407 research outputs found
Accessing the transport properties of graphene and its multi-layers at high carrier density
We present a comparative study of high carrier density transport in mono-,
bi-, and trilayer graphene using electric-double-layer transistors to
continuously tune the carrier density up to values exceeding 10^{14} cm^{-2}.
Whereas in monolayer the conductivity saturates, in bi- and trilayer flling of
the higher energy bands is observed to cause a non-monotonic behavior of the
conductivity, and a large increase in the quantum capacitance. These systematic
trends not only show how the intrinsic high-density transport properties of
graphene can be accessed by field-effect, but also demonstrate the robustness
of ion-gated graphene, which is crucial for possible future applications.Comment: 4 figures, 4 page
Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors
Electrostatic modification of functional materials by electrolytic gating has
demonstrated a remarkably wide range of density modulation, a condition crucial
for developing novel electronic phases in systems ranging from complex oxides
to layered chalcogenides. Yet little is known microscopically when carriers are
modulated in electrolyte-gated electric double-layer transistors (EDLTs) due to
the technical challenge of imaging the buried electrolyte-semiconductor
interface. Here, we demonstrate the real-space mapping of the channel
conductance in ZnO EDLTs using a cryogenic microwave impedance microscope. A
spin-coated ionic gel layer with typical thicknesses below 50 nm allows us to
perform high resolution (on the order of 100 nm) sub-surface imaging, while
maintaining the capability of inducing the metal-insulator transition under a
gate bias. The microwave images vividly show the spatial evolution of channel
conductance and its local fluctuations through the transition, as well as the
uneven conductance distribution established by a large source-drain bias. The
unique combination of ultra-thin ion-gel gating and microwave imaging offers a
new opportunity to study the local transport and mesoscopic electronic
properties in EDLTs.Comment: to be published on Nano Lette
Adaptive incentive for cross-silo federated learning: A multi-agent reinforcement learning approach
Cross-silo federated learning (FL) is a typical FL that enables
organizations(e.g., financial or medical entities) to train global models on
isolated data. Reasonable incentive is key to encouraging organizations to
contribute data. However, existing works on incentivizing cross-silo FL lack
consideration of the environmental dynamics (e.g., precision of the trained
global model and data owned by uncertain clients during the training
processes). Moreover, most of them assume that organizations share private
information, which is unrealistic. To overcome these limitations, we propose a
novel adaptive mechanism for cross-silo FL, towards incentivizing organizations
to contribute data to maximize their long-term payoffs in a real dynamic
training environment. The mechanism is based on multi-agent reinforcement
learning, which learns near-optimal data contribution strategy from the history
of potential games without organizations' private information. Experiments
demonstrate that our mechanism achieves adaptive incentive and effectively
improves the long-term payoffs for organizations
Polysaccharides Derived From the Brown Algae Lessonia nigrescens Enhance Salt Stress Tolerance to Wheat Seedlings by Enhancing the Antioxidant System and Modulating Intracellular Ion Concentration
Soil salinity reduces plant growth and is a major factor that causes decreased agricultural productivity worldwide. Seaweed polysaccharides promote crop growth and improve plant resistance to abiotic stress. In this study, polysaccharides from brown seaweed Lessonia nigrescens polysaccharides (LNP) were extracted and further separated and fractionated. Two acidic polysaccharides (LNP-1 and LNP-2) from crude LNP were obtained and characterized. The latter had a lower molecular weight (MW) (40.2 kDa) than the former (63.9 kDa), but had higher uronic acid and sulfate content. Crude LNP and LNP-2 were composed of mannose, glucuronic acid, fucose, and xylose, whereas LNP-1 has little mannose. Moreover, the effects of the three polysaccharides on plant salt tolerance were investigated. The results showed that crude LNP, LNP-1, and LNP-2 promoted the growth of plants, decreased membrane lipid peroxidation, increased the chlorophyll content, improved antioxidant activities, and coordinated the efflux and compartmentation of intracellular ion. All three polysaccharides could induce plant resistance to salt stress, but LNP-2 was more effective than the other two. The present study allowed to conclude that both MW and sulfate degree contribute to salt resistance capability of polysaccharides derived from L. nigrescens
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