Welcome

• Christian Joas (Niels Bohr Archive)

Welcome

• Lene B. Oddershede

Some Treasures at the Niels Bohr Archive

• Vilhelm A. Bohr

Keynote Lecture: Physics and History

• John L Heilbron (UC Berkeley)

Physicists and, before their existence, natural philosophers and applied mathematicians, made fundamental contributions to the development of the historical sciences as well as to the history of science. That was not mere coincidence: both the historical and experimental sciences had their origins in the Scientific Revolution. I shall give a few Indicators of the parallel rise of the historical and experimental sciences before giving examples of serious contributions to historiography by early modern natural philosophers; of applications of history to epistemology and religious controversy by physicists around 1900; and of support by physicists and their organizations of the study of the history of physics by historians.

Welcome dinner for all History-of-Science speakers and organizers

All participants must be seated by 13.45 for the arrival of HRH Crown Prince Frederik

HRH Crown Prince Frederik arrives

Welcome by Mogens Høgh Jensen (NBI, UCPH, Organizing committee)

Opening by HRH Crown Prince Frederik

Mads Krogsgaard Thomsen (CEO Novo Nordisk Foundation)

Stinus Lindgreen (Member of the Danish Parliament)

Emil Bjerrum-Bohr (NBIA, Organizing committee) introduces Henrik Wegener, Vilhelm Bohr, Amin Doostmohammadi

Henrik C. Wegener (Rector UCPH)

Vilhelm Bohr (UCPH, Bohr family, Organizing committee) – Niels Bohr: Biomedicine and History

Amin Doostmohammadi (NBI, UCPH, Organizing committee) introduces Nobel Laureate Morten Meldal Member of the organizing committee. Will introduce Nobel Laureate Prof. Morten Meldal

Lecture by Prof. Morten Meldal (UCPH, Nobel Laureate in Chemistry 2022)

Final remarks by Christian Joas (Niels Bohr Archive, Organizing committee)

Festive reception

Welcome

• Joachim Mathiesen (NBI)

The Other Bohr and Biology’s Greatest Model

• Rob B. Phillips (Caltech)

Only ten years after the discovery of the iconic structure of DNA, new questions were on biologist’s minds, namely, how are the macromolecules of the cell regulated so that they do what they are supposed to when and where they are needed. The initial resolution of the challenging question of biological regulation came in the form of the notion of “allostery”, an idea that its discoverer Jacques Monod himself referred to as "the second secret of life". We recently celebrated the 50th anniversary of the classic paper of Monod, Changeux and Jacob that introduced this far reaching idea. That important paper was followed shortly thereafter by a second one that revealed their musings on how simple statistical mechanical models can be used to capture how such allosteric transitions work mechanistically. In this talk, I will review the key features of the famed Monod-Wyman-Changeux (MWC) model and then describeits broad reach across many different domains of biology including the famed Bohr effect in hemoglobin. In this talk I will make special reference to the physics underlying how genes are turned on and off. One of the intriguing outcomes of this class of models is a beautiful and predictive scheme for collapsing data from entire libraries of mutants. Once we have considered some of the traditional uses of the MWC model, I will turn to more speculative recent ideas which use the MWC approach to consider the nature of kinetic proofreading.

Topological puzzles in cell biology

• Manu Prakash (Stanford)

Recreational mathematics is a century-old field which involves mathematical puzzles and games, often appealing to children and untrained adults, inspiring deep study of the subject. Can a similar analogy be drawn in biology? One place to explore these ideas is the role of geometry and topology (geometric properties invariant to continuous change in shape or size) in biological form and function. Without making any claims of usefulness, in this talk I will explore a wide range of topological and geometrical puzzles in cellular physiology: Can single cells be toroidal in nature? Can cellular geometry (cytoskeleton) explain complex behavior in single cells? Can "Klein bottles" help us understand a fungal pathogen? Do cells get stuck forever in topological traps? Finally, we will reflect on the role of curiosity as an engine for discovery in life sciences.

Building molecules and the ingredients for life in space

• Ewine van Dishoeck (Leiden)

Thousands of planets have been discovered around stars other than our Sun. But how and where are these exo-planets born, and why are they so different from those in our own solar system? Which ingredients are available to build them? Thanks to powerful new telescopes, including the James Webb Space Telescope, astronomers can now zoom in to planetary construction sites and study their composition. Water and a surprisingly rich variety of organic materials are found near forming stars, including simple sugars, ethers, alcohols and hydrocarbons. How are these molecules made under the extreme conditions in space and can they be delivered to new planets to form the basis for life elsewhere in the universe?

Modelling collective cell dynamics using active matter physics

• Julia Yeomans (Oxford)

The motion of epithelial cells is key to many life processes from morphogenesis to wound healing. Despite its importance, and considerable recent attention, much remains to be understood about collective cell motility, both in terms of elucidating the underlying biochemistry, and at a more coarse-grained level of identifying the primary forces involved. In this talk I will describe recent work modelling confluent cell layers and tissues using phase field and hydrodynamic models and discuss the extent to which approaches based on active matter physics are proving useful in interpreting tissue dynamics and patterning.

Active Antagonism: Reproducing Microorganisms and Fluid Flows

• David Nelson (Harvard)

The growth and evolution of microbial populations is often subject to advection by fluid flows in spatially extended environments, with immediate consequences for spatial population genetics in marine ecology, planktonic diversity and fixation times. We review recent progress made in understanding this rich problem in the simplified setting of two competing genetic microbial strains subjected to fluid flows. We first review microbial range expansion experiments on liquid substrates and then move on to discuss antagonism, i.e., two killer microorganism strains, each secreting toxins that impede the growth of their competitors (competitive exclusion), both with and without stationary fluid flows. Recent experiments that reveal the presence of a genetic line tension are described. Coupled reaction-diffusion equations that include advection by simple steady cellular flows composed of characteristic flow motifs in two dimensions reveal how local flow shear and compressibility effects can interact with selective advantage to have a dramatic influence on genetic competition and fixation in spatially distributed populations. We analyze a variety of 1d and 2d flow geometries including sources, sinks, vortices and saddles, and show how simple analytical models of the dynamics of the genetic interface can be used to shed light on the nucleation, coexistence and flow-driven instabilities of genetic drops.

Randomness and precision: using experiment and theory to understand epigenetic regulation

• Leonie Ringrose (Humboldt Univ. Berlin)

I am a molecular biologist on a journey towards theoretical biology. My field of research is epigenetic gene regulation by the Polycomb and Trithorax groups of proteins. I am fascinated by the apparently incompatible properties of randomness and precision in this system, both of which have been observed experimentally. The field of Polycomb and Trithorax regulation has seen a rapid expansion in the last 20 years, fuelled in part by an explosion of high-throughput technologies enabling the generation of vast amounts of data. Like any large, fast moving field, different ideas have risen to popularity, not only due to their scientific merits but also for more esoteric reasons. These latter include catchy names for ideas, misconceptions of journalists about the magical properties of the epigenome, and a tendency amongst scientists to assume that things must be very different between mammals and fruit flies. I will use examples from the field and from my own research to present the case for biologists to make more use of mathematical modeling and theoretical thinking, as a way to question dogma, to reconcile apparently conflicting experimental observations, to convert information into understanding, and perhaps most importantly, to raise good questions about what we still don’t understand.

Dinner for Science Speakers

Sticky liquids make soft solids

• David Weitz (Harvard)

This talk will discuss new observations of the role of weak interactions in liquids that can transform them into solids. This includes interactions between oil and water that can lead to anomalous stability of water-oil mixtures and the interactions of of proteins that can lead to phase separation, gelation and self-assembly of proteins.

Broken symmetries in living matter

• Nikta Fakhri (MIT)

Active processes in living systems create a novel class of nonequilibrium matter composed of many interacting components that individually consume energy and collectively generate motion or mechanical stress. In this talk, I will discuss experimental tools and conceptual frameworks we develop to uncover laws governing fluctuations, order, and self-organization in systems in which individual components break time reversal symmetry. I will describe how such frameworks provide powerful insight into dynamics of nonequilibrium living systems across scales, from the emergence of thermodynamic arrow of time to spatiotemporal organization of signaling protein patterns and discovery of odd elasticity.

Structure formation in molecular and organoid systems

• Andreas Bausch (TU Munich)

Living matter relies on the self organization of its components into higher order structures, on the molecular as well as on the cellular, organ or even organism scale. Collective motion due to active transport processes has been shown to be a promising route for attributing fascinating order formation processes on these different length scales. Here I will present recent results on structure formation on actively transported actin filaments, as well as the cell migration induced structure formation in the developmental phase of organoids.

Filopodia rotate and coil by actively generating twist in their actin shaft

• Natascha Leijnse (NBI)

The cells in our bodies are highly dynamic: Myriads of vital processes take place inside a cell every second. An individual cell can use filopodia, dynamic 'cellular fingers', to 'feel', explore, and manipulate its close by environment for instance during development as well as during cancer invasion. In this talk I will explain how we use optical tweezers in combination with fluorescence microscopy, to visualize the rotational dynamics of single filopodia as we simultaneously measure the forces they exert. I will furthermore show that a simple active mechanism is sufficient to explain much of the observed filopodial dynamics.

Oscillations and condensation in cellular regulation

• Mathias Heltberg (NBI)

The fundamental mechanisms that control and regulate biological organisms exhibit a surprising level of complexity. The protein, p53, is a master regulator of DNA damage response and when the cell is exposed to multiple DNA double-strand breaks, it exhibits sustained oscillations. A characteristic hallmark of the response is the formation of sub-compartments around the site of damage, known as foci. Following multiple DNA breaks, the transcription factor p53 exhibits oscillations in its nuclear concentration, but how this dynamics can affect the repair remains unknown. In this talk, I will present different ways in which the the oscillations can be stimulated and how complex dynamics might stimulate groups of genes. Finally I will discuss the future prospects and how we aim to investigate the possibilities of oscillatory transcription factors.

Collective cell communication via intercellular force transmission

• Siavash Monfared (NBI)

The emergence of organization from the collective interactions of cells with no central guidance is a fundamental question in developmental biology, regeneration and biomedicine. Though widely studied from biochemistry and genetics perspectives, the interplay of mechanical interactions and the dynamics of self-organization remains elusive. In this talk, I will focus on the role of intercellular force transmission in three-dimensional, dense and squishy cell collectives. Using both a high-fidelity computational model and experimental data, I will show how altering local mechanical interactions at the single cell scale affects intercellular force transmission and order with consequences for biological functions: (1) cell extrusion program and (2) solid-to-fluid transition in active cell layers.

Dynamics of active nematic defects on cones

• Farzan Vafa (Harvard)

Cones with orientational order in the local tangent plane provide a soft matter analog of the Aharonov-Bohm effect. We investigate the dynamics of a compressible active nematic on a cone. Imposing strong anchoring boundary conditions at the base gives rise to a rich phase diagram of periodic orbits of one or two +1/2 flank defects, with transitions between these states mediated by defect absorption, defect unbinding, or defect pair nucleation at the apex. Numerical simulations confirm theoretical predictions of not only the nature of the circular orbits but also defect unbinding from the apex.

Closing remarks

• Mogens H. Jensen (NBI)