Student lectures abstracts
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FEBID, nanofabrication and its applications
FEBID (Focused Electron Beam Induced Deposition) is a technique were a so called precursor gas is injected into the chamber of a Scanning electron microscope. The precursor gas adsorbs to the surface and when the electron beam is turned on, on the position where it hits the surface, the gas molecules split up into a volatile and a non-volatile parts. The non-volatile part forms a deposition on the surface. This can be used as a 3D printer for nanoscale resulting in 3D structures down to a size of 50 nm.
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Light trapping in the Organic Solar Cells
The organic solar cells seems to be the future of the energy industry. They are not only eco-friendly but also very cheap to produce. Despite of all these virtues, they are not common due to its fast aging-process resulting in poor efficiency in less than half a year. Impedance spectroscopy allows for the exploration of the light dependence on cells’ structure and, thus, for the more conscious development of the device. The measurement of the electric permittivity and modulus of the PCBM:P3HT solar cells before and after the light exposure was followed by the evolution of the relaxation processes.
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Radio Frequency (RF) source for Optically Detected Magnetic Resonance
The development and utilization of a uniquely designed, tunable resonator microwave antenna is pursued here. The purpose of such design is for Optically Detected Magnetic Resonance (ODMR) in Nanodiamond (ND) Nitrogen-Vacancy (NV) centers. Both simulation and experimental results demonstrating our ability to tune the Q-factor of the resonator are shown – this tunability made possible via variation in the inductive-capacitive coupling network of the antenna. The goal is the address the spin transitions of the NV centers with both optical and microwave excitation – the bandwidth of the NV centers spin transition, with center 2.87 GHz, is approximately 20 MHz. By employing the thermally stable, mechanically independent, and tunable system proposed, it is possible to easily and comfortably probe the resonances of the NV centers. We also investigate the correlation of ND lifetimes with the measured fluorescence. Preliminary results are shown and RF source performance will be the focus of this part of the talk. The novelty in controlling these spin transitions with coupled RF and optical sources is quite promising and applications are in abundance. These applications include, but are not limited to, quantum computing and information technology and single-photon emission sources.
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Physics in Neuroscience - measuring and modeling of neural circuits.
The major challenge for a student in neuroscience is to integrate the diverse knowledge derived from various levels of analysis, such as measurements of the electrical activity of neurons, of the distributions of neurotransmitters in space and time, and the description of the connectivity of neural circuits in order to explain how nervous systems are organized, and how they function to generate behavior.
Recent advances in electrophysiology techniques allows to record electrical signals of neurons in the deepest region of the brain, giving new insights on how our brain regulates hunger, fear, stress, and emotions.
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Measuring the effect of local electric field in biomimetic self-assembled membranes
The purpose of my study is the investigation of the effect of a local electric field on a lipid bilayer. The local electric field was created by platinum tip which was in the contact with the water. The bilayer was deposited on a flat transparent electrode (ITO glass) using Langmuir trough. The bilayer on the ITO glass surface was immersed in the water. The potential and electric field were calculated using the method of images. It is known that a membrane undergoes a curvature change under the action of an electric field (flexoelectricity effect). This should lead to the generating of the bump, but this require water below the bilayer. In the theoretical part of my report I described the water transfer in the surrounding of a membrane.We evaluated two possible mechanisms for water transfer and find that water permeation through the bilayers most likely. By analyzing experimental data, I discovered the existence three phenomenons at least - oscillation of bumps on the membrane surface, oscillation of the lipid tubes which attached to the membrane, and spider-like oscillation of the vesicles. The period of mentioned oscillations are completely corresponding to the period of the alternative electric field used in the experiments. The explanation of these phenomenons based on undulation instability of lipid membrane under electric field.
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Categories in physics
Categories were introduced in the 40s by Eilenberg and Mac Lane in the context of algebraic topology. In the last decades, categories have been used to understand and study the structure of quantum field theories, especially topological field theories and conformal field theories. Furthermore, categories are used to give a more conceptional approach to quantum mechanics.
In my talk I will introduce the basic concepts of category theory, like functors and natural transformations. Afterwards, I will explain on an example, how these notions appear naturally in physics.
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What is understanding in science?
In the age of Big Data and the explosion of machine learning techniques, the question whether prediction equals understanding became one of the most fundamental issues in the philosophy of science. Based on the ideas of algorithmic information theory (Chaitin, 2006), I will discuss why and how these formerly similar concepts 'bifurcate' nowadays and why is it important to be aware of it as a scientist.
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Jack Polynomials and Quantum Hall Effects
Quantum Hall Effects are still not completely understood. Classically, Hall resistivity measured in semiconductors in magnetic fields grows linearly in the magnetic field strenght. In high magnetic field conditions, and very low temperatures, the behaviour changes and the resistivity shows plateaux at certain integer and fractional multiples of a resistivity quantum. The theoretical picture to explain these plateaux is far to be complete. Understanding those effects would be a big improve in our knowledge of interacting electrons in magnetic fields. A witty guess for the ground state of the problem was made by Laughlin, who discovered a simple wavefunction which highly overlaps the numerically computed ground state. This ansatz opened the way for more and more ground state approximations in the following years. The problem is that it's not clear why such apporximate ground states should work as well as they seem to. Recently, both Laughling and other approximate wavefunctions were recognised as Jack Polynomials, a particular class of symmetric functions whose properties may throw some light on the problem. I will review the Quantum Hall problem to finally present my bachelor thesis work on Jack Polynomials.
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The Development of Cosmic-Ray Detectors in Bucharest
Primary cosmic rays entering the Earth’s atmosphere, initiate Extensive Air Showers (EAS). The Astroparticle Physics Group from IFIN-HH Bucharest is involved in the development of muon detectors, studying the behaviour of EAS at different angles, building and using detectors of various capabilities and sensitivity, in order to better understand the processes that they undergo. Also, different experiments around the world, employing mini-arrays of detectors to study the cosmic-ray air showers are reviewed.
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Neutron-mirror neutron oscillations in a residual gas environment
A precise measurement of the neutron lifetime is important for calculating the rate at which nucleosynthesis occurred after the Big Bang. The history of neutron lifetime measurements has demonstrated impressive continuous improvement in experimental technique and in accuracy. However, two most precise recent measurements performed by different techniques differ by about 3 standard deviations. This difference of 9.2 seconds can possibly be resolved by future experiments, but it may also be evidence of a mirror matter effect present in these experiments. Both mirror matter, a candidate for dark matter, and ordinary matter can have similar properties and self-interactions but will interact only gravitationally with each other, in accordance with observational evidence of dark matter. Although mirror matter does not couple to ordinary matter by Standard Model interactions, some additional interactions might exist, providing small mixing of ordinary matter neutral states, like the neutron, with mirror components. Three separate experiments have been performed in the last decade to detect the possibility of neutron-mirror neutron oscillations. This work provides a formalism for understanding the interaction of the residual gas in an experiment with ultra-cold neutrons. This residual gas effect was previously considered negligible but can have a significant impact on the probability of neutron to mirror neutron transition. This formalism is used to evaluate the three previous experiments and can provide a framework for future experiments. This work was performed in collaboration with Prof. Z. Berezhiani (University of L’Aquila, Italy), Prof. B. Kerbikov (Institute for Theoretical and Experimental Physics, Moscow) and Prof. Y. Kamyshkov (University of Tennessee).
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When atomic nucleus goes pear-shaped
Atomic nucleus is a quantum many-body system whose shape is determined by the number of nucleons and the interaction between them. Consequently, a variety of different shapes has been observed so far, including the quadrupole-deformed prolate (cigarette-like) and oblate (pancake-like) shapes, or triaxial shapes where axial symmetry has been explicitly broken. During the last decade, new experiments have established the existence of yet another shape in several nuclei. The octupole-deformed nuclei, marked by breaking of the reflection symmetry, are known to distort to the characteristic pear-like shape. In this talk, theoretical tools for studying nuclear structure, based on the relativistic mean-field theory and the generator coordinate method, will be presented. In particular, the application to study of octupole-deformed nuclei will be illustrated with few examples and the obtained results will be compared with new experimental results.
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Mass in de Sitter space
Nowadays our Universe is in accelerating expanding era. It goes as far as we know to asymptotically de Sitter space. In General Relativity there are certain ways to describe mass eg. Hawking mass. Those definitions are applicable in different circumstances. First I will briefly present main concepts. Then I will show how to construct Penrose diagrams for de Sitter space. Finally I will talk about the problems in definition of mass in de Sitter space and I will present some of my solutions to this problem.
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Wide-field analysis of VLBI survey data
Sky surveys allow us to conduct statistical investigations of large source samples, and also to discover new phenomena or types of objects. Radio surveys are special, because the the resolution and the field of view of a single dish is relatively small. Nevertheless we can perform simultaneous observations using several antennas to increase the resolution, thus the innermost pc-scale structure of radio-loud active galactic nuclei (AGN) can be directly studied with this technique called very long baseline interferometry (VLBI). High-resolution VLBI imaging observations reveal the geometry and the physical properties of relativistic jets emanating from the vicinity of the accreting central supermassive black holes. High-quality VLBI imaging of hundreds or thousands of radio sources is an observationally and computationally intensive task. Moreover, the compact radio jet structure in AGN is usually confined to the central region of tens of milli-arcseconds (mas). The VLBI technique does not allow imaging with an undistorted field of view larger than typically a few arcseconds at cm wavelengths. However, for practical reasons, often a much smaller fraction of the field, the central region is imaged only. Here I introduce an automated imaging process and present its application to the publicly available calibrated visibility data of a prominent VLBI survey. I imaged the ~1.5-arcsec radius fields around more than 1000 radio sources, and found a variety of radio structures that extend to ~100-mas scales in a small subset of the sample. Some of them were missed in the original survey and are yet unknown in the literature. I also give possible interpretations of these structures.
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A new old compound is the star in photovoltaics
Organometal halide perovskite are a small class of perovskite structure compounds which were first synthesized in 1978 by D. Weber and intensively studied in the early nineties by Mitzi, Miura and co-workers in the context of superconductivity. The compound was then forgotten until 2009 when the introduction of hybrid perovskite structures in photovoltaic started. In the last 7 years solar cell efficiencies of devices using these materials have increased from 3.8% to 22.1%, making this the fastest-advancing solar technology to date. Today this compound is used in many potential applications from already mentioned solar cells to lasers, light-emitting diodes, photodetectors and hydrogen production. My Laboratory of Physics of Complex Matter at EPFL Lausanne immediately picked up this material and I will present some work I’ve done on it during the first year of my PhD.
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Characterization of density fluctuations during the inter-ELM periods in the MAST spherical tokamak
The tokamak is so far the most developed type of the magnetic confined fusion devices. In a tokamak, the fuel is in plasma state. Special periodic plasma instabilities, the so-called Edge Localized Modes (ELMs) exist in high confinement operational mode. During an ELM significant amount of energy and particle is lost which cause large damage on the plasma facing components. But the ELMs also have advantages, such as throwing out impurities. Thus the understanding of the emergence of the ELMs is crucial for a future fusion reactor, like ITER.
The intervals between the ELMs are called inter-ELM periods. The profiles of the plasma parameters mostly stay stably during an inter-ELM period. In various fusion devices radially localized fluctuation modes can be observed during the inter-ELM periods. In this study these kind of fluctuations were examined. These are probably connected with the phenomenon or structure that dominates the transport in an inter-ELM period and holds the profiles stably during it. In the presentation it will be presented that this kind of fluctuation can be also observed in the MAST (Mega Amp Spherical Tokamak) and some characterization of it will be given. The MAST is equipped with a 2D turbulence imaging spectroscopy diagnostic, called Beam Emission Spectroscopy, where the measured data is proportional to the local density. Thus the results are suitable for researching the density fluctuations. Data from this diagnostic was examined mostly.
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Characterization of Striated Muscular Tissue- Device development and testing method
This study aims to investigate the dynamics of muscular tissue response to a mechanical impulse using an in-house developed device. The present device is capable of applying a short moderate impulse (dirac impulse) and show on a screen the muscle response by recording normal acceleration values from different muscle fiber regions. This research continues our work on the subject of complex myotonometric measures, with the goal of creating both a device and testing methodology for the assessment of muscular health in the context of micro-gravity countermeasures.
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Introduction to Nondestructive Testing in Nuclear Power Applications
Due to potentially catastrophic consequences that might occur in case of failure, safety is of top priority in all countries with operational nuclear power plants. In order to maintain the plant and perform repairs, every reactor must be periodically shut down for inspection, and only after receiving a green light from an independent inspection company may be reactivated. A nuclear reactor is a fairly complex machine, and it is constantly under extreme stress. Consequently, a number of failure modes are possible, which complicates the inspection process. Likewise, a number of different materials may be used in construction of the reactor, each requiring special attention. This talk will address the basic construction of a power plant, the most common failure modes and methods of inspection usually employed, as well as some of the current challenges in the field.
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Neural networks and High Energy Physics
Artificial neural networks (ANNs) have become important tools for particle physicists in the recent years. There are many problems ranging from data filtering and reconstruction to offline analysis that can be solved with neural networks. In this talk I will present the concept of ANNs and some situations where they are useful, give concrete examples how they are used in particle physics and discuss their advantages and shortcomings. The talk is aimed to the beginner level in the subject.
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Geo-neutrinos as messengers of the Earth’s interior and as radioactive background in new generation of neutrino oscillations experiments
The study of the electronic antineutrinos of low energy (≲ 10 MeV) is an active and multidisciplinary field. The next generation of large underground neutrino detectors used to study neutrino oscillations is affected by the presence of nuclear reactors and in the same time is influenced by the continuously emitted of geo-neutrinos from the beta decays of the antineutrinos from the progenies of U, Th and 40K decays in the Earth . Also geo-neutrinos represent a new probe of composition and structure of our planet and contributed to the heat of the Earth. Accidentally, bursts of antineutrinos in the same energetic range are registered by Earth following a supernova explosion in our Galaxy. In this contribution the effects of the geo-neutrinos are discussed and are taken into consideration as essentials elements for the knowledge of the Earth mantle and for the detection of low-energy antineutrinos in the next oscillations experiments.
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GLAD technique in plasma polymerization - controlling morphological growth of polymers
Plasma polymerization uses plasma sources to generate a gas discharge that provides energy to enable or fragment a liquid or gaseous monomer which often contains a vinyl group, to initiate polymerization. Polymers formed by this method are generally highly branched and highly reticulated, and adheres well to solid surfaces unlike polymers obtained by the classical method. This work presents a new method of obtaining different morphological surfaces by combining the Glancing Angle Deposition technique with plasma polymerization. By controlling the different discharge parameters as well as the angle and rotational speed of the substrate, unique patterns can be obtained. The polymer thin films obtained by this method can be used in a wide range of applications like liquid crystal cells, polarizers and anti-reflex coatings. Structural and morphological studies (FTIR, SEM, AFM) as well as applications of the thin films are presented.
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Optomechanics of photonic crystal membranes
The placement of a mechanical membrane into an optical cavity is an interesting case of interaction between the light field and a mechanical system. While the positioning of such a membrane inside the cavity has been theoretically studied as well as experimentally realized, the usage of it as an incoupling mirror has not yet been investigated due to material limitations. In this talk I will give a brief introduction to the optomechanics of such a system as well as possible applications to gravitational wave interferometry.
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Diffusion of Radon in Tissue
To better understand the biological effects of radon, the knowledge of the distribution and accumulation in the human body is important. An unequal distribution of radon and its radioactive daughter nuclei and subsequent local low dose irradiation could be an explanation of the anti-inflammatory effect of radon treatment. We exposed tissue samples like muscle or fat in a radon exposure chamber and measured the γ-spectra of the decay products Pb-214 and Bi-214. We then calculated back to the initial amount of radon in the sample. To measure the diffusion of radon directly through different materials, we constructed a radon diffusion chamber that can be located inside our radon exposure chamber. Subsequently, we performed experiments with different materials like polymer films, fatty tissue or water. We also used different thicknesses of the samples. We want to present the measurement setup for alpha spectroscopy, the interpretation of the spectra and first data of the diffusion parameters.
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Combining Multiple Mid-Infrared Laser Diodes into a 'Superbeam'
New-generation 2 μm laser diodes were characterised with the aim of spatially combining multiple beams into a single well-collimated beam. Wavelength, polarisation and M^2 quality factor of the sources were measured using the chopper method and produced results with interesting applications to defence. Two beams were successfully combined and the M^2 was compared to those of the individual diodes. The comparison showed that the beams had been effectively combined, using a repeatable method. Future work may involve combining more diodes to increase the output power. The properties of an unexpected multimode pattern being emitted from the diodes, and the thermal stability of the sources are also discussed.
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Testing globular cluster models with future detections of gravitational waves from eccentric binary black holes
The proper modelling of GCs can be difficult due to the high number of constituents, each interacting with one another. Accordingly, there are many different analytic and numeric GC models competing against each other. Thus, an efficient observational method is required to test these models, and to find the most realistic one. Electromagnetic observations are limited in this regard, because they cannot provide us information about the deeper structure of GCs. However, detections of gravitational-waves (GWs) from eccentric binary black holes (EBBHs) could serve as a tool for testing and constraining these GC models. EBBHs are expected to form in dense stellar systems, such as GCs. Properties of GCs affect the formation of EBBHs within them, and consequently, we may gain information about properties of GCs by detecting EBBHs and reconstructing their parameters. Our goal is to determine the minimal number of EBBH detections with GW detectors that allows testing implications of different GC models on the observable distribution of EBBH parameters, such as orbital eccentricity and pericenter distance at the time EBBH signals enter the sensitive band of Advanced LIGO (aLIGO). When aLIGO reaches its full sensitivity, which is proposed to happen in 2019, the expected rate of EBBH observations will be 5-20/year. We find that this detection rate can already provide enough data to carry out an actual test of GC models on a reasonable timescale.
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Novel rock sampling technique for use on Mars
The Small Planetary Linear Impulse Tool (SPLIT), developed in Space Research Centre, University of Leicester, was started as a response for NASA's Call for Proposals for this mission Mars 2020 (Mars Sample Return). It is a novel geotechnical tool for use on Mars and other rocky or icy planets or moons. Its aim is to sample rocks for biosignature search in an efficient and highly controlled way from as well as scientific, as engineering point of view. SPLIT’s main advantages, when compared to currently working devices are minimized contamination of stone’s pristine surface, extended depth of penetration and lower usage of energy.
The focus of the interdisciplinary student's project was to use the new prototype in order to learn to search for water traces and morphological biosignatures on pristine rocks’ surfaces and look at the dependence of the above on stones’ chemical composition and its structure. From the technical point of view, the project was aimed a finding the most efficient way of sampling the rocks.
Results turned out to be very encouraging - with use of a variety of planetary analogues from local sources and Atacama Desert, it was demonstrated that SPLIT is able to deliver its primary function - to uncover perfect location for biosignatures search in Martian conditions. What is more, we learned a few technical issues about its operation modes, and micro-astrobiology, which can improve the science of future planetary missions.
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The KASCADE-Grande and Pierre Auger Cosmic Ray Experiments
The Pierre Auger Observatory is a ''hybrid detector'' employing two independent methods to detect and study high-energy cosmic rays. One technique detects high energy particles through their interaction with water placed in surface detector tanks. The other technique tracks the development of air showers by observing ultraviolet light emitted high in the Earth's atmosphere.
In this context, I will describe the experimental techniques used in both Pierre Auger and KASCADE-Grande which studies the cosmic ray primary composition and the hadronic interactions in the energy range E0=1016-1018eV.
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Neuromagnetic studies of the earliest effects of the spatial visual attention
MEG is a noninvasive method of research of human brain which has a great time resolution, on the order of magnitude 1 ms. Earlier research showed first effects of selective visual attention in the primary visual cortex (V1) already on 150 ms in return connection with V2, in opposite with the traditional model of serial processing when the effect is expected at 300 ms. Using the experimental paradigm of top-down cuing we can even show that earliest effects can be seen on the latencies before 100 ms. Using the non-linear model of spatio-temporal localising we are trying to get the insight on the cortical level how much the earliest visual responses are sensitive to the modulation by selective visual attention.
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A new way to determine causality
What are the consequences of X? Will changing Y cause a change in Z? Questions like these are old and arise everywhere in science as well as in everyday life. Although the questions are old answering them is still a scientific challenge of our days. There are widely-used methods to answer them but each of them has its own flaws.
In my lecture I wish to introduce a relatively new theoretical approach to determine causality between two quantities. Quick overlook of possible casual relations, introducing the method, simple applications, improving the method, where next?, examples of complex applications.
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Modelling reactions with ReaxFF in MOFs with defects
Local and long-range defects strongly affect sorption and catalytic properties of metal organic frameworks (MOFs), but are very difficult to study both experimentally and computationally.
The reactive MD method ReaxFF is suitable to tackle such complex chemical systems, however, suitable force field parameters are usually not immediately available. I will discuss a systematic approach to tackle ReaxFF parameterization as well as automated tools for analyzing reactive events.
We improve the effectiveness of global optimization methods, which sample a vast, complex parameter space, by grouping ReaxFF parameters and statistically analyzing them across many sets, and applying smart filters.
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A quick course on physics teaching
If you’ve ever wondered how to approach teaching physics in a classroom, this lecture is for you. We will discuss questions such as what basic didactic and developmental psychology principles to keep in mind and what should be the goal of our teaching? An overview of the most effective physics teaching methods will be given and we will see how to implement them in teaching a few physics chapters.
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Particle creation in expanding universes
The research for a unified theory yields today two fundamentally different theories. On one hand Quantum Field Theory, describing the electroweak and strong interactions using exchange particles (known as the standard model of particle physics), and on the other hand General Relativity, identifying gravity as the dynamics of the spacetime geometry. So, why don't combine these two theories? That's exactly what Quantum Field Theory in Curved Spacetimes is doing. This combined theory - first investigated by Leonard Parker - leads to the prediction of Hawking radiation, the Unruh effect as well as particle creation in expanding universes.
In my talk, I will explain this mechanism considering the most easiest case the scalar field. Since solving Einstein's field equations is in general not easy, I'm considering a cosmological model instead to get the metric and its evolution. Imposing this metric into the equation of motion shows that, in general, particles are created over time.
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Quantum dynamics
Following Moore's law are transistors rapidly approach the molecular and atomic limit where physics gets interesting again. Especially quantum effects manifesting in strongly correlated electrons play an important role for the current characteristics and give rise to interesting effects like Coulomb blockade or the Kondo effect. I will present some of the well established tools to address such strongly correlated electron systems out of equilibrium to look at quantum current.
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Transcranial magnetic stimulation (TMS) for in vivo brain research
In this lecture, I will introduce the audience to the basics of transcranial magnetic stimulation (TMS), and its possibilities in non-invasive brain research using healthy volunteers.
The lecture will cover at least the basics of TMS, major existing clinical and research applications for TMS, combining electroencephalography (EEG) with TMS, and some future prospects for TMS.
The lecture will be introductory in nature, so that it will be suitable for all physicists. That is, I'll assume you know the basics of electrodynamics.
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Numerical simulations of flexible thermoelectrics
Energy is one of the main requests of our society nowadays since our modern world depends largely on it to live. The necessity for the improvement of energy generation boosts the search of alternative energy generation. Thermoelectrics appear as one of the best candidates since around 60% of the wasted energy is in the form of heat. Thermoelectric generators are small, possess no moving parts and require almost no maintenance. These qualities make them an improved way of generating energy, but their efficiency is still low for large scale applications. Thus, the study and improvement of their efficiency is of utmost importance. In this presentation, thermoelectric devices are explained. Simulations performed using the COMSOL Multiphysics software regarding the efficiency of thermoelectric devices are discussed, emphasising how to optimize and improve their operation. Finally, developed flexible thermoelectric devices and their COMSOL’s simulation will be presented.
Co-authors - Pedro Resende and André Pereira
References [1] Teixeira, S.F. and Pereira, A.M. (2016), Geometrical optimization of a Thermoelectric Device numerical simulations, submitted to Applied Energy [2] Bell, L.E. (2008), Cooling, heating, generating power, and recovering waste heat with thermoelectric systems, Science, 321(5895), 1457-1461.
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Laser Power Effects on the Size of an Optically Trapped Aerosol Droplet Determined Via Whispering Gallery Modes
A laser can be used as an optical trap to catch and hold small, transparent objects. Observations of optically trapped aqueous aerosol droplets have demonstrated that the droplet moves between two or more stable positions dependent upon the power of the trapping laser. It is hypothesized that this movement coincides with a resonance between the trapping light and the droplet’s surface, called a Whispering Gallery Mode. When this resonance occurs, forces acting on the droplet cause it to move. To investigate this behavior, Raman scattered light from the droplet as well as the droplet’s position are measured. The Raman spectrum exhibits a series of peaks resulting from the droplet’s spherical shape, referred to as Cavity Enhanced Raman Spectroscopy (CERS). The location and spacing of these peaks are known to be related to the diameter and the optical properties of the droplet. From this spectrum, the magnitude of the electric and magnetic fields of the scattered light are calculated. This allows for a precise measurement of the droplet’s radius at the moment that the droplet moves between stable positions. After determining the droplet’s radius from the spectrum, the effect of varying the intensity of the trapping laser beam on the droplet radius can be investigated.
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Engineering dielectric tunability at perovskite interfaces; a first principles study
Perovskite oxide materials show a wide range of physical properties of scientific and technological interest, such as ferroelectricity, multiferroicity, and superconductivity. They also exhibit a large degree of tunability of their properties via variation of their chemical composition (A and B cations). For example, perovskites can be found in many different structural polymorphs, which is often determined by the relative ionic sizes of the ions.
Using first-principles simulations, we investigate the tunability of the properties of a variety of different perovskite oxide materials. This will give us insight into the general design principles for engineering the dielectic of perovskite oxide materials. The combination of high-throughput and structure searching methods will enable searching in previously unexplored phase space in the hope of identifying altogether new structural polymorphs with large tunability.
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What Makes a Flute a Flute? A Mathematical Analysis of Timbre
Musical instruments all have their own, distinctive sounds. Even when they appear to be playing the same note (or emitting the same frequency), humans are capable of distinguishing which instrument they hear.
In this study, three main instruments have been selected (flute, clarinet and violin) and their audible differences have been explored and explained by physics. Firstly, a recording of a single note played by a selected instrument was taken. Then by taking a Fourier Transform of the resulting sound spectrum, we see the true frequencies which are produced by the instrument. As an example, in the Western music scale the musical note A4 corresponds to a frequency of 440 Hz and yet the spectrum shows many more peaks than one at this frequency.
Upon seeing this, it becomes clear why it is so difficult to produce digital music which can truly replicate these instruments. A spectral analysis was also conducted on notes from Sibelius software as an example and their differences compared to that of a real instrument. There are some clear similarities between the spectra of the “real” musical instrument and the artificially created one, however there is still something which, to the ear, sounds different.
In addition, this analysis was also carried out on the progression of a single note as it is played. Through time, the frequency spectrum shifts, typically beginning and ending with only the dominant frequency. When changing between instruments, this characteristic shift changes again.
All of these things combined contribute to the set of subconscious criteria which humans use to determine which instrument they hear. The knowledge of such phenomena allows us to not only to work towards the creation of digital music, but also to appreciate the mathematical complexity of something as “simple” as music.
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Motion of charged particles in strong magnetic field of pulsar
There is a strong magnetic field near pulsars and any charged particle is highly influenced by it. The charged particles are accelerated in magnetosphere and sometimes achieve relativistic speed because pulsars are rotating very rapidly around their axis. In my research I have numerically investigated motion of charged particles near pulsars. To obtain results I had to solve the several problems. A charged particle moves alongside a spiral-like path in a very strong magnetic field so we can divide its motion into two components circular motion in the plane perpendicular to the field lines and motion alongside the field lines. If I included this circular motion in numerical simulation, there would be needed huge amount of computational power and time. I observed that the behavior of particle’s motion alongside field line is similar to motion of particle attached to a string with shape of this field line and capable only of moving alongside it. So I could interpret whole simulation as particle moving alongside string. This leads us to second problem. Let’s assume that a solid straight string of infinite length is rotating and we are observing it from this inertial reference frame. A particle, which is attached to this string and can only move alongside it, is accelerating radially because of centrifugal force in rotating reference frame. At some point its tangential speed should exceed speed of light but it is impossible. So the particle never reaches this point and starts periodical motion on the string. I have theoretically investigated that phenomenon and applied this theory to my model of particle’s motion in strong magnetic field. After this I could make numerical simulation for large amount of charged particles and observe their behavior. I have investigated several interesting parameters such as concentration of particles at some point, speed of particle as it accelerates alongside field line and etc.
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DFT study of the diffusion of S adsorbates on a Br pre-covered Cu(100)-surface
Diffusion at electrochemical interfaces is a decisive factor for, e.g., metal electrodeposition using halogen ion containing electrolytes [1,2]. Nanoscale processes determining the growth dynamics during such processes are not yet fully understood. The potential dependent growth has been ascribed to the variation of activation energy barriers due to the interaction of adsorbate induced electric dipoles with the electric field at the surface [1-3]. In order to identify relevant mechanisms in the diffusion process of a S atom on a Br-c(2x2) covered Cu(100)-surface, a study based on density-functional total-energy calculations with VASP[6-9] was realized that took advantage of the nudged elastic band method and yielded a first insight into the dependence of the S atom’s hopping rate on sample potential.
References [1] M. Ruge, F. Golks, J. Zegenhagen, O. Magnussen, J. Stettner, Phys. Rev. Lett. 112, 055503 (2014). [2] F. Golks, Y. Gründer, J. Stettner, K. Krug, J. Zegenhagen, O. Magnussen, Surf. Sci. 631, 112 (2015). [3] M. Giesen, G. Beltramo, S. Dieluweit, J. Müller, H. Ibach, W. Schmickler, Surf. Sci. 595, 127 (2005). [4] G. Mills, H. Jonsson and G. K. Schenter, Surface Science, 324, 305 (1995). [5] H. Jonsson, G. Mills and K. W. Jacobsen, in 'Classical and Quantum Dynamics in Condensed Phase Simulations', 1998. [6] G. Kresse, J. Hafner, Phys. Rev. B 49, 14251 (1994). [7] G. Kresse, J. Furthmüller, Comput. Mat. Sci. 6, 15 (1996). [8] G. Kresse, J. Furthmüller, Phys. Rev. B 54 , 11 169 (1996). [9] See //www.vasp.at.
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Quantisation from the perspective of knot invariants
Usually the quantisation is presented as a pretty obscure and little magical procedure enforced by black body radiation and other physical phenomena. In this talk I would like to look at it from a different point of view. I will put it into very simple abstract constructions in order to be closer to its essence.
When looking on quantum mechanics as a “modern symplectic geometry” [1] one can analyse knot theory in this language. The results of this approach contain new ideas in mathematics, some closely connected to works by Edward Witten and Vaughan Jones awarded the Fields Medal.
I will present a glimpse of this striking face of quantum mechanics and hope that the reward for the audience will be not only joy of watching how physics helps mathematics, but also better understanding of the quantisation itself.
[1] Lectures on Knot Homology and Quantum Curves, Sergei Gukov, Ingmar Saberi, arXiv:1211.6075
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A little bit of photon pair generation in optical fibers
A study about the generation of entangled photon-pair in gas-filled kagome photonic crystal fibers, through the process of spontaneous four wave mixing, is going to be described, from the process of producing the photon pair state, describing how to manipulate their state of entanglement and some of its applications. Results about spectral correlation properties of the two-photon states and details of a particular source design, likewise the advances in its experimental implementation, will be shown.
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Quantum Spin Correlations
The phenomenon of quantum spin correlations will be presented beginning with the famous EPR paradox and Bell inequalities. Results of historical experiments will also be shortly summarized. The talk will, however, focus on recent theoretical discoveries and experimental plans regarding the relativistic regime, which has not yet been experimentally investigated. A planned experiment investigating quantum spin correlations of relativistic electrons will be presented. Electron pairs under study will originate from polarized electron beam scattering on atomic electrons (Moller scattering). The measurement regards correlations of spin projections on chosen directions for the final state pair. The detector is planned as a double Mott polarimeter. This measurement, planned for year 2017, will be the first attempt to verify the predictions of quantum mechanics in the domain of spin correlations of massive relativistic particles.
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Neutron detection in NeuLAND
The NeuLAND (new Large-Area Neutron Detector) is a next-generation fast neutron detector, which is designed for the R3B group. Exotic nuclei are being studied by detecting all reaction products and measuring their moments. Because of the high detection efficiency a lot of hits are being detected (usually 10 per incoming neutron), and for that reason finding the first hit is problematic. Therefore the reconstruction of the incoming neutron's moment and thus measuring the excitation energy of the nucleus is anything but trivial. Our aim was to solve this problem. I have made examinations with the aid of a Geant4 simulation. Based upon the results of the analysis I have developed an algorithm, which determines the number of the incoming neutrons, and chooses the best hits for the reconstruction. The algorithm uses neutron tracking and examine energy depletion. I would like to show my results after presenting the methods of the analysis.
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Reference frame-free spacetime model
The fundamental structure behind mechanics (and most of physics) is a spacetime model that tries to describe the properties of the physical reality in which events take place. Sadly, spacetime models are usually unmentioned in the treatment of physics, or are covered by simply stating that the framework is non-, special- or general-relativistic.
It is also important to keep in mind that physicists use a lot of mathematical structures that aren't linked to spacetime such as coordinates, synchronisation, concrete units of measurement-observers.
These are of course essential when treating real life problems, but do not reflect the general properties of spacetime. Thus, a mathematical model for it has to be void of any such unnecessary structures. This is the main idea behind a 'reference frame-free' spacetime model.
The lecture gives a semi-formal introduction to a flat spacetime model based on human scale observations, developed in the book 'Spacetime Without Reference Frames' by Tamás Matolcsi. It places emphasis on the ideas governing the choices for the structures in the model and will show how, by restraining the general structure of the model, one can arrive at the non-relativistic and the special relativistic ones.
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Sky's Law - light pollution
Light pollution is a serious problem that interferes with numerous aspects of our lives such as our sleep cycle, but also with scientific issues like astronomical observations, specially on those cities with observatories nearby. This lecture is about those problems, how can we help to reduce them and the physics behind light pollution as well as its consequences on scientific research. Also, it shows the law that exists in my hometown of Ensenada to prevent this excess of light reaching the National Astronomical Observatory of San Pedro Mártir and the importance of other countries on creating similar laws.
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Journey to Mars
In this lecture I will show you the concepts and equations that we need in order to be in Mars, such as Kepler's laws, gravitational equations, Hohmann transfer, the Tsiolkovsky equation, etc. But the main idea is to show an experiment that we are trying to develop at the Astronomy Institute in Ensenada, the use of a drone on the red planet to do some measurements such as temperature and humidity and to take some pictures. The problem that we are trying to solve right now gravity and the density of air. So, enjoy this lecture and please comment your ideas and suggestions.
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Ferroelectric properties of BFBT thin films
Ferroelectric materials show many promising features for applications in tomorrow’s electronics. The ability to use polarization to store information in a dense space and good endurance make them one of the top contestants for the next generation memory applications, such as Ferroelectric or Resistive Random-Access Memory elements (FeRAM / ReRAM). The ReRAM elements are also a promising type for the missing circuit element, memristor, which links together the magnetic induction flux and the electric charge.
Some materials also exhibit simultaneous ferroelectric polarization and magnetization. These are called multiferroics and could be a key towards magnetoelectric memories and a realization of four-state logic in a single device.
A solid state ceramic, BiFeO 3 , has been under recent interest for such a multiferroic material since it exhibits large polarization simultaneously with magnetization. The challenges of BiFeO 3 include its high conductivity for an insulator and poor phase stability. Other materials with similar unit cell structure have been mixed with the material to successfully improve the properties.
The lecture shows results of various electric measuement on 0.80[BiFe _{0.95} Mn_{0.05} O_3]–0.20[BaTiO_3], or BFBT(Mn). They vonfirm that the material is ferroelectric. They also show that the conduction mechanism inside the material varies with the applied electric field, hinting to Space Charge Limited Conduction mechanism and Resistive Switching. The phenomenon is expected to be linked to migration of oxygen vacancies inside the sample and formation of conductive filaments.
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Nanoparticles - Production and characterization
Producing samples of nanoparticles usually is a drawn-out process, taking up quite a lot of time. To increase the efficiency of the production of samples, the method of sputterdepostion is used to sputter silver-nanoparticels into an ionic liquid. The magnetron sputter device bundles up electrons in front of a small sample of silver to ionize argon atoms. These argon atoms crush into the silver sample, detaching small silver particles that fall into the ionic liquid. The ionic liquid BMIM-PF6 is used for its specific characteristics in high vacuum and for its ability to store nanoparticles in a stable condition. Using this method, it is possible to produce a sample within 30 minutes. In order to measure the quality of this process, the characterisation of the produced nanoparticles is necessary.
Characterisation can be optained using optical methods like spectral analysis of the transmission and extincion of the sample.
They are used to find plasmon resonances in the spectrum of the nanoparticles.
The position and size of these resonances are an indication for the dimension and the growth behavior of the synthesised nanoparticles. \
By now varying the settings of the sputtering process, the possiblilitys of this method can be investigated.
Also the aging process in ionic liquids is studied to improve stable storage and transport of these particles. \
At the end, a measurement method will be shown, that will help to measure the growth behavior in ionic liquids by using total reflection at the brewster angle.
Applying this method, it should be possible to measure the plasmon resonance and, using this, the dimension of the nanoparticle at any given point of time during the sputtering process.
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Massive Stellar Evolution and Neutrino Physics
This lecture is based on the study the evolution of high mass stars with all the physical processes that occur from their formation and until they collapse and also aspects of the properties of neutrinos and how these can be deduced using fundamental equations. Regarding this, nuclear fusion features were introduced and calculations were made based on the reactions that take place within the core of massive stars in order to better understand stellar evolution.
Further, properties of neutron stars were modeled, this being the key to better comprehend what is happening to a star and how it modifies in the last stage of its evolution: going supernova.
By studying the hypercritical phase of a new neutron star, we can deduce the neutrino cooling effect in the formation of a supernova’s gas envelope which is in quasistatic equilibrium.
In particular, Supernova 1987A was studied and the analysis of the registrations that took place in the time it was observed gave the possibility to make the statement that the collapse of a star starts with the modification of the massive electron neutrinos.
The properties of neutrino flux that was registered by the ground detector Kamiokande were consistent with the calculations.
Also, it will be shown that by investigating the luminosities in SNe IIn and linking them with the element diversity in the wind, one can assume that these luminosities are affected mainly by the intrinsic properties of the supernovae.
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From London to Msida - A Decade of ICPS
Since I was a freshman attending my first ICPS in London in 2007, this conference has held a special place in my heart; the people, the places, and the parties! From the tent sauna driven all the way from Finland to Poland, to claiming a whole Croatian street filled with bars as our own, I bring you an introspective and recollection from the view of a normal attender, with injections of presumed insight into how to keep a gathering of hundreds of physicists happy, fed and entertained. Come join me on a trip down memory lane to round up my ICPS career!
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Dynamics of Molecular Ring Currents
Internal Molecular processes occur on an ultrafast timescale (faster than 10-12s). To explore the dynamics of these process measurements need to be taken during a shorter time to accurately describe the evolution of the system as it progress along the reaction coordinate, this is achieved through the use of time resolved spectroscopy using pulses of light of the order femtoseconds (10-15s) in length. These pulses first ‘pump’ the molecule to a higher lying electronic state and then ‘probe’ the state through the process of multiphoton ionisation. Molecular ring currents have shown to be produced in aromatic compounds with π electron systems, through the use of circularly polarised pulses of light of the order of a hundred femtoseconds. These ring current allow selective excitation to degenerate excited states within the molecule. This project set out to explore the dynamics of how ring currents evolve in a molecule as well as to probe how the molecule reacts when the chemical bonding in the ring is broken and the molecule fragments. The development of a technique involving the use of molecular ring currents may allow further dynamical as well as electronic information to be gleaned from molecules, due to the large variety of molecules that possess an aromatic element to there electronic structure.
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Fighting quantum with quantum.
With technological progress over the past few decades, working universal quantum computers look like they may become reality in the near future. While this would be fantastic for quantum simulation, there is a real worry that a universal quantum computer could be used for malicious attacks on cryptographic systems. Many cryptographic systems used online today implement public-key cryptography, where the security is based on the assumption that it is difficult to reverse a one-way function. Unfortunately for us, Shor’s algorithm, which can be implemented using a universal quantum computer, is very efficient at reversing commonly used one-way functions. This will allow a malicious party the ability to crack cryptosystems much much faster than on a conventional computer.
This talk gives an overview of two research field which are developing cryptographic systems that are thought to be robust against quantum computer attacks. One field implements quantum mechanics is the protocols, essentially fighting fire with fire. The other field implements mathematics which cannot easily be solved with quantum algorithms, therefore there is no advantage in using a quantum computer to try break the system.
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Simulating a sun with your computer
Turbulent movement of ionized plasma within solar convection zone that spans from the radiative zone at r on Ro approximately 0.7 to the photosphere visible to the naked eye is the main cause of large scale magnetic phenomena in the sun. These magnetic fields in turn result in e.g. solar activity cycles, sunspots and flares.
Even though these effects are widely known and documented, studying their creation is hard mathematically as the system consists of Navier-Stokes equations coupled with Maxwell equations under the extreme circumstances of the sun.
Mean field theory was created in the 20th century to ease these calculations. These theories average over turbulence and obtain a mean electromotive force that drives the solar dynamo. Mean field theory was very successful in providing insight of solar phenomena, but due to their generality they lose some specificity.
Within last few decades solving these equations by straight integration with magnetohydrodynamic simulation programs has become an another option, but due to computational costs it is still hard to get knowledge of the processes that create solar magnetic fields.
In my masters thesis I implemented a mean field simulator routines to a widely used magnetohydrodynamic simulator and compared results from mean field simulations to ones done by large scale simulations. The goal was to make the gap between theory and widely used methods in computational astrophysics shorter.
In my lecture I will try to explain how solar magnetic field is generated, how turbulence can be averaged over in mean field theories and how to simulate a simple version of the sun in your computer.
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Physical String - Analysis of the Effect String Properties have on String Instrument Sound
The primary goal in string instrument construction is obtaining good sound. While opinions on what is considered good may differ, physics allows us to represent sound as superposition of oscillations of various frequencies and amplitudes. The effect of string properties such as tension, length, radius, mass and material on the frequency-amplitude graph (representing string sound) will be considered for a physical string, with the goal of determining how valid is the ''ideal string'' approximation and what effects should an instrument designer (as well as a working musician) have in mind when choosing strings.
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Reconstruction of the CMS Pixel Pilot Blade
The Compact Muon Solenoid (CMS) is a general-purpose detector used to study the products of high energy particle interactions at the CERN LHC. The silicon pixel detector is the innermost component of the CMS tracking system. The present pixel detector will be replaced by an upgraded version, called the Phase 1 Pixel Upgrade in the beginning of 2017.
During the last shutdown period of the LHC, a third disk was inserted into the present two-disk forward pixel detector. The new disk consists of eight modules that use new digital Read-Out Chips and a prototype readout system. Testing the performance of this Pilot System enables us to gain experience with the CMS Pixel Phase 1 Upgrade modules. In the talk, my experiences with the Pilot System simulation, the offline calibration procedures, and the re-commissioning of the pixel detector during first data taking in 2016 will be presented, with special regard to these new modules.
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Cosmological axion - a Dark Matter candidate
The aim of this talk is to present the kind of reasoning behind a new theory of high energy physics. Specifically, we look at the Strong CP Problem in QCD - starting with a quick review of the QCD Lagrangian, we explain how the complex structure of the QCD vacuum leads us to include an additional term in the Lagrangian, which turns out to violate CP symmetry. Comparing this prediction to negative experimental results, we conclude that the new CP-violating term must be heavily suppressed, for reasons that go beyond the Standard Model. This is indeed a good example of the so-called naturalness problem theoretical physicists often run into. We then motivate the Peccei-Quinn proposal of an additional U(1) global symmetry as the simplest and most elegant solution to the Strong CP Problem, and work through its consequences both in particle physics and cosmology. In particular, we are interested in the dynamics of the pseudo-Nambu-Goldstone boson that arises from the breaking of this additional symmetry - the axion - and the way it explains the observed absence of CP violation in the strong sector. We narrow down the properties of the axion to those of a very light, very weakly interacting, neutral, scalar particle, which in turns makes it a good candidate for Dark Matter. Focusing now on the cosmological aspects of the theory, we discuss thermal and non-thermal productions in the early universe. Time permitting, we close our presentation with a brief overview of the status of experimental searches for axions, both in collider particle physics and cosmology/astrophysics.
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Outreach and Physics Education in the 2020
The way we communicate with each other is changing each day. We have gone from face to face interactions using the World Wide Web on Desktop computers, to using smart phones for Skype or FaceTime, and recently having watches send replies to each other in a matter of seconds. If we traveled back in time to the 1950s and spoke directly to people about the future, they would probably respond by saying, “I would never expect a person to see another person live on a television screen.” Even growing up watching Willy Wonka and the Chocolate Factory, nobody would have imagined during the scene when TV boy is transported to a small screen disappearing in front of everyone. Today, I will tell you a story of how outreach and physics education will be done in 2020. Just imagine sitting in a classroom by yourself, with no classmates or even a professor. Think of a hologram appearing in front of your eyes, asking you questions in Physics, and moving around in the classroom teaching you the Theory of Relativity. The hologram would be programmed to look exactly how you want, with your own specifications, and speak to you in a way that makes you learn the materials. Many of you would say exactly what someone back in 1950s would, “This is futuristic, and not possible to have someone teach me without being physically present in a room.” However, this idea is currently being tested, and we are not far away from universities moving towards buying technology to replace professors. In my talk, the focus will be on discussing the physics of holograms, and how in 2020 you will be taught by one.
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Nuclear reactor, neutrons and perfect-crystalls
Nuclear research reactors are located for instance in Vienna (Austria), Garching (Germany), Villigen (Switzerland), or Grenoble (France). They can be used e.g. to produce a neutron beam for neutron scattering experiments, tomography, as well as interferometry. Such an interferometer, which is similar to the one used for x-ray interferometry was successfully tested for the first time in 1974 in Vienna with thermal neutrons.
The extracted neutron beam of the reactor can pass through a crystalline medium. In this case the neutron beam changes its phase, however at a certain angle between the beam and the crystal (Bragg condition) an additional diffracted beam appears (beam splitter). Such beam splitters are used as part of a neutron-interferometer as well as a sample within this interferometer.
We study the phase shift of the neutron beam, induced by a crystalline sample in the vicinity of the Bragg condition. The interferometer with its phase shifter is necessary to measure this phase shift.
We also searched for further influences on the phase and found a sensitive dependence on the rocking angle, monochromator function and beam divergence. The rocking angle describes the alignment of the monochromator crystal relative to the interferometer. The monochromator function describes which monochromator is used (mosaicity of the crystal). While its neutron beam divergence depends on the wavelength.
Our calculations with the software IFMSIM are in good agreement with the observed data.
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Optically Induced Dielectric Changes in Organic Semiconductors and their Non-Adherence to Classical Plasma Theory
In organic electronics on can optically induce dielectric changes. Current Classical Plasma Theory was derived for high mobility silicon and fails to account for the dielectric changes observed in low mobility organic semiconductors. This talk explains the basics of organic electronics, how one can measure dielectric changes, both experimentally and as predicted by theory and what causes the differences between them.
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Reducing effect of RV scatter around active M Dwarfs
In the last 20 years, since the discovery of the first exoplanet around a main sequence type star, there has been a great period of discovery of new planets. Many of these planets are of types that had not even been considered before their discovery and do not exist within our own solar system. Some of these, such as Hot Jupiters, exist in areas of their systems that they could not have formed in and has resulted in additional research and understanding of how planetary systems form. These planets have been discovered by an ever increasing variety of methods. The first, and still most used, method was that of high precision radial velocity measurements of the planet’s parent star. The second, most popularized by NASA’s Kepler mission, is the transit method. This method observes a star for a long period of time to see the periodic luminosity decrease of a planet moving in front of the star. Other methods include gravitational microlensing, direct imaging and astrometry. Each method has a particular set of planets that is ideal for detection and reveals differing information about these planets once discovered. Additionally each of these methods can be affected by differing characteristics of the observed star such as stellar activity influence on precision radial velocity measurements. Taken together these factors have lead to a very informative distribution of discovered planets that still has significant observational biases. It is the hope of everyone in the field that upcoming missions and surveys, such as GAIA, JWST and CARMENES, will help to close some of these gaps and give us a better picture of the planetary distribution in our galaxy.
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Active Galactic Nuclei - Are they responsible for the IceCube neutrino detections?
An Active Galactic Nucleus (AGN) is a compact central region of a galaxy that has extremely high luminosity that even outshines the combined luminosity of the rest of the galaxy. The emissions from these galaxies are observed to be bright at all wavelengths. Radio-loud AGN have relativistic outflows of matter, perpendicular to the disk of the host galaxy. In a subclass of AGN, called blazars, these jets point at Earth.It has been theoretically predicted that AGNs can emit neutrinos. Neutrinos can travel large cosmic distances greatly undisturbed owning to their small size, extremely low mass and charge neutrality. Moreover, neutrinos cannot be detected directly, because they do not ionize the materials they are passing through. In the IceCube detector, they are indirectly detected by the Cherenkov radiation emitted when an incoming neutrino creates an electron (or muon) in the ice. An analysis of this radiation can help us determine the general direction for the incoming neutrino ’event’ and also the energy of the event. We investigated if blazars from the Fermi 3LAC catalogue within the error bars of certain neutrino events observed by the IceCube Neutrino Observatory could explain the respective neutrino counts.
There are certain estimated atmospheric processes that can amount to neutrino production in the atmosphere. These are however lower in energy. Hence to account for neutrinos of mainly cosmic origin, neutrino events with energies greater than 100 TeV were considered in our investigation and the observations were limited to the X-ray and γ-ray ranges. The sources (AGNs) that were considered for each event were the Fermi 3LAC sources which were within the error boxes of the respective neutrino events.The X-ray data was used from Swift/XRT, ROSAT and INTEGRAL observations. The γ -ray data was used from the Fermi/LAT 3FGL catalogue. The data was taken over a period of 998 days. Log parabolic model was used to understand the behaviour of blazars and to fit the data. Fitting for the observations was done in the ISIS software package developed by the MIT. Chi-sqr analysis was used to obtain the best fit for observational data of each blazar. The parameters obtained by the best fit were used to calculate the neutrino counts from the respective blazars. The neutrino counts were tallied with the neutrino observations published by the IceCube Neutrino Observatory.
94 AGNs were analyzed from 7 neutrino events. It was observed that most of the sources gave very low neutrino count. However, the combined count from all the blazars in each event was significant.
Preliminary results show that AGNs can explain the neutrino counts in certain events. This is, however, not true for all the events considered as AGNs for certain events did not have good observational data and thus those sources couldn’t be trusted.
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The Molecular Biocompass
Want to know how migratory birds can find their way to Africa? Several species of animals, most notably migration birds, have been shown to use the Earth's magnetic field to navigate by. This talk will briefly cover the quantum biological theory of radical pair formation that explains the sensitivity to magnetic fields. A receptor molecule called cryptochrome located in their eyes was suggested to serve as a magnetoreceptor. However, the exact mechanism of how the magnetoreceptive properties of cryptochrome causes birds' ability to navigate is not fully understood, especially when the changes of the external magnetic field are small. A recent investigation suggests that cryptochrome couple to a larger protein complex that acts as a biological compass needle. This talk will guide you through the construction and validity of the proposed biological compass needle.
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Topological insulators - Synthesis and transport measurements
Topological insulators (TI) are a new class of quantum materials. What makes them interesting is their insulating bulk and conducting surface states. The goal of this work was to synthesise a TI with a large bulk resistivity so that the surface states could be studied by transport measurements. Two different TI were synthesized BiSbTeSe2 and BiSbTe2S. Both showed an increase in resistivity with lowering the temperature. An increase of an order of magnitude in resistivity was observed in BiSbTeSe2 and two orders of magnitude in BiSbTe2S. A holder for the ionic-liquid gating experiment was also built in order to make the study of surface states easier with transport measurements. A successful manipulation of surface state carrier concentration was achieved with the ionic-liquid gating setup.
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n-MOSFET Aging Measurements and Modeling
The presented work focuses on aging effects due to hot-carrier-injection (HCI) in MOSFETs. Hot carrier refers to fast electrons in the conducting channel. Electrons are accelerated by very high electric fields in the pinch-off region of the transistor. Their energy is high enough to generate trap states at the interface between the semiconductor and the gate oxide. Those traps capture charge which shifts the characteristics of the transistor. To gain knowledge about the HCI effects, various measurements on n-MOSFET devices with a channel length of 0.18 µm have been performed. The devices were provided by ams AG. Aging experiments were conducted with different stress voltages and important device parameters were extracted to find how they change over time. It is observed that the stress effects scale with stress voltage and time. A short stress at high voltage causes the same threshold voltage shift as a long stress at low bias voltage. This scaling behavior is used to predict aging effects at real life operating conditions. Since device aging due to stress is a major issue in modern semiconductor fabrication, it is of importance to understand the effects and find reliable ways of predicting how changes in the devices will affect the overall circuit performance. We used the HiSIM2 aging model developed at Hiroshima University. This model predicts the device degradation based on the bulk current which is affected by impact ionization events. A beta version of HiSIM2 was used to fit the behavior of the ams AG 0.18 µm MOSFET technology.
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Gravity - It can be derived from matter!
Einstein postulated the dynamics of gravity by writing down the theory of General Relativity in 1915. With the dynamics, one gets the kinematics of spacetime for free. However, it was shown in the 1970's by Kuchar et al that the other way round is actually far more convenient. By specifing the kinematics of a spacetime carrying a Lorentzian metric -- that is, saying how three-dimensional hypersurfaces carrying physical data evolve -- one can fully derive the gravitational Lagrangian from General Relativity. The only question remains how to arrive at the kinematics of spacetime.
This question was answered by Schuller et al in recent years. The kinematics of spacetime determined by the matter present on the spacetime. This matter does not necessarily need to be from the Standard Model of Particle Physics. Rather, any matter theory that is predicitive and canonically quantizable is allowed. That means, a matter model has to allow basic physics, namely well-posed time evolution and having a corresponding quantum theory of matter. Then, the kinematics of the corresponding spacetime are settled. Based on the concept of geometrodynamics by Wheeler et al, Schuller et al then were able to show how to find the dynamics of spacetime and thus gravity as the solution of a set of partial differential equations.
In my talk, I will show the main results regarding the matter input into the kinematics of spacetime as well as the way from the kinematics to the gravitational dynamics. In the end, I will give a first glimpse at possible physical examples for new gravitational dynamics.
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Study of exotic nuclei with radioactive ion beams
Studies of exotic nuclei (nuclei with ratios of neutron number N to proton number Z much larger or much smaller than those of nuclei found in nature) are at the forefront of nuclear research. Radioactive ion beam experiments are held in Japan, France and the USA. A lot of phenomena can be observed in exotic nuclei only. Certain nuclei have a nuclear halo (a core nucleus is surrounded by a halo of orbiting protons or neutrons). We have been working with the data collected in an experiment performed at Michigan NSCL (National Superconducting Cyclotron Laboratory) in 2012. I have used ROOT and GrROOT for the analysis of data. After incoming and transmitted beam identification I examined parallel momentum and gamma energy distributions of the identified nuclei. I would like to present the results of the data-analysis after a short description of the experiment.
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A path-sum approach for Weyl and Dirac Quantum Walks
Quantum Walks are the quantum counterpart of classical Random Walks which are models describing the motion of a particle on a lattice in discrete time-steps. Recently they have been considered as a possible fundamental description of relativistic particles [1-9]. We consider here the Weyl and Dirac Quantum Walks, derived in [10] from general principles, from which one recovers Weyl's and Dirac's equations in the limit of small wave-vectors.
The walk dynamics is given by an update rule which can be conveniently expressed in terms of transition matrices acting on the internal degree of freedom (coin space). Exploiting the semigroup structure of the matrices one can study the walk evolution in terms of a path-sum on the lattice, leading to analytical solutions of the walk in direct space. Numerical analysis of the walk can be performed exploiting the update rule in direct space or by efficient FFT algorithms in momentum space, showing some general properties of these models, such as the Zitterbewegung effect [11].
A quantum walk, as its classical counterpart, can be viewed as the dynamical description of a single particle hopping in discrete steps from one lattice site to another. In order to study multi-particles systems one has to generalise the framework of quantum walks this leads to the notion of Quantum Cellular Automata, which are the corresponding quantum version of Cellular Automata, originally introduced by von Neumann. The connection between these two structures can be made explicit by replacing the quantum state with a quantum field, evaluated at each lattice site, obtaining a ''second quantisation'' of the walk. It would be interesting to explore the phenomenology of free quantum cellular automata in the thermodynamic limit. For example, one can study how the Chandrasekhar limit of white dwarfs is modified within this framework.
[1] Succi, S.; Benzi, R. Lattice Boltzmann equation for quantum mechanics. Physica D Nonlinear Phenomena 1993, 69, 327–332.
[2] Bialynicki-Birula, I. Weyl, Dirac, and Maxwell equations on a lattice as unitary cellular automata. Physical Review D 1994, 49, 6920–6927.
[3] Meyer, D.A. From quantum cellular automata to quantum lattice gases. Journal of Statistical Physics 1996, 85, 551–574.
[4] Strauch, F. Relativistic quantum walks. Physical Review A 2006, 73, 054302.
[5] Yepez, J. Quantum lattice-gas model for computational fluid dynamics. Physical Review E 2001, 63, 046702.
[6] D’Ariano, G.M. The quantum field as a quantum computer. Physics Letters A 2012, 376, 697 – 702.
[7] Bisio, A.; D’Ariano, G.M.; Tosini, A. Quantum field as a quantum cellular automaton The Dirac free evolution in one dimension. Annals of Physics 2015, 354, 244 – 264.
[8] Arrighi, P.; Nesme, V.; Forets, M. The Dirac equation as a quantum walk higher dimensions, observational convergence. Journal of Physics A Mathematical and Theoretical 2014, 47, 465302.
[9] Farrelly, T.C.; Short, A.J. Discrete spacetime and relativistic quantum particles. Phys. Rev. A 2014, 89, 062109.
[10] D’Ariano, G.M.; Perinotti, P. Derivation of the Dirac equation from principles of information processing. Physical Review A 2014, 90.
[11] D'Ariano, Giacomo Mauro, et al. ''Discrete time Dirac quantum walk in 3+ 1 dimensions.'' arXiv preprint arXiv:1603.06442 (2016).
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CDT -A Nonperturbative Quantum Gravity Theory
Numerical methods are playing an important role in many fields of theoretical physics and the power of computational technology is able to support the needs of it. There is some progress that allowed to understand and solve the problems of quantum gravity via these methods, e.g. Causal Dynamical Triangulations (CDT). CDT is using a nonperturbative quantum field approach via lattice regularization. CDT is based on Feynman path integral method and Reggie Calculus, where d-dimensional triangles (simplices) generate the lattice and Wick rotated (t $\rightarrow$ -i$\tau$) Lorentzian path integral turns to Euclidean regime. This theory deals with causality problems after summing over causal geometries only. Previous researches measured the behaviour of the coupling constants and other attributes of CDT in spherical ($ S^3 \times S^1 $ ) topology. During the recent studies we measured the toroidal condition ($M=T^3 \times S^1$, where $ T^3=S^1 \times S^1 \times S^1$ ) and realised the that the theory of CDT is not topology independent, however there is some behaviour of the system that remains the same in both cases.
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Creation of Superoxide at the Qo active site of the BC1 complex
The creation of superoxide is thought to be a major cause for cellular ageing due to the highly toxic effects of even small concentrations. The cytochrome bc1 complex, also called Complex III, is the third protein in the electron transport chain, which, coupled with proton transport serves to create an electrochemical gradient across the membrane.
Using a combination of molecular dynamics simulation and quantum chemistry, carried out numerically on the Abacus 2.0 supercomputer at SDU, the details of the electron pathways near the Qo site is studied.
This topic illustrates well how the boundaries between physics, chemistry and biology fades when entering the world of quantum mechanics.
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Electric and magnetic characterization of the fluorescence properties of a quantum dot-liquid crystal composite
Fluorescence is a type of luminescence which can occur in the mostly known chemical states are gas, liquid and solid. Fluorescence is a secondary effect of a photon absorption, which promotes a singlet ground state to a singlet excited one. In comparison with phosphorescence, the spin of the excited electron remains paired with the one in the ground state. When the excited atom or molecule returns to its ground state, a photon is emitted leading to a visible luminescent effect. The emitted photon has lower energy, which means it has a longer wavelength than the absorbed photon. Fluorescence has found its place in various applications. These include fields such as biotechnology and life sciences, where fluorescence can be used in cellular signaling or DNA/RNA sequence identification, technology, when used in a quantum dot setup, display technology, one of the advantages being low power consumption, photonics and communications. In this paper, we study the wavelength shift of the quantum dot transition and the optical transmission performance of the nematic liquid crystal-quantum dot sample under external magnetic and electric fields.
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A trigger ASIC for the Cherenkov Telescope Array
High energy astrophysics became increasingly more advanced since its discovery by Viktor Hess in 1912. Very high energetic (VHE) gamma-ray radiation is produced by cosmic rays arising from a number of different sources in the universe. Examples for such sources are AGN or supernova remnants. For detecting VHE gamma rays, large detectors are required due to the fact that their flux is very low. The future Cherenkov Telescope Array (CTA) will cover such a big area 4 km2 and is expected to be sensitive to gamma-rays in the range between 10 GeV and 300 TeV. Gamma rays produce an air shower in the atmosphere whose particles emit short flashes of Cherenkov light. Therefore, fast cameras with special read-out electronics need to be developed to allow for very short (nanosecond) exposure to fulfill the scientific goals of CTA. In this talk the trigger ASIC T5TEA will be presented which is able to trigger at very low thresholds of a few single photo-electrons (p.e.). T5TEA is one of the proposed systems to be implemented in the cameras of the future CTA.
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Oxidic Thin-Film Quasicrystals
The discovery of quasicrystals in 1982 by Dan Shechtman[1] led not only to the award of a Nobel Prize, but opened a new field of research in the physics community. It was believed that due to the restriction theorem, crystalline structures could only exist in two-, three-, four- and sixfold symmetry. The definition of a crystal was connected to translational symmetry, which is not fulfilled for quasicrystals. Due to their discovery, the definition had to be broadened to any solid having an essentially discrete diffraction diagram, and by 'aperiodic crystal' we mean any crystal in which three-dimensional lattice periodicity can be considered to be absent[2].\
Quasicrystals do not only differ from other structures because of their art and beauty in nature. They vary in electronical, mechanical and chemical properties such as an extremely high electric resistivity in aluminium dominated alloys, brittleness at low temperatures and on the same hand extremely deformation at high temperatures, or low wetting of surfaces and hydrogen storage,
to name just a few. \
A new member in the family of quasicrystals it the recently discovered 2D oxide quasicrystal formed from BaTiO$_3$ grown on Pt(111)[3]. This example of ultrathin quasicrystals derived from a prototypical periodic perovskite oxide extends the quasicrystal concept to a broader range of materials. \
This talk will give an introduction to the concepts of quasicrystals as a third form of solid state matter besides periodic crystals and the amorphous state. Furthermore, I will present the whole new field of oxide quasicrystals on the example of BaTiO$_3$ on Pt(111). The most recent results on SrTiO$_3$ which also shows a perovskite structure, will be covered. Despite a slightly reduced lattice constant, it also forms an oxidic quasicrystal at the Pt(111) surface, hence it paves the way to a deeper understanding of this interesting example of quasicrystal-crystal heteroepitaxy.
[1] D.Shechtman, J. Blech, D.Gratias, J.W. Cahn; Phys.Rev. Lett. 53, 1951 (1984)
[2] Acta Crystallographica Section A, 48, 922 (1992)
[3] S.Förster, K.Meinel, R.Hammer, M.Trautmann and W.Widdra, Nature, 502, 215 (2013)
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Large-$N_c$ Contraints on Nuclear Forces
Nuclear Forces have been studied for a long time, leading to the modern theory of Quantum Chromodynamics (QCD). Out of the several approaches to QCD, two are being tested for mutual consistency Large-$N_c$ QCD and Chiral Perturbation Theory (ChPT).\
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Large-$N_c$ is a perturbative analysis for QCD, where the number of colors, $N_c$, is assumed to be large (instead of 3).\
ChPT is an effective field theory (i.e. a low energy approximation) with Hadrons (e.g Nucleons and Pions) as effective degrees of freedom.\
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This talk will give a general introduction to Large-$N_c$ QCD, followed by a small showcase of its implications and a consistency check with ChPT.
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Quantum game theory
What do we get if we combine game theory with quantum theory? My lecture aims to answer that question.
Game theory is one of the most widely used mathematical tool in all sciences. It gives us a deeper understanding of some evolutionary proccesses, it is often used to analyze social dilemmas, not to mention the applications in economy. The reason of this popularity is the mathematical simplicity, it is easy to modify game theory to certain problems. In my lecture I will focus on quantum game theory, which will be hopefully applicable in quantum computing in the future.
I will start my presentation with a brief introduction to classical game theory, showing some easy examples. Then, I will introduce quantum game theory and explain the differences through one example. Knowledge of basic quantummechanics is recommended.
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Accelerators on a Chip
Nowadays commonly used particle accelerators consist of radio-frequency cavities. Their performance is limited by the electromagnetic breakdown field of the inner metallic cavity surfaces. This breakdown happens at a field strength of approximately 100 MV/m [1] which restricts the achievable acceleration gradient of the device. To overcome this limitation, there has been developed several techniques of laser-driven acceleration in recent years.
In this contribution we focus on one of these techniques, namely the dielectric laser acceleration (DLA), which is based on the synchronous interaction between electron and optical near-fields of a nanostructure and allows to apply accelerating fields with amplitude exceeding GV/m [2]. By using dielectrics instead of metals or superconductors and optical frequencies of the driving field, the field breakdown threshold increases by two orders of magnitude. Although the laser-driven particle acceleration in the vicinity of metallic grating was proposed already in 1960s [3, 4], it took until 2013 to demonstrate the first experimental proof of this concept. It was confirmed nearly simultaneously by DLA experiments of the AChIP collaboration in Erlangen [5] and Stanford [6].
The designated mid-term aim of DLA is achieving acceleration rates which are beyond GV/m. Up to now, peak acceleration gradients of 300 MeV/m have already been observed [7]. Current tasks include both development of a suitable laser-triggered nanotip electron source and further development of the nanostructures used for generation of accelerating near-fields. Overall millimetre-sized sub-relativistic electron guns appear to be possible within the next years [8].
References [1] Solyak, N. A., Schroeder, C. B., Leemans, W. & Esarey, E. Gradient Limitations in Room Temperature and Superconducting Acceleration Structures. In AIP Conference Proceedings, 365–372 (AIP, 2009). [2] Rosenzweig, J., Murokh, A. & Pellegrini, C. A proposed dielectric-loaded resonant laser accelerator. Physical Review Letters 74, 2467–2470 (1995). [3] Shimoda, K. Proposal for an Electron Accelerator Using an Optical Maser. Applied Optics 1, 33 (1962). [4] Takeda, Y. & Matsui, I. Laser linac with grating. Nuclear Instruments and Methods 62, 306–310 (1968). [5] Breuer, J. & Hommelhoff, P. Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure. Physical Review Letters 111, 134803 (2013). [6] Peralta, E. a., Soong, K., England, R. J., Colby, E. R., Wu, Z., Montazeri, B., McGuin- ness, C., McNeur, J., Leedle, K. J., Walz, D., Sozer, E. B., Cowan, B., Schwartz, B., Travish, G. & Byer, R. L. Demonstration of electron acceleration in a laser-driven dielectric microstructure. Nature 503, 91–94 (2013). [7] Breuer, J., McNeur, J. & Hommelhoff, P. Dielectric laser acceleration of electrons in the vicinity of single and double grating structures—theory and simulations. Journal of Physics B Atomic, Molecular and Optical Physics 47, 234004 (2014). arXiv:1407.6688v1. [8] McNeur, J., Kozak, M., Schonenberger, N., Leedle, K. J., Deng, H., Ceballos, A., Hoogland, H., Ruehl, A., Hartl, I. & Solgaard, O. Elements of a dielectric laser accelerator. arXiv preprint arXiv 1604.07684 1–7 (2016).
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Study of Instabilities in the Great Red Spot of Jupiter
We study hydrodynamic instabilities in the velocity shear flows. In particular, we discuss instabilities in the Great Red Spot of Jupiter. For this purpose, we derived the behavior of velocity and density of the flow by means of the governing equations, Euler equation and the continuity equation. We studied the linear analysis of the problem and solved the obtained differential equations by using MATLAB. It has been shown that initial velocity perturbations inevitably leads to generation of sound waves and vise versa – by inducing initially only sound waves in due course of time velocity perturbations also occur. We have found that wave energy increases exponentially so fast that the process either terminates by means of some processes or there are some other sources of energy.
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Influence of one specific turbulence on the stable structure of tornadoes
There is large diversity of instabilities in nature which are able to absorb the energy from pre-existing wave and abolish its stable structure. One more such kind of instability will be considered in this paper. More precisely, the role of this particular turbulence in decaying process of tornadoes will be verified by numerical methods. The idea of numerical analysis is that, possessing information about initial conditions of the flow (dissipation of velocities and density) we can determine the energy of turbulent wave at any moment in future. The period required for energy absorption will be compared with the life-span of average tornadoes on the earth.
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Gravitational dynamics beyond the standard model - a case study
Since the 70s it is known that Einstein's theory of general relativity can be derived by considering deformations of suitable initial data surfaces. In recent years, this idea was further developed by Schuller et al. and led to a universal set of linear partial differential equations that allows to determine the Lagrangians of any tensorial geometry. The only ingredient is a matter theory coupling to this geometry that is predictive and canonically quantizable.
In this talk, the geometry required for the most general linear electrodynamics is used as an exemplary theory beyond the standard model to discuss the programme, the physical effects one can now calculate within this setup and the relation to our current understanding of physics.
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High resolution imaging of scanning tunneling luminescence from InGaN/GaN QWs
The pioneers Isamu Akasaki, Hiroshi Amano and Shuji Nakamura were jointly rewarded with the 2014 Nobel prize ''for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources'' [1]. However nitride LEDs exhibit such high efficiency performances only when operated at low current densities.
If it would also be possible to improve the efficiency of LEDs at high current densities which is mandatory for cheap lamps, the energy consumption due to lighting and the cost of ownership would drastically lower [2]. Therefore LEDs have to work on their physical limit. However working at high current densities leads to a non-linear decrease of the efficiency, the so called droop [3]. To understand this droop and as a conclusion improve LEDs, the used materials InGaN/GaN have to be understood better. There are several processes from which this droop in the external quantum efficiency can origin e.g. quantum-confined stark effect, Auger recombination, electron overflow … [4]. Taking a look at the materials itself, strong disorder in the In content is exhibited [5] which leads to localisation effects. This might also decrease the external quantum efficiency. High resolution imaging of scanning tunneling luminescence from InGaN/GaN QWs might provide information about the impact of disorder and localisation on the droop.
References [1] ''The Nobel Prize in Physics 2014''. Nobelprize.org. Nobel Media AB 2014. Web. 25 Jun 2016. [2] Weisbuch, C., Piccardo, M., Martinelli, L., Iveland, J., Peretti, J. and Speck, J. S. (2015), The efficiency challenge of nitride light-emitting diodes for lighting. Phys. Status Solidi A, 212:899–913. doi:10.1002/pssa.201431868 [3] T. Mukai, M. Yamada and S. Nakamura, Characteristics of InGaN-Based UV/Blue/Green/Amber/Red Light-Emitting Diodes, Jpn. J. Appl. Phys., Part 1 38, 3976 (1999). [4] Polovodov, P. (2015), Cathodoluminescence in semiconductor structures under local tunneling electron injection (Doctoral dissertation) [5] Yuh-Renn Wu, R. Shivaraman, Kuan-Chung Wang, and J. S. Speck, Analyzing the physical properties of InGaN multiple quantum well LEDs from nano scale structure, Appl. Phys. Lett. 101, 083505 (2012)
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The role of cross-linking proteins and microtubule pivoting in formation of parallel bundles
During mitosis, microtubules (MT) form a spindle , which is responsible for proper segregation of the genetic material between two daughter cells. Most of the spindle MTs are organized into bundles by cross-linking proteins. A key question is what are the physical principles underlying the formation and stability of MT bundles. Mean field theory for the formation of MT bundles suggests that elastic forces from cross-linking proteins and thermally driven pivoting of MTs are sufficient for formation of stable parallel MT bundles. However, it is unsure how the discrete nature of cross-linking proteins affects this process. We have studied formation of parallel bundles using numerical simulations. By calculating cross-linking protein distributions and average bundling times for MTs, we can compare the results of the numerical simulations with the mean-filed theory and experimental data.
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Optical conductivity of graphene
We study the optical conductivity of graphene described by nearest neighbor tight binding (TB) model. The band structure of the graphene in TB model is presented. A closed expression is derived for the current-current correlation function and from this result the optical conductivity is obtained. Our closed analytical expression reflects the underlying symmetry of the graphene. To the best of our knowledge this result is not known in the literature. Using our general result the allowed electronic transitions between different electronic states are demonstrated. We also study numerically the optical conductivity as a function of the frequency of the incident light at a given temperature and chemical potential. Our theoretical approach can be extended to other 2D materials such as bilayer graphene, silicene and Dirac-Weyl system.
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Phase diagrams in QCD
QCD phase diagram is a conventional graph of strongly interacting matter phase transitions. Although the description of strong interactions is a main part of quantum chromodynamics, phase transitions in QCD can be described using traditional thermodynamic and statistical physics methods.
I formulate a transparent phenomenological model for the phase transition between quark-gluon plasma and hadronic phase which is approximated as an ideal pion gas. Comparing thermodynamic parameters (for example pressure) of two different hadronic states of QCD matter one can see an inconsistency between pion gas and quark-gluon plasma (QGP). It means that classical thermodynamic methods are not enough and we shall use another approximation for the diagram - MIT Bag Model, which corrects thermodynamic parameters of pion gas and QGP to make the phase transition possible.
References 1. Vogt R., Ultrarelativistic Heavy-Ion Collisions. First Edition, Elsevier, Amsterdam, The Netherlands ( 2007) 2. Braun-Munzinger P., Wambach J., The Phase Diagram of Strongly Interacting Matter. Rev. Mod. Phys. Vol 81 (2009) 1031-1050
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Prototype of Time-of-Flight detector for NA61/SHINE experiment
The NA61/SHINE experiment is a heavy-ion, fixed target experiment, constructed to investigate Quark Gluon Plasma and it's properties, and to describe the phase diagram of strongly interacting matter. One of the parts of the detector is the Time-of-Flight system – necessary for particle identification. Because of its meaning for the experiment, constant improvements are needed. In my work, I tried to decrease the costs of the detector without changing the most important parameters (time resolution). The prototype was constructed using the scintillation crystals and silicon photomultipliers. To obtain the time resolution of the prototype the SiPM waveforms were recorded and analyzed with the software constant fraction algorithm developed for this purpose.
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PEDOT:PSS as a transparent electrode in perovskite solar cells
Perovskites are a group of compounds crystallizing in a distinctive crystal structure ABX$_3$, called later perovskite structure. They appear in both, natural (e.g. calcium titanate) and synthetic (e.g. CH3NH3PbI3) form. CH3NH3PbI3 found use in solar cells, called later perovskite solar cells [1,2]. It is a material that belongs to mixed organic-inorganic lead halide perovskites. Thanks to their dual nature, they can be used for flexible, semi-translucent and easy in fabrication solar cells with efficiencies catching up those based on polycrystalline silicon – 22.1% [3]. Usually, in perovskite solar cells the transparent (bottom) electrode is made of ITO, which is a relatively expensive material. That is why research on substitutes is carried out.
My talk will be divided into two parts. In the first one I will introduce perovskites along with discussing their structure, main properties and applications in solar cells. Later I will present results of my work on PEDOT:PSS PH1000 as a possible transparent electrode in perovskite solar cells.
References [1] O. Malinkiewicz, A. Yella, Y. H. Lee, G. M. Espallargas, M. Grätzel, M. K. Nazeeruddin, H. J. Bolink, Perovskite solar cells employing organic charge-transport layers, Nature Photonics 2014, 8, 128-132. [2] H. Jung, N. Park, Perovskite solar cells: from materials to devices, Small, 2014, 11, 10-25. [3] NREL, available on-line: www.nrel.gov/ncpv/images/efficiency_chart.jpg
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Exotic nuclei decay products detection by using Optical Time Projection Chamber (OTPC)
Nuclei with ratios of neutron number N to proton number Z significantly different than occurring in nature are called exotic nuclei. Synthesis and study properties of nuclei at the border of stability are the main area of interest of Flerov Laboratory of Nuclear Reactions in Dubna. In order to detect light exotic nuclei decay products fragments is used separation system ACCULINNA and novel technique of charged particles detection OTPC - Optical Time Projection Chamber. Construction and principle of operation of OTPC spectrometer and analysis of experimental data - β - delayed particle emission radioactivity of 27S will be discussed.