Two-dimensional modeling of the self-limiting oxidation in silicon and tungsten nanowires

AbstractSelf-limiting oxidation of nanowires has been previously described as a reaction- or diffusion-controlled process. In this letter, the concept of finite reactive region is introduced into a diffusion-controlled model, based upon which a two-dimensional cylindrical kinetics model is developed for the oxidation of silicon nanowires and is extended for tungsten. In the model, diffusivity is affected by the expansive oxidation reaction induced stress. The dependency of the oxidation upon curvature and temperature is modeled. Good agreement between the model predictions and available experimental data is obtained. The developed model serves to quantify the oxidation in two-dimensional nanostructures and is expected to facilitate their fabrication via thermal oxidation techniques

Seismic response of highway viaducts equipped with lead-rubber bearings under low temperature

Based on a FEM based nonlinear dynamic numerical method, this study investigates the detrimental effects of low temperature on the seismic responses of a highway viaduct equipped with Lead-Rubber Bearings (LRBs). In this method, a dynamic bearing property definition is introduced to account for the temperature variation caused by the absorbed earthquake energy and the corresponding property variation of LRBs. Under low temperature conditions, the base isolation effect of LRBs which are well-designed for room temperature is significantly weakened, manifested by shorter fundamental structural natural periods and more damages and forces imposed to structure members, such as a 5-13% increment of shear force transferred by the LRBs, an increasing area of the hysteresis loop of the bending moment at the bottom of piers, and an increasing residual displacement at the top of piers. In addition, through jointed investigating the seismic responses under both long and short durations of earthquake motions, it is demonstrated that the heat production in LRBs over an earthquake can alleviate the detrimental effect of low temperature, and the extent of this alleviation is positively correlated to the earthquake duration. Therefore, the low temperature effect and the property variation of LRBs over an earthquake should be comprehensively considered for the designation of LRBs installed in bridge viaducts located in cold regions and the realization of an accurate seismic analysis of the bridge viaducts

SEISMIC RESPONSE OF CURVED GRILLAGE GIRDER VIADUCTS WITH BASE ISOLATION SYSTEM IN COLD REGION

The Thirteenth East Asia-Pacific Conference on Structural Engineering and Construction (EASEC-13), September 11-13, 2013, Sapporo, Japan

Derivation of water flooding characteristic curve for high water-cut oilfields

The linear relationship between relative permeability ratio (Kro/Krw) and water saturation (Sw) on the semi-log coordinate in the stage of middle water-cut is the theoretical basis for the derivation of traditional water flooding characteristic curve. However, the relationship of Kro/Krw versus Sw deviates from the straight line in the high water-cut stage, which results in the upwarping of water flooding characteristic curve. In order to accurately predict the production performance and recoverable reserves in the late development stage, the relative permeability curves of actual cores were averaged. Furthermore, using the core data in the reference, a new expression of Kro/Krw versus Sw was obtained by regression for the high water-cut stage. On the basis of the frontal-drive equation and the average water saturation equation proposed respectively by Buckley-Leverett and Welge, a new water flooding characteristic curve was derived which is more applicable for high water-cut oilfields. The calculation results indicate that the recoverable reserve calculated by the new approach is almost equal to the result of the production decline method, proving it is a practical tool in the prediction of production indexes in the late development stage of oilfields. Key words: water flooding characteristic curve, high water-cut, relative permeability, water saturation, production decline, recoverable reserve

Synthesis and Antiproliferative Activity of Steroidal Thiosemicarbazone Platinum (Pt(II)) Complexes

Steroidal compounds exhibit particular physiological activities. In this paper, some steroidal thiosemicarbazones platinum (Pt(II)) complexes were synthesized by the condensation of steroidal ketones with thiosemicarbazide using estrone, chenodeoxycholic acid, and 7-deoxycholic acid as starting materials and complexation of steroidal thiosesemicarbazones with Pt(II). The complexes were characterized by IR, NMR, and MS, and their antiproliferative activities were evaluated. The results showed that some steroidal thiosemicarbazones platinum (Pt(II)) complexes displayed moderate cytotoxicity to HeLa and Bel-7404 cells. Thereinto, complex 6 showed an excellent inhibited selectivity to HeLa cells with an IC50 value of 9.2 μM and SI value of 21.7. At the same time, all compounds were almost inactive to HEK293T (normal kidney epithelial cells). The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs

Synthesis and Antiproliferative Activity of Steroidal Thiosemicarbazone Platinum (Pt(II)) Complexes

Steroidal compounds exhibit particular physiological activities. In this paper, some steroidal thiosemicarbazones platinum (Pt(II)) complexes were synthesized by the condensation of steroidal ketones with thiosemicarbazide using estrone, chenodeoxycholic acid, and 7-deoxycholic acid as starting materials and complexation of steroidal thiosesemicarbazones with Pt(II). The complexes were characterized by IR, NMR, and MS, and their antiproliferative activities were evaluated. The results showed that some steroidal thiosemicarbazones platinum (Pt(II)) complexes displayed moderate cytotoxicity to HeLa and Bel-7404 cells. Thereinto, complex 6 showed an excellent inhibited selectivity to HeLa cells with an IC 50 value of 9.2 M and SI value of 21.7. At the same time, all compounds were almost inactive to HEK293T (normal kidney epithelial cells). The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs

Synthesis and Cytotoxic Evaluation of Steroidal Copper (Cu (II)) Complexes

Using estrone and pregnenolone as starting materials, some steroidal copper complexes were synthesized by the condensation of steroidal ketones with thiosemicarbazide or diazanyl pyridine and then complexation of steroidal thiosemicarbazones or steroidal diazanyl pyridines with Cu (II). The complexes were characterized by IR, NMR, and HRMS. The synthesized compounds were screened for their cytotoxicity against HeLa, Bel-7404, and 293T cell lines in vitro. The results show that all steroidal copper (II) complexes display obvious antiproliferative activity against the tested cancer cells. The IC50 values of complexes 5 and 12 against Bel-7404 (human liver carcinoma) are 5.0 and 7.0 μM