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  • 1
    Electronic Resource
    Electronic Resource
    Microscopic characterization of low-field switching in ferroelectric triglycine sulfate (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3802-3805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-field (〈1 kV/cm) switching has been investigated for thin plates (0.06〈d〈0.15 cm) of triglycine sulfate by means of field pulses with a linear rise time. The dependence of the maximum current density, jm, with the field value Em at which this maximum occurs is jm≅B1(Em−Ecw1)3/2, for 0.3〈Em〈0.5 kV/cm, and jm≅B2(Em−Ecw2), for 0.5〈Em〈1.0 kV/cm. This is satisfactorily explained taking into account the dominant role played by sidewise and forward domain wall motion, respectively. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368590
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  • 2
    Electronic Resource
    Electronic Resource
    Liver injury caused by ebrotidine: a new example of the utility of the postmarketing surveillance (2000)
    Springer
    European journal of clinical pharmacology 56 (2000), S. 187-189 
    Details
    ISSN: 1432-1041
    Keywords: Key words Ebrotidine ; Liver injury ; Post-marketing surveillance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050739
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  • 3
    Electronic Resource
    Electronic Resource
    Classification of ancient Roman glazed ceramics using the neural network of Self-Organizing Maps (2000)
    Springer
    Fresenius' journal of analytical chemistry 367 (2000), S. 586-589 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artificial neural networks with unsupervised learning strategy known as Self-Organizing Maps were applied to classify ancient Roman glazed ceramics. Their clay ceramic bodies were analyzed by Inductively Coupled Plasma-Atomic Emission Spectroscopy and the chemical composition obtained was processed by this neural algorithm. The results obtained provide two types of information: firstly, classification of ceramic samples with identification of several groups and secondly, differentiation between the elemental chemical information. It was found that there are certain chemical elements which can be considered as principal and which can serve to differentiate between ceramics, whereas other elements give redundant information and do not contribute to sample differentiation. Seven chemical elements were considered principal and provide the necessary information. Two types of element were identified: 1 – a group formed by common elements, such as: Ca, Fe, Mg, Mn and 2 – another formed by optional elements: K or Na and Ba or Sr and Al or Ti.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000433
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of on-line coupling size exclusion chromatography electrothermal atomic absorption spectrometry for selenium speciation (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 837-843 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Chromatographic effluents were on-line analyzed by Zeeman-ETAAS, using a flow-through cell placed in a graphite furnace autosampler as interface. To obtain high sampling rates, the use of fast graphite furnace programmes was studied. Conventional programmes of 96 s were reduced to 18 s by using hot injection (120 °C) and reducing the charring step to 2 s. The increase of the injection volume from 20 to 60 μl lengthened the programme to 46 s. Nickel had to be added to get a comparable response for both inorganic and organic selenium species (selenite and selenomethionine) and to reduce the interferent effect produced in presence of the chromatographic eluent (TRIS 0.01 mol l-1, NH4NO3 0.1 mol l-1, pH 7). The optimized conditions were applied to the speciation of selenium in human erythrocyte lysates by size exclusion LC-ETAAS. Using a high performance size exclusion column selenium could be assigned to proteins of 100 and 35 kDa. Detection limits in the range of 1 ng (2 μg l-1 for 500 μl injection volume) were obtained for the combined technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050259
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of direct-bilirubin by a fluorimetric-enzymatic method based on bilirubin oxidase (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 516-521 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method for the determination of direct bilirubin by reaction with bilirubin oxidase (BOx) is reported. The procedure is based on the changes in fluorescence which take place during the enzymatic reaction of BOx with any of the three forms of bilirubin (free, conjugated and with albumin) when the solution is excited at 240 nm and the emission is measured at 440 nm. The change in fluorescence was studied thoroughly. It seems mainly due to the fluorescence of one of the reaction products. A theoretical study was carried out to relate the changes in fluorescence observed to the species taking part in the reaction and to establish some of the enzymatic reaction constants. The optimum reaction conditions were studied for each of the three types of bilirubin together with their analytical characteristics (linear range and precision). Selective determination of direct bilirubin was carried out for various synthetic samples with good results. A linear response up to 7 mg L–1 of direct bilirubin was obtained. Using optimum conditions, the precision for free and conjugated bilirubin was 3.4% (n = 5) and 3.0% (n = 5), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000503
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  • 6
    Electronic Resource
    Electronic Resource
    Electrocatalytic behaviour of several cobalt complexes: Determination of hydrazine at neutral pH (1997)
    Springer
    Journal of applied electrochemistry 28 (1997), S. 65-70 
    Details
    ISSN: 1572-8838
    Keywords: carbon paste electrode ; mediator ; electrocatalysis ; hydrazine ; cobalt complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Four cobalt complexes (cobalt(II) acetylacetonate and 8-hydroxyquinolinate and cobalt(III) 8-hydroxyquinolinate and diethyldithiocarbamate) were tested as mediators to modify carbon paste electrodes with a view to obtaining a catalytic effect for the hydrazine. Cobalt(II) acetylacetonate was found to exert no catalytic effect as the likely result of ligand having to stabilize higher oxidation states of Co potentially involved in the catalytic process. The effects of the electrolyte and pH were examined and found to be important. The proposed chronoamperometric determination for hydrazine features limits of detection at the 99% confidence level of 1.6mM with cobalt(III) diethyldithiocarbamate, 1.5mM with cobalt(III) 8-hydroxyquinolinate and 2.0mM with Co(II) 8-hydroxyquinolinate. The RSD for 2mM hydrazine was always less than 8%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003249802216
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  • 7
    Electronic Resource
    Electronic Resource
    Study of a system for introducing metal chelate complexes in AAS (1988)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 332 (1988), S. 37-40 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The possibility of extending the sampling of volatile phases in AAS by use of metal beta-diketonates is considered. An electrically heated system was designed in which the chelate was injected, volatilized and then carried by a nitrogen stream to a silica tube, which was heated with an air-acetylene flame. The method was investigated for Cr, Zn and Mn using acetylacetone as chelating agent. The introduction of volatile chelates gives an increase in sensitivity with respect to the nebulization and atomization of solutions in the flame. This sampling system is limited to metallic chelates which are thermally stable and sufficiently volatile. The partial decomposition, which Zn acetyl-acetonate and, particularly Mn acetylacetonate undergo, causes a reduction in the sensitivity and precision of the determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00487027
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  • 8
    Electronic Resource
    Electronic Resource
    Some observations on the mechanisms for stabilization of chromium in graphite furnace-atomic absorption spectrometry (1988)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 332 (1988), S. 783-786 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Graphite atomization mechanisms of chromium in a graphite furnace are briefly reviewed and the influence of some compounds on stabilization of the analyte is investigated. For this purpose, charring curves for various salts and solvents were obtained. Elements which from stable oxides stabilize chromium oxide, avoiding losses of the volatile suboxide. Elements which form carbides and the organic solvents depress the signal due to the formation of chromium carbide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01129775
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  • 9
    Electronic Resource
    Electronic Resource
    Application of the ligand vapour technique to the volatilization of unstable chelate compounds (particularly iron(III) trifluoroacetylacetonate) in AAS (1990)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 338 (1990), S. 721-725 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes a method for volatilizing chelate complexes in AAS using a carrier gas containing ligand vapour in order to prevent chelate decomposition on heating. The method is evaluated with iron(III) trifluoroacetylacetonate. The sample containing chelate is injected into an electrically heated system, and is carried by nitrogen gas containing trifluoroacetylacetone H(TFA) to a silica tube where atomization occurs. This system increases the reproducibility of atomic absorption signals and decreases the high blanks which occur with the conventional method as a result of chelate decomposition. The characteristic mass of the combined analytical procedure is 1.30 ng Fe, the detection limit 12.0 ng Fe, and the relative standard deviation is 4.7% ng Fe (n=10). Sensitivity is improved 16-fold with respect to the system involving conventional nebulization and atomization of aqueous solutions in air-acetylene flame.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323413
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of chromium by AAS using volatileβ-diketonate complexes (1987)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 328 (1987), S. 56-60 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method is proposed for the determination of chromium, which is based on atomizing the volatile phase, generated from itsβ-diketonates, in a silica tube. For this purpose, an electrically-heated volatilization system was designed, in which the chelate is injected and volatilized, and then carried by nitrogen to the silica tube, which is heated with an air-acetylene flame. The system parameters were optimized and the analytical characteristics established, the following values being obtained: characteristic mass (measuring area under peak) 0.15 ng, reproducibility (expressed as the relative standard deviation) 5.6%, and linearity up to 25 ng. The results obtained were compared with those found when atomizing solutions ofβ-diketonates in an air-acetylene flame and in a graphite furnace. Atomization of chromiumβ-diketonates (after first volatilizing them) increases the sensitivity 54-fold as compared with the nebulization of aqueous solutions of dichromate with atomization in the flame.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00560948
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