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PubMed2002

Time dependence of the polarization of short X-ray pulses after crystal reflection.

The short X-ray pulses coming out of a SASE FEL (self-amplified stimulated emission free-electron laser) have stimulated a closer inspection of the response of a crystal reflection to them. As the reflectivity of a crystal reflection depends on the polarization of the incident radiation, the time response does so as well. The response to a delta-pulse incident either under 45 degrees linearly polarized with respect to the reflection plane of a monochromator crystal or circularly polarized is investigated in more detail. In contrast to the purely linear polarization perpendicular and parallel to the reflection plane, these mixed states show a very pronounced time dependence. In addition, a simulated SASE FEL bunch is investigated as an incident intensity distribution.

Journal Article↗

PubMed1995

Evaluation of Reflection Intensities for the Components of Multiple Laue Diffraction Spots. III. Using a Real-Space Density Modification Method.

In the Laue diffraction pattern, 10--20% of the spots result from the exact superposition of two or more reflections that are ;harmonics', e.g. hkl; 2h 2k 2l, ...; a high proportion of these are low-resolution reflections. For the solution of large or difficult structure problems, the intensities of the remaining 80-90% of the reflections, measurable as singles, may not be sufficient and thus the evaluation of the intensities of the components of the multiple spots is important. A new procedure, DECONV, for this deconvolution using real-space density modifications on the Patterson map is given. This development is based on a procedure in reciprocal space related to direct methods [Hao, Campbell, Harding & Helliwell (1993). Acta Cryst. A49, 528-531]. A Patterson map is calculated using single reflections and modified by removing negative densities and squaring with an appropriate adjustment at the origin peak. The procedure can be repeated until convergence is reached. It has been tested with Laue diffraction data from 4Zn insulin and cytochrome c peroxidase (CCP). 304 and 1134 reflection intensities were evaluated from multiple spots of insulin and CCP, respectively; the mean fractional differences (on F), showing the agreement with high-quality monochromatic data, were 0.27 and 0.21, respectively.

Journal Article↗

PubMed2004

Separation of diffuse and specular components of surface reflection by use of polarization and statistical analysis of images.

The image of an opaque object is created by observing the reflection of the light incident on its surface. The dichromatic reflection model describes the surface reflection as the sum of two components, diffuse and specular terms. The specular reflection component is usually strong in its intensity and polarized significantly compared to the diffuse components. On the other hand, the intensity of the diffuse component is weak and it tends to be unpolarized except near occluding contours. Thus, the observation of an object through a rotating polarizer approximately yields images containing constant diffuse component and specular component of different intensity. In this paper, we show that diffuse and specular components of surface reflection can be separated as two independent components when we apply Independent Component Analysis to the images observed through a polarizer of different orientations. We give a separation simulation of artificial data and also give some separation results of real scenes.

Algorithms↗

PubMed2004

A P-matrix based model for SAW grating waveguides taking into account modes conversion at the reflection.

Several models exist for analyzing the wave-guiding effect of a reflective grating. On the one hand, there are models based on scalar waveguide theory. These models consider that a device can be described as being made of several regions having different velocities. On the other hand, an extension of the coupling of modes (COM) model taking into account the transverse dimension has been developed. This paraxial COM model predicts that guidance is possible even when there is no velocity difference between the interior and the exterior of the grating region. Guidance, under such circumstances, is due only to differences in reflectivity between regions. Following from this insight, a new approach has been developed: guided modes and the continuum of radiating modes are first determined. At each period, reflections then are considered as occurring only in the reflective regions, so that the modes are truncated. Thus, at each reflection (and transmission), each mode is converted into a distribution of all modes. Dispersion curves very similar to those shown by other researchers are obtained by this method. They show, in particular, the existence of guided modes even when the wave velocity in all regions is identical. This model can be used to more easily analyze practical devices and exhibits a good agreement with experimental results.

Journal Article↗

PubMed1994

Illuminating dissertation supervision through reflection.

This paper describes a small research study designed to explore the role of the dissertation supervisor and to examine the potential of using reflection as a tool for learning and for enhancing professional educational practice. The authors met to discuss and reflect upon the processes of supervision and the role of the supervisor throughout the period of supervising three dissertation students. Each author maintained individual reflective written accounts of supervisory meetings with students. These accounts and the transcribed tape-recordings of the group meetings provided two sets of data which were analysed using qualitative techniques. From the data analysis the authors were able to identify various phases in dissertation supervision--partnership; setting the learning contract; signposting; ownership of the dissertation; letting go; the rush at the end; maintaining the balance--and also contextual issues of humanness; time; and energy, which were needed to sustain the supervisory processes. The role of the dissertation supervisor was illuminated and the potential of using reflection as a tool for developing professional educational practice was realized. The importance of constructive support while engaged in processes of reflection cannot be underestimated.

Academic Dissertations as Topic↗

PubMed1995

Reflection and critical incident analysis: ethical and moral implications of their use within nursing and midwifery education.

Despite the dearth of rigorous empirical investigation, reflection and reflective practice have become buzz words in nursing and midwifery education. Reflection and critical incident analysis may be tools which can facilitate the integration of theory and practice. It is proposed that in the absence of explicit and thorough preparation of lecturers and students, together with very careful curriculum planning, these activities may be counter-productive or even harmful. In the absence of structure, reflection and associated critical incident analysis may lead to student disaffection or, worse, the potential for actual psychological disturbance. Empirical studies on the use of identified models of reflection and critical incident analysis are urgently needed to assist nursing and midwifery lecturers and students to achieve predictable learning outcomes for this potentially valuable activity.

Attitude of Health Personnel↗

PubMed1996

Visualizing and realizing caring in practice through guided reflection.

Guided reflection provides a challenging and supportive milieu for practitioners to learn through reflection towards achieving desirable work. This work inevitably demands confrontation with self and the conditions of practice that limit the achievement of desirable work. It also demands an understanding of what is desirable nursing. From an ideological position, desirable work is generally defined in terms of humanistic caring. The paper discusses how caring can be visualized and realized in practice through the experiences practitioners reflect on and share within guided reflection. This work is illustrated using using guided reflection dialogue.

Conflict, Psychological↗

PubMed2005

SARS (severe acute respiratory syndrome): reflective practice of a nurse manager.

AIMS AND OBJECTIVES: This paper describes the reflective practice of a nurse manager in Hong Kong in supporting frontline nurses to overcome the crisis of SARS. BACKGROUND: SARS infection was a crisis for everyone in endemic areas because of its threat to physical and emotional health. Hong Kong was the second leading endemic area in the world. Inadequate supplies of protective devices and the death of a nurse infected with SARS triggered nurses' negative emotions. METHODS: A model of structured reflection was adopted to examine one's practice. A problem-solving model for crisis intervention was integrated into the reflective stage of structured reflection. RESULTS: Promotion of nurses' safety and emotional stability were the major goals in handling the crisis. Strategies were employed including self-awareness, empowerment and team building, information sharing, provision of personal protective equipment and emotional support for frontline nurses. CONCLUSIONS: SARS infection threatens the physical and emotional health of nurses. From a positive perspective, such a crisis created an opportunity to learn and grow in terms of ethical, personal and aesthetic arenas. RELEVANCE TO CLINICAL PRACTICE: SARS epidemic raised worldwide attention and challenged the Hong Kong's health care system. Reflective practice is useful to guide and examine nurses' professional action during the crisis, and to put the experience into a learning perspective.

Adaptation, Psychological↗

PubMed2006

Total internal reflection fluorescence imaging using an upconverting cover slip for multicolour evanescent excitation.

Total internal reflection fluorescence microscopy is well known as a means of studying surface-bound structures in cell biology. It is usually measured either by coupling a light source to the sample using a prism or with a special objective where light passing through the periphery of the lens illuminates the contact region beyond the critical angle. In this study we present a new and simple approach to total internal reflection fluorescence microscopy where the sample is mounted on a cover slip prepared from a high-index upconverting glass-ceramic. Excitation of the cover slip with a low-cost near-infrared laser diode generates intense narrow-band visible emission within the cover slip, some of which is totally internally reflected. This emission gives rise to an evanescent wave at the interface and hence can excite surface-bound fluorescent species. Depending on the excitation conditions the cover slip can generate violet, green and red emission and hence can excite a wide range of fluorescent labels. Fluorescence emission from the sample can be detected in spectral regions where the direct emission from the cover slip is very weak. The advantages and limitations of the technique are discussed in comparison with conventional total internal reflection fluorescence microscopy measurements and prospects for novel total internal reflection fluorescence microscopy geometries are considered.

Journal Article↗

PubMed2006

Students' views of reflective learning techniques: an efficacy study at a UK medical school.

OBJECTIVE: To describe the effects of a voluntary intervention using reflective learning techniques on students' learning. DESIGN: An interventional study with reflective learning techniques offered to medical students. SETTING: Year 3 of undergraduate medicine at Cardiff University where the curriculum is integrated with early clinical contact. PARTICIPANTS: All 232 Year 3 students were invited to participate. A total of 65 attended an introductory lecture. After the lecture 35 students agreed to take part; 15 of these subsequently dropped out (some before attending tutorial groups, others after taking part for some weeks). INTERVENTIONS: Participants kept learning journals for 2 terms and attended fortnightly, facilitated tutorial groups where they discussed their reflective journal entries. Main outcome measures were qualitative interviews and examination results. RESULTS: Interviews were carried out with 19 full participants, 4 initial participants and 7 non-participants. Participants perceived that they gained a greater ability to identify learning objectives and to integrate learning. The tutorial groups encouraged students to compare progress with their peers. Some students did not take part because they thought that the large factual content of the curriculum would make reflective learning less useful. There were no differences between the groups in examination results. CONCLUSIONS: Students among the small, self-selected group of participants were better able to identify what they needed to learn although there was no improvement in examination results. Students appear unlikely to take up voluntary reflective learning if they do not think it relates to the curriculum and assessments. Student culture exerts a potent effect on willingness to attend extra tutorial groups.

Attitude of Health Personnel↗

PubMed2006

'Do not ask who I am...': confession, emancipation and (self)-management through reflection.

AIM: This study explores and extends some recent Foucauldian critiques of reflection and clinical supervision in nursing. BACKGROUND: Although reflection is often accepted uncritically, several writers have claimed that it is being employed (albeit perhaps unwittingly) as a management tool to facilitate the governmentality of the workforce by establishing conditions whereby so-called reflective practitioners monitor and regulate their own practice in an essentially self-repressive way. EVALUATION/EXAMINATION: We evaluated these critiques and extended them with reference to Foucault's later writing, particularly on the 'care of self'. KEY ISSUES AND CONCLUSIONS: Our exploration of these critiques prompted us to distinguish between two different projects of reflection, which we term the ontological and the epistemological. The ontological project regards the aim of reflection as personal growth under the direction of an enlightened guide, and we argue that there is a real danger that such an approach might degenerate into what one critic has termed 'a subtle but persuasive exercise of power'. The epistemological project, on the other hand, is concerned with an exploration by practitioners of their own methods of thinking about their practice, and as such, has the potential to become truly emancipatory.

Attitude of Health Personnel↗

PubMed1995

Time to care? Time for reflection.

This paper develops a single shared experience within a guided reflection to highlight the process of guiding learning through reflection. The shared experience is a mundane everyday experience concerned with the ward sister on an acute elderly ward responding to a relative's request. From the reflective practice perspective, the analysis of a single experience becomes a significant source of knowledge to inform others' practice. Reflective practitioners always interpret extant knowledge for its relevance to their practice. This process is helped by reflective accounts because they are subjective and contextualized accounts and therefore aid interpretation.

Empathy↗

PubMed1997

Big battles for small gains: a cautionary note for teaching reflective processes in nursing and midwifery practice.

Since 1988, Australian university nursing courses have adopted the processes of educationalists in embracing reflective practitioner concepts and strategies. The assumption underlying reflective practice appears uniformly to be that if practitioners reflect on and in their practice worlds they can develop ways of changing them. This paper will outline some cautionary points in teaching reflective processes for use in nursing practice, given that they have been processes intent on mobilizing change in densely impacted hegemonic structures in healthcare organizations. To demonstrate that the limits of reflective practice may constitute big battles for small gains, a research project undertaken with practising midwives will be used as a case in point.

Curriculum↗

PubMed1997

Effect of location of the sensor on reflectance pulse oximetry.

OBJECTIVE: The influence of the location of the sensor on reflectance pulse oximetry during fetal monitoring in labour was investigated using the newborn infant as a model. METHODS: Seven healthy infants were studied between 19 and 48 hours after term delivery. Recordings of reflectance pulse oximetry were obtained from eight different sites on the infant's head. The relative changes in red to infrared light (R/IR) were determined. In pulse oximetry R/IR values are converted to arterial oxygen values by means of an empirically derived calibration curve. RESULTS: Significantly lower R/IR values were found at the forehead compared with the fontanelle, the parietal and occipital position, and the temporal area. Conversion to oxygen saturation values revealed a difference of up to 13.4% in oxygen saturation between the forehead and the occipital area. CONCLUSION: Assuming that the arterial blood oxygen saturation did not change substantially, our findings indicate that in reflectance pulse oximetry there is no unique relation between R/IR and arterial oxygen saturation. The differences in reflectance pulse oximetry at the various sites are explained by differences in optical properties (scattering and absorption) of the tissue underneath the sensor. These will affect the red and infrared light reaching the detectors in a different way, and consequently R/IR changes. Because during intrapartum monitoring exact positioning of the sensor on the fetal head is usually impossible, the accuracy of fetal reflectance pulse oximetry is impaired.

Fetal Monitoring↗

PubMed1986

Capillary permeability in rat hindquarters as determined by estimations of capillary reflection coefficients.

Osmotic reflection coefficients (sigma) for a variety of solutes ranging from NaCl to albumin were determined in perfused maximally vasodilated rat hindquarters employing the osmotic transient method (Vargas & Johnson 1964). Measurements were performed at high flows and using short tubings with small volumes. Intracapillary solute concentrations of the osmotic transients were measured or estimated for solutes of the size of inulin or smaller. The PS for Cr-EDTA and cyanocobalamine were determined repeatedly in half of the experiments using an on-line modification of the single injection (indicator diffusion) method (Rippe & Stage 1978) and capillary filtration coefficients (CFC or LpS) were followed in all experiments. The capillary osmotic reflection coefficient was determined to 0.05 for NaCl, to 0.08 for sucrose, to 0.39 for inulin, to 0.57 for myoglobin and to 0.87 for albumin. These reflection coefficients were compatible with a 'small pore radius' of approximately 40 A (slit width (w) of approximately 50 A) according to modern hydrodynamic theories for the reflection coefficient and the parallel transcapillary pathway hypothesis. The best fit of the osmotic transient data to current theories for the reflection coefficient occurred if the major portion (86-87%) of the hydraulic conductivity (Lp) was accounted for by this paracellular 'small pore' (slit) pathway and if 3.0-4.1% of Lp could be ascribed to a transcellular pathway (sigma approximately I) while the remaining fraction (10%) of Lp was accounted for by a non-selective paracellular pathway (sigma approximately o); that is, by 'large pores'.

Animals↗

PubMed1998

Effect of particle size and coating level on the diffuse reflectance of wax matrices.

The aim of this study was to examine the influence of particle size and extent of coating on the diffuse-reflectance spectra of wax matrices containing embedded potassium chloride. Near-infrared spectroscopy was used to analyse the diffuse-reflectance characteristics of the prepared multi-particulate matrices without destructive sample preparation. A 2-factor, 3-level face-centred central composite design was selected to construct a second-order polynomial model which described the effect of particle size and amount of coating on the intensity of the diffusely reflected light. A non-linear model was used to demonstrate the effect of the selected parameters on the intensity of the reflected light; good correlation was obtained between experimental and predicted results. The results indicated that the extent of coating and the particle size of the examined systems in the selected particle size-range modified the intensity of the reflected light. It can be concluded that near-infrared spectroscopy is a sensitive means of measuring not only the particle size of powders (substrates and their mixtures), but also that of coated multi-particulate systems.

Chemistry, Pharmaceutical↗

PubMed1971

Some reflective properties of the tapetum lucidum of the cat's eye.

1. Observation of the fresh, isolated tapetum of the cat with a low-power microscope showed it to be composed of multilayer reflectors (domains) each being less than 6 mum in diameter. It is concluded that these are subdivisions of the intracellular bundles of rodlets seen in electron micrographs.2. Apparatus was devised for illuminating a single domain with a pencil of white light and observing the colour and direction of the reflected light.3. Those domains which lie near the vitreal surface of the tapetum tend to reflect blue light and deeper ones reflect longer wave-lengths; this is attributed to differences in the layer spacings of the domains.4. Each domain has a set of reflecting planes lying within 15 degrees of the general plane of the tapetal surface. In addition, many domains have surfaces inclined to these at angles greater than 20 degrees which also can reflect visible light.5. The mechanism of reflexion is discussed in relation to the latticelike structure of the domain.6. It is suggested that under some conditions the nature of the tapetum may lead to significant local variations in the spectral sensitivity of the visual system.

Animals↗

PubMed2003

Measurement of skin stretch via light reflection.

A noninvasive technique for measuring the stretch of skin is described. The technique utilizes changes in the reflectivity of polarized light intensity as a monitor of skin stretch. Measurements of in vitro pigskin and in vivo human skin show that the reflectivity of polarized light intensity increases linearly with stretch. The changes in diffusive reflectivity properties of skin result from the alterations that take place in the roughness across the thickness of the skin layers due to stretch. Conceptually, as the roughness of a layer decreases with stretch, a smoother reflecting media is produced, resulting in a proportional increase in the specular reflection. Results can be easily extended to a real-time stretch analysis of large tissue areas that would be applicable for mapping the stretch of skin.

Animals↗