The hockey stick regression method is a convenient method to estimate safe doses, which is a kind of regression method using segmented lines. The method seems intuitively to be useful, but needs the assumption of the existence of the positive threshold value. The validity of the assumption is considered to be difficult to be shown. The alternative methods which are not based on the assumption, ...

The field of gas phase photochemistry has progressed explosively in the past few decades due to the development of ultra fast high power lasers. Unique properties of lasers such as monochromaticity, coherence, tunability over a wide wavelength range and high intensity makes them a powerful pump and probe tool for a number of spectroscopic as well as photochemical studies like laser induced fluo...

The chemical reservoir within protoplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon- nitrogen-rich chemistry at cold temperatures (≤ 50 K) is observed evolved planet-forming disks. This evidenced by bright emission from small organic radicals in 1–10 Myr aged systems that would otherwise have frozen out onto grains 1 Myr. We explain h...

In this paper, we discuss the results of our recent studies on the molecular mechanism, which stand at the basis of the photochemical processes occurring in photobiological systems. These results are obtained using modern, robust, and fairly accurate high-level quantum chemical methods.

The reactivity of higher plant derived 3-oxy-triterpenoids to sunlight was investigated using a series of pure reference standards both under simulated and real solar exposure. The majority of the exposed compounds showed reactivity to light, particularly to simulated sunlight and among others generated seco-derivatives. While photochemical processes have been suggested for the formation of suc...

In this work, the molecular structure, infrared spectrum and UV photochemistry of 2-methyl-2H-tetrazol-5-amine (2MTA) isolated in solid argon (10 K) were investigated. The experimental studies were supported by extensive DFT(B3LYP)/6-311++G(d,p) calculations. The infrared spectrum of matrix-isolated 2MTA was fully assigned and correlated with structural properties. Taking into consideration the...

In dense molecular clouds, the birthplace of stars and planets, interstellar atoms and molecules freeze onto extremely cold dust and ice particles. These ices are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of astrobiological interest. Eventually, these rain down on primordial planets where they take part in the young chemistry on these new ...

Atomic oxygen O(3P) is a potent oxidant that has been well-studied in the gas phase. However, exploration of its reactivity in the condensed organic phase has been hampered by the lack of an appropriate source. Dibenzothiophene-S-oxide (DBTO) and related derivatives have been promoted as photochemical O(3P) sources but suffer from low quantum yields. Photolysis of dibenzoselenophene-Se-oxide (D...