- Few, if any, big impact craters remain to be discovered on Earth, new model finds
- Antarctic Species Dwindle as Icebergs Batter Shores Year-Round
- Technique Could Make Sub-wavelength Images at Radio Frequencies
Posted: 17 Jun 2014 06:24 PM PDT
It is likely that most of the large impact craters on Earth have already been discovered and that others have been erased, according to a new calculation by a pair of Purdue University graduate students.
Posted: 17 Jun 2014 06:12 PM PDT
The Antarctic shore is a place of huge contrasts, as quiet, dark, and frozen winters give way to bright, clear waters, thick with algae and peppered with drifting icebergs in summer. But as the planet has warmed in the last two decades, massive losses of sea ice in winter have left icebergs free to roam for most of the year. As a result, say researchers reporting in the Cell Press journal Current Biology on June 16, boulders on the shallow seabed—once encrusted with a rich assemblage of species in intense competition for limited space—now mostly support a single species.
Posted: 17 Jun 2014 06:01 PM PDT
Imaging and mapping of electric fields at radio frequencies (RF) currently requires the use of metallic structures such as dipoles, probes and reference antennas. To make such measurements efficiently, the size of these structures needs to be on the order of the wavelength of the RF fields to be mapped. This poses practical limitations on the smallest features that can be measured.
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