Influence of nano alumina coating on the flexural bond strength between zirconia and resin cement

Akay, Canan,Tanis, Merve Cakirbay,Mumcu, Emre,Kilicarslan, Mehmet Ali,Sen, Murat The Korean Academy of Prosthodonitics 2018 The Journal of Advanced Prosthodontics Vol.10 No.1

PURPOSE. The purpose of this in vitro study is to examine the effects of a nano-structured alumina coating on the adhesion between resin cements and zirconia ceramics using a four-point bending test. MATERIALS AND METHODS. 100 pairs of zirconium bar specimens were prepared with dimensions of $25mm{\times}2mm{\times}5mm$ and cementation surfaces of $5mm{\times}2mm$. The samples were divided into 5 groups of 20 pairs each. The groups are as follows: Group I (C) - Control with no surface modification, Group II (APA) - airborne-particle-abrasion with $110{\mu}m$ high-purity aluminum oxide ($Al_2O_3$) particles, Group III (ROC) - airborne-particle-abrasion with $110{\mu}m$ silica modified aluminum oxide ($Al_2O_3+SiO_2$) particles, Group IV (TCS) - tribochemical silica coated with $Al_2O_3$ particles, and Group V (AlC) - nano alumina coating. The surface modifications were assessed on two samples selected from each group by atomic force microscopy and scanning electron microscopy. The samples were cemented with two different self-adhesive resin cements. The bending bond strength was evaluated by mechanical testing. RESULTS. According to the ANOVA results, surface treatments, different cement types, and their interactions were statistically significant (P<.05). The highest flexural bond strengths were obtained in nano-structured alumina coated zirconia surfaces (50.4 MPa) and the lowest values were obtained in the control group (12.00 MPa), both of which were cemented using a self-adhesive resin cement. CONCLUSION. The surface modifications tested in the current study affected the surface roughness and flexural bond strength of zirconia. The nano alumina coating method significantly increased the flexural bond strength of zirconia ceramics.

Endoscopic Ultrasound-Guided Fine Needle Aspiration Using a 22-G Needle for Hepatic Lesions: Single-Center Experience

Ebru Akay,Deniz Atasoy,Engin Altınkaya,Ali Koç,Tamer Ertan,Hatice Karaman,Erkan Caglar 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.3

Background/Aims: Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) has been accepted as a reliable tool indiagnosing and staging intra-abdominal tumors. In this study, we aimed to investigate the performance of EUS-FNA in theevaluation of liver masses and its impact on patient management and procedure-related complications retrospectively. Methods: Data of patients who underwent EUS-FNA biopsies due to liver masses between November 2017 and July 2018 wereretrieved retrospectively. Biopsies were performed using 22-G needles. The demographics, EUS-FNA results, sensitivity andspecificity of the procedure, negative predictive value, positive predictive value, and specimen sufficiency rates were assessed. Results: A total of 25 patients (10 females) were included in the study. The mean age was 62.73±15.2 years. The mean size of themasses was 34.50±16.04 mm. The technical success rate was 88%. During the EUS-FNA procedure, each patient had only one passwith 94.45% of aspirate sufficiency rate and 86.3% of biopsy sufficiency rate. The diagnostic accuracy rate was 86.3%. There were nocomplications. Conclusions: For the evaluation of liver masses, EUS-FNA using a 22-G needle with even one pass had high aspiration and biopsysuccess rates accompanied with high diagnostic accuracy rates.

Discrete system identification and self-tuning control of dissolved oxygen concentration in a stirred reactor

Bulent Akay,Suna Ertunc,Havva Boyacioglu,Hale Hapoglu,Mustafa Alpbaz 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.3

This work presents the applications of discrete-time system identification and generalized minimum variance (GMV) control of dissolved oxygen (DO) level in a batch bioreactor in which Saccharomyces cerevisiae is produced at aerobic condition. Air flow rate and mixing rate were varied to determine the maximum local liquid phase volumetric mass transfer coefficient (K_La). Maximum K_La value was determined at a mixing rate of 600 rpm and air flow rate of 3.4 Lmin^(−1). For control purpose, manipulated variable was selected as air flow rate due to its effectiveness on the K_La. To examine the dynamic behavior of the bioreactor, various input signals were utilized as a forcing function and three different model orders were tested. A second0order controlled auto regressive moving average (CARMA) model was used as the process model in the control algorithm and in the system identification step. It is concluded that the ternary input is more suitable than the other input types used in this work for system identification. Recursive least squares method (RLS) was used to determine the model parameters. GMV control results were compared with the traditional PID control results by using performance criteria of IAE and ITAE for different types of DO set point trajectories. DO concentration in the batch bioreactor was controlled more successfully with an adaptive controller structure of GMV than the PID controller with fixed parameters.

The Effect of Problem Posing Oriented Calculus-2 Instruction on Academic Success

Hayri Akay,Nihat Boz 한국수학교육학회 2009 수학교육연구 Vol.13 No.2

New Look on the Specific Factor Model: Empirical Evidence from Manufacturing Industries in Tanzania

Gokhan H. Akay 한국국제경제학회 2009 International Economic Journal Vol.23 No.2

This study analyzes the impact of trade on wages in the context of the specific factor model by focusing on the link between trade and the average real wage. A recent paper by Jones & Ruffin (2008) shows how one can use the specific factor model to predict how labor should fare from an improvement in the terms of trade, an increase in the price of exportables relative to importables. For this purpose, I use annual firm-level data on the manufacturing sector in Tanzania during the period 1992 to 1998. I find that a ceteris paribus increase in the price of exportables may benefit labor in the food-beverage industry but hurt labor in the textile-garment, wood-furniture and metal-machinery industries. There are industries where the specific factor model predicts that exporting would help workers, but where the Stolper-Samuelson theorem of the Hecksher-Ohlin model predicts the reverse.

Advances in Smartphone-Based Point-of-Care Diagnostics

Xiayu Xu,Akay, Altug,Huilin Wei,ShuQi Wang,Pingguan-Murphy, Belinda,Erlandsson, Bjorn-Erik,XiuJun Li,WonGu Lee,Jie Hu,Lin Wang,Feng Xu IEEE 2015 Proceedings of the Institute of Electrical and Ele Vol.103 No.2

<P>Point-of-care (POC) diagnostics is playing an increasingly important role in public health, environmental monitoring, and food safety analysis. Smartphones, alone or in conjunction with add-on devices, have shown great capability of data collection, analysis, display, and transmission, making them popular in POC diagnostics. In this article, the state-of-the-art advances in smartphone-based POC diagnostic technologies and their applications in the past few years are outlined, ranging from in vivo tests that use smartphone's built-in/external sensors to detect biological signals to in vitro tests that involves complicated biochemical reactions. Novel techniques are illustrated by a number of attractive examples, followed by a brief discussion of the smartphone's role in telemedicine. The challenges and perspectives of smartphone-based POC diagnostics are also provided.</P>

Evaluation of bite force, quality of life, and patients' satisfaction in elderly edentulous patients using implant overdentures

Esra Nur Avukat,Canan Akay,Emre Mumcu 대한치과보철학회 2023 The Journal of Advanced Prosthodontics Vol.15 No.4

Purpose. This study aimed to compare the bite force (BF) between complete dentures and implant overdentures (IODs) retained by two mandibular implants. Additionally, we evaluated the quality of life (QoL) and patient satisfaction among individuals using IODs. In addition, the effects of demographic parameters such as age and sex, and clinical parameters such as implant length, implant diameter, attachment height, attachment color, and interimplant distance on BF, QoL, and patient satisfaction were evaluated. Materials and methods. A total of 51 edentulous patients rehabilitated with the maxillary complete dentures and mandibular IODs retained by two implants were included in this study. BF was measured using a force meter pre- and post-implant in the same patients. Oral health-related quality of life (OHRQoL) was assessed with the Oral Health Impact Profile (OHIP-14) and patient satisfaction was assessed with the Visual Analog Scale (VAS) questionnaires. Results. It was found that BF values were statistically higher for IODs than complete dentures (P < .001). In terms of attachment height of the OHIP scores, there was a significant difference in the psychological disability and social disability domains (P < .05). When examining the change in patient satisfaction as a function of sex, it was found that mandibular retention satisfaction differed significantly by sex (P < .05), but there was no significant difference in the other domains. Conclusion. Within the limitations of this study, it was observed that the BF increased after the use of IODs. Several factors, including age, interimplant distance, attachment height, and attachment color, were found to impact OHRQoL. Sex and implant diameter were identified as factors affecting patient satisfaction.

In vitro shear bond strength between fluorinated zirconia ceramic and resin cements

Merve Çakırbay Tanış,Canan Akay,Turgut Cihan Akçaboy,Murat Şen,Pınar Akkaş Kavaklı,Kadriye Sapmaz 대한치과보철학회 2018 The Journal of Advanced Prosthodontics Vol.10 No.3

PURPOSE. The purpose of this study was to evaluate the efficiency of a gas-phase fluorination method under different fluorination periods through using two resin cements. MATERIALS AND METHODS. 84 zirconia specimens in dimensions of 5 mm × 5 mm × 2 mm were prepared and surface treated with 50 μm aluminum oxide particles or gas phase fluorination for 2 min, 5 min, or 10 min. One specimen in each group was surface analyzed under scanning electron microscope. The remaining specimens were bonded to composite cylinders in dimensions of 2 mm diameter and 3 mm high with Panavia SA Plus or Variolink N. Then, the specimens were stored in 37°C distilled water for 24 hours and shear bond strength test was applied at a speed of 1 mm/min. RESULTS. The highest shear bond strength values were observed in the samples fluorinated for 5 minutes and cemented with Panavia SA Plus. Variolink N did not elicit any statistical differences between surface treatments. Panavia SA Plus resin cement and Variolink N resin cements featured statistically significant difference in shear bond strength values only in the case of 5 minutes of fluorination treatment. CONCLUSION. According to the results of this study, application of 5 minutes of fluorination with 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP) containing Panavia SA Plus resin cement increased the resin bond strength of zirconia. Fluorination of the zirconia surface using conventional resin cement, Variolink N, did not lead to an increase in bond strength.

Ultrasonic assisted photocatalytic process for degradation of ciprofloxacin using TiO2-Pd nanocomposite immobilized on pumice stone

Parisa Yekan Motlagh,Sema Akay,Berkant Kayan,Alireza Khataee 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.104 No.-

Herein, Pumice (PM)-TiO2-Pd nanocomposite as an efficient catalyst was prepared by modified sol-gelmethod and used for sonophotocatalytic removal of ciprofloxacin (CIP). Various analyses were used toinvestigate the properties of the catalysts. Based on the SEM results, the TiO2 and Pd nanoparticles onthe PM surface were immobilized regularly without aggregation. Also, the crystalline structure and functionalgroups of PM-TiO2-Pd nanocomposite were identified successfully by XRD and FTIR analyses. Thebandgap energy of 2.52, 3.17, and 3.29 eV were calculated for PM-TiO2-Pd, PM-TiO2, and PM indicatinghigher sonophotocatalytic activity of PM-TiO2-Pd nanocomposite. 79.44 % of CIP was removed within120 min of treatment time using in the optimum condition ([PM-TiO2-Pd] = 0.5 g/L, [CIP]0 = 20 mg/Land pH = 6). By adding radical scavengers like EDTA, CrO3, formic acid, and enhancers like K2S2O8 andH2O2 the degradation efficiency was as follows respectively: 37.72, 31.71, 28.29, 88.78, and 72.43%. The reusability and stability of the composite after four consecutive runs was decreased only 9.44%. Also, 8 intermediate byproducts generated under sonophotocatalytic degradation of CIP by PM-TiO2-Pdnanocomposite were identified.

Determination of the parameters for the back-to-back switched Schottky barrier structures

M. Ahmetoglu (Afrailov),S.K. Akay 한국물리학회 2010 Current Applied Physics Vol.10 No.2

The Cr/n-GaAs/Cr and Ag/p-GaAs/Ag metal–semiconductor–metal (MSM) Schottky contacts have been fabricated by reactive radio frequency (RF) sputtering system. The current–voltage (I-V) and capacitance–voltage (C-V) characteristics of the devices have been investigated in the temperature range of 80–316 K for the back-to-back switched Schottky barrier contacts. These measurements establish that the room temperature barrier height determined from reverse branch of the current–voltage characteristics is close to the value obtained from capacitance–voltage measurements.