Synthesis,characterization and olefin polymerization behaviors of phenylene-bridged bis-β-carbonylenamine binuclear titanium complexes

Binuclear and multinuclear complexes have attracted much attention due to their unique catalytic performances for olefin polymerization compared with their mononuclear counterparts. In this work, a series of phenyl-bridged bis-β-carbonylenamine [O⁻NS^R] (R = alkyl or phenyl) tridentate ligands and their binuclear titanium complexes (Ti²L₁–Ti²L₅) were synthesized and characterized by ¹H NMR, ¹³C NMR, FTIR and elemental analysis. The molecular structure of ligand L₂ (R = ⁿPr) and its corresponding Ti complex Ti²L₂ were further investigated by single-crystal X-ray diffraction, which showed that each titanium coordinated with six atoms to form a distorted octahedral configuration along with the conversion of the ligand from β-carbonylenamine to β-imino enol form. Under the activation of MMAO, these complexes catalyzed ethylene polymerization and ethylene/α-olefin copolymerization with extremely high activity (over 10⁶ g mol (Ti)⁻¹ h⁻¹ atm⁻¹) to produce high molecular weight polyethylene. At the same time, wider polydispersity as compared with the mononuclear counterpart TiL₆ was observed, indicating that two active catalytic centers may be present, consistent with the asymmetrical crystal structure of the binuclear titanium complex. Furthermore, these complexes possessed better thermal stability than their mononuclear analogues. Compared with the complexes bearing alkylthio sidearms, the complex Ti²L₅ bearing a phenylthio sidearm exhibited higher catalytic activity towards ethylene polymerization and produced polyethylene with much higher molecular weight, but with an appreciably lower 1-hexene incorporation ratio. Nevertheless, these bis-β-carbonylenamine-derived binuclear titanium complexes showed much higher ethylene/1-hexene copolymerization activity and 1-hexene incorporation ratios as compared with the methylene-bridged bis-salicylaldiminato binuclear titanium complexes, and the molecular weight and 1-hexene incorporation ratio could be flexibly tuned by the initial feed of α-olefin commoners and catalyst structures.

Phenyl-bridged bis-β-carbonylenamine binuclear titanium complexes were synthesized, characterized and used to catalyze ethylene (co)polymerization with extremely high activity.     

Design,synthesis, insecticidal activity and 3D-QSR study for novel trifluoromethyl pyridine derivatives containing an 1,3,4-oxadiazole moiety

A series of trifluoromethyl pyridine derivatives containing 1,3,4-oxadiazole moiety was designed, synthesized and bio-assayed for their insecticidal activity. The result of bio-assays indicated the synthesized compounds exhibited good insecticidal activity against Mythimna separata and Plutella xylostella, most of the title compounds show 100% insecticidal activity at 500 mg L⁻¹ and >80% activity at 250 mg L⁻¹ against the two pests. Compounds E18 and E27 showed LC₅₀ values of 38.5 and 30.8 mg L⁻¹ against Mythimna separata, respectively, which were close to that of avermectin (29.6 mg L⁻¹); compounds E5, E6, E9, E10, E15, E25, E26, and E27 showed 100% activity at 250 mg L⁻¹, which were better than chlorpyrifos (87%). CoMFA and CoMSIA models with good predictability were proposed, which revealed the electron-withdrawing groups with an appropriate bulk at 2- and 4-positions of benzene ring could enhance insecticidal activity.

Novel trifluoromethyl pyridine derivatives bearing 1,3,4-oxadiazole whereas synthesized, their which showed good insecticidal activity; a 3D-QSAR model with good predictability was is proposed.     

Anisotropic tough poly(vinyl alcohol)/graphene oxide nanocomposite hydrogels for potential biomedical applications

Hydrogels, one of the most important bioinspired materials, are receiving increasing attention because of their potential applications as scaffolds for artificial tissue engineering and vehicles for drug delivery, etc. However, these applications are always severely limited by their microstructure and mechanical behavior. Here we report the fabrication of a tough polyvinyl alcohol/graphene oxide (PVA/GO) nanocomposite hydrogel through a simple and effective directional freezing–thawing (DFT) technique. The resulting hydrogels show well-developed anisotropic microstructure and excellent mechanical properties with the assistance of DFT method and lamellar graphene. The hydrogels with anisotropic porous structures that consisted of micro-sized fibers and lamellas exhibit high tensile strengths, up to 1.85 MPa with a water content of 90%. More interestingly, the PVA/GO composite hydrogels exhibit the better thermostability, which can maintain the original shape when swollen in hot water (65 °C). In addition, the hydrogels with biocompatibility show good drug release efficiency due to the unique hierarchical structure. The successful synthesis of such hydrogel materials might pave the way to explore applications in biomedical and soft robotics fields.

Tough PVA/GO nanocomposite hydrogel with well-developed anisotropic microstructure and excellent mechanical properties.     

Synergistic effect of CB and GO/CNT hybrid fillers on the mechanical properties and fatigue behavior of NR composites

In this paper, graphene oxide (GO) and carbon nanotube (CNT) hybrid fillers were used to replace partial carbon black (CB), and GO/CNT/CB/NR composites were prepared with excellent crack growth resistance, low heat build-up and superior mechanical properties. Mechanical testing revealed a significant synergistic reinforcement between GO/CNT and CB in NR composites. The improved dispersion of GO/CNT hybrid fillers and CB in the NR matrix was characterized by transmission electron microscopy (TEM). Through the fatigue test, the GO/CNT/CB/NR composites showed excellent fatigue crack growth resistance and low heat build-up compared to CB/NR composites. These properties provide the NR composites with better applications in industry.

Graphene oxide (GO) and carbon nanotube (CNT) hybrid fillers were used to replace partial carbon black (CB), and GO/CNT/CB/NR composites were prepared with excellent crack growth resistance, low heat build-up and superior mechanical properties.     

Molecular dynamics simulations of the self-organization of side-chain decorated polyaromatic conjugation molecules: phase separated lamellar and columnar structures and dispersion behaviors in toluene solvent

The self-organization of five model side-chain decorated polyaromatic asphaltene molecules with or without toluene solvent was investigated by means of atomistic molecular dynamic (MD) simulations. It was found that the organizational structure of polycyclic asphaltene molecules is significantly affected by the position and length of side chains. In the present study, two types of phase-separated stacking configurations, including the phase separated lamellar structure (PSLS) and the phase separated columnar structure (PSCS), were found. The PSLS and PSCS were also maintained in the presence of a small amount of toluene additive (30% wt fraction). When adding excess toluene molecules, the asphaltene molecules formed highly dispersed nanoaggregates. The dynamic properties of the π–π stacking structures in the PSLS and PSCS, as well as the nanoaggregates, were probed. It was found that the number and size of alkyl side chains significantly impacted the size and number of π–π stacking structures in the aggregates. Through tracking the structural evolution of the nanoaggregates, a possible dissociation mechanism of nanoaggregates is also suggested.

The self-organization of five model side-chain decorated polyaromatic asphaltene molecules with or without toluene solvent was investigated by means of molecular dynamic (MD) simulations.     

Silicone rubber membrane with specific pore size enhances wound regeneration

A porous structure is critically important for wound dressing or tissue engineering scaffolds. However, the influence of the pore sizes on cell proliferation, tissue regeneration and the underlying mechanism remains unclear. In this study, silicone rubber membranes with different pore sizes were prepared using certain constituents of liquid silicone rubber precursor/liquid paraffin/hexane based on our previous studies. It was found that pore size had a significant impact on cell proliferation and wound healing. The CCK8 analysis revealed that the membrane with a certain pore size (110.47 μm, middle pore membrane, MPM) was suitable for cell proliferation compared with the membranes with other pore sizes (218.03 μm, large pore membrane, LPM; 5.27 μm, small pore membrane, SPM; non‐porous membrane, NPM). Further studies demonstrated that the MPM promoted cell proliferation via activating the Wnt/β‐catenin signalling pathway. More importantly, wound healing experiments showed that 7 days post‐wounding, the rate of wound healing was 89.25% with the MPM, which was significantly higher than with LPM, SPM or NPM. The in vivo data indicated that wound healing was accelerated by treatment with a silicone rubber membrane with a pore size of 110.47 μm. Our results strongly suggest that different pore structures might affect cell proliferation and wound healing and that a silicone rubber membrane with a specific pore size could potentially be used as a promising wound dressing. Copyright © 2017 John Wiley & Sons, Ltd.     

间质金属蛋白酶基因多态性与中心性肥胖在非酒精性脂肪肝病中交互作用研究

目的 探讨间质金属蛋白酶-9(MMP-9)-1562C/T(rs3918242)以及MMP-2-1306C/T(rs243865)位点单核苷酸多态性(SNP)与非酒精性脂肪肝(NAFLD)遗传易感性以及与中心性肥胖交互作用。方法 对545例NAFLD患者和636例正常对照,采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)分析rs24386以及rs3918242基因型、非条件logistic分析各基因型与脂肪肝发病易感性关系,利用非条件logistic分析和广义多因子降维(GMDR)法分析rs3918242、rs243865与中心性肥胖的交互作用。结果 MMP-9 rs3918242位点T基因携带者(TT/CT)与非T基因携带者(CC)的NAFLD罹患风险明显增加(OR=1.67,95%CI:1.32～2.12,P=0.001;调整OR=1.65,95%CI:1.31～2.01,P=0.008);而MMP-2 rs243865位点T基因携带者(TT/CT)与非T基因携带者(CC)的NAFLD罹患风险明显降低(OR=0.68,95%CI:0.53～0.86,P=0.001;调整OR=0.66,95%CI:0.49～0.90,P=0.007)。广义多因子降维法分析结果显示,rs3918242与中心性肥胖在NAFLD发病中存在交互作用(P=0.001)。利用非条件logistic校正年龄、性别、腰围、BMI、LDL-C、HDL-C、FPG、胰岛素抵抗指数后,分析显示,携带rs3918242 TT/CT基因型中心性肥胖个体罹患NAFLD的风险高于携带CC基因非吸烟个体(OR=4.50,95%CI:2.78～7.17,P=0.007)。结论 MMP-9基因的rs3918242以及MMP-2基因的rs243865与NAFLD患病罹患风险紧密相关,rs3918242与中心性肥胖在NAFLD发病中具有协同效应。     

Fast removal of Co(ii) from aqueous solution using porous carboxymethyl chitosan beads and its adsorption mechanism

Porous carboxymethyl chitosan (PCMC) beads were synthesized via ionic coacervation/chemical crosslinking, using polyethylene glycol (PEG) as a porogen and calcium chloride and glutaraldehyde as physical and chemical cross-linkers. The as-synthesized PCMC beads were characterized using SEM, EDS, BET, TGA, FTIR and XPS analysis and then tested for the removal of Co(ii) from aqueous solution. The effects of the initial pH, Co(ii) concentration and temperature were investigated. It was found that the adsorption equilibrium is reached within 6 h and the maximum adsorption capacity is 46.25 mg g⁻¹. In addition, the kinetics and equilibrium data are well described by pseudo-second-order kinetics and the Langmuir isotherm model. Moreover, the desorption and re-adsorption performance was also studied, and the results revealed that the prepared new adsorbent still showed good adsorption performance after five cycles of regeneration. Finally, the adsorption mechanism, including chemical and physical adsorption, was proposed on the basis of the microstructure analysis, adsorption kinetics and isotherm results, and chemical adsorption was found to be the main adsorption mechanism during the process of the removal of Co(ii).

The as-prepared adsorbent exhibits excellent adsorption capacity and fast kinetics for Co(ii).     

PLNseq: a multivariate Poisson lognormal distribution for high‐throughput matched RNA‐sequencing read count data

High‐throughput RNA‐sequencing (RNA‐seq) technology provides an attractive platform for gene expression analysis. In many experimental settings, RNA‐seq read counts are measured from matched samples or taken from the same subject under multiple treatment conditions. The induced correlation therefore should be evaluated and taken into account in deriving tests of differential expression. We proposed a novel method ‘PLNseq’, which uses a multivariate Poisson lognormal distribution to model matched read count data. The correlation is directly modeled through Gaussian random effects, and inferences are made by likelihood methods. A three‐stage numerical algorithm is developed to estimate unknown parameters and conduct differential expression analysis. Results using simulated data demonstrate that our method performs reasonably well in terms of parameter estimation, DE analysis power, and robustness. PLNseq also has better control of FDRs than the benchmarks edgeR and DESeq2 in the situations where the correlation is different across the genes but can still be accurately estimated. Furthermore, direct evaluation of correlation through PLNseq enables us to develop a new and more powerful test for DE analysis. Application to a lung cancer study is provided to illustrate the practical utilities of our method. An R package implementing the method is also publicly available. Copyright © 2015 John Wiley & Sons, Ltd.     

An examination of the effects of mountaintop removal coal mining on respiratory symptoms and COPD using propensity scores

Previous research on public health consequences of mountaintop removal (MTR) coal mining has been limited by the observational nature of the data. The current study used propensity scores, a method designed to overcome this limitation, to draw more confident causal inferences about mining effects on respiratory health using non-experimental data. These data come from a health survey of 682 adults residing in two rural areas of Virginia, USA characterized by the presence or absence of MTR mining. Persons with a history of occupational exposure as coal miners were excluded. Nine covariates including age, sex, current and former smoking, overweight, obesity, high school education, college education, and exposure to coal as a home-heating source were selected to estimate propensity scores. Propensity scores were tested for balance and then used as weights to create quasi-experimental exposed and unexposed groups. Results indicated that persons in the mountaintop mining group had significantly (p?相似文献