one of a group of cells that develop in the walls of the seminiferous tubules. Spermatogenic cells include spermatogonia, spermatocytes, and spermatidsâall of which are transitional forms between primary sexual cells and spermatozoa.
long-haul optics. Long-haul optics refers to the transmission of visible light signals over optical fiber cable for great distances, especially without or with minimal use of repeaters. Normally, repeaters are necessary at intervals in a length of fiber optic cable to keep the signal quality from deteriorating to the point of non-usability. In long-haul optical systems, the goal is to minimize the number of repeaters per unit distance, and ideally, to render repeaters unnecessary.
Long-distance trails (or long-distance tracks, paths, footpaths or greenways) are the longer recreational trails mainly through rural areas, used for non-motorized recreational travelling (walking, backpacking, cycling, horse riding or cross-country skiing). number of long distance multi-use trails have been created in England, including three National Trails, the Pennine Bridleway, 192 km (119 miles), The Ridgeway, 139 km (86 miles), and South Downs Way, 160 km (99 miles). Rail trails /paths are shared-use paths that make use of abandoned railway corridors.