PubMed · 10314843
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G M Hoover. 1977. Low-flow humidifier data questioned.. https://pubmed.ncbi.nlm.nih.gov/10314843/
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Purpose of the work was to study the effect of the scanning speed of mercury porosimetry and moisture content of the sample on the mercury porosimetry result for mannitol tablets. Tablets were compressed at three different compression pressures from nonhygroscopic mannitol powder and granules. Pore structure of tablets was determined with three different scanning speeds of a high-pressure mercury porosimeter after storage in three different moisture conditions. With low scanning speed, smallest pores of tablets were determined more accurately. Small amounts of moisture, even as low as 1%, before evacuation in nonhygroscopic mannitol tablets decrease the porosity. Decrease in porosity was observed at a pore diameter range of 50-1000 nm, not at the smallest determined pores. Thus, the role of water in pharmaceutical samples appears to be complicated. Reasonably slow scanning is recommended in high-pressure mercury porosimetry. If total pore volume is the only parameter of interest, fast scanning can be used. Pretreatment of the samples by proper drying before mercury porosimetry is important.
The filamentous phage fd was studied by both contact- and tapping-mode atomic force microscopy under conditions of controlled variations in relative humidity and changes in the applied tip force. By spin-coating freshly cleaved mica with phage containing solutions having very low salt content followed by rapid humidity control, stable and reliable sample preparation was achieved. The apparent height of the phage varied by about 10-fold with a quadratic dependence on the stabilized relative humidity, extrapolating to 73% of the accepted X-ray diffraction-based height at 0% relative humidity. The variation in measured height with relative humidity largely reconciles previous widely varying atomic force microscopy estimates of this dimension for the filamentous phage. Our finding that contact-mode images of phage are more difficult to analyze than those acquired in tapping mode are consistent with previously published results on other biological specimens such as DNA.
The parameter m2 governing the volume recombination in ionization chambers has been measured under conditions which allow strict application of the basic theory. The method consists of measuring the ratio of ionization currents I(V1) and I(V2) obtained at two given voltages V1 and V2 as a function of I(V1). The value of m2 is derived from a linear extrapolation to zero current. Several pairs of voltages (V1, V2) were used. The value of m2 obtained in this work is 3.97 x 10(14) s m(-1) C(-1) V(2) with a relative uncertainty of 1.7%. The dependence of m2 on atmospheric conditions has also been investigated.