RELATIONSHIP OF NITROGEN METABOLISM CAPACITY, CARCASS QUALITY, AND EXPRESSION OF GLUTAMATE TRANSPORTERS AND METABOLIZING ENZYMES IN POLYPAY AND PERCENTAGE WHITE DORPER LAMBS

Two studies were conducted to compare nitrogen (N) and glutamate metabolism in Polypay and percentage White Dorper lambs.First, a two-phase digestion/N metabolism trial was conducted with 18 wether lambs of three genetic types: Polypay (PP), 1/2 White Dorper 1/2 Polypay (1/2 D), and 3/4 White Dorper 1/4 Polypay (3/4 D). Six lambs of each genetic type were fed a high roughage diet (HR; Phase 1) or high concentrate diet (HC; Phase 2). DM and N digestion was higher for 1/2 D than PP or 3/4 D fed HC. N retention was highest for 1/2 D regardless of diet.The second study analyzed the effect of genetic type on glutamate transporter and metabolizing enzyme expression in liver, kidney, longissimus dorsi muscle (LD muscle), and subcutaneous fat (Sub Q Fat) tissue of 18 wether lambs of three genetic types: PP, 1/2 D, and 15 /16 White Dorper 1/16 Polypay (15 /16 D). Tissue samples were analyzed for protein and mRNA content of GS, GDH, ALT, EAAC1, and GLT-1. Glutamate transport and metabolism capacity was lowest for the heavier muscled 15 /16 D lambs.The results suggest genetic type has an effect on N metabolism due to differential expression of glutamate transporters and metabolizing enzymes

Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas

The neoclassical transport optimization of the Wendelstein 7-X stellarator has not resulted in the predicted high energy confinement of gas fueled electron-cyclotron-resonance-heated (ECRH) plasmas as modelled in (Turkin et al 2011 Phys. Plasmas 18 022505) due to high levels of turbulent heat transport observed in the experiments. The electron-turbulent-heat transport appears non-stiff and is of the electron temperature gradient (ETG)/ion temperature gradient (ITG) type (Weir et al 2021 Nucl. Fusion 61 056001). As a result, the electron temperature Te can be varied freely from 1 keV–10 keV within the range of PECRH = 1–7 MW, with electron density ne values from 0.1–1.5 × 1020 m−3. By contrast, in combination with the broad electron-to-ion energy-exchange heating profile in ECRH plasmas, ion-turbulent-heat transport leads to clamping of the central ion temperature at Ti ∼ 1.5 keV ± 0.2 keV. In a dedicated ECRH power scan at a constant density of 〈ne〉 = 7 × 1019 m−3, an apparent \u27negative ion temperature profile stiffness\u27 was found in the central plasma for (r/a < 0.5), in which the normalized gradient ∇Ti/Ti decreases with increasing ion heat flux. The experiment was conducted in helium, which has a higher radiative density limit compared to hydrogen, allowing a broader power scan. This \u27negative stiffness\u27 is due to a strong exacerbation of turbulent transport with an increasing ratio of Te/Ti in this electron-heated plasma. This finding is consistent with electrostatic microinstabilities, such as ITG-driven turbulence. Theoretical calculations made by both linear and nonlinear gyro-kinetic simulations performed by the GENE code in the W7-X three-dimensional geometry show a strong enhancement of turbulence with an increasing ratio of Te/Ti. The exacerbation of turbulence with increasing Te/Ti is also found in tokamaks and inherently enhances ion heat transport in electron-heated plasmas. This finding strongly affects the prospects of future high-performance gas-fueled ECRH scenarios in W7-X and imposes a requirement for turbulence-suppression techniques