Search results for "disparity"
showing 10 items of 33 documents
3D Map Computation from Historical Stereo Photographs of Florence
2018
The analysis of early photographic sources is fundamental for documenting and understanding the evolution of a city so rich in history and art as Florence. Indeed, by the 1860s several photographers used to work in town, and their images (often obtained through stereoscopic set-ups) can help us to reconstruct Florence in 3D as it was by the time of the Italian unification. The first and most delicate part of such reconstruction process is the computation of disparity maps from the historical stereo pairs. This is a very challenging task for fully-automatic computer vision algorithms, since XIX century photographs are affected by several problems—ranging from superficial damages to asynchron…
Social Disparities in Education in Sub-Saharan African Countries
2007
In this paper we have two complementary objectives: the first is to describe the magnitude of social disparities that exist in the systems of education of sub-Saharan African countries; we focus on recent data but we also put these data in a time perspective. The second objective is to identify some of the factors that may explain these disparities and the impact of policies aimed at their reduction.
Assessment of spatial perception for a multi-layer volumetric display: the effect of exocentric and egocentric distance on relative depth judgements
2020
Three-dimensional images on multiple depth layers of the volumetric display provide the physiological depth cues which ensure the high precision of depth judgements at close viewing distances and enhance the user experience. However, the contribution of physiological cues declines with an increase of viewing distance (egocentric distance), and the human spatial perception varies depending on the inter-stimuli distance (exocentric distance). We conducted a psychophysical experiment to test the perception of three-dimensional images rendered on the volumetric display depending on exocentric and egocentric stimuli distance. The constant angular size visual stimuli were displayed on different d…
Morphometrics of hard structures in cuttlefish
2006
7 pages; International audience; Cuttlefishes exhibit several hard structures that have been characterised using morphometric analysis. Most of these data come from cuttlebones, although statoliths and beaks are also used. It appears that morphometric techniques are mainly used for taxonomic purposes. However, some analyses have emphasised functional morphology and macroevolution. Morphological features (including the inner shell) of cuttlefishes and their availability for study (numerous specimens, culture in the laboratory) make them a first rank model for numerous studies in life sciences that require morphometrics, and especially in the field of evolutionary biology.
Categorical versus geometric morphometric approaches to characterising the evolution of morphological disparity in Osteostraci (Vertebrata, stem-Gnat…
2020
Morphological variation (disparity) is almost invariably characterised by two non-mutually exclusive approaches: (i) quantitatively, through geometric morphometrics, and (ii) in terms of discrete, 'cladistic', or categorical characters. Uncertainty over the comparability of these approaches diminishes the potential to obtain nomothetic insights into the evolution of morphological disparity and the few benchmarking studies conducted so far show contrasting results. Here, we apply both approaches to characterising morphology in the stem-gnathostome clade Osteostraci in order to assess congruence between these alternative methods as well as to explore the evolutionary patterns of the group in …
Jauna stereoredzes testa izstrāde krustotās un nekrustotās disparitātes novērtēšanai
2017
Darbs uzrakstīts angļu valodā uz 49 lappusēm. Tas satur 47 attēlus, 3 tabulas un atsauces uz 27 literatūras avotiem. Darba mērķis bija izstrādāt jaunu datorizētu stereoredzes testu krustotās un nekrustotās disparitātes novērtēšanai. Lokālās un globālās stereoredzes sliekšņi tika novērtēti pielietojot psihofizikālo trepju metodi. Pētījuma dalībnieku uzdevums bija atpazīt telpiskus attēlus. Stimuliem tika izvēlēti dažādi ekspozīcijas laiki – 5 sekundes (ilgais laiks), 550 ms un 250 ms (īsie laiki). Stereoredzes novērtēšanai papildus tika pielietoti tradicionālie stereotesti – TNO, Titmus tests. Pētījumā piedalījās 37 dalībnieki vecumā no 16 līdz 42 gadiem. Rezultāti tika salīdzināti ņemot vēr…
Krustotās un nekrustotās disparitātes stereoslieksnis dažādos vecumos
2020
Maģistra darbs uzrakstīts uz 75 lappusēm, satur 40 attēlus, 10 tabulas un darbā ir atsauces uz 100 literatūras avotiem. Maģistra darba mērķis bija novērtēt krustotās un nekrustotās disparitātes atšķirības dažāda vecuma cilvēkiem. Pētījuma dalībnieki tika iedalīti četrās vecuma grupās. Pētījumā piedalījās 61 dalībnieks (vecumā no 19 līdz 78 gadiem). Pētījuma dalībniekiem nebija acu slimības, redzes asums bija vismaz 0,0 vai labāks (LogMAR sistēmā). Stereoredzes noteikšanai tika izmantots digitālais izliedēto punktu globālā principa stereotests, kopā ar pakāpjveida psihofizikālo metodi. Pētījums parādīja, ka nekrustotās disparitātes stimulu sliekšņi vienmēr bija augstāki, salīdzinot ar krusto…
Korelācija starp fuzionālām rezervēm un maksimālo stereoredzes leņķi
2021
Maģistra darbs ir uzrakstīts angļu valodā uz 43 lappusēm. Tas satur 20 attēlus, 3 tabulas un 63 atsauces uz literatūras avotiem. Pētījuma mērķis bija novērtēt, kāda korelācija pastāv starp fuzionālo verģenču rezervēm un maksimālo stereoredzes leņķi. Pētījumā piedalījās 22 dalībnieki, kuriem tika veikta redzes pārbaude Nove Mesto nad Vahom, Slovākijas klīnikā. Pētījumā tika paveikts, pirmkārt, tika analizētas pozitīvās un negatīvās fuzionālās verģences rezerves un salīdzinātās ar normām. Otrkārt, tika analizēti maksimālie stereoredzes krustotās un nekrustotās disparitātes leņķi. Treškārt, tika analizēta korelācija starp visām iespējamām kombinācijām (starp fuzionālām verģences rezervēm un st…
Data from: Empirical and theoretical study of Atelostomate (Echinoidea, Echinodermata) plate architecture: using graph analysis to reveal structural …
2015
Describing 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 most dive…
Data from: Specimens at the center: an informatics workflow and toolkit for specimen-level analysis of public DNA database data
2017
Major public DNA databases — NCBI GenBank, the DNA DataBank of Japan (DDBJ), and the European Molecular Biology Laboratory (EMBL) — are invaluable biodiversity libraries. Systematists and other biodiversity scientists commonly mine these databases for sequence data to use in phylogenetic studies, but such studies generally use only the taxonomic identity of the sequenced tissue, not the specimen identity. Thus studies that use DNA supermatrices to construct phylogenetic trees with species at the tips typically do not take advantage of the fact that for many individuals in the public DNA databases, several DNA regions have been sampled; and for many species, two or more individuals have been…