Transition metal oxides for high performance sodium ion battery anodes

Sodium-ion batteries (SIBs) are attracting considerable attention with expectation of replacing lithium-ion batteries (LIBs) in large-scale energy storage systems (ESSs). To explore high performance anode materials for SIBs is highly desired subject to the current anode research mainly limited to carbonaceous materials. In this study, a series of transition metal oxides (TMOs) is successfully demonstrated as anodes for SIBs for the first time. The sodium uptake/extract is confirmed in the way of reversible conversion reaction. The pseudocapacitance-type behavior is also observed in the contribution of sodium capacity. For Fe2O3anode, a reversible capacity of 386 mAh g-1at 100 mA g-1 is achieved over 200 cycles; as high as 233 mAhg-1is sustained even cycling at a large current-density of 5 A g-1

Max-Sliced Wasserstein Distance and its use for GANs

Generative adversarial nets (GANs) and variational auto-encoders have significantly improved our distribution modeling capabilities, showing promise for dataset augmentation, image-to-image translation and feature learning. However, to model high-dimensional distributions, sequential training and stacked architectures are common, increasing the number of tunable hyper-parameters as well as the training time. Nonetheless, the sample complexity of the distance metrics remains one of the factors affecting GAN training. We first show that the recently proposed sliced Wasserstein distance has compelling sample complexity properties when compared to the Wasserstein distance. To further improve the sliced Wasserstein distance we then analyze its `projection complexity' and develop the max-sliced Wasserstein distance which enjoys compelling sample complexity while reducing projection complexity, albeit necessitating a max estimation. We finally illustrate that the proposed distance trains GANs on high-dimensional images up to a resolution of 256x256 easily.Comment: Accepted to CVPR 201

Learning Pregrasp Manipulation of Objects from Ungraspable Poses

In robotic grasping, objects are often occluded in ungraspable configurations such that no pregrasp pose can be found, eg large flat boxes on the table that can only be grasped from the side. Inspired by humans' bimanual manipulation, eg one hand to lift up things and the other to grasp, we address this type of problems by introducing pregrasp manipulation - push and lift actions. We propose a model-free Deep Reinforcement Learning framework to train control policies that utilize visual information and proprioceptive states of the robot to autonomously discover robust pregrasp manipulation. The robot arm learns to first push the object towards a support surface and establishes a pivot to lift up one side of the object, thus creating a clearance between the object and the table for possible grasping solutions. Furthermore, we show the effectiveness of our proposed learning framework in training robust pregrasp policies that can directly transfer from simulation to real hardware through suitable design of training procedures, state, and action space. Lastly, we evaluate the effectiveness and the generalisation ability of the learned policies in real-world experiments, and demonstrate pregrasp manipulation of objects with various size, shape, weight, and surface friction.Comment: 8 pages open access version for ICRA2020 6 pages acceptance pape

Effects of mycorrhizal fungi on plant growth, nutrient absorption and phytohormones levels in tea under shading condition

High temperature and strong light could induce bitterness and astringency of tea (Camellia sinensis (L.) O. Kuntze) in summer. Arbuscular mycorrhizal (AM) fungus and shading could change tea growth surroundings and improve its quality. The present study evaluated the inoculated effects of an arbuscular mycorrhizal fungus (AMF), Glomus etunicatum, on plant growth, root morphology, leaf nutrient status, phytohormones and the relative expression of root CsCPC, CsTTG1, CsAUX1, CsYUCCA1, CsNCED2, CsGA3OX1, CsDWF4 and CsAOS genes in Camellia sinensis  ‘Xinyang population’ seedlings in sands under shading conditions. After 14 weeks of AMF inoculation, root mycorrhizal colonization ranged from 18.5% to 48.00%. AMF inoculation and shading heavily increased plant height, shoot and root biomass, total root length and volume, leaf nutrients content (except Fe), respectively. Both mycorrhizal inoculation and shading significantly increased root hair growth respectively, in company with up-regulation gene CsCPC and down-regulation gene CsTTG1. Root auxin level and its transport gene CsAUX1 was both up-regulated by mycorrhizal inoculation and shading. Interestingly, auxin biosynthesis gene CsYUCCA1 has not been affected, which suggested that both mycorrhizal and shading mainly regulate auxin transport but not biosynthesis pathway. The contents of gibberellin (GA) and brassinosteroid (BR) in root were notably increased by mycorrhizal inoculation and shading, accompanied with up-regulation of its biosynthesis genes, CsGA3OX1 and CsDWF4. With regard to the growth inhibiting phytohormones abscisic acid (ABA) and jasmonic acid (JA), mycorrhizal inoculation and shading significantly decreased their levels in root, in company with down-regulation of biosynthesis genes, CsNCED2 and CsAOS. These results implied that both AMF inoculation and shading could enhance the tea plant stress resistance and increase nutrient absorption, root biomass and the contents of root phytohormones by up-regulating its transport and biosynthesis pathway

Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating

Since the discovery of n-type copper oxide superconductors, the evolution of electron- and hole-bands and its relation to the superconductivity have been seen as a key factor in unveiling the mechanism of high-Tc superconductors. So far, the occurrence of electrons and holes in n-type copper oxides has been achieved by chemical doping, pressure, and/or deoxygenation. However, the observed electronic properties are blurred by the concomitant effects such as change of lattice structure, disorder, etc. Here, we report on successful tuning the electronic band structure of n-type Pr2-xCexCuO4 (x = 0.15) ultrathin films, via the electric double layer transistor technique. Abnormal transport properties, such as multiple sign reversals of Hall resistivity in normal and mixed states, have been revealed within an electrostatic field in range of -2 V to +2 V, as well as varying the temperature and magnetic field. In the mixed state, the intrinsic anomalous Hall conductivity invokes the contribution of both electron and hole-bands as well as the energy dependent density of states near the Fermi level. The two-band model can also describe the normal state transport properties well, whereas the carrier concentrations of electrons and holes are always enhanced or depressed simultaneously in electric fields. This is in contrast to the scenario of Fermi surface reconstruction by antiferromagnetism, where an anti-correlation between electrons and holes is commonly expected. Our findings paint the picture where Coulomb repulsion plays an important role in the evolution of the electronic states in n-type cuprate superconductors.Comment: 4 figures, SI not included. Comments are welcom

Stratified microbial structure and activity in sulfide- and methane- producing anaerobic sewer biofilms

Simultaneous production of sulfide and methane by anaerobic sewer biofilms has recently been observed, suggesting that sulfate-reducing bacteria (SRB) and methanogenic archaea (MA), microorganisms known to compete for the same substrates, can coexist in this environment. This study investigated the community structures and activities of SRB and MA in anaerobic sewer biofilms (average thickness of 800 mu m) using a combination of microelectrode measurements, molecular techniques, and mathematical modeling. It was seen that sulfide was mainly produced in the outer layer of the biofilm, between the depths of 0 and 300 mu m, which is in good agreement with the distribution of SRB population as revealed by cryosection-fluorescence in situ hybridization (FISH). SRB had a higher relative abundance of 20% on the surface layer, which decreased gradually to below 3% at a depth of 400 mu m. In contrast, MA mainly inhabited the inner layer of the biofilm. Their relative abundances increased from 10% to 75% at depths of 200 mu m and 700 mu m, respectively, from the biofilm surface layer. High-throughput pyrosequencing of 16S rRNA amplicons showed that SRB in the biofilm were mainly affiliated with five genera, Desulfobulbus, Desulfomicrobium, Desulfovibrio, Desulfatiferula, and Desulforegula, while about 90% of the MA population belonged to the genus Methanosaeta. The spatial organizations of SRB and MA revealed by pyrosequencing were consistent with the FISH results. A biofilm model was constructed to simulate the SRB and MA distributions in the anaerobic sewer biofilm. The good fit between model predictions and the experimental data indicate that the coexistence and spatial structure of SRB and MA in the biofilm resulted from the microbial types and their metabolic transformations and interactions with substrates