基于STEAM理念的高中化学创新实验研究——四氧化三铁磁流体的制备和性质探究

介绍了基于STEAM理念下让学生制备和表征四氧化三铁磁流体的化学实验探究。采用化学共沉淀法制备了磁性Fe3O4纳米颗粒。在外加磁场下磁流体能出现明显凸起。本实验简单、安全、现象明显、试剂用量小、适宜于学生独立实验操作。本研究旨在通过设置科学问题,让学生体验整个科研过程,培养学生的创造力。     

Chemical Constituents of Selaginella moellendorffii

Chemistry of Natural Compounds -     

高效、稳定Ⅱ-Ⅵ族量子点发光二极管(LED)的研究进展

量子点通常具有核-壳型的基本结构,它的发光效率及色纯度高。因具有优异的性能和可控合成的优点,Ⅱ-Ⅵ族量子点在发光二极管(light-emitting diode, LED)中的应用研究最为丰富。为了制备高效、稳定的量子点LED,量子点的结构、器件结构和载流子传输层都需要进行设计和优化。如今,量子点LED的效率已接近Organic LED(OLED),但它的发展仍存在挑战。     

Cytotoxicity of benzophenanthridine alkaloids from the roots of Zanthoxylum nitidum (Roxb.) DC. var. fastuosum How ex Huang

This work aimed to investigate benzophenanthridine from the roots of Zanthoxylum nitidum (Roxb.) DC. var. fastuosum How ex Huang for the first time. Thirteen benzophenanthridines were isolated, and our results of the cytotoxic activities indicated that compound 6 exhibited the best potency against A549, Hela, SMMC-7721 and EJ, with the IC₅₀ values of 27.50, 37.50, 16.95 and 60.42 μM, respectively. Compounds 7 and 11 also showed strong cytotoxicity when tested against the four human cancer cell lines (A549, Hela, SMMC-7721 and EJ), while only compounds 12 and 13 displayed cytotoxicity in inhibiting BALL-1 proliferation among all the compounds. These results suggested that benzophenanthridines may become a valid alternative of potential basis for new anti-proliferative agents.     

有机化学创新设计性实验“甲基化反应”的改进*

结合科研成果及实验教学经验,对有机化学实验中传统的甲基化反应实验进行改进。教材中涉及的传统甲基化试剂具有毒性大等缺点,不利于实验教学的实施。因此,提出使用三氟乙酸甲酯取代传统甲基化试剂,应用于本科有机化学实验教学中,加强学生对甲基化反应理论知识的理解。本实验结合新颖的科研内容,引入科研实验的设计思路,不仅有利于学生更好地掌握理论知识,而且有利于激发学生对科学研究的兴趣,提高学生的综合素养。     

La(OTf)3 catalyzed synthesis of α-aryl tetrasubstituted pyrroles through [4+1] annulation under microwave irradiation

A La(OTf)₃ catalyzed synthesis of tetrasubstituted pyrroles under microwave irradiation has been developed affording various α-aryl tetrasubstituted pyrroles in acceptable to good yields (36–82% yield) through condensation/alkyne azacyclization/isomerization sequence. Functionalized α-aryl pentasubstituted pyrroles could be prepared from tetrasubstituted pyrroles through easy transformations.     

Applicability of anthracite filtration‒micro electrolysis‒sand filtration for the treatment of surface waters containing high turbidity

The effect of combined filtration efficiency on the performance of anthracite filtration?micro electrolysis?sand filtration (AMS) was investigated. Impact of different operating parameters, such as iron?carbon ratio of micro electrolytic units, filtration velocity of AMS, were studied. It was found that when iron?carbon ratio was 6: 4, the AMS’s average turbidity removal rate was 96.75% at the filtration velocity of 3 m h^?1. The results showed that when the filtration rate was 3?9 m h^?1 and iron?carbon ratio was 6: 4, the turbidity removal efficiency was over 94%, and the turbidity of the effluent was less than 1 NTU in effective filtration cycle. The effective filtration cycle can last for more than 5 h or longer. Meanwhile, the removal rate of UV₂₅₄ was above 33%, and the concentration of iron ions in the effluent is less than 0.15 mg L^?1. Turbidity and iron indicators have reached the national drinking water standards. It was also found the mechanism of iron?carbon micro electrolytic enhanced filtration by infrared spectroscopy and scanning electron microscopy. And It was also speculated the reasons for the reaction passivation.     

A note on model structures on arbitrary Frobenius categories

We show that there is a model structure in the sense of Quillen on an arbitrary Frobenius category F such that the homotopy category of this model structure is equivalent to the stable category F as triangulated categories. This seems to be well-accepted by experts but we were unable to find a complete proof for it in the literature. When F is a weakly idempotent complete (i.e., every split monomorphism is an inflation) Frobenius category, the model structure we constructed is an exact (closed) model structure in the sense of Gillespie (2011).     

A new theorem on the prime-counting function

For \(x>0\), let \(\pi (x)\) denote the number of primes not exceeding x. For integers a and \(m>0\), we determine when there is an integer \(n>1\) with \(\pi (n)=(n+a)/m\). In particular, we show that, for any integers \(m>2\) and \(a\leqslant \lceil e^{m-1}/(m-1)\rceil \), there is an integer \(n>1\) with \(\pi (n)=(n+a)/m\). Consequently, for any integer \(m>4\), there is a positive integer n with \(\pi (mn)=m+n\). We also pose several conjectures for further research; for example, we conjecture that, for each \(m=1,2,3,\ldots \), there is a positive integer n such that \(m+n\) divides \(p_m+p_n\), where \(p_k\) denotes the k-th prime.