Effects of arsenic on reactive oxygen species and antioxidant defense system in tomato plants

In this study, the generation of reactive oxygen species, the induction of oxidative stress, and the response of the antioxidative system in hydroponically grown tomato plants as the cause of arsenic-induced phytotoxicity are investigated. Reduction in plant growth was measured in terms of dry weight and length of roots and shoots, the latter accumulating more arsenic than the roots. The treatment resulted in increased formation of superoxide anion (O₂^.?), H₂O₂, and thiobarbituric acid reactive substances, which indicate augmented lipid peroxidation. Superoxide dismutase, catalase (CAT), and ascorbate peroxidase activities were increased in arsenic-treated tomato plants while CAT activity was insignificantly increased.     

Cd胁迫下杂交水稻对Cd的吸收及其动态变化

镉（Cd）是非必需的有毒元素,是农业环境和农产品的重要污染物,易被水稻吸收并在籽粒中积累。不同水稻品种拥有不同的独特基因,导致水稻籽粒吸收积累Cd的能力存在一定的差异。因此,开展不同水稻品种耐Cd特性及其不同生育期的吸收转运效率研究具有重要意义。本文采用水培试验,研究了两个水稻（Oryza sativa L.）品种：D83A/R527（低吸收累积Cd）和辐优838（高吸收累积Cd）在不同质量浓度Cd胁迫下籽粒Cd质量分数及不同生育时期水稻根、茎、叶内Cd的吸收积累量及其动态变化特点。结果表明,两种水稻品种在Cd胁迫下籽粒Cd积累量差异显著,辐优838在1.0 mg·L^-1 Cd质量浓度胁迫下籽粒Cd质量分数就已超过国家食品卫生标准;在1.0~3.0 mg·L^-1 Cd质量浓度胁迫下,D83A/R527籽粒内Cd质量分数仅为辐优838的50~60%。随着Cd处理浓度增加和生育时期推进,两种水稻各部位Cd吸收量均表现为逐渐增加,其增加幅度总体表现为：辐优838〉D83A/R527;不同部位中,根的积累效应最强,叶片吸收积累能力最低,辐优838茎、叶吸收积累效率分别是D83A/R527的1.5~2.0倍左右。在1.0~3.0mg·L^-1 Cd胁迫下,水稻Cd积累差异较为显著的时期为灌浆期,辐优838的根系向茎、叶的转移效率大于D83A/R527,且D83A/R527主要表现为由根系向茎Cd转移效率较高,叶片Cd积累相对较少。灌浆期是水稻籽粒干物质积累的重要时期,也是吸收累积Cd的重要时期,这为筛选低吸收积累水稻品种和调控Cd在水稻籽粒中的吸收累积奠定了重要理论基础。     

Influence of arsenic stress on synthesis and localization of low-molecular-weight thiols in Pteris vittata

The roles of low-molecular-weight thiols (LMWTs), such as glutathione and phytochelatins, in arsenic (As) tolerance and hyperaccumulation in Pteris vittata an As-hyperaccumulator fern remain to be better understood. This study aimed to thoroughly characterize LMWT synthesis in P. vittata to understand the roles played by LMWTs in As tolerance and hyperaccumulation. LMWT synthesis in P. vittata was induced directly by As, and not by As-mediated oxidative stress. Expression of PvECS2, one of the putative genes of γ-glutamylcysteine synthetase (γECS), increases in P. vittata shoots at 48 h after the onset of As exposure, almost corresponding to the increase in the concentrations of γ-glutamylcysteine and glutathione. Furthermore, localization of As showed similar trends to those of LMWTs in fronds at both whole-frond and cellular levels. This study thus indicates the specific contribution of LMWTs to As tolerance in P. vittata. γECS may be responsible for the As-induced enhancement of LMWT synthesis.     

丁腈橡胶密封圈高温老化行为——自由状态和承压状态

目的研究丁腈橡胶密封圈自由状态和承压状态下的高温老化行为。方法以拉伸强度和拉断伸长率为参数,对各温度下的老化行为进行表征和分析。结果 70℃条件下机械应力大大加快了橡胶密封件拉伸强度的下降速率,以致试验64 d时拉伸强度甚至比110℃时还低,拉断伸长率的下降速率也明显加快了;90℃加速条件下机械应力对拉伸强度的下降有一定的促进作用,但对拉断伸长率的变化基本无影响;110℃加速条件下机械应力对拉伸强度和拉断伸长率均没有明显的影响。结论机械应力在较低温度下可以显著促进丁腈橡胶密封圈热氧老化,高温条件下促进作用不明显。     

半球形封头热拉深成形理论分析

利用主应力法对半球形封头的拉深成形进行了分析与研究。将板料划分为 4个区域 :法兰区、凹模圆角区、悬空锥形区和球形区 ,对每个区域的应力分布进行了理论推导与探讨 ,以期对该类产品的设计、生产和加工有所帮助     

The living environment and children's fears following the Indonesian tsunami

The tsunami that struck South-east Asia on 26 December 2004 left more than 500,000 people in Aceh, Indonesia, homeless and displaced to temporary barracks and other communities. This study examines the associations between prolonged habitation in barracks and the nature of fears reported by school-age children and adolescents. In mid-2007, 30 months after the tsunami, the authors interviewed 155 child and parent dyads. Logistic regression analysis was used to compare the fears reported by children and adolescents living in barracks with those reported by their peers who were living in villages. After adjusting for demographic factors and tsunami exposure, the data reveals that children and adolescents living in barracks were three times more likely than those living in villages to report tsunami-related fears. The study demonstrates that continued residence in barracks 30 months after the tsunami is associated with higher rates of reporting tsunami-related fears, suggesting that barracks habitation has had a significant impact on the psychological experience of children and adolescents since the tsunami.     

十溴二苯乙烷对蚯蚓亚急性毒性及微生物群落结构影响

新型溴系阻燃剂十溴二苯乙烷(DBDPE)生产和使用量日益增大,在环境中的检出率越来越高,其生态风险正受到广泛关注.然而,有关DBDPE对陆地无脊椎生物毒性效应以及微生物群落结构的影响知之甚少.探究了不同剂量(5、10、20、50和100mg·kg-1)DBDPE暴露对赤子爱胜蚓(Eisenia fetida)生长、行为...     

专业课教学中的思想教育探讨

针对我国理工科大学专业课教学工作的特点,本文提出了专业课教学中进行思想政治教育的建议,论述了教师在专业课教学中有效地融大学生的思想政治教育于专业课教学中的方法,以便起到合力育人目的,促进高校专业课教学工作.     

大气环境下风电塔筒金属材料的应力腐蚀

塔筒金属材料在大气中的应力腐蚀会导致脆性断裂,从而对产生严重的后果。本文重点论述了应力腐蚀的几种腐蚀机理以及Cl-对应力腐蚀的影响,并介绍了应用较广的慢应力速率试验方法。     

Determination of F2-isoprostanes in cultured human lung epithelial cells after exposure to metal oxide and silica nanoparticles by high-performance liquid chromatography/tandem mass spectrometry

The environmental impact of nanotechnology has caused a great concern. Many in vitro studies showed that many types of nanoparticles were cytotoxic. However, whether these nanoparticles caused cell membrane damage was not well studied. F₂-isoprostanes are specific products of arachidonic acid peroxidation by nonenzymatic reactive oxygen species and are considered as reliable biomarkers of oxidative stress and lipid peroxidation. In this article, we investigated the cytotoxicity of different nanoparticles and the degree of cellular membrane damage by using F₂-isoprostanes as biomarkers after exposure to nanoparticles. The human lung epithelial cell line A549 was exposed to four silica and metal oxide nanoparticles: SiO₂ (15 nm), CeO₂ (20 nm), Fe₂O₃ (30 nm), and ZnO (70 nm). The levels of F₂-isoprostanes were determined by using high-performance liquid chromatography/mass spectrometry. The F₂-isoprostanes’ peak was identified by retention time and molecular ion m/z at 353. Oasis HLB cartridge was used to extract F₂-isoprostanes from cell medium. The results showed that SiO₂, CeO₂, and ZnO nanoparticles increased F₂-isoprostanes levels significantly in A549 cells. Fe₂O₃ nanoparticle also increased F₂-isoprostanes level, but was not significant. This implied that SiO₂, CeO₂, ZnO, and Fe₂O₃ nanoparticles can cause cell membrane damage due to the lipid peroxidation. To the best of our knowledge, this is the first report on the investigation of effects of cellular exposure to metal oxide and silica nanoparticles on the cellular F₂-isoprostanes levels.