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PubMed1996

A Computational Model for Color Constancy by Separating Reflectance and Illuminant Edges within a Scene.

Several psychophysical experiments have revealed that color constancy exists even in shadowed scenes where the spatial power distribution of the illuminant has abrupt step changes, while previous models for color constancy fail to distinguish shadows and reflectance changes. This article addresses this problem and proposes a computational model for color constancy which separates reflectance and illuminant edges by two modules recovering both the spatial power distribution of the illuminant and surface reflectances of an object from an input scene. Each module has a line process which interprets whether a given edge is derived from a reflectance or illuminant change based on prior knowledge of shadows: it is mainly luminance that changes at the boundry of a shadowed area. Simulation results show that the proposed model correctly detects reflectance and illuminant edges and illuminant colors, and successfully removes the illuminant from the input scene. This suggests that recovering both surface reflectance and the spatial power distribution of the illuminant is one of the possible ways to achieve color constancy in shadows. Copyright 1996 Elsevier Science Ltd.

Journal Article↗

PubMed1998

Reflection: a reflex action?

Nursing appears to be regularly subjected to new and 'fashionable' ideas and practices, many of which come from the USA. Examples of these include the nursing process and models of nursing. In the pursuit of professionalization of nursing, the need for such innovations is supported by the author. What cannot be supported, however, is the haphazard way in which some of these initiatives are often badly introduced and accepted into the profession in the absence of any research supporting their benefits. This article seeks to explore the notion of reflective practice, some of the reasons it has been introduced, as well as some of the problems associated with investigating its benefits. The different types of reflective practice are discussed along with their implications for professional practice. Attempts are made to explain the difference between reflection and the mere recall of events, as well as some possible explanations as to why reflective practice has not been embraced by clinical nurses in the way it should or could have. Finally, the subject of how reflective practice could be practically implemented in clinical areas is discussed and an example for a model of reflection given.

Clinical Competence↗

PubMed2005

X-ray reflectivity and interfacial tension study of the structure and phase behavior of the interface between water and mixed surfactant solutions of CH3(CH2)19OH and CF3(CF2)7(CH2)2OH in hexane.

The interface between water and mixed surfactant solutions of CH(3)(CH(2))(19)OH and CF(3)(CF(2))(7)(CH(2))(2)OH in hexane was studied with interfacial tension and X-ray reflectivity measurements. Measurements of the tension as a function of temperature for a range of total bulk surfactant concentrations and for three different values of the molal ratio of fluorinated to total surfactant concentration (0.25, 0.28, and 0.5) determined that the interface can be in three different monolayer phases. The interfacial excess entropy determined for these phases suggests that two of the phases are condensed single surfactant monolayers of CH(3)(CH(2))(19)OH and CF(3)(CF(2))(7)(CH(2))(2)OH. By studying four different compositions as a function of temperature, X-ray reflectivity was used to determine the structure of these monolayers in all three phases at the liquid-liquid interface. The X-ray reflectivity measurements were analyzed with a layer model to determine the electron density and thickness of the headgroup and tailgroup layers. The reflectivity demonstrates that phases 1 and 2 correspond to an interface fully covered by only one of the surfactants (liquid monolayer of CH(3)(CH(2))(19)OH in phase 1 and a solid condensed monolayer of CF(3)(CF(2))(7)(CH(2))(2)OH in phase 2). This was determined by analysis of the electron density profile as well as by direct comparison to reflectivity studies of the liquid-liquid interface in systems containing only one of the surfactants (plus hexane and water). The liquid monolayer of CH(3)(CH(2))(19)OH undergoes a transition to the solid monolayer of CF(3)(CF(2))(7)(CH(2))(2)OH with increasing temperature. Phase 3 and the transition regions between phases 1 and 2 consist of a mixed monolayer at the interface that contains domains of the two surfactants. In phase 3 the interface also contains gaseous regions that occupy progressively more of the interface as the temperature is increased. The reflectivity determined the coverage of the surfactant domains at the interface. A simple model is presented that predicts the basic features of the domain coverage as a function of temperature for the mixed surfactant system from the behavior of the single surfactant systems.

Journal Article↗

PubMed1998

Reflectance pulse oximetry--principles and obstetric application in the Zurich system.

Transmission and reflectance are the two main modes of pulse oximetry. In obstetrics, due to the absence of a transilluminable fetal part for transmission oximetry, the only feasible option is the reflectance mode, in which sensor and detector are located on the same surface of the body part. However, none of the reflectance pulse oximeters developed for intrapartum use are fully satisfactory, as indicated by the fact that none have entered routine use. We have designed, developed, constructed and tested a reflectance pulse oximeter with the possibility to adjust the electronic circuits and signal processing in order to determine the effects of various parameters on signal amplitude and wave-form and to optimize the sensitivity and spatial arrangement of the optical elements. Following an explanation of the principles of reflectance pulse oximetry, we report our experience with the design, development, construction and field-testing of an in-house reflectance pulse oximetry system for obstetric application.

Adult↗

PubMed2006

Going beyond the reflectance limit of cholesteric liquid crystals.

Cholesteric liquid-crystalline states of matter are abundant in nature: atherosclerosis, arthropod cuticles, condensed phases of DNA, plant cell walls, human compact bone osteon, and chiral biopolymers. The self-organized helical structure produces unique optical properties. Light is reflected when the wavelength matches the pitch (twice periodicity); cholesteric liquid crystals are not only coloured filters, but also reflectors and polarizers. But, in theory, the reflectance is limited to 50% of the ambient (unpolarized) light because circularly polarized light of the same handedness as the helix is reflected. Here we give details of a cholesteric medium for which the reflectance limit is exceeded. Photopolymerizable monomers are introduced into a cholesteric medium exhibiting a thermally induced helicity inversion, and the blend is then cured with ultraviolet light when the helix is right-handed. Because of memory effects attributable to the polymer network, the reflectance exceeds 50% when measured at the temperature assigned for a cholesteric helix with the same pitch but a left-handed sense before the reaction. As cholesteric materials are used as tunable bandpass filters, reflectors or polarizers and temperature or pressure sensors, novel opportunities to modulate the reflection over the whole light flux range, instead of only 50%, are offered.

Journal Article↗

PubMed2006

Effect of chronic coffee consumption on aortic stiffness and wave reflections in hypertensive patients.

OBJECTIVE: Aortic stiffness and wave reflections are important markers and prognosticators of cardiovascular risk. Caffeine increases acutely aortic stiffness and wave reflections. Furthermore, chronic coffee consumption is associated with increased aortic stiffness and wave reflections in normotensive subjects. In the present study, we aimed to assess the association between chronic coffee consumption, and aortic stiffness and wave reflections in hypertensive patients. DESIGN: Epidemiological survey. SETTING: Hypertension Unit, University Hospital. SUBJECTS-METHODS: We examined 259 never-treated hypertensives (age 50+/-12 years, 165 males) without diabetes mellitus, who were asked to describe in detail the type and amount of coffee they consumed. Carotid-femoral pulse wave velocity (PWV) and augmentation index (AIx) were measured non-invasively as indices of aortic stiffness and wave reflections, respectively. RESULTS: When controlled for gender, age, height, smoking status, heart rate, mean pressure, HDL cholesterol and hsCRP, AIx was found to be higher with increasing daily coffee consumption. Post hoc analysis revealed that all groups of coffee consumption had higher AIx compared to no-consumption. PWV did not differ among groups of daily coffee consumption. Each participant had 35% higher relative risk of having high AIx for each cup (150 ml) of coffee per day, and 40% higher relative risk for each 10 cup-years. CONCLUSIONS: Coffee consumption is associated with increased wave reflections, but not aortic stiffness in never-treated hypertensive patients. This finding may have important clinical implications for cardiovascular health in hypertensive subjects.

Aorta↗

PubMed1999

Reflection coefficient for albumin and capillary fluid permeability in cat calf muscle after traumatic injury.

Surgery and traumatic injury are often followed by tissue oedema and a low plasma albumin concentration, indicating leakage of fluid and proteins from the intravascular to the interstitial space. Transcapillary leakage can be referred to as an increase in capillary hydraulic conductance and/or a decrease in the reflection coefficient for plasma macromolecules. This study evaluates if time-dependent variations in the reflection coefficient for albumin and capillary hydraulic conductance can be confirmed experimentally following a surgical trauma using a blood perfused cat skeletal muscle in vivo preparation. The hydraulic conductance was estimated by the capillary filtration coefficient, and was used to evaluate variation in capillary fluid permeability. According to the Starling fluid equilibrium, the ratio between the reflection coefficients for albumin on two occasions can be calculated from the maximum osmotic absorption rates induced by a fixed intravenous bolus infusion of albumin (0.5 g kg(-1)) and from the capillary filtration coefficients. We found a decrease in the reflection coefficient of about 30% up to 10 h after the preparation. The capillary filtration coefficient showed no significant change over time, but decreased by 5-10% following the albumin infusion. We conclude that: (1) the reflection coefficient for albumin is reduced after a trauma, whereas the effects on the capillary fluid permeability are small, (2) albumin in plasma contributes to preserve normal capillary fluid permeability and, (3) the model seems to be useful for evaluation of relative variations in the reflection coefficient for albumin.

Albumins↗

PubMed1997

Using patients: exploring the ethical dimension of reflective practice in nurse education.

Within nurse education there is a growing interest in the use of reflective practice as a vehicle for professional development. Additionally, clinically reflective practice is seen as an ideal way of improving performance and patient care. In this paper it will be argued that whilst this development is potentially valuable to both professionals and clients, there are major ethical issues which need to be addressed. The "how to' literature appears to focus predominately on the practitioners subjective description and interpretation of events. It is usual for these events to include details of clients: but not usual for clients to be aware that information about them is being used in this way. Within a deontological ethical framework the use of people as means rather than ends is considered to be morally wrong. However, clients have probably always been used by professionals to some extent: Things such as case conferences and clinical trials are legitimated by the intention to improve training and practice, and are regulated by various professional codes and committees. It would appear, however, that reflective practice is quantitatively and qualitatively different from the above, and thus may cross a moral boundary. Reflective practice is not simply re-examining someone's case: it involves personal interpretation and judgement. The reflector may be recording incidents, verbally or in written form, which would not otherwise be recorded, and may be controversial. This raises questions about the nature and ownership of knowledge, and the responsibilities of people who have such knowledge. Systematic and continued reflection may be akin to action research and, as such, considerations of rigour, authenticity and informed consent need to be addressed. Thus whilst reflective practice may prove to be a good thing, it cannot be seen in isolation from wider ethical concerns.

Education, Nursing↗

PubMed1999

Close encounters: the use of critical reflective analysis as an evaluation tool in teaching and learning.

Teaching and learning are complex activities which, when combined with professional practice-based activity, take on additional dimension and depth. This makes the use of traditional, product-based evaluation problematic in that a purely empirical approach does not facilitate thorough evaluation of every facet of such an encounter. This paper describes the use of critical reflective analysis as an alternative method of evaluation. The reflective framework facilitating this process has been adapted from three key sources: patterns of nursing knowledge; evaluative paradigms based upon knowledge - constitutive interests; descriptors for a reflective practicum. The reflective activity is structured around a teaching and learning encounter in a care-based setting and focuses on 'doing the drug round'. Descriptive vignettes are used to facilitate reflection-on-action and, through critical reflective analysis, the author identifies the essential value (e-value-ation) of the encounter in terms of credibility, utility and worth.

Education, Nursing, Graduate↗

PubMed2000

Reflections on intuition and expertise.

Reflective practice now appears firmly established in the English speaking world of professional nursing practice and development. Outside this linguistic context, however, the concept seems less well-known. This paper describes an experience drawn from clinical practice and education in French-speaking Switzerland followed by explicit reflection grounded in questions generated by Johns' model for structured reflection. Thus, a concept well-described in the English-language literature underpins an innovative approach to a French-language clinical teaching situation. The professional implications of this situation are explored through meaningful reflection providing new insight into familiar circumstances as they relate to the nurse tutor's role. This exploration is followed by a critical approach to the experience and the subsequent structured reflection in order to address relationships between intuition and expertise and self-awareness through reflection. A hermeneutic perspective provides additional insight into the nurse-patient relationship where both come to the situation with their own 'pre-understandings'. Individual horizons thus endorse a new understanding going beyond taken-for-granted meanings.

Attitude of Health Personnel↗

PubMed2001

Different aortic reflection wave responses following long-term angiotensin-converting enzyme inhibition and beta-blocker in essential hypertension.

1. In arterial hypertension, aortic wave reflections contribute to determining central systolic and pulse pressures. The present study assessed the central pressure alterations at the level of the common carotid artery following 1 month treatment with perindopril or atenolol and investigated during the 8 h following drug intake. 2. Twenty patients suffering from permanent hypertension were included after a 4 week run-in placebo period in a double-blind, randomized cross-over study comparing the angiotensin-converting enzyme (ACE) inhibitor perindopril with the beta-blocker atenolol during a 4 week treatment period. 3. Before and during the 8 h after drug intake, serial measurements included brachial artery systolic and diastolic blood pressures (SBP and DBP, respectively; mercury sphygmomanometer), carotid artery SBP and pulse pressure (PP; applanation tonometry), aortic pulse wave velocity (Complior; Colson, Les Lilas, France) and arterial wave reflections from the aorta (applanation tonometry; Sphygmocor; PWV Medical, Sydney, NSW, Australia). 4. Both treatments decreased brachial and carotid artery SBP, DBP and PP. Heart rate and pulse wave velocity decreased following atenolol (P < 0.001). Pulse wave velocity was reduced slightly following perindopril (NS). Arterial wave reflections were significantly (P < 0.001) decreased with perindopril in comparison with atenolol, but this effect on wave reflections was not associated with a larger decrease in carotid artery PP. 5. Thus, during chronic treatment, ACE inhibition and selective beta1-adrenoceptor blockade resulted in a similar decrease in brachial and carotid artery PP, but only atenolol reduced heart rate. Aortic pulse wave velocity was reduced with both drugs, but atenolol appeared more effective in improving aortic stiffness. Arterial wave reflections were decreased only following perindopril. 6. Central pulse pressure was improved following 1 month treatment with an ACE inhibitor or beta-adrenoceptor blockade following a decrease in arterial wave reflections with perindopril and a higher decrease in regional aortic stiffness with atenolol.

Adrenergic beta-Antagonists↗

PubMed2003

Perception of surface reflectance of 3-D geometrical shapes: influence of the lighting mode.

We examined in three experiments whether the perception of surface reflectance in 3-D geometrical shapes is influenced by the mode of lighting, the level of surface reflectance, the number of polyhedral faces, and the regularity of polyhedral shape. As stimuli, we used simulations of regular polyhedra in a 2AFC constant-stimuli procedure to measure how large variations in the reflectance needed to be for observers to be able to tell whether the whole surfaces were uniform or non-uniform. In almost all the cases observers were more successful in discriminating non-uniform polyhedra in the hemispherical diffuse lighting conditions than in the collimated lighting conditions. The different levels of reflectance had no effect on the discrimination of non-uniformity. Second, as the number of faces of the shape increased, discrimination thresholds became lower, indicating that the interpretation of reflectance variations was better when a shape had many faces. Finally, the regularity of the shape, such as the central symmetry, was not an important factor. These results suggest that the interpretation of surface reflectance is more precise when surfaces have less variance in relative strengths between the face luminance values; these surfaces were the ones obtained under hemispherical diffuse lighting.

Discrimination, Psychological↗

PubMed2005

Influence of community experiences on first-year medical students' reflective writing.

The purpose of this research was to investigate the usefulness of providing students with community-located experiences as a basis for reflection by observing the degree to which community-located experiences influenced the quality of a reflective writing exercise. Students were prepared for reflection by means of a lecture and a handout on the meaning, function and process of reflection. One hundred and twenty-eight students (66 Afrikaans-speaking, and 62 English-speaking) took part in the study. Initially, most students (71%) who revealed affect prior to the visit reported negative emotional states. For 54% of the students who revealed emotions upon arrival, positive emotional states replaced the negative and this increased to 67% as the visit continued. This represented the most important stage of the personal growth continuum, signifying awareness of perspective 'distortions'. The majority (94.3%) regarded the visit as being important prior to immersing themselves in the theory of primary healthcare. In the questionnaire survey, students were asked for their opinions on the value of reflective writing as a tool for promoting deep learning, as students' attitudes were considered an important determinant of increased uptake of this kind of activity. Reflective writing can be promoted through using a real-world experience as stimulus, and a framework for guiding students' thoughts.

Adult↗

PubMed2006

Discovering professionalism through guided reflection.

Doctors need to identify and understand the professional behaviours of both themselves and others. In order for students to think critically about these issues we encouraged them to use the tenets of the General Medical Council's Duties of a Doctor as a framework in which to reflect on the actions of healthcare professionals at work. Although the critical incident technique is a well-known process for encouraging reflection, little is known about its usefulness for assessment purposes in this setting. We aimed to discover the validity, feasibility and educational impact of the critical incident as an assessment method for first year students undertaking guided reflection in the context of their first exposure to multi-professional health and social care experiences. First year medical students submitted two critical incidents they had observed during multi-professional health and social care attachments and an evaluation of their experiences. Students engaged in the reflective cycle on the professional behaviours of others providing evidence of a varied range of situations. With adequate preparation, junior students are able to reflect on social and healthcare experiences using the Duties of a Doctor as a framework. Critical incidents are a valid and feasible method for assessing students' reflections on professionalism, with good educational impact.

Attitude of Health Personnel↗

PubMed1990

Studies of dust grain properties in infrared reflection nebulae.

We have developed a model for reflection nebulae around luminous infrared sources embedded in dense dust clouds. The aim of this study is to determine the sizes of the scattering grains. In our analysis, we have adopted an MRN-like power-law size distribution (Mathis, Rumpl, and Nordsieck) of graphite and silicate grains, but other current dust models would give results which were substantially the same. In the optically thin limit, the intensity of the scattered light is proportional to the dust column density, while in the optically thick limit, it reflects the grain albedo. The results show that the shape of the infrared spectrum is the result of a combination of the scattering properties of the dust, the spectrum of the illuminating source, and foreground extinction, while geometry plays a minor role. Comparison of our model results with infrared observations of the reflection nebula surrounding OMC-2/IRS 1 shows that either a grain size distribution like that found in the diffuse interstellar medium, or one consisting of larger grains, can explain the observed shape of the spectrum. However, the absolute intensity level of the scattered light, as well as the observed polarization, requires large grains (approximately 5000 angstroms). By adding water ice mantles to the silicate and graphite cores, we have modeled the 3.08 micrometers ice band feature, which has been observed in the spectra of several infrared reflection nebulae. We show that this ice band arises naturally in optically thick reflection nebulae containing ice-coated grains. We show that the shape of the ice band is diagnostic of the presence of large grains, as previously suggested by Knacke and McCorkle. Comparison with observations of the BN/KL reflection nebula in the OMC-1 cloud shows that large ice grains (approximately 5000 angstroms) contribute substantially to the scattered light.

Astronomical Phenomena↗

PubMed2001

UV reflectance spectroscopy probes DNA and protein changes in human breast tissues.

OBJECTIVE: The absorption spectrum obtained using diffuse reflectance measurements of malignant, fibroadenoma, and normal human breast tissues were studied. The spectral features in the spectrum were assigned to molecular components in the tissues. BACKGROUND DATA: Over the past decade, the methods of fluorescence, excitation, and Raman spectroscopy have been studied as potential noninvasive diagnostic tools. Useful spectroscopic information may be obtained from absorption spectra of tissues as well. However, direct measurement of absorption spectra of tissues by conventional transmission means is complicated by multiple photon scattering in tissues. Diffuse reflectance spectrum offers an indirect way to obtain absorption spectrum. METHODS: Excised malignant, fibroadenoma, and normal breast tissue samples without any treatment were obtained from pathology. Samples were placed in a quartz cuvette. The diffuse reflectance measurements between 250 nm to 650 nm were performed using an automated dual lamp spectrophotometer. The absorption spectra of breast tissues were obtained from the diffuse reflectance measurement. RESULTS: Twenty-one invasive carcinoma, 20 mixed in situ and invasive carcinoma, 14 fibroadenoma, and 39 normal breast tissue samples were studied. The absorption spectra of breast tissues were obtained from diffuse reflectance spectra. Spectral features were assigned to DNA and proteins in human breast tissue. Amplitude of changes averaged over 275 nm to 285 nm and 255 nm to 265 nm and were found to be different for malignant, fibroadenoma, and normal breast tissues. These changes arise from differences in content of protein and DNA. CONCLUSION: The peaks of absorption spectrum derived from diffuse reflectance measurements in the UV region revealed fingerprints from proteins and DNA components. The absorbance in the wavelength ranges of 275-285 nm and 255-265 nm were found to be different for malignant, fibroadenoma, and normal breast tissues. These differences provide a criterion to distinguish malignant from fibroadenoma and normal breast tissues.

Absorption↗

PubMed2006

Reflection a neglected art in health promotion.

Evaluation and quality assurance have, over time, become the bedrock of health promotion practice in ensuring effectiveness and efficiency of programme planning and delivery. There has been less emphasis, however, on formal recognition of the contribution of the personal characteristics and perspectives of those who plan and deliver programmes and to the more subtle underlying effects of prevailing societal and professional norms. This paper seeks to highlight the neglect of formal reflection as a key professional skill in professional health promotion practice. It outlines key theories underpinning the development of the concepts of reflection and reflective practice. The role of reflection in critical health education as it contributes to critical consciousness raising is highlighted through its contribution to the empowerment of change agents in a societal change context. A conceptual typology of reflective practice is described which provides a flexible structure with which professionals can reflect on the role of self, the context and the process of health promotion programme planning. Its use is illustrated from the author's published work in health promotion which is related to prevention of workplace violence.

Health Promotion↗

PubMed2000

Preceptors' use of reflection to teach in ambulatory settings: An exploratory study.

PURPOSE: Reflection on one's teaching behavior is a means to question teaching events to bring teaching actions to a conscious level, to interpret the consequences of those actions, and to conceptualize alternative teaching actions. Ambulatory teaching settings are variable, unpredictable, and discontinuous, often resulting in less focused teaching. The authors sought to measure the level of reflection on teaching used by preceptors to plan teaching in these settings. METHOD: Three preceptors who had participated in the Case Western Reserve University's peer-coaching program each answered four questions about how they planned to respond to two teaching case studies. The questions were posed by a medical educator who, for three of the four questions, also prompted the preceptors to stimulate their reflection. The audiotaped responses were assessed using Sparks-Langer and Colton's framework for reflective thinking. RESULTS: The levels of reflective thinking increased after prompting, but they did not exceed the rather low technical and practical levels, particularly for the more complex of the two cases. CONCLUSION: This exploratory intervention suggests that faculty rely more on external and non-reflective levels of thought when planning to teach in the ambulatory setting. The authors recommend further research to foster discussions about the cognitive processes involved in planning for teaching in this setting.

Adolescent↗