1,721,033 research outputs found
Influence of synapsin I on synaptic vesicles: An analysis by force-volume mode of the atomic force microscope and dynamic light scattering
No full textAbstractSynaptic vesicles (SVs) are small neuronal organelles that store neurotransmitters and release them by exocytosis into the synaptic cleft for signal transmission between nerve cells. They consist of a highly curved membrane composed of different lipids containing several proteins with specific functions. A family of abundant extrinsic SV proteins, the synapsins, interact with SV proteins and phospholipids and play an important role in the regulation of SV trafficking and stability. We investigated the interactions of one these proteins with the SV membrane using atomic force microscope and dynamic light scattering. We examined SVs isolated from rat forebrain both under native conditions and after depletion of endogenous synapsin I. We used the atomic force microscope in two modes: imaging mode for characterizing the shape and size of SVs, and force-volume mode for characterizing their stiffness. Synapsin-depleted SVs were larger in size and showed a higher tendency to aggregate than native vesicles, although their stiffness was not significantly different. Because synapsins are believed to cross-link SV to each other and to the actin cytoskeleton, we also measured the SV aggregation kinetics induced by synapsin I by dynamic light scattering and atomic force microscopy and found that the addition of synapsin I promotes a rapid aggregation of SVs. The data indicate that synapsin directly affects SV stability and aggregation state and support the physiological role of synapsins in the assembly and regulation of SV pools within nerve terminals
Imaging and elasticity measurements of the sarcolemma of fully differentiated skeletal muscle fibres.
No full textThis study aimed to describe the three-dimensional structure and the elastic properties
of the sarcolemma of adult, fully differentiated, skeletal muscle fibres combining Atomic
Force Microscopy (AFM) and optical microscopy. Single fibres were enzymatically dissociated from
Flexor Digitorum Brevis of adult mice and were maintained in culture up to 3 weeks. On the sixth
day after dissociation, the upper surface of intact fibres, either alive in solution or fixed and kept in
solution or fixed and exposed in air, was analysed with AFM. The most prominent features in AFM
images were periodic transversal foldings with an interval that corresponded to the sarcomere
length. More detailed analysis of the topography profile showed that the depth in the folding
decreased with increasing sarcomere length and that the crests of the foldings corresponded to the
Z-lines. Minor periodic structures could be detected in the valleys between the major foldings.
AFM images also showed deep depressions on the sarcolemma likely corresponding to openings of
T tubules and caveolae. Two-dimensional elasticity maps were obtained using AFM as an indenter
and showed that the crests of the transversal foldings correspond to higher stiffness regions. This
study provides the first complete three-dimensional topography and mechanical characterization
of intact, living skeletal muscle fibres and might form the basis for further investigations aimed to
compare healthy and dystrophic muscles
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
Effect of Hypergravity on the Dynamics of a Sessile Droplet on a flat solid surface
No full textWe present the experimental results on the behaviour of static and dynamic sessile drops under hypergravity (up to 19g), obtained at ESA Large Diameter Centrifuge (Noordwijk, The Netherlands). The goal of the experiment is to study the effect of the gravity on the shape of a static sessile drop and on the dynamic advancing contact angle in a growing sessile drop.
Seven surfaces with micro- and nano- coatings are used, providing different contact angles (CA) and different contact angle hysteresis (CAH). Distilled deionized water is used as the working liquid. The main variable parameters are: gravity (1 - 19g); drop volume (1μl - 1ml); liquid flow rate (0.0625 - 64 ml/min); CA (30 - 130o). The drop shape is visualized from the side with the help of the Shadow Technique with a resolution of 10 μm/pixel.
The results obtained during the experimental campaign show that for water sessile drops on hydrophilic surface, the advancing contact angle in the increased gravity environment is larger than that of the advancing CA in 1g (for example 10o for a PMMA-coated surface) for the same three-phase contact line advancing rates, while for water sessile drops on hydrophobic Teflon-coated surface (120° on-ground) the advancing contact angle decreases by 4°
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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