Heavy metal (Pb,Zn) uptake and chemical changes in rhizosphere soils of four wetland plants with different radial oxygen loss

Lead and Zn uptake and chemical changes in rhizosphere soils of four emergent-rooted wetland plants;Aneilema bracteatum,Cyperus alternifolius,Ludwigia hyssopifolia and Veronica serpyllifolia were investigated by two experiments：（1） rhizobag filled with ＂clean＂ or metal-contaminated soil for analysis of Pb and Zn in plants and rhizosphere soils;and （2） applied deoxygenated solution for analyzing their rates of radial oxygen loss （ROL）.The results showed that the wetland plants with different ROL rates had significant effects on the mobility and chemical forms of Pb and Zn in rhizosphere under flooded conditions.These effects were varied with different metal elements and metal concentrations in the soils.Lead mobility in rhizosphere of the four plants both in the ＂clean＂ and contaminated soils was decreased,while Zn mobility was increased in the rhizosphere of the ＂clean＂ soil,but decreased in the contaminated soil.Among the four plants,V.serpyllifolia,with the highest ROL,formed the highest degree of Fe plaque on the root surface,immobilized more Zn in Fe plaque,and has the highest effects on the changes of Zn form （EXC-Zn） in rhizosphere under both ＂clean＂ and contaminated soil conditions.These results suggested that ROL of wetland plants could play an important role in Fe plaque formation and mobility and chemical changes of metals in rhizosphere soil under flood conditions.

Supplement to the published paper"Theory-guided interventions for Chinese patients to adapt to heart failure:A quasi-experimental study"

We appreciate the question raised in a discussion with a reader and the editor about an instrument for outcome measure of the quality of life among people with chronic heart failure[1].We recognized that we should have described more details about how to convert the score of the Minnesota Living with Heart Failure Questionnaire(MLHFQ).Lack of scoring details might lead to some confusion to understand the results of this study.We thank the International Journal of Nursing Sciences for the opportunity to provide further information to clarify the process of data analysis and research findings.

在线课程师生交互与生生交互的话语分析——以国家开放大学“媒体辅助英语教学”课程为例

在线课程的实践对于教师、学习者等各方参与者都是重大挑战,如何将严谨的知识学习和学术训练放置于网络环境中,创造严肃活泼的师生、生生交互环境是众多教育从业者关心的问题。本文着眼于在线课程论坛的师生互动文本,以费尔克拉夫批判话语分析为理论基础,采用批判话语分析的"描述—阐释—解释"三维分析方法,从师生、生生在线互动中使用的高频词汇以及语气系统两个角度分析了一门在线课程教学中的互动文本的特点,发现教师和学生在词汇数目及种类方面有显著的差别,而在语气系统角度则存在一定的共性。最后,本文结合当前社会网络文化特点归纳了"互联网+教育"时代在线学习师生关系的平等与不平等性,并基于此探讨了师生在线互动关系及内容的重新构建,聚焦教师如何培养更符合网络社会的话语能力,以同时保持自身学术及话语的权威性与自身话语的可协商性,最终吸引学生深度参与在线讨论,成为在线课程师生交互的价值构建的主体。

Identification of rice cultivars with low brown rice mixed cadmium and lead contents and their interactions with the micronutrients iron,zinc,nickel and manganese

Paddy fields in mining areas are usually co-contaminated by a cocktail of mixed toxic heavy metals （e.g., Cd and Pb in Pb/Zn mines）. However, previous studies on rice cultivars screened for effective metal exclusion have mostly focused on individual metals, and have been conducted under pot-trial or hydroponic solution conditions. This study identified rice cultlvars with both low Cd and Pb accumulation under Cd- and Pb-contaminated field conditions, and the interactions of the toxic elements Cd and Pb with the micronutrient elements Fe, Zn, Mn and Ni were also studied. Among 32 rice cultivars tested, there were significant differences in Cd （0.06-0.59 mg/kg） and Pb （0.25-3.15 mg/kg） levels in their brown rice, and similar results were also found for the micronutrient elements. Significant decreases in concentrations of Fe and Mn were detected with increasing Cd concentrations and a significant elevation in Fe, Mn and Ni with increasing Pb concentrations. A similar result was also shown by Cd and Ni. Three cultivars were identified with a combination of low brown rice Cd and Pb, high micronutrient and grain yield （Wufengyou 2168, Tianyou 196 and Guinongzhan）. Present results suggest that it is possible to breed rice eultivars with low mixed toxic element （Cd, Pb） and high micronutrient contents along with high grain yields, thus ensuring food safety and quality.

Effects of root morphology and anatomy on cadmium uptake and translocation in rice(Oryza sativa L.)

A clear description of the certain mechanisms of cadmium(Cd) uptake and translocation in rice(Oryza sativa L.) may help to reduce Cd accumulation in rice grain. Hydroponic experiments were carried out to determine the effects of cultivation conditions(aerated and stagnant) on the uptake, translocation and subcellular distribution of Cd in relation to the morphology and anatomy of roots in two rice genotypes with different Cd accumulations in grains. Marked differences in morphology and anatomy were observed between these two genotypes under different cultivation conditions. Genotypes with low Cd accumulation in grains tended to develop fewer root tips per root surface area, larger root porosity and more mature apoplastic barriers. The stagnant cultivation condition decreased the number of root tips per root surface area but increased root porosity and accelerated apoplastic barrier formation in root tissues.Correlative Cd uptake studies revealed that rice plants with fewer number of root tips per root surface area reduced root Cd uptake ability, while mature apoplastic barriers increased root Cd retention in cell walls and the symplast. Thus, the fewer number of root tips per root surface area and the earlier formation of mature apoplastic barriers led to lower Cd uptake and translocation. The results indicated that the morphology and anatomy of roots could play important roles in Cd uptake and translocation in rice, and could be influenced by both genotype and cultivation conditions. The present results would be useful in screening and planting rice plants with low Cd accumulation.

Electron-ion collider in China

Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei.As a future high energy nuclear physics project,an Electron-ion collider in China(EicC)has been proposed.It will be constructed based on an upgraded heavy-ion accelerator,High Intensity heavy-ion Accelerator Facility(HIAF)which is currently under construction,together with a new electron ring.The proposed collider will provide highly polarized electrons(with a po-larization of 80%)and protons(with a polarization of 70%)with variable center of mass energies from 15 to 20 GeV and the luminosity of(2–3)×1033 cm^(−2)·s^(−1).Polarized deuterons and Helium-3,as well as unpolarized ion beams from Carbon to Uranium,will be also available at the EicC.The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region,including 3D tomography of nucleon;the partonic structure of nuclei and the parton interaction with the nuclear environment;the exotic states,especially those with heavy flavor quark contents.In addition,issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC.In order to achieve the above-mentioned physics goals,a hermetical detector system will be constructed with cutting-edge technologies.This document is the result of collective contributions and valuable inputs from experts across the globe.The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States.The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.

Metal accumulation and tolerance in wetland plants

This paper briefly reviews the progress in studies of wetland plants in terms of heavy metal pollution.The current research mainly includes the following areas:(1)metal uptake,translocation,and distributions in wetland plants and toxicological effects on wetland plants,(2)radial oxygen loss(ROL)of wetland plants and its effects on metal mobility in rhizosphere soils,(3)constitutional metal tolerance in wetland plants,and(4)mechanisms of metal tolerance by wetland plants.Although a number of accomplishments have been achieved,many issues still remain unanswered.The future research effort is likely to focus on the ROL of wetland plants affecting metal speciation and bioavailability in rhizosphere soils,and the development of rhizosphere management technologies to facilitate and improve practical applications of phytoremediation of metalpolluted soils.

Non-isolated high step-up DC–DC converter adopting auxiliary capacitor and coupled inductor

For grid-connected power system based on photovoltaic(PV) source and fuel cells, high step-up and high-efficiency DC–DC converters are needed, due to the bus voltage of the grid-connected inverter is much higher than the output voltage of PV and fuel cells. In this paper, a novel high step-up converter is proposed. An auxiliary capacitor is introduced into the boost converter, which serves as a voltage source. It is in series with the input voltage source with the same voltage polarities. Thus, the input voltage is increased equivalently and the voltage gain is increased accordingly. To reduce the voltage stresses of the switch and the diode, multiple output capacitors are introduced. The voltage of each output capacitor is degraded leading to the reduced voltage stress. To replenish energy for the multiple output capacitors, a coupled inductor is adopted. Based on this, high step-up converter adopting auxiliary capacitor and coupled inductor is derived. The operating principles and voltage gain of the proposed converters are analyzed in this paper. In theend, experiment results are given to verify the theoretical analysis.