Browsing by Author "Aydin, M"

Now showing 1 - 11 of 11
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    Diffusion Welding of Al-α-Si3N4 Composite Materials
    Arik, H; Erden, IO; Aydin, M
    In this study, Al-alpha-Si(3)N(4 )composite, produced by powder metallurgy method, were joined at 2.5 MPa pressure with various welding temperatures (620, 630, and 640 degrees C) and durations (1,1.5, and 2 h.) by diffusion welding method. Optical microscopy examination was carried out from welded interfaces and shear tests were also conducted to the sample interfaces to find out the effect of welding parameters and amount of alpha-Si3N4 reinforcement on the weldability properties of composite materials. The test results show that increase in the welding temperature and duration resulted in increase shear resistance of the welded zone. Results indicated that optimum parameters (welding temperatures, durations and amount of alpha-Si3N4 are 640 degrees C, 2 h., and 15wt % respectively) MMCs produced in this study could be joined by diffusion welding technique successfully with the 97.5 % strength of base material.
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    Production and Characterization of Composite Filaments for 3D Printing
    Çanti, E; Aydin, M; Yildirim, F
    In this study, various nano and micro particles with different properties, including density, surface area, purity and particle morphology were used as reinforcement particles for the production of polymer composite filaments to be used for 3D printing. Acrylonitrile Butadiene Styrene (ABS) was matrix material and Multi wall carbon nanotubes (MWCNTs), SiO2, ZrB2, and, Al particles were reinforcements. Production of the composite filaments was carried out by using a twin screw extruder. Produced composite filaments were characterized via Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), tensile test and surface roughness tests. Results showed that addition of micro/nano particles into ABS matrix improved the Ultimate Tensile Strength (UTS) of the composites by around 16% compared to non-reinforced one. As a result of reinforcing with micro particles, ZrB2 and Al, the tensile strain of neat-ABS filament increased by 17.8% and 40%, respectively
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    Production of Bioactive Various Lattices as an Artificial Bone Tissue by Digital Light Processing 3D Printing
    Dokuz, ME; Aydin, M; Uyaner, M
    This study aims to find which lattice type and which ingredient is the best for the bone lattice for future grafting operations. Four types of lattice parts with micro and high porosity were designed to resemble the human bone structure and reach its light-weight and high surface area properties. Hydroxyapatite (HA) and tricalcium phosphate (TCP) were used in the photopolymer resin mixture for (Digital Light Processing) DLP 3D printing to give high bioactivity capability to the parts. In conclusion, microporosity HA- and TCP-doped parts were printed successfully with the DLP technique. Bioactivity tests were carried out with parts that were soaked in simulated body fluid (SBF). There is no significant weight difference in lattice parts in the time. Four weeks are sufficient time for the test. End of 2 weeks, calcium phosphate particles with around a diameter of 50-75 mu m, and end of 4 weeks, calcium phosphate particles with around a diameter of 80-225 mu m were observed. Apatite precipitation areas were grown on the surface in time. SEM and XRD results indicate that HA-doped and TCP-doped specimens are bioactive. A more mass increase was observed in the HA-doped specimen compared to the TCP-doped specimen.
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    The effects of disodium pentaborate decahydrate on in-vivo neuroblastoma animal model
    Altun, Z; Serinan, EO; Aktas, S; Calisir, M; Aydin, M; Yilmaz, O; Korkmaz, M; Olgun, N
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    Widespread post-traumatic acute spinal subdural haematoma
    Özkan, Ü; Kemaloglu, MS; Aydin, M; Selçuki, M
    Study design: A case report of acute post-traumatic spinal subdural haematoma (ASSH). Objective: To report a rare post-traumatic problem. Setting: Dicle University Hospital, Diyarbakir, Turkey. Method: A 3-year-old boy was admitted to our clinic with paraplegia 24 h after falling from a height of about 5 meters. Investigation revealed all acute spinal subdural haematoma. Results: Following surgery there was marked improvement. The rehabilitation of the patient continues. Conclusion: MRI is the most valuable diagnostic method. In each case diagnosed as ASSH. prompt evacuation should be performed before irreversible neurological damage occurs.
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    Improved mechanical performance of three-dimensional woven glass/epoxy spacer composites with carbon nanotubes
    Yildirim, F; Aydin, M; Avci, A
    Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes-epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement.
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    Impact response of nanoparticle reinforced 3D woven spacer/epoxy composites at cryogenic temperatures
    Yildirim, F; Tatar, AC; Eskizeybek, V; Avci, A; Aydin, M
    Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to -196 degrees C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.
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    Prognostic Significance of Hemoglobin/Prognostic Nutritional Index and Hemoglobin/Red Blood Cell Distribution in Rectal Cancer
    Tuncel, ET; Parvizi, M; Kut, E; Aydin, M; Kasap, E
    Background: We aimed to investigate the effect of hemoglobin/prognostic nutritional index and hemoglobin/red blood cell distribution, which are indicators of inflammation and nutrition, on prognosis and survival in patients with rectal cancer. Methods: The retrospective study reviewed medical records of 138 patients with rectal cancer who were followed up between 2010 and 2021. The effects of hemoglobin/red blood cell distribution, hemoglobin/prognostic nutritional index, tumor stage, and lymph node status on survival and prognosis were evaluated using univariate and multivariate analyses. Overall survival and disease-free survival were calculated for both groups. Results: Survival and prognosis were found to be significantly better in nonanemic patients with the hemoglobin/prognostic nutritional index higher than the cut-off value than in anemic patients with a normal or lower hemoglobin/prognostic nutritional index. Similarly, survival and prognosis were found to be significantly better in nonanemic patients with a hemoglobin/red blood cell distribution higher than the cut-off value than in anemic patients with a normal or lower hemoglobin/red blood cell distribution. Conclusion: The results indicated that nutrition and inflammatory markers have independent prognostic significance in rectal cancer. These markers are simple, inexpensive, and useful biomarkers commonly used in clinical practice, and they were found to predict overall survival and disease-free survival independently.
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    Anterior odontoid screw fixation using Acutrak screw: Report of 19 patients
    Duransoy, YK; Mete, M; Ünsal, ÜÜ; Aydin, M; Zileli, M
    BACKGROUND: This paper aims to present clinical and radiological results of patients who underwent anterior odontoid screw fixation (AOSF). METHODS: In this study, 19 consecutive patients with an unstable odontoid fracture were operated on using an Acutrak screw. RESULTS: The patients were followed for a mean duration of 12.5 months. Radiological fusion on CT scans was detected in 87.5% of the patients. CONCLUSION: Acutrak screws can be used for AOSF. This study contains the maximum number of patients using the Acutrak screw in the literature. However, larger prospective clinical studies can provide more accurate information about the effectiveness of the Acutrak screws for odontoid fractures.
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    Evaluation of the prevalence of coronary artery disease in patients with valvular heart disease
    Emren, ZY; Emren, SV; Kiliçaslan, B; Solmaz, H; Susam, I; Sayin, A; Abud, B; Aydin, M; Bayturan, Ö
    Objectives: The aim of the present study was to retrospectively evaluate the prevalence of concurrent coronary artery disease in patients who underwent surgery due to severe valvular heart disease. The study also investigated the association of coronary artery disease with the type of valvular heart disease. Materials and methods: A total of 241 patients (123 females [51%]), who had underwent single valvular heart surgery, were included in the study. The patients who underwent valve replacement surgery were divided into four groups: patients with severe mitral stenosis (MS), patients with severe mitral regurgitation (MR), patients with severe aortic regurgitation (AR), and patients with severe aortic stenosis (AS). Age, DM, HT, history of smoking, and LDL values were recorded as the risk factors for CAD. Results: Coronary artery disease was detected in 26.4% of patients with mitral stenosis and 57.7% of patients with aortic stenosis. Of the patients with mitral insufficiency, 41.9% had CAD, and 44.4% of the patients with aortic insufficiency had CAD. Conclusion: The comparison of MS and AS groups revealed significantly higher prevalence of CAD in the AS group. There was no statistically significant difference between the MR and AR groups in terms of the prevalence of CAD. The comparison of MS and MR groups revealed significantly higher prevalence of CAD in the MR group. Furthermore, the comparison of these groups in terms of the extensiveness of the coronary artery disease revealed significantly higher Gensini score in the MR group.
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    Effect of using elastic-pressure socks in spinal surgery patients on orthostatic hypotension in the first mobilization
    Öztürk, G; Yilmaz, E; Aydin, M; Baydur, H
    Background: Orthostatic hypotension (OH) is a common early postoperative finding in patients who undergo major surgery, and it might delay early mobilization, which is the main building block of modern perioperative care programs. The aim of this study was to determine the effect of using thigh-length elastic pressure socks in patients who undergo spinal surgery in development of OH at first mobilization after surgery. Methods: The study was a randomized-controlled intervention study. A total of 70 patients who underwent spinal surgery were included in the study. The patients were allocated randomly to the intervention group (n = 35) who used thigh-length elastic pressure socks and the control group (n = 35) which received no intervention other than routine nursing care. Results: It was found in the study that 2.9% of the patients in the intervention group developed OH during the first mobilization after the surgery, and 48.6% of the patients in the control group developed OH at first mobilization. The patients in the intervention group were found to have the risk ratio (RR): 0.06 times less probability of developing OH than the patients in the control group (95% confidence interval [CI]:0.01-0.42). The OH symptoms were lower in the patients in the intervention group. Conclusion: It was found as a result of the study that using thigh-length elastic pressure socks in spinal surgery patients reduced OH development and symptoms at first mobilization after the surgery.