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PubMed2004

Diffuse reflectance spectroscopy of the human tympanic membrane in otitis media.

We have investigated if features in the diffuse reflectance spectra from in vivo spectroscopic measurements of the tympanic membrane could aid the diagnosis of otitis media in children. Diffuse reflectance spectroscopy, in the visible wavelength range, was used in 15 ears from children with otitis media with effusion before and after myringotomy and in 15 healthy ears as a reference. Two previously published erythema detection algorithms yielded numerical quantities of haemoglobin content. With a combination of the algorithms, induced erythema (after myringotomy) was distinguished from healthy ears using Student's t-test (p < 0.01). Otitis media with mucous effusion was distinguished from (1) otitis media with serous effusion, (2) induced erythema and (3) healthy ears, (p < 0.05) using Student's t-test for independent groups and the paired t-test for dependent groups. Our results imply that reflectance spectroscopy is a promising technique to be used for the diagnosis of otitis media.

Acute Disease↗

PubMed2001

Presence and reflection in training: support for learning to improve quality decision-making skills under time limitations.

Virtual Reality (VR) has been used for some time for training various skills. The results obtained are generally very reassuring, suggesting that Virtual Environments (VEs) are an effective new kind of educational tool. There are some, however, who argue that there are cases in which a 2D approach would achieve the same training effect. The literature suggests that the key features that distinguish VR from other training approaches is the sense of presence, which provides a first-person experience of the world. Usually, real world learning is multisensory and gives ownership and control over the experience, increases learner motivation, and triggers the construction of knowledge. Despite technical limitations, a VE is the most effective form of information technology for providing multisensory experience including visual, auditory, and to some extend haptic and tactile cues. The sense of presence ensures that the perceived experience is interpreted as being real and makes it likely that skills learned in the VE will be transferred to the real world. We argue that for training time-limited decision-making skills, the learner should also have an opportunity to reflect on actions/strategies to improve performance. Therefore a virtual environment for training should also provide support for students to reflect on their performance. This paper describes a prototype training system that aims to support both construction of knowledge and cognitive learning. It is also intended to trigger a sense of presence as well as provide support mechanisms, not available in the real world, that the students can exercise to reflect on the training experience.

Decision Making↗

PubMed2004

In search of reflective behavior and shared understanding in ad hoc expert teams.

The work reported on here concentrates on virtual ad hoc expert teams for the integration of learning and working, as ad hoc teams seem to be one way to cope with complexity in a knowledge-intensive society. In order to let ad hoc teams learn and work together, group members require effective communication and shared understanding among each other. Two empirical studies were conducted to study collaborative learning and shared understanding, one exploratory study and one experiment. In the first study, it was explored how virtual design teams work and learn together. Based on conceptual ideas, collaborative learning and shared understanding were observed and assessed in a design team over a period of four months. It was concluded that shared understanding was suboptimal; mainly due to the effect that hardly any questions were raised and answered. The second study elaborates on the need to encourage question-answer patterns and reflective behavior in such teams. A tool was developed that supported questioning behavior. As it was hypothesized that this tool leads to better questioning behavior, which in turn results in more reflective behavior and in increased shared understanding, an experiment was conducted. In the exploratory study, as well as in the experimental study, the perceived shared understanding increased over time. However, in both studies suboptimal questioning behavior and little reflective activity were noticed. The main results of the two empirical studies are compared and discussed.

Adult↗

PubMed1994

Arterial stiffness and wave reflections following acute calcium blockade in essential hypertension.

Antihypertensive agents are routinely studied in terms of changes in the level of systolic, diastolic, and mean arterial pressure. Pulse pressure may be independently modified from these parameters as a consequence of specific changes in the mechanical properties of the large arteries and in the timing of incident and reflected pressure waves. The aim of this study was to evaluate the changes in pulse pressure produced by acute calcium blockade by the dihydropiridine derivative, lacidipine, in a double-blind design versus placebo in 18 subjects with mild to moderate hypertension. Carotid and femoral pressure waveforms were recorded noninvasively by applanation tonometry using a Millar micromanometer-tipped probe. Early (Pi) and mid-to-late (Ppk) systolic peaks of carotid pressure waveform were evaluated, enabling the effect of incident pressure wave to be quantified as the ratio of Pi to the total height of carotid pulse wave (PP) (Pi/PP) and the effect of wave reflections as the ratio (Ppk-Pi)/PP. Travel time of the reflected wave (delta tp) was timed from the foot of the pressure wave to the foot of the late systolic peak. Pulsatile changes in diameter were studied using noninvasive echo-tracking techniques. Whereas mean arterial pressure significantly decreased following lacidipine, pulse pressure measured at three different sites (brachial, carotid, and femoral arteries) was unchanged. Carotid-femoral pulse wave velocity, carotid and femoral arterial stiffness, and delta tp were not modified, whereas the (Ppk-Pi)/PP ratio and left ventricular ejection time was significantly reduced and the Pi/PP ratio was significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗

PubMed1990

The areas ratio of normal arterial junctions and its implications in pulse wave reflections.

STUDY OBJECTIVE: The aim of the study was to establish measurements for the area ratios of normal arterial junctions at various anatomical sites in order to estimate the significance of pulse wave reflections in the healthy arterial system. DESIGN: Coronary cineangiograms were used for the coronary junctions measurements and routine arteriograms for the rest of the junctions studied. A pair of digital calipers served to take measurements at a distance of one vessel diameter from the junction centre. MEASUREMENTS AND MAIN RESULTS: A bell shaped distribution of arterial area ratios was found with mean value for coronary bifurcations of 1.179 (95% confidence limits, 1.138-1.220). Slightly higher values were found for the higher order coronary junctions. Other junctions had similar area ratio values with the exception of the aortoiliac junctions where the area ratio was found 0.848 (0.775-0.920). Overall area ratio was 1.14 (1.113-1.167). Asymmetrical coronary bifurcations had higher area ratio than symmetrical ones (p less than 0.05). CONCLUSIONS: In the majority of cases the area ratios are in close agreement with the theoretically predicted values for forward matched junctions. Minimal pulse wave reflections are therefore expected to arise from the junctions of a healthy arterial system. We therefore consider that, contrary to the established view, the presence of reflected waves in the central arterial system is a potential pathological phenomenon and not a characteristic of the healthy system. This may have important theoretical implications for the way hemodynamic findings are interpreted. Finally we suggest that arterial area ratio can be considered as another criterion of normality of arterial junctions in the interpretation of angiograms.

Anthropometry↗

PubMed1991

Reflection as a cause of mid-systolic deceleration of pulmonary flow wave in dogs with acute pulmonary hypertension: comparison of pulmonary artery constriction with pulmonary embolisation.

STUDY OBJECTIVE: The aim was to examine whether mid-systolic deceleration of the pulmonary flow wave occurred in acute pulmonary hypertension due to pulmonary artery constriction and pulmonary embolisation, and if so whether it was related to reflection. DESIGN: Various degrees of pulmonary hypertension were induced by both pulmonary artery constriction and pulmonary embolisation in dogs. During control periods and during pulmonary artery constriction and pulmonary embolisation, pulmonary flow and pulmonary artery pressure were recorded, and the forward and backward (reflected) flow waves were separated from the measured pulmonary flow wave by the method of Westerhof et al. MATERIALS: 20 adult mongrel dogs were used and 10 dogs qualified for analysis. The other 10 dogs, which died before both interventions were completed, were excluded. MEASUREMENTS AND MAIN RESULTS: During pulmonary artery constriction, a distinct mid-systolic deceleration of the pulmonary flow wave was observed in five of the 10 dogs, while during pulmonary embolisation, no mid-systolic deceleration was found in these five dogs. The distinct deceleration of the pulmonary flow wave was related to a steep fall and early negative peak in the backward flow wave. CONCLUSION: Mid-systolic deceleration of pulmonary flow wave is likely to be related to reflection.

Acute Disease↗

PubMed2005

Increased arterial wave reflections predict severe cardiovascular events in patients undergoing percutaneous coronary interventions.

AIMS: Increased arterial wave reflections are associated with the presence and extent of coronary atherosclerosis and with cardiovascular mortality in selected populations. We prospectively evaluated their prognostic value in the short- and long-term following percutaneous coronary interventions (PCIs). METHODS AND RESULTS: We non-invasively quantified wave reflections [expressed as augmentation index corrected for heart rate of 75 b.p.m. (AIx@75)] using applanation tonometry of the radial artery and a validated transfer function to obtain the corresponding aortic values in 262 patients undergoing PCI. During 2-year follow-up, 61 patients reached the primary endpoint [death, myocardial infarction (MI), and restenosis]. Increasing tertiles of Alx@75 were related to the rate of patients reaching the primary endpoint [15.2, 20 and 35.3%, respectively (P = 0.001)], as well as the secondary endpoints total mortality, myocardial infarction and death plus myocardial infarction (RR for the third vs. the first tertile 4.33, 3.25 and 3.46, respectively, P < 0.05). In a multivariable Cox-regression model, AIx@75 added prognostic value above and beyond clinical risk factors, angiographic variables, and medications (RR 1.8, 95%CI 1.18-2.76 per increasing AIx@75-tertile, P < 0.01). CONCLUSION: Increased arterial wave reflections are independently associated with an increased risk for severe short- and long-term cardiovascular events in patients undergoing PCI.

Aged↗

PubMed1992

Serum placental protein 14 (PP14) reflects endometrial status during hormone replacement therapy.

Healthy post-menopausal women were randomly assigned to treatment groups receiving 28 day treatment cycles of oestradiol valerate (2 mg, days 1-28) sequentially combined with levonorgestrel (75 micrograms, days 17-28) (n = 19); oestradiol valerate (2 mg, days 1-28) continuously combined with cyproterone acetate (1 mg, days 1-28) (n = 18), or placebo (n = 22). Treatment continued for 2 years. After therapy, the women receiving the sequential combination had an early secretory phase (74%) or atrophic endometrium (26%). All women receiving the continuous combination or placebo had inactive or atrophic endometrium, or the tissue was inadequate for assessment. Biochemical parameters of endometrial secretion [oestradiol dehydrogenase (EDH), isocitrate dehydrogenase (ICDH)] measured in endometrial tissue and placental protein (PP14) measured in serum were all low in the groups receiving the continuous combination and placebo. During sequential treatment, all biochemical parameters showed significantly higher mean values. Serum PP14 accurately reflected this pattern. Furthermore, in the sequentially treated group, serum PP14 correlated highly significantly with EDH (r = 0.70; P less than 0.001) and ICDH (r = 0.57; P = 0.01). These correlations were of the same magnitude as the correlations between the endometrial markers, which indicates that serum PP14 reflects the endometrial status. Furthermore, serum PP14 measurements at 3 months and at 2 years of treatment were highly correlated, reflecting the long-term validity of the measurement. The present data suggest that PP14 measured in serum may be used to assess endometrial status. Further studies are required to determine whether serum PP14 will discriminate pathological endometrial conditions.

Cyproterone Acetate↗

PubMed1986

Determining nitrogen status of young loblolly pine by leaf reflectance.

Five-year-old lobloliy pine (Pinus taeda L.) seedlings were grown in sand culture in a completely randomized experimental design with eight nitrogen concentrations and three replications. Nitrogen concentration in the nutrient solution varied from 2 to 400 ppm. After a full growing season under treatment, percent reflectance of sunlight by new foliage was determined. Foliar samples were analyzed for nitrogen and chlorophyll. There was a strong positive correlation between nitrogen content and chlorophyll content (r = 0.895). The natural logarithm of percent reflectance was negatively correlated with both percent nitrogen content (r = -0.845) and chlorophyll content (r = -0.838). From these results, prediction equations for estimating nitrogen and chlorophyll content, as a function of reflectance, were formulated by regression analysis.

Journal Article↗

PubMed1985

Pulmonary artery wedge pressure may fail to reflect left ventricular end-diastolic pressure in dogs with oleic acid-induced pulmonary edema.

We investigated the accuracy with which pulmonary artery wedge pressure (WP) reflected left ventricular end-diastolic pressure (LVEDP) in dogs with oleic acid-induced pulmonary edema. We compared hemodynamic variables before and during edema, as measured from a pulmonary artery catheter placed before oleic acid (PA-1) and from a second catheter (PA-2) placed 2 h after oleic acid infusion. Oleic acid decreased arterial oxygen saturation and cardiac output and increased pulmonary vascular resistance and phasic pulmonary artery pressure. LVEDP did not change after oleic acid, although WP measured by both catheters was increased. In addition, WP measured by PA-2 (7.1 +/- 0.7 mm Hg) was greater than that measured by PA-1 (5.6 +/- 0.5 mm Hg) (p less than or equal to 0.037). Using PA-1, we found that WP increased in a linear manner with LVEDP both before and after pulmonary injury (r2 = 0.91, 0.68, respectively). There was no relationship between LVEDP and WP using PA-2 (r2 = 0.07). We conclude that oleic acid-induced pulmonary edema lessens the accuracy with which WP reflects LVEDP, and that WP from a catheter placed after edema less accurately reflects LVEDP than does WP from a catheter placed before edema.

Animals↗

PubMed1988

Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients.

Measurement of intrapulmonary shunting (Qsp/Qt), a widely used method for monitoring disturbances of pulmonary oxygen transfer in critically ill patients, involves calculation of arterial and mixed venous oxygen contents. In circumstances where mixed venous blood samples are not readily available, oxygen tension-based indices such as the alveolar to arterial oxygen tension differences (P[A-a]O2), arterial oxygen tension to alveolar oxygen tension ratio (PaO2/PAO2), PaO2 to FIO2 ratio (PaO2/FIO2) and respiratory index (RI) are widely utilized to reflect Qsp/Qt. Oxygen content-based indices such as the estimated shunt are not as widely utilized as the oxygen tension indices. In 75 critically ill patients in whom a pulmonary artery catheter was being utilized to augment clinical care, comparisons were made between Qsp/Qt and P(A-a)O2, PaO2/PAO2, PaO2/FIO2, RI, and estimated shunt to determine which index best reflected Qsp/Qt. Correlations between Qsp/Qt and estimated shunt were good (r = .94) and poor for the P(A-a)O2 (r = .62), PaO2/PAO2 (r = .72), PaO2/FIO2 (r = .71), and RI (r = .74). We conclude that there are no real substitutes for venous oxygen contents in critically ill patients. When pulmonary artery blood is not available for analysis, oxygen tension-based indices are unreliable reflectors of Qsp/Qt while the estimated shunt, an oxygen content-based index, provides a more reliable reflection of Qsp/Qt.

Aged↗

PubMedDate not supplied

Reflection and professional education: art, science, and competency.

Reflection is the process of reviewing one's repertoire of clinical experience and knowledge to invent novel approaches to complex clinical problems. Reflection also provides data for self-evaluation and increases learning from experience. The author suggests several activities which are particularly useful in facilitating a reflective nursing practice. These activities may assist educators to encourage students' clinical competency.

Clinical Competence↗

PubMedDate not supplied

Developing a teaching portfolio in nursing education: a reflection.

Presenting teaching accomplishments through a portfolio promotes self-reflection and provides direction for improvement and advancement decisions. The authors examine experiences, insights, and reflections about their participation in a pilot project introducing teaching portfolios. Themes of taking stock, documenting practice, and reflecting emerge. Their experiences of completing teaching portfolios and personal growth as educators and colleagues are described.

Attitude of Health Personnel↗

PubMed2004

Wideband reflectance measures of the ipsilateral acoustic stapedius reflex threshold.

OBJECTIVE: The purpose of this study was to develop a method for acoustically measuring the ipsilateral acoustic stapedius reflex threshold by using wideband shifts in energy reflectance and admittance. DESIGN: A group of 27 young adult subjects with normal hearing participated in the study. Contralateral reflex thresholds were first measured for a 4000 Hz activator tone (maximum level, 92 dB SPL), using a clinical method with a 226 Hz probe tone. Ipsilateral and contralateral reflex thresholds were then measured by using an experimental wideband reflectance and admittance system that used a band-filtered click (200 to 2000 Hz) as the probe stimulus, presented simultaneously with the 4000 Hz activator tone. Reflex thresholds for the wideband system were determined by using statistical tests of the magnitude of the reflex responses as well as their correlation with other reflex responses. RESULTS: Clinical and experimental reflex thresholds were obtained for 9 of the 27 subjects for all conditions. Clinical reflex thresholds were absent for 8 subjects for whom experimental reflex thresholds were present and were present for 5 subjects who had absent experimental reflex thresholds for one or more conditions. An additional 5 subjects had absent reflex thresholds in all conditions, consistent with the low maximum level of the activator. Wideband measures of contralateral reflex thresholds were approximately 3 dB lower than those obtained with the clinical system. The magnitudes of the group means of the reflex responses were similar for ipsilateral and contralateral stimulations. CONCLUSIONS: Wideband measures of reflectance and admittance may be used to estimate the ipsilateral acoustic stapedius reflex threshold by separating in frequency the spectral energies of the wideband probe stimulus from the activator stimulus. This technique holds promise for measuring reflex thresholds for individuals with absent reflex thresholds through the use of standard clinical methods.

Acoustic Impedance Tests↗

PubMed2002

Experimental observation of superluminal pulse reflection in a double-Lorentzian photonic band gap.

We report on the experimental observation of superluminal reflection of picosecond optical pulses at 1.5 microm using a specially designed 30-cm-long fiber Bragg grating (FBG) that realizes a spectral reflectivity profile given by the superposition of two closely spaced Lorentzian lines. Probing pulses of 380 ps duration tuned midway between the two Lorentzian lines are reflected without appreciable distortion with a measured peak pulse advancement of approximately 60 ps. The achievement of the negative group delay is due to the interference of the two resonance modes of the FBG structure and has a close connection to the phenomenon of negative group velocity for pulse propagation in an inverted medium possessing a doublet line.

Journal Article↗

PubMed2002

Angle-resolved reflectivity of single-domain photonic crystals: effects of disorder.

Angle-resolved reflectivity has been measured from single-domain photonic crystals consisting of air spheres in a TiO2 backbone. Monochromatic beams are focused to a 10 microm spot, and kept on the rotation axis with a precision better than 10 microm. We report high reflectivity up to 94% and surface domains as large as 200 microm, with a mosaic spread of +/-3 degrees. The maximum reflectivity at normal incidence agrees well with theoretical calculations in the scalar-wave approximation, extended to include an extinction length due to diffuse scattering, that is obtained from independent experiments. The angle-resolved stop bands compare favorably with previous measurements using coarse beams as well as with prior theoretical calculations. Inhomogeneous broadening introduced by coarse beams in previous measurements is found to be small. Our results can only be understood if we assume multiple Bragg diffraction from more than one family of planes simultaneously to take place.

Journal Article↗

PubMed2004

Specular neutron reflectivity and the structure of artificial protein maquettes vectorially oriented at interfaces.

Artificial peptides can be designed to possess a variety of functionalities. If these peptides can be ordered in an ensemble, the functionality can impart macroscopic material properties to the ensemble. Neutron reflectivity is shown to be an effective probe of the intramolecular structures of such peptides vectorially oriented at an interface, key to ensuring that the designed molecular structures translate into the desired material properties of the interface. A model-independent method is utilized to analyze the neutron reflectivity from an alkylated, di- alpha -helical peptide, containing perdeuterated leucine residues at one or two pre-selected positions, in mixed Langmuir monolayers with a phospholipid. The results presented here are more definitive than prior work employing x-ray reflectivity. They show explicitly that the di-helical peptide retains its designed alpha -helical secondary structure at the interface, when oriented perpendicular to the interface at high surface pressure, with the helices projecting into the aqueous subphase without penetrating the layer of phospholipid headgroups.

Lipid Bilayers↗

PubMed2001

Phase modulation of intense ultrashort laser pulses reflected from steep, dense plasmas.

The phase modulation of intense ( I = 10(18) W/cm(2)) ultrashort laser pulses ( tau(p) = 70 fs) after reflection from steep, dense plasmas has been temporally resolved for the first time in particle-in-cell simulations. The position of the turning point from where the pulse reflects has been compared to the phase modulation, over a range of angles of incidence. At normal incidence or s polarization the phase modulation almost exactly represents the movement of the turning point due to the light pressure. As the angle of incidence is increased for p polarization, the simple Fresnel relationship between phase modulation and displacement of the reflection position, Delta phi(t) = -2k(0)Delta x(t)cos theta(0), increasingly breaks down.

Journal Article↗