Analysis of plane and axisymmetric flows of incompressible fluids with the stream tube method: Numerical simulation by trust-region optimization algorithm

New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method.     

Fast and continuous chemical isolation of short-lived isotopes of Hf,Ta and W as homologs of elements 104, 105 and 106

Some short-lived isotopes of Hf, Ta and W, synthesized at the U-400 cyclotron of JINR-Dubna, have been isolated using a previously elaborated fast continuous method of chemical isolation of element 104 from nuclear reaction products. The products were transported by a NaCl aerosol jet, from the irradiated targets to a separation device in which Hf, Ta and W were isolated by using three coupled ion-exchange columns.     

Reactivity of 3d transition metal cations in diethylene glycol solutions. Synthesis of transition metal ferrites with the structure of discrete nanoparticles complexed with long-chain carboxylate anions

Study of the reactivity of 3d transition metal cations in diethylene glycol solutions revealed several key features that made it possible to develop a new method for synthesis of the nanocrystalline transition metal ferrites. The 3-7 nm particles of [MFe2O4]n[O2CR]m, where M = Mn, Fe, Co, Ni, and Zn, ligated on their surface with long-chain carboxylate anions, have been obtained in an isolated yield of 75-90%. The key features are the following. Complexation of the first-row transition metal cations with diethylene glycol at a presence of alkaline hydroxide is sufficient to enable control over the rate of their hydrolysis. The reaction of hydrolysis leads to the formation of metal oxide nanocrystals in colloidal solution. The nanoparticles growth is terminated by an added long-chain carboxylic acid, which binds to their surface and acts as a capping ligand. The isolated nanocrystalline powders are stable against agglomeration and highly soluble in nonpolar organic solvents.     

Fluorescence from the second excited singlet state of [18] annulenes

The emission spectra of the second excited singlet state of [18] annulene and of monofluoro [18] annulene (in a 3-methylpentane glass at 4 K) are reported. The large energy gap between the first and second excited singlet states inhibits fast internal conversion and favours the appearance of S₂ → S₀ emission. In addition, fluorescence from the S₁ state can be observed in monofluoro [13] annulene by exciting into the S₂ or directly into the S₁ absorption.     

Angular hydroxymethyl directed intramolecular Diels-Alder approach for the stereo- and regioselective synthesis of pimaraditerpenes

The stereo- and regioselective synthetic route to pimaraditerpenes, employing an angular hydroxymethyl directed intramolecular Diels-Alder reaction of the decaline intermediate, has been developed. This synthetic approach allows prompt access to both natural pimaraditerpenes and the unnatural regioisomers, which would be potentially new anti-inflammatory pimaraditerpenes.     

Neutron diffraction study of [H(4)Co(4)(C(5)Me(4)Et)(4)], a tetrahedral metal cluster complex with four face-bridging hydride ligands

A single-crystal neutron diffraction analysis of the cluster complex [H(4)Co(4)(C(5)Me(4)Et)(4)] was carried out on the new quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin. The structure consists of four face-bridging hydrides attached to a tetrahedral cobalt metal core. Average distances and angles in the core of the molecule are as follows: Co-Co = 2.571(8), Co-C = 2.158(6), Co-H = 1.749(7), H.H = 2.366(9) A; Co-H-Co = 94.6(3), H-Co-H = 85.1(3) degrees. The hydride ligands are located off the Co-Co-Co planes by an average distance of 0.923(8) A. It is suggested that the dimensions of the HCo(3) fragments found in this molecule provide reasonable estimates for analogous distances and angles associated with chemisorbed H atoms situated on the 3-fold hollows of a cobalt surface. Crystallographic details: space group P2(1)/a (monoclinic); a = 21.979(2), b = 10.924(1), c = 34.406(2) A; beta = 90.81(1) degrees; Z = 8. Final agreement factor: R(F) = 0.099 for 3779 reflections [I > 2sigma(I)] collected at 20 K.     

Influence of SMA content on the electro-optical properties of polymer-dispersed liquid crystal prepared by monodisperse poly(MMA-co-SMA)/LC microcapsules

Monodisperse poly(methyl methacrylate) (PMMA) particles containing various concentrations of stearyl methacrylate (SMA) were prepared, and a liquid crystal (LC) was swollen into the particles using a solute co-diffusion method (SCM). Phase separation behaviors between the polymer and LC were monitored by utilizing an optical and a polarized microscope (OM/POM). The monodisperse LC microcapsules were then applied to a polymer-dispersed liquid crystal (PDLC), and the electro-optical properties were investigated. As a result, the threshold and driving voltages were improved when the SMA content increased. The long alkyl chains of SMA in the capsules should exist at the interface of the LC and polymer resulting in an enhancement of phase separation between the polymer and LC, which largely influences the electro-optical properties of PDLC.     

Ruthenium‐catalyzed synthesis of quinolines via reductive heteroannulation of nitroarenes with 3‐amino‐1‐propanols

Nitroarenes are reductively cyclized with 3‐amino‐1‐propanols in dioxane/H₂O in the presence of a ruthenium catalyst and tin(II) chloride dihydrate together with isopropanol to afford the corresponding quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from 3‐amino‐1‐propanols to anilines, N‐alkylation of anilines by 3‐anilino‐1‐propanols and heteroannulation of 1,3‐dianilinopropanes is proposed.