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Optical stimulation of cardiac cells with a polymer-supported silicon nanowire matrix
Parameswaran, Ramya,Koehler, Kelliann,Rotenberg, Menahem Y.,Burke, Michael J.,Kim, Jungkil,Jeong, Kwang-Yong,Hissa, Barbara,Paul, Michael D.,Moreno, Kiela,Sarma, Nivedina,Hayes, Thomas,Sudzilovsky, Ed National Academy of Sciences 2019 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.116 No.2
<P><B>Significance</B></P><P>Cardiac conduction disorders are potentially fatal illnesses caused by abnormalities in the heart’s electrical conduction system. Current treatments for these disorders, such as pacemakers, are effective but are bulky, rigid, and invasive. Here we develop a method to optically modulate cardiac beating frequency in primary cultured cardiomyocytes and adult rat hearts ex vivo, to a specified target frequency. Specifically, we use a low-irradiance moving laser stimulus and a biocompatible polymer–silicon nanowire composite material to achieve this modulation. This work has implications for future bioelectric studies of the cardiac conduction system as well as therapeutics for cardiac conduction disorders in the clinic.</P><P>Electronic pacemakers can treat electrical conduction disorders in hearts; however, they are invasive, bulky, and linked to increased incidence of infection at the tissue–device interface. Thus, researchers have looked to other more biocompatible methods for cardiac pacing or resynchronization, such as femtosecond infrared light pulsing, optogenetics, and polymer-based cardiac patches integrated with metal electrodes. Here we develop a biocompatible nongenetic approach for the optical modulation of cardiac cells and tissues. We demonstrate that a polymer–silicon nanowire composite mesh can be used to convert fast moving, low-radiance optical inputs into stimulatory signals in target cardiac cells. Our method allows for the stimulation of the cultured cardiomyocytes or ex vivo heart to beat at a higher target frequency.</P>
Evidence for indirect band gap in BaSnO3 using angle-resolved photoemission spectroscopy
주범수,장영준,Luca Moreschini,Aaron Bostwick,Eli Rotenberg,한문섭 한국물리학회 2017 Current Applied Physics Vol.17 No.5
Transparent BaSnO3 thin films have been proposed as an alternative transparent conducting oxide (TCO). Although bulk synthesis and high-quality fabrication of epitaxial films are well established, there are still unsolved aspects about their electronic structure, such as the direct or indirect nature and the size of the band gap. We investigated the electronic structure of epitaxial BaSnO3 thin films using in situ angleresolved photoemission spectroscopy. We directly measured an indirect band gap of 3.7 eV, a value compatible with those of previous reports, but we also identified additional in-gap states at 1.6 eV below the conduction band minimum that we attribute to intrinsic defects, mainly oxygen vacancies.
Electronic structure and charge-density wave transition in monolayer VS2
김혁진,최병기,이인학,김민재,천승현,Jozwiak Chris,Bostwick Aaron,Rotenberg Eli,Chang Young Jun 한국물리학회 2021 Current Applied Physics Vol.30 No.-
Vanadium disulfide (VS2) attracts elevated interests for its charge-density wave (CDW) phase transition, ferromagnetism, and catalytic reactivity, but the electronic structure of monolayer has not been well understood yet. Here we report synthesis of epitaxial 1T VS2 monolayer on bilayer graphene grown by molecular-beam epitaxy (MBE). Angle-resolved photoemission spectroscopy (ARPES) measurements reveal that Fermi surface with six elliptical pockets centered at the M points shows gap opening at low temperature. Temperature-dependence of the gap size suggests existence of CDW phase transition above room temperature. Our observations provide important evidence to understand the strongly correlated electron physics and the related surface catalytic properties in two-dimensional transition-metal dichalcogenides (TMDCs).
Fermi arcs in a doped pseudospin-1/2 Heisenberg antiferromagnet
Kim, Y. K.,Krupin, O.,Denlinger, J. D.,Bostwick, A.,Rotenberg, E.,Zhao, Q.,Mitchell, J. F.,Allen, J. W.,Kim, B. J. American Association for the Advancement of Scienc 2014 Science Vol.345 No.6193
<P><B>Identifying a cuprate look-alike</B></P><P>Superconductivity in cuprate compounds remains poorly understood. Recreating its features in an unrelated material may provide insight. Kim <I>et al.</I> used a spectroscopic technique to study the electronic states of the material Sr<SUB>2</SUB>IrO<SUB>4</SUB> at relatively high temperatures. They observed phenomenology similar to that of cuprates as they varied the surface carrier concentration. The study highlights the essential properties a material needs in order to exhibit cuprate-like features in the normal (nonsuperconducting) state.</P><P><I>Science</I>, this issue p. 187</P>