12,946 research outputs found
The Earth's Climate, 2005
The most advanced models of the Earth's climate predict gradual warming of the average surface temperature due to the release of carbon dioxide (CO2) from the burning of fossil fuels. With a good historical temperature record, this warming should be observable by climate monitoring stations. What have scientists observed about the Earth's climate to date?On January 13, 2006, the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC), the world's largest active archive of weather data, released their Climate of 2005 report. The report contains a number of sobering observations about the Earth's climate: average surface temperature continues to warm; polar ice is melting rapidly; hurricane activity is at a record high; and in the United States, low Northwest snowpack contributed to a period of drought in the region.The NOAA Climate of 2005 report is the highly reputed, carefully analyzed product of climate data from around the world, containing the most up-to-date information from the field of climate monitoring. This fact sheet summarizes some highlights from the report, including climate anomalies in the United States
Cyanobacteria in CELSS: Growth strategies for nutritional variation and nitrogen cycling
Cyanobacteria (blue-green algae) are versatile organisms which are capable of adjusting their cellular levels of carbohydrate, protein, and lipid in response to changes in the environment. Under stress conditions there is an imbalance between nitrogen metabolism and carbohydrate/lipid synthesis. The lesion in nitrogen assimilation is at the level of transport: the stress condition diverts energy from the active accumulation of nitrate to the extrusion of salt, and probably inhibits a cold-labile ATP'ace in the case of cold shock. Both situations affect the bioenergetic status of the cell such that the nitrogenous precursors for protein synthesis are depleted. Dispite the inhibition of protein synthesis and growth, photosynthetic reductant generation is relatively unaffected. The high O2 reductant would normally lead to photo-oxidative damage of cellular components; however, the organism copes by channeling the 'excess' reductant into carbon storage products. The increase in glycogen (28 to 35 percent dry weight increase) and the elongation of lipid fatty acid side chains (2 to 5 percent dry weight increase) at the expense of protein synthesis (25 to 34 percent dry weight decrease) results in carbohydrate, lipid and protein ratios that are closer to those required in the human diet. In addition, the selection of nitrogen fixing mutants which excrete ammonium ions present an opportunity to tailor these micro-organisms to meet the specific need for a sub-system to reverse potential loss of fixed nitrogen material
Application of photosynthetic N2-fixing cyanobacteria to the CELSS program
Commercially available air lift fermentors were used to simultaneously monitor biomass production, N2-fixation, photosynthesis, respiration, and sensitivity to oxidative damage during growth under various nutritional and light regimes, to establish a data base for the integration of these organisms into a Closed Ecological Life Support System (CELSS) program. Certain cyanobacterial species have the unique ability to reduce atmospheric N2 to organic nitrogen. These organisms combine the ease of cultivation characteristics of prokaryotes with the fully developed photosynthetic apparatus of higher plants. This, along with their ability to adapt to changes in their environment by modulation of certain biochemical pathways, make them attractive candidates for incorporation into the CELSS program
Feasibility of V/STOL concepts for short-haul transport aircraft
Feasibility of V/STOL concepts for short-haul transport aircraf
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