Erosion and deposition in interplain channels of the Maury channel system

Large turbidity currents originating on the insular margin of southern lceland have flowed clown a 2 500 km-long pathway comprising rise valleys, unchanneled plains and segments of erosional and depositional deep-sea channels that are collectively called the Maury Channel system. Two steep interplain reaches of the channel have been eut up to 100 m through volcanogenic turbidites of probable La te Pleistocene age. Near-bottom observations with side-scan sonars and profllers across the upper channels (at 59°24\u27N, 18°50\u27W, 2 750 m depth) and at the lower interplain channel (around 56°23\u27N, 24°25\u27W, 3 340 m depth) defmed their structure and morphology. The upper channels, and a tributary to the lower channel, start as broad, shallow depressions that deepen and narrow downstream. The lower channel bas a pattern of anastomosing branches that probably evolved by head ward extension of low-angle tribu taries to the original sinuous channel, and its branches are at different stages of development. Several hundred bottom photographs show well-indurated rocks on channel walls and floors, with such flysch-like characteristics as cyclic graded bedding, clastic dikes, and syndepositional deformation. The lower-channel branches have been eut by turbidity currents with speeds of 5- 12 rn/sec., and combined discharges exceeding 1 x 106 m3 /sec. Bedrock erosion in and around the channels bas proceeded by intense corrasion and fluid stressing, and is marked by such small-scale effects as rock polishing, fluting, pot-holing and ledge recession. Rockfalls have caused retreat of steep channel walls, and conglomerate or pcbbly mudstone deposits suggest that debris flows have been locally active. Sorne coarse debris delivered by these processes and clay halls torn from semi-lithifled outcrops remain in the channels, but the channel f1ll is generally thin, with a patch y veneer of pelagie mud that bas accumulated since the last major turbidity current event. The surfaces of the unconsolidated s~diment have been smoothed and lineated, or moulded into seo ur moats and occasional fields of ripples, by thermohaline currents

An Electrodeless Technique for Full Scale Simulation of the Re-Entry Environment

A current need exists for improved methods in the ground testing of re-entry vehicles; it is believed that this need may soon become acute. Based on the arcjet, the present generation of re-entry simulators is limited in exhaust enthalpy, physical size and purity of exhaust plasma. An electrodeless technique of plasma production at very high power levels has been developed, however, which removes many of these restrictions. In addition, the properties of a plasma generator based on the electrodeless discharge are such that the discharge can be maintained over a very wide range in applied power and gas density, and can be electronically controlled. It is thus possible that an entire entry trajectory can be reduced to data on punched cards which are fed into a computer that electronically controls the reproduction of the entry conditions for an arbitrary trajectory in an arbitrary atmosphere at the surface of a test model. A mathematical scaling law is presented which indicates that re-entry simulation based on the electrodeless technique can be extended to the full-scale case

Cable failures off Oahu, Hawaii caused by Hurricane Iwa

Six submarine telecommunications cables on the steep insular slope off southwest Oahu were damaged or broken by a combination of debris slides and large-block talus movement or, for the shallowest cables, wave induced chafe. These problems were caused by the sea floor's response to high surface energy produced by Hurricane Iwa. An examination of all available data does not support the concept of failure by turbidity currents.Funding was provided by the International Cable Engineering Division of A T & T Communications under contract number 47-5697

Navigation and guidance requirements for commercial VTOL operations

The NASA Langley Research Center (LaRC) has undertaken a research program to develop the navigation, guidance, control, and flight management technology base needed by Government and industry in establishing systems design concepts and operating procedures for VTOL short-haul transportation systems in the 1980s time period. The VALT (VTOL Automatic Landing Technology) Program encompasses the investigation of operating systems and piloting techniques associated with VTOL operations under all-weather conditions from downtown vertiports; the definition of terminal air traffic and airspace requirements; and the development of avionics including navigation, guidance, controls, and displays for automated takeoff, cruise, and landing operations. The program includes requirements analyses, design studies, systems development, ground simulation, and flight validation efforts

Compositional changes in particulate matter on the Iceland Rise, through the water column, and at the seafloor

Local resuspension of sediments along the Iceland Rise was substantiated by the collection in sediment traps of large particles whose source is clearly the seafloor. These resuspended components included benthic foraminifera, iron-oxide coated planktonic foraminifera, the glacial, subpolar assemblage planktonic foraminifera (N. pachyderma (sinistral)), and an increase in the volcanic glass and mineral grain/aggregate component with proximity to the seafloor.The horizontal flux of particulate matter in the near-bottom nepheloid layer through the region was ≃200 kg/s. The apparent vertical flux of sediment calculated from sediment traps at 500 m above bottom (mab) was an order of magnitude less than Recent sediment accumulation rates, suggesting a large fraction of the sediments in the region was brought in horizontally via bottom currents or turbidity currents.The compositional changes with depth in the material collected in the sediment traps indicated that most of the changes in the material due to dissolution, degradation, and decomposition occurred while the material resided on the seafloor or during periods of resuspension rather than during transit through the water column. Regional variations in clay mineralogy, organic carbon and carbonate content indicated preferential preservation in cores from a channel in the study region or preferential decomposition, dissolution, and/or erosion of the surface sediments beneath the bottom current

Display/control requirements for VTOL aircraft

Quantative metrics were determined for system control performance, workload for control, monitoring performance, and workload for monitoring. Pilot tasks were allocated for navigation and guidance of automated commercial V/STOL aircraft in all weather conditions using an optimal control model of the human operator to determine display elements and design

Examination of Surface Temperature Modification by Open-Top Chambers along Moisture and Latitudinal Gradients in Arctic Alaska Using Thermal Infrared Photography

Passive warming manipulation methodologies, such as open-top chambers (OTCs), are a meaningful approach for interpretation of impacts of climate change on the Arctic tundra biome. The magnitude of OTC warming has been studied extensively, revealing an average plot-level warming of air temperature that ranges between 1 and 3 °C as measured by shielded resistive sensors or thermocouples. Studies have also shown that the amount of OTC warming depends in part on location climate, vegetation, and soil properties. While digital infrared thermometers have been employed in a few comparisons, most of the focus of the effectiveness of OTC warming has been on air or soil temperature rather than tissue or surface temperatures, which directly translate to metabolism. Here we used thermal infrared (TIR) photography to quantify tissue and surface temperatures and their spatial variability at a previously unavailable resolution (3–6 mm2). We analyzed plots at three locations that are part of the International Tundra Experiment (ITEX)-Arctic Observing Network (AON-ITEX) network along both moisture and latitudinal gradients spanning from the High Arctic (Barrow, AK, USA) to the Low Arctic (Toolik Lake, AK, USA). Our results show a range of OTC surface warming from 2.65 to 1.27 °C (31%–10%) at our three sites. The magnitude of surface warming detected by TIR imagery in this study was comparable to increases in air temperatures previously reported for these sites. However, the thermal images revealed wide ranges of surface temperatures within the OTCs, with some surfaces well above ambient unevenly distributed within the plots under sunny conditions. We note that analyzing radiometric temperature may be an alternative for future studies that examine data acquired at the same time of day from sites that are in close geographic proximity to avoid the requirement of emissivity or atmospheric correction for validation of results. We foresee future studies using TIR photography to describe species-level thermodynamics that could prove highly valuable toward a better understanding of species-specific responses to climate change in the Arctic

Identification of generic study areas for the disposal of low level radioactive waste : western North Atlantic Ocean

There is a growing need to effectively dispose of the low level radioactive waste presently accumulating in the United States. It may be decided to "dump" radioactive contamination products onto the deep sea floor (within 200 miles of the U.S.) in accordance with present IAEA guidelines (see Appendix A) for ocean dumping of low level waste; in the event of such a decision suitable areas must be identified and carefully studied to determine the subsequent influence of the waste on the environment. Using the site suitability criteria mentioned above we have identified two areas of possible use for low level waste disposal, one north of Puerto Rico and one east of Cape Hatteras, as deserving further study. The following report describes the relevant physical and geological characteristics of these two areas that may be important in considering a dumping operation. We have also made some recommendations for confirmatory research. The Hatteras Abyssal Plain, lying close to the 200 mile limit, appears to be a viable region for the focus of future research efforts.Prepared for the Sandia Laboratories

Local-scale patterns of genetic variability, outcrossing, and spatial structure in natural stands of Arabidopsis thaliana

As Arabidopsis thaliana is increasingly employed in evolutionary and ecological studies, it is essential to understand patterns of natural genetic variation and the forces that shape them. Previous work focusing mostly on global and regional scales has demonstrated the importance of historical events such as long-distance migration and colonization. Far less is known about the role of contemporary factors or environmental heterogeneity in generating diversity patterns at local scales. We sampled 1,005 individuals from 77 closely spaced stands in diverse settings around Tübingen, Germany. A set of 436 SNP markers was used to characterize genome-wide patterns of relatedness and recombination. Neighboring genotypes often shared mosaic blocks of alternating marker identity and divergence. We detected recent outcrossing as well as stretches of residual heterozygosity in largely homozygous recombinants. As has been observed for several other selfing species, there was considerable heterogeneity among sites in diversity and outcrossing, with rural stands exhibiting greater diversity and heterozygosity than urban stands. Fine-scale spatial structure was evident as well. Within stands, spatial structure correlated negatively with observed heterozygosity, suggesting that the high homozygosity of natural A. thaliana may be partially attributable to nearest-neighbor mating of related individuals. The large number of markers and extensive local sampling employed here afforded unusual power to characterize local genetic patterns. Contemporary processes such as ongoing outcrossing play an important role in determining distribution of genetic diversity at this scale. Local "outcrossing hotspots" appear to reshuffle genetic information at surprising rates, while other stands contribute comparatively little. Our findings have important implications for sampling and interpreting diversity among A. thaliana accessions.Financial support came from an NIH Ruth Kirschstein NRSA Postdoctoral Fellowship (KB), a Human Frontiers Science Program Postdoctoral Fellowship (RAL), grants DFG ERA-PG ARelatives and FP6 IP AGRON-OMICS (contract LSHG-CT-2006-037704), from a Gottfried Wilhelm Leibniz Award of the DFG, and the Max Planck Society (DW)