Hyewon Hwang

Cyclooxygenase-2 expression in proliferative Ki-67-positive breast cancers is associated with poor outcomes.

In order to investigate the implications of cyclooxygenase-2 (COX-2) expression in combination with Ki-67 on breast cancer outcomes, the COX-2 and Ki-67 expression levels and other clinicopathologic parameters were investigated in 861 breast cancers. Clinicopathological parameters and survival were investigated in association with the expression levels of both COX-2 and Ki-67 using univariate and multivariate analyses. COX-2 expression was positive in 493 (57.3%) of invasive tumors. COX-2 was associated with favorable markers, but was not related to survival outcome by itself. However, COX-2 in proliferative tumors [COX-2(+)/Ki-67(+)] were significantly associated with unfavorable factors and the worst survival, but COX-2 in non-proliferative tumors [COX-2(+)/Ki-67(−)] showed significantly favorable parameters and better outcomes. COX-2(−)/Ki-67(any) showed intermediate prognosis. The statistical significance was maintained in stage-matched and multivariate analyses. The results of present study suggest that COX-2 expression is a common event in breast cancers and may play in a different ways by the proliferation status of the tumor cells. Further studies should be carried out to verify the role of COX-2 by proliferative conditions of breast tumor cells.

La2O3 interface modification of mesoporous TiO2 nanostructures enabling highly efficient perovskite solar cells

Perovskite solar cell performance is critically dependent on the characteristics of the electron transporting layer (ETL) and its interface. This work demonstrates the importance of interface modification in which the charge transport kinetics is improved through band gap engineering of the interfaces in perovskite solar cells with La2O3. The surface of a mesoporous TiO2 ETL (mp-TiO2) on CH3NH3PbI3-based solar cells is modified using a simple dip-coating method involving a lanthanum salt solution. The layer thickness of La2O3 was optimized, and its effects on the conduction band position, interfacial charge recombination, and photovoltaic performance were investigated. Modifying the mp-TiO2 ETL with La2O3 resulted in a nearly 46% enhancement of the power conversion efficiency because of the energetically favourable band gap engineering, which allowed the fast transfer of photo-generated electrons from the perovskite absorber layer to the ETL. Our simple interfacial control approach uses a new efficient interface-modifying material, demonstrating that interface engineering could be a key strategy for improving the performance of perovskite solar cells.

FUZZY SYSTEM MODELING AND ITS APPLICATION TO MOBILE ROBOT CONTROL

A systematic identification method that realizes fuzzy modeling using the input and output data pairs of system is presented. Such a model is composed of fuzzy implications. The implications are automatically generated by the structure and parameter identification. In the structure identification the optimal or near optimal number of fuzzy implications is determined in view of valid partition of data set. The parameters defining the fuzzy implications re identified by a GA (Genetic Algorithm) hybrid scheme to minimize mean square errors globally. Numerical examples are provided to evaluate the feasibility of the proposed approach. Comparison shows that the suggested approach can produce a fuzzy model with higher accuracy and a smaller number of fuzzy implications than the ones achieved previously in other methods. The proposed approach has also been applied to construct a fuzzy model for the navigation control of a mobile robot. The validity of the resultant model is demonstrated by experimentation.