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Öğe The calculation of correlation time (?) for T1 spin-lattice and T2 spin-spin relaxation times in agar solutions(Taylor & Francis Inc, 2004) Askin, M; Yilmaz, AIn this study, solvent proton spin-lattice (T-1) and spin-spin (T-2) relaxation times in agar Solutions vs. increasing agar concentrations were measured by a FT-NMR. Each of 1/T-1 and 1/T-2 rates was linearly proportional to the agar concentration. The relations between the relaxation rates and agar concentrations correspond to the formulas representing the fast chemical exchange of water protons between free water and water bound to agar. The present results suggest that the ratio of relaxation rates in bound phase (T-2b/T-1b) is equal to the ratio of the slopes in the relations (K-2/K-1), and the tau can be calculated from the equality of these ratios.Öğe Determinants of MR relaxation rates in jaw cysts: implications for diagnostic values of the relaxation times(British Inst Radiology, 2004) Erol, B; Yilmaz, U; Tanrikulu, R; Yilmaz, AObjectives: The MRI signal intensities and the relaxation times (T-1 and T-2) have already been used for comparisons among various types of cysts. The signal intensities (or T-1 and T-2) were suggested to be related to cyst content. However, such a relationship between the relaxation rates (1/T-1 and 1/T-2) and the aspirated content of jaw cysts was not given. Therefore, an investigation on the determinants of the relaxation rates in the jaw cysts may be helpful in elucidating the biological basis for the differences in relaxation rates among the categories of jaw cysts. Methods: The aspirated contents of 23 cysts (16 radicular and 7 haemorrhagic) were scanned using an MR imager operating at 1 T magnetic field strength. The viscosities and the dry-weight-to-water-weight ratios (Ms/Mw) were determined. Also, the mean values of cyst categories were compared using statistical analysis. Results: The 1/T-1 had a moderate correlation with viscosity (0.66) and Ms/Mw (0.56), while the 1/T-2 had a good correlation with viscosity (0.87) and Ms/Mw (0.82). The mean values of viscosity, Ms/Mw and relaxation rates in radicular cysts were significantly lower (P < 0.05) than those of haemorrhagic cysts. Conclusions: The present data suggest that similarities and differences between relaxation rates of radicular and haemorrhagic cysts can be explained by the solid content and viscosity of cysts.Öğe Determination of healthy serum iron content by MRI(John Libbey Eurotext, 1996) Yilmaz, A; Yurt, A; Longo, R; Tugrul, P; DallaPalma, L[Abstract Not Available]Öğe The effect of benzo substitution on complexation of diaza 18-crown-6 ethers derivatives with NaClO4(Springer, 2005) Köylü, MZ; Demirel, N; Polat, FD; Yilmaz, A; Hosgören, H; Balci, MThe complexation of the crown ethers with Na+ ion was studied. H-1-NMR chemical shifts are discussed in terms of structural modi. cation as well as also binding studies with UV-vis spectra were included.Öğe In vitro NMR proton T-1 measurements in peritoneal ascites(Iop Publishing Ltd, 1996) Yilmaz, A; Tez, M; Goral, V; Boylu, S; Kaplan, A; Kavak, GThe proton spin-lattice relaxation rate (1/T-1) in malignant and non-malignant ascites was measured with an FT NMR spectrometer operating at 60 MHz. The mean relaxation rate in non-malignant ascites was significantly smaller than that of malignant ascites. However, the 1/T-1 of malignant ascites overlaps with that of non-malignant ascites over all concentrations of total protein (TP) in samples. The 1/T-1 in non-malignant ascites correlates strongly with TP, whilst the 1/T-1 in malignant ascites shows only a moderate correlation. T-1 measurements before and after addition of ascorbic acid (reductant) suggest that there is a small paramagnetic contribution of ions to the 1/T-1 in malignant ascites. The least-squares fitting of 1/T-1 versus TP for non-malignant data gives a linear relationship, and suggests that the T-1 mechanism in non-malignant ascites is caused by a fast chemical exchange of water molecules between protein-bound water and free water.Öğe In vitro NMR proton T-1 measurements in peritoneal ascites.(W B Saunders Co-Elsevier Inc, 1997) Goral, V; Yilmaz, A; Tez, M; Boylu, S; Kaplan, A; Kavak, G[Abstract Not Available]Öğe Influence of transition metal ions on NMR proton T1 relaxation times of serum, blood, and red cells(Humana Press Inc, 1999) Yilmaz, A; Yurdakoç, M; Isik, BThe spin-lattice relaxation rates (1/T1) of serum, whole blood, and red cells were measured vs several concentrations of transition metal ions. For comparative purposes, the similar experiments were repeated in water. The rates show a linear dependence on concentration of each ion for water, but nearly a linear dependence for blood and its constituents. The influence of each ion on 1/T1 in a sample was expressed by the slope (relaxivity) of the least-squares fitting of 1/T1 vs ion concentration. The relaxivities of Mn(II) in serum and of Fe(III) in serum and blood are greater than those in water, whereas the relaxivities of these ions in the other cases and of all the other ions in call cases are smaller than those in water. However, the relaxivity data show that Cr(III) in serum and blood affects the 1/T1 rates. The ratio of relaxivity of each sample to that of water is known as proton relaxation enhancement (PRR) factor (epsilon). The epsilon factors for present data suggest that the added ions are bound to proteins, and only Mn(II) in serum and Fe(III) in blood and serum are accessible to water.Öğe NMR proton 1/T1 rates in bile fluid(Marcel Dekker Inc, 1996) Yilmaz, A; Boylu, S1/T1 rates in bile fluids from patients with gallstones in the gallbladder have been determined using a FT-NMR spectrometer operating at 60MHz. The inversion recovery pulse sequences (180 degrees-tau-90 degrees] were used for T1 measurements. Fluids from patients with nonobstructive. partially obstructive and complete obstructive gallstones have been studied. The mean 1/T1 in bile fluids from patients with obstructive gallstones was highly significantly different than those from patients with non-obstructive and partial obstructive gallstones. while the 1/T1 in the fluid of partially obstructive cases was significantly different than that of complete obstructive cases. This implies that in vivo MRI T1 measurements can be used for the clinical course of gallstone formation and for surgical decision about early intervention.Öğe NMR solvent spin-lattice relaxation rate in colostrum(Taylor & Francis Inc, 2005) Budak, H; Yilmaz, AIn this study, by using a FT-NMR spectrometer operating at 60 MHz for proton, the solvent spin-lattice relaxation times (T-1) in colostrum were measured versus the days of lactation, whereas the T-1 values in dehydrated colostrum were determined versus concentration of its hydrating solid. Data show that the spinlattice relaxation rate (1/T-1 or R-1) in colostrum is linearly dependent upon the inverse of time (1/days), and the R-1 in dehydrated colostrum increases linearly with increasing concentration of its hydrating solid content (C). From data, the total paramagnetic contribution of ions in colostrum to the R-1 was found to be negligible. The dehydrated colostrum data indicates that the R-1 in colostrum is linearly dependent upon its hydrating solid content. Therefore, the R-1 changes in colostrum were analyzed in terms of the relaxivities (increase in relaxation rate per unit concentration of solid) and the concentrations of milk constituents. Such an analysis provides a relation similar to that of the R-1 in dehydrated colostrum. The current data imply that the relaxation changes in colostrum by days may be explained through changes in the concentrations of milk constituents. Also, the data suggest that the relaxation mechanism in colostrum can be explained in terms of fast chemical exchange of protons between free water and water bound to milk constituents.Öğe Paramagnetic contribution of serum iron to the spin-lattice relaxation rate (1/T1) determined by MRI(Springer Wien, 1998) Yilmaz, A; Budak, H; Longo, RT-1 maps of phantoms containing the samples of pure serum or Mn(II)-doped serum at pH = 2 were imaged by 1.5 T and 1 T MR Imagers. The T-1 measurements made for the determination of the paramagnetic increase were carried out before and after adding ascorbic acid. The difference of the 1/T-1 in samples with and without ascorbic acid was evaluated as the paramagnetic contribution (PMC) of serum iron. As iron content of serum varied from iron deficient to iron overload, the PMC values increased from 0.93 to 0.565 s(-1) at 1.5 T and from 0.103 to 0.609 s(-1) at 1 T For confirmative purposes, serum iron of each sample was determined from the paramagnetic contribution and also by an autoanalyzer. The contents of serum iron determined from PMC were in good agreement with those by the autoanalyzer and also with the literature. The data suggest that the paramagnetic contribution of serum iron can be measured by MRI.Öğe Paramagnetic contribution of serum iron to the spin-spin relaxation rate (1/T2) measured by MRI(Springer Wien, 2002) Yilmaz, A; Yurdakoc, M; Bernarding, J; Vieth, HM; Braun, J; Yurt, ASpin-spin relaxation time T-2 values of serum with and without iron were measured by magnetic resonance imaging (MRI) to find the proton relaxivity of Fe(III) in serum. T-2 values in serum containing definite amounts of added iron were also measured before and after addition of ascorbic acid. The difference in the 1/T-2 of serum with and without ascorbic acid was used for recalculation of the added iron values, Recalculated iron values confirm that the difference in healthy serum is caused by iron only. In addition, in order to find the paramagnetic contribution of serum iron, T-2 values of iron-deficient, healthy and iron-overloaded serum were measured before and after addition of ascorbic acid. The difference in the 1/T-2 values was then applied to the calculation of the serum iron values. The consistency of iron values determined from the difference to those by autoanalyzer suggests that the differences in diseased serum also represent the paramagnetic contribution of serum iron. The data imply that serum iron content in healthy, iron-deficient and iron-overloaded serum may be assessed by MRI.Öğe Proton T1 and T2 relaxivities of serum proteins(Elsevier Science Inc, 2004) Yilmaz, A; Ulak, FS; Batun, MSIn the present study, T-1 and T-2 of phantoms containing serum sets with varying amounts of proteins, serum samples with certain amounts of proteins, serum diluted by distilled water, and serum treated with iron were measured. In addition, T-1 and T-2 of phantoms containing normal serum, diluted serum, and albumin-doped serum were also measured. Relaxation rates were plotted versus protein concentrations. The slope of relation was taken as relaxivity. The T-1 relaxivities of proteins were ranged from 0.035 to 0.080 s(-1)(g/dl)(-1), whereas T-2 relaxivities were ranged from 0.24 to 0.68 s(-1)(g/dl)(-1). The T-1 and T-2 relaxivities of transferrin iron were 2.40 and 2.60 mM(-1)s(-1), respectively. The contributions of diamagnetic proteins and transferrin iron to the relaxation rate of serum were also calculated for each of diluted serum, normal and albumin-doped serum. The contributions and the average TP relaxivities(calculated by using individual relaxivities and the ratios of protein fractions in TP) were used for TP calculations. The agreement between the calculated TP and TP by autoanalyzer and also the agreement between average TP relaxivities and the TP relaxivities determined from dilution experiments show that the data of relaxivities are reliable. The results suggest that individual protein relaxivities explain the influence of serum TP composition on T-1 and T-2 relaxation times. (C) 2004 Elsevier Inc. All rights reserved.Öğe Proton T1 and T2 relaxivities of serum proteins (vol 22, pg 683, 2004)(Elsevier Science Inc, 2004) Yilmaz, A; Ulak, FS; Batun, MS[Abstract Not Available]
