Optical properties of a Cr/4H-SiC photodetector in the spectral range from ultraviolet to extreme ultraviolet.

This work examines the electrical and radiometric characteristics of a photodiode based on a 4H-SiC semiconductor material with a semitransparent Cr Schottky barrier of about 7 nm thickness. The device had a photosensitive area 10 mm in diameter. The spectral responsivity was determined in the wavelength range from 40 nm to 400 nm, thus particularly extending the characterization into the vacuum- and extreme ultraviolet spectral ranges. The photodiode showed a maximum quantum efficiency of 50% at 253 nm with a relative uniformity of 4% in the photosensitivity over its surface. The linearity of the photoresponse was measured at wavelengths of 70 nm and 265 nm for incident radiant powers from 2 nW to 800 nW, and no significant deviation from linearity was found. Regarding its electrical characteristics, the photodiode showed less than 10-13 A dark current at a reverse voltage of 10 V.

Autotransplantation of cryopreserved ovarian tissue--effective method of fertility preservation in cancer patients.

OBJECTIVE: To review the literature and to present the latest advances in the autotransplantation of cryopreserved ovarian tissue. MATERIALS AND METHODS: A literature review was conducted for all relevant articles assessing the fertility preservation, ovarian tissue transplantation, standard freezing and vitrification of ovarian tissue. RESULTS: One of the promising and effective methods for fertility preservation may be the autotransplantation of cryopreserved ovarian tissue. At present, 30 babies have been born after orthotopic autotransplantation of frozen-thawed human ovarian tissue. Restoration of ovarian activity occurs between 3.5 months and 6.5 months. The longevity of autotransplanted ovarian tissue is about 5-7 years. The follicles are similarly preserved after all freezing methods; however, the ovarian stroma is significantly better preserved after vitrification than after slow freezing. An important topic for further research is preparation of the "vascular bed", optimization of vitrification technique and the development of alternative procedures to avoid the transmission of cancer cells via ovarian tissue autotransplantation - "artificial ovary". CONCLUSIONS: Cryopreservation of ovarian tissue has unique advantages over other strategies. This method: (1) does not delay cancer treatment; (2) is safer for hormone dependent malignancy; (3) can be done independent of menstrual cycles; (4) is the only option for prepubertal girls; (5) can restore not only fertility but endocrine function.