S C I a T I C A.

Exchange of Materials Between Terrestrial Ecosystems and the Atmosphere

“…The limited and rather difficult measurements of NO. fluxes from soils show that they generally correlate with N20 fluxes on an annual basis (51), although NO fluxes are relatively greater when the soil surface is dry. Thus seasonal tropical forests and ferdlized agriculture probably represent significant sources of NO,.…”

“…Most tropical forests circulate much more nitrogen annually than do most temperate or boreal forests (48), and even within the tropics, N20 fluxes are significantly larger from nitrogen-rich than nitrogen-poor forests (49). Fertilized agricultural ecosystems also emit more nitrous oxide than do most natural ecosystems (50,51). The global increase in nitrous oxide concentrations can be explained primarily by combustion sources (44); it is uncertain whether the increased use of nitrogen fertirs in agriculture or increases in deforestation and other land use changes (47,52) contribute significantly.…”

Piezoelectricity and crystal structure of α-nitrogen

“…An electron diffraction study supports the Pa3 structure (Venables, 1970), and numerous infrared and Raman spectroscopy experiments (St. Louis & Schnepp, 1969;Brith, Ron & Schnepp, 1969;Cahill & Leroi, 1969;Anderson, Sun & Donkersloot, 1970), have found no evidence of the P213 structure, which because of its noncentrosymmetry would tend to produce coincidences between infrared and Raman frequencies. Theorists thus far have been unable to explain why the translational distortions of the P2~3 structure should occur for nitrogen as all the assumed crystalline potential models have led to a prediction of the equilibrium molecular locations in the Pa3 structure.…”

THE TUBULAR REABSORPTION OF CALCIUM IN PRIMARY HYPERPARATHYROIDISM AND IN NON‐PARATHYROID HYPERCALCEMIA1

“…The disturbance of calcium metabolism in sarcoidosis is attributed to intestinal hyperabsorption of calcium (1,28). As hypercalcuria, with or without elevation of the serum total calcium concentration, may occur in spite of normoabsorption, it has been claimed that sarcoidosis may exert a specific effect on the TRCa % or on the bones (12, 27, 35).…”