Abstract: In my preliminary exam, I will discuss my paper on ultrahigh energy cosmic rays from gamma-ray sources. Ultra-high-energy cosmic rays (UHECRs) are the highest-energy particles ever observed. While the sources producing UHECRs are still unknown, the Pierre Auger Observatory has detected a large-scale dipole anisotropy in the arrival directions of cosmic rays above 8 EeV. My project explores whether resolved gamma-ray sources can reproduce the Auger dipole. I find that in all cases, the simulated dipole has an amplitude significantly larger than that measured by Auger, implying that the resolved gamma-ray sources are insufficient to account for the population of sources producing the highest-energy cosmic rays. Next, I will discuss my recent project on prospects of detecting GeV transients with IceCube DeepCore and Upgrade. A wide variety of transient sources have been predicted to emit GeV neutrinos. In light of the upcoming IceCube-Upgrade, which will extend the IceCube detector’s sensitivity down to a few GeV, I survey a variety of transient source models and compare the predictions and detector sensitivities. Finally, I will briefly discuss my intended thesis work, which involves using anticipated UHE neutrino data from the Payload for Ultrahigh Energy Observations balloon experiment to constrain the UHECR proton composition.