1,353 research outputs found
The verification of LANDSAT data in the geographical analysis of wetlands in west Tennessee
The reliability of LANDSAT imagery as a medium for identifying, delimiting, monitoring, measuring, and mapping wetlands in west Tennessee was assessed to verify LANDSAT as an accurate, efficient cartographic tool that could be employed by a wide range of users to study wetland dynamics. The verification procedure was based on the visual interpretation and measurement of multispectral imagery. The accuracy testing procedure was predicated on surrogate ground truth data gleaned from medium altitude imagery of the wetlands. Fourteen sites or case study areas were selected from individual 9 x 9 inch photo frames on the aerial photography. These sites were then used as data control calibration parameters for assessing the cartography accuracy of the LANDSAT imagery. An analysis of results obtained from the verification tests indicated that 1:250,000 scale LANDSAT data were the most reliable scale of imagery for visually mapping and measuring wetlands using the area grid technique. The mean areal percentage of accuracy was 93.54 percent (real) and 96.93 percent (absolute). As a test of accuracy, the LANDSAT 1:250,000 scale overall wetland measurements were compared with an area cell mensuration of the swamplands from 1:130,000 scale color infrared U-2 aircraft imagery. The comparative totals substantiated the results from the LANDSAT verification procedure
The verification of LANDSAT data in the geographical analysis of wetlands in western Tennessee
There are no author-identified significant results in this report
A New Genus and Two New Species in the Families Volutidae and Turbinellidae (Mollusca: Gastropoda) from the Western Pacific
Sigaluta pratasensis, new genus, new species, in the family Volutidae
is described from the South China Sea, off Hong Kong. Phenacoptygma Dall, 1918
is removed from the Volutidae and placed in the synonymy of Surculina Dall, 1908,
which in turn is removed from the Turridae and assigned to the Turbinellidae
near Benthovoluta Kuroda and Habe, 1950, on the basis of its radula. It is pro posed
that the families Turbinellidae (olim Xancidae) and Vasidae be of coordinate
rank. A new species of Benthovoluta, B. gracilior, is described from the
Sulu Sea, Philippines
Identifying drivers behind spatial variability of Methane concentrations in East Siberian ponds
Waterbody methane emissions per area are negatively correlated with the size of the emitting waterbody. Thus, ponds, defined here as having an area smaller than 8 · 104m2, contribute out of proportion to the aquatic methane budget compared to the total area they cover and compared to other waterbodies. However, methane concentrations in and methane emissions from ponds show more spatial variability than larger waterbodies. We need to better understand this variability to improve upscaling estimates of freshwater methane emissions. In this regard, the Arctic permafrost landscape is an important region, which, besides carbon-rich soils, features a high pond density and is exposed to above-average climatic warming. We studied 41 polygonal-tundra ponds in the Lena River Delta, northeast Siberia. We collected water samples at different locations and depths in each pond and determined methane concentrations using gas chromatography. Additionally, we collected information on the key properties of the ponds to identify drivers of surface water methane concentrations. The ponds can be categorized into three geomorphological types with distinct differences in drivers of methane concentrations: polygonal-center ponds, ice-wedge ponds and larger merged polygonal ponds. All ponds are supersaturated in methane, but ice-wedge ponds exhibit the highest surface water concentrations. We find that ice-wedge ponds feature a strong stratification due to consistently low bottom temperatures. This causes surface concentrations to mainly depend on wind speed and on the amount of methane that has accumulated in the hypolimnion. In polygonal-center ponds, high methane surface concentrations are mostly determined by a small water depth. Apart from the influence of water depth on mixing speed, water depth controls the overgrown fraction, the fraction of the pond covered by vascular plants. The plants provide labile substrate to the methane-producing microbes. This link can also be seen in merged polygonal ponds, which furthermore show the strongest dependence on area as well as an anticorrelation to energy input indicating that stratification influences the surface water methane concentrations in larger ponds. Overall, our findings underpin the strong variability of methane concentrations in ponds. No single driver could explain a significant part of the variability over all pond types suggesting that more complex upscaling methods such as process-based modeling are needed
Deep and Shallow-Water Mollusks from the Central Pacific
Recent shelled mollusks were trawled from deep water on four guyots in the Mid-Pacific Mountains and were dredged from shallow waters on Nero Bank and the lee shelf of Kure Island in Hawaii. Seven species of mollusks, six of which are new, have been identified from the deep waters on the guyots : two are trochids, Calliotropis hataii n. sp., and C. abyssicola n. sp., three are turrids, Comitas powelli n. sp., Pleurotomella dubia Schepman and P. allisoni n. sp., one is a bullid, Bulla argoblysis n. sp., and one a scaphopod, Dentalium mediopacificensis n. sp. Five of the seven species are identical or closely related to Indo-Pacific forms, one belongs to a small but cosmopolitan group, one is related to a species living near the Galapagos Islands in the eastern Pacific. Nine species of mollusks are identified from Nero Bank and 41 from Kure\u27s shelf, one being new. A total of 101 species are listed as occurring on these two sites and the Kure beaches and lagoon. More than one-third of the total listed appear to be endemic to Hawaii
Induced magnetism of carbon atoms at the graphene/Ni(111) interface
We report an element-specific investigation of electronic and magnetic
properties of the graphene/Ni(111) system. Using magnetic circular dichroism,
the occurrence of an induced magnetic moment of the carbon atoms in the
graphene layer aligned parallel to the Ni 3d magnetization is observed. We
attribute this magnetic moment to the strong hybridization between C and
Ni 3d valence band states. The net magnetic moment of carbon in the graphene
layer is estimated to be in the range of per atom.Comment: 10 pages, 3 figure
Superoxide Release And Cellular Gluthatione Peroxidase Activity In Leukocytes From Children With Persistent Asthma.
Asthma is an inflammatory condition characterized by the involvement of several mediators, including reactive oxygen species. The aim of the present study was to investigate the superoxide release and cellular glutathione peroxidase (cGPx) activity in peripheral blood granulocytes and monocytes from children and adolescents with atopic asthma. Forty-four patients were selected and classified as having intermittent or persistent asthma (mild, moderate or severe). The spontaneous or phorbol myristate acetate (PMA, 30 nM)-induced superoxide release by granulocytes and monocytes was determined at 0, 5, 15, and 25 min. cGPx activity was assayed spectrophotometrically. The spontaneous superoxide release by granulocytes from patients with mild (N = 15), moderate (N = 12) or severe (N = 6) asthma was higher at 25 min compared to healthy individuals (N = 28, P 0.05 in all times of incubation, Duncan test). cGPx activity of granulocytes and monocytes from patients with persistent asthma (N = 20) was also similar to healthy individuals (N = 10, P > 0.05, Kruskal-Wallis test). We conclude that, under specific circumstances, granulocytes from children with persistent asthma present a higher respiratory burst activity compared to healthy individuals. These findings indicate a risk of oxidative stress, phagocyte auto-oxidation, and the subsequent release of intracellular toxic oxidants and enzymes, leading to additional inflammation and lung damage in asthmatic children.371607-1
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