Influence of higher interpolation orders in mixed LSFEM for the incompressible Navier-Stokes equations

The focus of this contribution is the examination of the influence of different interpolation orders (especially for the pressure field) by solving the stationary incompressible Navier-Stokes equations with least-squares finite elements. We consider two different div-grad first-order systems which result in a three-field formulation with stresses, velocitites and pressure, see e.g. SCHWARZ & SCHRÖDER [1] and BOCHEV & GUNZBURGER [2]. Additionally, a numerical example is presented to show the performance of the considered formulations. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Straightforward Bienaymé and copper catalyzed N-arylation sequence to access diverse 5H-pyrido[2′,1′:2,3]imidazo[4,5-b]indoles and analogues

A two-step sequence is reported giving access to diverse 5H-pyrido[2′,1′:2,3]imidazo[4,5-b]indoles and analogues via a Bienaymé multicomponent reaction followed by N-arylation. The desired polycylic scaffolds were obtained in high yield using copper iodide in association with TMEDA in aqueous or dioxane media.     

Synthesis and characterization of all‐conjugated copolymers of 3‐hexyl‐thiophene and EDOT by grignard metathesis polymerization

Random regioregular copolymers of 3‐hexylthiophene and 3,4‐ethylenedioxythiophene were synthesized by grignard metathesis polymerization. Soluble copolymers were obtained with a high degree of regioregularity and with a monomer ratio close to the feed ratio. A comparison between the optical properties and the thin film morphologies of these copolymers and poly(3‐hexylthiophene) is also presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Evidence of Splitting 1,2,3‐Triazole into an Alkyne and Azide by Low Mechanical Force in the Presence of Other Covalent Bonds

The cycloaddition reaction of an alkyne and azide to form a 1,2,3‐triazole is widely used in many areas. However, the stability of the triazole moiety under mechanical stress is unclear. To see if a triazole could be selectively split into an alkyne and azide in the presence of other typical covalent bonds, a mica surface functionalized with a molecule containing a triazole moiety in the middle and an activated ester at the end was prepared. An atomic force microscope (AFM) tip with amino groups on its surface was ramped over the mica surface at predefined locations, which could temporarily link the tip to the surface through amide bond formation. During retraction, the triazole or another bond in the linkage broke, and a force was recorded. The forces varied widely at different ramps from close to 0 pN to 860 pN due to nonspecific adhesions and to the inherent inconsistency of single bond rupture. If some of the forces were from triazole cycloreversion, there would be alkynes at the predefined ramping locations. The surface was reacted with an azide carboxylic acid followed by labeling with amino Au nanoparticles (AuNPs). AFM imaging revealed AuNPs at the predicted locations, which provided evidence that under certain conditions triazole could be split selectively in the presence of other bonds at forces below 860 pN.     

On the correlation of crystal defects and band gap properties of ZnO nanobelts

The energetics and dynamics of electromigration of the oxygen vacancy is investigated with first-principles calculations and kinetic Monte Carlo methods. To simulate the charged oxygen vacancy under external fields within the first-principles approach, we introduce a slab model with electron-accepting dopants in the surface. The analysis of the density of states confirms that the oxygen vacancies are positively charged. When the external field is applied, the total energy of the slab linearly changes with respect to the position of the charged vacancy in the field direction, which allows for probing local permittivity around the vacancy site. The activation energy of vacancy migration is lowered along the field direction in a manner that the charge state of the vacancy is maintained along the migration path. Kinetic Monte Carlo simulations based on the first-principles inputs are also carried out and it is shown that the high-temperature condition is important for the fast redistribution of charged vacancies.     

Pd-catalyzed regiocontrolled Sonogashira and Suzuki cross-coupling reaction of 3,6-dihalogenoimidazo[1,2-a]pyridines: one-pot double-coupling approach

New and efficient regioselective Sonogashira and Suzuki-Miyaura palladium-catalyzed coupling reactions of 3,6-dihalogenoimidazo[1,2-a]pyridines followed by another cross-coupling has been successfully developed. Various solvents, palladium species and bases were tested. Scope and limitations of this regiocontrolled palladium-catalyzed reaction were investigated. The synthesis of 3,6-disubstituted imidazo[1,2-a]pyridine derivatives using one-pot regioselective double-coupling approach was developed. This procedure affords convergent syntheses of polysubstituted compounds in high yields in a very few steps.     

Rheological,morphological, and interfacial properties of compatibilized PLA/PBAT blends

The focus of this paper was to gain a true understanding of the impact of a multifunctional epoxide (Joncryl®;ADR-4368) on the interfacial properties of biopolymer blends based on poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). The effect of Joncryl on the shear rheological, morphological, and interfacial properties of the blends was systematically investigated. For the deformed drop retraction experiments, different sandwich model systems (droplet/matrix), representing various scenarios of compatibilization, were prepared, aiming to probe the role of the epoxy-functionalized chains on the interface. The decrease of the interfacial tension in the modified/compatibilized PLA_PBAT and the formation of the PLA-Joncryl-PBAT copolymer were highlighted. A new relaxation peak relative to this copolymer was detected by the relaxation spectrum. Transient start-up shear and nonlinear stress relaxation experiments were carried out and confirmed the obtained results. In addition, the interface contribution was demonstrated using the Lee and Park model. The relaxation time increased with the amount of added Joncryl. Hence, the coexistence of chain extension/branching chains coupled to the PLA-Joncryl-PBAT copolymer formation had to be taken into account to explain the improved mechanical properties.     

Synthesis and Characterization of [1,2,4,6]Thiatriazino[2,3-a][1,3]benzimidazol-1(2H)-one and [1,3,5]Thiadiazino[3,4-a][1,3]benzimidazol-2-imine

Abstract

The reaction of thionyl chloride with amidines 2, derived from N-benzimidazol-2-yl imidates 1, leads to [1,2,4,6]thiatriazino[2,3-a][1,3]benzimidazol-1(2H)-one 3 in good yields. [1,3,5]Thiadiazino[3,4-a][1,3]benzimidazol-2-imine 4 was prepared by condensation of NaSCN with benzimidazol-2-yl imidate 1. The isolated compounds 3 and 4 were identified by spectroscopic methods including IR, ¹H NMR, and ¹³C NMR as well as elemental analyses and MS of 3d and 4b.

GRAPHICAL ABSTRACT