Distributed Collision-Free Motion Coordination on a Sphere: A Conic Control Barrier Function Approach

This letter studies a distributed collision avoidance control problem for a group of rigid bodies on a sphere. A rigid body network, consisting of multiple rigid bodies constrained to a spherical surface and an interconnection topology, is first formulated. In this formulation, it is shown that motion coordination on a sphere is equivalent to attitude coordination on the 3-dimensional Special Orthogonal group. Then, an angle-based control barrier function that can handle a geodesic distance constraint on a spherical surface is presented. The proposed control barrier function is then extended to a relative motion case and applied to a collision avoidance problem for a rigid body network operating on a sphere. Each rigid body chooses its control input by solving a distributed optimization problem to achieve a nominal distributed motion coordination strategy while satisfying constraints for collision avoidance. The proposed collision-free motion coordination law is validated via simulation

The supersingular locus of the Shimura variety for GU(1,n-1) over a ramified prime

We analyze the geometry of the supersingular locus of the reduction modulo p of a Shimura variety associated to a unitary similitude group GU(1,n-1) over Q, in the case that p is ramified. We define a stratification of this locus and show that its incidence complex is closely related to a certain Bruhat-Tits simplicial complex. Each stratum is isomorphic to a Deligne-Lusztig variety associated to some symplectic group over F_p and some Coxeter element. The closure of each stratum is a normal projective variety with at most isolated singularities. The results are analogous to those of Vollaard/Wedhorn in the case when p is inert.Comment: A few more corrections, to appear in Math. Zeitschrif

Measuring Youth Program Quality: A Guide to Assessment Tools

Thanks to growing interest in the subject of youth program quality, many tools are now available to help organizations and systems assess and improve quality. Given the size and diversity of the youth-serving sector, it is unrealistic to expect that any one tool or process will fit all programs or circumstances. This report compares the purpose, history, structure, methodology, content and technical properties of nine different program observation tools

The trial is owned by the team, not by an individual:A qualitative study exploring the role of teamwork in recruitment to randomised controlled trials in surgical oncology

BACKGROUND: Challenges exist in recruitment to trials involving interventions delivered by different clinical specialties. Collaboration is required between clinical specialty and research teams. The aim of this study was to explore how teamwork influences recruitment to a multicentre randomised controlled trial (RCT) involving interventions delivered by different clinical specialties. METHODS: Semi-structured interviews were conducted in three centres with a purposeful sample of members of the surgical, oncology and research teams recruiting to a feasibility RCT comparing definitive chemoradiotherapy with chemoradiotherapy and surgery for oesophageal squamous cell carcinoma. Interviews explored factors known to influence healthcare team effectiveness and were audio-recorded and thematically analysed. Sampling, data collection and analysis were undertaken iteratively and concurrently. RESULTS: Twenty-one interviews were conducted. Factors that influenced how team working impacted upon trial recruitment were centred on: (1) the multidisciplinary team (MDT) meeting, (2) leadership of the trial, and (3) the recruitment process. The weekly MDT meeting was reported as central to successful recruitment and formed the focus for creating a ‘study team’, bringing together clinical and research teams. Shared study leadership positively influenced healthcare professionals’ willingness to participate. Interviewees perceived their clinical colleagues to have strong treatment preferences which led to scepticism regarding whether the treatments were being described to patients in a balanced manner. CONCLUSIONS: This study has highlighted a number of aspects of team functioning that are important for recruitment to RCTs that span different clinical specialties. Understanding these issues will aid the production of guidance on team-relevant issues that should be considered in trial management and the development of interventions that will facilitate teamwork and improve recruitment to these challenging RCTs. TRIAL REGISTRATION: International Standard Randomised Controlled Trial Number (ISRCTN): ISRCTN89052791

Physical Telepresence: Shape Capture and Display for Embodied, Computer-mediated Remote Collaboration

We propose a new approach to Physical Telepresence, based on shared workspaces with the ability to capture and remotely render the shapes of people and objects. In this paper, we describe the concept of shape transmission, and propose interaction techniques to manipulate remote physical objects and physical renderings of shared digital content. We investigate how the representation of user's body parts can be altered to amplify their capabilities for teleoperation. We also describe the details of building and testing prototype Physical Telepresence workspaces based on shape displays. A preliminary evaluation shows how users are able to manipulate remote objects, and we report on our observations of several different manipulation techniques that highlight the expressive nature of our system.National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant No. 1122374