Lewis icing research tunnel test of the aerodynamic effects of aircraft ground deicing/anti-icing fluids

A wind tunnel investigation of the effect of aircraft ground deicing/anti-icing fluids on the aerodynamic characteristics of a Boeing 737-200ADV airplane was conducted. The test was carried out in the NASA Lewis Icing Research Tunnel. Fluids tested include a Newtonian deicing fluid, three non-Newtonian anti-icing fluids commercially available during or before 1988, and eight new experimental non-Newtonian fluids developed by four fluid manufacturers. The results show that fluids remain on the wind after liftoff and cause a measurable lift loss and drag increase. These effects are dependent on the high-lift configuration and on the temperature. For a configuration with a high-lift leading-edge device, the fluid effect is largest at the maximum lift condition. The fluid aerodynamic effects are related to the magnitude of the fluid surface roughness, particularly in the first 30 percent chord. The experimental fluids show a significant reduction in aerodynamic effects

Comparing CEO Employment Contract Provisions: Differences Between Australia and the United States

This study compares CEO employment contracts across two common law countries: the United States and Australia. Although the regulatory regimes of these jurisdictions enjoy many comparable features, there are also some important institutional differences in terms of capital market, tax, and regulatory structures, which are discussed here. Debate has raged in the United States on the issue of whether executive compensation is efficient and determined at arm\u27s length, or skewed by a power imbalance between managers and shareholders. A comparative analysis of the kind undertaken in our study provides an additional perspective on the optimal contracting and managerial power models of executive pay in U.S. academic literature. Even if one model has greater explanatory power in the U.S. context, this will not necessarily be the case in other jurisdictions, such as Australia. In order to do our comparison, we create pairs of U.S. and Australian firms that are matched on a number of dimensions including firm size and industry. We find that Australian CEOs have significantly greater base salaries than their U.S. counterparts, while U.S. CEOs are more likely to be compensated with restricted stock and stock options than the Australian CEOs. More striking is the fact that U.S. CEO employment contracts tend to last longer than Australian contracts, and they are more likely to have arbitration provisions, change-in-control provisions, tax gross ups, do-not-compete clauses, and supplemental executive retirement plans. We also find that Australian contracts are much more apt to include performance hurdle requirements before CEOs can receive restricted stock and options, and restrictions on CEO hedging of restricted stock and options. A number of the contractual differences we document appear to be consistent with key institutional differences between the two countries

Separable approximation for mixed states of composite quantum systems

We describe a purely algebraic method for finding the best separable approximation to a mixed state of a composite 2x2 quantum system, consisting of a decomposition of the state into a linear combination of a mixed separable part and a pure entangled one. We prove that, in a generic case, the weight of the pure part in the decomposition equals the concurrence of the state.Comment: 13 pages, no figures; minor changes; accepted for publication in PR

Electrochemical and Structural Characterization of Azotobacter vinelandii Flavodoxin II

Azotobacter vinelandii flavodoxin II serves as a physiological reductant of nitrogenase, the enzyme system mediating biological nitrogen fixation. Wildtype A. vinelandii flavodoxin II was electrochemically and crystallographically characterized to better understand the molecular basis for this functional role. The redox properties were monitored on surfactant-modified basal plane graphite electrodes, with two distinct redox couples measured by cyclic voltammetry corresponding to reduction potentials of −483 ± 1 mV and −187 ± 9 mV (vs. NHE) in 50 mM potassium phosphate, 150 mM NaCl, pH 7.5. These redox potentials were assigned as the semiquinone/hydroquinone couple and the quinone/semiquinone couple, respectively. This study constitutes one of the first applications of surfactant-modified basal plane graphite electrodes to characterize the redox properties of a flavodoxin, thus providing a novel electrochemical method to study this class of protein. The X-ray crystal structure of the flavodoxin purified from A. vinelandii was solved at 1.17 Å resolution. With this structure, the native nitrogenase electron transfer proteins have all been structurally characterized. Docking studies indicate that a common binding site surrounding the Fe-protein [4Fe:4S] cluster mediates complex formation with the redox partners Mo-Fe protein, ferredoxin I, and flavodoxin II. This model supports a mechanistic hypothesis that electron transfer reactions between the Fe-protein and its redox partners are mutually exclusive

Definitive spectroscopic determination of the transverse interactions responsible for the magnetic quantum tunneling in Mn12-acetate

We present detailed angle-dependent single crystal electron paramagnetic resonance (EPR) data for field rotations in the hard plane of the S=10 single molecule magnet Mn12-acetate. A clear four-fold variation in the resonance positions may be attributed to an intrinsic fourth order transverse anisotropy (O44). Meanwhile, a four-fold variation of the EPR lineshapes confirms a recently proposed model wherein disorder associated with the acetic acid of crystallization induces a locally varying quadratic (rhombic) transverse anisotropy (O22). These findings explain most aspects of the magnetic quantum tunneling observed in Mn12-acetate.Comment: 7 pages, including figures, accepted for publication in Phys. Rev. Let

Observation of a Distribution of Internal Transverse Magnetic Fields in a Mn12-Based Single Molecule Magnet

A distribution of internal transverse magnetic fields has been observed in single molecule magnet (SMM) Mn12-BrAc in the pure magnetic quantum tunneling (MQT) regime. Magnetic relaxation experiments at 0.4 K are used to produce a hole in the distribution of transverse fields whose angle and depth depend on the orientation and amplitude of an applied transverse ``digging field.'' The presence of such transverse magnetic fields can explain the main features of resonant MQT in this material, including the tunneling rates, the form of the relaxation and the absence of tunneling selection rules. We propose a model in which the transverse fields originate from a distribution of tilts of the molecular magnetic easy axes.Comment: 4 page

Rate of change in abdominal aortic aneurysm diameter after endovascular repair

AbstractObjective: Untreated abdominal aortic aneurysms (AAAs) enlarge at a mean rate of 3.9 mm/y with great individual variability. We sought to determine the effect of endovascular repair on the rate of change in aneurysm size. Methods: There were 110 patients who underwent endovascular AAA repair at Stanford University Medical Center and who were followed up for 1 to 30 months (mean, 10 months) with serial contrast-infused helical computed tomography (CT). Maximal aneurysm diameter was determined using two independent methods: (1) measured manually, from cross-sectional computed tomography (XSCT) angiograms and (2) calculated from quantitative three-dimensional computed tomography (3DCT) data as orthonormal diameter. Results: Maximal cross-sectional aneurysm diameter measured by hand (XSCT) and calculated as orthonormal values (3DCT) correlated closely (r = 0.915; P <.001). The XSCT-measured diameter was larger by 2.3 ± 3.75 mm (P <.001), and the 95% CI for SE of the bias was 1.85 to 2.75 mm. Preoperative aneurysm diameter (XSCT 59.1 ± 8.4 mm; 3DCT 58.1 ± 9.3 mm) did not differ significantly from the initial postoperative diameter. Considering all patients, XSCT diameter decreased at a rate of 0.34 ± 0.69 mm/mo, and 3DCT diameter decreased at a rate of 0.28 ± 0.79 mm/mo. Aneurysms in patients without endoleaks had a higher rate of decrease, an XSCT diameter by 0.50 ± 0.74 mm/mo, and 3DCT diameter by 0.46 ± 0.84 mm/mo. In these patients, mean absolute decrease in diameter at 6 months was 3.4 ± 4.5 mm (XSCT) and 3.3 ± 5.9 mm (3DCT) and at 12 months, 5.9 ± 5.7 mm (XSCT) and 5.4 ± 5.7 mm (3DCT). Aneurysms in patients with persistent endoleaks did not change in mean XSCT diameter, and 3DCT diameter increased by 0.12 ± 0.52 mm/mo (not significant). Aneurysm diameter remained within 4 mm of original size in 68% (3DCT) to 71% (XSCT) of patients. In one patient, aneurysm diameter increased (XSCT and 3DCT) more than 5 mm. Four patients who had a new onset endoleak had a much higher expansion rate than those with a chronic endoleak (P <.05). Conclusions: The rate of decrease in aneurysm size (annualized 3.4-4.1 mm/y) after endovascular repair of AAA approximates the reported expansion rate in untreated aneurysms. However, individual aneurysm behavior is unpredictable, and the presence of an endoleak is unreliable in predicting changes in diameter. New onset endoleaks are associated with an enlargement rate greater than that of untreated aneurysms. (J Vasc Surg 2000;32:108-15.

Introduction of tau oligomers into cortical neurons alters action potential dynamics and disrupts synaptic transmission and plasticity

Tau is a highly soluble microtubule-associated protein that acts within neurons to modify microtubule stability. However, abnormally phosphorylated tau dissociates from microtubules to form oligomers and fibrils which associate in the somatodendritic compartment. Although tau can form neurofibrillary tangles (NFTs), it is the soluble oligomers that appear to be the toxic species. There is, however, relatively little quantitative information on the concentration-dependent and time-dependent actions of soluble tau oligomers (oTau) on the electrophysiological and synaptic properties of neurons. Here, whole-cell patch clamp recording was used to introduce known concentrations of oligomeric full-length tau-441 into mouse hippocampal CA1 pyramidal and neocortical Layer V thick-tufted pyramidal cells. oTau increased input resistance, reduced action potential amplitude and slowed action potential rise and decay kinetics. oTau injected into presynaptic neurons induced the run-down of unitary EPSPs which was associated with increased short-term depression. In contrast, introduction of oTau into postsynaptic neurons had no effect on basal synaptic transmission, but markedly impaired the induction of long-term potentiation (LTP). Consistent with its effects on synaptic transmission and plasticity, oTau puncta could be observed in the soma, axon and in the distal dendrites of injected neurons

Simulations of imperfect refractive index matching in scanning laser optical tomography and a method for correction

Since additive manufacturing has become increasingly popular in prototyping, printed optics are also beginning to enter the market. Novel characterization methods for printed optics are needed because traditional, destructive methods often do not work on these optics. The scope of investigation is also different for additively manufactured optics. Homogeneity of subtractive manufactured optics such as glass lenses is usually granted but for printed optics the interfaces in-between layers can cause absorption, scattering or refraction. Functionalized optics can also have characteristics such as fluorescence that cannot be tested with traditional methods. The presented work tries to fill the void for this particular challenge by studying two non-destructive methods for optical characterization of such components and expanding their use by clever combination. In Scanning Laser Optical Tomography (SLOT), a needle-like beam is formed and focused into the sample. The sample is scanned to form projection images and rotated to allow for reconstruction, which yields volumetric data about scattering, transmission and fluorescence of sample structures. Simulated SLOT measurements with imperfect Refractive Index (RI) matching of sample and medium are presented. A method to correct distorted measurements is presented and evaluated. The simulations imply that a measurement with a RI mismatch of up to 0.1 can still yield reasonable results. Copyright 2023 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited