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A large shortcoming of current chemistry trans- port models (CTM) for simulating the fate of ammonia in the atmosphere is the lack of a description of the bi-directional surface--atmosphere exchange. In this paper, results of an update of the surface--atmosphere exchange module DEPAC, i.e. DEPosition of Acidifying Compounds, in the chemistry transport model LOTOS-EUROS are discussed. It is shown that with the new description, which includes bi-directional surface--atmosphere exchange, the modeled ammonia concentrations increase almost everywhere, in particular in agricultural source areas. The reason is that by using a compensation point the ammonia lifetime and transport distance is increased. As a consequence, deposition of ammonia and ammonium decreases in agricultural source areas, while it increases in large nature areas and remote regions especially in southern Scandinavia. The inclusion of a compensation point for water reduces the dry deposition over sea and allows reproducing the observed marine background concentrations at coastal locations to a better extent. A comparison with measurements shows that the model results better represent the measured ammonia concentrations. The concentrations in nature areas are slightly overestimated, while the concentrations in agricultural source areas are still underestimated. Although the introduction of the compensation point improves the model performance, the modeling of ammonia remains challenging. Important aspects are emission patterns in space and time as well as a proper approach to deal with the high concentration gradients in relation to model resolution. In short, the inclusion of a bi-directional surface--atmosphere exchange is a significant step forward for modeling ammonia. [ABSTRACT FROM AUTHOR]

Background: Accreditation systems in medical education aim to assure various stakeholders that graduates are ready to further their training or begin practice. The purpose of this paper is to explore the current state of medical education accreditation around the world and describe the incidence and variability of these accreditation agencies worldwide. This paper explores trends in agency age, organization, and scope according to both World Bank region and income group., Methods: To find information on accreditation agencies, we searched multiple online accreditation and quality assurance databases as well as the University of Michigan Online Library and the Google search engine. All included agencies were recorded on a spreadsheet along with date of formation or first accreditation activity, name changes, scope, level of government independence, accessibility and type of accreditation standards, and status of WFME recognition. Comparisons by country region and income classification were made based on the World Bank's lists for fiscal year 2021., Results: As of August 2020, there were 3,323 operating medical schools located in 186 countries or territories listed in the World Directory of Medical Schools. Ninety-two (49%) of these countries currently have access to undergraduate accreditation that uses medical-specific standards. Sixty-four percent (n = 38) of high-income countries have medical-specific accreditation available to their medical schools, compared to only 20% (n = 6) of low-income countries. The majority of World Bank regions experienced the greatest increase in medical education accreditation agency establishment since the year 2000., Conclusions: Most smaller countries in Europe, South America, and the Pacific only have access to general undergraduate accreditation, and many countries in Africa have no accreditation available. In countries where medical education accreditation exists, the scope and organization of the agencies varies considerably. Regional cooperation and international agencies seem to be a growing trend. The data described in our study can serve as an important resource for further investigations on the effectiveness of accreditation activities worldwide. Our research also highlights regions and countries that may need focused accreditation development support.