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An Investıgatıve Study Of The Bıocompatıbılıty, Surface And Corrosıon Propertıes Of Tıtanıum Alloys Modıfıed Wıth A Novel Bıonanocomposıte
No full textTıbbi alanda yaygın olarak kullanılan Ti-6Al-4V alaşımının korozyon ve biyolojik özelliklerini geliştirmek amacıyla, yeni bir nano biyokompozit olan kitosan (CS) /hidroksiapatit (HA) /zirkonyum oksit (ZA) üçlü kaplaması ile bu alaşımın yüzey modifikasyonu gerçekleştirildi. İlk aşamada, HA ve ZA nanotanecikleri ıslak çöktürme yöntemiyle sentezlendi. Sentezlenen bu nanotanecikler, CS ile birlikte, elektroforetik biriktirme yöntemiyle Ti-6Al-4V alaşımı üzerine kaplanarak CS/HA/ZA nano biyokompoziti elde edildi. Elektroforetik biriktirme yöntemi uygulanırken; bileşenlerin derişimleri, uygulanan potansiyel, kaplama süresi, ortam pH'ı gibi parametrelerin kaplamaya olan etkileri incelendi. Sentezlenen nanotaneciklerin ve elde edilen kaplamaların karakterizasyonu, Taramalı elektron mikroskobu (SEM), X-ışını difraktometresi (XRD) ve Fourier dönüşümlü kızılötesi spektrometresi (FTIR) ile yapıldı. Nano biyokompozitin kalınlığı, yüzey pürüzlülüğü ve temas açısı sırasıyla optik mikroskop, yüzey profilometresi ve temas açısı ölçme sistemi ile ölçüldü. Hidrofilik özellikteki, yaklaşık 150-200 μm kalınlığa ve 3,33 μm yüzey pürüzlülüğüne (Ra) sahip nano biyokompozitin, substrat yüzeyine tutunma kuvveti, üniversal test cihazıyla 2,11 MPa olarak bulundu. Tutunma kuvveti, kaplama süspansiyonundaki ZA derişimiyle doğru orantılı bir şekilde artmıştır. Nano indentasyon yöntemiyle yapılan ölçümler sonucunda; nano biyokompozitin, 32,9 MPa sertliğe ve 3,8 GPa Young modülüne sahip olduğu anlaşıldı. İkinci aşamada, nano biyokompozit ile kaplı Ti-6Al-4V alaşımının korozyon davranışı; kaplanmamış, CS ve CS/HA kaplı Ti-6Al-4V alaşımların korozyon davranışlarıyla karşılaştırma yapılarak; açık devre potansiyeli (OCP), potansiyodinamik polarizasyon ve elektrokimyasal empedans spektroskopisi (EIS) ölçümleriyle incelendi. Bu ölçümler sonucunda korozyon dirençleri sıralaması büyükten küçüğe doğru CS/HA/ZA > CS/HA > CS > kaplanmamış olarak bulundu. Atomik absorpsiyon spektrometresi sonuçlarına göre; 60 günlük sürede yapay biyolojik sıvı (SBF)'ya en az titanyum, nano biyokompozit ile kaplı Ti-6Al-4V alaşımından sızdı. MTT testi ile yapılan biyolojik değerlendirmeye göre ise, nano biyokompozit ile kaplı Ti-6Al-4V alaşımı, diğer kaplanmamış ve kaplı alaşımlardan daha iyi bir biyouyumluluk sergiledi.In this study, the surface modification of Ti-6Al-4V alloy used in the medical field was carried out with a new nano biocomposite, chitosan (CS) /hydroxyapatite (HA) /zirconia (ZA) triple coating, to improve its the corrosion and biological properties. In the first step, HA and ZA nanoparticles were synthesized by the wet precipitation method. These synthesized nanoparticles were coated on Ti-6Al-4V alloy by electrophoretic deposition together with chitosan to obtain CS/HA/ZA nanocomposite. When the electrophoretic deposition method is applied, the effects of coating parameters such as concentrations of components, applied potential, coating duration and ambient pH were investigated. The characterization of the synthesized nanoparticles and resulting coatings was performed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry, X-ray diffractometry (XRD) and Fourier transform infrared spectrometry (FTIR). The thickness, surface roughness and contact angle of the nanocomposite were measured by optical microscope, surface profilometer and contact angle measurement system, respectively. The hydrophilic nanobiocomposite which has the thickness of about 150-200 μm and the roughness (Ra) value of 3.33 μm adheres to Ti-6Al-4V surface with the strength of 2.11 MPa measured by universal testing machine. It is found that the adhesion strength increases with increasing ZA concentration in the deposition medium. As a result of the measurements made by the nanoindentation method, the nano biocomposite has the hardness of 32.9 MPa and the Young modulus of 3.8 GPa. In the second step, the corrosion behavior of Ti-6Al-4V alloy coated with CS/HA/ZA nanocomposite was investigated by open-circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements by comparing it to that of bare, CS and CS/HA coated ones. The order of corrosion resistance was found as: CS/HA/ZA > CS/HA > CS > bare. According to the results of atomic absorption spectrometry, the minimum amount of titanium that released to the simulated biological fluid (SBF) at the end of 60 days was from the nanobiocomposite coated Ti-6Al-4V alloy and MTT cytotoxicity test showed that it has the best biocompatibility among the other bare and coated alloys
Preparıng a new bıosensor for glucose determınatıon by ımmobılızatıon of glucose oxıdase ın polyanılıne-polyvınylsulphonate fılm
No full textBu çalısmada, glukoz tayini için yeni bir amperometrik biyosensör gelistirildi. Bu amaçla, platin levha üzerinde anilinin polivinilsülfonat, potasyum ferrisiyanür ve metilen mavili ortamda elektropolimerlesmesi ile polianilin-polivinilsülfonat-ferrisiyanür ve polianilin-polivinilsülfonatmetilen
mavisi filmleri hazırlandı ve özellikleri birbirleriyle karsılastırıldı.
Polianilin-polivinilsülfonat-ferrisiyanür filminin optimum çalısma sartları belirlendi. Glukoz oksidaz enzimi, polianilin-polivinilsülfonatferrisiyanür
film içine hapsetme yöntemiyle immobilize edildi. Glukoz tayini, hazırlanan enzim elektrodun yüzeyinde gerçeklesen enzimatik tepkime sonucu olusan hidrojen peroksitin ve ferrisiyanür medyatörünün indirgenmis halinin 0,30 V'da yükseltgenmesine dayanarak yapıldı. Biyosensörün glukoz tayini için çalısma aralığı tayin
edildi. Glukoz biyosensörünün cevabına pH'nın ve sıcaklığın etkisi arastırıldı. Biyosensörün tekrar kullanılabilirliği ve raf ömrü tayin edildi.
Biyolojik ortamlarda olabilecek girisimlerin biyosensör cevabı üzerine etkileri incelendi.In this study, new amperometric biosensor for determination of glucose was developed. Polyaniline-polyvinylsulphonate-ferricyanide (PANIPVS-
FC) and polyaniline-polyvinylsulphonate-methylene blue (PANIPVS- MB) films have been prepared on the platinum electrode by the electropolymerization of aniline was carried out in the presence of PVS, FC and MB. Optimum conditions of PANI-PVS-FC film was determined. Glucose oxidase enzyme has been immobilized in PANI-PVS-FC film via the entrapment method. Glucose detection is based on the oxidation of hydrogen peroxide and reduced form of ferricyanide at 0,3 V produced by the enzymatic reaction on the enzyme electrode surface. The linear working range of biosensor for glucose was determined. The effects of pH and temperature on the response of the glucose biosensor were investigated. Reusability and storage stability were determined of the biosensor. Interference effects were investigated on the amperometric response of the biosensor
Yeni Bir Biyonanokompozit İle Modifiye Edilmiş Titanyum İmplant Ti-6Al-4V alaşımının Yüzey ve Korozyon Özelliklerinin İncelenmesi
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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