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PubMed1980

Skin reflectance relationships with temperature and skinfolds.

Skin reflectance measurements were taken with six filters at a site on the medial aspect of the upper arm (underarm) prior to and following topical application of a cold compress. Skinfolds were measured at the underarm and triceps sites. The experiment was designed to test for effects of skin surface temperature and subcutaneous fat variations on skin color as determined by reflectometry. Topical cold-induced erythema of the skin produced marked declines in % reflectance at the shorter visible wavelengths over the range of violet, blue, and green, and only slight declines in % reflectance at the longer visible wavelengths (red range). This is consistent with the observation from past work that there is little hemoglobin absorptance at the red end of the visible spectrum. A positive relationship between the change in % reflectance following topical cold application and underarm skinfold was recorded. Hence, the thickeness of fat deposits may contribute to variation in skin reflectance. Since only large temperature differences influenced skin reflectance measurements, the need is not great for fieldworkers to control for surface temperature at the underarm site during skin reflectance survey.

Adipose Tissue↗

PubMed2006

Hyaluronan molecular reflection by synovial lining is concentration dependent and reduced in dilute effusions in a rabbit model.

OBJECTIVE: Hyaluronan (HA) has a major role in regulating synovial fluid volume. This role depends on the synovium functioning as an ultrafilter that reflects HA during trans-synovial fluid drainage. Reflection boosts the HA concentration on the membrane surface, leading to osmotic retention of synovial fluid ("buffering"). In arthritic effusions, however, HA concentration and osmotic buffering are greatly reduced. We tested the hypothesis that reflection is reduced (escape increased) when the HA concentration falls below the molecular entanglement concentration (C*). METHODS: HA at 0.2 mg/ml ( C*) was infused continuously into rabbit knee joints to set up a steady trans-synovial filtration. Joint-derived lymph was sampled over 3 hours, and subsynovial fluid was sampled at the end of the 3-hour period. HA was quantified by high-performance liquid chromatography to evaluate the reflected fraction. C* was determined by viscometry. RESULTS: Viscometry showed that 0.2 mg/ml HA was below C* and 1.5 mg/ml was above it. At 0.2 mg/ml, the mean +/- SEM HA reflected fraction was 0.66 +/- 0.04 (n = 7). At 1.5 mg/ml the reflection increased to 0.88 +/- 0.04 (n = 5) (P < 0.005). HA permeation increased almost 3-fold, from 12% to 34%, at the lower concentration. CONCLUSION: Chain-chain interaction at >C* increases effective molecular domain size and hence HA reflection, promoting effective conservation of synovial fluid in normal joints. HA can fall below C* (approximately 1 mg/ml) in arthritic effusions, promoting loss of HA. The attendant failure of outflow buffering facilitates fluid escape and periarticular edema.

Animals↗

PubMed1991

Measurement of mechanical properties of bone material in vitro by ultrasound reflection: methodology and comparison with ultrasound transmission.

An ultrasound reflection technique was designed and implemented to study the mechanical properties of bone material. The technique uses the fact that an ultrasound beam produced in water undergoes total internal reflection off a bone sample at a critical angle formally related to the velocity of a pressure wave in bone. When the plane of scattering is rotated around the normal to the sample surface, the critical angle varies with a periodic dependence dictated by the intrinsic symmetry of the bone structure at the point being examined. Most current measurements of sound velocity are made using transmission techniques. A double-blind intercomparison between this technique and a transmission technique, which was previously validated against tensile mechanical testing, was performed for samples of isotropic materials and of human cortical bone. Strong correlations were found for both sets of samples. For the isotropic materials the velocities were approximately equal, but for bone they were on average 11% higher in reflection than in transmission. This was the result both of the higher frequency employed in reflection (3.5 rather than 2.25 MHz) and of the different effects of sample imperfections on the two measurements. In particular, the reflection technique used in this work studied the surface of the sample, but the ultrasound beam in the transmission method propagated through its interior. In assessing the mechanical properties of bone specimens by ultrasound, the reflection technique samples a discrete bone surface element and the transmission method analyzes the entire volume of the specimen. Thus the reflection technique may yield a measure of the mechanical property of bone trabeculae that is largely unaffected by the mass of the entire specimen, but mass and the structural density of the specimen affect the transmission method.

Biomechanical Phenomena↗

PubMed1983

Adaptations for reflection of bioluminescent light in the gas bladder of Leiognathus equulus (Perciformes: Leiognathidae).

The gas bladder of leiognathid fishes functions not only in buoyancy but also in reflection of bioluminescent light from the circumesophageal light organ. Purine distribution, quality (guanine/hypoxanthine ratio), and concentration, as the basis for reflectivity, were assayed enzymatically for different portions of the gas bladder lining of the common leiognathid, Leiognathus equulus (Forskal). For highly reflective areas, the percentage of tissue wet mass and dry mass represented by purine was also determined. The results indicate that total purine content in the reflective areas of the leiognathid bladder was significantly higher than values determined for other similar, shallow water fishes; instead, purine content in these reflective areas was similar to that known for very deep-dwelling fishes, in which heavy purine deposition is correlated with high pressures and high oxygen concentrations in the bladder. In addition, the results show that differential purine distribution within the bladder correlates strikingly with the path of bioluminescent light. The dorsal bladder lining, the primary site of incident luminescence, had extremely high purine concentrations (averaging 2.80 mg/cm2), whereas the secondary reflective surfaces, the lateral (1.81 mg/cm2) and ventral (1.22 mg/cm2), portions, although high in purine content, had concentrations significantly lower than the dorsum. Areas through which light is transmitted, the light organ-bladder interface (0.09 mg/cm2) and the posterior region (0.19 mg/cm2), were greatly reduced in purine content. The enhancement of purine in the reflective portions of the bladder and the correlation of the differential distribution of purines with the path of light indicate that the L. equulus gas bladder is exquisitely adapted to function as a reflector of bioluminescent light.

Air Sacs↗

PubMed2000

Noninvasive determination of hemoglobin and hematocrit using a temperature-controlled localized reflectance tissue photometer.

We performed visible/near-infrared optical measurements on the forearm of human subjects. We conducted four studies: one study using a commercial diffuse reflectance spectrometer, and three studies using a breadboard temperature-controlled localized reflectance tissue photometer. Calibration relationships were established between skin reflectance signal and either the reference blood hemoglobin (Hb) concentration or the hematocrit values (Hct). Prediction results were expressed as the prediction correlation coefficient (r(p)) and the standard error for cross-validation prediction (CV-SEP). Using diffuse reflectance measurement, r(p) = 0. 8, CV-SEP = 0.9 g/dL for Hb and r(p) = 0.7, CV-SEP = 3.3% for Hct (n = 40). In a localized reflectance study involving calculating the absorption and scattering coefficients and including effect of change of skin temperature in the calibration model, the best prediction results were r(p) = 0.9, CV-SEP = 0.8 g/dL for Hb and r(p) = 0.8, CV-SEP = 3% for Hct (n = 26). In a second localized reflectance study on a population having diverse skin colors at 34 degrees C, the optimal model led to r(p) = 0.8, CV-SEP = 0.9 g/dL for Hb and r(p) = 0.9, CV-SEP = 2.1% for Hct (n = 28) using the localized reflectance values without deducing the absorption and scattering coefficients. Improvement in the correlation was more noticeable for Hct than for the case of Hb. The photometer was used to screen prospective blood donors with low Hb concentration. It was possible to predict anemic subjects in the limited prospective blood donor population.

Calibration↗

PubMed1995

Reflection-polarization patterns at flat water surfaces and their relevance for insect polarization vision

It has recently been shown that horizontally polarized ultraviolet light reflected from the surface of water is the main optical cue for habitat finding by insects living in, on, or near water. What are the polarization properties that make the skylight reflected by water attractive to flying water insects in nature? In this paper, as an approach to this problem, the patterns of the degree and direction of polarization of skylight visible over a flat water surface are computed for unpolarized light from an overcast sky and for partially polarized skylight as a function of the zenith distance of the sun. These patterns are compared with the corresponding celestial polarization patterns. The effect of depolarizing clouds on these reflection-polarization patterns is demonstrated. Reflectivity patterns of a flat water surface are also calculated for clear and overcast skies. The polarization of the blue sky is described by the semi-empirical Rayleigh model. It is assumed that the reflection polarization of skylight at the water surface is governed by the Fresnel formulae. The effect of some modifying factors on the reflection-polarization field is briefly discussed. The adaptations of the visual system of insects living in, on, or near water to reflection-polarization patterns at water surfaces are briefly reviewed and discussed by means of three representative species: the waterstrider (Gerris lacustris), the backswimmer (Notonecta glauca), and the dragonfly (Hemicordulia tau). Copyright 1995 Academic Press Limited

Journal Article↗

PubMed1995

Reflective organelles in the anterior pigment epithelium of the iris of the European starling Sturnus vulgaris.

The ultrastructure and chemical composition of reflective organelles in the anterior pigment epithelium of the iris of the European starling Sturnus vulgaris were examined. The reflective organelles produced a diffuse white reflectance at the iris mid-section which was visible only when the stroma was removed. The pigment granules were clear, angular, and birefringent under the light microscope. In electron micrographs the granules were irregular in shape and density, sometimes crystalline in appearance, but more often they were lost during sectioning or staining. Guanine was abundant in the modified pigment epithelium of the starling, but not in the pigment epithelia of other birds that lacked birefringent granules. Pteridines, such as xanthopterin and leucopterin, were present in small amounts. Pteridines were also present in the iris stroma which had no reflective organelles. The reflective organelles in the starling pigment epithelium resemble both the reflecting platelets of lower vertebrate chromatophores and the reflective granules in the tapeta of various vertebrates. Possible derivation of the organelles from these sources is discussed.

Animals↗

PubMed1999

Sex and age-specific differences in ultraviolet reflectance of scent marks of bank voles (Clethrionomys glareolus).

Scent markings of voles are visible via their ultraviolet reflection. Kestrels, and possibly other diurnal raptors, may use this property when hunting. We performed a laboratory study on bank voles to determine whether UV-reflectance of scent marks differs in relation to sex, age and social status. When reflectance spectra of scent marks were measured with a spectro-radiometer, we found UV reflectance to be strongest in mature males. There were no differences between mature females and immature juveniles, nor between sexes in juveniles or mature and immature individuals in females. Moreover, we did not find any difference in UV reflectance between dominant and subordinate mature males. The results of this study support earlier findings that UV sensitive predators may use UV reflectance of scent marks as a prey cue. Consequently, studies on differing vulnerability of voles to avian predators should take into account not only their space use and behaviour but also the UV reflectance of their scent marks.

Aging↗

PubMed1994

The Clinical Learning Spiral: a model to develop reflective practitioners.

Reflective practice in clinical nursing is an exciting concept. Much of the literature on reflection has been derived from education. Recently the Australasian Nurse Registering Authority Committee (ANRAC) endorsed reflective practice as a registering prerequisite competency for beginning nurse practitioners. This paper examines the concept and development of an action research clinical learning spiral to foster reflective practice of both undergraduate students and their clinical teacher in the practice setting. The innovation of a mutual group, that is, teacher and students interacting through reflection to create a co-operative learning environment is explored. In designing the spiral a number of models were consulted and incorporated. The action research clinical learning spiral adds structure and focus to the process of reflection-on-action and provides an avenue for students and the clinical teacher to set mutual goals of action to trial for future experiences. This process of reflection allows the clinical facilitator to be an integral component of success to the students learning in the clinical context.

Clinical Competence↗

PubMed1994

Reflective practice in nursing: issues and implications for nurse education.

Reflective practice is a frequently used but inadequately defined concept in nursing. Part of the reason for this may be the inadequate conceptualisation of the process of reflection. This paper argues that now is an appropriate time to critically examine the notion of reflective practice and maintains that there is a need for more debate and research into the nature of reflection in nursing. This paper reviews recent nursing ideologies and explores the concept of reflective practice in relation to different forms of practical knowledge. It discusses and critically analyses the attraction of reflective practice to different interest groups and concludes by examining the implication of reflective practice models of nursing for nurse educators.

Education, Nursing↗

PubMed2006

Abnormal oral mucosal light reflectance in achondroplasia.

No markers for the unaffected parents of children with achondroplasia (ACH) are known to date. Here, the value of oral mucosal reflectance in identifying unaffected parents of ACH patients with sporadic mutations was assessed. The study involved ACH children (n = 30), unaffected ACH parents (n = 60), and a sex- and age-matched controls (control children, n = 30; control parents, n = 60). Light reflectance of the lower gingival and vestibular oral mucosa was measured using an imaging reflectance system in the optical spectrum (400-700 nm wavelengths). Significantly higher reflectance values in the 410 to 630 nm wavelength range were observed in ACH patients (P < or = .0063), whereas significantly lower reflectance values over the whole optical spectrum were observed in ACH parents (P < or = .0001). A reflectance cutoff value < or =4.71% at the 430 nm wavelength identified ACH parents with 100% sensitivity and 96.4% specificity. These findings indicate the presence of previously unrecognized oral mucosal reflectance abnormalities in unaffected ACH parents of ACH children.

Achondroplasia↗

PubMed2006

The utility of surface reflectance for the recognition of upright and inverted faces.

The variation among faces can be partitioned into two sources: (a) shape and (b) surface reflectance. To compare the utility of shape and reflectance for face recognition, we created two sets of faces, with individual exemplars differing only by shape in one set and only by reflectance in the other set. Grayscale and full color versions of the stimuli were used in separate experiments; the physical variation between exemplars was equated across the two sets with the grayscale but not the full color stimuli. Subjects performed a matching task in which both the target and distractor were drawn from the same set, so that only shape or only reflectance information could be used to perform the task. With the grayscale stimuli, performance was better in the shape condition, but with the color stimuli, performance was better in the reflectance condition. Inversion of the faces disrupted performance with the shape and reflectance sets about equally, suggesting that the inversion effect is not caused specifically by the spacing of facial features, or even by shape information more generally. These results provide evidence that facial identity is a function of reflectance as well as shape, and place important constraints on explanations of why inversion impairs face recognition.

Adaptation, Ocular↗

PubMed2005

Diffuse reflectance patterns in cervical spectroscopy.

OBJECTIVES: Our laboratory seeks to develop minimally invasive cost-effective methods to improve screening and detection of curable precursors to cervical cancer. Previously, we have presented pilot studies that assess the diagnostic power of auto-fluorescence and diffuse reflectance spectroscopy. In the present study, we evaluate diffuse reflectance spectra from a comprehensive 850 patient clinical trial to determine its ability to discriminate normal tissue from several grades of abnormal cervical tissue. METHODS: Diffuse reflectance spectra at four source detector separations measured from 549 cervical sites were available for analysis. Three classifiers were implemented: one used spectral data directly as input, a second used simple spectral features such as peak position and intensity, and one used principal component analysis for feature selection. Algorithms were developed and evaluated using leave-one-out cross-validation to classify normal and precancerous cervical tissue. The percentage of samples correctly classified was used to evaluate and compare the performance of the algorithms, as compared to histology. RESULTS: Diffuse reflectance spectra of cervical precancer showed consistent differences from that of normal tissue at all source detector separations; reflectance intensity of precancer was lower than that of normal tissue on average. Normal cervical tissue spectra show more intensity variation between patients than other tissue grades. Reflectance spectra acquired from the closest source detector separations consistently demonstrated the most relevant information for tissue classification. Two persistent spectral patterns demonstrated that the contribution of hemoglobin absorption and the wavelength-dependent spectral slope contained relevant information for classification. CONCLUSIONS: Spectral patterns in diffuse reflectance spectra can be used for the discrimination of normal cervical tissue from low grade and high grade squamous intraepithelial lesions.

Algorithms↗

PubMed2003

Reflection of structural waves at a solid/liquid interface.

This paper investigates the reflection characteristics of structural or guided waves in rods at a solid/liquid interface. Structural waves, whose wavelengths are much larger than the diameter of the rod, are described in a first approximation by classical one-dimensional wave theory. The reflection characteristics of such waves at a solid/liquid (melting) interface has been reported by two different ultrasonic measurement techniques: first, measuring the fast regression rate of a melting interface during the burning of metal rod samples in an oxygen-enriched environment, and second, monitoring the propagation of the solid/liquid interface during the slow melting and solidification of a rod sample in a furnace. The second work clearly shows that the major reflection occurs from the solid/liquid interface and not the liquid/gas interface as predicted by plane longitudinal wave reflectivity theory. The present work confirms this observation by reporting on the results of some specially designed experiments to identify the main interface of reflection for structural waves in rods. Hence, it helps in explaining the fundamental discrepancy between the reflection characteristics at a solid/liquid interface between low frequency structural waves and high frequency bulk waves, and confirms that the detected echo within a burning metallic rod clearly represents a reflection from the solid/liquid interface.

Aluminum↗

PubMed1998

Shape from shading: estimation of reflectance map.

The reflectance map used by the visual system for perception of shape from shading was estimated. In Experiment 1, an image of a cylinder or a sphere illuminated from the viewer's direction was presented, and subjects estimated the cross-section of perceived 3D-shape. The reflectance map was estimated from the relationship between the stimulus image intensities and the slants of the measured cross-section. The estimated reflectance maps were not the ones based on Lambertian reflectance properties. In Experiment 2, whether perceived shapes could be predicted based on the reflectance maps obtained in Experiment 1 was examined. Subjects performed the same shape estimation task with images of cylinders generated by the reflectance map obtained in Experiment 1. The perceived shapes coincided well with the shapes used for stimulus image generation. These results indicate that the visual system's estimation of shape from shading can be fully understood based on empirically obtained reflectance maps without mentioning its inaccurate nature which has been claimed by past studies.

Algorithms↗

PubMed1993

Reflection: a review of the literature.

This paper is a review of the literature on reflection. The purpose was to unravel and make sense of the complex literature, and to identify the skills required to engage in reflection. An analysis of the literature revealed that differences between authors' accounts of reflective processes are largely those of terminology, detail and the extent to which these processes are arranged in a hierarchy. Key stages of reflection are identified and represented by a model. Skills required to engage in reflection were found to be implicit in the literature and these are identified. Methodological issues related to empirical literature are discussed. It is suggested that reflection is an important learning tool in professional education and that the skills required for reflection need to be developed in professional courses.

Humans↗

PubMed1995

Hindsight bias in reflective practice: an empirical investigation.

Reflection is seen as a central component in the education and practice of nurses. It is through critical reflection on one's practice that expertise can be assured. This faith in the process of reflection has influenced much of pre and post registration nurse education. It is only in the past few years that reflection as a technique has being criticized. A small-scale study investigating the phenomenon of hindsight bias and its consequence on the reflective process is described. The effects of the hindsight bias is to influence people's recollection of events once they know the final outcome. The present study does indicate that nurses are susceptible to such a bias, which would question the validity of reflection as a way to enhance patient care. There is an urgent need to clarify the reflective process and then to examine its effect on patient outcomes.

Bias↗

PubMed2000

Achieving change through reflective practice: closing the loop.

This paper draws on a small scale, exploratory study which was conducted in the clinical area in the early 1990s (Page 1992). The study drew on the principles of reflective practice in order to enable practitioners to identify learning needs in relation to cardiopulmonary resuscitation (CPR) procedures. Whilst considerable benefit from the reflective sessions was noted, one unanticipated and unpalatable outcome was what might be termed professional apathy. This was manifest in several ways, most importantly in that issues 'for action', identified through reflection, were not prioritised or acted upon. Whilst partial responsibility for this may lie with the somewhat naive way in which the reflective process was facilitated, some responsibility also rests with the nurses in question. One possible explanation is that, for changes in practice to occur, the planning and management of change should form an integral part of the reflective cycle. This point has been largely absent in the reflection literature to date. Such concerns are reviewed here in the context of nurse education's ongoing involvement with the notion of reflective practice and the role of the educationalist in the clinical area. The current political backdrop of 'quality initiatives' to create and demonstrate high standards of clinical care may be useful in advancing the debate.

Attitude of Health Personnel↗