Preparation and characterization of extruded nanocomposite based on polycarbonate/butadiene‐acrylonitrile‐styrene blend filled with multiwalled carbon nanotubes

Nanocomposites of polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) with multiwall carbon nanotubes (MWCNT) prepared by masterbatch dilution are investigated in this work. Melt compounding with twin screw extruder is followed by complete characterization of morphology, rheological‐, mechanical‐, and thermal‐properties of the nanocomposites. Light‐transmission‐ and scanning electron microscopy shows the preferential location of MWCNT in the PC. Nevertheless, relatively good dispersion in the whole matrix is achieved, what is corroborated with the specific mechanical energy. The study of viscoelastic properties of PC/ABS‐MWCNT shows the fluid–solid transition below 0.5 wt % MWCNT. Beyond this point the continuous nanofiller network is formed in the matrix promoting the reinforcement. Addition of 0.5 wt % MWCNT reduces ductility of PC/ABS and enhances Young's modulus by about 30% and yield stress by about 20%. Moreover, theoretical values of stiffness calculated within this work agree with the experimental data. Electrical conductivity, showing percolation at 2.0 wt % MWCNT, are influenced by processing temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40271.     

Macrophages Compensate for Loss of Protein Tyrosine Phosphatase N2 in Dendritic Cells to Protect from Elevated Colitis

Protein tyrosine phosphatase nonreceptor type 2 (PTPN2) plays a critical role in the pathogenesis of inflammatory bowel diseases (IBD). Mice lacking PTPN2 in dendritic cells (DCs) develop skin and liver inflammation by the age of 22 weeks due to a generalized loss of tolerance leading to uncontrolled immune responses. The effect of DC-specific PTPN2 loss on intestinal health, however, is unknown. The aim of this study was to investigate the DC-specific role of PTPN2 in the intestine during colitis development. PTPN2^fl/flxCD11c^Cre mice were subjected to acute and chronic DSS colitis as well as T cell transfer colitis. Lamina propria immune cell populations were analyzed using flow cytometry. DC-specific PTPN2 deletion promoted infiltration of B and T lymphocytes, macrophages, and DCs into the lamina propria of unchallenged mice and elevated Th1 abundance during acute DSS colitis, suggesting an important role for PTPN2 in DCs in maintaining intestinal immune cell homeostasis. Surprisingly, those immune cell alterations did not translate into increased colitis susceptibility in acute and chronic DSS-induced colitis or T cell transfer colitis models. However, macrophage depletion by clodronate caused enhanced colitis severity in mice with a DC-specific loss of PTPN2. Loss of PTPN2 in DCs affects the composition of lamina propria lymphocytes, resulting in increased infiltration of innate and adaptive immune cells. However, this did not result in an elevated colitis phenotype, likely because increased infiltration of macrophages in the intestine upon loss of PTPN2 loss in DCs can compensate for the inflammatory effect of PTPN2-deficient DCs.     

Effect of sugars on the mechanical and thermal properties of agarose gels

The present study examines the thermal and mechanical properties of agarose/sugar mixtures using micro-DSC (Differential Scanning Calorimetry) and Dynamic Mechanical Thermal Analyser. In DSC experiments, addition of sugar was reflected in a broad exothermic event compared to sharp transitions generated by the aqueous agarose preparation. At high levels of co-solute, agarose networks show a reduced enthalpic content per gram of the polymer thus arguing for a transformation to a more entropic finely stranded networks of reduced number of junctions zones, the networks exhibited long large deformation properties. At high levels of sugar, agarose samples show a mechanical spectrum that can be modelled according to the WLF/free-volume theory, which requires an entropic lightly cross-linked network.     

Aluminium and Its Complexes in Teas and Fruity Brew Samples,Speciation and Ions Determination by Ion Chromatography and High-Performance Liquid Chromatography–Fluorescence Analytical Methods

The paper presents results of aluminium determination in samples of black and fruit teas. Total aluminium concentration was determined along with the concentration of aluminium in a cup of tea in tea samples in two price groups (>1€ and <1€). Based on the conducted study, no differences were found in aluminium concentration in black and fruit teas depending on the price group. Developed ion chromatography method was applied to determine inorganic and organic ions in tea samples, especially those which may form complexes with aluminium: fluoride, sulphate, oxalate and citrate ions. Analysis by this method using ion chromatography allowed for the determination of 12 anions: F^?, HCOO^?, CH₃COO^?, NO₂ ^?, Br^?, NO₃ ^?; Cl^?, CH₂(COO)₂ ^2?, SO₄ ^2?, C₂O₄ ^2?, PO₄ ^3? and C₃H₅O(COO)₃ ^3? in the time of 40 min. Speciation analysis of aluminium was performed in optimised HPLC-fluorescence analytical system (with Lumogallion as a post-column reagent). It was observed that organic aluminium complexes are quickly degraded to form Al³⁺ which is the reason why speciation analysis in tea samples does not provide the full image of speciation distribution. Nevertheless, this developed method was successfully used in the determination of aluminium complexes with fluorides in tea samples.     

Fusing two cytochromes b of Rhodobacter capsulatus cytochrome bc1 using various linkers defines a set of protein templates for asymmetric mutagenesis

Cytochrome bc(1) (mitochondrial complex III), one of the key enzymes of biological energy conversion, is a functional homodimer in which each monomer contains three catalytic subunits: cytochrome c(1), the iron-sulfur subunit and cytochrome b. The latter is composed of eight transmembrane α-helices which, in duplicate, form a hydrophobic core of a dimer. We show that two cytochromes b can be fused into one 16-helical subunit using a number of different peptide linkers that vary in length but all connect the C-terminus of one cytochrome with the N-terminus of the other. The fusion proteins replace two cytochromes b in the dimer defining a set of available protein templates for introducing mutations that allow breaking symmetry of a dimer. A more detailed comparison of the form with the shortest, 3 amino acid, linker to the form with 12 amino acid linker established that both forms display similar level of structural plasticity to accommodate several, but not all, asymmetric patterns of mutations that knock out individual segments of cofactor chains. While the system based on a fused gene does not allow for the assessments of the functionality of electron-transfer paths in vivo, the family of proteins with fused cytochrome b offers attractive model for detailed investigations of molecular mechanism of catalysis at in vitro/reconstitution level.     

Flow patterns and transport in Rayleigh surface acoustic wave streaming: combined finite element method and raytracing numerics versus experiments

This work presents an approach for determining the streaming patterns that are generated by Rayleigh surface acoustic waves in arbitrary 3-D geometries by finite element method (FEM) simulations. An efficient raytracing algorithm is applied on the acoustic subproblem to avoid the unbearable memory demands and computational time of a conventional FEM acoustics simulation in 3-D. The acoustic streaming interaction is modeled by a body force term in the Stokes equation. In comparisons between experiments and simulated flow patterns, we demonstrate the quality of the proposed technique.     

Determination of sensitivity coefficients of the elastic effective properties for periodic fiber-reinforced composites using the response function method

Derivation and implementation of the homogenization method including determination of sensitivity gradients of the effective elasticity tensor using combined numerical-analytical approach are addressed in this paper. This is possible thanks to an application of the numerical response function together with the effective moduli method known from classical homogenization theory. Computational procedure is implemented using 4-noded quadrilateral plane strain finite elements (program MCCEFF) and the symbolic computations system MAPLE. The sensitivity coefficients are determined on the basis of partial derivatives of the homogenized elasticity tensor calculated using the response function method with respect to all composite components’ elastic characteristics. They are further separately subjected to normalization procedure for a final comparison with each other. Such an enriched homogenization procedure is tested on the periodic fiber-reinforced two component composites; the results of computational analysis are compared to the results of the central finite difference approach applied before. Computational methodology proposed here may be further successively applied not only in the context of homogenization method but also to extend various discrete computational techniques like boundary/finite element, finite difference and volumes together with various meshless methods.     

Environmental friendly polysaccharide modification – microwave‐assisted oxidation of starch

A “green” method for oxidized starch preparation was presented. Hydrogen peroxide (H₂O₂) was used as the starch oxidant. Two main types of experiments were investigated: catalytic (by means of sodium tungstate – Na₂WO₄, the hydrogen peroxide activator) and non‐catalytic processes. The research covers low microwave level synthesis. Ninety and one hundred and ninety watts of microwave power were applied for the samples. All the microwave‐assisted reactions were compared to conventional ones carried out at 80 and 90°C, respectively. Reaction was monitored using manganometric determination of H₂O₂ consumption during the reaction progress. Obtained reaction products were tested by means of carbonyl and carboxyl group content. Additionally, molecular mass changes were investigated and a preliminary rheological study was done. The observed significant differences in the degree of oxidation (monitored by means of carboxyl and carbonyl group content) as well as the changes in molecular mass of polysaccharide comparing to those found at conventional conditions were showed and discussed.     

Preparation,Crystal Structure and Explosive Properties of Copper(II) Perchlorate Complex with 4‐Amino‐1,2,4‐Triazole and Water

A complex from copper(II) perchlorate with 4‐amino‐1,2,4‐triazole (4‐AT, C₂H₄N₄) was synthesized, and elemental composition, molecular structure, and explosive properties were determined. To this end, elemental and X‐ray analyses were carried out, sensitivity to mechanical and thermal stimuli was measured, mechanism of thermal decomposition was investigated, and kinetic parameters of decomposition were determined. In the next step measurements of heat of combustion and detonation velocity were performed. Detonation parameters were also calculated. It was stated that the complex has slightly distorted square bipyramidal (4+2) coordination. The four basal bonds are formed by nitrogen atoms of four 4‐AT molecules. The coordination of the metal is completed by two axial oxygen atoms, one of the perchlorate ion, and one of the water molecule. With respect to explosive properties, tetrakis(4‐AT)copper(II) perchlorate monohydrate belongs to the group of sensitive secondary explosives.     

Wet electroscrubbers for state of the art gas cleaning

Current trends observed in air pollution control technology are closely related to the development of new, more efficient hybrid systems, i.e., those, which simultaneously utilize two or more physical mechanisms for dust or gaseous contaminants removal. These systems can operate more economically than conventional devices, especially in the removal of PM2.5 particles. The electrostatic scrubber (electroscrubber), discussed in this paper, is one of such types of devices, which combines advantages of electrostatic precipitators and inertial wet scrubbers, and removes many shortcomings inherent to both of these systems operating independently. The electroscrubber is a device in which Coulomb attraction or repulsion forces between electrically charged scrubbing droplets (collector) and dust particles are utilized for the removal of particles from a gas. Unlike wet electrostatic precipitators in which particles are precipitated only on the collection electrode, in electroscrubbers, the collection of dust particles takes place in the entire precipitator chamber. Compared to inertial scrubbers, the electroscrubbers can operate at lower droplet velocities, but the collection efficiency for a single droplet can be larger than 1. The paper reviews the state-of-the-art of wet electrostatic scrubbing (electroscrubbing) technique used for gas cleaning from dust or smoke particles. Three groups of problems are discussed: (1) The fundamental problems concerning the charged dust particle deposition on a charged collector, usually a drop, with a focus on different models describing the process. (2) The experimental works of fundamental importance to our knowledge referring to the scrubbing process, which can be used for validating the theory. (3) The laboratory demonstrations and industrial tests of different constructions of electroscrubbers designed for effective gas cleaning. The electroscrubber is not designed to replace wet or dry electrostatic precipitators but can be used as a complementary device following the last stage of conventional electrostatic precipitator, which helps to remove submicron particles. It was shown in the paper that a higher collection efficiency of an electroscrubber could be obtained for higher values of Coulomb number (i.e., higher electric charges on the collector and particle), and for a Stokes number lower than5 (i.e., low particle-collector relative velocity).