Cerium Complex with Four Types of Ligands: (NH4)6[Ce(H2W12O40)(C4H2O4)(NO3)(H2O)3]

A novel polymer (NH₄)₆[Ce(H₂W₁₂O₄₀)(C₄H₂O₄)(NO₃)(H₂O)₃] ( 1 ) has been constructed at room temperature and characterized by single crystal X‐ray structural analyses, elemental analyses, cyclic voltammetry, IR spectrum, and thermogravimetry. X‐ray structural analysis reveals that through the W–Ot′–Ce–Ob–W linkages a one‐dimension infinitely linear chain with alternating cations and anions is formed. 1 represents the first characterized compound that the Ce³⁺ ions are coordinated by four different types of ligands, and maleinate as ligands in constructing LnPOM architecture.     

The Highly Controlled and Efficient Polymerization of Ethylene

The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo- or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand.     

Effect of chain density and conformation on protein adsorption at PEG-grafted polyurethane surfaces

Polyurethanes were modified using monobenzyloxy polyethylene glycol (BPEG) which possesses a bulky hydrophobic benzyloxy group at one end and a hydroxyl group at the other end as a preconstructed BPEG layer, and poly(ethylene glycol) (PEG) and monomethoxyl poly(ethylene glycol) (MPEG) with various chain lengths as fillers. Our objective was to investigate the effect of PEG graft density and conformation on protein adsorption at PEGlated surface. The graft density was estimated by a chemical titration method. The combination of ATR-FTIR, AFM and titration results provide evidences that the graft density can be increased by backfilling PEG or MPEG to a BPEG layer. However, fibrinogen and albumin adsorption significantly increased on all surfaces after PEG or MPEG backfilling. We conclude that the conformation of hydrophobic benzyloxy end groups of the BPEG layer plays a key role. The benzyloxy end groups of preconstructed PEG chains stretch to the surface after PEG backfilling, which possibly accounts for the observed increase in protein adsorption. The BPEG conformation change after backfilling with PEG or MPEG was also suggested by contact angles. Additionally, protein adsorption was slightly influenced by the length of filler, suggesting a change in surface morphology.     

凝胶色谱与多角激光光散射联用研究聚氧化乙烯的扩展效应和链构象

采用凝胶色谱与多角激光光散射联用的方法,测定了一系列不同分子量的聚乙二醇(PEG)和聚氧化乙烯(PEO)在色谱柱中的扩展效应.扩展因子随PEG/PEO分子量的增加而增大,经扩展效应改正后得到了样品的准确分子量和分子量分布.同时建立了PEO的Z均回转半径Rgz与重均分子量Mw之间的单分散标度关系:Rgz=0.0272 Mw0.56,结果表明,长链PEO在水溶液中由于排除体积效应采取溶胀的无规线团构象.     

Modification of poly(propylene carbonate) with chain extender ADR-4368 to improve its thermal,barrier, and mechanical properties

Melt blending with the application of epoxy compound ADR-4368 as a chain extender was used to chemically modify polypropylene carbonate (PPC). ¹H nuclear magnetic resonance spectroscopy (¹H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and tests using a universal material testing machine, a gas permeability tester, a water vapor permeability tester and other instruments were used to assess changes in the chemical structure, thermal and mechanical properties, and barrier efficacy of PPC before and after modification.The epoxy group in ADR-4368 reacted with the terminal hydroxyl group in PPC, considerably enhancing its mechanical properties, thermal stability and barrier efficacy to O₂ and CO₂. With the addition of 1% ADR-4368, the glass transition temperature of PPC was increased from 17 °C to 26.9 °C, while the thermal decomposition temperature (T_−5%) of PPC was increased from 177.3 °C to 240.6 °C. Moreover, the tensile strength of the modified PPC was improved from 3.3 MPa to 20.7 MPa.     

Solvent effects on the dielectric dispersion of poly(vinyl pyrrolidone)-poly(ethylene glycol) blends

The complex relative dielectric function , loss tangent , complex electric modulus and alternating current electrical conductivity dispersion behaviour of liquid poly(vinyl pyrrolidone)-poly(ethylene glycol) (PVP–PEG) blends in water, ethyl alcohol and 1,4–dioxane solvent over the entire volume mixture concentration range has been investigated in the frequency range of 20 Hz to 1 MHz at 25 °C. The PVP–PEG blends show the dielectric dispersion corresponding to the micro-Brownian motion of the PVP chain in the upper frequency region, whereas in the lower frequency region, dielectric dispersion is due to ionic conduction and electrode polarization phenomena. Results show that the conductivity values of these blends in water and dioxane can be monitored with the change in the solvent concentration, whereas it has a small variation with ethyl alcohol concentration. The comparative dielectric dispersion shape study confirms that the chain dynamics of polymers blend is influenced by heterogeneous interactions and solvent polar strength.     

Flocculation of dilute titanium dioxide suspensions by graft cationic polyelectrolytes

The flocculation of a dilute titanium dioxide (TiO₂) suspension using homopolymers and graft copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) was investigated. The graft copolymers produced by γ-irradiating the mixtures of polyacrylamide (PAM) and polyDADMAC gave better flocculating performance than homopolymers, reflecting the higher fractions of large particles and bigger floc size. A kinetic delay in the onset of flocculation was observed after adding the copolymers in the dose range 5–30 [mg polymer]/ [g TiO₂]. Increasing dosage resulted in a longer delay period. No significant flocculation was observed when the dose was above 50 [mg polymer]/[g TiO₂]. This delay was interpreted in terms of the re-conformation of polymer chains driven by charge neutralization, between the positively charged polymer branches and the negative particle surface. Depending on the dosage used, the flocculation behavior of the graft copolymer has been suggested to be equilibrium and non-equilibrium flocculation. It was also observed that re-conformation is not affected by the ion strength of the media, but a strong shear force significantly reduces the chain reconformation time. Received: 9 April 1998 Accepted in revised form: 28 August 1998     

Causal Algebras on Chain Event Graphs with Informed Missingness for System Failure

Graph-based causal inference has recently been successfully applied to explore system reliability and to predict failures in order to improve systems. One popular causal analysis following Pearl and Spirtes et al. to study causal relationships embedded in a system is to use a Bayesian network (BN). However, certain causal constructions that are particularly pertinent to the study of reliability are difficult to express fully through a BN. Our recent work demonstrated the flexibility of using a Chain Event Graph (CEG) instead to capture causal reasoning embedded within engineers’ reports. We demonstrated that an event tree rather than a BN could provide an alternative framework that could capture most of the causal concepts needed within this domain. In particular, a causal calculus for a specific type of intervention, called a remedial intervention, was devised on this tree-like graph. In this paper, we extend the use of this framework to show that not only remedial maintenance interventions but also interventions associated with routine maintenance can be well-defined using this alternative class of graphical model. We also show that the complexity in making inference about the potential relationships between causes and failures in a missing data situation in the domain of system reliability can be elegantly addressed using this new methodology. Causal modelling using a CEG is illustrated through examples drawn from the study of reliability of an energy distribution network.     

高分辨1H-NMR研究溶聚丁苯橡胶链化学结构

With a high-resolution 1H-NMR the features of solution-SBRs chain structures have been analyzed and made quantitative calculations of the chemical composites, inparticular, the contents of butadiene isomers have been made. It is reveal that the Bayer solution-SBR, whose performance is highly recognized inthe tire industry, has a high content of cis-1,4 butadiene isomers, allow content of trans-1,4 butadiene isomers, and a medium contents of 1,2add butadiene isomers and styrene units, as well as that the butadiene isomers display orderly characteristics in the sequence. The above structural features determine that Bayer solution-SBR can play good role in the balance of the low heat building up, antiwetskip and antiwear properties of green tire.     

Probabilistic abductive logic programming using Dirichlet priors

Probabilistic programming is an area of research that aims to develop general inference algorithms for probabilistic models expressed as probabilistic programs whose execution corresponds to inferring the parameters of those models. In this paper, we introduce a probabilistic programming language (PPL) based on abductive logic programming for performing inference in probabilistic models involving categorical distributions with Dirichlet priors. We encode these models as abductive logic programs enriched with probabilistic definitions and queries, and show how to execute and compile them to boolean formulas. Using the latter, we perform generalized inference using one of two proposed Markov Chain Monte Carlo (MCMC) sampling algorithms: an adaptation of uncollapsed Gibbs sampling from related work and a novel collapsed Gibbs sampling (CGS). We show that CGS converges faster than the uncollapsed version on a latent Dirichlet allocation (LDA) task using synthetic data. On similar data, we compare our PPL with LDA-specific algorithms and other PPLs. We find that all methods, except one, perform similarly and that the more expressive the PPL, the slower it is. We illustrate applications of our PPL on real data in two variants of LDA models (Seed and Cluster LDA), and in the repeated insertion model (RIM). In the latter, our PPL yields similar conclusions to inference with EM for Mallows models.