Seasonal CO2 amplitude growing
Levels of carbon dioxide (CO2) in the atmosphere rise and fall as plants take up the gas in spring and summer and release it in fall and winter through photosynthesis and respiration. Now the range of that cycle is growing as more CO2 is emitted from the burning of fossil fuels and other human activities, according to a study led by Scripps Institution of Oceanography, UC San Diego.
Results come from a multi-year, airborne survey of atmospheric chemistry in which observations of atmospheric CO2 at altitudes between 3 and 6 kilometers (10,000 to 20,000 feet) show seasonal CO2 variations have substantially increased in amplitude over the last 50 years. This increase is roughly 50 percent across high latitude regions north of 45-degrees N, in comparison to previous aircraft observations from the late 1950s and early 1960s.
This means more carbon is accumulating in forests and other vegetation and soils in the Northern Hemisphere during the summer, and more carbon is being released in the fall and winter.
It is not yet understood why the increase in seasonal amplitude of CO2 concentration is so large, but it is a clear signal of widespread changes in northern ecosystems.
— Findings appear in the journal Science. News release at http://bit.ly/149BHhO
Earthquake retrofits for ‘soft’ buildings
Earthquakes are particularly damaging to multi-story dwellings with first-floor parking garages or street-level storefronts because these open spaces are prone to collapse. Tens of thousands of such structurally weak or “soft” buildings are found throughout California and nationwide, constituting a serious safety issue.
Led by Colorado State University, a team of engineers from academic institutions, industry, and government entities spent last month shaking a four-story building at the Englekirk Structural Engineering Center (Jacobs School of Engineering at UC San Diego) – the world’s largest outdoor “shake table” – to learn how to make structures better withstand seismic shocks.
Earthquake retrofits were tested on a 44,000-square-foot building using a variety new and innovative materials: cross-laminated timber, straps and clips, steel special-moment-frames, anchor tied-down systems, and viscous fluid damper frames similar to car shocks.
The wood structure – three stories atop an open first floor – survived three of four simulated seismic events of increasing strength. While larger shakes did cause building damage, with the retrofits in place, it remained structurally safe for occupancy.
— News release at http://bit.ly/18ywXqf
Mechanism helps viruses shut down body’s immune defense
Researchers at the Salk Institute for Biological Studies have discovered a previously unknown mechanism by which viruses such as influenza, West Nile and Dengue evade the body’s immune response and infect humans with these potentially deadly diseases.
So-called “enveloped viruses” (because they possess an outer wrapping of a lipid membrane) disarm a host’s innate immune response by activating a class of molecules, known as TAM receptors, located on the outside of immune cells such as macrophages and dendritic cells. TAM receptors are used by these cells to clean up dead cells, and they are also central to the body’s immune response to bacteria, viruses and other pathogens.
Researchers found that a substance called phosphatidylserine (PtdSer) on the surface of enveloped viruses binds to extracellular proteins and activates TAM receptors on immune cells. In dendritic cells, TAM receptor activation turns off a set of genes disabling the interferon response which is key to antiviral defense.
— Findings appear in the journal Cell Host and Microbe. News release at http://bit.ly/14Q8VqV
Lynne Friedmann is a science writer based in Solana Beach.
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