Self Assembly–Assisted Additive Manufacturing: Direct Ink Write 3D Printing of Epoxy–Amine Thermosets

The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from their limited rheological tuneability and slow reactions kinetics. The direct ink write (DIW) 3D printing of a two‐part resin, Epon 828 and Jeffamine D230, using a self‐assembly approach is reported. Through the addition of self‐assembling, ureidopyrimidinone‐modified Jeffamine D230 and nanoclay filler, suitable viscoelastic properties are obtained, enabling 3D printing of the epoxy–amine pre‐polymer resin. A significant increase in viscosity is observed, with an infinite shear rate viscosity of approximately two orders of magnitude higher than control resins, in addition to, an increase in yield strength and thixotropic behavior. Printing of simple geometries is demonstrated with parts showing excellent interlayer adhesion, unachievable using control resins.     

Catalytic olefin polymerisation at short times: Studies using specially adapted reactors

Despite the fact that the very early stages (several tens of seconds) of catalysed olefin polymerisation processes appear negligibly short with respect to the residence time of most industrial reactors, they are critical in terms of catalyst activation, obtaining good particle morphology, and avoiding irreparable problems caused by particle overheating. The different types of reactors that have been used over the course of the past few years are discussed in this feature article. It is shown that despite the difficulties encountered in finding the perfect experimental tool for this purpose, different configurations of stopped flow reactors can be used successfully to explore different aspects of what happens to the catalyst (supported and molecular) during these critical moments of polymerisation. © 2012 Canadian Society for Chemical Engineering     

Sucrose supplementation during traditional carob syrup processing affected its chemical characteristics and biological activities

The addition of sucrose is optional during carob syrups traditional processing. In this work, the polyphenolic profiles of carob syrups supplemented (CSS) or not with sugar (CS) were analyzed using RP-HPLC–ESI-MS. Quantitative data showed that adding of sucrose significantly (p < 0.05) decreased the polyphenolic amounts of about 58.6%, from 4.5 ± 0.32 to 1.86 ± 0.26 mg/g of CS and CSS, respectively. Gallic acid was the most abundant compound in both syrups representing 60.93% (CS) and 69.26% (CSS) of the total phenolics. Moreover, the adding of sugar decreased (p < 0.05) the antiradical potentials of 28% and 74%, as determined, respectively, by the ABTS and DPPH assays. CS was found to exhibit stronger antibacterial and antifungal activities than CSS. Bacillus cereus was the most sensitive strain to the extracts with CMI ≈500 (CS) and 622 (CSS) μg/ml. Both syrup extracts were cytotoxic to human neuroblastoma (SH-SY5Y) and fibroblast (3T3) cell lines as well as to mouse embryonic stem cells (D3). Tumoral SH-SY5Y cells were the most susceptible to the extracts with IC50 = 311.7 ± 23.65 (CS) and 390.6 ± 34.97 μg/ml (CSS). This study provides, for the first time, new analytical insights into traditionally made carob syrups and highlights the negative effect of sugar supplementation during processing.     

Polyphenolic Extract of Barbary-Fig (Opuntia ficus-indica) Syrup: RP–HPLC–ESI–MS Analysis and Determination of Antioxidant, Antimicrobial and Cancer-Cells Cytotoxic Potentials

The traditionally derived syrup of Opuntia ficus-indica fruit is commonly used in homemade confectionery. Herein, the aqueous-acetone extract prepared from the Tunisian O. ficus-indica syrup was investigated. The qualitatively and quantitatively polyphenolic content was analysed using reversed-phase high-performance liquid chromatography–diode array detection (RP-HPLC–DAD) coupled to electrospray ionisation–mass spectrometry (ESI–MS). The extract contained 19.95?±?2.01 mg phenolics per gram of fresh starting material with isorhamnetin 3-O-robinobioside as the major compound (22.76%). The syrup extract showed strong antioxidant potentials as assessed by both ABTS and DPPH functional methods. It exhibited effective antimicrobial activity, particularly against Staphylococcus aureus and Staphylococcus epidermidis with a minimal bactericide concentration (MBC) of 1.3 mg phenolics/ml. Furthermore, at final concentrations in the range of 41.38–186.25 μg polyphenols/ml, the extract decreased human SH-SY5Y neuroblastoma and 3T3 fibroblast in vitro cell viability in a dose- and time-dependent manner compared to non-treated control cells. The observed effects were significantly (P?<?0.05) high against cancer lines. Extract concentrations higher than 106.43 μg/ml reduced cancer cells viability to 50–60% 1–3 h post-treatment. Further in vivo insight studies should emphasise and validate the herein obtained results.     

An Unprecedented Iridium(III) Catalyst for Stereoselective Dimerisation of Terminal Alkynes

A novel iridium(III) hydride complex, IrHCl(TIMP₃) {HTIMP₃=tris[1‐(diphenylphosphino)‐3‐methyl‐1H‐indol‐2‐yl]methane} was prepared and fully characterized in both the solid state and in solution. Chloride abstraction by silver cations provides a more reactive compound, [IrH(TIMP₃)][BF₄], which can react with pyridine (py) and phenylacetylene to yield the complexes [IrH(TIMP₃)(py)][BF₄] and [Ir(PhCHC CHCHPh)(TIMP₃)][BF₄], respectively. Interestingly, IrH(TIMP₃)(py)][BF₄] efficiently catalyses the stereoselective dimerisation of model terminal alkynes to the 1,4‐disubstituted (E)‐but‐1‐en‐3‐yne only.     

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

A specially conceived packed‐bed stopped flow minireactor (3 mL) suitable for short gas phase catalytic reactions has been used to study the start‐up of ethylene homopolymerization with a supported metallocene catalyst. Focus has been put on the heat transfer characteristics of the supported catalysts and on understanding the relationship between the initial rate and the relative gas/particle velocities and the influence of particle parameters in the packed bed. We performed a comprehensive study on the influence of various physical parameters on the heat transfer regime at start up conditions. The catalyst activity as well as the polymer morphology is shown to be dependent on heat transfer regime. The knowledge thus obtained is applicable to industrial problems like catalyst injection in fluidized beds and helps preventing experimental artifacts due to overheating in following studies. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Computation of the complexity of vector quantizers by affine modeling

Several methods for evaluation of the complexity of data compression systems and for including complexity measures in the traditional rate-distortion analysis have been published in recent works. In this work, we indicate that the relationship between rate-distortion performance and complexity for some practical coding schemes—entropy-constrained vector quantization (ECVQ) and interpolative vector quantization (IVQ)—can be represented by affine models. For the same rate-distortion performance, the complexity of an interpolative vector quantizer is known to be significantly smaller than the complexity of a full-search entropy constrained vector quantizer, and this complexity difference is a suitable illustration for the rate-distortion-complexity framework. We use high-resolution theory arguments to derive the affine models for ECVQ and IVQ. The proposed affine complexity modeling successfully predicts the cost of vector quantizers designed from data sets that were not used to generate the models.