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Kaptay G.,University of Miskolc | Kaptay G.,Bay Zoltan Nonprofit Ltd
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2017

The exponential model for the temperature (T) dependence of the excess Gibbs energy of liquid solutions within the framework of the Redlich-Kister polynomials is proven to be an efficient tool to avoid high-T artefacts, such as an artificial inverted miscibility gap, caused by the linear model. However, it has been claimed that the exponential model can lead to a low-T artefact, i.e. to the artificial low-T re-stabilization of the liquid solution. As shown here, this claim is un-supported for all the 15 binary systems studied so far by the exponential model in the literature. Still, the artefact might appear for other systems, or for lower temperatures, as the 15 systems were modelled at and above 298 K. To make sure the low-T artefact does not appear, this paper introduces a new, low-T polynomial, which is matched with the exponential model at temperature T*, defined as the lowest liquidus temperature of the given system. The low-T model is described by a four parameter polynomial, obtained analytically from the two fitted parameters of the exponential model, ensuring that the four excess functions (the excess Gibbs energy, the heat of mixing, the excess entropy and the excess heat capacity) are continuous functions of T in the whole T-interval at any composition. When the complexity of the liquid alloy requires more than two semi-empirical parameters, the combined linear-exponential model should be used instead of the exponential model, with the same matching low-T polynomial. The inherently inconsistent nature of the recent LET function (see S.M. Liang, P. Wang, R. Schmid-Fetzer, Calphad 54 (216) 82–96) is discussed, as it was introduced to replace the exponential model. It is proven by the new simplified assessment of the Mg-Si system that the exponential model can be applied to this system without any artifact, contrary to the claim of Schmid-Fetzer et al., Calphad 31 (2007) 131–142. © 2017 Elsevier Ltd

Szamecz B.,Institute of Biochemistry | Boross G.,Institute of Biochemistry | Kalapis D.,Institute of Biochemistry | Kovacs K.,Institute of Biochemistry | And 11 more authors.
PLoS Biology | Year: 2014

Adaptive evolution is generally assumed to progress through the accumulation of beneficial mutations. However, as deleterious mutations are common in natural populations, they generate a strong selection pressure to mitigate their detrimental effects through compensatory genetic changes. This process can potentially influence directions of adaptive evolution by enabling evolutionary routes that are otherwise inaccessible. Therefore, the extent to which compensatory mutations shape genomic evolution is of central importance. Here, we studied the capacity of the baker's yeast genome to compensate the complete loss of genes during evolution, and explored the long-term consequences of this process. We initiated laboratory evolutionary experiments with over 180 haploid baker's yeast genotypes, all of which initially displayed slow growth owing to the deletion of a single gene. Compensatory evolution following gene loss was rapid and pervasive: 68% of the genotypes reached near wild-type fitness through accumulation of adaptive mutations elsewhere in the genome. As compensatory mutations have associated fitness costs, genotypes with especially low fitnesses were more likely to be subjects of compensatory evolution. Genomic analysis revealed that as compensatory mutations were generally specific to the functional defect incurred, convergent evolution at the molecular level was extremely rare. Moreover, the majority of the gene expression changes due to gene deletion remained unrestored. Accordingly, compensatory evolution promoted genomic divergence of parallel evolving populations. However, these different evolutionary outcomes are not phenotypically equivalent, as they generated diverse growth phenotypes across environments. Taken together, these results indicate that gene loss initiates adaptive genomic changes that rapidly restores fitness, but this process has substantial pleiotropic effects on cellular physiology and evolvability upon environmental change. Our work also implies that gene content variation across species could be partly due to the action of compensatory evolution rather than the passive loss of genes. © 2014 Szamecz et al.

Kaptay G.,University of Miskolc | Kaptay G.,Bay Zoltan Nonprofit Ltd
Journal of Materials Science | Year: 2016

The Butler equation is extended to model equilibrium grain boundary (GB) energy and the equilibrium GB composition of a polycrystal, as a function of the following state parameters: bulk composition, temperature, pressure and the five degrees of freedom of the GB. In the simplest case of an ideal solution and equal atomic sizes of the components, the Butler equation reduces back to the well-known McLean equation of GB segregation. When the components repulse each other in the solid solution, grain boundary segregation transition (GBST) appears below the critical temperature of the bulk solid miscibility gap. The GBST line is a new equilibrium line in equilibrium phase diagrams. This new model is demonstrated for copper (Cu) segregation to the GBs in nickel (Ni) and for the phosphorous (P) segregation to the GBs in bcc iron (Fe). The GBST line appears in the Ni-rich (Fe-rich) corner of the Ni–Cu (Fe–P) phase diagram in coordinates of bulk Cu (P) mole fraction vs temperature at fixed pressure. The mole fraction of the solute (Cu or P), corresponding to the GBST line steadily increases with temperature. At a lower solute content (Cu or P), or at a higher temperature compared to the GBST line, the GB is composed mostly of the solvent atoms (Ni or Fe). Contrariwise, at a higher solute content (Cu or P), or at a lower temperature compared to the GBST line, the GB is composed mostly of the solute atoms (Cu or P). These low-segregation and high-segregation states of the GB are transformed into each other via a reversible first-order GBST. This latter process takes place when the GBST line is crossed by changing the bulk composition or the temperature. The results, theoretically estimated, are in agreement with earlier experimental results. © 2015, Springer Science+Business Media New York.

Beleznai R.,Bay Zoltan Nonprofit Ltd. | Paczelt I.,University of Miskolc
Engineering with Computers | Year: 2013

Parametric analysis of a two-layered axially loaded strand is performed using the recently developed p-version finite element code, which describes the geometry well and takes into account all possible inter-wire motions and frictional contact between the wires. A special nonlinear contact theory was developed based on the Hertz-theory. It is assumed that the wires have homogenous, isotropic, linear elastic material properties. The developed code is a tool for designing wire rope strands that require low computer resources and short computational time. Case studies are performed to verify and demonstrate the efficiency and applicability of the method. Design curves are presented according to the strand geometry parameters such as helix angle and ratio of the wire radius in the different layers. The optimal geometry parameters for a given strand can be determined using these design curves. © 2012 Springer-Verlag London Limited.

Janczak-Rusch J.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Kaptay G.,Bay Zoltan Nonprofit Ltd. | Kaptay G.,University of Miskolc | Jeurgens L.P.H.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Journal of Materials Engineering and Performance | Year: 2014

This paper gives an historic perspective of the concept of "Interfacial Design" in joined (e.g. soldered, brazed, diffusion bonded) assemblies. During the course of history, the awareness grew that the interface in a material joint can be perceived at different length scales. With the continuing development of joining materials and technologies, it became evident that the performance of assemblies is critically dependent on the structure and composition of the multiple internal interfaces in the material joints. Resulting trends in the microstructural design of soldering, brazing, and other bonding materials by smart engineering of internal interfaces, as driven by increasingly complex technological requirements, are briefly addressed. © 2014 ASM International.

Kaptay G.,Bay Zoltan Nonprofit Ltd | Kaptay G.,University of Miskolc | Janczak-Rusch J.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Pigozzi G.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Jeurgens L.P.H.,Empa - Swiss Federal Laboratories for Materials Science and Technology
Journal of Materials Engineering and Performance | Year: 2014

A general equation is derived for melting point depression (MPD) of pure metals, consisting of three terms: MPD due to high gas pressure, MPD due to high strain energy, and MPD due to small size of the metal. Particular equations are derived for different configurations of the solid metal, including grains embedded within a matrix. The equations obtained in this paper can be used to design nano-joining structures with improved MPD. © 2014 ASM International.

Sandor T.,Esab Kft. | Sandor T.,Hungarian Academy of Sciences | Mekler C.,BAY ZOLTAN Nonprofit Ltd. | Dobranszky J.,Hungarian Academy of Sciences | And 2 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2013

It is experimentally shown that a thin layer of silica flux leads to an increased depth of weld penetration during activated TIG (=A-TIG) welding of Armco iron. The oxygen-content is found higher in the solidified weld metal and it is linked to the increased depth of penetration through the reversed Marangoni convection. It is theoretically shown for the first time that the basic reason of the reversed Marangoni convection is the phenomenon called "surface phase transition" (SPT), leading to the formation of a nano-thin FeO layer on the surface of liquid iron. It is shown that the ratio of dissolved oxygen in liquid iron to the O-content of the silica flux is determined by the wettability of silica particles by liquid iron. It is theoretically shown that when the silica flux surface density is higher than 15 μg/mm2, reversed Marangoni flow will take place along more than 50 pct of the melted surface. Comparing the SPT line with the dissociation curves of a number of oxides, they can be positioned in the following order of their ability to serve as a flux for A-TIG welding of steel: anatase-TiO2 (best)-rutile-TiO2 (very good)-silica-SiO2 (good)-alumina-Al2O3 (does not work). Anatase (and partly rutile) are self-regulating fluxes, as they provide at any temperature just as much dissolved oxygen as needed for the reversed Marangoni convection, and not more. On the other hand, oxygen can be over-dosed if silica, and other, less stable oxides (such as iron oxides) are used. © 2012 The Minerals, Metals & Materials Society and ASM International.

Nagy E.,University of Szeged | Urban E.,University of Szeged | Becker S.,Bruker | Kostrzewa M.,Bruker | And 3 more authors.
Anaerobe | Year: 2013

Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used today for species determination of bacteria and fungi in routine microbiological laboratories, and can also be used for subtyping of bacteria, such as Bacteroides fragilis. Propionibacterium acnes is frequently referred to as an anaerobic skin commensal of relatively low pathogenicity. In addition to its accepted pathogenic role in acne, P. acnes is now emerging as an important opportunistic pathogen in many other clinical situations, including late-stage prosthetic joint infections, osteomyelitis, endocarditis, endophthalmitis, post-neurosurgical infections and possibly prostate cancer. At the population genetic level, P. acnes can be differentiated into a number of distinct phylogroups, known as types IA1, IA2, IB, IC, II and III, which may be associated with different types of infections and clinical conditions. The aim of the present study was to evaluate MS-based typing for resolution of these genetic groups after routine identification by MALDI-TOF MS (Bruker MALDI Biotyper). The software package ClinProTools 2.2 was used to analyze the protein based mass spectra of reference strains belonging to types IA, IB, IC, II and III. Phylogroup-specific peaks and peak shifts were then identified visually. In addition, peak variations between the different types of P. acnes were investigated by using FlexAnalysis 3.3 software (Bruker). A differentiating library was created, which was used to type further 48 clinical isolates of P. acnes. Typing data obtained by MALDI-TOF MS were then compared with the results from Multilocus Sequence Typing (MLST). Most of the clinical isolates (n = 19) belonged to the type IA grouping according to MALDI-TOF MS. By MLST, all isolates were identified as type IA1. Twenty-one clinical isolates belonged to the type IB cluster based on both MALDI-TOF MS and MLST typing. Eight clinical isolates were identified as type II strains by both typing methods and all the type III reference strains could be distinguished by the presence of a unique type III-specific peak (7238 Da) by the MALDI-TOF MS. Our study demonstrates that MALDI-TOF MS is a reliable and powerful tool for rapid identification and typing of P. acnes strains from the main genetic divisions of the species. © 2013 Elsevier Ltd.

Jano V.,Bay Zoltan Nonprofit Ltd | Buza G.,Bay Zoltan Nonprofit Ltd
Materials Science Forum | Year: 2013

Composites of ceramic particle reinforcement (such as alumina) have potential for high temperature structural applications. In contrast to conventional processing methods (e.g. mechanical alloying), in situ processing techniques can be inexpensive and can also lead to unique microstructures, such as very fine dispersions of the reinforcements or interconnecting phases. The feasibility of processing Fe/Al2O3 composites layer by an in situ displacement reaction between Fe2O3 and Al by using laser beam pre-experiments were carried out and the results are presented in this paper. © (2013) Trans Tech Publications, Switzerland.

Bezi Z.,Bay Zoltan Nonprofit Ltd | Szavai S.,Bay Zoltan Nonprofit Ltd
Advanced Materials Research | Year: 2014

In this study the repair weld simulation of an austenitic steel pipe is performed to measure the residual stresses caused by the welding. The simulation consists of three work tasks. First the girth welding of the pipe is performed on simplified geometries to decrease the calculation time. The next work task is the simulation of the machining of the repair weld excavation, performed in one simulation step. The last task is the simulation of the repair welding. Residual stress measurements are performed on weld repair to provide validation of the simulation performed on the model. © (2014) Trans Tech Publications, Switzerland.

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