In situ collection of dust grains falling from Saturn's rings into its atmosphere

Saturn's main rings are composed of >95% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft's traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We report the direct in situ detection of material from Saturn's dense rings by the CDA impact mass spectrometer. Most detected grains are a few tens of nanometers in size and dynamically associated with the previously inferred "ring rain." Silicate and water-ice grains were identified, in proportions that vary with latitude. Silicate grains constitute up to 30% of infalling grains, a higher percentage than the bulk silicate content of the rings

Structures and Aggregation of the Methylamine−Borane Molecules, MenH3−nN·BH3 (n = 1−3), Studied by X-ray Diffraction, Gas-Phase Electron Diffraction, and Quantum Chemical Calculations

The structures of the molecules methylamine-borane, MeH(2)N.BH(3), and dimethylamine-borane, Me(2)HN.BH(3), have been investigated by gas-phase electron diffraction (GED) and quantum chemical calculations. The crystal structures have also been determined for methylamine-, dimethylamine-, and trimethylamine-borane, Me(n)H(3-n)N.BH(3) (n = 1-3); these are noteworthy for what they reveal about the intermolecular interactions and, particularly, the N-H...H-B dihydrogen bonding in the cases where n = 1 or 2. Hence, structures are now known for all the members of the ammonia- and amine-borane series Me(n)H(3-n)N.BH(3) (n = 0-3) in both the gas and solid phases. The structural variations and energetics of formation of the gaseous adducts are discussed in relation to the basicity of the Me(n)H(3-n)N fragment. The relative importance of secondary interactions in the solid adducts with n = 0-3 has been assessed by the semi-classical density sums (SCDS-PIXEL) approach

Expression of connexins 40 and 43 in human left atrium in atrial fibrillation of different aetiologies

Objective: To test the hypothesis that atrial fibrillation (AF) is associated with changes in the expression of connexins 40 and 43 in the left atrium with more pronounced changes in mitral valve disease than in lone AF. Methods: Protein concentrations of connexin 40 and connexin 43 were analysed in left atrial tissue of patients undergoing cardiac surgery. One group of patients had lone AF (n  =  41), one group had AF and mitral valve repair (n  =  36), and one group in sinus rhythm served as controls (n  =  15). Results: Western blot analysis of connexin 40 and connexin 43 expression showed an increase of both gap junctional proteins (connexin 43 > connexin 40) in patients with AF of all forms compared with patients in sinus rhythm (p  =  0.01 and p  =  0.011, respectively). Subgroup analysis showed increased concentrations of connexin 40 in lone AF and AF with mitral valve disease compared with sinus rhythm (p  =  0.06 and p  =  0.029, respectively), whereas the same analysis for connexin 43 reached significance only in the mitral valve disease group (p  =  0.031). No differences in connexin 40 and connexin 43 expression were detectable between lone AF and AF with mitral valve disease. Within the groups connexin 40 and connexin 43 expression did not differ between patients with paroxysmal AF and patients with chronic AF. Conclusion: The present study shows for the first time that AF can induce changes in the left atrium with increased connexin expression. Furthermore, no systematic differences between patients with paroxysmal and chronic AF were detected

In situ collection of dust grains falling from Saturn’s rings into its atmosphere

Abstract Saturn’s main rings are composed of >95% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft’s traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We report the direct in situ detection of material from Saturn’s dense rings by the CDA impact mass spectrometer. Most detected grains are a few tens of nanometers in size and dynamically associated with the previously inferred “ring rain.” Silicate and water-ice grains were identified, in proportions that vary with latitude. Silicate grains constitute up to 30% of infalling grains, a higher percentage than the bulk silicate content of the rings