Ozone-initiated chemistry in an occupied simulated aircraft cabin

We have used multiple analytical methods to characterize the gas-phase products formed when ozone was added to cabin air during simulated 4-hour flights that were conducted in a reconstructed section of a B-767 aircraft containing human occupants. Two separate groups of 16 females were each exposed to four conditions: low air exchange (4.4 (h-1)), <2 ppb ozone; low air exchange, 61-64 ppb ozone; high air exchange (8.8 h(-1)), <2 ppb ozone; and high air exchange, 73-77 ppb ozone. The addition of ozone to the cabin air increased the levels of identified byproducts from approximately 70 to 130 ppb at the lower air exchange rate and from approximately 30 to 70 ppb at the higher air exchange rate. Most of the increase was attributable to acetone, nonanal, decanal, 4-oxopentanal (4-OPA), 6-methyl-5-hepten-2-one (6-MHO), formic acid, and acetic acid, with 0.25-0.30 mol of quantified product volatilized per mol of ozone consumed. Several of these compounds reached levels above their reported odor thresholds. Most byproducts were derived from surface reactions with occupants and their clothing, consistent with the inference that occupants were responsible for the removal of >55% of the ozone in the cabin. The observations made in this study have implications for other indoor settings. Whenever human beings and ozone are simultaneously present, one anticipates production of acetone, nonanal, decanal, 6-MHO, geranyl acetone, and 4-OPA.     

Harnessing the sol-gel process for the assembly of non-silicate mesostructured oxide materials

Mesostructured non-silicate oxides, with well-defined organization on the 2-50 nm size scale, may play a pivotal role in advancing vital disciplines such as catalysis, energy conversion, and biotechnology. Herein, we present selected methodologies for utilizing the sol-gel process, in conjunction with organic-directed assembly, to synthesize a variety of mesostructured oxides. The nature of the inorganic precursor is critical for this process. We discuss the development of general routes for yielding stable, nanoscopic, hydrophilic, inorganic precursors compatible with organic co-assembly. In particular, we highlight the use and characterization of organic-acid-modified transition metal oxide sol-gel precursors that allow for the synthesis and processing of designer mesostructured oxides such as titania hybrids for optical applications and porous multicomponent metal oxides useful for catalysis.     

Assessing the precision of model predictions and other functions of model parameters

Models fitted to data are used extensively in chemical engineering for a variety of purposes, including simulation, design and control. In any of these contexts it is important to assess the uncertainties in the estimated parameters and in any functions of these parameters, including predictions from the fitted model. Profiling is a likelihood ratio approach to estimating uncertainties in parameters and functions of parameters. A comparison is made between the optimization and reparameterization approaches to determining likelihood intervals for functions of parameters. The merits and limitations of generalized profiling are discussed in relation to the linearization approach commonly used in engineering. The benefits of generalized profiling are illustrated with two examples. A geometric interpretation of profiling is used to elucidate its value, and cases are identified for which the numerical algorithm fails. An alternative approach is suggested for these cases.     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.     

A pH-based method for measuring gaseous ammonia

Cumulative emission or gaseous concentrations of ammonia (NH₃) are commonly measured by trapping gaseous NH₃ in an acidic solution that is later analyzed for total ammonia content. This traditional acid trap method is inexpensive, reliable, and accurate, but it is labor-intensive and inconvenient for high-frequency sampling. This paper describes a new acid trap method in which total ammonia concentration in a citric acid solution is calculated from measured pH by applying a speciation model. With this new method, the quantity of captured ammonia in a single acid trap can be determined repeatedly over time. Testing through titrations, laboratory emission measurements, and field measurement of gaseous NH₃ showed that the method is accurate and reasonably precise. For the most sensitive case standard deviation was 8 μmol kg⁻¹ in titration results, and 10−20 μmol kg⁻¹ in the field trials. The lower quantitation limits from emission measurements and field trials were around 100 and 300 μmol kg⁻¹, respectively. Speciation modeling was used to assess the importance of interferences. Results showed that error due to minor contamination of chemicals and evaporation of water can be kept at low levels. Acidic gases may be a significant interference, but their presence is easy to recognize, and significant error can be avoided by selecting an appropriate acid concentration.     

Psychology in extremis: Preventing problems of professional competence in dangerous practice settings.

[Correction Notice: An erratum for this article was reported in Vol 42(2) of Professional Psychology: Research and Practice (see record 2011-08009-001). The title and authors for the first section of the article, beginning of the first column on page 95, were inadvertently omitted. The section should have begun with the following: “In Extremis Practice: Ensuring Competence During and After Deployment to a Combat Zone,” by W. Brad Johnson and Shannon J. Johnson.] When a psychologist provides services in a dangerous context—a work setting defined by persistent threat to the psychologist's own personal safety and well-being—the psychologist is said to practice in extremis. Psychologists who routinely function in extremis, such as those in correctional, disaster response, military, and police psychology—among other specialties—may be at increased risk for troubling experiences such as direct or vicarious traumatization, compassion fatigue, and empathy failure. Over time, in extremis experiences may contribute to decrements in professional competence. When psychologists become aware of personal problems that interfere with their work, they must take steps to ameliorate the problem while protecting consumers. In this Focus on Ethics, we discuss the difficulty inherent in self-identifying and correcting problems of professional competence when working in a high-threat environment. Three expert commentaries further elucidate in extremis competency concerns from the perspective of disaster response, police, and military psychology. The authors provide numerous recommendations for helping psychologists to ensure ongoing competence in in extremis jobs. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The inverse problem utilizing the boundary element method for a nonstandard female torso

This paper proposes a new method of rapidly deriving the transfer matrix for the boundary element method (BEM) forward problem from a tailored female torso geometry in the clinical setting. The method allows rapid calculation of epicardial potentials (EP) from body surface potentials (BSP). The use of EPs in previous studies has been shown to improve the successful detection of the life-threatening cardiac condition--acute myocardial infarction. The MRI scanning of a cardiac patient in the clinical setting is not practical and other methods are required to accurately deduce torso geometries for calculation of the transfer matrix. The new method allows the noninvasive calculation of tailored torso geometries from a standard female torso and five measurements taken from the body surface of a patient. This scaling of the torso has been successfully validated by carrying out EP calculations on 40 scaled torsos and ten female subjects. It utilizes the BEM in the calculation of the transfer matrix as the BEM depends only upon the topology of the surfaces of the torso and the heart, the former can now be accurately deduced, leaving only the latter geometry as an unknown.