Incorporation of graphene oxide nanosheets into boronate‐functionalized polymeric monolith to enhance the electrochromatographic separation of small molecules

Graphene oxide (GO) nanosheets were incorporated into an organic polymer monolith containing 3‐acrylamidophenylboronic acid (AAPBA) and pentaerythritol triacrylate (PETA) to form a novel monolithic stationary phase for CEC. The effects of the mass ratio of AAPBA/PETA, the amount of GO, and the volume of porogen on the morphology, permeability and pore properties of the prepared poly(AAPBA‐GO‐PETA) monoliths were investigated. A series of test compounds including amides, alkylbenzenes, polycyclic aromatics, phenols, and anilines were used to evaluate and compare the separation performances of the poly(AAPBA‐GO‐PETA) and the parent poly(AAPBA‐co‐PETA) monoliths. The results indicated that incorporation of GO into monolithic column exhibited much higher resolutions (>1.5) and column efficiency (62 000 ～ 110 000 plates/m for toluene, DMF, formamide, and thiourea) than the poly(AAPBA‐co‐PETA). The successful application in isocratic separation of peptides suggests the potential of the GO incorporated monolithic column in complex sample analysis. In addition, the reproducibility and stability of the prepared poly(AAPBA‐GO‐PETA) monolith was assessed. The run‐to‐run, column‐to‐column and batch‐to‐batch reproducibilities of this monolith for alkylbenzenes’ retention were satisfactory with the RSDs less than 1.8% (n = 5), 3.7% and 5.6% (n = 3), respectively, indicating the effectiveness and practicability of the proposed method.     

低碱度共沉淀法制备苯选择加氢Ru-Zn催化剂

在低碱度下采用共沉淀法成功制备了非负载型Ru-Zn催化剂,用于苯选择加氢制环己烯反应.固定氢氧化钠沉淀剂的量,考察了不同氯化锌加入量对催化剂结构和催化性能的影响,采用N2吸附、X射线衍射和程序升温还原等手段对催化剂进行了表征.同时考察了选用具有最佳锌含量的Ru-Zn催化剂时搅拌速度和硫酸锌添加剂等对催化反应性能的影响,最后考察了催化剂多次使用时的反应性能.研究表明, Zn含量16.7%(质量分数)的Ru-Zn催化剂具有最佳的催化性能;在ZnSO4水溶液(0.45 mol/L)中,优化反应条件(哈氏合金釜,1200 r/min,150oC, H2压5 MPa)下反应45 min,苯转化率57%时环己烯选择性可达80%(收率超过45%).钌催化剂中ZnO晶体对于环己烯选择性达到80%非常重要.催化剂回收循环反应5次时反应性能基本不变,表明低碱度下制备的催化剂具有良好的稳定性,显示了工业化应用前景.     

基于MSF的风洞试验分布式数据库系统同步设计

某风洞试验基地各试验外场分布在不同的物理区域,受多种条件制约,不宜采用集中式数据库,任务下达与数据上报采用手动分发与汇总,数据的时效性及完整性存在严重问题;分布式数据库可实现各场站的独立运行,但各场站与中心数据库的同步性、完整性、一致性成为最大的难题;文章根据分布式数据库的特点和风洞试验运行需求,提出了基于MSF(microsoft sync framework)框架并利用WCF(windows communication foundation)技术实现了数据自动上传下达并汇总的同步设计方案,解决了中心与下级场站之间的数据管理问题。     

Luminescent organic 1D nanomaterials based on bis(β-diketone)carbazole derivatives

A series of new triphenylamine-functionalized bis(β-diketone)s bridged by a carbazole (CnBDKC, n=1, 4, 8, 16) with twisted intramolecular charge-transfer emission in polar solvents has been synthesized. The length of the carbon chains has a significant effect on the self-assembling properties of the compounds. Well-defined 1D nanowires were easily generated from C1BDKC with a methyl group by a reprecipitation approach directed by π-stacking interaction, and the molecules packed into J-aggregates in the nanowires. In addition, 1D nanofibers based on C16BDKC bearing a long hexadecyl chain were prepared through the organogelation process, and H-aggregates were formed driven by the synergistic effect of π-stacking interaction and van der Waals force in the gel phase. C4BDKC and C8BDKC containing butyl and octyl side chains, respectively, cannot arrange into dispersed nanostructures, probably because π-π interaction between conjugated moieties might be disturbed by the interaction between the side chains, which is, however, not strong enough to dominate the self-assembling process. Notably, the nanowires based on C1BDKC and the gel nanofibers from C16BDKC can emit strong green light under irradiation, which suggests that these 1D nanomaterials may have potential applications in emitting materials as well as photonic devices.     

Species-specific and inhibitor-dependent conformations of LpxC: implications for antibiotic design

LpxC is an essential enzyme in the lipid A biosynthetic pathway in gram-negative bacteria. Several promising antimicrobial lead compounds targeting LpxC have been reported, though they typically display a large variation in potency against different gram-negative pathogens. We report that inhibitors with a diacetylene scaffold effectively overcome the resistance caused by sequence variation in the LpxC substrate-binding passage. Compound binding is captured in complex with representative LpxC orthologs, and structural analysis reveals large conformational differences that mostly reflect inherent molecular features of distinct LpxC orthologs, whereas ligand-induced structural adaptations occur at a smaller scale. These observations highlight the need for a molecular understanding of inherent structural features and conformational plasticity of LpxC enzymes for optimizing LpxC inhibitors as broad-spectrum antibiotics against gram-negative infections.     

New dendritic gelator bearing carbazole in each branching unit: selected response to fluoride ion in gel phase

A new dendritic gelator with carbazole as the building block (HBCD) was synthesized. It was found that H-bonding between the amide groups and π-π interaction between the aromatic rings played predominant roles in the gel formation. Meanwhile, significant aggregation-induced emission enhancement was observed in the gel state due to the formation of J-aggregates and the restricted molecular motion. Notably, the gel state of HBCD can be destroyed upon addition of F(-), accompanied by fluorescence enhancement on account of the formation of N-HF(-), which could further lead to the increased coplanarity of HBCD. The sensory capability of HBCD exhibited a high selectivity towards F(-) instead of the Cl(-), Br(-), I(-) and AcO(-) anions, which could be explained by the fact that the steric hindrance of the dendrimer would go against the interactions between the larger anions and HBCD.     

A covalently-linked microporous organic-inorganic hybrid framework containing polyhedral oligomeric silsesquioxane moieties

By a Yamamoto-type of Ullmann cross-coupling reaction, a well-defined covalently-linked microporous organic-inorganic hybrid framework polyoctaphenylsilsesquioxane (JUC-Z1) was effectively prepared from the nano building block p-iodio-octaphenylsilsesquioxane (I8OPS) with a yield of ca. 100%. The structure of JUC-Z1 was characterized by (13)C CP/MAS NMR and (29)Si MAS NMR experiments. Fourier transform infrared spectroscopy (FTIR) was performed to confirm the presence of functions in the framework. The results showed that inorganic silsesquioxane cubes were linearly covalently-linked by biphenyls, offering a highly cross-coupling framework. The powder X-ray diffraction (PXRD) pattern and transmission electron microscope (TEM) image show that JUC-Z1 is spherical with uniform micropores. N(2) adsorption results suggest that the hybrid framework has a narrow pore size distribution from 11.8 to 20.0 ?, with a BET surface area of 283 m(2)g(-1) and a pore volume of 0.226 cm(3)g(-1). A thermogravimetric (TG) analysis indicates the thermal stability of JUC-Z1 up to 397 °C in air. Moreover, a liquid sorption experiment reveals the favorable sorption of benzene and water.     

Preparation of electrospun luminescent polyimide/europium nanofibers by simultaneous in situ sol-gel and imidization processes

Comicellization of a star block copolymer poly(ε-caprolactone)-block-poly(diethylamino)ethyl methacrylate (S(PCL-b-PDEAEMA)) and a linear block copolymer methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (mPEG-b-PCL) was developed to enhance the stability and lower the cytotoxicity of the micelles. The two copolymers self-assembled into the mixed micelles with a common PCL core surrounded by a mixed PDEAEMA/mPEG shell in aqueous solution. This core-shell structure was transformed to the core-shell-corona structure at high pH due to the collapse of the PDEAEMA segment. The properties of the polymeric micelles were greatly dependent on the weight ratio of the two copolymers and the external pH. As increasing the mPEG-b-PCL content, the size and the zeta potential of the mixed micelles were lowered while the pH-dependent stability and the biocompatibility were improved. Moreover, an increase in pH accelerated the release of indomethacin (IND) from the mixed micelles in vitro. These results augured that the mixed micelles could be applied as a stable pH-sensitive release system.     

高细对称结构正交耦合振动响应的试验研究

高细对称结构是指具有较大的高度／直径比,且横向和纵向完全对称的结构形式。由于其典型的对称电磁场特性,在星载天线上得到了一定的应用。有研究发现：高细对称工程结构在振动试验过程中往往表现出正交耦合响应较大的现象,这些现象相当于产品单方向振动激励时在两个互相正交方向同时进行了振动载荷,从而造成了产品的过试验问题。但是,工程实物模型相对较为复杂,无法通过仿真直观地揭示这种特殊现象的本质。本文针对在实践工程高细对称结构中发现的正交耦合振动响应现象,对这类工程结构进行了简化（将某一类星载天线简化为板梁弯曲结构）。在此基础上提出了试验验证模型,并完成了正弦激励载荷下的振动响应试验。通过分析试验数据对比了对称结构和非对称结构的振动耦合响应异同,剖析了各种产生正交耦合振动响应的原因;指出正交耦合振动响应是高细对称结构的一种固有特性,采用非对称设计可以减小正交耦合响应;最后提出了一种针对这种高细对称结构进行准确仿真计算的方法。     

Stress singularity analysis of anisotropic multi-material wedges under antiplane shear deformation using the symplectic approach

Symplectic approach has emerged a popular tool in dealing with elasticity problems especially for those with stress singularities. However, anisotropic material problem under polar coordinate system is still a bottleneck. This paper presents a subfield method coupled with the symplectic approach to study the anisotropic material under antiplane shear deformation. Anisotropic material around wedge tip is considered to be consisted of many subfields with constant material properties which can be handled by the symplectic approach individually. In this way, approximate solutions of the stress and displacement can be obtained. Numerical examples show that the present method is very accurate and efficient for such wedge problems. Besides, this paper has extended the application of the symplectic approach and provides a new idea for wedge problems of anisotropic material.