Cellular Mechanics of Modulated Osteoblasts Functions in Graphene Oxide Reinforced Elastomers

We describe here favorable modulation of osteoblasts functions and cell–substrate interactions in hybrid silicone elastomers consisting of biocompatible graphene oxide. Pressure induced curing was used to synthesize the hybrid silicone elastomer with high strength–high elongation combination. It was intriguing that the cell–substrate interactions in the hybrid silicone elastomer were observed to be significantly different from those observed in stand alone silicone. The origin of differences in cell–substrate interactions in terms of cell attachment, viability, and proliferation and assessment of proteins actin, vinculin, and fibronectin are addressed and attributed to physico‐chemical properties (topography and hydrophilicity) and to the presence of graphene oxide. The end outcome of the study is a new family of nanostructured polymer composite with desired (enhanced cell functions) and bulk properties (long term stability—high strength‐at‐break). The integration of cellular and molecular biology with material science and engineering described here provides an insight into the ability to modulate cellular and molecular reactions in promoting osteoinductive signaling of surface adherent cells, in the present case, osteoblasts for joint reconstruction.     

Validation of a reduced combustion mechanism for light hydrocarbons

Due to the tremendous costs and difficulties associated with flare measurements, computational fluid dynamics (CFD) simulation could be a viable approach to predict the combustion efficiency as well as VOC/NO _x emissions from industrial flaring activities. However, consisting of a large number of reactions and species, most of the detailed kinetic mechanisms for the speciation study of flaring events are too complicated to use in the CFD simulation of industrial-scale flares. A reduced combustion mechanism will lead to improved computational efficiency; however, its fidelity must be validated. This study uses 2D CFD simulations and 1D Chemkin simulations to validate a reduced mechanism developed for the combustion of light hydrocarbons up to C₁–C₃. This mechanism, consisting of 50 species and 337 reactions, is applicable to C₁–C₃ hydrocarbons and can be used to predict the combustion efficiency and fate of pollutants released from industrial flares composed of C₁–C₃ waste gases. In this article, experimental data reported in the literatures have been used to validate the reduced mechanism. The key performance indicators used for comparison are laminar burner-stabilized flames, laminar flame speeds, adiabatic flame temperatures, ignition delay tests, and temperature and concentration profiles of the critical species. The software package CHEMKIN 4.1.1 was used to verify the computational results of laminar flame speeds, adiabatic flame temperatures, and ignition delays. The axial profiles of various critical species are simulated using the commercial CFD software package FLUENT. It is demonstrated that simulation results using this reduced mechanism are in good agreement with reported experimental results.     

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb₃₀Hf₃₅Co₃₅/Pd composite membranes was investigated. The diameter of Pd particle increases with increasing sputtering power. With this change, the membrane shows a signification reduction in hydrogen permeability/or flux, but its durability and stability increases significantly, which can be mainly attributed to a decrease in hydrogen solubility coefficient. In addition, H₂S impurity in mixed gases can greatly degrade membrane performance, especially the hydrogen permeability, whereas the Ar impurity content has less effect in the temperature range of 523–673 K. Lowering of permeability caused by the change of gas purity can be attributed to a decrease in hydrogen solubility, which is closely related to the stronger adsorption of H₂S molecules to the Pd overlayer of the membrane. Thus, it is concluded that aside from the optimum design for composition of Nb-based hydrogen permeable alloy to improve their permeability, the control of Pd overlayer film on membrane surface and gas purity in the feed gas is important.     

Comparative study of mechanical and chemical methods for surface cleaning of a marine shell‐and‐tube heat exchanger

In this article, experimental analysis is done on shell‐and‐tube heat exchanger of a marine vessel for removal of fouling using optimum surface‐cleaning techniques. The main objective is to compare the performance of the heat exchanger before and after maintenance. Two identical deteriorated systems of heat exchangers are taken and real‐time analysis is conducted. The log data are taken before and after undergoing maintenance for the two systems. Two different cleaning techniques are used, namely, chemical cleaning and mechanical cleaning. Detailed calculations are made for the shell‐and‐tube heat exchanger. From the obtained data, comparisons are made for different parameters on the tube side such as friction factor, heat transfer coefficient and pressure drop, as well as total heat transfer rate on the shell side. From the analysis and comparison, it was found that greater heat transfer takes place for the tubes cleaned using the chemical cleaning method than for tubes cleaned by the mechanical cleaning method. Pressure drop is found to be less for chemical cleaning method than mechanical cleaning method. This indicates that the fouling effect is reduced for tubes cleaned by the chemical cleaning method, and furthermore these tubes remain corrosion‐resistant for longer periods of time.     

Continuous cooling transformation behavior and impact toughness in heat-affected zone of Nb-containing fire-resistant steel

Simulated heat-affected zone continuous cooling transformation diagram was developed for advanced fireresistant steel. Over a wide range of cooling rates, corresponding to t_8/5 from 6 s to 150 s, granular bainite was the dominant transformation constituent, while the morphology of less dominant martensite-austenite (M-A) constituent changed from film-like to block-type constituent; but the hardness remained similar to the average value of 190-205 HV (0.2). The start and finish transformation temperature was high at 700 °C and 500 °C, and is different from the conventional high strength low alloy steels. It is believed that the high-content (0.09 wt%) of Nb may promote bainite transformation at relatively high temperatures. Martenistic matrix was not observed at high cooling rate and the film-like M-A constituent and blocky M-A constituent with thin film of retained austenite and lath martensite were observed on slow cooling. Excellent impact toughness was obtained in the heat-affected zone with 15-75 kJ/cm welding heat input.     

Microstructure and High Temperature Impression Creep Properties of Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) Alloys

The current study has investigated the influence of zirconium (Zr) addition to Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) alloys prepared using argon arc melting on the microstructure and impression properties at 448–498 K under constant stress of 380 MPa. Microstructural analysis of as-cast Mg–3Ca–xZr alloys showed grain refinement with Zr addition. The observed grain refinement was attributed to the growth restriction effect of Zr in hypoperitectic Mg–3Ca–0.3 wt% Zr alloys. Heterogeneous nucleation of α-Mg in properitectic Zr during solidification resulted in grain refinement of hyperperitectic Mg–3Ca–0.6 wt% Zr and Mg–3Ca–0.9 wt% Zr alloys. The hardness of Mg–3Ca–xZr alloys increased as the amount of Zr increased due to grain refinement and solid solution strengthening of α-Mg by Zr. Creep resistance of Mg–3Ca–xZr alloys increased with the addition of Zr due to solid solution strengthening of α-Mg by Zr. The calculated activation energy (Q_a) for Mg–3Ca samples (131.49 kJ/mol) was the highest among all alloy compositions. The Q_a values for 0.3, 0.6 and 0.9 wt% Zr containing Mg–3Ca alloys were 107.22, 118.18 and 115.24 kJ/mol, respectively.     

Iron Oxide Nanoparticles Employed as Seeds for the Induction of Microcrystalline Diamond Synthesis

Iron nanoparticles were employed to induce the synthesis of diamond on molybdenum, silicon, and quartz substrates. Diamond films were grown using conventional conditions for diamond synthesis by hot filament chemical vapor deposition, except that dispersed iron oxide nanoparticles replaced the seeding. X-ray diffraction, visible, and ultraviolet Raman Spectroscopy, energy-filtered transmission electron microscopy , electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to study the carbon bonding nature of the films and to analyze the carbon clustering around the seed nanoparticles leading to diamond synthesis. The results indicate that iron oxide nanoparticles lose the O atoms, becoming thus active C traps that induce the formation of a dense region of trigonally and tetrahedrally bonded carbon around them with the ensuing precipitation of diamond-type bonds that develop into microcrystalline diamond films under chemical vapor deposition conditions. This approach to diamond induction can be combined with dip pen nanolithography for the selective deposition of diamond and diamond patterning while avoiding surface damage associated to diamond-seeding methods.