Humidity conductivity method

Extrapolation (admittedly very approximate) of the thermalization time in humid air by microwave conductivity method (Warman et al, 1984) giving tth 4.5 x 10-15 s for unit water fraction. 

Chip Resistance of Surface Coatings Laboratory Cyclic Corrosion Test Method for Conducting Cyclic Humidity Tests Method for Conducting Moist SO Tests Cyclic Corrosion Test (CCT)... 

Electrostatic and electrical conductivity methods are very dependent on the condition of both the solids and the gas. If uniformity in these parameters can be guaranteed, then these electrical methods should work well. A change in the relative humidity or the type and uniformity of the solids flowing can upset any correlation that may have been performed on a particular flow system. 

In many cases, even the method of conditioning prior to test will influence the ratings. For example, flexural tests run on standard conditioned specimens (50% relative humidity and 73.5°F) may rank materials differently from tests conducted on specimens which have been immersed in water or which have been heated to some elevated temperature after outdoor exposure. 

In order to examine the process of ultrafine particle formation, a joint series of experiments were conducted at the Denver Research Center of the U.S. Bureau of Mines. In the Denver radon chamber, the activity size distribution of the ultrafine mode was measured using the mobility analyzer designed by Chu and Hopke (1985), the separate single screen method (Holub and Knutson, 1987), and the stacked single screen method (Holub and Knutson, 1987) for various relative humidities and for various concentrations of SO. The results... 

The candidate method is used to support drug synthesis, excipient compatibility, and ultimately to evaluate candidate formulations. Such support typically involves analyses of stressed materials to identify degradation trends. These studies are conducted in the solid state by exposing the DS and DP to relative humidity, temperature, light, and oxidizing... 

Light Exposures. Silk fabric samples, 0.25 m x 0.17 m, were mounted in Atlas Electric Devices aluminum sample holders according to AATCC Test Method 16E-1982 (7). An Atlas Ci-35 Weather-Ometer xenon-arc was used on continuous light cycle. Exposures were conducted at an irradiance of 0.35 W/m2 measured at 340 nm and the irradiance was monitored and controlled automatically. Borosilicate inner and outer filters were used to simulate the solar spectrum. The relative humidity was maintained at 65% and the black panel temperature was 50°C. The actual fabric temperature during the irradiation was measured, using small thermocouples threaded into the fabric, and was found to be 35 C. Control samples for these tests were kept in the dark at 35°C and 65% RH for the same time period as the illuminated samples. 

The balance between conduction and diffusion still operates for a much larger isolated wet object, provided radiation is excluded. This is the basis of the wet bulb thermometer method for measuring humidity. The actual rate of evaporation now is not as simply determined and is influenced by wind. The wet bulb temperature is almost independent of wind condition, owing to a convenient accident. Heat conduction is a diffusion process, and the diffusion coefficient for water vapor in air (0.24 sq. cm./sec.) is numerically close to the diffusion coefficient of temperature in air (thermal conductivity/specific heat = 0.20 sq. cm./sec.). Hence, the exact way in which each molecular diffusion process merges into the more rapid eddy diffusion process is not important because no matter how complex the transition is, it must be quantitatively similar for the two processes. 

Occlusion of the skin, seen with application of water-impermeable drug vehicles or patches, alters the rate and extent of toxicant absorption. As the skin hydrates, a threshold is reached where transdermal flux dramatically increases (approximately 80% relative humidity). When the skin becomes fully hydrated under occlusive conditions, flux can be dramatically increased. This occlusive effect must be accounted for when extrapolating toxicology studies conducted under occlusive conditions to field scenarios where the ambient environmental conditions are present. Hydration may also markedly affect the pH of the skin, which varies between 4.2 and 7.3. Therefore, dose alone is often not a sufficient metric to describe topical doses when the method of application and surface area become controlling factors. Dose must be expressed as mg/cm2 of exposed skin. 

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