Search results for "Reflection"
showing 10 items of 645 documents
Polar phonons in relaxor ferroelectric 0.2PSN-0.4PMN-0.4PZN
2008
Relaxor ferroelectrics 0-2PbSc(1/2)Nb(1/2)O(3) - 0.4PbMg(1/3)Nb(2/3)O(3)-0.4PbZn(1/3)Nb(2/3)O(3) ceramics were studied by means of the Fourier transform infrared reflection and THz transmission spectroscopy in the temperature range of 20-500 K. On heating from low temperatures, the A(1) component of the strongly split TO1 mode softens towards the Burns temperature, but the softening ceases near 400 K, which could be a signature of polar cluster percolation temperature.
Strukturelle Veränderungen in säuregeätztem Schmelz im konfokalen Laser-Scanning-Mikroskop
1996
The aim of the present investigation was to elucidate structural alternations in enamel subjected to acid etch technique and treatment under remineralizing conditions by means of a new microscopy technique known as confocal laser scanning microscopy (CLSM). Blocks of enamel were treated with 37% phosphoric acid and exposed for 3 weeks to an oral environment. Tomographic CLSM images were subsequently obtained and compared with controls. CLSM proved to be a reliable, highly reproducible and simple method of qualitative assessment of structural changes occurring on the surface of enamel and in areas below the surface as deep as 100 microns or more. Structural alterations associated with acid a…
Formation and Growth of Pd Nanoparticles Inside a Highly Cross-Linked Polystyrene Support: Role of the Reducing Agent
2014
Simultaneous time-resolved SAXS and XANES techniques were employed to follow in situ the formation of Pd nanoparticles in a porous polystyrene support, using palladium acetate as a precursor and gaseous H2 or CO as reducing agents. These results, in conjunction with data obtained by diffuse reflectance UV–vis and DRIFT spectroscopy and TEM measurements, allowed unraveling of the different roles played by gaseous H2 and CO in the formation of the Pd nanoparticles. In particular, it was found that the reducing agent affects (i) the reduction rate (which is faster in the presence of CO) and (ii) the properties of the hosted nanoparticles, in terms of size (bigger with CO), morphology (spherica…
Combining EXAFS and XRay Powder Diffraction to Solve Structures Containing Heavy Atoms
2005
Determination of structures using x-ray powder diffraction is complicated if the reflection intensities are mainly influenced by the scattering from heavy atoms and the atomic coordinates of light atoms remain uncertain. A method like EXAFS, which is sensitive to short range order, gives reliable atomic distances in the surroundings of heavy atoms with a precision of ±0.02 A. The probability for obtaining the complete structure from x-ray powder diffraction increases if one includes parameters derived from EXAFS measurements as restraints during the procedure of structure solving. We demonstrate the potential of combining EXAFS and x-ray powder diffraction by solving the structure UO2[H2AsO…
A Simple “Plastic Bag” Technique for Visible Spectra of Solid Metal Complexes
1979
The techniques commonly used to study the visible spectra of transition metal complexes in the solid state involve diffuse reflectance from the powdered sample or transmission through a mull of the compound in mineral oil on filter paper. Pressed KBr (for anhydrous compounds) and AgCl (for compounds containing water or other highly polar ligands) disk techniques have been used even for low temperature spectra. All of the transmission techniques mentioned are based on mixing the sample with another compound which may induce changes in the compound under study via chemical reactions. Air- and water-sensitive complexes also need special care. These interferences may be reduced by the use of th…
Effect of hydraulic coefficient on membrane performance for rejection of emerging contaminants
2018
International audience; The efficient removal of Endocrine Disruptive Chemicals (EDCs) namely oxybenzone and atrazine using polysulfone (PSf) composite membranes is reported in this article. A negatively charged hydrophilic mixed matrix membrane was prepared by using Polyaniline modified halloysite nanotubes (PANi-HNT) and polysulfone. The X-ray diffraction (XRD) and attenuated total reflectance infrared (ATR-IR) technique confirm the conversion of Halloysite nanotubes to Polyaniline modified halloysite nanotubes and their presence in membrane matrix. The microvoids observable in the SEM images depict the internal structure of the membrane. Further, increasing in the water uptake and decrea…
Contact probe pressure effects in skin multi-spectral photoplethysmography
2007
A novel technique ensuring parallel recording of reflection photoplethysmography signals in broad spectral range has been tested for assessment of pressure-induced vascular changes at various depths from the skin surface. PPG signals have been simultaneously detected at three combinations of the cw laser wavelengths 405 nm, 532 nm, 645 nm, 807 nm and 1064 nm. The PPG baseline responses to the probe-skin contact pressure changes and shapes of the PPG pulses originated from the same heartbeat but recorded at different wavelengths have been detected and analyzed.
Multi-wavelength photoplethysmography for simultaneous recording of skin blood pulsations at different vascular depths
2007
Parallel recording of reflection photoplethysmography (PPG) signals in broad spectral band has been performed, and potential of this approach for assessment of blood microcirculation at various vascular depths is discussed. PPG signals have been simultaneously detected at cw laser wavelengths sets comprising 405 nm, 532 nm, 645 nm, 807 nm and 1064 nm. Different signal baseline responses to breath holding at different wavelengths have been observed, as well as different shapes of the PPG pulses originated from the same heartbeat.
Spin polarization of magnetoresistive materials by point contact spectroscopy
2003
In the strive to find a straightforward method for determining the spin polarization, the analysis of the Andreev reflection process in point contact junctions has attracted much interest. However, the prerequisite for anevaluation of the transport spin polarization in this scheme is the existence of elastic (ballistic or diffusive) transport, which cannot be assumed a priori. We therefore also include inelastic processes in our analysis and exemplify that thermal effects can have a significant effect on data evaluation. As ferromagnetic samples with a predicted half metallic behavior and comparably low conductivity we used thin films of the double perovskite Sr 2 FeMoO 6 and bulk material …
Single-Element Reflective Digital Holographic Microscopy
2021
Digital holographic microscopy (DHM) is a well-known microscopy technique using an interferometric architecture for quantitative phase imaging (QPI) and it has been already implemented utilizing a large number of interferometers. Among them, single-element interferometers are of particular interest due to its simplicity, stability, and low cost. Here, we present an extremely simple common-path interferometric layout based on the use of a single one-dimensional diffraction grating for both illuminating the sample in reflection and generating the digital holograms. The technique, named single-element reflective digital holographic microscopy (SER-DHM), enables QPI and topography analysis of r…