Final shuttle-derived atmospheric database: Development and results from thirty-two flights

The final Shuttle-derived atmospheric data base is presented. The relational data base is comprised of data from 32 Space Transportation System (STS) descent flights, to include available meteorology data taken in support of each flight. For the most part, the available data are restricted to the middle atmosphere. In situ accelerations, sensed by the tri-redundant Inertial Measurement Unit (IMU) to an accuracy better than 1 mg, are combined with post-flight Best Estimate Trajectory (BET) information and predicted, flight-substantiated Orbiter aerodynamics to provide determinations up to altitudes of 95 km. In some instances, alternate accelerometry data with micro-g resolution were utilized to extend the data base well into the thermosphere. Though somewhat limited, the ensemble of flights permit a reasonable sampling of monthly, seasonal, and latitudinal variations which can be utilized for atmospheric science investigations and model evaluations and upgrades as appropriate. More significantly, the unparallel vertical resolution in the Shuttle-derived results indicate density shears normally associated with internal gravity waves or local atmospheric instabilities. Consequently, these atmospheres can also be used as stress-atmospheres for Guidance, Navigation and Control (GN and C) system development and analysis as part of any advanced space vehicle design activities

Final STS-35 Columbia descent BET products and results for LaRC OEX investigations

Final STS-35 'Columbia' descent Best Estimate Trajectory (BET) products have been developed for Langley Research Center (LaRC) Orbiter Experiments (OEX) investigations. Included are the reconstructed inertial trajectory profile; the Extended BET, which combines the inertial data and, in this instance, the National Weather Service atmospheric information obtained via Johnson Space Center; and the Aerodynamic BET. The inertial BET utilized Inertial Measurement Unit 1 (IMU1) dynamic measurements for deterministic propagation during the ENTREE estimation process. The final estimate was based on the considerable ground based C-band tracking coverage available as well as Tracking Data and Relay Satellite System (TDRSS) Doppler data, a unique use of the latter for endo-atmospheric flight determinations. The actual estimate required simultaneous solutions for the spacecraft position and velocity, spacecraft attitude, and six IMU parameters - three gyro biases and three accelerometer scale factor correction terms. The anchor epoch for this analysis was 19,200 Greenwich Mean Time (GMT) seconds which corresponds to an initial Shuttle altitude of approximately 513 kft. The atmospheric data incorporated were evaluated based on Shuttle derived considerations as well as comparisons with other models. The AEROBET was developed based on the Extended BET, the measured spacecraft configuration information, final mass properties, and the final Orbiter preoperation databook. The latter was updated based on aerodynamic consensus incrementals derived by the latest published FAD. The rectified predictions were compared versus the flight computed values and the resultant differences were correlated versus ensemble results for twenty-two previous STS entry flights

Critical Buckling Loads of the Perfect Hollomon's Power-law Columns

In this work, we present analytic formulas for calculating the critical buckling states of some plastic axial columns of constant cross-sections. The associated critical buckling loads are calculated by Euler-type analytic formulas and the associated deformed shapes are presented in terms of generalized trigonometric functions. The plasticity of the material is defined by the Hollomon's power-law equation. This is an extension of the Euler critical buckling loads of perfect elastic columns to perfect plastic columns. In particular, critical loads for perfect straight plastic columns with circular and rectangular cross-sections are calculated for a list of commonly used metals. Connections and comparisons to the classical result of the Euler-Engesser reduced-modulus loads are also presented.Comment: 15 page

Six-minute walk distance after coronary artery bypass grafting compared with medical therapy in ischaemic cardiomyopathy

Background: In patients with ischaemic left ventricular dysfunction, coronary artery bypass surgery (CABG) may decrease mortality, but it is not known whether CABG improves functional capacity. Objective: To determine whether CABG compared with medical therapy alone (MED) increases 6 min walk distance in patients with ischaemic left ventricular dysfunction and coronary artery disease amenable to revascularisation. Methods: The Surgical Treatment in Ischemic Heart disease trial randomised 1212 patients with ischaemic left ventricular dysfunction to CABG or MED. A 6 min walk distance test was performed both at baseline and at least one follow-up assessment at 4, 12, 24 and/or 36 months in 409 patients randomised to CABG and 466 to MED. Change in 6 min walk distance between baseline and follow-up were compared by treatment allocation. Results: 6 min walk distance at baseline for CABG was mean 340±117 m and for MED 339±118 m. Change in walk distance from baseline was similar for CABG and MED groups at 4 months (mean +38 vs +28 m), 12 months (+47 vs +36 m), 24 months (+31 vs +34 m) and 36 months (−7 vs +7 m), P>0.10 for all. Change in walk distance between CABG and MED groups over all assessments was also similar after adjusting for covariates and imputation for missing values (+8 m, 95% CI −7 to 23 m, P=0.29). Results were consistent for subgroups defined by angina, New York Heart Association class ≥3, left ventricular ejection fraction, baseline walk distance and geographic region. Conclusion: In patients with ischaemic left ventricular dysfunction CABG compared with MED alone is known to reduce mortality but is unlikely to result in a clinically significant improvement in functional capacity

High resistivity and ultrafast carrier lifetime in argon implanted GaAs

We have investigated the optoelectronic and structural properties of GaAs that has been implanted with Ar ions and subsequently annealed. The material exhibits all the basic optical and electronic characteristics typically observed in nonstoichiometric, As implanted or low‐temperature‐grown GaAs. Annealing of Ar implanted GaAs at 600 °C produces a highly resistive material with a subpicosecond trapping lifetime for photoexcited carriers. Transmission electron microscopy shows that, instead of As precipitates, characteristic for the nonstoichiometeric GaAs, voids ranging in size from 3 to 5 nm are observed in Ar implanted and annealed GaAs. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69637/2/APPLAB-69-17-2569-1.pd

Syntheses, characterization, density functional theory calculations, and activity of tridentate SNS zinc pincer complexes based on bis-imidazole or bis-triazole precursors

A series of tridentate pincer ligands, each possessing two sulfur- and one nitrogen-donor functionalities (SNS), based on bis-imidazole or bis-triazole salts were metallated with ZnCl2 to give new tridentate SNS pincer zinc(II) complexes [(SNS)ZnCl]+. The zinc complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH) and were characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies, electrospray mass spectrometry, and elemental analysis. The zinc complexes feature SNS donor atoms and pseudotetrahedral geometry about the zinc center, as is seen for liver alcohol dehydrogenase. The bond lengths and bond angles of the zinc complexes correlate well to those in horse LADH. The SNS ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies, elemental analysis, and cyclic voltammetry, and were found to be redox active. Gaussian calculations were performed and agree with the experimentally observed oxidation potentials for the pincer ligand precursors. The zinc complexes were screened for the reduction of electron-poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH), and it was determined that they enhance the reduction of electron-poor aldehydes. The SNS zinc pincer complexes with bis-triazole ligand precursors exhibit higher activity for the reduction of 4-nitrobenzaldehyde than do SNS zinc pincer complexes with bis-imidazole ligand precursors. Quantitative stoichiometric conversion was seen for the reduction of pyridine-2-carboxaldehyde via SNS zinc pincer complexes with either bis-imidazole or bis-triazole ligand precursors

Synthesis, Characterization, Density Functional Theory Calculations, and Activity of a Thione-Containing NNN-Zinc Pincer Complex Based on a Bis-triazole Precursor

A novel ambidentate tridentate pincer ligand based on a bis-triazole precursor, was prepared, characterized, and metallated with ZnCl2 to give a new tridentate NNN-bound pincer zinc(II) pincer complex: dichloro(η3-N,N,N)-[2,6-bis(3-[N-butyl]triazol-5-thione-1-yl)]pyridinezinc(II), [(NNN)ZnCl2]. This compound has pseudo-trigonal bipyramidal geometry at the zinc(II) center and exhibits metal–ligand binding that contrasts with our previously reported SNS-bound systems despite the availability of these same donor atoms in the current ligand set. The zinc complex was characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies, and electrospray mass spectrometry. The ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies, and cyclic voltammetry, and were found to be redox active. Density functional calculations, which investigate and support the nature of the NNN binding suggest that the experimentally observed oxidation and reduction waves are not the result of a simple one-electron process. The zinc complex was screened for the reduction of electron-poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH), and it was determined that they enhance the reduction of 4-nitrobenzaldehyde. Quantitative stoichiometric conversion was seen for the reduction of pyridine-2-carboxaldehyde

N-(4-Chloro-1,3-benzothia­zol-2-yl)-2-(3-methyl­phen­yl)acetamide monohydrate

In the title compound, C16H13ClN2OS·H2O, the dihedral angle between the mean planes of the benzothia­zole ring system and the methylphenyl ring is 79.3 (6)°. The crystal packing features inter­molecular O—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds involving the water mol­ecule and weak C—H⋯O, C—H⋯Cg and π–π stacking inter­actions [centroid–centroid distances = 3.8743 (7), 3.7229 (7) and 3.7076 (8) Å]