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  • 11
    Electronic Resource
    Electronic Resource
    Activation analysis of selenium in cancer research (1995)
    Springer
    Journal of radioanalytical and nuclear chemistry 195 (1995), S. 91-95 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The method described in a previous work to separate trace amounts of selenium in organic samples without using a carrier, based on the adsorption on active carbon filters of the complex formed with ammonium pyrrolidindithiocarbamate (APDC) at pH 1.5–2, has been applied to urine samples from 15 females patients suffering from cervical uterine cancer. With this type of sample the method reaches a maximum sensitivity (few ppb) with a good statistical variation (±12%). Since the highest concentration of selenium in human tissues is found in the kidney, and the elimination of this element is mainly by the urine, the method seems to be a powerful tool in the research about the human metabolism of selenium. This paper shows a possible relation of selenium concentration in human urine and the evolution time of cervical uterine cancer, in spite of limits imposed by the statistical error plus the inhomogeneity of the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02036477
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  • 12
    Electronic Resource
    Electronic Resource
    Interaction of uranyl ions with snake venom proteins fromLachesis muta muta (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 223 (1997), S. 187-191 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The reaction product of uranyl nitrate with whole-protein Bushmaster snake venom in nitrate buffer at pH 3.5 has been studied. The maximum uptake of uranium was 291 μmol U·g−1 of venom. The infrared spectrum of the product showed an asymmetric O−U−O vibration at 921 cm−1 typical of complex formation with the uranyl ion. Stability measurements with the UO 2 2+ -protein complex in neutral medium indicated moderate hydrolytic stability, with 14% dissociation after 16 hours at 0°C. Neutron irradiation and desorption studies with a235U-labelled complex showed that generated fission products such as lanthanides and barium were readily lixiviated at pH 7, whereas Ru and Zr were highly retained by the protein substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223382
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  • 13
    Electronic Resource
    Electronic Resource
    Activation analysis of Se in biological samples through75Se and77mSe (1990)
    Springer
    Journal of radioanalytical and nuclear chemistry 145 (1990), S. 445-452 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method is described to separate trace amounts of selenium in biological samples without using a carrier. This method is based on the adsorption on active carbon of the complex ion formed with APDC /ammonium salt of l-pyrrolidine carbodithioic acid/ at pH 1. The efficiency of the radiochemical separation described is measured by using carrier-free75Se labelled solutions of sodium selenite at selenium concentrations from 3.5×10−8 to 3.5×10−11 g ml−1. The results were between 95% and 98% with statistical variations from 2% to 10%. The determination of selenium can be made following this separation either through75Se in the traditional way, or through77mSe if the separation is performed prior to irradiation. The detection limits on the available conditions were 0.01 ppm for75Se and 0.1 ppm for77mSe. When the analysis is performed through75Se /t=120 d/, the statistical error is notably smaller because the counting time may be considerable, whereas through77mSe/t=17.5 s/it is higher than 20%, depending on the concentration and the available neutron flux. However, the advantages of gaining time and the fact of performing the trace separation from a non radioactive material, make both procedures competitive as useful tools for the research on the function of Se in vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02163717
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  • 14
    Electronic Resource
    Electronic Resource
    Activation analysis of selenium in organic samples, through selenium-77m, on a pre-separation basis (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 168 (1993), S. 15-21 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method is described to separate trace amounts of selenium in organic samples without using a carrier, based on the adsorption on active carbon filters of the complex formed with APDC at pH 1.5. The separation is made prior to the neutron irradiation and the correction for selenium in the reagents performed by the irradiation of a blank. The method has been successfully used in fodder samples as well as some other organic reference materials, using a fast pneumatic transfersystem, which takes the samples from the irradiation position to the counting position in 3s, with the only limitation of the thermal neutron flux available, 4.7·1011 cm−2·s−1. Detection limits of 0.1 μg are obtained under these experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02040873
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  • 15
    Electronic Resource
    Electronic Resource
    Relationship between the cervical uterine cancer evolution and selenium concentration in urine determied by NAA (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 217 (1997), S. 167-169 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Neutron activation analysis of Se in urine reaches an optimum sensitivity (few ppb) and precision (±12%) when the traces are complexed without using a carrier by ammonium pryrrolidindithiocarbamate (APDC) at pH 1.5–2 and adsorbed on activated carbon filters. In this way the selenium traces analysis have been carried out through77mSe in 45 urine samples on a pre-separation basis by cyclic activation ofthe carbon filters. The selenium concentration in our blanks is virtually zero, because APDC proved to be selnium free and selenium mass in 50 mg of activated carbon used as a filter is 20 times below our qualitative detection limit and 144 times below our quantitative detection limit. The samples were first of day urine from healthy and ill women suffering cervical uterine cancer, at different evolution stages: incipient, intemediate and advanced, with no treatment, and surgery, radiotherapy, chemotherapy, or a combined treatment. The results show a consistent tred to increase the selenium trace concentration during the intemediate stage, whereas it is the same than nomal for incipient cases, and it decreases to the lowest concentrations for advanced cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02034436
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  • 16
    Electronic Resource
    Electronic Resource
    Influence of central metal and ligand system on conduction type and charge carrier transport in phthalocyanine thin films (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 6 (1996), S. 239-244 
    Details
    ISSN: 1057-9257
    Keywords: molecular semiconductors ; organic semiconductors ; phthalocyanines ; conductivity ; thermopower ; seebeck effect ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: By changing the chemical composition of phthalocyanine molecules, the electrical properties of the ensemble in the solid state can be influenced directly. This is shown for phthalocyaninatomanganese (PcMn) as compared with purely divalent central metals and for complexes in which the ligand system has been modified by either electron-withdrawing heteroatoms such as N instead of CH leading to tetrapyridotetraazaporphyrinatozinc (TPyTAPZn) or substituents such as F instead of H leading to hexadecafluorophthalocyaninatozinc (F16PcZn). The accessibility of additional oxidation states of Mn or the stabilisation of frontier orbital states by the ligand leads to a lower ionisation potential and interactions with impurities or dopant molecules are changed. A change in the observed majority carrier (n-type behaviour) is seen even under UHV conditions. Measurements of the thermoelectric power and electrical conductivity are presented of the pure films and after exposure to oxidising ambient. During film growth either island growth or a growth following the Stranski-Krastanov mechanism was observed. The comparison of the temperature dependence of thermopower and electrical conductivity leads to a discussion of the type of majority carriers, their generation as well as their transportation. For the materials investigated in this study the band model fails to explain the observed properties and a localised transport mechanism has to be considered. A transport in localised states close to the Fermi edge is discussed for TPyTAPZn and F16PcZn.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Numerical calculation of profiles corresponding to given pressure distributions (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 4 (1988), S. 767-772 
    Details
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The pressure distribution over the profile of a body in fluid flow influences the forces, moments and flow separation on it. It is therefore often advantageous to design a profile in such a way that a predetermined pressure distribution is obtained over the final profile. In this paper a numerical procedure is proposed for calculating the profile corresponding to a given pressure distribution. The procedure employs a transformed version of the potential flow equation for the stream function, which makes the method very effective. Predicted profiles are verified against an analytical solution and against the profile of a NACA 0015 aerofoil. The measured pressure distribution on a calculated axisymmetrical profile is also found to compare favourably with its prescribed pressure distribution.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1630040610
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