Determination of the characteristic inactivation fluence for SARS-CoV-2 under UV-C radiation considering light absorption in culture media

The optical absorption coefficient of culture media is critical for the survival analysis of pathogens under optical irradiation. The quality of the results obtained from experiments relies on the optical analysis of the spatial distribution of fluence which also depends on the geometry of the sample. In this contribution, we consider both the geometrical shape and the culture medium’s absorption coefficient to evaluate how the spatial distribution of optical radiation affects pathogens/viruses. In this work, we exposed SARS-CoV-2 to UV-C radiation ($$\lambda$$ λ = 254 nm) and we calculated—considering the influence of the optical absorption of the culture medium—a characteristic inactivation fluence of $$F_i$$ F i = 4.7 J/m2, or an equivalent 10% survival (D90 dose) of 10.8 J/m2. Experimentally, we diluted the virus into sessile drops of Dulbecco’s Modified Eagle Medium to evaluate pathogen activity after controlled doses of UV irradiation. To validate the optical absorption mode, we carried out an additional experiment where we varied droplet size. Our model—including optical absorption and geometrical considerations—provides robust results among a variety of experimental situations, and represents our experimental conditions more accurately. These results will help to evaluate the capability of UV disinfecting strategies applied to a variety of everyday situations, including the case of micro-droplets generated by respiratory functions.

Determination of the characteristic inactivation fluence for SARS-CoV-2 under UV-C radiation considering light absorption in culture media

The optical absorption coefficient of culture media is critical for the survival analysis of pathogens under optical irradiation. The quality of the results obtained from experiments relies on the optical analysis of the spatial distribution of fluence which also depends on the geometry of the sample. In this contribution, we consider both the geometrical shape and the culture medium’s absorptivity to evaluate how the spatial distribution of optical radiation affects pathogens/viruses. In this work, we exposed SARS-CoV-2 to UV-C radiation (λ =254 nm) and we calculated – considering the influence of the optical absorption of the culture medium – a characteristic inactivation fluence of F i =4.7 J/m2 , or an equivalent 10% survival (D90 dose) of 10.8 J/m2. Experimentally, we diluted the virus into sessile drops of Dulbecco’s Modified Eagle Medium to evaluate pathogen activity after controlled doses of UV irradiation. To validate the optical absorption mode, we carried out an additional experiment where we varied droplet size. Our model – including optical absorption and geometrical considerations – provides robust results among a variety of experimental situations, and represents our experimental conditions more accurately. These results will help to evaluate the capability of UV disinfecting strategies applied to a variety of everyday situations, including the case of micro-droplets generated by respiratory functions.

THE FEATURES OF STRUCTURE PARAMETERS CHANGES Ag3AsS3 SEMICONDUCTOR

Influence of temperature and optical irradiation is investigated on the parameters of elementary cell and linear coefficients of thermal expansion of Ag3AsS3 proustite crystals. Object of the study - single-crystals of compounds - semiconductor Ag3AsS3. Purpose of the study - to determine an elementary cell parameters change features of Ag3AsS3crystals in the interval of temperatures of T= 120-300 К with presence of optical irradiation. Method of the study - X-rays metod. Temperature dependences of the elementary cell parameters and also linear coefficients of thermal expansion of crystals of proustite Ag3AsS3 are investigated in the temperature range of T=120 - 300 K both in the darken mode and with an intensive laser irradiation. It is discovered, that there is a change of the parameter Ac «0,003A as a height at cooling and reduction at heating at the temperature of T «150 K on condition of laser irradiation. The jump of values of parameter of elementary cell represents the change of character of processes of deserializing of cations of Ag+ in transition from the darken mode to the intensive laser irradiation, because the size of silver ions transition potential barrier between octahedral cavities change as a jump. KEY WORDS: CRYSTALLINE STRUCTURE, PHASE TRANSITION, PARAMETERS OF ELEMENTARY CELL, PROUSTITE.

Visible light-induced thymine dimerisation based on large localised field gradient by non-uniform optical near-field

The localised excitations of several molecular reactions utilising optical irradiation have been studied in the field of molecular physics. In particular, deoxyribonucleic acid (DNA) strands organise the genetic information of all living matter. Therefore, artificial methods for freely controlling reactions using only light irradiation are highly desirable for reactions of these strands; this in regard with artificial protein synthesis, regional genetic curing, and stochastic analysis of several genetic expressions. Generally, DNA strands have strong absorption features in the deep ultra-violet (DUV) region, which are related to the degradation and reconstruction of the strand bonding structures. However, irradiation by DUV light unavoidably induces unintended molecular reactions which can damage and break the DNA strands. In this paper, we report a photo-induced molecular reaction initiated by the irradiation of DNA strands with visible light. We utilised photo-dissociation from the vibrational levels induced by non-uniform optical near-fields surrounding nanometric Au particles to which DNA strands were attached. The results were experimentally observed by a reduction in the DUV absorbance of the DNA strands during irradiation. There was a much higher yield of molecular reactions than expected due to the absorbance of visible light, and no defects were caused in the DNA strands.