Germicidal Ultraviolet Radiation Research Articles

Influence of germicidal ultraviolet radiation UV-C on the quality of Apiaceae spices seeds

BackgroundSpices are susceptible to surface microbial contamination. Countries’ ban on ethylene oxide fumigation due to possible residual toxicity encouraged the usage of irradiation. Surface sterilization with low doses of ultraviolet radiation has been extensively researched as a safe, eco-friendly, and fast route. This study examines the quality of Apiaceae spices for consumption, including anise, fennel, caraway, and cumin, in response to germicidal ultraviolet radiation using a developed sterilization unit.MethodsThe influence of UV-C (254 nm, 10.5 mW/cm2) on the fungal and microbial count, germination percentage, respiration rate, phenolic content, essential oil, and the activity of antioxidant enzymes was investigated at exposure durations of 0–45 min in increments of 5 min. The treated seeds were packed in polyethylene bags in a naturally aerated storage room for 30 days before the inspection.ResultsThe obtained data showed that UV-C stimulated seeds germination and increased respiration rate for all studied types. The 25 min of exposure exhibited the highest significant values compared to the control, considered a good indicator of seed vigor. In addition, UV-C exposure between 20 and 35 min promoted the accumulation of phenolic compounds and increased the oil content as a defense mechanism against radiation. Conversely, higher exposure to UV-C led to a significant reduction in phenolic and oil contents. Furthermore, the exposure to UV-C radiation enhanced the activity of antioxidant enzymes in terms of peroxidase and catalase, which progressively increased with increasing exposure durations, reached their peak at 25–30 min, and subsequently declined with extended exposure time was extended. In a similar pattern, exposure to UV-C radiation increased polyphenol oxidase activity to its highest level at 25 min, owing to the development of antioxidant protective mechanisms against oxidative stress.ConclusionUV-C irradiation in the range of 25–30 min is the most appropriate pretreatment to maintain the vitality of the examined seeds.Graphical

Rare-Earth Doped Upconverting Nanophosphors for Light-Mediated Biocidal Surface Development

Since the earliest civilization, diminishing the occurrence and subsequent transmission of pathogenic microorganisms in the indoor environment has been one of the utmost priorities to the human society. In line with intensive research towards the surface disinfection through the use of several photocatalytic processes, rare-earth doped upconverting nanophosphors (UCNPs) have recently drawn a great attention on the basis of their purely optical phenomenon of directly converting visible light into germicidal ultraviolet radiation (namely ultraviolet C) via the unique photoluminescence process namely ‘upconversion’. The efficient upconversion of abundant visible light into ultraviolet photons in the germicidal range and, consequently, effective biocidal action while coated onto surfaces enable UCNPs as a potential candidate to be used for inhibiting germ spreading through the inanimate surface in public places, hospitals and so forth.

Origins and Evolution of Photocarcinogenesis Action Spectra, Including Germicidal UVC†.

Germicidal ultraviolet radiation (GUV) provides a means of dramatically reducing airborne spread of microorganisms in residential and workspace environments. Regarding design and use of GUV, both efficacy and safety data have accumulated over several decades, with a substantial increase of attention during the current COVID-19 pandemic. Considerations for skin and eye safety previously resulted in guidance on exposures in institutional and workplace settings. This report details the evolution of limits for skin exposures, with particular attention to the risk of skin neoplasia.

Disinfection of Bacillus globigii Spores Using an Atmospheric Pressure Microwave Plasma System

AbstractThis paper examines the application of atmospheric pressure microwave plasma (APMP) for disinfection of water contaminated by Bacillus globigii spores. The results were most promising when He−H2 or O2 were used as plasma gases. The most probable cause for disinfection due to He−H2 plasma can be attributed to the presence of germicidal ultraviolet radiation. On the other hand, the presence of metastable oxygen species (which are very reactive) in the oxygen plasma effluents was attributed as the most likely cause of sterilization of Bacillus globigii spores. By choosing the correct combination of gas mixtures and microwave power level, the authors were able to achieve greater than log5 inactivation. AMPM may be a suitable alternative to traditional disinfection techniques (e.g. chlorination) when they are difficult or impracticable.

A narrow-band photoluminescent optical fibre sensor for the detection of high-intensity germicidal ultraviolet radiation (254 nm) from a microwave plasma ultraviolet lamp

An ultraviolet (UV) optical fibre sensor with a narrow-band luminescent coating has been developed and tested in the presence of high-power UV light from an industrial scale microwave plasma UV lamp. A novel phosphor–epoxy mixture was used as a replacement cladding or coating for the fibre sensor. The combined absorption spectrum of the phosphor and the transmission spectrum of the epoxy result in the sensitization of the coating to a narrow band of wavelengths, centred around 254 nm. This paper describes the spectral characterization of the sensor in the laboratory and a comparison is made between it and a commercially available semiconductor-based UV sensor when illuminated by the lamp. The value of using the optical fibre sensor for this application is evident through this comparison, as the semiconductor sensor required extensive electromagnetic shielding prior to its use in the harsh environment of the microwave electric field. These sensors are likely to be used as on-line monitors for existing high-power UV sterilizing lamps for water supplies as European legislation increasingly requires the use of such monitors.

The Sugar Content and Density of Living and Dead Microsporidian (Protozoa: Microspora) Spores

Microsporidian (Microspora) spores were subjected to several kinds of stress: ultraviolet light (Nosema algerae); chilling in ice water (Edhazardia aedis); freezing and thawing, with or without glycerol as a cryoprotectant (Nosema disstriae, Thelohaniasp.); long-term cold storage (Vairimorphaspp.,Endoreticulatussp.,Thelohaniasp., andMicrosporidiumsp.); and extended periods at room temperature (Microsporidiumsp. andVairimorpha lymantriae).N. algeraespores were inactivated by incubation in 0.05mNaCl or 24 hr at 23°C. Viability of the spores was assessed either by infectivity to a susceptible host or byin vitrogermination. Carbohydrates were extracted from the spores for measurement of the total sugars (anthrone reactive) and reducing sugars (Nelson's test), and quantities and ratios of the two classes of sugars were compared. Buoyant density differences associated with sugar concentration and viability changes were estimated by Ludox density gradient centrifugation. Reducing sugar levels increased after germicidal ultraviolet radiation, chilling, or freezing, concurrent with loss of infectivity or capacity for germination. The smaller reducing sugar molecules apparently diffused slowly from the inviable spores, causing a gradual reduction in the total concentration of sugars. Many samples of spores held for long periods in cold storage were almost devoid of sugar. These changes were not seen inN. algeraespores that were temporarily inactivated. In all cases, spores that were severely depleted in carbohydrates had a significantly lower buoyant density. The bands of heavy spores had a mean density ± SE of 1.197 ± 0.010 g/ml and the mean density of the light, sugar-depleted spores was 1.137 ± 0.024 g/ml. These results suggest that, where no other means are possible, sugar concentrations or spore density might be used to assess the viability of spores.

Inactivation of Giardia lamblia cysts by ultraviolet irradiation.

Giardia lamblia cysts were found to be resistant to high doses of germicidal ultraviolet radiation.

Susceptibility of spores of the microsporidian Nosema algerae to sunlight and germicidal ultraviolet radiation

Spores of the microsporidian Nosema algerae exposed to 1, 2, and 4 hr of sunlight and 121 μW/cm 2 of germicidal ultraviolet light were fed to first-instar Anopheles albimanus. Twenty days after feeding, the incidence and intensity of infection (spores/mosquito) were recorded from adult mosquitoes. While sunlight-treated spores showed no significant decline in incidence of infection after 1-, 2-, and 4-hr exposures, intensity of infection decreased significantly after the 2- and 4-hr exposures. Incidence of infection of mosquitoes fed bactericidal ultraviolet light-treated spores declined 48.2, 76.2, and 99.9% after 1-, 2-, and 8-min exposures, respectively. Measured by intensity of infection, activity of bactericidal light-treated spores decreased 87.2% after 1 min, 91.7% after 2 min, and 99.9% after 8 min. Levels of radiation required to inactivate spores of N. algerae fell within the range reported for other Microsporidia.

Susceptibility of Legionella pneumophila to Ultraviolet Radiation

Distilled water suspensions of Legionella pneumophila were found to be sensitive to low doses of germicidal ultraviolet radiation.

Photostimulated thermoluminescence of lithium fluoride as an ultraviolet radiation dosimeter.

TLD-100 (lithium fluoride) thermoluminescence dosimeters are widely employed for the detection of ionizing radiations. This paper shows that these dosimeters may also serve as practical germicidal ultraviolet radiation dosimeters. To measure u.v. radiation, the TLD-100 dosimeters are first exposed to 500,000 R of gamma radiation and then heated to 300°C at a temperature rate of 3°C/sec and annealed at 300°C for 1 min. Subsequent dosage of u.v. radiation may be determined by observation of photostimulated thermoluminescence of the crystal. The presented data indicate that the thermoluminescence response is linear for exposures up to 6000 μJ/cm2 and independent of exposure rate from 0.1 μW/cm2 to above 50 μW/cm2. Optical absorption and sensitivity as a function of temperature of the dosimeters during u.v. exposure are presented.

Changes in buoyant density relationships of two cell types of Coxiella burneti phase I.

Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuffered sucrose gradients (pH 5.5 to 6.0) resulted in the formation of bands having the location and appearance of the original two bands. Recycling of the denser band of larger ovoid-shaped cells yielded a single band, suggesting that the larger cell type arose from the smaller cell. In contrast to vaccine-derived rickettsiae, live, cell culture-propagated phase I organisms formed a single band in unbuffered sucrose gradients, at the same density as the upper band of the vaccine preparation. Centrifugation of cell culture-derived rickettsiae for 26 to 48 h in sucrose gradients of pH 5.5 resulted in the formation of a second band, at the same density as the lower band of the vaccine preparation. This did not occur in gradients of pH 7.0. Treatment of cell culture-propagated rickettsiae with formalin or germicidal ultraviolet radiation induced a total shift of the less dense cell population to a zone of higher density when centrifuged isopycnically in CsC1 gradients. This density change did not occur in sucrose gradients, suggesting a difference in the effect of these treatments on the permeability of the cell membrane to sucrose and CsC1.

Protection of skin from germicidal ultraviolet radiation in the operating room by topical chemicals.

MERCURY-arc lamps emitting short-wavelength ultraviolet light (254 mμ) are widely used for their microbicidal effect in tissue-culture laboratories, food-preparation areas, hospital ventilation systems and operating rooms.1 , 2 Their use in operating rooms, however, has been somewhat limited because of the known erythema and desquamation; hyperpigmentation can occur when human skin is exposed to these wavelengths.3 , 4 To avoid these damaging effects on the skin, as well as a potential carcinogen effect of the radiation,5 operating-room personnel must wear cumbersome gear that leaves no cutaneous surface exposed. Commercially available lotions designed to minimize or block the sunburn reaction and permit tanning without discomfort . . .

GROWTH AND METABOLISM OF PERIPHYTIC BACTERIA: METHODOLOGY

Procedures for determining the growth rate and studying the metabolism of periphytic bacteria are presented. The number of unicellular bacteria or the aggregate length of bacterial filaments appearing on microscope slides after immersion in the habitat for varying lengths of time was determined by direct microscopy. To distinguish on the slides between in situ growth and passive attachment of organisms from the environment, germicidal ultraviolet radiation was used. A semimicro‐assay for amount of protein on colonized glass surfaces was developed. Growth curves based on protein determinations closely resembled those based on direct microscopic counts. Growth rates were determined in the Jordan River, Indiana, and in the effluent of Trinity Springs, a large cold‐water sulfur spring. Results obtained by direct microscopic counting and by protein assay were similar. Colonized glass surfaces were also used to demonstrate uptake of radioactive substrates by the periphytic flora.

Lack of response by growing-finishing pigs to germicidal ultraviolet radiation

Three tests—two winter and one summer—involving 134 growing-finishing pigs showed no response to germicidal ultraviolet radiation. The pigs received no direct sunlight and were irradiated nearly continuously for periods of 54–70 days. Lamps with a 2537 Å output of 5·2 W were provided at rates of one lamp per 11·1 m2 in two tests and one lamp per 3·35 m2 in one test.