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PubMed2004

Phases of the SAW reflection and transmission coefficients for short reflectors on 128 degree LiNbO3.

We study numerically the phase of surface acoustic waves reflected by or transmitted through short reflectors comprising only 1-3 aluminium electrodes on 128 degree YX-cut lithium niobate (LiNbO3). The electrodes have a finite thickness, and they are either open-circuited or grounded. The center-to-center distance between adjacent electrodes d corresponds roughly either to half of the characteristic wavelength d proportional to lambda0/2 or to d proportional to lambda0, for the reflectors operating at the fundamental and second harmonic modes, respectively. We use software based on the finite-element and boundary-element methods (FEM/BEM) for numerical experiments with a tailored test structure having 3 interdigital transducers (IDTs), simulating experimental conditions with an incident wave and reflected and transmitted surface acoustic wave (SAW). Using artificial enhancement of time resolution in conjunction with the fast Fourier transform (FFT) and time-gating, calculation of the Y-parameters in a relatively wide frequency range allows us to determine the phase of the reflection and transmission coefficients.

Journal Article↗

PubMed2005

Dual mode reflectance and fluorescence confocal laser scanning microscopy for in vivo imaging melanoma progression in murine skin.

A system was designed and developed for simultaneous fluorescence and reflectance contrast in vivo confocal imaging of murine skin using 488 nm (fluorescence mode) and 830 nm (reflectance mode) laser light sources. B16 melanoma cells and B16-enhanced green fluorescent protein (EGFP) cells were inoculated intradermally into transgenic C57BL/6-TgN (ACTbEGFP) 10sb and non-transgenic C57BL/6 mice, respectively. The inoculation sites were imaged sequentially over a 20 d period. The in vivo confocal images were correlated with ex vivo conventional microscopy. The combined modality system provided single-cell resolution and adequate image registration. In fluorescence mode, B16 melanoma cells appeared as dark objects in the bright background of the GFP expressing murine cells of the C57BL/6 transgenic mouse, and the B16-EGFP melanoma cells had a bright signal within a dark background in C57BL/6 mice. In the C57BL/6 transgenic mouse, a population of fluorescent dendritic cells was observed in the vicinity of the tumor cells. The reflectance images provide a useful reference for those areas in the dermal tissues lacking a fluorescent signal. Combined reflectance/fluorescence in vivo confocal laser scanning microscopy holds significant promise for studies of tumor progression in murine skin.

Animals↗

PubMed1993

The cutaneous corticosteroid vasoconstriction assay: a reflectance spectroscopic and laser-Doppler flowmetric study.

Cutaneous vasoconstriction induced by topical corticosteroids was investigated using non-invasive bioengineering techniques. Corticosteroids of different potency in alcoholic solution were applied topically, under occlusion, and cutaneous blanching was investigated using visual scoring, reflectance spectroscopy (RS) and laser-Doppler flowmetry (LDF). The RS technique allowed separation of cutaneous haemoglobin content into arterial oxygenated (OH) and venous deoxygenated haemoglobin (DOH) components. Application of alcohol decreased total haemoglobin by 10%, with a corresponding 8% increase in blood flow (BF). Clobetasol propionate was the most potent vasoconstrictor, inducing significant visible blanching and decreasing DOH (30%), OH (33%) and BF (18%) (P < 0.01). Fluocinolone acetonide, betamethasone-17-valerate and dexamethasone also caused visible blanching (P < 0.01). There was no significant decrease in BF, but reflectance spectroscopy showed a decrease in DOH (P < 0.01). Tixocortol, CMJ and hydrocortisone acetate did not produce significant blanching, although DOH was decreased compared with the alcohol control. Measured by reflectance spectroscopy, corticosteroid-induced blanching was predominantly venoconstriction and only the most potent corticosteroid caused a significant decrease in OH and blood flow. This may explain why previous attempts to improve cutaneous vasoconstriction assays using laser-Doppler flowmetry have been unsuccessful.

Adrenal Cortex Hormones↗

PubMed1995

Reflectance spectrophotometry in the objective assessment of dye laser-treated port-wine stains.

At present, the treatment of choice for congenital capillary malformations of the port-wine stain type (PWS) is the flashlamp pulsed dye laser. Good results can be obtained in the majority of patients with this technique, but there is a group of poor responders. In the search for predictive tools to determine the therapeutic outcome, we have used a new photoelectric reflectance instrument. Sixty-six patients with PWS, mainly on the face, were treated with a pulsed dye laser during a 21-month period. Using a hand-held reflectance photometer, erythema indices were obtained for the PWS and normal skin. Based on these indices, a relative blanching effect could be calculated. The therapeutic result was judged to be excellent in 19, good in 20, fair in 14 and poor in 13 patients. There was a good correlation (r = 0.844) between the degree of blanching and the therapeutic result. In the 'excellent' category, an average blanching effect of 47% was present after the first treatment, and this increased to between 75 and 100% after successive treatments. In the 'poor' category, the blanching effect after one treatment averaged 14%, increasing to only 40% after up to six treatments. It thus seems to be possible to predict the outcome of therapy, which is of considerable help in treatment planning. Reflectance measurements, an objective estimate of blanching, correlate well with the clinical results, and are helpful in monitoring and predicting the therapeutic outcome in dye laser-treated PWS.

Adolescent↗

PubMed1995

Developing reflective practice in mental health nursing through critical incident analysis.

Critical incident analysis has been espoused as a valuable method of promoting reflective nursing practice and as a tool for developing curriculum content. Despite an obvious application to mental health nursing, however, there has been little detailed examination of the practicalities and educational value of critical incident analysis within a mental health nursing curriculum. This paper is based on the use of critical incident analysis within the mental health branch of a Project 2000 diploma course. It presents the content of material brought by students, teaching methods used to facilitate learning, and the progressive development of students' reflective processes over the course of a complete branch programme. Using Benner's (1984) From Novice to Expert, the authors explore questions regarding the nature and effects of the critical incident technique in attaining competence in mental health nursing skills. The authors conclude with a theory-based evaluation and analysis of this student-centered experiential approach to learning as a method for developing reflective practice, and suggest areas for educational research.

Clinical Competence↗

PubMed1983

Total internal reflection fluorescent microscopy.

This review discusses applications of fluorescence microscopy using totally internally reflected excitation light. When totally internally reflected in a transparent solid at its interface liquid, the excitation light beam penetrates only a short distance into the liquid. This surface electromagnetic field, called the 'evanescent wave', can selectively excite fluorescent molecules in the liquid near the interface. Total internal reflection fluorescence (TIRF) has been used to examine the cell/substrate contact regions of primary cultured rat myotubes with acetylcholine receptors labelled by fluorescent alpha-bungarotoxin and human skin fibroblasts labelled with a membrane-incorporated fluorescent lipid. TIRF examination of cell/surface contacts dramatically reduces background from cell autofluorescence and debris. TIRF has also been combined with fluorescence photobleaching recovery and correlation spectroscopy to measure the chemical kinetic binding rates and surface diffusion constant of fluorescent labelled serum protein binding (at equilibrium) to a surface.

Animals↗

PubMed1995

A simple method for overcoming some problems when observing thick reflective biological samples with a confocal scanning laser microscope.

A simple device is described, which allows the range of depth of scanning to be reduced when observing thick reflecting biological samples with a confocal scanning laser microscope (CSLM). Thick histological sections of human skin and rat brain stem were mounted between two coverslips ('sandwich' style) and the optical tomography was performed from both sides by turning the 'sandwich' upside-down. The samples were impregnated using standard Golgi-Cox, 'rapid Golgi' or other silver methods. The ability to turn the 'sandwich' upside-down is particularly useful when the reflective structure inspected is deep inside the section, i.e., near the lower surface of the specimen, or when it is opaque to the laser beam or excessively reflective.

Animals↗

PubMed2006

Investigation of Si-Au vicinal surfaces using scanning tunnelling microscopy and reflection high-energy electron diffraction.

Silicon vicinal surfaces can be successfully used as substrates for the preparation of one-dimensional nanostructures. The quality of the structures prepared may be controlled using scanning tunnelling microscopy, as shown in this work. Additionally, it is possible to obtain valuable information using reflection high-energy electron diffraction. A typical way of employing reflection high-energy electron diffraction is to observe patterns of scattered electrons on a screen. However, it is possible to obtain more detailed information on the arrangement of atoms at the surface if azimuthal plots are collected. Azimuthal plots are measured by recording the intensity of specularly reflected electrons during the rotation of the sample around an axis perpendicular to its surface. So far, only flat surfaces have been examined in such a way. In this work, it is shown that such data, containing interesting features, can also be collected for vicinal surfaces.

Journal Article↗

PubMed1994

The growth of management connoisseurship through reflective practice.

Reflective practice offers a way to structure learning within supervision by paying attention to aspects of practice within reflected experiences, in such ways that the issues can be identified, understood, and worked through to resolve contradictions between desired outcomes and actual practice. In this process, emerging personal knowledge of practice is juxtaposed with relevant theory in such a way that the manager is able to meaningfully assimilate theory into his or her practice as appropriate. This paper illustrates how an H-grade unit nurse manager identified a number of situational management issues through reflecting and sharing experiences in a group clinical supervision milieu (over a period of 15 weeks). Clinical supervision is being advocated as a means to ensure practitioner development of effective practice (Vision for the Future, Department of Health 1993).

Education, Nursing, Continuing↗

PubMed2006

The reliability and validity of a matrix to assess the completed reflective personal development plans of general practitioners.

INTRODUCTION: We wished to determine whether assessors could make reliable and valid judgements about the quality of completed reflective personal development plans (PDPs) for the purpose of accrediting UK general practitioners (GPs) for a postgraduate education allowance using a marking matrix, and secondly, to plan a feasible model of PDP assessment in the context of forthcoming GP appraisal/revalidation that would overcome the main sources of error identified from this study. METHODS: Within generalisability theory, a variance components analysis on PDP scores estimated reliability and the effect on them of varying, for example, the number of assessors. We investigated the construct validity of the matrix through its internal consistency and detection of differences in the quality of PDPs. RESULTS: For a single PDP and one assessor, 37.6% of the variance in scores was due to true differences in the quality of the PDP. Between 5 and 7 PDP assessors are needed to achieve summative reliability of greater than 0.8. While increasing the number of judges is important, reliability could also be improved by addressing assessor subjectivity. Construct validity was demonstrated, as the matrix distinguished between good, satisfactory and poor PDPs, and it had good internal consistency. CONCLUSION: PDP assessment has reasonable summative characteristics for the purpose of assessing GPs' reflective continuing professional development. If doctors could include their PDPs within their revalidation folders as evidence of their reflections on pursuing better clinical performance, we have described a reliable, valid and feasible method of external assessment.

Accreditation↗

PubMed2006

Evidence for practice, epistemology, and critical reflection.

Evidence-based practice (EBP) has become a critical concept for ethical, accountable professional nursing practice. However, critical analysis of the concept suggests that EBP overemphasizes the value of scientific evidence while underplaying the role of clinical judgement and individual nursing expertise. This paper explores the empiricist position that valid evidence is the basis for all knowledge claims. We argue against the positivist idea that science should be regarded as the only credible means for generating evidence on which to base knowledge claims. We propose that the process of critically reflecting on evidence is a fundamental feature of empirical epistemology. We suggest that critical reflection on evidence derived from science, arts and humanities and, in particular, nursing practice experience can provide a sound basis for knowledge claims. While we do not attempt to define what counts as evidence, it is argued that there is much to be gained by making the processes of critical reflection explicit, and that it can make a valid contribution to expert nursing practice, without recourse to irreducible concepts such as intuition.

Art↗

PubMed1998

Direct evidence for the partial reflection of hyaluronan molecules by the lining of rabbit knee joints during trans-synovial flow.

1. In synovial joints hydraulic and turnover studies indicate that the synovial lining may partially reflect large macromolecules like hyaluronan, despite discontinuities in the lining cell layer. The reflection hypothesis was tested directly in the present study. 2. Solutions of high molecular weight hyaluronan were infused at controlled pressures into the cavity of rabbit knees under anaesthesia, at concentrations of 0.2 g l-1 (n = 5), 2 g l-1 (n = 5) and 4 g l-1 (n = 6). Time-averaged trans-synovial flows were 9.6, 4. 8 and 2.9 microl min-1, respectively. After 5 h infusion the intra-articular fluid was mixed and sampled. Hyaluronan concentration was determined by size-exclusion chromatography. 3. In all sixteen experiments the hyaluronan concentration in the aspirate was greater than that in the infusate (P = 0.0001, Student's paired t test). The increases averaged 2.28 +/- 0.04 times at high filtration rates (0.2 g l-1 infusates; mean +/- S.E.M.), 1.60 +/- 0. 09 times at intermediate filtration rates (2 g l-1 infusates) and 1. 26 +/- 0.08 times at low filtration rates (4 g l-1 infusates). 4. Between 48 and 95 % of the hyaluronan in the filtrand was retained in the joint cavity. The greater retention at 2 g l-1, viz.95 %, than at 0.2 g l-1, viz.48 %, was attributed to interactions between overlapping molecular domains in the more concentrated solution. 5. It is concluded that synovial interstitial matrix can partially reflect hyaluronan molecules, and thus conserve intra-articular lubricant.

Animals↗

PubMed2006

Attenuated total reflectance spectroscopy of plant leaves: a tool for ecological and botanical studies.

Attenuated total reflectance (ATR) spectra of plant leaves display complex absorption features related to organic constituents of leaf surfaces. The spectra can be recorded rapidly, both in the field and in the laboratory, without special sample preparation. This paper explores sources of ATR spectral variation in leaves, including compositional, positional and temporal variations. Interspecific variations are also examined, including the use of ATR spectra as a tool for species identification. Positional spectral variations generally reflected the abundance of cutin and the epicuticular wax thickness and composition. For example, leaves exposed to full sunlight commonly showed more prominent cutin- and wax-related absorption features compared with shaded leaves. Adaxial vs. abaxial leaf surfaces displayed spectral variations reflecting differences in trichome abundance and wax composition. Mature vs. young leaves showed changes in absorption band position and intensity related to cutin, polysaccharide, and possibly amorphous silica development on and near the leaf surfaces. Provided that similar samples are compared (e.g. adaxial surfaces of mature, sun-exposed leaves) same-species individuals display practically identical ATR spectra. Using spectral matching procedures to analyze an ATR database containing 117 individuals, including 32 different tree species, 83% of the individuals were correctly identified.

Membrane Lipids↗

PubMed2005

The late Nd reflects a memory trace containing amodal spatial information.

The early Nd reflects the analysis of simple features of selectively attended auditory stimuli, but the precise nature of the more complex processing reflected by the late Nd is unclear. The late but not the early Nd is sensitive to interference from a concurrently presented visual spatial attention switching task. This experiment investigated whether the late Nd is also sensitive to deeper visual attention switching. Twenty-one subjects performed a dichotic listening task concurrently with either visual spatial or visual letter matching attention switching tasks. Late Nd amplitude was reduced by the spatial but not the letter matching task, indicating insensitivity to deeper attention switching. P300 amplitude was reduced by both tasks. Reductions in N100 and P200 were uncorrelated. We propose that, in part, the late Nd reflects an amodal memory trace containing spatial information, possibly involving a "where" rather than a "what" auditory pathway.

Adolescent↗

PubMed1994

Digital photoplethysmography and light reflection rheography. A clinical comparison.

BACKGROUND: Light reflection rheography (LRR) is appropriate for the global assessment of calf-pump insufficiency regardless of whether it is caused by varicosity, the post-phlebitic syndrome, or deep venous thrombosis. The instrument has been increasingly used by many phlebologists. Digital photoplethysmography (D-PPG) is a further development of this well-established LRR. With this D-PPG instrument it is possible, in contrast to LRR, to calibrate the reflected light. OBJECTIVE AND METHODS: To compare the venous refilling times of both the LRR and the D-PPG when measured at the same time on the same leg. We also evaluated the practical use of both instruments. In total we performed 152 simultaneous measurements with both instruments. RESULTS: We found a statistically significant correlation when we compared the venous refilling time of both LRR and D-PPG (r = .664; P < .001). The observed agreement between both instruments for detecting a disturbed venous refilling time (< or = 25 seconds) is 92%. CONCLUSION: Both instruments seems to correlate as has been shown in this and other studies. The D-PPG has the advantage of being more handy. Furthermore the reflected light is calibrated, which enables to compare intra- and interindividual measurements.

Humans↗

PubMed1994

Mitochondrial function reflected by the decarboxylation of [13C]ketoisocaproate is impaired in alcoholics.

Mitochondria of patients with alcoholic liver disease exhibit structural abnormalities, and mitochondria isolated from animals exposed to ethanol are functionally deficient when studied in vitro. To assess possible functional consequences of these ethanol-associated alterations in vivo, we measured mitochondrial function in alcoholics noninvasively with a breath test. A mitochondrial function, the decarboxylation of ketoisocaproate (KICA), was assessed by measuring the exhalation of 13CO2 following the administration of 1 mg/kg 2-keto[1-13C]isocaproic acid, the decarboxylation of which occurs in mitochondria. The results of the KICA breath test in 12 alcoholic subjects were compared with the results in healthy controls and patients with nonalcoholic liver disease. The peak exhalation of 13CO2 and the fraction of the administered dose decarboxylated in 120 min were both significantly lower in alcoholics than in healthy controls and patients with nonalcoholic liver disease. In alcoholics, KICA decarboxylation was impaired in the presence of normal quantitative liver function tests such as the aminopyrine breath test and galactose elimination capacity, indicating that KICA decarboxylation does not simply reflect a decreased functional hepatic mass. The enrichment of circulating KICA with [13C]KICA was similar in alcoholics and controls, indicating that a decreased bioavailability or an increased dilution of labeled KICA cannot account for the decreased exhalation of 13CO2. It is concluded that mitochondrial function as reflected by KICA decarboxylation is impaired in chronic alcoholics. The functional impairment is specific for ethanol abuse and not a reflection of decreased global hepatic function. KICA decarboxylation could thus be useful as a marker for excessive ethanol consumption.

Adult↗

PubMed1991

Chemical and pharmacologic skin irritation in man. A reflectance spectroscopic study.

Attention is increasingly being focused on the relationship of dissociation constant (pKa) of chemicals and skin irritation presumably caused by pH effects at epidermal levels. Human skin studies of irritation have utilized both subjective visual-palpation scores and reflectance spectroscopy (RS) or laser Doppler velocimetry (LDV) respectively. Several studies document that erythema determined subjectively and objectively correlates with the degree of skin irritancy, but others report lack of correlation between LDV and irritancy scored subjectively. In this study, pharmacological and chemical in vivo skin irritation was evaluated utilizing an improved reflectance spectrophotometer equipped with computerized data analysis. In 16 white females, a model for skin irritation was induced by a 24-h patch application of 4 basic chemicals, imipramine, norephedrine, nicotine and 8-aminoquinoline, with pKa'S ranging from 3.8 to 9.5. Skin pigmentation (melanin) and the relative amounts of oxygenized (arterial) and deoxygenized (venous) hemoglobin present in the erythematous skin were calculated. A clear increase in the hemoglobin content was observed in chemical and vehicle exposed sites. Although skin irritation is a complex phenomenon involving chemical and solution properties, percutaneous absorption and the biological drug response, high pKa (p greater than 0.01) was predictive of acute skin irritation in man using computerized analysis of reflectance spectroscopy. A high correlation between visual score and RS was found (r = 0.91).

Adult↗

PubMed1996

Characterization of the reflective materials and organelles in the bright irides of North American blackbirds (Icterinae).

The reflective materials in the iris stroma of bright-irised American blackbirds (Icterinae, Emberizidae) and the red-eyed vireo (vireo olivaceus) (Vireonidae) were characterized using high-performance liquid chromatography (HPLC) and diode-array detection. Two purines, guanine and hypoxanthine, and two pteridines, leucopterin and xanthopterin, were detected in large amounts in all bright irides. The brown iris of the red-winged blackbird (Agelaius phoeniceus) by comparison contained only small amounts of these and additional unidentified compounds. The absolute and relative amounts of light-absorbing compounds in the iris varied somewhat among species of blackbirds with bright irides, and markedly within one species (brewer's blackbird, Euphagus cyanocephalus) between sexes and age classes that very in eye color. Differences in the types, numbers, and sizes of pigment organelles in the irides appeared to underlie the differences in amounts of light-absorbing compounds. Guanine was the most abundant light-absorbing compound in all bright irides, accounting for about 90% of the total absorption at 250 nm. A wide range of concentrations of guanine, from 96 to 9 micrograms per iris, produced bright irides. The primary pigment organelles of pigment cells in bright irides were reflecting platelets, which typically appeared as open spaces on electron micrographs. In the red-eyed vireo there were in addition red pterinosome-like pigment organelles in the pigment cells on the anterior surface of the iris stroma. Guanine was present even in irides with no overt reflecting platelets.

Animals↗