194 research outputs found
Optical Guidance System /OGS/ for rendezvous and docking Final report
Optical guidance system for Apollo rendezvous and dockin
Atomic-scale surface demixing in a eutectic liquid BiSn alloy
Resonant x-ray reflectivity of the surface of the liquid phase of the
BiSn eutectic alloy reveals atomic-scale demixing extending over
three near-surface atomic layers. Due to the absence of underlying atomic
lattice which typically defines adsorption in crystalline alloys, studies of
adsorption in liquid alloys provide unique insight on interatomic interactions
at the surface. The observed composition modulation could be accounted for
quantitatively by the Defay-Prigogine and Strohl-King multilayer extensions of
the single-layer Gibbs model, revealing a near-surface domination of the
attractive Bi-Sn interaction over the entropy.Comment: 4 pages (two-column), 3 figures, 1 table; Added a figure, updated
references, discussion; accepted at Phys. Rev. Let
Organizational and dynamical aspects of a small network with two distinct communities : Neo creationists vs. Evolution Defenders
Social impacts and degrees of organization inherent to opinion formation for
interacting agents on networks present interesting questions of general
interest from physics to sociology. We present a quantitative analysis of a
case implying an evolving small size network, i.e. that inherent to the ongoing
debate between modern creationists (most are Intelligent Design (ID) proponents
(IDP)) and Darwin's theory of Evolution Defenders (DED)). This study is carried
out by analyzing the structural properties of the citation network unfolded in
the recent decades by publishing works belonging to members of the two
communities. With the aim of capturing the dynamical aspects of the interaction
between the IDP and DED groups, we focus on key quantities, namely, the
{\it degree of activity} of each group and the corresponding {\it degree of
impact} on the intellectual community at large. A representative measure of the
former is provided by the {\it rate of production of publications} (RPP),
whilst the latter can be assimilated to the{\it rate of increase in citations}
(RIC). These quantities are determined, respectively, by the slope of the time
series obtained for the number of publications accumulated per year and by the
slope of a similar time series obtained for the corresponding citations. The
results indicate that in this case, the dynamics can be seen as geared by
triggered or damped competition. The network is a specific example of marked
heterogeneity in exchange of information activity in and between the
communities, particularly demonstrated through the nodes having a high
connectivity degree, i.e. opinion leaders.Comment: 10 pages, 4 figures, 2 tables, 52 reference
A systematic review on 'Foveal Crowding' in visually impaired children and perceptual learning as a method to reduce Crowding
Contains fulltext :
102577.pdf (publisher's version ) (Open Access)Background - This systematic review gives an overview of foveal crowding (the inability to recognize objects due to surrounding nearby contours in foveal vision) and possible interventions. Foveal crowding can have a major effect on reading rate and deciphering small pieces of information from busy visual scenes. Three specific groups experience more foveal crowding than adults with normal vision (NV): 1) children with NV, 2) visually impaired (VI ) children and adults and 3) children with cerebral visual impairment (CVI). The extent and magnitude of foveal crowding as well as interventions aimed at reducing crowding were investigated in this review. The twofold goal of this review is : [A] to compare foveal crowding in children with NV, VI children and adults and CVI children and [B] to compare interventions to reduce crowding. Methods - Three electronic databases were used to conduct the literature search: PubMed, PsycINFO (Ovid), and Cochrane. Additional studies were identified by contacting experts. Search terms included visual perception, contour interaction, crowding, crowded, and contour interactions. Results - Children with normal vision show an extent of contour interaction over an area 1.5-3x as large as that seen in adults NV. The magnitude of contour interaction normally ranges between 1-2 lines on an acuity chart and this magnitude is even larger when stimuli are arranged in a circular configuration. Adults with congenital nystagmus (CN) show interaction areas that are 2x larger than those seen adults with NV. The magnitude of the crowding effect is also 2x as large in individuals with CN as in individuals with NV. Finally, children with CVI experience a magnitude of the crowding effect that is 3x the size of that experienced by adults with NV. Conclusions - The methodological heterogeneity, the diversity in paradigms used to measure crowding, made it impossible to conduct a meta-analysis. This is the first systematic review to compare crowding ratios and it shows that charts with 50% interoptotype spacing were most sensitive to capture crowding effects. The groups that showed the largest crowding effects were individuals with CN, VI adults with central scotomas and children with CVI. Perceptual Learning seems to be a promising technique to reduce excessive foveal crowding effects.14 p
Transcultural adaptation of the Emotion Matching Task: an emotion neuropsychological assessment
Emotions play a central role in children’s relationships. Deficits in emotional understanding have been associated with several neuropsychiatric disorders. In Brazil, however, few psychological instruments are available to assess young children’s emotional development. The objective of the present study was to make a transcultural adaptation of the Emotion Matching Task (EMT). The EMT was translated and adapted by a team of bilingual researches and then back-translated to English. The preliminary versions were assessed by EMT’s authors and by Brazilians specialized judges. The final version was applied in a sample of 50 children between three and six years of age and answered by nine judges in three Brazilian states. The results indicate good semantic equivalence and good agreement with the answers provided (κ= 0.88, Z=95.2, p<0.001). The final version of the EMT was considered appropriate and satisfactory
Skin Lesions on Common Bottlenose Dolphins (Tursiops truncatus) from Three Sites in the Northwest Atlantic, USA
Skin disease occurs frequently in many cetacean species across the globe; methods to categorize lesions have relied on photo-identification (photo-id), stranding, and by-catch data. The current study used photo-id data from four sampling months during 2009 to estimate skin lesion prevalence and type occurring on bottlenose dolphins (Tursiops truncatus) from three sites along the southeast United States coast [Sarasota Bay, FL (SSB); near Brunswick and Sapelo Island, GA (BSG); and near Charleston, SC (CHS)]. The prevalence of lesions was highest among BSG dolphins (P = 0.587) and lowest in SSB (P = 0.380), and the overall prevalence was significantly different among all sites (p<0.0167). Logistic regression modeling revealed a significant reduction in the odds of lesion occurrence for increasing water temperatures (OR = 0.92; 95%CI:0.906–0.938) and a significantly increased odds of lesion occurrence for BSG dolphins (OR = 1.39; 95%CI:1.203–1.614). Approximately one-third of the lesioned dolphins from each site presented with multiple types, and population differences in lesion type occurrence were observed (p<0.05). Lesions on stranded dolphins were sampled to determine the etiology of different lesion types, which included three visually distinct samples positive for herpesvirus. Although generally considered non-fatal, skin disease may be indicative of animal health or exposure to anthropogenic or environmental threats, and photo-id data provide an efficient and cost-effective approach to document the occurrence of skin lesions in free-ranging populations
Density Distribution in the Liquid Hg-Sapphire Interface
We present the results of a computer simulation study of the liquid density
distribution normal to the interface between liquid Hg and the reconstructed
(0001) face of sapphire. The simulations are based on an extension of the
self-consistent quantum Monte Carlo scheme previously used to study the
structure of the liquid metal-vapor interface. The calculated density
distribution is in very good agreement with that inferred from the recent
experimental data of Tamam et al (J. Phys. Chem. Lett. 1, 1041-1045 (2010)). We
conclude that, to account for the difference in structure between the liquid
Hg-vapor and liquid-Hg-reconstructed (0001) Al2O3 interfaces, it is not
necessary assume there is charge transfer from the Hg to the Al2O3. Rather, the
available experimental data are adequately reproduced when the van der Waals
interactions of the Al and O atoms with Hg atoms and the exclusion of electron
density from Al2O3 via repulsion of the electrons from the closed shells of the
ions in the solid are accounted for.Comment: 26 pages, 11 figure
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