IMMOBILIZATION OF THALLIUM BY TANDEM OXIDATION REDUCTION COMPLEXATION OF THALLIUM(I/III)

Development of management procedures for toxic superconducting thallium-copper-alkaline earth ceramics and their byproducts requires better understanding of the complexometric chemistry of thallium in the presence of copper and alkaline earth cations. This study reveals that thallium can be immobilized as a thallium-rich mixed-valence solid[(Tl18c6)4CuCl4][TlCl4]2.nH2O(1, n = 0; 2, n = 0.25). When either Tl(I) or Tl(III) is treated with 18-crown-6 (18c6) in the presence of copper(II) (or zinc) chloride, tandem oxidation (or reduction) complexation occurs to an extent sufficient to form 1 and/or 2. The divalent transition metal ion (M) plays a beneficial role of concentrating Tl+ as a cation [(Tl18C6)4MCl4]2+, M = Cu or Zn. The template concerted reduction/oxidation-complexation reactions appear to take advantage of the high stability of the TlC14 anions. Similar complexes are obtained if Cl- is replaced by Br-, Tl+ by Rb+, and Cu2+ by Mn2+ and Co2+. The crystal structures of 1, 2, (Rb18c6)2Cu2Cl6 (5), and (Ba18c6)2(CuCl4)2-3H2O(6) along with solid-state thallium-205 NMR spectra of 1,2,[(Tl18c6)4ZnCl4][TlCl4]2 (3), and [(Rb18c6)4CuCl4][TlCl4]2 (4) are reported. The cubic (F23) complexes 1, 2, and 4 feature a room-temperature average T(d) geometry for CuCl42- anions, and the T(d) nature (required by symmetry) of the position it occupies is confirmed by the luminescence of T(d) MnCl42- and the blue color of T(d) CoCl42- ions substituting for CuCl42- species. Crystal data are as follows. 1: cubic, space group F23 with a = 20.728 (2) angstrom, V = 8905.1 (9) angstrom3, and Z = 4; with 661 reflections having I &gt; 1-sigma(I), R = 0.038. 2: cubic, space group F23 with a = 20.748 (5) angstrom, V = 8932 angstrom3, Z = 4; with 549 independent reflections having \F(o)\ &gt; 3-sigma(\F(o)\), R = 0.043. 5: monoclinic, space group P2(1)/c with a = 11.100 (2) angstrom, b = 8.168 (1) angstrom, c = 22.626 (5) angstrom, beta = 97.55 (2)-degrees, V = 2034 angstrom3, and Z = 2; with 2456 reflections (\F(o)\ &gt; 3-sigma(\F(o)\)), R = 0.042. 6: triclinic P1BAR with a = 8.757 (3) angstrom, b = 17.174 (5) angstrom, c = 17.616 (6) angstrom, alpha = 66.23 (3)-degrees, beta = 77.31 (3)-degrees, gamma = 75.71 (2)-degrees, V = 2327.9 (13) angstrom, and Z = 2; using 6214 reflections (I &gt; 3-sigma(I)), R = 0.051.</p

Effect of aging on transpyloric flow, gastric emptying, and intragastric distribution in healthy humans - Impact on glycemia

The original publication is available at www.springerlink.comThe aims of this study were to evaluate (i) the relationship between transpyloric flow (TF) assessed by Doppler ultrasonography and scintigraphy, (ii) the effects of healthy aging on TF and gastric emptying (GE), and (iii) the relationship between the glycemic response to oral glucose and TF. Ten healthy "young" (7 M, 3 F) and 8 "older" (4 M, 4 F), subjects had simultaneous measurements of TF, GE, and blood glucose after a 600-ml drink (75 g glucose labeled with 20 MBq 99mTc-sulfur colloid) while seated. TF measured by ultrasound was measured during drink ingestion and for 30 min thereafter. GE was measured scintigraphically for 180 min after drink ingestion. Blood glucose was measured before the drink and at regular intervals until 180 min. During drink ingestion, TF was greater (P < 0.05) and GE faster (retention at 60 min: 70.8+/-3.3 vs. 83.8+/-4.6%; P < 0.05) in young compared to older subjects. There was no difference in fasting blood glucose between the two groups but the magnitude of the rise in blood glucose was greater in the young compared to the older subjects; (at 15 min 2.4+/-0.3 vs. 1.5+/-0.5 mmol/L; P < 0.05). In contrast, after 90 min blood glucose concentrations were higher in the older subjects. There were significant relationships between the early blood glucose concentration and both TF (e.g., at 15 min: r = 0.56, P < 0.05) and GE (e.g., at 15 min: r = -0.51, P < 0.05). In conclusion, the results of this study indicate that (i) TF is initially less, and GE slower, in older compared to young subjects; (ii) the initial glycemic response to oral glucose is related to TF; and (iii) measurements of TF by ultrasound and scintigraphy correlate significantly.Deirdre O'Donovan, Trygve Hausken, Yong Lei, Antonietta Russo, Jennifer Keogh, Michael Horowitz and Karen L Jone