24 research outputs found
Correlation of Opioid Mortality with Prescriptions and Social Determinants: A Cross-sectional Study of Medicare Enrollees
No full textVisibility and acceptance of discrete-sampling artifacts in visual displays
No full textPh. D. ThesisDigital visual displays are aimed to provide an illusion of a continuous reality through a
discrete presentation of visual information. This thesis explored three topics on (i) angular, (ii)
spatial, and (iii) temporal sampling characteristics, related to distortion visibility, acceptance,
and discomfort. In the first topic, we addressed the issue of optimizing the view density
in continuous parallax visualization by replicating the changing views of a 3-D object for
a moving observer. We measured the visibility of the related artifacts and evaluated the
performance of full-reference visual quality metrics. We found that the state-of-the-art metrics
can indirectly characterize artifact visibility and established a quantitative relationship for
threshold estimation on varying conditions. The second topic addressed the relation of the
contrast sensitivity function (CSF) to adaptation luminance and specifically its asymptotic
behavior at high light levels essential to modern high-luminance displays. Using a custombuilt system, we measured the CSF at relatively high luminance levels and spatial frequency
range, integrating our dataset to the existing research. We found a gradual transition among
the linear to DeVries-Rose to Weber regions with steeper slopes for higher frequencies and
lower luminance. A further decreasing region was located at low to intermediate frequencies.
Following this construct, we adopted a model consisting of central elements in the visual
signal processing and proposed an eight-parameter form for the CSF in the luminance domain.
The final topic addressed the effects of frame rate on distortion acceptance and its impact on
visual discomfort during regular display use. We assessed the perceived symptoms, preference,
and task performance under varying conditions. The measurements indicated that for nondemanding everyday tasks, the frame rate could be reasonably reduced without severe effects
on the observer; however, this tolerance diminished under more dynamic content. A potential
association of discomfort with the blinking activity was also discussedThe European Union’s Horizon 2020 research
and innovation program under the Marie Skłodowska-Curie grant agreement No 676401,
European Training Network on Full Parallax Imaging and Huawei Technologies Co., Lt
Computational analysis of EMG time series using matrix factorization methods and wavelet coherence
No full textΕθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Υπολογιστική Μηχανική
Development of a complete digital system for the computational analysis and modelling of the human visuospatial perception and kinematics in three-dimensional space, within a virtual environment
No full text160 σ.Σε προηγούμενες μελέτες, έχει παρατηρηθεί η ύπαρξη φαινομένων ανισοτροπίας του ανθρώπινου οπτικού συστήματος αντίληψης, στον χώρο των δύο διαστάσεων, σε ποικίλες οπτικοκινητικές λειτουργίες όσον αφορά την είσοδο, την έξοδο, και γνωσιακές
απαιτήσεις. Η διερεύνηση αυτών των φαινομένων στον χώρο των τριών διαστάσεων αποτέλεσε το κίνητρο για την παρούσα μελέτη. Σκοπός αυτής της εργασίας ήταν, αρχικά, η δημιουργία ενός ολοκληρωμένου ψηφιακού συστήματος για την υπολογιστική ανάλυση κινήσεων του άνω άκρου στον χώρο των τριών διαστάσεων, εντός ενός εικονικού περιβάλλοντος. Προς αυτή την κατεύθυνση, πραγματοποιείται μια εισαγωγή στα βασικά στοιχεία της αρχιτεκτονικής ενός συστήματος εικονικής πραγματικότητας, εστιάζοντας στις συσκευές εισόδου - εξόδου και τη μηχανή δημιουργίας και λειτουργίας ενός εικονικού κόσμου. Παρουσιάζεται η διεπαφή επικοινωνίας με το σύστημα μαγνητικής ανίχνευσης θέσης που χρησιμοποιήθηκε, και μέσω μηχανής παιχνιδιού αναπτύσσεται μια πειραματική στερεοσκοπική εφαρμογή. Ύστερα, διερευνάται η ύπαρξη συστηματικών σφαλμάτων στα τελικά σημεία της κίνησης του άνω άκρου προς απομνημονευμένους στόχους, αλλά και με οπτική υποβοήθηση, στον χώρο των τριών διαστάσεων. Το πρώτο μοτίβο αποτέλεσε μια τάση των τελικών σημείων της κίνησης να σφάλουν προς τους διαγώνιους άξονες κάθε τεταρτημόριου ενός εικονικού περιστρεφόμενου κύκλου
που περιλάμβανε όλους τους στόχους (oblique effect). Το δεύτερο μοτίβο αποτέλεσε μια τάση των τελικών σημείων της κίνησης να σφάλουν προς το σώμα του υποκειμένου (z-effect). Και τα δύο μοτίβα συστηματικών σφαλμάτων αυξάνονταν σε μέτρο καθώς η πληροφορία σχετικά με το ερέθισμα διαταράσσονταν παραμετρικά. Ένα παρόμοιο μοτίβο συστηματικών σφαλμάτων αναφέρεται στην βιβλιογραφία και αποδίδεται στην αντιληπτική κατηγοριοποίηση του χώρου από το υποκείμενο.Our main motivation was to investigate anisotropic phenomena in the human visual perception system, in three dimensional space. Such phenomena were observed in two dimensional space, in previous studies, in diverse tasks both in terms of input,
output, and cognitive demands. Our goal was initially the development of a complete digital system for the computational analysis of the upper limb movements in three-dimensional space, within a virtual environment. We introduce the main components of virtual reality system architecture and concentrate on input - output devices and the virtual reality engine. We present an interface between the magnetic tracking system used and a host system and use a game engine to develop a stereoscopic experimental application. We then investigate the directional distortion of the endpoints in a task of memory and visually guided pointing movements in three-dimensional
space. The first pattern resulted in the clustering of movement endpoints toward the diagonals of the four quadrants of an imaginary rotating circular area encompassing all target locations (oblique effect). The second pattern resulted in a tendency of movement endpoints to be closer to the body (z-effect). Both these patterns of systematic error increased in magnitude as information about the stimulus parametrically degraded. A pattern of systematic errors similar to the oblique effect has already been reported in the literature and is attributed to the subject's conceptual categorization of space.Χρήστος Α. Κασπίρης-Ρουσέλλη
Seeing the future: predictive control in neural models of ocular accommodation - simulation and analysis/presentation code
No full textSimulink models and code to support "Seeing the future: predictive and classical control in neural models of ocular accommodation" ; paper available on biorxiv.org: BIORXIV/2021/471909</div
A visual discomfort questionnaire for use in research and applied settings
No full textMany people experience visual discomfort as a result of viewing visual stimuli such as stereoscopic content in novel display technologies. To prevent or mitigate its occurrence, we need to understand when and why visual discomfort occurs. However, our collective understanding of visual discomfort is hindered by the fact that there is no universally agreed definition or a standard measurement method that is both validated and useful across technologies, contexts, and populations. The present work addresses this gap by the delineation of a clear definition of visual discomfort as well as the development of a questionnaire that is valid and usable across different types of visual stimuli. We followed a rigorous questionnaire development process, including a literature review, qualitative and quantitative content validity research, and two large scale quantitative studies to assess the psychometric properties of a novel questionnaire. Results demonstrate that the 27 item visual discomfort questionnaire (VDQ) has adequate psychometric quality, such as content and structural validity. The VDQ comprises four subcomponents (sickness, vision, eye discomfort, and head discomfort), and is intended for use in research and applied settings. Further validation in different samples and studies is recommended to establish its psychometric stability across populations and contexts
Sclerostin and Its Involvement in the Pathogenesis of Idiopathic Scoliosis
No full textIdiopathic scoliosis is a disorder of unknown etiology. Bone biopsies from idiopathic scoliosis patients revealed changes at cellular and molecular level. Osteocytic sclerostin is downregulated, and serum level of sclerostin is decreased. Osteocytes in idiopathic scoliosis appear to be less active with abnormal canaliculi network. Differentiation of osteoblasts to osteocytes is decelerated, while Wnt/β-catenin signaling pathway is overactivated and affects normal bone mineralization that leads to inferior mechanical properties of the bone, which becomes susceptible to asymmetrical forces and causes deformity of the spinal column. Targeting bone metabolism during growth by stimulating sclerostin secretion from osteocytes and restoring normal function of Wnt/β-catenin signaling pathway could, in theory, increase bone strength and prevent deterioration of the scoliotic deformity
The Role of Sclerostin in Bone Diseases
No full textSclerostin has been identified as an important regulator of bone homeostasis through inhibition of the canonical Wnt-signaling pathway, and it is involved in the pathogenesis of many different skeletal diseases. Many studies have been published in the last few years regarding sclerostin's origin, regulation, and mechanism of action. The ongoing research emphasizes the potential therapeutic implications of sclerostin in many pathological conditions with or without skeletal involvement. Antisclerostin antibodies have recently been approved for the treatment of osteoporosis, and several animal studies and clinical trials are currently under way to evaluate the effectiveness of antisclerostin antibodies in the treatment of other than osteoporosis skeletal disorders and cancer with promising results. Understanding the exact role of sclerostin may lead to new therapeutic approaches for the treatment of skeletal disorders
The Role of Sclerostin in Bone Diseases
No full textSclerostin has been identified as an important regulator of bone homeostasis through inhibition of the canonical Wnt-signaling pathway, and it is involved in the pathogenesis of many different skeletal diseases. Many studies have been published in the last few years regarding sclerostin’s origin, regulation, and mechanism of action. The ongoing research emphasizes the potential therapeutic implications of sclerostin in many pathological conditions with or without skeletal involvement. Antisclerostin antibodies have recently been approved for the treatment of osteoporosis, and several animal studies and clinical trials are currently under way to evaluate the effectiveness of antisclerostin antibodies in the treatment of other than osteoporosis skeletal disorders and cancer with promising results. Understanding the exact role of sclerostin may lead to new therapeutic approaches for the treatment of skeletal disorders
