Numerical Studies of Models for Strongly Correlated Electrons Using Monte Carlo Mean Field and Density Matrix Renormalization Group Methods

The interplay of magnetism and superconductivity in the iron-based superconductors is investigated numerically using Monte Carlo mean field and density matrix renormalization group methods. The finite temperature magnetic and transport properties of the 2D oxypnitides are calculated using Monte Carlo mean field methods, capturing many experimentally relevant phases and predicting a new phase dubbed orbital selective directional conductor . Finally, pairing tendencies are explored using exact diagonalization and density matrix renormalization group for low dimensional iron-based superconductor, BaFe2S3, predicting hole pairs arranged along the diagonals or rungs of the ladders in real space. This dissertation further adds to the evidence that superconductivity in the iron based compounds has its origin in the magnetic fluctuations that are driven by correlations

Question Answering System for Yioop

Yioop is an open source search engine developed and managed by Dr. Christopher Pollett. Currently, Yioop returns the search results of the query in the form of list of URLs, just like other search engines (Google, Bing, DuckDuckGo, etc.) This paper created a new module for Yioop. This new module, known as the Question-Answering (QA) System, takes the search queries in the form of natural language questions and returns results in the form of a short answer that is appropriate to the question asked. This feature is achieved by implementing various functionalities of Natural Language Processing (NLP). By using NLP, the new Question-Answering (QA) System attempts to extract the necessary information from the query provided by the user and provides an appropriate answer from the available data

Towards Closed-loop, Robot Assisted Percutaneous Interventions under MRI Guidance

Image guided therapy procedures under MRI guidance has been a focused research area over past decade. Also, over the last decade, various MRI guided robotic devices have been developed and used clinically for percutaneous interventions, such as prostate biopsy, brachytherapy, and tissue ablation. Though MRI provides better soft tissue contrast compared to Computed Tomography and Ultrasound, it poses various challenges like constrained space, less ergonomic patient access and limited material choices due to its high magnetic field. Even after, advancements in MRI compatible actuation methods and robotic devices using them, most MRI guided interventions are still open-loop in nature and relies on preoperative or intraoperative images. In this thesis, an intraoperative MRI guided robotic system for prostate biopsy comprising of an MRI compatible 4-DOF robotic manipulator, robot controller and control application with Clinical User Interface (CUI) and surgical planning applications (3DSlicer and RadVision) is presented. This system utilizes intraoperative images acquired after each full or partial needle insertion for needle tip localization. Presented system was approved by Institutional Review Board at Brigham and Women\u27s Hospital(BWH) and has been used in 30 patient trials. Successful translation of such a system utilizing intraoperative MR images motivated towards the development of a system architecture for close-loop, real-time MRI guided percutaneous interventions. Robot assisted, close-loop intervention could help in accurate positioning and localization of the therapy delivery instrument, improve physician and patient comfort and allow real-time therapy monitoring. Also, utilizing real-time MR images could allow correction of surgical instrument trajectory and controlled therapy delivery. Two of the applications validating the presented architecture; closed-loop needle steering and MRI guided brain tumor ablation are demonstrated under real-time MRI guidance