GNSS Signal Authentication via Power and Distortion Monitoring

We propose a simple low-cost technique that enables civil Global Positioning System (GPS) receivers and other civil global navigation satellite system (GNSS) receivers to reliably detect carry-off spoofing and jamming. The technique, which we call the Power-Distortion detector, classifies received signals as interference-free, multipath-afflicted, spoofed, or jammed according to observations of received power and correlatio n function distortion. It does not depend on external hardware or a network connection and can be readily implemented on many receivers via a firmware update. Crucially, the detector can with high probability distinguish low-power spoofing from ordinary multipath. In testing against over 25 high-quality empirical data sets yielding over 900,000 separate detection tests, the detector correctly alarms on all malicious spoofing or jamming attack s while maintaining a <0.5% single-channel false alarm rate.Aerospace Engineering and Engineering Mechanic

Is the reduced growth of the halophyte Suaeda maritima under hypoxia due to toxicity of iron or manganese?

For most plants, submergence in water is a rare occurrence, but for plants that grow on salt marshes flooding with seawater may be a twice-daily event. This is the case for plants of the halophyte Suaeda maritima, growing at low elevations on salt marshes. These plants are, however, smaller than those growing at higher elevations, where flooding is less frequent and the soil is better drained. We investigated whether the reduced growth brought about by flooding with saline water was a consequence of toxicity of manganese or iron. Seedlings of S. maritima were grown both in a sold medium (a mixture of salt-marsh mud and sand) that was either submerged twice a day or continuously flooded with half-strength seawater and in a hydroponic solution where the oxygen concentration was adjusted by bubbling with nitrogen or air. Hypoxia, reduced the growth of plants in both solid and liquid media and resuted in increases in manganese and iron in the shoots and roots. Experiments in culture solution showed that elevated levels of manganese were unlikely to be toxic, but that iron did reach toxic concentrations in flooded plants

Archeological Survey and Testing of Selected Prehistoric Sites along FM 481, Zavala County, Texas

Between April 1981 and December 1982, Texas Department of Transportation (TxDOT) personnel conducted archeological fieldwork along an approximately 13-km segment of FM 481 in northwest Zavala County. The work was part of an evaluation of the impacts of road improvements to a series of sites along the right-of-way. All of the sites but one (41ZV202) were found not to be eligible for listing on the National Register of Historic Places and not to warrant designations as State Archeological Landmarks. Additional work, not reported here, was later conducted at 41ZV202. As part of Work Authorization #57015PD004, the Environmental Affairs Division of TxDOT contracted with the Center for Archaeological Research (CAR) of The University of Texas at San Antonio to report on the fieldwork carried out at the sites during the early 1980s, identify data types warranting additional research, and conduct the appropriate analyses. The current document provides descriptions of the work undertaken along FM 481, assesses the analytical utility of the data types recovered, and reports the results of limited new research of selected data types. Note that all documentation of the project, including notes, photographs, and a sample of recovered artifacts are curated at the Center for Archaeological Research. The sample includes all projectile points, as well as other chipped and ground stone tools, and the debitage recovered for a 10% sample of proveniences

Variable response of three Trifolium repens ecotypes to soil flooding by seawater.

BACKGROUND AND AIMS: Despite concerns about the impact of rising sea levels and storm surge events on coastal ecosystems, there is remarkably little information on the response of terrestrial coastal plant species to seawater inundation. The aim of this study was to elucidate responses of a glycophyte (white clover, Trifolium repens) to short-duration soil flooding by seawater and recovery following leaching of salts. METHODS: Using plants cultivated from parent ecotypes collected from a natural soil salinity gradient, the impact of short-duration seawater soil flooding (8 or 24 h) on short-term changes in leaf salt ion and organic solute concentrations was examined, together with longer term impacts on plant growth (stolon elongation) and flowering. KEY RESULTS: There was substantial Cl(-) and Na(+) accumulation in leaves, especially for plants subjected to 24 h soil flooding with seawater, but no consistent variation linked to parent plant provenance. Proline and sucrose concentrations also increased in plants following seawater flooding of the soil. Plant growth and flowering were reduced by longer soil immersion times (seawater flooding followed by drainage and freshwater inputs), but plants originating from more saline soil responded less negatively than those from lower salinity soil. CONCLUSIONS: The accumulation of proline and sucrose indicates a potential for solute accumulation as a response to the osmotic imbalance caused by salt ions, while variation in growth and flowering responses between ecotypes points to a natural adaptive capacity for tolerance of short-duration seawater soil flooding in T. repens. Consequently, it is suggested that selection for tolerant ecotypes is possible should the predicted increase in frequency of storm surge flooding events occur

Ecophysiology of the halophyte Suaeda maritima

Suaeda maritima is a widely occurring annual halophyte that experiences the fluctuating salinity and hypoxia of tidal cycles on salt-marshes. During dormancy, seeds survive in saline, hypoxic mud to germinate when spring-time temperatures reach about 15 °C. Plants of Suaeda maritima have wide salinity tolerance but little work has been published regarding interlinked waterlogging. The effects of saline waterlogging on growth and ion accumulation were investigated in tanks in a glasshouse where tidal flow was simulated and in aerated and hypoxic saline culture solution in a controlled environment cabinet.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

High phenotypic plasticity of Suaeda maritima observed under hypoxic conditions in relation to its physiological basis

Phenotypic plasticity, the potential of specific traits of a genotype to respond to different environmental conditions, is an important adaptive mechanism for minimizing potentially adverse effects of environmental fluctuations in space and time. Suaeda maritima shows morphologically different forms on high and low areas of the same salt marsh. Our aims were to examine whether these phenotypic differences occurred as a result of plastic responses to the environment. Soil redox state, indicative of oxygen supply, was examined as a factor causing the observed morphological and physiological differences. Reciprocal transplantation of seedlings was carried out between high and low marsh sites on a salt marsh and in simulated tidal-flow tanks in a glasshouse. Plants from the same seed source were grown in aerated or hypoxic solution, and roots were assayed for lactate dehydrogenase (LDH) and alcohol dehydrogenase, and changes in their proteome. Transplanted (away) seedlings and those that remained in their home position developed the morphology characteristic of the home or away site. Shoot Na, Cl and K concentrations were significantly different in plants in the high and low marsh sites, but with no significant difference between home and away plants at each site. High LDH activity in roots of plants grown in aeration and in hypoxia indicated pre-adaptation to fluctuating root aeration and could be a factor in the phenotypic plasticity and growth of S. maritima over the full tidal range of the salt marsh environment. Twenty-six proteins were upregulated under hypoxic conditions. Plasticity of morphological traits for growth form at extremes of the soil oxygenation spectrum of the tidal salt marsh did not correlate with the lack of physiological plasticity in the constitutively high LDH found in the roots

Oxygen dynamics in a salt-marsh soil and in Suaeda maritima during tidal submergence

Habitats occupied by many halophytes are not only saline, but are also prone to flooding and yet surprisingly few studies have evaluated submergence tolerance in halophytes. Sediment, floodwater, and intra-plant O-2 dynamics were evaluated during tidal submergence for the leaf-succulent halophyte Suaeda maritime (L.) Dum. For S. maritime growing in soil just above the mud flat in a UK salt marsh, the soil was only moderately hypoxic just prior to tidal inundation, presumably owing to drainage and O-2 entry facilitated by frequent, large cracks. O-2 declined to very low levels following high tide. By contrast, mud flat sediment remained waterlogged, lacked cracks, and was anoxic. Plant O-2 dynamics were investigated using field-collected plants in sediment blocks transported to a controlled-submergence system in a glasshouse. Submergence during night-time resulted in anoxia within leaves, whereas during day-time O-2 was produced by underwater photosynthesis. The thin lateral roots of S. maritima presumably access some O-2 from hypoxic sediments, but could also experience transient episodes of severe hypokia/anoxia, especially as any internal O-2 movement from shoots would be small owing to the low gas-filled porosity in roots. Fermentative metabolism to lactate, producing some ATP in the absence of O-2, might contribute to tolerance of transient O-2 deficits. Lactate was high in root tissues, whereas ethanol production (tissue and incubation medium contents) was low, both in comparison with values reported for other species. Our findings demonstrate the importance of tolerance to transient waterlogging and submergence for the halophyte S. maritime growing in a tidal salt marsh. (C) 2012 Elsevier B.V. All rights reserved

The effect of saline hypoxia on growth and ion uptake in Suaeda maritima

The widely occurring annual halophyte Suaeda maritima experiences fluctuating salt and oxygen concentration during tidal cycles in salt marshes and shows tolerance of extreme hypoxia. The effect of saline waterlogging on growth and ion accumulation was investigated in tanks in a glasshouse where tidal flow was simulated, and in an aerated and hypoxic saline nutrient solution in a controlled environment cabinet. Laboratory data were compared with data from a survey of growth in two salt marshes. Plants in the nutrient solution grew equally well in the alternative nitrogen sources, NO(3)(-) and NH(4)(+). Hypoxia, produced in the nutrient solution by nitrogen bubbling in the absence of turbulence and using stagnant agar, reduced root growth; hypoxia in waterlogged pot media in the glasshouse also reduced shoot growth and net K(+) uptake but increased net uptake of Na(+) and Cl(-). (22)Na(+) influx into shoots was only significantly reduced by hypoxia when combined with a sudden increase in salt concentration to 200 mM NaCl. S. maritima appears to be well adapted to tolerate severely hypoxic growth conditions

Do Conditions During Dormancy Influence Germination of Suaeda maritima?

Background and Aims Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2-3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination. Methods Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination. Key Results A temperature of about 15 degrees C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry. Conclusions The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 degrees C and the salinity is reduced