FAKULTÄT FÜR PHYSIK

PSRCPHYSICS STUDENT

RESEARCH CONFERENCE

June 9th, 2018Theresienstr. 37

w w w . e n . p h y s i k . l m u . d e / p s r cw w w . e n . p h y s i k . l m u . d e / p s r c

PSRC 2018

Dear Participants,

We are pleased to welcome you to the second Physics Student Research Conference at the Faculty of Physics!

Look forward to the talks of 24 selected fellow students who present their research work and results. Learn about various research topics at the faculty and discuss them vividly with the speakers. Listen to two outstanding young scientist of the faculty in their exciting Keynote-Talks.

In line with the motto "Science is you", the PSRC offers you the opportunity to experience the format of a scientific conference at an early stage of your academic life. Aiming at the strengthening of the research orientation of students, the conference is funded by Lehre@LMU.

We hope you will have an informative and inspiring time at PSRC 2018!

Your Conference Team 2018

2 3

Physics Student

Research Conference

9th June, 2018

The Student To Student Conference

at the Faculty of Physics

10:00

10:30

10:45

12:00

12:30

13:30

14:45

15:15

15:30

PSRCSession 1Astrophysics & Quantum Optics

J. HinzA. DjamaliM. SmollaN. Reiter

Session 2Biophysics & Medical Physics

C. HanauerS. SubramanianE. UnterauerC. Kroll

Session 3Solid State Physics & Nanophysics

V. KönigF. SchuknechtM. KöglL. Hille

Registration

Welcome by Dean of Studies Professor Dr. Weller

Lunch

Best Student Talk Award

Get Together

Session 4Medical Physics & Nanophysics

I. AmersdorfferM. StanislawskiM. KubullekJ. Förste

Session 5Biophysics

S. EzendamN. KerschbaumerA. HagerA. Venczel

Session 6Particle Physics

G. EdenhoferJ. RothJ. RahmanS. Giardino

2018

Keynote by Emanuel Reithmann

“Turning white into black: How the turning behavior of actively moving organelles determines intracellular organization“

Keynote by Marcel Lotz

“Orbital Dynamics of galaxies in galaxy clusters and ram—pressure stripping efficiencies“

Programme

Locations

Foyer

B 051&

B 004&

B 005&

B 006&

Theresienstr. 39

PSRC 20184 5

Emanuel Reithmann conducts research on non-equilibrium processes in cell biology at the chair of Professor Erwin Frey. He contributed talks e.g. at the March Meeting 2017 of the American Physical Society in New Orleans.

Marcel Lotz is doing his doctorate at the University Observatory in

Munich. With his presentation of his Master's thesis on the subject of dynamics in galaxy clusters he won

the second place in the Best Student Talk Award of the Physics

Student Research Conference 2017.

The effect of galactic orbits on a galaxy's internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To disentangle this relationship, the velocity anisotropy, phase space and the orbital evolution of cluster satellites is investigated. Through the use of the hydrodynamic cosmological Magneticum Pathfinder simulations, we evaluate the orbits of subhalos associated with clusters from redshift z = 2 to the present. Through the inspection of different cluster masses and redshifts, we are able to achieve a diverse statistically relevant sample of subhalos inside clusters, which we further split into quiescent and star forming subhalos. This split allows us to observe the internal subhalo evolution and study its dependence on the velocity anisotropy parameter and the radial distance. We find that independent of cluster mass and redshift, the star forming subhalo population experiences a continuous decrease in star formation in the vicinity of the virial radius. More importantly, after crossing below the virial radius the vast majority of star forming subhalos are quenched through ram-pressure stripping during their first passage.

Orbital dynamics of galaxies in galaxy clusters and ram-pressure stripping efficiencies

Turning white into black: How the turning behavior of actively moving organelles determines intracellular organization

Organization within cells critically relies on processes out of thermal equilibrium. In particular, a multitude of energy-consuming molecular motors cooperates to constantly move many of the cell’s organelles and constituents along a mikado-like network of biopolymer filaments (cyto-skeleton) and thereby maintains intracellular structure. While a precise positioning of molecules and organelles on this network and thus within the cell is vital, the underlying physical principles are largely elusive. Here we discuss potential physical mechanisms for intracellular organi-zation based on the most prominent experimental model system in this context: Specific vertebrate skin cells that possess organelles filled with dark pigments. These pigment-filled organelles are actively moved by molecular motors on the cell’s cytoskeleton and thereby determine the skin’s brightness. Interestingly, it is a well known but poorly understood effect that – depen-ding on the context - these pigment filled organelles may either aggre-gate at certain regions of the cell or disperse homogeneously within the cell. Based on a theoretical model that is fully grounded with experimen-tal data we show that an effective means to control the distribution of organelles along the seemingly random filament network is the rate at which moving organelles turn to a different filament at crossings of two filaments. Rather than other properties of the organelles’ motion, such as their run length or velocity, our analysis suggests that the turning rate is the central parameter which determines whether organelles aggregate at specific cell regions or disperse homogeneously within the cell.

PSRC 20186 7

K e y n o t eB 051 – 12:00

K e y n o t eB 051 - 14:45

Emanuel ReithmannMarcel Lotz

Optical lattices are routinely used to trap ultracold atoms in periodic optical potentials. To prevent heating of the atoms, a high phase stability of the lattice is essential. In this work a 1D large-spacing optical lattice consisting of two laser beams interfering at an angle was set up and its phase stability was examined. Furthermore, an active phase stabilization was implemented and characterized.

S e s s i o n 1B 004 – 10:45

Jennifer Hinz

Cool Core Clusters in the Magneticum Pathfinder Simulation

The nomenclature Cool Core (CC) or Non-Cool Core (NCC) Cluster is used to classify clusters according to their different thermodynamical properties of the Intra-Cluster Medium (ICM). Cool Core Cluster show short central cooling times, low central entropies, temperature drops towards their centers and high central electron number densities. Non-Cool Core Clusters lack of these properties and thus reveal longer central cooling times, higher central entropies and lower central electron number densities. Observations of cluster samples unveiled that CC and NCC clusters are nearly equally distributed with a slight trend towards a higher NCC frequency. In this thesis, the fraction of CC and NCC clusters in the Magneticum Pathfinder Simulation is investigated and further thermodynamical properties of the ICM are examined using the classification of CC and NCC clusters.

Marco Smolla

Vacuum and Dark Energy

My master thesis investigates the problem of the cosmological constant which is the 120 orders of magnitude mismatch between theory and observation for the magnitude of dark energy. Therefore I carefully investigate assumptions and implications of a particular model which aims to determine the gravitational effect of vacuum fluctuations by imposing a new fundamental principle.

Nicola Reiter

Phase stability of a large-spacing optical lattice

The detection of gravitational waves by LIGO was one of the most interesting discoveries in recent years. Now, for the first time, there is a new method to learn about the physics of the universe; one that is fundamentally different from electromagnetic measurements. In this talk you will learn firstly, how gravitational waves are created; secondly, how the LIGO observatories look for gravitational waves; and thirdly, which detection methods exist.

Alexander Djamali

Gravitational Wave Detection

PSRC 20188 9

Astrophysics & Quantum Optics

S e s s i o n 1B 004 - 10:45

Astrophysics & Quantum Optics

In my talk I review the model shortly to then discuss some critical points which outline the shortcoming of the proposed description.

One great advantage of clinical MR-imaging over CT-imaging is that it does not expose the patient to ionizing radiation. However this comes at the cost of increased image distortions which - especially in MR-LINAC system used for image-guided radiation therapy – poses challenges when an exact geometrical characterization is required.Since spatial encoding in MRI relies on well-defined B-fields a good understanding of the magnetic field alterations due to B0

inhomogeneities, gradient nonlinearities and tissue susceptibilities is needed to deal with distortion.In this work spatial distortion artifacts in MRI are quantified experimentally and separated into the individual sources with the help of numerical analysis. The results will be integrated into a MR-image registration simulation program allowing validation of MRI-guided radiation strategies.

Christian Hanauer

Active Transport in Bacterial Cells – Brownian Dynamics Simulation of Chromosome Segregation

Robust and faithful segregation of chromosomes is essential for the replication of bacterial cells. In recent years, experiments have identified the biochemical

Eduard Unterauer

Mapping the extreme mechanostability of pathogenic adhesion proteins to a calcium dependent molecular mechanism

The ability to withstand high mechanical stress is a key point of pathogenic adhesion and initiation of infection. Using atomic force microscopy-based single-molecule force spectroscopy the mechanical stability of the Staphyloccocus epidermidis adhesin SdrG targeting the human fibrinogen β-chain was probed. We could demonstrate that in addition to the previously measured extremely high forces of the SdrGN2N3- fibrinogen interaction, SdrG also contains the mechanically strongest protein fold measured to date, the SdrGB1 domain. Both systems yield forces over 2 nN, previously associated to the strength of covalent bonds. This unusually high mechanical stability could be traced back to the arrangement of Calcium ions in a highly coordinated structure of three loops that cover the N and C-Terminus of the B-domain.

Clarissa Kroll

Spatial Distortion Artifacts in MR-Imaging 𝐵0 Inhomogeneities, Gradient Nonlinearities and Susceptibilities

The problem of chromosome structure and organization is central to un-derstanding biological cells. We attempt a novel approach to model a bacterial chromosome with partitioning proteins using principles of Statistical Mechanics. The aim is to understand the clustering of these proteins on the chromosome arm. We show that from simple

Srikanth Subramanian

Organising Bacterial Chromosomes through interactingproteins

and the mechanical properties of the chromosome as key ingredients for active transport in bacterial cells. However, it remains unclear how these elements work together in order to generate a translocating force acting on the chromosome.We use a Brownian dynamics simulation to analyze the interplay between reactive protein and elastic polymer dynamics in order to develop a quantitative model for chromosome segregation.

physical principles and minimal assumptions one arrives at a robust model of the system, that correlates with relevant experimental results. We also discuss the possible predictions of our model.

PSRC 201810 11

S e s s i o n 2B 005 – 10:45

Biophysics & Medical Physics

S e s s i o n 2B 005 - 10:45

Biophysics & Medical Physics

Photosystem I (PSI) is a protein complex, which is at the heart of light‐dependent reactions in photosynthesis. Its outstanding properties in light-harvesting, stability and scalability make it a promising candidate for solar energy conversion. Within this research project the integration of PSI into a biohybrid system featuring graphene electrodes is investigated. Graphene is a 2D-Material that has attracted wide attention within the last years due to a lot of uncommon properties. One of these properties is a tunable workfunction, that could significantly enhance the generation of photocurrent in a biohybrid system consisting of PSI and graphene.

Veronika König

Activating CO2 for Photocatalytic Reduction on the Semiconductor Surface

Modern photocatalysis uses sunlight to convert water or CO2 to solar fuels like H2 or CH4. Due to the high potential barrier for the initial one-electron reduction step, the general stability and chemical inertness of the CO2 molecule, CO2 reduction faces some additional challenges, when compared to water splitting. Copper (I) compounds have been found to be promising candidates for CO2 reduction and have been shown by our group to produce CO and CH4. Using a nanocomposite made of Cu2O nanocrystals in combination with ZnO nanoparticles, we now investigate ways to increase the efficiency of photocatalytic CO2 reduction by vibronic activation of the CO2

molecule on the semiconductor surface.

Maximilian Kögl

Hybrid Light-Matter States for enhanced conductivity in Organic Semiconductors

The field of Cavity-QED offers great new opportunities for scientific as well as industrial applications e.g. high temperature Bose-Einstein condensation or Quantum nondemolition measurements. Due to the concentration of the electric field inside the optical cavity the matter eigenstates split up into new Hybrid Light-Matter States that completely change the properties of the material. Our goal is to enhance the charge-transport in an Organic-FET by altering the electronic structure of the Organic Semiconductor and to improve the understanding of the underlying mechanisms of Hybrid Light-Matter conductivity.

Lucas Hille

Biohybrid systems for solar energy conversion featuring Photosystem I and Graphene

Noble metal nanoparticles display fascinating optical properties. The most prominent example is the occurrence of strong plasmonic reso-nances due to collective oscillations of free electrons upon interaction with light. Because of their high absorption and scattering cross-sec-tions the particles can be investigated on a single particle level by dark-field microscopy, and also be manipulated with a focussed laser beam.Here, I will present, how single gold nanorods can be reshaped and deformed with a combination of plasmonic heating and optical force. Using a laser tuned to the longitudinal particle plasmon leads to very different results, compared to transversely resonant excitation. Whilst the former allows us to bend gold nanorods at a controlled angle, the latter leads to the rods melting into spheres. We explain this observation with temperature inhomogeneity, due to different plasmonic heating power densities of the two plasmonic modes.

Francis Schuknecht

Plasmonic Bending and Melting of Gold Nanorods

PSRC 201812 13

S e s s i o n 3B 006 – 10:45

Solid State Physics & Nanophysics

S e s s i o n 3B 006 - 10:45

Solid State Physics & Nanophysics

Transition metal dichalcogenite (TMD) monolayers have gotten a lot of attention because of their unique optical properties like a direct band gap and circular dichroism. These 2D-materials have been proposed for a wide range of applications, while their physical understanding is still incomplete. A complete model requires spectroscopic studies of high quality samples, that show narrow spectral lines and a tunable doping level. Implementing these features yields interesting data, that poses new and interesting open questions.

Ines Amersdorffer

Towards a nuclear clock:Neutralization of 229Th ions using carbon foils

The most precise time measurements at present are achieved with atomic clocks. However, it has been proposed that they could be outperformed by nuclear clocks, using a nuclear transition (especially in thorium 229Th) instead of an atomic shell transition. To realize

Maximilian Kubullek

Carrier Envelope Phase Measurements of Short Laser Pulses in Fused Silica

The Carrier Envelope Phase (CEP) is a key parameter of ultrashort high intensity laser pulses, since it significantly influences the temporal shape of the pulse. The measurement of this parameter is therefore of great importance. This talk presents the application of current measurements in fused silica, from which the CEP can be inferred for circularly and linearly polarised laser pulses.

Jonathan Förste

Spectroscopy of gate-tunable 2D-semiconductors

Michael Stanislawski

PET activation studies for range verification in proton therapy

such a clock, knowledge of the nuclear transition energy is equired. For an upcoming energy measurement, it is essential to neutralize thorium ions, which can be efficiently accomplished by sending them through a carbon foil. In the presented measurements, the exiting particles are analyzed and the results can be used to perform a background-free measurement of the nuclear transition energy.

To fully exploit the advantages of proton beams for radiation therapy in cancer treatment, accurate knowledge of proton range in tissue is required. One of the key ingredients for range calculations is the so-called stopping power ratio (SPR) of involved materials and tissues. This talk introduces the use of positron emission tomography to assess the accuracy of different methods to measure and calculate SPR and verify proton ranges.

PSRC 201814 15

S e s s i o n 4B 004 – 13:30

Medical Physics & Nanophysics

S e s s i o n 4B 004 - 13:30

Medical Physics & Nanophysics

Shigella flexneri bacteria are one of the leading causes of dysentery worldwide. According to estimates this pathogen causes up to 160 million cases and 2.6 million deaths annually. Using a type-III-secretion system, the bacterium injects a mix of invasin proteins to enter and spread in human intestinal epithelial cells. IpaA invasin is able to modify the actin cytoskeleton in order to facilitate spreading. This is done by blocking an important cell adhesion protein called vinculin. Here, we study the interaction of IpaA and vinculin at the single molecule level. Understanding this complex interaction would broaden our knowledge of bacterial endocytosis.

Simone Ezendam

mRNA Therapeutics - Quantifying the Effect of Poly(A)-tail Length on a Single-Cell Level

Antonia Hager

Investigating the Cooperativity of Receptor-Ligand-Binding via Atomic Force Microscopy

Cooperativity is a basic property of Receptor-Ligand systems in biochemical reactions. We used Atomic Force Microscopy to investigate Cooperativity by observing single molecules.

Aron Venczel

How bacterial proteins hijack focal adhesion

Antisense oligonucleotides for gene silencing present a promising therapeutic strategy. Transfer of antisense oligonucleotides across cell membranes is limited and the development of an efficient and safe encapsulation of such antisense oligonucleotides for specific delivery becomes increasingly desirable. In previous work mono-nucleic acid lipid particles (mNALPs) (1) (2)

Nicola Kerschbaumer

Turning off genes with nanoparticles

Many genetic diseases are caused by one or more non-functional proteins. Introducing artificial mRNA into cells is a promising therapeutic approach, because it allows the cells to produce the affected protein correctly. It is essential to be able to understand and influence the stability of the artificial mRNA inside the cell, since this has a direct effect on the protein produced. As one of the main influencing factors the effect of the Poly(A)-tail is further investigated in my Master's Thesis.

PSRC 201816 17

S e s s i o n 5B 005 – 13:30

BiophysicsS e s s i o n 5B 005 - 13:30

Biophysics

were shown to form nanoparticles which self-assemble in a microfluidic setup when placing the lipids DOTAP, DOPE, DOPC, and DSPE-PEG2000in a solvent solution using water as a buffer. Here we show that the same assembly strategy using microfluidic chips forms antisense lipid nucleic acid nanoparticles (LNPs) with high encapsulation efficiency. Our LNP carrier provides a reasonable and effective approach for targeted delivery of single-stranded oligonucleotides for gene silencing.

The motivation for this work stems from the idea of Dvali and Gomez that the end state of a gravitational collapse is a Bose-Einstein condensate at the critical point, with a large occupation number of soft gravitons, in which black holes are considered as purely quantum objects. The semi-classical features such as the central singularity and the structure of spacetime around the object are then explained as emergent phenomena. Recently, it has been shown that including the effect of soft gravitons in the description if the gravitational collapse allows to correctly reproduce the expected post-Newtonian correction to the potential energy and Bekenstein's area law. The condensate can then be described using two Gross-Pitaevskii equations. This thesis will study the Gross-Pitaevskii equations derived from the post-newtonian expansion of the equations of motion for the scalar field that describes the gravitons.

Gordian Edenhofer

Optimization of Particle Identification - The Analysis Software behind Particle Discoveries

The talk will provide a quick glance at the inner workings of the analysis software used at the Belle 2 experiment (and in parts at the LHC). The required terminology and its application will be described briefly before discussing current statistical tools as well as possible alternatives to them. Finally a comparison of some simple approaches and an outlook will be presented.

Jillur Rahman

Boundary Effective Field Theory near an Event Horizon

An event horizon separates two globally hyperbolic spacetimes, one of which is stationary and the other dynamic. It is curious to study the dynamics of a quantum (probe) field propagating between two such spacetimes. We would like to find out whether a quantum field theory on a classical background with a boundary as such, can be consistently formulated. In this regard, we begin with the study of a toy model where we study the propagation of a scalar field through a refracting boundary between localized detectors on either side of the boundary. Eventually we seek an effective description of the system when the boundary is moving, thereby mimicking the probing of an event horizon during a stellar collapse. .

Serena Giardino

Gross-Pitaevskii equation and post-Newtonian theory in the corpuscular model of black holes

PSRC 201818 19

Jakob Roth

Antideuteron Production - A sensitive probe for dark matter decays?

Due to a very low astrophysical background, antideuteron in cosmic rays might be a sensitive probe for dark matter decays. To accomplish these indirect dark matter searches a better understanding of the antideuteron formation is necessary. In this talk I want to investigate how the antideuteron production rate could be measured with the Belle II experiment.

S e s s i o n 6B 006 – 13:30

Particle PhysicsS e s s i o n 6B 006 - 13:30

Particle Physics

FAKULTÄT FÜR PHYSIK

PSRCPHYSICS STUDENT

RESEARCH CONFERENCE

June 9th, 2018Theresienstr. 37

w w w . e n . p h y s i k . l m u . d e / p s r cw w w . e n . p h y s i k . l m u . d e / p s r c