Interphase Chromatin Undergoes a Local Sol-Gel Transition Upon Cell Differentiation Cell differentiation, the process by which stem cells become specialized cells, is associated with chromatin reorganization inside the cell nucleus. Here, we measure the chromatin distribution and dynamics in embryonic stem cells in vivo before and after differentiation. We find that undifferentiated chromatin is less compact, more […]

Emergence of size in living cells The emergence of macroscopic phenomena from interactions of its microscopic components is a problem permeating much of modern physics. Successes include our understanding of phase transitions, while turbulence still remains mostly mysterious. In cell biology, for more than a hundred years, it has been observed that micron-sized structures within […]

Topology and “impossible” electronic devices Since the discovery of quantized Hall effects in the 1980s, topology has provided a useful new paradigm for understanding condensed matter systems, expanding our vocabulary for describing the distinctions between states of matter. I will focus on how topological properties can be harnessed to build otherwise impossible electronic devices--devices whose […]

Title: Photonic Pseudomagnetism and Landau Levels Abstract: When electrons moving in a two-dimensional plane are subject to a perpendicular magnetic field they move in circles called cyclotron orbits as a result of the Lorentz force.  Treated quantum mechanically, these orbits become quantized like the orbitals of an atom, forming highly degenerate states called Landau levels.  In this talk, […]

TITLE:  Absolutely Mindboggling! ABSTRACT: The fractional quantum Hall states are among the most beautiful, the most consequential, and the best understood strongly correlated states discovered in nature. I will begin with a brief introduction to their rich phenomenology and explanation as a manifestation of the formation of a new kind of emergent particle called the […]

TITLE:  The Many Frontiers of High Magnetic Field Research, ABSTRACT:  The National MagLab in the United States exists to provide magnetic fields that are more than a million times stronger than the Earth’s magnetic field to thousands of visiting researchers every year.  Why would anyone want to do such a thing?   It turns out that magnetic […]

TITLE: Mechanics of Domain Walls ABSTRACT: Domain walls, narrow regions separating domains of uniform magnetization, have a long history in the field of magnetism. As topological solitons, they present interest from the perspective of basic science and technological applications such as magnetic memory. Domain walls can be driven at speeds up to several kilometers per […]

Thank you to everyone who participated this past spring in the climate survey conducted by the department’s Committee on Diversity and Inclusion (CDI) in conjunction with JHU’s Office of Diversity and Inclusion. The CDI is very grateful for the valuable assistance that Christina Turner, Senior Diversity Strategist in the Office of Diversity and Inclusion, provided […]

TITLE: Energetic optimization during cell division ABSTRACT: Living systems are driven far from thermodynamic equilibrium through the continuous consumption of ambient energy. This energy is invested in the formation of complex, internal macromolecular structures and diverse spatial and temporal patterns in chemical and mechanical activities, which in turn orchestrate cell phenotypes and behaviors. This self-organization […]