Microstructure determination of AOT + phenol organogels utilizing small-angle X-ray scattering and atomic force microscopy.

Dry reverse micelles of the anionic twin-tailed surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) dissolved in nonpolar solvents spontaneously form an organogel when p-chlorophenol is added in a 1:1 AOT:phenol molar ratio. The solvents used were benzene, toluene, m-xylene, 2,2,4-trimethylpentane (isooctane), decane, dodecane, tetradecane, hexadecane, and 2,6,10,14-tetramethylpentadecane (TMPD). The proposed microstructure of the gel is based on strands of stacked phenols linked to AOT through hydrogen bonding. Small-angle X-ray scattering (SAXS) spectra of the organogels suggest a characteristic length scale for these phenol-AOT strands that is independent of concentration but dependent on the chemical nature of the nonpolar solvent used. Correlation lengths determined from the SAXS spectra indicate that the strands self-assemble into fibers. Direct visualization of the gel in its native state is accomplished by using tapping mode atomic force microscopy (AFM). It is shown that these organogels consist of fiber bundle assemblies. The SAXS and AFM data reinforce the theory of a molecular architecture consisting of three length scales-AOT/phenolic strands (ca. 2 nm in diameter) that self-assemble into fibers (ca. 10 nm in diameter), which then aggregate into fiber bundles (ca. 20-100 nm in diameter) and form the organogel.

Tests of small airway function in black smokers and nonsmokers.

Tests of small airway function (closing volume, forced expiratory flow in the middle half of the vital capacity, specific airway conductance, and peak expiratory flow) and routine spirometric tests (forced vital capacity, forced expiratory volume in one second, and residual volume) were performed in 848 adult black subjects of both sexes. The group included 422 smokers and 426 nonsmokers. No significant difference was found between smokers and nonsmokers for any of the tests, although some values were higher for men than for women. These findings suggest that reported abnormalities in small airway function in smokers in the general population may not be applicable to black smokers. This may be an important finding in ethnic variability in the incidence of chronic obstructive pulmonary disease.

Lung volumes and diffusion capacity in sickle cell trait.

Patients with sickle cell anemia have a restrictive ventilatory pattern, with reduction in diffusion capacity of the lung (DLco) and lung volumes. Diffusion capacity and lung volumes are reported as either normal or reduced in subjects with sickle cell trait. Thirteen subjects with sickle cell trait, age range 25 to 79 years, were compared with 13 normal subjects matched for age, sex, height, and smoking patterns. There was no significant difference in mean values of DLco or lung volume for the two groups. Neither was there a consistent difference for age-matched individuals. Normal lung function in sickle cell trait as opposed to sickle cell disease is probably related to the fact that the former have fewer, if any, pulmonary infectious and infarctive episodes.

Spirometric standards for healthy black adults.

Forced expiratory spirometric studies were performed on 512 nonsmoking black adult men and women with negative cardiorespiratory histories. Regression equations were calculated for forced vital capacity (FVC), percent vital capacity in 1 second (% FEV(1)), and forced midexpiratory flow rate FEF(25-75)%), using height and age. These equations resulted in predicted values 3.5 to 23 percent lower than commonly used standards. The wide range of variation means that a single correction factor is inadequate when considering ethnic differences. In contrast, FEV(1)/FVC was within the accepted range of normal for all ethnic groups. In the 30 percent of subjects in whom sitting height was measured, it was not significantly different from one half the standing height; thus, sitting height is also an inadequate correction factor. Tables of predicted values were constructed for easy reference, with the hope that use of racespecific standards for pulmonary function testing will become widespread.