Faculty of Engineering and Architecture https://hdl.handle.net/20.500.12294/414 2026-04-24T05:15:23Z 2026-04-24T05:15:23Z Acar, Tayfun Arvas, Melih Besir Arvas, Busra Ucar, Burcu Sahin, Yucel https://hdl.handle.net/20.500.12294/4139 2024-07-22T15:31:16Z 2024-01-01T00:00:00Z

Adsorption and desorption of hydroxychloroquine onto sulphur doped graphene powders as a potential drug for COVID-19 Acar, Tayfun; Arvas, Melih Besir; Arvas, Busra; Ucar, Burcu; Sahin, Yucel Hydroxychloroquine (HCQ) is a very substantial drug active substance that was approved for emergency use by the FDA during the peak of the COVID-19 pandemic due to its potent antiviral properties. In this study, adsorption and desorption of hydroxychloroquine on sulfur (S)-doped graphene powders were investigated. While the adsorption experiments were carried out in the environment of distilled water (pH 5.0-6.0), HEPES buffer (pH 7.6), and Tris.HCl buffer (pH 8.0) the desorption studies were performed in distilled water. The HCQ adsorbed S-doped graphene powders were characterized by UV-Vis, FT-IR, XRD, BET and TEM techniques. According to UV-Vis measurements, the adsorption efficiency in the HEPES buffer medium at pH 7.6 was the highest (68.72% for H3 (HCQ adsorption with SGr3 graphene in HEPES medium)). FT-IR and XRD analyses confirmed the presence of HCQ on the graphene powders' surface. While morphological changes on the surfaces of graphene powders were imaged by TEM, BET surface area changes proved the HCQ adsorption. The in vitro toxicity of the developed H3 was found to be lower than that of HCQ alone on the L929 cell line. These fundamental findings of the surface interaction between HCQ and graphene are precious for the design and optimization of a targeted drug based on this molecule and material. The adsorption/desorption features of HCQ onto graphene-based carrier systems which in particular doped with sulfur from functional metals have been investigated for the first time.

2024-01-01T00:00:00Z Bebekoglu, Sunay Topuz, Ahmet Cakir, Esin Adsoy, Abdulhamit Yildiran, Turgay https://hdl.handle.net/20.500.12294/4138 2024-07-22T07:16:53Z 2024-01-01T00:00:00Z

Development of sinter linings for high-speed trains Bebekoglu, Sunay; Topuz, Ahmet; Cakir, Esin; Adsoy, Abdulhamit; Yildiran, Turgay In this study, brake linings with Cu (copper)-based and Cu-10Sn (bronze)-based matrix structures have been developed and produced by the powder metallurgy method using sinter metal technology for use in high-speed trains. The developed linings were compared with commercial high-speed train linings. Firstly, the mixing process was carried out in a Turbulo 3V three-dimensional mixer for 4.5 h at 50 rpm. The pressing process was performed at room temperature, under the pressure of 350-450 MPa, and the sintering temperature for Cu-based linings was 1,000 °C, while for Cu-10Sn-based linings, it was 800 °C. After the pressing and sintering processes, lining sample density calculations were conducted, and hardness tests were carried out in the Rockwell L scale. Shear strength tests, friction coefficient, and wear tests were conducted according to SAE J 661 standards. It was observed that sinter metal brake linings with Cu and Cu-10Sn main matrix structures showed similar properties and met the technical requirements. It was determined that the developed production prescriptions are promising for industrial production and patent studies. © 2024 Walter de Gruyter GmbH, Berlin/Boston 2024.

2024-01-01T00:00:00Z Sarikaya, Burak Cetinkaya, Riza Aytac Ozyigitoglu, Derya Isik, Sinem Akkaya Kaplan, Mustafa Kirkik, Duygu Gorenek, Levent https://hdl.handle.net/20.500.12294/4122 2024-07-03T10:10:15Z 2024-01-01T00:00:00Z

High antibiotic resistance rates in Helicobacter pylori strains in Turkey over 20 years Sarikaya, Burak; Cetinkaya, Riza Aytac; Ozyigitoglu, Derya; Isik, Sinem Akkaya; Kaplan, Mustafa; Kirkik, Duygu; Gorenek, Levent Objective Helicobacter pylori (Hp) eradication therapy is crucial for preventing the development of gastritis, peptic ulcers, and gastric cancer. An increase in resistance against antibiotics used in the eradication of Hp is remarkable. This meta-analysis aims to examine the resistance rates of Hp strains isolated in Turkey over the last 20 years against clarithromycin (CLR), metronidazole (MTZ), levofloxacin (LVX), tetracycline (TET), and amoxicillin (AMX) antibiotics. Basic methods Literature search was carried out in electronic databases, by searching articles published in Turkish and English with the keywords 'helicobacter pylori' or 'Hp' and 'antibiotic resistance' and 'Turkey'. That meta-analysis was carried out using random-effect model. First, the 20-year period data between 2002 and 2021 in Turkey were planned to be analyzed. As a second stage, the period between 2002 and 2011 was classified as Group 1, and the period between 2012 and 2021 as Group 2 for analysis, with the objective of revealing the 10-year temporal variation in antibiotic resistance rates. Main results In gastric biopsy specimens, 34 data from 29 studies were included in the analysis. Between 2002-2021, CLR resistance rate was 30.9% (95% CI: 25.9-36.2) in 2615 Hp strains. Specifically, in Group 1, the CLR resistance rate was 31% in 1912 strains, and in Group 2, it was 30.7% in 703 strains. The MTZ resistance rate was found to be 31.9% (95% CI: 19.8-45.4) in 789 strains, with rates of 21.5% in Group 1 and 46.6% in Group 2. The overall LVX resistance rate was 25.6%, with rates of 26.9% in Group 1 and 24.8% in Group 2. The 20-year TET resistance rate was 0.8%, with 1.50% in Group 1 and 0.2% in Group 2. The overall AMX resistance rate was 2.9%, 3.8% between 2002-2011, and 1.4% between 2012-2021. Principal conclusion Hp strains in Turkey exhibit high resistance rates due to frequent use of CLR, MTZ, and LVX antibiotics. However, a significant decrease has been observed in TET and AMX resistance to Hp in the last 10 years. Considering the CLR resistance rate surpasses 20%, we suggest reconsidering the use of conventional triple drug therapy as a first-line treatment. Instead, we recommend bismuth-containing quadruple therapy or sequential therapies (without bismuth) for first-line treatment, given the lower rates of TET and AMX resistance. Regimens containing a combination of AMX, CLR, and MTZ should be given priority in second-line therapy. Finally, in centers offering culture and antibiogram opportunities, regulating the Hp eradication treatment based on the antibiogram results is obviously more appropriate.

2024-01-01T00:00:00Z Rouabeh, Aicha Benahmed, Baizid Palanci, Mehmet Aouari, Issam https://hdl.handle.net/20.500.12294/4119 2024-07-03T15:31:56Z 2024-01-01T00:00:00Z

The Derivation of Vertical Damping Reduction Factors for the Design and Analysis of Structures Using Acceleration, Velocity, and Displacement Spectra Rouabeh, Aicha; Benahmed, Baizid; Palanci, Mehmet; Aouari, Issam Damping reduction factors (DRFs) play a vital role in the seismic design of structures. DRFs have been widely studied due to their primary importance to the lateral resistance of structures subjected to earthquakes. On the other hand, devastating earthquakes have occurred all over the world, and recently, the Kahramanmara & scedil; earthquakes in Turkey revealed the import of the vertical component of earthquakes and their impact on structures and infrastructures. Considering the importance of this parameter, this paper aims to develop new damping reduction factor (DRF) equations for the acceleration (DRFa), velocity (DRFv), and displacement spectra (DRFd) of the vertical components of earthquakes. For this purpose, 775 real ground motion records were selected from the Pacific Earthquake Engineering Research (PEER) strong motion database, and the vertical elastic response spectra of selected records were computed according to linear dynamic analysis. Taking the 5%-damped vertical response spectra as the target, the vertical spectral damping reduction factors (DRFa, DRFv, and DRFd) were computed for 1%, 3%, 10%, 15%, 20%, 30%, and 40% damping ratios. The effect of the earthquake magnitude, distance, and soil types on the DRFs was investigated. The results indicated that magnitude, distance, and soil type had no particular effect on the trend in the DRFs. Based on the evaluations, extensive statistical analyses were carried out, and new prediction equations were developed according to the nonlinear regression method. The developed equations were then compared to those found in the literature and seismic design codes. The comparisons proved that the proposed DRFa, DRFd, and DRFv models are strongly compatible with real DRFs and show strong robustness compared to existing models.

2024-01-01T00:00:00Z