1,721,115 research outputs found
Imaging of highly scattering media by spatially modulated pulsed light
No full textThe use of spatially modulated light is finding application in biomedical optics having potential use in imaging and tomography of tissues and small animals. We describe the time-resolved propagation of spatial frequencies in turbid media. We present a set-up based on a ps laser source, spatially modulated by a micro-mirror device and a time-gated intensifier. We discuss the relevant information content that can be useful for imaging of tissues, in terms of the spatial Fourier components of the propagating pulse. We demonstrate that high spatial frequencies appear in the early time-gated signal whereas low frequencies persist for longer times and that the combined use of high spatial frequencies and early time gates can be used to improve the resolution in imaging
Temporal propagation of spatial information in turbid media
No full textThe time-resolved propagation of spatial frequencies in turbid media is investigated. We discuss the relevant
information content in terms of the spatial Fourier component of the propagating pulse. We present a
method to record and analyze the time-gated spatial frequency response of highly scattering media. We dem-
onstrate that high spatial frequency information appears in the early time-gated signal, whereas low fre-
quencies persist for longer times
Structured illumination and time gated detection for diffuse optical imaging
No full textStructured illumination and time gated detection for diffuse optical imagin
Northward field excursions in Saturn's magnetotail and their relationship to magnetospheric periodicities
Full text linkWe present results from an investigation of Cassini encounters with Saturn's magnetotail current sheet, using magnetic field and plasma data. In the first of two intervals shown, small periodic changes in the north-south component of the magnetic field are matched by periodic density enhancements associated with the plasma sheet center. In the second interval, a large plasmoid signature is observed set against a background of small-scale current sheet motions. We interpret the quasi-periodic small field deflections and density enhancements as large-scale wave-like motion of the current sheet. We stress that plasmoid signatures are of a clearly different character and occur much less frequently. Citation: Jackman, C. M., C. S. Arridge, H. J. McAndrews, M. G. Henderson, and R. J. Wilson (2009), Northward field excursions in Saturn's magnetotail and their relationship to magnetospheric periodicities, Geophys. Res. Lett., 36, L16101, doi:10.1029/2009GL039149
Supercorotating return flow from reconnection in Saturn's magnetotail
Full text linkDetecting plasma dynamics in Saturn's magnetosphere is essential for understanding energy flow through the system. It has been proposed that both the Dungey and Vasyliunas cycles operate at Saturn, and the competition between these cycles has been debated. We examine data taken by the Cassini spacecraft in Saturn's post-dawn magnetosphere, similar to 17.5 Saturn radii from the planet, and identify an example of return flow from magnetotail reconnection. The flow included water group ions and had elevated ion temperatures (of order 1 keV), consistent with Vasyliunas cycle return flow. The flow was also supercorotating (similar to 200 km s(-1), similar to 120% of corotation), which is highly atypical of Saturn's outer magnetosphere. Our results suggest that return flows are time-variable, and our results concerning Dungey cycle return flows are inconclusive. We propose that supercorotating flows in Saturn's dawn magnetosphere strongly influence the current system that is responsible for the planet's main auroral emission. Citation: Masters, A., M. F. Thomsen, S. V. Badman, C. S. Arridge, D. T. Young, A. J. Coates, and M. K. Dougherty (2011), Supercorotating return flow from reconnection in Saturn's magnetotail, Geophys. Res. Lett., 38, L03103, doi: 10.1029/2010GL046149
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
Novel approaches based on structured light for fast diffuse optical tomography
No full textDiffuse optical tomography (DOT) and Fluorescence mediated tomography (FMT) are powerful in-vivo optical imaging techniques but they are affected by long acquisition and computational times. Recently, the use of structured light has been proposed in order to reduce the acquisition time and also the computational time of the inverse problem. Additionally, it has been proposed to compress the measured data set to reduce the reconstruction time. Here we present our experimental approach, describing the instrument for structured illumination and wide field detection and we discuss the advantages to use a finite elements based approach. Then, we introduce the use of spatial wavelets. Our method is based on the projection of a small number of wavelet patterns (Haar and Battle-Lemarie wavelets). The detected images are wavelet transformed and the information content is compressed to achieve fast 3D reconstruction. Experimental results are presented, showing fast reconstruction of complex absorbing/fluorescent objects in thick diffusive samples. Implications for fast small animal imaging are discussed
- …
