1,721,175 research outputs found
Surface functionalization of additively manufactured Ti6Al4V scaffolds with CaP/ZnO coatings
No full textA biologically active coating with strong adhesion can improve the inherent bioinert nature of the additively manufactured Ti6Al4V scaffolds. In this research, a calcium phosphate coating containing antibacterial zinc oxide nanoparticles was applied onto the lattice-structured Ti6Al4V scaffolds using the plasma electrolytic oxidation (PEO) method, and its corrosion resistance and in vitro bioactivity were analyzed. The results revealed that the thickness of the CSh (Coat-Short: Scaffold with an approximate porosity size of 2.23 mm and coated) sample coating was approximately 1.8 times thicker that of the coating created on the CL (Coat-Long: Scaffold with an approximate porosity size of 3.74 mm and coated) sample. Zinc oxide nanoparticles in the coating were found to be uniformly dispersed, resulting in a 5.5% reduction in the hydrophilic behavior of the coatings. Moreover, both types of samples, with the reinforcement of the barrier layer, successfully improved the long-term corrosion behavior of the substrate, with a more pronounced effect on the CSh samples. After 14 days of immersion in simulated body fluid, cauliflower-shaped hydroxyapatite deposits were observed across the entire surface of the coatings. MG63 cells on the CSh sample demonstrated a wider spread and greater adhesion compared to other samples. Additionally, the cell viability increased from 83.3 +/- 4.1 (% control) in the uncoated sample to 94.9 +/- 1.1 (% control). These results suggest that coatings fabricated on scaffold surfaces with smaller porosity (CSh) exhibit more favorable corrosion and biological behavior, highlighting their potential applications in orthopedics
Electrospinning silk with selenium nanoparticles for antibacterial skin applications
No full textSkin is the largest organ in the body and the primary defense against microbes, viruses, and other interactions with the environment. Silk has been studied for skin regeneration and has been widely used as an additive in cosmetics.<sup>1</sup> Silk promotes collagen synthesis, re-epithelialization, wound healing, atopic dermatitis alleviation, and scar reduction. However, pure silk shows negligible or even negative antibacterial properties.<sup>2</sup>..
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
Dental bariyer membran uygulamaları için cam parçacıkları içeren ipek bazlı çift katmanlı membran tasarlanması
No full textDental barrier membranes (DBM) are widely used biomedical materials in alveolar bone defect sites for guided tissue regeneration (GTR). DBMs prevent soft tissue ingrowth into the area where regeneration of the relatively slower-growing bone tissue is desired. A DBM should have a degradation rate that matches the healing rate of the bone tissue at sites with insufficient bone, and have sufficient mechanical properties to exhibit barrier function. In this thesis, a bilayered DBM was designed and fabricated. The membrane was primarily composed of silk fibroin (SF) and silk sericin (SS), which are the two main components of silk fiber. SF possesses superior mechanical properties with a relatively lower degradation rate, while SS has poor mechanical properties and a relatively higher degradation rate. The layer on the bone regeneration side (BRS) consisted of 70 wt% SS and 30 wt% SF, to achieve a higher degradation rate. Aside from the polymer content, approximately 6.5 mol% and 1 mol% calcium- and strontium-doped glass particles (GPs) were incorporated to promote osteogenesis. Doping with osteogenic ions enhances biological functions. A high degradation rate was intended in this layer to allow the GPs to quickly interact with the juxtapposed bone tissue. The layer on the soft tissue side (STS) was composed of 60 wt% SF and 40 wt% SS to achieve a lower degradation rate and improve mechanical properties to ensure the barrier function for a sufficient period of time. The DBM was fabricated by solvent casting and evaporation method. The second layer was cast onto the other and dried. Scanning Electron Microscopy (SEM), Orbital Emission Spectroscopy (OES), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffractometer (XRD) data of GPs confirmed that amorphous particles were successfully synthesized at a particle size of approximately 350 nm. SEM images and AFM results showed that the incorporation of GPs created nanostructured roughness on the surface of the membranes. Degradation test results demonstrated that combining SS and SF in different ratios altered the degradation rates of the films compared to pure SS and SF. Tensile test results indicated that the membrane had a sufficient Young’s Modulus. When MC3T3-E1 preosteoblast cells were seeded on the bilayered membranes with and without GPs, cell proliferation on the membrane containing GPs increased. The results cumulatively showed that the designed bilayered composite membrane was a potential candidate for DBM applications.Dental bariyer membranlar (DBMs), alveolar kemik doku hasarının bulunduğu bölgelerde yönlendirilmiş doku rejenerasyonu (GTR) amacıyla yaygın olarak kullanılan biyomedikal malzemeledir. DBM'lar, yumuşak dokunun, göreceli olarak daha yavaş büyüyen kemik dokusunun rejenerasyonunun istendiği bölgelere taşmasını engeller. Bir DBM, yetersiz kemik dokusu bulunan bölgelerdeki kemik dokusunun iyileşme hızı ile uyuşan bir degradasyon hızına ve aynı zamanda bariyer fonksiyonunu yerine getirebilmek için yeterli mekanik özelliklere sahip olmalıdır. Bu tezde, çift katmanlı bir DBM tasarlanıp ve üretilmiştir. Membran başlıca, ipek lifinin iki ana bileşeni olan ipek fibroin (SF) ve ipek serisin (SS) bileşenlerinden oluşmaktadır. Fibroin, nispeten daha düşük bir degradasyon hızına ve üstün mekanik özelliklere sahipken, serisin daha zayıf mekanik özelliklere ve daha yüksek degradasyon hızına sahiptir. Membranın kemik rejenerasyonun gerçekleşeceği tarafındaki katman (BRS), diğer katmana kıyasla daha yüksek bir degradasyon hızı elde etmek amacıyla kütlece 70% SS ve 30% SF oranı içermektedir. Polimer içeriğinın yanı sıra, osteogenezi deteklemek amacıyla sırasıyla molce 6.5% ve 1% kalsiyum ve stronsiyum katkılı cam parçacıkları (GPs) eklenmiştir. Osteojenik iyonlar ile katkılama işlemi, biyolojik işlevlerin geliştirilmesi için yapılmaktadır. Bu katmanda, daha yüksek degradasyon hızı, cam parçacıklarının ortam ile daha hızlı etkileşime girebilmesi için amaçlanmıştır. Yumuşak doku tarafındaki (STS) diğer katman, bariyer fonksiyonunun yeterli süre boyunca korunmasını sağlamak için daha yavaş bir degradasyon hızı ve iyileştirilmiş mekanik özellikler elde etmek amacıyla kütlece 60% SF ve 40% SS içermektedir. DBM, çözücü döküm ve buharlaştırma yöntemiyle üretilmiştir. İkinci katman diğer katman üzerine dökülerek kurutulmuştur. Cam parçacıkları için yapılan Taramalı Elektron Mikroskobu (SEM), Optik Emisyon Spektroskopisi (OES), Fourier Dönüşümlü Kızılötesi Spektroskopisi (FTIR) ve X-Işını Difraktometresi (XRD) analizleri, amorf parçacıkların yaklaşık 350 nm parçacık boyutu ile başarıyla sentezlendiğini doğrulamıştır. SEM görüntüleri ve AFM sonuçları, parçacıkların membranın yüzeyinde nanoyapılı yüzey pürüzlülüğü yarattığını göstermektedir. Degradasyon testleri, farklı oranlarda SS ve SF kombinasyonu ile üretilen filmlerin, saf SS ve SF’den farklı degradasyon hızlarına sahip olduğunu göstermiştir. Çekme testi, üretilen membranın yeterli bir Young Modülü'ne sahip olduğunu belirtmiştir. MTT sonuçlarından yola çıkılarak, MC3T3-E1 preosteoblast hücrelerinin, GP içeren ve içermeyen çift katmanlı membranlara ekildiğinde, GP içeren membranda hücre proliferasyonunun arttığı gözlemlenmiştir. Elde edilen sonuçlar, tasarlanan çift katmanlı kompozit membranın DBM uygulamaları için potansiyel bir aday olduğunu göstermektedir.M.S. - Master of Scienc
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
NANOBOYUTLU YÜZEY PÜRÜZLÜLÜĞÜNÜN NÖRAL HÜCRELERİN YAPIŞMASINA, ÇOĞALMASINA VE PROTEİN EKSPRESYONUNA OLAN ETKİSİNİN İNCELENMESİ
No full textNeural guidance channels (NGCs) are tubular structures that are placed between distal and proximal ends of a damaged nerve to support the regeneration process. NGCs should support neural cell functions, conduct electrical impulses and have biomimetic surface characteristics. One of the approaches to attain these properties for NGCs properties is to use nanotechnology, which refers to altering physical and chemical properties of a material by controlling its size below 100 nm. There are various studies about the effects of submicron and micron sized surface features on the proliferation and biological functions of neural cells. However, studies concerning electrically conductive materials having surface features below 100nm are limited. For this reason, poly (lactic-co-glycolic) acid (PLGA), a currently-used material to fabricate NGCs, and a more accessible natural material, silk fibroin, were used to systematically obtain nanotopographical structures on their surfaces. This thesis provided data to the literature by comparing biological properties of PLGA films having 30 nm and 80 nm surface feature sizes. In addition, carbon nanofibres (CNFs) were incorporated as a secondary phase into silk fibroin films having nano and sub-micron level surface features (50 nm and 125 nm) to provide electrical conductivity, then these surfaces were tested for proliferation, viability, functions and morphologies of neural cells using neuroblastoma cell line, N2a. Findings from this thesis aimed to pave the way for future NGCs to regenerate damaged neural tissue in patients having neural tissue injury.Sinir yönlendirici kanallar (SYK’lar) hasarlı sinirin proksimal ucu ile distal ucu arasına yerleştirilen ve rejenerasyon sürecini destekleyen kanal yapılarıdır. SYK’lar, nöral hücre fonksiyonlarını destekleyen; iletken ve biyolojik yapılara benzer özelliklere sahip olmalıdır. SYK`lar üzerinde bu özellikleri elde etmek için yaygın bir şekilde kullanılan yöntemlerden biri de malzemenin fiziksel ve kimyasal özelliklerinin, malzeme boyutlarını 100 nm'nin altında kontrol ederek farklı uygulamalar için kullanılmasını ifade eden nanoteknolojidir. Literatürde mikron altı boyutlu ve mikron boyutlu pürüzlülük içeren malzeme yüzeylerinin sinir hücrelerinin çoğalması ve biyolojik işlevleri üzerindeki etkilerini inceleyen çeşitli çalışmalar bulunmaktadır. Ancak yüzeylerinde 100 nm'nin altında boyutlara sahip yapılar içeren iletken malzemelerle ilgili çalışmalar oldukça sınırlıdır. Bu nedenle, SYK’ların üretiminde sıklıkla kullanılan poli (laktik-ko-glikolik) asit (PLGA) ve bu malzemeye göre daha kolay erişilebilir olan ipek fibroinin kullanılması ve bu yüzeyler üzerinde sistematik olarak nano boyutlu yapıların elde edilmesi üzerine çalışılmıştır. Elde edilen nano boyutlu (30 nm ve 80 nm) yapılara sahip PLGA filmlerle karşılaştırma yapılarak literatüre yeni veriler kazandırılmıştır. Ayrıca ipek fibroin malzemesine elektriksel iletkenlik kazandırabilmek için ikincil bir faz olarak karbon nanofiber (KNF’ler) eklenmiş ve ardından yüzeyler üzerinde farklı nano ve mikron altı boyutlu yapılar (50 nm ve 125 nm) oluşturulmuştur. Elde edilen bu yüzeyler üzerinde nöral hücre çoğalması, canlılığı, fonksiyonları ve morfolojileri nöroblastoma hücre hattı, N2a kullanılarak incelenmiştir. Tezden elde edilen sonuçlarla geliştirilecek SYK’ların ileride sinir hasarı yaşayan hastalarda doku jenerasyonunun gerçekleşmesine katkıda bulunması amaçlanmaktadır.Ph.D. - Doctoral ProgramTÜBİTAK Hızlı Destek 217M95
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