The goal of this dissertation is to elucidate detailed pathways, products, and rates leading to soot oxidation by OH. Such information would supplement current soot modeling which has generally focused more on growth reactions. Indeed, OH oxidation of soot has received no detailed theoretical analysis. The results presented here are a first step to fill this gap in soot modeling.

Due to the presumed importance of oxyradical decomposition to soot oxidation, the thermal decomposition of armchair oxyradicals was pursued. A number of different armchair prototype reactions were investigated to determine how rates vary based on oxyradical location and prototype size. Potential energy surfaces were explored and thermal decomposition rates were calculated. The results indicated that armchair edge oxyradicals decompose at rates similar to zigzag edge oxyradicals. These results were used in subsequent OH oxidation study.

Next, OH oxidation was studied on a series of prototype soot surfaces to identify which edge sites would lead to rapid oxidation by OH. The potential energy surfaces of three different reactions were explored. The carbon radical site was identified as the most likely candidate for a single OH radical attack leading to CO expulsion. A phenanthrene radical was selected as the prototype structure for this site, and the kinetics of this most promising reaction, OH + phenanthrene radical, were explored. This system, including a number of barrierless reactions, was explored using both chemical-activation and thermal decomposition master-equation simulations. The results confirmed the assumption that oxyradicals are key intermediates; multiple oxyradicals were found, all leading to CO expulsion. The overall rate coefficient of phenanthrene radical oxidation by OH forming CO was found to be insensitive to pressure and temperature and was approximately 1E14 cm3 mol-1 s-1. The OH + phenanthrene radical was also studied on the triplet surface. The rate in this case was found to be about a factor of 6 smaller than the singlet surface results.

The two principal processes involved in phenanthrene radical oxidation by OH were H atom migration/elimination followed by oxyradical decomposition. H atom migration/elimination made possible the relatively rapid rearrangement of the PAH edge, forming kinetically favorable oxyradicals which then decomposed. These same two processes are expected to be present in soot surface oxidation by OH. As a preliminary comparison of these theoretical results to soot oxidation experimental results, the collisional efficiency of OH with a phenanthrene radical was calculated and found to be a close match to the experimentally calculated collision efficiency of OH with a soot particle.

Introduction: The discharge conversation is a critical component of the emergency department encounter. Studies suggest that emergency medicine (EM) residency education is deficient in formally training residents on the patient discharge conversation. Our goal was to assess the proficiency of EM residents in addressing essential elements of a comprehensive discharge conversation; identify which components of the discharge conversation are omitted; introduce “DC HOME,” a standardized discharge mnemonic; and determine whether its implementation improved resident performance and patient satisfaction.

Methods: This was a prospective observational pre- and post-intervention study done by convenience sampling of 400 resident discharge encounters. Resident physicians were observed by attending physicians who completed an evaluation, answering “yes” or “no” as to whether residents addressed six components of a comprehensive discharge. The six components include the following: diagnosis; care rendered; health and lifestyle modifications; obstacles after discharge; medications; and expectations – or “DC HOME.” Didactics introducing the mnemonic “DC HOME” was provided to resident physicians. Patient feedback and satisfaction were collected after each encounter, and we recorded differences between pre-intervention and post-intervention encounters.

Results: Resident physicians improved significantly in all six components of “DC HOME” from pre-and-post intervention: discharge diagnosis (P = 0.0036) and the remaining five components (P<0.0001). There was a statistically significant improvement in patients’ perception for health and lifestyle modifications, obstacles after discharge, medications, expectations after discharge (P<0.0001), and discharge diagnosis (P = 0.0029). Patient satisfaction scores improved significantly (P = 0.005). Time spent with patients during discharge increased from 2 minutes and 42 seconds to 4 minutes and 4 seconds (P<0.0001).

Conclusion: EM residents frequently omit key components of the discharge conversation. The implementation of the “DC HOME” discharge mnemonic improves resident discharge performance, patient perception, and overall patient satisfaction.