Robert M. Cowan

Clinical review: Emergency department overcrowding and the potential impact on the critically ill.

Critical care constitutes a significant and growing proportion of the practice of emergency medicine. Emergency department (ED) overcrowding in the USA represents an emerging threat to patient safety and could have a significant impact on the critically ill. This review describes the causes and effects of ED overcrowding; explores the potential impact that ED overcrowding has on care of the critically ill ED patient; and identifies possible solutions, focusing on ED based critical care.

Biological removal of gaseous ammonia in biofilters : Space travel and earth-based applications

ABSTRACT Gaseous NH3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO3 - early in the operation, but later both NO2 - and NO3 - accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N2O, which were detected in the biofilter exhaust.

Enzyme Based Membrane Reactor for CO 2 Capture

Control of carbon dioxide (CO 2 ) is crucial for all crew inhabited space-flight missions. Air revitalization requires safe and reliable CO 2 extraction systems characterized by small volume, low mass, low rate of energy use, minimal use of consumables, and little or no crew time for operation and maintenance. Current designs are relatively costly to operate due to consumable usage rates (e.g., LiOH), high mass and/or volume (solid amines), and/or high energy costs associated with regeneration of CO 2 adsorption capacity (e.g., metal oxide). Our work focuses on the development of a highly efficient enzyme catalyzed, Carbonic Anhydrase based liquid membrane biomimetic reactor. We report here on the use of aqueous chemistry modeling to guide the design of new liquid membrane compositions. We examine the effects of these new solutions on enzyme activity and on the solubility of other gases in the mix. We also discuss our initial efforts to enhance reactor performance through localized pH control.

Bioavailability of Fe(III) in natural soils and the impact on mobility of inorganic contaminants

Inorganic contaminants, such as heavy metals and radionuclides, can adhere to insoluble Fe(III) minerals resulting in decreased mobility of these contaminants through subsurface environments. Dissimilatory Fe(III)-reducing bacteria (DIRB), by reducing insoluble Fe(III) to soluble Fe(II), may enhance contaminant mobility. The Savannah River Site, South Carolina (SRS), has been subjected to both heavy metal and radionuclide contamination. The overall objective of this project is to investigate the release of inorganic contaminants such as heavy metals and radionuclides that are bound to solid phase soil Fe complexes and to elucidate the mechanisms for mobilization of these contaminants that can be associated with microbial Fe(III) reduction. This is being accomplished by (i) using uncontaminated and contaminated soils from SRS as prototype systems, (ii) evaluating the diversity of DIRBs within the samples and isolating cultures for further study, (iii) using batch microcosms to evaluate the bioavailability of Fe(III) from pure minerals and SRS soils, (iv) developing kinetic and mass transfer models that reflect the system dynamics, and (v) carrying out soil column studies to elucidate the dynamics and interactions amongst Fe(III) reduction, remineralization and contaminant mobility.