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Influence of Ga(Al)As substrates on surface morphology and critical thickness of InGaAs quantum dots
Yi Wang,Xiang Guo,Jiemin Wei,Chen Yang,Zijiang Luo,Jihong Wang,Zhao Ding 한국물리학회 2019 Current Applied Physics Vol.19 No.4
Influence of Ga(Al)As substrates on surface morphology of InGaAs quantum dots and critical thickness of In0.5Ga0.5As film grown by molecular beam epitaxy is investigated. The In0.5Ga0.5As quantum dots are grown on (001) surfaces of GaAs and Al0.25Ga0.75 A at 450 °C, scanning tunneling microscope images show that the size of quantum dots varied slightly for 10 ML of In0.5Ga0.5As grown on GaAs and Al0.25Ga0.75As surfaces. Reflection high energy electron diffraction (RHEED) is used to monitor the growth of 4 monolayers (ML) In0.5Ga0.5As on Al0.25Ga0.75As and GaAs surfaces during deposition. The critical thickness is theoretically calculated by adding energy caused by surface roughness and heat from substrate. The calculations show that the critical thickness of In0.5Ga0.5As grown on GaAs and Al0.25Ga0.75As are 3.2 ML and 3.8 ML, respectively. The theoretical calculation agrees with the experimental results.
Prevalence and Prognostic Role of PIK3CA/AKT1 Mutations in Chinese Breast Cancer Patients
Ling Deng,Xuehua Zhu,Yun Sun,Jiemin Wang,Xiaorong Zhong,Jiayuan Li,Min Hu,Hong Zheng 대한암학회 2019 Cancer Research and Treatment Vol.51 No.1
Purpose The prevalence of PIK3CA in Chinese breast cancer patients may be underestimated. Therefore, we investigated the distribution of somatic PIK3CA/AKT1mutations in Chinese breast cancer patients and explored their roles in tumor phenotypes and disease prognosis. Materials and Methods Tumors from 507 breast cancer patients were prospectively collected from the West China Hospital between 2008 and 2013. Whole exons of AKT1 and PIK3CAwere detected in freshfrozen tumors using next-generation sequencing, and correlations between PIK3CA/AKT1 mutations and clinicopathological features were analyzed. Results The AKT1mutation was found in 3.6% (18/507) of patients. Tumors from patients that carried the AKT1mutation were estrogen receptor (ER)+/progesterone receptor (PR)+/human epidermal growth factor receptor 2 (HER2) and were more likely to have high expression levels of Ki67. The prevalence of the PIK3CA mutation was 46.5% (236/507), and 35 patients carried two or three variants of the PIK3CA gene. PIK3CA mutations were associated with ER+/PR+/HER2 status. The prognosis of patients with one mutation in PIK3CA (or PIK3CA/AKT1) was not significantly different than that of patients with wild-type PIK3CA (or PIK3CA/AKT1), while patients with two or three variants in PIK3CA (or PIK3CA/AKT1) exhibited poorer outcomes in the entire group and in all three subgroups (ER+, HER2, Ki67 high), particularly with respect to overall survival. Conclusion A high frequency of somatic PIK3CA mutations was detected in Chinese breast cancer patients. In addition to the mutation frequency, the tumor mutational burden of the PIK3CA and AKT1 genes should also be of concern, as they may be associated with poor prognosis.