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Öğe Dependence of 400 MHz NMR Peak Line Widths of Crude Oil on well Characteristics(Springer, 2024) Kal, Duzgun; Sunkur, Murat; Koylu, M. Zafer; Yilmaz, AliToday, magnetic field inhomogeneity in high-field NMR machines is minimized by proper shimming of the machine and extensive dilution of the sample with deuteron solvents. Hence, the line width (LW) measurements of the NMR peaks are reliable for NMR studies. This study is aimed at examining the relationship between the crude oil properties and the LW values of the CH2 and CH3 peaks and the relationship between the LW of water in crude oil and the percentage of water. A set of 22 mixtures was prepared by adding 0.02 mL of each crude oil to each 0.98 mL of CDCl3. A suitable NMR spectrum, including the water peaks of the mixtures, was obtained with a spectrometer operating at 400 MHz. Paraffinic CH2 and CH3 peak LWs vary from well to well. Paraffinic CH3 LW decreases nearly linearly with American Petroleum Institute gravity. In addition, the LW of the water peak at 4.75 ppm is strongly related to the percentage of water in crude oil. The mixtures used in this study provide the appropriate NMR peaks for CH2, CH3, and water in crude oil. NMR peaks of water in crude oil were displayed for the first time in the high field. Some of the previous results obtained in the low-NMR field were found. Therefore, this study suggests an additional approach for high-field NMR studies in petroleum chemistry.Öğe Determination of Proton Relaxivities of Mn(II), Cu(II) and Cr(III) added to Solutions of Serum Proteins(Mdpi, 2009) Koylu, Mehmet Zafer; Asubay, Sezai; Yilmaz, AliRelaxometric studies are still of scientific interest due to their use in medicine and biology. In this study, proton T-1 and T-2 relaxivities of Mn(II), Cu(II) and Cr(III) in water were determined in the presence and absence of various proteins (albumin, alpha-globulin, gamma-globulin, lysozyme, fibrinogen). The 1/T-1 and 1/T-2 in all solutions are linearly proportional to the concentration of the paramagnetic ions. Mn(II) has the great influence to alter relaxations in all protein solutions, while Cu(II) and Cr(III) have a poor influence on the relaxations. In addition, Mn(II) and Cu(II) are bound to each protein, but Cr(III) is not bound to any protein.Öğe Determination of the effective correlation time modulating 1H NMR relaxation processes of bound water in protein solutions(Elsevier Science Inc, 2008) Yilmaz, Ali; Budak, Hatice; Ulak, F. SadanThe relaxation in protein solutions has mainly been studied by nuclear magnetic relaxation dispersion (NMRD) techniques. NMRD data have mostly been analyzed in terms of fast chemical exchange of water between free water and water bound to proteins. Several approaches were used for the estimation of correlation time modulating the relaxation mechanism of bound water. On the other hand, in a nuclear magnetic resonance experiment, the relaxation rates of protein solutions (1/T-1 and 1/T-2) and also those of free water (1/T-1f and 1/T-2f) are measurable. However, the relaxation rates of bound water (1/T-1b and 1/T-2b) are not. Despite this, equating (1/T-1-1/T-1f)/2(1/T-2-1/T-2f) to (1/T-1b)/2(1/T-2b) leads to an expression involving only an effective T that is related to the rotational correlation time (tau(r)) of proteins. Equating the ratios may therefore give a simple alternative method for the determination of tau(r) even if this method is limited to a single resonance frequency. In this work, a formula was derived for the solution of the effective tau. Then, the 1/T-1 and 1/T-2 in solutions of two globular proteins (lysozyme and albumin) and one nonglobular protein (gamma-globulin) were measured for different amounts of each protein. Next, the values of 1/T-1 and 1/T-2 were plotted vs. protein concentrations, and then the slopes of the fits were used in the derived equation for determining the effective tau values. Finally, the rotational correlation time tau(r), calculated from tau, was used in the Stokes-Einstein relation to reproduce relevant radii. The effective tau values of lysozyme, albumin and gamma-globulin were found to be 5.89 ns, 7.03 ns and 8.8 its, respectively. tau(r) values of albumin and lysozyme produce their Stokes radii. The present data suggest that use of the measurable ratio in the derived formula may give a simple way for the determination of the correlation times of lysozyme and albumin. (C) 2008 Elsevier Inc. All rights reserved.Öğe The effect of benzo substitution on complexation of diaza 18-crown-6 ethers derivatives with NaClO4 (vol 52, pg 51, 2005)(Springer, 2006) Koeylue, M. Zafer; Demirel, Nadir; Polat, F. Doganel; Yilmaz, Ali; Hosgoeren, Halil; Balci, Metin[Abstract Not Available]Öğe Efficacy and safety of bevacizumab in patients with low-grade serous ovarian cancer(Future Medicine Ltd, 2024) Karacin, Cengiz; Sunar, Veli; Urakci, Zuhat; Yilmaz, Ali; Ayhan, Murat; Ersoy, Mustafa; Guven, Deniz CanAim: To investigate the efficacy and safety of bevacizumab in patients with recurrent low-grade serous ovarian carcinoma. Materials & methods: The data of patients who received at least two cycles of bevacizumab in combination with chemotherapy were retrospectively recorded. Results: The median age of 51 patients was 56 (range: 33-75) years. The complete response rate was 10.4% and the partial response rate was 43.7%. The objective response rate was 54.1%. Median progression-free survival was 15.9 months (95% CI: 9.1-22.6) and median overall survival was 42.5 months (95% CI: 37.2-47.8). Conclusion: Bevacizumab with chemotherapy is an effective option for treating recurrent ovarian low-grade serous carcinoma.Öğe Elimination of Radiation Damping Effects from the NMR Relaxation Curves of H2O/D2O Mixtures Containing Protein and Ions(Physical Soc Republic China, 2013) Zengin, Bilgin; Koylu, Mehmet Zafer; Korunur, Sibel; Yilmaz, AliIn this work the T-1 and T-2 curves of H2O/D2O mixtures were obtained for several fractions of H2O and also for different amounts of albumin and manganese. The experiments were carried out with a 400 MHz proton NMR spectrometer. The T-1 and the T-2 curves were determined by the inversion recovery (IR) and Carr-Purcell-Meiboom-Gill (CPMG) sequences, respectively. The relaxation times in residual water and in a mixture with 0.05 ml H2O were found to be reliable either in the presence or in the absence of albumin. The mixtures containing 0.1 ml or higher H2O suffer from radiation damping (RD). RD was removed gradually by addition of albumin or manganese. RD in the protein solution with 0.1 ml H2O was removed by adding 1 mu g of manganese to one ml of solution. The data suggest that the relaxation times in H2O/D2O mixtures are measurable by conventional methods upon the addition of appropriate amounts of manganese and albumin.Öğe Estimation of ? value in proton NMR relaxation times of dibenzo diaza 18-crown-6 ether derivative in solution(Elsevier Science Bv, 2006) Yilmaz, Ali; Koylu, M. Zafer; Budak, HaticeSpin-lattice (T-1) and spin-spin (T-2) relaxation times of seven peaks in dibenzo diaza 18-crown-6 ether derivative were measured at 300K with a Bruker 400 MHz NMR spectrometer. An equation was derived for correlation time tau from the ratio of the (1/T-1)/2(1/ T-2) using relaxation formulas pertaining to dipolar interactions. The correlation time was calculated from the equation for each peak using experimental data for (1/T-1)/2(1/T-2) ratio. The estimated tau values ranged from 0.7 ns to 2 ns. The similarity of T values of the peaks belonging to the different parts of the molecule suggested that overall molecular tumbling may be responsible for relaxation mechanism of all the groups. (c) 2006 Elsevier B.V. All rights reserved.Öğe Investigation of the Hydration of Bovine Serum Albumin by an NMR Titration Method(Asian Journal Of Chemistry, 2010) Kavak, Gulten; Yilmaz, Ali; Morris, Gareth; Heatley, FrankIn this study, NMR titration method was used to determine the dynamics of hydration water. Solutions were made by dehydration procedures and relaxation measurements were carried out on a Vnmr (Varian NMR) spectrometer operating at 300 MHz for proton and relaxation rates (Irri) were plotted versus M(s)/M(w). It was seen that the NMR titration data was separated into 2 line segments. The intercepts of the first line segment with lower mass of solute/mass of water (M(s)/M(w)) ratio and the second line segment with higher M(s)/M(w), are 2.15 and 2,57, respectively. The correlation times for free and structured water were obtained as 5.56 x 10(-12) S and 1.5 x 10(-11) s, respectively. The 1/T(1) and 1/T(2) relaxation rates increase as the protein concentration increases. This implies that the protein is reducing the motion of water molecules. The correlation times (tau(c)) were calculated by using the experimental data and relaxation theory related. These results suggest that the relaxation times of water layers surrounding a protein could be determined by T, measured versus M(p)/M(w). Present results were correlated well with the results from other measurements techniques. The data also suggest that the relaxation mechanism of bovine serum albumin (or serum proteins) can be explained in terms of fast chemical exchange of protons between bulk water and water bound to proteins.Öğe Observation of Triplet Traces Obtained with Inversion Recovery Method in Both Residual Water- and H2O/D2O-Albumin Mixture by Using 400 MHz Proton NMR(Asian Journal Of Chemistry, 2013) Yilmaz, Ali; Zengin, Bilgin; Korunur, SibelNMR studies involving H2O/D2O mixtures are mainly based on a single spectrum of water. However, some recent papers have revealed the presence of an HDO triplet in H2O/D2O, which is caused by the splittings of H2O signal by deuterium (D). Observation of inversion recovery (IR) traces of this triplet should be very useful for analyzing relaxation data in such mixtures. In this work, in order to obtain the traces, inversion recovery signal intensities of residual water and a mixture of 0.10 H2O and 0.90 D2O were acquired versus a set of short delay times in the presence or absense of 0.2 g albumin. T-1 and T-2 curves of the same samples were also obtained by using different sets of much longer times for checking the effect of radiation damping on the traces. Experiments were carried out with a 400 MHz proton NMR spectrometer equipped with a topspin programme for relaxation measurements. Inversion recovery data of the traces and T-1 curves were obtained with the inversion recovery method, while T-2 curves were obtained with the Carr-Purcell-Meiboom-Gill method. Data was processed through an analysis programme of the topspin. Data showed that radiation damping is effectively reduced upon addition of albumin. Furthermore, the data of the residual water- and the mixture with albumin demonstrated the traces of the triplet at the initial part of a single inversion recovery line. Our results suggest that the splitting of water proton signal by deuterium can be detectable by the inversion recovery method for D2O- and the mixture containing albumin.Öğe Temperature-dependent behavior of Ti/p-InP/ZnAu schottky barrier diodes(Iop Publishing Ltd, 2008) Asubay, Sezai; Gullu, Omer; Abay, Bahattin; Turut, Abdulmecit; Yilmaz, AliThe current-voltage ( I-V) characteristics of Ti/p-InP Schottky diodes have been measured in a wide temperature range with a temperature step of 20 K. An experimental barrier height ( BH) Phi(ap) value of about 0.85 eV was obtained for the Ti/p-InP Schottky diode at 300 K. A decrease in the experimental BH Phi(ap) and an increase in the ideality factor n with a decrease in temperature have been explained on the basis of a thermionic emission mechanism with the Gaussian distribution of the barrier heights due to the BH inhomogeneities at the metal semiconductor interface. (Phi) over bar (b) and A* as 1.01 eV, and 138 A cm(-2) K-2, respectively, have been calculated from a modified ln( I-0/T-2) - q(2)sigma(2)(s)/2k(2)T(2) versus 1/T plot. This BH value is in close agreement with the values of 0.99 eV obtained from the Phi(ap) versus 1/T and ln( I-0/T-2) versus 1/nT plots.
