1,720,967 research outputs found
Structure of polymer and particle aggregates in hydrogel composites
No full textKnowledge of the structure of a biomaterial is usually vital to control its function. This article provides a structural characterization of a hyaluronan scaffold that has demonstrated good biocompatibility and is used to induce bone regeneration. Hyaluronan hydrogels are appealing materials that can function as a matrix to incorporate both organic and inorganic substances to enhance tissue growth. Because of the intrinsic properties of this swollen matrix, one needs a very sensitive technique that can be applied in situ to determine the organization of the polymers in a gel. Small-angle neutron scattering is used to determine the characteristics of the inhomogeneous structure of the hydrogel both with and without added particles. The results are interpreted using models of structure with two length scales that are beyond the traditional picture of homogeneous gels. The observed structure and the dimensions can explain the previously reported rheological properties of gels containing different amount of polymers. Hydroxyapatite nanoparticles added to the gel are frozen in the gel matrix. We are able to determine the distribution and shape of these particles as they aggregate around the polymer chains. We have also concluded, in this case, that the particle structure is concentration independent. Information about the nanostructure for an applicable biomaterial guides the formulation, preparation, and use that should lead to further understanding of its exploitation. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 201
Relating the Bulk and Interface Structure of Hyaluronan to Physical Properties of Future Biomaterials
No full textThis dissertation describes a structural investigation of hyaluronan (HA) with neutron scattering techniques. HA is a natural biopolymer and one of the major components of the extracellular matrix, synovial fluid, and vitreous humor. It is used in several biomedical applications like tissue engineering, drug delivery, and treatment of osteoarthritis. Although HA is extensively studied, very little is known about its three-dimensional conformation and how it interacts with ions and other molecules. The study aims to understand the bulk structure of a cross-linked HA hydrogel, as well as the conformational arrangement of HA at solid-liquid interfaces. In addition, the structural changes of HA are investigated by simulation of physiological environments, such as changes in ions, interactions with nanoparticles, and proteins etc. Small-angle neutron scattering and neutron reflectivity are the two main techniques applied to investigate the nanostructure of hyaluronan in its original, hydrated state. The present study on hydrogels shows that they possess inhomogeneous structures best described with two correlation lengths, one of the order of a few nanometers and the other in the order of few hundred nanometers. These gels are made up of dense polymer-rich clusters linked to each other. The polymer concentration and mixing governs the connectivity between these clusters, which in turn determines the viscoelastic properties of the gels. Surface-tethered HA at a solid-liquid interface is best described with a smooth varying density profile. The shape of this profile depends on the immobilization chemistry, the deposition protocol, and the ionic interactions. HA could be suitably modified to enhance adherence to metal surfaces, as well as incorporation of proteins like growth factors with tunable release properties. This could be exploited for surface coating of implants with bioactive molecules. The knowledge gained from this work would significantly help to develop future biomaterials and surface coatings of implants and biomedical devices
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
Kvinnors upplevelser efter genomförd mastektomi vid bröstcancer : En litteraturstudie
No full textBakgrund: Mastektomi är det vanligaste kirurgiska behandlingsformen vid bröstcancer och innebär att bröstkörtelvävnad avlägsnas. Allt fler yngre kvinnor diagnostiseras med bröstcancer. Detta kan komma att påverka kvinnans identitet genom kroppsuppfattning, självkänsla, sexuella samliv samt relationer. Det är operationssjuksköterskans intresse att förstå vad den individuella patienten upplever, för att efter bästa förmåga kunna genomföra en god perioperativ omvårdnad. Syfte: Studiens syfte var att beskriva kvinnors upplevelser efter genomförd mastektomi vid bröstcancer. Metod: En systematisk litteraturstudie där nitton vetenskapliga artiklar med kvalitativ design från databaserna Cinahl, PsychINFO och PubMed har analyserats med hjälp av Bettany-Saltikov och McSherry analysmetod. Resultat: I analysprocessen framkom det två kategorier, Den nya kroppen samt Den förlorade kroppen. Varav varje kategori innefattade fyra subkategorier. Den nya kroppen beskriver skapandet av en ny identitet genom acceptans och bearbetning av den förlorade kroppen. Genom dessa kategorier växte det fram ett tema, Vägen till det nya livet. Slutsats: Kvinnor upplever positiva och negativa känslor samt psykiska och fysiska förändringar efter en mastektomi. Självförtroendet och kroppsbilden kan förändras så att kvinnligheten och sexualiteten utmanas. Varje kvinnas upplevelse är unik och avspeglar varje kvinnas livsvärld och levda kropp. Operationssjuksköterskan behöver därför skapa en trygghet under den perioperativa vården.Bakgrund: Mastektomi är den vanligaste kirurgiska behandlingen för bröstcancer och innebär avlägsnande av bröstkörtelvävnad. Allt fler yngre kvinnor diagnostiseras med bröstcancer. Detta kan påverka kvinnans identitet genom kroppsuppfattning, självkänsla, sexuell intimitet och relationer. Det är kirurgsjuksköterskans intresse att förstå vad den enskilda patienten upplever, att kunna utföra god perioperativ vård. Syfte: Syftet med studien var att beskriva kvinnors erfarenheter efter att ha utfört mastektomi relaterad till bröstcancer. Metod: En systematisk litteraturstudie där nitton vetenskapliga artiklar med kvalitativ design från databaserna Cinahl, PsychINFO och PubMed har analyserats med analysmetoden Bettany-Saltikov och McSherry. Resultat: Under analysprocessen uppstod två kategorier, Den nya kroppen och den förlorade kroppen. Varje kategori innehöll fyra underkategorier. Det nya organet beskriver skapandet av en ny identitet genom acceptans och bearbetning av den förlorade kroppen. Genom dessa kategorier framkom ett tema, vägen till det nya livet. Slutsats: Kvinnor upplever positiva och negativa känslor samt mentala och fysiska förändringar efter en mastektomi. Självförtroende och kroppsuppfattning kan förändras på ett sätt där kvinnlighet och sexualitet utmanas. Varje kvinnas erfarenhet är unik och återspeglar varje kvinnas livsvärld och levande kropp. Därför måste den kirurgiska sjuksköterskan skapa en känsla av säkerhet under den perioperative vården
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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