西藏半干旱区三种柏树抗旱性研究

本文以西藏半干旱区分布的柏树为实验树种,采用盆栽控水干旱胁迫手段,比较和分析了3种柏树在持续水分胁迫条件下的生理响应,结果表明:①随着干旱胁迫时间推移,土壤含水量不断降低,各树种叶片水分饱和亏缺值持续上升,初期失水速率基本相同,至13d,各树种失水速率逐渐加快并产生差异,其中,巨柏失水速度最快、大果圆柏次之、香柏最小;②从叶绿素a+b值和叶绿素a/b值综合比较来看,香柏和巨柏的抗旱适应性、喜光性略高于大果圆柏;③遭受干旱胁迫后,巨柏、香柏和大果圆柏体内游离脯氨酸含量分别增加了68.73%、63.61%和47.66%;④在此过程中,各树种体内丙二醛含量基本保持相对稳定状态,胁迫后期与前期相比并没有出现大量积累的现象。不同胁迫阶段,大果圆柏的电解质外渗率处于较高水平,巨柏次之,香柏最低;⑤可溶性糖积累过程中巨柏和大果圆柏增量明显高于香柏;⑥随着干旱胁迫时间延长,3个树种体内保护酶SOD和CAT含量均有所下降,试验初期至结束,SOD活性分别下降了20.34%～39.35%,CAT活性下降了58.39%～72.30%。采用模糊数学隶属函数法对3种柏树抗旱性进行综合评价,其抗旱能力强弱排序依次为香柏巨柏大果圆柏。     

Prediction of stress levels in the workplace using surrounding stress

Occupational stress has a significant adverse effect on workers’ well-being, productivity, and performance and is becoming a major concern for both individual companies and the overall economy. To reduce negative consequences, early detection of stress is a key factor. In response several stress prediction methods have been proposed, whose primary aim is to analyse physiological and behavioural data. However, evidence suggests that solutions based on physiological and behavioural data alone might be challenging when implemented in real-world settings. These solutions are sensitive to data problems arising from losses in signal quality or alterations in body responses, which are common in everyday activities. The contagious nature of stress and its sensitivity to the surroundings can be used to improve these methods. In this study, we sought to investigate automatic stress prediction using both surrounding stress data, which we define as close colleagues’ stress levels and the stress level history of the individuals. We introduce a real-life, unconstrained study conducted with 30 workers monitored over 8 weeks. Furthermore, we propose a method to investigate the effect of stress levels of close colleagues on the prediction of an individual’s stress levels. Our method is also validated on an external, independent dataset. Our results show that surrounding stress can be used to improve stress prediction in the workplace, where we achieve 80% of F-score in predicting individuals’ stress levels from the surrounding stress data in a multiclass stress classification.     

Effect on growth and productivity of lutein from the chlorophyta microalga,strain MCH of Muriellopsis sp., when grown in sea water and outdoor conditions at the Atacama Desert

BackgroundMicroalgae are microorganisms that produce various products, for example, pigments, mainly carotenoids. This study aimed to used the strain of Muriellopsis sp. and to evaluate their behavior when grown in freshwater and seawater, along with indoor and outdoor conditions for both cultures. Growth of the strain was evaluated by determining its biomass, lutein productivity with high-performance liquid chromatography (HPLC), and antioxidant activity by using the 2,2-diphenyl-1-picrilhydrazil (DPPH method).ResultsMuriellopsis sp. strain in indoor cultures showed an increased antioxidant activity. In outdoor conditions, both cultures showed increased cells number, concentration of biomass, and lutein productivity. The percentage of lutein obtained from the strain MCH in indoor conditions was 25 times higher than that reported for calendula, reaching 0.75% of lutein in Muriellopsis sp. cultured in seawater, followed by 0.6% in Muriellopsis sp., cultures in freshwater at day 12 of both cultures. These values exceed that of microalgae Scenedesmus almeriensis, which reaches 0.53% lutein.ConclusionsThe results show that the native strain of the Atacama Desert is one of the largest producers of lutein as compared to those reported to date. The study demonstrated the feasibility of producing this carotenoid with well-known properties to prevent some diseases due to its high nutritional value. Muriellopsis sp. cultivation in open-air seawater is a good precedent for developing mass production of this species in an area where freshwater is scarce and costly.How to cite: Cruz-Balladares V, Marticorena P, Riquelme C. Effect on growth and productivity of lutein from the chlorophyta microalga, strain MCH of Muriellopsis sp., when grown in sea water and outdoor conditions at the Atacama Desert. Electron J Biotechnol 2021;54. https://doi.org/10.1016/j.ejbt.2021.09.001     

水分胁迫对黄淮海夏玉米农业气候资源利用的影响——水分胁迫对叶片生产力影响

文章对水分胁迫的夏玉米光合生产力变化进行了系统观测和实验 ,研究表明 :①可将土壤持水量的 4 0 6 89%～ 5 5 79%和 79 99%作为叶片缺水及最适的外部形态指标 ;②干旱可以使株高低 2 2 5 6 %左右 ,而短时间内水分一直维持在田间持水量水平 ,对玉米的株高影响并不大 ;③比叶重随土壤湿度增加而增大 ,到田间持水量的 79 9%时达到最大值 ,随着湿度的进一步增加 ,比叶重反而略微变小 ;④叶片含水量与土壤湿度成正相关 ,吸收辐射率则受叶片湿度与厚度的影响 ,当土壤湿度达到持水量的 79 99%时 ,叶片吸收辐射率可达到 80 %左右。在此研究基础上 ,给出了包含浓度、辐射强度、温度及土壤水分因子的夏玉米叶片生产力计算公式 ,为进一步准确推算水分胁迫对区域生产力的可能影响 ,为当地政府开发农业气候资源提供了前提条件。     

Karasek工作压力模型的扩展：自我效能感与工作控制匹配性模型的实证研究

在对Karasek工作压力模型相关研究进行回顾的基础上,本文引入个体差异变量--自我效能感,提出自我效能感与工作控制的匹配性模型,并利用层次回归方法对来自医疗行业的344份有效问卷进行实证分析,验证该扩展模型.匹配性模型在详细解释高自我效能者如何应对工作压力的基础上,提出了与低自我效能者相匹配的工作压力模式,对Karasek工作压力模型作了扩展.     

Longitudinal analysis of Chinese high school student’s stress in school and academic achievement

In previous research, few studies have examined the effects of adolescents’ stress in school on the change rates of their academic achievement. In the present study, we seek to examine the longitudinal relationships between adolescents’ stress in school and the change rates of their academic achievement. The results indicated that for those whose academic achievement significantly declined over time, the students’ stress from teacher–student interaction significantly predicted the change rates of their academic achievement. The findings provided support to the notion that stress was a risk factor in students’ academic development.     

Transgenic barley with overexpressed PTrx increases aluminum resistance in roots during germination

A transgenic barley line (LSY-11-1-1) with overexpressed Phalaris coerulescens thioredoxin gene (PTrx) was employed to measure the growth, protein oxidation, cell viability, and antioxidase activity in barley roots during germination on the presence of 2 mmol/L AlCl₃ on filter paper. The results show that (1) compared with the non-transgenic barley, LSY-11-1-1 had enhanced root growth, although both were seriously inhibited after AlCl₃ treatment; (2) the degree of protein oxidation and loss of cell viability in roots of LSY-11-1-1 were much less than those in roots of non-transgenic barley, as reflected by lower contents of protein carbonyl and Evans blue uptakes in LSY-11-1-1; (3) activities of catalase (CAT), glutathione peroxidase (GPX), ascorbate peroxidase (APX), and glutathione reductase (GR) in LSY-11-1-1 root tips were generally higher than those in non-transgenic barley root tips, although these antioxidase activities gave a rise to different degrees in both LSY-11-1-1 and non-transgenic barley under aluminum stress. These results indicate that overexpressing PTrx could efficiently protect barley roots from oxidative injury by increasing antioxidase activity, thereby quenching ROS caused by AlCl₃ during germination. These properties raise the possibility that transgenic barley with overexpressed PTrx may be used to reduce the aluminum toxicity in acid soils.     

断裂力学的工程应用

脆性破坏是零件失效的主要形式之一,传统的防脆断方法要么很保守要么照样产生脆性破坏.从断裂力学的角度讨论带裂纹体在实际工程中的应用.     

大学生压力应对研究的现状与思考

通过了解压力应对理论的发展和我国大学生压力应对研究的现状,认为当前我国大学生压力应对方面的研究虽然取得了一定成果,但在研究方法多维度、研究手段科学性、实践应用广泛性上存在不足等问题。因此,提出规范压力应对的科学研究、构建压力应对实践体系是增强大学生压力应对能力的关键。     

主应力轴旋转情况下土的各向异性理论研究进展

从理论方面,对国内外主应力轴旋转情况下土的各向异性研究进行了对比和总结,并提出了一些研究建议。指出在理论方面,应当对屈服面方程采用应力分量表示的模型在三维空间里进行屈服面性状的描述,同时考虑不同加载方向下屈服面的变化特性以及旋转硬化的问题,并应开展对加载方向变化时土体屈服面变化特性的实验研究及理论验证。