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High-impact polystyrene (HIPS)/nano-TiO 2 nanocomposites were prepared by surface pretreatment of nano-TiO 2 with special structure dispersing agent (TAS) and master batch manufacturing technology. The results show that when the nano-TiO 2 content is 2%, the notched impact strength, tensile strength, and elastic modulus of HIPS/ nano-TiO 2 nanocomposites increased to a maximum. This result indicates that nano-TiO 2 has both toughening and reinforcing effects on HIPS. The heat-deflection temperature and flame-retardance of HIPS/nano-TiO 2 nanocomposites are also obviously improved as the nano-TiO 2 content is increased. The nanocomposites manufactured by the twostep method have better mechanical properties than that made by a one-step method. HIPS/nano-TiO 2 nanocomposites are also non-Newtonian and pseudoplastic fluids.

Diets high in sugar are recognized as a serious health problem, and there is a drive to reduce their consumption. Steviol glycosides are natural zero-calorie sweeteners, but the most desirable ones are biosynthesized with low yields. UGT76G1 catalyzes the β (1–3) addition of glucose to steviol glycosides, which gives them the preferred taste. UGT76G1 is able to transfer glucose to multiple steviol substrates yet remains highly specific in the glycosidic linkage it creates. Here, we report multiple complex structures of the enzyme combined with biochemical data, which reveal that the enzyme utilizes hydrophobic interactions for substrate recognition. The lack of a strict three-dimensional recognition arrangement, typical of hydrogen bonds, permits two different orientations for β (1–3) sugar addition. The use of hydrophobic recognition is unusual in a regio- and stereo-specific catalysis. Harnessing such non-specific hydrophobic interactions could have wide applications in the synthesis of complex glycoconjugates.

An SIR epidemic model with incubation time and saturated incidence rate is formulated, where the susceptibles are assumed to satisfy the logistic equation and the incidence term is of saturated form with the susceptible. The threshold valueℜ0determining whether the disease dies out is found. The results obtained show that the global dynamics are completely determined by the values of the threshold valueℜ0and time delay (i.e., incubation time length). Ifℜ0is less than one, the disease-free equilibrium is globally asymptotically stable and the disease always dies out, while if it exceeds one there will be an endemic. By using the time delay as a bifurcation parameter, the local stability for the endemic equilibrium is investigated, and the conditions with respect to the system to be absolutely stable and conditionally stable are derived. Numerical results demonstrate that the system with time delay exhibits rich complex dynamics, such as quasiperiodic and chaotic patterns.