Effects of Different Freezing Temperatures on the Quality of Rice Dumpling Dough

To investigate the effects of different freezing temperatures on the quality of rice dumpling dough, this paper investigated the effects of freezing at −20, −30, −80, −196 ℃ (liquid nitrogen) on the physicochemical indexes of rice dumpling dough, such as texture characteristics, water loss rate and color. The water distribution and microstructures of rice dumpling dough were studied by NMR, MRI, SEM and other analytical techniques. The results showed that the lower the freezing temperature, the faster the freezing rate. With the decrease of freezing temperature, the water loss rate and light transmittance of rice dumpling dough improved significantly (P0.05) in whiteness, and the magnitude of textural changes was small. The microstructure of the rice dumpling dough was more complete at ultra-low temperature freezing. During the freezing process, the internal water state of the rice dumpling dough was changed, free water and multilayer water were transformed into bound water, liquid water molecules were reduced, and hydrogen proton density was decreased. Combined with the actual situation, the freezing temperature below −30 ℃ could significantly improve the quality of rice dumpling dough

Finite element analysis of the Poisson–Boltzmann equation coupled with chemical equilibriums: redistribution and transport of protons in nanophase separated polymeric acid–base proton exchange membranes

<p>The finite element analysis is applied to the study of the redistribution and transport of protons in model nanophase separated polymeric acid–base composite membranes by the Poisson–Boltzmann equation coupled with the acid and base dissociation equilibriums for the first time. Space charge redistribution in terms of proton and hydroxide redistributions is observed at the interfaces of acidic and basic domains. The space charge redistribution causes internal electrostatic potential, and thus, promotes the macroscopic transport of protons in the acid–base composite membranes.</p

Hydrogen Transfer Reaction in Polycyclic Aromatic Hydrocarbon Radicals

Density functional theory calculations have been successfully applied to investigate the formation of hydrocarbon radicals and hydrogen transfer pathways related to the chemical vapor infiltration process based on model molecules of phenanthrene, anthra­[2,1,9,8-<i>opqra</i>]­tetracene, dibenzo­[<i>a</i>,<i>ghi</i>]­perylene, benzo­[<i>uv</i>]­naphtho­[2,1,8,7-<i>defg</i>]­pentaphene, and dibenzo­[<i>bc</i>,<i>ef</i>]­ovalene. The hydrogen transfer reaction rate constants are calculated within the framework of the Rice–Ramsperger–Kassel–Marcus theory and the transition state theory by use of the density functional theory calculation results as input. From these calculations, it is concluded that the hydrogen transfer reaction between two bay sites can happen almost spontaneously with energy barrier as low as about 4.0 kcal mol^–1, and the hydrogen transfer reactions between two armchair sites possess lower energy barrier than those between two zigzag sites