Modified Biphasic Mixture Model and Its Numerical Penalty Formulation

A new term involving the rate of pressure change is introduced into the continuity equation of an existing biphasic mixture model. Based on this new continuity equation, a penalized numerical formulation of finite element method is given. Computational result shows that this new biphasic mixture model can provide better description of the transient response of biological media such as articular cartilage, muscle, and soft tissue.

Biphasic reduction model for predicting the impacts of dye-bath constituents on the reduction of tris-azo dye Direct Green-1 by zero valent iron(Fe^0)

Influence of common dye-bath additives, namely sodium chloride, ammonium sulphate,urea, acetic acid and citric acid, on the reductive decolouration of Direct Green 1 dye in the presence of Fe0 was investigated. Organic acids improved dye reduction by augmenting Fe0 corrosion, with acetic acid performing better than citric acid. Na Cl enhanced the reduction rate by its ‘salting out’ effect on the bulk solution and by Cl-anion-mediated pitting corrosion of iron surface.（NH4）2SO4induced ‘salting out’ effect accompanied by enhanced iron corrosion by SO42-anion and buffering effect of NH4＋ improved the reduction rates.However, at 2 g/L（NH4）2SO4concentration, complexating of SO42-with iron oxides decreased Fe0 reactivity. Urea severely compromised the reduction reaction, onus to its chaotropic and‘salting in’ effect in solution, and due to it masking the Fe0 surface. Decolouration obeyed biphasic reduction kinetics（R2〉 0.993 in all the cases） exhibiting an initial rapid phase,when more than 95% dye reduction was observed, preceding a tedious phase. Maximum rapid phase reduction rate of 0.955/min was observed at p H 2 in the co-presence of all dye-bath constituents. The developed biphasic model reckoned the influence of each dye-bath additive on decolouration and simulated well with the experimental data obtained at pH 2.

UV disinfection of Staphylococcus aureus in ballast water: Effect of growth phase on the disinfection kinetics and the mechanization at molecular level

This work aimed to study the inactivate kinetics of Staphylococcus aureus （S. aureus） in artificial seawater by ultraviolet radi- ation, establish relationships between model parameters and growth phases, and explain the mechanization of UV disinfection by molecular biological detection. Investigations were carried out for the validation of Chick-Watson, Collins-Selleck, Horn and Biphasic models when S. aureus was in stationary phase （t=14 h）. The results showed that the Biphasic kinetic model＇s R2 turned out to be the highest one （R2=0.9892） and RMSE was less than 0.5 （RMSE =0.2699）. The Biphasic kinetic model was better fit for ultraviolet disinfection than the other three models under the circumstance of this experiment and chosen to fit the ultraviolet disinfection curves for microorganisms at three growth phases. The sensitivity of microorganisms under ultraviolet radiation was in the following order： in exponential phase 〉 in stationary phase 〉 in lag phase by comparing the indexes of the Biphasic model （kl and x）. Besides, agarose gel electrophoresis was used in order to directly assess the damage to DNA of mi- croorganisms that were exposed to the different dose of UV irradiation. The results revealed that DNA damage caused by UV radiation was an important reason for the microorganism inactivation and as the UV dose increased, there was greater damage caused in DNA.

Kinetic studies of xylan hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor

Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric xylose was modeled by a series offirst-order reactions.Both biphasic and Saeman hydrolysis models were applied tofit the experimental data.The results confirmed that the kinetic data of xylan hydrolysisfitted afirst-order irreversible reaction model and the experimental data.The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature.Higher catalyst concentra-tion and lower reaction temperature result in high xylose yield.The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^(-1),respectively.Over 90%theoretical xylose obtained from corn stover can be used to produce ethanol,xylitol and fumaric acid by fermentation.