Janus: Launch of a NASA SmallSat Mission to Near-Earth Binary Asteroids

Janus is a two-spacecraft SmallSat mission to fly by two different pairs of binary near Earth asteroids, (175706) 1996 FG3 and (35107) 1991 VH. The two identical Janus spacecraft are scheduled to launch during a launch period opening 1 August 2022 as secondary payloads with the NASA Psyche mission, on a SpaceX Falcon Heavy launch vehicle. Janus is led by principal investigator Dr. Dan Scheeres at the University of Colorado Boulder and managed, built, and operated by Lockheed Martin. These planetary SmallSats share many deep space challenges similar to larger missions: Janus must execute deep space maneuvers to achieve hundreds of meters per second ΔV to reach its destinations, close a telecommunication link at ranges up to 2.4 AU, autonomously manage a several-month-long telecommunications blackout during solar conjunction, operate at a maximum Sun range of 1.62 AU, and survive for approximately four years in interplanetary space before encountering their target asteroids. During the encounters, the spacecraft will return high resolution visible and infra-red images of the asteroids. In getting Janus to the pad, the implementation team successfully managed an aggressive mission schedule despite COVID-19 related supply chain impacts and work environments, all while remaining on target for the SIMPLEx-2 cost cap. Janus is a pathfinder for achievable and affordable SmallSat science missions and demonstrates the valuable partnership between an experienced deep space mission engineering team, the SmallSat commercial component industry, and a forward- looking NASA model for Class-D science missions

Dynamic Switch of Negative Feedback Regulation in Drosophila Akt–TOR Signaling

Akt represents a nodal point between the Insulin receptor and TOR signaling, and its activation by phosphorylation controls cell proliferation, cell size, and metabolism. The activity of Akt must be carefully balanced, as increased Akt signaling is frequently associated with cancer and as insufficient Akt signaling is linked to metabolic disease and diabetes mellitus. Using a genome-wide RNAi screen in Drosophila cells in culture, and in vivo analyses in the third instar wing imaginal disc, we studied the regulatory circuitries that define dAkt activation. We provide evidence that negative feedback regulation of dAkt occurs during normal Drosophila development in vivo. Whereas in cell culture dAkt is regulated by S6 Kinase (S6K)–dependent negative feedback, this feedback inhibition only plays a minor role in vivo. In contrast, dAkt activation under wild-type conditions is defined by feedback inhibition that depends on TOR Complex 1 (TORC1), but is S6K–independent. This feedback inhibition is switched from TORC1 to S6K only in the context of enhanced TORC1 activity, as triggered by mutations in tsc2. These results illustrate how the Akt–TOR pathway dynamically adapts the routing of negative feedback in response to the activity load of its signaling circuit in vivo

Conceptual Modeling and Analysis of Drag-Augmented Supersonic Retropropulsion for Application in Mars Entry, Descent, and Landing Vehicles

The development of new decelerator technologies will be required as the desired payload mass for future Mars landing missions increases beyond the current state-of-the-art architecture capability. This thesis examines the potential for supersonic retropropulsion applied on entry, descent, and landing vehicles to increase the landed payload mass. Supersonic retropropulsion systems use rocket thrust directed into the free stream flow to decelerate the vehicle during descent. Under certain conditions the aerodynamic drag on the entry vehicle can be preserved or augmented using supersonic retropropulsion. The development of a model characterizing the drag augmentation capabilities of supersonic retropropulsion flow interactions is described. The model combines results from computational fluid dynamic simulations available in literature and analytic techniques to estimate the drag coefficient of a 70° sphere-cone aeroshell. The model is designed to capture the dominant flow physics of pressure conservation through various shock cascade structures more quickly than computational fluid dynamic simulations. This allows conceptual systems analysis to be performed across a wide range of input values beyond the current parameter space evaluated in experiments or computational simulations. The drag coefficient model developed is validated against available results from wind tunnel tests and computational simulations to within 10%. In addition, the sensitivity of the computed drag coefficient to inputs estimated from computational simulation results in literature is analyzed. A study of drag-augmented supersonic retropropulsion operation concepts for use in Mars entry, descent, and landing is presented. The feasible entry and payload masses for ballistic entries are determined for a range of supersonic retropropulsion operation intervals to illustrate the flight regimes where supersonic retropropulsion is most effective. The use of supersonic retropropulsion is shown to reduce the required propellant mass by 65% when the operation interval is focused in the region of maximum dynamic pressure. In addition, the feasibility of two concepts combining supersonic decelerator concepts is investigated: a combination of drag-augmented and high-thrust supersonic retropropulsion, and a combination of drag-augmented supersonic retropropulsion and inflatable aerodynamic decelerators. The potential for these hybrid solutions to increase the payload mass capability by up to 708% using each technology in the appropriate flight regime is demonstrated

A Formal Model of Crash Recovery in a Distributed Systems

Abstract-A formal model for atomic commit protocols for a distributed database system is introduced. The model is used to prove existence results about resilient protocols for site failures that do not partition the network and then for partitioned networks. For site failures, a pessimistic recovery technique, called independent recovery, is introduced and the class of failures for which resilient protocols exist is identified. For partitioned networks, two cases are studied: the pessimistic case in which messages are lost, and the optimistic case in which no messages are lost. In all cases, fundamental limitations on the resiliency of protocols are derived. Index Tenns-Commit protocols, crash recovery, distributed database systems, distributed systems, fault tolerance, transaction management. I

Stem cell tourism and spinal cord injury in South Africa

Imagine a world in which disease management is highly personalised. Drug treatments would be specific to the individual concerned, taking into account genetic background and environmental factors. Therapies would be effective, tailored to the individual’s needs, with few or no side-effects. Given that at present many of our treatments are based on a one-size-fits-all approach, which clearly has its limitations, personalised medicine is an important ideal to pursue. The highly publicised notion of precision medicine on the other hand aims to identify differences at a population level, guiding the application recent technological advances.http://www.samj.org.zapm2020ImmunologyPhysiotherap

Status of the population of Karamoja Apalis Apalis karamojae in north-eastern Uganda

The distribution of the Karamoja Apalis Apalis karamojae, an East African endemic, has been sparsely documented in Uganda. In October 2011, a survey of the species was carried out near Iriiri in north-eastern Uganda. The main aim was to find out if there is a viable population of the species and to highlight the threats to its population. Sixteen 1-km transects in four sites were surveyed. The survey recorded nine individuals including a pair at an occupied nest, which is not conclusive for determining the viability of the population. The main threats to the species were cutting of the dominant shrub Vachellia drepanolobium (Acacia drepanolobium) in the area, farming and grazing. When we attempted luring the birds using the recorded song of the Karamoja Apalis from Tanzania, these individuals did not respond. We therefore recommend (1) to undertake a more detailed GIS survey to discover the extent of the suitable habitat, (2) to repeat the survey with improved effort to better estimate the viability of this population, (3) to conduct a study to ascertain the successful breeding of the species in the area, (4) to conduct a DNA analysis to compare the Iriiri population with the Tanzanian population, and (5) to record the song of the Ugandan birds for song analysis and to determine the response of Tanzanian birds.Keywords: Karamoja Apalis, nest record, range extension, Uganda, voice call

An investigation of energy flow through coupled plate structures

This PhD thesis presents research aims to improving the dynamic modelling of coupled plate structures across a wide frequency range by using analytical, statistical and experimental methods. The analytical waveguide method is used to model the flexural displacement of coupled plate structures which are simply supported along two parallel edges. A method of quickly predicting the average energy level in a plate from details of the waveguide model is described, and used for comparison with SEA models. The Poynting and Impedance methods of predicting the energy flow in coupled plate structures are investigated. Transmission coefficients for coupled plate structures are evaluated using the analytical waveguide method for both semi-infinite and finite coupled plate structures. Finite transmission coefficients have traditionally been more difficult to evaluate due to the presence of a reverberant field, but in this work a novel method of separating the reverberant field using a scattering matrix method is presented. The transmission coefficients for semi-infinite and finite structures are then compared for L-shaped plates. A modal transmission coefficient is also defined and for the cases considered, and is used to develop an alternative method of deriving the transmission coefficient in a finite structure. Frequency averaged transmission coefficients are also considered, and the transmission coefficients derived for finite and semi-infinite structures are found to be very similar after frequency averaging. Statistical Energy Analysis models of coupled plates are evaluated using transmission coefficients derived from waveguide models. The results of the SEA models are compared to those predicted by the analytical waveguide method. A modal transmission coefficient based SEA model is also investigated. In an attempt to validate the numerical work presented in this thesis, experiments have been conducted. Using a wave extraction technique, both the wave amplitudes and plate properties have been evaluated from experimental data, and are subsequently used to experimentally measure the transmission coefficient for two plates coupled at different angles

Assessment of Carbon Tetrachloride Groundwater Transport in Support of the Hanford Carbon Tetrachloride Innovative Technology Demonstration Program

Groundwater modeling was performed in support of the Hanford Carbon Tetrachloride Innovative Treatment Remediation Demonstration (ITRD) Program. The ITRD program is facilitated by Sandia National Laboratory for the Department of Energy Office of Science and Technology. This report was prepared to document the results of the modeling effort and facilitate discussion of characterization and remediation options for the carbon tetrachloride plume among the ITRD participants. As a first step toward implementation of innovative technologies for remediation of the carbon tetrachloride (CT) plume underlying the 200-West Area, this modeling was performed to provide an indication of the potential impact of the CT source on the compliance boundary approximately 5000 m distant. The primary results of the modeling bracket the amount of CT source that will most likely result in compliance/non-compliance at the boundary and the relative influence of the various modeling parameters