Development of Encapsulation Systems from Zein and Metal-Organic Frameworks (MOFs) for Improved Functional Properties of Essential Oils

Essential oils (EOs), which are derived from plants, have antifungal, insecticidal and antimicrobial activities, but they are slightly soluble in water and impart to the water their odor and taste, which limit their applications in food area. Zein, a prolamin from corn, is able to form nanoparticles by liquid-liquid dispersion process. These nanoparticles are well dispersed in water and stable, which can be further applied to encapsulate functional materials that are insoluble in water. We have developed zein nanoparticles to encapsulate thymol and carvacrol in order to improve their solubility. The DLS (dynamic light scattering) and SEM (scanning electron microscopy) proved that zein nanoparticles encapsulated with EO were formed. The particles size was between 200~300nm before lyophilizing. 65-75% EOs have been encapsulated in the nano-sized particles. DPPH assay results proved good antioxidant property of the product. For the Ferric-ion spectrophotometric assay, hydroxyl free radicals had been cleared by 60~90% in overall. In the antimicrobial experiment, the nanoparticles encapsulating EOs reduced 0.8-1.8 log units of E. coli after 48h incubation. Furthermore, we have applied Metal-Organic Frameworks (MOFs) to encapsulate thymol. Metal-Organic Frameworks (MOFs) or porous coordination polymers (PCPs) is a new class of hybrid materials, which are formed by the self-assembly of metal-connecting points and polydentate bridging ligands. MOFs in this study was synthetized by Zinc nitrate hexahydrate and 2-aminoterephthalic acid in N, N-dimethylformamide (DMF). Thymol was then loaded inside the MOFs at the loading rate of 3.95%. The structure of porous crystal MOFs was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Inhibition to E. coli O157:H7 was measured both in TSB medium and on TSA agar. An E. coli O157:H7 reduction of 4.4 log CFU/mL have been achieved at a thymol to broth ratio of 0.04g/100g. An inhibition area of 223.73 mm2 was observed after 12h incubation. With the two methods (zein nano-particles and MOFs), EOs can be encapsulated and well dispersed in water solution. The enhanced antioxidant activity and antimicrobial ability of the encapsulated EOs promise their further applications in food industries

Thermal and dynamic behaviors of wheel/rail contact system considering thermal-mechanical coupling effects

In order to research the temperatures and dynamic characteristics of wheel/rail at different creep ratios, a thermal-mechanical coupling model of 3-D wheel/rail-foundation contact system and a new experimental device are introduced. The results indicate the temperatures ascend gradually with the growth of creep ratios, the maximum temperature of wheel and rail surface is respectively 626.1 °C and 514.2 °C. Because of the thermal effects, the accelerations of wheel/rail descend gradually with the rise of creep ratios. The influences of creep ratios on the vertical displacements are not obvious. The maximum absolute vertical displacement of wheel and rail is respectively 1.16 mm and 1.33 mm. And the normal contact force of wheel/rail and the dynamic factor ascend gradually with the rise of braking speeds

An Environment-Friendly Rock Excavation Method

Blasting is used as an economical tool for rock excavation in mines. However, part of the explosive energy is converted into elastic waves, resulting in ground vibration and excessive vibration, which may cause damage to nearby buildings. Meanwhile, toxic gases are also produced during the explosion. In this paper, an environment-friendly method for rock excavation is proposed. A series of vibration tests were conducted, and the peak particle velocity was monitored. The results showed that the proposed method can replace the conventional blasting method in mines. Besides that, the vibration caused by the proposed method is much smaller than by the conventional method. By adjusting the direction of the high-pressure gas injection, buildings around the mine can be protected well from vibration. Also, the production of toxic gases during excavation will no longer be a problem. Thus, a milder environmental impact can be achieved. However, the rocks excavated by the proposed method are relatively large, which still need to be broken further. On this issue, further study is required

Dynamic characteristics of vehicle-wheel/rail nonlinear contact-foundation system

To study the dynamic characteristics of the vehicle-wheel/rail-foundation system of high-speed trains with consideration of nonlinear wheel/rail contact relationship and effects of nonlinear wheel/rail contact behavior on the railway rail, foundation structure and vehicle, a three-dimensional finite element model of vehicle-wheel/rail nonlinear contact-foundation system is established by using ANSYS software in which, the special contact element is used to simulate wheel/rail nonlinear contact and instantaneous separation. The vertical vibration of the whole system and its spread parts due to the track irregularities are calculated. At the same time, the relationships between the vibration of the wheel/rail system and the train speed, foundation stiffness are analyzed. The numerical results show that the appropriate foundation stiffness is conducive to weaken the vertical acceleration of the vehicle and wheel/rail system, and the vertical displacement and wheel/rail contact stress on the rail top increase with the growth of the train speed. The procedure and results from this paper can provide reference for the design of vehicle-wheel/rail system

An Environment-Friendly Rock Excavation Method

Blasting is used as an economical tool for rock excavation in mines. However, part of the explosive energy is converted into elastic waves, resulting in ground vibration and excessive vibration, which may cause damage to nearby buildings. Meanwhile, toxic gases are also produced during the explosion. In this paper, an environment-friendly method for rock excavation is proposed. A series of vibration tests were conducted, and the peak particle velocity was monitored. The results showed that the proposed method can replace the conventional blasting method in mines. Besides that, the vibration caused by the proposed method is much smaller than by the conventional method. By adjusting the direction of the high-pressure gas injection, buildings around the mine can be protected well from vibration. Also, the production of toxic gases during excavation will no longer be a problem. Thus, a milder environmental impact can be achieved. However, the rocks excavated by the proposed method are relatively large, which still need to be broken further. On this issue, further study is required