Search results for "Flicker"
showing 10 items of 51 documents
Measurement of the activation energies of oxygen ion diffusion in yttria stabilized zirconia by flicker noise spectroscopy
2019
The low-frequency noise in a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope (CAFM) probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. YSZ is a promising material for the memristor application since it is featured by high oxygen ion mobility, and the oxygen vacancy concentration in YSZ can be controlled by varying the molar fraction of the stabilizing yttrium oxide. Due to the low diameter of the CAFM probe contact to the YSZ film (similar to 10nm), we are able to measure the electric current flowing through an individual filament both in the low resistive state (LRS) and in the high r…
Clinical Predictors for Poor Quality of Life in Patients With Covert Hepatic Encephalopathy.
2018
Background Current EASL/AASLD guidelines recommend treatment of covert hepatic encephalopathy (HE) only in symptomatic patients, for example, in those with impaired quality of life or with affected driving abilities. Goals Because testing for impaired quality of life is time consuming, the aim of the present study was to identify simple clinical predictors for poor quality of life in patients with covert HE (CHE). Study In total, 139 cirrhotic in- and outpatients without a history of overt hepatic encephalopathy were enrolled. Diagnosis of HE grade 1 (HE1) was diagnosed clinically according to the West-Haven Criteria. Critical flicker frequency and the Psychometric Hepatic Encephalopathy Sc…
Serum nitrotyrosine and psychometric tests as indicators of impaired fitness to drive in cirrhotic patients with minimal hepatic encephalopathy
2013
BACKGROUND & AIMS: Cirrhotic patients with minimal hepatic encephalopathy (MHE) show impaired driving ability and increased vehicle accidents. The neurological deficits contributing to impair driving and the underlying mechanisms are poorly understood. Early detection of driving impairment would help to reduce traffic accidents in MHE patients. It would be therefore useful to have psychometric or biochemical parameters reflecting driving impairment. The aims of this work were as follows: (i) to shed light on the neurological deficits contributing to impair driving; (ii) to assess whether some psychometric test or biochemical parameter is a good indicator of driving impairment. METHODS: We a…
Changes in pattern induced flicker colors are mediated by the blue-yellow opponent process.
1992
The colors of Benham's Top [pattern induced flicker colors (PIFCs)] were matched with color stimuli provided by a computer aided color mixer. Subjects viewed a series of specifically modified black and white disks and matched the resulting subjective color with a comparison field containing the color generated by additive mixing. Different phase relations between the apparently colored ring and the surround were tested. The color loci of all PIFCs were found to lie on a plane in receptor three-space which is given by the axis of the shortwave receptor excitation and a vector given by combining the middle and long wave receptor excitation directions in a fixed ratio of nearly 1:1. From the o…
Timing flickers across sensory modalities
2009
In tasks requiring a comparison of the duration of a reference and a test visual cue, the spatial position of test cue is likely to be implicitly coded, providing a form of a congruency effect or introducing a response bias according to the environmental scale or its vectorial reference. The precise mechanism generating these perceptual shifts in subjective duration is not understood, although several studies suggest that spatial attentional factors may play a critical role. Here we use a duration comparison task within and across sensory modalities to examine if temporal performance is also modulated when people are exposed to spatial distractors involving different sensory modalities. Di…
Patients with minimal hepatic encephalopathy show impaired mismatch negativity correlating with reduced performance in attention tests
2012
Attention deficit is an early event in the cognitive impairment of patients with minimal hepatic encephalopathy (MHE). The underlying mechanisms remain unclear. Mismatch negativity (MMN) is an auditory event-related potential that reflects an attentional trigger. Patients with schizophrenia show impaired attention and cognitive function, which are reflected in altered MMN. We hypothesized that patients with MHE, similarly to those with schizophrenia, should show MMN alterations related with attention deficits. The aims of this work were to assess whether (1) MMN is altered in cirrhotic patients with MHE, compared to those without MHE, (2) MMN changes in parallel with performance in attentio…
Event-related potentials reveal rapid registration of features of infrequent changes during change blindness.
2009
Abstract Background Change blindness refers to a failure to detect changes between consecutively presented images separated by, for example, a brief blank screen. As an explanation of change blindness, it has been suggested that our representations of the environment are sparse outside focal attention and even that changed features may not be represented at all. In order to find electrophysiological evidence of neural representations of changed features during change blindness, we recorded event-related potentials (ERPs) in adults in an oddball variant of the change blindness flicker paradigm. Methods ERPs were recorded when subjects performed a change detection task in which the modified i…
Light scattering in artificial fog and simulated with light scattering filter.
2009
Disability glare, affecting e.g. road safety at night, may result either from intraocular light scattering or from external conditions such as fog. Measurements were made of light scattering in fog and compared with intraocular straylight data for normal eyes and eyes with simulated cataract. All measurements were made with a direct compensation flicker method. To estimate light scattering levels in fog, straylight measurements were carried in a fog chamber for different densities of fog. Density was characterized by the meteorological term visibility V and ranged from 7 to 25. Test distance for measurements in the fog was constant at 5 m. Cataract eye conditions were simulated by placing a…
Learning Curve and Fatigue Effect of Flicker Defined Form Perimetry
2011
To evaluate the learning curve and fatigue effect of flicker defined form (FDF) perimetry.Prospective cross-sectional study.One hundred forty-one eyes of 75 healthy subjects were included in the study. Every subject was measured 3 times on 3 different days within 3 months. Differences among the tests were analyzed for mean sensitivity (MS), mean deviation (MD), pattern standard deviation (PSD), reliability indices, test duration, and test points5% and0.5% in 75 right eyes on the basis of linear mixed models for repeated measurements. To assess the effect of fatigue, differences of MS, MD, and PSD values between 66 left and right eyes were evaluated regarding alterations between these 3 exam…
Multicolour LEDs in educational demonstrations of physics and optometry
2014
LED light sources are used to design experimental setup for university courses teaching human color vision. The setup allows to demonstrate various vision characteristics and to apply for student practical exercises to study eye spectral sensitivity in different spectral range using heterochromatic flicker photometry. Technique can be used in laboratory works for students to acquire knowledge in visual perception, basics of electronics and measuring, or it can be applied as fully computer control experiment. Besides studies of the eye spectral sensitivity students can practice in trichromatic color matching and other visual perception tasks