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"Ladd, Andrew"
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Robotics-Based Location Sensing Using Wireless Ethernet
A key subproblem in the construction of location-aware systems is the determination of the position of a mobile device. This article describes the design, implementation and analysis of a system for determining position inside a building from measured RF signal strengths of packets on an IEEE 802.11b wireless Ethernet network. Previous approaches to location-awareness with RF signals have been severely hampered by non-Gaussian signals, noise, and complex correlations due to multi-path effects, interference and absorption. The design of our system begins with the observation that determining position from complex, noisy and non-Gaussian signals is a well-studied problem in the field of robotics. Using only off-the-shelf hardware, we achieve robust position estimation to within a meter in our experimental context and after adequate training of our system. We can also coarsely determine our orientation and can track our position as we move. Our results show that we can localize a stationary device to within 1.5 meters over 80% of the time and track a moving device to within 1 meter over 50% of the time. Both localization and tracking run in real-time. By applying recent advances in probabilistic inference of position and sensor fusion from noisy signals, we show that the RF emissions from base stations as measured by off-the-shelf wireless Ethernet cards are sufficiently rich in information to permit a mobile device to reliably track its location. [PUBLICATION ABSTRACT]
Journal Article
Anti-CD3 microporous annealed particle hydrogel protects stem cell derived beta cells from autoreactive T cells
Type 1 diabetes (T1D) results from autoimmune destruction of pancreatic beta cells, leaving patients dependent on exogenous insulin and at risk of severe hypoglycemic episodes. Stem cell-derived beta-like cells (sBCs) offer a promising approach for beta cell replacement therapy, but clinical translation is limited by immune-mediated rejection, recurrent autoimmunity, and inhospitable transplantation sites. Biomaterials have been investigated to provide localized immune-isolation and immunomodulation, but foreign body responses and rapid depletion of therapeutic agents remain as obstacles to clinical translation. Here, we present a microporous annealed particle (MAP) hydrogel functionalized with an anti-CD3 monoclonal antibody (αCD3) to provide a localized immunomodulatory microenvironment for beta cell replacement therapy. MAP hydrogels consisting of guest-host interlinked polyethylene glycol-maleimide (PEG-MAL) microgels supported rapid vascularization, minimal foreign body response, and engraftment of syngeneic islets in mice. αCD3 MAP hydrogel halted T cell migration
and protected transplanted sBCs from immune-mediated destruction by HLA-matched diabetogenic T cells
. Subcutaneous αCD3 functionalized MAP hydrogel also protected the endogenous islets in the pancreas, demonstrating potential for systemic immune modulation. These findings establish αCD3 MAP hydrogels as a promising strategy for localized immune modulation in cell replacement therapy.
Journal Article
Inhibition of cell-mediated immunity in type 1 diabetes by beta cell-targeted PD-1 agonists in pancreas tissue slices
Tissue-targeted immunotherapies for type 1 diabetes (T1D) hold potential to protect pancreatic beta cells while minimizing systemic immunosuppression. We used a bispecific agonist called Immune Modulating Monoclonal-TCR Against Autoimmune Disease (ImmTAAI), consisting of a T cell receptor (TCR) targeting domain fused with a PD-1 agonist to specifically bind beta cells and suppress autoreactive T cells. We used live pancreas slices to demonstrate targeting of ImmTAAI molecules to pre-proinsulin peptide-HLA-A2 complexes on human beta cells. ImmTAAI protected beta cells from T cell killing by increasing T cell motility and inhibiting cytokine secretion. ImmTAAI treatment also increased the motility of islet-infiltrating T cells in slices from a donor with recent-onset T1D and preserved insulin secretion in slices co-cultured with T cell avatars transduced with diabetogenic TCRs. These data demonstrate that ImmTAAI molecules have the potential to limit T cell activity locally, making this an attractive platform to elicit targeted immunoregulation in T1D.
Journal Article
Homelessness and the World Cup
Homelessness and the World Cup is a thesis about how the planning of the 2014 World Cup soccer tournament affected the lives of the homeless in Rio de Janeiro, Brazil. It is an ethnographic study that looks into the presence, use, and destruction of informal settlements near the Maracanã stadium. Maracanã was the sight of some of the matches in the 2014 World Cup soccer tournament. The study relied on observational data regarding before and after uses of informal settlements as well as the phenomenological approach to ethnography. That approach to ethnography aims to understand the subject’s experience of their day-to-day lives. The thesis argues that the policies of mega event planning often directly contradict the needs of homeless individuals exercising their rights to inhabit public places.
Dissertation
Motion planning for physical simulation
Motion planning research has been successful in developing planning algorithms which are effective for solving problems with complicated geometric and kinematic constraints. Various applications in robotics and in other fields demand additional physical realism. Some progress has been made for non-holonomic systems. However systems with complex dynamics, significant drift, underactuation and discrete system changes remain challenging for existing planning techniques particularly as the dimensionality of the state space increases. This thesis develops a novel motion planning technique for the solution of problems with these challenging characteristics. The novel approach is called Path Directed Subdivision Tree Exploration algorithm (PDST-EXPLORE) and is based on sampling-based motion planning and subdivision methods. PDST-EXPLORE demonstrates how to link a planner with a physical simulator using the latter as a black box, to generate realistic solution paths for complex systems. The thesis contains experimental results with examples with simplified physics including a second order differential drive robot and a game which exemplifies characteristics of dynamical systems which are difficult for planning. The thesis also contains experimental results for systems with simulated physics, namely a weight lifting robot and a car. Both systems have a degree of physical realism which could not be incorporated into planning before. The new planner is finally shown to be probabilistically complete.
Dissertation
Theatres must get used to social distancing - it's what audiences want
After crunching the numbers of recent audience surveys by Indigo, SOLT and YouGov, former ticketing manager Andrew Ladd says the results couldn't be clearer - if theatres want audiences to return, they will need social distancing in place Audiences are looking forward to returning to theatres once they reopen. Even supposing the 13% figure is a true reflection of all potential ticket-buyers, there's something else to bear in mind: the number is going down. In the After the Interval survey, the support for social distancing was even higher: a whopping 80% of regular audience members said limited numbers would make them more likely to come back.
Newspaper Article
Online ticketing is Kafkaesque - it's time for smarter systems
Too many venues rely on clunky, third-party box office solutions, says former ticketing manager Andrew Ladd. Sites such as TodayTix have shown that providing a smooth user experience can reap rewards.
Newspaper Article
Analysis of probabilistic roadmap methods for motion planning and applications to polygon manipulation
Motion planning deals with the problem of finding trajectory between two configurations in some space under some constraints. The science of motion planning deals with solving this problem efficiently in different spaces and under varying sets of constraints. This thesis provides an extended analysis of the PRM algorithm by using tools from measure theory to obtain greater generality. We then apply the results to planning in finite CW complexes and detail an application to planning with a polygonal robot in a polygonal workspace when contact is allowed. The final part of thesis deals with an application of motion planning to untangling mathematical knots. This problem is particularly interesting as it addresses motion planning with large number of degrees of freedom in a reconfigurable space. Planning applications with flexible robots, reconfigurable robots, molecular biology and other instances that share similar characteristics are some of the most challenging in planning today.
Dissertation