Fiber‐reinforced composite hydrogels for bioadhesive and sealant applications

The use of bioadhesives and sealants for wound closure and healing applications is becoming more and more popular, particularly when other techniques, such as stapling or suturing, are impractical or inefficient. Loading adhesives with fibers has tremendous potential for improving their mechanical properties. The concept of fiber‐reinforced bioadhesives and sealants is novel and has not been investigated to date. In the present study, natural cellulose fibers were selected for enhancement of bioadhesive properties. A bioadhesive formulation based on a combination of gelatin and alginate crosslinked with water‐soluble carbodiimide was used as a generic formulation for this study, on the basis of our previous studies. The polymeric matrix and the cellulose fibers showed high affinity, which resulted in a dramatic increase in the viscosity and in the burst strength. They moderately affected the curing time, swelling, and weight loss. A mixed response was found in the compression modulus and the bonding strength in lap shear. We demonstrated that fiber‐reinforced bioadhesives have a great potential for surgical sealant applications because of improvement in the cohesive strength of the composite hydrogel. This study presents proof of the concept of using fibers for the enhancement of bioadhesive properties as a result of fiber‐reinforcement and may comprise the basis for future studies in this field. Copyright © 2017 John Wiley & Sons, Ltd.     

Geisterpeaks in der temperaturprogrammierten Gas-Chromatographie; Diskussion der Ursachen und ihre Beseitigung

Zusammenfassung Bei der temperaturprogrammierten Gas-Chromatographie treten in den Chromatogrammen Peaks auf, die nicht aus der dosierten Probe stammen. Die Herkunft dieser Geisterpeaks wird untersucht. Es werden Maßnahmen zur Beseitigung dieser Fehlerquellen innerhalb des chromatographischen Systems vorgeschlagen.

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Ghost peaks in temperature-programmed gas chromatography Discussion of reasons and their elimination

Summary In temperature-programmed gas chromatography peaks occur in the chromatograms, which do not belong to the sample being injected. The origin of these ghost peaks is studied. Proposals to avoid those sources of error within the chromatographic system are made.

     

Über die Kapazitätsabnahme des Ionenaustauschers Duolite C-63 durch γ-Bestrahlung

Analytical and Bioanalytical Chemistry -     

Porcelain tile surface modification with isocyanate coupling agent: interactions between EVA modified mortar and silane improving adherence

Adhesion between tiles and mortar is of paramount importance to the overall stability of ceramic tile systems. The interfaces between ceramic tiles and polymer‐modified Portland cement mortar are derived from several physical and chemical phenomena that take place during their formation. From the chemical perspective, weak forces are expected to occur preferably at the tiles and polymer‐modified Portland cement mortar interfaces. Therefore, the purpose of this study was to promote a new chemical functionalization of ceramic tile surfaces by modifying with isocyanate‐trialkoxysilane coupling agent in order to enhance the interfacial adhesion with poly (ethylene‐co‐vinyl acetate), EVA, polymer‐modified mortar. Pull‐off tests and Fourier Transformed Infrared Spectroscopy (FTIR), using the Attenuated Total Reflectance method, were carried out in order to characterize the system. The bond strength results have provided evidence toward improvements in adherence at the tile–polymer modified mortar interface, thus reflecting the development of urethane linkages between silane and EVA polymer, as detected by FTIR. Copyright © 2010 John Wiley & Sons, Ltd.     

Chromogenic and fluorogenic sensing of Cu based on coumarin

A new highly selective, reversible, chromogenic, and fluorogenic chemosensor (4) based on thiazole-coumarin moieties for quantification of copper ions in aqueous-DMSO was designed and synthesized. The mechanism of fluorescence was based on ICT, which was modified by the introduction of an electron-donating diethylamino group making it chromogenic and increasing the binding affinity. The selectivity toward copper ions was not affected by the presence of representative alkali metals, alkali earth metals, or other transition metals.     

Intramolecular Cross-Linking: Addressing Mechanochemistry with a Bioinspired Approach

Many of the attractive properties in polymers are a consequence of their high molecular weight and therefore, scission of chains due to mechanochemistry leads to deterioration in properties and performance. Intramolecular cross-links are systematically added to linear chains, slowing down mechanochemical degradation to the point where the chains become virtually invincible to shear in solution. Our approach mimics the immunoglobulin-like domains of Titin, whose structure directs mechanical force towards the scission of sacrificial intramolecular hydrogen bonds, absorbing mechanical energy while unfolding. The kinetics of the mechanochemical reactions supports this hypothesis, as the polymer properties are maintained while high rates of mechanochemistry are observed. Our results demonstrate that polymers with intramolecular cross-links can be used to make solutions which, even under severe shear, maintain key properties such as viscosity.     

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON2

Non-centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON₂, which shows a polar 6H polytype. Synchrotron X-ray and neutron powder diffraction, and annular bright-field in scanning transmission electron microscopy indicate that it crystalizes in the non-centrosymmetric space group P6₃mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX₃ layers. A synergetic second-order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W⁶⁺ cations, induce large distortions at two inequivalent face-sharing octahedra that lead to long-range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity.