On the Motion of Substance in a Channel of a Network: Extended Model and New Classes of Probability Distributions

We discuss the motion of substance in a channel containing nodes of a network. Each node of the channel can exchange substance with: (i) neighboring nodes of the channel, (ii) network nodes which do not belong to the channel, and (iii) environment of the network. The new point in this study is that we assume possibility for exchange of substance among flows of substance between nodes of the channel and: (i) nodes that belong to the network but do not belong to the channel and (ii) environment of the network. This leads to an extension of the model of motion of substance and the extended model contains previous models as particular cases. We use a discrete-time model of motion of substance and consider a stationary regime of motion of substance in a channel containing a finite number of nodes. As results of the study, we obtain a class of probability distributions connected to the amount of substance in nodes of the channel. We prove that the obtained class of distributions contains all truncated discrete probability distributions of discrete random variable ω which can take values 0,1,⋯,N. Theory for the case of a channel containing infinite number of nodes is presented in Appendix A. The continuous version of the discussed discrete probability distributions is described in Appendix B. The discussed extended model and obtained results can be used for the study of phenomena that can be modeled by flows in networks: motion of resources, traffic flows, motion of migrants, etc.     

Thermoresponsive polymersome from a double hydrophilic block copolymer

The article describes synthesis and thermally triggered self‐assembly of a Poly (ethylene oxide)‐block‐poly (N‐insopropylacrylamide) (PEO‐b‐PNIPAm) in aqueous medium. At rt, the polymer remains as unimer, however, at lower critical solution temperature (LCST) of PNIPAm (32 °C), it forms a rather large undefined aggregate which at slightly elevated temperature (～40 °C) converges to well defined polymersome structure (Critical aggregation concentration = 0.45 mg/mL) with hydrodynamic diameter of 40–50 nm. By lowering the temperature, initial swelling of the compact vesicle followed by reversible disassembly to unimer was noticed. The polymersome exhibits encapsulation ability to a hydrophilic dye Calcein which can be spontaneously released by lowering the temperature below cloud point. Likewise a hydrophobic dye namely 8‐Anilino‐1‐naphthalenesulfonic acid (ANS) can also be encapsulated and released by thermal trigger. Detail photoluminescence studies reveal ANS dye can be used as a generalized probe molecule for detecting LCST of a thermoresponsive polymer by “fluorescence on” above LCST even by cursory observation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2444–2451     

金色梦想，一触即发——化学专业校外实践教学基地建设与思考

高等教育要适应世界潮流和时代变化,本科教育须进一步提高实践教学的比重,加强理论教学与实践教学相结合,完善协同育人机制。结合学科发展和企业发展需求,中山大学化学学院与金发科技股份有限公司(简称金发科技)共同建设大学生实践教学基地。本文以中山大学-金发科技本科实践教学基地为例,探讨大学生校外实践基地建设过程中遇到的问题以及实践基地的建设内容与成果体会。     

不同版本高中化学教科书中学生必做实验的分析与启示——基于“科学探究与创新意识”素养

以人教版、苏教版、鲁科版(2019年版)和沪科版(2020年版)高中化学教科书中的学生必做实验文本为研究对象,基于“科学探究与创新意识”素养构建高中化学教科书中学生必做实验文本的分析框架,分析和比较4个版本教科书中学生必做实验文本“科学探究与创新意识”素养的体现及其异同,为学生必做实验教学提供启示和建议。     

Bioinspired Design of a Giant [Mn86] Nanocage-Based Metal-Organic Framework with Specific CO2 Binding Pockets for Highly Selective CO2 Separation

Adsorption-based removal of carbon dioxide (CO₂) from gas mixtures has demonstrated great potential for solving energy security and environmental sustainability challenges. However, due to similar physicochemical properties between CO₂ and other gases as well as the co-adsorption behavior, the selectivity of CO₂ is severely limited in currently reported CO₂-selective sorbents. To address the challenge, we create a bioinspired design strategy and report a robust, microporous metal–organic framework (MOF) with unprecedented [Mn₈₆] nanocages. Attributed to the existence of unique enzyme-like confined pockets, strong coordination interactions and dipole-dipole interactions are generated for CO₂ molecules, resulting in only CO₂ molecules fitting in the pocket while other gas molecules are prohibited. Thus, this MOF can selectively remove CO₂ from various gas mixtures and show record-high selectivities of CO₂/CH₄ and CO₂/N₂ mixtures. Highly efficient CO₂/C₂H₂, CO₂/CH₄, and CO₂/N₂ separations are achieved, as verified by experimental breakthrough tests. This work paves a new avenue for the fabrication of adsorbents with high CO₂ selectivity and provides important guidance for designing highly effective adsorbents for gas separation.     

Ortho-Alkoxy-benzamide Directed Formation of a Single Crystalline Hydrogen-bonded Crosslinked Organic Framework and Its Boron Trifluoride Uptake and Catalysis

Boron trifluoride (BF₃) is a highly corrosive gas widely used in industry. Confining BF₃ in porous materials ensures safe and convenient handling and prevents its degradation. Hence, it is highly desired to develop porous materials with high adsorption capacity, high stability, and resistance to BF₃ corrosion. Herein, we designed and synthesized a Lewis basic single-crystalline hydrogen-bond crosslinked organic framework (H_COF-50) for BF₃ storage and its application in catalysis. Specifically, we introduced self-complementary ortho-alkoxy-benzamide hydrogen-bonding moieties to direct the formation of highly organized hydrogen-bonded networks, which were subsequently photo-crosslinked to generate H_COFs. The H_COF-50 features Lewis basic thioether linkages and electron-rich pore surfaces for BF₃ uptake. As a result, H_COF-50 shows a record-high 14.2 mmol/g BF₃ uptake capacity. The BF₃ uptake in H_COF-50 is reversible, leading to the slow release of BF₃. We leveraged this property to reduce the undesirable chain transfer and termination in the cationic polymerization of vinyl ethers. Polymers with higher molecular weights and lower polydispersity were generated compared to those synthesized using BF₃ ⋅ Et₂O. The elucidation of the structure–property relationship, as provided by the single-crystal X-ray structures, combined with the high BF₃ uptake capacity and controlled sorption, highlights the molecular understanding of framework-guest interactions in addressing contemporary challenges.     

超高效液相色谱-串联质谱法测定烟用水基胶中邻苯二甲酸酯类化合物

建立了一种测定烟用水基胶中17种邻苯二甲酸酯类(PAEs)化合物的超高效液相色谱-串联质谱(UPLC-MS/MS)法。样品经水分散,以甲醇定容,涡旋振荡萃取。萃取液离心后,过有机相滤膜进行UPLC-MS/MS分析。通过增加延时柱的方法,排除色谱系统带入的PAEs干扰。结果表明:在0~5μg/m L范围内,方法的线性关系良好,相关系数均大于0.994,定量下限为0.010~0.479μg/g。该方法的回收率为87.6%~106.0%,相对标准偏差(RSD,n=6)为0.8%~6.2%。将该方法与YC/T 333-2010标准方法进行对比,结果显示两种方法的检测数据不存在显著性差异。方法用于烟用水基胶中17种PAEs的测定,操作简单,稳定性好。     

搅拌速率对β-PbO_2-CeO_2-ZrO_2复合电极材料电化学性能的影响

为了提高三价铬镀铬工艺中阳极材料的性能,采用阳极氧化法制备了掺杂纳米颗粒的β-Pb O2-Ce O2-Zr O2复合电极材料。通过扫描电化学显微镜和析氧极化曲线的测量,考察了不同搅拌速率条件下制备的复合电极材料在硫酸盐体系三价铬镀液中的电催化活性,利用塔菲尔曲线考察了复合电极材料的耐蚀性,并辅以扫描电镜表征了电极材料的微观形貌。结果表明:当施镀搅拌速率为350 r·min-1时,所制备的复合电极材料具有结构致密、电催化活性高、耐蚀性强等特点。     

硅胶键合膦的制备及其对铑络合物催化1-辛烯氢甲酰化反应的影响

Using silica as a support, 2-(diphenylphosphino)ethyltriethoxysilane (DPPES) was anchored on silica surface by a grafting method to produce a bonded phosphine (denoted as SiO₂(PPh₂)), which displays excellent performance. The supported SiO₂(PPh₂)/Rh catalyst was formed in situ in 1-octene hydroformylation with SiO₂(PPh₂) as ligand and Rh(acac)(CO)₂ as precursor (acac: acetylacetone). SiO₂(PPh₂) and SiO₂(PPh₂)/ Rh were characterized by Fourier transform infrared (FTIR) spectroscopy. The effects of the ratio of phosphine to rhodium ([P]/[Rh]) and reaction temperature on 1-octene hydroformylation were investigated. Results show that an increase of the ratio of phosphine to rhodium can greatly improve the selectivity for aldehydes and decrease the rhodium leaching in organic phase. Under the moderate conditions: [P]/[Rh]=12, 363 K, 2 MPa, and 1.5 h, the conversion of 1-octene and the selectivity for aldehydes were 98.4% and 95.3%, respectively. The catalytic activity could compare with homogeneous catalysis with DPPES or triphenylphosphine (TPP) as ligand. The reaction activity was clearly unchanged after the SiO₂(PPh₂)/Rh catalyst was reused four times, with the conversion of 1-octene remaining at 97.0%, the rhodium content leaching in organic phase detected by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) was less than 0.1%.     

Sunlight curable hybrid organic–inorganic methacrylic‐based coatings: analysis of the cure mechanism and functional properties

An experimental ultraviolet (UV) polymerizable hybrid organic–inorganic protective coating, mainly intended for the surface protection of porous calcareous stone substrates, has been recently proposed and patented. The hybrid product evidenced an extraordinary hydrophobicity character, able to guarantee a high protection of the stone against water actions, as well as a high traspirability. Furthermore, it is able to equal the performance of commercial available coatings, with the important adjunctive advantage to be free solvent. The application of this product involves the use of a “dual curing” treatment, necessary to harden the coating applied on the substrate, representing this latter a technological limit. The dual curing treatment consists of 6 hr of exposure to a UV‐lamp plus 1 hr at 140°C in oven. In order to avoid this procedure, not easy to realize in situ, two different modifications of the composition of the hybrid product are proposed in this paper. The first one allows the photopolymerization of the hybrid coating only by sunlight exposure. The second one, even though requiring a UV exposure to photo‐polymerize the coating, does not need the subsequent thermal treatment at 140°C. Several experimental characterizations were performed on the newly developed hybrid products, in order to select an optimal composition for the formulations. The selected innovative products were, finally, applied on a calcareous stone substrate, typical of Apulia Region (Pietra Leccese, PL). Both coatings exhibit excellent water‐repellent action and a slight variation of the natural stone color. Copyright © 2014 John Wiley & Sons, Ltd.