Characterization of (68)Zn uptake, translocation, and accumulation into developing grains and young leaves of high Zn-density rice genotype

Zinc (Zn) is an essential micronutrient for humans, but Zn deficiency has become serious as equally as iron (Fe) and vitamin A deficiencies nowadays. Selection and breeding of high Zn-density crops is a suitable, cost-effective, and sustainable way to improve human health. However, the mechanism of high Zn density in rice grain is not fully understood, especially how Zn transports from soil to grains. Hydroponics experiments were carried out to compare Zn uptake and distribution in two different Zn-density rice genotypes using stable isotope technique. At seedling stage, IR68144 showed higher ⁶⁸Zn uptake and transport rate to the shoot for the short-term, but no significant difference was observed in both genotypes for the long-term. Zn in xylem sap of IR68144 was consistently higher, and IR68144 exhibited higher Zn absorption ratio than IR64 at sufficient (2.0 μmol/L) or surplus (8.0 μmol/L) Zn supply level. IR64 and IR68144 showed similar patterns of ⁶⁸Zn accumulation in new leaves at seedling stage and in developing grains at ripening stage, whereas ⁶⁸Zn in new leaves and grains of IR68144 was consistently higher. These results suggested that a rapid root-to-shoot translocation and enhanced xylem loading capacity may be the crucial processes for high Zn density in rice grains.     

流动儿童受教育问题研究

由于制度不完善、家庭条件有限等原因,目前我国的流动儿童在接受教育时还面临机会不平等、学习条件差、家庭教育薄弱等方面的问题。为此应完善我国的相关制度,为流动儿童提供更多的受教育机会;对流动儿童家长进行培训,以提高他们的家庭教育能力;发动社会力量参与流动儿童教育,以弥补家庭方面不足,提升流动儿童受教育质量。     

关于提高《液压与气压传动》教学质量的思考

根据高职院校的特点,结合《液压与气压传动》课程理论及实验教学中的体会,针对目前《液压与气压传动》课程教学的质量问题提出了从教材、实验及教学方法等多个方面的解决方法。     

焦虑情绪和适应能力对大学新生学习生活的影响

采用焦虑自评量表和心理适应性自测量表对67名大学新生进行三次心理健康状况调查,结果显示有一般心理问题的学生占28.36%;有严重心理问题的学生占6.00%。焦虑产生的原因有生理需要不满足、安全感缺失、没有归属感、实现自我价值有压力。高校可以通过素质教育,加强校园文化建设,提高学生的适应能力,完善心理健康教育系统,缓解大学生的心理焦虑。     

中世纪大学的内部组织及管理

中世纪大学是欧洲中古时代留给现代社会的一笔很有价值的财富。中世纪大学很多组织要素历经时代变迁为后世大学所效仿,有些方面甚至为今天的大学所不及。通过对中世纪大学的内部组织运行特点的探讨可以看到,其组织、领导和管理方式至今仍给我们很多启发。     

A destructive field study on the behavior of piles under tension and compression

This paper involves a series of destructive full-scale load tests on long bored piles instrumented with strain gauges along the shafts, including two compression and two tension loading tests. The load-displacement response, axial force, skin friction, and the thresholds of the slip displacement for fully mobilizing the skin resistances in different soils are discussed. Moreover, the theoretical solution for estimating the pile tip settlement under compression was adopted to analyze the test results. It was found that the measured skin frictions for the piles under compression were about 6% to 42% higher than the estimated values of the cone penetration tests (CPTs), whereas the measured skin frictions in the uplift cases were about 16% to 50% smaller than the estimated values. In addition, the average limited skin frictions for the tension piles were about 0.36 to 0.78 times the average ultimate skin frictions for the piles under compression. It also can be indicated that the skin friction along the pile depth approached the limited state, and decreased from a peak value with increasing loads.     

基于步进电机的流苏丝线绕制机智能控制器的设计

针对流苏丝线绕制过程中对动力机构的控制要求,系统设计以ATMEL89S52系列单片机为核心控制器,采用SANY0步进电机作为动力机,利用东芝公司的TB6560AHQ步进电机细分驱动器和ATMEL公司的I2C总线器件AT4C02芯片对系统掉电时的实时速度、圈数和转向等数据进行保护,实现了丝线绕制过程中对力矩、转向、速度、圈数和捻度等参数的精确控制,减轻了工人的劳动强度,提高了流苏的生产质量和效率.     

强结构扰动理论在唯一稳态消谐法中的应用:以零序电阻消除铁磁谐振分析为例

将唯一稳态消谐法应用在中性点接地电力系统铁磁谐振的分析中,以强结构扰动理论为工具,得到了相应的消谐条件.结果表明,消除谐振的条件可以用一个矩阵的稳定性条件来决定,并用数值模拟进行验证,表明结果正确,同时也说明唯一稳态消谐法有效性.     

电压补偿法测晶体二极管的正向特性

晶体二极管的主要内部结构为PN结,故晶体二极管具有单向导电性能,且其单向导电性能随PN结掺杂浓度和晶体二极管所处的环境温度的改变而改变。晶体二极管属于非线性元件,理论推导可知其伏安特性曲线为指数曲线。     

安顺市城郊土地利用变化与驱动因素分析

城郊区是人类活动影响强烈之地带,土地利用变化与土地持续研究利用,对生态安全和地区持续发展具有十分重要的意义。文章以安顺市城郊区为研究区域,在地理信息系统支持下,以乡镇为研究单元,研究城郊区土地利用时空变化过程,并分析其变化驱动因素。