The George Washington University, USA October 6 -10

Abstract: The SEPTD mission is a stepping stone leading to a reusable electric propulsion stage by demonstrating transfers from LEO to GEO and back to LEO. This set of high V trajectories demonstrates long-term SEP operations and flies the SEPTD space vehicle through the radiation belts, sustained plasma environments, diverse distributed inertia Space Vehicle control environments and repeated Space Vehicle occultations. A large number of trades cases and point designs have been analyzed for requirements development, system sizing, and concept of operations definition. The trades and point designs have been completed using various methods and tools at ranging levels of fidelity. The focus was to find high V solutions that fit within the budget (and hence mass) constraints of the SEPTD Mission requirements. Mass is purposefully constrained to constrain cost. The Baseline Mission begins in LEO, performs a low-thrust transit to GEO, transits back down to an equatorial LEO orbit, and then optionally spirals out from LEO to L1. There are a wide range of mission variants including EP system selection, and the Baseline Mission provides the performance capability for flexibility; including extended missions to NEOs, low lunar orbit, or the moons of Mars. Nomenclatur

Plasma Imaging, LOcal Measurement, and Tomographic experiment (PILOT): a mission concept for transformational multi-scale observations of mass and energy flow dynamics in Earth’s magnetosphere

We currently do not understand the fundamental physical processes that govern mass and energy flow through the Earth’s magnetosphere. Knowledge of these processes is critical to understanding the mass loss rate of Earth’s atmosphere, as well as for determining the role that a planetary magnetic field plays in atmospheric retention, and therefore habitability, for Earth-like planets beyond the solar system. Mass and energy flow processes are challenging to determine at Earth in part because Earth’s planetary magnetic field creates a complex “system of systems” composed of interdependent plasma populations and overlapping spatial regions that perpetually exchange mass and energy across a broad range of temporal and spatial scales. Further, the primary mass carrier in the magnetosphere is cold plasma (as cold as ∼0.1 eV), which is invisible to many space-borne instruments that operate in the inner magnetosphere. The Plasma Imaging LOcal and Tomographic experiment (PILOT) mission concept, described here, provides the transformational multi-scale observations required to answer fundamental open questions about mass and energy flow dynamics in the Earth’s magnetosphere. PILOT uses a constellation of spacecraft to make radio tomographic, remote sensing, and in-situ measurements simultaneously, fully capturing cold plasma mass dynamics and its impact on magnetospheric systems over an unprecedented range of spatial and temporal scales. This article details the scientific motivation for the PILOT mission concept as well as a potential mission implementation.AGS-1845151 - National Science FoundationPublished versio

On-orbit performance of the MIPS instrument

The Multiband Imaging Photometer for Spitzer (MIPS) provides long wavelength capability for the mission, in imaging bands at 24, 70, and 160 microns and measurements of spectral energy distributions between 52 and 100 microns at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The Si:As BIB 24 micron array has excellent photometric properties, and measurements with rms relative errors of 1% or better can be obtained. The two longer wavelength arrays use Ge:Ga detectors with poor photometric stability. However, the use of 1.) a scan mirror to modulate the signals rapidly on these arrays, 2.) a system of on-board stimulators used for a relative calibration approximately every two minutes, and 3.) specialized reduction software result in good photometry with these arrays also, with rms relative errors of less than 10%

Neuroanatomy Curriculum Development and Learning Outcomes via Virtual Dissection: A Survey of Students

Virtual dissection’sefficacy is being studied due to its constantly changing technology. The discussion regarding the extent of use of virtual dissection in professional education could benefit from thisquantitative study reflecting students’achievement of learning course objectives, perceived learning of course objectives, and discussion of the data’simpact on curriculum development

Increasing postmortem aging time decreases color and flavor stability of top sirloin steaks

Top sirloin butts are commonly blade-tenderized to significantly increase tenderness, but minimal data have shown the relationship between blade tenderization and color stability as well as the effect of extended postmortem aging periods past 30 days on color stability. Tenderness plays a significant role in consumer satisfaction with beef products, and blade tenderization and extended postmortem aging periods are effective ways to ensure that beef cuts are tender. Therefore, the objectives of this study were to: (1) determine color and flavor stability of beef gluteus medius during extended postmortem aging times with and without mechanical tenderization, and (2) determine the biochemical factors responsible for color stability of beef gluteus medius at five different aging periods

\u3ci\u3eDrosophila\u3c/i\u3e Muller F Elements Maintain a Distinct Set of Genomic Properties Over 40 Million Years of Evolution

The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu