similar results were observed for 3-phosphoadenosine 5-phosphosulfate reduction in the inorganic sulfate assimilation pathway. Results from both assays suggested that yeast cells have additional cytoplasmic thioredoxin reductase activity that could compensate for methionine sulfoxide reduction and sulfate assimilation in the absence of TRR1. This report also constitutes the first evidence that thioredoxins are the in vivo electron donors for methionine sulfoxide reductases in yeast.Article Citation - WoS: 2Citation - Scopus: 3Synthesis and Characterization of Nitrosyl[tris(3,5dimethylpyrazolyl) Borato]molybdenum Complexes Containing Aryloxo, Arylamido and Arylcyano Ligands(TUBITAK, 2005) Sözüer, Hikmet Işıl; Dülger İrdem, SeçkinerThe complexes [MoTp*(NO)X(ZC6H4CN-p)] [Tp* = 3,5-dimethylpyrazolyl; X = Cl, Z = O and NH; X = I, Z = CN) were prepared and characterized using 1H-NMR, IR, FAB mass spectroscopy and micro analysis.Article Citation - WoS: 16Citation - Scopus: 19Genetic Multivariate Calibration Methods for Near Infrared (nir) Spectroscopic Determination of Complex Mixtures(TUBITAK, 2004) Özdemir, Durmuş; Öztürk, BetülThe simultaneous determination of ternary mixtures of methylene chloride, ethyl acetate, and methanol using near infrared (NIR) spectroscopy and 4 different genetic algorithms based multivariate calibration methods was demonstrated. The 4 genetic multivariate calibration methods are genetic partial least squares (GPLS), genetic regression (GR), genetic classical least squares (GCLS) and genetic inverse least squares (GILS). The sample data set contains the NIR spectra of 63 ternary mixtures and covers the range from 900 to 2000 nm in 2 nm intervals. Of these 63 spectra, 42 were used as the calibration set, and 21 were reserved for the prediction purposes. Several calibration models were built with the 4 genetic algorithm based methods for each component that makes up the mixtures. Overall, the standard error of calibration (SEC) and the standard error of prediction (SEP) were in the range of 0.22 to 2.5 (% by volume (v/v)) for all the 4 methods. A comparison of genetic algorithm selected wavelengths for each component and for each method was also included.Article Citation - Scopus: 2Inequalities for the Vibrating Clamped Plate Problem(TUBITAK, 2001) Mchale, K. P.; Ufuktepe, ÜnalWe study the eigenvalues of the vibrating clamped plate problem. We have made improvements on the bounds of the ratios of the eigenvalues of the biharmonic operator (clamped plate) using the methods of Payne, Polya, and Weinberger. The difference in our proof lies mainly with the trial functions and the orthogonality arguments. While Payne, Polya, and Weinberger and Hile and Yeh project away components along u1, u2,...,uk to meet the orthogonality conditions, we use a translation/rotation argument to meet these conditions.