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- Tripathy, Devjit, et al.
(author)
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Importance of obtaining independent measures of insulin secretion and insulin sensitivity during the same test - Results with the Botnia clamp
- 2003
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In: Diabetes Care. - 1935-5548. ; 26:5, s. 1395-1401
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Journal article (peer-reviewed)abstract
- OBJECTIVE - To validate and apply a method for independent assessment of insulin secretion and insulin sensitivity (S-l) during file same test that is, an intravenous glucose tolerance test followed by a euglycemic-hyperinsulinemic clamp, also called the Botnia clamp. This test was then applied to nondiabetic subjects with (FH+)and without (FH-) a first-degree family history of diabetes. RESEARCH DESIGN AND METHODS - The Botnia clamp measures the first-phase insulin response (FPIR) to 0.3g/k, glucose i.v. and insulin sensitivity (NI-value) front a 2-h euglycemic clamp begun 60 ruin alter the glucose bolus. The W-value obtained during the Botnia clamp was compared With M-values obtained during a regular euglycemic clamp without prior glucose bolus. Repeated tests were performed in random order in subjects with normal and abnormal glucose tolerance, Finally, the test was applied to subjects with and without a family history of type 2 diabetes. RESULTS - S-l and insulin secretion from this test showed a high degree of reproducibility, and the M-value obtained with the Botnia clamp correlated strongly,with the M-value from a euglycemic clamp without prior glucose bolus (r - 0.953, P < 0.005). FH+ subjects showed decreased S-l (P = 0.02), hut similar FPIR, compared with FH- subjects, However, insulin Secretion adjusted for file degree of insulin resistance was significantly impaired (P = 0.04). CONCLUSIONS - In conclusion, the Botnia clamp provides reliable and independent measures of S-l and beta-cell function during, the same test. As illustrated above, knowledge of the degree of S-l is mandatory When presenting data on insulin secretion.
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- Wang, Ping, et al.
(author)
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Large eddy simulation and experimental studies of a confined turbulent swirling flow
- 2004
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In: Physics of Fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 16:9, s. 3306-3324
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Journal article (peer-reviewed)abstract
- Laser Doppler velocimetry (LDV) measurement and large eddy simulation (LES) were used to study confined isothermal turbulent swirling flows in a model dump combustor. The aim was to gain deeper understanding of the flow and turbulence structures in dump combustors and to examine the capability of LES for prediction of turbulent swirling flows. A refractive index matching technique is used in the LDV measurement to improve the near-wall data. A high-order finite difference scheme on Cartesian grids with a scale-similarity subfilter scale model is used in the LES. Turbulent inflow boundary conditions with different energy spectra, different outflow boundary conditions, and grid resolutions are tested in the LES. Three test cases with different swirl numbers and Reynolds numbers are studied in the measurements and the simulations. The Reynolds numbers range from 10 000 to 20 000, and the swirl number is varied from 0 to 0.43. With appropriate inflow, outflow boundary conditions, and fine grid resolution, the LES results are in fairly good agreement with the LDV data. The experimental and numerical results show that turbulence in the dump combustor is highly anisotropic behind the sudden expansion and in the internal recirculation zone near the axis of the combustor. Turbulence decays rapidly along the streamwise direction downstream, and the structure of turbulence depends highly on the level of inlet swirl. At low swirl numbers, turbulence is primarily generated in the shear layer behind the sudden expansion; at high swirl numbers the near axis flow becomes very unstable and vortex breakdown occurs. The shear layer near the axis of the combustor caused by vortex breakdown generates most of the turbulent kinetic energy. Large-scale motions (coherent structures) are found in the near axis vortex breakdown region. A helical flow in the guiding pipe breaks down near the sudden expansion to form a large bubble-like recirculation zone whose center moves slowly around the axis. Downstream of the bubble the core of the rotational large scale azimuthal flow motion is off the combustor axis and rotates around the axis at a frequency about 18-25 Hz (Strouhal number about 0.17-0.4). As the swirl number increases the coherent structure becomes more evident, and the internal recirculation zone moves upstream. LES successfully simulated the vortex breakdown, the internal recirculation zones and the anisotropic turbulence structures for all the swirl numbers considered. (C) 2004 American Institute of Physics.
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