Simulation of premixed combustion with varying equivalence ratio in gas turbine combustor

RANS simulation of a gas turbine combustor with complex geometry is performed. The turbulence is modelled using a two-equation approach. The scalar mixing and combustion is modelled using a flamelet based approach for partially premixed combustion. In this approach transport equations to described scalar mixing and reacting fields and their statistical interactions are solved along with standard conservation equations. The boundary conditions are specified using measured values. The computed spatial variations of averaged temperature and dry mole fractions of various scalars, including CO and NOx, compared quite well with measured values. The results of this combustion model are compared to the eddy-dissipation-concept (EDC) model commonly used for gas turbine combustion calculation and this comparison showed that the results of partially premixed combustion model is improved considerably.This is the author accepted manuscript. The final version is available from the American Institute of Aeronautics and Astronautics via http://dx.doi.org/10.2514/1.B3551

Long-term prevention of renal insufficiency, excess matrix gene expression, and glomerular mesangial matrix expansion by treatment with monoclonal antitransforming growth factor-ß antibody in \u3ci\u3edb/db\u3c/i\u3e diabetic mice

Emerging evidence suggests that transforming growth factor-(TGF-β) is an important mediator of diabetic nephropathy. We showed previously that short-term treatment with a neutralizing monoclonal anti-TGF-antibody (αT) in streptozotocin-diabetic mice prevents early changes of renal hypertrophy and increased matrix mRNA. To establish that overactivity of the renal TGF-system mediates the functional and structural changes of the more advanced stages of nephropathy, we tested whether chronic administration of αT prevents renal insufficiency and glomerulosclerosis in the db/db mouse, model of type 2 diabetes that develops overt nephropathy. Diabetic db/db mice and nondiabetic db/m littermates were treated intraperitoneally with α or control IgG, 300 µg three times per week for 8 wk. Treatment with αT, but not with IgG, significantly decreased the plasma TGF-β1 concentration without decreasing the plasma glucose concentration. The IgG-treated db/db mice developed albuminuria, renal insufficiency, and glomerular mesangial matrix expansion associated with increased renal mRNAs encoding α 1(IV) collagen and fibronectin. On the other hand, treatment with α completely prevented the increase in plasma creatinine concentration, the decrease in urinary creatinine clearance, and the expansion of mesangial matrix in db/db mice. The increase in renal matrix mRNAs was substantially attenuated, but the excretion of urinary albumin factored for creatinine clearance was not significantly affected by α treatment. We conclude that chronic inhibition of the biologic actions of TGF-with neutralizing monoclonal antibody in db/db mice prevents the glomerulosclerosis and renal insufficiency resulting from type diabetes

Superconductivity and Rattling under High Pressure in the beta-Pyrochlore Oxide RbOs2O6

Rattling-induced superconductivity in the beta-pyrochlore oxide RbOs2O6 is investigated under high pressures up to 6 GPa. Resistivity measurements in a high-quality single crystal show that the superconducting transition temperature Tc increases gradually from 6.3 K at ambient pressure to 8.8 K at 3.5 GPa, surprisingly remains almost constant at 8.8 \pm 0.1 K in a wide pressure range between 3.5 (Po) and 4.8 GPa, and suddenly drops to 6.3 K at Ps = 4.9 GPa, followed by a gradual decrease with further pressure increase. Two anomalies in the temperature dependence of the normal-state resistivity are observed at Po Ps, revealing the presence of two high-pressure phases corresponding to the changes in Tc. The rattling of the Rb ion inside a cage made of Os and O atoms may be slightly and seriously modified in these high-pressure phases that probably have cages of reduced symmetry, respectively, so that electron-rattler interactions that govern the superconducting and transport properties of beta-RbOs2O6 are significantly affected.Comment: arXiv admin note: text overlap with arXiv:1009.035

Upper airway dynamics during negative expiratory pressure in apneic and non-apneic awake snorers

BACKGROUND: The ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated. METHODS: Forty-eight subjects with sleep disordered breathing (SDB) and 7 healthy subjects, as non-snorer controls, underwent the NEP application of -5 and -7 cmH(2)O in the seated and supine position during wakefulness, after performing a sleep study. The upper airway collapsibility was assessed by computing the volume exhaled during the first 0.5 sec. (V,NEP(0.5)) and 1 sec. (V,NEP(1)) following the NEP start. RESULTS: Patients with severe (AHI ≥ 30) (n = 19) and mild-to-moderate (AHI <30 and >5) (n = 15) OSAH had lower V,NEP(0.5 )(340 ± 88 ml) as compared to snorers (AHI ≤ 5) (n = 14) (427 ± 101 ml; p < 0.01) and controls (n = 7) (492 ± 69 ml; p < 0.001) in the supine position with NEP -5 cmH(2)O. Less significant differences among the different groups were observed for V,NEP(0.5 )in the seated position with NEP -5 cmH(2)O and in both positions with NEP -7 cmH(2)O (only OSAH patients vs controls, p < 0.001). Similar results were obtained for V,NEP(1 )in either position by using both NEP -5 cmH(2)O and -7 cmH(2)O. In spite of this, a substantial overlapping of V,NEP(0.5 )and V,NEP(1 )between snorers and OSAH patients did not allow to identify a reliable diagnostic cut-off level. An inverse correlation with AHI was found for V,NEP(0.5 )in the supine position with NEP -5 cmH(2)O (r(s )= -0.46, p < 0.05) in severe OSAH patients. CONCLUSION: The awake OSAH patients exhibit values of V,NEP(0.5 )and V,NEP(1 )lesser than those of awake snorers. The NEP technique, however, appears to have a limited usefulness as clinical tool for routine screening of the OSAH patients during wakefulness

Effects of high glucose and TGF-β1 on the expression of collagen IV and vascular endothelial growth factor in mouse podocytes

Effects of high glucose and TGF-β1 on the expression of collagen IV and vascular endothelial growth factor in mouse podocytes.BackgroundThe podocyte takes center stage in the pathogenesis of glomerular basement membrane (GBM) thickening and proteinuria in diabetic glomerulopathy. In part, GBM thickening may occur when the podocyte synthesizes increased amounts of collagen IV. Proteinuria may develop if the podocyte secretes excessive amounts of vascular endothelial growth factor (VEGF), which may increase the glomerular permeability to macromolecules. The augmented production of collagen IV and VEGF may be caused by metabolic mediators of diabetes such as hyperglycemia and transforming growth factor-β (TGF-β).MethodsThe effects of high glucose and exogenous TGF-β1 were examined on a mouse podocyte cell line that retains its differentiated phenotype. The gene expression and protein production of certain alpha chains of collagen IV, the major isoforms of VEGF, and components of the TGF-β system were assayed. An inhibitor of TGF-β signaling was used to determine whether some of the high glucose effects might be mediated by the TGF-β system.ResultsCompared with normal glucose (5.5 mmol/L), high glucose (HG, 25 mmol/L) for 14 days stimulated [3H]-proline incorporation, a measure of collagen production, by 1.8-fold, and exogenous TGF-β1 (2 ng/mL) for 24 hours stimulated proline incorporation by 2.4-fold. Northern analysis showed that exposure to HG for 14 days increased the mRNA level of α1(IV) collagen by 51% and α5(IV) by 90%, whereas treatment with TGF-β1 (2 ng/mL) for 24 hours decreased the mRNA level of α1(IV) by 36% and α5(IV) by 40%. Consistent with these effects on mRNA expression, Western blotting showed that HG increased α1(IV) protein by 44% and α5(IV) by 28%, while TGF-β1 decreased α1(IV) protein by 29% and α5(IV) by 7%. In contrast to their opposing actions on α1 and α5(IV), both HG and exogenous TGF-β1 increased α3(IV) collagen and VEGF, with TGF-β1 having the greater effect. An inhibitor of the TGF-β type I receptor (ALK5) was able to prevent the stimulation of α3(IV) and VEGF proteins by HG. Unlike in other renal cell types, HG did not increase TGF-β1 mRNA or protein in the podocyte, but HG did induce the expression of the ligand-binding TGF-β type II receptor (TβRII). Because HG had up-regulated TβRII after two weeks, the addition of physiological-dose TGF-β1 (0.010 ng/mL) for 24 hours stimulated the production of α3(IV) and VEGF proteins to a greater extent in high than in normal glucose. Up-regulation of TβRII in the podocyte was corroborated by immunohistochemistry of the kidney cortex in the db/db mouse, a model of type 2 diabetes.ConclusionsHigh glucose and exogenous TGF-β1 exert disparate effects on the expression of α1 and α5(IV) collagen. However, high glucose and TGF-β1 coordinately induce the production of α3(IV) collagen and VEGF in the podocyte. The HG-induced increases in α3(IV) collagen and VEGF proteins are mediated by the TGF-β system. By increasing the expression of TβRII, high glucose may augment the response of the podocyte to ambient levels of TGF-β1

Sensitivity of the superconducting state and magnetic susceptibility to key aspects of electronic structure in ferropnictides

Experiments on the iron-pnictide superconductors appear to show some materials where the ground state is fully gapped, and others where low-energy excitations dominate, possibly indicative of gap nodes. Within the framework of a 5-orbital spin fluctuation theory for these systems, we discuss how changes in the doping, the electronic structure or interaction parameters can tune the system from a fully gapped to nodal sign-changing gap with s-wave ($A_{1g}$) symmetry ($s^\pm$). In particular we focus on the role of the hole pocket at the $(\pi,\pi)$ point of the unfolded Brillouin zone identified as crucial to the pairing by Kuroki {\it et al.}, and show that its presence leads to additional nesting of hole and electron pockets which stabilizes the isotropic $s^\pm$ state. The pocket's contribution to the pairing can be tuned by doping, surface effects, and by changes in interaction parameters, which we examine. Analytic expressions for orbital pairing vertices calculated within the RPA fluctuation exchange approximation allow us to draw connections between aspects of electronic structure, interaction parameters, and the form of the superconducting gap

Holographic Wilsonian flows and emergent fermions in extremal charged black holes

We study holographic Wilsonian RG in a general class of asymptotically AdS backgrounds with a U(1) gauge field. We consider free charged Dirac fermions in such a background, and integrate them up to an intermediate radial distance, yielding an equivalent low energy dual field theory. The new ingredient, compared to scalars, involves a `generalized' basis of coherent states which labels a particular half of the fermion components as coordinates or momenta, depending on the choice of quantization (standard or alternative). We apply this technology to explicitly compute RG flows of charged fermionic operators and their composites (double trace operators) in field theories dual to (a) pure AdS and (b) extremal charged black hole geometries. The flow diagrams and fixed points are determined explicitly. In the case of the extremal black hole, the RG flows connect two fixed points at the UV AdS boundary to two fixed points at the IR AdS_2 region. The double trace flow is shown, both numerically and analytically, to develop a pole singularity in the AdS_2 region at low frequency and near the Fermi momentum, which can be traced to the appearance of massless fermion modes on the low energy cut-off surface. The low energy field theory action we derive exactly agrees with the semi-holographic action proposed by Faulkner and Polchinski in arXiv:1001.5049 [hep-th]. In terms of field theory, the holographic version of Wilsonian RG leads to a quantum theory with random sources. In the extremal black hole background the random sources become `light' in the AdS_2 region near the Fermi surface and emerge as new dynamical degrees of freedom.Comment: 37 pages (including 8 pages of appendix), 10 figures and 2 table

Microscopic Realization of the Kerr/CFT Correspondence

Supersymmetric M/string compactifications to five dimensions contain BPS black string solutions with magnetic graviphoton charge P and near-horizon geometries which are quotients of AdS_3 x S^2. The holographic duals are typically known 2D CFTs with central charges c_L=c_R=6P^3 for large P. These same 5D compactifications also contain non-BPS but extreme Kerr-Newman black hole solutions with SU(2)_L spin J_L and electric graviphoton charge Q obeying Q^3 \leq J_L^2. It is shown that in the maximally charged limit Q^3 -> J_L^2, the near-horizon geometry coincides precisely with the right-moving temperature T_R=0 limit of the black string with magnetic charge P=J_L^{1/3}. The known dual of the latter is identified as the c_L=c_R=6J_L CFT predicted by the Kerr/CFT correspondence. Moreover, at linear order away from maximality, one finds a T_R \neq 0 quotient of the AdS_3 factor of the black string solution and the associated thermal CFT entropy reproduces the linearly sub-maximal Kerr-Newman entropy. Beyond linear order, for general Q^3<J_L^2, one has a finite-temperature quotient of a warped deformation of the magnetic string geometry. The corresponding dual deformation of the magnetic string CFT potentially supplies, for the general case, the c_L=c_R=6J_L CFT predicted by Kerr/CFT.Comment: 18 pages, no figure

Hidden Conformal Symmetry of the Reissner-Nordstr{\o}m Black Holes

Motivated by recent progresses in the holographic descriptions of the Kerr and Reissner-Nordstr{\o}m (RN) black holes, we explore the hidden conformal symmetry of nonextremal uplifted 5D RN black hole by studying the near horizon wave equation of a massless scalar field propagating in this background. Similar to the Kerr black hole case, this hidden symmetry is broken by the periodicity of the associated angle coordinate in the background geometry, but the results somehow testify the dual CFT description of the nonextremal RN black holes. The duality is further supported by matching of the entropies and absorption cross sections calculated from both CFT and gravity sides.Comment: 14 pages, no figur