Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O₂) injected and hydrogen peroxide (H₂O₂) added discharge in water was achieved. The effect of H₂O₂ dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H₂O₂ addition with O₂ injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH^•, H, and O). Interestingly, the results demonstrated that O₂ injected and H₂O₂ added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

The influence of multi-line pulsed excitation of target isotopes within the method of selective laser assisted retarded condensation (SILARC) on the efficiency of boron isotopes separation is investigated. In pulsed mode simultaneous excitation of all four isotopologues ${}^{11}{B}^{35}C{l}_n^{37}C{l}_{3-n}$ is possible. In order to study it, a new formula for multi-line excitation rate is derived. The total number of photons absorbed by target isotopologues for proposed physical parametrization of the laser pulse is compared with continuous wave excitation case, corresponding to the minimal level of laser intensity, required to excite all four isotopologues. It is found that irradiation efficiency of the pulsed mode is 20.59 times smaller than for CW-mode one. Influence of multi-pass cavity on the efficiency of excitation has been also considered.

More cheap production of boron isotopes is needed to provide further progress in nuclear engineering, microelectronics, and nuclear medicine. Separation of boron isotopes by laser-assisted retarded condensation scheme is considered. Continuous irradiation of steady gas flow is considered. In this case, interaction time of gas flow with laser beam (gas flow length) is desirable to make as long as possible in order to increase excitation probability. It can be provided by suitable choice of gas flow expansion conditions, such as small molar fraction of target gas in carrier gas, gas flow, and ambient small gas pressure and temperature. We propose irradiation cell design as a resonant multipass cavity. In order to estimate its length that can be used for efficient isotopes separation, we calculated laser field distribution inside the cavity for different assumed values for mirror wall reflectivities and average photo-absorption cross sections. It has been shown, that significant saving of electricity (4.2-4.6 times less) can be expected.

It is assumed that strong chromofields are generated at early stages of ultrarelativistic heavy-ion collisions which give rise to a collective deceleration of net baryons from colliding nuclei. We have solved classical equations of motion for baryonic slabs under the action of a time-dependent longitudinal chromoelectric field. It is demonstrated that the slab final rapidities are rather sensitive to the strength and decay time of the chromofield as well as to the back reaction of the produced partonic plasma. The net-baryon rapidity loss of about 2 units, found for most central Au-Au collisions at RHIC, can be explained by the action of chromofields with the initial energy density of about 50 GeV/fm^3. Predictions for the baryon stopping at the LHC are made.Comment: 10 pages in revtex, 3 eps figure