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Cadmium and Selenate Exposure Affects the Honey Bee Microbiome and Metabolome, and Bee-Associated Bacteria Show Potential for Bioaccumulation
Materials selection for long life in LEO: A critical evaluation of atomic oxygen testing with thermal atom systems
The use of thermal atom test methods as a materials selection and screening technique for low-Earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined to be in thermal atom environments are compared to those observed in LEO and in high quality LEO simulations. Reaction efficiencies measured in a new type of thermal atom apparatus are one-hundredth to one-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of 8 in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain specific thermal test environments can be used as reliable materials screening tools. Using thermal atom methods to predict material lifetime in LEO requires direct calibration of the method against LEO data or high quality simulation data for each material
Shuttle on-orbit contamination and environmental effects
Ensuring the compatibility of the space shuttle system with payloads and payload measurements is discussed. An extensive set of quantitative requirements and goals was developed and implemented by the space shuttle program management. The performance of the Shuttle system as measured by these requirements and goals was assessed partly through the use of the induced environment contamination monitor on Shuttle flights 2, 3, and 4. Contamination levels are low and generally within the requirements and goals established. Additional data from near-term payloads and already planned contamination measurements will complete the environment definition and allow for the development of contamination avoidance procedures as necessary for any payload
Spectral signatures of photosynthesis II: coevolution with other stars and the atmosphere on extrasolar worlds
As photosynthesis on Earth produces the primary signatures of life that can
be detected astronomically at the global scale, a strong focus of the search
for extrasolar life will be photosynthesis, particularly photosynthesis that
has evolved with a different parent star. We take planetary atmospheric
compositions simulated by Segura, et al. (2003, 2005) for Earth-like planets
around observed F2V and K2V stars, modeled M1V and M5V stars, and around the
active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as
well as very low O2 content in case anoxygenic photosynthesis dominates. We
calculate the incident spectral photon flux densities at the surface of the
planet and under water. We identify bands of available photosynthetically
relevant radiation and find that photosynthetic pigments on planets around F2V
stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in
the NIR, in bands at 0.93-1.1 microns, 1.1-1.4 microns, 1.5-1.8 microns, and
1.8-2.5 microns. In addition, we calculate wavelength restrictions for
underwater organisms and depths of water at which they would be protected from
UV flares in the early life of M stars. We estimate the potential productivity
for both surface and underwater photosynthesis, for both oxygenic and
anoxygenic photosynthesis, and for hypothetical photosynthesis in which longer
wavelength, multi-photosystem series are used.Comment: 59 pages, 4 figures, 4 tables, forthcoming in Astrobiology ~March
200
Invasion Triangle: An Organizational Framework for Species Invasion
Species invasion is a complex, multifactor process. To encapsulate this complexity into an intuitively appealing, simple, and straightforward manner, we present an organizational framework in the form of an invasion triangle. The invasion triangle is an adaptation of the disease triangle used by plant pathologists to help envision and evaluate interactions among a host, a pathogen, and an environment. Our modification of this framework for invasive species incorporates the major processes that result in invasion as the three sides of the triangle: (1) attributes of the potential invader; (2) biotic characteristics of a potentially invaded site; and (3) environmental conditions of the site. The invasion triangle also includes the impact of external influences on each side of the triangle, such as climate and land use change. This paper introduces the invasion triangle, discusses how accepted invasion hypotheses are integrated in this framework, describes how the invasion triangle can be used to focus research and management, and provides examples of application. The framework provided by the invasion triangle is easy to use by both researchers and managers and also applicable at any level of data intensity, from expert opinion to highly controlled experiments. The organizational framework provided by the invasion triangle is beneficial for understanding and predicting why species are invasive in specific environments, for identifying knowledge gaps, for facilitating communication, and for directing management in regard to invasive species
On the Method to Infer an Atmosphere on a Tidally-Locked Super Earth Exoplanet and Upper limits to GJ 876d
We develop a method to infer or rule out the presence of an atmosphere on a
tidally-locked hot super Earth. The question of atmosphere retention is a
fundamental one, especially for planets orbiting M stars due to the star's
long-duration active phase and corresponding potential for stellar-induced
planetary atmospheric escape and erosion. Tidally-locked planets with no
atmosphere are expected to show a Lambertian-like thermal phase curve, causing
the combined light of the planet-star system to vary with planet orbital phase.
We report Spitzer 8 micron IRAC observations of GJ 876 taken over 32
continuous hours and reaching a relative photometric precision of 3.9e-04 per
point for 25.6 s time sampling. This translates to a 3 sigma limit of 5.13e-05
on a planet thermal phase curve amplitude. Despite the almost photon-noise
limited data, we are unable to conclusively infer the presence of an atmosphere
or rule one out on the non-transiting short-period super Earth GJ 876d. The
limiting factor in our observations was the miniscule, monotonic photometric
variation of the slightly active host M star, because the partial sine wave due
to the planet has a component in common with the stellar linear trend. The
proposed method is nevertheless very promising for transiting hot super Earths
with the James Webb Space Telescope and is critical for establishing
observational constraints for atmospheric escape.Comment: Published in Ap
Finding the elusive and causative autoantibody: An atypical case of autoimmune hemolytic anemia
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111227/1/ccr3203.pd
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