Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy

The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.

Development of a mafedine lyophilizate for parenteral use

Introduction. Cerebrovascular disease (CVD) is the most important medical and social problem of modern neurology because they have the highest rates of morbidity, mortality and disablement in the population. The growing incidence of CVD as a result of an aging population worldwide requires the emergent development of therapeutics, diagnostic and preventive tools. However, the development of drugs for the treatment of brain diseases has limitations due to the presence of the blood-brain barrier, which protects the brain against most molecules from the bloodstream entering the central nervous system. At the St. Petersburg State Chemical Pharmaceutical University of the Ministry of Health of Russia the alpha-2 adrenergic agonist mafedine was synthesized, which has mild psychostimulant and anxiogenic effects and which may be used in the treatment of traumatic brain injury as a neuroprotective agent.Aim. The development of a dosage form of mafedine in order to improve its penetration into the central nervous system.Materials and methods. Mafedine (pharmaceutical substance) [6-oxo-1-phenyl-2-(phenylamino)-1,6-dihydropyrimidin-4-olate sodium] (St. Petersburg State Chemical-Pharmaceutical University of the Ministry of Health of Russia); lecithin, span-60, Tween-80, Poloxamer 188, mannitol, vitamin E, ascorbic acid, methylene chloride, dimethyl sulfoxide, acetonitrile, trifluoroacetic acid. The fine emulsion of mafedine was obtained by ultrasound. The dosage form of mafedine was obtained by freeze drying. Residual solvents were determined by gas chromatography. Quantitative analysis of mafedine was performed by high-performance liquid chromatography. Particle size and zeta potential of emulsion were determined on a Zetasizer Nano ZS.Results and discussion. Lyophilizate of mafedine was obtained and presenting as a light yellow porous, odorless tablet. The average mass of dry tablet was (0,17 ± 0,01) g with mafedine content is (26 ± 1) mg. The water content in the lyophilizate was 3,85 %. The quantity of methylene chloride in the lyophilizate correspond to the requirements for residual solvent content. The reconstitution time of lyophilizate into a primary emulsion was 3–5 seconds. The reconstituted dispersion was yellow, odorless, and did not break within 2 days during storage. The pH of the reconstituted emulsion was 7,34. The average particle size was (164,7 ± 6,4) nm, the zeta potential was –32 mV.Conclusion. The developed dosage form is stable according to its physicochemical and pharmaceutical characteristics and is suitable for experimental study on models as a neuroprotective and neurorehabilitation agent.

Systematic kinetic study of magnesium production using magnesium oxide and carbonic materials at different temperatures

The main goal of this study was to determine the industrially best reductant for reduction of magnesium oxide to magnesium with wood charcoal and petroleum coke (petcoke) each in molar ratio 1:1 and 1:2 (oxidant:reductant) at high temperatures. In this study, a new and reliable combination of mathematical modeling and discrete numerical optimization theory by presenting 18 “mathematical filters” not relying only on statistical quantities of fitting (contrary to many similar researches) was introduced. The purpose of these filters was the determination of correct kinetic equation and therefore, the corresponding rate coefficient from among 18 equations most used at present in the challenging field of solid state chemical kinetics. With assistance of a new and fundamental mathematical function and the obtained values of rate coefficients, the function of rate coefficient in temperature was attained. The activation energy was then calculated as a function of temperature using the general definition of activation energy and the determined function for rate coefficient. The comparison between different reducing agents in the different conditions and with relevant previous study was accomplished to determine the best reducing agent from industry standpoint. Also, the areas under experimental data were calculated numerically and utilized for method validation and comparison. It turned out finally that relying only on fitting quantities in the solid state chemical kinetics can readily lead to wrong conclusions about the correct kinetic equation and about the most suitable reducing agent. It is obvious that the erroneous calculations and wrong decisions in the laboratory scale become significant and paramount in industry and this reveals the significance of rigorous mathematical analysis. Graphical abstract