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Molnar G.,Institute of Technical Physics and Materials Science
Journal of Materials Research | Year: 2013

A special type of epitaxial growth appears during solid-phase thin film reactions, wher. The reaction product grows epitaxially o. The substrate. Some metal silicide layers and nanostructures are known to develop such epitaxial structures. In this study, iron silicide was used to stud. The effect o. The growth mode o. The epitaxial growth. Strain-induced, self-assembled iron silicide nanostructures were grown on Si(001) substrates by electron gun evaporation of 1.0 nm iron and subsequent annealing at 500-850 °C for 60 min. The growth processes were checked by reflection high-energy electron diffraction, an. The formed structures were characterized by scanning electron microscopy and optical microscopy. The iron silicide nanostructures were oriented in square directions epitaxially fitting t. The surface of Si(001). The shape and size o. The nanostructures depended o. The annealing temperature. In some cases. The nanoparticles were arranged in circles. This might b. The direct consequence of a nucleation-controlled type transition of iron monosilicide to iron disilicide phase at nanoscale. © 2013 Materials Research Society.


Toke O.,Hungarian Academy of Sciences | Vonderviszt F.,University of Pannonia | Vonderviszt F.,Institute of Technical Physics and Materials Science
Biochemical and Biophysical Research Communications | Year: 2016

Export of external flagellar proteins requires a signal located within their N-terminal disordered part, however, these regions do not share any significant sequence similarity suggesting that the secondary/tertiary structure might be important for recognition by the export gate. NMR experiments were performed to reveal the conformational properties of the flagellin signal sequence in vitro. It assumed a largely disordered fluctuating structure in aqueous environment, but acquired a folded structure containing an amphipathic helical portion in 50% MeOH or upon addition of SDS micelles which are known to promote hydrophobic interactions. Our observations raise the possibility that the signal sequence may partially undergo amphipathic helical ordering upon interaction with the recognition unit of the flagellar export machinery in a similar way as revealed for protein import into intracellular eukaryotic organelles mediated by targeting signals of high diversity. © 2016 Elsevier Inc.


Tomas I.,ASCR Institute of Physics Prague | Kovarik O.,Czech Technical University | Vertesy G.,Institute of Technical Physics and Materials Science | Kadlecova J.,ASCR Institute of Physics Prague
Measurement Science and Technology | Year: 2014

A new revolutionary attitude toward investigation of fatigue damage in cyclically loaded steel samples is reported. The measurement is based on the method of magnetic adaptive testing, which - in contrast to traditional magnetic hysteresis investigations - picks up the relevant information from systematic measurement and evaluation of whole minor magnetic hysteresis loops and their derivatives. Satisfactory correlations between nondestructively measured magnetic descriptors and actual lifetime of the fatigued material were found. The presented method is able to serve as a powerful tool for indication of changes, which occur in the structure of the inspected objects during their industrial service lifetime, as long as they are manufactured from ferromagnetic materials. © 2014 IOP Publishing Ltd.


Vertesy G.,Institute of Technical Physics and Materials Science | Meszaros I.,Budapest University of Technology and Economics | Tomas I.,ASCR Institute of Physics Prague
NDT and E International | Year: 2013

Different nondestructive magnetic methods - major hysteresis loop measurement, Barkhausen noise measurement and minor hysteresis loop analysis (Magnetic Adaptive Testing) - were applied on a plastically deformed series of transformation induced plasticity (TRIP) steel samples. The results of the different methods were compared with each other. Good correlation was found between magnetic characteristics, measured in different ways. Magnetic Adaptive Testing (MAT) seems to be the most sensitive method. Good correlation was also found between magnetic parameters and with the destructively measured Vickers hardness values. MAT yields a linear correlation between Vickers hardness and magnetic descriptors, without magnetic saturation of the specimen. © 2012 Elsevier Ltd.


Biro L.P.,Institute of Technical Physics and Materials Science | Lambin P.,University of Namur
New Journal of Physics | Year: 2013

The scientific literature on grain boundaries (GBs) in graphene was reviewed. The review focuses mainly on the experimental findings on graphene grown by chemical vapor deposition (CVD) under a very wide range of experimental conditions (temperature, pressure hydrogen/hydrocarbon ratio, gas flow velocity and substrates). Differences were found in the GBs depending on the origin of graphene: in micro-mechanically cleaved graphene (produced using graphite originating from high-temperature, high-pressure synthesis), rows of non-hexagonal rings separating two perfect graphene crystallites are found more frequently, while in graphene produced by CVD - despite the very wide range of growth conditions used in different laboratories - GBs with more pronounced disorder are more frequent. In connection with the observed disorder, the stability of two-dimensional amorphous carbon is discussed and the growth conditions that may impact on the structure of the GBs are reviewed. The most frequently used methods for the atomic scale characterization of the GB structures, their possibilities and limitations and the alterations of the GBs in CVD graphene during the investigation (e.g. under e-beam irradiation) are discussed. The effects of GB disorder on electric and thermal transport are reviewed and the relatively scarce data available on the chemical properties of the GBs are summarized. GBs are complex enough nanoobjects so that it may be unlikely that two experimentally produced GBs of several microns in length could be completely identical in all of their atomic scale details. Despite this, certain generalized conclusions may be formulated, which may be helpful for experimentalists in interpreting the results and in planning new experiments, leading to a more systematic picture of GBs in CVD graphene. © IOP Publishing and Deutsche Physikalische Gesellschaft.

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