Aqueous Radical Initiated Oxidation of an Organic Monolayer at the Air-Water Interface as a Proxy for Thin Films on Atmospheric Aerosol Studied with Neutron Reflectometry.

Neutron reflectometry has been used to study the radical initiated oxidation of a monolayer of the lipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) at the air-solution interface by aqueous-phase hydroxyl, sulfate, and nitrate radicals. The oxidation of organic films at the surface of atmospheric aqueous aerosols can influence the optical properties of the aerosol and consequently can impact Earth's radiative balance and contribute to modern climate change. The amount of material at the air-solution interface was found to decrease on exposure to aqueous-phase radicals which was consistent with a multistep degradation mechanism, i.e., the products of reaction of the DSPC film with aqueous radicals were also surface active. The multistep degradation mechanism suggests that lipid molecules in the thin film degrade to form progressively shorter chain surface active products and several reactive steps are required to remove the film from the air-solution interface. Bimolecular rate constants for oxidation via the aqueous phase OH radical cluster around 1010 dm3 mol-1 s-1. Calculations to determine the film lifetime indicate that it will take ∼4-5 days for the film to degrade to 50% of its initial amount in the atmosphere, and therefore attack by aqueous radicals on organic films could be atmospherically important relative to typical atmospheric aerosol lifetimes.

Loss of NO(g) to painted surfaces and its re-emission with indoor illumination.

Heterogeneous surface reactions play a key role in the chemistry of the indoor environment because of the large indoor surface-to-volume ratio. The presence of photocatalytic material in indoor paints may allow photochemical reactions to occur at wavelengths of light that are present indoors. One such potential reaction is the heterogeneous photooxidation of NO to HONO. NO(g) is commonly found indoors, originating from combustion sources, ventilation and infiltration of outdoor air. We studied the interaction of NO(g) with painted surfaces illuminated with indoor fluorescent and incandescent lighting. There is a loss of NO(g) to painted surfaces in the dark at both 0 and 50% RH. At 50% RH, there is a re-release of some of that NO(g) under illumination. The same behavior is observed for illumination of different colored paints. This is in contrast to what is seen with TiO2 as the substrate, where photoenhanced uptake of NO(g) and formation of NO2 (g) are observed. We hypothesize that the loss of NO(g) is due to adsorption and diffusion into the paint. The re-release of NO under illumination is thought to be due to photooxidation of NO to HONO on the painted surface at higher relative humidities and subsequent HONO photolysis.

The reaction of oleic acid monolayers with gas-phase ozone at the air water interface: the effect of sub-phase viscosity, and inert secondary components.

Organic films that form on atmospheric particulate matter change the optical and cloud condensation nucleation properties of the particulate matter and consequently have implications for modern climate and climate models. The organic films are subject to attack from gas-phase oxidants present in ambient air. Here we revisit in greater detail the oxidation of a monolayer of oleic acid by gas-phase ozone at the air-water interface as this provides a model system for the oxidation reactions that occur at the air-water interface of aqueous atmospheric aerosol. Experiments were performed on monolayers of oleic acid at the air-liquid interface at atmospherically relevant ozone concentrations to investigate if the viscosity of the sub-phase influences the rate of the reaction and to determine the effect of the presence of a second component within the monolayer, stearic acid, which is generally considered to be non-reactive towards ozone, on the reaction kinetics as determined by neutron reflectometry measurements. Atmospheric aerosol can be extremely viscous. The kinetics of the reaction were found to be independent of the viscosity of the sub-phase below the monolayer over a range of moderate viscosities, , demonstrating no involvement of aqueous sub-phase oxidants in the rate determining step. The kinetics of oxidation of monolayers of pure oleic acid were found to depend on the surface coverage with different behaviour observed above and below a surface coverage of oleic acid of ∼1 × 1018 molecule m-2. Atmospheric aerosol are typically complex mixtures, and the presence of an additional compound in the monolayer that is inert to direct ozone oxidation, stearic acid, did not significantly change the reaction kinetics. It is demonstrated that oleic acid monolayers at the air-water interface do not leave any detectable material at the air-water interface, contradicting the previous work published in this journal which the authors now believe to be erroneous. The combined results presented here indicate that the kinetics, and thus the atmospheric chemical lifetime for unsaturated surface active materials at the air-water interface to loss by reaction with gas-phase ozone, can be considered to be independent of other materials present at either the air-water interface or in the aqueous sub-phase.

A Practitioner's Guide to Measuring Procedural Fidelity.

Ensuring high levels of procedural fidelity during behavior-analytic interventions is a crucial component of providing effective behavior-analytic services. However, few resources are available to help guide practitioners through measuring procedural fidelity. In fact, most published behavior-analytic research on procedural fidelity analyzes a single treatment procedure, which might not completely reflect the process of monitoring and addressing the procedural fidelity of a robust treatment package that might be necessary in clinical settings. The purpose of this article is to guide behavior analysts through the process of creating and using procedural fidelity measurement systems, with a focus on direct observation of implementation as a means of fidelity data collection. This process consists of six steps: (1) task analyze treatment procedures into measurable units; (2) assign measures to each treatment component; (3) plan the direct observation; (4) collect procedural fidelity data; (5) analyze and interpret procedural fidelity data; and (6) take action to improve procedural fidelity. Each step is described and discussed in the article.

Degradation and rearrangement of a lung surfactant lipid at the air-water interface during exposure to the pollutant gas ozone.

The presence of unsaturated lipids in lung surfactant is important for proper respiratory function. In this work, we have used neutron reflection and surface pressure measurements to study the reaction of the ubiquitous pollutant gas-phase ozone, O3, with pure and mixed phospholipid monolayers at the air-water interface. The results reveal that the reaction of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, with ozone leads to the rapid loss of the terminal C9 portion of the oleoyl strand of POPC from the air-water interface. The loss of the C9 portion from the interface is accompanied by an increase in the surface pressure (decrease in surface tension) of the film at the air-water interface. The results suggest that the portion of the oxidized oleoyl strand that is still attached to the lipid headgroup rapidly reverses its orientation and penetrates the air-water interface alongside the original headgroup, thus increasing the surface pressure. The reaction of POPC with ozone also leads to a loss of material from the palmitoyl strand, but the loss of palmitoyl material occurs after the loss of the terminal C9 portion from the oleoyl strand of the molecule, suggesting that the palmitoyl material is lost in a secondary reaction step. Further experiments studying the reaction of mixed monolayers composed of unsaturated lipid POPC and saturated lipid dipalmitoyl-sn-glycero-3-phosphocholine, DPPC, revealed that no loss of DPPC from the air-water interface occurs, eliminating the possibility that a reactive species such as an OH radical is formed and is able to attack nearby lipid chains. The reaction of ozone with the mixed films does cause a significant change in the surface pressure of the air-water interface. Thus, the reaction of unsaturated lipids in lung surfactant changes and impairs the physical properties of the film at the air-water interface.

Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads.

A method is described to measure the refractive index dispersion with wavelength of optically trapped solid particles in air. Knowledge of the refraction properties of solid particles is critical for the study of aerosol; both in the laboratory and in the atmosphere for climate studies. Single micron-sized polystyrene beads were optically trapped in air using a vertically aligned counter-propagating configuration of focussed laser beams. Each bead was illuminated using white light from a broadband light emitting diode (LED) and elastic scattering within the bead was collected onto a spectrograph. The resulting Mie spectra were analysed to accurately determine polystyrene bead radii to ±0.4 nm and values of the refractive index to ±0.0005 over a wavelength range of 480-700 nm. We demonstrate that optical trapping combined with elastic scattering can be used to both accurately size polystyrene beads suspended in air and determine their wavelength dependent refractive index. The refractive index dispersions are in close agreement with reported values for polystyrene beads in aqueous dispersion. Our results also demonstrate a variation in the refractive index of polystyrene, from bead to bead, in a commercial sample. The measured variation highlights that care must be taken when using polystyrene beads as a calibration aerosol.

Photochemical renoxification on commercial indoor photoactive paint.

Surface chemistry plays an important role in the indoor environment owing to the large indoor surface to volume ratio. This study explores the photoreactivity of surfaces painted with a photoactive paint in the presence of NOx. Two types of experiments are performed; illumination of painted surfaces with a nitrate deposit and illumination of painted surfaces in the presence of gaseous NO. For both types of experiments, illumination with a fluorescent bulb causes the greatest change in measured gaseous NOx concentrations. Results show that relative humidity and paint composition play an important role in the photoreactivity of indoor painted surfaces. Painted surfaces could contribute to gas-phase oxidant concentrations indoors.

On a persisting curious double standard in behavior analysis: Behavioral scholars' perspectives on procedural fidelity.

Procedural fidelity is the extent to which independent variables are implemented as designed. Despite 40 years of discussion about the importance of procedural fidelity for behavioral research, reporting of fidelity data remains an uncommon practice in behavior-analytic journals. Researchers have speculated about reasons for underreporting, but the perspectives of scholars about when reporting is warranted or necessary have not yet been explored. Thus, the purpose of this study was to evaluate possible reasons for infrequent reporting of fidelity data in behavior-analytic studies. To address this purpose, we conducted focus groups with scholars in applied behavior analysis. Five themes emerged regarding why procedural fidelity data are not typically reported. We provide a discussion about how these themes are interrelated and offer suggestions and recommendations to assist with the collection and reporting of fidelity data.

Reactive Uptake of Gas-Phase NO2 by Urban Road Dust in the Dark.

Road dust constitutes a prominent source of anthropogenic particulate matter, making its heterogeneous interactions with common atmospheric gas-phase compounds important. Here, we show that three distinct samples of urban road dust-including dust samples collected from city streets in summer and winter, and an urban park in summer-react with NO2 in the dark, forming NO and surface nitrite. The loss of NO2 ranged from ∼2 to 13% of its gas-phase concentration and scaled with its concentration as well as with the mass of the road dust sample. The uptake of NO2 by the winter dust was ∼4 times greater than that seen from summer street dust, which was in turn greater than that by the park dust. The conversion ratio of NO2 → NO ranged from 0.06 to 0.8 NO produced per NO2 lost and was greatest for the summer park dust. Exposure of the summer road dust to NO2 roughly doubles the concentration of inorganic nitrite anion in the dust but does not produce nitrate. The formation of NO and photolabile nitrite products means that heterogeneous NO x reactions occurring on the surface of road dust in the dark could have wide implications for the oxidative potential of urban areas.

Nominally acceptable integrity failures negatively affect interventions involving intermittent reinforcement.

The finding that differential reinforcement of alternative behavior (DRA) is efficacious at 80% integrity when continuous reinforcement is programmed for alternative responding may have contributed to a perception that integrity at 80% or above is acceptable. However, research also suggests that other interventions (e.g., noncontingent reinforcement) may not remain effective at 80% integrity. The conditions under which 80% integrity is acceptable for common behavioral interventions remains unclear. Therefore, we conducted two human-operant studies to evaluate effects of 80% integrity for interventions with contingent or noncontingent intermittent reinforcement schedules. During Experiment 1, we compared noncontingent reinforcement (NCR) and DRA when implemented with 80% integrity. During Experiment 2, we compared 2 variations of DRA, which included either a ratio or interval schedule to reinforce alternative behavior. Results replicated previous research showing that DRA with a FR-1 schedule programmed for alternative responding resulted in consistent target response suppression, even when integrity was reduced to 80%. In contrast, neither NCR nor interval-based DRA were consistently effective when implemented at 80% integrity. These results demonstrate that 80% integrity is not a uniformly acceptable minimal level of integrity.

Comparing training methods to improve volunteer skills during therapeutic horseback riding: A randomized control trial.

Although in-vivo behavioral skills training (BST) is often effective, it may be too resource-intensive for organizations that rely on volunteers. Alternatives to in-vivo BST include video models or interactive computer training (ICT), but the utility of these procedures for training volunteers remains largely unknown. We used a randomized control trial to teach multiple skills to new volunteers at a therapeutic riding center. A total of 60 volunteers were assigned to one of three groups using block randomization. Depending on group assignment, volunteers received instructions and modeling through in-vivo interactions, a video model, or ICT. All volunteers completed in-vivo role plays with feedback. Skills were measured by unblinded observers during role plays. There were no statistically significant differences in accuracy of role-play performance between volunteers in the in-vivo BST and ICT groups, but both outperformed the video-model group. The ICT and video model required statistically significantly less time from a live instructor than did in-vivo training. Thus, although in-vivo BST remains best practice, ICT may be a viable alternative when training resources are limited.

Reporting of demographic variables in the Journal of Applied Behavior Analysis.

Describing demographic variables (e.g., ethnicity/race, socioeconomic status, gender/sex, age) of participants may be important for identifying relations between these variables and behavior-analytic procedures. Previous research found that demographic variables were underreported in behavior-analytic studies dealing with particular populations (e.g., children with Autism Spectrum Disorder), interventions (e.g., verbal behavior), or for a subset of demographic variables. We evaluated the extent to which studies recently published in the Journal of Applied Behavior Analysis included descriptions of demographic variables of participants. Demographic variables were often underreported, which may limit the broader dissemination of these behavior-analytic studies and the development of culturally responsive modifications to behavioral interventions.