Subsonic high-angle-of-attack aerodynamic characteristics of a cone and cylinder with triangular cross sections and a cone with a square cross section

Experiments were conducted in the 12-Foot Pressure Wind Tunnel at Ames Research Center on three models with noncircular cross sections: a cone having a square cross section with rounded corners and a cone and cylinder with triangular cross sections and rounded vertices. The cones were tested with both sharp and blunt noses. Surface pressures and force and moment measurements were obtained over an angle of attack range from 30 deg to 90 deg and selected oil-flow experiments were conducted to visualize surface flow patterns. Unit Reynolds numbers ranged from 0.8x1,000,000/m to 13.0x1,000,000/m at a Mach number of 0.25, except for a few low-Reynolds-number runs at a Mach number of 0.17. Pressure data, as well as force data and oil-flow photographs, reveal that the three dimensional flow structure at angles of attack up to 75 deg is very complex and is highly dependent on nose bluntness and Reynolds number. For angles of attack from 75 deg to 90 deg the sectional aerodynamic characteristics are similar to those of a two dimensional cylinder with the same cross section

Structural Properties, Order-Disorder Phenomena and Phase Stability of Orotic Acid Crystal Forms

Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1) and dimethylsulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135°C and loses only a small part of the water when stored over desiccants (25°C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen-bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a non-layer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions different levels of order-disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration

Accretion variability of Herbig Ae/Be stars observed by X-Shooter. HD 31648 and HD 163296

This work presents X-Shooter/VLT spectra of the prototypical, isolated Herbig Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by timescales ranging from days to months. Each spectrum spans over a wide wavelength range covering from 310 to 2475 nm. We have monitored the continuum excess in the Balmer region of the spectra and the luminosity of twelve ultraviolet, optical and near infrared spectral lines that are commonly used as accretion tracers for T Tauri stars. The observed strengths of the Balmer excesses have been reproduced from a magnetospheric accretion shock model, providing a mean mass accretion rate of 1.11 x 10^-7 and 4.50 x 10^-7 Msun yr^-1 for HD 31648 and HD 163296, respectively. Accretion rate variations are observed, being more pronounced for HD 31648 (up to 0.5 dex). However, from the comparison with previous results it is found that the accretion rate of HD 163296 has increased by more than 1 dex, on a timescale of ~ 15 years. Averaged accretion luminosities derived from the Balmer excess are consistent with the ones inferred from the empirical calibrations with the emission line luminosities, indicating that those can be extrapolated to HAe stars. In spite of that, the accretion rate variations do not generally coincide with those estimated from the line luminosities, suggesting that the empirical calibrations are not useful to accurately quantify accretion rate variability.Comment: 14 pages, 7 Figures, Accepted in Ap

RENAL HOMOGRAFTS IN PATIENTS WITH MAJOR DONOR-RECIPIENT BLOOD GROUP INCOMPATIBILITIES.

Between November 24, 1962, and May 15, 1963, 12 renal homografts were done at the University of Colorado Medical Center. In half of the cases, a kidney was provided by a donor of the same major blood type as the recipient. In the other half, the major blood groups of the donor and recipient patients were different. The present study is concerned with an analysis of the results in these comparative series, in order to determine what influence the presence or absence of major blood group compatibility had upon the early success rate

Clopidogrel Bisulfate (Profiles of Drugs Substances, Excipients and Related Methodology)

Clopidogrel contains a center of dissymmetry, and hence is capable of being resolved into its two mirror image compounds. It has been found that only the (S)-enantiomer, which corresponds to the dextrorotatory form, has antithrombotic activity and that the (R)-enantiomer, which corresponds to the levorotatory form, does not exhibit antithrombotic activity. Moreover, in animal studies, the (R)-enantiomer triggered convulsions at high doses. Consequently, (R)-clopidogrel bisulfate is considered to be one of the impurities in (S)-clopidogrel bisulfate bulk drug substance. Clopidogrel is extensively metabolized in vivo by carboxylesterase hydrolysis on the ester function, resulting in the formation of clopidogrel carboxylic acid (CCA) as the inactive metabolite of clopidogrel. In addition, small amounts of clopidogrel are converted to a pharmacologically active metabolite (AM) via the intermediate metabolite inactive 2-oxoclopidogrel, which is then converted to an AM by a two-step cytochrome P450 oxidation process. Due to the instability of clopidogrel AM and the abundant availability of the more stable CCA in human plasma, CCA is used to indirectly determine the pharmacokinetics of clopidogrel. Furthermore, there is also a possibility that (S)-clopidogrel undergoes an in vivo chiral inversion into the other clopidogrel enantiomer, which becomes hydrolyzed to (R)-CCA. Metabolic pathways and potential in vivo chiral inversions of clopidogrel are described. Until recently, only chromatographic methods were used to determine clopidogrel in biological samples

Use of Living Donors for Renal Homotransplantation

The procedure is described which is followed at the University of Colorado Medical Center for the selection and evaluation of living donors for renal homotransplantation. Priority is given to volunteers who have a close genetic relationship to the recipient. The aortogram is the single most useful test for determining which kidney to be used. If either organhas a single artery, it can be employed for homografting without fear of encountering anatomic difficulties at the time of its subsequent insertion into the recipient. Twenty-two left and 18 right kidneys have been excised. The donor operation has been a safe one. The only complications have been two pneumothoraces, one atelectasis, one transient peroneal nerve palsy, and two subcutaneous wound infections. Renal hyperplasia of the remaining kidney apparently occurs promptly since the creatinine clearance returns to or toward normal within a few weeks after operation. Interestingly, the same phenomenon is also observed in the homograft in those recipients who have a successful result. The steps in the donor operation are described for both right and left sides. Wide exposure, block removal of the specimen, and meticulous technique are required both to protect the donor from surgical accidents and to insure a homograft of high quality. Homograft cooling is provided eitherby total body hypothermia of the donor or by a method in which intra-arterial infusion of a chilled electrolyte solution isused. The relative future roles of living and cadaveric donors are discussed. The results with parental or sibling donations have been good enough to justify further employment of these sources. In cases in which a genetically unrelated donor must be used, a sounder policy may be to seek cadaveric organs, especially if the recipient falls in an older age group. © 1964 American Medical Association All rights reserved