Corrections For Absorption Effects Research Articles

High-quality structures at high pressure? Insights from inclusions in diamonds

Abstract We describe the experimental protocols necessary to measure the crystal structures of minerals trapped within diamonds by single-crystal X-ray diffraction to the same quality as obtained from minerals studied at ambient conditions. The results show that corrections for X-ray absorption in complex cases can be made with good precision. Comparison of the refined structure of a single-crystal olivine inclusion inside a diamond with the structure of a similar olivine held in a high-pressure diamond-anvil cell shows that data resolution, not the correction for absorption effects, is the dominant factor in influencing the quality of structures determined at high pressures by single-crystal X-ray diffraction.

Effects of the Absorption Behaviour of ZnO Nanoparticles on Cytotoxicity Measurements

ZnO absorbs certain wavelengths of light and this behavior is more pronounced for nanoparticles of ZnO. As many toxicity measurements rely on measuring light transmission in cell lines, it is essential to determine how far this light absorption influences experimental toxicity measurements. The main objective was to study the ZnO absorption and how this influenced the cytotoxicity measurements. The cytotoxicity of differently sized ZnO nanoparticles in normal and cancer cell lines derived from lung tissue (Hs888Lu), neuron-phenotypic cells (SH-SY5Y), neuroblastoma (SH-SY5Y), human histiocytic lymphoma (U937), and lung cancer (A549) was investigated. Our results demonstrate that the presence of ZnO affected the cytotoxicity measurements due to the absorption characteristic of ZnO nanoparticles. The data revealed that the ZnO nanoparticles with an average particle size of around 85.7 nm and 190 nm showed cytotoxicity towards U937, SH-SY5Y, differentiated SH-SY5Y, and Hs888Lu cell lines. No effect on the A549 cells was observed. It was also found that the cytotoxicity of ZnO was particle size, concentration, and time dependent. These studies are the first to quantify the influence of ZnO nanoparticles on cytotoxicity assays. Corrections for absorption effects were carried out which gave an accurate estimation of the concentrations that produce the cytotoxic effects.

Direct deconvolution approach for depth profiling of element concentrations in multi-layered materials by confocal micro-beam X-ray fluorescence spectrometry

A new approach for the determination of element concentration profiles in stratified materials by confocal X-ray fluorescence spectrometry was elaborated. The method was based on a direct deconvolution of the measured depth-dependent X-ray fluorescence intensity signal with the established response function of the spectrometer. Since the approach neglects the absorption of primary and secondary radiation within the probing volume, it is applicable only to low absorbing samples and small probing volumes. In the proposed approach the deconvolution is performed separately for all detectable elements and it is followed by the correction of absorption effects. The proposed approach was validated by using stratified standard samples. The determined elemental profiles were compared with the results obtained by using existing analytical approaches.

Multiplex polarization spectroscopy of OH for flame thermometry

Σ-X2Π(0,0) band system. High resolution polarization spectra were also recorded in the same flame using a conventional, frequency scanned, narrow linewidth dye laser. Absorption effects were found to produce significant systematic errors in the temperatures derived from the unsaturated spectra produced by both multiplex and narrow linewidth scanning techniques. After correction for absorption effects, temperatures were derived from the single-shot multiplex spectra with a precision of 4% which agreed well with values obtained from scanned spectra and from the calculated adiabatic temperatures.

Energy-dispersive x-ray fluorescence analysis for sulphur, chlorine, potassium and calcium in aerosols

Problems in the use of x-ray spectrometry for the fast multi-element analysis of environmental samples such as aerosols collected on filters arise from absorption of the fluorescence intensity in the filter and in the collected matter. A procedure is described for the determination of the elements sulphur to calcium in aerosols collected on Whatman 41 filters. Two methods are compared for deconvolution of the spectra. These are based on counting in fixed energy channels or on non-linear least-squares analysis. Corrections for absorption effects have been calculated. Calibration is done with thin film standard deposits. The accuracy of the method is better than 15%. Difficulties in ascertaining the chlorine content of the filter are discussed. The evaporation of the chlorine fraction from the filter was studied in detail.

Rapid Quantitative Analysis by X-Ray Spectrometry

An x-ray fluorescence analysis method applicable to the case of fluorescent spectra excited with monoenergetic x-rays has been developed. The technique employs a minimum number of calibration steps using single element thin film standards and depends upon theoretical cross sections and fluorescent yield data to interpolate from element to element. The samples are treated as thin films and corrections for absorption effects are easily determined- Enhancement effects, if not negligible, are minimized by sample dilution techniques or by selective excitation.

A method for growing small spherical crystals of metals and alloys

A method of growth of small single crystals which are nearly perfect spheres is presented. The corrections for absorption effects in crystal diffraction peak measurements are most easily made with these crystals. Crystals of several dlfferent diameters are produced in one operation, and diffraction peak intensity data taken from crystals of different size give information concerning the relative importance of primary and secondary extinction effects. (J.R.D.)