ObjectiveThe aim of this study was to evaluate the clinical characteristics and survival outcomes of patients with primary mediastinal germ cell tumor (PMGCT) by identifying the prognostic factors and efficacies of different treatment modalities.MethodsFifty-five patients with PMGCT who were treated consecutively at Cancer Center, Sun Yat-sen University, Guangzhou, from 1988 to 2010 were evaluated retrospectively.ResultsFifty-two men and 3 women with a median age of 25 years were identified, of whom 17 (30.9%) had pure seminomatous, 38 (69.1%) had nonseminomatous histology, 27 (49.1%) had tumor located at mediastinum, 20 (36.4%) had lung metastases and/or effusions, and 8 (14.5%) had distant metastases. Three treatments surgery, chemotherapy, and radiotherapy were performed in 11 (20%) patients, two treatments chemotherapy plus surgery or radiotherapy were performed in 25 (45.6%), and single treatment surgery or chemotherapy was performed in 17 (30.9%). The other two patients (3.6%) received no treatment. After a median follow-up time of 31.4 months, the 5-year survival rate was 52%. The median overall survival time was 87.9 months. Patients who received two treatments had the longest survival time of 118.3 months, P = 0.000. Those who had pure seminoma histology, whose tumor confined to the mediastinum and who achieved complete or partial remission at initial evaluation, who had complete resection and radiotherapy were considered to have better prognosis according to univariate analysis. On multivariate analysis, extension and response rate at initial evaluation were independently predictive of survival.ConclusionsPrimary mediastinal germ cell tumor is rare with a dominant frequency in young male patients. Chemotherapy combined with local therapy like surgery or radiotherapy is a reasonable treatment strategy recommended. Extension and initial remission rate are independent prognostic factors.

In order to improve the atomic oxygen (AO) erosion resistance of polyimide films in low earth orbit space environment, a type PDMS/POSS hybrid coating on polyimide substrate was prepared based on a silanol terminated polydimethylsiloxane (PDMS-OH) and Octakis(trimethylsiloxy)octaprismosilsesquioxane (Q8[Si(CH3)3]8) by copolymerizing process in DMAc solution. The atomic oxygen exposure tests were carried out using a ground-based atomic oxygen simulation facility. The mass loss, surface morphology and surface chemical compositions of PDMS/POSS hybrid films before and after exposure to incremental AO flux were investigated by using microbalance and field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The data indicated that a silica-rich layer was formed on the surface of the hybrid coating when the coating is exposed to AO flux, which could provide a protective barrier on the surface preventing further degradation of the polymer during extended exposure to AO and obviously improved the AO resistance of polyimide films.

The polysilazane synthesized by aminolysis of dichloromethylviny was coated on kapton by dip-coating method, the AO exposure tests was carried out in a ground-based AO simulator. It is found that the erosion yield of kapton was decreases by about two orders of magnitude. After exposure the coated katpon still have a smooth surface, and its optical properties are still at a high level. The polysilazane coating exhibits a superior AO erosion resistance.

SiO2 coatings were deposited on silver foils substrate by sol–gel method and their atomic oxygen (AO) erosion resistance was tested in a ground-based AO simulator. The surface morphologies and structures of the SiO2 coatings were investigated by Scanning Electron Microscopy (SEM) 、X-Ray Photoelectron Spectroscopy (XPS). The experimental results clearly demonstrate that this kind of coatings provided a good protection from AO attack. The erosion yield of the coatings was 2×10-26 cm3/atom, decreased by 30 times compared with that of the uncoated silver foils. This SiO2 layer significantly retarded the penetration of oxygen atoms, preventing further oxidation of the bulk silver. It was found that after AO exposure, the film structure tends to transfer from SiOH to amorphous SiO2. This implies that a more stable amorphous SiO2 structure could be formed in sol-gel SiO2 film during AO exposure. The results demonstrate that the coatings prepared by sol-gel technique can protect the silver from atomic oxygen erosion and can be used easily for practical application.

A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) had been prepared by copolymerization of octa(aminophenyl)silsesquioxane (OAP-POSS), 4,4’ -oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The AO resistance of these POSS/PI hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces have been characterized by X-ray photoelectron spectroscopy and FTIR. The XPS data indicate that the carbon content of the near-surface region is decreased from 63.6 to 19.3 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increase after AO exposure. The data reveal the formation of a passive inorganic SiO2 layer on the POSS/PI hybrid films during the AO exposure, which serves as a protective barrier preventing further degradation of the underlying polymer with increased exposure to the AO flux. SEM images showed that the surface of the 10 wt% POSS/PI became much less rough than that of the pristine polyimide. The AO resistance of the POSS/PI hybrid films is up to several tenfold than that of the pristine polyimide.