Semesterübersicht Wintersemester 2022/2023

Wintersemester 2021/2022 - Sommersemester 2022 - Wintersemester 2022/2023

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25 Oct 2022

Physikalisches Kolloquium

Institut für Kernphysik

16:15 Uhr s.t., HS KPH

Prof. Dr hab. Wojciech Gawlik, JU Krakow, PL
I will begin with a historical introduction starting from Michael Faraday’s discovery of the magneto-optical phenomena and the basic physics behind it. Next, I will present the revolution caused by the advent of lasers in magneto-optics studies and the developments which made the nonlinear magneto-optics one of the most precise measurement techniques. While focusing on hot atomic-vapor samples, I will also present some magneto-optic studies with cold, trapped atoms and colour centers in diamonds and their applications to magnetometry.

08 Nov 2022

Physikalisches Kolloquium

Institut für Kernphysik

16:15 Uhr s.t., HS KPH

Prof. Dr. Horst Schmidt-Böcking, University of Frankfurt
In der Nacht vom 7. auf den 8. Februar 1922 gelang es Walther Gerlach und Otto Stern im sogenannten Stern-Gerlach-Experiment SGE, zum ersten Male das magnetische Moment eines Atoms, des Silberatoms, zu messen und den Beweis zu erbringen, dass Arnold Sommerfelds und Pieter Debyes Postulat der Richtungsquantelung von atomaren magnetischen Momenten in einem äußeren Magnetfeld der Wahrheit entsprach. Das Messprinzip des Experimentes als hochauflösendes Impulsspektrometer für einzelne Atome im Vakuum und der historische Weg der Durchführung dieses Experimentes werden dargestellt. Das Ergebnis des SGE zeigte damit auch erstmals, dass auch die inneratomaren Drehimpulse gequantelt sind. Die Bedeutung des SGE für die Entwicklung der Quantenphysik besprochen.

15 Nov 2022

Physikalisches Kolloquium

Institut für Kernphysik

16:15 Uhr s.t., HS KPH

Prof. Dr. Erwin Frey, University of Munich
Protein pattern formation is essential for the spatial organization of intracellular processes like cell division, and flagellum positioning. A prominent example of intracellular patterns is the oscillatory pole-to-pole oscillations of Min proteins in E. coli whose function is to ensure precise cell division. Cell polarization, a prerequisite for processes such as stem cell differentiation and cell polarity in yeast, is also mediated by a diffusion-reaction process. More generally, these functional modules of cells serve as model systems for self-organization, one of the core principles of life. Under which conditions spatio-temporal patterns emerge, and how these patterns are regulated by biochemical and geometrical factors are major aspects of current research. In this talk I will review recent theoretical and experimental advances in the field of intracellular pattern formation, focusing on general design principles and fundamental physical mechanisms.

20 Dec 2022

Physikalisches Kolloquium

Institut für Kernphysik

16:15 Uhr s.t., HS KPH

Prof. Dr. Sarah Köster, Uni Göttingen
We have about 200 different types of cell in our body, and each of them has very special mechanical properties. Illustrative examples are contracting muscle cells, migrating immune cells or elastic red blood cells. There intriguing mechanical properties are to a great part determined by the so-called cytoskeleton (the “skeleton of the cell”), a composite biopolymer network composed of three filament systems – intermediate filaments, actin filaments and microtubules – along with cross-linkers and molecular motors. In my talk, I will focus on intermediate filaments, the most flexible and the most extensible ones among the different types of filament, with an intriguing non-linear behavior. It has been shown previously that the presence of intermediate filaments in a cell has an influence on its mechanics. Here we unravel different contributions to network properties and cell mechanics, such as the assembly kinetics and mechanical properties of the individual filaments, filament-filament interactions, and network rheology. To explain our experimental results on molecular grounds, we design models that include the strictly hierarchical build-up of the filaments and non-equilibrium transitions between folded and un-folded states. Taken together, the experiments and the modelling indicate that intermediate filaments serve as “safety belts” and shock absorbers” for the cell, thus avoiding damage at strong and fast impact, while maintaining flexibility (e.g., during cell motility).