Flow patterns in nappe flow regime down low gradient stepped chutes

Although modern gravity dam spillways include often steep chutes operating in skimming flow regime, succession of free-falling nappes (i.e. nappe flow regime) are more common on low gradient chutes and cascades, and this flow situation received little attention to date. New experiments were conducted in nappe flows without hydraulic jump in two large-size facilities with flat slopes. The flow on the stepped cascade displayed complex, three-dimensional patterns. Detailed air-water flow measurements were performed in the jet, at nappe impact and in the downstream flow region. Key results demonstrated that the flow on each step was rapidly varied (RVF), highly three-dimensional and strongly aerated

The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism

Increased intake of dietary carbohydrate that is fermented in the colon by the microbiota has been reported to decrease body weight, although the mechanism remains unclear. Here we use in vivo11C-acetate and PET-CT scanning to show that colonic acetate crosses the blood–brain barrier and is taken up by the brain. Intraperitoneal acetate results in appetite suppression and hypothalamic neuronal activation patterning. We also show that acetate administration is associated with activation of acetyl-CoA carboxylase and changes in the expression profiles of regulatory neuropeptides that favour appetite suppression. Furthermore, we demonstrate through 13C high-resolution magic-angle-spinning that 13C acetate from fermentation of 13C-labelled carbohydrate in the colon increases hypothalamic 13C acetate above baseline levels. Hypothalamic 13C acetate regionally increases the 13C labelling of the glutamate–glutamine and GABA neuroglial cycles, with hypothalamic 13C lactate reaching higher levels than the ‘remaining brain’. These observations suggest that acetate has a direct role in central appetite regulation