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Szabó,, R.,Kollá,th, Z.,Molná,r, L.,Kolenberg, K.,Kurtz, D. W.,Bryson, S. T.,Benkő,, J. M.,Christensen‐,Dalsgaard, J.,Kjeldsen, H.,Borucki, W. J.,Koch, D.,Twicken, J. D.,C Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.3
<P><B>ABSTRACT</B></P><P>The first detection of the period doubling phenomenon is reported in the <I>Kepler</I> RR Lyrae stars RR Lyr, V808 Cyg and V355 Lyr. Interestingly, all these pulsating stars show Blazhko modulation. The period doubling manifests itself as alternating maxima and minima of the pulsational cycles in the light curve, as well as through the appearance of half‐integer frequencies located halfway between the main pulsation period and its harmonics in the frequency spectrum. The effect was found to be stronger during certain phases of the modulation cycle. We were able to reproduce the period‐doubling bifurcation in our non‐linear RR Lyrae models computed by the Florida–Budapest hydrocode. This enabled us to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode and a high‐order (ninth) radial overtone showing strange‐mode characteristics. We discuss the connection of this new type of variation to the mysterious Blazhko effect and argue that it may give us fresh insights into solving this century‐old enigma.</P>
<i>Kepler</i> photometry of the prototypical Blazhko star RR Lyr: an old friend seen in a new light
Kolenberg, K.,Bryson, S.,Szabó,, R.,Kurtz, D. W.,Smolec, R.,Nemec, J. M.,Guggenberger, E.,Moskalik, P.,Benkő,, J. M.,Chadid, M.,Jeon, Y.‐,B.,Kiss, L. L.,Kopacki, G.,Nuspl, J.,Still, M Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.411 No.2
<P><B>ABSTRACT</B></P><P>We present our analysis of the long‐cadence <I>Kepler</I> data for the well‐studied Blazhko star RR Lyr, gathered during the first two quarters of the satellite’s observations and covering a total of 127 d. Besides being of great importance for our understanding of RR Lyrae stars in general, these RR Lyr data can be regarded as a case study for observations of bright stars with <I>Kepler</I>. <I>Kepler</I> can perform high‐precision photometry on targets like RR Lyr, as the saturated flux is conserved to a very high degree. The <I>Kepler</I> data on RR Lyr are revolutionary in several respects. Even with long‐cadence sampling (one measurement per 29.4 min), the unprecedented precision (< mmag) of the <I>Kepler</I> photometry allows the study of the star’s extreme light‐curve variations in detail. The multiplet structures at the main frequency and its harmonics, typical for Blazhko stars, are clearly detected up to the quintuplets. For the first time, photometric data of RR Lyr reveal the presence of half‐integer frequencies, linked to a period‐doubling effect. This phenomenon may be connected to the still unexplained Blazhko modulation. Moreover, with three observed Blazhko cycles at our disposal, we observe that there is no exact repetition in the light‐curve changes from one modulation cycle to the next for RR Lyr. This may be due to additional periodicities in the star, or to transient or quasi‐periodic changes.</P>
Orosz, Erzsé,bet,Antal, Ká,roly,Gazdag, Zoltá,n,Szabó,, Zsuzsa,Han, Kap-Hoon,Yu, Jae-Hyuk,Pó,csi, Istvá,n,Emri, Tamá,s Hindawi 2017 International journal of genomics Vol.2017 No.-
<P>To better understand the molecular functions of the master stress-response regulator AtfA in <I>Aspergillus nidulans</I>, transcriptomic analyses of the <I>atfA</I> null mutant and the appropriate control strains exposed to menadione sodium bisulfite- (MSB-), <I>t</I>-butylhydroperoxide- and diamide-induced oxidative stresses were performed. Several elements of oxidative stress response were differentially expressed. Many of them, including the downregulation of the mitotic cell cycle, as the MSB stress-specific upregulation of FeS cluster assembly and the MSB stress-specific downregulation of nitrate reduction, tricarboxylic acid cycle, and ER to Golgi vesicle-mediated transport, showed AtfA dependence. To elucidate the potential global regulatory role of AtfA governing expression of a high number of genes with very versatile biological functions, we devised a model based on the comprehensive transcriptomic data. Our model suggests that an important function of AtfA is to modulate the transduction of stress signals. Although it may regulate directly only a limited number of genes, these include elements of the signaling network, for example, members of the two-component signal transduction systems. AtfA acts in a stress-specific manner, which may increase further the number and diversity of AtfA-dependent genes. Our model sheds light on the versatility of the physiological functions of AtfA and its orthologs in fungi.</P>
Nemec, J. M.,Smolec, R.,Benkő,, J. M.,Moskalik, P.,Kolenberg, K.,Szabó,, R.,Kurtz, D. W.,Bryson, S.,Guggenberger, E.,Chadid, M.,Jeon, Y.‐,B.,Kunder, A.,Layden, A. C.,Kinemuchi, K.,Kis Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.417 No.2
<P><B>ABSTRACT</B></P><P>Nineteen of the ∼40 RR Lyr stars in the <I>Kepler</I> field have been identified as candidate non‐Blazhko (or unmodulated) stars. In this paper we present the results of Fourier decomposition of the time‐series photometry of these stars acquired during the first 417 d of operation (Q0–Q5) of the <I>Kepler</I> telescope. Fourier parameters based on ∼18 400 long‐cadence observations per star (and ∼150 000 short‐cadence observations for FN Lyr and for AW Dra) are derived. None of the stars shows the recently discovered ‘period‐doubling’ effect seen in Blazhko variables; however, KIC 7021124 has been found to pulsate simultaneously in the fundamental and second overtone modes with a period ratio <I>P</I><SUB>2</SUB>/<I>P</I><SUB>0</SUB>∼ 0.593 05 and is similar to the double‐mode star V350 Lyr. Period change rates are derived from O − C diagrams spanning, in some cases, over 100 years; these are compared with high‐precision periods derived from the <I>Kepler</I> data alone. Extant Fourier correlations by Kovács, Jurcsik et al. (with minor transformations from the <I>V</I> to the <I>Kp</I> passband) have been used to derive underlying physical characteristics for all the stars. This procedure seems to be validated through comparisons of the <I>Kepler</I> variables with Galactic and Large Magellanic Cloud (LMC) RR Lyr stars. The most metal‐poor star in the sample is NR Lyr, with [Fe/H] =−2.3 dex; and the four most metal‐rich stars have [Fe/H] ranging from −0.6 to +0.1 dex. Pulsational luminosities and masses are found to be systematically smaller than <I>L</I> and <IMG src='/wiley-blackwell_img/equation/MNR_19317_mu1.gif' alt ='inline image'/> values derived from stellar evolution models, and are favoured over the evolutionary values when periods are computed with the Warsaw linear hydrodynamics code. Finally, the Fourier parameters are compared with theoretical values derived using the Warsaw non‐linear convective pulsation code.</P>
Pá,linká,s, Andrá,s,Molná,r, Gyö,rgy,Magda, Gá,bor Zsolt,Hwang, Chanyong,Tapasztó,, Levente,Samuely, Peter,Szabó,, Pavol,Osvá,th, Zoltá,n Elsevier 2017 Carbon Vol.124 No.-
<P>The development of functional composite nanomaterials based on graphene and metal nanoparticles (NPs) is currently the subject of intense research interest. In this study we report the preparation of novel type of graphene/Sn and graphene/SnOx (1 <= x <= 2) hybrid nanostructures and their investigation by scanning probe methods. First, we prepare Sn NPs by evaporating 7-8 nm tin on highly oriented pyrolytic graphite substrates. Graphene/Sn nanostructures are obtained by transferring graphene on top of the tin NPs immediately after evaporation. We show by scanning tunnelling microscopy (STM) and spectroscopy (STS) that tin NPs reduce significantly the environmental p-type doping of graphene. Furthermore, we demonstrate by low-temperature STM and STS measurements that superconductivity is induced in graphene, either directly supported by Sn NPs or suspended between them. Additionally, we prepare SnOx NPs by annealing the evaporated tin at 500 degrees C. STS measurements performed on hybrid graphene/SnOx nanostructures reveal the electronic band gap of SnOx NPs. The results can open new avenues for the fabrication of novel hybrid superconducting nanomaterials with designed structures and morphologies. (C) 2017 Elsevier Ltd. All rights reserved.</P>
Stello, D.,Bruntt, H.,Kjeldsen, H.,Bedding, T. R.,Arentoft, T.,Gilliland, R. L.,Nuspl, J.,Kim, S.-L.,Kang, Y. B.,Koo, J.-R.,Lee, J.-A.,Sterken, C.,Lee, C.-U.,Jensen, H. R.,Jacob, A. P.,Szabó,, R Blackwell Publishing Ltd 2007 Monthly notices of the Royal Astronomical Society Vol.377 No.2
<P>ABSTRACT</P><P>Measuring solar-like oscillations in an ensemble of stars in a cluster, holds promise for testing stellar structure and evolution more stringently than just fitting parameters to single field stars. The most-ambitious attempt to pursue these prospects was by Gilliland et al. who targeted 11 turn-off stars in the open cluster M67 (NGC 2682), but the oscillation amplitudes were too small (<20 μmag) to obtain unambiguous detections. Like Gilliland et al. we also aim at detecting solar-like oscillations in M67, but we target red giant stars with expected amplitudes in the range 50–500 μmag and periods of 1 to 8 h. We analyse our recently published photometry measurements, obtained during a six-week multisite campaign using nine telescopes around the world. The observations are compared with simulations and with estimated properties of the stellar oscillations. Noise levels in the Fourier spectra as low as 27 μmag are obtained for single sites, while the combined data reach 19 μmag, making this the best photometric time series of an ensemble of red giant stars. These data enable us to make the first test of the scaling relations (used to estimate frequency and amplitude) with an homogeneous ensemble of stars. The detected excess power is consistent with the expected signal from stellar oscillations, both in terms of its frequency range and amplitude. However, our results are limited by apparent high levels of non-white noise, which cannot be clearly separated from the stellar signal.</P>