Thermal analysis scheme aimed at better understanding of the Earth’s climate changes due to the alternating irradiation

Methodological scheme of thermal analysis is used for portraying the Earth environmental research and climate changes showing particularly the history, effect of atmosphere reflection (albedo) and absorption (so called greenhouse effect included). The net behavior of the Earth as a black body is reviewed. The most influential on climate changes is alteration of the geometry of the Earth trajectory and the irradiative power of the Sun (as a standard thermo-analytical pair of the sample and radiator). Thermodynamic basis of water vapor impacts is pointed out, the absorption spectra of atmosphere emphasized and temperature gradients indicated. The historical course of the Earth temperature and CO₂ concentration is put in analogy with the method of gas desorption analysis, which supports the view that the variation of CO₂ concentration recorded in the past may not be alone blamed for temperature changes.     

Substitution meta - to an aromatic hydroxyl group

It is suggested that the bromination of 4-methylphenol in superacid solvents involves a 1,2-shift of bromine within a protonated bromodienone.     

Luminescent properties of A1N activated by europium

The concentration and temperature dependence of emission and excitation spectra was measured on powder A1NEu phosphors. It was shown that A1N: Eu has two luminescent modifications which depend on the activator concentration. At low activator concentration the wide emission band is found in the blue-green region, while at high concentration it is in green region. The excitation spectra of A1NEu consist of wide bands extended from 40×10³ cm^–1 to 22 × × 10³ cm^–1. The emission and excitation spectra are interpreted as transitions between energy levels of Eu²⁺ ions (4f⁷4f⁶ 5d transitions). The structure of the Eu²⁺ luminescent centres and the temperature dependence of luminescence are discussed.The authors thank Dr. M.Polcarová for the RTG measurements and Mrs. I.Míková for the spectral analysis of the A1N: Eu samples. The authors are also grateful to Prof. M.Trlifaj, Dr. J.Pastrák and Dr. J.Kubátová for valuable discussions.     

Fluorescence decays and lifetimes of Nd3+, Ce3+ and Cr3+ in YAG

The present paper summarizes results of detailed studies of fluorescence decays and lifetimes of Nd³⁺, Ce³⁺ and Cr³⁺ carried out on a large group of YAC.: Nd, Ce and YAC.: Nd, Ce, Cr single crystals. The average and local lifetimes (mainly for⁴F_3/2 state of Nd³⁺) of these ions are given and an influence of various processes (energy transfers, cross-relaxation, nonequivalent centres etc.) on their decays are qualitatively discussed.The authors are grateful to J. Kvapil of Monokrystaly Turnov for supplying them with the samples and for many fruitful discussions.