101 research outputs found
Relationship between ecosystem productivity and photosynthetically-active radiation for northern peatlands
We analyzed the relationship between net ecosystem exchange of carbon dioxide (NEE) and irradiance (as photosynthetic photon flux density or PPFD), using published and unpublished data that have been collected during midgrowing season for carbon balance studies at seven peatlands in North America and Europe. NEE measurements included both eddy-correlation tower and clear, static chamber methods, which gave very similar results. Data were analyzed by site, as aggregated data sets by peatland type (bog, poor fen, rich fen, and all fens) and as a single aggregated data set for all peatlands. In all cases, a fit with a rectangular hyperbola (NEE = α PPFD Pmax/(α PPFD + Pmax) + R) better described the NEE-PPFD relationship than did a linear fit (NEE = ÎČ PPFD + R). Poor and rich fens generally had similar NEE-PPFD relationships, while bogs had lower respiration rates (R = â2.0ÎŒmol mâ2sâ1 for bogs and â2.7 ÎŒmol mâ2sâ1 for fens) and lower NEE at moderate and high light levels (Pmax = 5.2 ÎŒmol mâ2sâ1 for bogs and 10.8 ÎŒmol mâ2sâ1 for fens). As a single class, northern peatlands had much smaller ecosystem respiration (R = â2.4 ÎŒmol mâ2sâ1) and NEE rates (α = 0.020 and Pmax = 9.2ÎŒmol mâ2sâ1) than the upland ecosystems (closed canopy forest, grassland, and cropland) summarized by Ruimy et al. [1995]. Despite this low productivity, northern peatland soil carbon pools are generally 5â50 times larger than upland ecosystems because of slow rates of decomposition caused by litter quality and anaerobic, cold soils
The Particle Physics Reach of High-Energy Neutrino Astronomy
We discuss the prospects for high-energy neutrino astronomy to study particle
physics in the energy regime comparable to and beyond that obtainable at the
current and planned colliders. We describe the various signatures of
high-energy cosmic neutrinos expected in both neutrino telescopes and air
shower experiments and discuss these measurements within the context of
theoretical models with a quantum gravity or string scale near a TeV,
supersymmetry and scenarios with interactions induced by electroweak
instantons. We attempt to access the particle physics reach of these
experiments.Comment: Mini-review article for New Journal of Physics, "Focus on Neutrinos"
issue. 27 pages, 11 figure
A Global Mitigation Hierarchy for Nature Conservation
Efforts to conserve biodiversity comprise a patchwork of international goals, national-level plans, and local interventions that, overall, are failing. We discuss the potential utility of applying the mitigation hierarchy, widely used during economic development activities, to all negative human impacts on biodiversity. Evaluating all biodiversity losses and gains through the mitigation hierarchy could help prioritize consideration of conservation goals and drive the empirical evaluation of conservation investments through the explicit consideration of counterfactual trends and ecosystem dynamics across scales. We explore the challenges in using this framework to achieve global conservation goals, including operationalization and monitoring and compliance, and we discuss solutions and research priorities. The mitigation hierarchy's conceptual power and ability to clarify thinking could provide the step change needed to integrate the multiple elements of conservation goals and interventions in order to achieve successful biodiversity outcomes
Loxoscelismo en Chile: estudios epidemiolĂłgicos, clĂnicos y experimentales
Se presenta un enfoque panorĂĄmico de estudios epidemiolĂłgicos, clĂnicos y experimentales referentes a Loxosceles laeta y loxoscelismo efectuados en 1955-1988 en Santiago, Chile. Se estudiaron 216 casos de loxoscelismo. Los hechos mĂĄs relevantes fueron: 52,8% correspondiĂł a mujeres; edad entre 7 meses y 78 años; 84,3% fuĂ© loxoscelismo cutĂĄneo (LO y 15,7% loxoscelismo cutĂĄneo-visceral (LCV); 73,6% sucediĂł en Ă©poca calurosa; en 86,6% el accidente ocurriĂł en la vivienda, especialmente en dormitorios, mientras la persona dormĂa o se vestĂa. La araña fuĂ© vista en 60,2% de los casos e identificada en laboratorio como L. laeta en 17,7% (10,6% de los 216 casos). Los sitios mĂĄs frecuen temente afectados fueron las extremidades con 67,6%, lancetazo urente fuĂ© el sĂntoma inicial mĂĄs frecuente. Dolor, edema y placa livedoide, la cual posteriormente se transformarĂa en escara necrĂłtica, fueron las manifestaciones locales predominantes. En LCV hematuria y hemoglobinuria fueron constantes, ictericia, fiebre y compromiso de conciencia se presentaron en la mayorĂa de los casos. Tratamiento: LC con antihistamĂnicos o corticoides inyectables, LCV con corti-coides inyectables. La condiciĂłn de los pacientes en el Ășltimo control fuĂ©: curaciĂłn completa en 75,5%, curaciĂłn con secuela cicatrizal en 8,3%, muerte en 3,7% (todos con LCV) y abandono en 12,5%. Adicionalmente, se ha efectuado una serie de estudios experimentales, tanto in vivo como in vitro para esclarecer aspectos bĂĄsicos sobre el veneno de L. laeta y el tratamiento del loxoscelismo.A panoramic sight of epidemiological, clinical and experimental studies, referring to Loxosceles laeta and loxoscelism, carried out in 1955-1988, in Santiago, Chile is presented. Two-hundred and sixteen cases of loxosce lism were studied. The most relevant features were: 84.3% corresponded to cutaneous loxosce lism (CD and 15.7% to viscerocutaneous loxos celism (VCD; 73.6% ocurred in hot season; in 86.6% of cases the accident happened in the hou se, particularly in bedrooms, while the people were sleeping or dressing. The spider was seen in 60.2%r of cases and identified in the laboratory as L. laeta in 10.69c of all cases. The sites more frequently bitten were the limbs with 67.6% ; a burning stinging was the most frequent initial symptom. Pain, edema and livedoid plaque, which developed later into a necrotic eschar, we re the predominant local manifestations. In VCL, hematuria and hemoglobinuria were cons tant, while jaundice, fever and sensorial involve ment were present in most of the cases. CL patients were parenterally treated with antihistamine drugs or corticoids, while VCL ones were treated with corticoids by injection. The condition of patients in the last follow up was: complete cure in 75.5% , cure with a scarfed sequela in 8.3%, death in 3.7% (all VCL) and abandonment in 12.5%. Additionally, a series of experimental studies, both in vivo and in vitro, has been performed in order to clarify basic aspects on L. laeta venom and the treatment of loxoscelism
Origin and preservation of bacteriohopanepolyol signatures in Sphagnum peat from Bissendorfer Moor (Germany)
The impact of trawling on the epibenthic megafauna of the west Greenland shelf
Benthic habitats are important elements of polar marine environments, but can be vulnerable to anthropogenic influences such as trawling. Bottom trawling can reduce diversity and alter communities, although some habitats show resilience. The shrimp trawl fishery of West Greenland is a significant part of Greenland's economy. It operates along the west coast from the narrow rockier shelf of the south, up to deeper, muddy areas around Disko Bay. Here we use a benthic drop camera to sample 201 sites between latitudes 60â72°N and depths of 61â725m. Linear models examined relationships of taxon abundance and diversity with bottom trawling intensity and environment (depth, temperature, current, iceberg concentration). Trawling intensity is the most important factor determining the overall abundance of benthic organisms, accounting for 12â16% of variance, although environmental conditions also show significant associations. Sessile erect organisms such as corals show a significant negative response to trawling. Soft sediment communities show a higher resilience than rocky areas. On soft sediments significantly lower abundance characterises sites trawled under five years ago. On hard/mixed ground reduced abundance remains characteristic of sites trawled a decade ago. Continued monitoring of benthic habitats is an essential part of evaluating the ongoing impacts of trawl fisheries
Einleitung: Demokratisierung, Konsolidierung und Wohlfahrtsstaat â Ăberlegungen zu einem ungeklĂ€rten VerhĂ€ltnis
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