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Imaging chiral symmetry breaking from Kekulé bond order in graphene
Gutié,rrez, Christopher,Kim, Cheol-Joo,Brown, Lola,Schiros, Theanne,Nordlund, Dennis,Lochocki, Edward ,B.,Shen, Kyle M.,Park, Jiwoong,Pasupathy, Abhay N. Nature Publishing Group, a division of Macmillan P 2016 NATURE PHYSICS Vol.12 No.10
Chirality—or ‘handedness’—is a symmetry property crucial to fields as diverse as biology, chemistry and high-energy physics. In graphene, chiral symmetry emerges naturally as a consequence of the carbon honeycomb lattice. This symmetry can be broken by interactions that couple electrons with opposite momenta in graphene. Here we directly visualize the formation of Kekulé bond order, one such phase of broken chiral symmetry, in an ultraflat graphene sheet grown epitaxially on a copper substrate. We show that its origin lies in the interactions between individual vacancies in the copper substrate that are mediated electronically by the graphene. We show that this interaction causes the bonds in graphene to distort, creating a phase with broken chiral symmetry. The Kekulé ordering is robust at ambient temperature and atmospheric conditions, indicating that intercalated atoms may be harnessed to drive graphene and other two-dimensional materials towards electronically desirable and exotic collective phases.
Klein tunnelling and electron trapping in nanometre-scale graphene quantum dots
Gutié,rrez, Christopher,Brown, Lola,Kim, Cheol-Joo,Park, Jiwoong,Pasupathy, Abhay N. Nature Publishing Group 2016 NATURE PHYSICS Vol.12 No.11
Relativistic fermions that are incident on a high potential barrier can pass through unimpeded, a striking phenomenon termed the ‘Klein paradox’ in quantum electrodynamics. Electrostatic potential barriers in graphene provide a solid-state analogue to realize this phenomenon. Here, we use scanning tunnelling microscopy to directly probe the transmission of electrons through sharp circular potential wells in graphene created by substrate engineering. We find that electrons in this geometry display quasi-bound states where the electron is trapped for a finite time before escaping via Klein tunnelling. We show that the continuum Dirac equation can be successfully used to model the energies and wavefunctions of these quasi-bound states down to atomic dimensions. We demonstrate that by tuning the geometry of the barrier it is possible to trap particular energies and angular momentum states with increased efficiency, showing that atomic-scale electrostatic potentials can be used to engineer quantum transport through graphene.
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>
Bakonyi, Pé,ter,Kumar, Gopalakrishnan,Bé,lafi-Bakó,, Katalin,Kim, Sang-Hyoun,Koter, Stanislaw,Kujawski, Wojciech,Nemestó,thy, Ná,ndor,Peter, Jakub,Pientka, Zbynek Elsevier 2018 Bioresource technology Vol.270 No.-
<P><B>Abstract</B></P> <P>This review article focuses on an assessment of the innovative Gas Separation Membrane Bioreactor (GS-MBR), which is an emerging technology because of its potential for in-situ biohydrogen production and separation. The GS-MBR, as a special membrane bioreactor, enriches CO<SUB>2</SUB> directly from the headspace of the anaerobic H<SUB>2</SUB> fermentation process. CO<SUB>2</SUB> can be fed as a substrate to auxiliary photo-bioreactors to grow microalgae as a promising raw material for biocatalyzed, dark fermentative H<SUB>2</SUB>-evolution. Overall, these features make the GS-MBR worthy of study. To the best of the authors’ knowledge, the GS-MBR has not been studied in detail to date; hence, a comprehensive review of this topic will be useful to the scientific community.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel integrative system has been proposed for biohydrogen technology. </LI> <LI> Innovative Gas Separation Membrane Bioreactors are evaluated. </LI> <LI> Simultaneous biohydrogen production and separation is outlined. </LI> <LI> Gas separation membrane technology for CO<SUB>2</SUB> removal is suggested. </LI> <LI> Algae cultivation using the CO<SUB>2</SUB> removed and biohydrogen effluent is assessed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
The earliest phases of high-mass star formation, as seen in NGC 6334 by <i>Herschel</i>-HOBYS
Tigé,, J.,Motte, F.,Russeil, D.,Zavagno, A.,Hennemann, M.,Schneider, N.,Hill, T.,Nguyen Luong, Q.,Di Francesco, J.,Bontemps, S.,Louvet, F.,Didelon, P.,Kö,nyves, V.,André,, Ph.,Leuleu, Springer-Verlag 2017 Astronomy and astrophysics Vol.602 No.-
SPATIAL CLUSTERING FROM<i>GALEX</i>-SDSS SAMPLES: STAR FORMATION HISTORY AND LARGE-SCALE CLUSTERING
Heinis, Sé,bastien,Budavá,ri, Tamá,s,Szalay, Alex S.,Arnouts, Sté,phane,Aragó,n-Calvo, Miguel A.,Wyder, Ted K.,Barlow, Tom A.,Foster, Karl,Peter, Friedman G.,Martin, D. C IOP Publishing 2009 The Astrophysical journal Vol.698 No.2