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PubMed2002

Spectral reflectance and directional properties of structural coloration in bird plumage.

Bird plumage is coloured both by pigments and by spectrally selective interference in the light reflected from feather barbs. These barbs are composites of high- and low-refractive-index materials, and light is reflected at refractive index boundaries. The spatial structure determines the wavelengths where constructive interference occurs and, hence, the spectral tuning. The spectral tuning of interference colours often varies with angles of illumination and reflection, which produces iridescence. Iridescence and other optical effects mean that interference coloration looks different from pigmentation and is visually striking. To study the optical and visual properties of structural plumage colours, we recorded the reflectance spectra of feathers and in particular their directional properties. A fixed spot on a feather was viewed from a fixed position, whilst the feather orientation and the angle of illumination were varied. We recognise two main types of coloration, 'directional' and 'diffuse'. Within these types, there is considerable variation, and five examples illustrate some features of structural plumage colours and suggest how their optical and visual properties can be measured and described.

Animals↗

PubMed2002

Does reflection polarization by plants influence colour perception in insects? Polarimetric measurements applied to a polarization-sensitive model retina of Papilio butterflies.

Using imaging polarimetry, we have measured some typical reflection-polarization patterns of plant surfaces (leaves and flowers) under different illuminations. Using a quantitative model to determine photon absorptions in the weakly polarization-sensitive (PS approximately 2) photoreceptors of Papilio butterflies, we have calculated the influence of reflection polarization on the colours of leaves and flowers perceived by PAPILIO: Compared with a retina containing polarization-blind colour receptors, the colour loci of specularly reflecting and, thus, strongly polarizing areas on a plant are slightly shifted, which could cause the perception of false colours. However, the colour of specularly reflecting surfaces is strongly masked by white glare, which may prevent the perception of polarization-induced hue shifts. Although the perception of polarizational false colours by Papilio butterflies was previously demonstrated with artificial, strongly colour-saturated and totally linearly polarized stimuli, we expect that the weak polarization sensitivity of Papilio photoreceptors hardly influences colour perception under natural conditions.

Animals↗

PubMed2002

Guided reflection: transcending a routine approach in the management of sexually transmissible infections.

This paper describes a distinctive approach to the sexually transmissible infections (STI) clinical consultation: 'the guided reflection approach'. The authors coined this term and identified the guided reflection approach through analysis of 22 in-depth interviews with practitioners who provide care for people with STI, and 34 people who had attended a healthcare facility in Australia for screening or treatment of an STI. A grounded theory method was used to collect and analyse this information. The data revealed when the STI consultation is conducted using the principles characterized by the guided reflection approach creates contexts for sexual empowerment that have the potential to effectively assist people to gain autonomy for safe sex. Routinely, most of the practitioners in this study were shown to direct the STI consultation towards risk behaviours and practices and prevention of transmission, with minimal intervention. However, this study shows that if clinical interaction is to make a difference to the patient's autonomy for sexual behaviour, two changes will be required. First, practitioners need to adopt the goal of assisting patients to attain levels of autonomy, and second, practitioners require education to assist them to develop the interactive skills needed to engage patients in dialogue and reflection about sexual behaviour.

Adolescent↗

PubMed2005

Orthostatic systolic hypotension and the reflection pressure wave.

Orthostatic hypotension (OH) is a potent predictor of cardiovascular frailty. Although OH is determined by changes in brachial blood pressure (BP), it has been reported that there are significant differences between central BP and peripheral BP. The prevalence of OH has been reported to be higher in subjects with isolated systolic hypertension. Since an early returning of the reflection pressure wave due to advanced arterial stiffness is one of the underlying mechanisms of systolic hypertension, a significant association between alterations of the reflection pressure wave and OH has been hypothesized. To explore this hypothesis, the orthostatic changes in carotid BP and arterial waveform were evaluated. The study subjects were 155 community residents (69 +/- 7 years old). Carotid and brachial BP were measured simultaneously in the supine position and 1 min after standing using a cuff-oscillometric and tonometric method. The carotid augmentation index (AIx) was obtained from the pressure waveform. The orthostatic decline of BP was more prominent in the carotid artery than the brachial artery. Nine subjects were diagnosed with orthostatic systolic hypotension (OSH) from brachial BP, while 21 subjects were diagnosed from carotid BP (p < 0.001). The orthostatic change in carotid systolic BP was significantly associated with that in carotid AIx (r = 0.361, p < 0.001). The decline of the reflection component of carotid pulse pressure (-4.0 +/- 8.4 mmHg) was more prominent than that of the incident component (-1.2 +/- 9.9 mmHg, p = 0.002). These results indicate that evaluation of brachial BP may not represent the orthostatic changes in central BP. Alteration of the reflection pressure wave could be one of the underlying mechanisms of OSH in the central artery.

Aged↗

PubMedDate not supplied

Just 'doing the observations': reflective practice in nursing.

The first part of this article explores the development, definition, and design of reflective practice. In the second part the author relates an 'ordinary nursing' story--'10 minutes with Mr Kandinski'--and uses an existentialist framework for reflective analysis. Reflection on personal experience can expose something of the interrelationship of theory and practice, perhaps helping practitioners to improve their work. More importantly, reflective practice provides a means for nurses to reveal a more complete picture of the reality of nursing work to others.

Clinical Competence↗

PubMed2003

Using Edward de Bono's six hats game to aid critical thinking and reflection in palliative care.

This article describes the use of a creative thinking game to stimulate critical thinking and reflection with qualified health professionals undertaking palliative care education. The importance of reflective practice in nursing is well documented and numerous models are available. However, the author as a nurse teacher has found that many of these models are either too simple or too complex to be valuable in practice. The six hats game, devised by Edward de Bono, is a method that stimulates a variety of types of thinking and when used as a means of reflection helps students to become more critical about their practice. Using this game with a palliative care case study the author demonstrates how thinking more creatively about the patients' perceived needs and problems can assist in developing reflective skills. The article concludes with a discussion on some of the challenges of using this method and suggestions for future practical uses.

Education, Nursing↗

PubMed2005

Learning to reflect and to attribute constructively as basic components of self-regulated learning.

BACKGROUND: Higher education is facing a number of problems: adjusting to larger and more heterogeneous student populations, increasing the number of graduating students, and preparing for lifelong learning. Improving learning competence can make a substantial contribution to solving each of these major concerns. The growing knowledge base on self-regulated learning was taken as one of the main starting points for our study. AIMS: In this article we report on reflection and attribution as basic components of self-regulated learning. We examine their trainability and their effect on academic performance. This study is part of a wider research project aimed at improving meta-cognitive knowledge as well as affective, conative and regulation skills. The experimental treatment consisted of an integrated set of instructional conditions, which were operationalized in a series of training sessions, as well as practice and transfer tasks. SAMPLE: The participants in this study were 141 first year students of business economics. The experimental group and both control groups each consisted of 47 students. METHOD: The effects of the learning environment were investigated using a quasiexperimental design. To control for unintended effects of the design the experimental and the first control group had the same number of teaching hours (time-on-task) and both teachers and students were not informed about the experimental design. Attribution and reflection behaviour was measured through specific assignments; study results during and after the intervention period were taken as indicators of academic performance. To test the hypotheses, t tests and effect-sizes were calculated. RESULTS: After the intervention the experimental students showed a higher degree of reflective behaviour than the control students. Moreover, their attribution skills had also measurably improved. The experimental students obtained better study results than their peers in the control groups. CONCLUSIONS: This intervention study, focused on the combined training of learning to reflect and to attribute constructively, provides evidence of the successful fostering both of meta-cognitive and of conative learning activities resulting in a positive impact on academic achievement.

Adolescent↗

PubMed2002

Holographic optical elements recorded in silver halide sensitized gelatin emulsions. Part 2. Reflection holographic optical elements.

Silver halide sensitized gelatin (SHSG) holograms are similar to holograms recorded in dichromated gelatin (DCG), the main recording material for holographic optical elements (HOEs). The drawback of DCG is its low energetic sensitivity and limited spectral response. Silver halide materials can be processed in such away that the final hologram will have properties like a DCG hologram. Recently this technique has become more interesting since the introduction of new ultra-fine-grain silver halide (AgHal) emulsions. In particular, high spatial-frequency fringes associated with HOEs of the reflection type are difficult to construct when SHSG processing methods are employed. Therefore an optimized processing technique for reflection HOEs recorded in the new AgHal materials is introduced. Diffraction efficiencies over 90% can be obtained repeatably for reflection diffraction gratings. Understanding the importance of a selective hardening process has made it possible to obtain results similar to conventional DCG processing. The main advantage of the SHSG process is that high-sensitivity recording can be performed with laser wavelengths anywhere within the visible spectrum. This simplifies the manufacturing of high-quality, large-format HOEs, also including high-quality display holograms of the reflection type in both monochrome and full color.

Journal Article↗

PubMed2002

Nonlinear estimation of spectral reflectance based on Gaussian mixture distribution for color image reproduction.

Nonlinear estimation method of spectral reflectance from camera responses is proposed. The proposed method minimizes the mean square error of spectral reflectance when the reflectance can be regarded as a random sequence of Gaussian mixture distribution. In computer simulations, 168 samples of spectral reflectance from a color chart are estimated from their image signals obtained by three- and six-band cameras. It is confirmed that the proposed method improves the accuracy in comparison with the conventional Wiener estimation method.

Journal Article↗

PubMed2002

Dopant-dependent reflectivity and refractive index of microcrystalline HxWO3 and LixWO3 bronze thin films.

Reflectivity spectra of HxWO3 and LiWO3 thin films were measured over the photon energy range from 0.4 to 4.2 eV. It was found that microcrystalline tungsten bronzes have reflectances of 8%-30% over the dopant concentration range x (0 < or = x < or = 0.25). Values for the real part of refractive index n were also determined from the refined reflectivity data. The optical data are interpreted by use of a modified Drude-Zener model together with a single-oscillator model to differentiate between bound and free electronic states. The values of high-frequency dielectric constant epsilon(hf) of MxWO3 (M = H+, Li+) bronzes were determined from the refractive-index data for estimation of the effective electronic masses involved in optical and polaronic transitions. A single-oscillator model showed that oscillator energy Ea and dispersion energy Ed increased and decreased, respectively, with increasing x values, opposite what occurs in crystalline tungsten bronzes. These findings support the fact that Bloch electrons are almost absent; instead, the polaronic species (W5+ and W4+) are assumed to control the reflectivity modifications (or variations in the refractive index) that are associated with the microcrystalline tungsten bronzes.

Journal Article↗

PubMed2002

Determination of the refractive index and thickness of holographic silver halide materials by use of polarized reflectances.

A method to determine the refractive index and thickness of silver halide emulsions used in holography is presented. The emulsions are in the form of a layer of film deposited on a thick glass plate. The experimental reflectances of p-polarized light are measured as a function of the incident angles, and the values of refractive index, thickness, and extinction coefficient of the emulsion are obtained by using the theoretical equation for reflectance. As examples, five commercial holographic silver halide emulsions are analyzed. The procedure to obtain the measurements and the numerical analysis of the experimental data are simple, and agreement of the calculated reflectances, by use of the thickness and refractive index obtained, with the measured reflectances is satisfactory.

Journal Article↗

PubMed2003

Reflectance-based calibration of SeaWiFS. II. Conversion to radiance.

For instruments that carry onboard solar diffusers to orbit, such as the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), it is possible to convert the instrument's reflectance measurements to radiance measurements by knowledge of the solar irradiance. This process, which generally requires the application of a solar irradiance model, is described. The application of the irradiance model is separate from the measurements by the instrument and from the instrument's reflectance calibration. In addition, SeaWiFS was calibrated twice before launch for radiance response by use of radiance sources with calibrations traceable to the National Institute of Standards and Technology. With the inclusion of the at-launch diffuser-based radiance calibration, SeaWiFS has three possible radiance calibrations forthe start of on-orbit operations. The combination of these three into a single calibration requires changes of 4% or less for the current at-launch radiance calibration of the instrument. Finally, this process requires changes of 4% or less for the reflectance calibration coefficients to provide consistency among the radiance calibration, the reflectance calibration, and the solar irradiance.

Journal Article↗

PubMed2003

Spectral-reflectance reconstruction in the near-infrared region by use of conventional charge-coupled-device camera measurements.

Our aim is to develop a method for obtaining the reflectance spectra of samples in the near-infrared (NIR) region (800-1,000 nm) by using a small number of measurements performed with a conventional CCD camera (multispectral imaging). We experimentally determined the spectral sensitivity of the CCD camera in the NIR range, used a method based on principal component analysis to reconstruct the spectral reflectance of the samples, and analyzed the number and shape of the filters that need tobe used to apply this method. Finally we obtained the reflectance spectra of a set of 30 spectral curves by numerical simulation. The small amount of errors in the spectral reconstruction shows the potential of this method for reconstructing spectral reflectances in the NIR range.

Journal Article↗

PubMed2003

Remote-sensing reflectance in the Beaufort and Chukchi seas: observations and models.

Two semianalytical remote-sensing reflectance models were evaluated and validated by use of bio-optical data collected in the Beaufort and Chukchi seas. Both models were efficient at retrieving chlorophyll concentration, phytoplankton absorption coefficients,and particulate backscattering coefficients. In contrast, they were not accurate in predicting an absorption coefficient for colored dissolved organic matter plus nonpigmented particulates. The poor model performance is attributed to the high variability in the concentrations of these colored materials. A chlorophyll-dependent reflectance model was also assessed, and it proved to be highly successful in reproducing measured reflectance spetra. A four-component, case 2 model with mean absorption spectra for phytoplankton, soluble materials, and nonpigmented particulates was employed in Hydrolight radiative-transfer model simulations. The remote sensing reflectance spectra simulated inthe radiative-transfer model were in excellent agreement with field data. The similarity between the model and the measurement confirms the accuracy of the underlying bio-optical relationships and underscores the utility of modeling for better understanding of the variability of ocean color observations. The latest SeaWiFS algorithm (OC4V4) overestimated chlorophyll by approximately 1.5 fold across most of the observed range of biomass (0.07-9 mg chlorophyll m(-3)). Regionally tuned algorithms explained > 93% of the variability in the surface chlorophyll concentration.

Journal Article↗

PubMed2003

Analysis of antiresonant reflecting optical waveguide gratings by use of the method of lines.

The modal spectral response of an antiresonant reflecting optical waveguide (ARROW) with periodic corrugations or grating is calculated for both shallow and deep gratings with the Method of Lines. The effect of the ARROW layer thickness and the grating depth on the spectral response is studied. It is found that when the ARROW-layer thickness is close to resonance, the ripples in the reflection spectra become smooth and the peak reflectivity drops. This is attributed to the large increase in the leakage loss of the ARROW waveguide near resonance. The ARROW grating is characterized by modal reflectivity spectra, which exhibit a strong polarization discrimination property, in favor of the TE polarization.

Journal Article↗

PubMed2003

Retardation-film-compensated reflective bistable twisted nematic liquid-crystal displays.

The reflective bistable twisted nematic liquid-crystal-displays (RBTN-LCDs) with a single front polarizer have been compensated by front half-wave or integer-wave plates or both. The compensation has been optimized through maximizing the contrast ratio. The optimized RBTN-LCDs with one or two retardation plates showed great improvement in contrast ratio. The wavelength-dependent reflectance, viewing-angle properties, and effect of the retardation variation of these optimized RBTNs with retardation compensation were also investigated. The simulation was carried out by using realistic parameters on RBTN modes that have retardation values from 0.30 to 0.85 microm and a low contrast ratio. The viewing-angle properties did not change much before and after the retardation compensation. The reflectance varied little, but the contrast ratio varied significantly with the variation of the retardations of the bistable twisted nematic cells, for both compensated and uncompensated cases. It is shown that a high contrast ratio (100:1), high reflectance (30%), and low dispersion are possible for such RBTN-LCDs with proper retardation compensations. Black-white operations can be realized by compensating RBTN-LCDs.

Journal Article↗

PubMed2003

Symmetry X system and method for absolute measurements of reflectance and transmittance of specular samples.

A symmetry X system that has been constructed for the absolute measurements of reflectance and transmittance of specular samples in the infrared region is described. The system has been designed so that it can be incorporated into commercial Fourier-transform infrared spectrometers. Although ten mirrors were used in this system, it is disclosed that the geometric mean of two reflectance values is independent of the reflectance difference of the individual mirrors and the optical loss at each mirror. This system achieves spectral measurements with high accuracy and within a short period of time. In particular, the system affords us the self-diagnostic ability for measured spectra, and the simultaneous measurements of reflectance and transmittance under the same geometry enable us to evaluate measurement uncertainties. Although the symmetry X system is used for infrared spectral measurements, the measurement method, design principles, and features are generally applicable to other wavelengths as well.

Journal Article↗

PubMed2003

Diattenuation and polarization preservation of retinal nerve fiber layer reflectance.

The diattenuation spectrum of the retinal nerve fiber layer (RNFL) reflectance has been predicted to depend strongly on the relative refractive index (m) of light-scattering cylinders. To constrain the values of m, diattenuation of the RNFL reflectance of isolated rat retina was measured with a multispectral imaging micropolarimeter. The RNFL reflection has very weak intrinsic diattenuation at all wavelengths (400-830 nm), which rejects all values of m > or = 1.03. Degree of polarization (DOP) for reflection from the RNFL was also measured. DOP was close to unity at all wavelengths, which indicates that the RNFL is a polarization-preserving reflector.

Animals↗