Low-Energy Electron Attachment to the Dichlorodifluoromethane (CCl2F2) Molecule

Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl2F2) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl- wits measured over the energy range 0.001-1.8 eV at the gas temperature T-G = 300 K. It exhibits cusp structure at thresholds for vibrational excitation of the v(3)(a(1)) mode due to interaction with the attachment channels. With reference to the thermal attachment rate coefficient k(T-e;T-G = 300 K) = 2.2(8) x 10(-9) cm(-3) s(-1) (fitted average from several data), a new highly resolved absolute attachment cross section for TG = 300 K was determined. Partial cross sections for formation of the anions Cl-, Cl-2(-), F-, ClF-, and CCl2F- were measured over the range 0-12 eV, using three different electron beam experiments of medium energy resolution. The dependence of the attachment rate coefficient k(T-e;T-G = 300 K) on electron temperature T-e wits calculated over the range 50-15 000 K, based on a newly constructed total cross section for anion formation at T-G = 300 K. R-matrix Calculations for Cl- production have been carried out for comparison with the experimental data. The R-matrix results are in line with the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level v(3) and on the vibrational temperature. Furthermore, the cross section for I Vibrational excitation of the v(3) mode hits been computed.

Target Structure Induced Suppression of the Ionization Cross Section for Very Low Energy Antiproton-Hydrogen Collisions

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

Inactivation of V79 cells by low-energy protons, deuterons and helium-3 ions

Previous work by ourselves and by others has demonstrated that protons with a linear energy transfer (LET) about 30 V mu m(-1) are more effective at killing cells than doubly charged particles of the same LET. In this work we show that by using deuterons, which have about twice the range of protons with the same LET, it is possible to extend measurements of the RBE of singly charged particles to higher LET (up to 50 keV mu m(-1)). We report the design and use of a new arrangement for irradiating V79 mammalian cells. Cell survival. measurements have been made using protons in the energy range 1.0-3.7 MeV, deuterons in the energy range 0.9-3.4 MeV and He-3(2+) ions in the energy range 3.4-6.9 MeV;. This corresponds to volume-averaged LET (within the cell nucleus) between 10 and 28 keV mu m(-1) for protons, 18-50 keV mu m(-1) for deuterons, and 59-106 keV mu m(-1) for helium ions. Our results show no difference in the effectiveness of protons and deuterons matched for LET. However, for LET above about 30 keV mu m(-1) singly charged particles are more effective at inactivating cells than doubly-charged particles of the same LET and that this difference can be understood in terms of the radial dose distribution around the primary ion track.

Critical energies for SSB and DSB induction in plasmid DNA by low-energy photons: action spectra for strand-break induction in plasmid DNA irradiated in vacuum

Purpose: To measure action spectra for the induction of single- strand breaks (SSB) and double-strand breaks (DSB) in plasmid DNA by low-energy photons and provide estimates for the energy dependence of strand-break formation important for track-structure simulations of DNA damage.

Role of low-energy electrons in Ar emission from low-pressure radio frequency discharge plasma

Optical emission spectra from a low-pressure Ar plasma were studied with high spatial resolution. It has been shown that the intensity ratios of Ar lines excited through metastable levels to those excited directly from the ground state are sensitive to the shape of electron energy distribution function. From these measurements, important information on the spatial variation of plasma parameters can be obtained. (C) 1999 American Institute of Physics. [S0003-6951(99)01629-0].

Low-energy cranberry juice decreases lipid oxidation and increases plasma antioxidant capacity in women with metabolic syndrome

Cranberries, high in polyphenols, have been associated with several cardiovascular health benefits, although limited clinical trials have been reported to validate these findings. We tested the hypothesis that commercially available low-energy cranberry juice (Ocean Spray Cranberries, Inc, Lakeville-Middleboro, Mass) will decrease surrogate risk factors of cardiovascular disease, such as lipid oxidation, inflammation, and dyslipidemia, in subjects with metabolic syndrome. In a randomized, double-blind, placebo-controlled trial, participants identified with metabolic syndrome (n = 15-16/group) were assigned to 1 of 2 groups: cranberry juice (480 mL/day) or placebo (480 mL/day) for 8 weeks. Anthropometrics, blood pressure measurements, dietary analyses, and fasting blood draws were conducted at screen and 8 weeks of the study. Cranberry juice significantly increased plasma antioxidant capacity (1.5 ± 0.6 to 2.2 ± 0.4 µmol/L [means ± SD], P <.05) and decreased oxidized low-density lipoprotein and malondialdehyde (120.4 ± 31.0 to 80.4 ± 34.6 U/L and 3.4 ± 1.1 to 1.7 ± 0.7 µmol/L, respectively [means ± SD], P <.05) at 8 weeks vs placebo. However, cranberry juice consumption caused no significant improvements in blood pressure, glucose and lipid profiles, C-reactive protein, and interleukin-6. No changes in these parameters were noted in the placebo group. In conclusion, low-energy cranberry juice (2 cups/day) significantly reduces lipid oxidation and increases plasma antioxidant capacity in women with metabolic syndrome.

DNA damage by low-energy ions

Ion-beam irradiation provides a promising treatment for some types of cancer. This promise is due mainly to the selective deposition of energy into a relatively small volume (the Bragg peak), thus reducing damage to healthy tissue. Recent observations that electrons with energies below the ionization potential of DNA can cause covalent damage to the bases and backbone have led to investigations into the ability of low-energy (