Graduate Seminar, 3rd June

Speaker: Szymon Domański

Title: Dosimetry for radiation processing

Abstract: Radiation processing is a growing industry, and is commonly used in the sterilization of medical products for example, sutures, surgical gloves, gowns, face masks, syringes, sticking plasters, dressings and other single use healthcare supplies are all processed using gamma radiation. The use of ionizing radiation for these purposes does not make the underlying product radioactive, and generally has no effects on it that are any more pronounced than other sterilization or preservation technologies. Standards for radiation sterilization of medical and some other products are set by the International Organization for Standardization. In 1995, the ISO released the first edition of ISO-11137 outlining validation methods, quality controls and requirements for all activities related to the sterilization processes. In my presentation I will describe our dosimetry system developed for purposes of irradiation a variety of materials with spent nuclear fuel . I am going to present also current state of compliance with the standards.

Graduate Seminar, 27th May

Speaker: Artem Poliszczuk

Title: AGN selection in the AKARI NEP deep field with the fuzzy SVM algorithm

Abstract: In my presentation I will describe a new catalog of reliable AGN candidates selected from the AKARI NEP-Deep field. Selection of the AGN candidates was done by applying a fuzzy SVM algorithm, which allows to incorporate measurement uncertainties into the classification process. The training dataset was based on the spectroscopic data available for selected objects in the NEP-Deep and NEP-Wide fields. The generalization sample was based on the AKARI NEP-Deep field data including objects without optical counterparts and making use of the infrared information only. A high quality catalog of previously unclassified 275 AGN candidates was prepared.

Graduate Seminar, 13th May

Speaker: Oleg Shkola

Title: Search for heavy charged particles at CMS

Abstract: Many extensions of the Standard Model (SM) predict the existence of heavy, long-lived charged particles (HSCPs). These particles might have speed significantly less than speed of light and/or charge, not equal to ±1e. With lifetimes greater than a few nanoseconds, HSCPs  can travel distances larger than the typical collider detector and appear stable like pions or kaons. Because particle identification algorithms at hadron collider experiments generally assume signatures characteristic of Standard Model (SM) particles, e.g., speed close to the speed of light and a charge of ± 1e, HSCPs may go unidentified. A further complication arises from the fact that HSCPs might be charged during only a part of their passage through detectors, further limiting the ability of standard algorithms to identify them. It is however possible to detect HCPs making use of their higher rate of energy loss via ionization (dE/dx) and longer time of flight to the outer detectors, in comparison with SM particles. During the seminar, results of dedicated searches, done at Compact Muon Solenoid (CSM) experiment on data collected during 2016 will be discussed along with the improvements to the muon timing calculations done by the CMS Warsaw group.

Graduate Seminar, 15th April

Speaker: Artur Miroszewski

Title: Early universe cosmology and the coherent states

Abstract: The theory of General Relativity seems to be a well chosen tool to describe the evolution of the universe. Starting from very simplified model of the universe, Friedmann-Lemaître-Robertson-Walker spacetime, we are able to explain most of the observable phenomena on the cosmic scale. On the other hand the cosmological solutions in GR tend to contain past-incomplete geodesics, also know as singularities. The singularities occur in the very early universe regimes, where apart from the GR we should take into account quantum effects. Although the theory of Quantum Gravity seems to be far from invented and understood, the semi-classical approach may be able to point us to some features of it. During my talk I will present the semi-classical approach based on the coherent states, leading to the Big Bang singularity avoidance scenario- the Big Bounce.

Graduate Seminar, 8th April

Speaker: Chetan Bavdhankar

Title: Peculiar Velocities – a very important probe of cosmology

Abstract: Peculiar velocity of galaxies is one of the very important probes of the cosmological model (Strauss and Willick (1995)). Since peculiar velocities are induced by gravity only, they can be used to obtain various cosmological parameters such as mean matter density or the growth of structure (Nusser and Davis (2011)). The large-scale fluctuations of the matter distribution can be determined using bulk flows where a given volume of the sample shows the net peculiar motion of galaxies. To study these velocity dependent properties, I have started with estimating observers motion using the radial peculiar velocities of the galaxies in observers frame. In this analysis, I have simulated 1000 galaxies in a volume of a sphere of radius 350Mpc. These galaxies have peculiar velocities in random directions with gaussian magnitudes. Then we try to recover the observer’s motion from the observer frame updated data using chi-squared analysis. With real data, this type of analyses can be used to estimate the motion of the Local Group, bulk flows in at different scales, local voids, etc.

Graduate Seminar, 1st April

Speaker: Jakub Sierchuła

Title: Determination of the liquid eutectic metal fuel Dual Fluid Reactor (DFRm) design – steady state calculations

Abstract: The Dual Fluid Reactor (DFR) is a novel concept of a very high-temperature (fast) reactor which falls-off the classification of Generation IV International Forum (GIF). DFR makes best of the two previous designs: Molten Salt Reactor (MSR) and Lead-cooled Fast Reactor (LFR). During the presentation a novel reactor design (DFRm) with the liquid eutectic U-Cr metal fuel composition and the lead coolant will be present. By performing the first steady state neutronic calculations for such a reactor it will be shown that this 250 MWth reactor is critical, and that it can operate almost 20 years without refuelling. The geometry (reflector thickness, fuel tubes pin pitch) was optimise with respect to the multiplication factor. The optimisation together with some other opportunities for the liquid metal fuel design (e.g the use of electromagnetic pumps to circulate the medium) allows DFRm to be of a small size. This rises economy of the construction as expressed nicely in terms of the Energy Return on Invested (EROI) factor which is even higher than for the molten salt fuel design (DFRs). Last but not least, DFRm has all the (fuel, coolant, reflector) temperature coefficients negative, which is an important factor of the passive safety.

Graduate Seminar, 25th March

Speaker: Szymon Nakoneczny

Title: Catalog of quasars from the Kilo-Degree Survey Data Release 3

Abstract: Broad spectroscopic lines, large redshift range and variety of properties make quasar detection in photometric surveys a particularly difficult task. I will present a quasar detection method based on photometric ugri data in Kilo-Degree Survey (KIDS) – an imaging deep and wide field survey covering 447 sq. deg. on the sky. The KiDS third data release contains 49 millions of sources among which, however, a vast majority does not have any spectroscopically confirmed identification. We successfully trained a Random Forest classifier based on the KIDS data and a set of known quasars identified by the SDSS spectroscopic survey. The presented catalog consists of 190,000 quasar candidates, and its training purity equals 91%. Additional validation of the catalog was made by the means of comparison with GAIA second data release, other already existing quasar catalogs and WISE photometric data.

Graduate Seminar, 11th March

Speaker: Paritosh Verma

Title: Gravitational waves in the Jordan-Brans-Dicke theory

Abstract: I shall talk about gravitational waves in Jordan Brans Dicke (JBD) theory. There are two tensor polarization states in the General theory of relativity but there can also be vector and scalar polarization states in alternative theories of gravity. The JBD theory is one of the attempts to modify general theory of relativity by varying gravitational constant G and it has three polarization states. The first two states are the same as in GR and the third one is the scalar polarization.

Venue: Pasteura 7, Room 404.

Graduate Seminar, 28th January

Speaker: Grzegorz Żarnecki

Title: T2K results on CP violation in the neutrino sector

Abstract: Each of the three flavour states of neutrinos is a superposition of mass eigenstates. The flavour-mass mixing matrix may have an irreducible imaginary component resulting in possible CP symmetry violation in neutrino oscillations, i.e. asymmetries between neutrino and antineutrino oscillations. In the T2K experiment the CP is probed by the measurement of appearance probability of electron (anti)neutrinos originating from accelerator-produced muon (anti)neutrinos beam. Current T2K results indicates CP violation at 2 sigma confidence level.

Graduate Seminar, 14th January 2019

Speaker: Joanna Reszczyńska

Title: Modelling of human cell reactions to ionizing radiation – from a DNA lesion to a cancer growth

Abstract: Understanding the consequences of exposure to low dose ionizing radiation is an important public health concern. It has become clear that cellular responses can be very different at low compared to high radiation doses. Important biological mechanisms may play key role in dose-response at low doses, which has been described by many deterministic and stochastic models, that try to implement current radiobiological knowledge to experimental data. In this talk, I will discuss post-irradiation cellular processes. I will present dose and time-dependent analytic model of responses of cells in the body to ionizing radiation for two exposure categories: acute and protracted. Special emphasis will be dedicated on the new approach of capturing the key dynamics–formation of the tumour.