From continua to R-trees

We show how to associate an R-tree to the set of cut points of a continuum. If X is a continuum without cut points we show how to associate an R-tree to the set of cut pairs of X.Comment: This is the version published by Algebraic & Geometric Topology on 1 November 200

Bootstrapping in convergence groups

We prove a true bootstrapping result for convergence groups acting on a Peano continuum. We give an example of a Kleinian group H which is the amalgamation of two closed hyperbolic surface groups along a simple closed curve. The limit set Lambda H is the closure of a `tree of circles' (adjacent circles meeting in pairs of points). We alter the action of H on its limit set such that H no longer acts as a convergence group, but the stabilizers of the circles remain unchanged, as does the action of a circle stabilizer on said circle. This is done by first separating the circles and then gluing them together backwards.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-32.abs.htm

Quasi-convex groups of isometries of negatively curved spaces☆☆This research was supported by SERC grant GR/K 25618.

AbstractLet H be a properly discontinuous group of isometries of a negatively curved (Gromov hyperbolic) metric space X. We give equivalent conditions on H to be quasi-convex. The main application of this is to give alternate definitions of quasi-convex, or rational subgroups of negatively curved (word hyperbolic) groups

Convergence groups from subgroups

We give sufficient conditions for a group of homeomorphisms of a Peano continuum X without cut-points to be a convergence group. The condition is that there is a collection of convergence subgroups whose limit sets `cut up' X in the correct fashion. This is closely related to the result in [E Swenson, Axial pairs and convergence groups on S^1, Topology 39 (2000) 229-237].Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol6/paper22.abs.htm

Validating Deployment Dynamics of the Canisterized Satellite Dispenser (CSD)

Planetary Systems Corporation (PSC) designed the CSD to be a more secure, predictable, and consistent CubeSat deployment system. Though the CSD has proven its safety and reliability on orbit and in other air-and ground-based tests, there was still not enough data needed to develop analytical profiles describing CSD deployment angular and linear velocities and accelerations. The goal of this research effort is to first tune a dynamics model using experimental data collected from three sources: (1) PSC’s microgravity deployment tests onboard a C-9 aircraft in 2014; (2) AFIT led lab bench experiments in 2016; and (3) AFRL-AFIT led tests at NASA Glenn Research Center’s (GRC’s) microgravity drop tower in 2017. The second part of this presented research is to evaluate the model prediction performance against various configurations followed by an evaluation of which experimental data sources yields the best tuned dynamics model

Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

The thermal properties of carbon nanotube- (CNT-) sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries

The Near Earth Object (NEO) Scout Spacecraft: A Low-cost Approach to In-situ Characterization of the NEO Population

This paper describes a microsatellite spacecraft with supporting mission profile and architecture, designed to enable preliminary in-situ characterization of a significant number of Near Earth Objects (NEOs) at reasonably low cost. The spacecraft will be referred to as the NEO-Scout. NEO-Scout spacecraft are to be placed in Geosynchronous Equatorial Orbit (GEO), cis-lunar space, or on earth escape trajectories as secondary payloads on launch vehicles headed for GEO or beyond, and will begin their mission after deployment from the launcher. A distinguishing key feature of the NEO-Scout system is to design the spacecraft and mission timeline so as to enable rendezvous with and landing on the target NEO during NEO close approach (<0.3 AU) to the Earth-Moon system using low-thrust/high-impulse propulsion systems. Mission durations are on the order 100 to 400 days. Mission feasibility and preliminary design analysis are presented, along with detailed trajectory calculations

GWAS of QRS Duration Identifies New Loci Specific to Hispanic/Latino Populations

BACKGROUND: The electrocardiographically quantified QRS duration measures ventricular depolarization and conduction. QRS prolongation has been associated with poor heart failure prognosis and cardiovascular mortality, including sudden death. While previous genome-wide association studies (GWAS) have identified 32 QRS SNPs across 26 loci among European, African, and Asian-descent populations, the genetics of QRS among Hispanics/Latinos has not been previously explored. METHODS: We performed a GWAS of QRS duration among Hispanic/Latino ancestry populations (n = 15,124) from four studies using 1000 Genomes imputed genotype data (adjusted for age, sex, global ancestry, clinical and study-specific covariates). Study-specific results were combined using fixed-effects, inverse variance-weighted meta-analysis. RESULTS: We identified six loci associated with QRS (P CONCLUSIONS: Our QRS duration GWAS, the first in Hispanic/Latino populations, identified two new loci, underscoring the utility of extending large scale genomic studies to currently under-examined populations