Stannous chloride mediated one pot synthesis of functionalized indole-3-yl pyridines using 3-cyanoacetylindoles and 3-formylchromones

An efficient one-pot synthesis of functionalized indole-3-yl pyridines by condensation of 3-formylchromones, cyanoacetylindoles and ammonium acetate has been achieved. A series of 17 new compounds were synthesized and all of them were characterized by FT-IR and NMR. The crystal structure of a typical compound was determined by X-ray diffraction. A variety of substrates can participate in the process resulting in high purity and good yields, making this methodology suitable for library synthesis in drug discovery.     

Fractional-order modeling of neutron transport in a nuclear reactor

This paper deals with fractional-order (FO) modeling of the neutron transport process inside the core of a nuclear reactor. Conventional integer-order diffusion model of neutron transport has serious shortcomings. Firstly, due to its parabolic nature, it predicts infinite neutron speed, which is very unphysical. Secondly, it has a very limited spatial applicability as it is not applicable everywhere (especially near the strong absorbing regions) in heterogeneous reactor core.     

Highly ordered periodic array of metallic nanodots fabricated through template‐assisted nanopatterning and its use for surface‐enhanced Raman scattering spectroscopy of flexible crystalline‐silicon nanomembranes

We report on the fabrication of highly uniform periodic arrays of metallic nanodots formed on glass substrates through a facile anodic aluminum oxide template‐assisted process and their use in selective surface‐enhanced Raman scattering spectroscopy to probe the structural properties of flexible crystalline‐silicon nanomembranes deposited on polymer substrates. A 14‐fold enhancement in Raman scattering was observed from the thin flexible silicon membranes deposited on polyethylene terephthalate substrates, which were used to probe the internal strains in the silicon nanomembrane as a function of the bending radius. Copyright © 2011 John Wiley & Sons, Ltd.     

Transient chaos and crisis phenomena in butterfly valves driven by solenoid actuators

Chilled water systems used in the industry and on board ships are critical for safe and reliable operation. It is hence important to understand the fundamental physics of these systems. This paper focuses in particular on a critical part of the automation system, namely, actuators and valves that are used in so-called “smart valve” systems. The system is strongly nonlinear, and necessitates a nonlinear dynamic analysis to be able to predict all critical phenomena that affect effective operation and efficient design. The derived mathematical model includes electromagnetics, fluid mechanics, and mechanical dynamics. Nondimensionalization has been carried out in order to reduce the large number of parameters to a few critical independent sets to help carry out a broad parametric analysis. The system stability analysis is then carried out with the aid of the tools from nonlinear dynamic analysis. This reveals that the system is unstable in a certain region of the parameter space. The system is also shown to exhibit crisis and transient chaotic responses; this is characterized using Lyapunov exponents and power spectra. Knowledge and avoidance of these dangerous regimes is necessary for successful and safe operation.     

A simple, convenient method for the synthesis of maleic anhydrides from α-keto esters and alkanoic acid anhydrides using the TiCl4/n-Bu3N reagent system

Reaction of α-keto esters with alkanoic acid anhydrides using the TiCl₄/n-Bu₃N reagent system gives the corresponding maleic anhydrides in 62-95% yields.     

Analyzing coordination preferences of Mg2+ complexes: insights from computational and database study

Solvation of metal cations has attracted substantial interest on account of its functional importance in biological systems. In the present study, we undertake a comprehensive analysis of hydrated complexes of Mg²⁺ with up to 20 water molecules using MP2/cc-pVTZ and density functional theory (DFT) calculations. The effect of first, second, and higher solvation shells on magnesium coordination has been systematically analyzed by considering Mg²⁺(H₂O) _n complexes. Numerous competing conformations for each of the metal ion complexes have been explored and the minima structures obtained were further analyzed. The study probes the relative preferences among various coordination numbers and unambiguously establishes that coordination number 6 is the most optimal choice. The relative abundance of Mg²⁺ ion and its coordination with water and other ligands has been analyzed in the Protein Data Bank and Cambridge Structural Database. It is noted that the M–O distance and charge transfer to metal ion increase as the number of solvating water molecules increases. The computational studies are in excellent agreement with the experimental observations, and provide support to multiple coordinate site preferences for Mg²⁺.     

Double-diffusive convection with fine dust

The effect of fine dust (suspended particles) is considered on the thermosolutal convection. The principle of exchange of stabilities is satisfied for thermal Rayleigh number greater than or equal to solute Rayleigh number. If the solute Rayleigh number exceeds the thermal Rayleigh number, the oscillatory modes may come into play. The effect of stable solute gradient has a stabilizing effect whereas the effect of suspended particles is to destabilize the layer. The effect of a uniform rotation is also considered and is found to have a stabilizing effect in the presence of suspended particles on the thermosolutal convection.     

Constrained global optimization of multivariate polynomials using Bernstein branch and prune algorithm

We propose an algorithm for constrained global optimization to tackle non-convex nonlinear multivariate polynomial programming problems. The proposed Bernstein branch and prune algorithm is based on the Bernstein polynomial approach. We introduce several new features in this proposed algorithm to make the algorithm more efficient. We first present the Bernstein box consistency and Bernstein hull consistency algorithms to prune the search regions. We then give Bernstein contraction algorithm to avoid the computation of Bernstein coefficients after the pruning operation. We also include a new Bernstein cut-off test based on the vertex property of the Bernstein coefficients. The performance of the proposed algorithm is numerically tested on 13 benchmark problems. The results of the tests show the proposed algorithm to be overall considerably superior to existing method in terms of the chosen performance metrics.     

Reappraisal of the electric dipole moment enhancement factor for thallium

The electric dipole moment (EDM) enhancement factor of atomic Tl is of considerable interest as it has been used in determining the most accurate limit on the electron EDM to date. However, its value varies from -179 to -1041 in different approximations. In view of the large uncertainties associated with many of these calculations, we perform an accurate calculation employing the relativistic coupled-cluster theory and obtain -466, which in combination with the most accurate measurement of Tl EDM [Phys. Rev. Lett. 88, 071805 (2002)] yields a new limit for the electron EDM: |d(e)| < 2.0 × 10?2?e cm.