Bulky trialkylsilyl acetylenes in the Cadiot-Chodkiewicz cross-coupling reaction

Bulky trialkylsilyl-protected alkynes such as triethylsilyl (TES), tert-butyldimethylsilyl (TBS), and triisopropylsilyl (TIPS) acetylenes underwent the Cadiot-Chodkiewicz cross-coupling reaction with different bromoalkynes to form a variety of synthetically useful unsymmetrical diynes in good yields. The diyne alcohol 10 was transformed regio- and stereoselectively into enynes by hydrotelluration, carbometalation, and reduction reactions.     

Electrochemical performances of inorganic membrane coated electrodes for li-ion batteries

In the present study, we prepared new Li-ion batteries with inorganic membrane-coated electrodes fabricated by the direct coating of a 400-nm-sized Al₂O₃ particles onto the anodes and studied their charge–discharge characteristics for the first time. Being made of 94 wt.% Al₂O₃ powder and 6 wt.% polymeric binder, the membranes on the anodes showed excellent wettability with the liquid electrolytes, due to their high porosity and capillarity. The Li-ion batteries prepared by the assembly of the inorganic membrane-coated electrodes showed excellent charge–discharge behavior compared to conventional Li-ion batteries with a polymeric separator. However, their high-rate performance was affected by the binder contents in the inorganic membranes. The thermal properties of the Li-ion battery with the inorganic membrane-coated electrodes were compared with those of a conventional one with a polymeric separator.     

Surrogate-based modeling and dimension reduction techniques for multi-scale mechanics problems

Successful modeling and/or design of engineering systems often requires one to address the impact of multiple "design variables" on the prescribed outcome.There are often multiple,competing objectives based on which we assess the outcome of optimization.Since accurate,high fidelity models are typically time consuming and computationally expensive,comprehensive evaluations can be conducted only if an efficient framework is available.Furthermore,informed decisions of the model/hardware’s overall performance rely on an adequate understanding of the global,not local,sensitivity of the individual design variables on the objectives.The surrogate-based approach,which involves approximating the objectives as continuous functions of design variables from limited data,offers a rational framework to reduce the number of important input variables,i.e.,the dimension of a design or modeling space.In this paper,we review the fundamental issues that arise in surrogate-based analysis and optimization,highlighting concepts,methods,techniques,as well as modeling implications for mechanics problems.To aid the discussions of the issues involved,we summarize recent efforts in investigating cryogenic cavitating flows,active flow control based on dielectric barrier discharge concepts,and lithium(Li)-ion batteries.It is also stressed that many multi-scale mechanics problems can naturally benefit from the surrogate approach for "scale bridging."     

Preparation and characterization of a poly(vinylbenzyl sulfonic acid)‐grafted FEP membrane

In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP‐g‐PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base‐catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM‐EDX. A chemical stability study performed with Fenton's reagent (3% H₂O₂ solution containing 4 ppm of Fe²⁺) at 70 °C revealed that FEP‐g‐PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)‐grafted membranes (FEP‐g‐PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010     

Modification of microstructures and physical properties of ultra high molecular weight polyethylene by electron beam irradiation

An ultra high molecular weight polyethylene was irradiated with the electron beam at dose levels ranging from 100 kGY to 1 MGy. The microstructures of the irradiated samples were characterized by FTIR, gel fraction measurement, DSC, and small‐ and wide‐angle X‐ray scattering. For the mechanical properties, a static tensile test and creep experiment were also performed. The crosslinking and the crystal morphology changes were the main microstructural changes to influence the mechanical properties. It was found that 250 kGy appeared to be the optimal dose level to induce crosslinks in the amorphous area and recrystalliztion in the crystal lamellae. At doses above 250 kGy, the electron beam penetrates into the crystal domains, resulting in crosslinks in the crystal domains and reduction in the crystal size and crystallinity. The static mechanical properties (modulus, strength) and the creep resistance were enhanced by the electron beam irradiation. The stiffness rather correlated with the degree of crosslinks while the strength with the crystal morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3019–3029, 2005     

Pseudodifferential operators with real analytic symbols and approximation methods for pseudodifferential equations

This paper introduces some methods (including an approximation method) for investigating pseudodifferential equations and related problems (Cauchy problems, boundary value problems,…) based on the technique of pseudodifferential operators with real analytic symbols.     

A new classification system for bacterial Rieske non-heme iron aromatic ring-hydroxylating oxygenases

Background  

Rieske non-heme iron aromatic ring-hydroxylating oxygenases (RHOs) are multi-component enzyme systems that are remarkably diverse in bacteria isolated from diverse habitats. Since the first classification in 1990, there has been a need to devise a new classification scheme for these enzymes because many RHOs have been discovered, which do not belong to any group in the previous classification. Here, we present a scheme for classification of RHOs reflecting new sequence information and interactions between RHO enzyme components.     

The effects of P3HT crystallinity in bilayer structure organic solar cells

Because of favorable charge transport properties with a lower possibility of recombination, bilayer structure solar cells have received significant ongoing attention. The simplest approach to obtain better transport properties of a charge carrier is to increase the crystallinity of the active layer. In this work, we investigated the effect of the crystallinity of poly(3-hexylthiophene) (P3HT) on the PCE of bilayer solar cells. The self-assembled nano-fibril morphology induced by the addition of the non-soluble acetonitrile (AN) solvent induces a significant improvement of charge transport properties in field-effect transistors (FET). However, the self-assembled nano-fibril morphology of P3HT did not have a beneficial effect on the bilayer solar cells. Since the P3HT nano-fibrils were generally placed in parallel with the substrate, the FET device which uses lateral transport could produce an enhancement of the device properties. However, because of the difficulty of charge transport in the vertical direction between horizontally aligned fibrils, the properties of the solar cell device did not improve with increased P3HT crystallinity. Therefore, we concluded that simply increasing the crystallinity may not be sufficient to deliver a PCE enhancement in bilayer structures because of the anisotropic transport properties of the semiconducting polymer which depend on the orientation of the backbone.