22 research outputs found
ABJM Amplitudes in U-gauge and a Soft Theorem
We report progress in computing and analyzing all tree amplitudes in ABJM
theory. Inspired by the isomorphism between the orthogonal Grassmannian and the
pure spinor geometries, we adopt a new gauge, called u-gauge, for evaluating
the orthogonal Grassmannian integral for ABJM amplitudes. We carry out the
integral explicitly for the 8-point amplitude and obtain the complete
supersymmetric amplitude. The physical and spurious poles arise from the
integral as expected from on-shell diagrams. We also derive a double scalar
soft theorem of ABJM amplitudes and verify it for known amplitudes.Comment: 35 pages, 6 figures; v2. minor correction
Ultra-Sharp Nanowire Arrays Natively Permeate, Record, and Stimulate Intracellular Activity in Neuronal and Cardiac Networks
Intracellular access with high spatiotemporal resolution can enhance our
understanding of how neurons or cardiomyocytes regulate and orchestrate network
activity, and how this activity can be affected with pharmacology or other
interventional modalities. Nanoscale devices often employ electroporation to
transiently permeate the cell membrane and record intracellular potentials,
which tend to decrease rapidly to extracellular potential amplitudes with time.
Here, we report innovative scalable, vertical, ultra-sharp nanowire arrays that
are individually addressable to enable long-term, native recordings of
intracellular potentials. We report large action potential amplitudes that are
indicative of intracellular access from 3D tissue-like networks of neurons and
cardiomyocytes across recording days and that do not decrease to extracellular
amplitudes for the duration of the recording of several minutes. Our findings
are validated with cross-sectional microscopy, pharmacology, and electrical
interventions. Our experiments and simulations demonstrate that individual
electrical addressability of nanowires is necessary for high-fidelity
intracellular electrophysiological recordings. This study advances our
understanding of and control over high-quality multi-channel intracellular
recordings, and paves the way toward predictive, high-throughput, and low-cost
electrophysiological drug screening platforms.Comment: Main manuscript: 33 pages, 4 figures, Supporting information: 43
pages, 27 figures, Submitted to Advanced Material
Money for us versus money for them: cross-cultural differences in sensitivity to rewards for ingroup and outgroup
Economic decisions often involve consideration of social groups, as when a decision has consequences not just for oneself but also for an in-group or out-group member. Cultureāspecifically, differences between Western individualistic and Eastern collectivist culturesāhas direct influence on perception of social group identity. Yet, not many studies have investigated how culture might influence economic decision making involving social groups. The current study determined cultural influences on sensitivity to rewards directed towards their ingroup and outgroup. American and Korean students performed a simple card game, in which they earned money for ingroup and outgroup members by choosing from amongst four card decks each associated with different reward outcomes for the two groups. Performance on the card game showed a culture-by-reward-group interaction such that Koreans showed greater reward sensitivity for the ingroup than did Americans. These results demonstrate significant cross-cultural differences in the processing of rewards towards different social groups
Relationships among Permeability, Membrane Roughness, and Eukaryote Inhabitation during Submerged Gravity-Driven Membrane (GDM) Filtration
Gravity-driven membrane (GDM) filtration is one of the promising technologies for decentralized water treatment systems due to its low cost, simple operation, and convenient maintenance. The objective of this study was to evaluate the permeability of submerged GDM filtration with three different membranes, i.e., polyethersulfone and polyvinylidene difluoride ultrafiltration (PES-UF and PVDF-UF) and polytetrafluoroethylene microfiltration membrane (PTFE-MF). The GDM system was operated using lake water for about one year. The determined average permeability values were high for PVDF-UF (192.9 L/m2/h/bar (LMH/bar)) and PTFE-MF (80.6 LMH/bar) and relatively lower for PES-UF (46.1 LMH/bar). The observed higher permeability for PVDF-UF and PTFE-MF was thought to be related to the rougher surface of these two membranes compared to PES-UF. The fouling layers of PVDF-UF and PTFE-MF were characterized by high biomass and the presence of a number of nematodes, while PES-UF showed a thin fouling layer with no nematode. The relatively high and fluctuated permeability of PVDF-UF and PTFE-MF could thus be attributed to the high biological activity of nematodes making the fouling layer more loose and porous. This was supported by a good linear relationship among the permeability, biomass concentration, and the number of nematodes in the fouling layers. These results provide important insights into membrane selection as a critical factor affecting the flux performance of the GDM filtration system for a decentralized drinking water supply
Liquid electrolyte-free cathode for long-cycle life lithiumāoxygen batteries
Ether-based organic liquid electrolytes (OLEs) have been commonly used in lithiumāoxygen batteries (LOBs); however, they become unstable and cause rapid performance degradation during LOB operation. To address these problems, in this study we propose an OLE-free cathode architecture based on a Li+-selective solid membrane (LSSM). An LSSM with a seamless duplex (dense/porous) architecture is prepared by a tape casting process combined with co-sintering, and carbon nanotubes (CNTs) decorated with Au nanoparticles (CNT@Au) are directly formed on its porous framework. We show that the duplex-LSSM can effectively protect the metallic Li anode from parasitic reactions with impurity species and improve the cycling stability of Li. Furthermore, an LOB assembled with the duplex-LSSM and CNT@Au components exhibits a discharge capacity as high as 3650 mAh gā1 and improved cycling stability (>140 cycles) compared to a conventional OLE-based LOB; this can be explained in terms of the combined advantages provided by the OLE-free cathode and the LSSM-protected Li anode. Ā© 2021 Elsevier B.V.1
Dirac node arcs in PtSn4
In topological quantum materials1ā3 the conduction and valence bands are connected at points or along lines in the momentum space. A number of studies have demonstrated that several materials are indeed Dirac/Weyl semimetals4ā8 . However, there is still no experimental confirmation of materials with line nodes, in which the Dirac nodes form closed loops in the momentum space2,3 . Here we report the discovery of a novel topological structureāDirac node arcsāin the ultrahigh magnetoresistive material PtSn4 using laser-based angle-resolved photoemission spectroscopy data and density functional theory calculations. Unlike the closed loops of line nodes, the Dirac node arc structure arises owing to the surface states and resembles the Dirac dispersion in graphene that is extended along a short line in the momentum space. We propose that this reported Dirac node arc structure is a novel topological state that provides an exciting platform for studying the exotic properties of Dirac fermions.This is a manuscript of an article published as Yun Wu, Lin-Lin Wang, Eundeok Mun, D. D. Johnson, Daixiang Mou, Lunan Huang, Yongbin Lee, S. L. Budāko, P.C. Canfield, and Adam Kaminski, āDirac Node Arcs in PtSn4,ā Nature Physics 12, 667-671 (2016). DOI: 10.1038/NPHYS3712. Posted with permission.</p
Large-scale, single-oriented ZnO nanostructure on h-BN films for flexible inorganic UV sensors
We report the growth of large-scale, single-oriented zinc oxide (ZnO) nanowall networks on epitaxial hexagonal boron nitride (h-BN) films and their application to flexible inorganic ultraviolet (UV) light sensors. Using catalyst-free metal-organic vapor phase epitaxy, ZnO nanowall networks with good vertical alignment are grown on epitaxial h-BN films. The single-oriented crystal structure of the ZnO nanostructures on h-BN is investigated using x-ray diffraction (XRD) spectroscopy, and the heteroepitaxial relationship between ZnO and h-BN is revealed through synchrotron radiation XRD. Interestingly, when utilizing the grown ZnO nanostructure as a channel for UV sensors, better performance merits such as a high I-UV/I-dark ratio, faster recovery time, and low dark current are achieved if h-BN is employed as a growth template. As an example of inorganic flexible optoelectronic device applications, flexible UV sensors are fabricated using ZnO/h-BN heterostructures owing to the insulating and transferrable nature of h-BN substrates. The sensor maintained an excellent performance, even under highly bent conditions