Structure,mechanical, and thermal behavior of nylon 6‐polyisoprene block copolymers obtained via anionic polymerization

The structure and physicomechanical properties of nylon 6 (N‐6) modified with polyethylene oxide–polyisoprene–polyethylene oxide (PEO‐PI‐PEO) copolymers via activated anionic polymerization have been investigated by using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), thermogravimetric analysis (TGA), dynamic mechanical analysis (DTMA), and by optical microscopy. This study deals with the influence that the N‐6/PI ratio and the length of the PI segments have on the physicomechanical behavior, thermal stability, and the structural changes of the block copolymers. Literature does not report on previous investigations of this kind. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3251–3258, 2004     

Effect of water on the reduction of NOx with propane on Fe‐ZSM‐5. An FTIR mechanistic study

Adsorption of NO on Fe‐ZSM‐5 leads to formation of Feⁿ⁺–NO (n = 2 or 3) species (1880 cm^-1), Fe²⁺(NO)₂ complexes (1920 and 1835 cm^-1) and NO⁺ (2133 cm^-1). Water strongly suppresses the formation of NO⁺ and Feⁿ⁺(NO)₂ and more slightly the formation of Feⁿ⁺ –NO. Introduction of oxygen to NO converts the nitrosyls into surface nitrates (1620 and 1575 cm^-1) and this process is almost unaffected by water. The nitrates are thermally stable up to ca. 300^°C, but readily interact with propane at 200^°C, thus forming surface C–H–N–O deposit (bands in the 1700–1300 cm^-1 region). Here again, water does not hinder the process. The C–H–N–O deposit is relatively inert (it does not interact with NO or NO + O₂ at ambient temperature) but, at temperatures higher than 250 °C, it is decomposed to NCO^- species (bands at 2215 (Fe–NCO) and 2256 cm^-1 (Al–NCO)). In the presence of water, however, the Fe–NCO species only are formed. At ambient temperature the NCO^- species are inert towards NO and O₂, but easily react with a NO + O₂ mixture. The mechanism of the selective catalytic reduction of nitrogen oxides on Fe‐ZSM‐5 and the effect of water on the process are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dendronized Polymer Architectures for Fuel Cell Membranes

Multi‐step synthetic pathways to low‐ion exchange capacity (IEC) polysulfone (PSU) with sulfonic acid functionalized aliphatic dendrons and sulfonated comb‐type PSU structures are developed and investigated in a comparative study as non‐fluorinated proton exchange membrane (PEM) candidates. In each case the side chains are synthesized and introduced in their sulfonated form onto an azide‐functionalized PSU via click chemistry. Three degrees of substitution of each architecture were prepared in order to evaluate the dependence on number of sulfonated side chains. Solution cast membranes were evaluated as PEMs for use in fuel cells by proton conductivity measurements, and in the case of dendronized architectures: thermal stability. The proposed synthetic strategy facilitates exploration of a non‐fluorous system with various flexible side chains where IEC is tunable by the degree of substitution.     

Hexagonal mesoporous silicas with and without Zr as supports for HDS catalysts

Hexagonal mesoporous materials (HMS) with and without zirconium were used as supports for preparation of HDS catalysts. The catalysts prepared by modification of the supports with 12-phosphomolybdic acid (HPMo) were characterised by nitrogen adsorption, IR spectroscopy, TPD of ammonia, TPR and catalytic activity in thiophene hydrodesulphurisation. Parent silicas showed mesoporous structure with BET surface area between 1200 and 800 m² g⁻¹, pore size diameter around 3.3 nm and acidity around 0.3 mmol NH₃ g⁻¹. Molybdenum catalysts possess stronger acidity than the supports used. The catalytic activities in hydrodesulphurisation of thiophene of the molybdenum containing catalysts prepared with HMS were higher than the activity of the catalyst prepared with amorphous silica. Higher acidity of Zr–HMS supports lead to lower stability in the thiophene conversion.     

Dephosphorization equilibria between pure molten iron and CaO-saturated FeOn–CaO–SiO2 and FeOn–CaO–Al2O3 slags

Metal-slag refining reactions have been investigated to determine dephosphorization equilibria in steelmaking using CaO-saturated slags, low in P₂O₅–content, based on the systems FeO_n–CaO–SiO₂ and FeO_n–CaO–Al₂O₃. Slag compositions have been optimized with respect to basicity and oxygen potential to achieve maximum partition ratios wt.%(P₂O₅)/wt.%[P] and minimum phosphorus contents in pure molten iron at 1550, 1600 and 1700°C. Both slag systems prove to be effective dephosphorizers. Optimal slag compositions are around 10 wt.% SiO₂ near the CaO–3CaO · SiO₂ double saturation in the case of FeO_n–CaO–SiO₂ slags and at Al₂O₃ contents tending to zero in the case of FeO_n–CaO–Al₂O₃ slags. Attempts were also made to present phosphate capacities C_PO4^3?, fractions of free oxygen ions x_O^2? and theoretical optical basicities Λ as a function of the FeO_n content of slags.     

Fundamentals of power spectra of extracellular potentials produced by a skeletal muscle fibre of finite length. Part I: Effect of fibre anatomy

To provide a thorough understanding of the changes in the power spectrum of electromyographic (EMG) signals, the formation of the power spectrum (PS) of extracellular potentials (EPs) produced by a skeletal muscle fibre of finite length was analysed. It was shown that, as in the case of an infinite fibre, the PS could be represented as the product of power spectra of the input signal (the first temporal derivative of the intracellular action potential, IAP) and of the impulse response (IR) of the fibre of finite length as a system of EP generation. The interrelations between the two multipliers determine the sensitivity of the EP power spectrum to alterations in parameters. The anatomical parameters of the fibre (length, depth, position of the end-plate in respect of the fibre ends) affect the EP power spectrum through IR power spectrum. Variations of the EP characteristic frequencies along the fibre length as well as oscillations in the PS are intrinsic properties of the fibre of finite length.     

The effect of antenatal corticosteroid prophylaxis in premature newborns with the use of surfactant therapy

The influence of new probiotics from bacilli i.e. biosporin and subalin on the functional activity of murine peritoneal macrophages was studied. After a single oral administration of the probiotics the maximum activation of the macrophages was observed in 4 hours. The activation level depended on both the dose and the probiotic. The highest value of the stimulation index was recorded with subalin. Analogous regularities were stated with parenteral administration of the probiotics. Some mechanisms of activation of peritoneal macrophages after oral administration of probiotics from live microbial cultures are discussed.     

Competitive Weighted Matching in Transversal Matroids

Consider a bipartite graph with a set of left-vertices and a set of right-vertices. All the edges adjacent to the same left-vertex have the same weight. We present an algorithm that, given the set of right-vertices and the number of left-vertices, processes a uniformly random permutation of the left-vertices, one left-vertex at a time. In processing a particular left-vertex, the algorithm either permanently matches the left-vertex to a thus-far unmatched right-vertex, or decides never to match the left-vertex. The weight of the matching returned by our algorithm is within a constant factor of that of a maximum weight matching, generalizing the recent results of Babaioff et?al.