Zinc(II)/ketoxime system as a simple and efficient catalyst for hydrolysis of organonitriles

The hydrolysis of sterically hindered and unhindered alkyl nitriles, and also of benzyl and phenyl nitriles RCN (R = Me, CH(2)Cl, Et, n-Pr, i-Pr, n-Bu, t-Bu, p-MeOC(6)H(4)CH(2), Ph), to carboxamides is catalyzed by a novel system of superior simplicity consisting of cheap, widely commercially available, and rather environmentally friendly compounds, that is, a ZnX(2)/ketoxime combination, but it does not proceed at all with either the zinc salt or the ketoxime taken alone. The nature of the anion X(-) in the zinc salt (X = NO(3), Cl, CF(3)SO(3)) or of the ketoxime (Me(2)C=NOH, C(4)H(8)C=NOH, C(5)H(10)C=NOH) does not affect strongly the catalytic properties of the system, but the best results were obtained so far with a Zn(NO(3))(2).6H(2)O/2-propanone oxime molar ratio of 1:4; turnover numbers are typically above ca. 100 but reach as high as 1000 for p-MeOC(6)H(4)CH(2)C(=O)NH(2). The previously unknown structures of the two carboxamide products n-BuC(=O)NH(2) and p-MeOC(6)H(4)CH(2)C(=O)NH(2) were determined by X-ray diffraction studies. The complexes [ZnX(2)(R(2)C=NOH)(2)] (X = Cl, R(2) = 2Me, C(4)H(8), C(5)H(10); X = NO(3), R = C(4)H(8)), prepared by heating the appropriate zinc salts with 2 equiv of the ketoxime in acetone and characterized by C, H, N analyses, FAB-MS, (1)H and (13)C[(1)H] NMR spectroscopies, and also X-ray crystallography (for X = Cl, R(2) = 2Me; X = NO(3), R = C(4)H(8)), proved to be catalyst precursors in the conversions because the activity of these species is high only in the presence of 2 equiv of the ketoxime.     

The effect of reactor irradiation on the dielectric loss peaks of Nylon and Mylar

The effect of irradiation on the dielectric properties of nylon 66.6 and Mylar was studied. In the case of nylon the dielectric loss peak at 350 K measured with an annular frequency of 10⁴ l/s disappeared due to irradiation and the peak at higher temperaturcs shifted to still higher temperatures. In Mylar the α-peak grew in magnitude, indicating an increase in amorphousness, while the β-peak decreased. A rough estimate for the decrease in the magnitude of the effective number of dipoles is presented. The irradiation was carried out up to fast neutron fluence of 3 × 10¹⁷ nvt and gamma dose of 1 × 10⁹ rad.     

Phenomenological modeling of viscous electrostrictive polymers

A common usage for electroactive polymers (EAPs) is in different types of actuators, where advantage is taken of the deformation of the polymer due to an electric field. It turns out that time-dependent effects are present in these applications. One of these effects is the viscoelastic behavior of the polymer material. In view of the modeling and simulation of applications for EAP within a continuum mechanics setting, a phenomenological framework for an electro-viscoelastic material model is elaborated in this work. The different specific models are fitted to experimental data available in the literature. While the experimental data used for inherent electrostriction is restricted to small strains, a large strain setting is used for the model in order to account for possible applications where the polymers undergo large deformations, such as in pre-strained actuators.     

Preparation of amino acid nanoparticles at varying saturation conditions in an aerosol flow reactor

In this article, we describe the synthesis of new and ion-selective nanofiltration (NF) membranes using polyvinylidene fluoride (PVDF) nanofibers and hyperbranched polyethylenimine (PEI) as building blocks. These new nanofibrous composite (NFC) membranes consist of crosslinked hyperbranched PEI networks supported by PVDF nanofibrous scaffolds that are electrospun onto commercial PVDF microfiltration (MF) membranes. A major objective of our study was to fabricate positively charged NF membranes that can be operated at low pressure with high water flux and improved rejection for monovalent cations. To achieve this, we investigated the effects of crosslinker chemistry on membrane properties (morphology, composition, hydrophobicity, and zeta potential) and membrane performance (salt rejection and permeate flux) in aqueous solutions (2,000?mg/L) of four salts (NaCl, MgCl₂, Na₂SO₄, and MgSO₄) at pH 4, 6, and 8. We found that an NFC?CPVDF membrane with a network of PEI macromolecules crosslinked with trimesoyl chloride has a high water flux (~30?L?m^?2?h^?1) and high rejections for MgCl₂ (~88 %) and NaCl (~65 %) at pH 6 using a pressure of 7?bar. The overall results of our study suggest that PVDF nanofibers and hyperbranched PEI are promising building blocks for the fabrication of high performance NF membranes for water purification.     

The rheology of bread dough made from four commercial flours

 A selection of four commercial flours has been subjected to extensive rheological measurements as part of a comprehensive program of wheat improvement. The results have been used to determine which of the many types of rheological measurements provide significant discrimination between various types of modern baker's flours (including biscuit flours) and to procure data suitable for use in mathematical models describing the dough rheology. The rheological measurements undertaken include oscillatory shear at low amplitude, steady shear at a low shear rate, stress relaxation and extensional viscosity testing. Although oscillatory shear data show minor differences between these flours, the other tests show significant variations and these provide very good discrimination between the different flour types in comparison with conventional dough testing (e.g. by the extensograph). The current dough rheological measurements provide further insight into molecular structure. In the future, mathematical (constitutive) models are expected to provide a means of predicting processing and baking behaviour of bread dough. Received: 27 June 2001 Accepted: 28 August 2001     

The topological gradient in anisotropic elasticity with an eye towards lightweight design

We derive a representation formula for the topological gradient with respect to arbitrary quadratic yield functionals and anisotropic elastic materials, thus laying the theoretical foundations for topological sensitivity analysis in lightweight design. For compliance, minimization involving general anisotropic materials and ellipsoidal perturbations, we give a closed formula for the topological gradient, enabling topology optimization of integrated designs involving several reinforced materials. If the materials are transversely isotropic and the perturbations are spheriodal, we even obtain an analytical formula. For general anisotropy, recent advances in the computation of Eshelby's tensor enable rapid numerical computation of the topological gradient. Restricting to isotropic materials and spheroidal inclusions, we obtain an analytical formula for minimizing isotropic yield functionals with applications to microscale‐scale sensitivity analysis of fiber reinforced composites or reinforcing analysis of brittle materials. Copyright © 2013 John Wiley & Sons, Ltd.     

Small-angle scattering study of structural changes in the microfibril network of nanocellulose during enzymatic hydrolysis

The hydrolysis of nanofibrillated cellulose (NFC), consisting of individual cellulose fibrils, was followed using small-angle scattering techniques in order to reveal changes in the substrate structure caused by cellulose degrading enzymes. In particular, the nanoscale structure of the network of cellulose fibrils was characterized with the combination of small-angle neutron scattering and small-angle x-ray scattering. In the nanocellulose with higher xylan content, the interfibrillar distance was shown to remain unchanged during enzymatic degradation, whereas the distance increased in the nanocellulose with lower xylan content. The limiting effect of xylan on the hydrolysis and a faster hydrolysis of the more thoroughly fibrillated segments of the NFC network could be observed. Despite the extensive fibrillation of the raw material, however, the hydrolysis was eventually limited by the aggregated and heterogeneous structure of the substrate.