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Development of quantum dot based fluorescence sensor for metabolite detection
Full text linkVücutta meydana gelen hastalıkların çoğu metabolit miktarının değişimiyle saptanabilmektedir. Sağlıklı ve hasta bireylerde farklılık gösteren metabolit miktarları hastalıkların teşhisinde, evresinin belirlenmesinde ve tedavi planlanmasında önemli rol oynamaktadır. Metabolitlerin tespit edilmesinde birçok farklı yöntem kullanılsa da diğer yöntemlerle karşılaştırıldığında floresan yanıtlarına bağlı tespit yönteminde daha az numune tüketimi, ön hazırlığa ihtiyaç duyulmaması ve daha hızlı yanıt elde edilmesi bu yöntemin avantajları arasında yer almaktadır. Ayrıca floresan ışıması yapan kuantum noktaların (KN) yapılarının iyi bilinmesi, yüksek ışıma yapmaları, boyutlarının ayarlanabilir olması ve absorpsiyon kesit oranının yüksek olması KN'leri metabolit tespit çalışmalarında öne çıkarmaktadır. Bu tez çalışmasında, merkaptopropiyonik asit (MPA) ile sulu sentezlenen kadmiyum (Cd) bazlı KN'ler ilk kez kullanılarak C vitamini (CVit), folik asit (FA) ve glikozu hızlı, hassas, seçici ve güvenilir şekilde tespit edebilen floresan sensör sistemi geliştirilmiştir. Öncelikle, sentezlenen KN'lerin (CdSe, CdSeTe, CdTeSe, CdTe/ZnS ve CdSe/ZnS) UV-Vis, XRD, FT-IR ve HR-TEM ile karakterizasyonları yapılmıştır. Sentezlenen KN'lerin yüksek kalitede ve metabolit tespit çalışmaları için uygun KN'ler olduğu görülmüştür. KN konsantrasyonu, pH ve inkübasyon sürelerinin optimize edildiği sistemde, artan miktarlarda CVit, FA ve glikoz ilavesine karşı KN'lerden elde edilen floresan yanıtları incelenmiştir. Metabolitlerin eklenmesiyle, KN'lerin floresan yanıtlarında FRET mekanizmasına dayanan sönümlenmeler gözlemlenmiştir. Tez çalışmasında önerilen sensör sisteminde test edilen KN'ler için ölçüm yapılan konsantrasyon aralığı CVit için 0,3-8000 µg/mL, FA için 3,5E-4-3,5E+4 ng/mL ve glikoz için 0,175-90 mM olarak belirlenmiştir. Belirtilen dinamik aralıklar literatürde yapılan çalışmalara kıyasla daha geniş aralıkta yer almaktadır. Ayrıca, KN'lerin metabolitlere özgü yanıt verdiğini gözlemlemek amacıyla seçicilik çalışmaları gerçekleştirilmiş ve bunun sonucunda, KN'lerin metabolitlere karşı seçici yanıt verdiği belirlenmiştir. Sunulan bu yöntem, gerçek kan numunelerinde metabolitlerin miktarını ölçmek için de kullanılmıştır. Kan serum numunelerinde CVit için 10-20 µg/mL, FA için 7,5-20 ng/mL ve glikoz için 0,25-1,5 mg/mL lineer aralıklarda %95'in üzerinde doğruluk payı ile metabolit miktarları tespit edilmiştir. Bu sonuç lieratürdeki farklı KN'ler ve metabolitler için bulunan sonuçlar ile uyumluluk göstermekte fakat seçilen dinamik aralık ve elde edilen lineer aralık açısından üstünlük sağlamaktadır. Sonuç olarak, bu tez çalışması ile CVit, FA ve glikoz tespiti için tepki süresi hızlı, hassas, seçici, güvenilir, düşük maliyetli ve gerçek örneklerde kullanılabilecek mevcut KN'lere alternatif floresan tabanlı sensör sistemi literatüre kazandırılmıştır.Most of the diseases occurring in the body can be detected by changes in the amount of metabolites. Metabolite amounts that differ between healthy and patient individuals play an important role in diagnosing diseases, determining their stage and planning treatment. Although many different methods are used to detect metabolites, the advantages of fluorescence-based detection method include less sample consumption, no need for preliminary preparation, and faster response when compared to other methods. In addition, the well-known structures of quantum dots (QDs) that emit fluorescence, their high luminescence, adjustable size and high absorption cross-section ratio make QDs stand out in metabolite detection studies. In this study, a fluorescent sensor system has been developed that can detect vitamin C (VitC), folic acid (FA) and glucose quickly, sensitively, selectively and reliably for the first-time by using aqueously synthesized cadmium (Cd)-based QDs with mercaptopropionic acid (MPA). First of all, the synthesized QDs (CdSe, CdSeTe, CdTeSe, CdTe/ZnS and CdSe/ZnS) were characterized by UV-Vis, XRD, FT-IR and HR-TEM. It was observed that the synthesized QDs were of high quality and suitable for metabolite detection studies. In the system where QD concentration, pH and incubation times were optimized, the fluorescence responses obtained from QDs against the addition of increasing amounts of CVit, FA and glucose were examined. With the addition of metabolites, quenching of the fluorescence responses of QDs was observed based on the FRET mechanism. In this study, the dynamic range for the QDs tested in the sensor system has been determined 0.3-8000 µg/mL for CVit, 3.5E-4-3.5E+4 ng/mL for FA and 0.175-90 mM for glucose. These specified dynamic ranges are wider than the studies in the literature. In addition, selectivity studies were carried out to observe that QDs respond specifically to metabolites, and as a result, it was determined that QDs have selective responses to metabolites. This presented method has also been used to quantify metabolites in real blood samples. In blood serum samples, metabolite amounts were determined with over 95% accuracy in linear ranges of 10-20 µg/mL for CVit, 7.5-20 ng/mL for FA and 0.25-1.5 mg/mL for glucose. This result is compatible with the results found for different QDs and metabolites in the literature, but is superior in terms of the selected dynamic range and the obtained linear range. As a result, with this thesis, an alternative fluorescence-based sensor system to existing QDs that has a fast response time, sensitive, selective, reliable, low cost and can be used in real samples for the detection of CVit, FA and glucose has been introduced to the literature
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Solar cell production and characterization with CdTe nanomaterial
Full text linkYÖK Tez No: 523075Dünya genelinde enerjiye duyulan ihtiyacın artması buna karşın fosil yakıtların hızla azalması alternatif enerji kaynaklarının önemini artırmaktadır. Mevcut silisyum, germanyum bazlı birinci nesil güneş hücrelerinin yüksek maliyeti ve alternatif olarak ortaya çıkan ikinci nesil güneş hücrelerinin enerji dönüşüm verimlerinin %13 civarında kalması üçüncü nesil güneş hücreleri üzerine yoğunlaşma gereğini ortaya çıkarmıştır. Öyle ki henüz gelişim aşamasında olan üçüncü nesil güneş panelleri verim olarak birinci nesil güneş panellerini şimdiden yakalamışlardır. Üçüncü nesil güneş panelleri içinde Kuantum Nokta Duyarlı Güneş hücreleri (KNDGH) son beş yılda sergiledikleri aşama ile dikkat çekmektedir. Kolay işlenebilirlikleri, ayarlanabilir boyut ve bant aralıkları ve Çoklu Eksiton Üretimi (MEG) gibi benzersiz opto-elektronik özellikleri kuantum noktaları ilgi çekici hale getirmektedir. Bu özellikler KNDGH için teorik olarak enerji dönüşüm veriminin %44'e kadar çıkabileceğini göstermektedir. Bu çalışmada CdTe KNDGH tasarımı üzerine odaklanılmıştır. Tez çalışması 3 temel bölüme ayrılmıştır; CdTe KN sentezlenmesi, CdTe KN'nın tedavi edilmesi ve sentezlenen CdTe KN'lar ile KNDGH tasarlanması. CdTe KN sentezlenmesi için sıcak enjeksiyon metodu kullanılmış olup klasik metot ile sentezlenen CdTe KN Fotolümünesans Kuantum Verimi (PLQY) %8,12 olarak bulunmuştur. Sıcak enjeksiyon metodu daha sonra Kanula metoduyla modifiye edilmiş ve sentezlenen CdTe KN'nın PLQY değeri %25,66 ya çıkarılmıştır. Ayrıca KN'nın PL Maksimum Pik Noktasının Yarı Noktası (FWHM) 27nm seviyesine indirilmiş olup literatürdeki en yüksek monodispersi özelliği sergileyen organometalik CdTe KN sentezlenmiştir. Daha sonra sentezlenen CdTe KN'ya klorür pasifikasyon işlemi uygulanmış, farklı miktarda klorür (12-96 CdCI2/nm2) iyonu KN'ya enjekte edilmiştir. Yapılan analizler sonucunda 60 CdCI2/nm2 tedavisiyle CdTe(CI) KN'nın PLQY değeri %87,33'e çıkarılmıştır. Yapılan pasifleştirme tedavisi Kanula metoduyla %70 tekrarlanabilir hale getirilmiştir. Ayrıca CdTe KN'nın oksijen ortamında dayanım süresi 3 kat arttırılmıştır. Sentezleme ve tedavi işlemlerin ardından KNDGH tasarım aşamasına geçilmiştir. Bu aşamada KN'nın boyutu, TiO2 kalınlığı, FTO/TiO2 yüzeyine yapılan tedavi, CdTe KN'nın yüzeye tutturulması, redoks çifti ve toplayıcı elektrot seçimi üzerine birçok iyileştirme çalışması yapılmıştır. Tüm optimizasyon işlemleri sonucunda FTO/TiCI4/TiO2 (22µm) /TiCI4 /36 CdCI2/nm2 CdTe(CI) KN yüzey foto anot olarak kullanılırken, FTO/Pt yüzeyin toplayıcı elektrot olarak seçilmiştir. Bu iki yüzey arasına I-/I3- redoks çifti enjekte edilmiştir. Tasarlanan KNDGH için Jsc 3,22 mA/cm2, Voc 0,821V olurken, dolum faktörü %57,192 ve verim %1,515 olarak bulunmuştur. Bu verim değeri literatürdeki organometalik CdTe kullanılarak elde edilen en verimli (%0,197) CdTe KNDGH verimine göre 7,97 kat daha iyidir.The increasing need for energy throughout the world, while the rapid reduction of fossil fuels, increases the importance of alternative energy sources. The high cost of the existing silicon and germanium based first generation solar panels, and the fact that the energy generation efficiency of the second generation solar panels, which are available as an alternative, is around 13%, has led to the need to concentrate on third generation solar panels. The third-generation solar panels, which are still in development stage, have already caught the first-generation solar panels in efficiency. Within the third generation solar panels, the Quantum Dot Sensitized Solar Cell (QDSSC) has attracted attention in the past five years. Unique opto-electronic features such as easy machinability, adjustable size and band gap, and Multiple Exciton Generation (MEG) make quantum dots attractive. These characteristics demonstrate that theoretically the energy conversion efficiency for QDSSC can be up to 44%. This work focuses on CdTe QDSSC design. Thesis is divided into 3 basic divisions; Synthesis of CdTe QD, treatment of CdTe QD and design of QDSSC with synthesized CdTe QDs. The hot injection method was used for synthesis of CdTe QD. Photoluminescence Quantum Yield (PLQY) of CdTe QDs, synthesized by the conventional method, was found to be 8.12%. The hot injection method was then modified by the Cannula method and the PLQY value was increased to 25.66%. Furthermore, Full Width Half Maximum (FWHM) of PL pik of CdTe QD was reduced to 27 nm so that the organometallic CdTe QD, which exhibited the highest monodispersity in the literature, was synthesized. Then, the synthesized CdTe QD was subjected to chloride passivation and different amounts of chloride (12-96 CdCl2/nm2) ions were injected into the QD. As a result of the analysis, it was determined that the PLQY value increased to 87.33% with 60 CdCl2/nm2 treatment. The passivization treatment was made 70% reproducible by Cannula method. Furthermore, the duration of the CdTe QD in the oxygen environment has been increased 3 times. After synthesis and treatment, QDSSC design studies were started. At this stage, several healing studies have been performed on CdTe QD size, TiO2 thickness, treatment on FTO / TiO2 surface, attachment of CdTe KN to the surface, redox couple and collecting electrode. As a result of all the optimization processes, FTO/TiCI4/TiO2 (22µm) /TiCI4/36 CdCI2/nm2 CdTe(CI) QD surface was used as photo anode and FTO/Pt surface was used as collecting electrode. I-/I3- redox couple was injected between these two surfaces. For the designed QDSSC, Jsc is 3.223mA/cm2, Voc is 0.821V, filling factor is 57.192% and efficiency is 1.51%. This efficiency is 7.97 times bigger than the similarities work (%0,197) in the literature
Quantum dot sensitized solar cell design with surface passivized CdSeTe QDs
Full text linkOne of the main factors affecting the performance of quantum dot sensitized solar cells (QDSSCs) is charge recombination caused by surface traps. It is important to passivize the surface traps of the synthesized QDs as much as possible in order to raise the power conversation efficiency (PCE). Therefore, in this study, the effects of chloride passivation on the performance of CdSeTe QDSSCs were tested. CdSeTe QDs synthesized by the hot injection method were passivized with chlorine ions in different proportions (10-70%) by mass and CdSeTe(Cl) QDSSCs were designed. In order to detect the effects of chloride treatment, chloride passivation was applied to CdSeTe QDs with different growth time. The absorbance and emission characterizations of the synthesized CdSeTe and CdSeTe(Cl) QDs were removed, HR-TEM and X-ray diffraction (XRD) studies were performed. Photovoltaic, incident-photo-to-carrier conversation (IPCE), electrochemical impedance spectroscopy (EIS) measurements were performed for all designed CdSeTe QDSSCs. As a result of the analyses, it was determined that chloride treatment increased the PCE of CdSeTe (Cl) QDSSCs by 2.456 times compared to untreated CdSeTe QDSSCs. The average value of PCE for CdSeTe(Cl) (60% Cl) (5 min) QDSSCs was 3.379 +/- 0.08%, while J(SC) and V-OC values were measured as 10.048 mA/cm(2) and 0.664 V, respectively.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [217M897]This study was financially supported by Scientific and Technological Research Council of Turkey (TUBITAK), project number 217M897
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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