1,720,958 research outputs found
A novel sensitive coherent Raman imaging method for cellular imaging of photodynamic agents
No full textLabel free imaging techniques are becoming increasingly popular, with coherent Raman techniques among those leading the way. A shortcoming of coherent Raman techniques is that they have a high limit of detection, being unable to detect low concentrations like those found within cells for certain components. A few enhancement techniques for coherent Raman methodologies exist however these are underdeveloped in the literature. Here a resonance coherent Raman technique will be developed and applied. Resonance Raman is a long established Raman enhancement technique that uses electronic transitions to enhance the signal. Coherent resonance Raman was established over 45 years ago and since then very little biological imaging has been carried out with this technique. In this work a pre-resonance enhanced coherent anti-Stokes Raman scattering (CARS) methodology was developed and optimised. Multiple photodynamic agents with different absorption properties were analysed. Specifically, these were, protoporphyrin IX (PPIX), indocyanine green (ICG) and rhodamine 800 (Rh800). It was discovered that Rh800 and ICG showed pre-resonance enhancement. An improvement in the limit of detection of an order of magnitude was observed for ICG and Rh800. When applied to cellular detection it shows great promise for the robust detection of ICG and Rh800 within cells. Pre-resonance imaging of Rh800 allowed mitochondria to be imaged and mapping of bound water within cells was possible. The results for Rh800 showed a better signal to noise ratio. Using the knowledge gained about pre-resonance CARS enhancement, a further study was conducted to see if pre-resonance enhancement could be applied to a hyperspectral CARS imaging system using the spectral-focussing technique. A home built setup using a NKT-1050-NEG1 fibre was used which provided both broadband pump and Stoke pulses. The popular dyes Methylene blue and Nile blue were selected for use in this study as their absorption falls within the calculated ideal pre-resonance enhancement region. Cellular imaging of these compounds was successful. Overall this work demonstrates a step forward for CARS imaging, where it is getting closer to fluorescence spectroscopy in terms of limit of detection. Although currently it has only been shown with dyes, in principle, pre-resonance and resonance CARS could be applied to autofluorophores in biological cells. The additional advantages over fluorescence, such as better multiplexing with a greater number of different dyes, could see this technique being used in various applications going forward
Experimental data supporting the University of Southampton Doctoral Thesis "A novel sensitive coherent Raman imaging method for cellular imaging of photodynamic agents"
No full textThis dataset is supporting the University of Southampton Doctoral Thesis "A novel sensitive coherent Raman imaging method for cellular imaging of photodynamic agent</span
Selective imaging of microplastic and organic particles in flow by multimodal coherent anti-Stokes Raman scattering and two-photon excited autofluorescence analysis
No full textMicroplastic pollution is an urgent global issue. While spectroscopic techniques have been widely used for identification of plastics collected from aquatic environments, these techniques are often labour-intensive and time-consuming due to sample collection, preparation and long measurement times. In this study, a method for two-dimensional detection and classification of flowing microplastic and organic particles with high spatial and temporal resolutions has been proposed based on simultaneous detection of coherent anti-Stokes Raman scattering (CARS) and two-photon excited autofluorescence (TPEAF) signals. Poly(methyl methacrylate) (PMMA), polystyrene (PS), and low-density polyethylene (LDPE) particles with the size of several tens to hundreds of µm were selectively detected in flow with an average velocity of 4.17 mm/s by CARS line scanning. With the same velocity of flow, flowing PMMA and alga particles were measured using a multimodal system of CARS and TPEAF signals. The average intensity of both PMMA and alga particles in the CARS signals at the frequency of 2940 cm−1 were higher than the background level, while only algae emit TPEAF signals. Therefore, classification of PMMA and alga particles in flow has been successfully performed by simultaneous detection of CARS and TPEAF signals. With the proposed method, monitoring of microplastics in continuous water flow without collection or extraction is possible, which is game-changing for current sampling-based microplastic analysis
Dataset for: Widely-tunable synchronisation-free picosecond laser source for multimodal CARS, SHG and two-photon microscopy
No full textThis dataset supports the publication: Xu, D, Price, J, Xu, L & Richardson, 'Widely-tunable synchronisation-free picosecond laser source for multimodal CARS, SHG and two-photon microscopy', Biomedical Optics Express. https://doi.org/10.1364/BOE.411620</span
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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