News & Events

Colloquium: Elias Puchner

Exploring nanoscopic mechanisms of intra-cellular processes with quantitative single-molecule imaging techniques

Abstract:

Cellular processes are regulated by complex interactions of biomolecules. The spatio-temporal organization of these biomolecules such as their localization to intracellular organelles is critical for their function. With the breakthrough of optical single-molecule and super-resolution microscopy techniques it became possible to study the spatio-temporal organization of biomolecules on a nanoscopic length scale far below the optical diffraction limit of conventional microscopes. However, challenges remained for quantifying the abundance of biomolecules and for investigating living cells. Here, I will present our novel developments of quantitative live-cell super-resolution microscopy techniques as well as improved fluorescent probes that overcome these limitations. I will exemplify the power of such precision measurements by presenting our new insights in the protein complex initiating autophagosome formation, which degrades and recycles cellular components. Furthermore, we gained a deeper understanding of lipid droplet regulation by following fatty acid incorporation and changes in enzyme densities based on metabolic needs of cells. In my outlook I will summarize how ongoing and future applications of these techniques enable us to study phase transitions of regulatory proteins and to establish collaborative projects of biomedical relevance.

Colloquium: Lindsay Glesener

Lindsay Glesener, University of Minnesota

Colloquium: Rafael Fernandes

A hallmark of the phase diagrams of quantum materials is the existence of multiple electronic ordered states. In many cases, they cannot be simply described as independent competing phases, but instead display a complex intertwinement. In this talk, I will present a framework to describe intertwined phases in terms of a primary and a vestigial phase. While the former is characterized by a multi-component order parameter, the fluctuation-driven vestigial state is characterized by a composite order parameter formed by higher-order, symmetry-breaking combinations of the primary order parameter. Exotic electronic states with scalar and vector chiral order, spin-nematic order, Potts-nematic order, time-reversal symmetry-breaking order, and charge 4e superconductivity emerge from this simple underlying principle. I will present a rich variety of possible phase diagrams involving the primary and vestigial orders, and discuss possible realizations of these exotic composite orders in different quantum materials.

Colloquium: Claudia Scarlata

Claudia Scarlata, University of Minnesota will deliver the first colloquium on the topic of "Learning about the early Universe from Nearby galaxies."

School of Physics and Astronomy Colloquium

Speaker: Rudolf M. Tromp, IBM T.J. Watson
Subject: Low Energy Electron Microscopy

In Low Energy Electron Microscopy (LEEM) and Photo Electron Emission Microscopy (PEEM) the sample forms the cathode in a strongly decelerating/accelerating immersion objective lens. This enables low energy electrons at the sample (0-100 eV) to be used for high resolution (2 nm) image formation, diffraction, and spectroscopy. This form of microscopy came to fruition in the early 1990’s, much later than other forms of electron microscopy, and has undergone a rapid development since.

In this talk I will discuss some of the principles and unique capabilities of cathode lens microscopy (as it is generally known), and illustrate its wide range of applications with recent examples from our research program, including growth and properties of 2D materials, occupied and unoccupied momentum-resolved electronic structure, reflection/transmission experiments to study electron mean free path, and the effects of low energy electron irradiation on thin resist films. A unique feature of many of these experiments is that the lab is inside the electron microscope, rather than the other way around.I