Determining structural performance

An overview of the methods and concepts developed to enhance and predict structural dynamic characteristics of advanced aeropropulsion systems is presented. Aeroelasticity, vibration control, dynamic systems, and computational structural methods are four disciplines that make up the structural dynamic effort at LeRC. The aeroelasticity program develops analytical and experimental methods for minimizing flutter and forced vibration of aerospace propulsion systems. Both frequency domain and time domain methods were developed for applications on the turbofan, turbopump, and advanced turboprop. In order to improve life and performance, the vibration control program conceives, analyzes, develops, and demonstrates new methods for controlling vibrations in aerospace systems. Active and passive vibration control is accomplished with electromagnetic dampers, magnetic bearings, and piezoelectric crystals to control rotor vibrations. The dynamic systems program analyzes and verifies the dynamics of interacting systems, as well as develops concepts and methods for high-temperature dynamic seals. Work in this field involves the analysis and parametric identification of large, nonlinear, damped, stochastic systems. The computational structural methods program exploits modern computer science as an aid to the solutions of structural problems

Halide perovskites enable polaritonic \u3ci\u3eXY\u3c/i\u3e spin Hamiltonian at room temperature

Exciton polaritons, the part-light and part-matter quasiparticles in semiconductor optical cavities, are promising for exploring Bose–Einstein condensation, non-equilibrium many-body physics and analogue simulation at elevated temperatures. However, a room-temperature polaritonic platform on par with the GaAs quantum wells grown by molecular beam epitaxy at low temperatures remains elusive. The operation of such a platform calls for long-lifetime, strongly interacting excitons in a stringent material system with large yet nanoscale-thin geometry and homogeneous properties. Here, we address this challenge by adopting a method based on the solution synthesis of excitonic halide perovskites grown under nanoconfinement. Such nanoconfinement growth facilitates the synthesis of smooth and homogeneous single-crystalline large crystals enabling the demonstration of XY Hamiltonian lattices with sizes up to 10 × 10. With this demonstration, we further establish perovskites as a promising platform for room temperature polaritonic physics and pave the way for the realization of robust mode-disorder-free polaritonic devices at room temperature

Aqueous phase methylation as a potential source of methylmercury in wet deposition

Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V for personal use, not for redistribution. The definitive version was published in Atmospheric Environment 41 (2007): 1663-1668, doi:10.1016/j.atmosenv.2006.10.032.The source of monomethylmercury (MMHg) in wet deposition is unknown. Volatilization of gaseous MMHg, evasion and demethylation of dimethylmercury, and methylation of Hg0 have been either proposed or tested unsuccessfully as potential sources. Here, we show that MMHg in precipitation, sampled across a wide geographical range in North America, is related positively to an operationally defined and measured reactive Hg species (HgR), but connected weakly to total Hg. The mean molar ratio of MMHg:HgR measured in continental precipitation (0.025 ± 0.006) is comparable to the MMHg:Hg(II) ratio estimated from first-order rate constants for acetate-mediated Hg methylation and MMHg photolysis (0.025 ± 0.002). This suggests MMHg may be formed in the atmosphere through a reaction between labile Hg(II) complexes and an unknown methylating agent(s), potentially acetate or similar molecules. Availability of Hg(II) appears to limit the reaction, and accordingly, increased atmospheric loadings of Hg could lead to enhanced MMHg in precipitation.This study was supported by a grant from the National Science Foundation-Office of Polar Programs (0425562) and the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding from the Doherty Foundation

Effect of increasing intraperitoneal infusion rates on bupropion hydrochloride-induced seizures in mice

<p>Abstract</p> <p>Background</p> <p>It is not known if there is a relationship between input rate and incidence of bupropion-induced seizures. This is important, since different controlled release formulations of bupropion release the active drug at different rates.</p> <p>Methods</p> <p>We investigated the effect of varying the intraperitoneal infusion rates of bupropion HCl 120 mg/kg, a known convulsive dose₅₀(CD₅₀), on the incidence and severity of bupropion-induced convulsions in the Swiss albino mice. A total of 69 mice, approximately 7 weeks of age, and weighing 21.0 to 29.1 g were randomly assigned to bupropion HCl 120 mg/kg treatment by intraperitoneal (IP) administration in 7 groups (9 to 10 animals per group). Bupropion HCl was infused through a surgically implanted IP dosing catheter with infusions in each group of 0 min, 15 min, 30 min, 60 min, 90 min, 120 min, and 240 min. The number, time of onset, duration and the intensity of the convulsions or absence of convulsions were recorded.</p> <p>Results</p> <p>The results showed that IP administration of bupropion HCl 120 mg/kg by bolus injection induced convulsions in 6 out of 10 mice (60% of convulsing mice) in group 1. Logistic regression analysis revealed that infusion time was significant (p = 0.0004; odds ratio = 0.974) and increasing the IP infusion time of bupropion HCl 120 mg/kg was associated with a 91% reduced odds of convulsions at infusion times of 15 to 90 min compared to bolus injection. Further increase in infusion time resulted in further reduction in the odds of convulsions to 99.8% reduction at 240 min.</p> <p>Conclusion</p> <p>In conclusion, the demonstration of an inverse relationship between infusion time of a fixed and convulsive dose of bupropion and the risk of convulsions in a prospective study is novel.</p

Measurement of the neutrino component of an anti-neutrino beam observed by a non-magnetized detector

Two independent methods are employed to measure the neutrino flux of the anti-neutrino-mode beam observed by the MiniBooNE detector. The first method compares data to simulated event rates in a high purity \numu induced charged-current single \pip (CC1\pip) sample while the second exploits the difference between the angular distributions of muons created in \numu and \numub charged-current quasi-elastic (CCQE) interactions. The results from both analyses indicate the prediction of the neutrino flux component of the pre-dominately anti-neutrino beam is over-estimated - the CC1\pip analysis indicates the predicted \numu flux should be scaled by $0.76 \pm 0.11$, while the CCQE angular fit yields $0.65 \pm 0.23$. The energy spectrum of the flux prediction is checked by repeating the analyses in bins of reconstructed neutrino energy, and the results show that the spectral shape is well modeled. These analyses are a demonstration of techniques for measuring the neutrino contamination of anti-neutrino beams observed by future non-magnetized detectors.Comment: 15 pages, 7 figures, published in Physical Review D, latest version reflects changes from referee comment

A Search for Electron Antineutrino Appearance at the Δm2∼\Delta m^2 \sim 1 eV2\mathrm{eV}^{2} Scale

The MiniBooNE Collaboration reports initial results from a search for $\bar{\nu}_{\mu}\to\bar{\nu}_e$ oscillations. A signal-blind analysis was performed using a data sample corresponding to $3.39 \times 10^{20}$ protons on target. The data are consistent with background prediction across the full range of neutrino energy reconstructed assuming quasielastic scattering, $200 < E_{\nu}^{QE} < 3000$ MeV: 144 electron-like events have been observed in this energy range, compared to an expectation of $139.2 \pm 17.6$ events. No significant excess of events has been observed, both at low energy, 200-475 MeV, and at high energy, 475-1250 MeV. The data are inconclusive with respect to antineutrino oscillations suggested by data from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory.Comment: 5 pages, 3 figures, 2 table

Measurement of Muon Neutrino Quasi-Elastic Scattering on Carbon

The observation of neutrino oscillations is clear evidence for physics beyond the standard model. To make precise measurements of this phenomenon, neutrino oscillation experiments, including MiniBooNE, require an accurate description of neutrino charged current quasi-elastic (CCQE) cross sections to predict signal samples. Using a high-statistics sample of muon neutrino CCQE events, MiniBooNE finds that a simple Fermi gas model, with appropriate adjustments, accurately characterizes the CCQE events observed in a carbon-based detector. The extracted parameters include an effective axial mass, M_A^eff = 1.23+/-0.20 GeV, that describes the four-momentum dependence of the axial-vector form factor of the nucleon; and a Pauli-suppression parameter, kappa = 1.019+/-0.011. Such a modified Fermi gas model may also be used by future accelerator-based experiments measuring neutrino oscillations on nuclear targets.Comment: 5 pages, 3 figure