General Physical Colloquium in the WS 2022/23
Thursday, 16 o'clock (c.t.), Location: HS 2, IG 1, Wilhelm-Klemm-Str. 10, 48149 Münster
03.11.2022 PD Dr. Jens Soltwisch Antrittsvorlesung
Mass spectrometry imaging - developing new tools for the life sciences
Mass spectrometry imaging (MSI) combines the strength of mass spectrometry, to decipher the molecular composition of a sample, with spatial information. For this, the sample is analyzed in a pre-defined raster using a finely focused probe such as laser light or a beam of primary ions, recording a mass spectrum at every pixel. Post processing results in signal intensity distributions that can be reconstructed for every recorded ion species. In the life sciences, typical samples, such as tissue sections, are notoriously complex in their molecular make-up and the concentration of molecules of interest may vary over orders of magnitude. To investigate the full depth of this complexity, instrumentation has to provide high yields of ionization on the one hand and sensitive and highly resolving mass spectrometers on the other. In addition, many of the analyzed molecules are prone to thermal degradation, hampering their intact ionization and transfer to the gas phase.
Altogether, these prerequisites make the development of MSI equipment multifaceted and challenging. A successful advancement of the technique, therefore, relies on a thorough knowledge of the underlying physical and chemical processes and mechanisms. In his regard, fundamental research helps to identify and understand limitations and shortcomings of the employed techniques and may reveal new approaches to yet unsolved problems. The lecture will include a short introduction to the diverse approaches to MSI in the life sciences and present examples where a deeper understanding of fundamental mechanisms has helped to improve the analytical capabilities of different techniques in MSI.
10.11.2022 Prof. Zdenek Sofer
Layered materials beyond graphene
Beyond graphene, which is intensively studied over more than one decade, the other related materials remain almost unexplored. The research activities in the field of other layered materials like phosphorene, arsenene, silicene and germanene are rapidly growing in the last few years. Compare to graphene, all these materials are non-zero band-gap semiconductors. This property opens new application possibilities in electronic and optoelectronic devices. The properties of 2D materials can be further controlled by their functionalization. The chemistry of materials beyond graphene is none explored and shows high application potential in many fields. In addition also the methods of crystal growth and applications of 2D materials from group of chalcogens, halogens, thiophosphates and halogen-chalcogen will be presented.
Zdenek Sofer is a professor at the University of Chemistry and Technology Prague since 2019. He received his PhD also at University of Chemistry and Technology Prague, Czech Republic, in 2008. During his PhD he spent one year in Forschungszentrum Julich (Peter Grünberg Institute, Germany) and also one postdoctoral stay at University Duisburg-Essen, Germany. Research interests of prof. Sofer concerning on 2D based materials covering graphene, pnictogens, silicene, layered chalcogenides and other 2D nanomaterials, its chemical modifications and various applications covering electrocatalysis, gas separation and energy storage. Currently prof. Z. Sofer act as an associated editor of FlatChem Journal. He published over 560 articles, which received over 22 000 citations (h-index of 73).
01.12.2022 CRC 1459 Colloquium Center for Soft Nanoscience, 15 Uhr
Ort: Center for Soft Nanoscience (SoN), Busso-Peus-Str. 10
Juliane Simmchen, TU Dresden
How Smart Does a Material Have to Be to Mimic Biological Behaviours?
Michael Giese, Univ. Duisburg-Essen
Employing the Dynamics of Chemical Bonds for Functional Materials
08.12.2022 Dr. Nicolae Atodiresei
The Magic of Interfaces: Organic Molecules and 2D System Adsorbed on Metals and Magnetic Substrates
Theoretical simulations based on the density functional theory provide a framework with predictive power that can be used to describe hybrid materials in a realistic manner. In this respect, ab initio studies elucidate how the subtle interplay between the electrostatic, the weak van der Waals and the strong chemical interactions determine the geometric, electronic and magnetic structure of hybrid interfaces formed between organic molecules and 2D materials with metallic and magnetic substrates. More precisely, the interaction between the π-like electronic cloud of organic materials or the lone electron pairs of the 2D systems with the magnetic states of a metal influences the (i) spin-polarization, (ii) magnetic exchange coupling, (iii) magnetic moments and (iv) their orientation at the hybrid interfaces. I will briefly summarize how first-principles calculations (i) provide the basic insights needed to interpret surface-science experiments and most importantly (ii) represent a key tool to design novel materials.
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15.12.2022 Prof. Saskia Fischer
Why size matters: Charge and heat transfer in electronic materials
Understanding of charge and heat transfer in electronic materials is important for developing routes, both, for energy materials such as solar cells, batteries, low- and high-power electronics as well for future quantum electronic applications. In particular, dimensionality and size control may be advantageously introduced into material and device design. Commonly, charge and heat flow are considered to be well-understood by taking into account established transport material parameters for the bulk, such as the electrical and thermal conductivity. However, considerable deviations in electron-phonon and phonon-phonon interactions may occur when surfaces and interfaces effects come into play. Examples of the influence of size effects on material parameters will be given. Challenges for measurement techniques at the nanoscale will be discussed and recent progress demonstrated.
12.01.2023 Prof. Kathy Lüdge
Optimizing photonic reservoir computing with delay
Reservoir computing (RC) is a machine learning scheme that can be implemented in hardware, specifically with optical devices. Compared to deep neural networks, the RC paradigm has a much more efficient training procedure, one linear regression step on the output layer, and thus physical systems like a laser with an optical feedback loop and time-multiplexed input can be trained to solve complex time-series prediction tasks. The RC computing performance, however, depends on properly adjusted timescales of the physical system response which vary with the chosen task.
We present ways to improve the performance of delay-based RC systems via internal delay-time tuning. Furthermore, the analytic connection between the information processing capacity of a RC system and the linear system response of the underlying physical system will be clarified and the possibilities to predict parameters for good performance based on the memory of the reservoir will be explored.
19.01.2023 Prof. Paulina Plochocka
26.01.2023 PD Dr. Saeed Amirjalayer
02.02.2023 Prof. Kurt Aulenbacher
Highly spin polarized electron beams for scattering experiments in particle physics
Semiconductor superlattice structures play a vital role in many opto-electronic devices. An important application in physics research is production of high intensity spin polarized beams from negative electron affinity photocathodes.
The new electron accelerator MESA (Mainz Energy-recovering Superconducting Accelerator) will use such a beam for high-precision measurements. The P2-experiment at MESA aims at an accurate determination of the electroweak mixing angle at low momentum transfer. P2 will require a >85% longitudinally spin polarized beam with an intensity of 150 microamperes for a runtime of 10000 hours. The average beam polarization has to be measured with less than 1% accuracy. During the talk, special emphasis will be directed to the challenges to photocathode physics this implies.