SEARCH · PubMed Health

Results for “reflection”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources

PubMed1996

Monitoring de- and remineralisation of enamel in vitro using an infrared reflectance meter.

The aim of this study was to design and investigate the use of an inexpensive method of monitoring the progress of demineralisation and subsequent remineralisation in artificial carious lesions. A small infrared (IR) reflectance meter was built which illuminated a 4 mm x 4 mm area on the buccal surface of a tooth and measured the reflected IR intensity. Repeated measurements were taken over a period of 25 days, during which the enamel surface was exposed to demineralising and subsequently remineralising solutions. Thirty-six teeth were studied under a variety of de- and remineralising conditions. It was observed that the IR specular reflectance of the tooth surfaces decreased with time during lesion formation and increased with time during remineralisation. It is suggested that the decrease in IR specular reflectance during demineralisation and the increase during remineralisation are a result of continuous changes in the crystals at the enamel surface during these processes.

Dental Caries Activity Tests↗

PubMed2000

99mTc-N-NOET myocardial uptake reflects myocardial blood flow and not viability in dogs with reperfused acute myocardial infarction.

BACKGROUND: N-Ethoxy-N-ethyl-dithiocarbamato-nitrido-(99m)Tc ((99m)Tc-N-NOET) is a new neutral lipophilic (99m)Tc-labeled myocardial perfusion agent with a high first-pass extraction fraction and delayed redistribution kinetics after transient ischemia comparable to what is observed with (201)Tl. It is unknown whether the uptake of this tracer reflects myocardial viability or just reperfusion flow in the setting of a reperfused myocardial infarction. METHODS AND RESULTS: In 13 anesthetized open-chest dogs, the left anterior descending coronary artery was occluded for 180 minutes, followed by 180 minutes of reperfusion. (201)Tl and (99m)Tc-N-NOET were injected after either 60 (group 1, n=9) or 175 (group 2, n=4) minutes of reperfusion. Myocardial blood flow was measured by radioactive microspheres, and (201)Tl and (99m)Tc-N-NOET tissue activities were determined by gamma-well counting. Normalized myocardial blood flow in the central infarct zone fell from 0.80+/-0. 03 (SEM) and 0.89+/-0.01 at baseline to 0.18+/-0.04 and 0.13+/-0.02 during the occlusion in groups 1 and 2, respectively. Normalized (201)Tl activity in these segments was 0.39+/-0.04 and 0.43+/-0.04 and reflected myocardial viability rather than reperfusion flow (P<0. 001). Normalized (99m)Tc-N-NOET activity in the same segments was 0. 84+/-0.08 and 0.64+/-0.03, respectively (P<0.01 versus (201)Tl; P=NS versus reperfusion flow) and more accurately reflected reperfusion flow (0.99+/-0.17 and 0.70+/-0.04) than residual viability. CONCLUSIONS: The myocardial uptake of (99m)Tc-N-NOET reflects reperfusion myocardial blood flow and not viability in a canine model of reperfused acute myocardial infarction. The clinical use of early (99m)Tc-N-NOET imaging to assess the success of coronary reperfusion in patients with acute myocardial infarction should be investigated.

Animals↗

PubMed1990

Effect of age on the in vitro reflection coefficient of the aortoiliac bifurcation in humans.

The local reflection coefficient (r) at the aortoiliac junction was estimated in vessels removed at autopsy from 15 females and 31 males aged 2 months to 88 years by calculating the characteristic impedance (Zc) of the abdominal aorta and the two common iliac arteries. Zc was evaluated for each vessel by measuring cross-sectional area from radiographs and propagation velocity of an isolated pressure impulse generated by a solenoid-driven piston connected to the distal end of the abdominal aorta, and detected at several sites a known distance from the junction. Attenuation coefficients in the aorta were estimated from the peak amplitude of the impulse at these several sites. We observed significant decreases with age in abdominal aortic attenuation coefficient (gamma = 0.053-5 x 10(-4) age [yr], r = -0.42, p less than 0.005), and the area ratio (AR) of the junction (sum of the iliac cross-sectional areas/aortic cross-sectional area) (AR = 0.93-0.002 x age [yr], r = -0.31, p less than 0.05). Bifurcation angle (Angle) and aortic propagation velocity (caorta) increased significantly (angle = 40.2 + 0.26 x age [yr], r = 0.41, p less than 0.01; caorta (ms-1) = 7.59 + 0.175 x age [yr], r = 0.69, p less than 0.0001). No significant association between age and iliac propagation velocity was found. On the basis of area measurements alone, it has been argued that the observed decrease in area ratio with age causes r to become more positive. The lack of age-related changes in iliac propagation velocity (and hence stiffness), an observation confirmed by most of the few reports in the literature, and the large increase in abdominal aortic stiffness, however, greatly outweighed the area ratio changes and caused a significant decline in reflection coefficient from +0.3 in early life to -0.3 in old age. (Reflection coefficient = 0.30-0.0065 x age [yr], r = -0.68, p less than 0.0001). Between the ages of 30 and 60 years, its absolute value was less than 0.1, confirming in vivo work on subjects within this age range. In children, a significant positive reflection at the distal end of the aorta will amplify the pulse wave in this region. As this vessel becomes stiffer with increasing age, amplification will increase, whereas the increasingly negative value of r will partially offset this rise, reducing pulse pressure on either side of the junction.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed2003

Removal of reflections in the photographic assessment of PCO by fusion of digital retroillumination images.

PURPOSE: Automated image-analysis systems for objective assessment of posterior capsule opacification (PCO) depend on good image quality. One major drawback is the existence of light-reflection artifacts (Purkinje spots) in retroillumination images of the posterior capsule. Therefore, a software algorithm was developed that removes these artifacts by fusion of two or more digital images from the same eye, photographed in slightly different directions of gaze. METHODS: The image-fusion process comprises five steps: definition of a primary and a secondary image, automated segmentation of the region of interest and the Purkinje spots, manual selection of three pairs of corresponding points in both images, geometric registration and radiometric calibration of the regions to be inserted from the secondary image into the primary image. The program was tested with an image set of 30 eyes that had various degrees of PCO. A digital image acquisition system with a coaxial optical path was used to take retroillumination images from each eye in at least three different directions of gaze. RESULTS: In 28 cases all light-reflection artifacts within the capsulorrhexis rim could be removed entirely. In two cases, small parts of single Purkinje spots remained visible, because the reflections were located too closely in the primary and the secondary images. CONCLUSIONS: Fusion of digital retroillumination images provides high-quality, reflection-free PCO images. This allows objective PCO assessment systems to analyze 100% of the posterior capsule, leading to more accurate results.

Algorithms↗

PubMed1993

Psychoanalytic technique and the development of the capacity to reflect.

The capacity to reflect is an essential precondition for the existence and maintenance of an analytic process. This paper describes the technical environment that may enable the functional emergence and management of this precondition. In order that the specific features of such an environment may be addressed, psychoanalysis is differentiated from psychotherapy in terms of goals, and this is followed by a discussion of technical modalities that reflect uniquely analytic aims. In conjunction with these technical considerations, the underpinnings of the psychoanalytic situation are described as an "envelope of experience" within which the patient may develop the reflective capacity to participate in the analytic process. Finally, the acquisition of this essential reflective capacity is viewed in the context of a developmental line in an analysis, and is highlighted through the use of a clinical example.

Adult↗

PubMed1985

Pulse wave reflections at the aorto-iliac junction.

For pressure pulses to be transmitted to vital organ vascular beds, minimum loss through vascular branching junctions is necessary. Experimental measurements of pulse wave velocities and cross-sectional areas allowed branching reflections to be quantified. Wave reflections at normal aorto-iliac junction is minimal. Increased reflection occurs when the branch vessel is either narrowed or occluded. Also, geometric factors dominate over elastic factors in determining the amount of pulse wave reflections at the aorto-iliac junction.

Animals↗

PubMed1987

Evaluation of biangular reflection photometry for quantitative study of etched alloy surface roughness.

Biangular reflection photometry was correlated with quantitative stereology and direct pit-depth measurements for an electrolytically etched nickel-chromium-beryllium alloy. Effects of viewing angle, viewing aperture, and plane polarization of incident and viewing light were also studied. The results showed that architectural changes in the etched metal surface could be quantitatively described with the use of reflection photometry. An off-specular peak, located at an angle of reflection considerably different from the angle of incidence, was observed to have an intensity comparable with that of the specular reflection peak. Viewing aperture was found to affect one's ability to distinguish among degrees of surface roughness.

Acid Etching, Dental↗

PubMed1996

Analysis of edge-losses in reflectance measurements of pigmented maxillofacial elastomer.

Edge-losses occur during reflectance measurements of pigmented maxillofacial elastomer when light is scattered within a sample beyond that part of the surface exposed to the observation system of the optical device. A custom sample-holder is presented which redirects light that would not be measured during conventional reflectance measurement back into the sample. The amount of edge-loss occurring within thin layers of maxillofacial elastomer with tan pigment on black-and-white backings was found to depend on sample thickness, the backing, the beam size used during conventional reflectance measurement, and the optical term bS = (2KS + K2)1/2. Data analysis revealed a significant interaction among these four factors. Additionally, the edge-loss occurring during the tristimulus reflectance measurement of thick samples of maxillofacial elastomer with various concentrations of tan and black pigment was found to be linearly related to bS up to a limiting value, with no additional edge-loss occurring for bS values above this limiting value. Edge-loss is an important consideration during the matching of the optical characteristics of pigmented maxillofacial material to those of human skin.

Absorption↗

PubMed1988

Computation of local directivity, speed of sound and attenuation from ultrasonic reflection tomography data.

Ultrasound reflection tomography based on the compound scan principle, allows one to produce reflectivity images with high quality and reproducibility. In this paper, methods are discussed on how to extract additional physical parameters from the same set of reflection data for medical applications. Experimental results from a phantom object and in-vivo measurements illustrate the capabilities of such tomographic reflection systems.

Forearm↗

PubMed2004

Technical, practical, and emancipatory reflection for practicing holistically.

The intention to practice holistically brings with it many complexities in deciding how to manage the contingencies of practice in such a way as to embody the central tenets of holistic nursing. The challenge of making sense of daily work procedures, interpersonal interactions, and issues of power can be eased by attention to reflective processes designed for nursing practice. Reflective nurses who practice holistically optimize the likelihood of thinking systematically through practice issues as they encounter the world of nursing and the people and events within it. This article is an exploration of the phenomena of holism and reflection as they relate to technical, practical, and emancipatory reflective processes used by nurses in their daily work.

Clinical Competence↗

PubMed1998

Reflective questions in health counseling.

This study explores questions that nurses ask patients in order to awaken reflection on their health behavior in health counseling. Thirty-eight counseling situations were videotaped in a hospital. The data were analyzed using conversation analysis which was adapted for the purpose of this study. Nonverbal communication supported speech and was interpreted alongside it. This study found that nurses used only a few reflective questions, most of which were future-oriented or introduced hypotheses. In a nonreflective discussion, nurses used only check-up and alternative questions to get information about patients' illnesses and health care measures. Findings indicated that reflective conversation began with check-up questions about patients' immediate situation, followed by questions about patients' feelings in the past, present, or future. On the third level of questioning, the structure might vary between embedded questions, check-up, alternative, or feeling questions. Nonverbal communication supported the discussion. Reflective questions tended to ensure patient-centered conversation and might improve the effectiveness of health counselling.

Adult↗

PubMed2003

Effect of sildenafil on arterial stiffness and wave reflection.

While sildenafil (Viagra) is widely prescribed for erectile dysfunction, its effect on arterial function is not established. The elastic properties of the aorta, as well as the magnitude and timing of wave reflection, are important factors for efficient performance of the cardiovascular system and have been identified as prognosticators of cardiovascular risk. A total of 24 subjects with coronary artery disease, of whom 14 were hypertensives, aged 69 +/- 8 years, were studied in a randomized, placebo-controlled, double-blind, cross-over design. Measurements lasted for 3 h after the sildenafil intake (50 mg, p.o.) or placebo. Aortic elastic properties were evaluated with carotid-femoral pulse wave velocity; wave reflection was evaluated with augmentation index and augmented pressure of the aortic pressure waveform. Pulse wave velocity decreased significantly (by 0.65 m/s, p = 0.005), denoting a decrease in aortic stiffness. Augmentation index and augmented pressure decreased significantly (by 4.47% absolute and by 4.01 mmHg; p < 0.001 and p = 0.001, respectively), denoting a decreased effect of wave reflection from the periphery. Aortic pulse pressure decreased significantly (by 6.74 mmHg, p < 0.05). An active effect of the drug on aortic wall appears to contribute to the decrease in pulse wave velocity, although other mechanisms such as a decrease of blood pressure and autonomic reflexes could also have contributed. The effect of sildenafil lasted throughout the study (3 h), being evident 30 min after drug intake. In conclusion, this study shows, for the first time, that sildenafil has a favorable effect on aortic stiffness and wave reflection in patients with coronary artery disease. This finding may have important implications for cardiovascular performance and exercise capacity during intercourse.

Aged↗

PubMed1977

Reflective processes and anxiety.

Three hypotheses are abstracted from Laing's writings on the inter-relationships between self-consciousness, anxiety, and self-evaluation. Indicators of self-consciousness are obtained from an open-ended instrument which requires the respondent to provide twenty answers to the question (asked of himself): "Who am I?" Statements indicative of self-consciousness are those on which the respondent inserts a self-reference into the statement made about himself and are distinguished from statements in which no explicit self-reference is found. The data indicate that the mark of the self-conscious person is anxiety and that anxiety is largely restricted to those statements devoid of self-consciousness. The structure of a system likely to produce this configuration is considered by drawing upon Kierkegaard's conjectures on the joint emergence of consciousness and anxiety. Equating self-consciousness with "reflection", it is suggested that while reflection brings about anxiety in a system as a whole, the act of reflection deters the emergence of anxiety at the particular points within the system upon which it is deployed. Thus the function of reflection is two-fold, creating anxiety at the same time (but not at the same place) as anxiety is reduced.

Adult↗

PubMed1992

Reflectance pulse oximetry in fetal lambs.

Transmission pulse oximetry is used for monitoring in many clinical settings. However, for fetal monitoring during labor and in situations with poor peripheral perfusion, transmission pulse oximetry cannot be used. Therefore, we developed a reflectance pulse oximeter, which uses the relative intensity changes of the reflected red and infrared light (red/infrared ratio) to measure the arterial oxygen saturation. The performance of the reflectance pulse oximeter was studied in acute experiments in fetal lambs. By stepwise reduction of the inspired oxygen concentration of the ewe, measurements were done at the fetal scalp at various arterial oxygen saturation levels (17-82%). Reflectance pulse oximeter readings were averaged over periods of 15 s and compared with simultaneously taken fetal arterial blood samples. A calibration curve for the relationship between red/infrared ratio and arterial oxygen saturation was obtained from 53 measurements in four fetal lambs, by linear regression analysis [red/infrared = 4.088-(0.038.SaO2), r = 0.96]. In these experiments, the pulse oximeter showed a precision of 4.7% oxygen saturation around the calibration curve, with a 95% confidence interval of +/- 9.4%.

Animals↗

PubMed2004

Pairs, reflections, and the EgoI: exploration of a perceptual hypothesis.

In the Comprehensive System for the Rorschach (Exner, 2003), pair and reflection responses are combined into an Egocentricity Index (EgoI) that is said to measure self-focus and self-esteem. However, validation research over the past 30 years has found at most only limited support for these interpretations. This study suggests an alternative approach derived from Exner's (1969) suggestion prior to the EgoI that pairs and reflections are related to interpersonal perception and in particular to a tendency to perceive similarity. Forty custody litigants completed the Rorschach and Revised NEO Personality Inventory (Costa & McCrae, 1992b) Forms S and R. As the number of reflections increased, the description of the partner and the description of the self became increasingly dissimilar. As pairs increased, the description of the ex-partner on Form R and the self-description on Form S tended to become increasingly similar. This project suggests that pairs and reflections may be differentially related to perceived similarity and that combining them into a summative index may, at least in some circumstances, result in a loss of information.

Adult↗

PubMed2003

A reflection and evaluation model of comparative thinking.

This article reviews research on counterfactual, social, and temporal comparisons and proposes a Reflection and Evaluation Model (REM) as an organizing framework. At the heart of the model is the assertion that 2 psychologically distinct modes of mental simulation operate during comparative thinking: reflection, an experiential ("as if") mode of thinking characterized by vividly simulating that information about the comparison standard is true of, or part of, the self; and evaluation, an evaluative mode of thinking characterized by the use of information about the standard as a reference point against which to evaluate one's present standing. Reflection occurs when information about the standard is included in one's self-construal, and evaluation occurs when such information is excluded. The result of reflection is that standard-consistent cognitions about the self become highly accessible, thereby yielding affective assimilation; whereas the result of evaluation is that comparison information is used as a standard against which one's present standing is evaluated, thereby yielding affective contrast. The resulting affect leads to either an increase or decrease in behavioral persistence as a function of the type of task with which one is engaged, and a combination of comparison-derived causal inferences and regulatory focus strategies direct one toward adopting specific future action plans.

Affect↗

PubMed2003

Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus.

The Paradise whiptail (Pentapodus paradiseus) has distinct reflective stripes on its head and body. The reflective stripes contain a dense layer of physiologically active iridophores, which act as multilayer reflectors. The wavelengths reflected by these stripes can change from blue to red in 0.25 s. Transmission electron microscopy revealed that the iridophore cells contain plates that are, on average, 51.4 nm thick. This thickness produces a stack, which acts as an ideal quarter-wavelength multilayer reflector (equal optical thickness of plates and spaces) in the blue, but not the red, region of the spectrum. When skin preparations were placed into hyposmotic physiological saline, the peak wavelength of the reflected light shifted towards the longer (red) end of the visible spectrum. Hyperosmotic saline reversed this effect and shifted the peak wavelength towards shorter (blue/UV) wavelengths. Norepinephrine (100 micromol l(-1)) shifted the peak wavelength towards the longer end of the spectrum, while adenosine (100 micromol l(-1)) reversed the effects of norepinephrine. The results from this study show that the wavelength changes are elicited by a change of approximately 70 nm in the distance between adjacent plates in the iridophore cells.

Animals↗

PubMed1998

Why do mayflies lay their eggs en masse on dry asphalt roads? Water-imitating polarized light reflected from asphalt attracts Ephemeroptera.

We report on dry asphalt roads acting as 'mayfly traps'; that is, they lure swarming, mating and egg-laying mayflies in large numbers. To explain this surprising behaviour, we performed multiple-choice experiments with Ephemeroptera in the field, and measured and compared the reflection-polarization characteristics of an asphalt road and a mountain creek from which mayflies emerge. We show here that Ephemeroptera can be deceived by and attracted to dry asphalt roads because of the strongly horizontally polarized light reflected from the surface. Asphalt surfaces can mimic a highly polarized water surface to Ephemeroptera. The darker and smoother the asphalt surface, the higher is the degree of polarization of reflected light and the more attractive is the road to mayflies. We show that mayflies detect water by means of polarotaxis; that is, on the basis of the partially and horizontally polarized reflected light. Asphalt roads are excellent markers for swarming Ephemeroptera because of their conspicuous elongated form; the sky above them is usually open, which is the prerequisite of mayfly mating, and the higher temperature of the asphalt prolongs the reproductive activity of mayflies. These additional factors enhance the attractiveness of asphalt roads to swarming mayflies. Thus, asphalt roads near ephemeropteran emergence sites (lakes, rivers and creeks) are a great danger for mayflies, because eggs laid on the asphalt inevitably perish. Asphalt roads can deceive and attract mayflies en masse like the ancient tar pits and asphalt seeps or the recent crude or waste oil lakes deceive, lure and trap polarization-sensitive water-seeking insects in large numbers.

Animals↗