Concurrent effect of microporosity and chemical structure on the equilibrium sorption properties of cellulose-based hydrogels

Polyelectrolite hydrogels are crosslinked polymers which display high sorption capacity in water and water solutions. They are widely used in the marked of personal hygiene products, as well as in other biomedical and industrial applications. In the most industrial application they are not biodegradable and prepared starting from acrylamide.In this work, the chemical-physical analysis of a novel class of natural polymers-based microporous superabsorbent hydrogels has been presented. The main focus is the definition of the relationship between material's chemical-physical structure and its equilibrium sorption properties.The effect of the variation of the degree of crosslinking, the polyelectrolyte nature of the backbone and the hydrogel microporosity on its swelling properties has been analysed, and a good agreement with the theoretical statements has been displayed.The effect of the ionic strength and the pH of the external solution in contact with the hydrogel on its equilibrium sorption properties has also been assessed, and an high sensitivity to these variations was detected for all the tested chemical compositions and physical structures.This work have to be considered part of the efforts towards the reduction of the environmental impact of the large scale consumption industrial polymer based products.     

Cryptosporidium Log-inactivation with Ozone Using Effluent CT10, Geometric Mean CT10, Extended Integrated CT10 and Extended CSTR Calculations

The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit.     

Simulations of the mobile phase of polyethylene

Results are presented from atomistic molecular dynamics simulations of the mobile pseudo-hexagonal phase of polyethylene, which occurs under conditions of elevated pressure and temperature. Three different types of model are considered, all of which employ periodic boundary conditions. The first model consists of n-alkane sequences (48×-C₂₄H₄₈-) that are bonded across the simulation box boundaries to produce chains that are effectively infinite in extent. On heating, at high pressure, this system displays a rotator phase, in which the chains retain an all-trans conformation, and rotate as semi-rigid units. A second model, consisting of finite n-alkanes (48×C₂₄H₅₀) displays the same behaviour at low temperatures, but at high temperature and pressure forms a conformationally disordered rotator phase, characterised by a large proportion of gauche defects and a significant lattice expansion. The final model considered contains long n-alkanes (24×C₁₀₂H₂₀₆) which contain jog defects and each pass twice through the simulation box. This model forms a conformationally disordered rotator phase at high temperature and ambient pressure. The behaviour of the three models, in terms of the variations in chain conformation and rotational and translational dynamics, are compared. The conformationally disordered phases provide useful representations of the experimentally observed mobile phase.     

Electrocatalysis of chlorine evolution on different materials and its influence on the performance of an electrochemical reactor for indirect oxidation of pollutants

Two different Ti/Pt–Ir materials (commercial and home made) and Ti/PdO + Co₃O₄ were investigated for their electrocatalytic properties versus Cl₂ evolution reaction. The materials were used in a batch electrochemical reactor to treat biologically recalcitrant di-azo compound. An electrochemically driven oxidation, mediated by a Cl₂/Cl⁻ couple, proved efficient for destruction of this complex organic molecule, causing cleavage of the conjugated double bonds and destruction of unsatured bonds. Both Ti/Pt–Ir materials performed well; lower kinetics obtained with the Ti/PdO + Co₃O₄ anode was caused by adsorption of the model compound, evidenced in preliminary voltammetric measurements. The dye oxidation reaction followed the second order kinetics with partial orders in the model compound and (time varying) chlorine concentrations equal to one. Specific energy consumption of 3.12 kWh m⁻³ proved the process more economic than the homogeneous phase oxidation.     

The focusing magnetic resonance system with a new type of supersonic atomic beam source

A focusing magnetic resonance system (MRS) with a new type of supersonic atomic - and molecular - beam source is suggested. The beam sources used in the MRS are discussed and the main operation principles of the suggested supersonic beam source as well as the advantages of this type of source over the rest are shown. An optimization procedure for the magnetic resonance system with the effect of the finite source size taken into account is considered. Numerical results are given and analyzed. The MRS with the new type of beam source possesses higher transmission with low background and is simpler and cheeper in construction as compared to the conventional systems.     

Counterface topographical effects on the wear of polyetheretherketone and a polyetheretherketone-carbon fiber composite

The unlubricated sliding wear behavior of non-reinforced polyetheretherketone (PEEK) and a PEEK-carbon fiber (PEEK-C_f) composite was investigated under lightly loaded conditions against mild steel counterfaces. The results showed the occurrence of a relative minimum in wear for the non-reinforced PEEK-mild steel system, resulting from interfacial film formation. In addition, the wear particle morphology changed substantially as the counterface became rougher. For PEEK on abraded mild steel, attempts were made to correlate the wear rate with the average asperity radius model of Hollander and Lancaster. The PEEK-C_f composite, when compared under similar experimental conditions, also displayed a relative minimum in wear; however, it occurred against rougher counterfaces compared with those corresponding to the non-reinforced PEEK. In this case, the relative wear and transferred wear debris morphology reflected the addition of the carbon fibers.     

Low-thermal expansion polycrystalline tantalum tungstate ceramics

The synthesis of thermal-shock-resistant materials from the system Ta₂O₅WO₃ was investigated. Ta₂WO₈ had a very low unit-cell thermal expansion coefficient (+0.5 X 10^–6° C^–1). Ta₃₀W₂O₈₁ also had a relatively low coefficient (+4.0 X 10^–6 ° C^–1) and a thermal durability over 1600° C. The thermal expansion curves of these polycrystalline ceramics were lowered because of microcracks caused by the large thermal expansion anisotropy of the crystal axes and were accompanied by hysteresis loops. The densification of Ta₂WO₈ ceramic was promoted by the addition of some metal oxides, and the strong ceramic of Ta₃₀W₂O₈₁ was obtained by controlling grain growth.     

Microbial sensor for preliminary screening of mutagens utilizing a phage induction test

For the preliminary screening of mutagens, a novel microbial sensor system was developed utilizing a phage induction test. Escherichia coli lysogenic strain GY5027 and nonlysogenic strain GY5026 were used in this study. The number of living cells was determined by measuring the respiration of cells immobilized onto an oxygen electrode. The injection of a mutagen, such as AF-2 and MNNG, caused the phage induction in the lysogenic strain, resulting in the decreased respiration of only the lysogenic strain immobilized onto the oxygen electrode but not of nonlysogenic strain. The rate of current increase correlated well with the concentration of mutagens. The sensor responses to the antibiotics and bactericides were definitely different from those of mutagens. Therefore, utilization of this microbial sensor system makes possible the estimation of a substrate's mutagenicity.