Eccentricity effects on leakage of a brush seal at low speeds

The effects of eccentricity on brush seal leakage at low rotational speeds were investigated. Included are the leakage results for ambient temperature air and nearly saturated streams at three different rotor eccentricities at both 0 and 400 rpm. A brush seal with a nominal bore diameter of 13.647 cm. (5.3730 in.) was used. It had a radial concentric interference of 0.071 cm (0.0028 in.) and a fence height of 0.0927 cm (0.0365 in.). There were 1060 bristles per centimeter of circumference (2690 bristles per inch of circumference). Rotor eccentricities of 0.003, 0.010, 0.038, and 0.043 cm (0.001, 0.004, 0.015, and 0.017 in.) were achieved by using bushings with different offsets. The results were compared with an annular seal model (FLOWCAL) for air and to a standard labyrinth seal model for steam. The annular seal model was also compared with a bulk flow model of a concentric brush seal in air. Large eccentricities did not damage the brush seals or their Haynes 25 bristles. However, the 304 stainless steel rotor did not show wear, indicating a harder surface is needed. Only the stream data showed hysteresis and were affected by shaft rotation. The brush seal had lower leakage rates than those predicted for comparable annular and labyrinth seals (conventional) because of the large clearances those seals require to accommodate large shaft excursions

Hydrogen Atom Transfer-Driven Enantioselective Minisci Reaction of Amides.

Minisci-type reactions constitute one of the most powerful methods for building up complexity around basic heteroarenes. The most desirable variants involve formal oxidative coupling of a C-H bond on each partner, leading back to the simplest possible starting materials. We herein disclose a method that enables such a coupling of linear amides and heteroarenes with full control of enantioselectivity at the newly formed stereocenter as well as site selectivity on both the heteroarene and the amide. This is achieved by the use of a chiral phosphoric acid catalyst in conjunction with diacetyl as a combined hydrogen atom transfer reagent and oxidant. Diacetyl is directly photoexcitable, and thus, no extraneous photocatalyst is required: an added feature that contributes to the simplicity and practicality of the protocol.EPSRC, GlaxoSmithKline, ER

Probing Spectral Line Gradients Beyond One Effective Radius in NGC 3610

The outer region (0.75--1.25 r_e in the B-band) of the merger-remnant elliptical NGC 3610 is studied using extremely high signal to noise Keck spectra, with a supplementary spectrum of the galaxy center. Stellar population parameters -- age, [Z/H], [$\alpha$/Fe] -- are measured in several apertures along the slit. Using the multi-index simultaneous fitting method of Proctor et al. (2004), no significant stellar population gradients are detected in the outer parts of the galaxy. The overall gradients relative to the galaxy center are consistent with those found in many other early-type galaxies, though the metallicity gradient is much steeper than would be expected if NGC 3610 formed in a major merger event. Standard analysis methods using the H$\beta$ index are found to produce spurious radially variable gradients.Comment: 15 pages, 9 figures, accepted by A

A Computational and Experimental Investigation of the Origin of Selectivity in the Chiral Phosphoric Acid Catalyzed Enantioselective Minisci Reaction.

The Minisci reaction is one of the most valuable methods for directly functionalizing basic heteroarenes to form carbon-carbon bonds. Use of prochiral, heteroatom-substituted radicals results in stereocenters being formed adjacent to the heteroaromatic system, generating motifs which are valuable in medicinal chemistry and chiral ligand design. Recently a highly enantioselective and regioselective protocol for the Minisci reaction was developed, using chiral phosphoric acid catalysis. However, the precise mechanism by which this process operated and the origin of selectivity remained unclear, making it challenging to develop the reaction more generally. Herein we report further experimental mechanistic studies which feed into detailed DFT calculations that probe the precise nature of the stereochemistry-determining step. Computational and experimental evidence together support Curtin-Hammett control in this reaction, with initial radical addition being quick and reversible, and enantioselectivity being achieved in the subsequent slower, irreversible deprotonation. A detailed survey via DFT calculations assessed a number of different possibilities for selectivity-determining deprotonation of the radical cation intermediate. Computations point to a clear preference for an initially unexpected mode of internal deprotonation enacted by the amide group, which is a crucial structural feature of the radical precursor, with the assistance of the associated chiral phosphate. This unconventional stereodetermining step underpins the high enantioselectivities and regioselectivities observed. The mechanistic model was further validated by applying it to a test set of substrates possessing varied structural features.EPSRC GSSK ERC Leverhulme Trust Isaac Newton Trus

The Chemical Properties of Milky Way and M31 Globular Clusters: I. A Comparative Study

A comparative analysis is performed between high-quality integrated spectra of 30 globular clusters in M31, 20 Milky Way clusters, and a sample of field and cluster elliptical galaxies. We find that the Lick CN indices in the M31 and Galactic clusters are enhanced relative to the bulges of the Milky Way, M31, and elliptical spheroids. Although not seen in the Lick CN indices, the near-UV cyanogen feature (3883 A) is strongly enhanced in M31 clustesr with respect to the Galactic globulars at metallicities, --1.5<[Fe/H]<--0.3. Carbon shows signs of varying amongst these two groups. For [Fe/H]>--0.8, we observe no siginificant differences in the Hdelta, Hgamma, or Hbeta indices between the M31 and Galactic globulars. The sample of ellipticals lies offset from the loci of all the globulars in the Cyanogen--[MgFe], and Balmer--[MgFe] planes. Six of the M31 cluster spectra appear young, and are projected onto the M31 disk. Population synthesis models suggest that these are metal-rich clusters with ages 100--800 Myr, metallicities --0.20 < [Fe/H] <0.35, and masses 0.7 -7.0x10^4 Msun. Two other young clusters are Hubble V in NGC 205, and an older (~3 Gyr) cluster ~7 kpc away from the plane of the disk. The six clusters projected onto the disk rotate in a similar fashion to the HI gas in M31, and three clusters exhibit thin disk kinematics (Morrison et al.). Dynamical masses and structural parameters are required for these objects to determine whether they are massive open clusters or globular clusters. If the latter, our findings suggest globular clusters may trace the build up of galaxy disks. In either case, we conclude that these clusters are part of a young, metal-rich disk cluster system in M31, possibly as young as 1 Gyr old.Comment: 52 pages, 14 figures, 8 tables, minor revisions in response to referee, conclusions remain the same. Scheduled to appear in the October 2004 issue of The Astronomical Journa

A Deep Space Network Portable Radio Science Receiver

The Radio Science Receiver (RSR) is an open-loop receiver installed in NASA s Deep Space Network (DSN), which digitally filters and records intermediate-frequency (IF) analog signals. The RSR is an important tool for the Cassini Project, which uses it to measure perturbations of the radio-frequency wave as it travels between the spacecraft and the ground stations, allowing highly detailed study of the composition of the rings, atmosphere, and surface of Saturn and its satellites

Turbine Seal Research at NASA GRC

Low-leakage, long-life turbomachinery seals are important to both Space and Aeronautics Missions. (1) Increased payload capability (2) Decreased specific fuel consumption and emissions (3) Decreased direct operating costs. NASA GRC has a history of significant accomplishments and collaboration with industry and academia in seals research. NASA's unique, state-of-the-art High Temperature, High Speed Turbine Seal Test Facility is an asset to the U.S. Engine / Seal Community. Current focus is on developing experimentally validated compliant, non-contacting, high temperature seal designs, analysis, and design methodologies to enable commercialization

The fracture energy of ruptures driven by flash heating

We present a model for dynamic weakening of faults based on local flash heating at microscopic asperity contacts coupled to bulk heating at macroscopic scale. We estimate the fracture energy G associated with that rheology and find that for constant slip rate histories G scales with slip δ as math formula at small slip, while math formula at large slip. This prediction is quantitatively consistent with data from laboratory experiments conducted on dry rocks at constant slip rate. We also estimate G for crack-like ruptures propagating at constant speed and find that math formula in the large slip limit. Quantitative estimates of G in that regime tend to be several orders of magnitude lower than seismologically inferred values of G. We conclude that while flash heating provides a consistent explanation for the observed dynamic weakening in laboratory experiments with kinematically imposed slip, its contribution to the energy dissipation during earthquakes becomes negligible for large events when considering the elastodynamic coupling between strength and slip evolution

Designing high-quality implementation research: development, application, feasibility and preliminary evaluation of the implementation science research development (ImpRes) tool and guide

Background:  Designing implementation research can be a complex and daunting task, especially for applied health researchers who have not received specialist training in implementation science. We developed the Implementation Science Research Development (ImpRes) tool and supplementary guide to address this challenge and provide researchers with a systematic approach to designing implementation research. Methods:  A multi-method and multi-stage approach was employed. An international, multidisciplinary expert panel engaged in an iterative brainstorming and consensus-building process to generate core domains of the ImpRes tool, representing core implementation science principles and concepts that researchers should consider when designing implementation research. Simultaneously, an iterative process of reviewing the literature and expert input informed the development and content of the tool. Once consensus had been reached, specialist expert input was sought on involving and engaging patients/service users; and economic evaluation. ImpRes was then applied to 15 implementation and improvement science projects across the National Institute of Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care (CLAHRC) South London, a research organisation in London, UK. Researchers who applied the ImpRes tool completed an 11-item questionnaire evaluating its structure, content and usefulness. Results:  Consensus was reached on ten implementation science domains to be considered when designing implementation research. These include implementation theories, frameworks and models, determinants of implementation, implementation strategies, implementation outcomes and unintended consequences. Researchers who used the ImpRes tool found it useful for identifying project areas where implementation science is lacking (median 5/5, IQR 4–5) and for improving the quality of implementation research (median 4/5, IQR 4–5) and agreed that it contained the key components that should be considered when designing implementation research (median 4/5, IQR 4–4). Qualitative feedback from researchers who applied the ImpRes tool indicated that a supplementary guide was needed to facilitate use of the tool. Conclusions:  We have developed a feasible and acceptable tool, and supplementary guide, to facilitate consideration and incorporation of core principles and concepts of implementation science in applied health implementation research. Future research is needed to establish whether application of the tool and guide has an effect on the quality of implementation research