Search results for "Contrast"
showing 10 items of 1162 documents
Wider is better but sharper is not: optimizing the image of camera-monitor systems
2021
The replacement of rear-view mirrors with camera-monitor systems introduces new opportunities for design, such as altering the image quality and the rearward field-of-view. We investigated how the image quality and field-of-view might affect the distance and time-to-contact estimation of other vehicles. Eighty-six subjects estimated either their egocentric distance to a stationary vehicle (Experiment I) or the time-to-contact to an approaching vehicle (Experiment II). Throughout the experiments, the pixel density and either the field-of-view or the viewing condition varied. A larger field-of-view increased distance estimation accuracy and confidence. Reduced pixel density led to larger esti…
Subsecond fluorine-19 MRI of the lung
2006
Minimal scan times in rapid fluorine-19 MRI using sulfur hexafluoride (SF6) have been on the order of 10 s. Because of the very short T1 relaxation time of SF6 (T1 = 1.65 ms), high receiver bandwidths are necessary to allow for a high number of excitations. Since high bandwidths cause high levels of electronic noise, SNR per acquisition has been too low to further reduce scan time. The purpose of this study was to investigate whether scan times could be reduced using hexafluoroethane (C2F6), a gas with a longer T1 (T1 = 7.9 ms) at a relatively low bandwidth of 488 Hz/pixel. Gradient-echo images were acquired during and after completion of the wash-in of a 70% C2F6- 30% O2 mixture. Peak SNR …
Quattro studi sulla poesia d'amore mediolatina
2011
Il vol. presenta, debitamente ampliati, rielaborati e aggiornati, quattro studi (già precedentemente comparsi in varie sedi, dal 1993 al 2009) sulla poesia d’amore mediolatina, in un arco cronologico che va dal sec. VI (Venanzio Fortunato) al XIV (Giovanni del Virgilio e ser Nuccio da Tolentino), passando attraverso i secc. XI e XII (Ildeberto di Lavardin, il “contrasto” fra la monaca e il chierico). In genere, si tratta di un percorso fondato sull’analisi di testi particolarmente significativi (le poesie di Venanzio Fortunato, soprattutto quelle indirizzate a Radegonda di Turingia e ad Agnese di Poitiers; un carme di Ildeberto in lode della regina Matilde d’Inghilterra; il “contrasto” fra …
Implantable collamer lens and femtosecond laser for myopia: comparison using an adaptive optics visual simulator.
2014
Purpose: To compare optical and visual quality of implantable collamer lens (ICL) implantation and femtosecond laser in situ keratomileusis (F-LASIK) for myopia. Methods: The CRX1 adaptive optics visual simulator (Imagine Eyes, Orsay, France) was used to simulate the wavefront aberration pattern after the two surgical procedures for -3-diopter (D) and -6-D myopia. Visual acuity at different contrasts and contrast sensitivities at 10, 20, and 25 cycles/degree (cpd) were measured for 3-mm and 5-mm pupils. The modulation transfer function (MTF) and point spread function (PSF) were calculated for 5-mm pupils. Results: F-LASIK MTF was worse than ICL MTF, which was close to diffraction-limited MT…
Myopic astigmatism correction: comparison of a Toric Implantable Collamer Lens and a bioptics technique by an adaptive optics visual simulator.
2013
Purpose To compare the optical and visual quality of a simulated Toric Implantable Collamer Lens (TICL) and a bioptics technique to treat high myopic astigmatism. Methods An adaptive optics visual simulator was used to simulate the vision after TICL implantation and a bioptics procedure from the wavefront aberration pattern for moderate and high-myopic astigmatism. Visual acuity (VA) at different contrasts and contrast sensitivity (CS) at 10, 20 and 25 cycles degree−1 were measured for 3 and 5-mm pupils. Modulation Transfer Function (MTF) and Point Spread Function (PSF) were calculated for a 5-mm pupil. Results At a 3-mm pupil we only found statistically significant differences in VA betwee…
Fast multi-directional DSLM for confocal detection without striping artifacts
2020
In recent years light-sheet fluorescence microscopy (LSFM) has become a cornerstone technology for neuroscience, improving the quality and capabilities of 3D imaging. By selectively illuminating a single plane, it provides intrinsic optical sectioning and fast image recording, while minimizing out of focus fluorescence background, sample photo-damage and photo-bleaching. However, images acquired with LSFM are often affected by light absorption or scattering effects, leading to un-even illumination and striping artifacts. In this work we present an optical solution to this problem, via fast multi-directional illumination of the sample, based on an acousto-optical deflector (AOD). We demonstr…
Merits of vision in presence of light scattering using Tiffen ProMist filters
2020
Light scattering caused by Tiffen ProMist photographic filters of various grades at different laser radiation 640 nm, 532 nm and 405 nm was objectively studied and compared. The lack of removal of speckles from the scene of laser radiation scattering did not allow an accurate assessment of the effect of scattering on the decrease in image contrast. Subjective deterioration in visual acuity using various contrast optotypes and contrast sensitivity was assessed by scattering induction using filters up to grade #5. Vision contrast sensitivity diminishes within all studied spatial frequency range 0.5-18 cpd. The degradation of the impact factor to visual acuity without scattering filters when t…
What’s Wrong with the Diffusion of Innovation Theory?
2001
This paper examines the usefulness of the diffusion of innovation research in developing theoretical accounts of the adoption of complex and networked IT solutions. We contrast six conjectures underlying DOI research with field data obtained from the study of the diffusion of EDI. Our analysis shows that DOI based analyses miss some important facets in the diffusion of complex technologies. We suggest that complex IT solutions should be understood as socially constructed and learning intensive artifacts, which can be adopted for varying reasons within volatile diffusion arenas. Therefore DOI researchers should carefully recognize the complex, networked, and learning intensive features of te…
Empirical and theoretical study of atelostomate (Echinoidea, Echinodermata) plate architecture: using graph analysis to reveal structural constraints.
2015
AbstractDescribing patterns of connectivity among organs is essential for identifying anatomical homologies among taxa. It is also critical for revealing morphogenetic processes and the associated constraints that control the morphological diversification of clades. This is particularly relevant for studies of organisms with skeletons made of discrete elements such as arthropods, vertebrates, and echinoderms. Nonetheless, relatively few studies devoted to morphological disparity have considered connectivity patterns as a level of morphological organization or developed comparative frameworks with proper tools. Here, we analyze connectivity patterns among apical plates in Atelostomata, the m…
Converging Analysis of the Concept of Strategic Group in the Spanish Lighting Industry
2008
Strategic group literature does not seem to offer strong enough theoretical bases to state the very existence of strategic groups and their effects on firm’s conduct and performance. The empirical validation of the existence of strategic groups has been usually done trying to contrast their predictive validity in relation to performance, obtaining conflicting evidence. Other papers have decided to contrast the convergent validity of the strategic group concept using different definitions and measures of this construct. Our work belongs to the second type of studies. It tries to make progress in the development of a theoretical model, able to state the industry features which affect the prob…