1,721,069 research outputs found
Development of DNA based electrochemical biosensor for detection of genetically modified organisms
No full textFen Bilimleri Enstitüsü, Biyomühendislik Ana Bilim Dalı, Biyomühendislik Bilim DalıGenetiği değiştirilmiş organizmaların (GDO), artan gıda ihtiyacını karşılamak amacıyla geliştirilen verim artışı, yüksek besin değeri ve herbisitlere dayanıklılık gibi olumlu etkileri yanında doğadaki tür dağılımı ve alerjik reaksiyonlar gibi endişeler ülkelerin GDO teknolojisine karşı yaklaşımlarını etkilemiştir. Transgenik bitkilerin gıda ürünlerindeki kullanımlarının dünya genelinde giderek artması bu ürünlerin tespitine yönelik ihtiyacı beraberinde getirmiştir. GDO'lu ürünlerin tespiti için son yıllarda kullanımı basit ve iyi analitik özelliklere sahip biyosensörler tercih edilmektedir. Bu tez çalışmasında, gıda ürünlerinde transgenik soya içeriğinin tespiti amacıyla elektrokimyasal yöntemle yüzeyi altın (Au) ve gümüş (Ag) elementleri ile modifiye edilmiş grafen oksit (GO)/indirgenmiş grafen oksit (rGO) nanokompozit kaplı kalem grafit elektrotlar (PGE) tasarlanmış ve elektrokimyasal biyosensör özellikleri incelenmiştir. GDO ürünlerinin tespiti için yakalayıcı DNA probu olarak CaMV 35S promotör bölgesine spesifik tiyol işaretli oligonükleotidler ile hedef gen hibridizasyonuna bağlı olarak elde edilen sonuçlar elektrokimyasal empedans spektroskopisine (EIS) dayalı olarak değerlendirilmiştir. Bu sonuçlara göre 10-12-10-16 M doğrusal konsantrasyon aralığında tespit gerçekleştirilmiştir. Çalışmada farklı işlenmişlik seviyelerine sahip gıda ürünlerine (bisküvi, kek, kraker, mısır cipsi, soya unu, mısır unu) için en uygun DNA izolasyon yöntemleri belirlenmiştir. Moleküler taramalar sonucunda soya içeren bazı gıda ürünlerinde CaMV 35S bölgesi bakımından GDO taramaları yapılmıştır. Tasarlanan GDO biyosensöründe, gerçek örnek denemeleri için izole edilen genomik DNA ürünleri doğrudan hedef olarak kullanılmış ve işlenmiş gıda ürünlerinde GDO tespitine yönelik alternatif ve hızlı bir teknik geliştirilmiştir.Genetically modified organisms (GMOs) have positive effects such as increased yield, high nutritional value, and resistance to herbicides in order to meet the increasing food demand. However, concerns such as species distribution in nature and allergic reactions have affected countries approaches to genetically modified organism technology. The increasing use of transgenic plants in food products around the world has brought about the need for the detection of these products. In recent years, for the detection of GMO products, biosensors are preferred due to their ease to use, automation, and good analytical properties. In this thesis study, graphene oxide (GO)/reduced graphene oxide (rGO) nanocomposite-coated pencil graphite electrodes (PGEs) modified with gold (Au) and silver (Ag) elements were designed and used to determine the transgenic content in food products with the electrochemical method. Thiol-labeled oligonucleotides specific to the CaMV 35S promoter region were used as capture DNA probes. The results obtained due to target gene hybridization were evaluated according to electrochemical impedance spectroscopy (EIS). According to these results, detection was carried out in a linear range of 10-12-10-16 M. In the study, the most appropriate DNA isolation methods for processed food products (biscuits, cakes, crackers, corn chips, soy flour, corn flour) were determined. As a result of molecular studies, GMO was determined in terms of CaMV 35S region in some food products containing soy. In the designed GMO biosensor application, the isolated genomic DNA products were used as direct targets for real samples, and an alternative and rapid technique for GMO detection in processed food products was developed
Development of molecularly imprinted polymer-based FET biosensor via oxidative chemical vapor deposition
Get PDFBiosensors have been attracting an increasing interest in various fields including medical diagnosis and health monitoring due to its rapid, selective and sensitive detection of target analyte in real-time. As biological receptors require special environmental conditions, they limit the durability and long-term storage of the biosensors. However, molecularly imprinted polymers (MIPs) are artificially synthesized to mimic the recognition of biological macromolecules at a significantly lower cost and no need for any special storage. Here, we reported the usability of the polypyrrole (PPy) MIP as a synthetic biorecognition element on a FET based biosensor to detect CA-125 ovarian cancer biomarker. We used oxidative chemical vapor deposition (oCVD) technique which allows the conformal and controlled thin film conductive polymers, to produce MIP onto a sacrificial layer. Synthesized MIP then integrated onto the interdigitated electrode arrays to make a conductive bridge between source and drain terminals for the development of the FET biosensing platform. The oCVD technique has a great potential to be used in the development of MIP-based biosensors for the detection of target proteins without wasting as in the traditional bulk polymerization method
Simulation based design and fabrication of a PPy coated PDMS based pressure sensor
No full textFlexible sensors have attracted widespread attention because of their highly desired multifunctionality such as flexibility, high
sensitivity, and large workable range in electronic skin or wearable health monitoring applications. Among these,
piezoresistive pressure sensors are expected to deliver these functions in a stable fashion whilst being produced in a low cost
and scalable manner. It is known that sensor performance directly depends on the 3D geometrical and material composition.
In this study a flexible pressure sensor with a unique interconnected and porous geometry is designed and fabricated using a
simulation based design approach and a two-step manufacturing technique. The substrate of the sensor is cast using Poly-
dimethylsiloxane (PDMS) which is known for its mold-release properties and ability to replicate fine features with low
shrinkage and excellent elastic properties. The 3D PDMS structures were prepared by mixing base solution and curing agent
at a weight ratio of 10:1 following poured onto 3D printed molds and cured at 80 °C for over 2 h. The sensing capability of
the composite material was achieved by the facile solution based dip coating method of polypyrrole (PPy) thin film onto the
PDMS structure. The mechanical and electrical response of the proposed PPy coated PDMS sensor was characterized using
compression tests via a multimeter setup integrated to Universal Testing Machine and a four-point probe measurement system.
Micro-computed tomography characterizations were used to analyze the cast sensor’s geometrical features. Simulations
were carried out using Finite Element Analysis software COMSOL Multiphysics. Both simulations and measurements
demonstrate that the proposed sensor delivers a stable piezoresistive behavior with high sensitivity. The proposed production
technique’s flexibility to produce sensors with complex 3D geometries combined with the tuning potential of the sensor’s
sensitivity should prove useful for a wide range of applications with different desired pressure ranges
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
- 3 YAĞ ASİTLERİ : BİYOKİMYASAL VE POTANSİYEL KLİNİK ÖNEMİ
No full textDİYETLE ALINAN BALIK YAĞINDA BULUNAN - 3 YAĞ ASİTLERİNİN SAĞLIK ÜZERİNE YARARLI ETKİLERİ KONUSU OLDUKÇA İLGİ ÇEKİCİDİR
BESİNSEL BALIK YAĞI ALINIMI VE EİKOSANOİD METABOLİZMASI ÜZERİNE ETKİLERİ
No full textGEÇEN SON ÜÇ DEKAK BOYUNCA -3 YAĞ ASİTLERİNİN İNSAN BİYOLOJİSİ ÜZERİNE OLAN ETKİLERİ HAKKINDA PEK ÇOK BİLGİ ÖĞRENİLDİ
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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