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    Biyouyumlu Malzemelerin Üretimi için 4D Eklemeli İmalat Cihazı Tasarımı ve Üretimi
    (Kırıkkale Üniversitesi, 2023) Kartal, Yunus; Doğan, Deniz; Daş, Memik Taylan; Metin, Ayşegül Ülkü
    Bu çalışmanın amacı biyouyumlu malzemelerin üretimi için alışılagelmiş kartezyen eksenlerinin haricinde tablada bulunan ve ekseni etrafında dönen dördüncü eksene sahip dört boyutlu (4D) eklemeli imalat cihazı tasarımı ve üretimidir. Bu kapsamda çeşitli mekanik ve elektronik aksesuar veya bileşenlerin teorik ve teknik detayları verilmektedir. Çalışma kapsamındaki dört boyutlu yazıcı üretilen malzemelerin özelliklerinin atmosfer koşullarından etkilenmesini engellemek amacıyla izole bir ortamda çalışmaktadır. Tasarımı ve üretimi gerçekleştirilen cihazda ultraviyole ışın altında poli(2-hidroksietil metakrilat) üretilmiş ve mekanik özellikleri incelenmiştir.
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    Environmental remediation with nanozymes
    (Elsevier, 2024) Horzum, Nesrin; Metin, Ayşegül Ülkü
    Artificial enzymes based on nanomaterials, commonly referred to as nanozymes, have garnered considerable attention for their catalytic signal amplification abilities, making them promising candidates for pollutant detection. Their catalytic performance not only makes them adept at detecting pollutants but also positions them as potent tools for the removal of various contaminants, such as heavy metal ions; organic compounds, including antibiotics, dyes, phenolics, pesticides, and nano?/microplastics; and pathogens. A comprehensive analysis of nanozyme types, utilization in the detection and degradation of environmental pollutants, and mechanism were discussed, focusing on the recent advancements. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.
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    Immobilization studies and biochemical properties of free and immobilized Candida Rugosa lipase onto hydrophobic group carrying polymeric support
    (Polymer Soc Korea, 2013) Metin, Ayşegül Ülkü
    In this study, the hydrophobic group carrying support was prepared for the immobilization of Candida rugosa lipase through the reversible adsorption method. Epoxy groups containing poly(glycidyl methacrylate-methyl methacrylate-ethylene glycol dimethacrylate) (poly(GMA-MMA-EGDMA)) beads were synthesized by suspension polymerization, and the reactive epoxy groups of poly(GMA-MMA-EGDMA) beads were treated with ammonia while glutaraldehyde was used as a coupling agent. After the L-hydrophobic ligand phenylalanine amino acid was covalently attached on the activated polymeric matrix, the lipase enzyme was immobilized. The immobilization efficiency as a function of adsorption parameters was characterized. The maximum lipase immobilization capacity of the poly(GMA-MMA-EGDMA) beads was 68.25 mg/g. The activities of the free and immobilized enzymes were investigated in the hydrolysis reaction of olive oil. The activities of the free and the immobilized lipases were measured at different pH values and temperatures, and their thermal and storage stabilities were also determined. The optimum pH for immobilized lipase was 6.0, which was the same for free enzymes. In this pH value, the retained activity of immobilized lipase was 91.84%. The optimum activity temperatures of free and immobilized lipases were determined as 35 and 45 A degrees C, respectively. The optimum temperature for the lipase immobilized on the hydrophobic group carrying matrix was 10 A degrees C higher and it demonstrated activity in a broader temperature range than that of the free enzyme. The immobilized lipase had better resistance to temperature inactivation than the free form. The free enzyme lost all of its activity during the 28 days storage period, while immobilized lipase lost 34% of its activity during the 56 days storage period.
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    Investigation of the Effect of Ambient Conditions on the Storage Life of Nitrocellulose Based Fuels
    (Kırıkkale Üniversitesi, 2023) Çağlayan, Mehmet; Pul, Muharrem; Metin, Ayşegül Ülkü
    The fuels of the munitions, which are the subject of this study, are exposed to all kinds of climatic conditions (vibration, low and high altitude, high altitude in aircraft, extreme temperature, humidity, etc.). For this reason, it completes the storage life given after production in a shorter time and can explode on its own. For this purpose, rapid aging process was applied at three different temperatures (60?C-70?C-80?C) and 60% humidity conditions in order to simulate the environmental effects that the dual-base fuel is exposed to. Various tests were applied by observing the physical and chemical changes of the fuel whose aging process was completed. As a result of the stabilizer amount determination test, it was observed that the amount of stabilizer decreased below the minimum 0.2% w/w value, and the amount of stabilizer decreased with the effect of rapid aging. It was observed that the moisture content did not exceed the maximum value of 0.6% in the moisture determination test, the calorific value remained between 836-864 cal/g in the calorific value measurement test, and the heat flow amount did not exceed the maximum 114 µw/g in the stability test performed with the heat flow calorimeter (HFC). With the SEM microscope, the structure of the fuels was visualized and the changes in the fuel after natural aging and rapid aging processes were observed. By taking the FTIR spectra, the chemical changes occurring in naturally aged and fast aged fuels were investigated.
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    Novel magnetic gel beads based on ionically crosslinked sodium alginate and polyanetholesulfonic acid: Synthesis and application for adsorption of cationic dyes
    (ELSEVIER SCIENCE SA, 2020) Metin, Ayşegül Ülkü; Doğan, Deniz; Can, Muzaffer
    This study offers novel magnetic gel beads as an adsorbent containing bifunctional groups for cationic dye removal. The bifunctional composite gel beads were prepared from polyanetholesulfonic acid, alginate and magnetic zeolite (m-ALG/PESA), and characterized by FESEM-EDS, XRD, VSM, and TGA-FTIR. The adsorption capability of m-ALG/PESA beads was described using methylene blue (MB) and malachite green (MG). The maximum adsorption capacities of MB and MG onto m-ALG/PESA gel beads were 400 mg/g and 164 mg/g, respectively. Regeneration and reusability studies showed that both dyes were successfully desorbed from mALG/PESA gel beads with removal percentages approximately 90 in the first cycle and magnetic gel beads maintained their shapes after 10 times adsorption/desorption cycles in highly acidic conditions. It was also observed that MG was degraded during the desorption process. Therefore, the magnetic gel beads can be considered as a regenerable adsorbent making to the adsorption process is cost-effective and it is also biodegradable and environment-friendly material when used in pilot-scale applications.
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    Polyaniline grafted polyacylonitrile conductive composite fibers for reversible immobilization of enzymes: Stability and catalytic properties of invertase
    (Elsevier Sci Ltd, 2009) Bayramoğlu, Gülay; Karakışla, Meral; Altıntaş, Begüm; Metin, Ayşegül Ülkü; Saçak, Mehmet; Arıca, M. Yakup
    Polyacylonitrile fibers (PAN) surfaces were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN/PANI composite fibers was investigated. The surface resistance of the conductive composite fibers in this work was found to be between 8.0 and 0.5 k Omega/cm. As the amount of grafted PANI increased on the PAN fibers the electrical resistance of composite fibers decreased. The PAN/PANI composite fibers were characterized by SEM and FTIR studies. Composite PAN/PANI fibers were used for reversible immobilization of invertase. The immobilization efficiency and the activity of the immobilized invertase (from 1.0 mg/mL invertase solution at pH 5.5) were increased with increasing PANI contents of the composite fibers. The maximum amount of immobilized enzyme onto composite fibers containing 2.0% PANI was about 76.6 mg/g. The optimum pH for the free enzyme was observed at 5.0. On the other hand, immobilized invertase yielded a broad optimum PH profile between pH 5.0 and 7.0. Immobilized invertase exhibited 83% of its original activity even after two months storage at 4 degrees C while the free enzyme showed only 7% of its initial activity. (C) 2009 Elsevier Ltd. All rights reserved.
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    Reversible immobilization of glucose oxidase on polyaniline grafted polyacrylonitrile conductive composite membrane
    (Elsevier Sci Ltd, 2010) Bayramoğlu, Gülay; Metin, Ayşegül Ülkü; Altıntaş, Begüm; Arica, M. Yakup
    Polyacrylonitrile membrane surfaces were modified with chemical polymerization of conductive polyaniline. The effect of aniline concentration on the grafting efficiency was investigated As the amount of grafted PANI increased on the PAN membrane, the electrical resistance of composite membrane decreased Composite (PAN/PANI)-1-5 membrane were used for reversible immobilization of GOD. The immobilization efficiency and the activity of the immobilized GOD were increased with increasing PANI contents of the composite membrane. The maximum amount of immobilized enzyme into composite PAN/PANI-5 membrane containing 2.1% PANI was about 251 mu g/cm(2) Immobilized GOD exhibited 66% of its original activity even after two months of storage at 4 degrees C while the free enzyme lost its initial activity after three weeks (C) 2010 Elsevier Ltd. All rights reserved
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    Surface modification of polyacrylonitrile film by anchoring conductive polyaniline and determination of uricase adsorption capacity and activity
    (Elsevier, 2010) Bayramoğlu, Gülay; Metin, Ayşegül Ülkü; Arıca, M. Yakup
    Polyacrylonitrile (PAN) films were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN and (PAN/PANI)-1-3 composite film was investigated. The surface resistances of the conductive composite films were found to be between 6.32 and 0.97 k Omega/cm. As the amount of grafted PANI increased on the PAN films, the electrical resistance of composite film decreased. The PAN/PANI composite films were also characterized using SEM and FTIR. The changes in the surface properties of the films were characterized by contact angle measurements. As expected, the PAN, PAN/PANI and PAN/PANI-uricase immobilized films, exhibited different contact angle values and surface free energy due to different interactive functional groups of the films. The conductive films were well characterized and used for immobilization of uricase. The amount of adsorbed enzyme increases with the increase of surface concentration of grafted fibrous polyaniline polymer. The maximum amount of immobilized enzyme onto composite film containing 2.4% PANI was about 216 mu g/cm(2) (i.e., PAN/PANI-3). The immobilized uricase was reused 24 times in batch wise assay in a day. Finally, the immobilized uricase enzyme system was successfully fabricated and applied to determine the uric acid level in human serum samples. (C) 2010 Elsevier B.V. All rights reserved.
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    Yeni akrilat kökenli afinite kürelerin tasarlanması: Protein adsorpsiyonu ve saflaştırılmasında kullanılması
    (Kırıkkale Üniversitesi, 2008) Metin, Ayşegül Ülkü; Bayramoğlu, Gülay; Arıca, M. Yakup
    Bu tez çalışmasının ilk bölümünde, afinite kromatografisi uygulamalarında dolgu maddesi olarak kullanılabilecek farklı özelliklere sahip, monodispers p(glisidil metakrilat-etilenglikoldimetakrilat), p(GMA-EGDMA), partikülleri dispersiyon polimerizasyon tekniği ile hazırlandı. Farklı özellikteki ligandların IgG'ye karşı afinitesini belirlemek üzere glutarikdialdehit kullanılarak modifiye edilen p(GMA-EGDMA) partiküllerine L-histidin amino asidi (L-his), Kongo Kırmızısı (CR) boya ligandı ve Cu(II) iyonlarının şelatlanması amacı ile üç dişli iminodiasetik asit (IDA) ligandı yüzeye kovalent olarak bağlandı ve modifiye partiküllerin sulu çözeltiden IgG adsorpsiyonu araştırıldı. Hazırlanan üç farklı özellikteki monodispers afinite partiküllerin karakterizasyon çalışmaları (spesifik yüzey alanı, yoğunluğu, şişme oranı, mikroskop görüntüsü, FT-IR spektrumu, DSC ve TGA analizi ve yüzey aktif grupların tayini) tamamlanarak sulu çözeltilerden IgG proteininin adsorpsiyon davranışı araştırıldı. Adsorpsiyon koşullarının (pH, adsorpsiyon denge süresi, iyonik şiddet, sıcaklık, başlangıç protein derişimi gibi) monodispers partiküllerin IgG adsorpsiyon performansına etkileri incelendi. Bununla birlikte, adsorpsiyon kinetiği ve izoterm modeli ile monodispers afinite partiküllerin yeniden kullanılabilirliği gibi parametreler de belirlendi. Monodispers p(GMA-EGDMA)-L-his, p(GMA-EGDMA)-CR ve p(GMA-EGDMA)-İDA-Cu(II) partikülleri için maksimum adsorpsiyon kapasitesi sırası ile pH 7.0, 6.0 ve 7.5'de gözlendi. En yüksek adsorpsiyon kapasitesi, p(GMA-EGDMA)-İDA-Cu(II) partiküllerinin kullanıldığı sistemde 32.87 mg/g olarak belirlendi. Afinite partiküllerin adsorpsiyon kapasitesinde önemli bir azalma olmadan adsorpsiyon-desorpsiyon işlem döngülerinde yeniden kullanılabilirliği belirlendi.Tez çalışmasının ikinci bölümünde, biyolojik molekül ile etkileşimini incelemek üzere yeni manyetik özellik kazandırılmış akrilat kökenli afinite polimerik partikülleri hazırlandı. Bu doğrultuda, afinite kürelere farklı bir monomerin kopolimerizasyonu ve/veya monomerin yüzeyde aşılanması ve manyetik özellik kazandırılması gibi işlemlerle farklı özellikler kazandırılarak adsorpsiyon tekniği ile tripsin enzimi immobilizasyonu çalışmaları gerçekleştirildi. Manyetik p(glisidilmetakrilat-metilmetakrilat), mp(GMA-MMA), polimerik destek materyali süspansiyon polimerizasyon tekniği ile hazırlandı. p(GMA-MMA) mikrokürelerinin epoksi grupları, magnetizasyon reaksiyonu sırasında amin gruplarına dönüştürüldü. p(GMA-MMA) mikrokürelerinin yüzeyine metakrilik asit (MAA) monomeri aşı kopolimerizasyon reaksiyonu ile aşılandı ve manyetik p(glisidilmetakrilat-metilmetakrilat)-g-(metakrilik asit), mp(GMA-MMA)-g-MAA, mikroküreleri elde edildi. Yüzeyine metakrilik asit aşılanmış manyetik kürelere tripsin enzimi adsorpsiyon yoluyla immobilize edildi. Manyetik kürelere tripsin adsorpsiyonuna sistem parametrelerinin (başlangıç tripsin konsantrasyonu, ortam pH ve sıcaklığı) etkisi ve immobilize enzimin aktivitesindeki değişim belirlendi.Maksimum adsorpsiyon pH 7.0'de elde edildi. Maksimum immobilizasyon kapasitesinin 2.0 mg/ml enzim konsantrasyonunda 123.2 mg/g olduğu ve başlangıç aktivitesinin yaklaşık %84.2'sini koruduğu belirlendi. İmmobilize tripsinin desorpsiyonu, 1.0 M NaCl çözeltisi içeren 1.0 M formik asit çözeltisiyle gerçekleştirildi. Sonuçlar, manyetik p(GMA-MMA)-g-MAA küreleri üzerine adsorplanan tripsinin aktivitesinde kayıp olmaksızın tekrar tekrar kullanılabileceğini gösterdi. Belirlenen optimum adsorpsiyon koşullarında manyetik p(GMA-MMA)-g-MAA mikrokürelerine immobilize edilen tripsin enziminin sitokrom c ve insan serum albümini (HSA) proteinlerini parçalama etkisi HPLC yardımıyla belirlendi.