A review of the microflora structure in the digestive tract of marine finfish

从海水鱼消化道结构、消化道菌群结构、消化道菌群功能及消化道菌群结构研究手段等几个方面综述了海水鱼消化道菌群结构的研究进展。指出海水鱼消化道菌群结构受到生长发育阶段、养殖环境及饵料变化等因素的影响。论述了正常消化道菌群的重要功能,比较分析了目前消化道菌群结构不同研究手段,阐明了消化道微生物分子生态学研究的学术价值。为筛选高效、专一性、可定植性的海水鱼益生菌奠定了基础。This paper reviewed the research progresses of the microflora structure in digestive tract of marine finfish, including physiological structure of the digestive tract in marine finfish, the microflora structure in the digestive tract, the function of the microflora in the digestive tract, and the analysis means of the microflora structure in the digestive tract. It was pointed out in this paper that the microflora structure in digestive tract of marine finfish was affected by the developmental stage of the fish, aquaculture environment, variation of the diets, and so on. Besides, the key function of the normal microflroa in the digestive tract and the different analysis means for the study of the microflora structure were discussed. Lastly, the academic values of studies on the molecular ecology of the microflora in the digestive tract were elucidated, aiming at providing reference for screening the efficient, special, and indigestinous prebiotics for use in the culture of marine finfish.国际科技合作重点计划项目(2004DF060800);; 中国博士后科学基金项目(2005037625);; 淡水生态与生物技术国家重点实验室开放课题(2005FB05);; 广东省自然科学基金项目(05300945)共同资

国内高速列车气动噪声研究进展概述

随着运行速度的提升,气动噪声逐渐成为高速列车最主要的噪声源,并极有可能成为新设计高速列车的一个技术瓶颈。开展高速列车气动噪声研究,明晰高速列车气动噪声机理与规律,发展低噪声高速列车外形设计对更高速度级的高速列车研发具有重要意义。本文主要对自2010年以来国内进行的高速列车气动噪声研究进行梳理总结。首先详细介绍了高速列车气动噪声研究采用的一系列方法,主要从实车试验、风洞实验以及数值模拟方法三个方面展开。在掌握高速列车气动噪声研究方法的基础上,进而探讨了当前高速列车气动噪声研究的现状,重点就高速列车气动噪声源识别、主要噪声源机理与特性、噪声源优化等方向进行了阐述,并明确了当前研究获得的一些主要结论。最后简要探讨了高速列车气动噪声未来可能的研究方向

典型路基结构对高速列车横风气动特性影响分析

由于地域及环境的限制, 高速铁路采用多种路基结构如平直地面、不同高度路堤、高架桥等,当列车运行在路堤及高架桥上时,车体周围的绕流流场比平直地面更加复杂。在强横风的作用下,不同的路基结构上的高速列车横风气动特性存在明显差异,不合理的路基结构将影响列车的横风安全性。同时列车结构复杂,转向架、受电弓等都对列车的流场特性有重要作用,过于简化的短编组列车外形不能够精细反映列车的真实气动特性。为研究典型路基结构对高速列车横风气动特性的影响,以9编组动力集中型高速列车实车为研究对象,考虑风挡、转向架、受电弓等细节特征,对列车运行速度为200 km/h,横风速度分别为20 m/s、30 m/s、35 m/s、40 m/s,路基结构分别为平直地面、3 m路堤、6 m路堤、高架桥等四种场景下的高速列车空气动力学性能进行了仿真计算和对比,分析了不同路基地面条件下列车的横风气动特性的差异及规律,为横风条件下复杂路基结构的列车运行安全控制提供了参考

Parametric design and optimization of high speed train nose

Aiming at shortening the design period and improve the design efficiency of the nose shape of high speed trains, a parametric shape optimization method is developed for the design of the nose shape has been proposed in the present paper based on the VMF parametric approach, NURBS curves and discrete control point method. 33 design variables have been utilized to control the nose shape, and totally different shapes could be obtained by varying the values of design variables. Based on the above parametric method, multi-objective particle swarm algorithm, CFD numerical simulation and supported vector machine regression model, multi-objective aerodynamic shape optimization has been performed. Results reveal that the parametric shape design method proposed here could precisely describe the three-dimensional nose shape of high speed trains and could be applied to the concept design and optimization of the nose shape. Besides, the SVM regression model based the multi-points criterion could accurately describe the non-linear relationship between the design variables and objectives, and could be generally utilized in other fields. No matter the simplified model or the real model, the aerodynamic performance of the model after optimization has been greatly improved. Based on the SVR model, the nonlinear relation between the aerodynamic drag and the design variables is obtained, which could provide guidance for the engineering design and optimization

Parametric design and optimization of high speed train nose

Aiming at shortening the design period and improve the design efficiency of the nose shape of high speed trains, a parametric shape optimization method is developed for the design of the nose shape has been proposed in the present paper based on the VMF parametric approach, NURBS curves and discrete control point method. 33 design variables have been utilized to control the nose shape, and totally different shapes could be obtained by varying the values of design variables. Based on the above parametric method, multi-objective particle swarm algorithm, CFD numerical simulation and supported vector machine regression model, multi-objective aerodynamic shape optimization has been performed. Results reveal that the parametric shape design method proposed here could precisely describe the three-dimensional nose shape of high speed trains and could be applied to the concept design and optimization of the nose shape. Besides, the SVM regression model based the multi-points criterion could accurately describe the non-linear relationship between the design variables and objectives, and could be generally utilized in other fields. No matter the simplified model or the real model, the aerodynamic performance of the model after optimization has been greatly improved. Based on the SVR model, the nonlinear relation between the aerodynamic drag and the design variables is obtained, which could provide guidance for the engineering design and optimization

Probing the edge-related properties of atomically thin MoS2 at nanoscale

层状二维材料具有独特的物理化学性质，使其在光电器件、传感、能源和催化等领域得到了高度关注和广泛应用。二维材料在制备过程中不可避免引入结构缺陷，虽然这些缺陷尺度仅为数纳米甚至单原子，但是会极大地改变材料的结构和电子性质，从而影响其应用。化学化工学院任斌教授课题组在层状二维材料缺陷表征方面取得进展。该工作表明了TERS在原位、高空间分辨表征缺陷位的结构和电子性质方面具有独特的优势，可以进一步推广到其他二维材料，从而有效地指导缺陷设计和材料应用。 该工作通过校内外课题组紧密合作，在任斌教授、谭平恒研究员（中科院半导体研究所）和王翔博士共同指导下完成。实验部分主要由黄腾翔博士（第一作者，已毕业化学系博士生）完成，电子能带结构与光谱理论计算由谭平恒研究员课题组从鑫博士生（共同第一作者）完成，吴思思、林楷强、姚旭、何玉韩、吴江滨、包一凡、黄声超等参与了实验与讨论。【Abstract】Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to characterize small defects and correlate their structures with properties. Here, we show that tipenhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS2, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edgeinduced Raman peak (396 cm−1) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm−1. The power of TERS demonstrated in MoS2 can also be extended to other 2D materials, which may guide the defect engineering for desired properties.The authors acknowledge the final supports from MOST of China (2016YFA0200601 and 2016YFA0301204), NSFC (21633005, 21790354, 21503181, 21711530704, 21621091, 11874350, 11474277, and 11434010), Natural Science Foundation of Fujian Province (2016J05046), and China Postdoctoral Science Foundation (2017M622062). 研究工作得到科技部、国家自然科学基金委员会、福建省自然科学基金和中国博士后基金资助

Electrospun Poly(γ–glutamic acid)/β–Tricalcium Phosphate Composite Fibrous Mats for Bone Regeneration

[[abstract]]A poly(γ–glutamic acid)/β–tricalcium phosphate (γ–PGA/β–TCP) composite fibrous mat was fabricated using the electrospinning technique as a novel bone substitute. The mat was then cross-linked with cystamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide to improve its water-resistant ability. Scanning electron micrographs revealed that the γ–PGA/β–TCP fibers had a uniform morphology with diameters ranging from 0.64 ± 0.07 µm to 1.65 ± 0.16 µm. The average diameter of the fibers increased with increasing cross-linking time. Moreover, increasing the cross-linking time and decreasing the γ–PGA/β–TCP weight ratio decreased the swelling ratio and in vitro degradation rate of the composite fibrous mat. In vitro experiments with osteoblast-like MG-63 cells demonstrated that the mat with a γ–PGA/β–TCP weight ratio of 20 and cross-linked time of 24 h had a higher alkaline phosphatase activity and better cell adhesion. Furthermore, the rat cranial bone defect was created and treated with the γ–PGA/β–TCP composite fibrous mat to evaluate its potential in bone regeneration. After 8 weeks of implantation, micro computed tomography showed that the γ–PGA/β–TCP composite fibrous mat promoted new bone growth. These observations suggest that the γ–PGA/β–TCP composite fibrous mat has a potential application in bone tissue engineering

Three-dimensional dose comparison of flattening filter (FF) and flattening filter-free (FFF) radiation therapy by using NIPAM gel dosimetry

[[abstract]]Intensity-modulated radiotherapy and volumetric modulated arc therapy are modern radiation therapy technologies that can create the desired dose distribution by multileaf collimator movement and dose-rate control. However, the homogeneous dose delivery of small-field irradiation techniques shows disagreement with that of treatment planning system. The removal of the flattening filter by flattening filter free (FFF) beam irradiation increases dose conformity and further reduces treatment delivery time in radiosurgery. This study aims to investigate the dose distribution of FFF and flattened beams for small-field irradiation by using the 3D gel dosimeter. The N-isopropylacrylamide (NIPAM) polymer gel dosimeter was employed to record the 3D dose distribution. In addition, flattened and FFF beams were compared using the gamma evaluation technique. The use of an FFF accelerator resulted in excellent radiation treatments with short delivery times and low doses to normal tissues and organs. Results also showed that the passing rate increased with the decrease of field size (30 × 30, 20 × 20, and 10 × 10 mm2) at post-irradiation times of 24, 48, 72, and 96 h. The passing rates for each field size were retained at the same level when gamma criteria, namely, distance-to-agreement (DTA) = 3 mm/dose difference (DD) = 3%, were used. Nevertheless, the passing rates for each field size decreased slowly after 48 h when DTA = 2 mm/DD = 2%. The Wilcoxon signed-rank test was used to determine statistical difference with a significant level of p < 0.05. The passing rates of flattened and FFF beams showed no significant difference. The edge enhancement effect in the flattened beam was more evident than in the FFF beam. The 3D NIPAM gel dosimeter can be used for dose verification of small field for radiation therapy with high dose rate

Lithospermi radix Extract-Containing Bilayer Nanofiber Scaffold for Promoting Wound Healing in a Rat Model

[[abstract]]This study examined the in vitro characteristics and in vivo wound healing effect of novel Lithospermi radix (LR) extract-containing bilayer scaffolds in a rat model. LR extract, which has been used as a traditional herbal medicine for treating skin wounds, was added to a biocompatible gelatin solution. After glutaraldehyde vapor was used to modify the surface of chitosan scaffolds, various ratios of mammalian gelatin and fish collagen (GF100, GF91 and GF82) were electrospun onto the chitosan scaffolds to manufacture bilayer scaffolds. The porous chitosan scaffolds with a high swelling ratio showed efficient exudate absorption ability. GF91 gelatin nanofibers electrospun at a constant flow rate at 0.1 mL/h and a voltage of 20 kV displayed the optimal characteristics required for cell attachment and skin tissue regeneration. Moreover, the LR extract was successfully released slowly from the GF91 nanofibers. The investigation of the wound-healing activity of the chitosan/gelatin (CGF) bilayer scaffolds revealed that CGF91L provided the highest wound recovery rate in vivo in Sprague-Dawley (SD) rats. Based on its wound-healing effect and beneficial characteristics, the novel LR extract-containing CGF91 bilayer scaffold demonstrates potential as a material for treating skin wounds

Effect of genipin crossliked chitosan scaffolds containing SDF-1 on wound healing in a rat model

[[abstract]]Prolonged healing is a severe problem for elderly and diabetic patients. Impaired angiogenesis, stem cell differentiation, and migration have been shown to delay wound healing. The chemokine stromal cell-derived factor-1 (SDF-1) plays an essential role in recruiting cells to wound sites and is suggested to be a candidate for tissue engineering. In this study, chitosan (CHI) scaffolds were crosslinked with nontoxic genipin (Gp) and further heparinized for SDF-1 immobilization. Then, the structures were evaluated for their physicochemical properties (porosity, swelling ratio, and water vapor transmission rate (WVTR)). The interaction between SDF-1 and heparin could sustain SDF-1 release, which has been shown to enhance human umbilical vein endothelial cell (HUVEC) 2D/3D migration. The investigation of the wound-healing activity of the SDF-1-loaded CHI scaffolds revealed a better wound recovery rate in vivo in healthy and streptozotocin-induced diabetic Sprague-Dawley (SD) rats. The histological analysis illustrated that the local of SDF-1 treatment scaffold at the wound site enhanced neovascularization. The wounds treated with SDF-1 scaffolds also exhibited higher vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-β) expression in Western blot assays. Based on the wound-healing activity and beneficial characteristics, the SDF-1-loaded CHI scaffold demonstrates potential as a material for treating skin wounds