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The scope of the univalent gallium salts [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − and the new completely characterized [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al(OR F ) 4 ] − (R F = C(CF 3 ) 3 ) was investigated in terms of initiating or catalyzing the synthesis of highly reactive poly(2-methylpropylene)highly reactive polyisobutylene (HR-PIB)in several solvents. A series of polymerization reactions proved the high efficiency and quality of the univalent gallium salts for the polymerization of isobutylene. The best results were obtained using very low concentrations of [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − (down to 0.007 mol%) while working at reaction temperatures of up to ±0 °C and in the noncarcinogenic and non-water hazardous solvent toluene. Under these conditions, HR-PIB with an α-content of terminal olefinic double bonds up to 91 mol% and a molecular weight of 1000−2000 was obtained in good yields. Upon changing [Ga(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − for the electron richer [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al-(OR F ) 4 ] − , polymerization temperatures could be increased to +10 °C. The reactivity of the gallium(I) cations therefore seems to be tunable through ligand exchange reactions. Experimental results, density functional theory calculations, and mass spectrometric investigations point toward a coordinative polymerization mechanism. Article pubs.acs.org/Organometallics

SUMMARY We investigated the possibility that loperamide might influence absorption and secretion in the human jejunum in vivo. Using a triple lumen tube perfusion technique in healthy normal volunteers we showed that loperamide did not affect net absorption of water or electrolytes under basal condition. When secretion was induced by prostaglandin E2, however, loperamide significantly reduced that secretion and in three out of six subjects secretion was abolished. Loperamide was effective when it was given either before or after secretion had been initiated. The results lend support to the suggestion that the antidiarrhoeal activities of loperamide may include an antisecretory effect. screening. The mixing segment was 15 cm long, the test segment 30 cm and the infusion rate 10 ml/min. In basal studies the equilibration period was 40 minutes and the test period one hour. In experiments with prostaglandin E2 (PGE2) the equilibration period was 30 minutes and the test period 40 minutes. During test periods jejunal aspirate from the proximal end of the test segment was collected by suction with a hand held syringe at a rate of 1.5 ml/min. Aspirates from the distal end of the segment were collected by continuous low grade suction. At 15 minute intervals small samples of aspirate were withdrawn and used to measure pH and pCO2 for the calculation of bicarbonate concentration.Two perfusion solutions were used, one contained bicarbonate (Na, 135; K,5; Cl, 105; HCO3, 35; mmolI1) and the other was bicarbonate-free (Na, 135; K,5; Cl, 140; mmol/l). Both perfusates contained polyethylene glycol 4000 (PEG) 2 gm/l and 14C PEG 0 5 ,uCi/l as a non-absorbable marker.Loperamide solution was administered intraluminally as a bolus of 4 mg or 8 mg followed half an hour later by perfusion with a solution containing loperamide (3 mg/l or 6 mg/l). In control periods the same volumes of a placebo solution were given. PGE2 was administered intraluminally by adding it to the perfusate in a final concentration of 5x10-6M.Transit time was assessed by noting the time taken for a 1-5 ml bolus of bromsulphthalein dye (BSP) to pass along the 30 cm segment as previously described. The infusion rate was measured at the beginning and end of the experiment.

SUMMARYEchinoderms are important components of deep-sea communities because of their abundance and the fact that their activities contribute to carbon cycling. Estimating the echinoderm contribution to food webs and carbon cycling is important to our understanding of the functioning of the deep-sea environment and how this may alter in the future as climatic changes take place. Metabolic rate data from deep-sea echinoderm species are, however, scarce. To obtain such data from abyssal echinoderms, a novel in situ respirometer system, the benthic incubation chamber system (BICS), was deployed by remotely operated vehicle (ROV) at depths ranging from 2200 to 3600m. Oxygen consumption rates were obtained in situ from four species of abyssal echinoderm (Ophiuroidea and Holothuroidea). The design and operation of two versions of BICS are presented here, together with the in situ respirometry measurements. These results were then incorporated into a larger echinoderm metabolic rate data set, which included the metabolic rates of 84 echinoderm species from all five classes (Asteroidea, Crinoidea, Echinoidea, Holothuroidea and Ophiuroidea). The allometric scaling relationships between metabolic rate and body mass derived in this study for each echinoderm class were found to vary. Analysis of the data set indicated no change in echinoderm metabolic rate with depth (by class or phylum). The allometric scaling relationships presented here provide updated information for mass-dependent deep-sea echinoderm metabolic rate for use in ecosystem models, which will contribute to the study of both shallow water and deep-sea ecosystem functioning and biogeochemistry.Supplementary material available online at