Molecular iodine in [bmim][BF4]: a highly efficient green catalytic system for one-pot synthesis of 1,3-oxathiolan-5-one

Aldehydes and mercaptoacetic acid are coupled in the presence of a catalytic amount of economical and non-toxic molecular iodine in [bmim][BF₄] ionic liquid under mild conditions to afford the corresponding 1,3-oxathiolan-5-one in excellent yields. Molecular iodine acts faster in ionic liquids when compared to conventional solvents such as DMSO, DMF, ethyl acetate, and acetonitrile. The recovered ionic liquids can be recycled in subsequent reactions with consistent activity.     

Some polynomial inequalities in the complex domain

Let

Interaction of ZnS nanoparticles with flavins and glucose oxidase: A fluorimetric investigation

Interactions of luminescence, water soluble ZnS nanoparticles (NPs) with flavins and glucose oxidase have been thoroughly investigated through optical spectroscopy. The photoluminescence of ZnS nanoparticles was quenched severely (～60%) by riboflavin while other flavins such as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) show quenching to different extents under analogous conditions. However, interestingly no effect in luminescence intensity of ZnS NPs was observed with protein bound flavins such as in glucose oxidase. Fluorescence lifetime measurement confirmed the quenching to be static in nature. Scavenging of photo-generated electron of ZnS nanoparticles by the flavin molecules may be attributed to the decrease in luminescence intensity. Quenching of ZnS nanoparticles with flavins follows the linear Stern–Volmer plot. The Stern–Volmer constants decreased in the following order: K_S?V (Riboflavin)> K_S?V (FAD)> K_S?V (FMN). This interaction study could generate useful protocol for the fluorimetric determination of riboflavin (vitamin B₂) content and also riboflavin status in biological systems.     

A mild and efficient protocol for oxidation of thiols to disulfides in water

A novel vanadium polyoxometalate [(C₇H₇)(CH₃)₃N]₃[H₃V₁₀O₂₈].3H₂O works as a useful oxidant for the oxidation of thiols to disulfldes in water under mild reaction conditions in an excellent yield. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:231–234, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20760     

Time-independent description of rapidly driven systems in the presence of friction: multiple scale perturbation approach

The dynamics of a classical system driven by a rapidly oscillating field (with frequency ω) in the presence of friction has been investigated using the multiple scale perturbation theory (MSPT). By exploiting the idea of separation of time scales, the slow motion has been computed in a systematic expansion in the inverse of ω to the order ω(-3). This perturbation series can be viewed as a generalization of the calculation presented by Landau and Lifshitz for Kapitza's pendulum (where the point of suspension is moved periodically) in the presence of friction. The radiation induced dynamics of the system is found to be described by an effective time-independent potential with friction that controls the slow motion. The explicit appearance of friction in our computed effective potential is a manifestation of the dynamical effect due to the fast motion. The present study demonstrates that MSPT can be used to understand and predict the classical dynamics of a driven system in the presence of friction.     

Synthesis of two-dimensional metallic silver using sodium beta-alumina crystal channels

Sodium beta-alumina (β-NaAl₁₁0₁₇) crystals were grown within a gel containing Na₂O and Al₂O₃. The glass–crystal composite was put through a Na⁺ ? Ag⁺ ion-exchange reaction. The ion-exchanged glass–crystal was then subjected to an electrodeposition process. Nanosheets of metallic silver were found to have grown within the β-NaAl₁₁0₁₇ channels which usually contain the mobile sodium ions. The DC electrical resistance of the composites was caused due to charge transport in the two-dimensional crystal planes. The average silver layer thickness was ～0.6 nm and the interlayer separation ～1.13 nm.     

Structural studies of model peptides containing beta-, gamma- and delta-amino acids

The crystal structures of five model peptides Piv-Pro-Gly-NHMe (1), Piv-Pro-betaGly-NHMe (2), Piv-Pro-betaGly-OMe (3), Piv-Pro-deltaAva-OMe (4) and Boc-Pro-gammaAbu-OH (5) are described (Piv: pivaloyl; NHMe: N-methylamide; betaGly: beta-glycine; OMe: O-methyl ester; deltaAva: delta-aminovaleric acid; gammaAbu: gamma-aminobutyric acid). A comparison of the structures of peptides 1 and 2 illustrates the dramatic consequences upon backbone homologation in short sequences. 1 adopts a type II beta-turn conformation in the solid state, while in 2, the molecule adopts an open conformation with the beta-residue being fully extended. Piv-Pro-betaGly-OMe (3), which differs from 2 by replacement of the C-terminal NH group by an O-atom, adopts an almost identical molecular conformation and packing arrangement in the solid state. In peptide 4, the observed conformation resembles that determined for 2 and 3, with the deltaAva residue being fully extended. In peptide 5, the molecule undergoes a chain reversal, revealing a beta-turn mimetic structure stabilized by a C-H...O hydrogen bond.     

Non-recursive Haar Connection Coefficients Based Approach for Linear Optimal Control

In the present paper, two-fold contributions are made. First, non-recursive formulations of various Haar operational matrices, such as Haar connection coefficients matrix, backward integral matrix, and product matrix are developed. These non-recursive formulations result in computationally efficient algorithms, with respect to execution time and stack-and-memory overflows in computer implementations, as compared to corresponding recursive formulations. This is demonstrated with the help of MATLAB PROFILER. Later, a unified method is proposed, based on these non-recursive connection coefficients, for solving linear optimal control problems of all types, irrespective of order and nature of the system. This means that the single method is capable of optimizing both time-invariant and time-varying linear systems of any order efficiently; it has not been reported in the literature so far. The proposed method is applied to solve finite horizon LQR problems with final state control. Computational efficiency of the proposed method is established with the help of comparison on computation-time at different resolutions by taking several illustrative examples.     

Photochemical Symthesisof Aporphines: (±)-Thaliporphime. (±)-N-Nethyllaurotetanineand(±)-Isoboldime

Aporphines, (±)-thaliporphine (1). (±)-N-methyllaurotetatine (2), and (±)-isoboldine (3) were synthesised using photochemical cyclization as the key step.     

25-原子金纳米球和纳米棒催化性能的比较(英文)

The catalytic properties of two nanocluster catalysts with atomically precisely known structures,icosahedral two-shelled Au25(SC2H4Ph) 18 nanospheres and biicosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods,were compared. Their catalytic performance in the two reactions of the selective oxidation of styrene and chemoselective hydrogenation of α,β-unsaturated benzalacetone was investigated. The catalytic activities of icosahedral Au25(SC2H4Ph) 18 nanospheres were superior to those of the bi-icosahedral Au25(PP...