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At least 73 records · Page 4Linked to original sources
PubMed1999

Neutron reflectivity studies of critical adsorption: the correspondence between a critical adsorption profile and specular neutron reflection.

For interfacial order parameter profiles which decay as Az(-mu), such as the composition profile of the noncritical interface of a binary liquid mixture at a critical end point, there is a reported one-to-one correspondence between the profile and the reflectivity which can be described by an analytical theory [S. Dietrich and R. Schack, Phys. Rev. Lett. 58, 140 (1987)]. Evidence for mu=0.53+/-0.02 for adsorption at the hydrophilic silicon/liquid surface of the mixture (2-butoxyethanol+deuterium oxide) near its lower critical end point, determined from neutron reflectivity measurements, is presented. This value is in good agreement with the theoretical prediction of mu=0.516+/-0.004. Further examination of the data permits the determination of the asymptotic surface enrichment scaling factor amplitude P0 approximately 0.11, which is not in agreement with the theoretical value P(0) = 0.94+/-0.05 and values determined by other experimental methods.

Journal Article↗
PubMed1999

Reflections on ... the art of observation: reflecting on a spiritual moment.

Spiritual moments can occur at unexpected times and it is often upon reflection that the significance of the moment is understood. The author tells a personal story about her daughter and herself engaged in the activity of drawing flowers. The reflection which follows highlights both the process and outcomes of the experience. Exploring spiritual issues using this narrative medium assists health care workers to recognize better and understand spirituality in relation to the occupation of visual art.

Adult↗
PubMed2006

Reflections on reflecting as a dialogic accomplishment in counseling.

In this exploratory study, the author examines reflection as a dialogic phenomenon constructed in the back-and-forth of counseling dialogue. He videotaped and microanalyzed 11 one-hour lifestyle consultations for the conversational practices used by counselors and clients in collaboratively reflecting on developments in their dialogues. He then invited counselors and clients back to comment on their participation in videotaped passages of their dialogue selected for microanalysis, thus permitting a juxtaposition of their retrospective comments with the analysis. The author considers the results from this study with respect to training counselors and for pointing new ways to widen the evidence base with respect to interventions in counseling, particularly social constructionist approaches.

Alberta↗
PubMed1988

Mapping cell-glass contacts of Dictyostelium amoebae by total internal reflection aqueous fluorescence overcomes a basic ambiguity of interference reflection microscopy.

The widespread ability of eukaryotic cells to produce thin cytoplasmic sheets or lamellae 100-200 nm thick can give rise to uncertainties in the interpretation of interference reflection microscopy (IRM) images when cell-substratum topography is the key interest. If allowed to spread upon a poly-L-lysine-coated surface, Dictyostelium discoideum amoebae typically form ultrathin lamellae of approximately equal to 100 nm thickness by cytoplasmic retraction. Whereas the cell body is grey, the lamellae appear very dark under IRM optics. These dark areas could be misinterpreted as stemming from a closer cell-substratum apposition beneath the lamellae than the cell body. This ambiguity can be avoided if the technique of total internal reflection aqueous fluorescence (TIRAF) is used in conjunction with a high refractive index glass (n = 1.83) as substratum. Contributions to the image generated by thin cytoplasm and also variable cytoplasmic refractive index are thereby minimized due to the extremely short range of the 'illuminating' evanescent wave. From our comparative IRM and TIRAF study of the ultrathin lamellae of Dictyostelium amoebae it is concluded that the cell-glass gap is relatively uniform beneath the entire cell. We briefly discuss the sensitivity of several cell types to TIRAF, the generation of ultrathin lamellae and the nature of the cell-glass gap.

Cell Adhesion↗
PubMed2003

Remote-sensing reflectance of turbid sediment-dominated waters. Reduction of sediment type variations and changing illumination conditions effects by use of reflectance ratios.

Variations of sediment type (grain size and refractive index) and changing illumination conditions affect the reflectance signal of coastal waters and limit the accuracy of sediment-concentration estimations from remote-sensing measurements. These effects are analyzed from numerous in situ remote-sensing measurements carried out in the Gironde and Loire Estuaries and then reduced and partly eliminated when reflectance ratios between the near infrared and the visible are considered. These ratios showed high correlation with the sediment concentration. On the basis of the obtained relationships, performing correspondence functions were established that allow an accurate estimation of suspended sediments in the estuaries from Système Probatoire d'Observation de la Terre, Landsat, and Sea-Viewing Wide Field-of-View Sensor data, independently of the date of acquisition.

Journal Article↗
PubMed2002

Angular range for reflection of p-polarized light at the surface of an absorbing medium with reflectance below that at normal incidence.

The range of incidence angle, 0 < phi < phi(e), over which p-polarized light is reflected at interfaces between transparent and absorbing media with reflectance below that at normal incidence is determined. Contours of constant phi(e) in the complex plane of the relative dielectric constant epsilon are presented. A method for determining the real and imaginary parts of the complex refractive index, epsilon(1/2) = n + jk, which is based on measuring phi(e) and the pseudo-Brewster angle phi(pB), is viable in the domain of fractional optical constants, n, k < 1.

Journal Article↗
PubMed2006

Attenuated total internal reflection infrared microspectroscopic imaging using a large-radius germanium internal reflection element and a linear array detector.

The number of techniques and instruments available for Fourier transform infrared (FT-IR) microspectroscopic imaging has grown significantly over the past few years. Attenuated total internal reflectance (ATR) FT-IR microspectroscopy reduces sample preparation time and has simplified the analysis of many difficult samples. FT-IR imaging has become a powerful analytical tool using either a focal plane array or a linear array detector, especially when coupled with a chemometric analysis package. The field of view of the ATR-IR microspectroscopic imaging area can be greatly increased from 300 x 300 microm to 2500 x 2500 microm using a larger internal reflection element of 12.5 mm radius instead of the typical 1.5 mm radius. This gives an area increase of 70x before aberrant effects become too great. Parameters evaluated include the change in penetration depth as a function of beam displacement, measurements of the active area, magnification factor, and change in spatial resolution over the imaging area. Drawbacks such as large file size will also be discussed. This technique has been successfully applied to the FT-IR imaging of polydimethylsiloxane foam cross-sections, latent human fingerprints, and a model inorganic mixture, which demonstrates the usefulness of the method for pharmaceuticals.

Dermatoglyphics↗
PubMedDate not supplied

Reflections on being therapeutic and reflection.

This article offers a reflective account of an incident that occurred between a nurse tutor and a patient on a cardiology ward. It highlights the importance of interpersonal skills in creating a therapeutic relationship, in particular those of self-awareness, empathy and intuition. The author's difficulties in running reflective practice sessions for pre-registration students are discussed and insights are offered into why these difficulties arose.

Awareness↗
PubMed1990

New sensitive light microscopical detection of colloidal gold on ultrathin sections by reflection contrast microscopy. Combination of reflection contrast and electron microscopy in post-embedding immunogold histochemistry.

One simple post-embedding method for combined light- and electron microscopy is presented. Different types of antigens in normal rat and mouse kidneys as well as in tissues from cases of experimental induced nephritis were stained after Lowicryl K4M embedding by an immunogold (silver) method. The (silver-enhanced) gold particles were visualized by light microscopy, e.g. bright-field (BFM)- and reflection contrast (RCM) microscopy, as well as by electron microscopy. The potentials of RCM visualization in this field were investigated, resulting in the successful detection of colloidal gold (15 nm) particles, or silver enhanced gold particles, on ultrathin sections. Furthermore, an increased detection sensitivity of RCM compared with BFM together with an increase in the sensitivity of the immunostaining by RCM visualization was found. The different ways to use RCM, alone or in combination with bright-field- or phase contrast microscopy for visualization of plastic sections varying in thickness, type of plastic and staining, are discussed.

Animals↗
PubMed1999

Limits of detection of a total reflection X-ray fluorescence system with double reflection module.

An X-ray tube with a Mo target and Zr filter, operated at 45 kV/20 mA, was used to excite samples (5 microL deposited on a quartz support) and the total reflection angle condition was obtained with a double reflector module built with two 10-cm-long 7-mm-thick quartz crystals placed 50 microns apart. A high-resolution spectrometer based on a Si(Li) detector coupled to a multichannel analyzer was used for X-ray detection and the spectra were interpreted with the AXIL software. The system was calibrated with standard chemical solutions containing Cr, Fe, Cu, Zn, and Pb, and Y was used as an internal standard to correct eventual geometric errors and high-voltage instabilities of the X-ray generator. The limits of detection were 19, 9, 5, and 4 ng/mL for Cr, Fe, Cu, and Zn, respectively, analyzed through characteristic K alpha X-rays, and 7 ng/mL for Pb, through L alpha X-rays, considering 50 microL samples deposited and dried on a quartz support, to be excited/detected for 1000 s.

Calibration↗
PubMed2004

Characterization of commercial carrageenans by Fourier transform infrared spectroscopy using single-reflection attenuated total reflection.

The purity and composition of commercial carrageenans vary widely and, therefore, have to be checked prior to their use in the food industry. Infrared spectroscopy is an alternative method to the expensive and time-consuming wet chemical and NMR methods to characterize carrageenan samples. The use of an attenuated total reflection accessory coupled to a Fourier transform infrared spectrophotometer allows a direct analysis of the sample without any preparation step, which is an additional benefit for the rapid identification check of raw material at reception in an industrial environment. Using a set of calibration samples, three multivariate calibrations were developed to predict the total carrageenan content as well as the molar ratio of kappa- and iota-carrageenans. A validation with an independent set of samples confirmed the robustness of the calibrations and the accuracy of the predictions. The accuracies of the calibrations given by their respective standard errors of prediction are 5.6 g/100 g, and 6.1 mol %, and 6.6 mol %, respectively, for the total carrageenan content and the molar ratios of kappa- and iota-carrageenans. The total preparation and analysis time is <5 min per sample.

Calibration↗
PubMed2005

Determination of the polymorphic forms of bicifadine hydrochloride by differential scanning calorimetry-thermogravimetric analysis, X-ray powder diffraction, attenuated total reflectance-infrared spectroscopy, and attenuated total reflectance-near-infrared spectroscopy.

The pharmaceutical compound bicifadine hydrochloride, which has been found to crystallize in two polymorphic forms, has been characterized by thermal analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, and near-infrared (NIR) spectroscopy. A series of 22 sample mixtures of polymorph 1 and polymorph 2 were prepared and calibration models for the quantitation of these binary mixtures have been developed for each of the XRPD, attenuated total reflectance (ATR)-IR, and ATR-NIR analytical techniques. The quantitative results were obtained using a partial least squares (PLS) algorithm, which predicted the concentration of polymorph 1 from the XRPD spectra with a root mean standard error of prediction (RMSEP) of 4.4%, from the IR spectra with a RMSEP of 3.8%, and from the NIR spectra with a RMSEP of 1.4%. The studies indicate that when analyses are carried out on equivalent sets of spectra, NIR spectroscopy offers significant advantages in quantitative accuracy as a tool for the determination of polymorphs in the solid state and is also more convenient to use than both the ATR-IR and XRPD methods. Density functional theory (DFT) B3LYP calculations and IR spectral simulation have been used to determine the nature of the vibrational modes that are the most sensitive in the analysis.

Bridged Bicyclo Compounds, Heterocyclic↗