Rotorcraft handling-qualities design criteria development

Joint NASA/Army efforts at the Ames Research Center to develop rotorcraft handling-qualities design criteria began in earnest in 1975. Notable results were the UH-1H VSTOLAND variable stability helicopter, the VFA-2 camera-and-terrain-board simulator visual system, and the generic helicopter real-time mathematical model, ARMCOP. An initial series of handling-qualities studies was conducted to assess the effects of rotor design parameters, interaxis coupling, and various levels of stability and control augmentation. The ability to conduct in-flight handling-qualities research was enhanced by the development of the NASA/Army CH-47 variable-stability helicopter. Research programs conducted using this vehicle include vertical-response investigations, hover augmentation systems, and the effects of control-force characteristics. The handling-qualities data base was judged to be sufficient to allow an update of the military helicopter handling-qualities specification, MIL-H-8501. These efforts, including not only the in-house experimental work but also contracted research and collaborative programs performed under the auspices of various international agreements. The report concludes by reviewing the topics that are currently most in need of work, and the plans for addressing these topics

Activity of anidulafungin in a murine model of Candida krusei infection: evaluation of mortality and disease burden by quantitative tissue cultures and measurement of serum (1,3)-beta-D-glucan levels.

Experience with anidulafungin against Candida krusei is limited. Immunosuppressed mice were injected with 1.3 x 10(7) to 1.5 x 10(7) CFU of C. krusei. Animals were treated with saline, 40 mg/kg fluconazole, 1 mg/kg amphotericin B, or 10 and 20 mg/kg anidulafungin for 5 days. Anidulafungin improved survival and significantly reduced the number of CFU/g in kidneys and serum beta-glucan levels

Sacubitril/valsartan reduces serum uric acid concentration, an independent predictor of adverse outcomes in PARADIGM-HF

Aims: Elevated serum uric acid concentration (SUA) has been associated with an increased risk of cardiovascular disease, but this may be due to unmeasured confounders. We examined the association between SUA and outcomes as well as the effect of sacubitril/valsartan on SUA in patients with heart failure with reduced ejection fraction (HFrEF) in PARADIGM-HF. Methods and results: The association between SUA and the primary composite outcome of cardiovascular death or heart failure (HF) hospitalization, its components, and all-cause mortality was examined using Cox regression analyses among 8213 patients using quintiles (Q1–Q5) of SUA adjusted for baseline prognostic variables including estimated glomerular filtration rate (eGFR), diuretic dose, and log N-terminal pro-brain natriuretic peptide. Change in SUA from baseline over 12 months was also evaluated in each treatment group. Patients in Q5 (SUA ≥8.6 mg/dL) compared with Q1 (<5.4 mg/dL) were younger (62.8 vs. 64.2 years), more often male (88.7% vs. 63.1%), had lower systolic blood pressure (119 vs. 123 mmHg), lower eGFR (57.4 vs. 76.6 mL/min/1.73 m2), and greater diuretic use. Higher SUA was associated with a higher risk of the primary outcome (adjusted hazard ratios) Q5 vs. Q1 = 1.28 [95% confidence intervals (1.09–1.50), P = 0.003], cardiovascular death [1.44 (1.11–1.77), P = 0.001], HF hospitalization [1.37 (1.11–1.70), P = 0.004], and all-cause mortality [1.36 (1.13–1.64), P = 0.001]. Compared with enalapril, sacubitril/valsartan reduced SUA by 0.24 (0.17–0.32) mg/dL over 12 months (P < 0.0001). Sacubitril/valsartan improved outcomes, irrespective of SUA concentration. Conclusion: Serum uric acid concentration was an independent predictor of worse outcomes after multivariable adjustment in patients with HFrEF. Compared with enalapril, sacubitril/valsartan reduced SUA and improved outcomes irrespective of SUA

Type-1.5 Superconductors

We demonstrate the existence of a novel superconducting state in high quality two-component MgB2 single crystalline superconductors where a unique combination of both type-1 (kappa_1 0.707) superconductor conditions is realized for the two components of the order parameter. This condition leads to a vortex-vortex interaction attractive at long distances and repulsive at short distances, which stabilizes unconventional stripe- and gossamer-like vortex patterns that we have visualized in this type-1.5 superconductor using Bitter decoration and also reproduced in numerical simulations.Comment: accepted in Phys. Rev. Let

Photodisintegration of Three-Body Nuclei with Realistic 2N and 3N Forces

Total photonuclear absorption cross sections of $^3$H and $^3$He are studied using realistic NN and NNN forces. Final state interactions are fully included. Two NN potential models, the AV14 and the r-space Bonn-A potentials, are considered. For the NNN forces the Urbana-VIII and Tucson-Melbourne models are employed. We find the cross section to be sensitive to nuclear dynamics. Of particular interest in this work is the effect which NNN forces have on the cross section. The addition of NNN forces not only lowers the peak height but increases the cross section beyond 70 MeV by roughly 15%. Cross sections are computed using the Lorentz integral transform method.Comment: Results for Bonn potential with model Bonn rA instead of model rB. The Bonn rB results contained a small inexactness. After the correction it turned out that Bonn rA is more suited for our purpose because it leads to a binding energy of 8.15 MeV (about 0.25 MeV more than Bonn rB). In addition the results for the other realistic potentials models are improved at low energies (HH expansion was not completely convergent for the low-energy results). LaTeX, 8 pages, 4 ps figure

Test and analysis results for composite transport fuselage and wing structures

Automated tow placement (ATP) and stitching of dry textile composite preforms followed by resin transfer molding (RTM) are being investigated by researchers at NASA LaRC and Douglas Aircraft Company as cost-effective manufacturing processes for obtaining damage tolerant fuselage and wing structures for transport aircraft. The Douglas work is being performed under a NASA contract entitled 'Innovative Composites Aircraft Primary Structures (ICAPS)'. Data are presented in this paper to assess the damage tolerance of ATP and RTM fuselage elements with stitched-on stiffeners from compression tests of impacted three-J-stiffened panels and from stiffener pull-off tests. Data are also presented to assess the damage tolerance of RTM wing elements which had stitched skin and stiffeners from impacted single stiffener and three blade-stiffened compression tests and stiffener pull-off tests

Defect production due to quenching through a multicritical point

We study the generation of defects when a quantum spin system is quenched through a multicritical point by changing a parameter of the Hamiltonian as $t/\tau$, where $\tau$ is the characteristic time scale of quenching. We argue that when a quantum system is quenched across a multicritical point, the density of defects ($n$) in the final state is not necessarily given by the Kibble-Zurek scaling form $n \sim 1/\tau^{d \nu/(z \nu +1)}$, where $d$ is the spatial dimension, and $\nu$ and $z$ are respectively the correlation length and dynamical exponent associated with the quantum critical point. We propose a generalized scaling form of the defect density given by $n \sim 1/\tau^{d/(2z_2)}$, where the exponent $z_2$ determines the behavior of the off-diagonal term of the $2 \times 2$ Landau-Zener matrix at the multicritical point. This scaling is valid not only at a multicritical point but also at an ordinary critical point.Comment: 4 pages, 2 figures, updated references and added one figur

Surgical intervention for complications caused by femoral artery catheterization in pediatric patients

AbstractPurpose: This study evaluated the risk factors and surgical management of complications caused by femoral artery catheterization in pediatric patients. Methods: From January 1986 to March 2001, the hospital records of all children who underwent operative repairs for complications caused by femoral artery catheterization were reviewed. A prospective cardiac data bank containing 1674 catheterization procedures during the study period was used as a means of determining risk factors associated with iatrogenic femoral artery injury. Results: Thirty-six operations were performed in 34 patients (age range, 1 week-17.4 years) in whom iatrogenic complications developed after either diagnostic or therapeutic femoral artery catheterizations during the study period. Non-ischemic complications included femoral artery pseudoaneurysms (n = 4), arteriovenous fistulae (n = 5), uncontrollable bleeding, and expanding hematoma (n = 4). Operative repairs were performed successfully in all patients with non-ischemic iatrogenic femoral artery injuries. In contrast, ischemic complications occurred in 21 patients. Among them, 14 patients had acute femoral ischemia and underwent surgical interventions including femoral artery thrombectomy with primary closure (n = 6), saphenous vein patch angioplasty (n = 6), and resection with primary anastomosis (n = 2). Chronic femoral artery occlusion (> 30 days) occurred in seven patients, with symptoms including either severe claudication (n = 4) or gait disturbance or limb growth impairment (n = 3). Operative treatments in these patients included ileofemoral bypass grafting (n = 5), femorofemoral bypass grafting (n = 1), and femoral artery patch angioplasty (n = 1). During a mean follow-up period of 38 months, no instances of limb loss occurred, and 84% of children with ischemic complications eventually gained normal circulation. Factors that correlated with an increased risk of iatrogenic groin complications that necessitated surgical intervention included age younger than 3 years, therapeutic intervention, number of catheterizations (≥ 3), and use of 6F or larger guiding catheter. Conclusion: Although excellent operative results can be achieved in cases of non-ischemic complications, acute femoral occlusion in children younger than 2 years often leads to less satisfactory outcomes. Operative intervention can provide successful outcome in children with claudication caused by chronic limb ischemia. Variables that correlated with significant iatrogenic groin complications included a young age, therapeutic intervention, earlier catheterization, and the use of a large guiding catheter. (J Vasc Surg 2001;33:1071-8.

Anomalous Scaling of Structure Functions and Dynamic Constraints on Turbulence Simulations

The connection between anomalous scaling of structure functions (intermittency) and numerical methods for turbulence simulations is discussed. It is argued that the computational work for direct numerical simulations (DNS) of fully developed turbulence increases as $Re^{4}$, and not as $Re^{3}$ expected from Kolmogorov's theory, where $Re$ is a large-scale Reynolds number. Various relations for the moments of acceleration and velocity derivatives are derived. An infinite set of exact constraints on dynamically consistent subgrid models for Large Eddy Simulations (LES) is derived from the Navier-Stokes equations, and some problems of principle associated with existing LES models are highlighted.Comment: 18 page