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41.
Barkleit A Tsushima S Savchuk O Philipp J Heim K Acker M Taut S Fahmy K 《Inorganic chemistry》2011,50(12):5451-5459
Thermodynamic parameters for the complexation of Eu(3+) with pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, BTC) as a model system for polymerizable metal-complexing humic acids were determined using temperature-dependent time-resolved laser-induced fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC). At low metal and ligand concentrations (<50 μM Eu(3+), <1 mM BTC), a 1:1 monomeric Eu-BTC complex was identified in the range of 25-60 °C. At elevated concentrations (>500 μM Eu(3+) and BTC) a temperature-dependent polymerization was observed, where BTC monomers are linked via coordinating shared Eu(3+) ions. The two methods lead to comparable thermodynamic data (ΔH = 18.5 ± 1.5/16.5 ± 0.1 kJ mol(-1); ΔS = 152 ± 5/130 ± 5 J mol(-1) K(-1); TRLFS/ITC) in the absence of polymerization. With the onset of polymerization, TRLFS reveals the water coordination number of the lanthanide, whereas calorimetry is superior in determining the thermodynamic data in this regime. Evaluating the heat uptake kinetics, the monomer and polymer formation steps could be separated by "time-resolved" ITC, revealing almost identical binding enthalpies for the sequential reactions. Structural features of the complexes were studied by Fourier-transform infrared (FTIR) spectroscopy in combination with density functional theory (DFT) calculations showing predominantly chelating coordination with two carboxylate groups in the monomeric complex and monodentate binding of a single carboxylate group in the polymeric complex of the polycarboxylate with Eu(3+). The data show that pyromellitic acid is a suitable model for the study of metal-mediated polymerization as a crucial factor in determining the effect of humic acids on the mobility of heavy metals in the environment. 相似文献
42.
Barkleit A Geipel G Acker M Taut S Bernhard G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):549-552
For the first time Am(III) complexation with a small organic ligand could be identified and characterized with time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature and trace metal concentration. With pyromellitic acid (1,2,4,5-benzene-tetracarboxylic acid, BTC) as ligand spectroscopic characteristics for the Am-BTC complex system were determined at pH 5.0, an ionic strength of 0.1 M (NaClO4) and room temperature. The fluorescence lifetimes were determined to be 23.2±2.2 ns for Am3+(aq) and 27.2±1.2 ns for the Am-BTC 1:1 complex; the emission maximum for the 5D1-(7)F1 transition is 691 nm for both species. The complex stability constant for the Am-BTC 1:1 complex was calculated to be logβ110=5.42±0.16. 相似文献
43.
In this paper we study the variability reduction gain that results from the use of multiweighing proceedings in packing processes
with the objective of sales at constant nominal weights. According to this, we have proposed a packing algorithm that includes
the formation of units with variable number of pieces and we have obtained the value of the percentage variability reduction
index.
Collaborator in the Catalan Institute of Tecnology (ICT). 相似文献
44.
Ch. Berger H. Genzel R. Grigull W. Lackas F. Raupach A. Klovning E. Lillestöl E. Lillethun J.A. Skard H. Ackermann F. Barreiro J. Bürger L. Criegee H.C. Dehne R. Devenish A. Eskreys G. Flügge K. Wacker 《Physics letters. [Part B]》1980,91(1):148-151
We have performed a search for narrow resonances in the center of mass energy range from 29.90 to 31.46 GeV using the e+e? storage ring PETRA at DESY. We present the total cross section for hadron production and an upper limit for resonance production, indicating that no bound state of charge- quarks exists in this energy range. 相似文献
45.
Paul Baret Eliezer Barreiro Andrew E. Greene Jean-Louis Luch Marco-Antonio Teixeira Pierre Crabbe 《Tetrahedron》1979,35(24):2931-2938
New allenic prostanoids 5c, d, 7,9c, and 15b have been prepared by total synthesis. In each case a cuprate-propargylic acetate reaction was used as the key step. 相似文献
46.
Summary In this paper we study the variability reduction gain in the production processes that require a process of packing with the
objective of sales at constant nominal weights. We have obtained the value of the percentage variability reduction index in
the packing processes of units formed by a fixed number of pieces attending to random packing and multiple weighting with
variable number of scaling pan packing criteria. These indexes have been obtained both for only one packing objective processe
and for double objective packing processes.
Collaborator in the Catalan Institute of Technology (ICT). 相似文献
47.
Ch. Berger H. Genzel R. Grigull W. Lackas F. Raupach A. Klovning E. Lillestöl E. Lillethun J.A. Skard H. Ackermann G. Alexander F. Barreiro J. Bürger L. Criegee H.C. Dehne R. Devenish A. Eskreys K. Wacker 《Physics letters. [Part B]》1980,95(2):313-317
Measurements of the charged multiplicities for hadron production in e+e? annihilation in the center of mass energy range 9–32 GeV have been made. The average charged multiplicity has an energy dependence much stronger than ln s and similar to that reported for pp collisions. Quantitative differences are observed in the magnitude of both the average multiplicity 〈nch〉 and the dispersion Dch for e+e? and pp interactions at the same center of mass energy. 〈nch〉 and the ratio 〈nch/Dch in e+e? annihilations are significantly larger than in pp collisions and are found to be in overall agreement with QCD predictions. KNO scaling is seen to be satisfied. 相似文献
48.
The aqueous solution chemistry of niobium is rather unexplored, and well characterized aqua complexes are scarce. In this work, a new niobium aqua ion is obtained upon treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of a sulfide source. The red aqua ion, obtained upon cation-exchange chromatography, forms readily the thiocyanate complex which has been crystallized as Cs(4.26)Na(1.74)[Nb4SO5(NCS)10] . 0.33H2O. X-ray crystallography revealed an unprecedented metal-metal bonded tetranuclear Nb4(mu4-S)(mu2-O)5(4+) core with a capping mu4-S ligand. 相似文献
49.
50.
Astrid Zürn Beatrice Rabolt Manfred Gräfe Helmut Müller 《Fresenius' Journal of Analytical Chemistry》1994,349(8-9):666-669
A photolithographically fabricated membrane for enzyme immobilisation based on an Ion Sensitive Field Effect Transistor (ISFET) is described. The preparation of an Enzyme-FET (ENFET) containing urease was successful. The ENFET has been used for the determination of urea and pesticides; this depends on the chosen enzyme level in the membrane and can be employed in a flow-injection system. The urea sensitive sensor (high enzyme load) has a wide linear range (1–500 mmol/l) a fast response (t95=20 s) and a lifetime greater than 30 days. The application of this sensor to the determination of urea in the waste water from a fertilizer plant and in blood serum is discussed. The second sensor (low enzyme level) was able to detect pesticides in water based on the inhibition of urease. The detection limit was found to be 0.1 µg/l for Carbofuran (10 minutes incubation time, without preconcentration). 相似文献