The synergistic bactericidal effect of simultaneous 222 nm krypton-chlorine excilamp and 307 nm UVB light treatment on sliced cheese and its mechanisms.

In this study, we investigated the combined effect of 222 nm krypton-chlorine excilamp (EX) and 307 nm ultraviolet-B (UVB) light on the inactivation of Salmonella Typhimurium and Listeria monocytogenes on sliced cheese. The data confirmed that simultaneous exposure to EX and UVB irradiation for 80 s reduced S. Typhimurium and L. monocytogenes population by 3.50 and 3.20 log CFU/g, respectively, on sliced cheese. The synergistic cell count reductions in S. Typhimurium and L. monocytogenes in the combined treatment group were 0.88 and 0.59 log units, respectively. The inactivation mechanism underlying the EX and UVB combination treatment was evaluated using fluorescent staining. The combination of EX and UVB light induced the inactivation of reactive oxygen species (ROS) defense enzymes (superoxide dismutase) and synergistic ROS generation, resulting in synergistic lipid peroxidation and destruction of the cell membrane. There were no significant (P > 0.05) differences in the color, texture, or sensory attributes of sliced cheese between the combination treatment and control groups. These results demonstrate that combined treatment with EX and UVB light is a potential alternative strategy for inactivating foodborne pathogens in dairy products without affecting their quality.

Neuroprotective Effects of Krypton Inhalation on Photothrombotic Ischemic Stroke.

This is the first in vivo study to investigate the neuroprotective effects of krypton on focal cerebral ischemia. The aim of the study was to analyze the effect of 2 h of inhalation of a krypton-oxygen mixture (Kr 70%/O2 30%) on the recovery of neurological functions and the degree of brain damage in rats after photoinduced ischemic stroke (PIS) and to investigate the possible mechanisms responsible for this neuroprotection. Experiments were performed on male Wistar rats weighing 250-300 g (n = 32). Animals were randomized into four groups. Two groups (n = 20) underwent photoinduced ischemic stroke, followed by 2 h of inhalation of krypton-oxygen mixture consisting of Kr 70%/O2 30% or a nitrogen-oxygen breathing mixture consisting of N2 70%/O2 30%, followed by neurological examinations on days 3 and 7. The other two groups (n = 12) received only gas mixtures of the same concentration and exposure duration as in those in the PIS groups, then Western blot analysis of the potential molecular mechanisms was performed. The results of the study show that treatment with the krypton-oxygen mixture consisting of Kr 70%/O2 30% improves the neurological status on day 7 of observation, reduces the lesion volume according to the MRI examination and the number of Iba-1- and caspase-3-positive cells in the damaged area, promotes the activation of neoangiogenesis (an increase in the von Willebrand factor), and reduces the penumbra area and the number of NeuN-positive cells in it on day 14 of observation. Inhalation of the krypton-oxygen mixture also significantly increases the levels of phosphorylated AKT kinase (protein kinase B) and glycogen synthase kinase 3b (pGSK3b) and promotes the expression of transcription factor Nrf2, which was accompanied by the lowered expression of transcription factor NFkB (p50). Thus, we showed pronounced neuroprotection induced by krypton inhalation after stroke and identified the signaling pathways that may be responsible for restoring neurological functions and reducing damage.

Ventilation perfusion functional difference images in lung SPECT: A linear and symmetrical scale as an alternative to the ventilation perfusion ratio.

PURPOSE: Ventilation Perfusion SPECT is important in the diagnostics of e.g. pulmonary embolism and chronic obstructive pulmonary disease. Classical and reverse mismatched defects can be identified by utilizing the ventilation-perfusion ratio. Unfortunately, this ratio is only linear in the ventilation, the scale is not symmetrical regarding classical and reversed mismatches and small perfusion values give rise to artifacts. The ventilation-perfusion (VQ) difference is developed as an alternative. METHODS: For both VQ-ratio and VQ-difference a scaling factor for the perfusion is computed, so that voxels with matched ventilation and perfusion (on average) yield zero signal. The relative VQ-difference is calculated by scaling with the summed VQ-signal in each voxel. The scaled VQ-difference is calculated by scaling with the global maximum of this sum. RESULTS: The relative and scaled differences have a scale from -1 (perfusion only) to + 1 (ventilation only). Image quality of relative VQ-difference and VQ-ratio images is hampered by artifacts from areas with both low perfusion and low ventilation. Ratio and differences have been investigated in ten patients and are shown for three patients (one without defects). Clinical thresholds for the difference images are derived resulting in color maps of relevant (reversed) mismatches with a (reciprocal) ratio larger than two. CONCLUSIONS: The relative ventilation-perfusion difference is a methodological improvement on the ventilation-perfusion ratio, because it has a symmetrical scale and is bound on a closed domain. A better diagnostic value is expected by utilizing the scaled difference, which represents functional difference instead of relative difference.

222 nm Far-UVC from filtered Krypton-Chloride excimer lamps does not cause eye irritation when deployed in a simulated office environment.

Far-UVC, from filtered Krypton-Chloride lamps, is promising for reducing airborne transmission of disease. While significant research has been undertaken to investigate skin safety of these lamps, less work has been undertaken on eye safety. There is limited data on human eye safety or discomfort from the deployment of this germicidal technology. In this pilot study, immediate and delayed eye discomfort were assessed in a simulated office environment with deployment of Krypton-Chloride lamps, located on the ceiling and directed downwards into the occupied room. Discomfort was assessed immediately postexposure and several days after exposure using validated, Standard Patient Evaluation Eye Dryness (SPEED) and Ocular Surface Disease Index (OSDI) questionnaires. Our results show no significant eye discomfort or adverse effects from the deployment of Far-UVC in this simulated office environment, even when lamps were operated continuously with participants receiving head exposures of up to 50 mJ cm-2 . In addition, a statistically significant reduction in bacteria and fungi of 52% was observed. Far-UVC in this simulated office environment did not cause any clinically significant eye discomfort and was effective at reducing pathogens in the room. These results contribute an important step to further investigation of the interaction of Far-UVC with the human eye.

Validation of krypton as a new tracer gas for the standardization tests of collective and individual protection systems.

Sulfur hexafluoride (SF6) is the reference tracer gas in many international standards for characterizing respiratory protective devices (RPD), fume cupboards, building ventilations, and other installations. However, due to its significant impact on global warming, its use is becoming increasingly restrictive. Krypton 84 (Kr) was chosen to be a possible replacement based on theoretical and practical criteria for the properties that a substitute gas should possess. While compliance with these criteria is generally sufficient to guarantee the reliability of the choice, it is essential in the case of widespread use such as a standard to validate experimentally that this tracer has the same behavior as SF6. In this regard, numerous tests have been carried out to characterize the face leakage of RPD and the rupture of containment of fume cupboards performance tests under different operating conditions. The results obtained are identical with both tracers and lead us to propose the use of Kr as a new reference gas in standards for which SF6 was used.

A Microporous Hydrogen-Bonded Organic Framework Based on Hydrogen-Bonding Tetramers for Efficient Xe/Kr Separation.

Hydrogen-bonded organic frameworks (HOFs) have been emerging as a new type of very promising microporous materials for gas separation and purification, but few HOFs structures constructed through hydrogen-bonding tetramers have been explored in this field. Herein, we report the first microporous HOF (termed as HOF-FJU-46) afforded by hydrogen-bonding tetramers with 4-fold interpenetrated diamond networks, which shows excellent chemical and thermal stability. What's more, activated HOF-FJU-46 exhibits the highest xenon (Xe) uptake of 2.51 mmol g-1 and xenon/krypton (Kr) selectivity of 19.9 at the ambient condition among the reported HOFs up to date. Dynamic breakthrough tests confirmed the excellent Xe/Kr separation of HOF-FJU-46a, showing high Kr productivity (110 mL g-1 ) and Xe uptake (1.29 mmol g-1 ), as well as good recyclability. The single crystal X-ray diffraction and the molecular simulations revealed that the abundant accessible aromatic and pyrazole rings in the pore channels of HOF-FJU-46a can provide the multiple strong C-H⋅⋅⋅Xe interactions with Xe atoms.

Hydrogen-Bonding Assembly Meets Anion Coordination Chemistry: Framework Shaping and Polarity Tuning for Xenon/Krypton Separation.

Hybrid hydrogen-bonded (H-bonded) frameworks built from charged components or metallotectons offer diverse guest-framework interactions for target-specific separations. We present here a study to systematically explore the coordination chemistry of monovalent halide anions, i.e., F- , Cl- , Br- , and I- , with the aim to develop hybrid H-bond synthons that enable the controllable construction of microporous H-bonded frameworks exhibiting fine-tunable surface polarity within the adaptive cavities for realistic xenon/krypton (Xe/Kr) separation. The spherical halide anions, especially Cl- , Br- , and I- , are found to readily participate in the charge-assisted H-bonding assembly with well-defined coordination behaviors, resulting in robust frameworks bearing open halide anions within the distinctive 1D pore channels. The activated frameworks show preferential binding towards Xe (IAST Xe/Kr selectivity ca. 10.5) because of the enhanced polarizability and the pore confinement effect. Specifically, dynamic column Xe/Kr separation with a record-high separation factor (SF=7.0) among H-bonded frameworks was achieved, facilitating an efficient Xe/Kr separation in dilute, CO2 -containing gas streams exactly mimicking the off-gas of spent nuclear fuel (SNF) reprocessing.

Using 81Kr and isotopic tracers to characterise old groundwater in the Bangkok metropolitan and vicinity areas.

Krypton-81 was applied to investigate the age of groundwater in the aquifer system in the Bangkok metropolitan and vicinity areas. Stable (2H, 18O and 13C) and radioactive (3H, 85Kr and 14C) isotopes and noble gases were applied in parallel. Low levels of 14C and significant radiogenic 4He confirm that groundwater in the deep aquifers is older than 30 ka. 81Kr analysis identified groundwater with ages ranging from 17 to 300 ka. At some sites, large age discrepancies between 81Kr and 14C indicated that inter-aquifer mixing is likely occurring. The interpretation of the noble gases suggests that groundwaters in the deeper aquifers, with apparent ages of 300 to 10 ka, have recharged in slightly colder and wetter climates than those found in the upper aquifers with apparent ages < 10 ka. Degradation of water quality from seawater intrusion was identified in the upper four aquifers. This was also evidenced by higher δ18O and δ2H values, typical of seawater. The four deeper aquifers contain high quality water characterised by less enriched 18O and 2H. This work presents new findings of very old groundwater in the Bangkok aquifer system.

Supramolecular Assembly of One-Dimensional Coordination Polymers for Efficient Separation of Xenon and Krypton.

Efficient separation and purification of xenon (Xe) from krypton (Kr) represent an industrially crucial but challenging process. While the adsorption-based separation of these atomic gases represents an energy-efficient process, achieving highly selective adsorbents remains a difficult task. Here, we demonstrate a supramolecular assembly of coordination polymers, termed as M(II)-dhbq (M = Mg, Mn, Co, and Zn; dhbq = 2,5-dihydroxy-1,4-benzoquinone), with high-density open metal sites (5.3 nm-3) and optimal pore size (5.5 Å), which are able to selectively capture Xe among other chemically inert gases including Kr, Ar, N2, and O2. Among M(II)-dhbq materials, Mn-dhbq exhibits the highest Xe uptake capacity of 3.1 mmol/g and a Xe/Kr selectivity of 11.2 at 298 K and 1.0 bar, outperforming many state-of-the-art adsorbents reported so far. Remarkably, the adsorption selectivity of Mn-dhbq for Xe/O2, Xe/N2, and Xe/Ar at ambient conditions reaches as high as 70.0, 139.3, and 64.0, respectively. Direct breakthrough experiments further confirm that all M(II)-dhbq materials can efficiently discriminate Xe atoms from other inert gases. It is revealed from the density functional theory calculations that the strong affinity between Xe and the coordination polymer is mainly attributed to the polarization by open metal sites.

Switchable Xe/Kr Selectivity in a Hofmann-Type Metal-Organic Framework via Temperature-Responsive Rotational Dynamics.

The development of adsorbents for Kr and Xe separation is essential to meet industrial demands and for energy conservation. Although a number of previous studies have focused on Xe-selective adsorbents, stimuli-responsive Xe/Kr-selective adsorbents still remain underdeveloped. Herein, a Hofmann-type framework Co(DABCO)[Ni(CN)4 ] (referred to as CoNi-DAB; DABCO = 1,4-diazabicyclo[2,2,2]octane) that provides a temperature-dependent switchable Xe/Kr separation performance is reported. CoNi-DAB showed high Kr/Xe (0.8/0.2) selectivity with significant Kr adsorption at 195 K as well as high Xe/Kr (0.2/0.8) selectivity with superior Xe adsorption at 298 K. Such adsorption features are associated with the temperature-dependent rotational configuration of the DABCO ligand, which affects the kinetic gate-opening temperature of Xe and Kr. The packing densities of Xe (2.886 g cm-3 at 298 K) and Kr (2.399 g  cm-3 at 195 K) inside the framework are remarkable and comparable with those of liquid Xe (3.057 g cm-3 ) and liquid Kr (2.413 g cm-3 ), respectively. Breakthrough experiments confirm the temperature-dependent reverse separation performance of CoNi-DAB at 298 K under dry and wet (88% relative humidity) conditions and at 195 K under dry conditions. The unique adsorption behavior is also verified through van der Waals (vdW)-corrected density functional theory (DFT) calculations and nudged elastic band (NEB) simulations.

Reflection of UVC wavelengths from common materials during surface UV disinfection: Assessment of human UV exposure and ozone generation.

The COVID-19 pandemic has promoted interest in using devices emitting ultraviolet-C (UVC) irradiation (200-280 nm) for surface disinfection to reduce pathogen transmission, especially in occupied public spaces. While UVC devices have been shown to be highly effective against various pathogens, there are safety concerns when using conventional UVC devices for surface disinfection, including human exposure of reflected UVC irradiation and ozone generation. Emerging Far UVC devices (emitting at 200-230 nm), like the krypton chloride (KrCl*) excimer, have the potential to be safely applied in occupied spaces due to their minimal adverse effects on skin and eyes. In this study, UV reflection of 21 common materials was documented and compared using a filtered KrCl* excimer (installed with a bandpass filter at 222 nm), an unfiltered KrCl* excimer, and a conventional low-pressure mercury vapor lamp. The safety of Far UVC devices was evaluated based on the irradiance and spectrum of reflected UV irradiation and ozone generation measured at various locations around the device. Our results show that most common materials can reflect UV irradiation, among which some metals tend to have greater reflection. The Far UVC devices, especially the filtered KrCl* excimer, should be safe to be applied in occupied spaces for effective surface disinfection, with limited ozone generation and no health risk from reflected UV irradiation. However more caution is needed when using unfiltered KrCl* devices and conventional UV 254 nm light. This study provides urgently needed data on UV reflection of common materials and guidance for safety assessments of UVC devices for surface disinfection in occupied spaces.

UV 254 nm is more efficient than UV 222 nm in inactivating SARS-CoV-2 present in human saliva.

Ultraviolet (UV) light can inactivate SARS-CoV-2. However, the practicality of UV light is limited by the carcinogenic potential of mercury vapor-based UV lamps. Recent advances in the development of krypton chlorine (KrCl) excimer lamps hold promise, as these emit a shorter peak wavelength (222 nm), which is highly absorbed by the skin's stratum corneum and can filter out higher wavelengths. In this sense, UV 222 nm irradiation for the inactivation of virus particles in the air and surfaces is a potentially safer option as a germicidal technology. However, these same physical properties make it harder to reach microbes present in complex solutions, such as saliva, a critical source of SARS-CoV-2 transmission. We provide the first evaluation for using a commercial filtered KrCl excimer light source to inactivate SARS-CoV-2 in saliva spread on a surface. A conventional germicidal lamp (UV 254 nm) was also evaluated under the same condition. Using plaque-forming units (PFU) and Median Tissue Culture Infectious Dose (TCID50) per milliliter we found that 99.99% viral clearance (LD99.99) was obtained with 106.3 mJ/cm2 of UV 222 nm for virus in DMEM and 2417 mJ/cm2 for virus in saliva. Additionally, our results showed that the UV 254 nm had a greater capacity to inactivate the virus in both vehicles. Effective (after discounting light absorption) LD99.99 of UV 222 nm on the virus in saliva was ∼30 times higher than the value obtained with virus in saline solution (PBS), we speculated that saliva might be protecting the virus from surface irradiation in ways other than just by intensity attenuation of UV 222 nm. Due to differences between UV 222/254 nm capacities to interact and be absorbed by molecules in complex solutions, a higher dose of 222 nm will be necessary to reduce viral load in surfaces with contaminated saliva.

Monitoring Noble Gases (Xe and Kr) and Aerosols (Cs and Rb) in a Molten Salt Reactor Surrogate Off-Gas Stream Using Laser-Induced Breakdown Spectroscopy (LIBS).

This study with surrogate materials shows that laser-induced breakdown spectroscopy (LIBS) is a robust tool with promising capability toward monitoring gaseous (Xe and Kr) and aerosol (Cs and Rb) species in an off-gas stream from a molten salt reactor (MSR). MSRs will continually evolve fission products into the cover gas flowing across the reactor headspace. The cover gas entrains Xe and Kr gases, along with aerosol particles, before passing into an off-gas treatment system. Univariate models of Xe and Kr peaks showed a strong correlation to concentration indicated by their coefficients of determination of 0.983 and 0.997, respectively. Multivariate models were built for all four analytes using partial least squares regression coupled with preprocessing steps including normalization, trimming, and/or genetic algorithm derived filters. The models were evaluated by predicting the concentrations of the analytes in four validation samples, in which all calibration models were successfully validated at a confidence interval of 99.9%. Lastly, pressure controllers were used to regulate the mass flow rate of Kr flowing into the measurement cell in sinusoidal and stepwise waveforms to test the real-time monitoring capabilities of the regression models. Both univariate and partial least squares Kr models were able to successfully quantify the gas concentration in the real-time evaluation. The root mean squared error of prediction (RMSEP) values for these real-time tests were calculated to be 0.051, 0.060, and 0.121 mol% demonstrating the measurement systems' capability to perform online monitoring with acceptable accuracy.

A Microporous Hydrogen-Bonded Organic Framework for Efficient Xe/Kr Separation.

Separation of xenon/krypton gas mixtures is one of the valuable but challenging processes in the gas industries due to their close molecular size and similar physical properties. Here, we report a novel ultramicroporous hydrogen-bonded organic framework (termed as HOF-40) constructed from a cyano-based organic building unit of 1,2,4,5-tetrakis(4-cyanophenyl)benzene (TCPB), exhibiting superior separation performance for Xe/Kr mixtures, as clearly demonstrated by dynamic breakthrough curves. GCMC simulation results indicate that the pore confinement effect and abundant accessible binding sites play a synergistic role in this challenging gas separation. Furthermore, this cyano-based HOF displays excellent chemical stability from 12 M HCl to 20 M NaOH aqueous solutions.

Noble Gases Therapy in Cardiocerebrovascular Diseases: The Novel Stars?

Cardiocerebrovascular diseases (CCVDs) are the leading cause of death worldwide; therefore, to deeply explore the pathogenesis of CCVDs and to find the cheap and efficient strategies to prevent and treat CCVDs, these are of great clinical and social significance. The discovery of nitric oxide (NO), as one of the endothelium-derived relaxing factors and its successful utilization in clinical practice for CCVDs, provides new ideas for us to develop drugs for CCVDs: "gas medicine" or "medical gases." The endogenous gas molecules such as carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (SO2), methane (CH4), and hydrogen (H2) have essential biological effects on modulating cardiocerebrovascular homeostasis and CCVDs. Moreover, it has been shown that noble gas atoms such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) display strong cytoprotective effects and therefore, act as the exogenous pharmacologic preventive and therapeutic agents for CCVDs. Mechanistically, besides the competitive inhibition of N-methyl-D-aspartate (NMDA) receptor in nervous system by xenon, the key and common mechanisms of noble gases are involved in modulation of cell death and inflammatory or immune signals. Moreover, gases interaction and reduction in oxidative stress are emerging as the novel biological mechanisms of noble gases. Therefore, to investigate the precise actions of noble gases on redox signals, gases interaction, different cell death forms, and the emerging field of gasoimmunology, which focus on the effects of gas atoms/molecules on innate immune signaling or immune cells under both the homeostatic and perturbed conditions, these will help us to uncover the mystery of noble gases in modulating CCVDs.

Inactivation of biofilm-bound bacterial cells using irradiation across UVC wavelengths.

Opportunistic pathogens (OPs), such as Pseudomonas spp., Legionella spp., and mycobacteria, have been detected in biofilms in drinking water distribution systems and water storage tanks and pose potential risks to finished drinking water quality and safety. Emerging UV technologies, such as UV light emitting diodes (LEDs) and krypton chloride (KrCl*) excimers, could provide an alternative to chemical-based secondary disinfection (i.e., chlorine or chloramines) for controlling biofilm-bound OPs. UV systems offer long lifetimes, ability to select wavelength, small size with high power density, and limited-to-no disinfection by-product formation. In this study, inactivation of biofilm-bound Pseudomonas aeruginosa cells across different maturities was investigated using five UVC devices with different peak emission wavelengths, including a KrCl* excimer (222 nm), a low pressure mercury vapor lamp (254 nm), and three UV LEDs (260 nm, 270 nm, and 282 nm). The UV transmittance and absorbance through the biofilm structure was also documented for the first time using a unique approach. Our results show all UVC devices can inactivate biofilm-bound P. aeruginosa cells up to a point, among which the UV LED with peak emission at 270 nm provided the best disinfection performance. UV sensitivities of biofilm-bound cells decreased with biofilm maturity and while initial rates of inactivation were high, no more than 1.5-2.5 log reduction was possible. Re-suspended biofilm bacteria in aqueous solution were highly sensitive to UV, reaching greater than 6 log reduction. UV shielding by biofilm constituents was observed and was likely one of the reasons for UV resistance but did not fully explain the difference in UV sensitivity between biofilm-bound cells versus planktonic cells. This study improves upon fundamental knowledge and provides guidance for innovative designs using emerging UV technologies for biofilm and pathogen control in water distribution systems.

Hydrogen-Bonded Metal-Nucleobase Frameworks for Efficient Separation of Xenon and Krypton.

Xe/Kr separation is an industrially important but challenging process owing to their inert properties and low concentrations in the air. Energy-effective adsorption-based separation is a promising technology. Herein, two isostructural hydrogen-bonded metal-nucleobase frameworks (HOF-ZJU-201 and HOF-ZJU-202) are capable of separating Xe/Kr under ambient conditions and strike an excellent balance between capacity and selectivity. The Xe capacity of HOF-ZJU-201a reaches 3.01 mmol g-1 at 298 K and 1.0 bar, while IAST selectivity and Henry's selectivity are 21.0 and 21.6, respectively. Direct breakthrough experiments confirmed the excellent separation performance, affording a Xe capacity of 25.8 mmol kg-1 from a Xe/Kr mixed-gas at dilute concentrations. Density functional theory calculations revealed that the selective binding arises from the enhanced polarization in the confined electric field produced by the electron-rich anions and the electron-deficient purine heterocyclic rings.

Self-Adjusting Metal-Organic Framework for Efficient Capture of Trace Xenon and Krypton.

The capture of the xenon and krypton from nuclear reprocessing off-gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high-performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off-gas conditions remains challenging. Herein, we report a self-adjusting metal-organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off-gas. The self-adjusting behavior of ATC-Cu and its mechanism have been visualized by the in-situ single-crystal X-ray diffraction studies and theoretical calculations. The self-adjusting behavior endows ATC-Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g-1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off-gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.

Experimental measurements of Xe and Kr releases from UO2 and determination of their migration mechanisms - Release rate data.

We present the raw data obtained from release rate at 1300°C of Xe and Kr implanted in UO2, related to [1]. We performed different sample preparation (polishing treatment) on polycrystalline and monocrystalline UO2. Ion implantation were performed at various fluences between 9.5 × 1010 to 5 × 1014 i/cm2 in UO2 samples. Release rate of Xe and Kr are obtained at 1300°C under vacuum from desorption experiments performed on the PIAGARA plateform at the CENBG (Centre d'Etudes Nucléaires de Bordeaux-Gradignan). Since we made a variety of samples depending on multiple parameters (sample type, sample preparation, ion implantation type and fluence), these data represent a serious amount of work that could be saved for the scientific community that might use them for other purposes such as burst modelling.

Acaricidal efficacy of ultraviolet-C irradiation of Tetranychus urticae adults and eggs using a pulsed krypton fluoride excimer laser.

BACKGROUND: Pulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and also have high potential for use in a wide range of microbial decontamination applications. The acaricidal effect of an experimental UV-C irradiation device was assessed using female adults and eggs of a model organism, the two-spotted spider mite Tetranychus urticae. METHODS: UV-C light was generated by a pulsed krypton fluoride excimer laser operating at 248-nm emission wavelength. The pulse energy and pulse repetition rate were 5 mJ and up to 100 Hz, respectively. The distance from the light source to the target was 150 mm; the target surface area was 2.16 cm2. The exposure time for the mites and fresh eggs varied from 1 to 4 min at 5-300 mW, which corresponded to UV doses of 5-80 kJ/m2. Post-irradiation acaricidal effects (mite mortality) were assessed immediately and also measured at 24 h. The effects of UV-C irradiation on the hatchability of eggs were observed daily for up to 12 days post-irradiation. RESULTS: The mortality of mites at 5 and 40 kJ/m2 was 26% and 92%, respectively. Mite mortality reached 98% at 80 kJ/m2. The effect of exposure duration on mortality was minimal. The effect of irradiation on egg hatchability was even more significant than that on adult mite mortality, i.e. about 100% egg mortality at an accumulated dose of as little as 5 kJ/m2 for each exposure time. CONCLUSIONS: A high rate of mite mortality and lethal egg damage were observed after less than 1 min of exposure to 5 mJ UV-C pulsed irradiation at 60 Hz. Pending further developments (such as beam steering, beam shaping and miniaturisation) and feasibility studies (such as testing with mites in real-life situations), the reported results and characteristics of the UV-C generator (modulation of energy output and adaptability to varying spot sizes) open up the use of this technology for a vast field of acaricidal applications that require long-range radiation.