Aerothermodynamic Testing and Boundary Layer Trip Sizing of the HIFiRE Flight 1 Vehicle

An experimental wind tunnel test was conducted in the NASA Langley Research Center s 20-Inch Mach 6 Air Tunnel in support of the Hypersonic International Flight Research Experimentation Program. The information in this article is focused on the Flight 1 configuration, the first in a series of flight experiments. The article documents experimental measurements made over a Reynolds numbers range of 2.1x10(exp 6)/ft to 5.6x10(exp 6)/ft and angles of attack of -5 to +5 deg on several scaled ceramic heat transfer models of the Flight 1 configuration. Global heat transfer was measured using phosphor thermography and the resulting images and heat transfer distributions were used to infer the state of the boundary layer on the vehicle windside and leeside surfaces. Boundary layer trips were used to force the boundary layer turbulent and the experimental data highlighted in this article were used to size and place the boundary layer trip for the flight vehicle. The required height of the flight boundary layer trip was determined to be 0.079 in and the trip was moved from the design location of 7.87 in to 20.47 in to ensure that augmented heating would not impact the laminar side of the vehicle. Allowable roughness was selected to be 3.2x10(exp -3) in

On Petition for a Writ of Certiorari to The United States Court of Appeals for The Eighth Circuit, Brief of Law Professors Paul F. Rothstein, et. al., Office of the President v. Office of Independent Counsel

This Court should grant review not only because this is a case of national importance and prominence, but also because the decision below is a conspicuous departure from settled principles of evidence law. The panel majority concluded that communications between government lawyers and government officials are not protected by the attorney-client privilege, at least when those communications are sought by a federal grand jury. That conclusion conflicts with the predominant common-law understanding that the attorney-client privilege applies to government entities and that where the privilege applies, it is absolute (i.e., it protects against disclosure in all types of legal and investigative proceedings). In particular, the Court of Appeals\u27 decision rests on a fundamental misunderstanding of this Court\u27s decisions in Upjohn Co. v. United States, 449 U.S. 383 (1981), and United States v. Nixon, 418 U.s. 683 (1974). Moreover, this case warrants further review because the decision below has profound implications beyond the parties to this dispute. The Court of Appeals\u27 ruling, if allowed to stand, will create widespread uncertainty among federal, state, and local officials concerning the extent to which their communications with their agency lawyers, for the purpose of seeking legal advice in the conduct of governmental affairs, are protected by the attorney-client privilege. Unless this Court grants review and resolves this uncertainty, the decision below will likely have an adverse effect on the current and future operation of not only the Office of the President of the United States, but also government at all levels. At the very least, a decision of such vast implications (as in the present case) should be made by the highest court in the land. We accordingly urge the Court to grant the petition for review

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D2-tagged AlO1-4 − and Al2O3-6 − are measured in the region from 400 to 1200 cm−1. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al2O3-6 − anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO3 −. Terminal Al–O stretching modes are found between 1140 and 960 cm−1. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm−1) and lower energies (850-570 cm−1), respectively. Four modes in-between 910 and 530 cm−1 represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al–(O)2–Al ring

Predictors of aneurysmal formation after surgical correction of aortic coarctation

AbstractObjectivesWe sought to identify the predictors of aneurysmal formation after surgical correction of aortic coarctation.BackgroundIn 9% of patients, aneurysms develop late after corrective surgery of coarctation of the aorta, with a 36% mortality rate if left untreated. However, the predictors of postsurgical aneurysmal formation are unknown.MethodsOf 25 aortic aneurysms requiring corrective surgery 152 ± 78 months after the initial coarctation repair, 8 were located in the ascending aorta (type A) and 17 at the site of previous repair (local type). Seventy-four patients without progression of the aortic diameter within 189 ± 71 months after coarctation repair were used for categorical data analysis in an attempt to identify the predictors of postsurgical aneurysmal formation.ResultsAdvanced age at coarctation repair (p = 0.004) and patch graft technique (p < 0.0005) independently predicted local aneurysmal formation. Type A aneurysm was univariately associated with the presence of a bicuspid aortic valve (p = 0.02), advanced age at coarctation repair (p = 0.044) and a high preoperative peak systolic pressure gradient of 74 ± 21 mm Hg (p = 0.041). Conversely, multivariate analysis confirmed only the presence of a bicuspid aortic valve (p = 0.015) as an independent predictor of type A aneurysm. Receiver operating characteristic curve analysis revealed that 72% of patients with a postsurgical aneurysm had an operation at age 13.5 years or more, whereas 69% with no postsurgical aneurysm had an operation at a younger age.ConclusionsUse of the patch graft technique and late correction of coarctation can predict aneurysmal formation at the site of coarctation repair, although patients with a bicuspid aortic valve may be at risk for an aneurysm developing in the ascending aorta, particularly after late repair of aortic coarctation with high preoperative pressure gradients

Confrontation and the Utility of Rules

There is a good reason why evidence scholars continue to be fascinated and perplexed, and some courts continue at least to be perplexed, by the types of evidence that tend to be lumped together misleadingly under the headings nonassertive conduct or implied assertions. Evidence of this sort highlights a paradox of the prevailing law of hearsay. I believe that this paradox cannot be resolved without fundamentally transforming the structure of that law. Thus, while I agree - within the current framework - with many of the insights so ably stated in this Symposium, I think evidence scholars must devote their efforts to construction of a better structure

Global analysis by hidden symmetry

Hidden symmetry of a G'-space X is defined by an extension of the G'-action on X to that of a group G containing G' as a subgroup. In this setting, we study the relationship between the three objects: (A) global analysis on X by using representations of G (hidden symmetry); (B) global analysis on X by using representations of G'; (C) branching laws of representations of G when restricted to the subgroup G'. We explain a trick which transfers results for finite-dimensional representations in the compact setting to those for infinite-dimensional representations in the noncompact setting when $X_C$ is $G_C$-spherical. Applications to branching problems of unitary representations, and to spectral analysis on pseudo-Riemannian locally symmetric spaces are also discussed.Comment: Special volume in honor of Roger Howe on the occasion of his 70th birthda

A comprehensive study of GRB 070125, a most energetic gamma ray burst

We present a comprehensive multiwavelength analysis of the bright, long duration gamma-ray burst GRB 070125, comprised of observations in $\gamma$-ray, X-ray, optical, millimeter and centimeter wavebands. Simultaneous fits to the optical and X-ray light curves favor a break on day 3.78, which we interpret as the jet break from a collimated outflow. Independent fits to optical and X-ray bands give similar results in the optical bands but shift the jet break to around day 10 in the X-ray light curve. We show that for the physical parameters derived for GRB 070125, inverse Compton scattering effects are important throughout the afterglow evolution. While inverse Compton scattering does not affect radio and optical bands, it may be a promising candidate to delay the jet break in the X-ray band. Radio light curves show rapid flux variations, which are interpreted as due to interstellar scintillation, and are used to derive an upper limit of $2.4 \times 10^{17}$ cm on the radius of the fireball in the lateral expansion phase of the jet. Radio light curves and spectra suggest a high synchrotron self absorption frequency indicative of the afterglow shock wave moving in a dense medium. Our broadband modeling favors a constant density profile for the circumburst medium over a wind-like profile ($R^{-2}$). However, keeping in mind the uncertainty of the parameters, it is difficult to unambiguously distinguish between the two density profiles. Our broadband fits suggest that \event is a burst with high radiative efficiency ($> 60$).Comment: 50 pages, 33 figures, sty file included, Appeared in 20 Aug 2008 edition of Astrophysical Journa

EVLA Observations Constrain the Environment and Progenitor System of Type Ia Supernova 2011fe

We report unique EVLA observations of SN 2011fe representing the most sensitive radio study of a Type Ia supernova to date. Our data place direct constraints on the density of the surrounding medium at radii ~10^15-10^16 cm, implying an upper limit on the mass loss rate from the progenitor system of Mdot <~ 6 x 10^-10 Msol/yr (assuming a wind speed of 100 km/s), or expansion into a uniform medium with density n_CSM <~ 6 cm^-3. Drawing from the observed properties of non-conservative mass transfer among accreting white dwarfs, we use these limits on the density of the immediate environs to exclude a phase space of possible progenitors systems for SN 2011fe. We rule out a symbiotic progenitor system and also a system characterized by high accretion rate onto the white dwarf that is expected to give rise to optically-thick accretion winds. Assuming that a small fraction, 1%, of the mass accreted is lost from the progenitor system, we also eliminate much of the potential progenitor parameter space for white dwarfs hosting recurrent novae or undergoing stable nuclear burning. Therefore, we rule out the most popular single degenerate progenitor models for SN 2011fe, leaving a limited phase space inhabited by some double degenerate systems and exotic progenitor scenarios.Comment: Accepted to Ap

Constraints on Type Ib/c and GRB Progenitors

Although there is strong support for the collapsar engine as the power source of long-duration gamma-ray bursts (GRBs), we still do not definitively know the progenitor of these explosions. Here we review the current set of progenitor scenarios for long-duration GRBs and the observational constraints on these scenarios. Examining these, we find that single-star models cannot be the only progenitor for long-duration GRBs. Several binary progenitors can match the solid observational constraints and also have the potential to match the trends we are currently seeing in the observations. Type Ib/c supernovae are also likely to be produced primarily in binaries; we discuss the relationship between the progenitors of these explosions and those of the long-duration GRBs.Comment: 36 pages, 6 figure

Homophily and Contagion Are Generically Confounded in Observational Social Network Studies

We consider processes on social networks that can potentially involve three factors: homophily, or the formation of social ties due to matching individual traits; social contagion, also known as social influence; and the causal effect of an individual's covariates on their behavior or other measurable responses. We show that, generically, all of these are confounded with each other. Distinguishing them from one another requires strong assumptions on the parametrization of the social process or on the adequacy of the covariates used (or both). In particular we demonstrate, with simple examples, that asymmetries in regression coefficients cannot identify causal effects, and that very simple models of imitation (a form of social contagion) can produce substantial correlations between an individual's enduring traits and their choices, even when there is no intrinsic affinity between them. We also suggest some possible constructive responses to these results.Comment: 27 pages, 9 figures. V2: Revised in response to referees. V3: Ditt