Formation of the methyl cation by photochemistry in a protoplanetary disk.

Forty years ago, it was proposed that gas-phase organic chemistry in the interstellar medium can be initiated by the methyl cation CH3+ (refs. 1-3), but so far it has not been observed outside the Solar System4,5. Alternative routes involving processes on grain surfaces have been invoked6,7. Here we report James Webb Space Telescope observations of CH3+ in a protoplanetary disk in the Orion star-forming region. We find that gas-phase organic chemistry is activated by ultraviolet irradiation.

Spatially resolved images of reactive ions in the Orion Bar,☠☠.

We report high angular resolution (4.9″×3.0″) images of reactive ions SH+, HOC+, and SO+ toward the Orion Bar photodissociation region (PDR). We used ALMA-ACA to map several rotational lines at 0.8 mm, complemented with multi-line observations obtained with the IRAM 30 m telescope. The SH+ and HOC+ emission is restricted to a narrow layer of 2″- to 10″-width (≈800 to 4000 AU depending on the assumed PDR geometry) that follows the vibrationally excited [Formula: see text] emission. Both ions efficiently form very close to the H/H2 transition zone, at a depth of Av≲1 mag into the neutral cloud, where abundant C+, S+, and [Formula: see text] coexist. SO+ peaks slightly deeper into the cloud. The observed ions have low rotational temperatures (Trot≈10-30 K≪Tk) and narrow line-widths (~2-3 km s-1), a factor of ≃2 narrower that those of the lighter reactive ion CH+. This is consistent with the higher reactivity and faster radiative pumping rates of CH+ compared to the heavier ions, which are driven relatively faster toward smaller velocity dispersion by elastic collisions and toward lower Trot by inelastic collisions. We estimate column densities and average physical conditions from an excitation model (n(H2)≈105-106 cm-3, n(e-)≈10 cm-3, and Tk≈200 K). Regardless of the excitation details, SH+ and HOC+ clearly trace the most exposed layers of the UV-irradiated molecular cloud surface, whereas SO+ arises from slightly more shielded layers.

Efficacy and tolerability of budesonide aqueous nasal spray in chronic rhinosinusitis patients.

This study evaluated the efficacy and tolerability of budesonide in an aqueous nasal spray (BANS) in patients with chronic rhinosinusitis. In this double-blind, placebo-controlled, multicentre, parallel-group study, patients (n = 167) with persistent rhinosinusitis symptoms despite 2-weeks' antibiotic treatment were randomised to receive BANS 128 micrograms b.i.d. or placebo for 20 weeks. Morning combined symptom scores (CSS) in patients receiving BANS decreased by a mean of -1.85 (95% CI -2.27, -1.43), versus -1.02 (-1.43, -0.61) in the placebo group (p = 0.005); corresponding values for evening CSS were -1.78 (-2.22, -1.35) and -1.02 (-1.45, -0.60), respectively (p = 0.012). BANS produced significant reductions in nasal congestion and discharge scores, and improved patients' sense of smell (morning only), versus placebo. Peak nasal inspiratory flow (PNIF) increased significantly during BANS treatment. In allergic patients, BANS significantly (p < 0.001) reduced both morning -1.40 (-2.18, -0.62) and evening -1.37 (-2.15, -0.58) CSS from baseline versus placebo, but changes in non-allergic patients (morning: -0.04 [-0.95, 0.87]; evening: 0.14 [-0.81, 1.09]) were not significant. PNIF was significantly (p < 0.01) increased in both allergic and non-allergic patients from baseline versus placebo. BANS is an effective and well-tolerated treatment for chronic rhinosinusitis.

H3+ at the interface between astrochemistry and astroparticle physics.

The H(3)(+) molecular ion has been used by Oka and collaborators to trace the rate of ionization by cosmic rays in the interstellar medium. More energetic cosmic rays also produce diffuse γ-radiation. Now that several supernova remnants (SNRs) have been identified as γ-ray sources, it is possible to use spectroscopy of molecular ions to search for enhanced ionization rates that would pinpoint the SNRs as the accelerators of cosmic rays. It is proposed that the warm, dilute molecular gas revealed by H(3)(+) absorption in the central molecular zone of the Galaxy can also be investigated via radio recombination lines of atoms and possibly triatomic hydrogen.

Chemistry and cosmology.

The simplest elements, hydrogen and helium, offer a remarkably rich chemistry, which has controlled crucial features of the early evolution of the universe. Theoretical models of the origin of structure (stars, galaxies, clusters of galaxies, etc.) now incorporate this chemistry in some detail. In addition to the origin of structure, cosmologists are concerned with observational tests of competing world models. Primordial chemistry may give rise to some of the earliest departures from thermodynamic equilibrium in the universe. These effects may be observable as broad-band spectroscopic distortions of the cosmic background radiation, which otherwise exhibits a nearly perfect blackbody spectrum. The chemical history of the expanding universe is followed through a detailed calculation of the evolution of the abundances of H, H+, H-, H2, H2+, H3+, and other minor species. It is shown that continuous absorption by the small concentration of H- can produce a distortion in the cosmic background spectrum with a maximum at a frequency near nu/c = 9 cm-1 (wavelength 1.1 mm). The predicted effect lies only a factor of 5 below current limits. Its detection would provide an important test of our understanding of the recombination epoch of the universe.