Role of the stratosphere in the global mercury cycle.

Mercury (Hg) is a global pollutant with substantial risks to human and ecosystem health. By upward transport in tropical regions, mercury enters into the stratosphere, but the contribution of the stratosphere to global mercury dispersion and deposition remains unknown. We find that between 5 and 50% (passing through the 400-kelvin isentropic surface and tropopause, respectively) of the mercury mass deposited on Earth's surface is chemically processed in the lower stratosphere.

Langerhans cell histiocytosis oral manifestation: A case report.

Unlabelled: Introduction and importance: Langerhans cell histiocytosis is a rare disorder characterized by the proliferation of Langerhans cells in various tissues. While it commonly affects bones, skin, and other organs, oral manifestations are less frequent but can be diagnostically challenging.

Case Presentation: we present a clinical case of LCH with an oral manifestation in a 14-year-old adolescent.

The role of place and manner of articulation in Kurtöp tonogenesis: refining the model.

While the general acoustic mechanisms that explain the development of tone in language have been understood since at least Maspero (1912. Étude Sur La Phonétique Historique de La Langue Annamite: Les Initiales. 12.

Metals from spacecraft reentry in stratospheric aerosol particles.

Large increases in the number of low earth orbit satellites are projected in the coming decades [L. Schulz, K.-H.

Correlated cryo-SEM and CryoNanoSIMS imaging of biological tissue.

Background: The development of nanoscale secondary ion mass spectrometry (NanoSIMS) has revolutionized the study of biological tissues by enabling, e.g., the visualization and quantification of metabolic processes at subcellular length scales.

Kinetics of O with Ca and Its Higher Oxides CaO ( = 1-3) and Updates to a Model of Meteoric Calcium in the Mesosphere and Lower Thermosphere.

The room-temperature rate constants and product branching fractions of CaO ( = 0-3) + O are measured using a selected ion flow tube apparatus. Ca + O produces CaO + O with = 9 ± 4 × 10 cm s, within uncertainty equal to the Langevin capture rate constant. This value is significantly larger than several literature values.

Reply to the 'Comment on "Theoretical study of the NO radical reaction with CHClBr, CHICl, CHBrI, CHClBr, and CHClBr"' by C. J. Nielsen and Y. Tang, , 2022, , DOI: 10.1039/D2CP03013F.

In this Reply, we answer the main argument raised in the Comment about the energy of the NO radical and its influence in the reaction profiles of the reaction of the NO radical with CHClBr, CHICl, CHBrI, CHClBr, and CHClBr by C. J. Nielsen and Y.

Inhibition of platelet aggregation by activation of platelet intermediate conductance Ca -activated potassium channels.

Background: Within the vasculature platelets and endothelial cells play crucial roles in hemostasis and thrombosis. Platelets, like endothelial cells, possess intermediate conductance Ca -activated K (IK ) channels and generate nitric oxide (NO). Although NO limits platelet aggregation, the role of IK channels in platelet function and NO generation has not yet been explored.

The Chemistry of Mercury in the Stratosphere.

Mercury, a global contaminant, enters the stratosphere through convective uplift, but its chemical cycling in the stratosphere is unknown. We report the first model of stratospheric mercury chemistry based on a novel photosensitized oxidation mechanism. We find two very distinct Hg chemical regimes in the stratosphere: in the upper stratosphere, above the ozone maximum concentration, Hg oxidation is initiated by photosensitized reactions, followed by second-step chlorine chemistry.

Master equation modelling of non-equilibrium chemistry in stellar outflows.

A current challenge in astrochemistry is to explain the formation of Fe-Mg silicate dust around evolved stars. The dust is observed to form within 2 to 3 stellar radii of oxygen-rich AGB stars, where the typical conditions are kinetic (translational) temperatures between 1200 and 1600 K, and total gas densities below 10 cm. At these high temperatures, molecules with bond energies < 400 kJ mol should be short-lived, and this results in kinetic bottlenecks in postulated mechanisms for converting the observed Fe, Mg, SiO and HO into silicate.

Theoretical study of the NO radical reaction with CHClBr, CHICl, CHBrI, CHClBr, and CHClBr.

The potential reaction of the nitrate radical (NO), the main nighttime atmospheric oxidant, with five alkyl halides, halons (CHClBr, CHICl, CHBrI, CHClBr, and CHClBr) has been studied theoretically. The most favorable reaction corresponds to a hydrogen atom transfer. The stationary points on the potential energy surfaces of these reactions have been characterized.

Insights into the Chemistry of Iodine New Particle Formation: The Role of Iodine Oxides and the Source of Iodic Acid.

Iodine chemistry is an important driver of new particle formation in the marine and polar boundary layers. There are, however, conflicting views about how iodine gas-to-particle conversion proceeds. Laboratory studies indicate that the photooxidation of iodine produces iodine oxides (IO), which are well-known particle precursors.

Reaction of SO with HONO and Implications for Sulfur Partitioning in the Atmosphere.

Sulfur trioxide is a critical intermediate for the sulfur cycle and the formation of sulfuric acid in the atmosphere. The traditional view is that sulfur trioxide is removed by water vapor in the troposphere. However, the concentration of water vapor decreases significantly with increasing altitude, leading to longer atmospheric lifetimes of sulfur trioxide.

The reaction between HgBr and O: kinetic study and atmospheric implications.

The rate constants of many reactions currently considered to be important in the atmospheric chemistry of mercury remain to be measured in the laboratory. Here we report the first experimental determination of the rate constant of the gas-phase reaction between the HgBr radical and ozone, for which a value at room temperature of (HgBr + O) = (7.5 ± 0.

Surface Analysis by Secondary Ion Mass Spectrometry (SIMS): Principles and Applications from Swiss laboratories.

Secondary Ion Mass Spectrometry (SIMS) extracts chemical, elemental, or isotopic information about a localized area of a solid target by performing mass spectrometry on secondary ions sputtered from its surface by the impact of a beam of charged particles. This primary beam sputters ionized atoms and small molecules (as well as many neutral particles) from the upper few nanometers of the sample surface. The physical basis of SIMS has been applied to a large range of applications utilizing instruments optimized with different types of mass analyzer, either dynamic SIMS with a double focusing mass spectrometer or static SIMS with a Time of Flight (TOF) analyzer.

First Simultaneous Lidar Observations of Thermosphere-Ionosphere Fe and Na (TIFe and TINa) Layers at McMurdo (77.84°S, 166.67°E), Antarctica With Concurrent Measurements of Aurora Activity, Enhanced Ionization Layers, and Converging Electric Field.

We report the first simultaneous, common-volume lidar observations of thermosphere-ionosphere Fe (TIFe) and Na (TINa) layers in Antarctica. We also report the observational discovery of nearly one-to-one correspondence between TIFe and aurora activity, enhanced ionization layers, and converging electric fields. Distinctive TIFe layers have a peak density of ~384 cm and the TIFe mixing ratio peaks around 123 km, ~5 times the mesospheric layer maximum.

Photochemistry of oxidized Hg(I) and Hg(II) species suggests missing mercury oxidation in the troposphere.

Mercury (Hg), a global contaminant, is emitted mainly in its elemental form Hg to the atmosphere where it is oxidized to reactive Hg compounds, which efficiently deposit to surface ecosystems. Therefore, the chemical cycling between the elemental and oxidized Hg forms in the atmosphere determines the scale and geographical pattern of global Hg deposition. Recent advances in the photochemistry of gas-phase oxidized Hg and Hg species postulate their photodissociation back to Hg as a crucial step in the atmospheric Hg redox cycle.