Microstructural evolution of the coexistence for spinodal decomposition and ordering in Fe-23Al alloy during aging

The microstructural evolution of the coexistence ofspinodal decomposition and ordering ischaracterized by metallographic microscopy andtransmission electron microscopy in aged Fe-23Al(i.e. Fe-23at%Al) alloy. This paper discusses aphase transition mechanism of the microstructureevolution. The obtained results indicate that the asquenchedFe-23Al alloys with equiaxed grain sizeof about 500μm comprise two kinds of the orderedphase in nano-scale, i.e., B2-FeAl and DO3-Fe 3Alphases. The average size of B2-FeAl orderingphases is about 15nm, while the size of DO3-Fe 3Alordering phases is extreme fine in the as- quenchedFe-23Al alloys. The as-quenched Fe-23Al alloypresents characteristics of the coexistence ofspinodal decomposition and ordering during thesubsequent age ing at 565°C and 520°C. Thedomain size of B2-FeAl ordered phase rapidlyincreases while the one of DO3-Fe 3Al orderedphase slowly develops with the increase in agingtime/with increased ageing time. A conclusion isreached that the coarsening process of both B2-FeAl and DO3-Fe 3Al ordered phase is controlledby the spinodal decomposition mechanism

PLGSLAM: Progressive Neural Scene Represenation with Local to Global Bundle Adjustment

Neural implicit scene representations have recently shown encouraging results in dense visual SLAM. However, existing methods produce low-quality scene reconstruction and low-accuracy localization performance when scaling up to large indoor scenes and long sequences. These limitations are mainly due to their single, global radiance field with finite capacity, which does not adapt to large scenarios. Their end-to-end pose networks are also not robust enough with the growth of cumulative errors in large scenes. To this end, we introduce PLGSLAM, a neural visual SLAM system capable of high-fidelity surface reconstruction and robust camera tracking in real-time. To handle large-scale indoor scenes, PLGSLAM proposes a progressive scene representation method which dynamically allocates new local scene representation trained with frames within a local sliding window. This allows us to scale up to larger indoor scenes and improves robustness (even under pose drifts). In local scene representation, PLGSLAM utilizes tri-planes for local high-frequency features with multi-layer perceptron (MLP) networks for the low-frequency feature, achieving smoothness and scene completion in unobserved areas. Moreover, we propose local-to-global bundle adjustment method with a global keyframe database to address the increased pose drifts on long sequences. Experimental results demonstrate that PLGSLAM achieves state-of-the-art scene reconstruction results and tracking performance across various datasets and scenarios (both in small and large-scale indoor environments).Comment: Accepted by CVPR 202

MLVA genotyping of Chinese human Brucella melitensis biovar 1, 2 and 3 isolates

<p>Abstract</p> <p>Background</p> <p>Since 1950, <it>Brucella melitensis </it>has been the predominant strain associated with human brucellosis in China. In this study we investigated the genotypic characteristics of <it>B. melitensis </it>isolates from China using a multiple-locus variable-number tandem-repeat analysis (MLVA) and evaluated the utility of MLVA with regards to epidemiological trace-back investigation.</p> <p>Results</p> <p>A total of 105 <it>B. melitensis </it>strains isolated from throughout China were divided into 69 MLVA types using MLVA-16. Nei's genetic diversity indices for the various loci ranged between 0.00 - 0.84. 12 out 16 loci were the low diversity with values < 0.2 and the most discriminatory markers were bruce16 and bruce30 with a diversity index of > 0.75 and containing 8 and 7 alleles, respectively. Many isolates were single-locus or double-locus variants of closely related <it>B. melitensis </it>isolates from different regions, including the north and south of China. Using panel 1, the majority of strains (84/105) were genotype 42 clustering to the 'East Mediterranean' <it>B. melitensis </it>group. Chinese <it>B. melitensis </it>are classified in limited number of closely related genotypes showing variation mainly at the panel 2B loci.</p> <p>Conclusion</p> <p>The MLVA-16 assay can be useful to reveal the predominant genotypes and strain relatedness in endemic or non-endemic regions of brucellosis. However it is not suitable for biovar differentiation of <it>B. melitensis</it>. Genotype 42 is widely distributed throughout China during a long time. Bruce 16 and bruce 30 in panel 2B markers are most useful for typing Chinese isolates.</p

Context-dependent neocentromere activity in synthetic yeast chromosome VIII

Pioneering advances in genome engineering, and specifically in genome writing, have revolutionized the field of synthetic biology, propelling us toward the creation of synthetic genomes. The Sc2.0 project aims to build the first fully synthetic eukaryotic organism by assembling the genome of Saccharomyces cerevisiae. With the completion of synthetic chromosome VIII (synVIII) described here, this goal is within reach. In addition to writing the yeast genome, we sought to manipulate an essential functional element: the point centromere. By relocating the native centromere sequence to various positions along chromosome VIII, we discovered that the minimal 118-bp CEN8 sequence is insufficient for conferring chromosomal stability at ectopic locations. Expanding the transplanted sequence to include a small segment (~500 bp) of the CDEIII-proximal pericentromere improved chromosome stability, demonstrating that minimal centromeres display context-dependent functionality </p

Synthetic chromosome fusion: Effects on mitotic and meiotic genome structure and function

We designed and synthesized synI, which is ~21.6% shorter than native chrI, the smallest chromosome in Saccharomyces cerevisiae. SynI was designed for attachment to another synthetic chromosome due to concerns surrounding potential instability and karyotype imbalance and is now attached to synIII, yielding the first synthetic yeast fusion chromosome. Additional fusion chromosomes were constructed to study nuclear function. ChrIII-I and chrIX-III-I fusion chromosomes have twisted structures, which depend on silencing protein Sir3. As a smaller chromosome, chrI also faces special challenges in assuring meiotic crossovers required for efficient homolog disjunction. Centromere deletions into fusion chromosomes revealed opposing effects of core centromeres and pericentromeres in modulating deposition of the crossover-promoting protein Red1. These effects extend over 100 kb and promote disproportionate Red1 enrichment, and thus crossover potential, on small chromosomes like chrI. These findings reveal the power of synthetic genomics to uncover new biology and deconvolute complex biological systems  </p

The hybrid force/position anti-disturbance control strategy for robot abrasive belt grinding of aviation blade base on fuzzy PID control

The high-quality grinding of the aviation blade components with the industry robot presents tremendous challenges because of the complexity of blade surface. The hybrid force/position anti-disturbance control strategy is developed base on fuzzy PID control to improve the quality of grinding aviation blades. Firstly, according to gravity compensation technology, the perception of contact force is discussed to solve the contact force between the blades and abrasive belt machine. Then, the hybrid force/position anti-disturbance control strategy is designed to ensure the stability of robot automatic grinding system. The speed gain loop and the dual fuzzy PID control are introduced to enhance the anti-disturbance ability of the control system. Meanwhile, the analysis of stability and steady-state error for force control loop are performed to prove the validation of the feasibility of control system. Eventually, the simulation and experiments are carried out on the robot automatic grinding system. The experimental results reveal that the proposed control strategy can achieve better control effect and grinding quality compared with the traditional PID control

MIM_SLAM: A Multi-Level ICP Matching Method for Mobile Robot in Large-Scale and Sparse Scenes

In large-scale and sparse scenes, such as farmland, orchards, mines, and substations, 3D simultaneous localization and mapping are challenging matters that need to address issues such as maintaining reliable data association for scarce environmental information and reducing the computational complexity of global optimization for large-scale scenes. To solve these problems, a real-time incremental simultaneous localization and mapping algorithm called MIM_SLAM is proposed in this paper. This algorithm is applied in mobile robots to build a map on a non-flat road with a 3D LiDAR sensor. MIM_SLAM&#8217;s main contribution is that multi-level ICP (Iterative Closest Point) matching is used to solve the data association problem, a Fisher information matrix is used to describe the uncertainty of the estimated pose, and these poses are optimized by the incremental optimization method, which can greatly reduce the computational cost. Then, a map with a high consistency will be established. The proposed algorithm has been evaluated in the real indoor and outdoor scenes as well as two substations and benchmarking dataset from KITTI with the characteristics of sparse and large-scale. Results show that the proposed algorithm has a high mapping accuracy and meets the real-time requirements

Design and implementation of hybrid force/position control for robot automation grinding aviation blade based on fuzzy PID

The hybrid force/position control base on fuzzy proportional-integral-derivative (PID) is proposed to improve the quality of robotic automatic grinding aviation blades. First, the perception for the contact force/torque is discussed. A multi-source parameters gravity compensation matrix is established to identify the parameters through matrix reorganization. The contact force/torque is perceived according to the gravity compensation result. Then, the hybrid force/position control base on fuzzy PID is designed to realize active force control. Nevertheless, the sharp edge phenomenon occurs although the force control algorithm, which seriously affects the grinding quality of blades. Finally, the fusion control of force and torque is proposed to weaken the sharp edge phenomenon. The experiment proves that the introduction of torque control avoids effectively the sharp edge phenomenon. Meanwhile, comparing the proposed control algorithm with the traditional PID control, the results show that the proposed hybrid force/position control based on fuzzy PID can ensure the stability of the contact force and improve the quality of the aviation blades

Self-Assembly of a Diblock Copolymer with Pendant Disulfide Bonds and Chromophore Groups: A New Platform for Fast Release

An amphiphilic block copolymer comprising poly­(ethylene glycol) (PEG) and poly­(2-(methacryloyl)­oxyethyl-2′-hydroxyethyl disulfide) (PMAOHD) blocks was synthesized by atom transfer radical polymerization (ATRP). Pyrenebutyric acid was conjugated to the block copolymer by esterification, and a block copolymer with pendant disulfide bonds and pyrenyl groups (PEG-<i>b</i>-P­(MAOHD-<i>g</i>-Py)) was obtained. ¹H NMR and gel permeation chromatography (GPC) results demonstrated the successful synthesis of the block copolymer. The cleavage of the disulfide bonds and the degrafting of the pyrenyl groups were investigated in THF and a THF/methanol mixture. Fluorescence spectroscopy, GPC, and ¹H NMR results demonstrated fast cleavage of the disulfide bonds by Bu₃P in THF. Fluorescence results showed the ratio of the intensity of the excimer peak to the monomer peak decreased rapidly within 20 min. GPC traces of the block copolymer moved to a long retention time region after addition of Bu₃P, indicating the cleavage of the disulfide bonds and the degrafting of the pyrenyl groups. PEG-<i>b</i>-P­(MAOHD-<i>g</i>-Py) can self-assemble into micelles with poly­(MAOHD-<i>g</i>-Py) cores and PEG coronae in a mixture of methanol and THF (9:1 by volume). The dissociation of the micelles in the presence of Bu₃P was investigated. After cleavage of the disulfide bonds in the micellar cores, a pyrene-containing small molecular compound and a block copolymer with pendant thiol groups were produced. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and ¹H NMR were employed to track the dissociation of the polymeric micelles. All the techniques demonstrated the dissociation of the micelles and the fast release of pyrenyl groups from the micelles