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  • 1
    Call number: MOP 9652
    In: Geophysical memoirs
    Type of Medium: Monograph available for loan
    Pages: 40 S. : graph. Darst.
    Series Statement: Geophysical memoirs / Meteorological Office 48
    Location: MOP - must be ordered
    Branch Library: GFZ Library
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  • 2
    Publication Date: 2013-09-20
    Description: [1]  Controlled recovery of hydrated minerals subjected to planar shock loading is challenging because of the large difference in shock impedance between the natural samples and the engineering materials used as the recovery capsules. Significant differences in recovery capsule design confound straightforward interpretation of existing data on shock modification of hydrated minerals. We present x-ray diffraction and infrared spectroscopy results from new shock recovery experiments experiments on nontronite (a smectite clay observed on Mars) and identify major issues in the interpretation of recovered samples. Previous work assumes that the first shock pressure step in a ring-up configuration is the most important factor in the interpretation of shock modification. By comparing the x-ray diffraction and infrared spectroscopy data from experiments with similar first shock steps but significantly different final shock states, we show that one cannot simply interpret the recovered samples based upon the first shock pressure step. This work demonstrates the need for a deeper understanding of the thermodynamics of ring-up experiments in order to be able to interpret the results in terms of an equivalent single shock loading pressure for planetary applications. In this work we also show that venting of the samples does not matter significantly at low pressures but may be important at high pressures. We have developed a recovery method and validation test that allows us to address the major issues and technical tradeoffs with shock recovery experiments on volatile materials.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2015-10-14
    Description: Progress is being made in the development of an Ion Source Test Facility (ISTF) by D-Pace Inc. in collaboration with Buckley Systems Ltd. in Auckland, NZ. The first phase of the ISTF is to be commissioned in October 2015 with the second phase being commissioned in March 2016. The facility will primarily be used for the development and the commercialization of ion sources. It will also be used to characterize and further develop various D-Pace Inc. beam diagnostic devices.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
    Publication Date: 2016-09-17
    Description: With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. In particular, what allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time, are crucial issues. In this regard, Mars is uniquely suited, providing the solar system's longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify 6 broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early bombardment during an era of higher impact flux have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. The unique dataset recording the evolution of early Mars will feed forward to understanding divergent evolutionary paths of the Earth, Venus, and thousands of small rocky extrasolar planets yet to be discovered.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
    Publication Date: 2012-04-10
    Description: Thorson, J. T., Stewart, I. J., and Punt, A. E. 2012. Development and application of an agent-based model to evaluate methods for estimating relative abundance indices for shoaling fish such as Pacific rockfish ( Sebastes spp.). – ICES Journal of Marine Science, 69: 635–647. Many marine fish, including Pacific rockfish ( Sebastes spp.), exhibit habitat-selective and shoaling behaviours, which can lead to imprecision when using survey data to estimate an annual index of stock abundance. We develop a spatial agent-based model (ABM) for Pacific rockfish, which generates data similar to those observed in existing bottom-trawl surveys and can represent various spatial and shoaling behaviours. We use the ABM to evaluate the performance of a model that uses mixture distribution methods to account for fish shoals and delta-methods to account for range expansion or contraction. This delta-mixture model is compared with conventional delta-generalized linear models (delta-GLMs) and a quantile regression delta-model. The delta-mixture increases precision by 15% relative to delta-GLMs in estimated abundance indices when shoaling behaviours are present, whereas precision is similar between delta-GLM and delta-mixture models when shoals are absent. The delta-quantile method has similar improvements over conventional delta-GLM methods, and the improved precision from delta-mixture and delta-quantile methods is decreased but not eliminated by decreased sampling intensities. These simulations represent the first evaluation of delta-mixture models for index standardization and show a substantial improvement over conventional delta-GLMs for shoaling species such as Pacific rockfish.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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  • 6
    Publication Date: 2015-10-01
    Description: CW 13.56 MHz radio frequency-driven H − ion source is under development at the University of Jyväskylä for replacing an existing filament-driven ion source at the MCC30/15 cyclotron. Previously, production of 1 mA H − beam, which is the target intensity of the ion source, has been reported at 3 kW of RF power. The original ion source front plate with an adjustable electromagnet based filter field has been replaced with a new front plate with permanent magnet filter field. The new structure is more open and enables a higher flux of ro-vibrationally excited molecules towards the plasma electrode and provides a better control of the potential near the extraction due to a stronger separation of the main plasma from the plasma electrode. While the original system provided better control over the e − /H − ratio, the new configuration has led to a higher production efficiency of 1 mA H − at 1.75 kW RF power. The latest results and upgrade plans are presented.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 7
    Publication Date: 2016-01-20
    Description: ABSTRACT This work presents updated hydrologic projections for the Upper Colorado River Basin (UCRB) using downscaled (approximately 12 km) General Circulation Model (GCM) output from Coupled Model Intercomparison Project – Phase 5 (CMIP5) with a comparison to CMIP3 GCMs. We use the Soil and Water Assessment Tool model to simulate the impacts of end-of-century climate change on the UCRB using 21 CMIP5 and 18 CMIP3 GCMs, collected into one CMIP5 ensemble and one CMIP3 ensemble, respectively. Previous CMIP3 studies have identified a drier climate for the UCRB because of projected increases in temperature and decreases/little change in precipitation. Hydrologic simulations from CMIP5 inputs suggest wetter conditions than simulations based on CMIP3 inputs, yet drier conditions than the historical climate. Both ensembles lead to timing shifts in peak streamflow during the snowmelt season from changes in snowmelt, but the higher CMIP5 projected precipitation leads to, on average, peak streamflows 200–300 m 3  s −1 larger (25–40% difference) than the CMIP3 projections. This difference is largely generated in the northern UCRB region, where CMIP5 simulations project much more significant increases in streamflow than CMIP3. This increase is largely due to an overall larger rise in precipitation in the CMIP5 ensemble (57% of the total UCRB area) compared to the CMIP3 ensemble (5%). Even with projected increases in precipitation, snowmelt is projected to decrease dramatically throughout the UCRB for both ensembles. The increases in precipitation and decreases in snowmelt leads to significant differences in hydrologic flux components between the CMIP3 and CMIP5 ensembles, such as end-of-century rises in soil water content and evapotranspiration in the CMIP5 ensemble compared to the CMIP3 ensemble. The difference between the dry CMIP3 and the somewhat wetter CMIP5 projections may be critical for water management in the already over-allocated UCRB.
    Print ISSN: 0899-8418
    Electronic ISSN: 1097-0088
    Topics: Geosciences , Physics
    Published by Wiley
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  • 8
    Publication Date: 2011-02-11
    Description: Author(s): A. Perali, F. Palestini, P. Pieri, G. C. Strinati, J. T. Stewart, J. P. Gaebler, T. E. Drake, and D. S. Jin Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T_{c} , and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully ga... [Phys. Rev. Lett. 106, 060402] Published Thu Feb 10, 2011
    Keywords: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 9
    Publication Date: 2012-01-14
    Description: We develop a stream temperature model within the Soil and Water Assessment Tool (SWAT) that reflects the combined influence of meteorological (air temperature) and hydrological conditions (streamflow, snowmelt, groundwater, surface runoff, and lateral soil flow) on water temperature within a watershed. SWAT currently uses a linear air-stream temperature relationship to determine stream temperature, without consideration of watershed hydrology. As SWAT uses stream temperature to model various in-stream biological and water quality processes, an improvement of the stream temperature model will result in improved accuracy in modeling these processes. The new stream temperature model is tested on seven coastal and mountainous streams throughout the western United States for which high quality flow and water temperature data were available. The new routine does not require input data beyond that already supplied to the model, can be calibrated with a limited number of calibration parameters, and achieves improved representation of observed daily stream temperature. For the watersheds modeled, the Nash-Sutcliffe (NS) coefficient and mean error (ME) for the new stream temperature model averaged 0.81 and −0.69°C, respectively, for the calibration period and 0.82 and −0.63°C for the validation period. The original SWAT stream temperature model averaged a NS of −0.27 and ME of 3.21°C for the calibration period and a NS of −0.26 and ME of 3.02°C for the validation period. Sensitivity analyses suggest that the new stream temperature model calibration parameters are physically reasonable and the model is better able to capture stream temperature changes resulting from changes in hydroclimatological conditions.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
    Publication Date: 2015-04-01
    Description: Nature Geoscience 8, 269 (2015). doi:10.1038/ngeo2369 Authors: Richard G. Kraus, Seth Root, Raymond W. Lemke, Sarah T. Stewart, Stein B. Jacobsen & Thomas R. Mattsson Differentiated planetesimals delivered iron-rich material to the Earth and Moon in high-velocity collisions at the end stages of accretion. The physical process of accreting this late material has implications for the geochemical evolution of the Earth–Moon system and the timing of Earth’s core formation. However, the fraction of a planetesimal’s iron core that is vaporized by an impact is not well constrained as a result of iron’s poorly understood equation of state. Here we determine the entropy in the shock state of iron using a recently developed shock-and-release experimental technique implemented at the Sandia National Laboratory Z-Machine. We find that the shock pressure required to vaporize iron is 507 (+65, −85) GPa, which is lower than the previous theoretical estimate (887 GPa) and readily achieved by the high velocity impacts at the end stages of accretion. We suggest that impact vaporization of planetesimal cores dispersed iron over the surface of the growing Earth and enhanced chemical equilibration with the mantle. In addition, the comparatively low abundance of highly siderophile elements in the lunar mantle and crust can be explained by the retention of a smaller fraction of vaporized planetesimal iron on the Moon, as compared with Earth, due to the Moon’s lower escape velocity.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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