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od 2020-09-20 |
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1. |
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The structure and morphology of gold nanoparticles produced in cationic gemini surfactant systems Potential applications of gold nanoparticles (GNP) are strictly connected with their size and shape. The influence of different dicationic (gemini) surfactants, alkyloxymethylimidazolium derivatives derivatives, on the structure and morphology of GNP was studied. The synthesis of nanoparticles was performed in the presence of various gemini surfactants-dodecyloxymethylimidazolium nitrate (IMI_NO3_C4_C12), propionate (IMI_PROP_C4_C12) and 3,3'-[1,9-(2,8-dioxanonane)]bis-(1-nonyloxymethylimidazolium) chloride (IMI_Cl_oxyC7_C9), used as stabilizers and templates for obtaining different size and shape of gold nanoparticles. The samples obtained were examined using transmission electron microscopy (TEM), small angle scattering of synchrotron radiation (SAXS), UV-vis spectroscopy and NMR PFG spectroscopy. For the obtained solutions of nanoparticles the plasmon resonance was observed at the wavelengths corresponding to the presence of gold nanoparticles of sizes ranging from 5-100 nm, with a significant shift towards higher wavelength for the samples prepared with addition of dicationic surfactants. TEM images evidence the presence of gold nanoparticles with tetrahedral and spherical morphology in solutions prepared with the surfactants IMI_PROP_C4_C12, IMI_NO3_C4_C12, and those of spherical morphology, but strongly aggregated, in the solution with the cationic surfactant IMI_Cl_oxyC7_C9.
(C) 2013 Elsevier Ltd. All rights reserved. |
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Radiation Physics and Chemistry, 93, 160-167, (2013) |
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2. |
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SOLARIS: Waiting for the first light - Proceedings of XI International School and Symposium on Synchrotron Radiation in Natural Science 2012, Krakow, Poland Proceedings of XI International School and Symposium on Synchrotron Radiation in Natural Science 2012, Krakow, Poland
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Radiation Physics and Chemistry, 93, 1-3, (2013) |
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3. |
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The segmental and global dynamics in lamellar microphase-separated poly(styrene-b-isoprene) diblock copolymer studied by 1H NMR and dielectric spectroscopy The nuclear magnetic resonance (NMR) and dielectric spectroscopy (DS) methods were used to investigate the segmental and global dynamics in lamellar microphase separated poly(styrene-b-isoprene) (SI) diblock copolymer. For the first time, the susceptibility representation of the NMR relaxation data is applied to the analysis of the molecular dynamics in complex polymer systems like the diblock copolymer. This approach in combination with the frequency-temperature superposition (FTS) allows one to compare directly the NMR and DS data in an extended frequency range providing a unique comprehensive picture of various relaxation processes present in the system studied. The findings of these investigations include structural relaxations of the polyisoprene (PI) and the polystyrene (PS) blocks, a normal mode relaxation of the PI block, and an extra low frequency interfacial relaxation. Special attention has been devoted to influence of the copolymer morphology on the segmental and global dynamics in PI.
(C) 2013 Published by Elsevier Ltd. |
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European Polymer Journal, 49(12), 3986-3997, (2013) |
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4. |
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Structural elucidation of transmembrane transporter protein bilitranslocase: Conformational analysis of the second transmembrane region TM2 by molecular dynamics and NMR spectroscopy Membrane proteins represent about a third of the gene products in most organisms, as revealed by the genome sequencing projects. They account for up to two thirds of known drugable targets, which emphasizes their critical pharmaceutical importance. Here we present a study on bilitranslocase (BTL) (TCDB 2.A.65), a membrane protein primarily involved in the transport of bilirubin from blood to liver cells. Bilitranslocase has also been identified as a potential membrane transporter for cellular uptake of several drugs and due to its implication in drug uptake, it is extremely important to advance the knowledge about its 3D structure. However, at present, only a limited knowledge is available beyond the primary structure of BTL It has been recently confirmed experimentally that one of the four computationally predicted transmembrane segments of bilitranslocase, TM3, has a helical structure with hydrophilic amino acid residues oriented towards one side, which is typical for transmembrane domains of membrane proteins. In this study we confirmed by the use of multidimensional NMR spectroscopy that the second transmembrane segment, TM2, also appears in a form of alpha-helix. The stability of this polypeptide chain was verified by molecular dynamics (MD) simulation in dipalmitoyl phosphatidyl choline (DPPC) and in sodium dodecyl sulfate (SDS) micelles. The two alpha-helices, TM2 corroborated in this study, and TM3 confirmed in our previous investigation, provide reasonable building blocks of a potential transmembrane channel for transport of bilirubin and small hydrophilic molecules, including pharmaceutically active compounds.
(C) 2013 Elsevier B.V. All rights reserved. |
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Biochimica et Biophysica Acta, 1828(11), 2609-2619, (2013) |
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Molecular dynamics of the supercooled pharmaceutical agent posaconazole studied via differential scanning calorimetry and dielectric and mechanical spectroscopies This paper presents comprehensive studies on the molecular dynamics of a pharmaceutically important substance, posaconazole. In order to characterize relaxation dynamics in the supercooled liquid and glassy states, dielectric and mechanical spectroscopies were applied. Dielectric data have indicated multiple relaxation processes that appear above and below the glass transition temperature Tg (tau(alpha) = 100 s) of posaconazole. From the curvature of the dielectric log(10)(tau(alpha)) versus inverse of temperature dependence, we determine so-called "fragility", being a very popular parameter for classifying the structural dynamics of supercooled liquids and polymers. From the calculations, we get m = 150, which means that is one of the most fragile glass-forming liquids. In this paper, the relaxation dynamics of supercooled posaconazole extracted from the dielectric response function was also confronted with shear-mechanical relaxation. Finally, we have also presented a direct comparison of the fragility and the number of dynamically correlated molecules N-c determined from dynamic calorimetry curves and dielectric and mechanical spectroscopies, showing a clear deviation in the picture of glass-transition dynamics generated by calorimetric and spectroscopic techniques.
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Molecular Pharmaceutics, 10(10), 3934-3945, (2013) |
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6. |
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Molecular dynamics studies of polyurethane nanocomposite hydrogels Polyurethane PEO-based hydrogels have a broad range of biomedical applicability. They are attractive for drug-controlled delivery systems, surgical implants and wound healing dressings. In this study, a PEO based polyurethane hydrogels containing CloisiteA (R) 30B, an organically modified clay mineral, was synthesized. Structure of nanocomposite hydrogels was determined using XRD technique. Its molecular dynamics was studied by means of NMR spectroscopy, DMA and DSC analysis. The mechanical properties and thermal stability of the systems were improved by incorporation of clay and controlled by varying the clay content in polymeric matrix. Molecular dynamics of polymer chains depends on interaction of CloisiteA (R) 30B nanoparticles with soft segments of polyurethanes. The characteristic nanosize effect is observed.
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European Physical Journal - Special Topics, 222(9), 2179-2186, (2013) |
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7. |
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Synperiplanar to antiperiplanar conformation changes as underlying the mechanism of Debye process in supercooled ibuprofen In this Communication, we present experimental studies that put new insight into the puzzling nature of the Debye relaxation found in the supercooled liquid state of racemic ibuprofen. The appearance of D-relaxation in the loss spectra of non-hydrogen bonding methylated derivate of ibuprofen has proven that Debye relaxation is related solely with conformational changes of the carboxyl group, termed in this paper as synperiplanar-antiperiplanar. Our studies indicate that the presence of hydrogen bonding capabilities is not here the necessary condition to observe Debye process, however, their occurrence might strongly influence α- and D-relaxations dynamics. Interestingly, the activation energy of the D-process in ibuprofen methyl ester on approaching Tg was found to be perfectly consistent with that reported for ibuprofen by Affouard and Correia [J. Phys. Chem. B 114, 11397–11402 (2010)] (∼39 kJ/mol). Finally, IR measurements suggest that the equilibrium between conformers concentration depends on time and temperature, which might explain why the appearance of D-relaxation in supercooled ibuprofen depends on thermal history of the sample.
(C) 2013 AIP Publishing LLC. |
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Journal of Chemical Physics, 139(11), 111103-4, (2013) |
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8. |
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Interactions of a cationic surfactant - (benzyloxymethyl) dodecyldimethylammonium chloride with model biomembrane systems Phospholipids are the main components of biological membranes. The aim of the present study was to determine the influence of a cationic surfactant on phospholipid structure and dynamics. Fourier transform infrared (FTIR) and dielectric relaxation (DRS) spectroscopies as well as small-angle Xray scattering (SAXS) with synchrotron radiation have been used to analyse the structure of fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the presence of a quaternary ammonium surfactant: (benzyloxymethyl) dodecyldimethylammoniumchloride (BzMDDAC). The presence of the surfactant caused changes in the temperature of the DMPC phase transition, as revealed using FTIR and DRS measurements. This change results from the disappearance of the multilamellar phase of DMPC and the formation of the unilamellar (most likely bicellar) phase, as indicated by the SAXS results.
(C) 2013 Elsevier B.V. All rights reserved. |
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Colloids and Surfaces B: Biointerfaces, 108, 212-218, (2013) |
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9. |
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Molecular dynamics in PBA/PEO miktoarm star copolymers Molecular dynamics of miktoarm star copolymers consisting of poly(n-butyl acrylate) PBA and polyethylene oxide (PEO) arms was studied by means of Broadband Dielectric Spectroscopy (BDS) and Nuclear Magnetic Resonance (NMR) methods. The spectroscopic studies were performed for three types of copolymers differing in the composition, namely materials containing 76%, 46% and 16% molar fraction of PBA arms. The local processes, described by the Arrhenius law (e.g. the anisotropic rotation of methyl groups and the anisotropic local motions in the PEO chain), were observed for the studied systems below the glass transition temperature. It was found that the investigated PBA/PEO miktoarm star copolymers are characterized by single glass transition, which may result from similar values of glass transition temperatures of the PBA and PEO polymers. The segmental dynamics in the studied systems was quantitatively described by using the Vogel-Fulcher-Tammann (VFT) relation applied to combined NMR and BDS data. Moreover, above the glass transition temperature the interfacial polarization and conductivity phenomena were detected with the BDS method for all systems under study.
(C) 2013 Elsevier Ltd. All rights reserved. |
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Polymer, 54(13), 3341-3349, (2013) |
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10. |
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Stabilization, characterization and selective removal of Cystatin C amyloid oligomers The pathophysiological process in amyloid disorders usually involves the transformation of a functional monomeric protein via potentially toxic oligomers into amyloid fibrils. The structure and properties of the intermediary oligomers have been difficult to study due to their instability and dynamic equilibrium with smaller and larger species. In hereditary cystatin C amyloid angiopathy, a cystatin C variant is deposited in arterial walls and cause brain hemorrhage in young adults. In the present investigation, we use redox experiments of monomeric cystatin C, stabilized against domain swapping by an intramolecular disulfide bond, to generate stable oligomers (dimers, trimers, tetramers, decamers, and high molecular weight oligomers). These oligomers were characterized concerning size by gel filtration, polyacrylamide gel electrophoresis, and mass spectrometry, shape by electron and atomic force microscopy, and, function by assays of their capacity to inhibit proteases. The results showed the oligomers to be highly ordered, domain-swapped assemblies of cystatin C and that the oligomers could not build larger oligomers, or fibrils, without domain swapping. The stabilized oligomers were used to induce antibody formation in rabbits. After immunosorption, using immobilized monomeric cystatin C, and elution from columns with immobilized cystatin C oligomers, oligomer-specific antibodies were obtained. These could be used to selectively remove cystatin C dimers from biological fluids containing both dimers and monomers.
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Journal of Biological Chemistry, 288(23), 16438-16450, (2013) |
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11. |
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Structure and conformational dynamics of DMPC/dicationic surfactant and DMPC/dicationic surfactant/DNA systems Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The gemini surfactant molecule is composed of two hydrophilic "head" groups attached to hydrophobic chains and connected via molecular linker between them. The influence of different concentrations of 1,5-bis (1-imidazolilo-3-decyloxymethyl) pentane chloride (gemini surfactant) on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers with and without the presence of DNA was investigated using Fourier transformed infrared (FTIR) and circular dichroism (CD) spectroscopies, small angle scattering of synchrotron radiation and differential scanning calorimetry. With increasing concentration of surfactant in DMPC/DNA systems, a disappearance of pretransition and a decrease in the main phase transition enthalpy and temperature were observed. The increasing intensity of diffraction peaks as a function of surfactant concentration also clearly shows the ability of the surfactant to promote the organisation of lipid bilayers in the multilayer lamellar phase.
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International Journal of Molecular Sciences, 14(4), 7642-7659, (2013) |
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12. |
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Water status and water diffusion transport in lupine roots exposed to lead Water status and diffusion transport were studied in the roots of yellow lupine (Lupinus Luteus L, cv. Juno) treated for 48h with two selected concentrations of Pb(NO3)(2): 150 mg l(-1), which inhibited root growth by about 50% (medium stress intensity), as well as 350 mg l(-1), which almost entirely suppressed root elongation (severe stress intensity). Relative water content (RWC), which characterizes the degree of root water saturation, slightly increased at the lower lead concentration and remained unchanged at the higher lead dose. Ultrastructure analyses under a transmission electron microscope revealed that plasmolysis was not evoked by lead in the apical part of the meristem. Moreover, direct observation of meristem cells using Nomarsky optics indicated enhanced vacuolization in the presence of both lead concentrations. These data suggest that the water status of the roots was not affected by the metal. Due to the fact that proline is involved in the maintenance of turgor in the cells, the metabolism of this amino acid was investigated. In the roots, the activity of enzymes involved in proline synthesis, such as pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT), increased at 150 mg l(-1) Pb2+; nevertheless, proline content was diminished at the lower lead concentration. This effect is likely the result of proline degradation by proline dehydrogenase (PDH), since the activity of this enzyme increased at the lower lead dose. On the other hand, in the presence of 350 mg l(-1) Pb2+, a low level of proline was correlated with a decrease in the activity of P5CS and OAT, as well as unchanged PDH activity in lupine roots. These data may imply that enzymatic synthesis of proline was strongly damaged by the metal ions. The low level of proline in both experimental variants suggests that proline accumulation is inessential to maintaining the osmotic uptake of water into root cells. NMR spectroscopy showed that exposition of lupine seedlings to lead caused a deceleration in water transport in the roots due to a reduction in the water transfer rate across the membranes (transmembrane transfer) and vacuoles continuum, as well as water diffusion along the root apoplast. Fluorescence staining and immunogold labeling showed the presence of callose strands in cell walls and/or in the vicinity of them. In lead-treated lupine roots, callose was mainly localized in the parenchyma cortex placed lengthwise to the vascular cylinder. Callose deposits in the cell walls may reduce vacuolar transport, as well as increase cell wall resistance to water flow. Deceleration of diffusional water movement to the vascular system, may in turn, influence the rate of long-distance water transport to aerial parts of the plant.
(C) 2012 Elsevier B.V. All rights reserved. |
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Environmental and Experimental Botany, 87, 100-109, (2013) |
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13. |
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Analytical study on irradiated methylxanthine derivatives The effect of ionising radiation on the physico-chemical properties of three derivatives of xanthine: caffeine, theophylline and theobromine, has been studied. The above-drugs in the solid phase have been irradiated with E-beam of the energy 9.96 MeV with the doses varied from 25 to 400 kGy. The effects of the irradiation have been examined by differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR) and high-performance liquid chromatography (HPLC). The results have shown that the methylxanthine derivatives studied are resistant to ionising irradiation in the doses usually used for sterilisation (< 50 kGy), which means that they are relatively radiochemically stable and can be sterilised by irradiation.
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Journal of Thermal Analysis and Calorimetry, 111(3), 2165-2170, (2013) |
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14. |
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Silver nanoparticles incorporated onto ordered mesoporous silica from Tollen's reagent Noble metal nanostructures supported on mesoporous silica are bridge between traditional silica adsorbents and modern catalysts. In this work the Ag/SBA-15 mesoporous materials were synthesized and characterized. Various forms of nanosilver supported on ordered mesoporous template have been successfully obtained via proposed procedures. In all synthesized materials, Tollen's reagent (diammine silver complex [Ag(NH3)(2)](+)) was used as a silver source. Silver nanoparticles were prepared by reduction of ammoniacal silver complex by formaldehyde in the solution of stabilizer. After reduction, Ag nanoparticles could be deposited on SBA-15, or added during traditional synthesis of SBA-15 giving silver or silver chloride nanoparticles in the combination with porous silica. Silver nanostructures as nanoparticles or nanowires were also embedded onto the SBA-15 by incipient wetness impregnation of silver ions. Absorbed silver ions were next reduced under hydrogen at high temperature.
There are many advantages of utilized ammoniacal silver complex as a silver source. Proposed method is capable to synthesis of various metal nanostructures with controlled composition and morphology. The silver ammonia complex is composed of two ions surrounding and protecting the central silver ion, so it is possible to obtain very small nanoparticles using simple approach without any functionalization of external and internal surface of SBA-15. This approach allows obtaining greatly small silver nanoparticles on SBA-15 (4 nm) or nanowires depending on the metal loading amount. Moreover, the colloidal silver solution prepared from Tollen's reagent, in the presence of triblock copolymer, remains stable for a long time. Reduction of Tollen's reagent to silver colloidal solution seems to be efficient, fast and interesting approach for the preparation of supported silver nanostructures Obtained samples were characterized by powder X-ray diffraction, small angle X-ray scattering (SAXS), UV-vis spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms and photoacoustic spectroscopy (PAS).
(C) 2012 Elsevier B.V. All rights reserved. |
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Applied Surface Science, 266, 337-343, (2013) |
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15. |
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Biochemical and structural studies of plant circadian clock proteins Circadian clocks are biochemical oscillatory mechanisms that co-ordinate with a 24h period predicting the daily diurnal changes in the environment to regulate various metabolic, developmental and physiological processes in the
organisms. The plant circadian clock represents a network of interconnected multiple feedback loops at the core of
which lie two Myb-like transcription factors, Circadian Clock Associated 1 (CCA1) and Late Elongated Hypocotyl
(LHY), that express in the morning, and an evening expressing Timing of CAB Expression 1 (TOC1). Other components important for the clock are Early Flowering 3 and 4 (ELF3 and ELF4) and Lux Arrhythmo (LUX) that accumulate in the evening (Harmer, 2009). Previous studies have shown these to be part of an evening complex that is important for the regulation of the core oscillator (Nusinow et al., 2011; Herrero et al., 2012). Loss-of-function mutation studies of these components demonstrate arrhythmia under constant conditions of light (LL) and in darkness (DD) (Kolmos et al., 2009; Thines and Harmon, 2010). Recently, it has been shown (both in vivo and in vitro) that ELF3 and ELF4 interact physically with each other to perform their regulatory function (Herrero et al., 2012). Here, using various in silico and experimental approaches,
we have tried to understand the structural aspects of these two evening expressing plant clock proteins (ELF3 and 4). Due to the instability of the ELF4 and ELF3 proteins, crystallization and Small Angle X-ray Scattering (SAXS) measurements were carried out for recombinant variants tagged with fusion (MBP or NusA) proteins.
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Biotechnologia, 94(1), 40-41, (2013) |
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16. |
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Analiza danych i planowanie eksperymentu fizycznego zgodnie z normami ISO W artykule przedstawiono istotę pomiaru fizycznego i niezbędne słownictwo związane z przeprowadzaniem eksperymentu fizycznego. W skrócie podano według wskazań ISO procedurę określania standardowych niepewności pomiarowych pomiarów bezpośrednich i złożonych. Porównywanie wyników pomiarów przedstawiono jako uzgadnianie ich przedziałów utworzonych na podstawie niepewności standardowej rozszerzonej. Pokazane sposoby planowania pomiarów pozwalają określić, czy eksperyment można uznać za zakończony. Procedury takie umożliwiają zaplanowanie dokładniejszych pomiarów oraz są bardzo pomocne przy formułowaniu wniosków podsumowujących przeprowadzone doświadczenie.
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Postępy Fizyki, 64(2), 70-75, (2013) |
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Zaktualizowano: podstrony 2021-06-21 / bazę danych: 2024-04-23 by Webmaster: Zbigniew Fojud