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  • 1
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The kinetics of tetraphenylethylene radical cations in cyclohexane solutions investigated by nanosecond pluse radiolysis represents a model for an ion decay undisturbed by competing or subsequent reactions, i.e., it is caused only by pair and volume recombination of the solute ions. By dose variation it is shown that the ion decay is due to the interplay of these two processes.
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 3
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In the framework of a recently suggested recombination model it is shown that an increase of the initial ion concentration caused by higher irradiation doses leads to an increase of the fraction of ions recombining in the volume. This effect is represented for two different rate functions R/t/ assumed to describe the recombination rate for single ion pairs. Finally consequences of the volume recombination effect on the product yield of a competitive ion-scavenger reaction and for the determination of the real survival probability of the isolated ion pairs are discussed.
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  • 4
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sulfonamides with Heterocyclic Substituents as Extractants for Copper(II)With 2-picolylbenzenesulfonamide (N2NHO2SC6H5) as a model of the technical extractant LIX 34, the influence of functional variations on the extraction of copper(II) is studied and estimated by a comparison of the pH1/2 values.The relation pH1/2∼-σp is observed for extractants with substituents in p-position of the benzene ring. Turning to 2-pyridylethylbenzenesulfonamide, which forms six-membered rings, an increase of pH1/2 is observed. But no direct comparison is possible with 2-pyridylbenzenesulfonamide as the copper(II) complexes are dimeric having a structure analogous to copper(II) acetate. The substitution of the methylene group by an SO2-(PSA—H) or an NH-residue (PTSH—H) is connected with an with an increase of pH1/2 in the first case, but a decrease of pH1/2 in the second one (7,25 and 2,70). The application of PTSH—H as an extractant for copper(II) is confined by a slow redox reaction with this ion.π-electron delocalization within the chelate rings, which are derived from sulfonylhydrazones of heterocyclic ketones, is a factor which, in general, improves the extraction properties.There is a strong differentiation of PH1/2 (APSH—H 1,4; BBSH—H 6,9). An increase of the tetrahedral distortion of the chromophore CuN4, as it is indicated by ESR, measurements, is connected with a decrease of pH1/2.The benzenesulfonyl group influences the copper(II) extraction by bidentate nitrogen containing ligands in a twofold may: The protonation of the pyridyl and also that of other heterocyclic residues is rendered more difficult, but NH-acidity is increased. Some of the new extractants (APSH—H, BPSH—H) are as active as LIX reagents.
    Notes: Am Beispiel von 2-Picolylbenzensulfonamid (N2NHO2SC6H5), einem Modell des technischen Extraktanten LIX 34, wird der Einfluß funktioneller Veränderungen auf das Extraktionsverhalten gegenüber Kupfer(II) untersucht und zur Beurteilung der pH1/2 herangezogen.Bei Einführung von p-Substituenten am Benzenring erweist sich pH1/2∼-σp. Der übergang zu 2-Pyridylethylbenzensulfonamid (N3NHO2SC6H5), einem Sechsringbildner, ist mit einer Erhöhung von pH1/2 verbunden. Dagegen ist kein unmittelbarer Vergleich mit dem potentiellen Vierringbildner 2-Pyridylbenzensulfonamid möglich, weil die gebildeten Kupfer(II)-Komplexe eine dem Kupfer(II)-acetat analoge dimere Struktur haben.Die Substitution der Methylengruppe von N2NHO2SC6H5 durch einen SO2—(PSA—H) oder NH-Rest (PTSH—H) führt im ersten Fall zu einer Erhöhung, im zweiten zu einer Erniedrigung von pH1/2 (7,25 bzw. 2,70). Gegen den Einsatz von PTSH—H als Extraktionsmittel spricht eine langsame Redoxreaktion mit Kupfer(II).Die π-Elektronendelokalisierung in den Chelatringen, die sich von Sulfonylhydrazonen heterocyclischer Ketone ableiten, ist ein Faktor, der das Extraktionsverhalten im allgemeinen verbessert. Man findet eine starke Abstufung von pH1/2 (APSH—H 1,4; BBSH—H 6,9); der Wert sinkt mit wachsender tetraedrischer Verzerrung der ZKE CuN4 (Bestimmung durch ESR-spektroskopische Untersuchungen).Die Benzensulfonylgruppierung beeinflußt die Kupfer(II)-Extraktion mit zweizähligen stickstoffhaltigen Liganden in zweierlei Weise: Die Protonierung von Pyridin- und anderen heterocyclischen Stickstoffatomen wird erschwert, die NH-Acidität erhöht. Einige der untersuchten Extraktanten (APSH—H, BPSH—H) sind in ihrer Wirksamkeit mit den LIX-Reagenzien zu vergleichen.
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  • 5
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract From exposures of the CDHS detector at the CERN SPS we have obtained 367μ + μ − events in neutrino beams and 73μ + μ + events in an antineutrino beam. The magnitude of a prompt like-sign signal has been controversial in the past and moreover could not be explained by known production mechanisms. A critical discussion of the experimental situation is given. We have tried to reduce the systematic uncertainties of previous experiments and to get more information on the dependence of the signal with energy and the muon momentum cut-off. This experiment yields a signal of 2.8σ (2.4σ) of prompt like-sign dimuon events in the case of neutrinos (antineutrinos). The rate to charged current events is of the order of 10−4 forp μ〈9GeV andE〉100 GeV. The prompt signal has all the properties expected from the production and decay of charm-anticharm events. The magnitude, however, is substantially higher then the prediction of perturbative QCD but lower than some other experiments.
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  • 6
    ISSN: 0935-6304
    Keywords: Solvent effects ; Co-solvent effects ; Concurrent solvent evaporation ; Large sample volumes ; Coupled HPLC-GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept and some first results of a method are described for evaporating large volumes of solvent in a relatively short pre-column (retention gap) in such a way that solvent trapping retains volatile components in the inlet up to completion of solvent evaporation. The method was developed for transferring large volumes (easily exceeding 1 ml) of HPLC eluent to GC when using on-line coupled HPLC-GC, but is equally suited for injecting large sample volumes (at least some 50 μl) and could be particularly useful for introducing aqueous solutions.Concurrent solvent evaporation allows introduction of very large volumes of liquid into GC. However, peaks eluted up to some 40-80° above the column temperature during introduction of the liquid are strongly broadened due to the absence of solvent trapping. On the other hand, previous retention gap techniques involving solvent trapping were not suited for transferring very large volumes of liquid into GC. Using a relatively high boiling co-solvent added to the sample or the HPLC eluent, advantages of concurrent solvent evaporation can be combined with solute reconcentration by solvent effects, allowing elution of sharp peaks starting at the column temperature during introduction of the sample.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 1432-2048
    Keywords: Guard cell protoplast ; Photophosphorylation ; Stomatal opening, inhibition ; Tentoxin ; Vicia (guard cell)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fungal phytotoxin tentoxin and its natural derivative dihydrotentoxin impair light-induced stomatal opening in epidermal strips of broad bean (Vicia faba L.) incubated in a potassium-rich medium. Swelling of guard-cell protoplasts (GCPs) of the same species is inhibited in the presence of both substances. Swollen GCPs shrink after tentoxin or dihydrotentoxin treatment and these effects cannot be fully compensated by the phytoeffector fusicoccin. A comparison with the potassium carrier valinomycin shows that tentoxin acts in a different manner, because it is effective in the light only, whereas valinomycin causes shrinkage of GCPs also in the dark. Determination of adenine nucleotides in GCPs indicates a reduced ATP content and an enhanced ADP level after addition of tentoxin. At the same time, tentoxintreated GCPs contain more NADPH and less NAD+ than the control (NADP+ and NADH content does not differ). The results presented are consistent with the hypothesis that tentoxin closes stomata as a consequence of its inhibitory action on photophosphorylation.
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  • 8
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Investigations on the Creep Behaviour of a X 20 CrMoV 12 1 Bend, Fabricated by an Inductive Pipe Bending MachineA bend with a bend radius of 1700 mm -350 mm outer diameter and 25 mm wall thickness - of a X 20 CrMo V 12 1 steel, fabricated by an inductive pipe bending machine at 1050-900 °C deformation temperature was investigated. Heat treatment after fabrication: air cooling from 1050 °C, following a 2 hour annealing at 770 °C with air cooling. In addition to the usual mechanical and technological tests at ambient temperature and 530 °C, creep tests were conducted at 530 °C with unnotched and notched specimens. For comparison a straight pipe with the same dimensions was proofed, too.
    Notes: Ein Rohrbogen mit einem Biegeradius von 1700 mm - bei einem Rohraußendurchmesser von 350 mm und einer Wanddicke von etwa 25 mm - wurde aus dem warmfesten Röhrenstahl X 20 CrMo V 12 1, W.-Nr. 1.4922, nach dem Induktivbiegeverfahren bei einer Verformungstemperatur von 1050 bis 900 °C hergestellt. Die nachfolgende Wärmebehandlung erfolgte bei 1050 °C/Luft + 770 °C/2 h/Luft.Neben den üblichen mechanischen und mechanisch-technologischen Untersuchungen bei Raumtemperatur und bei 530 °C wurden auch Zeitstandversuche mit glatten und gekerbten Proben bei 530 °C durchgeführt. Zum Vergleich wurde auch ein gerades Rohr mit den gleichen Abmessungen zur Prüfung herangezogen.Alle ermittelten Werte entsprechen den Gewährleistungswerten. Rohrbogen und Rohr weisen auch nach langer Laufzeit noch hohe Werte der Duktilität auf.
    Additional Material: 9 Ill.
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Coupled HPLC-GC ; Loop-type interface ; Concurrent solvent evaporation ; PCBs in fish ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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