1,721,013 research outputs found
Microscopic Views of the Soil at the Phoenix Landing Site
No full textThe Optical Microscope (OM) onboard Phoenix (PHX) has returned high-resolution images (4 μm/px) of Martian soil collected on magnetic and non-magnetic substrates. Different types of material can be distinguished: (a) Orange sub-micron dust that is similar to classic Martian air-fall dust. (b) Dark (almost black) particles: 50-80 μm across, subrounded, substantially magnetic. (c) Translucent particles: Similar to previous type except for the color that ranges from ruby to brown. (d) Whitish splotches: No more than 10 μm across. Appear in all types of samples. Types (b) and (c) may actually be the dark, magnetic particles observed during the Mars Exploration Rover (MER) mission, but may also contain glassy volcanic particles or tectites from the nearby Heimdall crater. Type (d) may be dominated by salts. Soil particles appear to be very sticky, especially late in the (90 sols long) Primary Mission. Soil at the PHX site may be more altered than at previous landing sites as a result of diurnal and seasonal water vapor transported across the top soil layer
Microscopic Views of the Soil at the Phoenix Landing Site
No full textThe Optical Microscope (OM) onboard Phoenix (PHX) has returned high-resolution images (4 μm/px) of Martian soil collected on magnetic and non-magnetic substrates. Different types of material can be distinguished: (a) Orange sub-micron dust that is similar to classic Martian air-fall dust. (b) Dark (almost black) particles: 50-80 μm across, subrounded, substantially magnetic. (c) Translucent particles: Similar to previous type except for the color that ranges from ruby to brown. (d) Whitish splotches: No more than 10 μm across. Appear in all types of samples. Types (b) and (c) may actually be the dark, magnetic particles observed during the Mars Exploration Rover (MER) mission, but may also contain glassy volcanic particles or tectites from the nearby Heimdall crater. Type (d) may be dominated by salts. Soil particles appear to be very sticky, especially late in the (90 sols long) Primary Mission. Soil at the PHX site may be more altered than at previous landing sites as a result of diurnal and seasonal water vapor transported across the top soil layer
Spectral Properties of Soil Grains as Inferred from Images of the Optical Microscope onboard the Phoenix Mars Lander
No full textThe Optical Microscope (OM) onboard the Phoenix Mars Lander has returned high-resolution (4 μm/px) color images of soil particles at the landing site. Spectral information was acquired by illuminating the soil samples with four different types of Light Emitting Diodes (LEDs): UV (375 nm, weak emission at 705 nm), blue (B, 468 nm), green (G, 525 nm), and red (R, 636 nm) [Hecht et al., JGR 113, E00A22, 2008]. Analysis of images acquired in the visible channels (R, G, B) lead to the distinction of four different types of particles: (1) red fines (< 10 μm), (2) brown sand (20-100 μm), (3) black sand (20-100 μm), and (4) white fines (< 10 μm) [Goetz et al., JGR 115, E00E22, 2010]. Most particles (except white fines) were found to be substantially magnetic with a saturation magnetization in the range 0.5-2 A m2/kg. Different strategies were used to derive further information on these particles from the UV images. Their analysis is complicated due to the dual emission of the UV LEDs. Potential UV luminescent particles would be expected to belong to the brightest soil particle population, as dark (black) particles would auto-absorb luminescent emission. However, when taking into account the bright particles’ near-infrared reflectance (705 nm) that would be expected based on their known red reflectance (636 nm) analysis shows that particles with increasing brightness in the RGB color images do not become brighter in UV images. Statistical analysis of the UV images suggests that soil material as a whole does not show any measurable UV luminescence. Its potential quantum efficiency (QE) must be smaller than 0.01 %. An extensive search for particles that would shine up in the UV images was also unsuccessful. From these observations we conclude that the imaged soils do not show a measurable homogeneous level of luminescent emission. Furthermore we exclude the presence of strongly luminescent mineral grains in an (otherwise) non-luminescent soil matrix
Spectral Properties of Soil Grains as Inferred from Images of the Optical Microscope onboard the Phoenix Mars Lander
No full textThe Optical Microscope (OM) onboard the Phoenix Mars Lander has returned high-resolution (4 μm/px) color images of soil particles at the landing site. Spectral information was acquired by illuminating the soil samples with four different types of Light Emitting Diodes (LEDs): UV (375 nm, weak emission at 705 nm), blue (B, 468 nm), green (G, 525 nm), and red (R, 636 nm) [Hecht et al., JGR 113, E00A22, 2008]. Analysis of images acquired in the visible channels (R, G, B) lead to the distinction of four different types of particles: (1) red fines (< 10 μm), (2) brown sand (20-100 μm), (3) black sand (20-100 μm), and (4) white fines (< 10 μm) [Goetz et al., JGR 115, E00E22, 2010]. Most particles (except white fines) were found to be substantially magnetic with a saturation magnetization in the range 0.5-2 A m2/kg. Different strategies were used to derive further information on these particles from the UV images. Their analysis is complicated due to the dual emission of the UV LEDs. Potential UV luminescent particles would be expected to belong to the brightest soil particle population, as dark (black) particles would auto-absorb luminescent emission. However, when taking into account the bright particles’ near-infrared reflectance (705 nm) that would be expected based on their known red reflectance (636 nm) analysis shows that particles with increasing brightness in the RGB color images do not become brighter in UV images. Statistical analysis of the UV images suggests that soil material as a whole does not show any measurable UV luminescence. Its potential quantum efficiency (QE) must be smaller than 0.01 %. An extensive search for particles that would shine up in the UV images was also unsuccessful. From these observations we conclude that the imaged soils do not show a measurable homogeneous level of luminescent emission. Furthermore we exclude the presence of strongly luminescent mineral grains in an (otherwise) non-luminescent soil matrix
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
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