Fabrication of optically transparent chitin nanocomposites

This paper demonstrates the preparation of chitin nanofibers from crab shells using a simple mechanical treatment. The nanofibers are small enough to retain the transparency of neat acrylic resin. Possessing hydroxyl and amine/N-acetyl functionalities, water suspension of chitin nanofibers was vacuum-filtered 9 times faster than cellulose nanofibers to prepare a nanofiber sheet of 90 mm in diameter. This is a prominent advantage of chitin nanofibers over cellulose nanofibers in terms of commercial application. Interestingly, chitin acrylic resin films exhibited much higher transparency than cellulose acrylic resin films owing to the close affinity between less hydrophilic chitin and hydrophobic resin. Furthermore, the incorporation of chitin nanofibers contributes to the significant improvement of the thermal expansion and mechanical properties of the neat acrylic resin. The properties of high light transmittance and low thermal expansion make chitin nanocomposites promising candidates for the substrate in a continuous roll-to-roll process in the manufacturing of various optoelectronic devices such as flat panel displays, bendable displays, and solar cells.     

A study on 3-D stress distributions in the bi-adhesively bonded T-joints

In this study, the normal (σ_x, σ_y, σ_z) and shear stress (τ_xy, τ_yz, τ_zx) distributions occurring in a bi-adhesively bonded T-joint with was investigated via a non-linear three dimensional finite element analysis. For this purpose, first of all, using 2024-T3 aluminum alloy as the adherend and the support, a two-part paste (DP 460) and a film type (SBT 9244) as adhesive, two different types of T-joint samples (single-adhesively bonded T-joint and bi-adhesively bonded T-joint) were produced for experimental studies. After experimental studies on the three different T-joint types were conducted, stress analyses in the T-joints were performed with a three-dimensional finite element analysis by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460 and SBT9244) and adherend (AA2024-T3). Finally, for a given adherend, the lower the stiffness of the adhesive used in the overlap, the lower the stress concentration, leading to potentially higher joint strength. The use of relatively low stiffness adhesives at the ends of the overlap in a bi-adhesive can decrease the stress concentration and, therefore, potentially lead to higher joint strength.     

Transition Metal-Free Synthesis of meta-Bromo- and meta-Trifluoromethylanilines from Cyclopentanones by a Cascade Reaction

Anilines are key constituents in biologically active compounds and often obtained from transition metal-catalyzed coupling of an aryl halide with an amine. In this work, we report a transition metal-free method for the synthesis of meta-bromo- and meta-trifluoromethylanilines starting from 3-tribromomethylcyclopentanone or 3-(2-bromo-2-chloro-1,1,1-trifluoroethyl)cyclopentanone, respectively. The scope of the transformation is shown by application of primary, secondary and aromatic amines. The reaction proceeds in acceptable to high yields (20–81 %), and allows for the synthesis of anilines with substitution patterns otherwise difficult to access.     

Discrete lattice simulation of transient motions in elastic and viscoelastic composites

Discrete viscous lattices are studied in order to mathematically simulate the propagation of general disturbances in semi-infinite, elastic and viscoelastic periodic composites. Integral transform techniques are employed to derive exact and approximate solutions for the cases in which viscosity is introduced to the elastic lattice by adding dash pots in both series and parallel with the springs connecting adjacent particles. Solutions for the continuum models (for vanishing lattice spacings) are also derived either directly or as special cases. It is demonstrated that the effect of the periodic discretization in these systems induces oscillation about the continuum solutions. Comparison of the exact and approximate results shows excellent correlation, particularly near the wave front.     

Magnetic Field Effects on Spacetime Around?a?Magnetized Spherical Star

We investigate the effects of magnetic field on the background spacetime of a spherically symmetric relativistic star. Using the general relativistic Maxwell equations coupled to the Einstein field equations for the gravitational field, it is shown that not only the backreaction of the spacetime modifies the magnetic field of the star, but also the magnetic field of the star molds the spacetime in its vicinity. The part played by the poloidal as well as the toroidal components of the magnetic field on the exterior spacetime are investigated.