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Search Results: 1 - 10 of 1515 matches for " Eli Peli "
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A Pilot Evaluation of On-Road Detection Performance by Drivers with Hemianopia Using Oblique Peripheral Prisms
Alex R. Bowers,Mark Tant,Eli Peli
Stroke Research and Treatment , 2012, DOI: 10.1155/2012/176806
Abstract:
A Pilot Evaluation of On-Road Detection Performance by Drivers with Hemianopia Using Oblique Peripheral Prisms
Alex R. Bowers,Mark Tant,Eli Peli
Stroke Research and Treatment , 2012, DOI: 10.1155/2012/176806
Abstract: Aims. Homonymous hemianopia (HH), a severe visual consequence of stroke, causes difficulties in detecting obstacles on the nonseeing (blind) side. We conducted a pilot study to evaluate the effects of oblique peripheral prisms, a novel development in optical treatments for HH, on detection of unexpected hazards when driving. Methods. Twelve people with complete HH (median 49 years, range 29–68) completed road tests with sham oblique prism glasses (SP) and real oblique prism glasses (RP). A masked evaluator rated driving performance along the 25?km routes on busy streets in Ghent, Belgium. Results. The proportion of satisfactory responses to unexpected hazards on the blind side was higher in the RP than the SP drive (80% versus 30%; ), but similar for unexpected hazards on the seeing side. Conclusions. These pilot data suggest that oblique peripheral prisms may improve responses of people with HH to blindside hazards when driving and provide the basis for a future, larger-sample clinical trial. Testing responses to unexpected hazards in areas of heavy vehicle and pedestrian traffic appears promising as a real-world outcome measure for future evaluations of HH rehabilitation interventions aimed at improving detection when driving. 1. Introduction Driving is the primary mode of transportation in the USA. Cessation of driving decreases independence and employment opportunities and increases the risk of depression [1, 2]. Thus, returning to driving following a stroke is an important rehabilitation goal. However, since stroke may cause a number of visual, perceptual, cognitive, and motor impairments that could adversely affect driving skills, poststroke driving rehabilitation is not straightforward [3–5]. In this paper we focus on rehabilitation of people with homonymous hemianopia (HH), the loss of the same half of the visual field in each eye due to postchiasmal lesions, a severe visual consequence of stroke. People with spatial neglect or other significant cognitive impairments were not included, as our goal was to address the effects of the sensory visual loss without other confounding perceptual or cognitive impairments. In 2010, there were about 6.2 million stroke survivors in the USA [6] with at least 50% having partial or complete HH in the acute stage immediately following the stroke [7, 8]. Spontaneous recovery, either complete or partial, may occur within the first three months after the injury [8–11], but improvement after six months is rare [9]. About 30% of stroke patients still have chronic HH after nine months [12]. Chronic HH causes
Influence of Hemianopic Visual Field Loss on Visual Motor Control
Diederick C. Niehorster, Eli Peli, Andrew Haun, Li Li
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056615
Abstract: Background Homonymous hemianopia (HH) is an anisotropic visual impairment characterized by the binocular inability to see one side of the visual field. Patients with HH often misperceive visual space. Here we investigated how HH affects visual motor control. Methods and Findings Seven patients with complete HH and no neglect or cognitive decline and seven gender- and age-matched controls viewed displays in which a target moved randomly along the horizontal or the vertical axis. They used a joystick to control the target movement to keep it at the center of the screen. We found that the mean deviation of the target position from the center of the screen along the horizontal axis was biased toward the blind side for five out of seven HH patients. More importantly, while the normal vision controls showed more precise control and larger response amplitudes when the target moved along the horizontal rather than the vertical axis, the control performance of the HH patients was not different between these two target motion experimental conditions. Conclusions Compared with normal vision controls, HH affected patients' control performance when the target moved horizontally (i.e., along the axis of their visual impairment) rather than vertically. We conclude that hemianopia affects the use of visual information for online control of a moving target specific to the axis of visual impairment. The implications of the findings for driving in hemianopic patients are discussed.
Visual Contrast Processing is Largely Unaltered during Saccades
Miguel A. García-Pérez,Eli Peli
Frontiers in Psychology , 2011, DOI: 10.3389/fpsyg.2011.00247
Abstract: Saccadic suppression refers to a reduction in visual sensitivity during saccadic eye movements. This reduction is conventionally regarded as mediated by either of two sources. One is a simple passive process of motion smear during saccades also accompanied by visual masking exerted by high-contrast pre- and post-saccadic images. The other is an active process exerted by a neural mechanism that significantly reduces visual processing so that the perception of a stable visual environment is not disrupted during saccades. Some studies have actually shown that contrast sensitivity is significantly lower during saccades than under fixation, but these experiments were not designed in a way that could weigh the differential contribution of active and passive sources of saccadic suppression. We report the results of measurements of psychometric functions for contrast detection using stimuli that are only visible during saccades, thus effectively isolating any visual processing that actually takes place during the saccades and also preventing any pre- and post-saccadic visual masking. We also report measurements of psychometric functions for detection under fixation for stimuli that are comparable in duration and spatio-temporal characteristics to the intrasaccadic retinal stimulus. Whether during saccades or under fixation, the psychometric functions for detection turned out to be very similar, leaving room only for a small amount of sensitivity reduction during saccades. This suggests that contrast processing is largely unaltered during saccades and, thus, that no neural mechanism seems to be actively involved in saccadic suppression.
Using Pattern Classification to Measure Adaptation to the Orientation of High Order Aberrations
Lucie Sawides, Carlos Dorronsoro, Andrew M. Haun, Eli Peli, Susana Marcos
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070856
Abstract: Background The image formed by the eye's optics is blurred by the ocular aberrations, specific to each eye. Recent studies demonstrated that the eye is adapted to the level of blur produced by the high order aberrations (HOA). We examined whether visual coding is also adapted to the orientation of the natural HOA of the eye. Methods and Findings Judgments of perceived blur were measured in 5 subjects in a psychophysical procedure inspired by the “Classification Images” technique. Subjects were presented 500 pairs of images, artificially blurred with HOA from 100 real eyes (i.e. different orientations), with total blur level adjusted to match the subject's natural blur. Subjects selected the image that appeared best focused in each random pair, in a 6-choice ranked response. Images were presented through Adaptive Optics correction of the subject's aberrations. The images selected as best focused were identified as positive, the other as negative responses. The highest classified positive responses correlated more with the subject's Point Spread Function, PSF, (r = 0.47 on average) than the negative (r = 0.34) and the difference was significant for all subjects (p<0.02). Using the orientation of the best fitting ellipse of angularly averaged integrated PSF intensities (weighted by the subject's responses) we found that in 4 subjects the positive PSF response was close to the subject's natural PSF orientation (within 21 degrees on average) whereas the negative PSF response was almost perpendicularly oriented to the natural PSF (at 76 degrees on average). Conclusions The Classification-Images inspired method is very powerful in identifying the internally coded blur of subjects. The consistent bias of the Positive PSFs towards the natural PSF in most subjects indicates that the internal code of blur appears rather specific to each subject's high order aberrations and reveals that the calibration mechanisms for normalizing blur also operate using orientation cues.
Les mines de la péninsule Arabique d’après les auteurs arabes (VIIe - XIIe siècles)
Audrey Peli
Chroniques Yéménites , 2006,
Abstract: A la période islamique, les principales ressources minières étaient situées en Iran oriental, en Afghanistan, en Espagne et au Maghreb. Cependant, la lecture des textes géographiques arabes et les recherches archéologiques prouvent que la péninsule Arabique n’en était pas dépourvue. Ainsi, le Hijaz, riche en gisements aurifères, a t il vraisemblablement contribué à la frappe de d nars. En outre, le Yémen appara t comme le plus diversement pourvu alors qu’en Oman était majoritairement exploité du cuivre. Par ailleurs, plusieurs étapes sur les principales routes sillonnant la péninsule ont été établies aux abords de sites miniers. During the Islamic period, the principal metal resources were situated in eastern Iran, in Afghanistan, in Spain and in the Maghreb. However, the Arabic geographical texts and the archaeological research show that the Arabian peninsula was also rich in mines. In this way, the rich gold mining Hijaz probably contributed to minting d nars. Yemen was the richest region whereas, Oman exploited principally copper. Furthermore, a number of mining sites are known by the texts as stations on the principal roads of the Arabian peninsula.
Yeni ehir (Bursa) yan Sar cao lu Osman A a ve Muhallefat /// Sar caoglu Osman Aga the Ayan of Yenisehir (Bursa) and His Inheritance
?zer Küpeli
History Studies : International Journal of History , 2011,
Abstract: This study handles the activities and the confiscation of the assets of Sar cao lu Osman Aga, the ayan of Yenisehir district in Bursa. Osman Aga was a bandit initially. When Osman Aga got stronger due to the support of Kalyoncu Ali Aga, the ayan of Bilecik, he became the ayan of Yeni ehir. Since he continued to behave like a bandit, he was sentenced to death several times. Nevertheless he always escaped from the punishment by means of Kalyoncu Ali’s protection. Upon he continued illegal activities persistenly he was sentenced to death once again in 1813. Even he escaped he was caught and executed finally. Then his inheritance was confiscated. His total assets were estimated to be 600.000 kuru
Are Scale Free Networks Better?
Gergely Peli,Gabor Papp
Physics , 2003,
Abstract: We study the performance of Weibull and scale free Internet-like networks and compare them to a classical random graph based network. The scaling of the traffic load with the nodal degree is established, and confimed in a numerical simulation of the TCP traffic. The scaling allows us to estimate the link capacity upgrade required making and extra connection to an existing node.
CAS-Based Approach for Automatic Data Integration  [PDF]
Eli Rohn
American Journal of Operations Research (AJOR) , 2013, DOI: 10.4236/ajor.2013.31A017
Abstract:

Research of automatic integration of structured and semi-structured data has not resulted in success over the past fifty years. No theory of data integration exists. It is unknown what the theoretical necessary requirements are, to fully support automatic data integration from autonomous heterogeneous data sources. Therefore, it is not possible to objectively evaluate if and how much new algorithms, techniques, and specifically Data Definition Languages, move towards meeting such theoretical requirements. To overcome the serious reverse salient the field and industry are in, it will be helpful if a data integration theory would be developed. This article proposes a new look at data integration by using complex adaptive systems principles to analyze current shortcomings and propose a direction that may lead to a data integration theory.

Autonomous Data Exchange: The Malady and a Possible Path to Its Cure  [PDF]
Eli Rohn
Intelligent Information Management (IIM) , 2015, DOI: 10.4236/iim.2015.71003
Abstract: Data exchange is a goal-oriented social communications system implemented through computerized technology. Data definition languages (DDLs) provide the syntax for communicating within and between organizations, illocutionary acts, such as informing, ordering and warning. Data exchange results in meaning-preserving mapping between an ensemble (a constrained variety) and its external (unconstrained) variety. Research on unsupervised structured and semi-structured data exchange has not produced any significant successes over the past fifty years. As a step towards finding a solution, this article proposes a new look at data exchange by using the principles of complex adaptive systems (CAS) to analyze current shortcomings and to propose a direction that may indeed lead to workable and mathematically grounded solution. Three CAS attributes key to this research are variety, tension and entropy. We use them to show that older and contemporary DDLs are identical in their core, thus explaining why even XML and Ontologies have failed to a create fully automated data exchange mechanism. Then we show that it is possible to construct a radically different DDL that overcomes existing data exchange limitations—its variety, tension and entropy are different from existing solutions. The article has these major parts: definition of key CAS attributes; quantitative examination of representative old and new DDLs using these attributes; presentation of the results and their pessimistic ramification; a section that proposes a new theoretical way to construct DDLs that is based entirely on CAS principles, thus enabling unsupervised data exchange. The theory is then tested, showing very promising results.
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