Properties of Aluminum Nano Composites Bearing Alumina Particles and Multiwall Carbon Nanotubes Manufactured by Mechanical Alloying and Microwave Sintering

Ali Günen,Ömer Saltuk Bölükbaşı,Yasin Özgürlük,Derviş Özkan,Okan Odabaş,İlyas Somunkıran 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness,fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy(P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness,scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, surface profilometry, microhardness,and fracture toughness. The addition of Cr has a significant effect on both boride layer formation and friction-wearbehaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving effect on the microhardness, fracturetoughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boridelayer and low fracture toughness, thus reducing wear resistance. Coefficients of friction and wear volume losses at elevatedtemperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the samplecontaining 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtainedin the sample containing 6 wt% Cr, where the highest hardness value was obtained.

Effect of Cr Addition on Properties and Tribological Behavior at Elevated Temperature of Boride Layers Grown on Borosintered Powder Metallurgy Alloys

Ali Günen,Ömer Saltuk Bölükbaşı,Yasin Özgürlük,Derviş Özkan,Okan Odabaş,İlyas Somunkıran 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.3

This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness,fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy(P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness,scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, surface profilometry, microhardness,and fracture toughness. The addition of Cr has a significant effect on both boride layer formation and friction-wearbehaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving effect on the microhardness, fracturetoughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boridelayer and low fracture toughness, thus reducing wear resistance. Coefficients of friction and wear volume losses at elevatedtemperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the samplecontaining 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtainedin the sample containing 6 wt% Cr, where the highest hardness value was obtained.

Methacrylamidohistidine in Affinity Ligands for Immobilized Metal-ion Affinity Chromatography of Human Serum Albumin

Odaba, Mehmet,Garipacan, Bora,Dede, Semir,Denizli, Adil The Korean Society for Biotechnology and Bioengine 2001 Biotechnology and Bioprocess Engineering Vol.6 No.6

Different bioligands carrying synthetic adsorbents have been reported in the literature for protein separation, We have developed a novel and new approach to obtain high protein ad-sorption capacity utilizing 2-methacrylamidohistidine(MAH) as a bioligand. MAH was synthe-sized by reacting methacrylocholride and histidine, Spherical beads with an average size of 150-200㎛ were obtained by the radical suspension polymerization of MAH and 2-hydrosyethyl-methacrylate(HEMA) conducted in an aqueous dispersion medium. p(HEMA-co-MAH) beads had a specific surface area of 17.6㎡/g . Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling test, FTIR and elemental analysis. Then Cu(II) ions were incorporated onto the beads and Cu(II) loading was found to be 0.96 mmol/g.These affinity beads with a swelling ration of 65% and containing, 1.6 mmol MAH/g were used in the adsorption/desorption of human serum albumin(HSA) from both aqueous solutions and hu-man serum. The adsorption of HSA onto p(HEM-co-MAH) was low(8.8 mg/g). Cu(II) chelation onto the beads significantly increased the HSA adsorption (56.3 mg/g). The maximum HSA ad-sorption ws observed at pH 8.0 Higher HSA adsorption was observed from human plasma(94.6 mgHSA/g) Adsorption of other serum proteins were obtained as 3.7 mg/g for fibrinogen and 8.5mg/g for γ-globulin. The total protein adsorption was determined as 107.1mg/g. Desorption of HSA was obtained using 0.1 M Tris/HCl buffer containing 0.5 M NaSCN, High desorption rations(up to 98% of the adsorbed HSA) were observed. It was possible to reuse Cu(II) chelated-p(HEMA-co-MAH) beads without significant decreases in the adsorption capacities.

Can We Prevent Coffee Stains on Teeth?

Tugce Odabas,Rufat Hajiyev,Ahmet Gultekin,Ozge Ozer Atakoglu,Osman Tolga Harorli 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.12

This study evaluates whether some common beverages treated before coffee could protect or increase tooth staining caused by coffee. Initial color of 50 incisor teeth were measured with a spectrophotometer and recorded according to CIELAB color system. Teeth were randomly divided into five groups, water (control), milk, green tea, orange juice, and cola (n = 10) and were kept in selected beverage for 10 min. Immediately afterward, they were immersed in coffee and allowed to stand for 24 h. The treatment was repeated for 5 days. At the end of the fifth day, L*a*b* color measurements of the teeth were repeated. Calcium, phosphorus, potassium, and magnesium changes on representative teeth surfaces were also investigated with X-ray fluorescence spectroscopy. Color differences were calculated with both CIEab and CIE00 formulas. Groups were compared with Kruskal–Wallis test complemented by the Bonferroni correction and Mann–Whitney U test for pairwise comparisons (P = .05). The teeth submitted to coffee challenges after distillated water or beverages showed a perceptible color change. Soaking in cola or orange juice before coffee immersion caused severe tooth discoloration. All the beverages tested here were not able to protect the tooth from coffee staining. People should be informed that some acidic beverages consumed before a coffee can worsen the coffee-based tooth discolorations.

Observer Based Friction Cancellation in Mechanical Systems

Caner Odaba?,Omer Morgul 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10

An adaptive nonlinear observer based friction compensation for a special time delayed system is presented in this paper. Considering existing delay, an available Coulomb observer is modified and closed loop system is formed by using a Smith predictor based controller as if the process is delay free. Implemented hierarchical feedback system structure provides two-degree of freedom and controls both velocity and position separately. For this purpose, controller parametrization method is used to extend Smith predictor structure to the position control loop for different types of inputs and disturbance attenuation. Simulation results demonstrate that without requiring much information about friction force, the method can significantly improve the performance of a control system in which it is applied.

Risk factors of medication-related osteonecrosis of the jaw: a retrospective study in a Turkish subpopulation

Onur Ş,ahin,Onur Odabaş,Toghrul Aliyev,Birkan Tatar 대한구강악안면외과학회 2019 대한구강악안면외과학회지 Vol.45 No.2

Objectives: Medication-related osteonecrosis of the jaw (MRONJ) is a well-known side effect of certain drugs that are used to influence bone metabolism to treat osteometabolic disease or cancers. The purpose of our study was to investigate how high-concentration and low-concentration bisphosphonate (BP) intake affects the disease severity. Materials and Methods: Data collected from the medical records of 52 patients treated with BPs, antiresorptive, antiangiogenic drugs and diagnosed with MRONJ were included in this study. Age, sex, type of systemic disease, type of drug, duration of drug treatment, jaw area with MRONJ, drug administration protocol, and MRONJ clinical and radiological findings were obtained. Patients were divided into two groups: anti-neoplastic (Group I, n=23) and anti-osteoporotic (Group II, n=29). Statistical evaluations were performed using the IBM SPSS ver. 21.0 program. Results: In both groups, more females had MRONJ. MRONJ was found in the mandibles of 30 patients (Group I, n=14; Group II, n=16). When we classified patients according to the American Association of Oral and Maxillofacial Surgeons staging system, significant differences were seen between groups (χ 2 =12.23, P<0.01). More patients with advanced stage (stage 2-3) MRONJ were found in Group I (60.9%). Conclusion: According to our results, high-concentration BP intake, age and duration of drug intake increased disease severity.

Lung Cancer in Women: A Single Institution Experience with 50 Patients

Babacan, Nalan Akgul,Yucel, Birsen,Kilickap, Saadettin,Seker, Mehmet Metin,Kacan, Turgut,Olcas, Ilknur Koc,Eren, Ayfer Ay,Odabas, Hatice Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.1

Background: Lung cancer is the most common cause of cancer-related death worldwide. The incidence of lung cancer is aproximately 7-8 thousand percent in Turkish women. In this study, we aimed to evaluate the clinical, pathological properties and survival data of female patients with lung cancer who were treated in our center. Materials and Methods: From 2007 to 2012, 50 women with lung cancer were enrolled. Patient data were evaluated retrospectively. Results: The median age was 61 (40-81). Forty patients (80%) were diagnosed with non small cell lung cancer (NSCLC), 10 patients (20%) were small cell carcinoma (SCC). Twelve (24%) patients were smokers and 13 of 16 non-smokers had a history of exposure to asbestos. The most common histologic subtype was adenocarcinoma (46%) and this accounted for 71% in patients with exposure to asbestos. The most common initial Eastern Cooperative Oncology Group (ECOG) performance score was 1 (24 patients, 48%) and initial stage was IV (25 patients, 50%) in the study group. During the median 15 months (1-96 months) followup period: 1 year overall survival (OS) was 68%, 2year overall survival was 36% and the median survival time was 19 months. According to univariate analysis, poor ECOG performance status, advanced stage, anemia and weight loss at time of diagnosis were negative prognostic factors. However, adenocarcinoma sub-type was a positive prognostic factor. Conclusions: In this study NSCLC sub-type, poor ECOG performance score, advanced stage, anemia and weight loss were prognostic factors in Turkish women with lung cancer.