1,721,305 research outputs found
Broad-spectrum antimicrobial coatings for food safety
No full textGuaranteeing food safety is a key aspect, from supply chain to processing of raw materials and product packaging. Surfaces are a notorious source of contamination as they can host microbiota, including human pathogens, that can potentially be transmitted to the food chain and be responsible of outbreaks of infective diseases in the population. In this scenario, we developed a coating that can easily be applied to a variety of materials and successfully deactivate viruses and bacteria
Determination of monolayer-protected gold nanoparticle ligand–shell morphology using NMR
No full textIt is accepted that the ligand shell morphology of nanoparticles coated with a monolayer of molecules can be partly responsible for important properties such as cell membrane penetration and wetting. When binary mixtures of molecules coat a nanoparticle, they can arrange randomly or separate into domains, for example, forming Janus, patchy or striped particles. To date, there is no straightforward method for the determination of such structures. Here we show that a combination of one-dimensional and two-dimensional NMR can be used to determine the ligand shell structure of a series of particles covered with aliphatic and aromatic ligands of varying composition. This approach is a powerful way to determine the ligand shell structure of patchy particles; it has the limitation of needing a whole series of compositions and ligands' combinations with NMR peaks well separated and whose shifts due to the surrounding environment can be large enough
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
Comparative STM studies of mixed ligand monolayers on gold nanoparticles in air and in 1-phenyloctane
No full textScanning tunnelling microscopy (STM) studies have found stripe-like domains on gold nanoparticles (NPs) coated with certain binary mixtures of ligand molecules. The majority of these NPs' properties have been investigated for particles in solvents. Yet, most STM studies are for NPs in a dry state. Images of the same particles in air and liquid have not been obtained yet. In this work, a judicious choice of ligand molecules led to NPs with close-to-ideal STM imaging conditions in air and in 1-phenyloctane (PO). Large datasets under both conditions were acquired and rapidly evaluated through power spectral density (PSD) analysis. The result is a quantitative comparison of stripe-like domains in air and PO on the same NPs. PSD analysis determines a characteristic length-scale for these domains of ~1.0 nm in air and in PO showing persistence of striped domains in these two media. A length scale of ~0.7 nm for homoligand NPs was found
Physical determinants of nanoparticle-mediated lipid membrane fusion
No full textA wide range of fundamental cellular activities rely on lipid membrane fusion. Membrane fusion processes can be mimicked by synthetic approaches to understand fusion mechanisms and develop novel drug delivery systems and therapeutic agents. Recently, membrane-embedded amphiphilic gold nanoparticles (AuNPs) have been employed as artificial fusogens to induce finely tuned membrane fusion in vitro. However, the physical determinants driving and regulating the fusion process mediated by AuNPs remain largely unexplored, thus limiting the application potential of this synthetic fusion system. Herein, we focus on unraveling the effect of the interplay between the curvature of the lipid membrane and the size of amphiphilic AuNPs during fusion events. We employed AuNPs with the same surface chemistry but different core diameters (similar to 2 nm and similar to 4 nm) interacting with phosphatidylcholine unilamellar vesicles of different membrane curvatures containing a biologically relevant percentage of cholesterol. Based on a combination of fluorescence spectroscopy assays, dissipative quartz microbalance, and molecular dynamics simulations, our findings reveal that small AuNPs promote vesicle fusion regardless of the membrane curvature. In contrast, large AuNPs do not exhibit fusogenic properties with low curvature membranes and can induce fusion events only with significantly curved membranes. Large NPs impede the progression from the stalk state to the hemifused state via steric hindrance, an effect that is only partially compensated by the membrane curvature. These results offer novel insights into the role of AuNP core size and membrane curvature in mediating the interaction between the vesicles during fusion and highlight how understanding these physical determinants has broad implications in fully exploiting the application potential of novel synthetic fusion approaches.SUNMI
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
- …
