Electron bunching in the optimal operating regime of a carcinotrode

Electron bunching processes in a carcinotrode (backward-wave oscillator with self-modulation of electron emission) operating in the high-efficiency regime determined previously are investigated. The possibility of obtaining an efficiency of about 80% is explained from the physical viewpoint.     

Methodology of developing optimal nanotechnologies

The knowledge accumulated by chemical engineering makes it possible to create a methodology of the rational development of new science intensive technologies. One of the versions of such a methodology implies the formulation of principles and the revelation of methods for study, which shortens the way from the technological idea formation to its industrial implementation. This version implies passing from an a priori physicochemical model of phenomena which led to a technological idea to an a posteriori model of processes in industrial apparatuses where these phenomena should occur. In doing this, it seems expedient to combine numerical and real experiments with an iterative extension of the range of implementation conditions of phenomena from laboratory to industrial ones. The efficiency of such a methodological approach is evidenced by the experience of the development of the technology of an Ostim medicinal preparation.     

Phase transformation and dehydration of calcium sulphate dihydrate in solution studied by SEM

The transformation of separate crystals of CaSO₄·2H₂O (DH) into CaSO₄·O.5H₂O (HH) in an aqueous solution of H₃PO₄ and H₂SO₄ at 90–97°C was studied using a JSM-35CF SEM. The source DH and acids were reagent or commercial (taken from the production of H₃PO₄ by a wet process). DH was allowed to convert into HH and periodic samples of the suspension were drawn, filtered, and investigated in the solid phase by SEM. It was shown that the dehydration of reagent DH specimens occurred through the recrystallization mechanism, whereas the transformation of commercial DH into HH was basically topochemical and developed by a relay race mechanism without any phase transformation front. The observed difference between commercial and reagent DH specimens may be explained by differences in their crystalline structure, initial particle size and by the presence of impurities in DH and acids. It is established that chemical impurities can change the mechanism of the phase transformation of the crystals DH into HH.     

Kinetic model for radionuclide sorption

A mathematical kinetic model is developed for sorption of radionuclides, occurring via transition of the sorbate atoms initially to the subsurface layer of the particles of a polydisperse sorbent with a known particle size distribution function ?(R), and then to the bulk of these particles. The variance of the function ?(R) was demonstrated to have a considerable effect on the sorption rate. The simulated results are compared with the experimental data on the sorption of ⁹⁰Sr from an aqueous medium on polydisperse calcium carbonate in the forms of calcite and vaterite.