Characterizing the 18 April 2002 storm‐time sawtooth events using ground magnetic data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95189/1/jgra17938.pd

Strontium isotope compositions of river waters as records of lithology-dependent mass transfers : the Garonne river and its tributaries (SW France)

The relation of lithology in the drainage basin to the dissolved load of the Garonne river and its main tributaries, in southwestern France, was evaluated by determining 87Sr/86Sr ratios, and concentrations of major and trace elements during a 2-year-long survey. In the upper drainage basin, the Garonne river waters were isotopically varied at two observation points: 0.71131+/−0.00030 (2σ) for 84+/−18 ppb (2σ) and 0.71272+/−0.00044 for 86+/−10 ppb, respectively. In the lower drainage basin, the Garonne river waters were isotopically identical at three observation points at 0.71020+/−0.00024 for 125+/−22 ppb. By contrast, the tributaries (Lot, Truyère, Aveyron, Arriège, Gers and Salat) are widely varied in their 87Sr/86Sr ratios and Sr concentrations from 0.70836+/−0.00049 to 0.71058+/−0.00057, and from 18+/−8 to 280+/−116 ppb. The Sr isotope ratios and concentrations suggest a dominant supply of two reservoirs of Sr, one of which is with low 87Sr/86Sr ratios and high Sr contents that is typically characteristic of carbonate rocks, and the other with high 87Sr/86Sr ratios and low Sr concentrations that is characteristic of felsic rocks. Locally as in the Lot waters draining the Massif Central and within the Pyrénées mountains, a third source of Sr from mafic rocks may be involved. Mass-balance calculations based on the mean 87Sr/86Sr ratios and contents of the dissolved Sr, and on the mean discharges integrating the 2-year survey, suggest that contribution of the silicate reservoir amounts 3–8% of the total dissolved Sr flux. Mass-balance calculations also suggest that variation in the supply of Sr from either of the two major reservoirs does not exceed the analytical uncertainty at about +/−5%. The 87Sr/86Sr ratios of HCl and NH4Cl leachates of suspended loads of the Garonne river are different from that of the associated dissolved Sr. This leaching-related supplementary Sr represents less than 10% of the total amount of Sr transported by the Garonne waters. The Sr isotope characteristics of the leachates are probably records of an intermediate pedogenic episode in the weathering-erosion process occurring in the Garonne drainage basin

The role of grain size and shape in the strengthening of dispersion hardened nickel alloys

Thermomechanical processing was used to develop various microsstructures in Ni, Ni-2ThO2, Ni-20Cr, Ni-20CR-2ThO2, Ni-20Cr-10W-and Ni-20Cr-10W-2ThO2. The yield strength at 25 C increased with substructure refinement according to the Hall-Petch relation, and substructure refinement was a much more potent means of strengthening than was dispersion hardening. At elevated temperature (1093 C), the most important microstructural feature affecting strength was the grain aspect ratio (grain length, L, divided by grain width, 1. The yield strength and creep strength increased linearly with increasing L/1

High temperature deformation of dispersion strengthened nickel alloys. 1 - The influence of initial structure on tensile and creep deformation of TD nickel. 2 - The effect of matrix stacking fault energy on creep of Ni-Cr-ThO2 alloys Final report, 9 Feb. 1967 - 9 Feb. 1968

High temperature creep studies on unaltered, and recrystallized nickel alloy

Dynamics-A explorer RIMS data analysis

Activities of the RIMS instrument during the extended mission are planned. The modes of operation for RIMS to achieve the science requirements utilizing the new and exciting information on the composition and dynamics of the low energy (0-50eV) ions in the Earth's ionosphere and magnetosphere are determined. The specific science problems and the required RIMS operational modes needed to acquire the desired data are identified. The analysis was performed on the RIMS data to achieve the science results and this new information was used in determining RIMS operations during the latter part of the mission. Necessary sensitivity tests of RIMS operating modes and instrument performance was suggested. The inflight results was compared with theoretical models

Impact of nitrogen fertilizers on the natural weathering-erosion processes and fluvial transport in the Garonne basin

Knowledge of the impact of N-fertilizers on the weathering-erosion processes of soils in intensively cultivated regions is of prime importance. Nitrification of NH4− fertilizers produces HNO3 in the basin of the Garonne river, enhancing soil degradation. Their influence on the weathering rates was determined by calculating the consumption rate of atmospheric/soil CO2 by soil weathering and erosion, and its contribution to the total dissolved riverine HCO3−. This contribution was found to be less than 50% which corresponds normally to a complete carbonate dissolution by carbonic acid, suggesting that part of the alkalinity in the river waters is due to carbonate dissolution by an acid other than carbonic acid, probably HNO3

Advancing information technology at AGU

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95405/1/eost9018.pd

Polar UVI images to study steady magnetospheric convection events: Initial results

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94804/1/grl20687.pd