Synthesis of some monocyclic‐N‐acetyl 4′‐aza‐D‐nucleosides

1,2,3,5‐Tetra‐O‐acetyl‐4‐deoxy‐4‐(acetamido)‐β‐D‐ribofuranose 5 was prepared from L‐lyxose, which on condensation with silylated nucleoside bases gave the corresponding protected 4′‐azanucleosides. The protecting groups were removed using methanolic ammonia to afford the N‐acetyl‐4′‐azanucleosides, wherein the sugar ring oxygen is replaced with a substituted nitrogen atom, in good yields. Further, the 1‐(4‐deoxy‐4‐acetamido‐β‐D‐ribofuranosyl)thymine 16 was transformed to the corresponding 2′‐deoxy, 2′,3′‐dideoxy derivatives. The stereochemical assignments of the synthesized nucleosides were established based on NMR and X‐ray studies.     

Thermal properties,induction period,interfacial energy and nucleation parameters of solution grown benzophenone

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.     

Ru/g-al2o3 as reusable catalyst for dehydrogenation of alcohols without hydrogen acceptor

Summary Ru/g-Al₂O₃ catalyzed the dehydrogenation of alcohols to carbonyl compounds without employing hydrogen acceptor. The catalyst was readily recovered from the reaction mixture and could be reused.     

Periodic precipitation of cobalt(II) oxinate

The conditions for obtaining periodic precipitation of cobalt(II) oxinate in agar-agar gel are investigated. The dependence of the nature of periodic precipitation on the concentrations of inner and outer electrolytes is studied in detail. The spacing law of Jablczynski and the time law of Morse and Pierce are verified in this system. The dependence of velocity constant (K) and the spacing coefficient (p) on the concentrations of inner and outer electrolytes has been studied. The velocity constant shows a nonlinear variation with the concentrations of the inner and outer electrolytes. The spacing coefficient (p) is inversely proportional to the concentrations of the inner and outer electrolytes. According to Shouji Shinohara's revised flocculation theory, the flocculation values are computed. The dependence of the flocculation value on the concentrations of the outer and inner electrolytes is studied.     

Effect of bismuth on liquid-phase epitaxy (LPE) grown GaAs layer using Ga–As–Bi melt

GaAs epitaxial layers of high structural quality have been realised from Ga–As–Bi melt using liquid-phase epitaxy (LPE). LPE grown GaAs epitaxial layer using bismuth solvent on GaAs substrate has been found to be of good structural perfection as compared to layers using gallium solvent. The temperature-dependent PL spectra of GaAs layer, grown from Ga+Bi mixed solvent has shown that the use of bismuth does not change the band energy. ECV depth profile of heavily zinc-doped epitaxial layer shows uniform doping in the GaAs layer grown using gallium solvent as compared to the layer grown using bismuth solvent.     

Periodic crystallisation of magnesium hydroxide in agar-agar gel. Influence of temperature

The influence of temperature on periodic crystallisation of magnesium hydroxide in agar-agar gel has been studied. The increase in velocity constant with temperature is attributed to the increase in the diffusion constant with temperature. The activation energy for diffusion of aqueous ammonia is calculated from the temperature — velocity constant correlation. The solubility of Mg(OH)₂ decreases with temperature. The decrease in the spacing coefficient and fiocculation value of Mg(OH)₂ with temperature is also explained because of the increase in temperature. Matalon and Packter’s equation correlating the spacing coefficient and concentration of the inner electrolyte is suitably modified to satisfy the temperature dependence of the spacing coefficient.     

On the number of coprime integral solutions of y2 = x3 + k

Let N′(k) denote the number of coprime integral solutions x, y of y² = x³ + k. It is shown that lim sup_k→∞N′(k) ≥ 12.