VSO4.5H2O: A Mild and Efficient Catalyst for Chemo‐Selective Conversion of Aldehydes to 1,1‐Diacetates

Protection of aliphatic and aromatic aldehydes as 1,1‐diacetates using VSO₄.5H₂O under solvent‐free conditions is carried out. The products are obtained in good to excellent yields. Ketones are not affected under these conditions.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid,H<Subscript>5</Subscript>[PMo<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript>]

Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

Phase behaviors of strongly correlated Fermi gases in one-dimensional confinements

We report on the ground state of models for strongly correlated one-dimensional Fermi systems by means of theoretical studies of two-component atomic Fermi gases in highly anisotropic harmonic traps. In this context, we consider (i) the Gaudin-Yang model for a Luttinger liquid with repulsive interactions, including an analysis of the emergence of Wigner molecules in the 2k _F → 4k _F crossover, and (ii) the lattice Hubbard model yielding Luttinger liquid and Mott insulator or band-insulator phases for repulsive interactions and the Luther-Emery phase for attractive interactions, including in the former case an analysis of the role of disorder. Our calculations use novel versions of density and spin-density functional theory and a density-matrix renormalization-group technique. We also discuss preliminary results and future perspectives in the study of nonsymmetric two-component Fermi gases.     

Bifurcation and nonlinear dynamic analysis of a rigid rotor supported by two-lobe noncircular gas-lubricated journal bearing system

This paper presents the study of the dynamic analysis of a rigid rotor supported by a two-lobe non-circular gas-lubricated journal bearing. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations have been solved using Runge–Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under the different operating conditions, the dynamic trajectory, the power spectra, the Poincare maps, and the bifurcation diagrams are used. Results of this study indicates that by considering bearing number and rotor mass as the parameters of the system, complex dynamic behavior comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center has occurred.     

Widening basins of attraction of optimal iterative methods

In this work, we analyze the dynamical behavior on quadratic polynomials of a class of derivative-free optimal parametric iterative methods, designed by Khattri and Steihaug. By using their parameter as an accelerator, we develop different methods with memory of orders three, six and twelve, without adding new functional evaluations. Then a dynamical approach is made, comparing each of the proposed methods with the original ones without memory, with the following empiric conclusion: Basins of attraction of iterative schemes with memory are wider and the behavior is more stable. This has been numerically checked by estimating the solution of a practical problem, as the friction factor of a pipe and also of other nonlinear academic problems.     

KHSO4 Supported Onto Bentonite,A Versatile Reagent for Aromatization of Hantzsch 1,4‐Dihydropyridines

Aromatization of Hantzsch 1,4‐dihydropyridines was promoted by KHSO₄, a relatively green chemical, supported onto bentonite to yield the corresponding pyridine derivatives in excellent yields. The reaction was carried out under mild and convenient conditions.     

Wells-Dawson Type Heteropolyacid Catalyzed Synthesis of Quinoxaline Derivatives at Room Temperature

Summary. Wells-Dawson heteropolyacid (H₆P₂W₁₈O₆₂ · 24H₂O) was used as an effective catalyst for the synthesis of biologically active quinoxaline derivatives from the condensation of o-phenylenediamines with 1,2-dicarbonyl compounds at room temperature in excellent yields.     

Role of bremsstrahlung radiation in limiting the energy of runaway electrons in tokamaks

Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.     

10 Gbit/s tributary channel exchange of 160 Gbit/ssignals using periodically poled lithium niobate

We propose and demonstrate data exchange in both the wavelength and time domains at a fine granularity, i.e., low-speed tributary channel exchange of wavelength-division multiplexed high-speed optical time-division multiplexed signals. Using the parametric depletion effect of cascaded second-order nonlinear interactions in a periodically poled lithium niobate (PPLN) waveguide, we experimentally implement 10?Gbit/s tributary channel exchange between two 160?Gbit/s signals with a power penalty of less than 4?dB at a bit-error rate of 10(-9). Moreover, taking into account the waveguide propagation loss, we derive analytical solutions to investigate the signal depletion (SD) and extinction ratio (ER) performance of the PPLN-based data exchange. The theoretical analyses indicate that low waveguide propagation loss benefits large achievable SD and ER.