United States Department of the Army

About: United States Department of the Army is a government organization based out in Arlington, Virginia, United States. It is known for research contribution in the topics: Poison control & Population. The organization has 32668 authors who have published 42453 publications receiving 947075 citations. The organization is also known as: DA & U.S. Department of the Army.

Operation Everest II: structural adaptations in skeletal muscle in response to extreme simulated altitude.

Abstract: Alterations in skeletal muscle structure were investigated in 6 male subjects who underwent 40 days of progressive decompression in a hypobaric chamber simulating an ascent to the summit of Mount Everest. Needle biopsies were obtained from vastus lateralis of 5 subjects before and immediately after confinement in the chamber, and were examined for various structural and ultrastructural parameters. In addition, total muscle area was calculated in 6 subjects from CT scans of the thighs and upper arms. Muscle area at these sites was found to decrease significantly (by 13 and 15%) as a result of the hypobaric confinement. This was substantiated by significant (25%) decreases in cross sectional fibre areas of the Type I fibres and 26% decreases (non significant) in Type II fibre area. Capillary to fibre ratios remained unchanged following hypoxia as did capillary density although there was a trend (non significant) towards an increase in capillary density. There were no significant increases in mitochondrial volume density or other morphometric parameters. These data indicate that chronic, severe hypoxia on its own does not result in an increase in absolute muscle capillary number or a de novo synthesis of mitochondria. The trends toward an increase in capillary density and mitochondrial volume density were interpreted as being secondary occurrences in response to the pronounced muscle atrophy which occurred.

Evidence against a 40°C core temperature threshold for fatigue in humans

Abstract: Evidence suggests that core temperatures of ∼40°C can induce fatigue, although this may be confounded by coincident elevations in skin temperatures and maximal cardiovascular strain. In an observat...

Method of fabricating an air-filled waveguide on a semiconductor body

Abstract: A method of using layers of gold metallization and a thick film coating of photo-sensitive material to form an air-filled microwave waveguide structure on the outer surface of a semiconductor body, such as a monolithic microwave integrated circuit commonly referred to as an MMIC, so that the waveguide can be coupled to the active and passive devices of the MMIC. First, a patterned metallization layer is formed on a substrate. A mold of a waveguide is fabricated by masking and then etching another metallization layer. The mold is turned over face down on the patterned metallization layer and bonded to the patterned metallization layer, Then, any unnecessary material is etched away.