Yıldız Technical University Research Information System
Not a member yet
91324 research outputs found
Sort by
Mesoporous silica/reduced graphene oxide composite for fluoxetine and trimethoprim adsorption
No full textIn this study, a mesoporous silica/reduced graphene oxide (MS-rGO) composite was synthesised and characterised for the adsorption of two persistent pharmaceutical micropollutants, fluoxetine (FLX) and trimethoprim (TMP), from water. The adsorption performance of the MS-rGO composite was evaluated under various conditions including adsorbent dosage, pH, initial drug concentration, time and temperature. The results showed effective removal of both drugs, with FLX adsorption capacity reaching 13.07 mg/g (corresponding to 74.8 % removal) under conditions of 0.0025 g MS-rGO, pH 8 and 15 min, and TMP adsorption capacity reaching 17.60 mg/g (88.1 % removal) under conditions of 0.0025 g MS-rGO, pH 9 and 30 min, both at an initial concentration of 5 mg/L. Adsorption followed pseudo-second-order kinetics (R2 > 0.9977) and Langmuir isotherm models (R2 > 0.9921) with maximum capacities of 102.04 mg/g for FLX and 52.91 mg/g for TMP. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) confirmed that the adsorption was endothermic and spontaneous, mainly driven by electrostatic interactions between the MS-rGO composite and the drugs. These results highlight the potential of the MS-rGO composite as a promising adsorbent for the removal of pharmaceutical micropollutants from aqueous systems, offering rapid adsorption in a short time; however, its reusability is limited, with removal efficiencies decreasing by almost 50 % after three cycles.</p
A Computationally Efficient Approach to Nonlinear Control and Estimation of a Slider-to-Gimbal Platform
No full textThis paper introduces a novel control and estimation approach for a Slider-to-Gimbal platform, combining discrete-time feedback linearization with an Unscented Kalman Filter achieving real-time state estimation. The proposed framework handles complex nonlinear dynamics, center of gravity fluctuations, and strict constraints of real-time operation. In contrast to continuous-time controllers demanding huge computational power, the discrete-time feedback linearization ensures robust stability. Additionally, the presented work reduces sensor reliance by employing the UKF which decreases sensor interference and estimates velocities and the center of gravity from only position and orientation data. The experiments are performed in MATLAB/Simulink, with tests spanning multiple reference trajectories, sensor arrangements (2-3 sensor utilization), and sampling periods (0.1 to 0.0001). Tracking errors for slider position, pan, and tilt angles reach as low as 0.0286 m, 0.0887 rad, and 0.1925 rad, respectively. Even utilizing only two sensors, errors are lower than 0.0275 m, 0.0894 rad, and 0.1756 rad, proving the method's robustness. Furthermore, the force and torque remain within practical limits to be utilized in real time applications. A minimum sampling interval of 0.0001 s produces the highest accuracy, while 0.01 s interval offers a balanced compromise between performance and computational effort. The results demonstrate that the proposed methodology is the candidate for real time application in appropriate with applicable control and sensor signals
Potential zinc phthalocyanine-based photosensitizer for photodynamic therapy: Photophysical, theoretical and in vitro studies
No full textThe preparation of new photosensitizers and studies on photodynamic therapy (PDT) have provided promising results and realistic expectations for an efficient medical treatment. Phthalocyanines (Pcs) have become extremely attractive for this purpose owing to their molecular versatility and superior physicochemical properties. Motivated by these facts, in this study, non-peripherally substituted zinc(II) Pc (2) was prepared by cyclotetramerization of the phthalonitrile derivative bearing 3-methoxybenzyloxy units. Also, physicochemical and in vitro analyses were completed. In photochemical studies, the obtained singlet oxygen quantum yield (ΦΔ) values were 0.73 in dimethylsulphoxide (DMSO) and 0.55 in dimethylformamide (DMF). Theoretical calculations based on density functional theory (DFT) provide valuable information on the energies and character of the electronic excitations, thus allowing a prediction of their potential applicability to generate singlet oxygen. The PDT activity of the zinc(II) phthalocyanine bearing 3-methoxybenzyloxy substituents was tested via in vitro studies using the human colon cancer cell lines. In cytotoxicity experiments, the most effective incubation time for cell lines was found to be 24 h, and the most effective concentration was 8 μM. Furthermore, the cell viability rate decreased significantly with the increasing power density. The results suggested that the newly synthesized zinc(II) Pc is an effective photosensitizer with potential use for the treatment of colon cancer
Evaluation of Kocaeli Gulf Marine Solid Wastes as Binding Material in Geopolymer Composite Production
No full textHexagonal Boron Nitride Doped PVA Composite Nanofibers for Antimicrobial and Biocompatible Applications
No full textIn this study, boron nitride nanoparticles (BNNPs) doped polyvinyl alcohol (PVA) composite nanofibers were fabricated cost-effectively and straightforwardly using the electrospinning technique. The uniform PVA/BN composite nanofibers were measured as 376.26 ± 59.20 nm, observed through Scanning Electron Microscopy (SEM). The presence of hexagonal boron nitride (h-BNNPs) was confirmed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FT-IR) results indicated enhanced structural stability and the formation of new functional groups. Water absorption tests showed that the hydrophobic nature of BNNP is dominant. The degradation rate of the PVA/BN was found to be faster than PVA nanofibers. Antibacterial tests demonstrated that PVA/BN fibers exhibited inhibition zones against Escherichia coli (8.78 mm), Staphylococcus aureus (6.82 mm), and Candida albicans (21.54 mm). The Minimum Inhibitory Concentration (MIC) results reinforced these findings, with PVA/BN fibers achieving an impressive inhibition rate of 89.56% against E. coli. Utilizing the MTT assay, biocompatibility tests indicated cell viability rates exceeding 98% for PVA/BN fibers, confirming their safety for biomedical applications. This study illustrates that PVA/BN composite nanofibers enhance their antimicrobial and hydrophilic properties, leading to multifunctional materials for advanced tissue engineering. Summary: Electrospun PVA/BN composite nanofibers produced cost-effectively and straightforwardly. SEM images indicated that the average diameter of PVA/BN composite nanofibers was 376.26 ± 59.20 nm. SEM and TEM analyses revealed a uniform dispersion of BNNPs within the composite nanofibers. FT-IR confirmed the presence of strong chemical interactions and the formation of unique functional groups. XRD and TEM analyses validated the structural integrity of h-BN. PVA/BN fibers exhibited inhibition zones against Escherichia coli (8.78 mm), Staphylococcus aureus (6.82 mm), and Candida albicans (21.54 mm). MIC results showed that the BN-doped composite nanofibers achieved an impressive inhibition rate of 89.56% against Escherichia coli. MTT assay (L929 fibroblast) indicated excellent biocompatibility, with over 98% cell viability rates. PVA/BN composite nanofibers show potential for advanced wound dressings and tissue engineering
A Methodology for Identifying Critical Success Factors and Performance Measurement for Sustainable Schools
No full textComprehensive Energy, Exergy, and Environmental Assessment of a Tri-Generation Biomass System Integrating Gasification, Anaerobic Digestion, and Solid Oxide Fuel Cell
No full textGlobal warming presents a significant challenge, largely driven by carbon dioxide emissions from conventional power generation. Renewable energy technologies, particularly biomass-integrated systems, provide a promising pathway to mitigate these emissions sustainably. This study conducts a comprehensive energy, exergy, and environmental assessment of a tri-generation biomass system incorporating gasification, anaerobic digestion, and a Solid Oxide Fuel Cell (SOFC). Two configurations are examined: one utilizing syngas from gasification and the other biogas from anaerobic digestion. The results show that the biogas-based system achieves a superior exergy efficiency of 44.22%, compared to 39.18% for the gasification-based system, while also reducing CO2 emissions by 0.072 tons/MWh. Additionally, optimizing the fuel utilization factor (0.76 for the digester-SOFC and 0.78 for the gasifier-SOFC) significantly enhances system performance. These findings underscore the environmental benefits of biogas in tri-generation systems and provide valuable insights into optimizing biomass-based energy solutions