Regional sources and sinks of dust on Mars: Viking observations of Cerberus, Solis Planum and Syrtis Major

A study of seasonal variations of albedo features in the Cerberus, Solis Planum, and Syrtis Major regions was based on Viking Orbiter data obtained over more than one complete Martian year. Contour maps of Lambert albedo and single-point thermal inertia were constructed from the Infrared Thermal Mapper (IRTM) experiment data, and Orbiter images were used to determine the pattern and variability of regional winds (inferred from wind streak orientations). Coupled with ground-based radar data, these data allow the regional sediment transport direction, surface properties (texture, morphology, and roughness), and the implications of the observed seasonal and longer term dust redistribution to be investigated. Results are outlined

Dynamical Friction in a Gas: The Supersonic Case

Any gravitating mass traversing a relatively sparse gas experiences a retarding force created by its disturbance of the surrounding medium. In a previous contribution (Lee & Stahler 2011), we determined this dynamical friction force when the object's velocity was subsonic. We now extend our analysis to the supersonic regime. As before, we consider small perturbations created in the gas far from the gravitating object, and thereby obtain the net influx of linear momentum over a large, bounding surface. Various terms in the perturbation series formally diverge, necessitating an approximate treatment of the flow streamlines. Nevertheless, we are able to derive exactly the force itself. As in the subsonic case, we find that F=Mdot*V, where Mdot is the rate of mass accretion onto the object and V its instantaneous velocity with respect to distant background gas. Our force law holds even when the object is porous (e.g., a galaxy) or is actually expelling mass in a wind. Quantitatively, the force in the supersonic regime is less than that derived analytically by previous researchers, and is also less than was found in numerical simulations through the mid 1990s. We urge simulators to revisit the problem using modern numerical techniques. Assuming our result to be correct, it is applicable to many fields of astrophysics, ranging from exoplanet studies to galactic dynamics.Comment: Accepted to A&A. Comments from the community welcomed. 21 pages, 12 figure

Law-Based Arguments and Messages to Advocate for Later School Start Time Policies in the United States

The increasing scientific evidence that early school start times are harmful to the health and safety of teenagers has generated much recent debate about changing school start times policies for adolescent students. Although efforts to promote and implement such changes have proliferated in the United States in recent years, they have rarely been supported by law-based arguments and messages that leverage the existing legal infrastructure regulating public education and child welfare in the United States. Furthermore, the legal bases to support or resist such changes have not been explored in detail to date. This article provides an overview of how law-based arguments and messages can be constructed and applied to advocate for later school start time policies in U.S. public secondary schools. The legal infrastructure impacting school start time policies in the United States is briefly reviewed, including descriptions of how government regulates education, what legal obligations school officials have concerning their students\u27 welfare, and what laws and public policies currently exist that address adolescent sleep health and safety. On the basis of this legal infrastructure, some hypothetical examples of law-based arguments and messages that could be applied to various types of advocacy activities (e.g., litigation, legislative and administrative advocacy, media and public outreach) to promote later school start times are discussed. Particular consideration is given to hypothetical arguments and messages aimed at emphasizing the consistency of later school start time policies with existing child welfare law and practices, legal responsibilities of school officials and governmental authorities, and societal values and norms

Use of the Classroom Management Link System (CMLS) Across Multiple Classrooms

This manuscript was originally presented in a poster session at the 121st annual convention of the American Psychological Association, Honolulu, Hawaii.The purpose of this study was to determine the effect of the Classroom Management Link System (CMLS) across classrooms using a multiple baseline design. CMLS is a preventive system that uses rule development, self-monitoring, goal setting and increased positive teacher feedback to prevent disruptive classroom behavior and increase academic engaged time. Baseline data on off-task and disruptive behavior was taken in each classroom until CMLS was implemented. CMLS was implemented after three weeks of collecting baseline data in Classroom One and six weeks of collecting baseline data in Classroom Two. Each teacher completed surveys on non-academic factors impacting their classroom and their own classroom management skills. These surveys were completed at the time CMLS was implemented in each classroom as well as at the end of the study. An additional survey was administered at the end of the study to measure the acceptability of the intervention. The results suggest that the intervention had a large effect on off-task behavior and a small to moderate effect on disruptive behavior. Mixed results were found for each of the surveys. Results on the acceptability of the intervention were also mixed

Neural Network Memory Architectures for Autonomous Robot Navigation

This paper highlights the significance of including memory structures in neural networks when the latter are used to learn perception-action loops for autonomous robot navigation. Traditional navigation approaches rely on global maps of the environment to overcome cul-de-sacs and plan feasible motions. Yet, maintaining an accurate global map may be challenging in real-world settings. A possible way to mitigate this limitation is to use learning techniques that forgo hand-engineered map representations and infer appropriate control responses directly from sensed information. An important but unexplored aspect of such approaches is the effect of memory on their performance. This work is a first thorough study of memory structures for deep-neural-network-based robot navigation, and offers novel tools to train such networks from supervision and quantify their ability to generalize to unseen scenarios. We analyze the separation and generalization abilities of feedforward, long short-term memory, and differentiable neural computer networks. We introduce a new method to evaluate the generalization ability by estimating the VC-dimension of networks with a final linear readout layer. We validate that the VC estimates are good predictors of actual test performance. The reported method can be applied to deep learning problems beyond robotics

Design Principles for Signal Detection in Modern Job Application Systems: Identifying Fabricated Qualifications

Hiring a new employee is traditionally thought to be an uncertain investment. This uncertainty is lessened by the presence of signals that indicate job fitness. Ideally, job applicants objectively signal their qualifications, and those signals are correctly assessed by the hiring team. In reality, signal manipulation is pervasive in the hiring process, mitigating the reliability of signals used to make hiring decisions. To combat these inefficiencies, we propose and evaluate SIGHT, a theoretical class of systems affording more robust signal evaluation during the job application process. A prototypical implementation of the SIGHT framework was evaluated using a mock-interview paradigm. Results provide initial evidence that SIGHT systems can elicit and capture qualification signals beyond what can be traditionally obtained from a typical application and that SIGHT systems can assess signals more effectively than unaided decision-making. SIGHT principles may extend to domains such as audit and security interviews

On the 2:1 Orbital Resonance in the HD 82943 Planetary System

We present an analysis of the HD 82943 planetary system based on a radial velocity data set that combines new measurements obtained with the Keck telescope and the CORALIE measurements published in graphical form. We examine simultaneously the goodness of fit and the dynamical properties of the best-fit double-Keplerian model as a function of the poorly constrained eccentricity and argument of periapse of the outer planet's orbit. The fit with the minimum chi_{nu}^2 is dynamically unstable if the orbits are assumed to be coplanar. However, the minimum is relatively shallow, and there is a wide range of fits outside the minimum with reasonable chi_{nu}^2. For an assumed coplanar inclination i = 30 deg. (sin i = 0.5), only good fits with both of the lowest order, eccentricity-type mean-motion resonance variables at the 2:1 commensurability, theta_1 and theta_2, librating about 0 deg. are stable. For sin i = 1, there are also some good fits with only theta_1 (involving the inner planet's periapse longitude) librating that are stable for at least 10^8 years. The libration semiamplitudes are about 6 deg. for theta_1 and 10 deg. for theta_2 for the stable good fit with the smallest libration amplitudes of both theta_1 and theta_2. We do not find any good fits that are non-resonant and stable. Thus the two planets in the HD 82943 system are almost certainly in 2:1 mean-motion resonance, with at least theta_1 librating, and the observations may even be consistent with small-amplitude librations of both theta_1 and theta_2.Comment: 24 pages, including 10 figures; accepted for publication in Ap

Comparison of Muscle Activity During a Ring Muscle Up and a Bar Muscle Up

International Journal of Exercise Science 16(1): 1451-1460, 2023. The muscle up (MU) is a variation of a common gymnastics movement that combines a pull up and a dip. It can be performed on a bar (BMU) or a set of rings (RMU). The difference in upper extremity muscle recruitment (MR) between BMU and RMU has not been evaluated. Therefore, the purpose of this study was to compare the MR of select muscles during BMU and RMU. Ten active males (27.6 ± 7.9 years) performed 5 repetitions of BMU and RMU in randomized order. Muscle recruitment of the upper (UT) and lower trapezius (LT), serratus anterior (SA), pectoralis major (PM), latissimus dorsi (LD), triceps brachii (TB), biceps brachii (BB), and forearm flexors (FF) was assessed using electromyography. A 2 X 2 ANOVA (ring vs bar, pull phase vs push phase) with repeated measures was performed for each muscle. Least significant differences post hoc tests were performed when a significant interaction effect occurred. The RMU significantly elicited more muscle activation in the UT (p = 0.007), BB (p = 0.001), and FF (p = 0.001) during the pull phase. The RMU also significantly elicited more muscle activation in the TB (p = 0.025) and BB (p = 0.001) during the push phase. These results suggest that the instability of the RMU primarily increases the required recruitment of the upper limbs but does not significantly change the recruitment of the shoulder stabilizers. Appropriate upper limb development is needed to perform the RMU and the BMU may be a better technique to learn first due to its lower difficulty