16 results on '"Aktürk, Merve"'
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2. Comprehensive Analysis of Lutein and Loroxanthin in Scenedesmus obliquus : From Quantification to Isolation.
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Erdoğan, Ayşegül, Karataş, Ayça Büşra, Demir, Dilan, Demirel, Zeliha, Aktürk, Merve, Çopur, Öykü, Çağır, Ali, and Conk-Dalay, Meltem
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LUTEIN ,SCENEDESMUS obliquus ,LIQUID chromatography-mass spectrometry ,CAROTENOIDS ,ISOPENTENOIDS - Abstract
Carotenoids are hydrophobic pigments produced exclusively by plants, fungi, and specific microbes. Microalgae are well suited for the production of valuable carotenoids due to their rapid growth, efficient isoprenoid production pathway, and ability to store these compounds within their cells. The possible markets for bio-products range from feed additives in aquaculture and agriculture to pharmaceutical uses. The production of carotenoids in microalgae is affected by several environmental conditions, which can be utilized to enhance productivity. The current study focused on optimizing the extraction parameters (time, temperature, and extraction number) to maximize the yield of carotenoids. Additionally, the impact of various nitrogen sources (ammonia, nitrate, nitrite, and urea) on the production of lutein and loroxanthin in Scenedesmus obliquus was examined. To isolate the carotenoids, 0.20 g of biomass was added to 0.20 g of CaCO
3 and 10.0 mL of ethanol solution containing 0.01% (w/v) pyrogallol. Subsequently, the extraction was performed using an ultrasonic bath for a duration of 10 min at a temperature of 30 °C. This was followed by a four-hour saponification process using a 10% methanolic KOH solution. The concentration of lutein and loroxanthin was measured using HPLC–DAD at 446 nm, with a flow rate of 1.0 mL/min using a Waters YMC C30 Carotenoid column (4.6 × 250 mm, 5 μm). The confirmation of carotenoids after their isolation using preparative chromatography was achieved using liquid chromatography–tandem mass spectrometry (LC–MS/MS) with an atmospheric pressure chemical ionization (APCI) probe and UV–vis spectroscopy. In summary, S. obliquus shows significant promise for the large-scale extraction of lutein and loroxanthin. The findings of this study provide strong support for the application of this technology to other species. [ABSTRACT FROM AUTHOR]- Published
- 2024
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3. Preparation and characterization of conductive blends of polyaniline with polyphenol red
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ERDOĞAN, Ayşegül, primary, AKTÜRK, Merve, additional, and DURSUN, Zekeriya, additional
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- 2023
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4. Fabrication of Co3O4 particles‐modified multi‐walled carbon nanotube and poly(phenosafranine) composite electrode for selective and sensitive rutin detection
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Aktürk, Merve, primary and Dursun, Zekerya, additional
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- 2023
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5. Manipulation in Culture Conditions of Nanofrustulum shiloi for Enhanced Fucoxanthin Production and Isolation by Preparative Chromatography
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Erdoğan, Ayşegül, primary, Karataş, Ayça Büşra, additional, Demir, Dilan, additional, Demirel, Zeliha, additional, Aktürk, Merve, additional, Çopur, Öykü, additional, and Conk-Dalay, Meltem, additional
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- 2023
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6. Fabrication of Co3O4 particles‐modified multi‐walled carbon nanotube and poly(phenosafranine) composite electrode for selective and sensitive rutin detection.
- Author
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Aktürk, Merve and Dursun, Zekerya
- Subjects
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CARBON nanotubes , *RUTIN , *X-ray photoelectron spectroscopy , *ELECTRODES , *SCANNING electron microscopy , *IMPEDANCE spectroscopy - Abstract
The preparation and characterisation of a new composite electrode with Co3O4 particles‐modified multi‐walled carbon nanotube (MWCNT) and poly(phenosafranine), as well as its novel application for the voltammetric detection of rutin was described. The resulting composite electrode was characterised using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). In the optimised experimental conditions, the oxidation peak current (Ipa) of rutin showed a linear increase in concentration, between 0.008–0.6 and 0.80–6.0 μmol L−1, with a detection limit of 0.00379 μmol L−1. Due to its good selectivity and stability, the composite electrode was successfully applied in detecting rutin in pharmaceutical formulations. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Synergistic effects of b4c and zno nanomaterials as electrodes for supercapacitors
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Aktürk, Merve
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TA401-492 Materials of engineering and construction. Mechanics of materials - Abstract
Boron carbide (B4C) is one of the world’s hardest bulk materials with excellent stability in extreme chemical and thermal conditions. Despite its discovery in the 19th century and numerous studies since 1930s, its atomic structure, electronic properties and electrochemical behavior are yet one of the most debated topics among chemists, physicists and materials scientists. The difficulty in distinguishing the absolute accurate atomic positions with common characterization techniques is mainly due to the very close similarity of the scattering cross-sections of 11B and 12C, and the point defects formed within the crystal which affects the atomic arrangements and the charge densities in the elementary cells. Similarly, significant efforts have been devoted to reveal the unique electronic, optical, structural and magnetic properties of zinc oxide (ZnO) which is an n-type semiconductor and has been used in various applications including energy storage devices, particularly supercapacitors (SCs). The development of efficient and long-life electrodes from sustainable materials for SCs is of the utmost importance to satisfy the increasing energy demands. In this Ph.D. dissertation, B4C and ZnO were selected as electrodes for SCs due to their interesting defective properties that contribute to the enhanced capacitive performances by modifying their electronic and atomic structure. First, modified sol-gel synthesis of B4C nanostructures from aqueous solutions of B and C sources was described. The pure B4C phase was obtained by the heat treatment at temperatures ≤1500 ℃ which is lower than the conventional sintering temperatures (≥ 2000 ℃). Then, extensive thermal and microstructural characterizations were carried out to reveal the crystal structure, lattice parameters, mean particle size, and the microstructure of the synthesized B4C powders. Complementary X- and Q-band EPR analyses of defect centers in B4C and ZnO were performed to reveal the effects of intrinsic defects on the electrochemical performance of the SCs. The synthesized B4C and ZnO were v assembled in a custom-made all-in-one supercapacitor device, and their synergistic effects on the electrochemical performance was investigated by CV, EIS, and GCPL techniques.
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- 2022
8. Links between airborne microbiome, meteorology, and chemical composition in northwestern Turkey
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Lang-Yona, Naama, primary, Öztürk, Fatma, additional, Gat, Daniella, additional, Aktürk, Merve, additional, Dikmen, Emre, additional, Zarmpas, Pavlos, additional, Tsagkaraki, Maria, additional, Mihalopoulos, Nikolaos, additional, Birgül, Aşkın, additional, Kurt-Karakuş, Perihan Binnur, additional, and Rudich, Yinon, additional
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- 2020
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9. Chemical Mapping of Graphene-Based Material with X-ray Photoelectron Spectroscopy (XPS) Using Principal Component Analysis (PCA)
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ERDOĞAN, Ayşegül, AKTÜRK, Merve, DURSUN, Zekerya, and Ege Üniversitesi
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Engineering ,Kimyasal haritalama,X-Işını Fotoelektron Spketroskopisi,temel bileşenler analizi,grafen ,Computer Science::Computer Vision and Pattern Recognition ,Mühendislik ,[No Keywords] ,Chemical mapping,X-ray photoelectron spectroscopy,principal component analysis,graphene - Abstract
Öz XPS, malzemelerin yüzey kimyasının karakterize edilmesinde yaygın olarak kullanılmaktadır. Kalitatif, yarı kantitatif/kantitatif bilgilerin yanı sıra herhangi bir malzemenin yüzeyindeki kimyasal fonksiyonel gruplar ve türleme hakkındaki bilgilere ulaşmada önemli bir rol oynamaktadır. PCA, belirli bir veri setindeki değişkenliğin analizidir. Örnekler ve değişkenler arasındaki ilişkileri anlamak için en güçlü grafik araçlarını sağlamaktadır. İlk ana bileşen, verilerdeki değişkenliğin mümkün olduğunca çoğunu oluşturur ve en büyük özdeğere sahiptir. En önemli bilgileri elde etmek amacıyla, XPS tarafından elde edilen büyük görüntü veri setlerini pca kullanarak analiz edilebilmektedir. XPS verilerinden elde edilen bir alan taramasında PCA' nın amacı, birbiri ile ilişkili ya da ilişkili olmayan görüntüleri bulmak ve bu ilişkilerden sorumlu olan pikselleri görselleştirmektir/tanımlamaktır. Görüntüler, bir görüntü-spektrum deneyinde bağlanma enerjisinin bir fonksiyonu olarak elde edilir. Küçük alan spektrumları, tek bir piksel veya bir piksel grubu ile bağlanma enerjisine karşı görüntü piksel yoğunluğunu çizerek numunenin herhangi bir kısmından elde edilebilir. Bu çalışmada, grafen bazlı malzeme, Brodie yöntemi ile grafitin oksidasyonu yoluyla sentezlenmiştir. Daha sonra, spektral bilgiye dayalı olarak PCA ile kimyasal haritalama oluşturulmuştur. Bu amaçla, XPS alan taraması gerçekleştirilmiş ve sentezlenen grafen bazlı malzeme yüzeyindeki homojensizlikleri göstermek için veri setlerine PCA uygulanmıştır., XPS has been extensivelyused to characterize the surface chemistry of materials. It plays a unique rolein giving access to qualitative, semi-quantitative/quantitative information aswell as speciation and the presence of chemical functional groups on thesurface of any material. PCA is the analysis of variability in a particular setof data. The first principal component accounts for as much of the variabilityin the data as possible and has the largest eigenvalue. Large image data setsobtained by XPS can be analyzed using PCA in order to extract the mostsignificant information. The goal of PCA in an area scan of XPS is to findimages which are correlated or anti-correlated. Images are acquired as afunction of binding energy in an images-to-spectra experiment. Small areaspectra can be obtained from any part of the sample by plotting image pixelintensity for a single pixel or a group of pixels versus binding energy. In thepresent study, the graphene-based material was synthesized via oxidation ofgraphite by Brodie Method. Then, chemical mapping has been produced with PCA onthe basis of spectral information. For this purpose, XPS area scan has beenperformed and then the data sets were subjected to PCA in order to present thecompositional inhomogeneities on the surface of synthesized graphene-basedmaterial.
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- 2019
10. Development of hybrid organic-inorganic surface imprinted Mn-doped ZnS QDs as a phosphorescent sensor for the recognition and detection of tobramycin
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Aktürk, Merve, YILMAZ, HÜMA, Akbaba, Tuğba, ERTAŞ, NUSRET, and BASAN, HASAN
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- 2017
11. TAM GÜN VARDİYALI VE ÖZEL İZİN İSTEKLİ HEMŞİRE ÇİZELGELEME PROBLEMİNİN HEDEF PROGRAMLAMA İLE ÇÖZÜMÜ
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EREN, Tamer, VARLI, Emre, and AKTÜRK, Merve Sıla
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Social ,Hemşire Çizelgeleme,Vardiya Çizelgeleme,Hedef Programlama ,Sosyal - Abstract
Günümüzde hastanelerin her biri tüm gün hizmet vermektedir. Bu sebeple hastanede çalışan hemşirelerin psikolojik ve fiziksel açıdan iyi olması ile verdiği hizmetin de kaliteli olması arasında bir ilişki vardır. Verilen hizmetin en iyi şekilde yerine getirilmesi için hemşirelerin çalıştıkları vardiyalar dengeli ve adaletli olması gerekmektedir. Bu çalışmada da Kırıkkale’de bir devlet hastanesinde çalışan hemşirelerin belirlenmiş olan dört vardiyaya mümkün olduğu kadar eşit bir şekilde atanmaları için bir model geliştirilmiştir. Modelin çözümünde hedef programlama yönteminden ve ILOG Cplex Optimizasyon programından yararlanılmıştır.
- Published
- 2017
12. HEMŞİRE ÇİZELGELEME İÇİN MODEL ÖNERİSİ: ÖRNEK UYGULAMA
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Eren, Tamer, Şahiner, Miyase, Aktürk, Merve Sıla, Bedir, Neset, and Ünlüsoy, Sultan
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Hemşire Çizelgeleme,0-1 Hedef programlama ,Hemşire Çizelgeleme ,0-1 Hedef programlama - Abstract
DergiPark: 286825 trakyaiibf Günümüzde sağlık hizmetleri, toplumu doğrudanetkileyen en önemli konulardan biri haline gelmiştir. Sağlık sektörünün büyükbir kısmını hastaneler oluşturmaktadır. Hastalar birçok hastane arasındantedavi görecekleri hastaneyi seçerken o hastanenin sağlık hizmeti kalitesi bukararı etkilemektedir. Sağlık hizmetiveren hastaneler vardiya sistemi ile çalışmaktadır. Vardiya sistemi ileçalışmanın en büyük sorunu çalışma saatlerinin devamlı değişmesi ve dengesiz işyükleridir, bu değişimler çalışanları olumsuz etkilemektedir. Çalışanların-bilhassa hemşirelerin- yorgunluğu ve dikkatsizliği hastalar için hayati risktaşımaktadır. Hastanelerde hemşire çizelgeleme işlemi ilgili bölümün sorumluhemşiresi tarafından manuel olarak yapılmaktadır, bu işlem yaklaşık 10 saatsürmektedir ve çoğu zaman iş yüklerinde dengesizlikler söz konusudur. Buçalışmada hemşire çizelgeleme problemi ele alınmıştır. Hemşire çizelgelemeproblemini çözmek için 0-1 Hedef Programlama yöntemi ile bir modelgeliştirilmiştir. Kurulan model Kırıkkale'de bir devlet hastanesindeuygulanmıştır. Mevcut durum ve model sonucunda önerilen durumkarşılaştırılmıştır.
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- 2017
13. Fabrication of Cu−CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine
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Aktürk, Merve, primary, Karabiberoğlu, Şükriye Ulubay, additional, and Dursun, Zekerya, additional
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- 2017
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14. Preparation and application of metal oxide and metal nano particles modified carbon based composite electrodes for simultaneous determination of adenine and guanine
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Aktürk, Merve, Dursun, Zekerya, Kimya Anabilim Dalı, and Fen Bilimleri Enstitüsü
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Çok Duvarlı Karbon Nanotüp ,Multi-Walled Carbon Nanotube ,Adenine And Guanine ,Voltammetri ,Metal Hegzasiyanoferrat ,Kimya ,Metal Hexacyanoferrate ,Metal Nano Parçacık ,Chemistry ,Grafen Oksit ,Voltammetry ,Metal Nano Particles ,Graphene Oxide ,Adenin Ve Guanin - Abstract
In recent years, sensor studies that provide information on physic, chemistry and biology were increased with the progress on nanoscience and nanotechnology. The insufficient behaviour of conventional electrodes in some applications, cause the necessity of different active surfaces which were more selective and catalytically active towards analytes. The combination of metal nano particles with conductive polymers and carbon nanotubes which have high conductivity and wide active surface area was used as important new electrode materials. In the first part of this thesis which consisted of two different sections, metal nano particles modified acid treated carbon nanotube covered electrodes were prepared and their effect on adenine and guanine oxidation was investigated. The best catalytic activity towards adenine and guanine oxidation was obtained for coexistence of Cu and CeO2 nanoparticles on the carbon nanotube surface. The peak currents of A and G at metal nano particles modified carbon nanotube electrodes were found to be 15-20 times higher than bare GCE.The peak current of adenine on Cu-CeO2/MWCNT/GCE was linearity range from 1x10-7 to 8x10-6 mol L-1 with LOD value of 6.2x10-8 mol L-1 (S/N=3). The peak current of guanine on Cu-CeO2/MWCNT/GCE was linearity range from 2x10-7 to 6x10-6 mol L-1 with LOD values of 1.28x10-7 mol L-1 (S/N=3). In another part of this thesis, copper(II)hexacyanoferrate and graphene oxide modified electrodes were utilized for investigation of alone and simultaneous electrochemical behavior of adenine and guanine. It was observed that increasing catalytic activity for modified electrodes comparing bare GCE. The alone and simultaneous determination of adenine and guanine were studied by DPV. Under the optimal conditions, the oxidation peak currents were linearly regarding adenine and guanine concentrations in the range from 6x10-7 to 6x10-6 M and from 4x10-7 to 6x10-6 M , respectively. LOD values were 2x10-7 M for A and 1.33x10-7 M for G. All graphene oxide and multi-walled carbon nanotube modified electrode surfaces and their covered metal nano particles forms were characterized by Energy Dispersive X-Ray Spectroscopy (EDX), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS)., Son yıllarda nanoteknoloji ve nanobilimdeki gelişmeler ile fizik, kimya ve biyoloji konusunda bilgi sağlayan sensör çalışmaları da artmıştır. Geleneksel elektrotların kimi uygulamalardaki yetersizliği, analitlere karşı katalitik etkinliği ve seçimliliği yüksek, farklı yüzeylere ihtiyaç duyulmuştur. Bu amaca yönelik yüksek iletkenlik, geniş ve etkin yüzey alanlarına sahip karbon nanotüp, grafen oksit ve iletken polimer filmlerin metal nanoparçacıklar ile birleştirilmesi önemli yeni elektrot malzemeleri olarak kullanılmaktadır. İki bölümden oluşan bu tez çalışmasının ilk kısmında, metal nanoparçacıklar ile modifiye, koşullandırılmış çok duvarlı karbon nanotüp (MWCNT) kaplı elektrotlar hazırlanarak adenin ve guaninin yükseltgenme tepkimeleri incelenmiştir. Adenin ve guaninin yükseltgenmesine ilişkin en iyi katalitik etkinlik bakır ve seryum (IV) oksit nano parçacıkların karbon nanotüp yüzeyinde birarada olduğu koşullarda gözlenmiştir (Cu-CeO2/MWCNT/GCE). Metal nano parçacık modifiye karbon nanotüp kaplı elektrot camımsı karbon elektrot ile karşılaştırıldığında akımı 15-20 kat arttırmıştır. Adeninin Cu-CeO2/MWCNT/GCE de elde edilen pik akımı 1x10-7 – 8x10-6 mol L-1 aralığında doğrusaldır ve belirtme alt sınırı 6.2x10-8 mol L-1 olarak saptanmıştır (S/N=3). Guaninin ise Cu-CeO2/MWCNT/GCE de elde edilen pik akımı 2x10-7 – 6x10-6 mol L-1 aralığında doğrusaldır ve belirtme alt sınırı 2.7x10-8 mol L-1 olarak saptanmıştır (S/N=3). Tezin ikinci kısmında ise adenin ve guaninin tek başlarına ve birarada olduğu koşullarda elektrokimyasal davranışları yalın elektrot , grafen oksit ve bakır hegzasiyanoferrat ile modifiye edilmiş grafen oksit kaplı elektrotlar hazırlanıp döngüsel voltammetri tekniği kullanılarak incelenmiştir (CuHCF/GO/GCE). Modifiye elektrotta yalın camımsı karbon elektroda göre katalitik etkinin arttığı görülmüştür. A ve G moleküllerinin tek tek ve birarada bulunduğu koşullardaki davranışları diferansiyel puls voltammetrisi ve tekniği ile çalışılmıştır. Adenin için CuHCF/GO/GCE de elde edilen pik akımı 6x10-7 – 6x10-6 mol L-1 aralığında doğrusaldır ve belirtme alt sınırı 2x10-7 mol L-1 olarak saptanmıştır (S/N=3). Guanine için ise 4x10-7 to 6x10-6 M aralığında doğrusaldır ve belirme alt sınırı 1.33x10-7 M olarak saptanmıtır.(S/N=3). Hazırlanan tüm grafen oksit ve çok duvarlı karbon nanotüp ile modifiye edilmiş elektrot yüzeyleri ve onların metal nano parçacık kaplı formları enerji dağılımlı X-ışını spekroskopisi (EDX), taramalı elektron mikroskopu (SEM), X-ışını potoelektron spektroskopisi (XPS) ve elektrokimyasal empedans tekniği (EIS) ile karakterize edilmiştir.
- Published
- 2016
15. Fabrication of Cu−CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine.
- Author
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Aktürk, Merve, Karabiberoğlu, Şükriye Ulubay, and Dursun, Zekerya
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GUANINE , *ADENINE , *CARBON nanotubes , *NANOTUBES , *CARBON nanofibers , *NANOPARTICLES - Abstract
Abstract: A copper nano particles and cerium (IV) oxide modified carbon nanotube based composite on glassy carbon electrode (Cu−CeO2/MWCNT/GCE) was fabricated for simultaneous determination of guanine and adenine. The surface morphology, chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy dispersion X‐ray (EDX), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The Cu−CeO2/MWCNT/GCE improved electrochemical behaviour of guanine and adenine compared to other electrodes. The modified electrode was also used for individual and simultaneous determination of guanine and adenine. Under optimized conditions, the calibration curves were obtained linearly in the range of 0.20 to 6.00 μM for the guanine and 0.10 to 8.0 μM for the adenine by differential pulse voltammetry. The limits of detection of guanine and adenine were calculated as 0.128 and 0.062 μM, respectively. Interferences studies were also performed in the presence of inorganic and organic compounds. Moreover, the determination of guanine and adenine contents were carried out in a calf thymus DNA sample by the developed method with satisfactory results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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16. HEMŞİRE ÇİZELGELEME İÇİN MODEL ÖNERİSİ: ÖRNEK UYGULAMA.
- Author
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ŞAHİNER, Miyase, AKTÜRK, Merve Sıla, ÜNLÜSOY, Sultan, BEDİR, Neşet, VARLI, Emre, and EREN, Tamer
- Abstract
Copyright of Trakya University, Economics & Administrative Sciences Faculty E-Journal / Trakya Üniversitesi İktisadi ve İdari Bilimler Fakültesi E-dergi is the property of T.C. Trakya Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2017
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