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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 19 (1995), S. 362-365 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new temperature compensation technique for hot-wire anemometer is proposed in this article. In contrast to the available compensation techniques, a photoconductive cell is introduced here as a variable resistor in the bridge. The major advantage of adopting an active component such as photoconductive cell is that temperature compensation can be achieved by using any kind of temperature sensors, once the output of temperature sensor is given as a voltage. Validation experiments using a photoconductive cell with a thermocouple-thermometer are conducted in the temperature range from 30 to 50 °C and the velocity ranges from 8 to 18 m/s.
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  • 2
    ISSN: 1432-0649
    Keywords: 78.20.Hp ; 33.90.+h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract By means of photoacoustic spectroscopy it has been possible to detect U(IV) and U(VI) in aqueous solution in the 10−6 M/L range. Piezoelectric transducer detection, pulsed laser radiation and a differential method to reduce solvent and window absorption has been used. Photoacoustic spectroscopy seems to be a suitable method for the low level detection of actinide elements.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 737-745 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gel permeation chromatography (GPC) was applied for recognizing the origin of groundwater humic and fulvic acids. GPC was performed with Fraktogel TSK HW-50 in 0.1 M NaCl, pH 8.5 (0.05 M phosphate buffer), 1 mM EDTA, with 10% by volume methanol added. Humic substances from groundwaters and sediments of four different aquifer systems in Germany were isolated, purified and characterized. Both UV/Vis and fluorescence detection were applied. UV/Vis detection was found to be more powerful in identifying differences between the various humic and fulvic acids. The four aquifer systems investigated (“Gorleben”, “Fuhrberg”, “Franconian Albvorland” and “Munich”) differed from one another with respect to hydrological and geochemical conditions. The results showed that the GPC-elution behavior reflects the geochemical environment and origin (source material and generation process) of aquatic humic and fulvic acids.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 63 (1996), S. 299-306 
    ISSN: 1432-0649
    Keywords: PACS: 42.55; 42.80; 82.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract.  Laser-induced photoacoustic breakdown detection is applied for the determination of particles in aqueous dispersion. Polystyrene (latex), alumina and thoriasol particles of different sizes are investigated for demonstration. Laser pulses at 500 nm with 28 ns pulse width (FWHM), generated by an excimer (λ=308 nm) pumped dye laser, are focused into aqueous particle dispersions to produce breakdown. The dye laser pulse energy is fixed at a value lower than the breakdown threshold of pure water to initiate a dielectric breakdown only when particles are present in a given focus volume. Focus volume parameters and particle size dependent breakdown thresholds are calculated and the results are compared with data from literature. Dependence of breakdown threshold values on the chemical composition of the particles is determined for polystyrene, alumina and thoriasol particles.
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  • 5
    ISSN: 1432-0649
    Keywords: 78.20. Hp ; 33.90.+h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The oxidation-state specific detection of actinide ions, U(VI), Pu(IV), Pu(VI), and Am(III), was investigated by pulsed laser photoacoustic spectroscopy. With a single-beam differential technique, the solvent effect is compensated and thus the detection sensitivity substantially increased. The observed detection sensitivities are 8×10−7M/L for U(VI) 7×10−8M/L for Pu(IV) 3×10−8M/L for PU(VI) 2×10−8M/L for Am(III) The present method facilitates the study of complexation and polymerization of actinide ions in the submicromole concentration range.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 63 (1996), S. 299-306 
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.80 ; 82.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Laser-induced photoacoustic breakdown detection is applied for the determination of particles in aqueous dispersion. Polystyrene (latex), alumina and thoriasol particles of different sizes are investigated for demonstration. Laser pulses at 500 nm with 28 ns pulse width (FWHM), generated by an excimer (λ = 308 nm) pumped dye laser, are focused into aqueous particle dispersions to produce breakdown. The dye laser pulse energy is fixed at a value lower than the breakdown threshold of pure water to initiate a dielectric breakdown only when particles are present in a given focus volume. Focus volume parameters and particle size dependent breakdown thresholds are calculated and the results are compared with data from literature. Dependence of breakdown threshold values on the chemical composition of the particles is determined for polystyrene, alumina and thoriasol particles.
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  • 7
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Mono-Standard-Neutronen-Aktivierungs-Analyse großvolumiger Wasserproben ohne chemische Vorbehandlung wird zur Bestimmung anorganischer Spurenelemente in reinem Wasser, Flußwasser, Abwasser usw. eingesetzt. Die Richtigkeit, Genauigkeit und Empfindlichkeit der Methode wurden durch Analysen von Standard-Referenz-Material, eine Ringanalyse einer Wasserprobe und reinen Wassers überprüft. Die Methode wird zur Untersuchung des Verhaltens anorganischer Spurenelemente während des Reinigungsprozesses in einer Kläranlage angewandt. Die Verteilung der Elemente zwischen dem Abwasser und dem stabil suspendierten Schwebstoff wurde systematisch analysiert und das Verhalten der Elemente in dem System diskutiert.
    Notes: Summary Mono-standard neutron-activation analysis of large-volume water samples without preliminary chemistry is applied to the multielement determination of trace inorganic species in pure water, river water, urban effluent, etc. The accuracy, precision and sensitivity have been assessed by analysing a standard reference material, a water sample from a round-robin analysis and pure waters. The method is applied to investigate the behaviour of trace inorganic species in the course of the cleaning process in an urban sewage treatment plant. The distribution of the elements in the effluents and stably suspended materials has been systematically analysed and the behaviour of the elements in the system discussed.
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  • 8
    ISSN: 1572-8927
    Keywords: Sodium pertechnetate ; magnesium pertechnetate ; potassium pertechnetate ; osmotic coefficients ; activity coefficients ; solubility ; seawater system ; Pitzer model ; binary parameters ; mixing parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Isopiestic vapor pressure experiments are performed at 25°C with aqueous Mg(TcO4)2 solutions and with ternary mixtures containing various combinations of NaTcO4, Mg(TcO4)2, NaCl, MgCl2, Na2SO4, and MgSO4. The osmotic coefficients of the binary solutions are used to evaluate the binary Pitzer parameters β(0), β(1), and CΦ for Mg(TcO4)2. We previously reported these parameters for NaTcO4. The binary parameters for KTcO4 and Ca(TcO4)2 are evaluated from solubilities of KTcO4 in KCl and CaCl2 solutions, respectively. The mixing parameters Θ TcO 4 − /Cl −, ΨM/TcO 4 − /Cl −, Θ TcO 4 − /SO 4 2− , ΨM/TcO 4 − /SO 4 2− , and ΨNa + /Mg 2+ /TcO4 2− are calculated from either osmotic coefficients or solubilities in the corresponding ternary mixtures. The evaluated set of Pitzer parameters predicts well the activity coefficients and solubilities of KTcO4 in multicomponent systems.
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  • 9
    ISSN: 1572-8927
    Keywords: Ion product of water ; carbonic acid ; dissociation constants ; NaClO4 solution ; iomic strength ; activity coefficients ; Pitzer model ; mixing parameters ; solution thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The ion product of water and the dissociation constants of carbonic acid have been determined in 0.1, 1.0, 3.0, and 5.0M NaClO4 at 25°C. The ion product of water K w ' has been evaluated by emf measurements with a combined glass electrode in NaClO4 solutions containing 0.001–0.1M HCLO4 or NaOH. The product K H ' K l ' K 2 ' of the Henry constant for CO2 and the dissociation constants for H2CO3 have been determined by titration of carbonate solutions equilibrated with pCO2 =10−3.52 atm, and K 2 ' has been evaluated by potentiometric titration and by measuring the H+ concentration at fixed HCO 3 − and CO 3 2- concentrations. The ion interaction (Pitzer) equations are applied to describe the constants K w ' , K 2 ' and K H ' H 1 ' K 2 ' as a function of the NaClO4 concentration. The experimental data are used to evaluate the mixing parametersΘ i/ClO 4 andΨ i/ClO 4 -/Na+ fori = OH -,HCO 3 - andCO 3 2-
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  • 10
    ISSN: 1572-8927
    Keywords: Trivalent actinides ; curium ; americium ; solution thermodynamics ; carbonate complexation ; ionic strength ; Pitzer model ; concentrated solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The carbonate complexation reactions of Cm(III) were studied by time-resolved laser fluorescence spectroscopy in 0–6 m NaCl at 25°C. The ionic strength dependence of the stepwise formation constants for the carbonato complexes Cm(CO3) n 3−2n with n = 1, 2, 3, and 4 is described by modeling the activity coefficients of the Cm(III) species with Pitzer's ion-interaction approach. Based on the present results and literature data for Cm(III) and Am (III), the mean carbonate complexation constants at I = 0 are calculated to be: log β 101 o =8.1 ±0.3, log β 102 o =13.0 ± 0.6, log β 103 o =15.2 ± 0.4, and log β 104 o =13.0 ± 0.5. Combining these equilibrium constants at infinite dilution and the evaluated set of Pitzer parameters, a model is obtained, that reliably predicts the thermodynamics of bivalent actinide An(III) carbonate complexation in dilute to concentrated NaCl solution.
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