1,720,955 research outputs found
Swelling behavior of strongly anionic hydrogels in polymer solutions
Get PDFAkrilamid (AAm) ve N-izopropilakrilamid’in (NIPA), farklı oranlarda 2-akrilamido-2-metilpropansulfonik asit sodyum tuzu (AMPS) ile serbest radikal çapraz bağlanma kopolimerizasyonundan anyonik hidrojeller sentezlendi. Jellerin %10’dan 100’e kadar değişen hacim oranlarında poli(etilenglikol)(PEG) içeren sulu çözeltiler içersindeki şişme davranışları incelendi. Deneysel sonuçların teori ile açıklanması için jellerin su ve saf PEG eriyiği içersindeki şişme oranlarından yararlanarak polimer ağyapı-lineer polimer-çözücüden meydana gelen ve sistemi karakterize eden parametreler hesaplandı ve Flory-Huggins eşitliği yardımıyla sistemin teorik şişme oranları elde edildi. Teorik ve deneysel şişme oranlarının uyum içersinde olduğu görüldü, jellerin PEG çözeltileri içersindeki şişme davranışları açıklandı. Anahtar Kelimeler: Anyonik hidrojeller, Flory-Huggins eşitliği, serbest radikal çapraz bağlanma kopolimerizasyonu, şişme oranları, şişme davranışları.Hydrogels are materials show phase transition by swelling depending on their chemical structure, solvent, pH, temperature, light and electric field etc. In the literature many studies have been published on the swelling behavior of hydrogels in low molecular weight solvents and solvent mixtures. In contrast, a few number of investigations have been reported on the swelling behavior of hydrogels in polymer solutions. In this study of which purpose is determination of swelling behavior of neutral and ionic hydogels in linear polymer solutions, the neutral and ionic poly(acrylamide) (PAAm) and poly(N-isopropylacrylamide) (PNIPA) gels and poly(ethyleneglycole) (PEG) with different molecular weights were preferred as hydrogels and linear polymer, respectively. The effects of ionic group content, PEG concentration of outer aqueous PEG solution and molecular weight of PEG on the swelling behavior of hydrogels in PEG solutions are investigated. In addition of these effects, for PNIPA gels, the temperature effect on the swelling behavior was also researched. On the other hand, the theoretical calculations were performed to these ternary systems (polymer network-linear polymer-solvent) and tried to predict their swelling behavior by using Flory-Rehner theory. Finding from experiments were compared with the theoretical results and the differences between theory and experimental were interpreted. Keywords: Flory-Rehner theory, hydrogel, swelling behavior
Swelling Behavior Of Acrylamide-based Anionic Hydrogels In Polymer Solutions
No full textTez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2003Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2003İyonik ve iyonik olmayan hidrojellerin, lineer polimer çözeltileri içindeki şişme davranışlarını açıklamak için gerçekleştirilen bu çalışmada, hidrojel olarak iyonik ve iyonik olmayan poli(akrilamid) (PAAm) ve poli(N-izopropilakrilamid) (PNIPA) jelleri, lineer polimer olarak da farklı molekül ağırlığına sahip bir seri poli(etilenglikol) (PEG) seçildi. Sulu PEG çözeltileri içersine konulan iyonik ve iyonik olmayan PAAm jellerinin iyonik grup miktarının, dış çözeltideki PEG konsantrasyonunun ve PEG’in molekül ağırlığının şişmeye olan etkisi incelendi. Diğer taraftan PNIPA jellerinde yukarıda belirtilen etkenler ile birlikte sıcaklığın şişmeye olan etkisi de araştırıldı. Diğer taraftan bu çalışmada incelenen polimer ağyapı-lineer polimer ve çözücüden meydana gelen tersiyer sistemler için, Flory-Rehner teorisinden yararlanarak jelin şişme davranışı teorik olarak hesaplandı, deneysel sonuçlarla karşılaştırılıp, ortaya çıkan farkların nedenleri açıklandı.In this study, of which purpose is determination of the swelling behavior of neutral and ionic hydrogels in lineer polymer solutions, the neutral and ionic poly(acrylamide) (PAAm)and poly(N-isopropylacrylamide) (PNIPA) gels and poly(ethyleneglycol) (PEG) with different molecular weights were preferred as hydrogels and linear polymer, respectively. The effects of ionic group content, PEG concentration of outer aqueous PEG solution and molecular weight of PEG on the swelling behavior of hydrogels in PEG solutions are investigated. In addition to these effects, for PNIPA gels, the temperature effect on the swelling behavior was also researched. The effect of temperature on the swelling of PNIPA gels was also investigated together with the ionic group content and PEG concentration effects. On the other hand, the theoretical calculations were performed to these ternary systems (polymer network-linear polymer-solvent) and tried to predict their swelling behavior by using Flory-Rehner theory. Findings from experiments were compared with the theoretical results and the differences between theory and experiment were interpreted.DoktoraPh
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
