Novel high birefringence bistolane liquid crystals with lateral fluorosubstituent

Twelve compounds based on lateral fluorinated bistolane moieties with cyano or trifluoromethyl terminal groups were synthesised with Hagihara–Sonogashira cross-coupling reaction. The molecular structures of the compounds were confirmed by Fourier transform infrared, ¹H-nuclear magnetic resonance and mass spectrometry. The transition temperatures, optical textures and optical anisotropies were determined by differential scanning calorimetry, polarizing optical microscopy and ultraviolet microscopy. The effects of the terminal substituents and lateral fluorosubstituent group on their physical properties were investigated and discussed. The compounds with lateral double fluorosubstituent and cyano terminal group exhibited nematogenic texture, while other compounds showed smectic phase. All the compounds exhibited wide liquid crystal temperature ranges and high clearing points. Interestingly, the compounds have the high birefringence in the range of between 0.480 and 0.633.     

Effect of Inorganic Ions on the Oxidation of Methyl Violet with Gliding Arc Plasma Discharge

Gliding arc discharge process was used for the treatment of methyl violet wastewater. First, the intermediate products were studied by gas chromatography coupled with mass spectrometry and Fourier transform infrared spectrometry, and ultraviolet–visible spectrometer. Second, the effects of inorganic anions including chloride (Cl^?), carbonate (CO₃ ^2?), sulfate (SO₄ ^2?), phosphate (PO₄ ^3?), nitrate (NO₃ ^?) on the degradation efficiency of methyl violet were examined. The research results indicated that hydroxyl radicals attacked carbon atom that situated in the center of dye molecule, and the conjugating structure of methyl violet was destroyed, and dye was degraded and decolored, so a possible degradation pathway was proposed by the analysis of intermediate products detected. The methyl violet degradation rate decreased with increasing anions concentrations, and their order of sequence according to the inhibition reaction was CO₃ ^2? > Cl^? > SO₄ ^2? > NO₃ ^?.     

聚合物单晶生长的三维相场模拟研究

利用元胞自动机方法与相场模型的结合建立新型三维模拟相场模型.同时,为模拟真实的、三维的高分子结晶的过程,采用元胞自动机方法离散方程,且元胞几何形状的选取符合真实聚合物晶格扩散方式的物理规律,以及新建立的相场模型套用间规聚丙烯的实验参数.利用该模型模拟了多种三维立方体或者薄层的晶体形貌及其相互之间的演化过程,包括正方形、长方形、菱形、六边形、多层单晶等.通过模拟结果与真实形貌作对比来证明所建立的相场模型真实可靠性.     

纳米层状双金属氢氧化物改性PU/PMMA的制备及其弛豫行为

采用原位聚合法,制备了聚氨酯(PU)/聚甲基丙烯酸甲酯(PMMA)/层状双金属氢氧化物(LDH)纳米复合体系(PU/PMMA/LDH).通过广角X射线衍射(WXRD)、透射电子显微镜(TEM)对其结构和形貌进行了表征,并通过热失重(TGA)、动态力学分析(DMA)和宽频介电谱(BDRS)研究了LDH含量(φ)对PU/PMMA体系热稳定性和弛豫行为的影响.结果表明,当φ<1 wt%时,LDH在聚合物基体中以剥离结构为主,PU/PMMA/LDH体系的玻璃化温度(Tg)降低,最大损耗因子(tanδmax)增大;而当φ>1 wt%时,LDH在聚合物基体中以插层结构为主,插层结构对聚合物分子链的限制使复合体系的Tg升高、tanδmax降低.LDH表面与PU硬段间的氢键作用,使复合体系的α介电弛豫转变随φ增加而向高温方向移动,弛豫过程激活参数增大.     

Three New Coordination Compounds with Neodymium Based on Tetrazole Containing Carboxylic Acid Ligands

Reactions of three tetrazole containing carboxylic acid ligands, namely, Hpztza, Htzpya, and Hpytza [Hpztza = 5‐(2‐pyrazinyl)tetrazole‐2‐acetic acid, Htzpya = 3‐(5‐tetrazolyl)pyridine‐1‐acetic acid, Hpytza = 5‐(3‐pyridyl)tetrazole‐2‐acetic acid] with NdCl₃ · 6H₂O under hydrothermal conditions, afforded the complexes [Nd(pztza)₂(H₂O)₆] · pztza · 3H₂O ( 1 ), [Nd₂(tzpya)₂(H₂O)₁₂]Cl₄ · 2H₂O ( 2 ), and [Nd(pytza)₂Cl(H₂O)₂] ( 3 ). The compounds were structurally characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. X‐ray diffraction analyses revealed that compound 1 displays a mononuclear structure, 2 shows a dinuclear structure, and 3 features a 1D polymeric chain structure via pytza as linker. Furthermore, the luminescent properties investigated at room temperature in the solid state show that compound 2 has an obvious decrease in its luminescence, when compared to the ligand.     

Practical and Highly Selective C?H Functionalization of Structurally Diverse Ethers

A trityl ion mediated C H functionalization of ethers with a wide range of nucleophiles at ambient temperature has been developed. The reaction displays high chemoselectivity and good functional group tolerance. The protocol also exhibits excellent regio‐ and diastereoselectivities for the unsymmetric ethers, thus stereoselectively generating highly functionalized disubstituted 2,5‐trans tetrahydrofurans (THF), 2,6‐trans tetrahydropyrans (THP), 2,6‐trans dihydropyrans (DHP), and 1,3‐trans isochromans, and highlighting the capacity of the protocol in complex molecule synthesis.     

Glucose detection at attomole levels using dynamic light scattering and gold nanoparticles

Glucose is directly related to brain activity and to diabetes.Therefore,developing a rapid and sensitive method for glucose detection is essential.Here,label-free glucose detection at attomole levels was realized by detecting the average diameter change of gold nanoparticles(AuNPs)utilizing dynamic light scattering(DLS).Single-strand DNA(ssDNA)adsorbed into the AuNPs’surfaces and prevented them from aggregating in solution that contained NaCl.However,ssDNA cleaved onto ssDNA fragments upon addition of glucose,and these fragments could not adsorb onto the AuNPs’surfaces.Therefore,in high-salt solution,AuNPs would aggregate and their average diameter would increase.Based on monitoring the average diameter of AuNPs with DLS,glucose could be detected in the range from 15 pmol/L to 2.0 nmol/L,with a detection limit of 8.3 pmol/L.Satisfactory results were also obtained when the proposed method was applied in human serum glucose detection.     

致癌性卤代醌类消毒副产物造成 DNA 损伤的分子机理研究

卤代醌是一类卤代芳烃类环境污染物的致癌中间体,也是在饮用水中新发现的氯化消毒副产物。我们最近发现卤代醌和 H₂O₂ 或有机氢过氧化物体系可以不依赖过渡金属离子,而产生高活性的羟基/烷氧自由基和醌氧/醌碳自由基。目前尚不清楚这些卤代醌类致癌物和氢过氧化物共存能否诱导 DNA 产生氧化损伤和修饰,以及其潜在的分子机制是什么。我们的研究发现 DNA 在四氯-1,4-苯醌/H₂O₂体系中可被氧化产生 8-氧脱氧鸟苷、DNA 链断裂和三种甲基氧化产物,这些反应不依赖过渡金属离子,且由于卤代醌与 DNA 的嵌入作用而导致其氧化作用增强。其他卤代醌也观察到了类似的现象,而且通常比经典的 Fenton 体系更有效。我们进一步将研究从纯化的 DNA 扩展到了活细胞的基因组 DNA。同时还发现卤代醌和有机氢过氧化物(如叔丁基过氧化氢或在正常生理条件下产生的 13S-过氧羟基-9Z,11E-十八碳二烯酸(13-HPODE))共存时,可通过独特的醌氧自由基介导机制诱导 DNA 氧化生成致突变性更强的咪唑啉酮类产物 dIz。这些发现为解释普遍存在的卤代醌类致癌中间体和消毒副产物的潜在基因毒性、致突变性和致癌性提供了新思路。     

Pure Ion Chromatograms Combined with Advanced Machine Learning Methods Improve Accuracy of Discriminant Models in LC–MS-Based Untargeted Metabolomics

Untargeted metabolomics based on liquid chromatography coupled with mass spectrometry (LC–MS) can detect thousands of features in samples and produce highly complex datasets. The accurate extraction of meaningful features and the building of discriminant models are two crucial steps in the data analysis pipeline of untargeted metabolomics. In this study, pure ion chromatograms were extracted from a liquor dataset and left-sided colon cancer (LCC) dataset by K-means-clustering-based Pure Ion Chromatogram extraction method version 2.0 (KPIC2). Then, the nonlinear low-dimensional embedding by uniform manifold approximation and projection (UMAP) showed the separation of samples from different groups in reduced dimensions. The discriminant models were established by extreme gradient boosting (XGBoost) based on the features extracted by KPIC2. Results showed that features extracted by KPIC2 achieved 100% classification accuracy on the test sets of the liquor dataset and the LCC dataset, which demonstrated the rationality of the XGBoost model based on KPIC2 compared with the results of XCMS (92% and 96% for liquor and LCC datasets respectively). Finally, XGBoost can achieve better performance than the linear method and traditional nonlinear modeling methods on these datasets. UMAP and XGBoost are integrated into KPIC2 package to extend its performance in complex situations, which are not only able to effectively process nonlinear dataset but also can greatly improve the accuracy of data analysis in non-target metabolomics.     

Experimental Investigation on the Mass Diffusion Behaviors of Calcium Oxide and Carbon in the Solid-State Synthesis of Calcium Carbide by Microwave Heating

Microwave (MW) heating was proven to efficiently solid-synthesize calcium carbide at 1750 °C, which was about 400 °C lower than electric heating. This study focused on the investigation of the diffusion behaviors of graphite and calcium oxide during the solid-state synthesis of calcium carbide by microwave heating and compared them with these heated by the conventional method. The phase compositions and morphologies of CaO and C pellets before and after heating were carefully characterized by inductively coupled plasma spectrograph (ICP), thermo gravimetric (TG) analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in both thermal fields, Ca and C inter-diffused at a lower temperature, but at a higher temperature, the formed calcium carbide crystals would have a negative effect on Ca diffusion to carbon. The significant enhancement of MW heating on carbon diffusion, thus on the more efficient synthesis of calcium carbide, manifested that MW heating would be a promising way for calcium carbide production, and that a sufficient enough carbon material, instead of CaO, was beneficial for calcium carbide formation in MW reactors.