1,720,956 research outputs found
Two-photon excitated fluorescence microscope
No full textThe microscope (100) has a laser source (1) suitable for emitting a light beam. An optical arrangement (3,5,6) receives light beam from the laser source and shapes the light beam so that the light beam is collimated in a first transverse direction (x) perpendicular to a propagation direction (z) of the light beam at an output of microscope. The light beam is focused in a second transverse direction (y) perpendicular to the first transverse direction and to propagation direction to form a line parallel to the first transverse direction
Fast calculation of the line-spread-function by transversal directions decoupling
No full textWe propose a simplified method to calculate the optical spread function of a paradigmatic system constituted by a pupil-lens with a line-shaped illumination ('line-spread-function'). Our approach is based on decoupling the two transversal directions of the beam and treating the propagation by means of the Fourier optics formalism. This requires simpler calculations with respect to the more usual Bessel-function-based method. The model is discussed and compared with standard calculation methods by carrying out computer simulations. The proposed approach is found to be much faster than the Bessel-function-based one (CPU time. less than or similar to 5% of the standard method), while the results of the two methods present a very good mutual agreement
Lipoprotein (a) Internalization by RAW 264.7 Cells is Associated with Morphological Changes and Accumulation of Lipids Detectable by Two-photon Scanning Microscopy
No full textLipoprotein (a) [Lp(a)] is an independent cardiovascular risk factor and its pathogenic mechanism
is not completely clear. Lp(a) has been detected in atherosclerotic plaques and macrophages are
one of the major cell types involved in atherogenesis. In order to characterize internalization of
Lp(a) by RAW 264.7 cells, an established model of mouse macrophages, cells were treated with Lp(a) samples purified from plasma by affinity chromatography, and evaluated by western blotting.
By 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, a tetrazolium salt, assay, Lp(a)
was found to be non-cytotoxic for the cells at all the concentrations tested (0.0165-1.65 mg/ml). An
ELISA performed on the lysate of Lp(a)-treated cells allowed to identify the highest intracellular
accumulation of Lp(a) at 72 h treatment. Already at 24 h, however, important morphological
alterations were detected upon Oil red and Nile red staining. A three-dimensional reconstruction
obtained by two-photon scanning microscopy of the intracellular distribution of Nile red stained
structures in treated cells shows preferential uptake of lipids in extra-nuclear regions. These data
are useful to clarify the temporal and spacial aspects of intracellular accumulation of Lp(a) in RAW
264.7 cells and pose new bases for future studies on intracellular Lp(a) accumulation
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
A novel technique for the measurement of two photon absorption spectra of dyes for nonlinear fluorescence microscopy
No full textWe present a novel technique for the measurement of two-photon absorption spectra. A line-shaped excitation beam generates a strong induced fluorescence signal that can be easily detected by an image sensor
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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