1,645 research outputs found

    The verification of LANDSAT data in the geographical analysis of wetlands in western Tennessee

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    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

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    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

    The verification of LANDSAT data in the geographical analysis of wetlands in west Tennessee

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    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

    Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

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    Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at ?400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that ?60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at <100 m water depth produces methane concentrations of up to 615 nM. The diffusive flux of methane from sea to air in the vicinity of the landward limit of the GHSZ is ?4–20 ?mol m?2 d?1, which is small relative to other Arctic sources. In support of this, analyses of mole fractions and the carbon isotope signature of atmospheric methane above the seeps do not indicate a significant local contribution from the seafloor source

    Feature integration in natural language concepts

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    Two experiments measured the joint influence of three key sets of semantic features on the frequency with which artifacts (Experiment 1) or plants and creatures (Experiment 2) were categorized in familiar categories. For artifacts, current function outweighed both originally intended function and current appearance. For biological kinds, appearance and behavior, an inner biological function, and appearance and behavior of offspring all had similarly strong effects on categorization. The data were analyzed to determine whether an independent cue model or an interactive model best accounted for how the effects of the three feature sets combined. Feature integration was found to be additive for artifacts but interactive for biological kinds. In keeping with this, membership in contrasting artifact categories tended to be superadditive, indicating overlapping categories, whereas for biological kinds, it was subadditive, indicating conceptual gaps between categories. It is argued that the results underline a key domain difference between artifact and biological concepts

    Identifying drivers behind spatial variability of Methane concentrations in East Siberian ponds

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    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

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    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

    Glucose-6-phosphate dehydrogenase deficiency with recurrent infections: case report

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    OBJECTIVE: To report a case of rare neutrophil functional disorder with clinical and laboratory findings similar to those of chronic granulomatous disease. METHODS: Patient with extremely reduced level of glucose-6-phosphate dehydrogenase and recurrent infections that improved after continuous use of cotrimoxazole. The patient presented leukocytes with defective respiratory burst, similar to what occurs in chronic granulomatous disease. COMMENTS: The diagnosis of glucose-6-phosphate dehydrogenase deficiency in neutrophils should be considered in any patient with hemolytic anemia whose level of G6PD is extremely low or in any patient that presents recurrent infections as differential diagnosis of chronic granulomatous disease.OBJETIVO: relatar a ocorrência de uma deficiência funcional de neutrófilos rara, com quadro clínico e laboratorial semelhante ao da doença granulomatosa crônica. MÉTODOS: relato de caso de paciente com deficiência acentuada da glicose-6-fosfato desidrogenase e infecções de repetição. Realizada pesquisa bibliográfica utilizando as bases de dados Medline e Lilacs, abrangendo o período de 1972 a 2000. RESULTADOS: paciente com nível da glicose-6-fosfato desidrogenase extremamente reduzido e quadro de infeções graves com melhora clínica após uso de cotrimoxazol contínuo. Os leucócitos do paciente apresentam defeito no metabolismo oxidativo, similar ao da doença granulomatosa crônica. CONCLUSÕES: o diagnóstico da deficiência da glicose-6-fosfato desidrogenase em neutrófilos deve ser considerado em qualquer paciente com anemia hemolítica não esferocítica congênita no qual o nível da glicose-6-fosfato desidrogenase esteja anormalmente baixo ou apresente infeções de repetição. É diagnóstico diferencial da doença granulomatosa crônica.Univ. Federal de São Paulo Depto. de Pediatria Disc. de Alergia, Imunologia ClínicaUniv. Federal do Rio de Janeiro Fac. de Medicina Depto. de Medicina PreventivaUNICAMP Faculdade de Ciências Médicas Depto. de PediatriaUniv. de São Paulo Fac. de MedicinaUNIFESP-EPM Depto. de PediatriaUSP Instituto de Ciências Biomédicas Depto. de ImunologiaUFRJ Fac. Med. Depto. de Medicina PreventivaUFRJ Fac. de Medicina Depto. de PediatriaUNIFESP, EPM, Depto. de PediatriaSciEL
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