149 research outputs found
Cryptic photosynthesis, Extrasolar planetary oxygen without a surface biological signature
On the Earth, photosynthetic organisms are responsible for the production of
virtually all of the oxygen in the atmosphere. On the land, vegetation reflects
in the visible, leading to a red edge that developed about 450 Myr ago and has
been proposed as a biosignature for life on extrasolar planets. However, in
many regions of the Earth, and particularly where surface conditions are
extreme, for example in hot and cold deserts, photosynthetic organisms can be
driven into and under substrates where light is still sufficient for
photosynthesis. These communities exhibit no detectable surface spectral
signature to indicate life. The same is true of the assemblages of
photosynthetic organisms at more than a few metres depth in water bodies. These
communities are widespread and dominate local photosynthetic productivity. We
review known cryptic photosynthetic communities and their productivity. We link
geomicrobiology with observational astronomy by calculating the disk-averaged
spectra of cryptic habitats and identifying detectable features on an exoplanet
dominated by such a biota. The hypothetical cryptic photosynthesis worlds
discussed here are Earth-analogs that show detectable atmospheric biomarkers
like our own planet, but do not exhibit a discernable biological surface
feature in the disc-averaged spectrum.Comment: 23 pages, 2 figures, Astrobiology (TBP) - updated Table 1, typo in
detectable O2 correcte
Getting Better Hospital Alarm Sounds Into a Global Standard
The reserved set of audible alarm signals embodied within the global medical device safety standard, IEC 60601-1-8, is known to be problematic and in need of updating. The current alarm signals are not only suboptimal, but there is also little evidence beyond learnability (which is known to be poor) that demonstrates their performance in realistic and representative clinical environments. In this article, we describe the process of first designing and then testing potential replacement audible alarm signals for IEC 60601-1-8, starting with the design of several sets of candidate sounds and initial tests on learnability and localizability, followed by testing in simulated clinical environments. We demonstrate that in all tests, the alarm signals selected for further development significantly outperform the current alarm signals. We describe the process of collecting considerably more data on the performance of the new sounds than exists for the current sounds, which ultimately will be of use to end users. We also reflect on the process and practice of working with the relevant committees and other practical issues beyond the science, which also need constant attention if the alarms we have developed are to be included successfully in an updated version of the standard
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