Enantiospecific synthesis of the sugar amino acid (2S,5S)-5-(aminomethyl)-tetrahydrofuran-2-carboxylic acid

An enantiospecific synthesis of the tetrahydrofuran amino acid (2S,5S)-5-(aminomethyl)-tetrahydrofuran-2-carboxylic acid 1 is reported. The sugar enone 2-(S)-octyl 6-O-acetyl-3,4-dideoxy-α-d-glycero-hex-3-enopyranosid-2-ulose 2a, derived from galactose, was employed as a chiral precursor. The enone 2a was converted by chemical manipulation of the functional groups into the 6-azido-2-O-tosyl-3,4,6-trideoxy-d-erythro-hexono-1,5-lactone 9 as key intermediate. Methanolysis of 9 induced the opening of the lactone and the attack of the hydroxyl group at C-5 to C-2 with the displacement of the tosylate. This reaction led to the formation of the tetrahydrofuran ring of methyl (2S,5S)-5-(azidomethyl)-tetrahydrofuran-2-carboxylate 10, which was readily converted into 1. The overall yield of the sequence was 35%, and all the intermediates and the final product have been fully characterized. In addition, the preferential conformations in solution of lactone 9 and target molecule 1 have been established.     

On the existence of weak solutions of anisotropic generally restrained plates

This paper presents investigations of free vibration of anisotropic plates of different geometrical shapes and generally restrained boundaries. The existence and uniqueness of weak solutions of boundary value problems and eigenvalue problems which correspond to the statical and dynamical behaviour of the mentioned plates is demonstrated. It is determined that when the plates have corner points formed by the intersection of edges free or elastically restrained against translation, the corresponding bilinear forms maintain the V – ellipticity property.     

On the Extremal Properties of Hashin’s Hollow Cylinder Assemblage in Nonlinear Elasticity

Counterexamples are given of 2D isotropic porous nonlinear elastic solids whose responses under hydrostatic loading are stiffer than that of the corresponding hollow cylinder assemblage. In addition to disproving existing conjectures in the literature, the results serve to illustrate that radially symmetric deformation—contrary to common belief—is not necessarily the stiffest possible deformation mechanism to accommodate hydrostatic loading. Instead, depending on the growth conditions of the material at hand, other types of deformations may lead to stiffer responses.     

Use of Sea Fennel as a Natural Ingredient of Edible Films for Extending the Shelf Life of Fresh Fish Burgers

The growing interest from consumers toward healthy and nutritious products and their benefits for health has increased the consumption of whole and processed fish. One of the main problems of fish is the short shelf life, especially when it is processed as in the case of burgers. The use of edible coating is an interesting strategy to extend the quality and safety of the product, reducing the need for artificial preservatives. This study evaluated the use of chitosan-based edible film formulated with sea fennel plant and sea fennel extracts. The analyses showed than the use of edible film extended the shelf life of fish burgers regardless of the incorporation of sea fennel mainly associated to the gas barrier properties and selective permeability of the film applied to the fish surface. The incorporation of sea fennel in the films did not produce any antimicrobial enhancement, although sea fennel (mostly extract) produced a better pH and enhanced the antioxidant properties and lipid oxidation of fish burgers. However, sensory analyses showed than fish burgers coated with sea fennel film plant had better acceptability than those with sea fennel extracts, probably due to the better odour and colour of the whole plant during storage. The study showed that the use of sea fennel plant at 12.5% extended the shelf life of fish burgers using a safe and clean label strategy.     

Synthesis and characterization of poly(ethylene glycol) diacrylate copolymers containing azobenzene groups prepared by frontal polymerization

A novel polymer matrix containing amino–nitro substituted azobenzene groups was obtained by frontal polymerization. (E)‐2‐(Ethyl(4‐((4‐nitrophenyl)diazenyl)phenyl)amino)ethyl methacrylate (MDR‐1) was copolymerized with poly(ethylene glycol) diacrylate (PEGDA) using this easy and fast polymerization technique. The effect of the amount of the incorporated azo‐monomer into the polymer matrix was studied in detail and correlated to front velocity, maximum temperature, initiator concentration, and monomer conversion. The obtained materials were characterized by infrared spectroscopy (Fourier transform infrared), and their thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. Moreover, the optical properties of the polymers were studied by absorption spectroscopy in the UV–Vis region. Absorption spectra of the copolymers exhibit a significant blue shift of the absorption bands with respect to the azo‐monomer, due to the presence of H‐aggregates. Cubic nonlinear optical (NLO) characterizations of the PEGDA/MDR‐1 copolymers were performed according to the Z‐Scan technique. It has been proven that samples with higher MDR‐1 content (0.75 mol %) exhibited outstandingly high NLO‐activity with negative NLO‐refractive coefficients in the promising range of n₂ = ?8.057 × 10^?4 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Screening of a modular sugar-based phosphoroamidite ligand library in the asymmetric nickel-catalyzed trialkylaluminium addition to aldehydes

A modular sugar-based phosphoroamidite ligand library for the Ni-catalyzed trialkylaluminium addition to aldehydes has been synthesized and screened. After systematic variation of the sugar backbone, the substituents at the phosphoroamidite moieties and the flexibility of the ligand backbone, the monophosphoroamidite ligand 3-amine-3-deoxy-1,2:5,6-di-O-isopropylidene-((3,3′-di-trimethylsilyl-1,1′-biphenyl-2,2′-diyl)phosphite)-α-d-glucofuranose 1d were found to be optimal. Activities were high and enantioselectivities were good (ees up to 78%) for several aryl aldehydes.     

Analysis of hydrolysis process of γ-methacryloxypropyltrimethoxysilane and its influence on the formation of silane coatings on 6063 aluminum alloy

In this paper the hydrolysis process of γ-methacryloxypropyltrimethoxysilane (MPS) at 1% in an aqueous solution by means of Fourier transform infrared (FTIR) spectroscopy was studied. The aim of this work is to determine the hydrolysis time for which a greater number of Si-OH groups has been obtained. Different hydrolysis times at pH 4 were studied to establish the most optimal application conditions for bonding to the substrate. It was possible to observe how the bands corresponding to the Si-O-C groups present in the pure silane spectrum continued to appear after short periods of hydrolysis. However these bands practically disappeared upon increasing of this hydrolysis time, with other new ones appearing corresponding to the Si-OH vibration. The silanization of 6063 aluminum alloy samples was also carried out. Analysis of the silane layers by means of FTIR indicated that the immersion time may be important according to the hydrolysis conditions, and it also allowed optimizing the drying time.     

Spectral theory for non-associative complete normed algebras and automatic continuity

This paper concerns normed algebras whose product is free of the requirement of associativity. For these algebras, a very natural notion of spectrum is provided and basic spectral properties of (associative) Banach algebras are extended to this general non-associative setting. These results are applied to generalize Rickart's dense-range homomorphism theorem. Our approach sheds some light on the classical associative theory.     

The influence of roughness on the mechanical spectroscopy of SiO2 nanorods grown by e-beam irradiation

An extension of Euler–Bernoulli theory based on variational methods for solving flexural vibrations of nanorods has been developed which takes into account geometrical surface roughness effects, as well as internal and external friction. We apply this method to study the vibrations of e-beam induced SiO₂ nanorods in the range of 10 nm in diameter and 450 nm in length. Image detection of surface roughness was carried out with the Canny edge detection algorithm. The measured surface height–height correlation function is used to characterize the surface roughness and to test for self-affine behavior. A scheme for generating random rough surfaces representative of the measured SiO₂ is described along with a statistical analysis of their effect on resonant frequencies and quality factors.