Search results for "absorption"
showing 10 items of 2701 documents
Electrothermal Atomic Absorption Determination of Chromium in Sediments
1999
Abstract An electrothermal atomic absorption spectrometric method has been developed to determine total chromium concentration in natural sediment samples. Samples were mineralized by dry ashing at 550°C and fused at 1100°C for 30 min with lithium metaborate. Dissolved samples were injected in graphite tubes, mineralized at 1100°C, and atomized at 2600°C. Standard addition calibration made unnecessary the use of chemical modifiers. The method provided a limit of detection from 23 to 45 ng liter −1 . The relative standard deviation for chromium determination was between 3 and 14%. Results obtained for a standard reference material agree well with the certified value. A series of natural samp…
Optical Properties of Natural and Synthetic Minerals
2015
The results of investigation of optical absorption and photoluminescence (PL) of topaz, beryl and yttrium aluminium garnet crystals doped with different concentrations of transition ions exposed to fast neutron irradiation and electron irradiation are presented. We suppose that irradiation leads to the formation of two types of complex centers: "Me2+-F+ (or F) centre" and complex centers, which consist of a cation vacancy and an impurity (iron, manganese and chromium) ion. Exchange interaction between radiation defects and impurity ions during neutron or electron irradiation gives rise to appearance of additional absorption and luminescence band broadening in investigated crystals.
The study of time-resolved absorption and luminescence in PbWO4 crystals
2000
Abstract The transient absorption and luminescence under pulsed electron beam excitation were studied for undoped and La3+ doped PbWO4 crystals. The absorption band at ∼1.0 eV is suggested to be due to self-trapped electrons and the absorption band at 3.5 eV may be due to self-trapped holes. The formation of luminescence centers via electron–hole recombination is affected by La3+ in doped crystals. The large fraction of electrons and holes undergoes thermostimulated recombination within geminate pairs and the spatial separation of geminate pairs components is important in recombination process. The intrinsic (blue) luminescence arises in this recombination. The mechanism of La3+ influence o…
Evaluation of Antimony, Cadmium and Lead Levels in Vegetables, Drinking and Raw Water from Different Agricultural Areas
1990
Abstract Lead and cadmium levels in edible vegetables and antimony, lead and cadmium in drinking and raw waters from three agricultural areas exposed to different levels of environmental pollution (1-high industrial pollution, 2-high urban pollution, 3-standard low industrial and urban pollution) are determined. The organic matter is destroyed by repeated attack with nitric acid. Cadmium and lead are determined by graphite furnace atomic absorption spectrometry (GFAAS) and antimony by hydride generation atomic absorption spectrometry (HGAAS). When the results obtained for three different areas are compared, differences between cadmium and lead contents in vegetables are observed. Waters are…
Quantification of cadmium-induced metallothionein in crustaceans by the silver-saturation method
1995
Metallothionein (MT) has been proposed as a specific biochemical probe for metal exposure of aquatic organisms. It is recognized that its usefulness as a monitoring tool depends on the full understanding of its function and on the possibility of measuring its concentration in tissues. Therefore the study of MT in crustaceans is interesting from two different points of view: the need to understand mechanisms associated with the toxicology of metals, and the potential use of this protein for monitoring metal-contamined environments. Several methods have been developed for quantitative measurements of MT in biological samples. Immunochemical and electrochemical procedures are reliable techniqu…
A surface EXAFS study of thin nickel deposits on (110) TiO2 surfaces
1997
Abstract The first stages of nickel deposition on a clean (110) TiO 2 surface were studied using surface extended X-ray absorption fine structure (EXAFS). Experiments were performed on two kinds of nickel deposits, one of 0.8 equivalent monolayers and another of 1.6 equivalent monolayers. Depositions were performed on well characterized TiO 2 (110)-p(1 × 1) surfaces. The correlation of Auger experiments with EXAFS results showed that no islands were present on the surface; only two-dimensional growth of nickel was observed. Moreover, it was shown, in the case of the thinner deposit, that a model with nickel atoms forming chains in the channels determined by oxygen atoms on the surface is co…
Electrostatic phenomena in ion exchange membranes
1971
Abstract Specific and transport properties of a cation and an anion exchange membrane in Na + and Cl - form respectively have been measured in water and dioxane water mixtures. A greater electrolyte absorption and a lesser specific conductivity and counterion transport number in solvents at higher dioxane content indicate strong electrostatic interactions between fixed groups in the membrane and counterions.
Measurement of the low-energy antideuteron inelastic cross section
2020
In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of th…
Research data supporting 'Short hydrogen bonds enhance nonaromatic protein-related fluorescence'
2021
Raw data for experimental figures. Files contain .cif (crystallographic information file) for XRD data of the L-pyro-amm structure. .xlsx file containing spectra for absorption of L-glutamine, L-pyroglutamine and L-pyro-amm. .xlsx file contains spectra for fluorescence excitation and emission collected over 8 days for L-glutamine conversion to L-pyro-amm.