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PubMed2005

International community health networking project: two year follow-up of graduates.

AIM: This paper presents the perceptions of graduates 2 years post-exchange in a USA-European Union funded programme. The primary goal of this 8-week exchange programme was to increase cultural knowledge and sensitivity by teaching a common module of community health assessment and planning to multi-national groups of undergraduate students in four countries. BACKGROUND: Cultural diversity and globalization are among the factors that encourage faculty in nursing to develop programmes of international exchange for students. The challenge is to combine the exchange with the teaching of other courses required by the home institution during the same semester. METHODS: Twenty-one graduates of participating USA schools responded to an open-ended interview by telephone or email 2 years after graduation. Bennett's continuum (1993) of intercultural sensitivity was used to assess cultural development. FINDINGS: Graduates overwhelmingly supported international education and described its continued impact personally and professionally. Gains in cultural sensitivity were perceived as the greatest benefit and influence on their practice. The majority of graduates were believed to be in Bennett's ethnorelative categories of acceptance and adaptation. The depth and breadth of previous cultural experiences, specific host and home schools, and previous travel were found to be related to development on the intercultural sensitivity continuum. DISCUSSION: Most important are the findings from this evaluation that provide insight into the factors enhancing growth of intercultural sensitivity. Previous travel, characteristics of the home and host institutions, and the opportunity and willingness to be a cultural outsider were important influences.

Adult↗
PubMed1979

Lateral interactions in human cone dark adaptation.

1. The course of cone dark adaptation after exposure to a strong bleaching light depends on the size of the bleached region. Threshold for brief, tiny test flash centred in the bleached region is elevated more, and recovery is retarded by a small bleach. This effect has its parallel in the sensitization effect observed with steady backgrounds. 2. Previous results, that a similar sensitization effect is not observed in rod dark adaptation, are confirmed. 3. This sensitization effect in cone dark adaptation does not transfer binocularly, and is unaffected by pressure blinding during the bleaching exposure. 4. Threshold following a small bleach may be lowered by adding a steady annular background to the region surrounding the bleached patch. Conversely, bleaching the area surrounding a small, steady background can lower threshold for a test flash centred on the background. 5. These interactions between backgrounds and bleaches may be explained if bleaches produce long-lasting signals from neurones in the bleached area, which then lead into a spatially opponent stage of processing. 6. It is likely that the persisting signals come from the cone receptors, since the Bunsen-Roscoe Law (intensity-time reciprocity) holds for small bleaches as well as large, for durations up to about 3 sec.

Dark Adaptation↗
PubMed1973

Disparity detectors in human depth perception: evidence for directional selectivity.

Viewing a target moving in depth depresses visual sensitivity to depth when test and adapting stimuli simulate motion along closed paths with the same directions of rotation. However, for opposite directions of rotation, sensitivity is either unaffected or increased. This points to two classes of disparity detectors. Either eye's input to a single class of disparity detector consists of the physiological responses to a single direction of horizontal movement.

Adaptation, Ocular↗
PubMed2004

Monte Carlo modeling of optical coherence tomography imaging through turbid media.

We combine a Monte Carlo technique with Mie theory to develop a method for simulating optical coherence tomography (OCT) imaging through homogeneous turbid media. In our model the propagating light is represented by a plane wavelet; its line propagation direction and path length in the turbid medium are determined by the Monte Carlo technique, and the process of scattering by small particles is computed according to Mie theory. Incorporated into the model is the numerical phase function obtained with Mie theory. The effect of phase function on simulation is also illustrated. Based on this improved Monte Carlo technique, OCT imaging is directly simulated and phase information is recorded. Speckles, resolution, and coherence gating are discussed. The simulation results show that axial and transversal resolutions decrease as probing depth increases. Adapting a light source with a low coherence improves the resolution. The selection of an appropriate coherence length involves a trade-off between intensity and resolution.

Computer Simulation↗
PubMed1986

Note on nonveridical visual perception and pedestrian accidents at night.

It is sometimes supposed that increase of pedestrian conspicuity could lead to substantial reductions in pedestrian accidents at night. Available evidence is, however, not particularly encouraging. It is suggested that other factors affecting drivers' and pedestrians' perception may be involved.

Acceleration↗
PubMedDate not supplied

Scotopic vision, color vision, and stereopsis in infants.

Infants as young as 1 month postnatal have scotopic spectral sensitivity closely resembling the CIE standard curve and thus appear to have a functional, rhodopsin-based rod system. Neutrally adapted photopic spectral sensitivities are broad and roughly equal to those of adults tested under similar conditions, although infants may show an elevated sensitivity in the short-wavelength region of the spectrum. Spectral sensitivity has been shown to change with changes in chromatic adaptation. Some wavelength discriminations are possible under conditions in which brightness artifacts can be ruled out. All of these factors support the conclusion that young infants are at least dichromats. However, 2-month-olds to date have shown some unpredicted failures of chromatic discrimination (for example, yellow-greens from white), and the percentage of infants who demonstrate discriminations (for example, among wavelengths greater than or equal to 550 nm) improves with age in early infancy. Thus the status of young infants as trichromats is not yet clearly established. Stereopsis develops rapidly during months 3 to 7, and stereoacuities as good as 1' have been reported by 5 months postnatal. In summary, a variety of visual capabilities can now be measured in infants. Infants' visual capacities are rather surprisingly well established shortly after birth and undergo clear improvements during the first few postnatal months. The interpretation of developmental data and their bearing on visual theory are discussed.

Adult↗
PubMed1990

Visual alleys as a function of instructions under informative and reduced conditions of viewing.

Three experiments were designed to explore parallel and distance alleys as a function of instructions (apparent and objective) under three different distance-cue conditions. The main findings were that (1) the alleys for the apparent instructions were positioned closer to the median plane than those for the objective instructions, (2) in an indoor setting, the parallel and distance alleys were not different under either the apparent or the objective instructions, and (3) in an outdoor setting, the parallel alley lay inside the distance alley under both the apparent and the objective instructions. On the basis of comparison with some of the previous alley studies, it is suggested that exact control of instructions will not produce great discrepancy between the parallel and the distance alleys that were constructed indoors.

Adult↗
PubMed1982

Aging and visual function of military pilots: a review.

This report reviews what is known about the effects of age on visual function and discusses the implications of age-related changes in vision for the flying performance of military pilots. Most visual functions decline to some degree with age, and the rate of decline has been roughly characterized in the general population. There is, however, virtually no data on military pilots, and extrapolation from the general population requires caution. Individual variation in the effects of age is great, and military pilots are a select group presumably in better general health than the general population. Several visual functions that decline with age seem particularly relevant to pilot performance: contrast sensitivity, dynamic acuity, recovery from glare, function under low illumination, and information processing. Vision examinations currently given to military and commercial pilots do not measure these visual functions. The feasibility of supplementing existing vision examinations with measurements of these functions should be explored; such an assessment should consider both research issues and policy implications. Research is needed on several major problems in this area. It is not possible at present to characterize well the effect of changes in visual function on the performance of complex tasks, such as flying. This report suggests several specific measures that might help characterize the effects of changes in visual function on pilot performance. Data on changes in visual functions with age should be collected from military pilots, preferably with multivariate, longitudinally designed studies. Research is suggested to assess the extent to which experienced pilots may compensate for declining visual functions and to determine how such compensation is achieved. The report suggests studies on the interaction of age with other factors, such as cardiovascular changes, that may affect performance, especially under stress.

Adaptation, Physiological↗
PubMed1993

[A preliminary enquiry into the normal values of vision in motor vehicle drivers].

A study on distant vision, visual sense and colour vision in 2,218 motor vehicle drivers in Inner Mongolia Region was carried out and the effect of age on vision was analysed. The results showed that vision in drivers diminish with increasing age and the age threshold for visual acuity was 45 years. This paper discusses the normal values of vision in two age groups of pre-and-after the threshold age line, and these results may offer a scientific basis for drawing up occupational examination standards for drivers at their posts or under training.

Adolescent↗
PubMed1981

Adaptation to the reversal of binocular depth cues: effects of wearing left-right reversing spectacles on stereoscopic depth perception.

The principle of stereopsis, that crossed disparity causes a convex perception and uncrossed disparity a concave one, has for a long time been considered to depend on a very rigid neural mechanism not affected by experience. Experiments are reported here which show that this relationship between disparity and perceived depth can be reversed by experience. An observer wore a pair of left-right reversing spectacles continuously for nine days. The spectacles also reversed the relation between the direction of perceived depth and the direction of binocular depth cues, ie disparity and vergence. For a period starting two days before wearing the spectacles and continuing until seventy-nine days after their removal the observer was examined with a haploscope and an electrooculograph. All the stereoscopic experiments were carried out without spectacles in order to examine some aftereffects of wearing spectacles. For the stereograms with linear contours not only the adaptive reversal of the relation between disparity and perceived depth, but also some abnormal depth perceptions and long-lasting aftereffects were found. For Julesz's random-dot stereograms, however, in which contours can be seen only after binocular combination, no adaptive change or reversal occurred. These results suggest that the process of stereopsis consists of two concurrent subprocesses.

Adaptation, Ocular↗
PubMed2004

Depth-dependent contrast gain-control.

Contrast adaptation that was limited to a small region of the peripheral retina was induced as observers viewed a multiple depth-plane textured surface. The small region undergoing contrast adaptation was present only in one depth-plane to determine whether contrast gain-control is depth-dependent. After adaptation, observers performed a contrast-matching task in both the adapted and a non-adapted depth-plane to measure the magnitude and spatial specificity of contrast adaptation. Results indicated that contrast adaptation was depth-dependent under full-cue (disparity, linear perspective, texture gradient) conditions; there was a highly significant change in contrast gain in the depth-plane of adaptation and no significant gain change in the unadapted depth-plane. A second experiment showed that under some monocular viewing conditions a similar change in contrast gain was present in the adapted depth-plane despite the absence of disparity information for depth. Two control experiments with no-depth displays showed that contrast adaptation can also be texture- and location-dependent, but the magnitude of these effects was significantly smaller than the depth-dependent effect. These results demonstrate that mechanisms of contrast adaptation are conditioned by 3-D and 2-D viewing contexts.

Adaptation, Ocular↗
PubMed2000

Osmotic and ionic hemolymph concentrations of bathyal and abyssal amphipods of Lake Baikal (Siberia) in relation to water depth.

We studied the adaptive variations of the hemolymph concentrations in relation to water depth and pressure using deep-dwelling amphipods from Lake Baikal. Hemolymph osmolality was determined in six bathyal and abyssal species immediately after capture when values come closest to the habitat concentrations. In three species, hemolymph osmolalities correlated positively with depth of capture. Prevalent ions in the hemolymph are sodium and chloride. Lactate, our indicator for capture stress, was highest after trawling (2-6 mM) and lowest after retrieval from cages (0-0.6 mM). Acclimation to different pressure was studied by exposing the specimens to different water depths over several days. Hemolymph concentrations did not change after acclimation to surface pressure in the sublittoral Acanthogammarus albus, a native also to shallow water, but decreased by 30-80 mosmol/kg H2O in the bathyal and abyssal species Acanthogammarus grewingki, Acanthogammarus reicherti, and Parapallasea lagowskii. Similarly, hemolymph osmolality decreased in A. reicherti and P. lagowskii originating from deep water, when acclimated to reduced water depth, and, in A. reicherti hemolymph osmolality reached its original high value when returned to the depth of capture. Higher hemolymph osmolalities and NaCl concentrations, demonstrated here for the first time, may provide selective advantages to abyssal species.

Adaptation, Physiological↗
PubMed1996

Disparity tuning of the stereoscopic (cyclopean) motion aftereffect.

Across five experiments this study investigated the disparity tuning of the stereoscopic motion aftereffect (adaptation from moving retinal disparity). Adapting and test stimuli were moving and stationary stereoscopic grating patterns, respectively, created from dynamic random-dot stereograms. Observers adapted to moving stereoscopic grating patterns presented with a given disparity and viewed stationary test patterns presented with the same or differing disparity to examine whether the motion aftereffect is disparity contingent. Across experiments aftereffect duration was greatest when adapting motion and test pattern both were presented with zero disparity and in the plane of fixation. Aftereffect declined as disparity of adapting motion and/or test pattern increased away from fixation, even under conditions in which depth position of adapt and test was equal. This argues against a relative depth separation explanation of the decline, and instead suggests that the amount of adaptable substrate decreases away from fixation.

Adaptation, Physiological↗
PubMed1986

Effect of cavity depth and application technique on marginal adaptation of resins in dentin cavities.

The wall-to-wall polymerization contraction of two restorative resins was investigated in butt-joint dentin cavities prepared in extracted human teeth. The cavity diameter was 4 mm, and the cavity depth ranged between 0.5 and 3.0 mm. The width of the maximum marginal contraction gap was measured, using a light microscope, approximately 0.1 mm below the original free surfaces of the fillings. It was found that increasing the cavity depth from 0.5 to 3.0 mm did not influence the marginal contraction gap close to the free surfaces of the fillings. It was also found that a two-phase application technique, where the surface of the first layer was placed parallel to the free surface of the cavity, did not reduce the marginal contraction gap, while a two-phase technique with oblique layers resulted in approximately a 25% reduction.

Acrylic Resins↗
PubMed2005

Stereoscopic depth aftereffects without retinal position correspondence between adaptation and test stimuli.

To clarify whether stereo-slant aftereffects are independent of stimulated retinal position, two experiments compared the magnitude of aftereffects between the following two conditions: when the adaptation and test stimulus fell on (1) the same retinal position, and (2) on different retinal positions separated by 0.5 degrees -20 degrees . In Experiment 1, disc- or ring-shaped surface consisting of random-dots was presented at the central or peripheral visual fields. In Experiment 2, rectangular surface was presented at the upper or lower visual fields. After two minutes inspection of a random-dot stereogram depicting a +/-30 degrees slanted surface, the observer adjusted the slant of the test stimulus to appear fronto-parallel. The results of the experiments showed that significant aftereffects were observed similarly in both conditions. Moreover, the separation nor the stimulus shape scarcely affected the magnitude of the aftereffects. Based on these results we concluded that the depth processing mechanism which operates independently from the stimulated retinal position is responsible for the depth aftereffects we found.

Adaptation, Physiological↗