Detectability of biosignatures in anoxic atmospheres with the James Webb Space Telescope: A TRAPPIST-1e case study

The James Webb Space Telescope (JWST) may be capable of finding biogenic gases in the atmospheres of habitable exoplanets around low mass stars. Considerable attention has been given to the detectability of biogenic oxygen, which could be found using an ozone proxy, but ozone detection with JWST will be extremely challenging, even for the most favorable targets. Here, we investigate the detectability of biosignatures in anoxic atmospheres analogous to those that likely existed on the early Earth. Arguably, such anoxic biosignatures could be more prevalent than oxygen biosignatures if life exists elsewhere. Specifically, we simulate JWST retrievals of TRAPPIST-1e to determine whether the methane plus carbon dioxide disequilibrium biosignature pair is detectable in transit transmission. We find that ~10 transits using the Near InfraRed Spectrograph (NIRSpec) prism instrument may be sufficient to detect carbon dioxide and constrain methane abundances sufficiently well to rule out known, non-biological CH$_{4}$ production scenarios to ~90% confidence. Furthermore, it might be possible to put an upper limit on carbon monoxide abundances that would help rule out non-biological methane-production scenarios, assuming the surface biosphere would efficiently drawdown atmospheric CO. Our results are relatively insensitive to high altitude clouds and instrument noise floor assumptions, although stellar heterogeneity and variability may present challenges.Comment: 21 pages, 7 figure

A comparison of exoplanet spectroscopic retrieval tools

Over the last several years, spectroscopic observations of transiting exoplanets have begun to uncover information about their atmospheres, including atmospheric composition and indications of the presence of clouds and hazes. Spectral retrieval is the leading technique for interpretation of transmission spectra and is employed by several teams using a variety of forward models and parameter estimation algorithms. However, different model suites have mostly been used in isolation and so it is unknown whether the results from each are comparable. As we approach the launch of the James Webb Space Telescope, we anticipate advances in wavelength coverage, precision, and resolution of transit spectroscopic data, so it is important that the tools that will be used to interpret these information-rich spectra are validated. To this end, we present an intermodel comparison of three retrieval suites: TAUREX, NEMESIS, and CHIMERA. We demonstrate that the forward model spectra are in good agreement (residual deviations on the order of 20-40 ppm), and discuss the results of cross-retrievals among the three tools. Generally, the constraints from the cross-retrievals are consistent with each other and with input values to within 1σ. However, for high precision scenarios with error envelopes of order 30 ppm, subtle differences in the simulated spectra result in discrepancies between the different retrieval suites, and inaccuracies in retrieved values of several σ. This can be considered analogous to substantial systematic/astrophysical noise in a real observation, or errors/omissions in a forward model such as molecular line list incompleteness or missing absorbers

Influence of array interspacing on the force required for successful microneedle skin penetration: theoretical and practical approaches

Insertion behaviour of microneedle (MN) arrays depends upon the mechanical properties of the skin and, MN geometry and distribution in an array. In addressing this issue, this paper studies MN array insertion mechanism into skin and provides a simple quantitative basis to relate the insertion force with distance between two MNs. The presented framework is based on drawing an analogy between a beam on an elastic foundation and mechanism of needle insertion, where insertion force is separated into different components. A theoretical analysis indicates that insertion force decreases as interspacing increases. For a specified skin type, insertion force decreased from 0.029 to 0.028N/MN when interspacing at MN tip was increased from 50μm (350μm at MN base) to 150μm (450μm at MN base). However, dependence of insertion force seems to decrease as the interspacing is increased beyond 150μm. To assess the validity of the proposed model, a series of experiments was carried out to determine the force required for skin insertion of MN. Experiments performed at insertion speed of 0.5 and 1.0mm/s yielded insertion force values of 0.030 and 0.0216N, respectively, for 30μm interspacing at MN base (330μm interspacing at tip) and 0.028 and 0.0214N, respectively, for 600μm interspacing at MN base (900μm interspacing at tip). Results from theoretical analysis and finite element modelling agree well with experimental results, which show MN interspacing only begins to affect insertion force at low interspacing (<150μm interspacing at MN base). This model provides a framework for optimising MN devices, and should aid development of suitable application method and determination of force for reliable insertion into skin. © 2013 Wiley Periodicals, Inc

Evaluation of Corn Bran Plus Solubles on Performance and Carcass Characteristics in Finishing Diets

A finishing study was conducted to determine the effect of feeding corn bran plus solubles, a new feed resulting from a pre-fermentation fiber removal process, compared to wet distillers grains plus solubles at two levels of inclusion (20% and 40% of diet DM). Intake increased with inclusion of byproduct, and steers fed 20% wet distillers had the greatest intakes numerically. Byproduct inclusion, regardless of type, increased daily gain over the corn-based control. Feed conversions were improved with increased inclusion of both Bran + Solubles and wet distillers, and both were superior to the control. Increased inclusion of both byproducts resulted in a linear increase in carcass weight. Feeding Bran+Solubles resulted in performance and carcass characteristics similar to wet distillers at both 20% and 40% inclusion

Evaluation of Fractionated Distillers Grains (High Protein and Bran Plus Solubles) on Performance and Carcass Characteristics in Finishing Diets

A finishing study evaluated the effect of feeding a new, high protein distillers grains along with corn bran plus condensed distillers solubles compared to traditional wet distillers grains, traditional dry distillers grains and a corn-based control. Each byproduct replaced corn at 40% of the diet dry-matter. Intake was not affected by treatment; however gain and carcass weight were greater and feed conversion improved for high protein distillers and corn bran plus solubles than either type of traditional distillers grains or corn. Based on feed efficiency, the feeding values of high protein distillers grains and corn bran plus solubles are 121% and 125% that of corn, respectively. These new byproducts appear to be viable options for producers to utilize in finishing diets

Evaluation of the Energy Value and Nutrient Digestibility of Distillers Grains That Have Undergone a Fiber Separation Process in Finishing Diets

A digestion study was conducted to determine the effects of feeding a new, high protein distillers grains and corn bran plus solubles on nutrient digestibility. Treatments included a corn-based control, high protein distillers at both 20% and 40%, corn bran plus solubles, traditional wet distillers grains and traditional dry distillers grains all at 40% of diet DM. Feeding high protein distillers grains or corn bran plus solubles resulted in decreased digestibility compared to corn or traditional wet and dry distillers grains, but increased energy intake. Traditional wet and dry distillers grains also resulted in decreased digestibilities while energy intake was increased. Volatile fatty acid profiles and pH parameters were not different across treatments. Overall, nutrient digestibility for high protein distillers grains and corn bran plus solubles is similar to traditional wet or dry distillers grains

Dopaminergic dysregulation in mice selectively bred for excessive exercise or obesity

Dysregulation of the dopamine system is linked to various aberrant behaviors, including addiction, compulsive exercise, and hyperphagia leading to obesity. The goal of the present experiments was to determine how dopamine contributes to the expression of opposing phenotypes, excessive exercise and obesity. We hypothesized that similar alterations in dopamine and dopamine-related gene expression may underly obesity and excessive exercise, as competing traits for central reward pathways. Moreover, we hypothesized that selective breeding for high levels of exercise or obesity may have influenced genetic variation controlling these pathways, manifesting as opposing complex traits. Dopamine, dopamine-related peptide concentrations, and gene expression were evaluated in dorsal striatum (DS) and nucleus accumbens (NA) of mice from lines selectively bred for high rates of wheel running (HR) or obesity (M16), and the non-selected ICR strain from which these lines were derived. HPLC analysis showed significantly greater neurotransmitter concentrations in DS and NA of HR mice compared to M16 and ICR. Microarray analysis showed significant gene expression differences between HR and M16 compared to ICR in both brain areas, with changes revealed throughout the dopamine pathway including D1 and D2 receptors, associated G-proteins (eg. Golf), and adenylate cyclase (eg. Adcy5). The results suggest similar modifications within the dopamine system may contribute to the expression of opposite phenotypes in mice, demonstrating that alterations within central reward pathways can contribute to both obesity and excessive exercise