1,721,152 research outputs found
Investigation of Antibacterial Effect of Biosynthesized Silver Nanoparticles Using Thyme (Thymus Vulgaris L.) Extract
Full text linkAfyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri DergisiNano boyutlu metaller, bakterilere karşı direnç oluşturma noktasında etkili birer antibakteriyel ajan olarak bilinir. Bu ajanlar özellikle insanlık için ciddi bir tehdit oluşturan ilaca dirençli bakterilerle mücadele etmek için doğal kökenli alternatifler oluşturmaktadır. Gümüş nanopartiküllerin (AgNP'ler) iyi derecede antimikrobiyal aktiviteye sahip olduğu kanıtlanmıştır. AgNP'lerin biyosentezi diğer nanopartikül üretim yöntemlerine kıyasla daha güvenli, düşük maliyetli ve çevre dostu bir yöntem olarak kabul edilmektedir. Bu çalışmada, biyosentez yöntemi kullanılarak Thymus Vulgaris L. sulu özütüyle enkapsüle olmuş gümüş nanopartikül (eAgNP) üretimi başarıyla gerçekleştirilmiştir. AgNP’lere kekik bitkisinin antiseptik, antimikrobiyal ve antioksidatif özelliklerinin kazandırılması amaçlanmıştır. eAgNP üretimini sağlayacak optimum bitki özütü ve AgNO3 konsantrasyonu UV-vis spektrofotometre analizi ile belirlenerek bulunan oranlar doğrultusunda yeşil sentez gerçekleştirilmiştir. Sentezlenen eAgNP'ler UV-Vis spektral analizi, FT-IR, XRD analizi ve TEM görüntü analizi ile karakterize edilmiştir. eAgNP'lerin antimikrobiyal aktivitesi E. coli ve S. aureus bakterileri kullanılarak disk difüzyon metodu ile araştırılmıştır. TEM analizi ile biyosentezlenmiş eAgNP'lerin bitki özütü ile enkapsülasyonunun gerçekleştiği ve 6-70 nm boyut aralığında küresel bir şekle sahip olduğu bulunmuştur. eAgNP'leri çevreleyen bitki kaynaklı fitokimyasalların varlığı FT-IR ile, AgNP oluşumu ise XRD analizi ile kanıtlanmıştır. 5 mg/mL'lik bir konsantrasyonda disklere emdirilen eAgNP'ler, E. coli ve S.aureus bakterilerine karşı sırasıyla 20.5 mm ve 23.2 mm ortalama inhibisyon çapları ile antimikrobiyal aktivite göstermiştir. Sonuçlar, oldukça güçlü antimikrobiyal aktiviteye sahip, çevre dostu eAgNP'lerin Thymus Vulgaris L. özütü kullanılarak hazırlanabileceğini ve biyomalzeme alanında önemli bir potansiyel oluşturabileceğini ortaya koymuştur.Nano-sized metals are known as effective antibacterial agents at the point of creating resistance against bacteria. These agents are alternatives of natural origin to struggle drug-resistant bacteria, which pose a serious threat to humanity. Silver nanoparticles (AgNPs) have been proven to have good antimicrobial activity. Biosynthesis of AgNPs is accepted as a safer, lower cost, and more environmentally friendly method compared to other nanoparticle production methods. In this study, silver nanoparticles (eAgNPs) encapsulated with Thymus Vulgaris L. aqueous extract were successfully produced using the biosynthesis method. It is aimed to bring in the antiseptic, antimicrobial, and antioxidative properties of the thyme plant to AgNPs. The optimum plant extract and AgNO3 concentration that is required for eAgNP production were determined by UV-vis spectrophotometer analysis and green synthesis was carried out in line with the ratios found. The synthesized eAgNPs were characterized by UV-Vis spectral analysis, FT-IR, XRD analysis, and TEM analysis. The antimicrobial activity of eAgNPs was investigated using a disc diffusion method against E. coli and S. aureus. It has been confirmed that the encapsulation of biosynthesized eAgNPs with the plant extract was successfully carried out by TEM analysis and spherical-shaped biosynthesized nanoparticles had a size range of 6-70 nm. The presence of plant-derived phytochemicals surrounding eAgNPs was confirmed by FT-IR and the formation of AgNP was analyzed by XRD spectrum. Biosynthesized eAgNPs adsorbed into discs at a concentration of 5 mg/mL showed antimicrobial activity against E. coli and S. aureus with mean inhibition diameters of 20.5 mm and 23.2 mm, respectively. The results introduced that eco-friendly eAgNPs with strong antimicrobial activity can be prepared using Thymus Vulgaris L. plant extract and may create a significant potential in the field of biomaterials
In vitro assessment of Momordica charantia/Hypericum perforatum oils loaded PCL/Collagen fibers: Novel scaffold for tissue engineering
Full text linkThe research on tissue engineering applications has been progressing to manufacture ideal tissue scaffold biomaterials. In this study, a double-layered electrospun biofiber scaffold biomaterial including Polycaprolactone (PCL)/Collagen (COL) fibrous inner layer and PCL/ Momordica charantia (MC) and Hypericum perforatum (HP) oils fibrous outer layer was developed to manufacture a functional, novel tissue scaffold with the advantageous mechanical and biological properties. The main approach was to combine the natural perspective using medicinal oils with an engineering point of view to fabricate a potential functional scaffold for tissue engineering. Medicinal plants MC and HP are rich in functional oils and incorporation of them in a tissue scaffold will unveil their potential to augment both new tissue formation and wound healing. In this study, a novel double-layered scaffold prototype was fabricated using electrospinning technique with two PCL fiber layers, first is composed of collagen, and second is composed of oils extracted from medicinal plants. Initially, the composition of plant oils was analyzed. Thereafter the biofiber scaffold layers were fabricated and were evaluated in terms of morphology, physicochemistry, thermal and mechanical features, wettability, in vitro bio-degradability. Double-layered scaffold prototype was further analyzed in terms of in vitro biocompatibility and antibacterial effect. The medicinal oils blend provided antioxidant and antibacterial properties to the novel PCL/Oils layer. The results signify that inner PCL/COL layer exhibited advanced biodegradability of 8.5% compared to PCL and enhanced wettability with 11.7° contact angle. Strength of scaffold prototype was 5.98 N/mm2 thanks to the elastic PCL fibrous matrix. The double-layered functional biofiber scaffold enabled 92% viability after 72 h contact with fibroblast cells and furthermore provided feasible attachment sites for the cells. The functional scaffold prototype’s noteworthy mechanical, chemical, and biological features enable it to be suggested as a different novel biomaterial with the potential to be utilized in tissue engineering applications
Multi-Scale Mechanical Behavior of Liquid Elium® Based Thermoplastic Matrix Composites Reinforced with Different Fiber Types: Insights from Fiber–Matrix Adhesion Interactions
Full text linkKorean Fiber SocietyElium® liquid thermoplastic resin, with room-temperature curing and recyclability, enables large-scale production. However, limited research exists on the fiber–matrix interface, and understanding micro-scale interactions is key to influencing the composite’s macro-scale mechanical properties. This study investigates the interfacial adhesion of glass, carbon, basalt, and aramid fibers-reinforced liquid Elium® thermoplastic matrix composites at micro-, meso-, and macro-scales. Contact angle measurements show 53-56º for glass fibers, indicating superior wettability with the Elium® matrix, while carbon, aramid, and basalt fibers exhibit 58-62º, 73-74º, and 79-86º, respectively. Micro-bond tests demonstrate the highest load-carrying capacity in the interface between glass fibers and the matrix, with glass fibers carrying 11.4 more load than carbon fibers and 25.8 more than basalt fibers. Fiber bundle tests, including transverse and 45° fiber bundle tests, highlight the superior load-carrying performance of glass fibers, with all fiber types showing increased load-carrying capacities in the 45° tests. The micro-scale and meso-scale data obtained from micro-bond and fiber bundle tests corroborated the results of the macro-scale interlaminar shear stress (ILSS) tests, confirming the significant influence of the fiber–matrix interface on the mechanical integrity of the composites. The shear strength at the glass/Elium® interface was 47.54MPa, which was 8.5 higher than carbon, 20.3 higher than aramid, and 25.9 higher than basalt interfaces. These findings advance our understanding of the mechanical behavior and interfacial adhesion in thermoplastic matrix composites. They underscore the crucial role of the fiber/matrix interface in determining the mechanical properties of composites and offer insights into the compatibility of diverse fiber reinforcements with the innovative Elium® matrix. © The Author(s), under exclusive licence to the Korean Fiber Society 2024
Combined effect of fiber hybridization and matrix modification on mechanical properties of polymer composites
No full textPROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART L-JOURNAL OF MATERIALS-DESIGN AND APPLICATIONSGlass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites' tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC](S), [CGCGCG](S), and [G(6)C(6)] were manufactured. Fiber hybridization dramatically improved tensile strength between 51 and 76 compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10 and 16 concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5 and decreases by 7 for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70 for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis
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
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