Integrated Calendar

The nucleon and its structure are the focus of intense study on all energy scales, in both current and upcoming experiments. It is one of the simplest systems in non-perturbative QCD and the accurate description of its properties are a touchstone for theoretical calculations.

Recent precision experiments have provided a wealth of information, but have also illuminated two glaring discrepancies: the proton radius puzzle and the form factor ratio divergence. The former, still unsolved, may have opened the door to the discovery of physics beyond the Standard Model, while a solution for the latter seems in reach.

In this talk, I will discuss the Mainz high precision form factor measurement and global form factor analysis, which are corner stones of the radius puzzle; the OLYMPUS experiment, which is poised to give the final confirmation of the solution to the ratio problem; the MUSE experiment, which will provide a missing piece for the proton radius puzzle; and the DarkLight experiment, which will search for physics beyond the Standard Model at the intensity frontier.

The recent discovery of giant DNA viruses and the understanding that such viruses are diverse and abundant blurred the difference between viruses and cells. Our laboratory studies two members of the constantly growing family of giant viruses. One of them is the Mimivirus with its famous Stargate. The cytoplasmic replication cycle of Mimivirus is carried out in specific intracellular compartments called viral factories, has been studied extensively in our laboratory. We use advanced microscopic methods such as high-resolution electron and light microscopy, along with biochemical approaches. Some of our open questions focus on the viral assembly process, infection cycle, and the generation and composition of the complex and dynamic structures of the viral factories that some claim may be the origin of the nucleus in eukaryotes.

Visual motion cues are used by many animals to guide navigation through their environments. Long-standing theoretical models have made predictions about the computations that compare light signals across space and time to detect motion. Separate candidate ON and OFF pathway that can implement various algorithmic steps have been proposed in the Drosophila visual system based on connectomic and physiological approaches. However, proposed circuit elements are often not functionally required, suggesting redundant circuits at least.

Using forward genetic approaches, we identified neurons of a third visual pathway in which the first order interneurons L3 provides a key input to direction-selective T5 neurons via the medulla neuron Tm9. While neurons of this pathway are behaviorally required for OFF motion detection, their physiological properties do not line up with predicted features of motion detection. Using in vivo 2 photon calcium imaging, we show that this pathway carries sustained responses to contrast changes and exhibits wide field properties that inform elementary motion detectors about wide regions of visual space. Given that these signals are essential for elementary motion-detection, we are currently investigating the full microcircuit architecture of this OFF pathway, as well as its molecular and physiological specializations. Our goal is to understand the circuits and computations that implement behavioral responses to visual motion.