Search results for "thermal [correlation function]"
showing 10 items of 1923 documents
Ultratrace analysis and isotope ratio measurements of long-lived radioisotopes by resonance ionization mass spectrometry (RIMS).
2003
Resonance Ionization Mass Spectrometry (RIMS) is a sensitive and selective method for ultratrace analysis of long-lived radioisotopes and isotope ratio measurements. It provides extremely high isobaric suppression and good overall efficiency. The experimental limits of detection are as low as 10(6) atoms per sample and isotopic selectivities of 5x10(12) have been obtained. The widespread potential of RIMS, using different experimental arrangements, is demonstrated for the determination of the radiotoxic isotopes Pu-238 to Pu-244 and Sr-89/Sr-90 in various environmental samples as well as for Ca-41 in nuclear reactor components and biomedical samples.
Resonance ionization mass spectrometry for ultratrace analysis of plutonium with a new solid state laser system
2004
Abstract Resonance ionization mass spectrometry (RIMS) is well-suited for isotope selective ultratrace analysis of long-lived radioactive isotopes due to its high element and isotope selectivity and good sensitivity. For the analysis of plutonium with a pulsed RIMS apparatus, a powerful, reliable and easy to handle Nd:YAG pumped titanium–sapphire laser system has been developed and combined with a time-of-flight mass spectrometer. Spectroscopic measurements led to an efficient three step excitation and ionization scheme for plutonium with λ1 = 420.76 nm, λ2 = 847.28 nm, and λ3 = 767.53 nm. The isotope shifts in this scheme for the plutonium isotopes 238 Pu through 244 Pu have been determine…
Recent developments in isotope ratio measurements by resonance ionization mass spectrometry
2005
Resonance ionization mass spectrometry (RIMS) has become a sensitive and highly selective technique for the determination of extremely low elemental or isotopic abundances, involving isotope ratio measurements with dynamical ranges of 109 and beyond. The experimental detection limits are as low as 106 atoms per sample, and isotopic selectivities of up to 1013 have been achieved under optimal conditions. The potential of RIMS using different experimental systems is outlined in the determination of lowest abundances and isotope ratios of long-lived radioisotopes of general importance like Pu238–244, 41Ca, and 236U for studies in geosciences, environmental, bio-medical or fundamental research.
Resonance ionization mass spectrometry for trace analysis of long-lived radionuclides
2008
Resonance ionization mass spectrometry (RIMS) is a sensitive and selective method for the determination of extremely low abundances of long-lived radionuclides. The detection limits are about 106 atoms per sample and an isotopic selectivity up to 1013 has been achieved. The potential of RIMS using different experimental arrangements is outlined for the determination of isotope ratios and lowest abundances of long-lived radioisotopes of interest like 238–244Pu, 90Sr, and 41Ca. Recent developments in improving detection limits and the spatial resolution of this technique are briefly discussed.
Use of thermal ionization isotope dilution mass spectrometry (TI-IDMS) as an oligo-element method for the determination of photographically relevant …
1998
Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used as an oligo-element method for the determination of Cr, Cd and Pb in photographic AgCl emulsions. After addition of an appropriate amount of isotopically enriched spikes (53Cr, 116Cd and 206Pb) to the solid samples, the latter were completely dissolved in NH3 solution, permitting isotopic exchange to take place. Thereafter, AgCl was selectively removed by precipitation, whereby ultrasonic treatment was used to enhance the recovery of the elements of interest. Despite the use of concentrated HNO3 and H2O2 during further sample processing, preliminary experiments indicated the presence of a substantial remainder of the o…
Identification of ground water contaminations by landfills using precise boron isotope ratio measurements with negative thermal ionization mass spect…
1997
Precise boron isotope ratio measurements with negative thermal ionization mass spectrometry were used for the identification of ground water contaminations by leakages of landfills. BO 2 - thermal ions were produced to determine the 11 B/ 10 B isotope ratio, which was expressed as δ 11 B value in ‰ normalized to the standard reference material NIST SRM 951. For example, household waste influences the boron isotope ratio by specific components such as washing powder. In the case of one investigated landfill low δ 11 B values correlate well with high boron concentrations in contaminated seepage water samples and vice versa for uncontaminated ground water samples. Possible boron contributions …
Thermal lens spectrometric determination of cerium with oxine
1991
Abstract The spectrophotometric and photothermal (TLS) procedures for cerium determination using 8-hydroxyquinoline (oxine), after extraction into chloroform, are compared. Photothermal measurements are made using a coaxial pump/probe thermal lens spectrometer. The use of high-purity reagents at low concentrations permits a decrease in the TLS blank signal and noise, leading to a limit of detection of 9 × 10−9 M (cerium extract concentration), 40-fold lower than the spectrophotometric value. The dynamic range extended up to 6 × 10−7 M and the relative standard deviation for 5 × 10−7 M cerium was 3.9%.
Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites
2017
[EN] The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from - 130 degrees C to 130 degrees C) and frequency ranges (from 10(-2)-10(7) Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulc…
Thermal studies of sulphonamide derivative complexes
1991
Abstract A thermal study of a new series of acetazolamidate complexes of Co(II), Ni(II) and Cu(II) using the TG, DTG and DTA techniques in flowing air, static air and N 2 atmospheres is described. From the TG-DTG and DTA curves, different thermal behaviours can be observed. Although in all the complexes the processes of dehydration, deammination and pyrolysis can be clearly observed, in some cases they appear as several well-separated steps and, in others, as continuous stages which take place simultaneously. The differences observed between the pyrolytic decomposition in flowing air and in nitrogen are described. In flowing air, metal sulphate is formed from the thiadiazole ring, except fo…
Development of a new peat-based oil sorbent using peat pyrolysis
2013
The growing use and transport of crude oil and oil products has led to increasing numbers of oil spillages of various scales. Oil sorbents have been extensively used for remediation of the consequences of such accidents. The aim of this study is to investigate the possible use of peat and its thermal treatment products for oil sorption. Peat as an oil sorbent has poor buoyancy characteristics, relatively low oil sorption capacity and low hydrophobicity. However, thermal treatment (low-temperature pyrolysis and synthesis of peat-based activated coal) helps to significantly improve its sorptive characteristics. Peat is a potential material for oil sorption because it has such advantages as lo…