Hydrogen migration plays an important role in the chemistry of hydrocarbons which considerably influences their chemical functions. The migration of one or more hydrogen atoms occurring in hydrocarbon cations has an opportunity to produce the simplest polyatomic molecule, i.e. H3+. Here we present a combined experimental and theoretical study of H3+ formation dynamics from ethane dication. The experiment is performed by 300 eV electron impact ionization of ethane and a pronounced yield of H3+ + C2H3+ coincidence channel is observed. The quantum chemistry calculations show that the H3+ formation channel can be opened on the ground-state potential energy surface of ethane dication via transition state and roaming mechanisms. The ab initio molecular dynamics simulation shows that the H3+ can be generated in a wide time range from 70 to 500 fs. Qualitatively, the trajectories of the fast dissociation follow the intrinsic reaction coordinate predicted by the conventional transition state theory. The roaming mechanism, compared to the transition state, occurs within a much longer timescale accompanied by nuclear motion of larger amplitude.

Absolute differential cross sections are reported for electron capture and loss by 1–5 keV H atoms incident on CH4 for laboratory scattering angles up to 1.62°, and for charge transfer of 0.5–5 keV H+ with CH4 for scattering angles up to 2.09°. Electron-loss collisions are seen to result in comparatively large scattering angles and a very clear similarity exists between the present differential cross sections and those reported for other molecular targets. The present charge-transfer differential cross sections are consistent with that of Gao et al (1990 Phys. Rev. A 41 5929–33) but not with the calculations of Kimura et al (1995 Phys. Rev. A 52 1196–205). Prior experimental studies of electron-loss and charge-transfer are generally in good accord with the integral values reported here as are the calculations of Kusakabe et al (2000 Phys. Rev. A 62 062715).

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Background Takayasu arteritis (TAK) is a chronic granulomatous large vessel vasculitis with multiple immune cells involved. Chemokines play critical roles in recruitment and activation of immune cells. This study aimed to investigate chemokine profile in the peripheral blood and vascular tissue of patients with TAK. Methods A total of 58 patients with TAK and 53 healthy controls were enrolled. Chemokine array assay was performed in five patients with TAK and three controls. Chemokines with higher levels were preliminarily validated in 20 patients and controls. The validated chemokines were further confirmed in another group of samples with 25 patients and 25 controls. Their expression and distribution were also examined in vascular tissue from 8 patients and 5 controls. Correlations between these chemokines and peripheral immune cells, cytokines, and disease activity parameters were analyzed. Their serum changes were also investigated in these 45 patients after glucocorticoids and immunosuppressive treatment. Results Patients and controls were age and sex-matched. Twelve higher chemokines and 4 lower chemokines were found based on the chemokine array. After validation, increase of 5 chemokines were confirmed in patients with TAK, including CCL22, RANTES, CXCL16, CXCL11, and IL-16. Their expressions were also increased in vascular tissue of patients with TAK. In addition, levels of RANTES and IL-16 were positively correlated with peripheral CD3+CD4+ T cell numbers. Close localization of CCL22, CXCL11, or IL-16 with inflammatory cells was also observed in TAK vascular tissue. No correlations were found between these chemokines and cytokines (IL-6, IL-17, IFN-γ) or inflammatory parameters (ESR, CRP). No differences were observed regarding with these chemokines between active and inactive patients. After treatment, increase of CCL22 and decrease of RANTES and CXCL16 were found, while no changes were showed in levels of CXCL11 and IL-16. Conclusions CCL22, RANTES, CXCL16, CXCL11, and IL-16 were identified as the major chemokines involved in the recruitment of immune cells in the vascular tissue of patients with TAK. Additionally, the persistently high levels of CCL22, CXCL11, and IL-16 observed after treatment indicate their role in vascular chronic inflammation or fibrosis and demonstrate the need for developing more efficacious treatment options.

Absolute partial and total cross sections for electron-impact ionization of CCl4 and CCl2F2 are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ion species are collected with equal efficiency irrespective of their initial kinetic energies. Data are presented for production of CCl3(+), CCl2(+), CCl+, C+, Cl2(+), and CCl3(2+) from CCl4; and for production of CCl(2)F+, CClF2(+), CClF(+), (CCl+ + CF2(+)), Cl+, CF+, F+, and C+ from CCl2F2. Data are also reported for formation of (CCl2(+),Cl+) and (CCl+, Cl+) ion pairs from CCl4. The total cross section for each target is obtained as the sum of the partial cross sections. The overall uncertainty in the absolute cross sections for most of the singly charged ions is +/- 5-7 %. The present partial cross sections for lighter fragment ions are found to be considerably greater than had been previously reported but the most recent total cross section measurements agree well with those reported here. Neither the binary-encounter-Bethe theory nor the Deutsch-Mark theory reproduces the experimental cross sections correctly for both targets.

Absolute differential cross sections are reported for electron capture and loss by ͑1-5͒-keV oxygen atoms incident on He, H 2 , N 2 , and O 2 for scattering angles between 0.02°and 1.73°in the laboratory frame. The form of the differential cross sections is seen to vary significantly with energy and between different targets. Differences between the present O-atom electron-loss cross sections and those for H atoms reported previously imply that the underlying physical mechanism may not be the same. The integral cross sections, also reported here, are consistent with most previous studies. The consensus of the available electron-loss data suggests that the cross sections of Fogel et al. [Soviet Phys. JETP 35, 601 (1959)] are in error.

The absolute electron capture cross sections for single and double charge exchanges (CEs) between the highly charged ion O6+ and CO2, CH4, H2, and N2, the dominant collision processes in the solar wind, have been measured in the energies from 7 keV · q (2.63 keV u−1) to 52 keV · q (19.5 keV u−1). These measurements were carried out in the new experimental instrument setup at Fudan University, and the errors of the cross sections for single and double CEs at the 1σ confidence level were about 11% and 16%, respectively. Limited agreement is achieved with single electron capture results calculated by the classical overbarrier model. These cross section data are useful for the simulation of ion–neutral processes in astrophysical environments and to improve the present theoretical model of fundamental atomic processes.

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