Polymer track membranes as a trap support for reagent in fiber optic sensors

The article presents a new idea of the application of polymer track membranes (PTM) for immobilization of a reagent in fiber optic chemical sensors. PTM was made of a poly(ethylene terephthalate) foil (10 μm in thickness, pores of 0.2 μm in diameter). The usefulness of membranes additionally covered by poly(vinyl chloride) was tested in a fiber optic redox titrator. The titrator utilized N,N′-diphenylbenzidine as a reagent which changes its absorbance in dependence on the redox potential. The measuring system is based on a lightemitting diode and a silicon photodiode connected to a bifurcated fiber optic bundle. The gain is in price and availability of the membrane. © 1996 John Wiley & Sons, Inc.     

Polyphosphazene membranes. I. Solid-state photocrosslinking of poly[(4-ethylphenoxy)-(phenoxy)phosphazene]

Dense films of poly[(4-ethylphenoxy)(phenoxy)phosphazene] (PEPP), a potentially attractive ion-exchange membrane material, were crosslinked to varying degrees using UV light and a photoinitiator. This polymer contained two kinds of substituents: phenoxy groups to be used for possible functionalization (e.g., sulfonation) and ethylphenoxy side-chains for photocrosslinking, where hydrogens at the benzylic carbons could be abstracted by a photoinitiator-leaving macroradicals that after recombination formed covalent bonds. The polyphosphazene polymer was synthesized, mixed with a photoinitiator, shaped into a thin film by solvent casting, and irradiated with UV light for a specified period of time. Benzophenone (BP), was selected as the photoinitiator because it was miscible with poly-phosphazene, had the highest rate of hydrogen abstraction, and absorbed UV light of 365 nm wavelength. The half-life of benzophenone in 50 μm-thick irradiated films was determined to be 20 min. When the BP–PEPP molar ratio was increased from 0 to 0.5, the glass transition temperature increased after irradiation from −8.8 to 53.5°C. At the same time, the equilibrium swelling in dimethylacetamide, at 25°C, decreased from infinity to 0.31. Tensile strength tests of the crosslinked films revealed a nonlinear dependence on BP–PEPP molar ratio. © 1996 John Wiley & Sons, Inc.     

An approach to modeling the rheological properties of food materials

The aim of this study was to develop a mathematical model describing the rheological properties of food materials, including the elastic modulus, consistency index, flow index and flow limit, that are not dependent on the tests (creep and compression stress relaxation) used to establish those values. A rheological model was designed as a parallel combination of spring, viscous and plastic elements. The model was verified logically and empirically based on the results of creep tests and compression stress relaxation tests performed on 10 × 10 × 10 mm cubes cut out from roasted turkey breast muscles. An analysis of the model’s susceptibility to variations in rheological properties indicates that the model is sensitive to changes in the values of the elastic modulus, flow limit and flow index, but it is less susceptible to changes in the consistency index. The model generates similar values of the rheological properties of the studied materials regardless of whether they had been determined based on the results of the creep test or the compression stress relaxation test.     

Quantification of Se-Methylselenocysteine and Its γ-Glutamyl Derivative from Naturally Se-Enriched Green Bean (Phaseolus vulgaris vulgaris) After HPLC-ESI-TOF-MS and Orbitrap MS n -Based Identification

Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-methylselenocysteine and γ-glutamyl-Se-methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes.     

Mechanism of MxOy nanoparticles/CNTs for catalytic carbonization of polyethylene and application to flame retardancy

Three kinds of metal oxide nanoparticles (Fe₃O₄, Co₃O₄, and Ni₂O₃) are produced on carbon nanotubes (CNTs). The synergistic effects rendered by the CNTs and metal oxide nanoparticles on carbonization of polyethylene (PE) are studied and applications to flame retardancy of PE are investigated systematically. The CNT‐Ni₂O₃ delivers the best performance and the mechanism pertaining to the enhanced flame retardancy is proposed and discussed. It is found that under the same conditions, the carbonization rate can be a factor to influence the flame retardancy performance. Among Fe, Co, and Ni, Ni has the fastest carbonation rate, which leads to the best flame retardancy performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45233.     

Unsaturated ester resins

Vinyl ester resins (VERs) are often described as a cross between unsaturated polyester resins and epoxy resins. VERs offer an upgrade to epoxy resins, and they tend to be selected when chemical and temperature resistance is required. This research was aimed at developing the synthesis of unsaturated ester resins (UERs), which are similar to VERs. UERs were synthesized by the addition of dihydrodicyclopentadienyl hydrogen maleate to the terminal epoxy groups in low‐molecular‐weight bisphenol A/epichlorohydrin epoxy resins. The effect of urethanization of UERs on the properties of the crosslinked polymer was also investigated. As crosslinking monomers, styrene and glycol dimethacrylates were used. The following properties of cured UERs were determined: the heat deflection temperature, alkali resistance, and the mechanical strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2627–2631, 2006     

Coat of Arctic Fox (Alopex lagopus L.) of Different Genetic Groups in Micro- and Macroscopic Studies and in DSC Investigations

The objective of this research project was to compare in different genetic groups of arctic foxes the composition of the coat, hair length, and thickness as well as the medulla of four hair types but, primarily, to investigate the hair of the two layers of the coat hair (the underhair and the overcoat) using, for this purpose, the differential scanning calorimetry (DSC) method. Generally speaking, Finnish foxes were characterized by the most favorable indices of these traits. Different proportions of genes exerted a different impact on the level of these traits.     

Electrostrictive properties of ceramics obtained on the basis of ferroelectrk relaxors

We present the results for search of the best ceramic materials for electrostrictive transducers. We performed the following investigations: (1) investigation of different types of ferroelectric, antiferroelectric and non-polar complex oxides with perovskite (OPS) and tetragonal tungsten bronze (TBS) structures; (2) the investigations of the OPS with different degrees of the cations ordering; (3) the measurements of the electrostrictive coefficient Q, Curie-Weiss constant C_W, coefficient of linear thermal expansion λ, polarization P and dielectric permittivity ^σ_r; (4) the X-ray analysis of the structure. The electrostrictive deformation may be very high and the relative strain can be of the order 10^-3 in such materials.