Since two years, the FACT telescope is operating on the Canary Island of La Palma. Apart from its purpose to serve as a monitoring facility for the brightest TeV blazars, it was built as a major step to establish solid state photon counters as detectors in Cherenkov astronomy. The camera of the First G-APD Cherenkov Telesope comprises 1440 Geigermode avalanche photo diodes (G-APD), equipped with solid light guides to increase the effective light collection area of each sensor. Since no sense-line is available, a special challenge is to keep the applied voltage stable although the current drawn by the G-APD depends on the flux of night-sky background photons significantly varying with ambient light conditions. Methods have been developed to keep the temperature and voltage dependent response of the G-APDs stable during operation. As a crosscheck, dark count spectra with high statistics have been taken under different environmental conditions. In this presentation, the project, the developed methods and the experience from two years of operation of the first G-APD based camera in Cherenkov astronomy under changing environmental conditions will be presented.

Since two years, the FACT telescope is operating on the Canary Island of La Palma. Apart from its purpose to serve as a monitoring facility for the brightest TeV blazars, it was built as a major step to establish solid state photon counters as detectors in Cherenkov astronomy. The camera of the First G-APD Cherenkov Telesope comprises 1440 Geigermode avalanche photo diodes (G-APD), equipped with solid light guides to increase the effective light collection area of each sensor. Since no sense-line is available, a special challenge is to keep the applied voltage stable although the current drawn by the G-APD depends on the flux of night-sky background photons significantly varying with ambient light conditions. Methods have been developed to keep the temperature and voltage dependent response of the G-APDs stable during operation. As a crosscheck, dark count spectra with high statistics have been taken under different environmental conditions. In this presentation, the project, the developed methods and the experience from two years of operation of the first G-APD based camera in Cherenkov astronomy under changing environmental conditions will be presented.

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Purpose: The present study analyzed the polymorphisms of DNA repair genes and their impact on survival of patients with early breast cancer.Patients and methods: A total of 240 patients with surgically resected early invasive ductal breast cancer were enrolled in the present study, where patients who underwent neoadjuvant treatment were excluded. The genomic DNA was extracted from paraffin-embedded tumor-free tissue or blood, and thirteen single nucleotide polymorphisms of 12 DNA repair genes were determined using the Sequenom Mass array system.Results: Among the target SNPs, VARS2 rs2074511 and POLE rs5744857 were found to correlate with relapse-free survival (RFS) after curative surgery in the log-rank test. There was no difference in the clinical and tumor characteristics according to the genotypes of these two coding variants except for the higher incidence of positive ER in patients with the GG genotype of POLE rs5744857 (p = 0.025). Multivariate analysis showed that the GG genotype of VARS2 V552V (rs2301717) was marginally associated with a better RFS than the combined AA and AG genotype (HR = 0.298; 95% CI = 0.089-0.995; p = 0.049). However, there was no significant association with overall survival.Conclusion: VARS2 V552V may be considered as a prognostic factor of survival in patients with early breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6055.