A new atmospherically relevant oxidant of sulphur dioxide.

Atmospheric oxidation is a key phenomenon that connects atmospheric chemistry with globally challenging environmental issues, such as climate change, stratospheric ozone loss, acidification of soils and water, and health effects of air quality. Ozone, the hydroxyl radical and the nitrate radical are generally considered to be the dominant oxidants that initiate the removal of trace gases, including pollutants, from the atmosphere. Here we present atmospheric observations from a boreal forest region in Finland, supported by laboratory experiments and theoretical considerations, that allow us to identify another compound, probably a stabilized Criegee intermediate (a carbonyl oxide with two free-radical sites) or its derivative, which has a significant capacity to oxidize sulphur dioxide and potentially other trace gases. This compound probably enhances the reactivity of the atmosphere, particularly with regard to the production of sulphuric acid, and consequently atmospheric aerosol formation. Our findings suggest that this new atmospherically relevant oxidation route is important relative to oxidation by the hydroxyl radical, at least at moderate concentrations of that radical. We also find that the oxidation chemistry of this compound seems to be tightly linked to the presence of alkenes of biogenic origin.

A computational fluid dynamics approach to nucleation in the water-sulfuric acid system.

This study presents a computational fluid dynamics modeling approach to investigate the nucleation in the water-sulfuric acid system in a flow tube. On the basis of an existing experimental setup (Brus, D.; Hyvärinen, A.-P.; Viisanen, Y.; Kulmala, M.; Lihavainen, H. Atmos. Chem. Phys. 2010, 10, 2631-2641), we first establish the effect of convection on the flow profile. We then proceed to simulate nucleation for relative humidities of 10, 30, and 50% and for sulfuric acid concentration between 10(9) to 3 x 10(10) cm(-3). We describe the nucleation zone in detail and determine how flow rate and relative humidity affect its characteristics. Experimental nucleation rates are compared to rates gained from classical binary and kinetic nucleation theory as well as cluster activation theory. For low RH values, kinetic theory yields the best agreement with experimental results while binary nucleation best reproduces the experimental nucleation behavior at 50% relative humidity. Particle growth is modeled for an example case at 50% relative humidity. The final simulated diameter is very close to the experimental result.

[Self-manipulated disease and Munchausen syndrome in adolescents. A case report]. / Selbstmanipulierte Erkrankung und Münchhausen-Syndrom bei Jugendlichen. Ein kasuistischer Bericht.

In recent years factitious disorders have gained increasing significance in all medical specialties although in child psychiatry publications on this topic are rare. In this article these and other somatoform disorders are discussed with reference to a case report on a 14-year-old girl. Psychodynamic aspects of this syndrome are presented and differentiated from simulation. Conversion syndromes and hysterical neurosis and comparisons are made with other publications on this topic. Treatment of these patients, who repeatedly succeed in subjecting themselves to invasive and sophisticated diagnostic procedures is difficult because of minimal compliance. The prognosis is affected by the extent to which changes in personality structure and development of alternative problem-solving mechanisms can be achieved.

Acute megakaryocytic myelosis preceded by myelodysplasia. Report of a case and review of the literature.

Acute megakaryocytic myelosis represents a distinct disease entity. As shown by a survey of the literature, it is a rapidly fatal disease, not preceded by a chronic myeloproliferative disorder, and mostly refractory to cytotoxic treatment. The first manifestation is pancytopenia with initial absence but quick development of hepatosplenomegaly. In contrast to "acute myelofibrosis", which is characterized by hyperplasia of all three haematopoietic lineages, a purely megakaryocytic proliferation develops together with a slight reticulinic fibrosis. Immature megakaryocytic cells may appear in the circulation, allowing classification of the disease as a variant of acute non-lymphatic leukaemia. This view is stressed by the observation of a preceding myelodysplastic phase in the case reported here.