13,14-Seco-steroids: A New Type of Modified Steroids Containing a Nine-Membered Ring

Oxidations of 14α-hydroxy-5α-cholestan-3β-yl acetate ( 5 ) with lead tetraacetate under thermal or photolytic conditions or in the presence of iodine proceed mainly by fragmentation of the C(13)−C(14) bond to give as the primary products the 13,18-didehydro-13,14-seco derivative 6 and the (E )-Δ¹²-13,14-seco ketone 11 , respectively. Further transformations of these compounds under conditions of their formation afforded, in addition, the acetoxy derivatives 7 – 9 (from 6 ), and the D-homo-C-nor compound 12 and (12R,13R)-epoxide 13 (from 11 ). Unexpectedly, the photolytic lead-tetraacetate oxidation of 5 resulted partly (to ca. 20%) in a reversible fragmentation involving scission and recombination of the C(8)−C(14) bond followed by formation of the 14β,22-ether 10 . Possible mechanisms for the observed transformations are discussed.     

Mechanism of sorption of pertechnetate onto ordered mesoporous carbon

Ordered mesoporous carbon (OMC) was used as an adsorbent for the removal of pertechnetate (TcO₄ ^?) anion. The maximum uptake (93 %) of TcO₄ ^? was obtained after 60 min of contact. The adsorption of TcO₄ ^? is almost pH-independent in very wide pH region (from 4.0 to 10.0). Maximum K _d of 6.6 × 10³ cm³ g^?1 was found at pH 2.0. TcO₄ ^? interacts with carboxylic functional groups present at the surface of the OMC by displacing the OH^? ions with TcO₄ ^? via ion exchange mechanism.     

The Chemi-Ionization Processes in Slow Collisions of Rydberg Atoms with Ground State Atoms: Mechanism and Applications

In this article the history and the current state of research of the chemi-ionization processes in atom–Rydberg atom collisions is presented. The principal assumptions of the model of such processes based on the dipole resonance mechanism, as well as the problems of stochastic ionization in atom–Rydberg atom collisions, are exposed. The properties of the collision kinetics in atom beams of various types used in contemporary experimentations are briefly described. Results of the calculation of the chemi-ionization rate coefficients are given and discussed for the range of the principal quantum number values 5 ≤ n ≤ 25. The role of the chemi-ionization processes in astrophysical and laboratory low-temperature plasmas, and the contemporary methods of their investigation are described. Also the directions of further research of chemi-ionization processes are discussed in this article.     

Enhancement of dissociation by metal-support interaction: reaction of NO on Rh supported by ceria films of controlled oxidation state

Highly oriented thin films of cerium oxide with variable ratio of Ce³⁺/Ce⁴⁺ were grown on Ru(0 0 0 1) single crystal surface and loaded with a fixed, low coverage of Rh. The chemisorption of NO on the resulting model catalyst was studied by soft X-ray photoemission which yielded the relative quantities of N containing species on the surface as a function of temperature, and by thermal desorption which yielded the relative yields of NO and N₂ desorbed. It is found that the ability of the reduced Rh clusters to dissociate NO depends upon the oxidation state of the ceria upon which it is deposited, and for highly reduced ceria surfaces effectively 100% of Rh-adsorbed NO dissociates by 350 K. Possible causes of this surprising behavior are discussed.     

Thermal study and mechanism of Ag2S oxidation in air

The results of thermal study and mechanism of the oxidation process of synthetic Ag₂S in air are presented in this article based on the comparative analysis of DTA and XRD results, as well as by constructed phase stability diagrams (PSD) for the Ag–S–O system.     

Common fixed point theorems for weakly compatible quasi contraction mappings

Summary Recently, Pathak [13] has made an extension of the notion of compatibility to weak compatibility, and extended the coincidence theorem for compatible mappings in Kaneko and Sessa [11] to weakly compatible mappings [13]. In the present paper, we define a new class of weakly compatible mappings (Definition 4) and prove some common fixed point theorems for these mappings, which satisfy Condition (2) below. Although our main theorem is formulated for weakly compatible mappings, its corresponding formulation for commutative mappings is also a new result, thus presenting a generalization of some theorems of Fisher, Das and Naik, Khan and Kubiaczyk, Reich, Ćirić and Rhoades and Watson.     

Photochemistry of β,γ-unsaturated 5,10-seco-steroidal ketones

UV irradiation of the β,γ-unsaturated 5,10-seco-steroidal ketones 1 and 2 in dioxane or isopropanol resulted in Z/E isomerization, while similar irradiation in acetone effected, besides, epoxidation (in the presence of air) and addition of solvent to the olefinic double bond.     

The unified theory of Davydov's and Fröhlich's models

Starting from the experimental facts and from quite general theoretical assumptions a theoretical model was formulated and the Hamiltonian derived which describes the possible excitations in a biological system. Davydov's and Fröhlich's models are also devoted to the same problem, although it seems that these models are not connected. Our results show that the Hamiltonians of Davydov's and Fröhlich's models can be easily obtained from the Hamiltonian of our model. More precisely, our theory could be considered as the microscopic theory of Fröhlich's model, from which Davydov's theoretical model follows as a particular case.