1,720,964 research outputs found
Multifunctional bioinspired surfaces for different host responses
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Advances in the physical and chemical characterization of tanned leather
No full textThe tanning process significantly alters the physical and chemical properties of leather, making it durable and versatile for various applications. A comprehensive understanding of these transformations requires advanced characterization techniques to analyze the surface, structure, and chemical composition of tanned leather. This review provides a critical overview of the state-of-the-art methods employed to characterize tanned leather, including spectroscopy, microscopy, thermal analysis, and mechanical testing, as well as their applicability to investigate processing, quality control, characterization, and preservation of leather. Moreover, particular attention is given to innovative approaches that offer deeper insights into the structural and chemical modifications induced by tanning agents, processing and their potentialities in a broad-spectrum characterization of leather. Additionally, we discuss the applicability, advantages, and limitations of these techniques, highlighting their role in advancing leather science and enabling the development of more sustainable leather processing techniques. This work aims to serve as a reference for researchers and industry professionals, guiding the selection of appropriate characterization methods and fostering innovation in leather production and quality control
Nano-topography and functionalization with the synthetic peptoid GN2-Npm9 as a strategy for antibacterial and biocompatible titanium implants
Full text linkIn recent years, antimicrobial peptides (AMPs) have attracted great interest in scientific research, especially for biomedical applications such as drug delivery and orthopedic applications. Since they are readily degradable in the physiological environment, scientific research has recently been trying to make AMPs more stable. Peptoids are synthetic N-substituted glycine oligomers that mimic the structure of peptides. They have a structure that does not allow proteolytic degradation, which makes them more stable while maintaining microbial activity. This structure also brings many advantages to the molecule, such as greater diversity and specificity, making it more suitable for biological applications. For the first time, a synthesized peptoid (GN2-Npm9) was used to functionalize a nanometric chemically pre-treated (CT) titanium surface for bone-contact implant applications. A preliminary characterization of the functionalized surfaces was performed using the contact angle measurements and zeta potential titration curves. These preliminary analyses confirmed the presence of the peptoid and its adsorption on CT. The functionalized surface had a hydrophilic behaviour (contact angle = 30°) but the hydrophobic tryptophan-like residues were also exposed. An electrostatic interaction between the lysine residue of GN2-Npm9 and the surface allowed a chemisorption mechanism. The biological characterization of the CT_GN2-Nmp9 surfaces demonstrated the ability to prevent surface colonization and biofilm formation by the pathogens Escherichia coli and Staphylococcus epidermidis thus showing a broad-range activity. The cytocompatibility was confirmed by human mesenchymal stem cells. Finally, a bacteria-cells co-culture model was applied to demonstrate the selective bioactivity of the CT_GN2-Nmp9 surface that was able to preserve colonizing cells adhered to the device surface from bacterial infection
Biofilm prevention and quorum sensing interference via surface-bound peptoid
Full text linkThe emergence of antibiotic resistance has ushered in a post-antibiotic era, highlighting the urgent need for alternative, cytocompatible antimicrobial strategies. Among these, antimicrobial peptides (AMPs) are promising to overcome antibacterial resistance being at the same time cytocompatible, but they are limited by fast enzymatic degradation. Peptoids are synthetic and bio-mimetic biomolecules that overcome the limitations of AMPs with resistance to proteolytic degradation. This study examined the antibacterial and cytocompatible peptoid GN2-Npm9 to reduce the risk of infection in titanium implants. Ti6Al4V samples were chemically pre-treated (CT) to favour osteointegration and functionalization. The zeta potential titration curves evidenced a mechanism of electrostatic attraction between the peptoid and CT substrate on the functionalized samples (CT_GN2-Npm9). XPS analysis and fluorescence microscopy confirmed the presence of the peptoid on CT_GN2-Npm9 and evidenced a uniform distribution. The peptoid was released in water with slow kinetics for at least 9 days (HPLC analyses). CT and CT_GN2-Npm9 specimens were subjected to biological assays against oral plaque collected from patients affected by periodontitis, showing a direct biofilm reduction of 60 % in comparison to CT and a specific effect towards pathogens as evidenced by proteomics studies. For investigating the mechanism of biofilm prevention, a culture of Pseudomonas aeruginosa was performed by conditioning the culture medium with the supernatant from the plaque test. It was observed that the biofilm of P. aeruginosa was significantly reduced due to a peptoid’s indirect effect demonstrated by the expression of genes involved in the quorum sensing network and elastase gene (lasB) that resulted in down-regulation only by the supernatants from CT-GN2-Npm9 specimens
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
Conferring Antioxidant Activity to an Antibacterial and Bioactive Titanium Surface through the Grafting of a Natural Extract
Full text linkThe main unmet medical need of bone implants is multifunctional activity, including their ability to induce rapid and physiological osseointegration, counteract bacterial biofilm formation, and prevent in situ chronic inflammation at the same time. This research starts from an already developed c.p. titanium surface with proven bioactive (in vitro hydroxyl apatite precipitation) and antibacterial activities, due to a calcium titanate layer with nano- and micro-scale roughness and loaded with iodine ions. Here, antioxidant ability was added to prevent chronic inflammation by grafting polyphenols of a green tea extract onto the surface, without compromising the other functionalities of the surface. The surface was characterized before and after functionalization through XPS analysis, zeta potential titrations, ion release measurements, in vitro bioactivity tests, SEM and fluorescence microscopy, and Folin–Ciocalteu and biological tests. The presence of grafted polyphenols as a homogeneous layer was proven. The grafted polyphenols maintained their antioxidant ability and were anchored to the surface through the linking action of Ca2+ ions added to the functionalizing solution. Iodine ion release, cytocompatibility towards human mesenchymal stem cells (hMSC), and antibacterial activity were maintained even after functionalization. The antioxidant ability of the functionalized surface was effective in preserving hMSC viability in a chemically induced pro-inflammatory environment, thus showing a scavenger activity towards toxic active species responsible for inflammation
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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