A passlve sampler was developed for short-term, low-level air monltorlng applications. The small, Stainless steel devlce Is simply designed and Inexpenslve. I t has a hlgh equlvalent sampling rate, Is reusable and rechargeable, and Is designed for thermal desorptlon. Laboratory and field tests wlth Tenax GC as the sorbent have shown that the device compares very favorably wlth active (pump-based) samplers and has much better sensltlvlty than commercial passive monltors which utlllze actlvated charcoal. Performance was examlned under controlled test chamber atmospheres and In actual outdoor and Indoor sltuatlons. Sampling rates were calculated for several volatlle organlc chemlcals. An extensive evaluation of the effects of alr veloclty on performance also was undertaken.Most passive sampling devices (PSDs) function on the basis of molecular diffusion. Ideally, the sampling rate follows Fick's first law of diffusionwhere m is the mass flow rate, D is the diffusion coefficient of the chemical of interest, A is the area of the diffusion channels, 1 is the length of the diffusion channels, C, is the external (ambient) concentration of the chemical, and Co is the gas-phase concentration of the chemical at the surface of the collector or sorbent. Since PSDs require no pump or flow regulation system, they are considerably smaller, less costly, and less obtrustive than active sampling devices. Provided that the collected chemicals are tightly bound to the sorbent ( Co -0) , they may be left unattended for prolonged periods, since they do not depend on power sources. These characteristics make PSDs ideally suited not only for personal exposure monitoring but also for microenvironment applications and for use at remote sites where electrical power is unavailable.Most commercial devices use activated carbon as the collector; therefore, for most organic chemicals sorption is thermally irreversible in a practical sense and Co is essentially zero. Solvents such as carbon disulfide or a mixture of CS2 in methanol must be used to desorb the chemicals for analysis. Concentration by evaporation of the solvent extract is impractical for the analysis of volatile organic compounds. Consequently, carbon-based commercial dosimeters generally do not have adequate sensitivity for ambient (ppbv level) air Present address: University of Akron, Akron, OH 44325.

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SynopsisVacuum ultraviolet spectra are reported for a series of poly-a-amino acids which were film cast onto lithium fluoride discs. The solvents used for film casting were chosen such that chain conformations representative of those normally found for polypeptides were produced. Comparison of the spectra obtained suggests that the peptide group has a t least one conformationally sensitive transition in the vacuum ultraviolet region a t -165 nm. For the 8, or extended, form of the polymers, the intensity of this transition appears to be greater than that found for the monomer units, whereas the formation of a more compact helix results in a reduction in the intensity of this transition relative to that found for the monomers.

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A B S T R A C T Hageman factor (factor XII) is activated by exposure to surfaces such as glass or by solutions of certain compounds, notably ellagic acid. Changes in the structure of Hageman factor accompanying activation have been examined in this study by circular dichroism spectroscopy. The spectrum of unactivated Hageman factor in aqueous solutions suggests that its conformation is mainly aperiodic. Various perturbants altered the conformation of Hageman factor in differing ways, demonstrating the sensitivity of Hageman factor to its environment.After activation of Hageman factor with solutions of ellagic acid, a negative trough appeared in the region of the circular dichroism spectrum commonly assigned to tyrosine residues, along with other minor changes in the peptide spectral region. Some of these changes are similar to changes that occurred upon partial neutralization of the basic residues at alkali pH. Activation of Hageman factor by adsorption to quartz surfaces (in an aqueous environment) also produced changes similar to those in the ellagic acid-activated Hageman factor, including the negative ellipticity in the tyrosine region.These observations suggest that the activation process may be related to a change in status of some of the basic amino acid residues, coupled with a specific change in the environment of some tyrosine residues. The importance of these changes during the activation process remains to be determined. The