Atomic Insights into Aluminium-Ion Insertion in Defective Anatase for Batteries

Aluminium batteries constitute a safe and sustainable high-energy-density electrochemical energy-storage solution. Viable Al-ion batteries require suitable electrode materials that can readily intercalate high-charge Al³⁺ ions. Here, we investigate the Al³⁺ intercalation chemistry of anatase TiO₂ and how chemical modifications influence the accommodation of Al³⁺ ions. We use fluoride- and hydroxide-doping to generate high concentrations of titanium vacancies. The coexistence of these hetero-anions and titanium vacancies leads to a complex insertion mechanism, attributed to three distinct types of host sites: native interstitial sites, single vacancy sites, and paired vacancy sites. We demonstrate that Al³⁺ induces a strong local distortion within the modified TiO₂ structure, which affects the insertion properties of the neighbouring host sites. Overall, specific structural features induced by the intercalation of highly polarising Al³⁺ ions should be considered when designing new electrode materials for polyvalent batteries.     

利用卫星遥感NO2监测结果分析COVID-19疫情对我国社会经济活动的短期影响

NO2作为一种与市内交通及重化工业产能密切相关的大气污染物，其浓度的变化能直接反映社会经济活动的强弱.利用OMI卫星反演的对流层NO2柱浓度日产品合成的周均值结果，构建了2019年及2020年春节期间的标准化社会经济活动指数的周尺度变化序列.结果显示正常年份春节假期也会对社会经济活动有所抑制，但COVID-19疫情导致节后我国的社会经济活动减弱期延长了2～3周，而社会经济活动强度的最低值降低了0.10.虽然社会经济活动在短期内有明显抑制作用，但随着春节后第三周开始各地复工复产逐步展开，社会经济活动强度稳步上升，节后第7周已达到节前最高水平的60.91%.     

关于应对疫情开展化学类专业课程线上教学的探究

This paper aims at the implementation of the online courses of chemistry majors in Sichuan University in response to the epidemic, and explores a more effective and reasonable way to organize teaching. Based on the investigation and feedback of teachers and students, this paper points out the difficulties and challenges of online teaching at the present stage:the classroom interaction and discussion are not smooth, the online teaching tools and methods are diversified, and the chemistry laboratory courses are not matched. Therefore, the School of Chemistry of Sichuan University will coordinate the online teaching platform, enhance the classroom interaction, and launch the "chemistry virtual simulation experiment teaching center" to ensure the teaching progress and quality during the epidemic prevention and control.     

Partially Fluorinated Copolymers as Oxygen Sensitive 19F MRI Agents

Effective diagnosis of disease and its progression can be aided by ¹⁹F magnetic resonance imaging (MRI) techniques. Specifically, the inherent sensitivity of the spin–lattice relaxation time (T₁) of ¹⁹F nuclei to oxygen partial pressure makes ¹⁹F MRI an attractive non-invasive approach to quantify tissue oxygenation in a spatiotemporal manner. However, there are only few materials with the adequate sensitivity to be used as oxygen-sensitive ¹⁹F MRI agents at clinically relevant field strengths. Motivated by the limitations in current technologies, we report highly fluorinated monomers that provide a platform approach to realize water-soluble, partially fluorinated copolymers as ¹⁹F MRI agents with the required sensitivity to quantify solution oxygenation at clinically relevant magnetic field strengths. The synthesis of a systematic library of partially fluorinated copolymers enabled a comprehensive evaluation of copolymer structure–property relationships relevant to ¹⁹F MRI. The highest-performing material composition demonstrated a signal-to-noise ratio that corresponded to an apparent ¹⁹F density of 220 mm , which surpasses the threshold of 126 mm ¹⁹F required for visualization on a three Tesla clinical MRI. Furthermore, the T₁ of these high performing materials demonstrated a linear relationship with solution oxygenation, with oxygen sensitivity reaching 240×10⁻⁵ mmHg⁻¹s⁻¹. The relationships between material composition and ¹⁹F MRI performance identified herein suggest general structure–property criteria for the further improvement of modular, water-soluble ¹⁹F MRI agents for quantifying oxygenation in environments relevant to medical imaging.     

面向COVID-19传播模式的多因素影响分析

目前,新型冠状病毒肺炎(COVID-19)的传播仍在持续,其传播模式以及影响传播行为的主要因素仍有待深入挖掘。鉴于此,本文从数据分析的角度,通过构造一个特殊的多源数据集(包括COVID-19历史数据、气象数据、人口迁徙数据和空间地理信息数据),以此建立多元Poisson.回归模型(类Poisson回归)来着重分析国内疫情的病毒传播模式及其影响因素。分析结果显示,湿度、平均每日风速、每日的降雨量等气象因素与COVID-19的传播模式显著相关,但与每日温度变化显著不相关。除此之外,COVID-19的传播速度及传播范围与武汉迁出目的地的人口比例、迁入武汉来源地的人口比例以及武汉与其他城市的空间距离均有一定的关联性。全文可视化及模型分析的R代码见:https://github.com/thwgithub/COVID-19 Rcodes.     

疫情背景下微积分“课程思政”的教学探索与实践

结合当前的疫情,采用画龙点睛式、隐性渗透式等教学方式,多角度、全方位把“思政”元素融入到微积分教学之中,通过调查问卷评估了课程思政教学效果,为高校微积分课程的“课程思政”改革提供一种思路.     

Repetition in reduced decompositions

Given a permutation w, we show that the number of repeated letters in a reduced decomposition of w is always less than or equal to the number of 321- and 3412-patterns appearing in w. Moreover, we prove bijectively that the two quantities are equal if and only if w avoids the ten patterns 4321, 34 512, 45 123, 35 412, 43 512, 45 132, 45 213, 53 412, 45 312, and 45 231.     

Poly(ethylene-glycol)-based fluorinated esters: a readily available entry for novel F-MRI agents

Readily available, low cost, hydrosoluble poly(ethylene-glycol) derivatives of 2-(trifluoromethyl)-3,3,3-trifluoro-propanoic acid were easily synthesized and their properties as MRI agents are preliminarily investigated. Two novel polymers, of 2356 Da and 756 Da, respectively, both showing a single ¹⁹F signal at NMR in deuterated chloroform and D₂O were fully characterized; both compounds were shown to be soluble in water. However when experiments of in vitro MR imaging were conducted a clear imaging was obtained only with the sample of 756 MW, pointing at the importance of the fluorine content of the carrier.     

Hysteresis loss reduction in self-bias FeSi/SrFe12O19soft magnetic composites

The magnetic field provided by magnetized SrFe₁₂O₁₉particles in FeSi/SrFe₁₂O₁₉composites is used to replace the applied transverse magnetic field,which successfully reduces the magnetic loss of the composites with minor reduction of permeability.This magnetic loss reduction mainly comes from the decrease in hysteresis loss,while the eddy current loss is basically unaffected.The hysteresis loss reduction in magnetized composites is believed to be due to the decrease in domain wall displacement caused by the increase in the average magnetic domain size in a DC magnetic field.This is an effective method for reducing the magnetic loss of soft magnetic composites with wide application potential,and there is no problem of increasing the cost and the volume of the magnetic cores.