Morphologic Parameters for Successful Lunar Landing Sites

The Moon, with its abundant resources, intriguing science questions, and vast unexplored surface area, is the most attainable and useful near-term target for future human exploration. In recognition of this fact, Presidential Space Policy Directive 1 (PSPD-1) has directed the United States to return to the Moon for long-term exploration and utilization, beginning with the 7th American human lunar landing by 2024 and building to sustainable surface presence by 2028

High-Brilliance, High-Flux Compact Inverse Compton Light Source

The Old Dominion University Compact Light Source (ODU CLS) design concept is presented-a compact Inverse Compton Light Source (ICLS) with flux and brilliance orders of magnitude beyond conventional laboratory-scale sources and greater than other compact ICLS designs. This concept utilizes the physics of inverse Compton scattering of an extremely low emittance electron beam by a laser pulse of rms length of approximately two-thirds of a picosecond (2/3 ps). The accelerator is composed of a superconducting radio frequency (SRF) reentrant gun followed by four double-spoke SRF cavities. After the linac are three quadrupole magnets to focus the electron beam to the interaction point (IP). The distance from cathode surface to 1P is less than 6 m, with the cathode producing electron bunches with a bunch charge of 10 pC and a few picoseconds in length. The incident laser has 1 MW circulating power, a 1 micron wavelength, and a spot size of 3.2 microns at the IP. The repetition rate of this source is 100 MHz, in order to achieve a high flux despite the low bunch charge. The anticipated x-ray source parameters include an energy of 12 keV, with a total flux of 2.2 x 10(13) ph/s, the flux into a 0.1% bandwidth of 3.3 x 10(10) ph/(s0.1%BW), and the average brilliance of 3.4 x 10(14) ph/ (s mm(2 )mrad(2) 0.1%BW)

Beam Dynamics Studies of 499 Mhz Superconducting RF-Dipole Deflecting Cavity System

A 499 MHz deflecting cavity has been designed as a three-way beam spreader to separate an electron beam into 3 beams. The rf tests carried out on the superconducting rf-dipole cavity have demonstrated that a transverse voltage of 4.2 MV can be achieved with a single cavity. This paper discusses the beam dynamics on a deflecting structure operating in continuous-wave mode with a relativistic beam. The study includes the analysis on emittance growth, energy spread, and change in bunch size including effects due to field non-uniformities

Laser Pulsing in Linear Compton Scattering

Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions in collision. The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse Compton source. Many of the results allow easy scaling estimates to be made of the expected spectrum

CAMEMBERT: A Mini-Neptunes GCM Intercomparison, Protocol Version 1.0. A CUISINES Model Intercomparison Project

With an increased focus on the observing and modelling of mini-Neptunes, there comes a need to better understand the tools we use to model their atmospheres. In this paper, we present the protocol for the CAMEMBERT (Comparing Atmospheric Models of Extrasolar Mini-neptunes Building and Envisioning Retrievals and Transits) project, an intercomparison of general circulation models (GCMs) used by the exoplanetary science community to simulate the atmospheres of mini-Neptunes. We focus on two targets well studied both observationally and theoretically with planned JWST Cycle 1 observations: the warm GJ~1214b and the cooler K2-18b. For each target, we consider a temperature-forced case, a clear sky dual-grey radiative transfer case, and a clear sky multi band radiative transfer case, covering a range of complexities and configurations where we know differences exist between GCMs in the literature. This paper presents all the details necessary to participate in the intercomparison, with the intention of presenting the results in future papers. Currently, there are eight GCMs participating (ExoCAM, Exo-FMS, FMS PCM, Generic PCM, MITgcm, RM-GCM, THOR, and the UM), and membership in the project remains open. Those interested in participating are invited to contact the authors.Comment: Accepted to PS

The Spectral Energy Distribution of Fermi bright blazars

(Abridged) We have conducted a detailed investigation of the broad-band spectral properties of the \gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48 LBAS blazars.The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual Log $\nu$ - Log $\nu$ F$_\nu$ representation, the typical broad-band spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SEDs to characterize the peak intensity of both the low and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broad-band colors (i.e. the radio to optical and optical to X-ray spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency $\nu_p^S$ is positioned between 10$^{12.5}$ and 10$^{14.5}$ Hz in broad-lined FSRQs and between $10^{13}$ and $10^{17}$ Hz in featureless BL Lacertae objects.We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron - inverse Compton scenarios. However, simple homogeneous, one-zone, Synchrotron Self Compton (SSC) models cannot explain most of our SEDs, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. (...)Comment: 85 pages, 38 figures, submitted to Ap

Tangible Distributed Computer Music for Youth

Computer music research realizes a vision of performance by means of computational expression, linking body and space to sound and imagery through eclectic forms of sensing and interaction. This vision could dramatically impact computer science education, simultaneously modernizing the field and drawing in diverse new participants. In this article, we describe our work creating an interactive computer music toolkit for kids called BlockyTalky. This toolkit enables users to create networks of sensing devices and synthesizers, and to program the musical and interactive behaviors of these devices. We also describe our work with two middle school teachers to co-design and deploy a curriculum for 11- to 13-year-old students. We draw on work with these students to evidence how computer music can support learning about computer science concepts and change students’ perceptions of computing. We conclude by outlining some remaining questions around how computer music and computer science may best be linked to provide transformative educational experiences

Life Beyond the Solar System: Remotely Detectable Biosignatures

For the first time in human history, we will soon be able to apply to the scientific method to the question "Are We Alone?" The rapid advance of exoplanet discovery, planetary systems science, and telescope technology will soon allow scientists to search for life beyond our Solar System through direct observation of extrasolar planets. This endeavor will occur alongside searches for habitable environments and signs of life within our Solar System. While these searches are thematically related and will inform each other, they will require separate observational techniques. The search for life on exoplanets holds potential through the great diversity of worlds to be explored beyond our Solar System. However, there are also unique challenges related to the relatively limited data this search will obtain on any individual world

Transcriptomic and Epigenetic Regulation of Disuse Atrophy and the Return to Activity in Skeletal Muscle

Physical inactivity and disuse are major contributors to age-related muscle loss. Denervation of skeletal muscle has been previously used as a model with which to investigate muscle atrophy following disuse. Although gene regulatory networks that control skeletal muscle atrophy after denervation have been established, the transcriptome in response to the recovery of muscle after disuse and the associated epigenetic mechanisms that may function to modulate gene expression during skeletal muscle atrophy or recovery have yet to be investigated. We report that silencing the tibialis anterior muscle in rats with tetrodotoxin (TTX)—administered to the common peroneal nerve—resulted in reductions in muscle mass of 7, 29, and 51% with corresponding reductions in muscle fiber cross-sectional area of 18, 42, and 69% after 3, 7, and 14 d of TTX, respectively. Of importance, 7 d of recovery, during which rodents resumed habitual physical activity, restored muscle mass from a reduction of 51% after 14 d TTX to a reduction of only 24% compared with sham control. Returning muscle mass to levels observed at 7 d TTX administration (29% reduction). Transcriptome-wide analysis demonstrated that 3714 genes were differentially expressed across all conditions at a significance of P ≤ 0.001 after disuse-induced atrophy. Of interest, after 7 d of recovery, the expression of genes that were most changed during TTX had returned to that of the sham control. The 20 most differentially expressed genes after microarray analysis were identified across all conditions and were cross-referenced with the most frequently occurring differentially expressed genes between conditions. This gene subset included myogenin (MyoG), Hdac4, Ampd3, Trim63 (MuRF1), and acetylcholine receptor subunit α1 (Chrna1). Transcript expression of these genes and Fboxo32 (MAFbx), because of its previously identified role in disuse atrophy together with Trim63 (MuRF1), were confirmed by real-time quantitative RT-PCR, and DNA methylation of their promoter regions was analyzed by PCR and pyrosequencing. MyoG, Trim63 (MuRF1), Fbxo32 (MAFbx), and Chrna1 demonstrated significantly decreased DNA methylation at key time points after disuse-induced atrophy that corresponded with significantly increased gene expression. Of importance, after TTX cessation and 7 d of recovery, there was a marked increase in the DNA methylation profiles of Trim63 (MuRF1) and Chrna1 back to control levels. This also corresponded with the return of gene expression in the recovery group back to baseline expression observed in sham-operated controls. To our knowledge, this is the first study to demonstrate that skeletal muscle atrophy in response to disuse is accompanied by dynamic epigenetic modifications that are associated with alterations in gene expression, and that these epigenetic modifications and gene expression profiles are reversible after skeletal muscle returns to normal activity

TRAPPIST Habitable Atmosphere Intercomparison (THAI) workshop report

This is the final version. Available on open access from IOP Publishing via the DOI in this recordThe era of atmospheric characterization of terrestrial exoplanets is just around the corner. Modeling prior to observations is crucial in order to predict the observational challenges and to prepare for the data interpretation. This paper presents the report of the TRAPPIST Habitable Atmosphere Intercomparison (THAI) workshop (14-16 September 2020). A review of the climate models and parameterizations of the atmospheric processes on terrestrial exoplanets, model advancements and limitations, as well as direction for future model development was discussed. We hope that this report will be used as a roadmap for future numerical simulations of exoplanet atmospheres and maintaining strong connections to the astronomical community