Double ionization of helium by electron-impact: complete pictures of the four-body breakup dynamics

The dynamics of He double ionization by 2 keV electron impact is studied experimentally for a momentum transfer of 0.6 a.u. at excess energies of 10 and 40 eV. Complete sets of fivefold differential cross sections are presented for all electron emission angles in coplanar geometry. Contributions beyond the first Born approximation are identified comparing experimental data with first order convergent close-coupling calculations which are in considerably better agreement with the present experiment than with the earlier measurement of Kheifets et al. [J. Phys. B 32, 5047 (1999)]

Appearance and disappearance of the second Born effects in the (e,3e) reaction in He

We demonstrate, both experimentally and theoretically, clear manifestation of the second Born effects in the angular distributions of two ejected electrons produced by a 500 eV electron impact on the He atom in the so-called (e,3e) reaction. The second Born contribution, due to subsequent interaction of the projectile with the target, is most prominent for glancing collisions with small momentum transfer. However, these effects are absent for hard knock-out collisions with large momentum transfer

The Acute Liver Injury in Mice Caused by Nano-Anatase TiO2

Although it is known that nano-TiO2or other nanoparticles can induce liver toxicities, the mechanisms and the molecular pathogenesis are still unclear. In this study, nano-anatase TiO2(5 nm) was injected into the abdominal cavity of ICR mice for consecutive 14 days, and the inflammatory responses of liver of mice was investigated. The results showed the obvious titanium accumulation in liver DNA, histopathological changes and hepatocytes apoptosis of mice liver, and the liver function damaged by higher doses nano-anatase TiO2. The real-time quantitative RT-PCR and ELISA analyses showed that nano-anatase TiO2can significantly alter the mRNA and protein expressions of several inflammatory cytokines, including nucleic factor-κB, macrophage migration inhibitory factor, tumor necrosis factor-α, interleukin-6, interleukin-1β, cross-reaction protein, interleukin-4, and interleukin-10. Our results also implied that the inflammatory responses and liver injury may be involved in nano-anatase TiO2-induced liver toxicity

Induction of CYP1A1 in rat lung cells following in vivo and in vitro exposure to quartz

Respirable quartz has been classified as a human lung carcinogen, but the mechanism by which quartz exposure leads to lung cancer has not been clarified. Consistently higher risks of lung cancer are reported in smokers with quartz exposure and we therefore hypothesised that quartz exposure may alter the expression of enzyme systems involved in activation/detoxification of pre-carcinogens in cigarette smoke. More specifically we studied cytochrome P4501A1 (CYP1A1) expression using reverse transcriptase polymerase chain reaction and immunohistochemistry (IHC) upon in vitro and in vivo quartz exposure. In vitro incubation of rat lung epithelial cells with DQ12 quartz for 24 h showed a dose-dependent induction of CYP1A1-mRNA. On the other hand, CYP1A1 message was not increased in lung epithelial cells isolated from rats at 3, 28 or 90 days after intratracheal instillation of 2 mg DQ12. Following IHC for CYP1A1 protein in rat lung sections from later time-points (180 and 360 days), we observed an increase in the number of CYP1A1 positive cells. After in vivo quartz exposure, protein expression of the Aryl hydrocarbon receptor (AhR) was increased and nuclear translocation of AhR was observed at the same time-points. In conclusion, our findings demonstrate an effect of quartz exposure on chronic CYP1A1 expression in vivo, whereas the in vitro models show an immediate upregulation. We suggest that this upregulation of CYP1A1 may act as a co-carcinogenic pathway in quartz exposed workers by activation of pre-carcinogens such as those present in cigarette smoke

Double ionization of helium by electron impact in the impulsive regime

The dynamics of helium double ionization by 2 keV electron impact has been investigated experimentally and theoretically at large momentum transfer of \q\ = 2 a. u. Fully resolved fivefold differential cross sections (FDCS's) are presented for symmetric and asymmetric energy sharing between the two ejected electrons at excess energies from 10 to 40 eV, and for the coplanar as well as the out-of-plane scattering geometries. Experimentally, a multielectron-recoil-ion coincidence technique has been applied and a large part of the final-state momentum space has been mapped. The presently employed theoretical model treats the interaction between the two slow ejected electrons nonperturbatively using the convergent close- coupling method, whereas the projectile-target interaction is described in the first Born approximation. The experimental and theoretical FDCS's agree well in shape. The cross section is dominated by two pairs of strong peaks. From this pattern it can be concluded that the two-step 1 mechanism, which is due to interelectron interaction after a single ionizing collision, is the dominant ionization process for the present kinematics

DNA damage in lung epithelial cells isolated from rats exposed to quartz: role of surface reactivity and neutrophilic inflammation

DNA damage in lung epithelial cells isolated from rats exposed to quartz: role of surface reactivity and neutrophilic inflammation. Knaapen AM, Albrecht C, Becker A, Hohr D, Winzer A, Haenen GR, Borm PJ, Schins RP. Institut fur umweltmedizinische Forschung at the University of Dusseldorf, Department of Particle Toxicology, Auf'm Hennekamp 50, 40225 Dusseldorf, Germany. Respirable quartz has been classified as a human lung carcinogen (IARC, 1997). However, the mechanisms involved in quartz-induced carcinogenesis remain unclear. The aim of the present study was to investigate acute DNA damage in epithelial lung cells from rats exposed to quartz. Since surface reactivity is considered to play a crucial role in the toxicity of quartz, the effect of surface modifying agents polyvinylpyridine-N-oxide (PVNO) and aluminium lactate (AL) was evaluated. Therefore, rats were instilled with quartz (DQ12, 2 mg/rat) or quartz treated with PVNO or AL. After 3 days animals were killed and brochoalveolar lavage (BAL) was performed to evaluate inflammatory cell influx. BAL-fluid levels of lactate dehydrogenase (LDH), alkaline phosphatase (AP) and total protein were used as lung damage markers. Neutrophil activation was assessed by myeloperoxidase (MPO) measurement, and total antioxidant capacity of the BAL-fluid was determined using the TEAC (trolox equivalent antioxidant capacity) assay. Lung epithelial cells were isolated and DNA strand breakage was determined by single cell gel electrophoresis (comet assay). DNA damage was significantly increased in epithelial cells from rats instilled with DQ12, whereas no enhanced DNA strand breakage was observed when quartz was treated with PVNO or AL. Total protein, LDH and TEAC were increased in rats treated with native quartz, and this was inhibited by both coatings. A significant correlation between neutrophil numbers and MPO levels was observed, indicating neutrophil activation. Inhibition of DNA damage by both coatings was paralleled by a reduction of neutrophil influx as well as MPO activity. In this study we provide evidence that modification of the particle surface prevents DNA strand breakage in epithelial lung cells from quartz-exposed rats. Furthermore, the present data show the feasibility of our in vivo model to evaluate the role of inflammation, antioxidant status, and cytotoxicity in particle-induced DNA damage

Double ionization of helium by electron impact in the impulsive regime

Experimental and theoretical fully differential cross sections were considered for double ionization of helium by 2-keV electron impact. The measurements were performed employing the reaction microscope which allows to detect simultaneously a large part of the final-state momentum space. Data were obtained for a noncoplanar geometry where one electron is emitted 45°C above and the second electron 45°C below the scattering plane