α-Methoxy Ketones by the Reaction of Trimethylsilyl Enol Ethers with Lead Tftraacetate in Methanol

Trimethylsily1 enol ethers of acetophenone, 2-acetylthiophene and 2-acetylfuran react with lead tetraacetate in methanol at room temperature to give the α-methoxy ketones in good yields.     

An Improved Synthesis of Ethyl Azodicarboxylate and 1,2,4-Triazoline-3,5-Diones Using Hypervalent Iodine Oxidation

ARSTRACT: Hypervalent iodine oxidstion of 1,2-dicarhethoxy hydrazine (1) and 4-substituted urazoles (3) using iodobenzene diacetate or pentafluoroiodobenzene bis-trifluoroacetate in CH₂Cl₂ at room temperature proceeds smoothly to yield ethyl azodicarboxylate (2) and 4-substituted 1,2,4-triazoline-3,5-diones (4) in excellent yields.     

Steric effects in the hypervalent iodine oxidation of ketones

Oxidation of 3-cholestanone (1) with C₆H₅I(OAc)₂ or o-OIC₆H₄COOH or C₆H₅IO₂ in KOH/MeOH yields 2 α-carbomethoxy-A-norcholestane (2). This result is interpreted on mechanistic grounds and compared with the course of the reaction with other sterically hindered ketones such as friedelin, 3-keto, 12-keto, 17-keto steroids, and 2,2,6,6-tetramethyl-4-piperidone.     

Electrochemical behaviour of zinc in alkaline solutions

The cathodic and anodic polarization of zinc in different concentrations of alkaline solutions has been studied under constant-current conditions. The changes of zinc electrode-potential with reference to a Hg/HgO/KOH system have been measured both in KOH and zincate solutions using a “Luggin” capillary and a specially designed cell, current being drawn from an electronic current stabilizer. Time-potential curves have been plotted and it is found that the anodic zinc passivates at a certain stage showing a sudden rise in potential by as much as 3–4 volts. Before the passivation, the main electrode reaction is the formation of Zn⁺⁺, while after the passivation it changes to gas evolution. No definite relationship as previously suggested by Muller, between the current density and the passivation time was found, perhaps due to migration and non-linear diffusion effects and other reasons discussed in the paper. It has been found that the behaviour of zinc differs in concentrated alkaline solutions (i.e., 0·5 N to 5 N) from that in dilute solutions (0·2 N to 0·01 N), in which case the open circuit rest-potential of zinc is indefinite and may vary by as much as 500–600 mV., while the maximum passivation jump in potential is about 2 volts only. Also the passivation and the decay of current on breaking the circuit are found to be slower than in the case of concentrated solutions. Colour changes of the zinc electrode, during the polarization, are also briefly described and discussed.     

Cloning, characterization, and expression of a new cry2Ab gene from Bacillus thuringiensis strain 14-1

Bacillus thuringiensis is the major source for transfer of genes to impart insect resistance in transgenic plants. Cry2A proteins of B. thuringiensis are promising candidates for management of resistance development in insects owing to their difference from the currently used Cry1A proteins, in structure and insecticidal mechanism. The cry2Ab gene was found to lack a functional promoter and, hence, is cryptic in nature. The cry2Ab7 gene was cloned from a new indigenous B. thuringiensis strain, 14-1. Nucleotide sequencing of the cry2Ab gene cloned from B. thuringiensis strain 14-1 revealed an open reading frame of 1902 bp. The deduced amino acid sequence of Cry2Ab of B. thuringiensis strain 14-1 showed a variation in three amino acid residues in comparison to the holotype sequence, Cry2Ab1. Expression of the newly cloned cry2Ab gene was studied in an acrystalliferous strain of B. thuringiensis (4Q7) by fusing the cry2Ab gene downstream of cry2Aa promoter and orf1+orf2 sequences. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of a spore-crystal mixture obtained from transformants of B. thuringiensis strain 4Q7 showed production of Cry2Ab protein of about 65 kDa. Alkali solubilized Cry2Ab7 protein showed toxicity against Helicoverpa armigera neonates.     

A real space approach to study the effect of off-diagonal disorder on superconductivity

We present an efficient numerical methodology to study the effect of off-diagonal randomness on superconductivity. This is a real space approach using Bogoliubov-de-Gennes (BdG) method coupled with augmented space vector recursion (ASVR) technique for disorder averaging. We find in the presence of off-diagonal randomness s-wave superconductivity is favoured by greater hopping integral strength between similar species as compared to that between dissimilar ones and d-wave superconductivity is suppressed by off-diagonal randomness much like diagonal randomness. Combined diagonal and off-diagonal randomness leads to asymmetry in both the normal as well as the superconducting densities of states.     

Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD

This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface.