[1] Gas tracer experiments were carried out in dynamically compressed sediments to investigate the mass transfer between a trapped multicomponent gas phase and a mobile water phase. The saturation state of the column was characterized by three independent methods: (1) by gravimetric measurements, (2) by bromide tracer tests, and (3) by hydraulic conductivity measurements. For inverse modeling a new kinetic model was developed allowing volume change of the entrapped gas. The new kinetic model consistently explains oxygen elution curves, the time evolution of the integral gas saturation, and integral hydraulic conductivity. The sensitivity of three different velocity-dependent mass transfer correlations to the dissolution process was investigated: (1) a classical square-root, single-sphere correlation, Sh $ Pe 0.5 , (2) a multisphere correlation, Sh $ Pe n (n = 0.5-1.0), and (3) an empirical correlation, Sh $ Pe 0.8 . It was found that all correlations yield nearly the same elution curves for 10 gas tracer experiments with three different two-component gas phases: O 2 /He, O 2 /N 2 , and O 2 /Ar and for different flow velocities ranging from 5 to 20 m d À1 . For all gas tracer experiments a distinct minimum of the longitudinal dispersivity was found during gas dissolution, i.e., in the unsaturated state. For the saturated state we found that the experimental values could be described by Saffman's theory:D p / Pe ln (Pe) with a normalized mean square root error of 6%.Citation: Geistlinger, H., A. Beckmann, and D. Lazik (2005), Mass transfer between a multicomponent trapped gas phase and a mobile water phase: Experiment and theory, Water Resour. Res., 41, W11408,

Context Dipeptidylpeptidase (DPP)-4 is a key regulator of the incretin system. It exists in a membrane bound form and a soluble form (= sDPP-4). Initial human studies suggested sDPP-4 to be an adipokine involved in metabolic inflammation. However, recent mechanistic data in genetically modified mice questioned these findings. Objectives We examined circulating sDPP-4 in a cohort of n = 451 humans with different metabolic phenotypes and during three different weight loss interventions (n = 101) to further clarify its role in human physiology and metabolic diseases. Design sDPP-4 serum concentrations were measured by ELISA and related to several phenotyping data including gut microbiome analysis. Results sDPP-4 increased with age and body weight and was positively associated with insulin resistance and hypertriglyceridemia but was reduced in manifest type 2 diabetes. In addition, we found reduced serum concentrations of sDPP-4 in subjects with arterial hypertension. In contrast to earlier reports, we did not identify an association with systemic markers of inflammation. Impaired kidney and liver functions significantly altered sDPP-4 concentrations while no relation to biomarkers for heart failure was observed. Having found increased levels of sDPP-4 in obesity, we studied surgical (gastric bypass and sleeve gastrectomy) and non-surgical interventions revealing a significant association of sDPP-4 with the improvement of liver function tests but not with changes in body weight. Conclusions Our data suggest that sDPP-4 is related to hepatic abnormalities in obesity rather than primarily functioning as an adipokine and that sDPP-4 is implicated both, in glucose and lipid metabolism, but not fundamentally in systemic inflammation.

Obesity is associated with a “natriuretic handicap” indicated by reduced N-terminal fragment of proBNP (NT-proBNP) concentration. While gastric bypass surgery improves the natriuretic handicap, it is presently unclear if sleeve gastrectomy exhibits similar effects. We examined NT-proBNP serum concentration in n = 72 obese participants without heart failure before and 6 months after sleeve gastrectomy (n = 28), gastric bypass surgery (n = 19), and 3-month 800 kcal/day very-low calorie diet (n = 25). A significant weight loss was observed in all intervention groups. Within 6 months, NT-proBNP concentration tended to increase by a median of 44.3 pg/mL in the sleeve gastrectomy group (p = 0.07), while it remained unchanged in the other groups (all p ≥ 0.50). To gain insights into potential effectors, we additionally analyzed NT-proBNP serum concentration in n = 387 individuals with different metabolic phenotypes. Here, higher NT-proBNP levels were associated with lower nutritional fat and protein but not with carbohydrate intake. Of interest, NT-proBNP serum concentrations were inversely correlated with fasting glucose concentration in euglycemic individuals but not in individuals with prediabetes or type 2 diabetes. In conclusion, sleeve gastrectomy tended to increase NT-proBNP levels in obese individuals and might improve the obesity-associated “natriuretic handicap”. Thereby, nutritional fat and protein intake and the individual glucose homeostasis might be metabolic determinants of NT-proBNP serum concentration.

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