Optical Attenuators Extend Dynamic Range but Alter Angular Response of Planar Ultraviolet-C Dosimeters.

Effective ultraviolet C light disinfection of respirators demonstrated in challenges with Geobacillus stearothermophilus spores and SARS-CoV-2 virus

Controlling sprouting in potato tubers using ultraviolet-C irradiance

Star Ruby grapefruit [Citrus paradisi (Macf.)] were harvested in November, February, and May, treated with ultraviolet C (UV-C) light at 0.5, 1.5, or 3.0 kJ.m(-)(2), and then stored at 7 degrees C and 90-95% relative humidity (RH) for 4 weeks with 1 additional week at 20 degrees C and approximately 80% RH. Untreated fruits were used as control. UV-C irradiation at 0.5 kJ.m(-)(2) effectively reduced decay development as compared to nontreated fruit without causing damage. Irradiation at dosages >0.5 kJ.m(-)(2) did not further improve decay control and caused rind browning and necrotic peel, the extent of damage depending on treatment dosage and harvest date. The percentage of damaged fruit after irradiation at the higher UV-C dosages was significantly higher in fruit harvested in November; differences between fruits harvested in February and May were negligible. After UV-C irradiation, the phytoalexins scoparone and scopoletin accumulated in flavedo tissue, their amounts depending on harvest date and UV-C dosage. Both phytoalexins showed similar accumulation patterns, although the concentrations of scoparone were much lower than those of scopoletin. Phytoalexin levels increased in most samples as the treatment dosage increased. No detectable levels of scoparone and scopoletin could be found in nonirradiated fruit. The influence of UV-C treatments on soluble solids concentration and titratable acidity of juice was negligible.

AimThe study of minimal ter operon as a determinant of tellurium resistance (TeR) is important for the purpose of confirming the relationship of these genes to the pathogenicity of microorganisms. The ter operon is widespread among bacterial species and pathogens, implicated also in phage inhibition, oxidative stress and colicin resistance. So far, there is no experimental evidence for the role of the Escherichia coli (E. coli) minimal ter operon in ultraviolet C (UVC) resistance, biofilm formation and auto-aggregation. To identify connection with UVC resistance of the minimal ter operon, matched pairs of Ter-positive and -negative E. coli cells were stressed and differences in survival and whole genome sequence analysis were performed. This study was aimed also to identify differences in phenotype of cells induced by environmental stress.MethodsIn the current study, a minimal ter operon(terBCDEΔF) originating from the uropathogenic strain E. coli KL53 was used. Clonogenic assay was the method of choice to determine cell reproductive death after treatment with UVC irradiation at certain time intervals. Bacterial suspensions were irradiated with 254 nm UVC-light (germicidal lamp in biological safety cabinet) in vitro. UVC irradiance output was 2.5 mW/cm2 (calculated at the UVC device aperture) and plate-lamp distance of 60 cm. DNA damage analysis was performed using shotgun sequencing on Illumina MiSeq platform. Biofilm formation was measured by a crystal violet retention assay. Auto-aggregation assay was performed according to the Ghane, Babaeekhou & Ketabi (2020).ResultsA large fraction of Ter-positive E. coli cells survived treatment with 120-s UVC light (300 mJ/cm2) compared to matched Ter-negative cells; ∼5-fold higher resistance of Ter-positive cells to UVC dose (p = 0.0007). Moreover, UVC surviving Ter-positive cells showed smaller mutation rate as Ter-negative cells. The study demonstrated that a 1200-s exposure to UVC (3,000 mJ/cm2) was sufficient for 100% inhibition of growth for all the Ter-positive and -negative E. coli cells. The Ter-positive strain exhibited of 26% higher auto-aggregation activities and was able to inhibit biofilm formation over than Ter- negative strain (**** P < 0.0001).ConclusionOur study shows that Ter-positive cells display lower sensitivity to UVC radiation, corresponding to a presence in minimal ter operon. In addition, our study suggests that also auto-aggregation ability is related to minimal ter operon. The role of the minimal ter operon (terBCDEΔF) in resistance behavior of E. coli under environmental stress is evident.

Disinfection of surfaces by ultraviolet-C (UV-C) radiation is gaining importance in diverse applications. However, there is generally no accepted computational procedure to determine the minimum irradiation times and UV-C doses required for reliable and secure disinfection of surfaces. UV-C dose distributions must be comparable for devices presently on the market and future ones, as well as for the diverse surfaces of objects to be disinfected. A mathematical model is presented to estimate irradiance distributions. To this end, the relevant parameters are defined. These parameters are the optical properties of the UV-C light sources, such as wavelength and emitted optical power, as well as electrical features, like radiant efficiency and consumed power. Furthermore, the characteristics and geometry of the irradiated surfaces as well as the positions of the irradiated surfaces in relation to the UV-C light sources are considered. Because mercury (Hg) lamps are competitive with UV-C light-emitting diodes, a comparative analysis between these two light sources based on the simulation results is also discussed.

Marine fouling, or the unwanted accumulation of plants and animals on submerged surfaces, can lead to many functional and financial setbacks. Standard methods of combating fouling can be labor intensive or otherwise limiting in their effectiveness and value. Thus, novel efforts are being studied to achieve antifouling in more cost-friendly and environmentally sustainable ways. One emerging approach is the application of ultraviolet C (UVC) light. This study compared the results from modeled relative irradiance to in situ observations by analyzing consequential field effectiveness and other secondary UVC impacts. UVC-emitting lamps (254 nm) were modeled using ray tracing simulations to mimic light scatter underwater. Simulations contained surfaces placed at 25-mm intervals from the light source until a consistently negligible UVC reach was found at 150 mm. The computed findings were then validated through comparison to field immersions in the marine environment of Port Canaveral, FL. Test surfaces and the UVC lamps were placed in frames with 25-mm and 50-mm standoff distances (from light to panel). Surfaces were exposed for 10 min/day for 8 weeks with respective resulting UVC doses of 636.20 mJ/cm 2 and 429.67 mJ/cm 2 . Following underwater immersion, surfaces were examined for fouling development and other UVC impacts. The field results resembled the modeled simulations in both fouling and surface degradation patterns, with the most impact occurring in areas of the highest modeled irradiance. This improves understanding of how modeling can be used to predict impacts of UVC exposure in optimizing fouling prevention, including considering photodegradation and energy usage. Additionally, numerical data were gathered, which helps to inform species- and material-specific thresholds to be used in future development of biofouling management systems.

Combined ultraviolet-C and modified atmosphere packaging treatments for reducing microbial growth of fresh processed lettuce

In-vitro and in-use efficacy of a rapid, targeted UVC decontamination system

Due to the COVID-19 virus being highly transmittable, frequently cleaning and disinfecting facilities is common guidance in public places. However, the more often the environment is cleaned, the higher the risk of cleaning staff getting infected. Therefore, strong demand for sanitizing areas in automatic modes is undoubtedly expected. In this paper, an autonomous disinfection vehicle with an Ultraviolet-C (UVC) lamp is designed and implemented using an ultra-wideband (UWB) positioning sensor. The UVC dose for 90% inactivation of the reproductive ability of COVID-19 is 41.7 J/m2, which a 40 W UVC lamp can achieve within a 1.6 m distance for an exposure time of 30 s. With this UVC lamp, the disinfection vehicle can effectively sterilize in various scenarios. In addition, the high-accuracy UWB positioning system, with the time difference of arrival (TDOA) algorithm, is also studied for autonomous vehicle navigation in indoor environments. The number of UWB tags that use a synchronization protocol between UWB anchors can be unlimited. Moreover, this proposed Gradient Descent (GD), which uses Taylor method, is a high-efficient algorithm for finding the optimal position for real-time computation due to its low error and short calculating time. The generalized traversal path planning procedure, with the edge searching method, is presented to improve the efficiency of autonomous navigation. The average error of the practical navigation demonstrated in the meeting room is 0.10 m. The scalability of the designed system to different application scenarios is also discussed and experimentally demonstrated. Hence, the usefulness of the proposed UWB sensor applied to UVC disinfection vehicles to prevent COVID-19 infection is verified by employing it to sterilize indoor environments without human operation.

On Mars, the amount of ultraviolet C (UVC) radiation that reaches the surface is sufficiently deleterious for life as we know it. However, it has been predicted that some ancient lakes on Mars had high concentrations of Fe3+, an ionic species known for a high absorption of UVC radiation. Some models of UV attenuation have already been established; however, there is a lack of reliable simulations that make the connection between this radiation absorption in an aqueous medium and its impact on the viability of microorganisms. This work proposes a simple model to estimate the viability of microorganisms irradiated in solution with different concentrations of Fe3+ and constrains the lethal UVC dose in these conditions. In experimental assays, the median lethal dose of Saccharomyces boulardii increased consistently with the model's predictions, which thereby demonstrated the model's predictive validity. This ability was then used in a case study to simulate the viability of life in a Fe3+-containing lake on ancient Mars. Although the actual conditions of this kind of environment are not known, the simulations showed that lakes with small water columns that contain Fe3+ should have been able to protect growing microorganisms. This model enhances the ability to assess potentially habitable conditions on ancient Mars. Key Words: Photoprotection-UVC radiation-Fe3+ ions-Mars-Astrobiology. Astrobiology xx, xxx-xxx.

In recent years, nosocomial infection, including that by multiple-drug-resistant Acinetobacter&lt;br/&gt;(MDRA), has become an increasing concern in Japan. Typically, Acinetobacter inhabits soil and river water and is usually harmless to humans. However, bacteria of this genus can become pathogens in inpatients with weakened immune systems, resulting in opportunistic infection. Currently, hospital infection by MDRA is spreading not only in Japan, but also worldwide. This is a very serious problem, and little is known about effective countermeasures. The present study sought to examine the microbiome status in a hospital visitor waiting room as a first step in establishing countermeasures for use against Acinetobacter. Specifically, we performed a so-called metagenomic analysis to directly analyze DNA collected from the environment, without an intervening cultivation step. Indoor airborne bacteria and surface bacteria were sampled and analyzed. The results show that in a visitor waiting room, the top-ten most-abundant genera included (in decreasing order) Acinetobacter, Streptococcus, Prevotella, Pseudomonas, Bifidobacterium, Fusobacterium, Neisseia, Porphyromonas, Leptotrichia, and Haemophilus. Thus, Acinetobacter constituted the mostdetected genus and was present in all collected samples. Furthermore, we assessed the bactericidal effect of ultraviolet C (UVC) against Acinetobacter sp. 7206, a hospital isolate. A UVC dose of 4.0 sec·mW/cm2 was required to kill the 99.9% Acinetobacter sp. 7206 on solid culture medium.

Accurate measurements of solar ultraviolet radiation are needed for air quality monitoring, especially to understand the formation and photolysis of tropospheric ozone near the ground. It is interesting to investigate whether this demand could be met using recently developed low-cost UV sensors and new communication technologies. Despite the promising possibilities, their use is still scarce and their potential applications have not yet been thoroughly explored. This study aims to use low-cost sensors to develop devices that accurately measure solar ultraviolet radiation. The de vices should be low-cost, small, portable, and have low power consumption and IoT connectivity. For this purpose, three popular low-cost commercial sensors ML8511, UVM30A and VEML6075 are selected and implemented in several prototypes. The sensors are analyzed in terms of their spectral response, leveling, angular response and comparison with reference data. For that aim, experimental measurements are performed at the radiometric station of the Physics Department of the University of Extremadura in Badajoz, Spain. Results indicate that sensors of the same model might have different calibrations. The leveling and the angular response measurements indicate a strong azimuth dependence for the ML8511 and, especially, VEML6075 sensors, while the UVM30A sensor shows a much weaker dependence, probably due to the use of a circular diffuser. The angular response is identified as the main issue of the sensors, notably limiting their accuracy and preventing a widespread use. With the knowledge gained, a final version with LoRa communication and optimized power consumption is developed. The strength of the LoRa connection is measured at different locations on the University Campus using Receiver Signal Strength Indication. It ranges from -27 dB near the gateway to -122 dB at the farthest location on the Campus. The optimization of the power consumption allows 14 days of autonomy if operating only during daylight hours. The study illustrates the suitability of low-cost sensors for UV applications, provided that a good angular response of the sensors is ensured. It contributes to a wider use of these sensors for the measurement of air quality variables by identifying those characteristics that need to be improved by manufacturers to meet the standards.

A recent breakout of the COVID-19 pandemic inspired researchers to find ideal solutions for removing SARS-CoV-2 from indoor air. In-duct ultraviolet germicidal irradiation was employed in rooms with heating, ventilation, and air conditioning (HVAC) systems to stop the spread of COVID-19. The current investigation introduces Bunimovich stadium-inspired flow channels inside the square-shaped duct. The impact of the Bunimovich channel shape on light distribution is studied and compared with the traditional rectangular-shaped duct. The core of the Bunimovich channel is a square with δ and γ equal to 0.5. A semi-circle surrounds the square's left and right sides. The air velocity in the HVAC system with the Bunimovich channels varies from 10 m/s to 15 m/s, resulting in variation in aerosol particles’ residence period in front of the ultraviolet-C (UVC) source. The Bunimovich channel delivered better UVC irradiance uniformity than a rectangular duct. The uniformity ratio for the Bunimovich channel was 0.788 compared to 0.6949 for the rectangular duct. The UVC dose delivered by the source in the Bunimovich channel varies from 1.48 mJ/cm2 to 3.03 mJ/cm2. The delivered dose is higher than the required 1.2 mJ/cm2 dose for log-4 reduction (i.e. 99.99%).

The generation of X-rays is discussed in the first section of this chapter. X-rays are generated by (1) the bombardment of a target by electrons, (2) the decay of certain radio isotopes, (3) as part of the synchrotron-radiation spectrum and (4) in plasmas produced by bombarding targets with high-energy laser beams. The spectra produced by the first method consist of a line spectrum characteristic of the target material accompanied by a continuum of white radiation (Bremsstrahlung). The intensities and wavelengths of these components are discussed and the nomenclatures of the lines in the characteristic spectrum are compared. Synchrotron radiation and plasma generation of X-rays are discussed very briefly. X-ray wavelengths are discussed in the second section of the chapter. Tables of K- and L-series reference wavelengths and K- and L-emission lines and absorption edges are provided. X-ray absorption spectra are discussed in the third section of the chapter. A detailed discussion of the problems associated with the measurement of X-ray absorption and the requirements for the absolute measurement of the X-ray attenuation coefficients is followed by a description of the problems which are encountered in making measurements at X-ray absorption edges of atomic species in materials. The popular, and extremely valuable, experimental technique of X-ray absorption fine structure (XAFS) is discussed. This is a relative, rather than an absolute measurement of X-ray absorption, and the theoretical analysis of XAFS spectra depends on the deviation of the data points from a cubic spline fit to the data rather that the deviation from the extrapolation of the free-atom absorption. A brief description of the origin and use of X-ray absorption near edge structure (XANES) is given. In the fourth section of the chapter, X-ray absorption (or attenuation) coefficients are considered. A detailed description of the theoretical and experimental techniques for the determination of X-ray absorption (and attenuation coefficients) is given. The tables supercede the existing experimental and theoretical tables that were available up to 2001. The theoretical values given here are restricted to the characteristic radiations commonly available from laboratory X-ray sources (Ti Kβ to Ag Kα). Computational problems become significant for elements in the lanthanide and actinide series of the periodic table. These tables include a significant recalculation of the absorption and attenuation coefficients for the lanthanide series. Note that although many theory-based tables exist, few accurate experimental measurements have been made on atomic species with atomic numbers greater than 50, especially in the region of absorption edges. A comparison is given of the extent to which theoretical and experimental data agree. A recent tabulation discusses soft X-ray absorption in the XANES region. Filters and monochromators are discussed in the fifth section of the chapter. This section serves as an introduction to the use of filters and monochromators in experimental apparatus. It discusses, using synchrotron-radiation experimental configurations as examples, the use of X-ray reflectivity, X-ray refraction and X-ray Bragg (and Laue) or Fresnel scattering for the production of monochromatic or quasi- monochromatic (pink) beams from polychromatic sources. Amongst the techniques discussed are: bent and curved mirrors, capillaries, quasi-Bragg (multilayer) mirrors, multiple filters, crystal monochromators, polarization and polarization-producing systems, and focusing using a Bragg–Fresnel optical system. The development of monochromators for synchrotron-radiation research is a rapidly evolving field, but in practice all depend on either the processes of reflection, refraction or scattering, or combinations of these processes. In the final section of the chapter, X-ray dispersion corrections are considered. The various theoretical methods for the computation of the X-ray dispersion corrections and the experimental techniques used for their determination are described in some detail. The theoretical values given here are restricted to the characteristic radiations commonly available from laboratory X-ray sources (Ti Kβ to Ag Kα). An artificial distinction is made between the relativistic Dirac–Hartree–Fock–Slater (RDHFS) formalism used to calculate the data in these tables and the S-matrix method used by a number of theoreticians. Formally, the two techniques are equivalent: in terms of the computations the two approaches are different, and the outcomes are different. Comparison with experimental data shows that the RDHFS formalism gives a better fit to experimental results. Keywords: absorption; anomalous dispersion; atomic form factor; atomic scattering factors; attenuation coefficients; Auger shifts; Bijvoet-pair techniques; black-body radiation in X-ray region; characteristic line spectrum; continuous spectrum; Dirac–Fock method; dispersion corrections; EXAFS; extended X-ray absorption fine structure; filters; Friedel-pair techniques; generation of X-rays; intensity; monochromators; normal attenuation; photo-effect data; QED corrections; Rayleigh scattering; scattering; synchrotron radiation; theoretical Rayleigh scattering data; theoretical photo-effect data; wavelengths; X-ray absorption coefficients; X-ray absorption spectra; X-ray attenuation coefficients; X-ray dispersion corrections; X-ray sources; X-ray tubes; X-ray wavelengths; XAFS; X-ray absorption near-edge structure; XANES

PurposeThis paper proposes a model for the angular dependency of MatriXX response and investigates whether MatriXX, with the angular‐model‐based approach can be applied to true composite dose verification for IMRT plans.MethodThis model attributes the angular dependence of MatriXX response to dynamical translation of its effective measurement plane (EMP) due to the change of beam angle. Considering this mechanism, true composite dose verifications for IMRT plans specified in AAPM TG 119 report using both MatriXX and Gafchromic EBT3 films were undertook and compared to validate the applicability of MatriXX for patient specific QA of composite beam IMRT plans. Dose verifications using MatriXX with and without angular‐model‐based approach were performed.ResultsMatriXX with angular‐model‐based approach achieved gamma passing rates with 3%/3 mm and 3%/2 mm criteria better than 98.3% and 98.1% respectively for true composite dose verification of plans in AAPM TG 119 report. The 3%/3 mm and 3%/2 mm gamma passing rates using MatriXX without angular‐model‐based approach ranged from 85.8% to 98.2% and from 81.3% to 96.5%, respectively. The p‐values from the single sided paired t‐test indicated no statistical difference between the passing rates from MatriXX with angular‐model‐based approach and from films, and significant difference between the passing rates from uncorrected MatriXX and from films.ConclusionThe proposed model for angular dependent MatriXX response is necessary and effective. Dose verification using MatriXX with angular‐model‐based approach is acceptable for true composite beam IMRT plans with required accuracy to simplify patient specific QA.