Wydział Fizyki (WF)/Faculty of Physics
Permanent URI for this community
Browse
Browsing Wydział Fizyki (WF)/Faculty of Physics by Issue Date
Now showing 1 - 20 of 172
Results Per Page
Sort Options
Item Badanie stanów magnetycznych jonu żelaza w ferroelektromagnetycznym PbFe₀‚₅Nb0₃(1980) Maryanowska, Anna; Pietrzak, JerzyItem ALPL-1 Newtonian Ephemeris of the Planetary System Spanning 4000 years(Acta Astronomica, 1986) Dybczyński, P. A.; Jopek, TadeuszNumerical integration of the equations of motion of the Solar System Planets (except Mercury) is described. The continuous ephemeris obtained in result, spanning the time interval from 1918 BC to 2092 AD is presented.Item Pprównanie dwóch algorytmów identyfikacji strumieni meteoroidowych(Obserwatorium Astronomiczne UAM, 1989) Jopek, Tadeusz J.Porównano dwie metody analizy skupień w próbie 1932 orbit meteoroidów fotograficznych. Wykonane badania ukazują istotne trudności związane z wyszukiwaniem strumieni meteoroidowych. Zastosowano algorytm pojedynczego linkowania oraz iteracyjną metodę Sekaniny. Zidentyfikowano 65 strumieni, połowa z nich nie wymaga dalszych zabiegów. Jednak w pozostałych przypadkach uzyskane tymi metodami rezultaty niekiedy istotnie się różnią. Algorytm Sekaniny działa bardziej selektywnie, daje strumienie o mniejszej liczbie członków, bardziej zwarte. Jednak ze względu na konieczność iterowania, obliczania orbity średniej, rezultaty uzyskane metodą Sekaniny mogą być nieoczekiwane. W tym kontekście algorytm pojedynczego linkowania, jako bezpieczny, jest bardziej godnym polecenia.Item TV meteor streams searching(Astronomical Institute Slovak Academy of Sciences, Bratislava, 1993) Jopek, Tadeusz J.Using a modified D-criterion (threshold Do=0.2), among 531 TV meteor orbits, 23 streams has been identified. Adout 30% of the orbits belongs to the stream component. Only 3 streams have orbits inclined more than 30deg. Four streams have reciprocal orbits. The major stream Herculids shown to be a complex structure, sensitive on the choice of the D- threshold value. The Taurids complex differs slightly from the photographic one. The theta Piscids stream has very small orbit, the mean semi-major axis equals to 0.79AU. This stream seems to be TV component of the Eccentrides system, but with Do=0.21 the theta Piscids have joined S. Taurids. The TV Orionids appeared in two branches. One of them includes a single orbit which belongs to the eta Aquariids.Item Separation of meteor streams from the sporadic background(Kluwer Academic Publishers, 1995-01) Jopek, TadeuszA cluster analysis procedure has been used to estimate the fraction of the sporadic interlopers (sporadis bias) identified as stream members among the observed meteor orbits. Using the artificial meteor orbits with the same distribution as the observed one, the sporadic bias is estimated for the given threshold value of the orbital similarityD c. It has been shown that in case of the radio meteor catalogues theD c values given by the formula proposed in Southworth and Hawkins (1963)and in Lindblad (1971) correspond to the sporadic bias of 8 21%. For the five radio meteor catalogues the values ofD c corresponding to the fixed bias equal to 10% and 15% are given.Item Meteor stream identification: a new approach. Application to 3675 radio meteors(Astronomical Institute of the Slovak Academy of Sciences, 1999) Jopek, T.J.; Valsecchi, G.B.; Froeschle, Cl.The new criterion DN for meteoroid streams identification, based on variables directly linked to observations, was applied to a set of radio meteors observed in Adelaide. 28 streams, combinning 28% of the 3675 orbits have been detected. 8 streams have a single crossing point with the Earth orbit, 20 groups were identified as twin showers.Item On the atmospheric dynamics of the Tunguska cosmic body(ESA Publication Division, 2001-11) Foschini, Luigi; Longo, Giuseppe; Jopek, Tadeusz J.; Froeschle, Christiane; Gonczi, Robert; Michel, PatricWe studied the available scientific literature on the Tunguska event of 30 June 1908 to obtain parameter sets of the Tunguska Cosmic Body atmospheric dynamics. We performed a comparative analysis by means of available theoretical models and with the help of interplanetary dynamics, and we excluded unphysical orbits. Our results indicate a very high probability that the TCB was an asteroid.Item A Main Belt Asteroid: the Most Probable Cause of the Tunguska Event(Societa Astronomica Italiana, 2002) Jopek, Tadeusz J.; Gonczi, Robert; Froeschle, Christiane; Michel, Patric; Longo, Giuseppe; Foschini, LuigiWe studied the available scientific literature on the Tunguska event of 30 June 1908 to select a sample of atmospheric trajectories. Then we calculated a set of parameters from which we obtained 886 orbits. Using the model of Bottke and colleagues on dynamical properties of celestial bodies, we estimated the probabilities of different origins of the Tunguska Cosmic Body (TCB). Event though 6 of 886 orbits can be both asteroidal or cometary, the probability of an asteroidal origins remain s the highest.Item Propagacja dźwięku w pobliżu przemiany fazowej(Wydawnictwo Naukowe UAM, 2004) Pawlak, Andrzej; Muzia, KatarzynaThe book deals with the theoretical studies of critical behaviour of ultrasonic wave attenuation and propagation velocity in magnets. The effect of spin-lattice relaxation on the ultrasonic attenuation and velocity is investigated on the basis of the stochastic model including the energy relaxation and the sound mode. A novel high frequency regime in the ultrasonic attenuation is predicted. The scaling functions are calculated in the one-loop approximation within the renormalisation group formalism. In the diffusive version of the model a detailed analysis of the connection between the heat conduction and sound propagation is studied. An overview of experimental and theoretical sound attenuation exponents is also given. The ultrasonic attenuation measurements in MnF2 are interpreted in terms of the theoretical model proposed.Item The effect of ionizing radiation on chloramphenicol(Springer Netherlands, 2006) Marciniec, Barbara; Stawny, Maciej; Kozak, Maciej; Naskrent, MarekThe effect of ionizing radiation on the physicochemical properties of chloramphenicol in solid state has been studied. The compound was e-beam irradiated with doses from the range 25–400 kGy and the possible changes were detected in the organoleptic methods (colour, form, odour, solubility and clarity), by SEM observations, X-ray, chromatography (TLC), spectrophotometry (UV, IR, EPR) and thermal (DSC) methods. No significant changes relative to the unirradiated sample were observed as a result of irradiation with the dose of 25 kGy – a standard dose for radiation sterilization, besides free radicals generation. Higher doses were found to produce a change in colour, increase in absorbance (UV), changes in the XRD spectra and appearance of products of radiolysis. The presence of the radiolysis products was confirmed by the TLC method, indirectly by DSC showing a decrease in the melting point from 0.2 to 4.5°C and enthalpy from 3.8 to 23.3 J g–1, respectively. A linear relationship was obtained between the irradiation dose (25–400 kGy) and the melting point of chloramphenicol, characterised by the correlation coefficient r=0.9968. The EPR signal intensity increased with increasing dose of irradiation and the lifetime of the free radicals was longer than 6 months. No changes were detected in SEM and IR spectra. As follows from our results, the DSC method is most suitable for a fast monitoring of the drugs subjected to sterilization by irradiation as it permits detection of changes occurring even on irradiation with low doses and their quantitative description.Item Thermal study of four irradiated imidazoline derivatives in solid state(Springer Netherlands, 2007) Marciniec, Barbara; Kozak, Maciej; Naskrent, Marek; Dettlaff, Katarzyna; Ogrodowczyk, Magdalena; Stawny, Maciej; Wachowski, LeszekFour imidazoline derivatives: antazoline (AN), naphazoline (NN), tymazoline (TM), xylometazoline (XM), in the form of hydrochlorides in solid phase have been subjected to high energy e-beam irradiation from an accelerator (10 MeV) at a dose varied from 25 to 200 kGy. The effects of the irradiation have been assessed by DSC, X-ray diffraction, FTIR, EPR and TLC. The standard sterilisation dose of 25 kGy has been found to produce changes in the properties of one derivative (XM), two other ones (AN and TM) have been found sensitive to doses >100 kGy, whereas NN has been resistant to irradiation in the whole range studied (25–200 kGy). EPR results indicated that the changes taking place in the therapeutic substances studied are related to radical formation. The irradiation induced changes in colour, a decrease or increase in the melting point, changes in the XRD pattern, small changes in the shape of FTIR peaks and the presence of radiolysis products. The XM compounds cannot be sterilised by irradiation because of the radiation induced changes in its physico-chemical properties.Item Radiation sterilization of ephedrine in the solid state(Polish Chemical Society and the Committee on Analytical Chemistry of Polish Academy of Sciences with cooperation of the Czech Chemical Society, the Slovak Chemical Society and the Hungarian Chemical Society, 2008) Dettlaff, Katarzyna; Teżyk, Artur; Marciniec, Barbara; Wachowiak, Roman; Naskrent, Marek; Bednarek, BartłomiejThe effects of the e-beam ionising radiation of energy 9.96 MeV in doses 25 800 kGy on the stability of solid ephedrine hydrochloride (1R,2S)-(-)-2-methylamino-1-phenyl-1-propanol hydrochloride) have been studied. These effects have been observed using the following analytical methods: organoleptic (form, colour, smell, clarity of solution), scanning electron microscope SEM, pH measurement, chirality and water content measurement (Karl Fischer method), spectrometric methods (UV, FT IR, EPR), chromatography (TLC), and combined chromatography (TLC UV, GC MS). Even the standard sterilisation dose of 25 kGy has been found to cause a change in colour from white to pale yellow, the appearance of free radicals in the concentration of 3.05×10^15 spin/g, and about 1% loss of the content. The effects of higher doses 50 800 kGy have shown that radiodegradation degree of the compound is proportional to the dose applied. The main product of radiodegradation, formed at a yield of G = 17.17×10^7 mol/J, has been identified as 2-methylamino-1 phenyl-1-propanone (methcathinone, ephedrone), a psychoactive compound of the activity similar to that of amphetamine. For the above reasons ephedrine hydrochloride can not be subjected to radiative sterilisation with a dose of 25 kGy, however, assuming sufficiently low microbiological contamination of the initial substance, lower doses could be probably used for sterilisation purposes. Our results have not confirmed the earlier reports from 1970s on the resistance of ephedrine to ionising radiation in doses up to 60 kGy.Item Ampere NMR School 2008 Abstracts(Wydział Fizyki Uniwersytet im. Adama Mickiewicza w Poznaniu, 2008-06) Jurga, StefanItem Critical Sound Propagation in Magnets(Nova Science Publishers, 2009) Pawlak, AndrzejThe critical dynamics of sound is a very interesting field in which we can test modern concepts of the phase transition theory such as the universality of critical exponents, scaling or the crossover to another universality class etc. It is the aim of the study to present a general theory of critical sound propagation, which takes also into account some important nonasymptotic effects. In metallic magnets the critical anomalies in the sound attenuation coefficient are of different types than in magnetic insulators.The difference in the critical exponents used to be explained by the occurrence of different kinds of magnetoelastic coupling in the two classes of magnets mentioned. We will show in this chapter that one should assume coexistence of both types of coupling in all magnets. A very important role is played by the ratio of the spin-lattice relaxation time to the characteristic time of spin fluctuations. It is a crucial parameter determining whether the sound attenuation coefficient reveals a strong or a weak singularity in a given material. After a short introduction the fundamental concepts of the phase transition theory such as critical exponents, the scaling and universality hypothesis etc are reviewed in Section 2 of this chapter. Section 3 presents the idea of critical slowing down, dynamic scaling as well as the presentation of the basic dynamic universality classes. In Section 4, the model describing the static behavior of acoustic degrees of freedom is investigated. The expressions for the adiabatic and the isothermal sound velocity are also derived. The phenomenological theory of critical sound propagation is presented in very intuitive way in Section 5, while Section 6 contains a detailed description of the dynamic model based on the coupled nonlinear Langevin equations of motion. Three basic regimes characterized by different critical exponents and scaling functions are distinguished in the sound attenuation coefficient. Crossover effects from the insulator-type regime to the metallic-type regime and to the high-frequency regime are demonstrated on the example of the ultrasonic data for MnF2. The concept of the effective sound attenuation exponent is introduced using the data reported for FeF2 and RbMnF3. The frequency dependent longitudinal sound velocity and its relation to the static quantities are discussed. Finally, the unsolved questions and future prospects in this field are outlined.Item NMR imaging and cryoporometry of swelling clays(EGU General Assembly, 2010) Dvinskikh, Sergey V; Szutkowski, Kosma; Petrov, Oleg V; Furó, IstvánCompacted bentonite clay is currently attracting attention as a promising “self-sealing” buffer material to build in-ground barriers for the encapsulation of radioactive waste. It is expected to fill up the space between waste canister and surrounding ground by swelling and thus delay flow and migration from the host rock to the canister. In environmental sciences, evaluation and understanding of the swelling properties of pre-compacted clay are of uttermost importance for designing such buffers. Major goal of present study was to provide, in a non-invasive manner, a quantitative measure of bentonite distribution in extended samples during different physical processes in an aqueous environment such as swelling, dissolution, and sedimentation on the time scale from minutes to years. The propagation of the swelling front during clay expansion depending on the geometry of the confining space was also studied. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were adapted and used as main experimental techniques. With this approach, spatially resolved movement of the clay/water interface as well as clay particle distributions in gel phase can be monitored [1]. Bulk samples with swelling in a vertical tube and in a horizontal channel were investigated and clay content distribution profiles in the concentration range over five orders of magnitude and with sub-millimetre spatial resolution were obtained. Expansion rates for bulk swelling and swelling in narrow slits were compared. For sodium-exchanged montmorillonite in contact with de-ionised water, we observed a remarkable acceleration of expansion as compared to that obtained in the bulk. To characterize the porosity of the clay a cryoporometric study [2] has been performed. Our results have important implications to waste repository designs and for the assessment of its long-term performance. Further research exploring clay–water interaction over a wide variety of clay composition and water ionic strength as well as investigating the effect of the confining geometry and material surface properties seem to be worth to pursue.Item Study of meteoroid stream identification methods(Cambridge University Press, 2010) Rudawska, Regina; Jopek, Tadeusz J.We have tested the reliability of various meteoroid streams identification methods. We used a numerically generated set of meteoroid orbits (a stream component and a sporadic background) that were searched for streams using several methods.Item Dysfunkcja akomodacji i metody jej badań(2010) Przekoracka-Krawczyk, Anna; Naskręcki, RyszardItem Ocena wiarygodności metod identyfikacji strumieni meteoroidowych(2010-02-26T12:10:23Z) Rudawska, Regina; Jopek, Tadeusz J. PromotorProcedura wyszukiwania strumieni meteoroidowych w bazie danych orbitalnych następuje za pomocą jednej z technik analizy skupień, która w połączeniu z wartością graniczną Dk i odpowiednim D-kryterium definiują jednocześnie sam strumień. Analizą skupień wykorzystaną przez Southwortha i Hawkinsa w pracy z 1963 roku była metoda pojedynczego łączenia. Natomiast Sekanina (1976) i Welch (2001) zaproponowali iteracyjną metodę. Całkowicie inną metodę, tzw. metodę wskaźników, zaproponowali Svoreň i in. (2000). Podczas gdy Galligan i Baggaley (2002) oraz Brown i in. (2008) zdefiniowali strumień meteoroidowy, wykorzystując metody falkowe. Celem niniejszej pracy była ocena wiarygodności metod identyfikacji strumieni meteoroidowych, w których wykorzystano funkcje podobieństwa orbitalnego DSH i DV oraz kilka algorytmów analizy skupień. Badania wykonano w oparciu o symulacje wyrzutu i ewolucji cząstek strumieni meteoroidowych pochodzących z 15 ciał macierzystych, które identyfikowano za pomocą algorytmów analizy skupień: dwóch wariantów algorytmu Welcha, metody pojedynczego łączenia i metody wskaźników.Item Workshop: the basics of NMR diffusometry. Ampere conference (Zakopane 2009)(2010-03-26T10:36:52Z) Szutkowski, KosmaThe basics of NMR diffusometry. Ampere conference 2009.Item Charge and spin transport through magnetic molecules(2010-04-06T06:53:50Z) Misiorny, Maciej; Barnaś, Józef. PromotorDue to their peculiar physical properties such as an energy barrier for the spin reversal or long spin relaxation times, single-molecule magnets (SMMs) are inherently predestined for applications in novel molecular electronic and spintronic devices. The following thesis is devoted to studying transport properties of such molecules, with the main emphasis laid on discussing how the flow of spin-polarized current through a SMM can affect the magnetic state of the molecule. The system under investigation consists of a SMM bridged between two metallic, ferromagnetic electrodes with collinear magnetic moments. Furthermore, electronic transport is assumed to take place via the lowest unoccupied molecular orbital (LUMO) level of the molecule. I show that due to exchange interaction between an electron occupying the LUMO level and the SMM's core spin, during tunneling of spin-polarized electrons through a molecule one can observe an effect analogous to the current-induced magnetic switching (CIMS) phenomenon, known from other magnetic systems, for instance, nanowires or spin valves. The origin of the CIMS mechanism in SMMs stems from angular momentum transfer between a spin-polarized current and the molecule, and it allows for manipulating the SMM's spin state without application of an external magnetic field. I also focus on studying dynamical aspects of the magnetic switching mechanism, together with other spin effects that can arise in the situation under consideration. Finally, I analyze the possibility of employing a pulse of circularly polarized electromagnetic radiation for stimulating the mechanism of CIMS.