Using 157Gd doped carbon and 157GdF4 nanoparticles in proton-targeted therapy for effectiveness enhancement and thermal neutron reduction: a simulation study.

There are two major problems in proton therapy. (1) In comparison with the gamma-ray therapy, proton therapy has only ~ 10% greater biological effectiveness, and (2) the risk of the secondary neutrons in proton therapy is another unsolved problem. In this report, the increase of biological effectiveness in proton therapy has been evaluated with better performance than 11B in the presence of two proposed nanomaterials of 157GdF4 and 157Gd doped carbon with the thermal neutron reduction due to the presence of 157Gd isotope. The present study is based on the microanalysis calculations using GEANT4 Monte Carlo tool and GEANT4-DNA package for the strand breaks measurement. It was found that the proposed method will increase the effectiveness corresponding to the alpha particles by more than 100% and also, potentially will decrease the thermal neutrons fluence, significantly. Also, in this work, a discussion is presented on a significant contribution of the secondary alpha particles in total effectiveness in proton therapy.

Inactivation of Escherichia coli by atmospheric pressure plasma jet in water.

The main aim of this work is inactivation of Escherichia coli in water using a laboratory-scale radio-frequency atmospheric pressure Argon plasma jet. This bacterium is widely present in the environment, especially in drinking water, and its pathogenic effects are very harmful. For this purpose, an Argon flow rate of 3.5 slm, maximum plasma power of 200 W, and discharge frequency of 13.56 MHz was conducted to generate a uniform plasma plume for water treatment. 150 ml of drinking water contaminated by E. coli was exposed to the radiation of plasma placed about 3 cm within the water, the treatment time varied from 2 to 6 minutes at 100, 150, and 200 W of plasma input power. The temperature of the plume, discharge current and voltage, and electron density were all measured to characterize the plasma. Active species such as excited molecules, ions, and radicals produced in the plasma in water were detected using the optical emission spectroscopy method. The decreasing behavior of live bacteria versus exposure time and plasma jet input power was observed, and finally, at the discharge power of 200 W and 6 min, an effective inactivation was achieved and the number of bacteria reduced from 92×104 to less than 1.7 MPN/100 ml.