ckiewicz University In Poznan

Poznań, Poland

ckiewicz University In Poznan

Poznań, Poland
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Pal S.,Thematic Unit of Excellence on Nanodevice Technology | Klos J.W.,ckiewicz University In Poznan | Das K.,Thematic Unit of Excellence on Nanodevice Technology | Hellwig O.,A Western Digital Company | And 3 more authors.
Applied Physics Letters | Year: 2014

We present an all-optical time-resolved measurement of spin wave (SW) dynamics in a series of antidot lattices based on [Co(0.75nm)/Pd(0.9nm)]8 multilayer (ML) systems with perpendicular magnetic anisotropy. The spectra depend significantly on the areal density of the antidots. The observed SW modes are qualitatively reproduced by the plane wave method. The interesting results found in our measurements and calculations at small lattice constants can be attributed to the increase of areal density of the shells with modified magnetic properties probably due to distortion of the regular ML structure by the Ga ion bombardment and to increased coupling between localized modes. We propose and discuss the possible mechanisms for this coupling including exchange interaction, tunnelling, and dipolar interactions. © 2014 AIP Publishing LLC.


Szczucinski W.,ckiewicz University In Poznan | Kokocinski M.,ckiewicz University In Poznan | Rzeszewski M.,ckiewicz University In Poznan | Chague-Goff C.,University of New South Wales | And 5 more authors.
Sedimentary Geology | Year: 2012

The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5. km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, diatom assemblages and nannoliths. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2. km of the coastline and very poorly to poorly sorted mud farther inland. More specifically, there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Few diatoms were present in beach sediments, soils and tsunami deposits within 1. km of the coastline, while diatoms were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~. 1. km of the coastline were mostly derived from beach and dune erosion. From 1 to 2. km landward the contribution of these sources decreased, while sources comprising local soil erosion and the entrainment of sediments from the Teizan-bori canal increased. Farther inland, local soil erosion was the major sediment source for the mud deposits. The tsunami deposits were most likely deposited during at least two inundations, mostly out from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening, position on C-M diagrams and frequent horizontal lamination. The present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin (marine diatoms, foraminifera, nannoliths, marine sediments) may be of limited use. © 2012 Elsevier B.V.


Wojtera-Kwiczor J.,University of Osnabrück | Wojtera-Kwiczor J.,ckiewicz University In Poznan | Gross F.,University of Osnabrück | Leffers H.-M.,University of Osnabrück | And 3 more authors.
Frontiers in Plant Science | Year: 2012

The cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12, GapC) plays an important role in glycolysis by providing the cell with ATP and NADH. Interestingly, despite its glycolytic function in the cytosol, GAPDH was reported to possess additional non-glycolytic activities, correlating with its nuclear, or cytoskeletal localization in animal cells. In transiently transformed mesophyll protoplasts from Arabidopsis thaliana colocalization and interaction of the glycolytic enzymes with the mitochondria and with the actin cytoskeleton was visualized by confocal laser scanning microscopy (cLSM) using fluorescent protein fusions and by bimolecular fluorescence complementation, respectively. Yeast two-hybrid screens, dot-blot overlay assays, and co-sedimentation assays were used to identify potential protein-protein interactions between two cytosolic GAPDH isoforms (GapC1, At3g04120; GapC2, At1g13440) from A. thaliana with the neighboring glycolytic enzyme, fructose 1,6-bisphosphate aldolase (FBA6, At2g36460), the mitochondrial porin (VDAC3; At5g15090), and actin in vitro. From these experiments, a mitochondrial association is suggested for both glycolytic enzymes, GAPDH and aldolase, which appear to bind to the outer mitochondrial membrane, in a redox-dependent manner. In addition, both glycolytic enzymes were found to bind to F-actin in co-sedimentation assays, and lead to bundling of purified rabbit actin, as visualized by cLSM. Actin-binding and bundling occurred reversibly under oxidizing conditions. We speculate that such dynamic formation of microcompartments is part of a redox-dependent retrograde signal transduction network for adaptation upon oxidative stress. © 2013 Wojtera-Kwiczor, Groß, Leffers, Kang, Schneider and Scheibe.


Chague-Goff C.,University of New South Wales | Chague-Goff C.,Australian Nuclear Science and Technology Organisation | Niedzielski P.,ckiewicz University In Poznan | Wong H.K.Y.,Australian Nuclear Science and Technology Organisation | And 3 more authors.
Sedimentary Geology | Year: 2012

Large areas of farmland in the Sendai Plain, Japan, were inundated by the 11 March 2011 Tohoku-oki tsunami and covered by a discontinuous 30-0.2cm thick sediment layer consisting of sand and/or mud and generally thinning and fining inland. Two months after the tsunami, numerous rice paddy fields and depressions remained ponded with brackish or saline water. A series of field surveys in May, August and October 2011 were carried out north of Sendai airport, in order to assess the environmental impact of the tsunami. While evaporation had resulted in elevated conductivity in ponded water in May (up to 68.2mScm-1), rainfall over the next five months led to dilution, although brackish water was still recorded in depressions and on paddy fields. Tsunami sediments, underlying soil and soil beyond the tsunami inundation limit were collected at 43 sites along and near a transect extending over 5km inland, and analysed for grain size, organic content, water leachable ions, acid leachable metals and exchangeable metalloids. Water leachable anion and cation concentrations were elevated in sandy and muddy tsunami deposits and soils particularly in areas, where seawater had stagnated for a longer period of time after the tsunami, with up to 10.5% Cl, 6.6% Na, 2.8% SO4, 440mgkg-1 Br measured in surface sediments (<0.5cm depth). Vertical variations were also recorded, with higher concentrations often measured in the surface samples. A similar trend could be observed for some of the metalloids (As) and metals (Zn, Cu and Ni), although in general, maximum concentrations of metals and metalloids were not much higher than in soils not inundated by the tsunami and were within background levels for uncontaminated Japanese soils.The impact of saltwater inundation was documented in the chemistry of soils underlying tsunami sediments, which were affected by salt contamination down to ~. 15. cm depth, and soils not covered by tsunami deposits. The latter implies that the extent of tsunami inundation may successfully be determined using geochemical markers in absence of any sedimentological evidence. Water leachable ions mostly decreased over time, however, they remained high enough to impact on rice farming, which was completely halted in 2011. Although further work is required to assess the longer term impact of tsunami inundation, flushing of salt with freshwater, as well as the possible removal of sandy/muddy sediments and underlying soil are recommended to allow crop production to resume. © 2012 Elsevier B.V.


Chague-Goff C.,University of New South Wales | Chague-Goff C.,Australian Nuclear Science and Technology Organisation | Andrew A.,Environmental Isotopes Pty. Ltd | Szczucinski W.,ckiewicz University In Poznan | And 2 more authors.
Sedimentary Geology | Year: 2012

The geochemical signature of the Tohoku-oki tsunami deposit and underlying soil was assessed two months, five months and seven months after the 11 March 2011 tsunami inundated the Sendai Plain. The extent of the recognisable sand deposit was traced up to 2.9km inland while a mud deposit was found up to 4.65km inland, representing 60% and nearly 95% of the maximum tsunami inundation, respectively. The limit of tsunami inundation was identified 4.85km from the shore using geochemical marine markers (S and Cl) two months after the tsunami, in the absence of any sedimentological evidence. Concentrations of other geochemical markers (K, Ca, Sr) indicative of the marine incursion and associated minerals were found to decrease landward. δ13C and δ15N and C/N ratios suggested a mixture of terrestrial and marine organic sources in the sediment, while δ34S of sulphate reflected the marine source of water soluble salts. The chemical composition of the 869AD Jogan tsunami sand deposit was characterised by high Sr and Rb concentrations and was comparable to that of the Tohoku-oki tsunami deposit, suggesting that the sources of sediment may be similar. Marked decreases in S and Cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments. However, both S and Cl markers as well as Sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami. This suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition, in particular when marine microfossils are sparse or lacking as is the case on the Sendai Plain. This would allow researchers to redraw palaeotsunami inundation maps and re-assess the magnitude of events such as the Jogan tsunami and other palaeotsunamis, not only on the Sendai Plain but also elsewhere around the world. This has important implications for tsunami risk assessment, hazard mitigation and preparedness. © 2012 Elsevier B.V.


Depondt Ph.,University Pierre and Marie Curie | Levy J.-C.S.,CNRS Materials and Quantum Phenomena Laboratory | Mamica S.,ckiewicz University in Poznan
Journal of Physics Condensed Matter | Year: 2013

Langevin simulations at finite temperature of two-dimensional magnetic nanodots were performed using the Landau-Lifshitz equation with exchange and dipolar interactions. In a wide range of temperatures, the dynamics of square samples with one central vortex was studied, focusing on the out-of-plane magnetic component at the vortex-core. This vortex-core undergoes polarization sign reversals in a thermally activated process. In the intervals between polarization flips, the out-of-plane spin components at the vortex-core show oscillations with identifiable frequencies connected with certain eigenfrequencies of the system associated with polarity active modes. The vortex-core positions were also monitored. © 2013 IOP Publishing Ltd.


Kozirog A.,University of Lodz | Brycki B.,ckiewicz University In Poznan
Acta Biochimica Polonica | Year: 2015

Quaternary ammonium salts (QAS) belong to surfactant commonly used both, in the household and in different branches of industry, primarily in the process of cleaning and disinfection. They have several positive features inter alia effectively limiting the development of microorganisms on many surfaces. In the present work, two compounds were used as biocides: hexamethylene-1,6-bis-(N, N-dimethyl-N-dodecylammonium bromide) that belongs to the gemini surfactant (GS), and its single analogue - dodecyl(trimethyl)ammonium bromide (DTAB). Two fold dilution method was used to determine the minimum concentration of compounds (MIC) which inhibit the growth of bacteria: Staphylococcus aureus (ATCC 6538 and an environmental strain), Pseudomonas aeruginosa (ATCC 85327 and an environmental strain), and yeast Candida albicans (ATCC 11509 and an environmental strain). The viability of cells in liquid cultures with addition of these substances at 1/4 MIC, 1/2 MIC and MIC concentrations were also determined. The obtained results show that DTAB inhibits the growth of bacteria at the concentration of 0.126-1.010 μM/ml, and gemini surfactant is active at 0.036-0.029 μM/ml. Therefore, GS is active at more than 17-70-fold lower concentrations than its monomeric analogue. Strains isolated from natural environment are less sensitive upon testing biocides than the references strains. Both compounds at the MIC value reduced the number of cells of all strains. The use of too low concentration of biocides can limit the growth of microorganisms, but often only for a short period of time in case of special environmental strains. Later on, they can adapt to adverse environmental conditions and begin to evolve defence mechanisms.


Czaplinska J.,ckiewicz University In Poznan | Decyk P.,ckiewicz University In Poznan | Ziolek M.,ckiewicz University In Poznan
Applied Catalysis A: General | Year: 2015

Commercial silica (Ultrasil - BET surface area 158 m2/g) was modified with platinum and/or silver. Before metal loading, the silica was functionalized with one of the following organosilanes, 3-aminopropyltrimethoxysilane (APTMS) and 2-mercaptopropyltrimethoxysilane (MPTMS) or both of them. It was proved that the nature of organosilane (MPTMS or APTMS) used for functionalization of silica before silver and platinum loading, played an important role in the anchoring of Pt and Ag species and affected the kinds of bimetallic particles formed. The creation of alloy-like bimetallic structure depends on a combination of two parameters, the nature of organosilane and the method of modification by platinum and silver. If the one-pot method of modification was used, the functionalization of silica by MPTMS favoured alloy formation (PtAg/Si-M and PtAg/Si-AM samples). APTMS functionalization promoted alloy formation if the step-by-step modification was applied, independently of the sequence of metals loading. Core-shell structure was formed only if MPTMS functionalization of silica was used and silver species were loaded first (1Ag2Pt/Si-M sample). Bimetallic particles were not formed in two samples, PtAg/Si-A and 1Pt2Ag/Si-M. The presented results have proved that selectivity of bimetallic catalysts in methanol oxidation depends on metals loading and dispersion, whereas their activity is influenced by the interaction between platinum and silver in bimetallic particles. The highest selectivity to methyl formate (84%) for 100% conversion of methanol was reached over PtAg/Si-M at 373 K. © 2015 Elsevier B.V. All rights reserved.


Szwajca A.,ckiewicz University In Poznan | Koroniak H.,ckiewicz University In Poznan
Phosphorus, Sulfur and Silicon and the Related Elements | Year: 2016

Due to their insulating properties, small organic molecules deposited on the silicon surfaces, can be used as organic transistors. Since the molecular resistance is known to increase with increasing content of electron withdrawing groups, the self-assembled monolayers (SAMs) with the fluorocarbon moieties have been used to study the electronic properties of underlying solid substrate. Moreover, fluorinated SAMs may undergo charge transfer with leading materials designed for organic electronic devices. This minireview focuses on the structure of underlying silicon surface after wet-chemical routes towards the formation of silicon-organic monolayers and describes ways of potential changes in the electronic properties of covered silicon surface. © 2016 Taylor & Francis Group, LLC.


Mamica S.,ckiewicz University In Poznan
Acta Physica Polonica A | Year: 2015

We use a microscopic theory taking into account the nearest-neighbour exchange and dipolar interactions to study two-dimensional magnetic nanodots and nanorings. Magnetic configuration is assumed to form an inplane vortex (circular magnetization). We examine the dependence of the frequencies and profiles of spin waves on the dipolar-to-exchange interaction ratio d and the size of the dot (ring). Special attention is paid to some particular modes, including the lowest mode in the spectrum and the fundamental mode, the frequency of which proves almost independent of d. In the case of the lowest mode different profiles are observed: azimuthal, fundamental (quasiuniform) or highly localized, depending on d and the size. We also study the fundamental mode evolution including its hybridization and explain the selection rules.

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