The Reduction of Uncertainties for Absolute Piston Gage Pressure Measurements in the Atmospheric Pressure Range.

NIST pressure calibration services with nitrogen are now based on two transfer standard piston gages for which the effective areas have been determined by calibration with the manometer developed at NIST for gas thermometry. Root-sum-squared three sigma uncertainties for the areas for the two gages are 3.05 ppm and 4.18 ppm.

An Intercomparison of Pressure Standards Between LNE and NBS.

An intercomparison between a transfer piston gage used by the Laboratoire National d'Essais (LNE) and a primary standard piston gage of the National Bureau of Standards was performed over the range of pressure of 0.4 to 3.9 MPa. The agreement between the computation of the effective area of the LNE gage by the two laboratories was within 6.4 ppm and the agreement between the average of the pressures generated by these two gages was within 3.3 ppm, well below the estimated uncertainty of either gage (NBS 30 ppm and LNE 24 ppm).

Trace composition of human respiratory gas.

A multistage cryogenic trapping system was used to sample and concentrate trace organic constituents in human respiratory gas. Chemical analysis was conducted by gas chromatography and mass spectrometry. Respiratory compound identification and production rate data are given for eight human test subjects. This study reports on the use of the sampling technique to diagnose metabolic diseases and for application in the study of industrial exposure.

Growth of Chlorella sorokiniana at hyperbaric oxygen pressures.

The growth rate of Chlorella sorokiniana decreased in a linear fashion as the partial pressure of oxygen was increased from 711 to 1,478 mm of Hg. Under two atmospheres of oxygen pressure, growth ceased after 10 to 12 hr. This cessation of growth was not due to any permanent injury, as growth resumed when oxygen partial pressure was reduced to ambient levels. The inhibition occurred under both autotrophic and heterotrophic growth conditions and was not accompanied by an increase in cell size. The results indicated that the tolerance of Chlorella cells to elevated oxygen pressures was not an absolute immunity, and that inhibition of growth at very high oxygen pressures cannot be accounted for by an inhibition of photosynthesis alone.

Oxygen-tolerant strain of chlorella sorokiniana.

An oxygen-tolerant strain (OTS) of Chlorella sorokiniana was isolated by growing and continuously subculturing the oxygen-sensitive strain (OSS) in growth medium bubbled continuously with 95% O(2)-5% CO(2). Under these conditions, 6 to 8 hr were required before the OSS began to grow. The growth rates of the OTS and the OSS were the same when grown in an atmosphere of air-5% CO(2), and the growth rate of the OTS was the same when aerated with 95% O(2)-5% CO(2) and air-5% CO(2). The adaptive process was irreversible since serial transfers of the OTS grown with air-5% CO(2) did not alter the ability of the OTS to grow with 95% O(2)-5% CO(2). Inasmuch as photosynthesis in the OTS and the OSS was inhibited to a similar extent by oxygen and the adaptive process occurred heterotrophically in the absence of photosynthesis, it was concluded that the adaptive process was independent of photosynthesis. Morphological differences between the OTS and the OSS are presented and discussed with respect to the adaptive process.