Thermostable variants constructed via the structure-guided consensus method also show increased stability in salts solutions and homogeneous aqueous-organic media

Enzyme instability is a major factor preventing widespread adoption of enzymes for catalysis. Stability at high temperatures and in the presence of high salt concentrations and organic solvents would allow enzymes to be employed for transformations of compounds not readily soluble in low temperature or in purely aqueous systems. Furthermore, many redox enzymes require costly cofactors for function and consequently a robust cofactor regeneration system. In this work, we demonstrate how thermostable variants developed via an amino acid sequence-based consensus method also showed improved stability in solutions with high concentrations of kosmotropic and chaotropic salts and water-miscible organic solvents. This is invaluable to protein engineers since deactivation in salt solutions and organic solvents is not well understood, rendering a priori design of enzyme stability in these media difficult. Variants of glucose 1-dehydrogenase (GDH) were studied in solutions of different salts along the Hofmeister series and in the presence of varying amounts of miscible organic solvent. Only the most stable variants showed little deactivation dependence on salt-type and salt concentration. Kinetic stability, expressed by the deactivation rate constant k(d,obs), did not always correlate with thermodynamic stability of variants, as measured by melting temperature T(m). However, a strong correlation (R(2) > 0.95) between temperature stability and organic solvent stability was found when plotting T(50)(60) versus C(50)(60) values. All GDH variants retained stability in homogeneous aqueous-organic solvents with >80% v/v of organic solvent.     

A new approximate solution for chlorine concentration decay in pipes

Biswas et al. (1993. A model for chlorine concentration decay in pipes. Water Res. 27(12), 1715-1724) presented an analytical solution of a two-dimensional (2-D) steady-state chlorine transport equation in a pipe under the turbulent condition and employed fractional error function and regression technique to develop an approximate solution. However, their approximate solution may not give a good result if the wall decay parameter is large. This paper provides a more accurate approximate solution of the 2-D steady-state chlorine transport equation under the turbulent condition. This new approximate solution has advantages of easy evaluation and good accuracy when compared with the approximate solution given by Biswas et al. (1993). In addition, this paper also develops a methodology that combines simulated annealing (SA) with this new approximate solution to determine the wall decay parameter. Two cases are chosen to demonstrate the application of the present approximate solution and methodology. The first case is to use this new approximate solution in simulating chlorine decay in pipes with the experiment-observed data given by Rossman (2006. The effect of advanced treatment on chlorine decay in metallic pipes. Water Res. 40(13), 2493-2502), while the second case presents the determination of the wall consumption at the end of the pipe network.     

Adsorption of Cu from water using raw and modified coal fly ashes

In this study, we found that both raw and modified coal fly ashes effectively adsorb Cu²⁺ from wastewater. The adsorption capacities followed the order CFA> CFA-600> CFA-NaOH. The adsorption isotherms for Cu²⁺ on the raw and modified coal fly ashes fit the Langmuir, Freundlich, and DKR isotherms quite well. These adsorptions were endothermic in nature; the values of E (between 1.3 and 9.6 kJ mol⁻¹) were consistent with an ion-exchange adsorption mechanism. The adsorptions of Cu²⁺ onto CFA, CFA-600, and CFA-NaOH followed pseudo-second-order kinetics.     

Negative air ions releasing properties of tourmaline contained ethylene propylene diene terpolymer/polypropylene thermoplastic elastomers

The releasing properties of negative air ions of tourmaline contained polypropylene (PP) and ethylene propylene diene terpolymer/polypropylene (EPDM/PP) composite films under varying testing conditions were investigated in this study. It is interesting to note that the C_ion− values of EPDM/PP/tourmaline specimens tested at varying conditions are significantly higher than those of the PP/tourmaline specimens with the same loadings of tourmaline powders. Moreover, all C_ion− values of PP/tourmaline and EPDM/PP/tourmaline film specimens tested at dynamic impact mode are significantly higher than those of the corresponding specimens tested at static mode but the same temperature. A beneficial temperature effect on C_ion− values of the PP/tourmaline and EPDM/PP/tourmaline film specimens tested at static and dynamic impact conditions was found. To understand these interesting negative air ion properties of PP/tourmaline and EPDM/PP/tourmaline film specimens, energy dispersive X-rays analysis of the tourmaline powders, scanning electron microscope morphology, and tensile property analysis of the PP/tourmaline and EPDM/PP/tourmaline film specimens were performed. Possible reasons account for the interesting negative air ion properties of the PP/tourmaline and EPDM/PP/tourmaline film specimens are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of the ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends on their physical properties

This study examined the effect of the ultradrawing behavior of gel film specimens of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and UHMWPE/low‐molecular‐weight polyethylene (LMWPE) blends on their physical properties. The concentration of a gel film approximated its critical concentration at a fixed drawing temperature; its achievable draw ratio was higher than that of other blend specimens with various concentrations. Noticeably, when about 5 wt % LMWPE was added to a UHMWPE/LMWPE gel film specimen, the achievable draw ratio of the gel film increased, and this contributed to an apparent promoting effect on its anticreeping properties and thermal stability. Therefore, when UL_B?0.9 was drawn to a draw ratio of 300, the anticreeping behavior was improved to less than 0.026%/day. Moreover, with respect to the thermal stability, when the same specimen was drawn to a draw ratio of 300, the retention capability of its storage modulus could resist a high temperature of 150°C, which was obviously much higher than the temperature of an undrawn gel film specimen (70°C). To study these interesting behaviors further, this study systematically investigated the gel solution viscosities, anticreeping properties, dynamic mechanical properties, thermal properties, molecular orientations, and mechanical properties of undrawn and drawn UHMWPE/LMWPE gel film specimens. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Crystallization of poly(butylene terephthalate)/poly(ethylene octene) blends: Nonisothermal crystallization

Poly(ethylene octene) (POE), maleic anhydride grafted poly(ethylene octene) (mPOE), and a mixture of POE and mPOE were added to poly(butylene terephthalate) (PBT) to prepare PBT/POE (20 wt % POE), PBT/mPOE (20 wt % mPOE), and PBT/mPOE/POE (10 wt % mPOE and 10 wt % POE) blends with an extruder. The melting behavior of neat PBT and its blends nonisothermally crystallized from the melt was investigated with differential scanning calorimetry (DSC). Subsequent DSC scans exhibited two melting endotherms (T_mI and T_mII). T_mI was attributed to the melting of the crystals grown by normal primary crystallization, and T_mII was due to the melting of the more perfect crystals after reorganization during the DSC heating scan. The better dispersed second phases and higher cooling rate made the crystals that grew in normal primary crystallization less perfect and relatively prone to be organized during the DSC scan. The effects of POE and mPOE on the nonisothermal crystallization process were delineated by kinetic models. The dispersed phase hindered the crystallization; however, the well‐ dispersed phases of an even smaller size enhanced crystallization because of the higher nucleation density. The nucleation parameter, estimated from the modified Lauritzen–Hoffman equation, showed the same results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Low-temperature mild partial oxidation of ethanol over supported platinum catalysts

Supported platinum catalysts containing 1.2% Pt loaded on Al₂O₃ (1.2% Pt/Al₂O₃) and 1.9% Pt loaded on ZrO₂ (1.9% Pt/ZrO₂) were prepared by incipient wetness impregnation and sol–gel method, respectively. The activity of these catalysts in the partial oxidation of ethanol (POE) was examined in a fixed-bed reactor in a temperature range between 373 and 473 K. The results indicated that significant ethanol conversion (C_EtOH > 50%) was found at the low reaction temperature with a feed ratio of O₂/EtOH ratio >0.75. Oxygen molecules introduced in reactant were completely consumed in POE reactions performed. H₂, H₂O, CO and CO₂ were the major products detected. The selectivity of hydrogen (S_H2) and CO (S_CO) varied significantly with reaction conditions. High selectivity of hydrogen (S_H2 > 95%) and low selectivity of CO (S_CO  0%) were found from a mild oxidation at T_R = 373 K over Pt/ZrO₂. However, these two selectivities were drastically deteriorated through oxidation at high T_R, high O₂/EtOH ratio or over Pt/Al₂O₃ catalyst.     

Understanding the Effects of CoAl2O4 Inoculant Additions on Microstructure in Additively Manufactured Inconel 718 Processed Via Selective Laser Melting

The effect of varying amounts of CoAl₂O₄ inoculant ranging from 0 to 2 wt pct on the microstructure evolution of Inconel 718(IN718) fabricated by selective laser melting (SLM) was evaluated. Characterization of the as-built microstructure revealed that addition of CoAl₂O₄ resulted in a modest degree of grain refinement with a slight increase in microstructural anisotropy. Increasing the total CoAl₂O₄ content beyond 0.2 wt pct resulted in severe agglomeration of the non-metallic particles and the formation of slag inclusions measuring up to 100 μm in size present in the as-built microstructure. In addition to large agglomerates, the inoculant was chemically reduced to form a fine dispersion of submicron-sized Al₂O₃ particles throughout the IN718 matrix. The fine dispersion of oxides significantly hindered grain recrystallization during the post-fabrication heat treatment due to a Zener pinning effect. The findings from this study indicate in order to effectively utilize CoAl₂O₄ as a grain refining inoculant for additive manufacturing, the process parameters need to be optimized to avoid agglomeration of the non-metallic particles and other process-related defects.

     

Synthesis and electroluminescent property of tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum

An emission material, tris{2-(naphtha [3,4]imidazol-2-yl) pyridinato} Aluminum (AlNIP) used for organic light emitting devices, has been synthesized. The decomposition temperature was observed at 510 °C and no melting transition (T_m) of AlNIP was observed up to 400 °C. The emission spectrum of organic emitting device using AlNIP as emitted layer exhibits a broad maximum at 536 nm. The color of the emitted light is in the orange region in the CIE coordinate of x = 0.41 y = 0.53.