Studies Toward the Total Synthesis of Hinckdentine A using Under Utilised Reactions and Functional Groups

Many useful organic transformations remain underutilised because they have not been thoroughly investigated and understood. We have sought to expand the utility of neglected reactions and functional groups by investigating their mechanism and examining their scope. We planned to demonstrate utility of these transformations by incorporating them as key steps in the total synthesis of the natural product hinckdentine A. We developed a rational and consistent theory for mechanism of on-water catalysis. This new theory has allowed us to identify previously unrecognised examples of this phenomenon. The traditionally difficult conjugate addition of anilines was found to be facile under on-water conditions and this reaction was further improved through the incorporation of N-acylpyrroles. N-Acylpyrroles were also found to facilitate the Stetter reaction and expand the scope of subsequent transformations. The understanding gained from these studies allowed us to undertake studies toward the total synthesis of hinckdentine A, by an innovative route which included the aforementioned reactions as integral transformations

Multi-Task Recurrent Neural Network for Surgical Gesture Recognition and Progress Prediction

Surgical gesture recognition is important for surgical data science and computer-aided intervention. Even with robotic kinematic information, automatically segmenting surgical steps presents numerous challenges because surgical demonstrations are characterized by high variability in style, duration and order of actions. In order to extract discriminative features from the kinematic signals and boost recognition accuracy, we propose a multi-task recurrent neural network for simultaneous recognition of surgical gestures and estimation of a novel formulation of surgical task progress. To show the effectiveness of the presented approach, we evaluate its application on the JIGSAWS dataset, that is currently the only publicly available dataset for surgical gesture recognition featuring robot kinematic data. We demonstrate that recognition performance improves in multi-task frameworks with progress estimation without any additional manual labelling and training.Comment: Accepted to ICRA 202

Accessing the distribution of linearly polarized gluons in unpolarized hadrons

Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this distribution of linearly polarized gluons is through cos(2 phi) asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future Electron-Ion Collider (EIC) or Large Hadron electron Collider (LHeC) experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.Comment: 4 pages, 2 figures, to appear in the proceedings of the XIX International Workshop on Deep Inelastic Scattering and Related Subjects (DIS 2011), Newport News, VA, USA, 11-15 April 201

The effect of crack length and maximum stress on the fatigue crack growth rates of engineering alloys

The fatigue crack growth rate (FCGR) curve of metallic alloys is usually divided into three regions. Region II is often referred to as the Paris regime and is usually modelled with a power law relationship with a single exponent. Regions I and III are located at the beginning and end of the FCGR curve, respectively, and are frequently modelled with asymptotic relationships. In this paper we hypothesize that fatigue crack growth is governed by power law behaviour at all crack lengths and all stress intensity factor ranges (ΔK). To accommodate for the changes in the FCGR slope at regions I - III mathematical pivot points are introduced in the Paris equation. Power law behaviour with the presence of pivot points enables direct fitting of the crack length vs. cycles (a-N) curve to obtain the FCGR as a function of ΔK. This novel approach is applicable to small and long crack growth curves and results in accurate multilinear FCGR curves that are suitable for reconstruction of the measured a-N curves. The method is subsequently applied to i) different alloys to show local changes in the FCGR curve for changes in alloy composition and heat treatments, ii) naturally increasing ΔK testing of microstructurally small cracks to obtain accurate small crack FCGR data. The comparison with accurate long crack data shows that small cracks are faster, but the transition from region I to region II occurs at a specific fatigue crack growth rate which results in an apparent shift in ΔK at the transition. iii) Long cracks, which show that the FCGR increases with maximum stress for a given ΔK and stress ratio when the maximum stress approaches the yield stress. The maximum stress phenomenon becomes important in the case of fatigue testing, where the initial crack lengths are usually small and maximum stresses are high. It is concluded that for long cracks the phenomenon explains why the Paris equation is applicable rather at low maximum stress, while the Frost-Dugdale equation is more applicable at high maximum stress