Patrick Feeney

A detailed theory is presented for nucleation kinetics in emulsion polymerization systems based on the coagulation of precursor particles (which may themselves be formed by either homogeneous nucleation or micellar entry). These precursor particles differ from true latex particles by a slower rate of polymerization and the lack of stability against coagulation. The coagulative nucleation theory combines extended Müller-Smoluchowski coagulation kinetics with DLVO theory. Expressions are provided for the time evolutions of the nucleation rate, particle number, and particle size distribution (PSD). With physically reasonable values for the parameters for the coagulation kinetics, agreement is obtained with data for styrene emulsion polymerization systems. In particular, excellent accord is obtained with the early-time evolution of the PSD, such data being especially sensitive to assumptions as to the nucleation mechanism. In addition, agreement is obtained with data on the dependence of particle number on surfactant and initiator concentrations.

Equations are set down for the formation of latex particles in emulsion polymerization systems in the absence of added emulsifier. The model describes the formation of colloidally unstable precursor particles through homogeneous nucleation, followed by their coagulation and propagational growth to form colloidally stable latex particles. Coagulation rates are obtained through DLVO theory and its modifications, with due allowance for the partial attraction that occurs in the coagulation between particles with different radii. Calculations show good agreement with the experimental data of Ottewill and co-workers for the variation of particle number density with initiator concentration and ionic strength.

OBJECTIVES: To characterise the effects of noise exposure, including intermittent and peaky exposure, on hearing damage as assessed by standard pure-tone thresholds and otoacoustic emissions, a longitudinal study was conducted on newly hired construction apprentices and controls over a 10-year period. METHODS: Among the 456 subjects recruited at baseline, 316 had at least two (mean 4.6) examinations and were included in this analysis. Annual examinations included hearing threshold levels (HTLs) for air conducted pure tones and distortion product otoacoustic emission (DPOAE) amplitudes. Task-based occupational noise exposure levels and recreational exposures were estimated. Linear mixed models were fit for HTLs and DPOAEs at 3, 4 and 6 kHz in relation to time since baseline and average noise level since baseline, while controlling for hearing level at baseline and other risk factors. RESULTS: Estimated L(EQ) noise exposures were 87±3.6 dBA among the construction workers. Linear mixed modelling demonstrated significant exposure-related elevations in HTL of about 2-3 dB over a projected 10-year period at 3, 4 or 6 kHz for a 10 dB increase in exposure. The DPOAE models (using L1=40) predicted about 1 dB decrease in emission amplitude over 10 years for a 10 dB increase in exposure. CONCLUSIONS: The study provides evidence of noise-induced damage at an average exposure level around the 85 dBA level. The predicted change in HTLs was somewhat higher than would be predicted by standard hearing loss models, after accounting for hearing loss at baseline. Limited evidence for an enhanced effect of high peak component noise was observed, and DPOAEs, although similarly affected, showed no advantage over standard hearing threshold evaluation in detecting effects of noise on the ear and hearing.

It has long been recognized that information on particle size distributions in atmospheric aerosals is necessary for meaningful evaluations of potential health hazards. Such information is also important in establishing particulate sources, transport, transformations, and sinks, especially in combination with elemental and chemical data. While instruments exist to collect size segregated samples of particulates, they are too complex and expensive to encourage use of multiple units in field situations.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMonitoring California's aerosols by size and elemental compositionRobert G. Flocchini, Thomas A. Cahill, Danny J. Shadoan, Sandra J. Lange, Robert A. Eldred, Patrick J. Feeney, Gordon W. Wolfe, Dean C. Simmeroth, and Jack K. SuderCite this: Environ. Sci. Technol. 1976, 10, 1, 76–82Publication Date (Print):January 1, 1976Publication History Published online1 May 2002Published inissue 1 January 1976https://pubs.acs.org/doi/10.1021/es60112a008https://doi.org/10.1021/es60112a008research-articleACS PublicationsRequest reuse permissionsArticle Views53Altmetric-Citations50LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts