Three-dimensional visualization of mission planning and control forthe NPS autonomous underwater vehicle

The Naval Postgraduate School (NPS) is constructing a small autonomous underwater vehicle (AUV) with an onboard mission control computer. The mission controller software for this vehicle is a knowledge-based artificial intelligence (AI) system requiring thorough analysis and testing before the AUV is operational. The manner in which rapid prototyping of this software has been demonstrated by developing a controller code on a LISP machine and using an Ethernet link with a graphics workstation to simulate the controller's environment is discussed. The development of a testing simulator using a knowledge engineering environment (KEE) expert system shell that examines AUV controller subsystems and vehicle models before integrating them with the full AUV for its test environment missions is discussed. This AUV simulator utilizes an interactive mission planning control console and is fully autonomous once initial parameters are selected     

Vegetation change and surface elevation dynamics in estuarine wetlands of southeast Australia

Vertical accretion and surface elevation trends were studied in mangrove and saltmarsh wetlands in southeast Australia. A total of 69 surface elevation tables, each associated with three feldspar marker horizons, was deployed in 10 wetlands across 7 estuaries, and monitored for three years. Saltmarsh and mangrove vegetation distributions were mapped for the same estuaries, and elevation characteristics of the wetlands were modelled. Rates of vertical accretion were found to correlate with tidal range. No relationship was found between rates of vertical accretion and surface elevation increase. A positive relationship was demonstrated between contemporary rates of saltmarsh surface elevation change and longer-term rates of mangrove encroachment into saltmarsh. We conclude that landward mangrove encroachment may be facilitated by local factors contributing to saltmarsh compaction during drought conditions.     

The response of selected terrestrial organisms to the Martian environment: A modeling study

An energy balance model has been developed to investigate how the Martian atmospheric environment could influence a community of photosynthetic microorganisms with properties similar to those of a cyanophyte (blue-green algal mat) and a lichen. Surface moisture and soil nutrients are assumed to be available. The model was developed to approximate equatorial equinox conditions and includes parameters for solar and thermal radiation, convective and conductive energy transport, and evaporative cooling. Calculations include the diurnal variation of organism temperature and transpiration and photosynthetic rates. The influences of different wind speeds and organism size and resistivity are also studied. The temperature of organisms in mats less than a few millimeters thick will not differ from the ground temperature by more than 10°K. Water loss is actually retarded at higher wind speeds, since the organism temperature is lowered, thus reducing the saturation vapor pressure. Typical photosynthetic rates lead to the production of 10^?6 to 10^?7 mole O₂ cm^?2 day^?1.     

Evidence for inherited Sm−Nd isotopes in granitoid zircons

This study presents evidence to show that, in addition to preserving U–Pb isotope systematics, refractory zircons also preserve, at least in part, an inherited Sm–Nd isotope component. The zircons analyzed during this study were taken from the Strontian granitoid (NW Scotland). The inner intrusion of this composite pluton is known from a previous study to contain substantial U–Pb zircon inheritance, whereas the outer part has only minor inheritance. Zircons from the inner intrusion were found to have significantly lower Nd₄₂₅ values than either their host rock, separated apatite or monazite. It is argued that this isotopic disequilibrium is due to the presence of an inherited Sm–Nd isotope component, rather than being due to a post-crystallization disturbance of the zircons. The preservation of inherted Sm–Nd isotopes within refractory zircons implies that they remain closed systems with respect to the diffusion of Sm and Nd (and presumably the other REE) to temperatures in excess of 700°C. The fact that zircons commonly have high Sm/Nd ratios, relative to sialic crustal material, means that the Nd isotopic evolution of inherited zircons will be very different to that of much of the continental crust.     

Micro-spectroscopic investigations of highly heterogeneous waste repository materials

Assuring safe disposal and long-term storage of radioactive and toxic wastes corresponds to a primary environmental task of present societies. To improve any technical limitation, a mechanistic understanding of the processes governing the binding of heavy metals and radionuclides is required. In this study, the significance of synchrotron-based X-ray microprobes for elucidating the spatial distribution and the speciation of radionuclides in highly heterogeneous waste repository materials will be outlined. A case study on the uptake process of Co in cementitious engineered barrier materials exposed to microbial degradation will be presented.     

Imposing Age and Spatial Structures on Inadequate Migration‐Flow Datasets*

With the elimination of the long‐form questionnaire from future decennial censuses and its replacement by a much smaller continuous monthly sampling survey (the American Community Survey), students of territorial mobility may find it necessary to deal with inadequate, missing, or inaccurate sample data on migration by adopting an approach that “improves” such data using information from different geographical areas, time periods, and data sources. We develop such an approach in this article and illustrate it with interregional migration flow data reported by the U.S. decennial censuses of 1980 and 1990 and by the 1985 Current Population Survey.     

Relationship of Avalonian and Cadomian terranes to Grenville and Pan-African events

Suturing of the supercontinent Rodinia in the Grenville event (˜ 1000 Ma) was followed by rifting in the late Proterozoic (˜ 800-700 Ma), reorganization to Gondwana in the Pan-African (˜ 700-500 Ma) and further accretion to develop Pangea at the end of the Paleozoic. One of the Rodinian rifts followed part of the Grenville suture, it produced the margin of eastern North America and southern Baltica and the contrasting margin of west Gondwana in present South America. The Paleozoic accretionary wedge against the Grenville-age margin of North America and Baltica contains Avalonian/Cadomian terranes that exhibit Pan-African erogenic events ± sediments apparently developed while the terranes were in or near Gondwana. These terranes carry lower-Paleozoic fauna (Acado-Baltic) that are not indigenous to North America and Baltica.U---Pb zircon ages range from 1500-1000 Ma in Grenville terranes and from 800–500 Ma with minor inheritance in Avalonian terranes; they are generally much older in Cadomian terranes, implying very little resetting during Pan-African events. T_DM ages are generally 2000–1200 Ma in Grenville terranes, 1300–600 Ma in Avalonian terranes and 2000–1200 in Cadomian terranes. These summary data show that: (1) the Grenville orogenic event produced almost no juvenile crust; (2) the Avalonian terranes of North America contain crust that evolved primarily in the late Proterozoic, possibly as a mixture of juvenile Pan-African material and Grenville or slightly older material; (3) the Cadomian terranes of Europe consist of old (middle-Proterozoic to Archean) crust with minor juvenile Pan-African material. The Avalonian terranes apparently evolved near, and partly on, the Grenville-age crust now in South America during the intense orogeny associated with rotation of Gondwana away from North America. The Cadomian terranes of Europe, however, appear to be fragments of other parts of Gondwana, probably West Africa.     

Calcareous algae and cyanobacteria

Algae is an informal term used to describe a broad group of simple organisms from the plant kingdom. The organisms included within this grouping are aquatic photosynthetic biota with an extensive range of life habits and forms. These organisms range from micron-sized unicellular forms to giant seaweeds and kelps, which can grow to several metres long. Both benthic and planktonic modes of life are known and display a wide variety of life cycles.     

Geophysical surveys to help map buried igneous intrusions,Snowdonia, North Wales,UK

The geology of the Snowdonia National Park in North Wales comprises a mixture of Lower Palaeozoic shallow marine sediments, acidic igneous rocks and basic intrusions of the Welsh Basin that were subsequently deformed during the Caledonian Orogeny. Thin igneous intrusions are challenging to map due to variable surface exposures, their intrusive origin, structural deformation and burial by glacial sediments. This study used a combination of traditional geological techniques, near‐surface geophysical surveys and remote sensing to detect and map a buried dolerite sheet intrusion. Both simple and mathematical analysis of magnetic anomalies and numerical modelling allowed the dolerite position, depths and target widths to be determined. Results showed that calibrated magnetic surveys can characterize buried igneous bodies in such mountainous environments.     

Habitat Restoration from an Ecosystem Goods and Services Perspective: Application of a Spatially Explicit Individual-Based Model

Estuarine ecosystems provide many services to humans, but these ecosystems are also under pressure from human development, which has led to large investments in habitat protection and restoration. Restoration in estuaries is typically focused on emergent and submerged vegetation with the goal of achieving target areal coverage based on historic conditions. Such restoration targets assume no spatial heterogeneity in habitat value and bypass the functional target of restoring or maintaining delivery of ecosystem goods and services (EGS). We have developed a spatially explicit individual-based behavioral model intended to explore the functional role of habitat restoration on EGS delivery in an index system (Tampa Bay, FL) and for an index EGS (recreational fishing). Model scenarios are based on interaction of inter-annual differences in salinity/temperature patterns (wet, dry, average) with hindcasted “increases” in coverage and distribution of seagrass. Model predictions indicated that the effect of seagrass restoration to historic (1950s) levels on both fish and fishery production is dependent on salinity and temperature. This dependence is based on predicted fish response both to habitat changes and the effective spatial scale of different habitat components. Overall, average salinity/temperature conditions facilitated the highest positive functional response to seagrass restoration with extreme wet/dry years yielding lower or even negative functional responses, but these responses were localized and not homogenous about the estuary. The results of this study provide a methodology for using functional targets in restoration planning and highlight the importance of considering the entire habitat mosaic in valuing restored habitat from an EGS perspective.