Evolutionary Reinforcement Learning via Cooperative Coevolutionary Negatively Correlated Search

Evolutionary algorithms (EAs) have been successfully applied to optimize the policies for Reinforcement Learning (RL) tasks due to their exploration ability. The recently proposed Negatively Correlated Search (NCS) provides a distinct parallel exploration search behavior and is expected to facilitate RL more effectively. Considering that the commonly adopted neural policies usually involves millions of parameters to be optimized, the direct application of NCS to RL may face a great challenge of the large-scale search space. To address this issue, this paper presents an NCS-friendly Cooperative Coevolution (CC) framework to scale-up NCS while largely preserving its parallel exploration search behavior. The issue of traditional CC that can deteriorate NCS is also discussed. Empirical studies on 10 popular Atari games show that the proposed method can significantly outperform three state-of-the-art deep RL methods with 50% less computational time by effectively exploring a 1.7 million-dimensional search space

A sacrificial coating strategy toward enhancement of metal-support interaction for ultrastable Au nanocatalysts

Supported gold (Au) nanocatalysts hold great promise for heterogeneous catalysis; however, their practical application is greatly hampered by poor thermodynamic stability. Herein, a general synthetic strategy is reported where discrete metal nanoparticles are made resistant to sintering, preserving their catalytic activities in high-temperature oxidation processes. Taking advantage of the unique coating chemistry of dopamine, sacrificial carbon layers are constructed on the material surface, stabilizing the supported catalyst. Upon annealing at high temperature under an inert atmosphere, the interactions between support and metal nanoparticle are dramatically enhanced, while the sacrificial carbon layers can be subsequently removed through oxidative calcination in air. Owing to the improved metal–support contact and strengthened electronic interactions, the resulting Au nanocatalysts are resistant to sintering and exhibit excellent durability for catalytic combustion of propylene at elevated temperatures. Moreover, the facile synthetic strategy can be extended to the stabilization of other supported catalysts on a broad range of supports, providing a general approach to enhancing the thermal stability and sintering resistance of supported nanocatalysts

Efficient current-induced spin torques and field-free magnetization switching in a room-temperature van der Waals magnet

The discovery of magnetism in van der Waals (vdW) materials has established unique building blocks for the research of emergent spintronic phenomena. In particular, owing to their intrinsically clean surface without dangling bonds, the vdW magnets hold the potential to construct a superior interface that allows for efficient electrical manipulation of magnetism. Despite several attempts in this direction, it usually requires a cryogenic condition and the assistance of external magnetic fields, which is detrimental to the real application. Here, we fabricate heterostructures based on Fe3GaTe2 flakes that possess room-temperature ferromagnetism with excellent perpendicular magnetic anisotropy. The current-driven non-reciprocal modulation of coercive fields reveals a high spin-torque efficiency in the Fe3GaTe2/Pt heterostructures, which further leads to a full magnetization switching by current. Moreover, we demonstrate the field-free magnetization switching resulting from out-of-plane polarized spin currents by asymmetric geometry design. Our work could expedite the development of efficient vdW spintronic logic, memory and neuromorphic computing devices

Integration of Solexa sequences on an ultradense genetic map in Brassica rapa L.

<p>Abstract</p> <p>Background</p> <p>Sequence related amplified polymorphism (SRAP) is commonly used to construct high density genetic maps, map genes and QTL of important agronomic traits in crops and perform genetic diversity analysis without knowing sequence information. To combine next generation sequencing technology with SRAP, Illumina's Solexa sequencing was used to sequence tagged SRAP PCR products.</p> <p>Results</p> <p>Three sets of SRAP primers and three sets of tagging primers were used in 77,568 SRAP PCR reactions and the same number of tagging PCR reactions respectively to produce a pooled sample for Illumina's Solexa sequencing. After sequencing, 1.28 GB of sequence with over 13 million paired-end sequences was obtained and used to match Solexa sequences with their corresponding SRAP markers and to integrate Solexa sequences on an ultradense genetic map. The ultradense genetic bin map with 465 bins was constructed using a recombinant inbred (RI) line mapping population in <it>B. rapa</it>. For this ultradense genetic bin map, 9,177 SRAP markers, 1,737 integrated unique Solexa paired-end sequences and 46 SSR markers representing 10,960 independent genetic loci were assembled and 141 unique Solexa paired-end sequences were matched with their corresponding SRAP markers. The genetic map in <it>B. rapa </it>was aligned with the previous ultradense genetic map in <it>B. napus </it>through common SRAP markers in these two species. Additionally, SSR markers were used to perform alignment of the current genetic map with other five genetic maps in <it>B. rapa </it>and <it>B. napus</it>.</p> <p>Conclusion</p> <p>We used SRAP to construct an ultradense genetic map with 10,960 independent genetic loci in <it>B. rapa </it>that is the most saturated genetic map ever constructed in this species. Using next generation sequencing, we integrated 1,878 Solexa sequences on the genetic map. These integrated sequences will be used to assemble the scaffolds in the <it>B. rapa </it>genome. Additionally, this genetic map may be used for gene cloning and marker development in <it>B. rapa </it>and <it>B. napus</it>.</p

Deciphering RNA structural diversity and systematic phylogeny from microbial metagenomes

Metagenomics has been employed to systematically sequence, classify, analyze and manipulate the entire genetic material isolated from environmental samples. Finding genes within metagenomic sequences remains a formidable challenge, and noncoding RNA genes other than those encoding rRNA and tRNA are not well annotated in metagenomic projects. In this work, we identify, validate and analyze the genes coding for RNase P RNA (P RNA) from all published metagenomic projects. P RNA is the RNA subunit of a ubiquitous endoribonuclease RNase P that consists of one RNA subunit and one or more protein subunits. The bacterial P RNAs are classified into two types, Type A and Type B, based on the constituents of the structure involved in precursor tRNA binding. Archaeal P RNAs are classified into Type A and Type M, whereas the Type A is ancestral and close to Type A bacterial P RNA. Bacterial and some archaeal P RNAs are catalytically active without protein subunits, capable of cleaving precursor tRNA transcripts to produce their mature 5′-termini. We have found 328 distinctive P RNAs (320 bacterial and 8 archaeal) from all published metagenomics sequences, which led us to expand by 60% the total number of this catalytic RNA from prokaryotes. Surprisingly, all newly identified P RNAs from metagenomics sequences are Type A, i.e. neither Type B bacterial nor Type M archaeal P RNAs are found. We experimentally validate the authenticity of an archaeal P RNA from Sargasso Sea. One of the distinctive features of some new P RNAs is that the P2 stem has kinked nucleotides in its 5′ strand. We find that the single nucleotide J2/3 joint region linking the P2 and P3 stem that was used to distinguish a bacterial P RNA from an archaeal one is no longer applicable, i.e. some archaeal P RNAs have only one nucleotide in the J2/3 joint. We also discuss the phylogenetic analysis based on covariance model of P RNA that offers a few advantages over the one based on 16S rRNA

Trajectory Planning of the Exit Point for a Cable-Driven Parallel Mechanism by Considering the Homogeneity of Tension Variation

Considering the uniformity of cable tension variation, in this paper, the trajectory planning problem of the exit point for a continuously reconfigurable four-cable-driven two-degrees-of-freedom (DOF) parallel mechanism was studied. Furthermore, an improved quadratic programming model-based trajectory planning method is proposed, which greatly reduces the change in cable tension and can be used to solve the problem of excessive cable tension change when the existing mechanism moves on the moving platform. First, the structural characteristics of the parallel mechanism with a fixed exit point were analyzed, and the static model was established. Considering the cable length and tension constraints, the feasible workspace of the mechanism force was solved. Then, based on the dynamic modeling, an improved quadratic programming model was used to solve the cable tension values under the typical trajectory in the force-feasible workspace. Finally, considering the influence of structural parameters on the change in cable tension, the improved quadratic programming model was transformed, and an exit point trajectory planning model was proposed. The uniform change in cable tension was realized by continuously changing the exit point position. The results show that the cable tension can change uniformly in a very small range by planning the trajectory of the exit point, and the stability of the moving platform movement is guaranteed to the greatest extent

An archaeal P RNA identified from Sargasso Sea with a J2/3 of a single G

<p><b>Copyright information:</b></p><p>Taken from "Deciphering RNA structural diversity and systematic phylogeny from microbial metagenomes"</p><p></p><p>Nucleic Acids Research 2007;35(7):2283-2294.</p><p>Published online 27 Mar 2007</p><p>PMCID:PMC1874661.</p><p>© 2007 The Author(s)</p> () The folding of this P RNA (AACY01084936) is drawn according to the INFERNAL alignment. In the inset box, an alternative folding of P2 stem and its flanking regions is provided. () The folding of AB201308. Nucleotides in blue are those identical ones in these two sequences. () Functional reconstitution of metagenomic P RNA (AACY01084936) with RNase P proteins (Rpps). RNase P activity was reconstituted by mixing 500 nM RNA with 5 µM protein ( RNase P protein C5, Rpp, or Rpps, lanes 5 and 6) and assayed at 55°C for 2 h using 2 µM ptRNA as substrate. Lane 2 represents a control reaction RNase P. Lanes 3 and 4 represent control reactions in which the substrate was incubated with either the RNA alone or Mja Rpps, respectively

Control over large-volume changes of lithium battery anodes via active-inactive metal alloy embedded in porous carbon

Large volume changes and limited access to redox sites of high capacity anode materials are great challenges. Although, various strategies were adopted but still results are far from required values for their practical usage. Here, we have designed a unique structure to prevent surface reaction and structural disintegration meanwhile intrinsic conductivity is improved to involve all redox sites in conversion reaction. CoSnx@C-PAn hybrid was synthesized through aqueous chemical route, Co doping in tin make accessible all redox sites by faster conduction of electrons while its hard nature relaxes internal stress, carbon shell prevents surface reaction and brings well control on solid electrolyte interface (SEI) film by maintaining barrier between electrode surface and electrolyte and nitrogen doped porous carbon provides faster diffusion of Li+ deep in electrode make possible high mass loadings and conduction highway for electrons. Furthermore, porous carbon also provides room to compensate volume expansion and keeps electrode structure stable. Because of its unique structure hybrid shows excellent reversible capacity of 2044mAh/g (retention 100%) with mass loading of 3.8mg/cm2 along with long cyclic life up to 1000 cycles and bears high rate capability (20A/g).We believe that present study makes possible the use of high capacity materials in applications

Graphene and its composites with nanoparticles for electrochemical energy applications

Graphene is a two dimensional (2D) planar and hexagonal array of carbon atoms and has been studied extensively as advanced nanomaterials for important technological applications. This review summarizes the recent developments in chemistry, materials and energy applications of graphene, doped graphene and their composites with nanoparticles (NPs). It first highlights the new chemistry used to synthesize high quality graphene. It then outlines the methodologies developed to dope graphene with heteroatoms to modify and control graphene properties. It further describes the general approaches to graphene-NP composites via either direct NP growth onto graphene or self-assembly of the pre-formed NPs on graphene surface. These graphene-NP composites provide some ideal systems for studying synergistic effects between graphene and NPs on catalysis. The review focuses on applications of graphene-NP composites in increasing electrochemical energy storage density and in catalyzing chemical reactions with much desired electrochemical efficiencies