Material technology

Advanced high pressure O2/H2 propulsion systems as exemplified by the Space Shuttle Main Engine (SSME) create challenging operating environments for materials. Many components operate in either hydrogen or hydrogen-steam environments which may significantly degrade the performance of common alloys. The objective of the materials technology projects is to develop and evaluate candidate materials for application in advanced high pressure O2/H2 propulsion systems. These new and improved materials are to improve the durability or performance of the SSME or derivative engine. The program includes projects on the following topics: (1) Hydrogen Resistant Alloys; (2) High Pressure O2 Ignition and Burning; (3) Improved Turbine Blades; (4) Improved Turbine Disk Material; (5) Impact Reactivity in High Pressure O2; and Fiber Reinforced Superalloys

Performance Of Third Harmonic Ground Fault Protection Schemes For Generator Stator Windings

The paper shows how the normally generated third-harmonic voltage can be used to protect the lower ten to twenty percent of generator stator windings against ground faults. A method of determining the applicability of the scheme to a given machine is described which takes into account the design of the generator and its externally connected apparatus. The effects of finite resistence ground faults are also investigated and other advantages of the scheme, such as protection of the neutral, are also highlighted. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc

Assessing invasive plant species as threats in Mojave Desert parks

The invasion and persistence of exotic plant species threatens the natural features that national parks are designed to protect. For example, park managers have witnessed an increase in the frequency, extent and intensity of fires along with a reduction in native species richness and diversity. Many park managers are familiar with a suite of highly invasive plants, but lack a comprehensive and systematic way of prioritizing invasive plant species based on potential threats to the parks’ resources. We have entered into a collaborative project with the National Park Service’s Inventory and Monitoring program to develop an invasive plant early detection and monitoring protocol for the Mojave Desert Network (MOJN),which includes seven national park units. Our first step was to identify and prioritize invasive plants presently occurring or having the potential to invade each of the seven parks. To date, we have compiled a list of 350 species considered unnatural or weedy to the Mojave Desert region. From this comprehensive list, 154 were identified as having a medium or higher impact on the desert ecosystem. Since the MOJN hosts a wide variety of habitat types, our second step was to identify locations that are most vulnerable to invasion. We are currently synthesizing existing literature on species richness and elevation relationships, life-history and spatial distribution for these plants species

Effect of transient pinning on stability of drops sitting on an inclined plane

We report on new instabilities of the quasi-static equilibrium of water drops pinned by a hydrophobic inclined substrate. The contact line of a statically pinned drop exhibits three transitions of partial depinning: depinning of the advancing and receding parts of the contact line and depinning of the entire contact line leading to the drop's translational motion. We find a region of parameters where the classical Macdougall-Ockrent-Frenkel approach fails to estimate the critical volume of the statically pinned inclined drop

Early oral contraceptive use and breast cancer: results of another case-control study.

We report the results of a case-control study of oral contraceptive use and breast cancer conducted in London, Oxford and Edinburgh between 1980 and 1984. One thousand one hundred and twenty-five women aged 16-64 years with newly diagnosed breast cancer and a like number of matched controls were interviewed and asked about their past due use of oral contraceptives (OCs). Among women aged 45 years or more at diagnosis there was no evidence of an association between OC use and breast cancer. Among the 351 pairs of women aged under 45 years at diagnosis there was a significantly elevated risk associated with increasing duration of use before first full term pregnancy (relative risk for 4+ years use versus never use = 2.6, 95% confidence limits, 1.3-5.4). Since this result is at variance with the findings in some other studies we have investigated the nature of this association with particular emphasis on possible bias, pill type and a latent effect

Echolocation detections and digital video surveys provide reliable estimates of the relative density of harbour porpoises

Acknowledgements We would like to thank Erik Rexstad and Rob Williams for useful reviews of this manuscript. The collection of visual and acoustic data was funded by the UK Department of Energy & Climate Change, the Scottish Government, Collaborative Offshore Wind Research into the Environment (COWRIE) and Oil & Gas UK. Digital aerial surveys were funded by Moray Offshore Renewables Ltd and additional funding for analysis of the combined datasets was provided by Marine Scotland. Collaboration between the University of Aberdeen and Marine Scotland was supported by MarCRF. We thank colleagues at the University of Aberdeen, Moray First Marine, NERI, Hi-Def Aerial Surveying Ltd and Ravenair for essential support in the field, particularly Tim Barton, Bill Ruck, Rasmus Nielson and Dave Rutter. Thanks also to Andy Webb, David Borchers, Len Thomas, Kelly McLeod, David L. Miller, Dinara Sadykova and Thomas Cornulier for advice on survey design and statistical approache. Data Accessibility Data are available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.cf04gPeer reviewedPublisher PD

Extending NASA Research Results to Benefit Society: Rapid Prototyping for Coastal Applications

The mission of the NASA Applied Sciences Program is to expand and accelerate the use of NASA research results to benefit society in 12 application areas of national priority. ONe of the program's major challenges is to perform a quick, efficient, and detailed review (i.e., prototyping) of the large number of combinations of NASA observations and results from Earth system models that may be used by a wide range of decision support tools. A Rapid Prototyping Capacity (RPC) is being developed to accelerate the use of NASA research results. Here, we present the conceptual framework of the Rapid Prototyping Capacity within the context of quickly assessing the efficacy of NASA research results and technologies to support the Coastal Management application. An initial RPC project designed to quickly evaluate the utility of moderate-resolution MODIS products for calibrating/validating coastal sediment transport models is also presented

Spectroscopy of 54^{54}Ti and the systematic behavior of low energy octupole states in Ca and Ti isotopes

Excited states of the $N=32$ nucleus $^{54}$Ti have been studied, via both inverse-kinematics proton scattering and one-neutron knockout from $^{55}$Ti by a liquid hydrogen target, using the GRETINA $\gamma$-ray tracking array. Inelastic proton-scattering cross sections and deformation lengths have been determined. A low-lying octupole state has been tentatively identified in $^{54}$Ti for the first time. A comparison of $(p,p')$ results on low-energy octupole states in the neutron-rich Ca and Ti isotopes with the results of Random Phase Approximation calculations demonstrates that the observed systematic behavior of these states is unexpected.Comment: 7 pages, 8 figure

Spectroscopy of 54^{54}Ti and the systematic behavior of low energy octupole states in Ca and Ti isotopes

Excited states of the $N=32$ nucleus $^{54}$Ti have been studied, via both inverse-kinematics proton scattering and one-neutron knockout from $^{55}$Ti by a liquid hydrogen target, using the GRETINA $\gamma$-ray tracking array. Inelastic proton-scattering cross sections and deformation lengths have been determined. A low-lying octupole state has been tentatively identified in $^{54}$Ti for the first time. A comparison of $(p,p')$ results on low-energy octupole states in the neutron-rich Ca and Ti isotopes with the results of Random Phase Approximation calculations demonstrates that the observed systematic behavior of these states is unexpected.Comment: 7 pages, 8 figure