短梗五加多糖的结构解析及抗氧化活性分析

对短梗五加中的多糖组分进行分离纯化,通过实验解析组分结构,并对其抗氧化活性进行分析。从短梗五加茎中分离纯化短梗五加多糖,通过高效液相色谱法、气相色谱-质谱分析、傅里叶变换红外光谱和紫外-可见光光谱法、^(1)H NMR和^(13)C NMR等对其组成结构特征进行研究和分析,并考察了短梗五加多糖对1,2-二苦基-2-三硝基苯亚肼(DPPH)、2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(ABTS)的抗氧化能力和铁离子还原能力。实验结果表明,短梗五加多糖由甘露糖、葡萄糖、半乳糖、阿拉伯糖组成,结构主要由吡喃糖环状构成,可以有效清除DPPH、ABTS阳离子自由基,还原铁离子。证明短梗五加多糖具有较好的抗氧化生物活性。

Effect of climate change and railway embankment on the degradation of underlain permafrost

Because of the global warming and the increasing human activity, the air temperature and the precipitation along the Qinghai-Tibet Railway increased gradually in recent years, which endanger the permafrost table, the embankment of the railway. The statistics of the air temperature, the precipitation and the geothermal temperature in recent 50 years in this dissertation come from the four weather station along the railway, that are Wudaoliang Station, Fenghuo Mountains Sta- tion, Tuotuo River Station and Ando Station. This dissertation analyzes the change of climate along the railway and then develops a research on the effect of the changing geothermal temperature on permafrost table and its countermeasures. The experiment result shows that the air temperature of the permafrost region rise steadily in about 50 years, especially in this century, the tendency of rising temperature is more obvious. The precipitation fluctuates but it is also rising rapidly, for the largest precipitation reached 492.6 mm. For 30 years now, the Qinghai-Tibet Plateau has been in the megathermal period, which also affects the permafrost region along the railway. The condition of permafrost is degrading greatly.

A system for automated monitoring of embankment deformation along the Qinghai-Tibet Railway in permafrost regions

At present, the monitoring of embankment deformation in permafrost regions along the Qinghai-Tibet Railway is mainly done manually. However, the harsh climate on the plateau affects the results greatly by lowering the observation frequency, so the manual monitoring can barely meet the observational demand. This research develops a system of automated monitoring of embankment deformation, and aims to address the problems caused by the plateau climate and the perma- frost conditions in the region. The equipment consists of a monitoring module, a data collection module, a transmission module, and a data processing module. The field experiments during this program indicate that （1） the combined auto- mated monitoring device overcame the problems associated with the complicated and tough plateau environment by means of wireless transmission and automatic analysis of the embankment settlement data; （2） the calibration of the combined settlement gauge at -20 ℃ was highly accurate, with an error rate always 〈0.5%; （3） the gauge calibration at high-temperature conditions was also highly accurate, with an error rate 〈0.5% even though the surface of the instrument reached more than 50 ℃; and （4） compared with the data manually taken, the data automatically acquired during field monitoring experiments demonstrated that the combined settlement gauge and the automated monitoring system could meet the requirements of the monitoring mission in permafrost regions along the Qinghai-Tibet Railway.

Structure-regulated fluorine-containing additives to improve the performance of perovskite solar cells

Perovskite solar cells(PSCs)have seen remarkable progress in recent years,largely attributed to various additives that enhance both efficiency and stability.Among these,fluorine-containing additives have garnered significant interest because of their unique hydrophobic properties,effective defect passivation,and regulation capability on the crystallization process.However,a targeted structural approach to design such additives is necessary to further enhance the performance of PSCs.Here,fluoroalkyl ethylene with different fluoroalkyl chain lengths(CH_(2)CH(CF_(2))nCF_(3),n=3,5,and 7)as liquid additives is used to investigate influences of fluoroalkyl chain lengths on crystallization regulation and defect passivation.The findings indicate that optimizing the quantity of F groups plays a crucial role in regulating the electron cloud distribution within the additive molecules.This optimization fosters strong hydrogen bonds and coordination effects with FA+and uncoordinated Pb^(2+),ultimately enhancing crystal quality and device performance.Notably,1H,1H,2H-perfluoro-1-hexene(PF_(3))with the optimal number of F presents the most effective modulation effect.A PSC utilizing PF_(3)achieves an efficiency of 24.05%,and exhibits exceptional stability against humidity and thermal fluctuations.This work sheds light on the importance of tailored structure designs in additives for achieving high-performance PSCs.

Paleogeography control of Indian monsoon intensification and expansion at 41 Ma

As a crucial part of the Asian monsoon stretching from tropical India to temperate East Asia, the Indian monsoon(IM) contributes predominant precipitation over Asian continent. However, our understanding of IM’s onset, development and the underlying driving mechanisms is limited. Increasing evidence indicates that the IM began in the Eocene or even the Paleocene and was unexceptionally linked to the early rise of the Tibetan Plateau(TP). These were challenged by the heterogeneous and diachronous uplift of the TP and all the reported records were confined to tropical zone under tropical monsoon driven by the Intertropical Convergence Zone(ITCZ) that is irrelevant to the TP. Therefore, reliable paleoclimatic records from the extra-tropical IM region is crucial to reveal how the tropical IM expanded to subtropical and temperate zones and what driving factors might be related to it. Here we present robust Eocene paleoenvironmental records from central Yunnan(~26°N) in subtropical East Asia. The multiproxy results of two sites demonstrate a consistent sudden switch from a dry environment in the early Eocene to a seasonally wet one at 41 Ma, suggesting a jump of the tropical IM to the southern subtropical zone at 41 Ma.The full collision of India with Asia, and the resulting changes in paleogeography at 41 Ma(closure of the Neotethys sea, retreat of the Paratethys seas, fast northward movement of the southern margin of the TP and rise of the central TP), aided by synchronous Antarctic cooling, might have worked together to drive the IM enhancement and northward expansion.

Electrostatic self-assembly of 2D/2D CoWO_(4)/g-C_(3)N_(4)p-n heterojunction for improved photocatalytic hydrogen evolution:Built-in electric field modulated charge separation and mechanism unveiling

Two-dimensional(2D)semiconductor heterojunctions are considered as an effective strategy to achieve fast separation of photoinduced carriers.Herein,a novel CoWO_(4)/g-C_(3)N_(4)(CWO/CN)p–n junction was synthesized using an electrostatic selfassembly method.The constructed 2D/2D p–n heterostructure had a rich hetero-interface,increased charge density,and fast separation efficiency of photoinduced carriers.The in-situ Kelvin probe force microscopy confirmed that the separation pathway of photoinduced carriers through the interface obeyed an II-scheme charge transfer mechanism.Experimental results and density functional theory calculations indicated the differences of work function between CWO and CN induced the generation of built-in electric field,ensuring an efficient separation and transfer process of photoinduced carriers.Under the optimized conditions,the CWO/CN heterojunction displayed enhanced photocatalytic H_(2)generation activity under full spectrum and visible lights irradiation,respectively.Our study provides a novel approach to design 2D/2D hetero-structured photocatalysts based on p–n type semiconductor for photocatalytic H_(2)generation.