Three‐dimensional trajectory of electrospun polymer solution jet using digital holographic microscopy

The three‐dimensional trajectories of polymer solution jets during the electrospinning of polymer nanofibers were experimentally investigated. Test conditions included water solutions of polyethylene oxide (PEO) with concentrations typical of those producing beaded nanofibers, driving voltages ranging from 5 kV to 15 kV to generate a single polymer jet and injection pressures ranging from 0 kPa to 55 kPa. The present holographic imaging setup resolved the spatial growth of the bending instabilities, which is beneficial for validating numerical models. The results also showed the bead formation on the polymer fiber in‐flight. POLYM. ENG. SCI., 54:1765–1773, 2014. © 2013 Society of Plastics Engineers     

TiB2 Powders Synthesis by Borothermal Reduction in TiO2 Under Vacuum

TiB₂ powders were synthesized by borothermal reduction in nanoscale TiO₂ with boron under vacuum. Reaction processes were investigated, and the effect of by‐product B₂O₃ was evaluated. Results showed that TiO₂ was firstly reduced by boron to form TiBO₃ and Ti₂O₃, and then to produce TiB₂ and B₂O₃ with increasing temperature. The reaction processes of TiB₂ powders synthesis included two‐step reduction in TiO₂ by boron and the removal of B₂O₃. The presence of B₂O₃, which was previously reported as the most important factor in promoting the coarsening of ZrB₂ and HfB₂ powders by borothermal reduction, did not lead to significant coarsening of TiB₂ powders. Due to the minor effect of B₂O₃, TiB₂ powders with small particle size and low oxygen content could be prepared by direct heat treatment of TiO₂ and boron at 1550°C under vacuum for 1 h. The particle size and oxygen content of synthesized TiB₂ powders were ~0.9 μm and ~1.7 wt%, respectively.     

Sintering Behavior and Dielectric Properties of Ultra‐Low Temperature Fired Silver Molybdate Ceramics

Ag₂MoO₄ ceramic was prepared by using the solid‐state reaction method, which could be sintered at 450°C for 2 h, having a relative permittivity of 8.08, a Qf value of 17 000 GHz, and a temperature coefficient of resonance frequency about ?133 ppm/°C. Ag₂MoO₄ ceramic was chemically compatible with silver but reacted seriously with aluminum to form (Ag_0.5Al_0.5)MoO₄ during the sintering. The fitting of infrared spectra and the Shannon's additive rule were employed to study intrinsic dielectric behaviors of the ceramics at microwave region. Ionic displacive polarization and the electronic polarization contributed almost equally to the dielectric permittivity of the ceramic at microwave region. The Ag₂MoO₄ ceramics could be a good candidate for ultra‐low temperature co‐fired microwave devices.     

Advanced Chamfering Technology for Edge Strengthening

Damage‐free chamfering method for strengthening a glass edge was introduced and its effect on the edge property was discussed in detail. The chamfered surface was evaluated using an optical microscope, a confocal LSM, and a birefringence measurement system. The mechanical properties were characterized by measuring hardness, Young's modulus, and bending strength. The results revealed that the cut edge of 0.55t thin glass sheet containing median cracks and chips was exfoliated uniformly to a thickness of 200 μm, and a smooth edge surface was created (Ra = 0.03 μm). We also reported that the chamfered surface had a compressive stress enabling hardness and Young's modulus increase, and the edge strength improved from 117 to 199 MPa.     

Rheology of natural fibers thermoplastic compounds: Flow length and fiber distribution

The presented study investigates the flow length and the corresponding fiber content distribution in the injection‐moulded natural fiber reinforced thermoplastics and its relation to fiber type and processing parameters such as injection pressure, temperature, injection rate and mould tempering by increasing die temperature. In this research, polypropylene compounds with nominally 30 wt % hemp and sisal fibers are investigated. The influence of the injection pressure (500 and 1000 bar), melt temperature (180°C, 200°C, and 220°C), and die temperature (23°C and 80°C) on the fiber content distribution all over the sample is investigated. An increasing linear trend of fiber content along the spiral length is observed as an evidence of a fiber/polymer multiflow system. A pattern for fiber content distribution with respect to the fiber length along the injected spiral can be distinguished, where the longer fibers are usually found at the end of the injected part and the shorter fibers remain near mould entrance point. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39861.     

Zein‐based ultrathin fibers containing ceramic nanofillers obtained by electrospinning. II. Mechanical properties,gas barrier,and sustained release capacity of biocide thymol in multilayer polylactide films

The combination of electrospinning technology and nanomaterials such as nanoclays can synergistically lead to novel materials with enhanced properties and functionalities for their usage in passive and active packaging applications. Part I of this work was focused on the development of ultrathin zein fibers containing nanoclays, which were oriented along the fiber axis and increased the thermal properties. Part II presents the use of the hybrid fibers as passive and active components in multilayer packaging structures. The hybrid fibers are incorporated in poly(lactic acid) films via a two‐step process: Electrospinning and compression molding. The composites thus produced presented improved mechanical and barrier properties than the unfilled material. The natural biocide extract thymol is then incorporated in the coating, and its sustained release properties are shown. The antimicrobial capacity of the hybrid fibers was also determined against foodborne bacteria. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40768.     

Social context cognition crowd‐sourcing and semi‐automatic parametrization

This paper presents a semi‐automatic method of parameterizing an existing social context cognition model. It discusses benefits of the social context cognition models for example in personality modeling and their key issue that is parametrization. It briefly introduces social context cognition model and describes a new method of its crowd‐sourcing‐based parametrization. Later, validation is provided, and ability to recreate social context cognition in the provided samples is presented with good generalization for the unknown cases. Finally, model's stability for the continuous stream of dynamic social context input data is shown. Presented system contributes to the believable agent modeling and social simulations by making much needed applications of social context cognition models easier by addressing the so far unsolved troublesome parametrization issues. Copyright © 2016 John Wiley & Sons, Ltd.     

Dynamic Reductive Kinetic Resolution of Benzyl Ketones using Alcohol Dehydrogenases and Anion Exchange Resins

Dynamic reductive kinetic resolutions of racemic 3‐arylalkanones have been performed by the proper combination of an alcohol dehydrogenase and a basic anionic resin. The best results were found for the bioreduction with the alcohol dehydrogenase type A from Rhodococcus ruber DSM 44541 overexpressed in Escherichia coli (E. coli/ADH‐A) and the commercially available evo‐1.1.200, while the Amberlite IRA‐440 C and the DOWEX‐MWA‐1 resins allowed efficient in situ racemizations. Reaction conditions were optimized in terms of enzyme source and loading, type and amount of resin, pH, temperature and reaction times, obtaining a series of (R,R)‐substituted propan‐2‐ols with good conversions and both diastereoselectivity and stereoselectivity. As a proof of concept, the subsequent intramolecular cyclization of a selected propan‐2‐ol substrate afforded a valuable isochroman heterocycle without any loss of the optical purity.

     

Copper‐Catalyzed Aerobic Formation of Unstable Sulfinyl Radicals for the Synthesis of Sulfinates and Thiosulfonates

Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided.

     

Synthesis of [60]Fullerene‐Fused Tetralones via Palladium‐ Catalyzed Ketone‐Directed sp2 C?H Activation and sp3 C?H Functionalization

The palladium‐catalyzed ketone‐directed dual sp² C H activation and sp³ C H functionalization has been applied for fullerene functionalization for the first time. The sec‐alkyl aryl ketones have been exploited to react with [60]fullerene (C₆₀) to provide the novel and scarce C₆₀‐fused tetralones. The combined use of a highly active cationic palladium(II) catalyst and trifluoromethanesulfonic acid is crucial for the improvement of the reaction yield. A plausible reaction mechanism leading to the observed products has been proposed, and the electrochemistry of the fullerene products has also been investigated.