Physiochemical Changes of Starch During Maize Tortilla Production

The physiochemical changes of starch in maize tortillas and their intermediate products commercially processed by the traditional way have been determined. Samples of maize, nixtamal, dough or masa, tortilla and nejayote (steep liquor) were analyzed. The samples were assayed for water absorption index (WAI), resistant starch (RS), X-ray diffraction patterns, viscosity and with Differential Scanning Calorimetry (DSC). Enthalpy of fusion (ΔH), initial temperature (T_o) and transition temperature (T_p) of gelatinization were obtained from DSC curves. Resistant starch contents increased as the products advanced in the process. Significant differences (p > 0.05) in the fusion enthalpy values of maize, nixtamal and masa could not be found. X-ray diffraction patterns of maize, nixtamal and masa did not show significant changes; however, when masa was transformed into tortillas there was a large loss in crystallinity. The viscoamylograph peak viscosities increased from maize to masa and decreased drastically in tortillas. The data showed that the tortilla baking stage caused the most pronounced changes in starch.     

Apolipoprotein CIII Reduction Protects White Adipose Tissues against Obesity-Induced Inflammation and Insulin Resistance in Mice

Apolipoprotein CIII (apoCIII) is proinflammatory and increases in high-fat diet (HFD)-induced obesity and insulin resistance. We have previously shown that reducing apoCIII improves insulin sensitivity in vivo by complex mechanisms involving liver and brown adipose tissue. In this study the focus was on subcutaneous (SAT) and visceral (VAT) white adipose tissue (WAT). Mice were either given HFD for 14 weeks and directly from start also treated with antisense oligonucleotide (ASO) against apoCIII or given HFD for 10 weeks and HFD+ASO for an additional 14 weeks. Both groups had animals treated with inactive (Scr) ASO as controls and in parallel chow-fed mice were injected with saline. Preventing an increase or lowering apoCIII in the HFD-fed mice decreased adipocytes’ size, reduced expression of inflammatory cytokines and increased expression of genes related to thermogenesis and beiging. Isolated adipocytes from both VAT and SAT from the ASO-treated mice had normal insulin-induced inhibition of lipolysis compared to cells from Scr-treated mice. In conclusion, the HFD-induced metabolic derangements in WATs can be prevented and reversed by lowering apoCIII.     

Solid‐supported synthesis of hyperbranched polymer with β,β‐diethynylstyryl units

Two novel aromatic polyamide supports bearing aromatic bromine and iodine functionality have been synthesised and tested for the solid‐supported polymerization of AB₂ type monomer 4‐(5‐hexynyloxy)‐β,β‐dibromostyrene via Pd‐catalysed cross‐coupling of vinyl halides and terminal acetylenes. It was found that the solid‐supported polymerization leads to a decrease in molecular weight and increase in the degree of branching from 17 000–18 000 g mol⁻¹ to 8000–4000 g mol⁻¹ and from 30–35 % to 50–65 %, respectively, compared to solution polymerization. All other things being equal, the decrease in molecular weight of hyperbranched polymer on solid‐supported polymerization is a function of the distance between adjacent active sites of the polymer support. © 2001 Society of Chemical Industry     

Compressive behavior of rigid polyurethane foams nanostructured with bacterial nanocellulose at low and intermediate strain rates

Nanocellulose reinforced foams are lightweight with improved mechanical properties; however, the strain-rate effect on their mechanical response is not yet fully understood. In this work, rigid polyurethane foams (PUFs) nanostructured with bacterial nanocellulose at 0.2 wt % (BNCF) and without it (PUF) are synthesized and subjected to compression tests at different strain rates. The BNC acts as a nucleation agent, reducing the cell size but maintaining a similar apparent density of 40.4 ± 3.3 kg m⁻³. Both BNCF and PUF exhibit strain-rate effect on yield stress and densification strain. The BNCF exhibits localized progressive crushing and reduced friability, causing a remarkable recovery in the transverse direction. Numerical simulations show that functionally graded foams subjected to impact could be designed using different layers of PUF and BNCF to vary energy absorption and acceleration rate. The results presented herein warrant further research of the mechanical properties of nanostructured foams for impact applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48701.     

Amphiphilic Core/Shell Nanoparticles to Reduce Biocide Leaching From Treated Wood, 1 – Leaching and Biological Efficacy

Core/shell nanoparticles containing the fungicide tebuconazole were prepared from amphiphilic copolymers of gelatin grafted with MMA. The grafting was performed in water at levels of 1.5–15 wt.‐% solids based on matrix mass, to give core/shell nanoparticles with median diameters ranging from ≈200 to 400 or ≈10 to 100 nm depending on composition, conditions used, and work‐up. The biocide‐containing nanoparticles were delivered into wood in up to 85% efficiency. Wood blocks treated with tebuconazole‐containing nanoparticles leached less tebuconazole than wood blocks treated with tebuconazole solutions. The best nanoparticle formulations afforded wood blocks with a biological efficacy comparable to solution‐treated wood block controls in soil jar decay tests.

     

Development of water‐blown bio‐based thermoplastic polyurethane foams using bio‐derived chain extender

Water‐blown bio‐based thermoplastic polyurethane (TPU) formulations were developed to fulfill the requirements of the reactive rotational molding/foaming process. They were prepared using synthetic and bio‐based chain extenders. Foams were prepared by stirring polyether polyol (macrodiol), chain extender (diol), surfactant (silicone oil), chemical blowing agent (distilled water), catalyst, and diisocyanate. The concentration of chain extender, blowing agent, and surfactant were varied and their effects on foaming kinetics, physical, mechanical, and morphological properties of foams were investigated. Density, compressive strength, and modulus of foams decrease with increasing blowing agent concentration and increase with increasing chain extender concentration, but are not significantly affected by changes in surfactant concentration. The foam glass‐transition temperatures increase with increasing blowing agent and chain extender concentrations. The foam cell size slightly increases with increasing blowing agent content and decreases upon surfactant addition (without any dependence on concentration), whereas chain extender concentration has no effect on cell size. Bio‐based 1,3‐propanediol can be used successfully for the preparation TPU foams without sacrificing any properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Uni‐ and biaxial impact behavior of double‐gated nanoclay‐reinforced polypropylene injection moldings

Polypopylene/nanoclay three‐dimensional parts were produced without intermediate steps by direct injection molding to explore the influence of flow features and nanoclay incorporation in their impact performance. The nanocomposite was obtained by direct compounding of commercial PP with nanoclay masterbatch. The as‐molded morphology was analyzed by X‐ray and TEM analyses in terms of skin‐core structure and nanoclay particle dispersion. The nanoclay particles induced the reduction of β‐form spherulites, a known toughener. The impact behavior was assessed in tensile and biaxial modes. The PP nanocomposite molding toughness was practically unaffected by the processing melt temperature and flow rate. Conversely the nanoclay presence is influent in the impact performance. Under biaxial stress impact, the regions close to weld lines are tougher than the bulk and the fracture develops with main crack paths along the flow direction and the weld line. Cracking along the weld line results from less macromolecular interpenetration and chain entanglement, and unfavorable nanoparticle orientation. It seems that a failure mechanism which involves nanoclay delamination and multiple matrix crazing explains the toughening of PP in the directions where the nanoparticle orientation with respect to loading is adequate. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Integrated synthetic, pharmacological, and computational investigation of cis-2-(3,5-dichlorophenylcarbamoyl)cyclohexanecarboxylic acid enantiomers as positive allosteric modulators of metabotropic glutamate receptor subtype 4

2‐(3,5‐Dichlorophenylcarbamoyl)cyclohexanecarboxylic acid ( 1 ) is a potent and selective positive allosteric modulator of metabotropic glutamate receptor subtype 4 (mGluR4). The activity of 1 was reported to reside in the cis diastereomer with equal potency between its enantiomeric forms (Niswender et al., Mol. Pharmacol. 2008 , 74, 1345–1358). In the present study, the asymmetric synthesis of each of the cis enantiomers was performed, and their activities were compared with that of the racemic trans. In our assays, the cis enantiomers differ in potency, with one of them (1R,2S) higher and the other (1S,2R) lower than the racemic trans. High‐level quantum chemical calculations were carried out to characterize the structures of minimum energy in all‐isomer conformational space as well as particular intermediates between conformational transitions. Computational analysis identified structural features of 1 that can play a role in mGluR4 functionality and establish the basis for subsequent work, in which molecular chirality constructed on conformations derived from those found for the active (1R,2S) enantiomer can provide new ideas for drug discovery. Comparison between experimental and theoretical circular dichroism spectra confirmed both the absolute configuration of the (1R,2S) compound and its calculated most stable conformation, thereby supporting experimental and theoretical work.     

Advanced solution methods for microkinetic models of catalytic reactions: A methanol synthesis case study

Microkinetic models, combined with experimentally measured reaction rates and orders, play a key role in elucidating detailed reaction mechanisms in heterogeneous catalysis and have typically been solved as systems of ordinary differential equations. In this work, we demonstrate a new approach to fitting those models to experimental data. For the specific example treated here, by reformulating a typical microkinetic model for a continuous stirred tank reactor to a system of nonlinear equations, we achieved a 1000‐fold increase in solution speed. The reduced computational cost allows a more systematic search of the parameter space, leading to better fits to the available experimental data. We applied this approach to the problem of methanol synthesis by CO/CO₂ hydrogenation over a supported‐Cu catalyst, an important catalytic reaction with a large industrial interest and potential for large‐scale CO₂ chemical fixation. © 2013 American Institute of Chemical Engineers AIChE J, 60: 1336–1346, 2014     

Thermoplastic modification of urea–formaldehyde wood adhesives to improve moisture resistance

Urea–formaldehyde (UF) resins are prone to hydrolytic degradation, which limits their use to indoor applications. This study examined the modification of UF resin with various thermoplastics as a means to increase the moisture resistance of the adhesive. UF adhesives were modified in situ with various hydrophobic and hydrophilic thermoplastic formulations, using either polar or nonpolar initiators. Unmodified and modified UF resins were characterized in terms of viscosity, pH, and gel time in their prepolymer suspension state. Cured solid UF resin plaques were prepared to isolate moisture sorption effects of the cured UF resin from that of the wood component in composites, which dominates their moisture uptake. Relative crosslink density and moisture sorption tests were run on cured UF resin plaques. Results indicated that viscosity increased after modification in most cases, with higher viscosities resulting from formulations using an acidic (polar) initiator. In all cases, activation energies of the curing reactions of thermoplastic‐modified UF suspensions were lower than the unmodified UF. High relative crosslink density compared to the unmodified UF was found for one sample, which correlated well with lower overall moisture sorption. Higher relative crosslink density of cured UF resin plaques appeared to be an indicator of lower moisture uptake. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4222–4229, 2006