Impact of the assimilation of ozone from the Tropospheric Emission Spectrometer on surface ozone across North America

We examine the impact of assimilating ozone observations from the Tropospheric Emission Spectrometer (TES) on North American surface ozone abundances in the GEOS-Chem model in August 2006. The assimilation reduces the negative bias in the modeled free tropospheric ozone, which enhances the ozone flux into the boundary layer. Surface ozone abundances increased by as much as 9 ppb in western North America and by less than 2 ppb in the southeast, resulting in a total background source of ozone of 20-40 ppb. The enhanced ozone in the model reduced the model bias with respect to surface ozone observations in the western USA, but exacerbated it in the east. This increase in the bias in the boundary layer in the east, despite the agreement between the assimilation and ozonesonde measurements in the free troposphere, suggests errors in the ozone sources or sinks or in boundary layer mixing in the model. © 2009

The efficacy of silver diamine fluoride in arresting caries in children

Data sourcesPubMed, Scopus, Web of Science, the Latin American and Caribbean Health Sciences Literature database (LILACS), the Brazilian Library in Dentistry (BBO), Cochrane Library and grey literature.Study selectionTwo reviewers selected randomised clinical trials (RCTs) that compared the efficacy of SDF application with other active treatments or placebo in arresting carious lesions.Data extraction and synthesisThree authors extracted data using customised extraction forms, and risk of bias was assessed by two independent reviewers. Meta-analyses were performed on studies classified at 'low' or 'unclear' risk of bias, where similar outcomes were recorded in primary teeth, and that compared SDF to active treatments.ResultsEleven studies were included; five studies were at 'low', two at 'unclear' and four studies at 'high' risk of bias. Eight were conducted with primary teeth, two with permanent first molars and one conducted on both. Six studies used 38% SDF, two 30% SDF, one 12% SDF, one compared 38% SDF to 12% SDF and one used Nano Silver Fluoride (NSF).ConclusionsSDF is more effective than active treatments or placebo for carious lesion arrest in primary teeth. The body of evidence was of high quality for primary teeth. However, there was not enough high quality evidence to draw conclusions about carious lesion arrest in first permanent molars

The photochemistry of carbon monoxide in the stratosphere and mesosphere evaluated from observations by the Microwave Limb Sounder on the Aura satellite

The photochemical production and loss rates for carbon monoxide (CO) in the stratosphere and mesosphere are evaluated using measurements from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). The distributions of reactive trace gases involved in the photochemistry of CO, including OH, CH4, O(D-1), Cl, as well as temperatures for calculating reaction rates, are either directly observed or constrained from observations. We map the CO net production and loss as a function of pressure (10-0.02 hPa, about 30-75 km altitude), latitude (approximately +/- 70 degrees), and season. The results indicate that photochemical loss dominates over production for nearly all conditions considered here. A minimum photochemical loss lifetime of about 10 days occurs near the 2 hPa pressure level, and it follows the region of maximum sunlight exposure. At high latitudes during winter, the CO lifetime is generally longer than 30 days. Time scales become much shorter in spring, however, when CO lifetimes can be 15-20 days poleward of 60 degrees latitude in the upper stratosphere. On the basis of these results, CO is a suitable tracer during autumn to spring above the 0.1 hPa pressure level but not in the upper stratosphere near 1 hPa.</p