Electrical properties of tri-n-butyl tin acrylate-methylmethacrylate copolymers

The copolymerization of tri-n-butyl tin acrylate (TBTA) with methylmethacrylate (MMA) has been investigated in dioxane. The composition of these copolymers was determined quantitatively by ¹H nuclear magnetic resonance (NMR) spectroscopy. The tin contents were estimated by gravimetric as well as thermogravimetric techniques (TGA). The reactivity ratio of such copolymers was estimated by application of the Kelen-Tudos method. The dielectric properties of the copolymers have been studied over a frequency range of 100–50 kHz at different temperatures from 20 to 70°C. The electrical conductivity for such copolymers was also measured. The results are interpreted in terms of the tin content of the copolymers.     

Determination of water activities and osmotic and activity coefficients of the system NaCl–BaCl2–H2O at 298.15 K

The water activities of the mixed aqueous electrolyte NaCl–BaCl₂(aq) are measured at total molalities from 0.25 mol kg⁻¹ to about saturation for different ionic strength fractions (y) of NaCl with y=0.33,0.50,0.67. The results allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii, Stokes, and Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LSII), Reilly, Wood, and Robinson (RWR), and Pitzer models. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The excess Gibbs energy is also determined.     

Polyurethane foams with 1,3‐pyrimidine ring

Attempts of obtaining of polyurethane foams using polyetherols with 1,3‐pyrimidine ring (obtained in reactions of 6‐aminouracil with oxiranes) are reported. Properties of the foams are investigated, especially their thermal stability. The foams show an improved thermal stability up to 200°C for a long time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Potentiometric studies of oxidation–reduction reactions with redox copolymers

Polymeric oxidants in the bead form that were macroporous styrene/divinylbenzene copolymers containing N‐chlorosulfonamide functional groups (in sodium or hydrogen form) or N‐bromosulfonamide groups (in sodium form) were synthesized and investigated to determine their oxidizing powers. The redox potentials of the N‐chlorosulfonamide/sulfonamide and N‐bromosulfonamide/sulfonamide systems were determined by potentiometric studies at different pH values with aqueous solutions of Na₂SO₃, KCN, and KSCN as reducers. The formal redox potentials of the N‐chlorosulfonamide copolymers were 0.79, 0.44, and ?0.12 V at pH's of 1.8, 8.45, and 13.6, respectively. The formal redox potential of the N‐bromosulfonamide copolymer was about 100 mV higher in comparable conditions and in solutions over pH = 5 (e.g., 0.56 V at pH = 8.56). The comparatively higher oxidizing power of the N‐bromosulfonamide copolymer was particularly evident in a strong alkaline medium (in which the N‐chlorosulfonamide copolymer was not reactive). In contrast, the N‐chlorosulfonamide copolymer showed strong oxidative properties in acidic media (in which the N‐bromosulfonamide copolymer decomposed itself). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Quantification of ageing of ultracapacitors during cycling tests with current profile characteristics of hybrid and electric vehicles applications

The ageing quantification of ultracapacitors in cycle-life tests has been studied. Current profiles and the characteristics of the ultracapacitors used in hybrid and electric vehicle applications are specified and validated. With these profiles, significant self-heating occurs but without exceeding the manufacturers' limits. Thus, ultracapacitors are aged in a short time with the same degradation mechanisms observed in normal use. Ageing evaluation is based on the measurement of the electrical parameter changes. A particular phenomenon is performance recovery during rest periods when power-cycling is interrupted for electrical characterisation. Therefore, an online characterisation procedure was added for more accurate evaluation of the ultracapacitors' ageing. A number of devices from two manufacturers are cycled with different current profiles. The obtained results are presented and discussed.     

Overexpression of amyloid precursor protein of Alzheimer's type in brains of intoxicated children

The coincidence of neuronal stress induced by intoxication and an overexpression of amyloid precursor protein (APP) in the brains of children was examined. Brains of ten children accidentally intoxicated by poisonous mushroom were studied by means of immunohistochemical methods using monoclonal antibodies generated against different domains of APP and glial cell markers. Overexpression of APP was found in the brain neurons of all intoxicated children. Neurons were immunopositive with the antibodies generated against the middle (amyloid beta protein) domain of APP. No extracellular deposits were found in the tissue. Our results provided, for the first time, the evidence that overexpression of APP concomitant with the neuronal stress is age-independent phenomenon appearing not only in the brain of adults but in very young individuals as well.     

Controlling orthopoxvirus infections--200 years after Jenner's revolutionary immunization

An 11-year global WHO campaign for eradication of smallpox finished in October 1977 as the result of Edward Jenner's primary success in 1796, who for the first time applied human vaccination against variola virus (VARV). The 200th anniversary of this happening is a good occasion to summarize the current status of the knowledge about the role of B and T lymphocytes in the control of orthopoxvirus infections. This short review concentrates on general characteristics of orthopoxviruses and the immune response to infection, mainly by vaccinia virus (VV) and ectromelia virus (EV).     

Cracking orientation and induced anisotropy of a ceramic matrix composite under off-axis loading

The effect of matrix microcracking on the stiffnesses of a carbon-fibre/SiC-matrix woven composite is studied by means of an ultrasonic method. It provides the whole set of the stiffness tensor coefficients which are inaccessible by classical strain measurements and which are required to identify anisotropic damage. The induced anisotropy depends on the loading direction. If a tensile solicitation in a fibre direction leads to stiffnesses decreases without any rotation of principal axes, a tensile solicitation of 45° from a fibre direction creates microcracks with a predominant orientation that does not coincide with the elastic symmetry axes, and induce a fully anisotropic elastic degradation.