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PubMed2006

Control of reflection at an optical interface in the absence of total internal reflection for a retroreflective display application.

Reflection at an interface between two materials can be modulated by means of varying the optical properties at the interface. We have studied this modulation of the reflected light with an aim to develop a flashing retroreflector for roadside conspicuity applications. Reflectance modulation has previously been studied under the conditions of total internal reflection (TIR), where a light-absorbing material placed in the associated evanescent wave region can be used to attenuate the intensity of the reflected light. If instead the light rays strike the interface at an angle that is slightly smaller than the critical angle required for TIR, they instead undergo a substantial, but partial, reflection. We have demonstrated that an analogous attenuation effect to the TIR situation is observed, even though there is no evanescent wave present under these circumstances. We have studied this behavior and have developed a model to describe the motion of the absorbing material and the related interference effects that occur.

Journal Article↗
PubMedDate not supplied

Moving from technical to critical reflection in journalling: an investigation of students' ability to incorporate three levels of reflective writing.

This paper outlines a research project aimed at changing the levels of reflection of preregistration nursing students in a tertiary institution. Whilst reflection is widely espoused now in nursing, few studies have been found that identify whether the level of reflective writing can be identified or developed by students. Anecdotal and research evidence (Powell 1989; van Manen 1977) however indicates that most student reflective writing occurs at the technical level. A descriptive exploratory study using both qualitative and quantitative techniques was undertaken to apply van Manen's (1977) levels in a structured way in an attempt to facilitate the student's understanding and use of the levels in their reflective writing. The findings of the study indicate that student self evaluation and identification of the levels in their own writing can lead to change in the levels of critical reflective writing achieved by undergraduate students.

Adult↗
PubMed1997

Ultrasound reflections fail to reflect the histopathology of the prostate.

High-resolution profiles of the reflections of a broad-band 4 MHz ultrasound pulse from radical prostatectomy and autopsy specimens in vitro have been captured and analyzed. An attempt was made to correlate the histopathology of each prostate reflection site with the profile of the pulse reflected from that site. Reflections from 125 sites on 22 prostate specimens were studied. Although the reflected pulse from each site displayed a distinctive profile, we could find no obvious correlation between the shape of that profile and the histologic findings at that site.

Autopsy↗
PubMed2005

Medical students' mindset for reflective learning: a revalidation study of the reflection-in-learning scale.

The aims of this paper are to examine the measurement properties of the Reflection-in-Learning Scale (RLS) and to identify whether there are relationships between RLS scores early in the medical program and outcomes of the students' academic activity later on. The 14-item RLS was administered to second-year students (N = 275) at start and at end of the third semester, after the students had reviewed their previous learning experience with the Course Valuing Inventory. The internal consistency, temporal stability and dimensionality of the RLS scores were investigated in relation to the start-end perspectives. Furthermore, a 2-year follow-up allowed the assessment of the relationships of third-term RLS scores with sixth-term measures of both academic achievement and diagnostic reasoning as appraised by the Diagnostic Thinking Inventory (DTI). Findings indicate that RLS data have acceptable unidimensionality and consistency of measurement, notwithstanding a significant individual-context interaction. Repeated measures revealed distinct patterns of RLS scores relating to perceived self-efficacy on the ability to reflect. Third-term RLS scores were significant, albeit weak, predictors of sixth-term cognitive achievement and DTI-related diagnostic reasoning ability. In conclusion, the results do not support a major explanatory role for RLS on knowledge representation. Nevertheless, the findings appear to substantiate the construct validity of this tool as an index of the students' frame of mind as regards reflective learning. They suggest that the RLS captures a self-regulation or cognitive housekeeping dimension of the students' reflective learning. The individual pattern of such (reflective) activity is likely to vary with specific learning conditions.

Adolescent↗
PubMed2004

Neutron reflectivity and external reflection FTIR studies of DL-aspartic acid crystallization beneath nylon 6 spread films.

The crystallization of DL-aspartic acid beneath nylon 6 spread films has been studied for 150% supersaturated systems using neutron reflectivity and external reflection FTIR. The neutron reflectivity data showed the gradual incorporation of DL-aspartic acid within a nylon 6 spread film layer over a period of 6-8 h, culminating in over 50 vol % of the "film" layer comprising DL-aspartic acid. Accumulation of further DL-aspartic acid material to produce microscopic/macroscopic surface crystals occurred, but on a more limited scale, resulting in approximately 1-5% surface coverage of crystals over the same period. External reflection FTIR studies revealed very weak bands attributable to DL-aspartic acid in surface regions devoid of visible crystals, in agreement with the neutron reflectivity studies. In regions with visible crystals, much larger and sharper DL-aspartic acid bands were seen. Changes in the intensity of the nylon 6 NH stretch band were often observed during the visible crystallization and dissolution of DL-aspartic acid and were consistent with the reversible accumulation of nylon 6 around the growing crystals.

Aspartic Acid↗
PubMed2004

Comparison of diffuse-reflectance absorbance and attenuated total reflectance FT-IR for the discrimination of bacteria.

A collection of bacteria belonging to the genus Bacillus were analysed by diffuse reflectance absorbance and attenuated total reflectance Fourier transform infrared (FT-IR) spectroscopy in the mid-infrared. The diffuse reflectance absorbance method is a rapid whole organism fingerprinting method, which generates a biochemical profile of the bacteria, where samples are presented to the FT-IR spectrometer dried on a metal carrier. The attenuated total reflectance FT-IR used in conjunction with a diamond attenuated total reflectance (ATR) accessory produces a biochemical profile of the surface chemistry of bacteria directly without the need for drying, and has not previously been used in the discrimination of bacteria. Principal component, discriminant function and hierarchical cluster analysis were performed on the data to discriminate the bacteria. The differentiation of the bacteria to species level was observed in both analyses however, it was concluded that the ATR FT-IR illustrated better sub-species differentiation of the microorganisms. This may imply that the total biochemical profiling infers discrimination to species level whereas strain specific markers are present on the cell surface chemistry.

Bacillus↗
PubMed2001

Preschoolers' use of reflective properties: identification of reflections on partially transparent surfaces.

This exploratory study extended past studies of children's ability to reference the mirror as a tool in locating the source of reflected images to preschoolers' ability to use the affordances of a transparency. Thirty-six children (3.5 to 5 years old) were shown nonreflected lights and lights reflected on a partially transparent, glassy surface. Children did not spontaneously locate the source of the reflected image. However, they were able to verbally discriminate reflected from nonreflected images following training. These findings indicate that, although preschoolers may not spontaneously use transparencies as a perceptual tool, the ability to distinguish visual differences of reflected from nonreflected images on transparencies is likely within preschool children's developmental capacity.

Child Behavior↗
PubMed2001

Small group learning in the final year of a medical degree: a quantitative and qualitative evaluation.

The new undergraduate medical curriculum in Manchester uses problem-based learning (PBL) throughout the course. However, the major difference from other PBL schools is that in years 3 & 4 (phase 2) the students can use clinical experience when discussing the paper cases. The process is then developed further in year 5 (phase 3), in which there are no set PBL 'triggers' and students bring their own cases to the groups for discussion. In this study, we have explored what happens in the phase 3 (year 5) group sessions and how the students view them. A questionnaire and focus groups were used to generate data, from which a model was developed of what happens in a 'good' group session. The data suggest that most groups run on a case-presentation and discussion format, most commonly about clinical management and diagnosis. Students want tutors to act as an expert resource and to be flexible in allowing students to direct the discussions. University guidance about the group sessions was not generally used.

Journal Article↗
PubMed2003

The role of ultraviolet-A reflectance and ultraviolet-A induced fluorescence in the appearance of budgerigar plumage: insights from spectrofluorometry and reflectance spectrophotometry.

Fluorescence has so far been found in 52 parrot species when illuminated with ultraviolet-A (UVA) 'black' lamps, and two attempts have been made to determine whether such fluorescence plays any role in sexual signalling. However, the contribution of the reflectance versus fluorescence to the total radiance from feathers, even in the most studied species to date (budgerigars), is unclear. Nor has the plumage of this study species been systematically assessed to determine the distribution of fluorescent patches. We therefore used spectrofluorometry to determine which areas of budgerigars fluoresce and the excitation and emission spectra involved; this is the first time that such a technique has been applied to avian plumage. We found that both the yellow crown and (normally hidden) white downy chest feathers exhibit strong UVA-induced fluorescence, with peak emissions at 527 nm and 436 nm, respectively. Conversely, the bright-green chest and dark-blue tail feathers do not fluoresce. When comparing reflectance spectra (400-700 nm) from the yellow crown using illuminants with a proportion of UVA comparable to daylight, and illuminants with all UVA removed, no measurable difference resulting from fluorescence was found. This suggests that under normal daylight the contribution of fluorescence to radiance is probably trivial. Furthermore, these spectra revealed that males had fluorescent crowns with substantially higher reflectance than those of females, in both the UV waveband and at longer wavelengths. Reflectance spectrophotometry was also performed on a number of live wild-type male budgerigars to investigate the chromatic contrast between the different plumage areas. This showed that many plumage regions are highly UV-reflective. Overall our results suggest that rapid surveys using UVA black lamps may overestimate the contribution of fluorescence to plumage coloration, and that any signalling role of fluorescence emissions, at least from the yellow crown of budgerigars, may not be as important as previously thought.

Animals↗
PubMed1993

Pteridines as reflecting pigments and components of reflecting organelles in vertebrates.

This paper reviews evidence for the presence of pteridines in iridophores, leucophores, and xanthophores in a wide variety of vertebrate chromatophores, and argues that the chemical and functional distinction between pterinosomes and reflecting platelets is not as clear-cut as previously believed. Observations indicate that: (1) Pteridines may, either alone or in conjunction with purines, form pigment granules that reflect light, (2) these pigment granules are highly variable ranging from fibrous pterinosomes to typical reflecting platelets and may be colored, reflect white light, or be iridescent, and (3) many "leucophores" probably contain typical pterinosomes and presumed associated colorless pteridines and are therefore more closely related to erythrophores and xanthophores than to iridophores with which they are usually classified. We propose that the classification of pigment cells should be modified to reflect these facts.

Animals↗
PubMed2005

Coherent reflection in a two-dimensional cochlea: Short-wave versus long-wave scattering in the generation of reflection-source otoacoustic emissions.

The theory of coherent reflection filtering explains the empirical form of the cochlear reflectance by showing how it emerges from the coherent "backscattering" of forward-traveling waves by impedance perturbations in the mechanics of the cochlear partition. Since the theory was developed using the one-dimensional (1-D) transmission-line model of the cochlea, an obvious logical shortcoming is the failure of the long-wavelength approximation near the peak of the traveling wave, where coherent backscattering is purported to occur. Indeed, existing theory suggests that wave reflection may be strongly suppressed in the short-wave regime. To understand how short-wave behavior near the peak modifies the predictions of the long-wave theory, this paper solves the scattering problem in the 2-D cochlear model. The 2-D problem is reduced to a 1-D wave equation and the solution expressed as an infinite series in which successive terms arise via multiple scattering within the cochlea. The cochlear reflectance is computed in response-matched models constructed by solving the inverse problem to control for variations in mechanical tuning among models of different heights and dimensionality. Reflection from the peak region is significantly enhanced by the short-wave hydrodynamics, but other conclusions of the 1-D analysis--such as the predicted relation between emission group delay and the wavelength of the traveling wave--carry over with only minor modifications. The results illustrate the important role of passive hydromechanical effects in shaping otoacoustic emissions and cochlear tuning.

Basilar Membrane↗
PubMed2006

Aortic reflection coefficients and their association with global indexes of wave reflection in healthy controls and patients with Marfan's syndrome.

Early return of reflected pressure waves increases the load on central arteries and may increase the risk of aortic rupture in patients with Marfan's syndrome (MFS). To assess whether wave reflection is elevated in MFS, we used ultrasound and MRI to measure central pressure and flow waveforms in 26 patients (13-54 yr of age) and 26 age- and gender-matched controls. Aortic systolic and diastolic cross-sectional areas were measured at the ascending and descending aorta (AA and DA), diaphragm (DIA), and lower abdominal aorta (AB). From these measurements, local characteristic impedance (Z(0-xx)) and local reflection coefficients (Gamma(xx-yy)) were calculated. Calculated global wave reflection indexes were the augmentation index (AIx) and the ratio of backward to forward pressure wave (P(b)/P(f)). The aorta was wider in MFS patients at AA (P < 0.01) and DA (P < 0.01). Aortic pulse wave velocity was 42 cm/s higher in MFS patients (P < 0.05). Z(0-xx) was not different between groups, except at DA, where it was lower in MFS patients. In controls, Gamma(AA-DA) was 0.31 +/- 0.08, Gamma(DA-DIA) was 0.00 +/- 0.11, and Gamma(DIA-AB) was 0.31 +/- 0.16. Mean values of Gamma(xx-yy) were not different between MFS patients and controls. In controls, aging diminished Gamma(AA-DA) but increased Gamma(DIA-AB). Clear age-related patterns were absent in MFS patients. AIx or P(b)/P(f) was not higher in MFS patients than in controls. There were indications for enhanced wave reflection in young MFS patients. Our data demonstrated that the major determinants of AIx were pulse wave velocity and the effective length of the arterial system and, to a lesser degree, HR and P(b)/P(f).

Adolescent↗
PubMed2005

Angular dependence of the reflectance from an isotropic polydomain medium: effect of large domain size on total reflection.

We investigate the angular dependence of the reflectance from an isotropic medium consisting of optically large and anisotropic, randomly oriented domains, assuming a highly refractive, isotropic, and homogeneous incidence medium, which is presumed to have a higher refractive index than any of the domains' principal indices of refraction. By employing average reflectance and transmittance theory, we are able to show that the onset of total reflection is considerably shifted to higher angles of incidence compared with an isotropic medium with domains that are small compared with the wavelength. The onset of total reflection for a random medium with large domains is found to be dependent only on the largest principal index of refraction of the domains, assuming that all domains have the same optical properties. Therefore the shift of the onset depends on the magnitude of the optical anisotropy of the domains. Even in the case of a small optical anisotropy, large cross-polarization terms are predicted in the vicinity of the onset of total reflection. These terms show a pronounced maximum near that onset and extend beyond it.

Journal Article↗
PubMed2005

Infrared reflectance spectra of some optically biaxial crystals: on the origin of isosbestic-like points in the polarized reflectance spectra.

An investigation of the IR polarized reflectance spectra of the orthorhombic K2SO4, KHSO4 and monoclinic CaSO4 x 2H2O, K2Ni(SO4)2 x 6H2O, (NH4)2Ni(SO4)2 x 6H2O was performed in order to explain the appearance of particular intersection points in their spectra. The analogy in the origin of the appearance of intersection points and the well-known isosbestic points in UV-vis and IR spectra was discussed. The reason for such an appearance was identified in the way that the individual reflectances (for radiation polarized along principal dielectric axes) sum up to give the reflectance under arbitrary polarization. This summation may also produce supplementary bands in the reflectance spectra, not predicted by the group theory. It was shown that relatively large LO-TO splitting is needed for the supplementary band(s) to appear, but also the overlapping region must be taken into account.

Crystallization↗
PubMed1997

A three-step method of self-reflection using reflective journal writing.

Fiscal and financial constraints present a challenge for nurse educators to broaden the diversity and scope of teaching/learning methodologies. One method designed to promote autonomy and self-direction of nursing students is self-reflection combined with reflective journal writing. This paper describes a three-step process of self-reflection encompassing critical appraisal, peer group discussion and self-awareness. This process of self-reflection was initiated with one group of clinical nursing students. Using student and teacher feedback, implications for employing this teaching/learning strategy in clinical practice are suggested.

Education, Nursing↗
PubMed2001

Reflective practice and clinical outcomes: practitioners' views on how reflective practice has influenced their clinical practice.

There has been a recent increasing interest in reflective practice in nursing. There is a wealth of literature about its apparent advantages and benefits, but very little empirical research into clinical outcomes consequent to reflective practice. This study attempts an initial exploration into this area. A retrospective, three-phase, multi-method study in a single department of nursing was conducted. The research sample comprised students and former students of the department who had previously participated in an assessed reflective practice course or module. Years of experience, speciality or academic level did not have a significant influence, but the effectiveness of the facilitator was an important factor. The results suggest that reflective practice is regarded highly and that most respondents could identify significant, long-term changes to clinical practice resulting from it.

Attitude of Health Personnel↗
PubMed1995

Reflective midwifery practice: facilitating midwives' practice insights using a distance education reflective practitioner model.

A study was undertaken to evaluate a reflective practitioner model with midwives, who self-selected into the project when they were studying the Bachelor of Health Science (Nursing) unit NR278, Advanced Nursing Practice, Midwifery. The theoretical assumptions that influenced the research were those forwarded by Schon (1983) and Boud, Keogh and Walker (1985), who argued that practitioners are often unaware of the sophisticated knowledge they have regarding the intricacies of their practice, but that this personal knowledge can be make explicit through reflective processes. The aim of the study was to research the use of a distance education reflective practitioner process that encouraged midwives to examine their practice with a view to making changes where necessary. All the research objectives were met to some extent, although each experience of the research process was particular to the individual participant. Analysis consisted of: interpretation of the participant's insights into their individual experiences; the researcher's interpretations of participant's experiences; and collective themes arising out of the research. This paper concentrates mainly on the participant's insights into their individual experiences of practising midwifery, using a reflective practitioner model.

Education, Nursing, Baccalaureate↗
PubMed2003

Reflections on the intersection of power and competition in reflecting teams as applied to academic settings.

This article explores the author's experiences with the concepts of power and competition as they intersect with aspects of reflecting team practices in academic settings. It draws upon Bishop's (2002) work, the elements of which are based on Starhawk's (1987) ideas of power with and power over. The article describes how competition and other power over practices of domination might unfold and intersect with reflecting-team practices. It is proposed that a power over practice, such as competition, which is prevalent in our society and universities, can be incompatible with the collaborative nature of reflecting teams. Suggestions for addressing the dissonance between the environment and reflecting team practice are offered.

Competitive Behavior↗