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PubMed1989

Modified asymmetric T-tube model to infer arterial wave reflection at the aortic root.

A modified version of the T-tube model was constructed to represent the systemic arterial loading system as "seen" by the left ventricle (LV). This model consisted of two uniform tubes connected in parallel. It differs from the original T-tube model in that the transmission paths have no frictional losses and are terminated with complex impedances, rather than simple resistors. To estimate model parameters (load and tube compliances, tube inertances, characteristic impedances, and peripheral resistances) we measured ascending aortic pressure and flow in a group of five open-chest, anesthetized dogs. Parameter estimates were obtained by fitting experimental pressure to the pressure predicted by the model from experimental flow. To check the reliability of the model, an additional experiment was performed where flow in the upper descending thoracic aorta was measured in addition to ascending aorta pressure and flow. The fit between the experiment and model predicted ascending aortic pressure was satisfactory in all six dogs. This pressure was always characterized by the presence of a prominent diastolic oscillation. Our model showed that this oscillation is due to reflections from the lower body, the effective reflection site being most probably located at the level of middle to low abdominal aorta. The effective reflection site located in the upper body is closer to the heart. The related reflected wave affects pressure in late systole.

Analog-Digital Conversion↗

PubMed2003

Comparison of multiexcitation fluorescence and diffuse reflectance spectroscopy for the diagnosis of breast cancer (March 2003).

Nonmalignant (n = 36) and malignant (n = 20) tissue samples were obtained from breast cancer and breast reduction surgeries. These tissues were characterized using multiple excitation wavelength fluorescence spectroscopy and diffuse reflectance spectroscopy in the ultraviolet-visible wavelength range, immediately after excision. Spectra were then analyzed using principal component analysis (PCA) as a data reduction technique. PCA was performed on each fluorescence spectrum, as well as on the diffuse reflectance spectrum individually, to establish a set of principal components for each spectrum. A Wilcoxon rank-sum test was used to determine which principal components show statistically significant differences between malignant and nonmalignant tissues. Finally, a support vector machine (SVM) algorithm was utilized to classify the samples based on the diagnostically useful principal components. Cross-validation of this nonparametric algorithm was carried out to determine its classification accuracy in an unbiased manner. Multiexcitation fluorescence spectroscopy was successful in discriminating malignant and nonmalignant tissues, with a sensitivity and specificity of 70% and 92%, respectively. The sensitivity (30%) and specificity (78%) of diffuse reflectance spectroscopy alone was significantly lower. Combining fluorescence and diffuse reflectance spectra did not improve the classification accuracy of an algorithm based on fluorescence spectra alone. The fluorescence excitation-emission wavelengths identified as being diagnostic from the PCA-SVM algorithm suggest that the important fluorophores for breast cancer diagnosis are most likely tryptophan, NAD(P)H and flavoproteins.

Algorithms↗

PubMed2006

General theory of remote gaze estimation using the pupil center and corneal reflections.

This paper presents a general theory for the remote estimation of the point-of-gaze (POG) from the coordinates of the centers of the pupil and corneal reflections. Corneal reflections are produced by light sources that illuminate the eye and the centers of the pupil and corneal reflections are estimated in video images from one or more cameras. The general theory covers the full range of possible system configurations. Using one camera and one light source, the POG can be estimated only if the head is completely stationary. Using one camera and multiple light sources, the POG can be estimated with free head movements, following the completion of a multiple-point calibration procedure. When multiple cameras and multiple light sources are used, the POG can be estimated following a simple one-point calibration procedure. Experimental and simulation results suggest that the main sources of gaze estimation errors are the discrepancy between the shape of real corneas and the spherical corneal shape assumed in the general theory, and the noise in the estimation of the centers of the pupil and corneal reflections. A detailed example of a system that uses the general theory to estimate the POG on a computer screen is presented.

Computer Simulation↗

PubMed2005

An image model and segmentation algorithm for reflectance confocal images of in vivo cervical tissue.

The automatic segmentation of nuclei in confocal reflectance images of cervical tissue is an important goal toward developing less expensive cervical precancer detection methods. Since in vivo confocal reflectance microscopy is an emerging technology for cancer detection, no prior work has been reported on the automatic segmentation of in vivo confocal reflectance images. However, prior work has shown that nuclear size and nuclear-to-cytoplasmic ratio can determine the presence or extent of cervical precancer. Thus, segmenting nuclei in confocal images will aid in cervical precancer detection. Successful segmentation of images of any type can be significantly enhanced by the introduction of accurate image models. To enable a deeper understanding of confocal reflectance microscopy images of cervical tissue, and to supply a basis for parameter selection in a classification algorithm, we have developed a model that accounts for the properties of the imaging system and of the tissues. Using our model in conjunction with a powerful image enhancement tool (anisotropic median-diffusion), appropriate statistical image modeling of spatial interactions (Gaussian Markov random fields), and a Bayesian framework for classification-segmentation, we have developed an effective algorithm for automatically segmenting nuclei in confocal images of cervical tissue. We have applied our algorithm to an extensive set of cervical images and have found that it detects 90% of hand-segmented nuclei with an average of 6 false positives per frame.

Algorithms↗

PubMed2002

Reflection of plate acoustic waves produced by a periodic array of mechanical load strips or grooves.

The reflection of fundamental acoustic waves propagating in a thin piezoelectric plate by a periodic array of conducting strips of finite thickness or grooves has been theoretically and experimentally investigated. The analysis has shown that electrical shorting and mass loading affect the relationship of neighboring region impedances in a contrary manner. In some cases, these effects are comparable, and there exists a certain strip thickness for each piezoactive fundamental plate mode at which the reflection coefficient can become zero. A high efficiency of grooved reflector for plate acoustic waves was theoretically revealed. Experimental results for mass loading and grooved reflections, which have been obtained for an SH0 wave propagating in the Y-X lithium niobate plate, are in a good agreement with the theory. They show a high efficiency of such reflectors and confirm an opportunity of using a model based on equivalent circuit for the analysis of their operation. Investigations indicate that nearly 100% reflection of the SH0 wave in the lithium niobate plate can be obtained with the use of a mass loading reflector containing 10 silver strips of thickness d/h = 0.08 or a grooved reflector containing eight grooves of depth d/h = 0.25. Here h is the plate thickness and d is the reflector thickness or depth.

Acoustics↗

PubMedDate not supplied

Rendering deformable surface reflectance fields.

Animation of photorealistic computer graphics models is an important goal for many applications. Image-based modeling has emerged as a promising approach to capture and visualize real-world objects. Animating image-based models, however, is still a largely unsolved problem. In this paper, we extend a popular image-based representation called surface reflectance field to animate and render deformable real-world objects under arbitrary illumination. Deforming the surface reflectance field is achieved by modifying the underlying impostor geometry. We augment the impostor by a local parameterization that allows the correct evaluation of acquired reflectance images, preserving the original light model on the deformed surface. We present a deferred shading scheme to handle the increased amount of data involved in shading the deformable surface reflectance field. We show animations of various objects that were acquired with 3D photography.

Algorithms↗

PubMedDate not supplied

Interactive approximate rendering of reflections, refractions, and caustics.

Reflections, refractions, and caustics are very important for rendering global illumination images. Although many methods can be applied to generate these effects, the rendering performance is not satisfactory for interactive applications. In this paper, complex ray-object intersections are simplified so that the intersections can be computed on a GPU, and an iterative computing scheme based on the depth buffers is used for correcting the approximate results caused by the simplification. As a result, reflections and refractions of environment maps and nearby geometry can be rendered on a GPU interactively without preprocessing. We can even achieve interactive recursive reflections and refractions by using an object-impostor technique. Moreover, caustic effects caused by reflections and refractions can be rendered by placing the eye at the light. Rendered results prove that our method is sufficiently efficient to render plausible images interactively for many interactive applications.

Algorithms↗

PubMed2004

Senescence and hyperspectral reflectance of cotton leaves exposed to ultraviolet-B radiation and carbon dioxide.

The objectives of this study were to determine the effects of UV-B radiation and atmospheric carbon dioxide concentrations ([CO(2)]) on leaf senescence of cotton by measuring leaf photosynthesis and chlorophyll content and to identify changes in leaf hyperspectral reflectance occurring due to senescence and UV-B radiation. Plants were grown in controlled-environment growth chambers at two [CO(2)] (360 and 720 micro mol mol(-1)) and three levels of UV-B radiation (0, 7.7 and 15.1 kJ m(-2) day(-1)). Photosynthesis, chlorophyll, carotenoids and phenolic compounds along with leaf hyperspectral reflectance were measured on three leaves aged 12, 21 and 30 days in each of the treatments. No interaction was detected between [CO(2)] and UV-B for any of the measured parameters. Significant interactions were observed between UV-B and leaf age for photosynthesis and stomatal conductance. Elevated [CO(2)] enhanced leaf photosynthesis by 32%. On exposure to 0, 7.7 and 15.1 kJ of UV-B, the photosynthetic rates of 30-day-old leaves compared with 12-day-old leaves were reduced by 52, 76 and 86%, respectively. Chlorophyll pigments were not affected by leaf age at UV-B radiation of 0 and 7.7 kJ, but UV-B of 15.1 kJ reduced the chlorophylls by 20, 60 and 80% in 12, 21 and 30-day-old leaves, respectively. The hyperspectral reflectance between 726 and 1142 nm showed interaction for UV-B radiation and leaf age. In cotton, leaf photosynthesis can be used as an indicator of leaf senescence, as it is more sensitive than photosynthetic pigments on exposure to UV-B radiation. This study revealed that, cotton leaves senesced early on exposure to UV-B radiation as indicated by leaf photosynthesis, and leaf hyperspectral reflectance can be used to detect changes caused by UV-B and leaf ageing.

Journal Article↗

PubMed2004

Effect of acid on duodenal blood flow and mucus secretion measured by reflectance spectrophotometry: a prospective, randomized-controlled study.

BACKGROUND: In animals, hydrochloric acid increases blood flow and mucus secretion in the duodenal mucosa. A significant correlation between index of haemoglobin oxygen saturation and mucosal blood flow, and between change in index of haemoglobin concentration and mucus thickness, respectively, has been demonstrated by reflectance spectrophotometry. AIM: To examine the effect of topical hydrochloric acid upon mucosal blood flow and mucus secretion in the human duodenum. METHODS: This prospective study of 120 patients undergoing routine upper endoscopy, examined the effect of topical 0.1 n hydrochloric acid or 0.9% saline on the duodenal bulb in a randomized, double-blind fashion. Duodenal mucosal index of haemoglobin oxygen saturation and index of haemoglobin concentration were measured by endoscopic reflectance spectrophotometry before and after hydrochloric acid or saline. RESULTS: Baseline index of haemoglobin oxygen saturation, calculated blood flow and index of haemoglobin concentration measurements were comparable between hydrochloric acid (n = 60) and saline (n = 60) treated groups. A history of current use of non-steroidal anti-inflammatory drug was associated with a significantly lower baseline index of haemoglobin oxygen saturation and calculated blood flow. Hydrochloric acid resulted in a significant increase in index of haemoglobin oxygen saturation and calculated blood flow, but a decrease in index of haemoglobin concentration, reflecting an increase in mucus thickness compared with saline. CONCLUSIONS: Our observations in humans confirm data in animal studies that topical exposure to hydrochloric acid induces an increase in duodenal mucosal blood flow and mucus secretion. Post hoc analysis of the data also revealed that attenuation of basal duodenal mucosal blood flow is associated with a history of current non-steroidal anti-inflammatory drug use. Endoscopic reflectance spectrophotometry appears to be adequate to assess factors that influence duodenal defence mechanisms of blood flow and mucus secretion in humans.

Duodenum↗

PubMed2006

Significance of interleukin-16, macrophage-derived chemokine, eosinophil cationic protein and soluble E-selectin in reflecting disease activity of atopic dermatitis--from laboratory parameters to clinical scores.

BACKGROUND: The search for the ideal clinical score reflecting atopic dermatitis (AD) severity has developed in parallel with unveiling key events in disease pathogenesis and finding laboratory parameters for monitoring disease activity. A major difficulty in assessing the relevance of reported serum markers of AD severity is the use of nonvalidated referent tools, which compromises comparison of results across studies. OBJECTIVES: The aim of our study was to compare the significance of serum levels of interleukin (IL)-16, macrophage-derived chemokine (MDC), soluble E-selectin (sE-selectin) and eosinophil cationic protein (ECP) in reflecting AD severity and identify the most relevant parameter for monitoring the course of disease. Serum levels were tested against the same referent severity score in the same time frame and group of patients. METHODS: The Severity Scoring of Atopic Dermatitis (SCORAD) index was used for assessment of disease severity in 21 adult patients in acute stage of AD and after complete resolution of clinical findings. Serum levels of IL-16, MDC, ECP and sE-selectin were measured at the same time points in 18 patients and compared with healthy nonatopic controls. The correlation between SCORAD and each laboratory parameter was tested for significance and compared. RESULTS: Serum levels of IL-16, MDC, ECP and sE-selectin were significantly higher in patients in acute stage of AD compared with controls and decreased significantly after treatment, in parallel with clinical improvement. All monitored parameters reflected disease severity assessed by the clinical score. We found the highest significance level of correlation with SCORAD for IL-16 (r = 0.68, P =0.0019), followed by ECP (r = 0.65, P = 0.0032) and MDC (r = 0.55, P =0.0326). There was significant correlation between serum levels of IL-16 and MDC (r = 0.53, P = 0.0443) and ECP and sE-selectin (r = 0.48, P = 0.0427). CONCLUSIONS: The study established a significant correlation between serum levels of IL-16 and SCORAD in adult AD patients. We report a significant correlation between IL-16 and MDC, both T-helper 2 activation markers. Our data suggested that IL-16 reflects most convincingly disease severity and may be used as a marker in clinical studies preferentially in combination with a clinical activity score.

Adolescent↗

PubMed1989

The reflective practitioner in nursing.

This work is a study of eight practising registered nurses and their use of reflection-in-action in their everyday work. Schon's work on reflection-in-action forms the theoretical basis, and the research tool uses the work of Mezirow and Lazzara's use of Colaizzi's reduction. The findings are that, of the sample used, reflection-in-action is present extensively in the form of description and of planning of actions, but to a much lesser extent in the area of recognition of value judgements and the areas of reflection-in-action leading to learning taking place. Where these were present, albeit in small quantities, they were almost exclusively confined to the community nurses and the nurse practitioner. The tool also helped determine whether or not practice was founded on the use of nursing research and/or that of other disciplines. In the nurses studied here, this was somewhat erratic. With changes in technology, social and environmental changes, and the advancement of nursing and social science research, it is important for registered nurses to be able to both learn from their everyday work and use knowledge from nursing and other disciplines in this, rather than, as is demonstrated here, separate theory from practice and be relatively unable to learn from their work. In view of the changes presently proposed in nurse education, this work has implications for nurse educators as well as for practising nurses.

Awareness↗

PubMed1996

Using individual and group reflection in and on assessment as a tool for effective learning.

This paper outlines the background to the current United Kingdom educational scene for post-registration nurse education, highlighting the influence of the English National Board (ENB) framework and higher award. The study reported was undertaken with the help of two student cohorts who were registered consecutively on a 6 month ENB course at diploma level. Formal reflection using both individual written and group discussion was introduced focusing on the two summative course assessments. This kind of formal reflection was seen as a learning strategy to influence positively students' educational outcomes and professional practice via six key factors: (a) academic self-concept; (b) task awareness; (c) views of knowledge; (d) the influence of knowledge on behaviour; (e) writing as a learning activity; and (f) generating knowledge by reflecting in and on assessment with discussion. The findings, reported under the six factor-headings, fully support the use of reflection in this way for these purposes.

Curriculum↗

PubMed2006

Teaching critical reflection skills for advanced mental health nursing practice: a deconstructive-reconstructive approach.

AIM: This paper presents a literature review conducted to establish what was already known about critical reflection in the nursing literature and what work had been done on using a critical social theory framework as the basis for critical reflection. BACKGROUND: Critical thinking emerged as a significant aspect of nursing education and practice in the late 1980s. It has been promoted as a means by which issues in clinical practice can be examined through a systematic process of exploration and reasoning. Traditionally, critical thinking has commonly involved an attempt to link practice with theory using a scenario or exemplar from practice to illustrate a practice dilemma. This process is often constructed as a retrospective narrative of events. This paper provides a deconstructive-reconstructive approach that differs from some traditional approaches by taking a critical social theory perspective with an emphasis on improving practice. METHODS: The nursing literature reviewed was accessed through Cumulative Index of Nursing and Allied Health Literature (CINAHL). The search was restricted to English language and published between 1995 and 2005. Based on these findings, we developed a postgraduate advanced mental health nursing programme. FINDINGS: There were 490 articles related to 'nursing' and 'critical thinking'; 34 articles related to 'nursing' and 'critical reflection'; 23 articles related to 'nursing' and 'critical social theory'; 15 articles related to 'mental health nursing' and 'critical thinking'; and two articles related to 'mental health nursing' and 'critical reflection'. In the programme we developed based on these findings, students were facilitated to deconstruct concepts and knowledge integral to their own practice. In the reconstructive phase, students implement a change project in clinical practice, supported by a mentor. CONCLUSION: The deconstructive-reconstructive approach to the development of critical thinking skills provides advanced practitioner with the opportunity to integrate practice, theory and research.

Education↗

PubMed1990

A confocal video-rate laser-beam scanning reflected-light microscope with no moving parts.

A no-moving-parts, 30 frames/s, laser-beam scanning confocal reflected-light microscope has been developed. In principle, the technique can be extended to fluorescence and transmission light microscopy. Acousto-optic beam deflectors controlled by digital electronics move a laser beam in a 512-line interlaced 8.5 x 8.5-mm raster. The light passes through a beam splitter, enters an inverted microscope through the side camera port, and is imaged at the object by the microscope objective. Reflected light returns through the objective, exits the camera port, is reflected off the beam splitter, and is imaged on to the photocathode of an image dissector tube (IDT). Confocality is provided by raster scanning the IDT aperture coincident with the congruent image of the laser beam incident on the object. Real-time jitter-free reflected light images of a variety of biological objects have been produced. Computer-controlled alignment of the laser scan and IDT is performed in several seconds.

Animals↗

PubMed1996

Towards optimization of wave reflection: therapeutic goal for tomorrow?

1. The conventional approach to drug therapy of hypertension and heart failure considers only effects of such drugs on peripheral resistance, cardiac output and heart rate. 2. A more complete approach needs to consider the pulsatile nature of cardiac ejection and so the influence of arterial stiffness and wave reflection properties and the effects of drugs on these. 3. Wave reflection normally aids cardiac function when full body height is achieved and arterial distensibility is high. However, with ageing or in hypertension the arteries stiffen and wave reflection returns early, augmenting systolic pressure, increasing pulse pressure and reducing the capacity for coronary perfusion. 4. In mature or older adults, delay of or reduction in wave reflection is an important therapeutic strategy for management of hypertension, angina pectoris and cardiac failure. 5. Beneficial effects of such therapy cannot always be gauged from conventional recordings of blood pressure, but can be inferred from analysis of pulse waveform.

Aging↗

PubMed1975

Visual information-processing speed in reflective and impulsive children.

A backward-masking procedure was used to measure the rate of visual information processing in 8- and 10-year-old reflective and impulsive children. The test stimulus (TS) and the masking stimulus (MS) which followed it were presented tachistoscopially. The subject's information-processing threshold was defined as the next highest TS-MS interval above the interval where at least 3 of the 4 TSs were incorrectly identified. Reflective children were significantly faster than impulsive children at processing information. This finding was related to research indicating that reflective and impulsive children employ similar cognitive strategies; it was suggested that performance differences between these children might be related to reflective children employing their strategies with more adequate information.

Age Factors↗

PubMed2005

Nondestructive assessment of leaf chemistry and physiology through spectral reflectance measurements may be misleading when changes in trichome density co-occur.

Reflectance indices are frequently used for the nondestructive assessment of leaf chemistry, especially pigment content, in environmental or developmental studies. Since reflectance spectra are influenced by trichome density, and trichome density displays a considerable phenotypic plasticity, we asked whether this structural parameter could be a source of variation in the values of the most commonly used indices. Trichome density was manipulated in detached leaves of three species having either peltate (Olea europaea and Elaeagnus angustifolius) or tubular (Populus alba) trichomes by successive removal of hairs. After each dehairing step, trichome density was determined by light or scanning electron microscopy and reflectance spectra were obtained with a diode-array spectrometer. Although species-specific differences were evident, most of the indices were considerably affected even at low trichome densities. In general, the less-affected indices were those using wavebands within the visible spectral region. The index that could be safely used even at very high hair densities in all species was the red edge index (lambda(RE)) for chlorophyll. The results indicate that changes in reflectance indices should be interpreted cautiously when concurrent changes in trichome density are suspected. In this case, the red edge for chlorophyll content may be the index of choice.

Elaeagnaceae↗

PubMed2005

Digital ultraviolet reflectance photography can be used to quantify improvements in photodamage.

OBJECTIVE: Increasing attention has focused on the treatment and reversal of ultraviolet- induced photodamage. This study was designed to determine whether ultraviolet reflectance photography could quantify the clinical effects of erbium:YAG laser resurfacing on photoaged skin. METHODS: Twenty patients (ages 46-67) with moderate to severe photodamage underwent dual-mode variable pulsed erbium:YAG laser facial resurfacing. Pretreatment and post-treatment evaluations at 3 and 6 months were performed clinically and photographically with white and ultraviolet reflectance photography. RESULTS: Image conversion of the ultraviolet reflectance imaging data demonstrated an average of 36% and 42% reduction in photodamage at 3 and 6 months, respectively. This correlated well with the wrinkle reduction and correction of dyspigmentation observed in all patients following laser resurfacing. Histologic examination confirmed a thicker, more orderly epidermis and dermal collagen remodeling after treatment. CONCLUSION: Reduction in photodamage using the dual-mode variable pulsed erbium:YAG laser can be quantitatively measured with ultraviolet reflectance photography using digital imaging. This model should prove useful in developing treatment regimens for photodamage.

Journal Article↗