Characterization of relativistic electron-positron beams produced with laser-accelerated GeV electrons.

The characterization of an electron-positron beam generated from the interaction of a multi-GeV electron beam with a lead plate is performed using GEANT4 simulations. The dependence of the positron beam size on driver electron beam energy and lead converter thickness is investigated in detail. A pancake-like positron beam structure is generated with a monoenergetic multi-GeV driver electron beam, with the results indicating that a 5 GeV driver electron beam with 1 nC charge can generate a positron beam with a density of 1015-1016 cm-3 at one radiation length of lead. In addition, we find that electron-positron beams generated using above-GeV electron beams have neutralities greater than 0.3 at one radiation length of lead, whereas neutralities of 0.2 are observed when using a 200 MeV electron beam. The possibility of observing plasma instabilities in experiments is also examined by comparing the plasma skin depth with the electron-positron beam size. A quasi-neutral electron-positron plasma can be produced in the interaction between a 1 nC, 5 GeV electron beam and lead with a thickness of five radiation lengths. Our findings will aid in analyzing and interpreting laser-produced electron-positron plasma for laboratory astrophysics research.

Pueraria montana var. lobata root extract inhibits photoaging on skin through Nrf2 pathway.

Pueraria montana var. lobata is a bioactive substance, in possession of a variety of beneficial health effects, which has long been extensively used as a traditional medication for the treatment of fever, acute dysentery, diabetes, and cardiovascular diseases in North-East Asian countries. The purpose of this study was to evaluate the cytoprotective activity of Pueraria montana var. lobata ethanol extract (PLE) for ultraviolet B (UVB) induced oxidative stress in human dermal fibroblasts (HDF). It was hypothesized that PLE treatment (25-100 µg/mL) would reduce intracellular reactive oxygen species (ROS) levels as well as increase collagen production in UVB-irradiated HDF. The results confirmed this theory, with collagen production increasing in the PLE treatment group in a dose-dependent manner. In addition, regulators of cellular ROS accumulation, including HO-1 and NOQ-1, were activated by Nrf2, which was mediated by PLE. Hence, intracellular levels of ROS were also reduced in the PLE treatment group in a dose-dependent manner. In conclusion, PLE increases collagen production and maintains hyaluronic acid (HA) levels in human dermal fibroblasts exposed to UVB-irradiation, thereby inhibiting photoaging.