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PubMed1990

Auditory localization: effects of reflecting surfaces.

Based on anatomical and evolutionary conceptions of the human ear, an experiment was conducted in which forty-eight human subjects were asked to localize sounds (a human voice) emitted by one of twenty-seven stationary loudspeakers in an anechoic chamber. The position of the active loudspeaker varied with respect to azimuth, distance, and elevation in three steps each. The position of a single sound-reflecting surface (about 6 m2) was varied: on the floor, on the ceiling, to the left, and to the right. The accuracy of identifying the active loudspeaker for each position of the sound-reflecting surface was compared intraindividually with the absence of reflection. The results show an overall increase in correct localizations with a sound-reflecting surface on the floor. Especially the elevation of the sound source can be detected with greater precision. Additionally, the percentage of correct localizations decreased systematically with the presence of a sound-reflecting ceiling, while the presence of sound-reflecting walls did not systematically affect the localization performance. Judgments in the horizontal plane and those of distance were not systematically influenced by the presence of a sound-reflecting surface.

Adult↗

PubMed2004

A biologically inspired algorithm for the recovery of shading and reflectance images.

We present an algorithm for separating the shading and reflectance images of photographed natural scenes. The algorithm exploits the constraint that in natural scenes chromatic and luminance variations that are co-aligned mainly arise from changes in surface reflectance, whereas near-pure luminance variations mainly arise from shading and shadows. The novel aspect of the algorithm is the initial separation of the image into luminance and chromatic image planes that correspond to the luminance, red-green, and blue-yellow channels of the primate visual system. The red-green and blue-yellow image planes are analysed to provide a map of the changes in surface reflectance, which is then used to separate the reflectance from shading changes in both the luminance and chromatic image planes. The final reflectance image is obtained by reconstructing the chromatic and luminance-reflectance-change maps, while the shading image is obtained by subtracting the reconstructed luminance-reflectance image from the original luminance image. A number of image examples are included to illustrate the successes and limitations of the algorithm.

Algorithms↗

PubMed2006

Errors in judging information about reflections in mirrors.

We investigated people's perception and knowledge of planar mirror reflections. People were accurate at deciding when they could first see their reflection as they approached a mirror from the side, but only if their reflection was visible. Most people stopped too early if the mirror was covered up. People also overestimated the size of the reflection of their face on the surface of a mirror if they were shown a covered mirror. Their accuracy improved somewhat if their reflection was visible but, unlike the first task, they still made striking errors. Perceptual feedback thus improved performance at predicting the behaviour of mirror reflections in both tasks but failed to eliminate errors in the second task. The overestimation of reflection size was not face-specific as it generalised to novel stimuli (paper ellipses) and it was found with both a matching response and for verbal size estimations. The early error in the first task appears to be due to an inaccurate belief that can be overridden by perceptual feedback. The overestimation in the second task is primarily caused by a powerful size-constancy effect.

Adolescent↗

PubMed2003

Relationships between leaf chlorophyll content and spectral reflectance and algorithms for non-destructive chlorophyll assessment in higher plant leaves.

Leaf chlorophyll content provides valuable information about physiological status of plants. Reflectance measurement makes it possible to quickly and non-destructively assess, in situ, the chlorophyll content in leaves. Our objective was to investigate the spectral behavior of the relationship between reflectance and chlorophyll content and to develop a technique for non-destructive chlorophyll estimation in leaves with a wide range of pigment content and composition using reflectance in a few broad spectral bands. Spectral reflectance of maple, chestnut, wild vine and beech leaves in a wide range of pigment content and composition was investigated. It was shown that reciprocal reflectance (R lambda)-1 in the spectral range lambda from 520 to 550 nm and 695 to 705 nm related closely to the total chlorophyll content in leaves of all species. Subtraction of near infra-red reciprocal reflectance, (RNIR)-1, from (R lambda)-1 made index [(R lambda)(-1)-(RNIR)-1] linearly proportional to the total chlorophyll content in spectral ranges lambda from 525 to 555 nm and from 695 to 725 nm with coefficient of determination r2 > 0.94. To adjust for differences in leaf structure, the product of the latter index and NIR reflectance [(R lambda)(-1)-(RNIR)-1]*(RNIR) was used; this further increased the accuracy of the chlorophyll estimation in the range lambda from 520 to 585 nm and from 695 to 740 nm. Two independent data sets were used to validate the developed algorithms. The root mean square error of the chlorophyll prediction did not exceed 50 mumol/m2 in leaves with total chlorophyll ranged from 1 to 830 mumol/m2.

Algorithms↗

PubMed1999

Reflective properties of domestic fowl (Gallus g. domesticus), the fabric of their housing and the characteristics of the light environment in environmentally controlled poultry houses.

1. The light intensity and spectral power distribution in 3 broiler and 6 layer houses were sampled and converted to a measure which takes account of the domestic fowl's spectral sensitivity (termed lux corrected). Light intensity was highly variable around the layer houses (mean 33.2, s.d. 37.7 lux (corrected)) and to a lesser extent in the broiler houses (mean 5.2, s.d. 2.2 lux (corrected)). The mean intensities were also very much lower than on a sunny, June day at midday at Silsoe (42,937 lux (corrected)) and of different power distributions. 2. The reflectivity of the plumage of 15 traditional breeds of domestic fowl was surveyed. Most feathers showed a characteristic pattern of reflectivity, increasing either side of a wavelength of lambda = 400 nm. In 13 breeds the tail and wing feathers were darker than the breast and back feathers. Reflectivity at lambda = 700 nm was a good predictor of reflectivity at lambda = 320 nm. Food, bedding, wood and skin all had similar reflectivities to feathers. Metal, plastic and rubber all had more constant reflectivities across the spectrum. 3. The reflectivities of the fresh, feathered carcases of 3 male broilers (Cobb) and 3 layer hens (ISA Brown) were measured. There were small changes in hue and saturation within and between individual carcases, even for the apparently white broiler chickens. 4. Photographs were taken, with and without a UV(A)-only pass filter, of a broiler cock (Cobb), layer hen (ISA Brown) and cock jungle fowl. No additional patternation was evident in the UV(A)-only photographs and the jungle fowl lost most of its ornamentation. The texture of bare skin was enhanced in the UV(A)-only photographs. 5. The implications of these results for poultry behaviour are discussed.

Animals↗

PubMed2006

Reflective practice in physiotherapy curricula: a survey of UK university based professional practice coordinators.

There has been recent increasing interest in reflective practice within physiotherapy education as a method for reducing the 'theory-practice gap' and as a means of articulating, exposing and developing knowledge embedded in practice. Several contrasting theories have been developed to explain the role, place, purpose and definition of reflection in learning and teaching; however, much of the research to date has relied on theoretical debate rather than high quality empirical evidence. The aim of this paper was therefore, to report how a group of United Kingdom (UK) based physiotherapy Professional Practice Coordinators (n = 33) with their unique insight into the concept from both the academic and clinical perspective viewed and interpreted the use of reflective practice within their physiotherapy curriculum. Consent for the study was obtained via the professional body (The Chartered Society of Physiotherapists) (CSP) and data was collected via postal questionnaire. Results indicated a diversity of experience in respondents both in terms of their role as Coordinator and their training in reflective practice. There was also no clear consensus regarding facilitative models or assessment methods even though the majority of coordinators believed that reflective practice should be considered to be a central component of physiotherapy teaching strategies. The results of this survey provide a focus for further empirical research into reflective practice as part of the physiotherapy curricula, while advancing the understanding of reflective practice from a broader perspective and clarifying the benefits to students, teachers, patients and practitioners.

Attitude of Health Personnel↗

PubMed1979

Quantitative reflection contrast microscopy of living cells.

Mammalian cells in culture (BHK-21, PtK2, Friend, human flia, and glioma cells) have been observed by reflection contrast microscopy. Images of cells photographed at two different wavelengths (546 and 436 nm) or at two different angles of incidence allowed discrimination between reflected light and light that was both reflected and modulated by interference. Interference is involved when a change in reflected intensity (relative to glass/medium background reflected intensity) occurs on changing either the illumination wavelength or the reflection incidence angle. In cases where interference occurs, refractive indices can be determined at points where the optical path difference is known, by solving the given interference equation. Where cells are at least 50 nm distant from the glass substrate, intensities are also influenced by that distance as well as by the light's angle of incidence and wavelength. The reflected intensity at the glass/medium interface is used as a standard in calculating the refractive index of the cortical cytoplasm. Refractive indices were found to be higher (1.38--1.40) at points of focal contact, where stress fibers terminate, than in areas of close contact (1.354--1.368). In areas of the cortical cytoplasm, between focal contacts, not adherent to the glass substrate, refractive indices between 1.353 and 1.368 were found. This was thought to result from a microfilamentous network within the cortical cytoplasm. Intimate attachment of cells to their substrate is assumed to be characterized by a lack of an intermediate layer of culture medium.

Animals↗

PubMed2003

Reflectance of Alaskan black spruce and white spruce foliage in relation to elevation and latitude.

Leaf reflectance at visible and near-infrared wavelengths (400-1000 nm) is related primarily to pigmentation, leaf structure and water content, and is an important tool for studying stress physiology and relationships between plants and their growth environment. We studied reflectance of two co-occurring Alaskan conifers, black spruce (Picea mariana (Mill.) BSP) and white spruce (Picea glauca (Moench) Voss), at elevations from 60 to 930 m a.s.l. along a latitudinal gradient from 61 degrees to 68 degrees N. Black spruce samples were collected from 24 sites and white spruce from 30 sites. Overall, reflectance spectra of the two species were similar, but from 400 to 700 nm, needle reflectance was consistently higher in black spruce than in white spruce (all P <or= 0.05). This difference is probably related to differences in epicuticular wax morphology or amount, and may represent a photoprotective mechanism in black spruce. Reflectance at visible wavelengths generally increased with elevation and latitude in both species, consistent with a general stress response. However, in a multiple regression, latitude and elevation explained only 25-45% of the total variation in the indices studied. Reflectance indices suggested that needle yellowness increased, whereas chlorophyll content and photochemical efficiency decreased with both elevation and latitude. These trends were consistent between species, but white spruce generally showed a much smaller (and insignificant) reflectance response to latitude compared with black spruce. Differences between species could be related to black spruce's ability to colonize more stressful sites and white spruce's greater competitiveness on less stressful sites, coupled with the effects of drainage and microtopography (which may vary less predictably with latitude than elevation) on species distribution. The black spruce results suggest that a 1000-m increase in elevation is roughly comparable with a 6 degrees increase in latitude.

Altitude↗

PubMed1995

Exit rounds: a reflection exercise.

This paper questions the long-held assumption that "experience is the best teacher". Reflection, it is argued, is the element that turns experience into learning. Unfortunately, reflection is the experiential learning skill in which student are most deficient. Further, clinical teachers may not appreciate the reciprocal and synergistic relationship of experience and reflection, and therefore they may not exploit its full potential. This paper argues for the formal and explicit use of reflection to clinical teaching. In addition to providing a theoretical rationale for the use of reflection is learning, one example of a reflection exercise--exit rounds--is described. Exit rounds focus on recently discharged patients and provide students with an opportunity to reflect on what they have learned from working with these patients. In addition to being a learning exercise, exit rounds provide attending physicians with an opportunity to address emotional issues, to evaluate students' learning and performances, to deal with "housekeeping" details, and to provide closure.

Clinical Competence↗

PubMed2000

An optical model of the human retinal nerve fiber layer: implications of directional reflectance for variability of clinical measurements.

PURPOSE: The reflectance of the retinal nerve fiber layer is highly directional--that is, it depends strongly on the angles of illumination and viewing. This study explored and illustrated the implications of this directional reflectance for nerve fiber layer measurements in the human eye. METHODS: The retina was modeled as a sphere centered on the optic axis of a schematic eye. Nerve fiber ribbons were projected onto the retina and cylindrical light scattering was calculated along each ribbon. The reflectance along the ribbon was then determined for the illuminating and viewing apertures of two hypothetical optical instruments, a fundus camera and a confocal scanning laser ophthalmoscope. Results were displayed as reflectance maps. RESULTS: Uniformly illuminated nerve fiber ribbons exhibited a nonuniform reflectance pattern that was very sensitive to the location in the pupil of the instrument apertures. Ribbon reflectance at the superior and inferior disc margins varied with ribbon orientation, being higher with temporal tilt and lower with nasal tilt. Ribbons nasal to the disk could be quite dim. CONCLUSIONS: In quantitative nerve fiber layer assessment technologies, the observed reflectance depends on the configuration of the illuminating and viewing apertures of the measuring instrument and on the retinal position and orientation of each nerve fiber bundle. In clinical practice, this dependence may cause significant measurement variability that can be reduced by specific measurement maneuvers.

Fundus Oculi↗

PubMed1990

Reflectance as an indirect measurement of the extent of laser-induced coagulation.

Two-dimensional reflectance images and surface thermal distributions were recorded during argon laser induced coagulation. During laser irradiation, coagulated egg yolk formed a white lesion. The whiteness, or reflectance caused by backscattering of light from the forming lesion, would be measured after a short delay from the onset of laser irradiation. In the experiments which covered exposure time from 4.5 to 17.0 s, we found that it started slowly, the reflectance increased rapidly once the surface temperature of the lesion reached approximately 90 degrees C. After this rapid rise, the reflectance began to taper off until no change in reflectance was recorded. There was a 0.98 correlation between lesion diameter measured from a two dimensional reflectance image and the lesion diameter that was measured microscopically. There was a 0.92 correlation between reflectance at the center of the lesion and microscopically measured depth of coagulation at the same point. However, the correlation between microscopically measured coagulation depth and width was only 0.88.

Egg Yolk↗

PubMed1990

In vivo reflectance of blood and tissue as a function of light wavelength.

Light reflectance from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph and the reflectance pulse oximeter. Incident light on the skin travels into the underlying layers and is in part reflected back to the surface. This paper describes the reflectance of light from in vivo tissue for wavelengths in the range from 420 to 940 nm, based on photon diffusion theory and on experimental results from studies of 17 subjects. The results show a minimum reflectance and a peak sensitivity to the blood pulsations in the wavelength range from 510 to 590 nm. Skin pigmentation is seen to attenuate reflectance rather than altering the character of the modulation spectra. Based on the model introduced in this paper, the dependence of modulation spectra on mean blood fractional volume as well as wavelength is also described theoretically, and corroborated by further experimental data at 570 and 630 nm. At these latter wavelengths, the signal-to-noise ratio was calculated for the blood volume pulsation signal in the presence of physiological noise. The median for calculated ratios of reflectance modulation by blood pulsation and ratios of signal to noise between the two wavelengths were 13.1 and 7.5, respectively, for 93 sites in nine subjects. These results are seen to be consistent with the theory.

Blood Volume↗

PubMed2004

Separating reflection components based on chromaticity and noise analysis.

Many algorithms in computer vision assume diffuse only reflections and deem specular reflections to be outliers. However, in the real world, the presence of specular reflections is inevitable since there are many dielectric inhomogeneous objects which have both diffuse and specular reflections. To resolve this problem, we present a method to separate the two reflection components. The method is principally based on the distribution of specular and diffuse points in a two-dimensional maximum chromaticity-intensity space. We found that, by utilizing the space and known illumination color, the problem of reflection component separation can be simplified into the problem of identifying diffuse maximum chromaticity. To be able to identify the diffuse maximum chromaticity correctly, an analysis of the noise is required since most real images suffer from it. Unlike existing methods, the proposed method can separate the reflection components robustly for any kind of surface roughness and light direction.

Algorithms↗

PubMed2005

Light source position and reflectance estimation from a single view without the distant illumination assumption.

Several techniques have been developed for recovering reflectance properties of real surfaces under unknown illumination. However, in most cases, those techniques assume that the light sources are located at inifinity, which cannot be applied safely to, for example, reflectance modeling of indoor environments. In this paper, we propose two types of methods to estimate the surface reflectance property of an object, as well as the position of a light source from a single view without the distant illumination assumption, thus relaxing the conditions in the previous methods. Given a real image and a 3D geometric model of an object with specular reflection as inputs, the first method estimates the light source position by fitting to the Lambertian diffuse component, while separating the specular and diffuse components by using an iterative relaxation scheme. Our second method extends that first method by using as input a specular component image, which is acquired by analyzing multiple polarization images taken from a single view, thus removing its constraints on the diffuse reflectance property. This method simultaneously recovers the reflectance properties and the light source positions by optimizing the linearity of a log-transformed Torrance-Sparrow model. By estimating the object's reflectance property and the light source position, we can freely generate synthetic images of the target object under arbitrary lighting conditions with not only source direction modification but also source-surface distance modification. Experimental results show the accuracy of our estimation framework.

Algorithms↗

PubMedDate not supplied

Sample-based cameras for feed forward reflection rendering.

This paper presents sample-based cameras for rendering high quality reflections on convex reflectors at interactive rates. The method supports change of view, moving objects and reflectors, higher order reflections, view-dependent lighting of reflected objects, and reflector surface properties. In order to render reflections with the feed forward graphics pipeline, one has to project reflected vertices. A sample-based camera is a collection of BSP trees of pinhole cameras that jointly approximate the projection function. It is constructed from the reflected rays defined by the desired view and the scene reflectors. A scene point is projected by invoking only the cameras that contain it in their frustums. Reflections are rendered by projecting the scene geometry and then rasterizing in hardware.

Algorithms↗

PubMed2004

Undergraduate medical students' views about a reflective portfolio assessment of their communication skills learning.

INTRODUCTION: To date, no studies have examined preclinical medical students' views about portfolios. Since portfolios are becoming increasingly valued in medical education, this study explores second-year medical students' views about a reflective portfolio assessment of their communication skills. METHODS: 178 second-year medical students at the University of Nottingham completed the 18-item reflective portfolio questionnaire (RPQ) (alpha = 0.716) and a personal details questionnaire three days before submitting their portfolio assessment for communication skills. Data were analysed using univariate and multivariate statistics on SPSS Version 10.0. RESULTS: Total scores on the RPQ ranged from 40 to 75 (mean 58.28, SD 7.08). Significant relationships existed between RPQ total scores and students' ratings of their reflection skills (rs = 0.322, P < 0.001), RPQ total scores and students' confidence building another portfolio (T = 4.381, d.f. = 176, P < 0.001), and RPQ total scores and students' marks for their reflective portfolio assessment (rs = 0.167, P = 0.029). Students with more positive views about reflective portfolios were more likely to rate their reflection skills as good, receive better marks for their portfolio assessment, and be more confident building another portfolio. DISCUSSION: This study begins to highlight preclinical medical students' views about reflective portfolios. However, further research is required using qualitative studies to explore students' views in depth. Medical educators should be encouraged to consider introducing portfolios as a method of formative and summative assessment earlier in the medical curriculum.

Adolescent↗

PubMedDate not supplied

Oral cancer detection using diffuse reflectance spectral ratio R540/R575 of oxygenated hemoglobin bands.

A low-cost, fast, and noninvasive method for early diagnosis of malignant lesions of oral mucosa based on diffuse reflectance spectral signatures is presented. In this technique, output of a tungsten halogen lamp is guided to the tissue through the central fiber of a reflection probe whose surrounding six fibers collects tissue reflectance. Ex vivo diffuse reflectance spectra in the 400 to 600-nm region is measured from surgically removed oral cavity lesions using a miniature fiber optic spectrometer connected to a computer. Reflectance spectral intensity is higher in malignant tissues and shows dips at 542 and 577 nm owing to absorption from oxygenated hemoglobin (HbO2). Measurements carried out, within an hour of surgical excision, on malignant lesion and adjoining uninvolved mucosa show that these absorption features are more prominent in neoplastic tissues owing to increased microvasculature and blood content. It is observed that reflectance intensity ratio of hemoglobin bands, R540/R575, from malignant sites are always lower than that from normal sites and vary according to the histological grade of malignancy. The diffuse reflectance intensity ratio R540/R575 of the hemoglobin bands appears to be a useful tool to discriminate between malignant lesions and normal mucosa of the oral cavity in a clinical setting.

Biomarkers, Tumor↗

PubMed2003

The reflection of the fundamental torsional mode from cracks and notches in pipes.

A quantitative study of the reflection of the T(0,1) mode from defects in pipes in the frequency range 10-300 kHz has been carried out, finite element predictions being validated by experiments on selected cases. Both cracklike defects with zero axial extent and notches with varying axial extents have been considered. The results show that the reflection coefficient from axisymmetric cracks increases monotonically with depth at all frequencies and increases with frequency at any given depth. In the frequency range of interest there is no mode conversion at axisymmetric defects. With nonaxisymmetric cracks, the reflection coefficient is a roughly linear function of the circumferential extent of the defect at relatively high frequencies, the reflection coefficient at low circumferential extents falling below the linear prediction at lower frequencies. With nonaxisymmetric defects, mode conversion to the F(1,2) mode is generally seen, and at lower frequencies the F(1,3) mode is also produced. The depth and circumferential extent are the parameters controlling the reflection from cracks; when notches having finite axial extent, rather than cracks, are considered, interference between the reflections from the start and the end of the notch causes a periodic variation of the reflection coefficient as a function of the axial extent of the notch. The results have been explained in terms of the wave-number-defect size product, ka. Low frequency scattering behavior is seen when ka < 0.1, high frequency scattering characteristics being seen when ka > 1.

Journal Article↗