Magtrieve™ (CrO2) and MnO2 mediated oxidation of aldoximes: studying the reaction course

Magtrieve™ (CrO₂) and MnO₂ mediated oxidation of aldoximes to nitrile oxides were studied in details. In presence of external radical source, TEMPO, these reagents did not furnish nitrile oxides, instead favoured deoximation to aldehydes. A common trend of deoximation was established from electronically tuned aldoximes, which is: aliphatic>aromatic>aldoximes with strong electron-withdrawing group, though the extent of deoximation was less in case of CrO₂. Above effects were not observed with chloramine-T and diacetoxyiodobenzene, reagents known to produce nitrile oxides via hydroximoyl halide or equivalent ionic intermediates. A putative reaction mechanism is proposed for MO₂ (M=Cr, Mn) mediated oxidation of aldoximes through formation of a nitroso-oxime tautomeric pair. Formation of nitrile oxide is possibly occurred from the oxime tautomer via a σ-type iminoxy radical intermediate. The deoximation process, dominating in presence of external radical environment, is explained following decomposition of the nitroso tautomer.     

Noncovalent assembly of ferrocene on modified gold surfaces mediated by uracil–adenine base pairs

Redox-active ferrocene was assembled on gold surfaces through the hydrogen bonding interactions between adenine-substituted ferrocene and a uracil-terminated organothiol monolayer. The surface coverage of ferrocene Γ could be varied from ca. 4 × 10^? 11 to 2.0 × 10^? 10 mol cm^? 2 by diluting the thiol-modified uracil derivative with inert 1-octanethiol. A decrease in the apparent electron transfer rate constant for ferrocene, k_app, from ca. 50 to 10 s^? 1 was observed upon increasing Γ.     

Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition processes

The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition. Unexpectedly, the starch volume fraction (as probed through thermal gravimetry) decreases with T at a higher rate than the free volume fraction (as probed through PALS).     

Arylbenzo[<Emphasis Type="Italic">h</Emphasis>][1, 6]naphthyridine Derivatives: Synthesis and Photophysical Properties

Suzuki-Miyaura cross coupling was successfully used for C5-arylation in 4-amino-2-chloroquinoline-3-carbaldehyde using arylbornic acid and tetrakistriphenylphosphine palladium catalyst in water. Friedländer condensation reaction on 4-amino-2-chloro/2-arylquinoline-3-carbaldehyde and aromatic ketones gave novel aryl and diarylbenzo[h] [1, 6]naphthyridines in good yields. Fluorescence quantum yields were increased by introducing C2 and C5 π donor aryl benzo[h][1, 6]naphthyridines derivatives.

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Figure Synthesis of Fluorescent Arylbenzo[h][1, 6]naphthyridine

     

Superconductivity in Supersymmetric Theory in Restricted Chromodynamics

The study of superconductivity, dual superconductivity and color superconductivity has been undertaken through the breaking of super symmetric gauge theory in restricted chromo dynamics (RCD) which automatically incorporates the condensation of monopoles and dyons leading to confining and superconducting phases. Dyonic supermultiplets in N=1 super symmetry have been obtained quantum mechanically in RCD and it has been shown that dyon appears in RCD theory only through restricted part of the generalized potential and it is only this part of this potential which is responsible for quark confinement and the resulting superconductivity through the mechanism of dyonic condensation.     

On Using Tabu Search for Design Automation of VLSI Systems

Tabu search is a meta-heuristic problem solving technique that, when applied carefully, provides near optimal solutions in a very short time. In this paper, we have described the use of tabu search for solving problems related to very large scale integrated (VLSI) circuit design automation. Specifically, we have demonstrated the use for VLSI circuit partitioning and placement. We present a tabu search based circuit bi-partitioning technique that partitions circuits with the goal of minimizing the size of the cutset between the partitions. Then, we use tabu search techniques along with force directed placement techniques to accomplish the physical placement of VLSI circuits on regular two-dimensional arrays with the goal of minimizing the placement time. We use empirical data from partitioning and placement of benchmark circuits to test our techniques. Our methods show improvement when compared to partitioning techniques from the literature and commercially available placement tools. Relative to the literature, our tabu search bi-partitioning technique improves on the best known minimum cuts for several benchmark circuits. Relative to commercially available computer aided design tools, our tabu search based placement approach shows dramatic (20×) speedup in execution time without negative impact on the quality of the solution.