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Erdem, Sezer,Erdem, Beyhan,Oksuzoglu, Ramis Mustafa,Citak, Alime Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.5
Bifunctional Fe-SBA-15-$SO_3H$ mesoporous materials with different Si/Fe molar ratios (3, 5, and 7) have been synthesized via a simple direct hydrothermal method and characterized by XRD, $N_2$-adsorption/desorption, TG/DTG and FT-IR techniques, and used as solid acid catalysts in the esterification of lactic acid with methanol. XRD and $N_2$ sorption characterizations show successful iron doping within the mesoporous channels of SBA-15-$SO_3H$. The FT-IR and TG/DTG characterizations also reveal the presence of iron. With the incorporation of Fe ions into the SBA-15-$SO_3H$, the acid sites substantially increased because of the self-separated acidity of the hydrolysis of $Fe^{3+}$ solutions. However, in the Si/Fe = 3 molar ratio, the catalytic conversion decreased which is caused by the reduced cooperation effect between the acid pairs due to the weakened hydrogen bonds and collapse of the pore structure. This further suggests that the mesoporous structure decreases with the decrease in Si/Fe ratio.
Sezer Erdem,Beyhan Erdem,Ramis Mustafa Öksüzo lu,Alime Ç tak 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.5
Bifunctional Fe-SBA-15-SO3H mesoporous materials with different Si/Fe molar ratios (3, 5, and 7) have been synthesized via a simple direct hydrothermal method and characterized by XRD, N2-adsorption/desorption, TG/DTG and FT-IR techniques, and used as solid acid catalysts in the esterification of lactic acid with methanol. XRD and N2 sorption characterizations show successful iron doping within the mesoporous channels of SBA-15-SO3H. The FT-IR and TG/DTG characterizations also reveal the presence of iron. With the incorporation of Fe ions into the SBA-15-SO3H, the acid sites substantially increased because of the selfseparated acidity of the hydrolysis of Fe3+ solutions. However, in the Si/Fe = 3 molar ratio, the catalytic conversion decreased which is caused by the reduced cooperation effect between the acid pairs due to the weakened hydrogen bonds and collapse of the pore structure. This further suggests that the mesoporous structure decreases with the decrease in Si/Fe ratio.
Sezer Erdem,Naim Derebasi 한국자기학회 2010 Journal of Magnetics Vol.15 No.4
The design of joints in a transformer core significantly affects the transformer’s efficiency. Air gaps cause variations in the flux distribution at the joints of the laminations, which depend on the geometry. Two similar samples consisting of electrical steel strips and amorphous ribbons were made. The spatial flux distributions were determined using an array of search coils for each sample. 2D models of these samples were created and examined by finite element analysis. The magnetic flux distribution for each lamination in the samples was computed. The results show that the flux density in amorphous ribbons above and below the air gap starts to approach saturation at lower flux density levels than for electrical steel. The flux density measured using the search coil under the air gap is increased in amorphous ribbons and decreased in the electrical steel with increasing frequency.
Beyhan Erdem,Sezer Erdem,Nalan Tekin 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.7
Fe3O4-SiO2-NH2, Fe3O4-CTABSiO2-NH2 and Fe3O4-SiO2-CTABSiO2-NH2 magnetic adsorbents were successfully prepared and could be used effectively for the adsorption of Light Green from aqueous solutions. Unlike the first sample, mesoporous silica coatings were created using cetyltrimethylammoniumbromide micelles as molecular templates on superparamagnetic iron oxide in one sample, and on silica-coated iron oxide in the other sample to improve the adsorptive properties of the nanocomposites. The characterization by FT-IR, SEM/EDX, Zeta-potential, XRD, VSM, and N2-adsorption/desorption confirmed the production of mesoporous silica layer. Although coating processes with both silica and mesoporous silica layers led to a vaguely decrease in saturation magnetization of the Fe3O4- SiO2-CTABSiO2-NH2, the nanoparticles were protected with silica coatings for environment conditions and made more suitable for subsequent amino functionalization. The results determined from Batch adsorption experiments fitted to Langmuir isotherm model with maximum adsorption capacity (qmax) equal to 56.18, 196.08 and 227.27mg g1, for Fe3O4-SiO2-NH2, Fe3O4-CTABSiO2-NH2 and Fe3O4-SiO2-CTABSiO2-NH2, respectively, and it was seen from the kinetic results, the LG adsorption was identified by pseudo-second-order kinetics, revealing that LG adsorption process is homogeneous, monolayer and based on chemical interactions. According to the results, both silica and mesoporous silica coating strategy can play crucial role in improving the adsorptive properties of nanocomposites.
Fatma Sezer Şenol,Ilkay Erdogan Orhan,Sinem Aslan Erdem,Murat Kartal,Bilge Şener,Yu¨ksel Kan,Ferhat Celep,Ahmet Kahraman,Musa Dogan 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.11
In European folk medicine, Salvia species have traditionally been used to enhance memory. In our previous study of 55 Salvia taxa, we explored significant anticholinesterase activity of cultivated S. fruticosa. In this study, we compared the inhibitory activity of dichloromethane, ethyl acetate, and ethanol extracts of 3 wild-grown samples and 1 cultivated sample of S. fruticosa against acetylcholinesterase and butyrylcholinesterase enzymes (which are associated with pathogenesis of Alzheimer's disease) by using the spectrophotometric Ellman method. Antioxidant activities were assessed by determining 2,2-diphenyl-1-picrylhydrazyl radical–scavenging activity, iron-chelating capacity, and ferric-reducing antioxidant power. The dichloromethane extract of the cultivated sample was then subjected to fractionation by using open column chromatography and medium-pressure liquid chromatography to obtain the most active fraction by activity-guided fractionation. All fractions and subfractions were tested in the same manner, and inactive subfractions were discarded. The essential oil of the cultivated sample was analyzed by gas chromatography–mass spectrometry.
Domain of Euler-totient matrix operator in the space $\mathcal{L}_{p}$
Serkan Demiriz,Sezer Erdem 강원경기수학회 2020 한국수학논문집 Vol.28 No.2
The most apparent aspect of the present study is to introduce a new sequence space $\Phi^\star(\mathcal{L}_{p})$ derived by double Euler-Totient matrix operator. We examine its topological and algebraic properties and give an inclusion relation. In addition to those, the $\alpha-$, $\beta(bp)-$ and $\gamma-$duals of the space $\Phi^\star(\mathcal{L}_{p})$ are determined and finally, some 4-dimensional matrix mapping classes related to this space are characterized.