WorldWideScience

Sample records for afterimage

  1. Neural locus of color afterimages.

    Science.gov (United States)

    Zaidi, Qasim; Ennis, Robert; Cao, Dingcai; Lee, Barry

    2012-02-07

    After fixating on a colored pattern, observers see a similar pattern in complementary colors when the stimulus is removed [1-6]. Afterimages were important in disproving the theory that visual rays emanate from the eye, in demonstrating interocular interactions, and in revealing the independence of binocular vision from eye movements. Afterimages also prove invaluable in exploring selective attention, filling in, and consciousness. Proposed physiological mechanisms for color afterimages range from bleaching of cone photopigments to cortical adaptation [4-9], but direct neural measurements have not been reported. We introduce a time-varying method for evoking afterimages, which provides precise measurements of adaptation and a direct link between visual percepts and neural responses [10]. We then use in vivo electrophysiological recordings to show that all three classes of primate retinal ganglion cells exhibit subtractive adaptation to prolonged stimuli, with much slower time constants than those expected of photoreceptors. At the cessation of the stimulus, ganglion cells generate rebound responses that can provide afterimage signals for later neurons. Our results indicate that afterimage signals are generated in the retina but may be modified like other retinal signals by cortical processes, so that evidence presented for cortical generation of color afterimages is explainable by spatiotemporal factors that modify all signals.

  2. Luminance contours can gate afterimage colors and 'real' colors

    NARCIS (Netherlands)

    Anstis, S.; Vergeer, M.L.T.; Lier, R.J. van

    2012-01-01

    It has long been known that colored images may elicit afterimages in complementary colors. We have already shown (Van Lier, Vergeer, & Anstis, 2009) that one and the same adapting image may result in different afterimage colors, depending on the test contours presented after the colored image. The c

  3. Visual Afterimages of Emotional Faces in High Functioning Autism

    Science.gov (United States)

    Rutherford, M. D.; Troubridge, Erin K.; Walsh, Jennifer

    2012-01-01

    Fixating an emotional facial expression can create afterimages, such that subsequent faces are seen as having the opposite expression of that fixated. Visual afterimages have been used to map the relationships among emotion categories, and this method was used here to compare ASD and matched control participants. Participants adapted to a facial…

  4. Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical ON and OFF Poststimulus Responses.

    Science.gov (United States)

    Li, Hui; Liu, Xu; Andolina, Ian M; Li, Xiaohong; Lu, Yiliang; Spillmann, Lothar; Wang, Wei

    2017-02-22

    Humans are more sensitive to luminance decrements than increments, as evidenced by lower thresholds and shorter latencies for dark stimuli. This asymmetry is consistent with results of neurophysiological recordings in dorsal lateral geniculate nucleus (dLGN) and primary visual cortex (V1) of cat and monkey. Specifically, V1 population responses demonstrate that darks elicit higher levels of activation than brights, and the latency of OFF responses in dLGN and V1 is shorter than that of ON responses. The removal of a dark or bright disc often generates the perception of a negative afterimage, and here we ask whether there also exist asymmetries for negative afterimages elicited by dark and bright discs. If so, do the poststimulus responses of subcortical ON and OFF cells parallel such afterimage asymmetries? To test these hypotheses, we performed psychophysical experiments in humans and single-cell/S-potential recordings in cat dLGN. Psychophysically, we found that bright afterimages elicited by luminance decrements are stronger and last longer than dark afterimages elicited by luminance increments of equal sizes. Neurophysiologically, we found that ON cells responded to the removal of a dark disc with higher firing rates that were maintained for longer than OFF cells to the removal of a bright disc. The ON and OFF cell asymmetry was most pronounced at long stimulus durations in the dLGN. We conclude that subcortical response strength differences between ON and OFF channels parallel the asymmetries between bright and dark negative afterimages, further supporting a subcortical origin of bright and dark afterimage perception.SIGNIFICANCE STATEMENT Afterimages are physiological aftereffects following stimulation of the eye, the study of which helps us to understand how our visual brain generates visual perception in the absence of physical stimuli. We report, for the first time to our knowledge, asymmetries between bright and dark negative afterimages elicited by

  5. Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

    Science.gov (United States)

    Atkinson, R P; Crawford, H J

    1992-01-01

    To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.

  6. Multisensory Tracking of Objects in Darkness: Capture of Positive Afterimages by the Tactile and Proprioceptive Senses.

    Directory of Open Access Journals (Sweden)

    Brian W Stone

    Full Text Available This paper reports on three experiments investigating the contribution of different sensory modalities to the tracking of objects moved in total darkness. Participants sitting in the dark were exposed to a brief, bright flash which reliably induced a positive visual afterimage of the scene so illuminated. If the participants subsequently move their hand in the darkness, the visual afterimage of that hand fades or disappears; this is presumably due to conflict between the illusory visual afterimage (of the hand in its original location and other information (e.g., proprioceptive from a general mechanism for tracking body parts. This afterimage disappearance effect also occurs for held objects which are moved in the dark, and some have argued that this represents a case of body schema extension, i.e. the rapid incorporation of held external objects into the body schema. We demonstrate that the phenomenon is not limited to held objects and occurs in conditions where incorporation into the body schema is unlikely. Instead, we propose that the disappearance of afterimages of objects moved in darkness comes from a general mechanism for object tracking which integrates input from multiple sensory systems. This mechanism need not be limited to tracking body parts, and thus we need not invoke body schema extension to explain the afterimage disappearance. In this series of experiments, we test whether auditory feedback of object movement can induce afterimage disappearance, demonstrate that the disappearance effect scales with the magnitude of proprioceptive feedback, and show that tactile feedback alone is sufficient for the effect. Together, these data demonstrate that the visual percept of a positive afterimage is constructed not just from visual input of the scene when light reaches the eyes, but in conjunction with input from multiple other senses.

  7. Interaction between contours and eye movements in the perception of afterimages: A test of the signal ambiguity theory.

    Science.gov (United States)

    Powell, Georgie; Sumner, Petroc; Harrison, James J; Bompas, Aline

    2016-05-01

    An intriguing property of afterimages is that conscious experience can be strong, weak, or absent following identical stimulus adaptation. Previously we suggested that postadaptation retinal signals are inherently ambiguous, and therefore the perception they evoke is strongly influenced by cues that increase or decrease the likelihood that they represent real objects (the signal ambiguity theory). Here we provide a more definitive test of this theory using two cues previously found to influence afterimage perception in opposite ways and plausibly at separate loci of action. However, by manipulating both cues simultaneously, we found that their effects interacted, consistent with the idea that they affect the same process of object interpretation rather than being independent influences. These findings bring contextual influences on afterimages into more general theories of cue combination, and we suggest that afterimage perception should be considered alongside other areas of vision science where cues are found to interact in their influence on perception.

  8. Visible light induced ocular delayed bioluminescence as a possible origin of negative afterimage

    CERN Document Server

    Bokkon, I; Wang, C; Dai, J; Salari, V; Grass, F; Antal, I

    2011-01-01

    The delayed luminescence of biological tissues is an ultraweak reemission of absorbed photons after exposure to external monochromatic or white light illumination. Recently, Wang, B\\'okkon, Dai and Antal (Brain Res. 2011) presented the first experimental proof of the existence of spontaneous ultraweak biophoton emission and visible light induced delayed ultraweak photon emission from in vitro freshly isolated rat's whole eye, lens, vitreous humor and retina. Here, we suggest that the photobiophysical source of negative afterimage can also occur within the eye by delayed bioluminescent photons. In other words, when we stare at a colored (or white) image for few seconds, external photons can induce excited electronic states within different parts of the eye that is followed by a delayed reemission of absorbed photons for several seconds. Finally, these reemitted photons can be absorbed by nonbleached photoreceptors that produce a negative afterimage. Although this suggests the photobiophysical source of negativ...

  9. Marcin Stańczyk’s Afterimages and Aftersounds – Reflections and Self-Reflections

    Directory of Open Access Journals (Sweden)

    Tabakiernik Marta

    2015-12-01

    Full Text Available One of the most frequently recurring topics in Marcin Stańczyk’s (b. 1977 self-commentaries is the idea of translating the phenomenon of afterimages into music, in the form of his original concept of aftersounds. Direct inspiration for this concept came from a cycle of solarist paintings by Władysław Strzemiński entitled Afterimages of the Sun. The concept of aftersounds can be considered on the level of music material (resonances and reflections of various kinds, contrasts on the sound level as well as metaphorically (when the composition becomes an afterimage of an external phenomenon. Particularly important to Stańczyk’s work as a composer are explorations in the field of music perception and the theatricalisation of performance, which turns every gesture of the performers into a meaningful element of the composition, as well as an element of expression. This paper aims to present an outline of the ways in which Stańczyk implements the idea of aftersounds in music. The text is based on the composer’s own statements as well as on characteristic examples from his works.

  10. 海丁格刷引导定位的后像仪对偏心注视性弱视的疗效研究%Research on the clinical efficacy of Haidinger brush guided and located afterimage amblyopic therapeutic apparatus in patients with eccentric fixation amblyopia

    Institute of Scientific and Technical Information of China (English)

    倪灵芝; 施颖辉; 江龙飞

    2011-01-01

    Objective: To explore the clinical efficacy of Haidinger brush guided and located afterimage amblyopic therapeutic apparatus in training of eccentric fixation amblyopia.Methods: 25 children with eccentric fixation amblyopia who received amblyopic training in outpatient department of the hospital were selected, the corrected visual acuity of 11 children was 0.2 ~ 0.5, and the corrected visual acuity of 14 children was below 0.1, the average corrected visual acuity was 0.178 0.A self - designed Haidinger brush guided and located afterimage amblyopic therapeutic apparatus was used for amblyopic training, the changes of corrected visual acuity and fixation property before and after the training were recorded.Results: There was significant difference in average corrected visual acuity before (0.178 0) and after the training (0.716 0) showed by paired t test (P <0.001 ).There was significant difference in fixation property before and after the training showed by non - parameter rank sum test.Conclusion: Haidinger brush guided and located afterimage amblyopic therapeutic apparatus is effective in the treatment of eccentric fixation amblyopia.%目的:探讨海丁格刷引导定位的后像弱视治疗仪用于偏心注视性弱视训练的疗效.方法:取该院门诊弱视训练患儿中偏心注视患者25例,其中矫正视力0.2~0.511例,矫正视力0.1以下14例,平均矫正视力为0.1780.应用本科室自行研究设计的海丁格刷引导定位的后像弱视治疗仪进行弱视训练,记录训练前后矫正视力的变化及注视性质的改变.结果:①采用配对t检验比较训练前后矫正视力变化,训练前平均矫正视力为0.178 0,训练后平均矫正视力为0.716 0,P<0.001,有统计学差异.②用非参数秩和检验比较训练前后注视性质的变化,P<0.001,有统计学差异.结论:海丁格刷引导定位的后像弱视治疗仪用于治疗偏心注视性弱视有显著疗效.

  11. [Appraisal of the formation of afterimages by means of a new computer application in patients with demyelinating optic neuropathies].

    Science.gov (United States)

    Fernandez Jimenez-Ortiz, H; Reche-Sainz, J A; Villarrubia-Torcal, B; Toledano-Fernandez, N; Perucho-Martinez, S

    2016-10-16

    Introduccion. En las neuritis opticas se afecta, entre otras funciones visuales, la percepcion del color. La mayoria de las pruebas existentes para evaluar discromatopsias se basa en evaluar el matiz, pero no se ha estudiado clinicamente la formacion de postimagenes en la retina en estos pacientes. Objetivo. Evaluar la discromatopsia adquirida en las neuritis opticas desmielinizantes mediante la formacion de postimagenes en la retina. Sujetos y metodos. Estudio observacional, transversal, de casos y controles. Los casos son pacientes con al menos un episodio de neuritis optica y esclerosis multiple confirmada. Se selecciono un control sano por cada caso, emparejado por edad y sexo. La variable principal es la capacidad de ver postimagenes tras saturar los fotorreceptores retinianos. Para evaluar dicho fenomeno se desarrollo una aplicacion informatica especifica. Resultados. La muestra comprende 30 casos y 30 controles (63% mujeres; edad media: 33 años; rango: 18-48 años). Los casos mostraron menor probabilidad de ver la postimagen (el 36,6% de los casos y ningun control no veian postimagen) y, en caso de verla, una menor permanencia de ella. La curva ROC muestra una sensibilidad del 86,3% y una especificidad del 83,3%. La odds ratio era de 5 (intervalo de confianza al 95%: 2,21-11,3) para la probabilidad de ver la postimagen en los controles frente a los casos. Conclusiones. Los pacientes con al menos un episodio de neuritis optica presentan una menor capacidad de observar postimagenes, por lo que la prueba es util para la evaluacion y el seguimiento del daño funcional en neuropatias opticas desmielinizantes.

  12. ["One makes a distinction between 2 color contrasts, the instantaneous and the afterimage". Several color theory comments by Gottfried Semper in the "style" of 1860].

    Science.gov (United States)

    Rehm, Robin

    2010-01-01

    Gottfried Semper (1803-1879) is well-known for his work on colour schemes in architecture. The architect published several books and articles on related topics, such as polychromy in Greek and Roman edifices, mural paintings of Pompeii, and the colouring of the renaissance architecture. It has been less discussed, however, that Semper was also engaged in the contemporary discourse on colour theory as pursued in Natural Science research. The paper examines theoretical remarks on colour in Semper's publication "Der Stil" of 1860. His terminology, the modality of his explanations and his discussion of colour experiments suggest that Semper was familiar with Michel-Eugène Chevreul's theory of colour. Semper's reception of Chevreul is not surprising. The French chemist wrote one of the most important studies of colour of the nineteenth century. His famous book "De la loi du contraste simultané des couleurs" was published in Paris in 1839, where he developed some of the principles of "harmony and contrast of colours" and their application to the arts. Especially Chevreul's synthesis between theoretical consolidation and practical transformation seem to have attracted Semper's attention.

  13. A dissociation of attention and awareness in phase-sensitive but not phase-insensitive visual channels

    NARCIS (Netherlands)

    Brascamp, J.W.; van Boxtel, J.J.A.; Knapen, T.H.J.; Blake, R.

    2010-01-01

    The elements most vivid in our conscious awareness are the ones to which we direct our attention. Scientific study confirms the impression of a close bond between selective attention and visual awareness, yet the nature of this association remains elusive. Using visual afterimages as an index, we in

  14. Perceived visual motion as effective stimulus to pursuit eye movement system

    Science.gov (United States)

    Yasui, S.; Young, L. R.

    1975-01-01

    Human eye tracking of a foveal afterimage during angular head oscillation in the dark produced smooth eye movements exceeding those for normal vestibular nystagmus, and a reduction in the frequency of the fast phase component of nystagmus eye movements. These results may support a closed loop extension of the corollary discharge theory, with oculomotor commands based on perceived object velocity.

  15. How Were Eye Movements Recorded Before Yarbus?

    Science.gov (United States)

    Wade, Nicholas J

    2015-01-01

    Alfred Yarbus introduced a new dimension of precision in recording how the eyes moved, either when attempts were made to keep them stationary or when scanning pictures. Movements of the eyes had been remarked upon for millennia, but recording how they move is a more recent preoccupation. Emphasis was initially placed on abnormalities of oculomotor function (like strabismus) before normal features were considered. The interest was in where the eyes moved to rather than determining how they got there. The most venerable technique for examining ocular stability involved comparing the relative motion between an afterimage and a real image. In the late 18th century, Wells compared afterimages generated before body rotation with real images observed following it when dizzy; he described both lateral and torsional nystagmus, thereby demonstrating the directional discontinuities in eye velocities. At around the same time Erasmus Darwin used afterimages as a means of demonstrating ocular instability when attempting to fixate steadily. However, the overriding concern in the 19th century was with eye position rather than eye movements. Thus, the characteristics of nystagmus were recorded before those of saccades and fixations. Eye movements during reading were described by Hering and by Lamare (working in Javal's laboratory) in 1879; both used similar techniques of listening (with tubes placed over the eyelids) to the sounds made during contractions of the extraocular muscles. Photographic records of eye movements during reading were made by Dodge early in the 20th century, and this stimulated research using a wider array of patterns. Eye movements over pictures were examined by Stratton and later by Buswell, who drew attention to the effects of instructions on the pattern of eye movements. In midcentury, attention shifted back to the stability of the eyes during fixation, with the emphasis on involuntary movements. The suction cap methods developed by Yarbus were applied

  16. Bigness is in the eye of the beholder. [size and distance perception of pilots in flight

    Science.gov (United States)

    Roscoe, S. N.

    1985-01-01

    This report reviews an investigation of judgments of size and distance as required of pilots in flight. The experiments covered a broad spectrum of basic psychophysiological issues involving the measurement of visual accommodation and its correlation with various other dependent variables. Psychophysiological issues investigated included the size-distance invariance hypothesis, the projection of afterimages, the moon illusion, night and empty-field myopia, the dark focus and its so-called Mandelbaum effect, the nature and locus of the accommodative stimulus, the relation between accommodation, retinal size, and perceived size, and possible relationships among accommodative responses, autonomic balance, and personality variables.

  17. Aftereffect of Adaptation to Illusory Brightness

    Directory of Open Access Journals (Sweden)

    Xinguang Cao

    2011-05-01

    Full Text Available Several figures are known to induce illusory brightness. We tested whether adaptation to illusory brightness produced an aftereffect in brightness. After viewing a gray square area having illusory brightness (e.g., due to brightness contrast or illusory contours for ten seconds, the illusion-inducing surround vanished. After three seconds, subjects reported whether the square area was seen as brighter than, darker than, or the same brightness as a control gray square area. The luminance of the tested square area was physically unchanged. The results show that when the black surround inducing brightness contrast suddenly became gray (i.e., vanished, the center gray square tended to look darker than a control gray square. Similarly, after viewing a subjective square consisting of black-line terminations, the square area tended to look darker than the control even though the afterimage of the lines could not be seen. These results indicate that induced or illusory brightness causes an aftereffect in brightness regardless of the appearance of negative afterimages of the illusion-inducing components.

  18. The Darwins and Wells: from revolution to evolution.

    Science.gov (United States)

    Wade, Nicholas J

    2010-04-01

    In the biography of his grandfather (Erasmus Darwin), Charles Darwin hinted that his father (Robert Darwin) had received parental assistance in conducting and writing his medical thesis (which concerned afterimages). The experiments also involved visual vertigo, and they were elaborated by the senior Darwin in his Zoonomia, published in 1794. Erasmus Darwin's interpretation was in terms of trying to pursue peripheral afterimages formed during rotation; it was at variance with one published two years earlier by William Charles Wells, who had investigated the visual consequences of body rotation when the body is subsequently still. Wells penned two retorts to the Darwins' theory; although they were not accepted by Erasmus, he did devise a human centrifuge, models of which were employed in later studies of vertigo. Wells's ideas on evolution were expressed in a paper delivered to the Royal Society (in 1813) but not published in its Transactions. Commenting on the case of a white woman, part of whose skin was black, he proposed a process of change that was akin to natural selection. His ideas were acknowledged by Charles Darwin in the fourth edition of On the Origin of Species.

  19. Development of high-frame-rate LED panel and its applications for stereoscopic 3D display

    Science.gov (United States)

    Yamamoto, H.; Tsutsumi, M.; Yamamoto, R.; Kajimoto, K.; Suyama, S.

    2011-03-01

    In this paper, we report development of a high-frame-rate LED display. Full-color images are refreshed at 480 frames per second. In order to transmit such a high frame-rate signal via conventional 120-Hz DVI, we have introduced a spatiotemporal mapping of image signal. A processor of LED image signal and FPGAs in LED modules have been reprogrammed so that four adjacent pixels in the input image are converted into successive four fields. The pitch of LED panel is 20 mm. The developed 480-fps LED display is utilized for stereoscopic 3D display by use of parallax barrier. The horizontal resolution of a viewed image decreases to one-half by the parallax barrier. This degradation is critical for LED because the pitch of LED displays is as large as tens of times of other flat panel displays. We have conducted experiments to improve quality of the viewed image through the parallax barrier. The improvement is based on interpolation by afterimages. It is shown that the HFR LED provides detailed afterimages. Furthermore, the HFR LED has been utilized for unconscious imaging, which provide a sensation of discovery of conscious visual information from unconscious images.

  20. Process of timbral composing

    Science.gov (United States)

    Withrow, Sam

    In this paper, I discuss the techniques and processes of timbral organization I developed while writing my chamber work, Afterimage. I compare my techniques with illustrative examples by other composers to place my work in historical context. I examine three elements of my composition process. The first is the process of indexing and cataloging basic sonic materials. The second consists of the techniques and mechanics of manipulating and assembling these collections into larger scale phrases, textures, and overall form in a musical work. The third element is the more elusive, and often extra-musical, source of inspiration and motivation. The evocative power of tone color is both immediately evident yet difficult to explain. What is timbre? This question cannot be answered solely in scientific terms; subjective factors affect our perception of it.

  1. A model for visual image-background discrimination by relative movement

    Institute of Scientific and Technical Information of China (English)

    陆惠民; 王秀春; 刘守忠; 史美德; 刘芳; 郭爱克

    1997-01-01

    Biologically plausible electronic neural network setup for real time processing motion image informa-tion was built. Using this setup the first part of the model was examined and real time discrimination of moving object image was realized from complex background in high resolution. Afterimages may play an important role in filtering moving object image and the aperture problem should be separated into two parts: the first part, i.e. the incomplete filtered moving object image, can be better resolved by parallel integration of multi-channel visual information, howev-er, the second part, i.e. the inaccurate measurement results for movement direction, may only get certain compensa-tion by visual integration.

  2. Mapping Collected Memory: An Exploration of Memory-Based Navigation in Amman, Jordan

    Directory of Open Access Journals (Sweden)

    Regina Mamou

    2014-06-01

    Full Text Available The purpose of this research is to explore navigational and image-making methods in a context where maps and formal address systems have been minimally consulted in recent years. This investigation is approached by way of a research-based art project on subjective cartography, which was carried out from 2009 to 2010 during a Fulbright fellowship to Amman, Jordan. The project examines the mutability of a specific location as well as its relationship between obsolescence in cartographic resources and the photographic medium. By reaching out to Ammani residents for informal tours of the city, selected guides were asked to narrate their experiences of navigating the city by memory and then directed to point out key landmarks during this process. Later, these tours were re-memorized and landmarks were photographed as a representation of the afterimage to capture high-quality still images through the use of a large-format photographic device. These afterimages are not intended to serve as documents or memorials of Amman but rather as ruminations on the faculties of memory in an ever-changing environment. This subjective experience, or the observation of a city’s minutiae amid wayfinding, poses a series of inquiries, vis-à-vis memory-based navigation and the role of still images, as an alternative to the panoptic view of a map. The result is a meditative project considering the plasticity of an urban entity, presented as a composition of written material and large-scale photographs, fragments of the city that when viewed as a series come together as a constellation of a subjective whole. 

  3. Follow-up of hearing thresholds among forge hammering workers

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, A.A.; Mikael, R.A.; Faris, R. (Ain Shams Univ., Abbasia, Cairo (Egypt))

    1989-01-01

    Hearing threshold was reexamined in a group of forge hammering workers investigated 8 years ago with consideration of the age effect and of auditory symptoms. Workers were exposed to impact noise that ranged from 112 to 139 dB(A)--at an irregular rate of 20 to 50 drop/minute--and a continuous background noise that ranged from 90 to 94 dB(A). Similar to what was observed 8 years ago, the present permanent threshold shift (PTS) showed a maximum notch at the frequency of 6 kHz and considerable elevations at the frequencies of 0.25-1 kHz. The age-corrected PTS and the postexposure hearing threshold were significantly higher than the corresponding previous values at the frequencies 0.25, 0.5, 1, and 8 kHz only. The rise was more evident at the low than at the high frequencies. Temporary threshold shift (TTS) values were significantly less than those 8 years ago. Contrary to the previous TTS, the present TTS were higher at low than at high frequencies. Although progression of PTS at the frequencies 0.25 and 0.5 kHz was continuous throughout the observed durations of exposure, progression at higher frequencies occurred essentially in the first 10 to 15 years of exposure. Thereafter, it followed a much slower rate. Tinnitus was significantly associated with difficulty in hearing the human voice and with elevation of PTS at all the tested frequencies, while acoustic after-image was significantly associated with increment of PTS at the frequencies 0.25-2 kHz. No relation between PTS and smoking was found. PTS at low frequencies may provide an indication of progression of hearing damage when the sensitivity at 6 and 4 kHz diminishes after prolonged years of exposure. Tinnitus and acoustic after-image are related to the auditory effect of forge hammering noise.

  4. Removing the remaining ridges in fingerprint segmentation

    Institute of Scientific and Technical Information of China (English)

    ZHU En; ZHANG Jian-ming; YIN Jian-ping; ZHANG Guo-min; HU Chun-feng

    2006-01-01

    Fingerprint segmentation is an important step in fingerprint recognition and is usually aimed to identify non-ridge regions and unrecoverable low quality ridge regions and exclude them as background so as to reduce the time expenditure of image processing and avoid detecting false features. In high and in low quality ridge regions, often are some remaining ridges which are the afterimages of the previously scanned finger and are expected to be excluded from the foreground. However, existing segmentation methods generally do not take the case into consideration, and often, the remaining ridge regions are falsely classified as foreground by segmentation algorithm with spurious features produced erroneously including unrecoverable regions as foreground. This paper proposes two steps for fingerprint segmentation aimed at removing the remaining ridge region from the foreground. The non-ridge regions and unrecoverable low quality ridge regions are removed as background in the first step, and then the foreground produced by the first step is further analyzed for possible remove of the remaining ridge region. The proposed method proved effective in avoiding detecting false ridges and in improving minutiae detection.

  5. Hazards in air-, rail-, and road traffic arising from laserpointers; Gefaehrdungen des Luft-, Schienen- und Strassenverkehrs durch Laserpointer

    Energy Technology Data Exchange (ETDEWEB)

    Reidenbach, H.D. [Fachhochschule Koeln (Germany). Forschungsschwerpunkt Medizintechnik und Nichtionisierende Strahlung; Deutsch-Schweizerischer Fachverband fuer Strahlenschutz e.V., Garching (Germany). Arbeitskreis Nichtionisierende Strahlung (AKNIR)

    2012-07-01

    Visible laser radiation with sufficient irradiance or radiant exposure might result in permanent damage of the eyes especially in the retina. In order to prevent this exposure limit values have been established based on current scientific knowledge. In addition visible laser radiation might result in effects like temporary blinding at even much lower exposure values. In this case irritations, flash-blindness and afterimages appear whose extent might exceed the respective damage level while vision is temporarily compromised in critical visual tasks more or less. The easy accessibility of hand-held laser products (laser pointers) with relatively high power might result in a modification of the security situation especially in air traffic via thoughtless and careless use of such products or in terroristic acts. In addition an increasing number of incidents in rail and road traffic where not only temporary blinding might be anticipated but permanent damage of the eyes as a result of overexposure due to laser pointer irradiation cannot be excluded any longer. Using laser pointers, which are available on the market in the power range up to 1 watt and at different wavelengths new hazard scenarios and threats with serious consequences are possible. Here the radiation protection is in great demand. (orig.)

  6. True Detective Stories: Media Textuality and the Anthology Format between Remediation and Transmedia Narratives

    Directory of Open Access Journals (Sweden)

    Cristina Demaria

    2014-12-01

    Full Text Available Through the analysis of the recent HBO first season TV series True Detective (2014-, the essays focuses on the renewed anthology format of contemporary seriality as a way to inscribe the form of the novel in the transmedia imagination and its narrative models. While the first part of the essay concentrates on Media and Literary Studies’ debates on the statute of media texts, their materiality and the transformations of their contents in the participatory and convergent culture of prosumers, the second part is devoted to an in-depth reading of some of the main features of True Detective’s first season: from the ways it remediates many other genres and media, to how – as an audiovisual sychretyc text -  it plays with dialogues, cinematography, music and its temporal, spatial and seeing enunciative strategies and positions in order to construct a (quasidystopic narrative of America as an after-image, or, better, a post-collapse America and its Southern Gothic landscapes. In the lst paragraph, this writing briefly engages with how this particular format of TV series helps developing narrative models that fan we bpages and fanfic archives are still struggling not so much to comprehend, but to actually transform into an expanded textuality  able to tell a more ‘true’ story.

  7. Evaporative respiratory cooling augments pit organ thermal detection in rattlesnakes.

    Science.gov (United States)

    Cadena, Viviana; Andrade, Denis V; Bovo, Rafael P; Tattersall, Glenn J

    2013-12-01

    Rattlesnakes use their facial pit organs to sense external thermal fluctuations. A temperature decrease in the heat-sensing membrane of the pit organ has the potential to enhance heat flux between their endothermic prey and the thermal sensors, affect the optimal functioning of thermal sensors in the pit membrane and reduce the formation of thermal "afterimages", improving thermal detection. We examined the potential for respiratory cooling to improve strike behaviour, capture, and consumption of endothermic prey in the South American rattlesnake, as behavioural indicators of thermal detection. Snakes with a higher degree of rostral cooling were more accurate during the strike, attacking warmer regions of their prey, and relocated and consumed their prey faster. These findings reveal that by cooling their pit organs, rattlesnakes increase their ability to detect endothermic prey; disabling the pit organs caused these differences to disappear. Rattlesnakes also modify the degree of rostral cooling by altering their breathing pattern in response to biologically relevant stimuli, such as a mouse odour. Our findings reveal that low humidity increases their ability to detect endothermic prey, suggesting that habitat and ambush site selection in the wild may be influenced by external humidity levels as well as temperature.

  8. Robust Foreground Detection: A Fusion of Masked GreyWorld, Probabilistic Gradient Information and Extended Conditional Random Field Approach

    Directory of Open Access Journals (Sweden)

    David Rawlinson

    2012-05-01

    Full Text Available Foreground detection has been used extensively in many applications such as people counting, traffic monitoring and face recognition. However, most of the existing detectors can only work under limited conditions. This happens because of the inability of the detector to distinguish foreground and background pixels, especially in complex situations. Our aim is to improve the robustness of foreground detection under sudden and gradual illumination change, colour similarity issue, moving background and shadow noise. Since it is hard to achieve robustness using a single model, we have combined several methods into an integrated system. The masked grey world algorithm is introduced to handle sudden illumination change. Colour co-occurrence modelling is then fused with the probabilistic edge-based background modelling. Colour co-occurrence modelling is good infiltering moving background and robust to gradual illumination change, while an edge-based modelling is used for solving a colour similarity problem. Finally, an extended conditional random field approach is used to filter out shadow and afterimage noise. Simulation results show that our algorithm performs better compared to the existing methods, which makes it suitable for higher-level applications.

  9. Engineering the just war: examination of an approach to teaching engineering ethics.

    Science.gov (United States)

    Haws, David R

    2006-04-01

    The efficiency of engineering applied to civilian projects sometimes threatens to run away with the social agenda, but in military applications, engineering often adds a devastating sleekness to the inevitable destruction of life. The relative crudeness of terrorism (e.g., 9/11) leaves a stark after-image, which belies the comparative insignificance of random (as opposed to orchestrated) belligerence. Just as engineering dwarfs the bricolage of vernacular design 'moving us past the appreciation of brush-strokes, so to speak' the scale of engineered destruction makes it difficult to focus on the charred remains of individual lives. Engineers need to guard against the inappropriate military subsumption of their effort. Fortunately, the ethics of warfare has been an ongoing topic of discussion for millennia. This paper will examine the university core class I've developed (The Moral Dimensions of Technology) to meet accreditation requirements in engineering ethics, and the discussion with engineering and non-engineering students focused by the life of electrical engineer Vannevar Bush, with selected readings in moral philosophy from the Dao de Jing, Lao Tze, Cicero, Aurelius Augustinus, Kant, Annette Baier, Peter Singer, Elizabeth Anscombe, Philippa Foot, and Judith Thomson.

  10. Adjusting to a sudden “aging” of the lens.

    Science.gov (United States)

    Tregillus, Katherine E M; Werner, John S; Webster, Michael A

    2016-03-01

    Color perception is known to remain largely stable across the lifespan despite the pronounced changes in sensitivity from factors such as the progressive brunescence of the lens. However, the mechanisms and timescales controlling these compensatory adjustments are still poorly understood. In a series of experiments, we tracked adaptation in observers after introducing a sudden change in lens density by having observers wear glasses with yellow filters that approximated the average spectral transmittance of a 70-year-old lens. Individuals were young adults and wore the glasses for 5 days for 8 h per day while engaged in their normal activities. Achromatic settings were measured on a CRT before and after each daily exposure with the lenses on and off, and were preceded by 5 min of dark adaptation to control for short-term chromatic adaptation. During each day, there was a large shift in the white settings consistent with a partial compensation for the added lens density. However, there was little to no evidence of an afterimage at the end of each daily session, and participants’ perceptual nulls were roughly aligned with the nulls for short-term chromatic adaptation, suggesting a rapid renormalization when the lenses were removed. The long-term drift was also extinguished by brief exposure to a white adapting field. The results point to distinct timescales and potentially distinct mechanisms compensating for changes in the chromatic sensitivity of the observer.

  11. Eye protection practices and symptoms among welders in the Limpopo Province of South Africa+

    Directory of Open Access Journals (Sweden)

    H. L. Sithole

    2009-12-01

    Full Text Available Welding is associated with several ocular and systemic hazards especially where adequate protective measures are not taken.  The purpose of this project was to study the eye protection practices and symptoms among welders in the Capricorn District of Limpopo Province, South Africa. Questionnaires designed to investigate eye protection practices and symptoms experienced were completed byone hundred and fifty (150 welders. The types of welding done were shielded metal arc (84%, oxyacetylene gas (4% and silver brazing (12%. The number of years spent in the welding industry ranged from one to 10 years with a mean of 5 ± 3.1 years and the number of hours of welding per day ranged from one to 10 hours with a mean of 6 ± 2.1 hours. A large percentage of the welders (89% reported wearing protective devices when welding and the most common protective devices used by the welders were: helmets (57%, goggles(22%, and face shields (15%. Six percent used inefficient protective devices such as sunglasses.  Sixty one percent reported occasional exposure to welding flashes when not wearing any eye protection. Welding-related eye symptoms reported included foreign body sensation (18%, persistent after-images (31%, and watery eyes (50%.  Al-though the majority of the welders wore protective devices while welding, a few did not always use such devices while others used sunglasses for protection.  Moreover, many of the welders were occasionally, and only a few were always, exposed to welding flashes when protective devices were not used. Therefore, we concluded that eye protectionpractices amongst the welders appeared to be inadequate to avoid hazards associated with welding.  It is recommended that an eye protection educational campaign for welders should form part of the SouthAfrican Government’s workplace safety program. 

  12. Reduced Interocular Transfer of Spatial Adaptation for Fast Stimuli

    Directory of Open Access Journals (Sweden)

    Daniel H Baker

    2012-05-01

    Full Text Available Threshold elevation following monocular adaptation is weaker in the unadapted eye than in the adapted eye. At least 15 studies have measured this interocular transfer (IOT phenomenon, and typically report around 60% transfer. Yet almost all of these studies used spatial frequencies above 3c/deg, very slow temporal parameters, and criterion sensitive methods (method of adjustment, yes/no. In recent work, we (Meese and Baker 2011, i-Perception 2 159–182 found markedly weaker interocular transfer at low spatial and high temporal frequencies. Here, we measure IOT in 9 observers for a broad range of spatiotemporal frequencies (0.5, 2, and 8c/deg; 1, 4, and 15Hz using a 2AFC paradigm. Targets were horizontal Gabor patches with a full-width-at-half height of 1.67 (lower frequencies or 6.68 (8c/deg grating cycles. Adaptors were larger gratings with the same spatiotemporal properties as the targets. Observers adapted for 2 min initially, and 5 s between each trial, with monocular presentation enabled by shutter goggles. We typically found weaker IOT than previously reported (<50%, particularly for our fastest stimuli (lowest spatial and highest temporal frequencies, where it was virtually absent in all cases. Binocular summation and monocular adaptation were normal in all conditions. This implies that adaptation to ‘magno’ stimuli, not investigated in previous studies, occurs at a monocular locus. We also consider possible methodological confounds in classical studies which might have inflated the levels of IOT. These include the formation of retinal afterimages from static adaptors and changes in criterion unrelated to changes in sensitivity.

  13. ANALYSIS OF MULTIPATH PIXELS IN SAR IMAGES

    Directory of Open Access Journals (Sweden)

    J. W. Zhao

    2016-06-01

    Full Text Available As the received radar signal is the sum of signal contributions overlaid in one single pixel regardless of the travel path, the multipath effect should be seriously tackled as the multiple bounce returns are added to direct scatter echoes which leads to ghost scatters. Most of the existing solution towards the multipath is to recover the signal propagation path. To facilitate the signal propagation simulation process, plenty of aspects such as sensor parameters, the geometry of the objects (shape, location, orientation, mutual position between adjacent buildings and the physical parameters of the surface (roughness, correlation length, permittivitywhich determine the strength of radar signal backscattered to the SAR sensor should be given in previous. However, it's not practical to obtain the highly detailed object model in unfamiliar area by field survey as it's a laborious work and time-consuming. In this paper, SAR imaging simulation based on RaySAR is conducted at first aiming at basic understanding of multipath effects and for further comparison. Besides of the pre-imaging simulation, the product of the after-imaging, which refers to radar images is also taken into consideration. Both Cosmo-SkyMed ascending and descending SAR images of Lupu Bridge in Shanghai are used for the experiment. As a result, the reflectivity map and signal distribution map of different bounce level are simulated and validated by 3D real model. The statistic indexes such as the phase stability, mean amplitude, amplitude dispersion, coherence and mean-sigma ratio in case of layover are analyzed with combination of the RaySAR output.

  14. 'Visual snow' - a disorder distinct from persistent migraine aura.

    Science.gov (United States)

    Schankin, Christoph J; Maniyar, Farooq H; Digre, Kathleen B; Goadsby, Peter J

    2014-05-01

    Patients with 'visual snow' report continuous tiny dots in the entire visual field similar to the noise of an analogue television. As they frequently have migraine as a comorbidity with ophthalmological, neurological and radiological studies being normal, they are offered various diagnoses, including persistent migraine aura, post-hallucinogen flashback, or psychogenic disorder. Our aim was to study patients with 'visual snow' to characterize the phenotype. A three-step approach was followed: (i) a chart review of patients referred to us identified 22 patients with 'visual snow'. Fifteen had additional visual symptoms, and 20 patients had comorbid migraine, five with aura; (ii) to identify systematically additional visual symptoms, an internet survey (n = 275) of self-assessed 'visual snow' subjects done by Eye On Vision Foundation was analysed. In two random samples from 235 complete data sets, the same eight additional visual symptoms were present in >33% of patients: palinopsia (trailing and afterimages), entoptic phenomena (floaters, blue field entoptic phenomenon, spontaneous photopsia, self-light of the eye), photophobia, and nyctalopia (impaired night vision); and (iii) a prospective semi-structured telephone interview in a further 142 patients identified 78 (41 female) with confirmed 'visual snow' and normal ophthalmological exams. Of these, 72 had at least three of the additional visual symptoms from step (ii). One-quarter of patients had 'visual snow' as long as they could remember, whereas for the others the mean age of onset was 21 ± 9 years. Thirty-two patients had constant visual symptoms, whereas the remainder experienced either progressive or stepwise worsening. Headache was the most frequent symptom associated with the beginning or a worsening of the visual disturbance (36%), whereas migraine aura (seven patients) and consumption of illicit drugs (five, no hallucinogens) were rare. Migraine (59%), migraine with aura (27%), anxiety and depression

  15. Beyond body experiences: phantom limbs, pain and the locus of sensation.

    Science.gov (United States)

    Wade, Nicholas J

    2009-02-01

    Reports of perceptual experiences are found throughout history. However, the phenomena considered worthy of note have not been those that nurture our survival (the veridical features of perception) but the oddities or departures from the common and commonplace accuracies of perception. Some oddities (like afterimages) could be experienced by everyone, whereas others were idiosyncratic. Such phenomena were often given a paranormal interpretation before they were absorbed into the normal science of the day. This sequence is examined historically in the context of beyond body experiences or phantom limbs. The experience of sensations in lost body parts provides an example of the ways in which novel phenomena can be interpreted. The first phase of description probably occurred in medieval texts and was often associated with accounts of miraculous reconnection. Ambroise Paré (1510-1590) initiated medical interest in this intriguing aspect of perception, partly because more of his patients survived the trauma of surgery. Description is followed by attempts to incorporate the phenomenon into the body of extant theory. René Descartes (1596-1650) integrated sensations in amputated limbs into his dualist theory of mind, and used the phenomenon to support the unity of the mind in comparison to the fragmented nature of bodily sensations. Others, like William Porterfield (ca. 1696-1771), did not consider the phenomenon as illusory and interpreted it in terms of other projective features of perception. Finally, the phenomenon is accepted and utilized to gain more insights into the functioning of the senses and the brain. The principal features of phantom limbs were well known before they were given that name in the 19th century. Despite the puzzles they still pose, these phantoms continue to provide perception with some potent concepts: the association with theories of pain has loosened the link with peripheral stimulation and emphasis on the phenomenal dimension has slackened

  16. In Search of Lost Community: The Literary Image between “Proust” and “Baudelaire” in Walter Benjamin’s Modernization Lament

    Directory of Open Access Journals (Sweden)

    Karyn Ball

    2015-02-01

    Full Text Available This essay takes up the encounter between philosophy and literature through a reconsideration of Walter Benjamin’s remarks from “On Some Motifs in Baudelaire” about Henri Bergson’s Matière et mémoire as an attempt “[t]owering above” other ventures into Lebensphilosophie to “lay hold of the ‘true’ experience, as opposed to the kind that manifests itself in the standardized, denatured life of the civilized masses”. Despite his initial affirmation of Bergson’s understanding of experience as connected with tradition, Benjamin criticizes the philosopher’s account for sidestepping “the alienating, blinding experience of the age of large-scale industrialism” in reaction to which, as Benjamin insists, Bergson’s philosophy of memory developed. Yet even as Bergson shuts out the historical import of modernization, according to Benjamin, he also spotlights a “complementary” visual experience “in the form of its spontaneous afterimage”. Benjamin subsequently defines Bergson’s philosophy as “an attempt to specify this afterimage and fix it as a permanent record”, an endeavor that inadvertently “furnishes a clue to the experience which presented itself undistorted to Baudelaire’s eyes, in the figure of his reader”. If the literary critic might be viewed here as weighing in on a long-running antagonism between philosophy and literature, then his assessment is resolute: by praising the self-conscious historicity of Baudelaire’s lyric, Benjamin declares that poetry succeeds where Lebensphilosophie fails. Notably, Baudelaire is not the only figure to upstage “ahistorical” Bergson, since Marcel Proust and Sigmund Freud facilitate this victory. To contextualize the second section of “Motifs”, where Benjamin discusses the novelist’s “immanent critique of Bergson” this essay offers a reading of “On the Image of Proust” as a propadeutic to Benjamin’s privileging of “Baudelaire” over

  17. Embedded Endoscopic Ultrasound Image Processing System Based on Wavelet Transform%基于小波变换的嵌入式超声内窥图像处理系统

    Institute of Scientific and Technical Information of China (English)

    时一峰; 白宝平; 陈晓冬; 汪毅; 郁道银

    2016-01-01

    During acquiring images,the equipment is affected by the size of the transducer and other factors which make the images have low contrast and big noise, cannot provide clear imaging basis for medical diagnostic. Scientists have proposed a variety of methods. However, these methods are mostly after-imaging processing algorithms and having a poor real-time performance, unable to meet the real-time endoscopic ultrasound imaging requirements (25 frames/s). Therefore, this paper designs the embedded endoscopic ultrasound real-time image processing system based on lifting Wavelet Transform. And the system processes echo signals of each scan line with wavelet denoising, then obtains two-dimensional ultrasound images after CORDIC algorithm and interpolation processing using the imaging characteristics of circular scan and FPGA pipeline concept. Through building my own endoscopic ultrasound experimental system which makes the chicken tissue imaging use circular scan, the experiments show that the system imaging speed is up to 25 frames /s and SNR improves 3.8 dB, verifying the feasibility of the system.%医学内窥超声成像设备在获取图像时受到换能器尺寸等多种因素的影响,使得超声图像对比度较低和噪声较大,无法为医疗诊断提供清晰的影像依据。为此科学家们提出了多种处理方法,但这些方法多为成像后处理算法,实时性较差,无法满足内窥超声系统实时成像的要求(25 f/s)。针对以上问题,本文设计了基于提升式小波变换的嵌入式超声内镜实时图像处理系统,利用超声内窥系统环扫成像特点以及FPGA流水线概念,对每条扫描线的回波信号进行小波去噪,再经过CORDIC算法、插值处理后得到二维超声图像。本文利用自行搭建超声内镜实验系统对鸡肉组织进行环扫成像,实验表明该系统成像速度可达25 f/s,信噪比提高了3.8 dB,从而验证了系统的可行性。

  18. 不同时距条件下面孔表情知觉的时间整合效应%Temporal Integration Effects in Facial Expression Recognition in Different Temporal Duration Condition

    Institute of Scientific and Technical Information of China (English)

    陈本友; 黄希庭

    2012-01-01

    通过把面孔表情分割成三部分,按照不同的时间间隔以及不同的呈现时间相继呈现,考察了被试对面孔表情的时间整合效果,以此探讨时间整合的加工过程和影响因素。结果发现:(1)面孔表情的时间整合效果受时间结构和刺激材料的影响。(2)分离呈现的面孔表情能否进行时间整合与S0A的大小有关。(3)面孔表情的时间整合存在类型差异。(4)面孔表情的时间整合是在一个有限的视觉缓冲器内进行的,图像记忆和长时记忆与面孔表情的时间整合过程关系密切。%Temporal integration is the process of perception processing,in which the successively separated stimuli are combined into a significant representation.It is a complicated process,which is known to be influenced by multiple factors,such as the temporal structure and stimulus components.Although this process has been explored in inter-stimulus interval in face perception,little is known about the temporal integration effect in facial expression recognition.More importantly,there has been no relevant evidence demonstrating that stimulus duration and stimulus category can affect the temporal integration of facial expression. In the present study,the part-whole judgment task was used to examine the influencing factors of temporal integration in the facial expression.In two experiments,each of three whole facial expression pictures was segmented into three parts,and each including a salient facial feature:eye,nose,or mouth.These parts were presented sequentially to the participants by some interval or presentation durations, with a fixed sequence:eye part first,nose followed,and mouth last.Following the last part,a mask,which eliminated effects of afterimages or other types of visual persistence was displayed.Then,participants were asked to judge the category of the facial expression, by pressing one of three number keys;"1","2" and "3",corresponding to anger,happy and