Modeling biomass burning organic aerosol atmospheric evolution and chemical aging

The changes in the concentration and composition of biomass-burning organic aerosol (OA) downwind of a major wildfire are simulated using the one-dimensional Lagrangian chemical transport model PMCAMx-Trj. A base case scenario is developed based on realistic fire-plume conditions and a series of sensitivity tests are performed to quantify the effects of different conditions and processes. Temperature, oxidant concentration and dilution rate all affect the evolution of biomass burning OA after its emission. The most important process though is the multi-stage oxidation of both the originally emitted organic vapors (volatile and intermediate volatility organic compounds) and those resulting from the evaporation of the OA as it is getting diluted. The emission rates of the intermediate volatility organic compounds (IVOCs) and their chemical fate have a large impact on the formed secondary OA within the plume. The assumption that these IVOCs undergo only functionalization leads to an overestimation of the produced SOA suggesting that fragmentation is also occurring. Assuming a fragmentation probability of 0.2 resulted in predictions that are more consistent with available observations. Dilution leads to OA evaporation and therefore reduction of the OA levels downwind of the fire. However, the evaporated material can return to the particulate phase later on after it gets oxidized and recondenses. The sensitivity of the OA levels and total mass balance on the dilution rate depends on the modeling assumptions. The high variability of OA mass enhancement observed in past field studies downwind of fires may be partially due to the variability of the dilution rates of the plumes

Rationale and Plan for Vitamin D Food Fortification: A Review and Guidance Paper.

Vitamin D deficiency can lead to musculoskeletal diseases such as rickets and osteomalacia, but vitamin D supplementation may also prevent extraskeletal diseases such as respiratory tract infections, asthma exacerbations, pregnancy complications and premature deaths. Vitamin D has a unique metabolism as it is mainly obtained through synthesis in the skin under the influence of sunlight (i.e., ultraviolet-B radiation) whereas intake by nutrition traditionally plays a relatively minor role. Dietary guidelines for vitamin D are based on a consensus that serum 25-hydroxyvitamin D (25[OH]D) concentrations are used to assess vitamin D status, with the recommended target concentrations ranging from ≥25 to ≥50 nmol/L (≥10-≥20 ng/mL), corresponding to a daily vitamin D intake of 10 to 20 μg (400-800 international units). Most populations fail to meet these recommended dietary vitamin D requirements. In Europe, 25(OH)D concentrations <30 nmol/L (12 ng/mL) and <50 nmol/L (20 ng/mL) are present in 13.0 and 40.4% of the general population, respectively. This substantial gap between officially recommended dietary reference intakes for vitamin D and the high prevalence of vitamin D deficiency in the general population requires action from health authorities. Promotion of a healthier lifestyle with more outdoor activities and optimal nutrition are definitely warranted but will not erase vitamin D deficiency and must, in the case of sunlight exposure, be well balanced with regard to potential adverse effects such as skin cancer. Intake of vitamin D supplements is limited by relatively poor adherence (in particular in individuals with low-socioeconomic status) and potential for overdosing. Systematic vitamin D food fortification is, however, an effective approach to improve vitamin D status in the general population, and this has already been introduced by countries such as the US, Canada, India, and Finland. Recent advances in our knowledge on the safety of vitamin D treatment, the dose-response relationship of vitamin D intake and 25(OH)D levels, as well as data on the effectiveness of vitamin D fortification in countries such as Finland provide a solid basis to introduce and modify vitamin D food fortification in order to improve public health with this likewise cost-effective approach

Ambient aerosol size distributions and number concentrations measured during the Pittsburgh Air Quality Study (PAQS)

Twelve months of aerosol size distributions from 3 to 560nm, measured using scanning mobility particle sizers are presented with an emphasis on average number, surface, and volume distributions, and seasonal and diurnal variation. The measurements were made at the main sampling site of the Pittsburgh Air Quality Study from July 2001 to June 2002. These are supplemented with 5 months of size distribution data from 0.5 to 2.5μm measured with a TSI aerosol particle sizer and 2 months of size distributions measured at an upwind rural sampling site. Measurements at the main site were made continuously under both low and ambient relative humidity. The average Pittsburgh number concentration (3-500nm) is 22,000cm-3 with an average mode size of 40nm. Strong diurnal patterns in number concentrations are evident as a direct effect of the sources of particles (atmospheric nucleation, traffic, and other combustion sources). New particle formation from homogeneous nucleation is significant on 30-50% of study days and over a wide area (at least a hundred kilometers). Rural number concentrations are a factor of 2-3 lower (on average) than the urban values. Average measured distributions are different from model literature urban and rural size distributions. © 2004 Elsevier Ltd. All rights reserved

An algorithm for combining electrical mobility and aerodynamic size distributions data when measuring ambient aerosol

Ambient aerosol particles vary in size from a few nanometers to several micrometers. No instrument is currently available to cover such a wide size range, and so a combination of several instruments is usually used. One such combination is that of electrical mobility classifiers and an aerodynamic sizer. Because of the differences in measurement principles between the instruments, difficulties arise in the combination of the measurements into a single size distribution. Here we report a simple algorithm that was developed to combine aerosol size distributions measured with commercially available scanning mobility particle sizers (SNIPS; TSI Inc.) and an aerodynamic particle sizer (APS; TSI Inc.). This algorithm was tested during July 2001 in the Pittsburgh Air Quality Study. The aerosol during the study had both urban and regional origin and is characteristic of urban atmosphere in the Northeastern U.S. The integrated volume concentrations from the SMPS-APS showed a good correlation with PM2.5 mass concentration measurements using a TEOM. The relation of the aerosol mass to its volume is an ``effective{''} density, a ratio of the bulk aerosol density to the shape factor. As a result of the comparison with the TEOM the ambient aerosol in the Pittsburgh area was found to have an effective density of 1.5 +/- 0.3 g cm(-3). Given that the aerosol during the study was found to always contain water, the particles are expected to be spherical and thus the shape factor may be assumed to be 1. This assumption has been supported by a comparison with the MOUDI, using the aerosol density of 1.5 g/cm(3). It should be noted that the estimated aerosol density and the shape factor are applicable to this study only and may be different in other locations

Nucleation events during the Pittsburgh air quality study: Description and relation to key meteorological, gas phase, and aerosol parameters

During the Pittsburgh Air Quality Study (PAQS) aerosol size distributions between 3 nm and 680 nm were measured between July 2001 and June 2002. These distributions have been analyzed to assess the importance of nucleation as a source of ultrafine particles in Pittsburgh and the surrounding areas. The analysis shows nucleation on 50\% of the study days and regional-scale formation of ultrafine particles on 30\% of the days. Nucleation occurred during all seasons, but it was most frequent in fall and spring and least frequent in winter. Regional nucleation was most common on sunny days with below average PM2.5 concentrations. Local nucleation events were usually associated with elevated SO2 concentrations. The observed nucleation events ranged from weak events with only a slight increase in the particle number to relatively intense events with increases of total particle counts between 50,000 cm(-3) up to 150,000 cm(-3). Averaging all days of the study, days with nucleation events had number concentrations peaking at around noon at about 45,000 cm(-3). This is compared to work days without nucleation, when the daily maximum was 8 am at 23,000 cm-3, and to weekends without nucleation, when the daily maximum was at noon at 16,000 cm(-3). Twenty-four-hour average number concentrations were approximately 40\% higher on days with nucleation compared to those without. Nucleation was typically observed starting around 9 am EST, although the start of nucleation events was later in winter and earlier in summer. The nucleation events are fairly well correlated with the product of {[}UV intensity {*} SO2 concentration] and also depend on the effective area available for condensation. This indicates that H2SO4 is a component of the new particles. Published correlations for nucleation by binary H2SO4-H2O cannot explain the observed nucleation frequency and intensity, suggesting that an additional component (perhaps ammonia) is participating in the particle formation

An Assessment of the Risk of Bias in Randomized Controlled Trial Reports Published in Prosthodontic and Implant Dentistry Journals

PURPOSE The objective of this study was to assess the risk of bias of randomized controlled trials (RCTs) published in prosthodontic and implant dentistry journals. MATERIALS AND METHODS The last 30 issues of 9 journals in the field of prosthodontic and implant dentistry (Clinical Implant Dentistry and Related Research, Clinical Oral Implants Research, Implant Dentistry, International Journal of Oral & Maxillofacial Implants, International Journal of Periodontics and Restorative Dentistry, International Journal of Prosthodontics, Journal of Dentistry, Journal of Oral Rehabilitation, and Journal of Prosthetic Dentistry) were hand-searched for RCTs. Risk of bias was assessed using the Cochrane Collaboration's risk of bias tool and analyzed descriptively. RESULTS From the 3,667 articles screened, a total of 147 RCTs were identified and included. The number of published RCTs increased with time. The overall distribution of a high risk of bias assessment varied across the domains of the Cochrane risk of bias tool: 8% for random sequence generation, 18% for allocation concealment, 41% for masking, 47% for blinding of outcome assessment, 7% for incomplete outcome data, 12% for selective reporting, and 41% for other biases. CONCLUSION The distribution of high risk of bias for RCTs published in the selected prosthodontic and implant dentistry journals varied among journals and ranged from 8% to 47%, which can be considered as substantial

Reporting of Statistical Results in Prosthodontic and Implantology Journals: P Values or Confidence Intervals?

PURPOSE: Confidence intervals (CIs) are integral to the interpretation of the precision and clinical relevance of research findings. The aim of this study was to ascertain the frequency of reporting of CIs in leading prosthodontic and dental implantology journals and to explore possible factors associated with improved reporting. MATERIALS AND METHODS: Thirty issues of nine journals in prosthodontics and implant dentistry were accessed, covering the years 2005 to 2012: The Journal of Prosthetic Dentistry, Journal of Oral Rehabilitation, The International Journal of Prosthodontics, The International Journal of Periodontics & Restorative Dentistry, Clinical Oral Implants Research, Clinical Implant Dentistry and Related Research, The International Journal of Oral & Maxillofacial Implants, Implant Dentistry, and Journal of Dentistry. Articles were screened and the reporting of CIs and P values recorded. Other information including study design, region of authorship, involvement of methodologists, and ethical approval was also obtained. Univariable and multivariable logistic regression was used to identify characteristics associated with reporting of CIs. RESULTS: Interrater agreement for the data extraction performed was excellent (kappa = 0.88; 95% CI: 0.87 to 0.89). CI reporting was limited, with mean reporting across journals of 14%. CI reporting was associated with journal type, study design, and involvement of a methodologist or statistician. CONCLUSIONSS: Reporting of CI in implant dentistry and prosthodontic journals requires improvement. Improved reporting will aid appraisal of the clinical relevance of research findings by providing a range of values within which the effect size lies, thus giving the end user the opportunity to interpret the results in relation to clinical practice

Light scattering by fine particles during the Pittsburgh Air Quality Study: measurements and modeling

{[}1] Light scattering by fine particulate matter was measured during the Pittsburgh Air Quality Study (PAQS) as close to ambient conditions as possible. Several approaches are used for the theoretical calculation of the scattering coefficient and the results are compared to the direct measurements. The first approach uses ambient high time and daily resolved PM2.5 composition concentrations to estimate the scattering coefficient assuming that the aerosol is an external mixture. The second approach uses a thermodynamic model and Mie theory to predict the scattering coefficient of aerosols from daily size composition distributions. The third approach introduces high time and daily resolved ambient aerosol water concentrations and concentrations of sulfate, nitrate, organic material, and soil with fixed scattering efficiencies. During the summer the first two approaches underestimate the measured scattering coefficient by around 20\%. Agreement within experimental error is obtained between the measured scattering coefficient and the model, incorporating measured water aerosol concentrations. During the winter the first two approaches tend to overpredict the measured scattering by around 15\%. This overprediction is weakly correlated to the organic mass. The modeling approaches suggest that sulfate and the associated water contribute 65 - 73\% to the scattering coefficient during the summer, with organic material contributing 25 - 30\%. During the winter, sulfate accounts for 35 - 43\%, nitrate accounts for 24 - 32\%, and organic material accounts for 30 - 40\% of the scattering coefficient