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- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 7. |
- Goodyear, LJ, et al.
(författare)
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Glucose ingestion causes GLUT4 translocation in human skeletal muscle
- 1996
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 45:8, s. 1051-1056
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Tidskriftsartikel (refereegranskat)abstract
- In humans, ingestion of carbohydrates causes an increase in blood glucose concentration, pancreatic insulin release, and increased glucose disposal into skeletal muscle. The underlying molecular mechanism for the increase in glucose disposal in human skeletal muscle after carbohydrate ingestion is not known. We determined whether glucose ingestion increases glucose uptake in human skeletal muscle by increasing the number of glucose transporter proteins at the cell surface and/or by increasing the activity of the glucose transporter proteins in the plasma membrane. Under local anesthesia, ∼1 g of vastus lateralis muscle was obtained from six healthy subjects before and 60 min after ingestion of a 75-g glucose load. Plasma membranes were isolated from the skeletal muscle and used to measure GLUT4 and GLUT1 content and glucose transport in plasma membrane vesicles. Glucose ingestion increased the plasma membrane content of GLUT4 per gram muscle (3,524 ± 729 vs. 4,473 ± 952 arbitrary units for basal and 60 min, respectively; P < 0.005). Transporter-mediated glucose transport into plasma membrane vesicles was also significantly increased (130 ± 11 vs. 224 ± 38 pmol · mg−1 · s−1; P < 0.017), whereas the calculated ratio of glucose transport to GLUT4, an indication of transporter functional activity, was not significantly increased 60 min after glucose ingestion (2.3 ± 0.4 vs. 3.0 ± 0.5 pmol · GLUT4 arbitrary units−1 · s−1; P < 0.17). These results demonstrate that oral ingestion of glucose increases the rate of glucose transport across the plasma membrane and causes GLUT4 translocation in human skeletal muscle. These findings suggest that under physiological conditions the translocation of GLUT4 is an important mechanism for the stimulation of glucose uptake in human skeletal muscle.
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- Jessen, N, et al.
(författare)
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Exercise increases TBC1D1 phosphorylation in human skeletal muscle
- 2011
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Ingår i: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 301:1, s. E164-E171
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Tidskriftsartikel (refereegranskat)abstract
- Exercise and weight loss are cornerstones in the treatment and prevention of type 2 diabetes, and both interventions function to increase insulin sensitivity and glucose uptake into skeletal muscle. Studies in rodents demonstrate that the underlying mechanism for glucose uptake in muscle involves site-specific phosphorylation of the Rab-GTPase-activating proteins AS160 (TBC1D4) and TBC1D1. Multiple kinases, including Akt and AMPK, phosphorylate TBC1D1 and AS160 on distinct residues, regulating their activity and allowing for GLUT4 translocation. In contrast to extensive rodent-based studies, the regulation of AS160 and TBC1D1 in human skeletal muscle is not well understood. In this study, we determined the effects of dietary intervention and a single bout of exercise on TBC1D1 and AS160 site-specific phosphorylation in human skeletal muscle. Ten obese (BMI 33.4 ± 2.4, M-value 4.3 ± 0.5) subjects were studied at baseline and after a 2-wk dietary intervention. Muscle biopsies were obtained from the subjects in the resting (basal) state and immediately following a 30-min exercise bout (70% V̇o2 max). Muscle lysates were analyzed for AMPK activity and Akt phosphorylation and for TBC1D1 and AS160 phosphorylation on known or putative AMPK and Akt sites as follows: AS160 Ser711(AMPK), TBC1D1 Ser231(AMPK), TBC1D1 Ser660(AMPK), TBC1D1 Ser700(AMPK), and TBC1D1 Thr590(Akt). The diet intervention that consisted of a major shift in the macronutrient composition resulted in a 4.2 ± 0.4 kg weight loss ( P < 0.001) and a significant increase in insulin sensitivity ( M value 5.6 ± 0.6), but surprisingly, there was no effect on expression or phosphorylation of any of the muscle-signaling proteins. Exercise increased muscle AMPKα2 activity but did not increase Akt phosphorylation. Exercise increased phosphorylation on AS160 Ser711, TBC1D1 Ser231, and TBC1D1 Ser660but had no effect on TBC1D1 Ser700. Exercise did not increase TBC1D1 Thr590phosphorylation or TBC1D1/AS160 PAS phosphorylation, consistent with the lack of Akt activation. These data demonstrate that a single bout of exercise regulates TBC1D1 and AS160 phosphorylation on multiple sites in human skeletal muscle.
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