Ion density of positive and negative ions at ambient pressure in air at 12-136 mm from 4.9 kV soft x-ray source

The abundance of ions is an essential parameter for ion mobility and mass spectrometry instrument design and for the control or optimization of chemical reactions with reactant ions. This information also advances the study of atmospheric pressure ion kinetics under continuous ionization, which has a role in developing trace level chemical analyzers. In this study, an ionization chamber is described to measure the abundance of ions produced by a 4.9 keV, model L12535, soft x-ray source from Hamamatsu Corporation. Ions of positive and negative polarity were measured independently in an 8 x 30 mm(2) cross section at distances of 12-136 mm at ambient air from an uncollimated beam. Ions were collected using electric fields and 16 sets of plates. The ion current decreased exponentially with distance from the source, and the calculated ion concentration varied between 1.0 x 10(8) and 3.8 x 10(5) ions cm(-3) on plates. A 2D-COMSOL model including losses by recombination and diffusion was favorably matched to changes in ion current intensity in the ionization chamber. Although the ionization chamber was built to characterize a commercial ion source, the design may be considered generally applicable to other x-ray sources. (C) 2021 Author(s).Peer reviewe

Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes

It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani-ons are emitted with low kinetic energy due to many-body processes. Model calcu-lations show that both nucleus-nucleus interactions and electronic excitations con-tribute to the observed large anion emission yield.Comment: 5 pages, 4 figure

Parametric Sensitivity in a Generalized Model for Atmospheric Pressure Chemical Ionization Reactions

Gas phase reactions between hydrated protons H+(H2O)(n) and a substance M, as seen in atmospheric pressure chemical ionization (APCI) with mass spectrometry (MS) and ion mobility spectrometry (IMS), were modeled computationally using initial amounts of [M] and [H+(H2O)(n)], rate constants k(1) to form protonated monomer (MH+(H2O)(x)) and k(2) to form proton bound dimer (M2H+(H2O)(z)), and diffusion constants. At 1 x 10(10) cm(-3) (0.4 ppb) for [H+(H2O)(n)] and vapor concentrations for M from 10 ppb to 10 ppm, a maximum signal was reached at 4.5 mu s to 4.6 ms for MH+(H2O)(x) and 7.8 mu s to 46 ms for M2H+(H2O)(z). Maximum yield for protonated monomer for a reaction time of 1 ms was similar to 40% for k(1) from 10(-11) to 10(-8) cm(3).s(-1), for k(2)/k(1) = 0.8, and specific values of [M]. This model demonstrates that ion distributions could be shifted from [M2H+(H2O)(z)] to [MH+(H2O)(x)] using excessive levels of [H+(H2O)(n)], even for [M] > 10 ppb, as commonly found in APCI MS and IMS measurements. Ion losses by collisions on surfaces were insignificant with losses ofPeer reviewe

Ten_m3 Regulates Eye-Specific Patterning in the Mammalian Visual Pathway and Is Required for Binocular Vision

Binocular vision requires an exquisite matching of projections from each eye to form a cohesive representation of the visual world. Eye-specific inputs are anatomically segregated, but in register in the visual thalamus, and overlap within the binocular region of primary visual cortex. Here, we show that the transmembrane protein Ten_m3 regulates the alignment of ipsilateral and contralateral projections. It is expressed in a gradient in the developing visual pathway, which is consistently highest in regions that represent dorsal visual field. Mice that lack Ten_m3 show profound abnormalities in mapping of ipsilateral, but not contralateral, projections, and exhibit pronounced deficits when performing visually mediated behavioural tasks. It is likely that the functional deficits arise from the interocular mismatch, because they are reversed by acute monocular inactivation. We conclude that Ten_m3 plays a key regulatory role in the development of aligned binocular maps, which are required for normal vision

Bioprosthetic mitral valve thrombosis less than one year after replacement and an ablative MAZE procedure: a case report

Occurrence of bioprosthetic valve thrombosis less than a year after replacement is very uncommon. Here, we describe a case of a 57 year old male, who presented 10 months after receiving a bioprosthetic mitral valve replacement with a two week history of dyspnea on exertion, worsening orthopnea and decreased exercise tolerance. Echocardiography revealed severe mitral regurgitation (MR), thrombosis of the posterior mitral leaflet, left atrial (LA) mural thrombus and a depressed left ventricular ejection fraction of twenty-five percent. Given severe clot burden and decompensated heart failure (New York Heart Association - NYHA class III) repeat sternotomy was done to replace the bioprosthetic mitral valve and remove LA mural thrombus. MR was resolved postoperatively. This brief report further reviews promoting factors, established guidelines and management strategies of bioprosthetic valve thrombosis