茶树愈伤组织诱导与共培转化的初步研究

以福鼎大白无性系茶树大田种子胚为材料，切取子叶、胚芽、胚轴和胚根进行培养，诱导形成愈伤组织。选用较致密的愈伤组织切块与带ＮＰＴⅡ和ＧＵＳ基因Ｔｉ质粒的根癌农杆菌共培养，通过卡那霉素抗性选择，得到了抗性愈伤组织并得到了芽的分化。抗性愈伤组织的诱导率在５％左右。共培过程中发现茶树愈伤组织能较强烈地促进农杆菌生长，表现在农杆菌在茶树愈伤组织周围的聚结。这可能是由于茶树多酚类含量较高，而通常酚基复合物有利于农杆菌对植物细胞的附着和转化。     

信宜地区鸡大肠杆菌耐药性的调查

近几年来,由致病性大肠杆菌引起的鸡大肠杆菌病在广东省信宜市有明显上升趋势,由于多方面原因,特别是临床上随意及超量使用抗菌药物,致使大肠杆菌的耐药性不断加强,呈现难以控制的局面.     

论建筑工程造价审核

工程造价的审核是一门专业性、知识性、政策性、技术性很强的工作。工程造价的审核是合理确定工程造价的必要程序及重要手段。通过对工程造价进行全面、系统的检查和复核，及时纠正，使之更加合理地确定工程造价。     

试论建筑工程造价的控制

工程造价控制应贯穿于建设项目的全过程，但要控制重点应转移到项目建设的前期，即转移到项目决策和设计阶段，而一但投资决策后，控制的重点应放在设计阶段。     

1989—2013年西洞庭湖土地类型及水禽栖息地变动研究

选取1989年、2002年和2013年的遥感影像对西洞庭湖土地利用类型转移格局及水禽栖息地进行遥感解译与变动分析。结果表明:1989—2013年,保留率最高的仍然是水体(87.34%)和泥滩地(59.61%),保留率最低的是林地(13.79%),草滩地的保留率仅为30.54%,而向芦苇滩地、旱地、林地的转化率则分别达20.26%、20.91%、18.93%,远高于向水体与泥滩地转化的比例。虽然林地向泥滩地转化的比例达到了34.77%,但芦苇滩地、旱地、林地以相互转化为主。西洞庭湖湿地破碎度升高,各种土地利用类型分布均匀度也增高。西洞庭湖的水禽栖息地变动大致可分为2个阶段:1989—2002年水体面积增长近14%,湿地优势度增长;2002—2013年水体面积减少近11%,林地面积增长约4%。在影响西洞庭湖水禽栖息地变动的驱动因素中,退田还湖、围湖养鱼、三峡工程、芦苇种植与杨树栽培等人类活动是最为重要的驱动因子,不适当的人为干预往往导致水禽生境退化。     

Effect of individual and combined exposure of Fe2O3 nanoparticles and oxytetracycline on their bioaccumulation by rice (Oryza sativa L.)

Purpose

It has been reported the bioaccumulation of γ-ferric oxide nanoparticles (Fe₂O₃ NPs) or oxytetracycline (OTC) in crops. However, there have been little references investigating their uptake and bioaccumulation in crops after the combined exposure. The present study focused on Fe₂O₃ NPs and OTC accumulation on root surface and in the tissues of rice (Oryza sativa L.) seedlings under combined exposure. And, the interactive influence mechanism was also discussed.

Materials and methods

Hydroponic experiments were conducted to investigate the Fe and OTC accumulation on root surface and in rice tissues under individual and combined exposure of Fe₂O₃ NPs and OTC. The dynamic change of particulate Fe, ionic Fe, and Fe plaque concentrations on root surface was determined under the influence of OTC from Fe₂O₃ NPs and Fe-EDTA exposure. Fe²⁺ from Fe-EDTA was selected in order to compare the Fe bioaccumulation from ionic Fe and nanoparticle Fe exposure. Hydrodynamic diameter and ζ-potential of Fe₂O₃ NPs in solution were investigated when OTC was present or not, and the changes of OTC concentrations were also determined during hydroponic culture. SEM, XRD, and TEM were used to analyze Fe₂O₃ NP distribution on root surface and inside root under the influence of OTC.

Results and discussion

OTC promoted surface-Fe and shoot-Fe accumulation in Fe₂O₃ NPs treatments, which was just an opposite result from Fe-EDTA treatments. Upon Fe₂O₃ NP exposure, Fe plaque was formed through the direct adsorption of NPs on the outside root surface and then incorporated into plaque as its crystalline components. OTC elevated notably surface-Fe accumulation mainly through increasing adsorption and precipitation of Fe₂O₃ NPs on the root surface due to low repulsive electrostatic interaction between NPs and the root surface after adding OTC. Fe₂O₃ NPs increased surface-OTC and root-OTC levels. Compared to Fe-EDTA, surface-Fe from NP treatments can hold strongly OTC due to Fe₂O₃ particle precipitated on root surface with high specific surface area. NPs reduced shoot-OTC under 25 mg L^?1 OTC, but not under 100 mg L^?1 OTC.

Conclusions

This study clearly demonstrates that Fe/OTC accumulation in rice was always in the order root surface > shoot > root, whether Fe₂O₃ NPs/OTC was individual or combined exposure. The combined exposure will increase their root surface distribution comparing with individual exposure, and Fe₂O₃ NPs increased also root-OTC levels, which could pose a potential risk to food safety in subsequent growth of rice.

     

化学生物学综合创新实验——基于pMAL蛋白融合表达系统的蛋白纯化

化学生物学是当代出现的一门新兴交叉学科,其专业实验课程的建设成为很多高等院校教学改革中的重要课题。本文介绍了一个基于麦芽糖结合蛋白的蛋白质纯化的系统,使用E.coli克隆载体pMAL-p5X,适用于表达及纯化重组蛋白质。可得到无亲和标签的目的蛋白,减低其对蛋白质的影响,优于以往的蛋白质亲和层析方法。此实验可作为化学生物学专业本科或研究生综合性创新实验内容。     

基于贝叶斯方法的收割机发动机盖有限元模型修正

收割机发动机缸盖较为复杂,在进行有限元分析时,如果模型简化或计算模型选择错误对计算效果影响很大。为此,提出了一种基于贝叶斯方法的发动机缸盖有限元模型修正方法,在进行缸盖的有限元分析时,采用了贝叶斯方法对缸盖的刚度参数进行修正,有效地提高了计算仿真的准确性。为了验证修正模型的可行性和可靠性,利用Pro/E软件对收割机发动机缸盖进行了三维建模,并将模型直接导入到ANSYS软件中进行了网格划分,网格划分采用了分块网格划分的形式,提高了计算效率和计算的准确性。最后,运用ANSYS对发动机缸盖在工作条件下的应力分布进行了有限元仿真计算,结果表明:采用修正模型可以成功地计算得到较为准确的应力分布情况,从而验证了模型的可靠性,为收割机发动机缸盖的设计提供了重要的数据参考。     

作物设施栽培基质消毒机的设计与研究

根据土壤高温蒸汽消毒原理,结合作物设施栽培的农艺要求,设计制造了一种自走式作物栽培基质蒸汽消毒机。利用Solid Works软件分析了消毒机的基本工作原理、总体结构组成及关键零部件设计,对各零部件结构图与装配图进行绘制并对重要工作部件进行了强度校核和运动轨迹分析;通过有限元软件ANSYS针对消毒机的抛土机构等开展静力学及模态的研究;依靠样机采用正交实验方法完成了田间性能试验,验证其设计的合理性与可行性。结果表明:设计的消毒机结构简单、操作简便,在减轻劳动强度的同时缩短了消毒时间,有利于提高设施栽培作物的产量和质量,为后续小型育苗基质消毒机械的设计提供了参考。