Equivariant infinite loop space theory, I. The space level story

We rework and generalize equivariant infinite loop space theory, which shows how to construct G-spectra from G-spaces with suitable structure. There is a naive version which gives naive G-spectra for any topological group G, but our focus is on the construction of genuine G-spectra when G is finite. We give new information about the Segal and operadic equivariant infinite loop space machines, supplying many details that are missing from the literature, and we prove by direct comparison that the two machines give equivalent output when fed equivalent input. The proof of the corresponding nonequivariant uniqueness theorem, due to May and Thomason, works for naive G-spectra for general G but fails hopelessly for genuine G-spectra when G is finite. Even in the nonequivariant case, our comparison theorem is considerably more precise, giving a direct point-set level comparison. We have taken the opportunity to update this general area, equivariant and nonequivariant, giving many new proofs, filling in some gaps, and giving some corrections to results in the literature.Comment: 94 page

Sliding to predict: vision-based beating heart motion estimation by modeling temporal interactions

Purpose: Technical advancements have been part of modern medical solutions as they promote better surgical alternatives that serve to the benefit of patients. Particularly with cardiovascular surgeries, robotic surgical systems enable surgeons to perform delicate procedures on a beating heart, avoiding the complications of cardiac arrest. This advantage comes with the price of having to deal with a dynamic target which presents technical challenges for the surgical system. In this work, we propose a solution for cardiac motion estimation. Methods: Our estimation approach uses a variational framework that guarantees preservation of the complex anatomy of the heart. An advantage of our approach is that it takes into account different disturbances, such as specular reflections and occlusion events. This is achieved by performing a preprocessing step that eliminates the specular highlights and a predicting step, based on a conditional restricted Boltzmann machine, that recovers missing information caused by partial occlusions. Results: We carried out exhaustive experimentations on two datasets, one from a phantom and the other from an in vivo procedure. The results show that our visual approach reaches an average minima in the order of magnitude of 10-7 while preserving the heart’s anatomical structure and providing stable values for the Jacobian determinant ranging from 0.917 to 1.015. We also show that our specular elimination approach reaches an accuracy of 99% compared to a ground truth. In terms of prediction, our approach compared favorably against two well-known predictors, NARX and EKF, giving the lowest average RMSE of 0.071. Conclusion: Our approach avoids the risks of using mechanical stabilizers and can also be effective for acquiring the motion of organs other than the heart, such as the lung or other deformable objects.Peer ReviewedPostprint (published version

Using Lenses to Understand Policy Failures: The Case of the 2012 Census in Chile

Policy failures are controversial, costly, and above all, messy. More often than we wish, what begins as a well-intentioned policy becomes a failure. In all countries and policy areas, some initiatives end up failing miserably, wasting resources, creating endless political struggles, and even affecting countries\u27 governance. However, the perceptions and understanding of failure are dissimilar. Different actors, including researchers, have diverse and indeed conflicting viewpoints of what constitutes failure, its characteristics and avenues of resolution. The growing policy failure literature offers concepts and models to approach this elusive phenomenon, emphasizing the critical role of social perceptions, characteristics of failure episodes, multiple dimensions, and the wide and complex spectrum between failure and success. This study recognizes the multifaceted nature of policy failure as a starting point. Based on the existing literature, and assuming there are always different perspectives or lenses involved, this dissertation proposes the Lenses Framework as a novel approach to explore the understanding of policy failure, by analyzing the case of the 2012 census in Chile. In 2012, the National Statistics Institute (INE) conducted the census under a new methodology, and what could have been a significant advance on data quality and efficiency became a huge controversy. The census had significant implementation problems, low coverage, accusations of data mishandling, several investigations to assess the errors, and endless political and technical disputes, all of which ended with discarding the census and conducting a new census in 2017. By using the policy, organizational, and societal lenses, the analysis reveals the different angles of understanding the causes, characteristics and interpretations of the census failure. The policy lens emphasizes the abrupt change of census strategy, the troubled implementation, and differing evaluation criteria. Instead, the organizational lens exposes difficulties in INE\u27s structure, leadership weakness, internal disagreements, and other escalating struggles. In turn, the societal lens unveils the institutional context, political turmoil, the rising power of social media, and the student movement\u27s strength with the profound clash of ideas at stake. Like this, the Lenses Framework tackles the policy failure\u27s messy character, providing new insights for a meaningful, but also helpful, understanding of this complex phenomenon