Electrically pumped lasing from Ge Fabry-Perot resonators on Si.

Room temperature lasing from electrically pumped n-type doped Ge edge emitting devices has been observed. The edge emitter is formed by cleaving Si-Ge waveguide heterodiodes, providing optical feedback through a Fabry-Perot resonator. The electroluminescence spectra of the devices showed optical bleaching and intensity gain for wavelengths between 1660 nm and 1700 nm. This fits the theoretically predicted behavior for the n-type Ge material system. With further pulsed electrical injection of 500 kA/cm2 it was possible to reach the lasing threshold for such edge emitters. Different lengths and widths of devices have been investigated in order to maintain best gain-absorption ratios.

A novel marker of tissue junctions, collagen XXII.

Here we describe a novel specific component of tissue junctions, collagen XXII. It was first identified by screening an EST data base and subsequently expressed as a recombinant protein and characterized as an authentic tissue component. The COL22A1 gene on human chromosome 8q24.2 encodes a collagen that structurally belongs to the FACIT protein family (fibril-associated collagens with interrupted triple helices). Collagen XXII exhibits a striking restricted localization at tissue junctions such as the myotendinous junction in skeletal and heart muscle, the articular cartilage-synovial fluid junction, or the border between the anagen hair follicle and the dermis in the skin. It is deposited in the basement membrane zone of the myotendinous junction and the hair follicle and associated with the extrafibrillar matrix in cartilage. In situ hybridization of myotendinous junctions revealed that muscle cells produce collagen XXII, and functional tests demonstrated that collagen XXII acts as a cell adhesion ligand for skin epithelial cells and fibroblasts. This novel gene product, collagen XXII, is the first specific extracellular matrix protein present only at tissue junctions.