Influence of quantum effects on the initiation of ignition and detonation

A theoretical analysis that allows one to quantify the quantum corrections to the rate constants of endothermic reactions associated with an increase in the high-energy tails of the momentum distribution functions at high pressures due to a manifestation of the uncertainty principle for the energy of the colliding particles at a high collision frequency is performed. The initiation of ignition of hydrogen-oxygen mixtures is investigated and special series of experiments on the initiation of detonation waves of condensation in carbon suboxide and acetylene at elevated pressures near the low-temperature limits have been carried out. The experimentally observed deviations in the Arrhenius dependences of the induction periods of the initiation of hydrogen ignition and detonation waves of condensation are shown to be well described by the proposed quantum corrections.     

Study of the distribution of elements between a cyanobacterial community and a carbonate body of a hot spring via synchrotron XRF analysis

The contents of many elements in a microbial community and various associations of a carbonate body from the Garga hot spring (Barguzin Valley, Baikal Rift Zone) were analyzed with a synchrotron X-ray fluorescence analysis. The coefficients of biological accumulation have been determined. The contents of practically all elements, except for Sr, in the microbial community are higher than in the carbonate body, and the Ge and Zn contents are higher by an 2 order of magnitude. The vertical cross section of the carbonate body contains three associations two of which formed as a result of microbial activity. The contents of elements in all associations are similar. The Ge content in the microbial community is 270 ppm, on average, whereas in the carbonate body it is less than 2 ppm. The elevated Ge contents could serve as a diagnostic indicator of the microbial community??s development around the sulfide-less alkaline hot springs in the presence of increased contents of radium isotopes. A sample of the carbonate body with layers formed as a result of the microbial community activity was continuously scanned with a step of 0.5 mm. No Ge-rich areas were determined, which indicates its removal by solutions during the destruction of organic matter.     

EDTA and DTPA modified ligands as sequestering agents for uranyl decorporation

Synthesis of modified EDTA and DTPA ligands and determination of their binding affinities for the uranyl cation are described.Thanks to a screening method, based on a chromophoric complex displacement procedure, chelating properties were studied in aqueous media under various pH conditions for evaluation of their in vivo uranyl-removal efficacy. Each ligand showed a more or less pronounced affinity for uranium. Specific ligands based on EDTA or DTPA analogues containing sulfocatecholamide (CAMS) were found to exhibit a significant affinity towards uranyl ion in acidic, neutral or basic conditions.     

Numerical analysis of the influence of metallization nonuniformity on the thermal regime of microcircuits

A numerical analysis of the thermalized regime of metallized sections has revealed that local overheating occurs at sites of nonuniformity together with short circuiting, which results in failure of the microcircuits. Zh. Tekh. Fiz. 68, 90–92 (December 1998)     

Late‐Stage Isotopic Carbon Labeling of Pharmaceutically Relevant Cyclic Ureas Directly from CO2

A robust, click‐chemistry‐inspired procedure for radiolabeling of cyclic ureas was developed. This protocol, suitable for all carbon isotopes (¹¹C, ¹³C, ¹⁴C), is based on the direct functionalization of carbon dioxide: the universal building block for carbon radiolabeling. The strategy is operationally simple and reproducible in different radiochemistry centers, exhibits remarkably wide substrate scope with short reaction times, and demonstrates superior reactivity as compared to previously reported systems. With this procedure, a variety of pharmaceuticals and an unprotected peptide were labeled with high radiochemical efficiency.     

Singularities of ferroelectric properties of BaTiO3 crystals obtained with different crystallization rates

Ferroelectric properties are investigated of BaTiO₃ particles as a function of their growth rates. This latter was given as the rate of reduction of the temperature = dT/dt of the mother solution BaTiO₃-KF and varied between the limits 3.6–43 K/h. It is established that as a grows the reversible macroscopic polarization P_m diminishes according to the law , where P_m0 = 22·10^–2 C/m² and k = 6·10^–2 h/K. The coercive force E_c increases here while the domain contribution to measured in weak fields diminishes. It is shown that diminution of the growth rate results in improvement of the reverse polarization characteristics of BaTiO₃ crystals, a rise in the efficiency of their mono-domainization that would permit utilization of crystals obtained for = 3.6 K/h for optical purposes.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 76–78, November, 1990.     

4-Hydroxy-2-quinolones 19. A new synthesis of 3-Alkyl-2-oxo-4-hydroxyquinolines

3-Alkyl-substituted 2-oxo-4-hydroxyguinolines were obtained in high yields from N,N-di-2-alkoxycarbonylanilides of alkylmalonic acids under conditions of the Dieckmann condensation. Some types of biological activity were found for the compounds synthesized.For Communication 18, see [1].Ukrainian Pharmaceutical Academy, Khar'kov 310002. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 673–678, May, 1994. Original article submitted May 6, 1994.     

Investigation of the interaction between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranium(VI)

A detailed study, using a panel of spectroscopic analytical methods, of the complexation between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranyl ion (UO(2)(2+)) is reported. Results suggest that the metal complex is present as only 1:1 (metal/ligand) species at low concentration (<10(-)(4) M). The conditional constants of this complex were determined at various pH using time-resolved laser-induced fluorescence (TRLIF) and electrospray ionization mass spectrometry (ESI-MS). Further investigations indicate the presence of a 1:2 (metal/ligand) complex at higher concentrations ( approximately 10(-)(2) M). Selectivity studies as well as structural aspects are presented.     

Electrical Double Layer as a Model of Interaction between Cellulose and Solid Acid Catalysts of Hydrolysis

Solid acid catalysts of cellulose hydrolysis in aqueous media attract considerable research interest because of the ease of their separation from the reaction products. The nature of interaction between the two solids is a relevant topic of ongoing research. One aspect of behavior of solid acids in water was not previously discussed in literature with regard to hydrolysis of cellulose: electrolytic dissociation and formation of electric double layers. In this work, on theoretical level, we consider the role of the double layer created by the solid acid when cellulose hydrolysis takes place. The diffuse layer of protons is regarded as the medium where the hydrolysis reaction occurs. Protonation of cellulose by these protons imparts positive charge onto its surface, and cellulose is electrostatically attracted to the polyanion of the catalyst. Thus, the two solid surfaces stay close to each other despite Brownian motion; this allows explaining the high activity of solid catalysts even when chemisorption of carbohydrates on a catalyst is not favorable.