This work reports the design and characterization of a rotating gliding arc (RGA) reactor developed with novel electrode configuration. This RGA uses gas swirl discs having 'tangential gas entry ports/holes' (NH) to achieve arc rotation and does not employ any external magnets. This work investigates the effect of gas dynamics on (1) arc dynamics such as the arc's rotation and shape; (2) voltage fluctuation pattern; and (3) plasma discharge power for the designed RGA. Experiments were conducted using argon as the plasma forming gas with (a) two gas swirl discs (NH=3 and 12) and (b) three different gas flow rates (Q=5, 25 and 50 LPM) as control parameters. Cold flow simulation (CFS) studies using a multidimensional solver were used to understand gas dynamics. The arc rotational frequency (f arc ) measured from (1) a high-speed camera (HSC) and (2) fast Fourier transform (FFT) analysis of voltage, shows linear dependency on the Reynolds number (Re) calculated from CFS, with an R 2 =0.98. The agreement improves (R 2 =0.99) by applying linear fit only for the cases having turbulent Re. A close match between gas rotational frequency (f gas ) calculated from CFS and experimentally measured f arc is seen. The turbulent regime of the gas flow causes: (1) twisting and bending of the arc; (2) sawtooth-like voltage fluctuations with irregular and non-sinusoidal waveform; and (3) arc blow off. The highfrequency voltage fluctuations were reduced/absent when the flow Re reduced from ≈6.0×10 4 to ≈1.0×10 4 . These findings establish that the gas dynamics, in particular, the bulk flow phenomenon of the gas, has an explicit influence on arc dynamics of the RGA reactor. This novel RGA design has the potential to replace magnetically driven rotating gliding arc systems.

This work investigates the reliability of the function called ‘regionprops’ which is used for measuring the 2D length of the plasma discharge. Work was conducted in a Rotating Gliding Arc (RGA) reactor, using air as plasma forming gas. Arc rotational images at three different gas flow rates i.e. 5, 25 and 50 litres per minute LPM were captured using high speed camera with an exposure of 100 μs. A total of 6799 images from all the three flow rates were considered for analysis. The 2D length of the discharge was measured by two methods namely, (a) ‘regionprops’ function (Python) and (b) manual tracing (ImageJ). The 2D arclength measured using ‘regionprops’ function matched very closely to that measured by manual hand tracing technique using ImageJ tool. A linear relation between both the methods was observed for all the three flow rates, with the coefficient of determination i.e. R 2 > 0.9 . The validation of ‘regionprops’ function shown in this work marks an important step as the function is simple to use and adapt compared to any other techniques such as shortest–path algorithm.

DNA double helix structure is stabilized by the base-pairing and the base-stacking interactions. Base-stacking interactions originating from hydrophobic interactions between the nucleobases predominantly contribute to the duplex stability. A comprehensive understanding of dinucleotide base-stacking interactions is lacking owing to the unavailability of sensitive techniques that can measure these weak interactions. Earlier studies attempting to address this question only managed to estimate the base-pair stacking interactions, however, disentangling individual base-stacking interactions was enigmatic. By combining multiplexed DNA-PAINT imaging with designer DNA nanostructures, we experimentally measure the free energy of dinucleotide base-stacking at the single-molecule level. Multiplexed imaging enabled us to extract binding kinetics of an imager strand with and without additional dinucleotide stacking interactions in a single imaging experiment, abolishing any effects of experimental variations. The DNA-PAINT data showed that a single additional dinucleotide base-stacking results in as much as 250-fold stabilization of the imager strand binding. We found that the dinucleotide base-stacking energies vary from -1.18 ± 0.17 kcal/mol to -3.57 ± 0.08 kcal/mol for C|T and A|C base-stackings, respectively. We demonstrate the application of base-stacking energetics in designing DNA-PAINT probes for multiplexed super-resolution imaging. Our results will aid in designing functional DNA nanostructures, DNA and RNA aptamers, and facilitate better predictions of the local DNA structure.

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Non-thermal plasma discharge in air generates several species, including reactive oxygen and nitrogen species (RONS). If, plasma is generated above a water column, some of these species gets transferred into the water column below generating plasma activated water (PAW), which is known to have several applications. These applications are attributed to the reactive species generated by the plasma discharge. To cater specifically to each application, a complete chemical characterization of plasma discharge in air and PAW is vital, as each of these species have their own unique contribution to the application of PAW. In this work, analysis of the plasma discharge in air using optical emission spectroscopy (OES) and detailed characterization of PAW for its chemical constituents was done. In PAW, the parameters namely, pH, electrical conductivity ( ), 2 2 , 3 − , and 2 − were quantified as a function of plasma exposure time. The values of 3 − ( 6000) and ( 4600) obtained in this study were about 50% and 130% higher respectively, than what has generally been reported. The antimicrobial nature of the PAW on Pseudomonas aeruginosa, one of the bacteria responsible for nosocomial infections was also tested, and PAW was able to inactivate the bacterium.