27 research outputs found
Precision Pointing Control System (PPCS) system design and analysis
The precision pointing control system (PPCS) is an integrated system for precision attitude determination and orientation of gimbaled experiment platforms. The PPCS concept configures the system to perform orientation of up to six independent gimbaled experiment platforms to design goal accuracy of 0.001 degrees, and to operate in conjunction with a three-axis stabilized earth-oriented spacecraft in orbits ranging from low altitude (200-2500 n.m., sun synchronous) to 24 hour geosynchronous, with a design goal life of 3 to 5 years. The system comprises two complementary functions: (1) attitude determination where the attitude of a defined set of body-fixed reference axes is determined relative to a known set of reference axes fixed in inertial space; and (2) pointing control where gimbal orientation is controlled, open-loop (without use of payload error/feedback) with respect to a defined set of body-fixed reference axes to produce pointing to a desired target
Uranium diagenesis in sediments underlying bottom waters with high oxygen content
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 73 (2009): 2920-2937, doi:10.1016/j.gca.2009.02.014.We measured U in sediments (both pore waters and solid phase) from three
locations on the middle Atlantic Bight (MAB) from the eastern margin of the United
States: a northern location on the continental shelf off Massachusetts (OC426, 75 m water
depth), and two southern locations off North Carolina (EN433-1, 647 m water depth and
EN433-2, 2648 m water depth). These sediments underlie high oxygen bottom waters
(250-270 μM), but become reducing below the sediment-water interface due to the
relatively high organic carbon oxidation rates in sediments (EN433-1: 212 μmol C/cm2/y;
OC426: 120±10 μmol C/cm2/y; EN433-2: 33 μmol C/cm2/y). Pore water oxygen goes to
zero by 1.4-1.5 cm at EN433-1 and OC426 and slightly deeper oxygen penetration depths
were measured at EN433-2 (~4 cm).
All of the pore water profiles show removal of U from pore waters. Calculated
pore water fluxes are greatest at EN433-1 (0.66±0.08 nmol/cm2/y) and less at EN433-2
and OC426 (0.24±0.05 and 0.13±0.05 nmol/cm2/y, respectively). Solid phase profiles
show authigenic U enrichment in sediments from all three locations. The average
authigenic U concentrations are greater at EN433-1 and OC426 (5.8±0.7 nmol/g and
5.4±0.2 nmol/g, respectively) relative to EN433-2 (4.1±0.8 nmol/g). This progression is
consistent with their relative ordering of ‘reduction intensity’, with greatest reducing
conditions in sediments from EN433-1, less at OC426 and least at EN433-2. The
authigenic U accumulation rate is largest at EN433-1 (0.47±0.05 nmol/cm2/y), but the
average among the three sites on the MAB is ~0.2 nmol/cm2/y. Pore water profiles
suggest diffusive fluxes across the sediment-water interface that are 1.4-1.7 times greater
than authigenic accumulation rates at EN433-1 and EN433-2. These differences are
consistent with oxidation and loss of U from the solid phase via irrigation and/or
bioturbation, which may compromise the sequestration of U in continental margin
sediments that underlie bottom waters with high oxygen concentrations.
Previous literature compilations that include data exclusively from locations
where [O2]bw < 150 μM suggest compelling correlations between authigenic U
accumulation and organic carbon flux to sediments or organic carbon burial rate.
Sediments that underlie waters with high [O2]bw have lower authigenic U accumulation
rates than would be predicted from relationships developed from results that include
locations where [O2]bw < 150 μM.The
authors appreciate the financial support from NSF (JLM, WRM: OCE-0220892; and
OCE-0526389 to WRM), Research Corporation (JLM, CMC), Franklin & Marshall
College, and the Hackman Summer Research Program (CMC) at F&M
You don't see the world through the same eyes any more: The impact of sexual offence work on police staff
This paper examines the experiences of Police staff in England who work with sexual offence material (SOM). Eleven officers completed a questionnaire then took part in semi-structured interviews. The data were analysed in two stages: Interpretative Phenomenological Analysis was used to illuminate the ‘lived experience’ of participants, and establish a theme structure. Clinical models of workplace trauma were then employed to explore the theme ‘Impact of working with sexual offending’. Impact includes cognitive intrusions and increased suspiciousness. The authors identify where officers’ accounts intersect with nascent symptoms of both Vicarious Traumatisation (McCann and Pearlman, 1990) and Post-Traumatic Stress Disorder (PTSD)