Accordion Folds Research Articles

Electron microscopic observations on the pecten of the nighthawk (Chordeiles minor).

The pecten of a nocturnally active bird, the nighthawk (Chordeiles minor) has been examined by light and electron microscopy. In this species the pecten consists of a pleated, highly vascular pigmented structure. It is situated over the optic nerve head and projects into the vitreous. Several accordion folds (4-5) are joined apically by a bridge of tissue which holds the pecten in a fan-like shape widest at the base. The entire pecten is enclosed in a fine basal lamina. Within each fold are numerous capillaries, larger blood vessels which could not be differentiated as to arterioles or venules and melanocytes. The capillaries are surrounded by extremely thick basal laminae composed of several fibrillar layers. These capillaries display extremely numerous microfolds on both the luminal and abluminal borders. The cell body is extremely thin with most organelles present in a paranuclear location. Pericytes are often associated with the capillaries. The melanocytes form an incomplete sheath around the capillaries and other blood vessels. The morphology of the pecten is indicative of a heavy involvement in the transport of materials.

Field Sound Transmission Loss Tests of Movable Partitions for School Classrooms

Field sound transmission loss tests have been made on a number of movable partitions installed in the Chicago Laboratory School of the University of Chicago on an experimental basis. Installation and tests were supported by the Educational Facilities Laboratories, Inc., New York City, to obtain performance information. Partitions tested included individually movable panels with perimeter seals, accordion folding units, and a new, heavy curtain type incorporating woven lead thread. A 6-in. lightweight aggregate concrete block wall was included for comparison. Results indicate a range of performance from satisfactory to inferior for the purpose. The nine-frequency average of both noise reduction and sound transmission loss do not, however, rank order the units ia agreement with subjective judgment.