Mehmet KOBYA

Article | 2023 | Journal of Water Process Engineering56

The near-widespread presence of poly- and perfluoroalkyl substances (PFASs) in humans has generated concerns regarding the potential negative impact of these chemicals on human health, as some PFASs are exceedingly persistent and bioaccumulative. Among the perfluorinated PFASs, which exhibit high polarity and strong carbon–fluorine bonds, perfluorooctanesulfonate (PFOS) is one of the frequently encountered species. In this study, the efficiency of electrooxidation (EO) and its application in groundwater simulation were first evaluated as a realistic approach to PFOS removal. After optimizing EO parameters including the solution pH, . . .current density, and the effects of inlet concentration and the anode material, 83 total organic carbon (TOC) removal was obtained. In groundwater experiments, in which the infiltration of PFOS from soil layers into groundwater was simulated, 79 TOC removal efficiency was achieved in the more complex groundwater; moreover, an F− ion concentration of 8.78 mg/L was obtained from the decomposition of PFOS. To increase the realism of the simulation, the leachate process was repeated four times, and the EO process was applied to each sequential leachate. In addition, the process efficiency was studied in real landfill leachate wastewater to which PFOS had been added. Despite the challenging wastewater composition, 84 TOC removal efficiency was achieved. Together, these results indicate that BDD-anodic oxidation may be a practical method to treat PFOS-contaminated groundwater and wastewater. Keyword: electrochemical treatment; groundwater treatment; landfill leachate treatment; PFAS More less

Ali Osman SOLAK

Article | 2013 | Sensors and Actuators B: Chemical188

A highly sensitive method for detection of DNA hybridization was developed. This method was based on the modification of glassy carbon electrode with gold nanoparticles (AuNPs) involving p-aminothiophenol (ATP) functionalized graphene oxide (GO). This GO was used as a platform for impedimetric genosensing using 5′-TA GGG CCA CTT GGA CCT-(CH2)3-SH-3′ single-stranded probe (ss-DNA), 5′-AGG TCC AAG TGG CCC TA-3′ (target DNA), 5′-SH-C6-TAG GGC CA-3′ (non-complementary-1) and 5′-SH-C6-TGC CCG TTA CG 3-′ (non-complementary-2) oligonucleotide sequences. The film exhibited excellent properties for immobilizing DNA probes and sensing DNA hyb . . .ridization. The DNA immobilization and hybridization on the film were studied by cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), and found that the charge transfer resistance (Rct) of the electrode increased with the concentration of the target DNA hybridized with the ss-DNA. The linear detection range was from 1.0 × 10−13 M to 1.0 × 10−7 M and the detection limit was 1.10 × 10−14 M (n = 6). Compared with the other electrochemical DNA biosensors, the proposed biosensor showed its own performance of simplicity, good stability, and high sensitivity. - Keywords: Graphene oxide; Gold nanoparticles; Electrochemical impedance spectroscopy; DNA nanobiosenso More less

Nahit AKTAŞ

Article | 2023 | Materials Chemistry and Physics298

Ovarian cancer is a gynecological disease causing many deaths among women around the world. Carbohydrate antigen 125 (CA-125) is a single biomarker known to be a tumor marker of ovarian cancer. CA-125 is widely used to monitor the treatment process, recurrences, and for the detection of ovarian cancer. Herein, organo-hydrogels were prepared in order to detect CA-125 sensitively in serum medium with electrochemical methods. Organo-hydrogels were obtained by the free radical polymerization reaction using agar and glycerol with varying proportions of sweet almond oil using methylene bisacrylamide (MBA) or glutaraldehyde (GA) crosslinke . . .rs. Electrochemical measurements were performed with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) on organo-hydrogel sweet almond oil (OHSAO) prepared in the presence and absence of CA-125. As a result of these measurements, two distinct linear ranges of 1–50 ng/mL and 100–1000 ng/mL were obtained. In addition, LOD and LOQ values for the sensor were calculated as 0.41 μU/mL and 1.24 μU/mL, respectively. In conclusion, the OHSAO-based electrochemical sensor is a promising electrode for CA-125 detection.Keywords: Organo-hydrogel, Sweet almond, CA-125, Ovarian cancer, Senso More less

Tahir GÖNEN

Article | 2018 | Construction and Building Materials177

Millions of tires are discarded every year. Disposal or recycling-reusing of waste tire rubber has become a big environmental problem in the world. In this study, it was aimed to determine the freezing-thawing, impact resistance, compressive strength and capillary water absorption rate, when the granulated waste rubber parts are used in the non-load-bearing concrete. Granulated crumb rubbers obtained from waste tires were used at two different grain diameters of 1 and 2 mm as the maximum value. A total of 9 different series were prepared, one of them being the control group and the others being changed with the aggregate in the rati . . .os of 0.5%, 1%, 2% and 4%. In all of the blends, the water/cement ratio was kept constant at 0.50. A drop-weight type impact test was applied to the specimens produced with and without waste rubbers. The impact energy required for the first crack and final dent was determined with the free-falling steel ball at a certain height. Freezing thawing experiments were carried out on the samples with 3% NaCl solution ponded on the surface, and weight losses were determined. As the result, significant improvements were observed in the freezing-thawing and impact resistances of waste tire added samples. Weight loss of specimens because of the freezing-thawing was decreased about 90% and impact resistance was increased different rate depending using rate. (C) 2018 Elsevier Ltd. All rights reserve More less

İbrahim Halil SUGÖZÜ

Article | 2023 | Borsa Istanbul Review23 ( 1 )

This study investigates the linkage between portfolio investment and economic growth in 18 developed and 27 developing countries. Furthermore, it compares and analyzes interest-bearing and non-interest-bearing assets and the economic development level. The results of our analysis show that long-term portfolio investment is positively associated with economic growth in developing countries. Long-term portfolio investment through non-interest-bearing assets contribute more to economic growth in developing countries. However, stocks and long-term bond portfolio investment are unrelated to economic growth in developed countries. Moreove . . .r, capital accumulation positively affects growth in developing and developed countries, but trade openness decreases growth in developing countries. Our policy recommendation is for the relation between long-term portfolio investment and economic growth to be evaluated by the characteristics of their assets, instead of a general framework, and for decision makers to adapt their policies accordingly. In addition, non-interest-bearing portfolio investment is encouraged for better growth performance in developing countries.Keywords: Capital inflows. Economic growth. Portfolio investmen More less

Mehmet KOBYA

Article | 2021 | Chemosphere286 ( 2 )

Herein, ZnCr layered double hydroxide (ZnCr LDH), and its nanocomposites with GO and rGO were synthesized using the co-precipitation method. The samples were characterized using XRD, FT-IR, SEM, TEM, BET, and XPS techniques. The sonophotocatalytic activity of the ZnCr LDH, ZnCr LDH/GO, and ZnCr LDH/rGO was investigated via the degradation of rifampicin (RIF) in the ultrasonic bath under visible light irradiation. The synergy index of more than 1 determined for ZnCr LDH/rGO indicated the positive interaction of sonocatalysis and photocatalysis resulted by hybridizing the LDH nanosheets with rGO. The maximum sonophotocatalytic degrada . . .tion efficiency of 87.3?as achieved in the presence of ZnCr LDH/rGO nanocomposite with the concentration of 1.5 g L-1 for degradation of RIF with an initial concentration of 15 mg L-1 within 60 min sonication under visible light irradiation. The addition of different scavengers indicated that hydroxyl radicals, superoxide anion radicals, and the generated holes played a dominant role in the degradation of the pollutant molecules. A possible degradation mechanism was suggested based on the intermediates. The antibacterial tests confirmed the higher antibacterial activity of ZnCr LDH/GO compared with ZnCr LDH and ZnCr LDH/rGO against Grampositive Staphylococcus aureus More less

Asılbek ÇEKEEV

Proceedings Paper | 2019 | Topology and its Applications252

The various types of ultrafilter-completeness on zero-sets of uniformly continuous functions are introduced, their properties are studied and characterizations in the category are given.

Ebru DURAL

Article | 2024 | Heliyon10 ( 3 )

The delamination phenomena of laminated glass structures are issues that are not perfectly understood and remain problematic to predict due to the nonlinearity of the geometric response. A research study is undertaken to investigate the behavior of laminated glass curved beams with initial delamination exposed to different boundary conditions. A mathematical model which contains nonlinear field equations and boundary conditions is developed. An iterative procedure for the solution of field equations is implemented. In addition, experiments are conducted and finite element model is developed to determine the effectiveness of model. T . . .he results are in good agreement. These results contribute to a better understanding of the complex response phenomena exhibited by curved laminated glass beams subjected to initial delaminations. Research findings allow a better insight in the behavior of the delamination in laminated glass, including the deflections and stresses. Based on the developed model it is possible to determine the effects of position and size of delaminations on the behavior of laminated glass curved beams under different boundary conditions. Keywords: curved beam; delamination; laminated glass; nonlinear behavio More less

Kubatbek TABALDİYEV

Article | 2009 | Russian Geology and Geophysics50 ( 1 )

We report a macroseismic study of a ruined medieval building, a small caravanserai located along the caravan way from the Talas valley to the Chatkal and Fergana valleys in Kyrgyzstan. The ruins document several events in which the caravanserai was destroyed, apparently during earthquakes, and was rebuilt or repaired. The earliest earthquake occurred soon after the building was put up, about 400 years ago, according to radiocarbon dating of charcoal, and another event shook the area between 400 and 50 years BP. After being damaged in the ultimate earthquake, in the middle of the 20th century, the building was eventually abandoned. - . . . Keywords: Archeoseismology; earthquake-induced damage to buildings; damage patterns; Talas valley; Kyrgyzsta More less

Nahit AKTAŞ

Article | 2019 | Applied Surface Science471 ( 31 )

Herein, it is reported an effective method to prepare novel molecularly imprinted polymers (MIP) on poly(dimethylsiloxane) (PDMS) elastomer via a combination of non-covalent imprinting approach and surface initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization for sensitive and selective detection of folic acid (FA). For this purpose, 2-(2-Methoxyethoxy) ethyl methacrylate (MEOMA), ethylene glycol dimethacrylate (EGDMA), azobisisobutyronitrile (AIBN), FA and dimethylsulfoxide (DMSO) were used as functional monomer, cross-linker, initiator, template molecule, and porogen, respectively. The adsorption beha . . .vior followed the Scatchard equation between FA and PDMS-MIP with a saturation adsorption capacity of 4.51 mg/g and pseudo-second-order kinetics with 60 min equilibrium adsorption time. Furthermore, PDMS-MIP elastomer was successfully applied for selective extraction and detection of FA from orange juice with sufficient recovery (95.5–100.5?and relative standard deviation less than 7.0?The limit of detection (LOD) for FA was found to be 0.0031 µg/mL with a linear range between 0.01 and 100 µg/mL and a correlation coefficient of 0.9997. Results showed the proposed method could easily, efficiently and selectively extracted FA from complex media. Note that this novel proposed method will open a new way to detect any selected molecules such as pesticide, protein, drug, etc. using molecularly imprinted PDMS elastomer materials More less

Asılbek ÇEKEEV

Article | 2020 | Topology and its Applications281 ( Special Issue )

For a Tychonoff space X, the Dieudonne tau-completion of X, denoted by mu TX, is investigated. The space mu TX is defined as the completion of X with respect to the uniformity uTX, where uTX is generated by all continuous mappings of X to metric spaces of weight

Mehmet KOBYA

Article | 2021 | Process Safety and Environmental Protection152

Phosphates are a major cause of eutrophication and growth of algal blooms in surface waters. The current study investigated phosphorus removal from sludge centrate effluent (SCE) of a municipal wastewater plant by packed-bed electrocoagulation (EC) reactor. Distinctively, iron (Fe), aluminum (Al) and Al-Fe hybrid scrap anodes were used. The influence of initial pHi, applied current and packed anode bed density were evaluated. Phosphorous removal efficiency of 99.99 ?as obtained at applied current of 0.20A with anode bed densities of 0.18 kg Al/m3 (pHi 5.0) and 0.48 kg Fe/m3(pHi 7.0). Optimum operating costs entailing sludge disposal . . ., chemical, energy and electrode consumption were calculated as 0.379 US $/m3 (6.04 $/kg PO4-P) for Fe scrap, 0.494 US $/m3 (9.46 $/kg PO4-P) for Al scrap and 0.501 US $/m3 (9.59 $/kg PO4-P) for Al-Fe hybrid scraps. Phosphorus removal per electrochemically generated metal was 191.22 mg P/g Al, 104.88 mg P/g Fe, and 61.08 mg P/g (Al Fe). The molar metal to phosphorus ratio at optimum conditions were calculated as 5.41, 3.97 and 7.65 mol/mole for Al, Fe and Al-Fe, respectively. The key mechanisms for phosphorus removal were metal-phosphorus precipitation and adsorption. Herein, metal scrap anodes have been proved effective for phosphorous removal from SCE. (c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved More less