نتایج جستجو برای: ultraviolet rays
تعداد نتایج: 79452 فیلتر نتایج به سال:
In high-order harmonic generation, resonant harmonics (RH) are sources of intense, coherent extreme-ultraviolet radiation. However, intensity enhancement of RH only occurs for a single harmonic order, making it challenging to generate short attosecond pulses. Moreover, the mechanism involved behind such RH was circumstantial, because of the lack of direct experimental proofs. Here, we demonstra...
The first dataset of a complete year of biologically damaging spectral UV at a sub-tropical latitude in the southern hemisphere has been presented. The new data provides a baseline dataset against which comparisons can be made in the future to establish if there have been any long term trends in the biologically damaging UV. The general shape of the variation of the daily biologically damaging ...
The genetic changes taking place during adaptive evolution are particularly interesting in evolutionary biology. As a consequence of adaptive evolution, natural populations of an organism under selective conditions change genetically and phenotypically after a number of generations in order to survive in that particular environment. When a DNA-damaging and mutagenic agent like UV light is exper...
The general appearance of certain Azotobacter cultures when viewed under an ultraviolet lamp has been suggested as a suitable method of distinguishing species (Johnstone, 1955). In addition, pH fluorescence curves of the crude culture filtrates of Azotobacter have shown differences which might also be of taxonomic significance in distinguishing the species involved (Johnstone and Fishbein, 1956...
Metal clusters serve as model systems to study basic problems of electronic correlation. Vacuum ultraviolet light from the free-electron laser FLASH ionizes 5d electrons from mass-separated negatively charged clusters, thus transiently leading to core-ionized neutral systems. Shielding of the core hole affects the electron binding energy. From the strong deviation from expectations of the metal...
Ultraviolet (UV) fluorescent lamps are widely used in the manufacturing process of biomaterials. The possibility of replacing these lamps with ultraviolet light emitting diodes (UV-LEDs) was investigated and the results are presented here. A number of emission characteristics, including the spectral output and intensity of both light sources were measured and compared. The warm up time of the U...
We explore the correlated dynamics of an electron hole and a proton after ionization of a protonated water cluster by extreme ultraviolet light. An ultrafast decay mechanism is found in which the proton-hole dynamics after the ionization are driven by electrostatic repulsion and involve a strong coupling between the nuclear and electronic degrees of freedom. We describe the system by a quantum-...
Recent experimental developments of high-intensity, short-pulse extreme ultraviolet light sources are enhancing our ability to study electron-electron correlations. We perform time-dependent calculations to investigate the so-called "sequential" regime (variant Planck's over 2piomega > 54.4 eV) in the two-photon double ionization of helium. We show that attosecond pulses allow us not only to pr...
Previous investigations (Kinsloe et al., 1954) of the effect of time, pH, temperature and acoustic field on the destruction of microorganisms by vibratory energy showed the destruction to be due largely to mechanical breakdown and that the rate of destruction was dependent on the acoustic field. The objectives of the present study include a comparisoii of the effect on microorganisms of a focus...
There are many benefi ts that are brought by sun, such as positive feeling and mood and trigger the production of vitamin D in skin. But giving to the skin an overdose of ultraviolet rays (UV) may be harmful to our bodies and result in premature skin ageing, skin cancers, eye damage and photoimmunosuppression. UV radiation is made up of three types of rays with different wavelength (λ): ultravi...
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