Variations of oxidative potential of PM2.5 in a medium-sized residential city in South Korea measured using three different chemical assays.

Although it is evident that PM2.5 has serious adverse health effects, there is no consensus on what the biologically effective dose is. In this study, the intrinsic oxidative potential (OPm) and the extrinsic oxidative potential (OPv) of PM2.5 were measured using three chemical assays including dithiothreitol (DTT), ascorbic acid (AA), and reduced glutathione (GSH), along with chemical compositions of PM2.5 in South Korea. Among the three chemical assays, only OPmAA showed a statistically significant correlation with PM2.5 while OPmGSH and OPmDTT were not correlated with PM2.5 mass concentration. When the samples were categorized by PM2.5 mass concentrations, the variations in the proportion of Ni, As, Mn, Cd, Pb, and Se to PM2.5 mass closely coincided with changes in OPm across all three assays, suggesting a potential association between these elements and PM2.5 OP. Multiple linear regression analysis identified the significant PM components affecting the variability in extrinsic OPv. OPvAA was determined to be significantly influenced by EC, K+, and Ba while OC and Al were common significant factors for OPvGSH and OPvDTT. It was also found that primary OC was an important variable for OPvDTT while secondary OC significantly affected the variability of OPvGSH.

Optimized pleat geometry at specific pleat height in pleated filters for air purification.

The performance of an air purifier is determined by its clean air delivery rate (CADR), expressed as the product of the air flowrate and filter collection efficiency. A high CADR in a commercial air purifier is achieved using a pleated air filter with high filtration performance at a given air flowrate. However, obtaining this high filtration performance depends on the knowledge of the manufacturer, including the optimal pleating design, which remains uncertain to date. In this study, test pleated filters were prepared by folding a flat electrostatically-charged E12 filter medium to obtain different pleating geometries. The proper pleat geometry of the pleated filter, which has a minimum pressure drop at a fixed air flowrate, was dependent on the pleat length (PL ) and pleating ratio (α = pleat height/pleat width), wherein as the PL increases, the α range required to achieve a minimum pressure drop similarly increases. Based on the filter quality factor (qF ), the optimal pleat geometry of a pleated filter was between α values of 6-8, irrespective of the PL . Although both PL and α have certain influences on the qF , α has a greater influence on the pleated filter with no dead zone.

Effect of filter collection efficiency on the clean air delivery rate in an air cleaner.

The performance of an air cleaner is evaluated by the clean air delivery rate (CADR), which is defined as the measure of the delivery of contaminant-free air. Herein, we conducted comparative analyses of various particulate air filters with various collection efficiencies. We installed each filter in identical commercial air cleaners to determine the effects of the collection efficiency on the CADR. Three different filters (E11, E12, and H13 classes) were prepared to determine the effects of the filter collection efficiency and pressure drop on the air cleaner performance (ie, the CADR). Based on experimental data, filters E11 and E12 had similar CADRs and flow rates. However, filter H13, which had the highest collection efficiency and the lowest flow rate, had the lowest CADR. This indicates that even if a filter with higher collection efficiency is installed in an air cleaner, the larger pressure drop causes a reduction in the air flow rate. The CADR value is widely distributed for a flow rate range for commercially available models; however, the collection efficiencies for most air cleaners on the market lie in a narrow range. Therefore, the flow rate has the most direct impact on the performance of a commercial air cleaner.

Direct conversion of NO and SO2 in flue gas into fertilizer using ammonia and ozone.

This study focused on the simultaneous removal of NO and SO2 from an industrial flue gas stream. To evaluate the removal efficiency of NO and SO2 using O3 and NH3, the consumption of two reactants (O3 and NH3) in line with the conversion of NO and SO2 was quantified experimentally. In addition, NO and SO2 were converted to valuable fertilizers, NH4NO3 and (NH4)2SO4. To identify a principle strategy to enhance the generation of fertilizer, Fourier transform infrared spectroscopy was used to examine the reaction mechanisms for the formation of NH4NO3 and (NH4)2SO4. Acceleration of SO2 oxidation could be achieved effectively by adding NO to a gas mixture of SO2, NH3, and O3. The formation of HNO3 might be enhanced by the simultaneous feeding of NO and SO2. Particle generation was also 10 times higher for NH3/(NO + SO2) than for NH3/NO and for NH3/SO2, which is a prominent feature of this study. Moreover, the introduction of steam had a positive influence on particle generation. This method offers dual applications for NO and SO2 removal from a flue gas stream and direct fertilizer generation.

Application of powdered activated carbon coating to fabrics in a hybrid filter to enhance mercury removal.

Elemental mercury (Hg0) is predominant constituent of flue gas emitted from coal-fired power plants. Adsorption has been considered the best available technology for removal of Hg0 from flue gas. However, adsorbent injection increases the amount of ash generated. In the present study, powdered activated carbon (PAC) was coated on polytetrafluoroethylene/glass fiber filters to increase Hg0 removal while concurrently reducing the amount of ash generated. The optimal PAC coating rate was determined in laboratory experiments to ensure better Hg0 removal with low pressure drop. When PAC of particle size less than 45 µm was used, and the areal density was 50 g/m2, the pressure drop remained under 30 Pa while the Hg0 removal efficiency increased to 15.8% from 4.3%. The Hg0 removal efficiency also increased with decrease in filtration velocity. The optimal PAC coating rate was applied on a hybrid filter (HF), which was combined with a bag filter and an electrostatic precipitator in a single chamber. Originally designed to remove fine particulates matter, it was retrofitted to the flue gas control device for simultaneous Hg0 removal. By employing the PAC coating, the Hg removal efficiency of the HF increased to 79.79% from 66.35%. Also, a temporary reduction in Hg removal was seen but this was resolved following a cleaning cycle in which the dust layer was removed.

Neighborhood environment and marijuana use in urban young adults.

Risk factors for marijuana use in older adolescents and young adults have focused primarily on family environment and peer affiliation. A growing body of work has examined the relationship between environmental context and young adult substance use. This study builds on previous research linking neighborhood environment to young adult marijuana use by exploring two distinct features of neighborhoods, namely the physical (e.g., broken windows) and social environment (e.g., adults watching youth). Data were obtained from a longitudinal sample of 398 predominately African American young adults living in an urban environment. The data also included observational measures of physical and social order and disorder collected on the young adult's residential block. Exploratory structural equation modeling (ESEM) was utilized to test hypothesized relationships between these two features of the neighborhood environment and past year young adult marijuana use. A two-factor model of neighborhood environment with good fit indices was selected (CFI = 0.97, RMSEA = 0.037). There was a positive and significant direct effect from neighborhood physical disorder to marijuana use (0.219, p < 0.05) controlling for gender, race, and free and reduced price meal (FARPM) status. The direct effect from neighborhood social environment to marijuana use was not significant. These results converge with previous research linking vacant housing with young adult marijuana use but do not provide empirical support for the neighborhood social environment as a determinant of drug taking. Better explication of the social environment is needed to understand its relationship to drug use.

Preparation of electrospun polyurethane filter media and their collection mechanisms for ultrafine particles.

UNLABELLED: Electrospinning is a simple and versatile process to produce polymer nanofibers, which are useful for ultrafine particle filtration. In this study, a polyurethane filter with an average fiber diameter of 150-250 nm was prepared through the electrospinning process and its filtration characteristics were investigated. We found that the electrospun fiber diameter was highly dependent on the polyurethane concentration, electric field, and tip-to-collector distance. As the polyurethane concentration, electric field, and tip-to-collector distance under the same electric field increased, the fiber diameter increased. We also found that the produced filter media had a minimum collection efficiency at particles sizes from 80 to 100 nm, which implies an electrostatic attraction between the filter and the test particles. Furthermore, we observed that interception was a predominant collection mechanism at Peclet numbers higher than 10 in nanofiber filtration for ultrafine particles. IMPLICATIONS: A polyurethane nanofiber filter with excellent mechanical properties was prepared, and the effect of operating conditions on fiber morphology was examined. The filter fabricated by an electrospinning process is charged and has high filtration efficiency due to electrostatic force. Therefore, it can be a good alternative to control hazardous ultrafine particles.

Influence of pleat geometry on filter cleaning in PTFE/glass composite filter.

A pleated filter bag is often used to treat exhaust gas in many industrial applications, due to its fairly high dust collection efficiency and relatively low pressure drop. This work deals with the optimum pleating geometries of a pleated filter made with a newly developed PTFE/glass composite filter. It was found that pleating geometries, including pleat height and pleat pitch, directly affect the cleaning efficiency The design index, alpha, which stands for the ratio of pleat height to pleat pitch, is 1.48 for optimum operation. When the alpha value was higher than 1.48, the pressure drop across the pleated filter medium increased, resulting in a decreased cleaning interval due to the difficulty of filter cleaning. Therefore, it is necessary that the optimum pleating geometry should be determined by employing the dimensionless parameter, alpha, in the design of cartridge filters.

Sex specific trajectories in cigarette smoking behaviors among students participating in the unplugged school-based randomized control trial for substance use prevention.

OBJECTIVES: Understanding the developmental pathways and sex differences in cigarette smoking behaviors in adolescents has the potential to positively impact substance abuse prevention and to reduce smoking-related health problems. Using data from the Unplugged school-based prevention trial, we investigated different patterns of smoking behavior development among secondary school students in the Czech Republic. METHODS: Growth mixture modeling was used to examine different trajectories in cigarette smoking behaviors among male and female students (N=1874 6th graders; 50.4% male, mean age 11.8 years at baseline) participating in the Unplugged school-based randomized control trial for substance use prevention. RESULTS: A two-class model characterized cigarette use as a function of sex and Unplugged intervention status. More rapid cigarette use increases were observed in females (OR=1.17, p=0.01 in both rapid/moderate and slow smoking escalator classes) as compared to males. Further, in both classes, more rapid increases in smoking were observed for the control group as compared to the intervention group (OR=1.22, p<0.01 slow escalators; OR=1.54, p=0.08 rapid/moderate escalators). There was no difference in sex distribution when comparing the two classes (OR=1.02, p=0.98). CONCLUSIONS: This study adds to a growing literature on developmental and sex differences in cigarette use among adolescents. This research supports additional multi-year prevention strategies aimed at adolescent females and early treatment programs for adolescent smokers to prevent increasing cigarette use with age.

In vitro mineralization of dense collagen substrates: a biomimetic approach toward the development of bone-graft materials.

Bone is an organic-inorganic composite which has hierarchical structuring that leads to high strength and toughness. The nanostructure of bone consists of nanocrystals of hydroxyapatite embedded and aligned within the interstices of collagen fibrils. This unique nanostructure leads to exceptional properties, both mechanical and biological, making it difficult to emulate bone properties without having a bone-like nanostructured material. A primary goal of our group's work is to use biomimetic processing techniques that lead to bone-like structures. In our prior studies, we demonstrated that intrafibrillar mineralization of porous collagen sponges, leading to a bone-like nanostructure, can be achieved using a polymer-induced liquid precursor (PILP) mineralization process. The objective of this study was to investigate the use of this polymer-directed crystallization process to mineralize dense collagen substrates. To examine collagen scaffolds that truly represent the dense-packed matrix of bone, manatee bone was demineralized to isolate its collagen matrix, consisting of a dense, lamellar osteonal microstructure. This biogenic collagen scaffold was then remineralized using polyaspartate to direct the mineralization process through an amorphous precursor pathway. The various conditions investigated included polymer molecular weight, substrate dimension and mineralization time. Mineral penetration depths of up to 100 µms were achieved using this PILP process, compared to no penetration with only surface precipitates observed for the conventional crystallization process. Electron microscopy, wide-angle X-ray diffraction and thermal analysis were used to characterize the resulting hydroxyapatite/collagen composites. These studies demonstrate that the original interpenetrating bone nanostructure and osteonal microstructure could be recovered in a biogenic matrix using the PILP process.

The growth of neighborhood disorder and marijuana use among urban adolescents: a case for policy and environmental interventions.

OBJECTIVE: This study examines the growth of neighborhood disorder and subsequent marijuana use among urban adolescents transitioning into young adulthood. METHOD: Data are derived from a longitudinal sample of 434 predominately African American 12th graders followed-up at 2 years after high school. The data are rich in repeated measures documenting substance use and misuse and neighborhood characteristics. Growth mixture modeling was used to examine how neighborhood disorder trajectories, measured through the presence of abandoned buildings on the blocks where participants reside, influence subsequent drug use beginning in late adolescence and into young adulthood. RESULTS: A four-class solution characterizing neighborhood growth was selected as the final model and included rapidly improving, slightly improving, always-good, and deteriorating neighborhoods. Young adults living in neighborhoods that had been deteriorating over time were 30% more likely to use marijuana 2 years after high school than adolescents living in always-good neighborhoods (odds ratio = 1.30, p = .034). There was no relationship between living in a neighborhood that was improving and marijuana use. CONCLUSIONS: This study identified a salient and malleable neighborhood characteristic, abandoned housing, which predicted elevated risk for young-adult marijuana use. This research supports environmental strategies that target abandoned buildings as a means to improve health and health behaviors for community residents, particularly young-adult substance use.

Preparation and characterization of porous composite filter medium by polytetrafluoroethylene foam coating.

The high costs of ceramic and Teflon filter media for hot gas cleaning has limited their industrial applications. This paper presents a foam coating technology that can be used to produce an inexpensive and highly efficient filter for industrial applications. A new apparatus was designed and built that coats porous glass mats with liquid-phase polytetrafluoroethylene (PTFE). The machine generates bubbles, enables the formation of uniform micropores less than 45 microm in diameter, and produces a product with air permeability greater than 5.5 cm3/cm2/sec. The resulting filter was found to be thermally stable up to 270 degrees C without any visible distortion and was comparable in dust collection efficiency to other commercial filter media. In addition, its de-dusting efficiency was greater than 85%, which is similar to that of other test filter media.

Airborne virus capture and inactivation by an electrostatic particle collector.

Airborne virus capture and inactivation were studied in an electrostatic precipitator (ESP) at applied voltages from -10 to +10 kV using aerosolized bacteriophages T3 and MS2. For each charging scenario, samples were collected from the effluent air stream and assayed for viable phages using plaque assays and for nucleic acids using quantitative polymerase chain reaction (qPCR) assays. At higher applied voltages, more virus particles were captured from air with maximum log reductions of 6.8 and 6.3 for the plaque assay and 4.2 and 3.5 for the qPCR assay at -10 kV for T3 and MS2, respectively. Beyond corona inception (i.e., at applied voltages of -10, -8, +8, and +10 kV), log reduction values obtained with the plaque assay were much higher compared to those of the qPCR assay because nonviable particles, while present in the effluent were unaccounted for in the plaque assay. Comparisons of these assays showed that in-flight inactivation (i.e., inactivation without capture) was greater for the highest applied voltages with a log inactivation of 2.6 for both phages at -10 kV. We have demonstrated great potential for virus capture and inactivation via continual ion and reactive species bombardment when conditions in the ESP are enforced to generate a corona discharge.

Nanostructured sorbents for capture of cadmium species in combustion environments.

The pathways of cadmium species to form a submicrometer-sized aerosol in a combustion system exhaust were established. Cadmium oxide was the predominant species formed in the experiments and resulted in particles of a mean size of 26-63 nm with number concentrations in the range of 2-8 x 10(6) cm(-3). Two different nanostructured sorbents, a solid montmorillonite (MMT) and an in situ generated agglomerated silica, were used for capture of the cadmium species. The MMT sorbent was not stable at 1000 degrees C, and structural changes resulted. MMT did not suppress nucleation of cadmium species and partially captured it by weak physisorption as established by the leachability tests. In contrast, the in situ generated silica nanostructured agglomerates had a high surface area, suppressed nucleation of cadmium species vapors, and chemisorbed them effectively resulting in a firm binding, as compared to the MMT sorbent. There is an optimal temperature-time relationship at which the capture process is expected to be most effective. The leaching efficiency under these conditions was less than 3.2%. The nanostructured silica agglomerate size can be tuned for effective capture in existing particle control devices.