Student posters abstracts
Laser driven ion acceleration at ELI-NP
Laser driven particle acceleration concentrate since the year 1990 the join efforts of multiple research communities laser, plasma and nuclear physics related. This interdisciplinary field has a deep impact not only on the theoretical studies of laser-plasma interaction, but also to a long series of applications related to plasma physics (ex. controlled fusion studies) to particle production (ex. neutrons,) are to the development of a new generation of particle acceleration. The laser driven particle acceleration is essentially on experiment driven field. On the other hand, the analysis of experimental data has always been related to PIC simulations and analytical modelling. In the presented work we try to use the analytical modelling of laser plasma interactions for the prediction of the particle acceleration characteristics in the case of ELI-NP facility. We are focused on the proton acceleration since the theoretical development is in this case the most developed. We consider also some cases of heavy ion acceleration relevant for ELI-NP.
Merging black holes
Scientist have detected a strong force at the middle of our galaxy that even light can not escape from this region. This is called ''black hole'' which has great effects on the geometry of the galaxies even though on universe while they are merging. It is possible that two black holes can merge when they become close enough. So, tremendous energy is released and the space fluctuate as producing gravitational waves. Physicist have found out thanks to LIGO experiment -ESA's project- that these ripples can be detected. I will explain how black holes are evolving and creating such waves in my poster.
Studies of Li/W interactions and their temperature dependence
Studies of Li/W interactions.In a Fusion Reactor based on liquid metals with a hot metal first wall, the issue of first wall erosion by the leaking metal from the divertor has to be addressed. Furthermore, the simultaneous impact of T ions may cause the formation of metal composites with an intolerable level of radioactive fuel. In particular, for a liquid lithium divertor and a hot W wall , chances of forming tritiated Li-W compounds must be considered, at least in the coldest parts of the first wall.
Physical properties of some transparent conductor oxides
The transparent conductors oxides(TCOs) exhibit a useful combination of physical properties (high optical transparency and high electrical conductivity). Here we provide an overview of the results on the structural, optical and electrical characterization of In2O3:Sn(ITO) and ZnO:Nd transparent oxide thin-films deposited on glass using rf-sputtering and Pulsed Electron Deposition (PED),respectively. Temperature dependent Hall effect and resistivity measurements was performed in the range 30 - 300 K; scattering mechanisms are discussed in order to explain the unusual temperature dependence of the electrical resistivity.
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).
The role Condensation Particle Counters in aerosol research
Concensation Particle Counters (also known as Condensation Nucleus Counters) measure the total number concentrations of particles which is an important measurement technique for particles less than 200 nm in aerosol research. However, particles in this size range are very difficult to measure using optical methods. That's why the main idea of CPC is to make the particles grow by condensing to a size range of 5-15 μm to make it possible to measure them by optical methods. In this poster I will introduce the specific working principle of CPCs, what types of CPC are used and what applications they have in aerosol science.
Magnetotransport properties of rare-earth-bearing half-Heusler phases (RTSb)
Polycrystalline samples of several ternaries with the chemical formula RTSb (R = Er, Lu, Y, Tb, Gd; T = Ni, Pd, Pt), crystallizing with the cubic MgAgAs-type structure, were investigated by means of magnetic susceptibility, electrical resistivity and magnetoresistivity measurements, carried out from 2 to 300 K. The nonmagnetic compounds LuNiSb, LuPdSb and YPdSb were found to exhibit negative temperature coefficients of the resistivity in the whole temperature range studied. In contrast, the resistivity of antiferromagnetic ErPdSb, GdPtSb and TbPtSb was found to decrease with lowering the temperature down to the onset of the ordered state. In turn, the resistivity of nonmagnetic YPtSb and antiferromagnetic ErNiSb was established to vary with temperature in a more complex non-monotonic manner. All the materials studied were classified as semimetals or narrow band-gap semiconductors, in line with the results of electronic band structure calculations, reported in the literature.
Remarkably, the low-temperature electrical resistivity of LuNiSb, ErNiSb, YPdSb and YPtSb, measured in zero and finite applied magnetic fields, was found to increase proportionally to the square-root of temperature, in a manner characteristic of structurally disordered metals, in which the low-temperature transport is notably influenced by electron-electron interactions. The scenario of quantum interference effects is supported by the observed large magnitude of the electrical resistivity and small values of the residual resistivity ratio, which both imply that the electrical transport in these materials is likely dominated by scattering conduction electrons on crystal structure imperfections.
Nano-surface Vanadim redox flow battery
As our society grows, the energy equirements of our devices and machines
increase. As we can see, there are many ways to generate electrical power. However there are less ways to store it. The only logical solution to this problem is to change our approach, to slowly move toward developing technologies that generate the energy demanded by our society in a friendlier and more efficient manner. Thus the demand for more efficient storage units will increase. To make use of all that energy , we have to develop new
energy storrage technologies that are both efficient and cheap. With this in mind, the subject discussed is about a flow battery that, with enough research and evelopement, can be one of the solutions for our future energy storage problem.
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.
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.
Comparative study of dALA as a precursor of Porphyrins and a Hypericum perforatum extract
Light-biological matter interactions have a great importance in our life; therefore, using sunlight as a therapeutic method has been explored and practiced since old times by the ancient civilizations. PDT (Photodynamic therapy), also known as photochemotherapy, uses nontoxic compounds that are light-sensitive; exposed selectively to light, they exhibit phototoxicity, becoming invasive to diseased cells (targets). The aim of this paper is to elaborate a comparative study of aminolevulinic acid as a precursor of porphyrins (used in Photodynamic therapy) and a Hypericum perforatum extract. Aminolevulinic acid (also known as 5-aminolevulinic acid or dALA) is the condensation result between Succynil-CoA and glycine in the heme forming process in mammals and chlorophyll in plants. Porphyrines are cyclic compounds generated by dALA that play an important role in the process of oxygen cycle. The study will consist of different monochromatic laser sources irradiation and UV irradiation (UV mercury lamp will be used). The spectral stability of the extract and dALA for different concentrations at various irradiation doses is studied.
The atomic scale structure of palladium nanoparticles studied by X-ray diffraction
Over the last few years an increasing interest in nanomaterials can be observed, mostly due to their numerous applications. Palladium nanoparticles show good catalytic properties, therefore it is essential to acquire information about their structure. The nanopalladium samples were obtained by deposition of the metal precursor in sol-gel silica and then chemically purified. In this work structural studies of palladium nanoparticles using X-ray powder diffraction and transmission electron microscopy methods are presented.
High quality experimental data were recorded using a laboratory powder diffractometer. After correction and normalization the diffraction data were converted to the real space representation in the form of the pair distribution function (PDF) via the Fourier sine transform. Such an approach is widely used when examining the structure of nanomaterials, as their structure cannot be described by the use of conventional crystallography. 
The X-ray diffraction studies were complemented by additional tests using the Rietveld refinement and the transmission electron microscopy observations. Using these techniques additional information about the structure of the investigated material was obtained. Transmission electron microscopy, as the most direct method, was applied to determine the size of nanoparticles.
All gained results were used to construct a computer model of the structure of palladium nanoparticles. Cartesian coordinates of atoms were computer generated under assumptions about the cell and disorder parameters. Then theoretical functions for a given cluster in both real and reciprocal space were calculated and compared with experimental results. 
Assumption about the undistorted crystalline struture is not valid for the examined palladium nanoparticles. Due to this reason, the theory of paracrystal  was applied to the computer simulations. This led to the significantly better agreement with experimental data. From the simulated model, information about structure such as lattice constants, Debye-Waller factors and grain sizes were extracted.
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Time-Resolved Photoion Yields of Hydroxyindoles
Rapid and efficient energy redistribution processes in biological chromophores following ultraviolet (UV) absorption are vital in providing an inherent photoprotection. Important examples of this include the DNA bases and the melanin pigments. Utilising gas-phase spectroscopic techniques can provide valuable insight into the fundamental dynamics of this mechanism, free of intermolecular and solvent effects. However, many large molecules of interest have low vapor pressures, with a propensity to decompose under vigorous heating, making gas-phase spectroscopy difficult.
This work presents a soft thermal desorption technique, incorporated within a time-of-flight mass spectrometer (TOFMS) set-up, facilitating studies of the UV-photoprotection in non-volatile model biological chromophores. Back irradiation of a thin sample foil with a CW laser produces neutral plumes of the molecule of interest. Time-resolved pump-probe photoion yield measurements have been used to investigate UV relaxation dynamics in 4, 5 and 6-hydroxyindole, as well as 5,6-dihydroxyindole. These are constituent building-blocks of the eumelanin complex. 5,6-dihydroxyindole appears to exhibit significantly different energy redistribution mechanisms by comparison, possibly confirming previous hypotheses of intramolecular group migration.
El Nino Southern Oscillation 's projections on different fields
Wavelet analysis is a powerful tool used to identify stationary and non-stationary oscillatory components in geophysical timeseries. I applied this technique on climate indices associated with the El Niño–Southern Oscillation(ENSO) phenomena, derived from several data sets, in order to investigate the stationarity of interanual variability related to ENSO in data obtained from different sources. The goal is to identify the fields in which ENSO related variations are most prominent.
Superconductivity on the edge of ferromagnetism – physical properties of La3Co compound
Numerous intermetallic compounds containing ferromagnetic elements like Ni, Fe or Co exist, but only few of them exhibit superconducting properties. Generally, compounds consisting of strongly magnetic atoms do not exhibit superconducting behaviour. However, superconductivity in the intermetallic compound La3Co, which contains a ferromagnetic element of the d block (Co), was reported , , . This unexpected result motivated us to carry out a detailed experimental examination of the properties of this material, which is the subject of this presentation.
The superconducting transition (Tc≈4.57 K) of La3Co was studied by measuring the magnetic susceptibility, resistivity and specific heat using the experimental system PPMS (Physical Property Measurement System) and the highlights of our results are presented. We also describe the procedure of preparation of the La3Co compound (arc melting under an atmosphere of highly purified argon; subsequent annealing in vacuum at 500 °C), the crystallographic structure of this material (orthorhombic, space group Pnma, number 62) and results of powder X-ray diffraction, which enabled the determination of the phase composition of the sample. Values of relevant physical parameters, recovered as a result of our experiments, and their implications for our understanding of the mechanism of superconductivity in this compound, will also be discussed.
Peak Effect on the DC Magnetization Curves of Nb-rich Nb-Ti alloys
We investigated the evolution of the peak effect on the DC magnetic hysteresis curves of Nb0.89Ti0.11 bulk samples by increasing the deformation degree. The alloy was prepared by arc melting. With a homogenization heat treatment at ~900 oC in vacuum, the critical temperature Tc becomes ~9.4 K. After a first cold-rolling (~60% deformation), the sample exhibits the well known anomalous peak effect (PE) not far from the DC irreversibility, and it can be evidenced over a wide temperature interval, up to close to Tc. By further increasing the deformation degree (through a second cold rolling, where the thickness was reduced from ~0.2 mm to 0.09 mm), the PE disappears, and a second magnetization peak (SMP) sets is, with the onset field located well below the DC irreversibility line. While the standard (zero-field cooling) magnetic measurements at low temperatures are strongly affected by thermo-magnetic instabilities, in the high-temperature range (T above 7 K) a true SMP develops. The change of PE into an SMP is due to the increase of vortex pinning through deformation, and both effects appear to be caused by the pinning induced disordering of the low field Bragg vortex glass.
Global Positioning System and Einstein's Theory
My poster is devoted to present the connection between the relativity theory and the GPS system. It is quite surprising that without taking the in uence of the gravity eld into account, one could not bene t from the ad- vantages of the global positioning system. The problem lies in the di erence of the time measurement on the orbit and on the Earth. In practice, this issue was solved via lowering the frequency of the system installed on the satellite.
Detection method for accelerated particles in high intensity laser-matter interaction
In this study, we present the main methods for detection and characterization of charged particles, resulting from high power laser field (PW) -solid target interaction. The characterization employs the description of Scintillators, Radiochromic Films (RCF), Image Plates (IP) and Thomson Parabola (TP), as devices that are able to characterize the accelerated particles in function of type and energy and are immune to parasite EMP pulses, usually present in this type of applications.
Quantum Galielo's experiment and WEP in QM
We address the problem of estimating the mass of a (quantum) particle interacting with a classical gravitational field. In particular, we analyze in details the ultimate bounds to precision imposed by quantum mechanics and study the effects of gravity in a variety of settings. In addition, we discuss the compatibility of the weak equivalence principle (WEP) within the quantum regime using as a guide the notion of Fisher Information. Our results show that in an information-theoretic framework, no clash occurs between quantum mechanics and the WEP.
Two-dimensional MoS2 - Optical properties
Layered materials in their bulk form are widely known and were utilized for a long time, while the ability of extracting single or few layers of atoms has attracted considerable interest in the study of two-dimensional materials. Although, graphene, being the first and best-known example of two-dimensional atomic crystals, demonstrates unique physical, optical and mechanical properties, its lack of bandgap limits its use in various applications. Thus, other graphene-like two-dimensional materials such as molybdenum disulphide (MoS2) have recently been focused on in order to overcome the weakness of gapless graphene and to extend the field of possible applications. These two-dimensional transition metal dichalcogenides (TMDCs) are atomically thin and possess bandgaps lying in the visible range which makes them interesting for use in optoelectronic devices.
Nanopowders of cerium (IV) oxide - synthesis and applications.
Cerium oxide (ceria) is well known for its interesting, both mechanical and electrical, properties. While doped it exhibits relatively high values of oxygen ionic conductivity. It makes it a very good material for various applications like electrolyte in solid oxide fuel cells. Recently the main interest is put on the nanosize ceria. In our work the nanopowders of undoped and lanthacerium (IV) oxide were synthesised using the co-precipitation method. The series of samples was obtained each being prepared at different annealing temperature, ranging from 500 to 1100oC. All samples were measured by the means of X-ray diffraction. The direct correlation between the annealing temperature and grain size was observed. The higher annealing temperature was, the bigger nanoparticles were obtained. The size of nanoparticles was from the rage approximately 5 to 100 nm. After synthesis the nanopowders were pressed, sintered, and their electrical properties were tested. Using the co-precipitation method it is easy to synthesize ceria. In this work the synthesis route and properties of ceria, and lanthanum doped ceria (in 10 and 20mol%) was described.
Broadband transition radiation measurements for the diagnosis of ultra-short plasma-accelerated electron bunches
At Flash Forward (DESY, Hamburg) we receive ultra short electron bunches from plasma acceleration. One of the most important characteristics of these bunches are they're longitudinal appearance, or put in simpler terms - the length of such an electron bunch is what one wants to measure.
In order to do this one uses transition radiation (TR) which is a form of electromagnetic radiation emitted when charged particles move between to media of different dielectric constants. The longitudinal width of each electron bunch determines whether the transition radiation is coherent or not. To keep it simple, at wavelengths longer than the longitudinal length of an electron bunch we can detect coherent TR (CTR) resulting in a high intensity at the given wavelength due to interference. At wavelengths shorter than the longitudinal length of a bunch the TR interferes destructively thus minimising the intensity. This way one will be able to extract information about the electron bunch.
Analysis of topological properties of Chern insulators
Chern insulators are band insulators exhibiting a nonzero Hall conductance but preserving the lattice translational symmetry.  Unusual protection of quantized conductance is related to nontrivial topology of energy bands characterized by topological invariant, Chern number; topological properties are stable against small perturbations. In this work we investigate different Chern insulator lattice models. We analyze their common features by looking at band structures, edge states behavior, and Berry curvature. We emphasize differences that can be responsible for distinct many body effects when electron-electron interactions are included. In particular, we indicate models that support stabilization of Fraction Chern Insulator (FCI) phases. [3-6]
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Technology saves people
In a world where heart disease is the number one cause of death in the last years, a young electrical engineer studied the relation between the electric shocks and its effects on human heart. His invention has been called a defibrillator and it has been used for the first time on a human in 1947.
Nowadays research is directed on lowering the dimensions of defibrillators and make them more accessible to operate. The most important part of this invention is the capacitor. This little piece stores a large amount of energy in the form of electrical charge and then releases it over a short period of time. The maximum working voltage is the voltage that when is voltage that cause a dielectric breakdown when is exceeded.
In my poster I will try to make and test a small defibrillator, charged from batteries to considerably reduce device dimensions. Also, I will explain how condensators in my circuit works and how the power of electrical current affect the heart beats. If you can understand how it works you can figure it out how to control a large amount of energy. I hope you will enjoy my presentation and you will remember how you can save the world with your own hands.
Solvophobic Solvation and Interaction of Small Apolar Particles in Imidazolium-Based Ionic Liquids
Ionic liquids are a new class of solvents for use in environmentally benign industrial processes and are seen as an alternative to toxic volatile organic compounds. The ionic nature of them has important consequences for the structure of the liquid on nanosomic level. Spectroscopic evidence is suggested the presence and importance of the formation of intermolecular cation-anion hydrogen bonds. Specific ion-cation interactions seem to the formations of a persistent anion-cation network, which has been shown to the quite tolerable to adding both and apolar particles.
The St. Petersburg paradox - The problem of unrealistic expectations
An optimal decision is a decision that leads to the best possible outcome for an agent. When facing lotteries, a naive decision criterion would be the comparison between the price of a lottery ticket and the expected value of a random variable representing the prize. However, it is possible to conceive of lotteries with finite prizes, but a divergent expected prize. In this case, the naive criterion would suggest playing as the optimal strategy for any finite price, and could lead to a suboptimal outcome for the agent. We will explore the St. Petersburg paradox, originally proposed by Nicolaus Bernoulli, as an example of this problem. The paradox arises when considering a theoretical lottery in which a player tosses a coin repeatedly until the first time it lands tails. If the number of times the coin had landed heads before landing tails (k) is greater than zero, the prize of 2 to the power of k cookies is awarded. Though many resolutions of the paradox have been proposed (most notably by Daniel Bernoulli), it is unclear if any of them are satisfactory. Our aim is to determine the most appropriate decision criterion. We will offer a theoretical consideration of the problem, and present the results of a simulation approach.
Phase retrieval for BEC in harmonic optical traps
Ultra-cold atoms trapped in optical lattices are being intensively investigated both theoretically and experimentally. All spatial parameters of such system can easily be controlled in a laboratory. This allows one to reproduce quantum problems which are tremendous to be solved theoretically, leading to quantum simulators. However, one can directly measure only the atoms density distribution (the square modulus of the system’s wave function). The phase is lost.
After removing the optical trap, after the time-of-flight, atoms distribution replicates initial momentum distribution. We use this information to recover the phase of the initial wave function. Iterative phase retrieval algorithm, widely known from diffraction imaging techniques, is employed.
We implement and test the algorithm for 2D and 3D triangular optical lattices, successfully recognizing macroscopic areas of different phases of Bose systems. The recovery efficiency for different noise and imaging resolution is shown.
Exclusive Jet Production at the LHC
Jets are strongly collimated particle beams produced by the hadronization of quarks or gluons and are observed in the proton-proton collisions at the Large Hadron Collider. In exclusive jet production event (pp->p+jet+jet+p) both interacting protons stay intact and the final state contains two jets. According to the theoretical predictions in the region between proton and jet should be no particles. As the result of reconstruction these events some particles outside jets are observed and their properties have been measured.
Spatial and temporal resolved study of some atmospheric pressure discharges
Atmospheric pressure discharges are interesting for many applications - material processing, textile modification, cleaning of archaeological artefacts, sterilization of agricultural products and medical instruments, skin treatment etc. For optimization of their applications, study of theirs spatial and temporal characteristics is very important. Namely, spatial distribution of neutrals, ions and electrons is always present in this type of sources forming different areas, so-called layers of plasma. Also, many of these discharges rapidly change their characteristics with time.
To visualize development of an atmospheric pressure discharge, short exposure time images were recorded using an iCCD camera (gated intensified charge coupled detector) coupled to an imaging spectrometer. iCCD camera can work in different modes, among others - image and full vertical binning (FVB). Plasma images are recorded with wide open slit and with zero order of the diffraction grating of the spectrometer. After analyzing gathered photographies, FVB mode allows us to record spectrum of wanted area by narrowing slit width and by changing the grating angle. Temporal evolution was performed using the signal from the current probe which triggers the camera with various time gate widths (tG) and delay times (tD).
Time-resolved images of discharge show us the beginning and duration of discharge. This is very significant because plasma volume and temperature evolves over time causing changes in line intensity. Thus, by choosing appropriate exposure time it is possible to monitor evolution of spectral lines.
From recorded spectral lines it is possible to do analytical measurement, but also to determine plasma parameters such as electron density and temperature. Here, for the electron density determination we used the measurement of the distance between allow and forbidden component of He I 447.1 nm neutral line. The plasma temperature may be estimated through the relative emission intensities of spectral lines using Boltzmann plot.
Two types of discharges were analyzed. In first case, plasma is created by combining laser pulse and spark discharge. The main applications of such combined discharges are for detecting elements difficult to excite, such as carbon, chlorine, sulphur and fluorine. The main disadvantage of combined excitation is existence of a strong background induced by overlap of analytical lines with emission lines of matrix elements. By selecting proper area this problem has been overcome. Spatial distribution of present species mostly depends of temperature which is different in every layer of plasma. It means that two spectra recorded in same time but from different layers would be dissimilar, as it will be shown. Spatially resolved spectra show that limiting the recording volume improves signal to background ratio, enhances the analytical possibilities of such plasma and enable study of conditions for enhancement of analytical lines intensity. Thus, fast imaging enables choosing proper area for recording spectrum lines with good intensity and signal to noise ratio. Also, imaging of spatial distribution was used to monitor changes in the shape of plasma.
In second case, our source was microjet. The ultimate goal was to shed light on how the discharge morphology and emission intensity evolves over time.
Synthesis and physical properties of Nd6-xYxCo1.67Si3
We present the physical properties of Nd6-xYxCo1.67Si3 synthesised by arc-melting of pure elements (neodymium, yttrium, cobalt, silicon). The purity of crystallographic structure of the samples were tested by powder X-diffraction. Nd6Co1.67Si3 has been reported to crystalize in a hexagonal structure (space group P63/m) as well as the whole family of RE6Co1.67Si3 (RE=rare earths). A strong disorder of cobalt atoms in the chains of face-shared octahedral of neodymium is observed. Magnetization measurements reveal the existence of two ferromagnetic transitions, around 35 K and 85 K. Although, this phenomenon is also seen for yttrium doped compound it reveals different values. In this poster we present, discuss and compare measurements of the specific heat, heat capacity, electrical resistance and magnetic susceptibility, performed for yttrium doped Nd6-xYxCo1.67Si3.
Changes in Adriatic-Ionian thermohaline circulation
There are many causes that affect changes in the Adriatic-Ioninan thermohaline circulation - the movement of seawater in a pattern of flow caused by changes in density. Here we examine the influence of geostrophic current which enables water masses to enter the Mediterranean. Since different water masses have different properties, thermohaline properties will variate. Sea Surface Height (SSH) data from Aviso, between years 2012 and 2015 were used in order to determine the variations.
Uncertainties of Weibull Distribution Parameters Obtained by Monte Carlo Simulations of a Dielectric Breakdown in Thin Oxides
A dielectric breakdown in thin oxides is simulated by a Monte Carlo type of simulator based on the percolation concept. The outcomes of a series of numerical experiments, performed on samples with different size, are analyzed in order to estimate the statistical spread of the Weibull slope and the mean critical density of defects. Two widely used models are tested, the lattice model with nearest neighbors’ connections and the randomly distributed sphere model. An attempt is done to estimate the confidence intervals of the distribution parameters and to determine the minimum/optimal sample size which should be used for a quantitative comparison of of computational results with experimental ones.
Technological processes in the manufacturing of electronic devices
With the evolution of the world, humanity has become more and more dependent on their own creations. Electronic devices can now be found literally everywhere. So, we need to discuss the processes in creating such a device, more specifically we will be talking about the manufacturing of microprocessors.
Silicon is a key ingredient in electronics, due to its properties (good thermal conductivity, non-toxicity, excellent passivation by SiO2 ), so we will be using a silicon based wafer. By Plasma Enhanced Chemical Vapor Deposition (PECVD) we deposit SiO2 onto the silicon wafer and then with the photolithographic processes that include the etching process (RIE and DRIE) we reach our final product. Images were taken with a Scanning Electron Microscope (SEM), in between all processes and of the final product.
Feed-forward correction for amplification
Quantum communications, which allows for secure sharing of digital signatures and key exchange, is a promising field for creating secure communications in a world with eavesdroppers and malicious attacks. One current issue is the limitation in transmission distance of the protocols. This is because of the low mean photon number used when implementing in experiments. Conventional communications systems can simply use optical amplifiers (at the cost of adding noise) to overcome losses, and allow inter-continental distances to be covered. Added noise is not a problem in conventional systems however it is an issue for our quantum signals, as noise will swamp any quantum state properties of the original signal.
We proposed a state comparison measurement which allows for non-deterministic noiseless amplification of low intensity coherent states. Initial experiments showed large gain, high fidelity and success rates. To improve the success rate further, a feed-forward mechanism is proposed to correct for mistakes during the initial state comparison. This device could be used as a coherent state receiver and repeater in quantum communications.
Entropy of Interval in Two-dimensional Conformal Field Theory
Conformal field theories are widely explored in many branches oh theoretical physics. We consider two-dimensional conformal quantum theory and in its frame we derive entropy of interval. Then we compare it with results of Ising model for a spin chain. As a result we find correspondence between continuous system of the interval and discrete system of spins. The result is one of many examples for application of two-dimensional conformal field theory in condensed matter.
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 poster 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.
Reducing effect of RV scatter around active M Dwarfs
The most abundant type of star in the galaxy is the M dwarf. These low-mass stars are, at first glance, ideal for planet surveys, such as CARMENES, attempting to detect terestrial-like planets as the planet will have a proportionally larger radial-velocity impact on its host as compared to a more massive Sun-like star. However,many M dwarfs are also extremely active with frequent flaring events and strong emission lines of the sodium doublet, Hα and the calcium Infraredtriplet which complicate the aquisition of the high accuracy [1 m/s] radial-velocity measurements required for detection of an exoEarth. Therefore we have begun observations of CN Leo, a particularly active M Dwarf, with the high accuracy CARMENES spectrometer at the Calar-Alto Observatory in order to determine any correlation between these activity lines and the observed 10 m/s activity-induced radial-velocity scatter of CN Leo. After conducting 10 observations a correlation seems to be emerging but additional observations are required in order for this to be considered statistically significant.
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.
The Multi-Stage Theory of Carcinogenesis in the Genomic Era.
Today the individual fields of science do not terminate sharply from each other, rather support each other. We can use their combined knowledge and methods for tackling a wide variety of problems, for instance carcinogenesis, despite of its complexity, may be explained by applying the tools of biophysics, evolutionary biology and mathematics. Cancer is the breakdown of controls over cellular birth and death due to several key mutations. Through the examination of cancer, we shed light to the mechanisms and agents conducing and protecting against cancer formation, which may be useful in prevention and elaboration of more efficient treatment strategies. In my poster I will briefly present my bachelor’s thesis in which I made an attempt at recapitulation the development of the multi-stage theory of carcinogenesis according to the most important articles over the past century. From the first experimental observations to the analysis of age-specific incidence patterns we get to know the first quantitative theories. Armitage and Doll’s article, published in 1954, made a seminal contribution recognizing the role of rate-limiting mutations, which still stands its ground. Subsequent models have built on this concept, whereas through clonal expansion and the information gained from genome sequencing we get to the up-to-date mathematical models which have been supplemented by evolutionary parameters considering the impact of passenger mutations. These models make it possible, arm-in-arm with genomic data, to estimate certain parameters, for instance selective advantage of a driver, which may lead to better understanding of cancer progresson.
The amount of energy released in thunderstorms
A thunderstorm, also known as an electrical storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. They are usually accompanied by strong winds, heavy rain, and sometimes snow. The amount of energy released in thunderstorms mostly depends on quantity of water. If the quantity of water that is condensed in and subsequently precipitated from a cloud is known, then the total energy of a thunderstorm can be calculated. In a typical thunderstorm, approximately 5×108 kg of water vapor are lifted, and the amount of energy released when this condenses is 1015 joules. This is more energy than that released during the atomic bomb blast at Hiroshima, Japan in 1945.
Molybdenum bronzes - synthesis, structure and physical properties
A new transition metal molybdenum bronzes have received much attention due to their electronic and structural properties. These have found applications as electrode materials in solid state secondary lithium batteries and electrochemical sensors. By solid state synthesis, the series of samples was obtained for compounds of a formula MxMoO3 (for M = Cu, Bi). Crystallographic parameters have been determined by X-ray diffraction (XRD) analysis. The results are reported for a set of powder X-ray diffraction patterns for the product materials corresponding to various initial metal contents. Measurements of electrical resistivity and specific heat have been also carried out. On our poster we will discuss the synthesis methods, our results and future perspectives.
Automation of parts in a XRF spectrometer with tri-axial geometry
This work has the main purpose of automate parts of a XRF spectrometer with a secondary target in a triaxial geometry existing in LIBPhys, DF, FCT-UNL.
The existent XRF spectrometer only allows users to have one filter (silver (Ag) 25 Ãm), one secondary target (molybdenum (Mo)) and one sample. With this setup, users should turn off the X-ray tube in each measurement, decreasing the lifetime of it, because of the effects of ramp up and ramp down of its applied current. Another problem on it is the number of times that users should change samples and be exposed to radiation. The restriction of having only one secondary target and one filter, doesn’t allow changing them without turning off the system.
COMET AG, in , defines continuous operation as an operation that switches ON/OFF maximum 15 times per day . It also advises to slow ramp-up (> 1 s of high voltage when switching ON the tube) and ramp-down (> 300 ms of high voltage when switching OFF the tube) .
This new system allows users to have up to six samples on a cylindrical rotatory platform, moved by a stepper motor and controlled by an Arduino, up to four secondary targets (Nickel (Ni), Mo, Tantalum (Ta) and Bismuth (Bi)) in a sliding platform moved by a linear actuator and up to five filter brackets (No Filter, Aluminum (Al) 100 Ãm, Aluminum-Titanium (AlTi), Aluminum-Titanium-Copper (AlTiCu) and Ag).
As it is possible to have up to six samples, four secondary targets and five filter brackets users do not need to turn off the x-ray tube, increasing its lifetime. As users do not need to change samples so many times, their exposition to radiation is minimized. The access to different targets allows better lower limits of detection values throughout an extended atomic number region. The use of filters allows a more efficient monochromatization of the beam, which is of the utmost importance for several applications.
References  Technical Services Business Unit X-ray, COMET AG, Life time of HP-Tubes, Service-Bulletin 2012/003