<p>Astrophysical jets are collimated streams of magnetized plasma launched from compact objects, such as neutron stars or black holes. These jets, powered by the accretion of surrounding gas onto the compact object, can accelerate particles to extreme energies and produce powerful radiation.</p> <p><br></p> <p>In this report, I investigate energy dissipation and particle acceleration in two key regions in jets: (i) external shocks which form where jets interact with ambient gas and (ii) internally in the jet where particles are likely to be energized through the process of magnetic reconnection.</p> <p><br></p> <p>First, I explore inverse Compton scatterings of electrons accelerated at the external shock as a candidate for the high energy emissions from gamma-ray burst afterglows. I consider two sources of seed photons for scattering: synchrotron photons from the blast wave (synchrotron self-Compton) and photon fields external to the shock (external Compton) from the star-forming region in the host galaxy. I develop an analytical model to predict the high-energy spectra from these blasts and reproduce the observed spectra and lightcurves of GRB~190114C. The model implies that inverse Compton can dominate the sub-TeV/TeV emission in this event.</p> <p><br></p> <p>Second, I study the particle acceleration mechanism of magnetic reconnection internally in astrophysical jets. I employ particle-in-cell (PIC) simulations of 3D relativistic magnetic reconnection. My analysis reveals a novel acceleration mechanism that only operates in 3D that results in faster particle acceleration. Unlike in 2D simulations where particles are trapped in the reconnected plasma and stop being accelerated, a fraction of particles in 3D can escape from this region (along the third direction) and be further accelerated. The escaped particles are characterized by a harder energy spectrum with a higher cutoff compared to those found in previous studies. Based on the PIC simulation findings, I build an analytical model for the particle kinetics, which divides particles into two groups --- one undergoing fast energization in the reconnection upstream region and the other residing in the reconnected plasma without energy change. The model predicts a power-law spectra for both groups of particles. PIC simulations reveal a universal magnetization-independent spectra with $dN/d\gamma\propto \gamma^{-2}$ for the overall particle population. The results demonstrate that relativistic reconnection in jets may be a promising mechanism for generating Ultra-High-energy Cosmic Rays. </p>

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This investigation is concerned with change in school-directed aspirations of middle and upper-middle-class Jewish public high school students over a fifteen-year period of time.

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<p> Certain concepts in the final year of Ontario's high school chemistry course, SCHOA, are often difficult for students to understand. This project presents the results of a study of selected computer programs that could be used to enhance the teaching of selected difficult concepts in an attempt to make them easier to understand. </p> <p> The identification of the difficult concepts was an important component of this project. They were identified by means of a student survey, teacher interviews, literature review and personal experience. The difficult concepts were identified, in order of decreasing difficulty, as: 1. Buffers, 2. Solubility, 3. Redox, 4. Independent Investigation, 5. Acid/Base Equilibrium, 6. Reaction Mechanisms, 7. Free Energy. </p> <p> Two programs were selected for evaluation - The Electric Chemistry Building and Chem1 Problem Proctor and a checklist was established to examine these computer programs. The two programs address the identified difficult concepts and use a variety of teaching techniques (tutorial, drill and simulation). </p> <p> Chem1 Problem Proctor consists of tutorial and drill lessons, suitable for use by students of SCHOA. The key objectives of this program are to encourage problem-solving and to promote an understanding of the principles underlying the chemistry concepts. The program accomplishes this to various degrees of success by requiring the student to make decisions, to make qualitative estimates before some of the calculations and by asking questions related to the concept but not necessarily part of the solution to the problem. </p> <p> The Electric Chemistry Building is a simulation of a building made up of three laboratories, two of which were evaluated in this project. The key objective of this program is to develop problem-solving skills by providing students with the opportunity to design and perform experiments, make observations and draw conclusions. </p> <p> Based on the evaluations of Chem1 Problem Proctor and The Electric Chemistry Building in this project, both programs appear to be worthwhile for use in SCHOA. The Electric Chemistry Building is a very good simulation program which would enhance the teaching of the difficult concepts of SCHOA. Chem1 Problem Proctor is a good tutorial/drill program which should be improved with respect to its presentation of chemical notation and mathematical formulae, and the feedback to its drill questions. Once these aspects of the program are corrected, it will also be effective in enhancing the teaching of difficult concepts of SCHOA. </p> / Thesis / Master of Science (MSc)

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