A flexible, unified radical-based approach to polycyclic structures

Cis- and trans-decalins, trans-perhydroazulenes, and [5.3.1]-bicyclo-undecanone scaffolds can be readily constructed starting from unsaturated ketones and using the degenerative xanthate transfer technology to accomplish unusual and otherwise difficult radical cyclisations.     

Chemical and nanomechanical analysis of rice husk modified by ATRP-grafted oligomer

Rice husk (RH), an abundant agricultural residue, was reacted with 2-bromoisobutyryl bromide, to convert it to a heterogeneous polyfunctional macroinitiator for Atom Transfer Radical Polymerization (ATRP). The number of active sites placed on the RH surface was small, but they were ATRP active. Non-polar methyl methacrylate (MMA) and polar acrylonitrile (AN) were polymerized from the RH, and a sequential monomer addition was used to prepare an amphiphilic PMMA-b-PAN copolymer on RH surface. FTIR qualitatively confirmed the grafting. Gravimetric and XPS analysis of the different RH surface compositions indicated thin layers of oligomeric PMMA, PAN, and PMMA-b-PAN. The modified surfaces were mapped by nanomechanical AFM to measure surface roughness, and adhesion and moduli using the Derjaguin-Muller-Toropov model. RH grafted with MMA possessed a roughness value of 7.92, and a hard and weakly adhering surface (13.1 GPa and 16.7 nN respectively) while RH grafted with AN yielded a roughness value of 29 with hardness and adhesion values of 4.0 GPa and 23.5 nN. The PMMA-b-PAN modification afforded a surface with a roughness value of 51.5 nm, with hardness and adhesion values of 3.0 GPa and 75.3 nN.     

Chelation-mediated palladium(II)-catalyzed domino Heck-Mizoroki/Suzuki-Miyaura reactions using arylboronic acids: increasing scope and mechanistic understanding

A palladium(II)-catalyzed Heck-Mizoroki/Suzuki-Miyaura domino reaction involving metal coordinating dimethylaminoethyl vinyl ethers and a number of electron-rich and electron-deficient arylboronic acids has been developed. Through variation of the temperature and the concentration of the p-benzoquinone (p-Bq) ligand/reoxidant, conditions for the robust and convenient one-pot generation of diarylated-saturated ethers were identified. With the aid of coordination of the dimethylamino group to the arylpalladium intermediate, the otherwise predominant formation of the β-arylated olefin could be reversed. A reaction route involving a chelation-controlled carbopalladation, providing a p-Bq stabilized six-membered palladacycle, followed by transmetalation and reductive elimination is suggested to explain the selective formation of saturated diarylated ether products.     

A general copper powder-catalyzed Ullmann-type reaction of 3-halo-4(1H)-quinolones with various nitrogen-containing nucleophiles

3-(N-Substituted) 4(1H)-quinolinones were synthesized using the copper-catalyzed Ullmann C-N bond forming strategy in moderate to quantitative yields. Starting from 3-halo-4(1H)-quinolones, various nucleophiles including amides, lactams, sulfonamides and NH-containing azoles have been used successfully. In all cases, the reactions take place rapidly in toluene and proceed by using copper powder as a catalyst, DMEDA as a ligand and K(2)CO(3) as a base. In addition, other related heterocycles such as 3-bromoquinolin-2(1H)-ones, 3-bromocoumarin, and 3,5-dibromo-2-pyridone show good to very high reactivity with various nucleophiles under our Cu/DMEDA catalyst system.     

Steady-state photoinduced absorption of CdSe/CdS octapod shaped nanocrystals

Colloidal branched nanocrystals have been attracting increasing attention due to evidence of an interesting relationship between their complex shape and charge carrier dynamics. Herein, continuous wave photoinduced absorption (CW PIA) measurements of CdSe/CdS octapod-shaped nanocrystals are reported. CW PIA spectra show strong bleaching due to the one-dimensional (1D) CdS pod states (480 nm) and the zero-dimensional (0D) CdSe core states (690 nm). The agreement with previously reported ultrafast pump-probe experiments indicates that this strong bleaching signal may be assigned to state filling. Additional bleaching features at 520 and 560 nm are characterized by a longer lifetime and are thus ascribed to defect states, localized at the pod-core interface of the octapod, showing that some of the initially photogenerated carriers get quickly trapped into these long-lived defect states. However, we remark that a relevant part of electrons remain untrapped: this opens up the opportunity to exploit octapod shaped nanocrystals in photovoltaics applications, as electron acceptor materials, considering that several efficient hole extracting materials are already available for the realization of a composite bulk heterojunction.     

The planar jet-plate oscillator

The aeroacoustic noise generated by a high speed, planar gas jet impinging on a flat plate is investigated experimentally. The jet used in this study is typical of those commonly found in industrial applications such as in various coating control and heat transfer processes. Normal jet impingement on the plate is found to generate strong acoustic tones over a wide range of impingement distances and jet velocities. The characteristics of these tones, as a function of the jet velocity and impingement distance, are quantified. Phase and amplitude measurements of the pressure fluctuations on the impingement plate indicate that the acoustic tones are generated by an antisymmetric instability mode of the jet oscillation. The effect of plate inclination in both the transverse and span-wise directions, with respect to the incident jet, is also studied. The jet-plate tone is found to be much more sensitive to changes in the span-wise plate inclination than to changes in the transverse inclination, but in both cases, a complete suppression of the tone is found to be possible.     

Numerical approximation of the generalized regularized long wave equation using Petrov–Galerkin finite element method

The generalized regularized long wave (GRLW) equation has been developed to model a variety of physical phenomena such as ion‐acoustic and magnetohydrodynamic waves in plasma, nonlinear transverse waves in shallow water and phonon packets in nonlinear crystals. This paper aims to develop and analyze a powerful numerical scheme for the nonlinear GRLW equation by Petrov–Galerkin method in which the element shape functions are cubic and weight functions are quadratic B‐splines. The proposed method is implemented to three reference problems involving propagation of the single solitary wave, interaction of two solitary waves and evolution of solitons with the Maxwellian initial condition. The variational formulation and semi‐discrete Galerkin scheme of the equation are firstly constituted. We estimate rate of convergence of such an approximation. Using Fourier stability analysis of the linearized scheme we show that the scheme is unconditionally stable. To verify practicality and robustness of the new scheme error norms L₂, L_∞ and three invariants I₁, I₂, and I₃ are calculated. The computed numerical results are compared with other published results and confirmed to be precise and effective.     

The Cauchy Problem for Non-linear Higher Order Hartree Type Equation in Modulation Spaces

Journal of Fourier Analysis and Applications - We study the Cauchy problem for Hartree equation with cubic convolution nonlinearity $$F(u) = (K \star |u|^{2k})u$$ under a specified condition on...     

Calorimetric investigation of the interaction between a macromolecular prodrug of diflunisal and human platelets

The thermal effect due to the interaction between human platelets and α,β poly(N-hydroxy-ethyl)-DL-aspartamide (PHEA) or the PHEA-Diflunisal conjugate was measured by the calorimetric technique at 25°C. The experimental data confirm that PHEA is a biocompatible macromolecule and that its conjugate influences the physiological activity of human platelets.