Master Tezleri

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Adhesion of dopa functionalized gels to spin labeled surfaces
(Izmir Institute of Technology, 2017-07) Göksel, Yaman; Akdoğan, Yaşar; Emrullahoğlu, Mustafa
This study investigates the force free adhesive properties of synthetic polymer in aqueous media using electron paramagnetic resonance (EPR) spectroscopy. Due to poor performance of commercial adhesives in wet environments, scientists are interested in different types of adhesives to overcome this difficulty. On this context, mussels attract attention because of their versatile properties to adhere different types of surfaces from rocks to ship hulls underwater. Adhesion occurs when mussel secretes mussel foot proteins (MFPs) in order to form threads and plaques. Seven types of MFPs are unique in plaque contains high amount of L-3,4-dihydroxyphenylalanine (DOPA) amino acid which is reputed to be responsible for adhesion. In this research, branched polyethylene glycol (PEG) based polymers functionalized with DOPA were synthesized and their force-free adhesive properties to hydrophobic polystyrene and hydrophilic silica nanobeads were investigated in solution. These nanobead surfaces were conjugated with spin label molecules to probe adhesion dynamics using EPR spectroscopy. In addition, gel forms of polymers obtained using NaIO4, FeCl3 and Cr2O7 were used as adhesive materials for EPR measurements. All of these adhesive materials showed adhesion to spin labeled polystyrene (SL-PS) surface. However, non-DOPA containing PEG showed no indication of adhesion thus, demonstrating the importance of DOPA in wet adhesion. In addition, EPR results showed that DOPA based PEG polymers were unable to adhere to spin labeled silica (SL-SiO2) surface. This behavior was attributed to hydration layers around silica nanobeads. These layers formed around hydrophilic SiO2 surface prevent interaction between nanobead surface and polymeric material.
Adsorption kinetics of methane reformer off-gases on aluminum based metal-organic frameworks
(Izmir Institute of Technology, 2017-07) Angı, Deniz; Çakıcıoğlu Özkan, Seher Fehime
Over the last decades, with the development in industrialization, the combustion of fossil fuels has generated an increasing level of emission of greenhouse gases into atmosphere. Considerable efforts have been endeavored to advance alternative cleaner energy source to relieve the stress on environmental concerns and depletion of oil reserves. Hydrogen is regarded as an ideal clean energy carrier. A great majority of ultrapure hydrogen is produced by hydrogen rich steam methane reformer (SMR) off-gas mainly composed of 60-80% H2, 15-25% CO2, 3-6% CH4 and 1-3% CO, which severely requires an efficient separation and purification process associated with gas adsorption principle. A novel class of porous adsorbents known as metal-organic frameworks (MOFs) represent outstanding separation performance due to possessing large surface area and tunable pore size. Aluminum based metal organic frameworks (Al-TPA) are widely utilized in gas separation/purification applications due to its breathing characteristics by adjusting cell volume reversibly. The highest surface area of Al-TPA was found to be 1270 m2/g by performing solvothermal synthesis route. Diffusion studies of SMR off-gas components on the Al-TPA were carried out at different flow rates (80, 168 and 175 mL/min), temperatures (34, 70 and 100 °C) and concentrations (15 and 28%). High value of parameter L demonstrated that system was under kinetic control. The diffusivity values were found to be ranging from 5.73 x 10-13-8.04 x 10-13 for CO2, 5.03 x 10-13-6.64 x 10-13 for CH4, 1.36 x 10-12-1.56 x 10-12 for H2 and 1.01 x 10-13- 5.03 x 10-13 m2/g for CO respectively with increasing temperature.
Air monitoring of polychlorinated bibhenyls in ambient air of suburban area in Izmir, Turkey
(Izmir Institute of Technology, 2004) Bozacıoğlu, Sevde Seza; Sofuoğlu, Aysun
Polychlorinated biphenyls (PCBs) are human made toxic chemicals which were first synthesized in 1920s. Because of their inverse effects on environment and human health the usage and production of PCBs were banned in 1970s in United States and all over the Europe. PCBs are prone to long- range atmospheric transport and this makes them ubiquitous in the environment. Due to the importance of long-range transport of PCBs, their concentrations have been measured in many different countries. In order to determine the atmospheric concentration levels of total (gas+particle) PCBs (.PCB) and 41 PCB congeners in İzmir, two sampling programs were designed. 20 successive day and nighttime (called short-term), and 40 a year around representing particle and gas phase samples (called long-term) were collected from May 2003 to March 2004. Effects of temperature, wind speed and direction, and seasonal change on atmospheric concentrations of PCBs were investigated. In the short-term period, average .PCB(41) concentration was 520 pg m-3, while congener base total (gas+particle) polychlorinated biphenyl concentrations ranged from 0.37 . 0.65 pg m-3 (PCB 158) to 305.07 . 86.01 pg m-3 (PCB 33). Similarly, in the long-term analysis average .PCB(41) concentration was found as 419 pg m-3, while the minimum and maximum concentrations of congener base total (gas+particle) PCB concentrations ranged from 0.11 . 10.58 pg m-3 (PCB 70) to 919.69 . 281.18 pg m-3 (PCB 208). Short-term average total concentration was higher than a year average total concentration. The reason could be the revolatilization of these compounds from the contaminated surfaces due to the increase in temperature in early summer/late spring.Generally, the levels of PCB were within the ranges previously measured at different sites. The temperature dependence of gas-phase atmospheric concentrations of PCBs was investigated by using Clausius-Clapeyron relationship. The results were statistically significant for 12 PCB congeners (PCB 74, 70, 101, 99, 87, 82/151, 153, 138, 158, and 128). In addition to temperature, the effect of wind speed and direction was investigated using multiple linear regression analysis. Results of the multiple regression analysis indicated that wind speed was a statistically significant factor for PCB 18 and PCB 17, which have low molecular weights and tendency to be in gas phase. In the long-term data analysis with respect to Clausius-Clapeyron relationship 13 congeners (PCB 18, 17, 31, 28, 33, 74, 70, 95, 99, 153, 138, 187, and 209) were statistically significant with temperature. Introduction of wind speed and wind direction to the Clausius-Clapeyron equation did not resulted in a better correlation. The statistically significant correlated congeners were attributed as they were originated from short-range transport. The other congeners with lower R2 values and poor correlations exhibited that their sources were originated from long-range transport. The only positive slope was obtained for PCB 209 and this could be attributed to the influence of its ongoing source. Since the usage and production of PCBs were banned, the source may be the exchange processes from buildings, indoor air, soils, etc., to overlying atmosphere.
Analysis of fingerprint matching performance with deep neural networks
(01. Izmir Institute of Technology, 2022-03) Göçen, Alper; Erdoğmuş, Nesli; 01. Izmir Institute of Technology
Fingerprints are unique biometric properties for each person. In the literature and industry, they are widely used for identification purposes. Collecting biometric datasets is a tedious work since it is not possible without the owners’ consent, and existing fingerprint datasets are either not sufficient to use in deep learning tasks by means of size or most of them are kept private to the collectors’ use. This increases the need of synthetic fingerprint images and their use in a variety of tasks especially for training deep learning models. In this study, the performance of a CNN architecture named Finger ConvNet[1] is compared to well-known networks and the question of whether a mixed dataset consisting of synthetically generated and real fingerprint images can reach a performance close or equal to ones having only real images is discussed. As a result of experiments, it is shown that the number of real images in the dataset is an important factor and that the performance of the mixed dataset was less than the one having only real images proposed in the referred study.
Assesment of chronological life span dependent molecular damages of S.cerevisiae deficient in mitochondrial antioxidant genes
(Izmir Institute of Technology, 2009) Demir, Ayşe Banu; Koç, Ahmet
Aging is referred as the time-dependent accumulation of biological and physiological changes in an organism. This complex process is the major factor that is associated with many diseases such as cancer, diabetes and neurodegenerative disorders.The free radical theory of aging, which states that the molecular damages formed upon free radicals lead to the aging process, is the most widely accepted aging theory. The free radicals that are primarily produced in the mitochondria upon aerobic metabolism, are known to damage the biomolecules such as DNA, proteins and lipids. However, cells have evolved different defense systems for the elimination of these molecular damages. Antioxidant defense mechanism is one these systems that play role in the repair of the molecular damages. Since mitochondria are the main sites for the free radical production, the antioxidant genes that function in mitochondria gained an importance for their roles in preventing the molecular damages in a cell. In this study, the differences in the life spans and levels of molecular damages among different mitochondrial antioxidant gene mutants of Saccharomyces cerevisiae were tried to be identified throughout the chronological aging process, which is the model that mimics post-mitotic cell aging in higher eukaryotes. It was shown that deletion of some mitochondrial antioxidant genes resulted in different levels of biomolecular damages as well as different sensitivities against reactive species, which may be a critical outcome for the prevention of the detrimental effects of free radicals on biomolecules formed during chronological aging.
Assessment of impact of reservoir's contaminated bottom sediments on surfacewater quality by sediment-water interaction model
(Izmir Institute of Technology, 2011) Şimşek, Sinem Elif; Elçi, Şebnem
In this study, an approach for the assessment of the life-long impact of submersed contaminated bottom sediments in projected reservoirs on surface water quality is presented. A sediment-water interaction model designed to simulate contaminants in the sediments and in the overlying water column is developed and the impact of contaminated bottom sediments on water quality is investigated under different scenarios. One goal of this study is to investigate the contribution of contaminated soils underlying the reservoir compared to the contaminants transported by surface and groundwater influx. The proposed study predicts the long term impact of the selected site on water quality before the construction of the dam. The sediment-water interaction model developed in this study consists of three main layers: water column which can be specified as well mixed or stratified according to the temperature profile in the vertical column, a mixed sediment layer and a deep sediments layer. In the model, mass balance equations for contaminants are solved for the water column and the mixed sediment layer.This study further presents the projection of possible contamination in a reservoir based on the analysis of the soil samples collected from the reservoir bottom before the filling of the reservoir. Reverse modeling approach for the prediction of contaminant concentration in the water column originating from the bottom sediments is applied. Transfer of five heavy metals; Copper, Zinc, Chromium, Nickel, and Lead existing in bottom sediments of Çamlı Basin to the reservoir water is modeled.
BaTiO3 based ferroelectric materials for electrocaloric cooling applications
(Izmir Institute of Technology, 2018-12) Şanlı, Keriman; Adem, Umut; Akdoğan, Yaşar
The aim of this project was to produce electrocaloric materials and to determine the potential of these materials for electrocaloric cooling applications. The electrocaloric effect (ECE) of lead-free Ba0.8Sr0.2Ti1-xZrxO3 (0 ≤ x ≤ 0.10) ferroelectric ceramics was studied. The phase analysis of each ceramic composition that was synthesized by conventional solid-state reaction technique was performed by X-ray Diffraction. Dielectric measurements were done to determine the phase transition temperatures (Curie temperature, Tc) of all compositions and also construct a phase diagram. ΔT values were calculated indirectly using electrical polarization curves measured at different temperatures and Maxwell's equations. ΔT values that were obtained from different regions of the phase diagram are compared. The most suitable composition for applications was chosen considering the ΔT value, temperature range where relatively large ΔT is preserved and the Curie temperature of all ceramics. Ba0.8Sr0.2Ti0.93Zr0.07O3 ceramic located near the critical point shows the best performance with ΔT value of 0.40 K under 20 kV/cm. In comparison with the lead-free ceramics studied in the literature, Ba0.8Sr0.2Ti1-xZrxO3 system can be considered as one of the best candidates for future electrocaloric cooling technologies.
Bending behavior of hybrid fiber reinforced concrete beams
(Izmir Institute of Technology, 2020-12) Aloui, Sarra; Saatçi, Selçuk; 01. Izmir Institute of Technology
Fiber reinforced concrete is widely used in various applications in concrete members. In this study, effect of fiber hybridization, using different types of fibers in concrete mix, on the bending behavior of concrete beams was investigated. For this purpose, eight beam specimens, 2500x500x50 mm in dimension, were cast in pairs with four different steel fiber content. One of the two specimens with the same steel fiber content had additional Polyvinyl Alcohol (PVA) fibers. The specimens were first tested under three-point bending. After these tests, failed specimens, which had a single crack at the midspan, were broken into two halves and the half with no visible damage was tested again under four-point loading to obtain the behavior for a constant moment region.The ultimate strength and the load-displacement behaviorwas investigated for each specimen. It was seen that fiber hybridization obtained by addition of PVA had an adverse effect for three-point bending tests. Specimens with additional PVA fibers had a lower ultimate load and deflection capacity compared to specimens with only steel fibers. However, fiber hybridization had a positive effect for same specimens under four-point bending test. It was concluded that hybridization of steel and PVA fibers had a positive effect on the bending behavior for loading conditions that result in a uniform moment distribution. However, for cases where a single crack dominates the behavior, such as a three-point bending case, hybrid fibers were not as effective or even had an adverse effect.
Biocompatibility and microstructural characterization of PVD coated and nitrogen implanted Co-Cr alloy
(Izmir Institute of Technology, 2004) Türkan, Uğur; Öztürk, Orhan
In this study, the effectiveness of nitrogen ion implanted and TiN coated layers on CoCrMo alloy (ISO 5832-12) in preventing metal ion release during in vitro exposure of these layers to simulated body fluid (SBF) was investigated. The experimental results clearly show higher levels of cobalt ion release from nitrogen implanted CoCrMo material surfaces into simulated body fluid as compared to the as-polished CoCrMo alloy. The results clearly indicate that nitrogen ion implantation used for modification of fcc CoCrMo alloy surfaces lead to the development of various near surface microstructures. Nitrogen ion implantation was carried out at 60 and 30 keV ion energies with the corresponding current densities of 0.1 and 0.2 mA/cm2, respectively, for the substrate temperatures of 100, 200 and 400 °C and implantation time of 30 minutes. Near surface crystal structures and phases, nitrogen ion implanted and TiN coated layer thicknesses were characterized by a combination of symmetric (.-2.) and grazing incidence x-ray diffraction (XRD and GIXRD) and cross-sectional scanning electron microscopy (SEM). Metal ion release into the simulated body fluid was analyzed by atomic absorption spectrometry (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The experimental XRD results clearly show the formation of a metastable, fcc, high-N phase (.N) in mainly fcc CoCrMo alloy for the ion beam conditions at 400 °C. The lower implantation temperatures, 100 and 200 °C, for both 60 and 30 keV ion energies, result in a nitride phase, (Co, Cr, Mo)2+xN. The cross sectional SEM results for the specimens implanted at the 60 and 30 keV ion energies at 400 °C reveal quite clearly the uniform nature of the .N layers. The .N layer thicknesses, based on the SEM data, were found to be 450 and 540 nm for the 60 and 30 keV implanted specimens, while the (Co, Cr, Mo)2+xN nitride layer has a thickness range from 150 to 250 nm for the 60 and 30 keV at 100 and 200 °C implantation conditions. The SEM results also indicate that the (Co, Cr, Mo)2+xN nitride and .N phase layers on the CoCrMo alloys have high etch resistance suggesting enhanced corrosion resistance for the N implanted specimens compared to the substrate material. The XRD and SEM results for the TiN coated (via PVD) specimens show that the fcc TiN coatings exhibit (111) preferred orientation and have a coating thickness of . 3 µm with a columnar type of growth mode. The experimental AAS results show that in vitro exposure of the N implanted layers result in higher levels of cobalt ion release into the SBF than the as-polished substrate CoCrMo alloy. This was attributed to the rougher surfaces of the N implanted specimens compared to that of the substrate material (i.e, rougher surface implying a larger area is available for metal ion release). It was also found that the specimens implanted at the lower substrate temperatures of 100 and 200 °C have lower levels of Co ion release compared to those specimens implanted at the substrate temperature of 400 °C. The limited dissolution of cobalt, in this case, was explained by the stronger bonds of metal-N in the nitride phase than those of .N phase. Furthermore, the AAS data indicate higher cobalt ion release rate for the N implanted specimens compared to the substrate alloy and suggest transport (diffusion) controlled dissolution reaction mechanism. The AAS results show no cobalt ions are released from the TiN coated specimens (i.e, the release levels were below the analytical detection limit of the AAS apparatus). This indicates that the TiN coated layer can be an effective barrier for reducing the metal ion release from the substrate alloy. The SEM/EDX study of the surface morphologies of the N implanted, TiN coated and as-polished CoCrMo alloy test specimens after the static immersion test clearly indicate calcium phosphate formation on the as-polished alloy, while there was almost no phosphate precipitates on the surface of N implanted and TiN coated specimens. While the experimental results show higher levels of cobalt ion release for the N implanted specimens compared to the substrate material, the overall release levels are found to be below toxic levels for the human body.
CaP coating of porous sintered Ti6Al4V powder compacts using biomimetic and sol-gel methods
(Izmir Institute of Technology, 2006) Altındiş, Mustafa; Güden, Mustafa
In this study, two methods of CaP coating, dip coating and biomimetic, on porous Ti6Al4V powder compacts to be used in novel spinal cages were experimentally investigated. The powder compacts produced by sintering of compacted green powders contained 37% open porosity with an average pore size of 63 micrometers. Dip-coating solutions were prepared using sol-derived and commercially available HA powders.Biomimetic CaP coatings were performed in 1(at 37°C, Ph . 7.4) °, 5 (at 37°C, pH .6.0) and 10x (at room temperature, pH . 5.8) simulated body fluid (SBF).The porous Ti6Al4V powder compacts were successfully coated using HA dip coating solutions. The optimum soaking times were 3 and 1-minute for sol-derived and milled and unmilled comercial HA powders, respectively. Increasing soaking times further started to fill the originally open pores. The thicker deposit and cracks were observed at the sintering necks of the particles was believed to be due to capillary effects drawing the coating solution into this concave region. Milling of HA powder induced more homogenous coating layer on the Ti6Al4V particles.Increasing Ca and P concentrations in SBF increased the rate of CaP nucleation.Alkaline (NaOH) and heat-treatment (600oC for 1 hour) further accelerated CaP formation. The complete coating of treated and untreated compacts was 14 and 21 days using 1xSBF, 24 and 36 hours using 5xSBF and 4 and 6 hours using 10xSBF, respectively. When considered crack free and homegenous coating layer, dip coating using milled commercial HA powder was found to be the most appropriate method for the coating present powder compacts.
A case study of material testing for corrosion in low temperature geothermal systems
(Izmir Institute of Technology, 2005) İnce, Umut; Güden, Mustafa
The main goal of this study is to determine the corrosion rate and mechanisms of an St-37 steel material currently used as a pipeline material in Izmir.Balçova Geothermal District Heating System. Alternative steel piping materials, AISI 304, AISI 316, AISI 316L austenitic stainless steels, were also investigated for their corrosion behaviour in the same geothermal system. Two fluid velocities, 0.02 and 9.6 m/s, showing the low or stagnant and high velocity fluid flow respectively were selected for the corrosion experiments at the site. Intentionally prepared tensile St-37 test specimens were used to investigate the effect of corrosion (particularly pitting type of corrosion) on the ultimate tensile strength of the steel, while conventional test coupons were usedin the testing of stainless steels. These tests were further accompanied by the qualitative laboratory tests involving Ryznar stability index and electropotential measurements. It was found that laboratory measurements, Ryznar stability index, pitting resistance equivalent and electropotential measurements showed good agreement with the result of corrosion experiments conducted at the site. Although the uniform corrosion rates were relatively low in the tested steels, the pitting corrosion rate was greatly promoted in St-37 samples at the low fluid velocity, mainly driven by the SRB activity and tubercle formation. The tensile tests on the St-37 corroded samples have further shown that the UTS decreased as the exposure time increased. The decrease in the UTS of St-37 was more pronounced in the samples tested at the lower fluid velocity, which showed a good agreement with the measured maximum pitting depths found in these samples. The service life time of the St-37 was further predicted for two selected fluid velocities using the equations developed for the effect of defects on the bursting pressure of the pipelines. The predicted service life of St-37 was 57 and 95 months for low and high velocity fluid flow respectively. These service lives were also comparable with the reported service life of the pipelines used in the studied geothermal system. Finally, a solution were proposed to increase the service lifetime of St-37 pipes: addition of SRB activity reducing reagents to the fluid.
Cation exchange in zeolites structure modification by using a microwave
(Izmir Institute of Technology, 1999) Akdeniz, Yelda; Ülkü, Semra
In this research, characterization and modification of clinoptilolite minerals from different deposits have been studied to determine its utility for different Clinoptilolite minerals obtained from the source located in Western (FTIR) to determine the structural properties. The FTIR spectra of the samples showed the characteristic vibrations of the clinoptilolite framework. Thermal properties were determined using Differential Thermal Analyzer (DTA), Thermal Gravimetric Analyzer (TGA), and Differential Scanning Calorimetry (DSC). The analysis showed that the structure of the samples were stable up to 650 DC and due to the Fe203 present in the tuff, phase inversion was observed. Accelerated Surface Area and Porosimeter (ASAP 2010) used to determine the adsorptionrelated properties using N2 and Ar adsorption isotherms. The samples showed different adsorption behaviour toward each gas. The pore size distribution of clinoptilolite samples showed that they have mesaporous structure.The clinoptilolite was modified by ion exchange using 1N NaCI salt solution in waterbath, and in microwave maintained at 80 DC for 10 min, 60 min and 120 min. The efficiency of each method on ion exchange was compared. The Na+ amount in the zeolite was found to be 2.25 and 3.24 % by weight after 2 hours of exchange in waterbath and microwave, respectively. The results showed that microwave method used for modification was more efficient.
Chacterization of drug resistance mechanisms against antifungal agent Voriconazole
(Izmir Institute of Technology, 2015-07) Ercan, İlkcan; Koç, Ahmet
The rapid progress in medicine provides an increase in both average life span but also increases number of patients who need intensive care throughout the world. The morbidity and mortality of systemic fungal infections have become a serious problem because of suppressed immunity due to chemotherapy or intentional use of suppressants after tissue/organ transplantations. Voriconazole (Vfend, Pfizer) is one of antifungal agent against these fungal infections as a derivative of fluconazole. However some fungi types gain resistance against this agent. In this project, we use budding yeast Saccharomyces cerevisiae as a model organism to identify the genes that cause resistance Voriconazole by performing a genome wide screening. MRS3 and TRI1 genes were determined as resistant genes against lethal dose of Voriconazole. Their overexpression exhibited resistance to Voriconazole and also Ketoconazole in cross-resistance test. According to real-time PCR results, both MRS3 and TRI genes showed overexpression in IC50 of Voriconazole treatment when compare with their untreated status. Microaaray analysis indicated the expression change of our resistant genes is not more than 2 fold. In addition to expression analysis, functional analysis such as membrane dynamics tests have salt (NaCl, LiCl) and cationic drug (HygB,spermine,TMA) tolerance, membrane potential, volume/size measurements and cytoplasmic pH values were analyzed to reveal the mechanisms of resistance. Our results showed that no linkage between Variconozole resistance provided by MSR3 and TRI1 genes and functional analyses mentioned above.
Characterization and expansion behaviour of perlite
(Izmir Institute of Technology, 2016-07) Gül, Dilek; Demir, Mustafa; Şentürk, Ufuk; Demir, Mustafa Muammer
Perlite is a silica-based organic glass. When it is instantaneously heated, it shows expansion by releasing a certain amount of water. Approximately 70% of perlite reserves in the world are found in Turkey. The porous structure of expanded perlite leads to use this material in many industrial areas; therefore, this is highly advantageous from the economic standpoint. In this study, the expansion behaviours of perlite samples, which were taken from İzmir (Bergama Mine), Kütahya (Avdan Mine), and Erzincan (Mollatepe Mine) were both characterized and investigated in the laboratory. The instrumentation techniques, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Optic Microscope were used to characterize the perlite. The determination of the amorphous and crystal structure of perlite, the chemical composition of perlite, the measurement of loss of mass, the morphological characterization of perlite, and the form of raw and expanded perlite samples were obtained by XRD, XRF, TGA, SEM and Optic Microscopy, respectively. Four different heat treatments as 600 ˚C, 800 ˚C , 900 ˚C and 1000 ˚C and four different sizes 400-500 μm, 315-400 μm, 200-315 μm and 160-200 μm were conducted in the laboratory and the their bulk volumes and densities were compared before and after heat treatment. The perlite sample from Bergama 01 showed the largest expansion in all samples. As results of the analyses, the amount of crystal and water release in the perlite which had an influence on expansion process were consistent with the literature. The analyses were conducted until 1000 ˚C due to forming sinter above softening temperature. Additionally, the expanded perlite samples in the industrial furnace were compared with the expanded perlite samples in the laboratory more porous structure was observed. As a conclusion, the perlite samples from the different regions of Turkey were characterized and analyzed in terms of expansion behaviour in this study.
Characterization and recyclability of pharmaceutical blisters
(01. Izmir Institute of Technology, 2023-07) Çapkın, İrem Yaren; Gökelma, Mertol; Akkurt, Sedat
Packaging is one of the largest industries in the world. Pharmaceutical blister packages are the most preferred packaging type in the pharmaceutical industry. Especially after the COVID-19 pandemic, the use of pharmaceutical packaging has become widespread with the increasing demand for drugs. Pharmaceutical blister packages typically contain thin sheets of plastic and aluminium and generate substantial solid waste. Since these packages have a multi-layered and complex structure, they are difficult to recycle. Before recycling, plastic and aluminium need a separation process. Chemical separation or thermal processes can be used for separation. The aim of this study is to characterize different pharmaceutical blister types with SEM-EDS (Scanning electron microscopy- Energy dispersive X-ray spectroscopy), TGA (Thermogravimetric Analysis), DSC (Differential scanning calorimetry), ICP-MS (Inductively coupled plasma mass spectrometry), and FTIR (Fourier Transform Infrared Spectroscopy) and to review the different reagents used in the pharmaceutical blister layer separation process. In addition to thermal degradation, the parameters and results of the separation processes were evaluated using hydrochloric acid, formic acid, acetic acid, sulfuric acid, ethanol, acetone, and organic solvents. It also evaluates the recyclability of the separated layers (plastic and aluminium). Its recyclability was evaluated by melting the aluminium fraction under salt consisting of a mixture of NaCl-KCl-CaF2. The plastic fraction was obtained in solid and liquid form by thermal degradation and analysed by GC-TCD (Gas Chromatography-Thermal conductivity detector).
Circulating nucleic acid (CNA) separation from serum by electrospun membranes
(Izmir Institute of Technology, 2015-07) Işık, Tuğba; Demir, Mustafa; Demir, Mustafa Muammer; Horzum Polat, Nesrin
Early detection of diseases is a key factor that can be made provision and successfully treated. There is a wide array of methods to diagnose cancer like biopsy, endoscopy, magnetic resonance imaging (MRI) and blood tests. In blood, while some nucleic acids are found in intracellular fluids, circulating nucleic acids (CNAs) circulate freely in extracellular fluids. They are located at genomic regions and increased levels of CNAs imply a connection with cancer and tumor initiation. For further analysis, separation and concentration of CNAs have high potential in early cancer detection. A model system was constructed with bovine serum albumin (BSA) and single stranded Deoxyribonucleic acid (ss-DNA) for the investigation of membrane separation efficiency. The membranes made of poly styrene (PS) and poly(methylmethacrylate) (PMMA) were fabricated by electrospinning and they were placed in syringe columns. By using the absorption spectroscopy, the sorption efficiency of membranes was determined. The electrospun membranes are promising for BSA uptake over a wide pH range. Under the same circumstances, thanks to PS fibers, ss-DNA uptake is very with respect to BSA uptake. Our results revealed that PS membranes show a better affinity to BSA molecules by hydrophobic interactions. In the mixture of BSA and ss-DNA, ss- DNA cannot be held on the surface of the membrane and pass through with low sorption efficiency. By altering the membrane amount in syringe column and modifiying the surface of the membranes, the separation could be enhanced. The proposed technology promises fast and effective separation of CNAs from whole blood and body fluids.
Coating of La1-xSrxCo1-yFeyO3-δ films on zirconia and CGO (Cerium gadolinium oxide) by electrostatic spray deposition (ESD)
(Izmir Institute of Technology, 2010) Büyükkebabçı, Hande; Akkurt, Sedat
In this study preparation and characterization of coating of La0.6Sr0.4Co0.8Fe0.2O3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ materials on TZ-3Y (3 mol % doped yttria) and CGO (Ce0.9Gd0.1Oxide) ceramic electrolytes was studied. Electrostatic spray deposition (ESD) was used for depositing the coatings on ceramic electrolytes to develop a well bonded electrolyte-cathode material for potential IT-SOFCs (intermediate temperature solid oxide fuel cells) applications. Precursor solutions having La0.6Sr0.4Co0.8Fe0.2O3-δ or La0.6Sr0.4Co0.2Fe0.8O3-δ stoichiometry were prepared from various salts before being sprayed on a heated ceramic substrate which rapidly evaporated the solvent in the salts and the droplets struck and covered its surface. A high voltage was maintained to accelerate the droplets to high speeds. A coating with a minimal 1 µm of thickness was successfully produced. Effects of experimental parameters like the flow rate of the solution (0.3-1.5 ml/h), distance between the nozzle and substrate (15-45 mm), temperature of the substrate (250-375 °C), post heat treatment temperature (900-1300 °C) of the coated substrate and applied voltage on the quality of the coating were studied. Analytical tools like DTA/TGA, Scanning Electron Microscopy (SEM) and Xray Diffraction (XRD) were used to investigate the samples to check for the quality of the coating. Coating microstructures ranged from dense to porous depending on the deposition parameters. Sample with 30 mm distance and 0.7 ml/h of flow rate produced the best reticulated structure of the coating. No preferential landing effect was observed on any of the samples studied. Zirconia was not an effective substrate for formation of La0.6Sr0.4Co0.8Fe0.2O3-δ or La0.6Sr0.4Co0.2Fe0.8O3-δ. Cerium gadolinium oxide, however, was effective for La0.6Sr0.4Co0.8Fe0.2O3-δ but not for La0.6Sr0.4Co0.2Fe0.8O3-δ.
Coating of spinel layers on alumina by electrostatic spray deposition (ESD)
(01. Izmir Institute of Technology, 2023-04) Demirkol, İrem; Akkurt, Sedat
MgAl2O4 spinel layer was coated on dense alumina pellets by advantageous ESD among the other deposition methods in terms of providing a simple, inexpensive setup and good control of the layer morphology. The main goals are successfull deposition of spinel layers on alumina pellets by ESD, to investigate the effect of ESD parameters (working distance, flow rate of precursors, applied voltage) on coating microstructure by conducting full factorial design experiments and to determine the best experimental conditions for a porous layer. Besides, MgCr2O4 layer was coated on dense alumina and MgAl2O4 layer was deposited on bisque-fired alumina pellet to extend the scope of the work. Alumina powders were compressed and sintered, respectively to obtain pellets. MgAl2O4 spinel precursor solution was sprayed on the alumina pellets by changing the parameters accordingly the full factorial design. MgAl2O4 and MgCr2O4 solutions were also sprayed on the bisque-fired and the dense alumina pellets with the parameters given the best porous layer. Elemental analysis of the residues obtained after evaporation of the solutions by energy dispersive X-ray spectroscopy (EDX), both unheated and post-heated residual powders of solutions by X-ray diffraction (XRD) and surface morphologies of coated pellets by scanning electron microscopy (SEM-EDS) were analyzed. Spinel layers on alumina pellets were successfully coated by ESD, which could provide variable surface morphologies. The optimum conditions for a porous layer were obtained as working distance of 15 mm, flow rate of 0.25 mL/h and applied voltage of 6 kV in this study. The coatings on the pellets before further heating were amorphous. Post-heating of the pellets were required to obtain crystalline spinel structure.
A computational chemistry study on the interactions between hydrogenated borophene and amino acids
(Izmir Institute of Technology, 2022-07) Bozkurt, Yağmur; Elmacı Irmak, Nuran
In this work, the adsorption behavior of hydrogenated borophene to amino acids was examined to provide its geometric and electronic structures information and to check whether hydrogenated borophenes’ potential can be used in new biosensor devices for amino acids or not. In the aspect of this thesis adsorption of 4 amino acids from different types of amino acid classes (acidic, basic, nonpolar, and polar) on hydrogenated borophene surfaces has been studied by computational chemistry methods. Electronic and geometric structures of B36H6 and its complexes with glycine, tyrosine, aspartic acid, and histidine were obtained by DFT calculations at B3LYP-D2 / 6-311G** level of theory. In the energetically most favorable configurations of complexes, amino acids approaching from the bottom of the B36H6 surface with a horizontal orientation (exception for histidine complexes) of amino acid was observed. The most reactive parts of the B36 structure (edges) have been stabilized with hydrogenation, the whole boron cluster became more stable and adsorption ability has fallen. It was found that hydrogenated borophene has indistinguishable electronic responses for each the amino acids studied in this thesis since the complexes exhibited nearly the same band gap. Thus, hydrogenated borophene shows no sensor ability to GLY, TYR, ASP, and HIS.
A computational study of excitation dynamics on semiconductor surfaces
(Izmir Institute of Technology, 2019-12) Kaya, Birnur; Sevinçli, Haldun; Özçelik, Serdar
Recent experimental studies have shown that collodial quantum dots can be produced in large quantities and their optical properties can be tailored by controlling their composition, size and surface characteristics. Motivated by these studies, this thesis is devoted to the investigation of excitation dynamics on semiconductor surfaces, which are passivated with organic molecules. First, constructing a simplified model, excitation dynamics is investigated by computing time dependent occupations of frontier molecular orbitals for various scenarios regarding the values for the energy gap between the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO), as well as the coupling strengths. Second, the model is enhanced to address realistic systems. Passivation of ZnS surface with oleic acid (OA) is modeled using density functional theory based tight binding (DFTB) simulations. Extracting the Hamiltonian and overlap matrices, excitation dynamics is studied for Zn rich and S rich surfaces and different coverage ratios of surfaces. The excitation dynamics is compared and contrasted against the simplified model. Characteristic features are identified and typical decay rates are calculated for various molecular configurations. In addition to these, X-Ray diffraction spectra of quaternary ZnCdSSe nanoalloys have been investigated.

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