Enhanced Production of Natural Carotenoids from Genetically Engineered Rhodobacter sphaeroides Overexpressing CrtA

Carotenoids act as precursors of vitamin A,antioxidants,enhancers of immunity,and are thus widely used in food and pharmaceutical industry.Microbial fermentation is one of the most important solutions for production of natural carotenoids.Rhodobacter sphaeroides is one of most promising bacteria employed for large scale production of carotenoids.In the present study,crtA located in the carotenoids biosynthesis pathway in R.sphaeroides was amplified by PCR.The overexpression vector pRKcrtA was constructed and subsequently transferred into R.sphaeroides,producing the genetically engineered strain R.sphaeroides 2.4.1/pRKcrtA overexpressing crtA.The carotenoid production from the genetically engineered strain was significantly increased.Fermentation procedure was optimized for further enhanced carotenoids production.

The osteogenesis of Ginsenoside Rb1 incorporated silk/micro-nano hydroxyapatite/sodium alginate composite scaffolds for calvarial defect

Ginsenoside Rb1, the effective constituent of ginseng, has been demonstrated to play favorable roles in improving the immunity system. However, there is little study on the osteogenesis and angiogenesis effect of Ginsenoside Rb1. Moreover, how to establish a delivery system of Ginsenoside Rb1 and its repairment ability in bone defect remains elusive. In this study, the role of Ginsenoside Rb1 in cell viability, proliferation, apoptosis, osteogenic genes expression, ALP activity of rat BMSCs were evaluated firstly. Then,micro-nano HAp granules combined with silk were prepared to establish a delivery system of Ginsenoside Rb1, and the osteogenic and angiogenic effect of Ginsenoside Rb1 loaded on micro-nano HAp/silk in rat calvarial defect models were assessed by sequential fluorescence labeling, and histology analysis, respectively. It revealed that Ginsenoside Rb1 could maintain cell viability, significantly increased ALP activity, osteogenic and angiogenic genes expression. Meanwhile, micro-nano HAp granules combined with silk were fabricated smoothly and were a delivery carrier for Ginsenoside Rb1. Significantly, Ginsenoside Rb1 loaded on micro-nano HAp/silk could facilitate osteogenesis and angiogenesis. All the outcomes hint that Ginsenoside Rb1 could reinforce the osteogenesis differentiation and angiogenesis factor’s expression of BMSCs. Moreover, micro-nano HAp combined with silk could act as a carrier for Ginsenoside Rb1 to repair bone defect.

正六边形孔蜂窝组合梁腹板纯弯屈曲研究

蜂窝构件具有承载力高、抗弯刚度大和方便穿越管线等优点,近年来广泛应用于各类高层建筑和大跨度结构中。对于蜂窝构件来说,腹板的局部屈曲是其主要破坏模式之一,屈曲会导致腹板局部变形的急速增加,直至退出工作,并可能导致构件整体失稳及结构上的连锁反应。在传统钢结构设计中通过对腹板高厚比进行限制来避免腹板局部屈曲的发生,而蜂窝构件相比于实腹构件受力更加复杂,孔间墩板及其桥板都有可能发生局部屈曲。目前对于蜂窝构件局部稳定问题的研究大多围绕着纯钢蜂窝梁开展,对于蜂窝组合梁的研究较少。因此有必要对蜂窝组合梁的纯弯屈曲开展研究。在已有2个纯钢蜂窝梁的基础上,设计并制作了两个简支蜂窝组合梁,对这两根蜂窝组合梁在四分点处施加集中力进行静力加载试验研究,通过观察钢梁上屈曲发生位置及混凝土裂缝开展的位置及形态,对腹板屈曲性能、承载力和蜂窝孔应变等进行分析,与纯钢蜂窝梁进行对比,研究混凝土板和腹板间加劲肋的设置对蜂窝钢梁试件破坏形态、应力分布及承载力的影响。利用有限元软件ABAQUS建立模型进行数值模拟,将试验结果与有限元模拟结果进行对比,发现模型结果与试验结果较为吻合。以试验模型为基础,分析纯弯作用下,高厚比和开孔率的改变对蜂窝组合梁的纯弯屈曲和极限承载力的影响规律,得到蜂窝组合梁发生强度破坏和屈曲破坏的临界值。研究表明:纯钢蜂窝梁在上翼缘及相应桥板屈曲,组合梁试件在桥板和墩板屈曲,混凝土板可以有效提高组合梁的屈服荷载和极限荷载,提高试件延性,有效避免局部屈曲的发生;组合梁腹板间设置加劲肋可以提高对腹板的约束作用,减弱孔角处应力集中,避免孔间墩板屈曲失稳;组合梁共出现两种屈曲模式,均为孔间墩板发生半波形平面外失稳,区别在于平面外位移分布方式;第一种屈曲模式位移相对跨中呈对称轴分布,第二种屈曲模式位移相对跨中呈中心对称分布。高厚比是影响组合梁破坏模式和纯弯屈曲的决定性因素,高厚比小于80时,发生强度破坏,高厚比大于80时,发生屈曲破坏,减小腹板高厚比可以有效提高组合梁屈曲荷载,提高试件抗屈曲能力;开孔率是影响组合梁破坏模式和纯弯屈曲的重要因素,在一定范围内增大开孔率可以提高试件屈曲荷载。