1,721,073 research outputs found
Solvent-Assisted Lipid Bilayer Formation on Au Surfaces: Effect of Lipid Concentration on Solid-Supported Membrane Formation
No full textSolvent-assisted lipid bilayer (SALB) formation is emerged as a versatile approach in forming supported lipid membranes (SLBs) on metal surfaces, interesting platforms for transducing a biological signal to an electrical readout where vesicle rupture is not straightforward. Herein, the effect of the lipid concentration in the organic solvent, a key parameter controlling SALB, is addressed in the low and high concentration limits of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipid on a Au surface. Quartz crystal microbalance with dissipation (QCM-D) responses are correlated with atomic force microscopy (AFM) topographic and nanomechanical measurements. Upon SALB completion at both concentrations, QCM-D and AFM topographical characterization suggest the formation of thin, although incomplete, lipid layers at the Au–liquid interface, with frequency and dissipation plateau values departing from well-established homogeneous SLB responses. Nanomechanical analysis reveals the presence of mostly monolayers at low concentration due to lack of lipid material, while at high concentration excess of lipid material leads to the coexistence of diverse structures. Their formation stems from the SALB formation mechanism, based on lyotropic transformations upon solvent exchange, which differs from customarily vesicle rupture. Such mechanism leads to peculiar two-step features in approach force curves on SLBs pointing toward a decoupling in bilayer leaflets when supported.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Quartz Crystal Microbalance With Dissipation Monitoring: A Versatile Tool to Monitor Phase Transitions in Biomimetic Membranes
No full textSolid-supported lipid membranes are popular models that connect biological and artificial materials used in bio-technological applications. Controlling the lipid organization and the related functions of these model systems entails understanding and characterizing their phase behavior. Quartz crystal microbalance with dissipation monitoring (QCM-D) is an acoustic-based surface-sensitive technique which is widely used in bio-interfacial science of solid-supported lipid membranes. Its sensitivity to mass and energy dissipation changes at the solid-lipid layer-liquid interface allows the detection of phase transformations of solid-supported membrane geometries. In this perspective, we highlight this valuable feature and its related methodology, review current advances and briefly discuss future perspectives. Furthermore, a specific example is also provided on the ability of QCM-D to detect changes in lipid organization of cholesterol containing solid-supported lipid vesicle layers (SVLs) upon the addition of aspirin.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
In Operando Atomic Force Microscopy Imaging of Electrochemical Interfaces: A Short Perspective
No full textElectrochemical interfaces are at the core of many important current applications, from corrosion and biophysics to electrocatalytic and battery interfaces. Further understanding in the processes taking place at these interfaces is often linked to better observation techniques. In situ or in operando imaging and characterization of the electrochemical interface helps improve our understanding of structural sequences and kinetics of complex processes. Atomic force microscopy (AFM) offers a unique combination to monitor surface morphology and mechanical properties at micro- and nanoscale surfaces and solid–electrolyte interfaces. Two examples are given where the application of AFM during electrochemical processes is clearly useful. Organic inhibitors and their behavior play an important role in corrosion mitigation and the influence of thiol monolayers on dealloying is reported: Zinc films find application for coatings or Zn batteries and an in situ electrodeposition study is shortly described. With the ongoing improvement of computational simulations, the broadening of spatiotemporal scales possible with AFM imaging and its combination with mechanical information points in a prospective future for in operando AFM.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Stability of supported hybrid lipid bilayers on chemically and topographically-modified surfaces
No full textHybrid lipid bilayers are a particular case of supported lipid bilayers with the two monolayer leaflets composed by different types of molecules. These nanostructures can be produced in a well-controlled array fashion and are suitable for the study of biomembrane-related phenomena via electrochemical or plasmonic sensing. Understanding how the underlying solid surface affects the supported membrane formation and organization is necessary for the potential use of these hybrid platforms in applications for which surfaces are not flat and topographically complex. Here we assess the role of lipid phase, substrate surface energy and topography on the formation and stability of hybrid supported membranes from vesicle precursors using complementary surfacesensitive techniques, namely quartz crystal microbalance with dissipation and atomic force microscopy. The stability of hybrid bilayers against thermal and osmotic changes is evaluated and compared to standard supported lipid bilayers formed onto hydrophilic SiO2. Force spectroscopy measurements reveal an overall weaker lateral organization of hybrid membranes as a result of the underlying self-assembled monolayer being not optimally organized. Hybrid bilayers display a decoupled behavior between the two leaflets when vertically compressed at constant speed. On microcontact printed Au surfaces, hybrid bilayers were formed over printed patches, while surprisingly, supported lipid bilayers were observed on non-patterned Au regions suggesting a non-trivial self-assembled monolayer reorganization when in aqueous environment.P.L.P. acknowledges MIS and HTMSoft projects 40003040 and 40008129 by ‘Fonds de la Recherche Scientifique’ (FNRS). A.V.R. and F. U.R. thank Prof. Andreas Terfort, Goethe-Universit¨ at Frankfurt for providing PDMS stamps and finantial support from FWO Odysseus Program under G0D0115N Project
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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