Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 2Citation - Scopus: 3Comparision of in Situ Spectroscopic Ellipsometer and Ex Situ X-Ray Photoelectron Spectroscopy Depth Profiling Analysis of Hfo2/Hf Multilayer Structure(IOP Publishing Ltd., 2018) Cantaş, Ayten; Özyüzer, Lütfi; Aygün, GülnurA HfO2 film was grown by RF magnetron sputtering technique on a Si substrate Using in situ Spectroscopic Ellipsometry (SE), the film thickness and refractive index were examined as a function of deposition time. Ex situ x-ray Photoelectron Spectroscopy (XPS) was used in depth profile mode to determine the phase evolution of HfO2/Hf/Si multilayer structure after the growth process. The chemical composition and the crystal structure of the film were investigated by Fourier Transform Infrared (FTIR) spectroscopic measurements and x-ray Diffraction in Grazing Incidence (GI-XRD) mode, respectively. The results showed that the film was grown in the form of HfO2 film. According to SE analysis, reactive deposition of HfO2 directly on Hf/Si results to SiO2 interface of about 2 nm. The final HfO2 films thickness is 5.4 nm. After a certain period of time, the XPS depth profile revealed that the film was in the form of Hf-rich Hf silicate with SiO2 interfacial layer. In reference to XPS quantification analysis from top to bottom of film, the atomic concentration of Hf element reduces from 19.35% to 7.13%, whereas Si concentration increases from 22.99% to 74.89%. The phase change of HfO2 film with time is discussed in details.Article Citation - WoS: 24Citation - Scopus: 25Investigation of the Structure of Alpha-Lactalbumin Protein Nanotubes Using Optical Spectroscopy(Cambridge University Press, 2014) Tarhan, Özgür; Tarhan, Enver; Harsa, ŞebnemAlpha-lactalbumin (α-la) is one of the major proteins in whey. When partially hydrolysed with Bacillus licheniformis protease, it produces nanotubular structures in the presence of calcium ions by a self-assembly process. This study presents investigation of α-la protein structure during hydrolysis and nanotube formation using optical spectroscopy. Before spectroscopic measurements, nanotubes were examined with microscopy. The observed α-la nanotubes (α-LaNTs) were in the form of regular hollo strands with a diameter of about 20 nm and the average length of 1 μm. Amide and backbone vibration bands of the Raman spectra displayed remarkable conformational changes in α and β domains in the protein structure during nanotube growth. This was confirmed by the Fourier-transform infrared (FTIR) spectroscopy data. Also, FTIR analysis revealed certain bands at calcium (Ca++) binding sites of COO- groups in hydrolysed protein. These sites might be critical in nanotube elongation.Article Citation - WoS: 3Citation - Scopus: 3Evaluation of High Hydrostatic Pressure Effects on Bovine Red Blood Cells and Platelets(Taylor and Francis Ltd., 2009) Ceylan, Çağatay; Severcan, Mete; Bozoğlu, Faruk; Severcan, FerideThe objective of this study was to investigate the effects of high hydrostatic pressure (HHP) on the stability of red blood cells (RBCs) and platelets. Bovine blood cells (n=5) were treated with the pressure of 55, 110, 154 and 220MPa at 25°C for 5min. Light microscopy, atomic force microscopy and flow cytometry studies revealed that RBCs were morphologically stable up until the 220MPa pressure treatments, at which surface modifications were observed. The platelets were found to be less stable than RBCs. HHP application did not cause any significant change in the signal intensity, band area and frequency values of the infrared bands with the exception that a significant variation was observed in the area of the cholesterol band. No statistically significant variations were observed in the secondary structure elements due to HHP treatment according to the artificial neural network study based on the FTIR data.Article Citation - WoS: 68Citation - Scopus: 76Differentiation of Mixtures of Monovarietal Olive Oils by Mid-Infrared Spectroscopy and Chemometrics(John Wiley and Sons Inc., 2007) Gürdeniz, Gözde; Tokatlı, Figen; Özen, Fatma BanuFourier transform infrared (FT-IR) spectroscopy in combination with chemometric techniques has become a useful tool for authenticity determination of extra-virgin olive oils. Spectroscopic analysis of monovarietal extra-virgin olive oils obtained from three different olive cultivars (Erkence, Ayvalik and Nizip) and mixtures (Erkence-Nizip and Ayvalik-Nizip) of monovarietal olive oils was performed with an FT-IR spectrometer equipped with a ZnSe attenuated total reflection sample accessory and a deuterated tri-glycine sulfate detector. Using spectral data, principal component analysis successfully classified each cultivar and differentiated the mixtures from pure mono-varietal oils. Quantification of two different monovarietal oil mixtures (2-20%) is achieved using partial least square (PLS) regression models. Correlation coefficients (R2) of the proposed PLS regression models are 0.94 and 0.96 for the Erkence-Nizip and Ayvalik-Nizip mixtures, respectively. Cross-validation was applied to check the goodness of fit for the PLS regression models, and R 2 of the cross-validation was determined as 0.84 and 0.91, respectively, for the two mixtures.