Tire abrasion particles negatively affect plant growth even at low concentrations and alter soil biogeochemical cycling

Tire particles (TPs) are a major source of microplastic on land, and considering their chemical composition, they represent a potential hazard for the terrestrial environment. We studied the effects of TPs at environmentally relevant concentrations along a wide concentration gradient (0–160 mg g−1) and tested the effects on plant growth, soil pH and the key ecosystem process of litter decomposition and soil respiration. The addition of TPs negatively affected shoot and root growth already at low concentrations. Tea litter decomposition slightly increased with lower additions of TPs but decreased later on. Soil pH increased until a TP concentration of 80 mg g−1 and leveled off afterwards. Soil respiration clearly increased with increasing concentration of added TPs. Plant growth was likely reduced with starting contamination and stopped when contamination reached a certain level in the soil. The presence of TPs altered a number of biogeochemical soil parameters that can have further effects on plant performance. Considering the quantities of yearly produced TPs, their persistence, and toxic potential, we assume that these particles will eventually have a significant impact on terrestrial ecosystems

Structure effects on the Coulomb dissociation of 8B at relativistic energies

We investigate the Coulomb dissociation of 8B on 208Pb target at the beam energy of 250 MeV/nucleon, employing the cross sections for the radiative capture reaction 7Be(p,gamma)8B calculated within the Shell Model Embedded in the Continuum (SMEC) approach. In contrast to the situation at lower beam energies, the Coulomb breakup cross sections are found to be sensitive to the M1 transitions. Comparisons of SMEC and single-particle potential model predictions show that the Coulomb breakup cross sections at these high energies are sensitive to the structure model of 8B. Analysis of the preliminary data taken recently at GSI reveal that E2 multipolarity contributes up to 25 % to the cross sections even for the relative energies of p - 7Be below 0.25 MeV.Comment: 22 pages, 7 figure

Study of the 7Be(p,γ)8B^7Be(p,\gamma)^8B and 7Li(n,γ)8Li^7Li(n,\gamma)^8Li capture reactions using the shell model embedded in the continuum

We apply the realistic shell model which includes the coupling between many-particle (quasi-)bound states and the continuum of one-particle scattering states to the spectroscopy of mirror nuclei: $^8$B and $^8$Li, as well as to the description of low energy cross sections (the astrophysical S factors) in the capture reactions:$^7Be(p,\gamma)^8B$ and $^7Li(n,\gamma)^8Li$.Comment: 36 pages, 10 figure

Description of the 17F(p,gamma)18Ne radiative capture reaction in the continuum shell model

The shell model embedded in the continuum is applied to calculate the astrophysical S-factor and the reaction rate for the radiative proton capture reaction 17F(p,gamma)18Ne. The dominant contribution to the cross-section at very low energies is due to M1 transitions J_i^pi = 2^+ --> J_f^pi = 2_1^+ whose magnitude is controlled by a weakly bound 2_2^+ state at the excitation energy E_x = 3.62 MeV.Comment: 31 pages, latex (uses elsart.cls), 14 figures, submitted to Nuclear Physics

A Magnetically Guided Slow Positron Beam for Defect Studies

The design and construction of a compact, magnetically guided slow positron beam is discussed. The system uses a 30 mCi $\text{}^{22}$Νa source. It consists of three main parts: (i) the source chamber with a tungsten foil transmission moderator and the extraction optics, (ii) the beam line with magnetic beam guidance, a bent tube for the separation of the fast positrons and the accelerator stage, (iii) the target chamber with the sample holder and the detector electronics. The energy of the incident positrons can be varied from 30 eV up to 50 keV. Furthermore source geometries, pre-acceleration, main acceleration sections and various magnetic induction profiles have been considered, such as (i) rectangular, conical and bent Wehnelt electrodes, (iii) pre-accelerator voltage shared over several electrodes, (iii) weak, strong, constant and z-dependent B-profiles, (iv) geometric options in the main accelerator region, (v) purely electrostatic and combined electric/magnetic fields. The beam is mainly designed for defect profile studies in ultra high vacuum conditions