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PubMed2006

Study on the surface density of surface-active substances through total-reflection X-ray absorption fine structure measurement.

The total-reflection X-ray absorption fine structure (XAFS) method previously employed for the adsorption of dodecyltrimethylammonium bromide (DTAB) at the air/water interface was applied to that in the presence of NaBr. The surface concentration of the bromide ions Gamma(X)(B) of DTAB and NaBr was evaluated by using the Br K-edge absorption jump values of the total-reflection XAFS spectra and was compared to the corresponding value Gamma(H)(B) estimated from the dependence of surface tension on the bulk concentrations of DTAB m(1) and NaBr m(2). The Gamma(X)(B) values trace almost perfectly the Gamma(X)(B) versus m(1) curve up to a concentration near the critical micelle concentration (cmc) and deviate gradually above the concentration. This behavior is basically similar to that of the single DTAB system and ensures that the XAFS method is also applicable to the DTAB system, even in the presence of NaBr. In addition, this method was extended to the single nonionic amphiphile with covalently bonded bromine, and the surface concentrations of 6-bromo-1-hexanol (BrC6OH), Gamma(X)(1) and Gamma(H)(B), were evaluated and compared with each other. It was found that the Gamma(X)(1) value almost perfectly traces the Gamma(H)(1) versus m(1) curve, even at high surface concentrations. The excellent coincidence confirmed that the total-reflection XAFS method can be applied to the nonionic amphiphile system as well as a cationic surfactant with or without an added salt system. Finally, the difference between the Gamma(X)(B) and Gamma(H)(B) values observed in the DTAB with and without an added salt system is briefly described.

Journal Article↗

PubMed2006

Reversible control of light reflection of a colloidal crystal film fabricated from monodisperse mesoporous silica spheres.

In this letter, we report a novel method for controlling the light reflection of a colloidal crystal. Highly monodisperse mesoporous silica spheres have been successfully organized into a hexagonally close-packed colloidal crystal film. Just by introducing water vapor into the fabricated colloidal film, the structural color and reflection spectra were changed dramatically because of water vapor adsorption occurring in the mesoporous channels. This phenomenon can be observed reversibly over five cycles. We are convinced that this is the first report on controlling the light reflection of a colloidal crystal film dynamically by taking advantage of adsorption properties inherent to mesoporous silica spheres.

Journal Article↗

PubMed2006

In-situ infrared study of the adsorption and oxidation of oxalic acid at single-crystal and thin-film gold electrodes: a combined external reflection infrared and ATR-SEIRAS approach.

The adsorption and oxidation of oxalic acid at gold electrodes were studied by in-situ infrared spectroscopy. External reflection experiments carried out with gold single-crystal electrodes were combined with internal reflection (ATR-SEIRAS) experiments with gold thin-film electrodes. These gold thin films, with a typical thickness of ca. 35 nm, were deposited on silicon substrates by argon sputtering. As previously reported for evaporated gold films, the voltammetric curves obtained in sulfuric acid solutions after electrochemical annealing show typical features related to the presence of wide bidimensional (111) domains with long-range order. The in-situ infrared data collected for solutions of pH 1 confirmed the potential-dependent adsorption of either oxalate (Au(100)) or a mixture of bioxalate and oxalate (Au(111), Au(110), and gold thin films) anions in a bidentate configuration. The better signal-to-noise ratio associated with the SEIRA effect in the case of the gold thin-film electrodes allows the observation of the carbonyl band for adsorbed bioxalate that was not detected in the external reflection experiments. Besides, additional bands are observed between 2000 and 3000 cm(-)(1) that can be tentatively related to the formation of hydrogen bonds between neighboring bioxalate anions. The intensities of these bands decrease with increasing solution pH values, disappearing for pH 3 solutions in which adsorbed oxalate anions are the predominant species. The analysis of the intensities of the nu(s)(O-C-O) and nu(C-OH) + delta(C-O-H) bands for adsorbed oxalate and bioxalate, respectively, suggests that the pK(a) for the surface equilibrium between these species is significantly lower than that for the solution equilibrium.

Journal Article↗

PubMed2002

In vivo measurement of the photostability of sunscreen products using diffuse reflectance spectroscopy.

BACKGROUND/AIM: The issue of the photostability of sunscreens has been frequently raised because of the possible loss of photoprotection, mainly in the UVA range, during sun exposure. Up to now, in vitro techniques have been mainly proposed to evaluate photostability. These techniques have generated controversial debates concerning the predictive value of these in vitro observations in relation to the in vivo reality during sun exposure. METHODS: Diffuse reflectance spectroscopy (DRS) is a recently developed technique that allows measurement of the UVA efficacy of sunscreen products in vivo on human volunteers. The absorption spectrum of the product is obtained by measuring the change in reflection of the skin with and without product. From this absorption spectrum, the UVA protective efficacy of the test product can be calculated for an appropriate source and a given biological action spectrum. We have used the DRS technique in vivo to determine the photostability of sunscreen products by measuring reflection spectra in the UVA range (320-400 nm) before and after product application and before and after UV exposure of the test products. Comparison between these spectra or between the corresponding calculated UVA protection factors has made it possible to determine the remaining level of protection in the UVA range after exposure. This study was designed to compare in vivo the protective efficiency and the photostability of three marketed sunscreen products (SPF 23-30) after solar-simulated exposure for SPF testing or after actual sun exposure. These in vivo data were then compared to in vitro photoinstability results. RESULTS: According to the in vitro measurements, one sunscreen product was found photostable and two products photo-unstable. After UVe exposure for in vivo SPF determination, a decrease in UVA absorption and UVA-PF was observed for the two photo-unstable products, while the photostable product did not present any decrease in UVA absorption. These results were confirmed through exposure to actual sun. CONCLUSION: Our study confirms the prediction of the in vitro methods previously used to assess the photostability of sunscreen products. In addition, DRS provides a powerful new tool for the in vivo simultaneous evaluation of photostability and estimation of the UVA protection factor of sunscreen products performed during the test for SPF determination.

Drug Stability↗

PubMed2003

Reflectance spectroscopy can quantify cutaneous haemoglobin oxygenation by oxygen uptake from the atmosphere after epidermal barrier disruption.

BACKGROUND: The supply of oxygen to the viable skin tissue within the upper layers is not only secured by the cutaneous blood vascular system, but to a significant part also by oxygen diffusion from the atmosphere through the horny layer. The aim of this study was to examine whether changes in haemoglobin oxygenation can be observed within the isolated perfused bovine udder skin used as a skin model by removing the upper horny layer by adhesive tape stripping. METHODS: Diffuse reflectance spectroscopy in the visible spectral range was used for non-invasive characterisation of haemoglobin oxygenation in skin under in vitro conditions. Mid-infrared attenuated total reflectance spectroscopy was employed for analysing the surface layer of the stratum corneum with respect to keratin, water and lipid components. Skin barrier disruption was achieved by repeated stripping of superficial corneocyte layers by adhesive tape. RESULTS AND CONCLUSION: Significant changes in skin haemoglobin oxygenation were observed for skin areas with reduced lipid concentration and a reduced stratum corneum layer, as determined from the quantitative evaluation of the diffuse reflectance skin spectra. The result can be interpreted as an increase of oxygen diffusion after the removal of the upper horny layer.

Animals↗

PubMed2002

Naive optics: understanding the geometry of mirror reflections.

Paper-and-pencil tasks showed that many university students believed that when laterally approaching a mirror, they would see a reflection in the mirror before it was geometrically possible. Participants failed to adequately factor in the observer's location in the room. However, when asked about the behavior of a ray of light, participants knew about the law of reflection. No differences between psychology and physics students were detected, suggesting that the phenomenon is widespread and refractory to training. The findings were replicated with observers making judgments about image locations in a real room using a pretend mirror. Possible heuristics about mirror reflection that might explain the data are discussed. Naive optics is a promising venue to further knowledge of how observers understand basic laws of physics.

Adolescent↗

PubMed1991

Surface reflectances and human color constancy: comment on Dannemiller (1989)

Dannemiller's (1989) computational approach to color constancy is discussed in relation to human color constancy. A reflectance channel that requires a priori information is shown to be less plausible for the human visual system than Dannemiller argued. The resemblance of Dannemiller's hypothetical visual system to the human visual system is misleading because it implies that surface reflectance is the illuminant-invariant object color descriptor that the human visual system uses to achieve color constancy. However, an alternative type of descriptor is available that is not used to recover reflectance spectra. It has the advantage of allowing an interpretation that is preferable from a human perceptual point of view.

Attention↗

PubMed2006

Of snakes and flowers: does preferential detection of pictures of fear-relevant animals in visual search reflect on fear-relevance?

Previous research in visual search indicates that animal fear-relevant deviants, snakes/spiders, are found faster among non fear-relevant backgrounds, flowers/mushrooms, than vice versa. Moreover, deviant absence was indicated faster among snakes/spiders and detection time for flower/mushroom deviants, but not for snake/spider deviants, increased in larger arrays. The current research indicates that the latter 2 results do not reflect on fear-relevance, but are found only with flower/mushroom controls. These findings may reflect on factors such as background homogeneity, deviant homogeneity, or background-deviant similarity. The current research removes contradictions between previous studies that used animal and social fear-relevant stimuli and indicates that apparent search advantages for fear-relevant deviants seem likely to reflect on delayed attentional disengagement from fear-relevance on control trials.

Adolescent↗

PubMed2005

Neuroprotective activity of the mGluR5 antagonists MPEP and MTEP against acute excitotoxicity differs and does not reflect actions at mGluR5 receptors.

1 Neuroprotection has been reported after either activation or blockade of the group I metabotropic glutamate receptor subtype 5 (mGluR5). However, some recent evidence suggests that protection provided by mGluR5 antagonists may reflect their ability to inhibit N-methyl-D-aspartate (NMDA) receptor activity. 2 Here, in both rat and mouse cortical neurons, we compare the neuroprotective actions of two mGluR5 antagonists: 2-methyl-6-(phenylethynyl)-pyridine (MPEP), which has been commonly used and 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP), a more recently developed compound believed to have greater mGluR5 selectivity. We have previously shown that MPEP directly reduces single-channel NMDA receptor open time at the same concentrations (20 microM or greater) that show neuroprotection, whereas MPEP antagonizes mGluR5 agonist ((RS)-2-chloro-5-hydroxyphenylglycine (CHPG))-induced changes in inositol phosphates (IP) at concentrations as low as 0.2 microM. 3 In the present studies, MTEP significantly inhibited CHPG-mediated IP hydrolysis at concentrations as low as 0.02 microM. In contrast to MPEP, which significantly reduced glutamate- or NMDA-mediated cell death in primary rat neuronal cultures at a concentration of 20 microM, small neuroprotective effects were observed with MTEP only at a concentration of 200 microM. Neither MPEP- nor MTEP-mediated mGluR5 inhibition had any effect on etoposide-induced apoptotic cell death. In rat cortical neurons, the neuroprotective effects of MTEP at very high concentrations, like those of MPEP, reflect ability to directly reduce NMDA receptor peak and steady-state currents. 4 We also compared the effects of MPEP and MTEP in primary cortical neuronal cultures from parental and mGluR5 knockout mice. Both agents were neuroprotective, at high concentrations in normal as well as in the knockout cultures. In contrast to rat cortical neurons, neither MPEP nor MTEP appears to directly alter NMDA receptor activity. 5 Combined, these studies support the conclusion that MTEP has greater mGluR5 selectivity than MPEP, and that neuroprotection provided by either antagonist in neuronal cultures does not reflect inhibition of mGluR5 receptors.

Animals↗

PubMed2005

Reflective thermal lens detection device.

A reflective thermal lens detection device was developed for realizing a portable and sensitive detector for a microsystem. An aluminum mirror was formed on the main plate of a microchip, and a reflected probe beam was detected with a single pick-up unit. The background signal due to light absorption of the aluminum mirror was 60 times reduced when the microchannel and the mirror were separated with an interval of 600 microm. The tilt angle of the microchip significantly affected the precision of the measurement. Then a quadrant photodiode was used to detect the center of gravity of the reflected probe beam to regulate the tilt angle within +/-0.05 degrees , and this value was enough to achieve 1% CV (coefficient of variance) precision in the measurements. The limit of detection (LOD) was 60 nM for xylene cyanol solution, and the absorbance was 9.4 x 10(-6) AU. About 40 times higher sensitivity was obtained in comparison with a spectrophotometer.

Aluminum↗

PubMed2003

Contralateral acoustic reflex thresholds for tonal activators using wideband energy reflectance and admittance.

The purpose of this study was to evaluate a new method for estimating the acoustic reflex threshold incorporating wideband (250-8000 Hz) measures of energy reflectance and admittance (M. P. Feeney & D. H. Keefe, 2001). The wideband technique incorporates both a correlation method to assess the pattern of the reflex-induced shifts in reflectance and admittance across frequency and a magnitude method to determine if the amplitude of the shifts exceeds baseline variability. Contralateral reflex thresholds for 1000- and 2000-Hz activators were obtained for 34 young adults with both the wideband method and a clinical method using a 226 Hz probe tone. Average reflex thresholds obtained with the new method were 12 to 13.7 dB lower than than obtained with the clinical method. When the bandwidth of analysis of admittance and reflectance responses was limited to 250 to 2000 Hz, the reduction in reflex thresholds was accompanied by the rejection of 96% of nonactivator-baseline responses as reflexes. The method holds promise for extending reflex threshold testing to patients with reflexes elevated beyond current equipment limits, for reducing the sound levels used in reflex testing, and for obtaining sensitive measures of reflex threshold in infants.

Acoustic Impedance Tests↗

PubMed1999

Acoustic reflex detection using wide-band acoustic reflectance, admittance, and power measurements.

The measurement of the acoustic reflex threshold is a basic component of the diagnostic audiological test battery that may subject patients to potentially harmful sound pressures. A wide-band acoustic impedance and reflectance system (D. H. Keefe, R. Ling, & J. C. Bulen, 1992) was investigated as a means of obtaining reflex thresholds at a reduced level and as a means of providing a more complete characterization of the reflex than current clinical methods provide. Reflex thresholds obtained by measuring changes in wide-band admittance, reflectance, and power were at least 8 dB lower than those obtained with the standard clinical technique. These reflex-induced changes were accounted for by a simple oscillator model of the middle ear, assuming that the acoustic reflex results in an increase in stiffness. The results support further investigation of reflectance-based measures of the acoustic reflex as a clinical tool and as a means of studying the reflex mechanism.

Acoustic Impedance Tests↗

PubMed1995

Exploring the lived experiences of psychiatric nursing students through self-reflective journals.

This study explores the use of journals to identify important issues facing nursing students when learning in a psychiatric setting. During a 13-week psychiatric clinical experience, 18 third-year students kept journals describing the most significant event that occurred each week, reflecting on the impact and accompanying attitudes of that event. Throughout the clinical experience, the nursing faculty read the students' journals and provided written feedback on a bi-weekly basis. Major themes that students wrote about in their journals were identified. These included: meaningful learning, issues of the novice, relationships, control, self-reflection, and identification with clients. Keeping a journal provided the students with an opportunity to become more self-reflective in their practice. The issues identified by students in their journals may assist nurse educators to anticipate the learning needs of their students in psychiatry.

Female↗

PubMed1998

Caring for demented people in their homes or in sheltered accommodation as reflected on by home-care staff during clinical supervision sessions.

This study aimed to illuminate both the content of and the care given to demented people and the reflections of home care staff about it as revealed in two clinical group supervision sessions (n = 36). Verbatim transcriptions were analysed using a phenomenological hermeneutic approach and the following were found to be reflected on: the pensioners' personal situation--disease-related behaviour, ADL-functions, social network and self-esteem; the pensioners' environment--their relationships to significant others, adequate level of housing/care, access to activities, and satisfactory personal space; pensioner/staff interaction--their relations to each other, the staffs' relation to the pensioners' family, and the balance between reality-orientation vs. validation; the staff's situation--co-operation with other professionals, in primary health care, hospital, and within the social services; job satisfaction, lack of knowledge and sharing of knowledge, and lack of resources, especially time. The reasoning of the participants under supervision was found to be based on medical, historical, psychological, and environmental explanations, or personal beliefs. Feelings explored during supervision were directed towards the pensioners or the pensioners' families, towards themselves or towards the management. The findings were interpreted within a nursing model based on the four central concepts of nursing; person, environment, nursing intervention and health. The reasoning about nursing care revealed in the supervision sessions reflected a holistic approach and the relationship between the staff and the demented person stood out as central for care quality. Thus focusing on what promotes or, respectively, obstructs this relationship is likely to be one important focus in clinical supervision not only to achieve improvement and high quality in home care but also to develop and enhance the quality of the working life of the staff. Since the results could be understood within a theoretical nursing care model, it may well be that if the supervisor functions within some theoretical model the participants may reach a more conscious approach and the risk of losing important aspects of caring will decrease.

Adaptation, Psychological↗

PubMed1998

Learning by reflection: the effect on educational outcomes.

Learning by experience involves being able to reflect on a personal happening and through a process of analysis, come to understand it. Such an activity should result in 'deep learning' when carried out in a structured way. Higher education establishments are keen to develop such learning methods in students, as a secondary effect of this form of learning is to create student independence from the teacher. This is a much sought after ability as recent government changes have meant higher student numbers without a corresponding rise in teacher numbers. This threatens the quality of student knowledge unless it is compensated for in some way. This study sets out to examine the learning of two student groups. The experimental design was that of group comparison using matched pairs of students. One group, the experimental group, were exposed to reflective teaching methods, whilst the other group (the control group) were exposed to conventional teaching methods only. At the end of a set period of time, the learning achieved in both groups was estimated using an especially designed test paper. The results obtained from both groups were compared and it was found that there was no significant difference obtained in the learning between the groups (P>5%) Therefore, we concluded that students learnt just as well using reflective methods when compared to the conventional methods of learning. However, the potential for enhancement of learning was evident and invites further investigation. All the students in this study were on the Diploma in Higher Education (Nursing) course. The subject area used throughout the study was in the biological sciences.

Adolescent↗

PubMed1999

Critical reflective inquiry for knowledge development in nursing practice.

This paper presents a method of inquiry which uses nurses' situated, individual instances of nursing practice as the basis for developing knowledge for nursing and improving practice. This method of inquiry is founded upon the ideas in action science and reflective practice, and critical philosophy. Nursing practice is viewed as a rich source of new knowledge as practitioners are engaged in creating as well as modifying knowledge to respond to specific clinical situations. At the same time, practitioners may be in practice without recognizing deficiencies or ineffectiveness. As a method to tap these two aspects of practice, the inquiry is designed to encompass three phases, i.e. descriptive, reflective and critical/emancipatory, and is oriented to provide understanding to practitioners of the nature and meaning of their own practice, to correct and improve practice through self-reflection and critique, and to generate models of 'good' practice and theories of application as well as to discover processes of practice as played out in clinical situations. This method of inquiry can be used by nurses and nursing students in collaboration with researches or mentors to develop nursing knowledge about practice, improve individual practice, and engage in shared learning.

Communication↗

PubMed1999

Reflective inquiry framework for nurse administrators.

Problematic situations comprise a significant proportion of nurse administrators' practice. Reflective inquiry is recommended as a method for identifying the problem and its solution. This approach is consistent with pragmatic philosophy which recognizes the fallacy of basing one's action on an a priori conclusion. Dewey's elements of reflective inquiry are used as the framework to analyse its relevance to administrative practice. Emphasis is placed on the importance of using empirical observations and thoughts in a serial back and forth process to discover the problem and its solution. The problems associated with non-empirical inquiry are examined. Reflective inquiry provides a directed rather than a haphazard approach to effective and efficient administrative practice.

Habits↗

PubMed2000

Cultural challenges in end-of-life care: reflections from focus groups' interviews with hospice staff in Stockholm.

Cultural challenges in end-of-life care: reflections from focus groups' interviews with hospice staff in Stockholm During the past few decades, Swedish society has changed from a society with a few ethnic groups to one with over a hundred groups of different ethnic backgrounds, languages and religions. As society is becoming increasingly multicultural, cultural issues are also becoming an important feature in health care, particularly in end-of-life care where the questions of existential nature are of great importance. However, cultural issues in health care, especially at hospices, have not been studied sufficiently in Sweden. The purpose of this study was to gather reflections about cultural issues among hospice staff after a 3-day seminar in multicultural end-of-life care, by using a qualitative focus groups method. The 19 participants (majority nurses) were divided into three groups, one per hospice unit. A discussion guide was developed with the following themes: 1) post-training experiences of working with patients with multicultural background; 2) experiences gained by participating in the course of multicultural end-of-life care; 3) post-training reflections about one's own culture; 4) ideas or thoughts regarding work with patients from other cultures arising from the training; and 5) the need for further training in multicultural end-of-life care. One of the study's main findings was that to better understand other cultures it is important to raise awareness about the staff's own culture and to pay attention to culture especially in the context of the individual. The findings from focus groups provide insight regarding the need for planning flexible training in cultural issues to match the needs of the staff at the hospice units studied.

Adult↗