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Emission Properties of Laser Plasma Excited on Molecular-Cluster Carbon Dioxide Jets
摘要： We report on the results of investigation of a gas-jet laser-plasma source of extreme ultraviolet radiation based on a conical supersonic nozzle. As a target, we used molecular-cluster CO2 jets. Different regimes of the gas flow were obtained by varying the gas parameters at the gas inlet and the influence of these regimes on the emission and technical characteristics of the radiation source was analyzed. It has been shown experimentally that radiation emission is intensified upon an increase in the amount of clustered material in the jet.
关键词： EUV radiation intensity,extreme ultraviolet radiation,gas-jet target,molecular-cluster CO2 jets,laser-plasma source
更新于2025-09-16 10:30:52
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Observation of Laser-Induced Spark in the Density Jump in a Gas-Jet Target
摘要： In the design of powerful laser-plasma sources of extreme ultraviolet radiation with a gas jet as the target, the problem of degradation of gas nozzles is topical. Degradation is observed due to insufficient distance from the generation zone of the laser-induced spark to the nozzle exit. The comprehensive solution to this problem is proposed by forming the laser-induced spark in the density jumps that are generated upon deceleration of the supersonic gas jet. In such a density jump, the laser-induced spark is obtained and measurements of emission radiation intensity are performed.
关键词： density jumps,laser-induced spark,degradation of gas nozzles,extreme ultraviolet radiation
更新于2025-09-12 10:27:22
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Association between seasonal serum folate levels and ultraviolet radiation
摘要： UV radiation has been consistently reported to cause folate photodegradation in vitro and in human skin. Seasonal variations in UV radiation might explain seasonal changes in folate levels in blood. Yet, few studies have addressed this phenomenon. The main objective of this study was to investigate whether a relationship exists between seasonal variations in serum folate levels in a population of Spain (Latitude: 36° 41' 6.88''; Longitude: 4° 30' 0.64'') and the annual variations of solar ultraviolet reached in the localization. From a sample of 118831 serum folate determinations, two studies were performed. The first one, which included all subjects, showed a decreased in mean folate concentrations in all seasons with respect to winter with lower values in summer. The risk of folate deficiency was 1.37 times greater in summer than in winter (95%CI: 1.29-1.46). In the second study, subjects with a first folate determination in winter and a second one in summer were 3.32 more likely to develop folate deficiency than those with a first folate determination in summer and a second one in winter (95%CI: 1.55 to 7.11). Folate levels showed a seasonal variation inversely related to solar total UV radiation reached in our location, with maximum daily doses of 5000 J m-2 reached in June. A gradual increase in percentage of folate deficiency is observed since spring. So, patients with folate levels close to deficiency are at a higher risk of having folate deficiency in summer.
关键词： folic acid,solar ultraviolet radiation,seasonal variation,folate deficiency,folate,photodegradation,population study
更新于2025-09-09 09:28:46
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A comprehensive three-dimensional radiative magnetohydrodynamic simulation of a solar flare
摘要： Solar and stellar flares are the most intense emitters of X-rays and extreme ultraviolet radiation in planetary systems. On the Sun, strong flares are usually found in newly emerging sunspot regions. The emergence of these magnetic sunspot groups leads to the accumulation of magnetic energy in the corona. When the magnetic field undergoes abrupt relaxation, the energy released powers coronal mass ejections as well as heating plasma to temperatures beyond tens of millions of kelvins. While recent work has shed light on how magnetic energy and twist accumulate in the corona and on how three-dimensional magnetic reconnection allows for rapid energy release, a self-consistent model capturing how such magnetic changes translate into observable diagnostics has remained elusive. Here, we present a comprehensive radiative magnetohydrodynamics simulation of a solar flare capturing the process from emergence to eruption. The simulation has sufficient realism for the synthesis of remote sensing measurements to compare with observations at visible, ultraviolet and X-ray wavelengths. This unifying model allows us to explain a number of well-known features of solar flares, including the time profile of the X-ray flux during flares, origin and temporal evolution of chromospheric evaporation and condensation, and sweeping of flare ribbons in the lower atmosphere. Furthermore, the model reproduces the apparent non-thermal shape of coronal X-ray spectra, which is the result of the superposition of multi-component super-hot plasmas up to and beyond 100 million K.
关键词： extreme ultraviolet radiation,solar flares,X-rays,magnetohydrodynamics,coronal mass ejections
更新于2025-09-09 09:28:46
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Inativa??o de microrganismos indicadores de contamina??o fecal por radia??o ultravioleta e avalia??o dos fen?menos de fotorreativa??o e recupera??o no escuro
摘要： This research aimed to evaluate the performance of ultraviolet radiation (UV) for disinfecting effluents from a municipal wastewater treatment plant, in laboratory bench scale and batch operation. The interference of the operational parameters of exposure time (s) to the radiation and the level of liquid blade (cm) of the effluent in the UV reactor were analyzed. The efficiency of the disinfection process was checked using the indicators microorganisms Clostridium perfringens (C. perfringens), coliphages, Escherichia coli (E. coli) and total coliforms (TC). After disinfection, some tests were carried out to evaluate the phenomena of microbiological recovery: photoreactivation and dark repair, for E. coli and TC. The results indicate effective inactivation of indicator microorganisms by UV radiation during the time of exposure, which was statistically proved by repeated measures ANOVA. C. perfringens was the microorganism that showed the highest resistance against UV inactivation. In microbiological recovery tests, both mechanisms were considered insignificant, which was statistically proven by the Student (t test — parametric data) and the Wilcoxon (nonparametric data) tests. In all analyses, the level of significance was 5%.
关键词： disinfection,indicators microorganisms,ultraviolet radiation,mechanisms of microbiological recovery
更新于2025-09-04 15:30:14