Splicing of reinforcement bars with epoxy joints

The splicing of reinforcement bars in tension using epoxy-sleeve joints is described. The optimum length of the splicing sleeve required and the optimum bonding layer of epoxy resin in the joint were determined in direct tension tests. The performance of the epoxy-sleeve joint made to these optimum dimensions is then compared to that of a lap splice made according to the provisions of CP 110 in a beam flexure test. A sleeve length of 12 bar diameters and an optimum average thickness of 2 mm of the bonding layer of epoxy are shown to develop the full strength of the splices bar. Tensile reinforcement bars spliced using epoxy-sleeve joints are shown to perform satisfactorily as flexural reinforcement in beams and compare favourably with the standard CP 110 lap splice. Epoxy-sleeve joints are shown to produce stiffer beams and reduced crack width at the joints.     

High-precision imaging of an encapsulated Lindqvist ion and correlation of its structure and symmetry with quantum chemical calculations

Low-voltage aberration-corrected transmission electron microscopy (AC-TEM) of discrete Lindqvist [W(6)O(19)](2-) polyoxometalate ions inserted from an ethanolic solution of [NBu(4)](2)[W(6)O(19)] into double walled carbon nanotubes (DWNTs) allows a higher precision structural study to be performed than previously reported. W atom column separations within the constituent W(6) tungsten cage can now be visualized with sufficient clarity that reliable correlation with structural predictions from density functional theory (DFT) can be achieved. Calculations performed on [W(6)O(19)](2-) anions encapsulated in carbon nanotubes show good agreement with measured separations between pairs of W(2) atom columns imaged within equatorial WO(6) polyhedral pairs and also single W atom positions located within individual axial WO(6) octahedra. Structural data from the tilted chiral encapsulating DWNT were also determined simultaneously with the anion structural measurements, allowing the influence of the conformation of the encapsulating tubule to be included in the DFT calculation and compared against that of other candidate encapsulating nanotubes. Additional DFT calculations performed using Li(+) cations as a model for the [NBu(4)](+) counterions indicate that the latter may help to induce charge transfer between the DWNT and the [W(6)O(19)](2-) ion and this may help to constrain the motion of the ion in situ.     

Self-assembly of a sulphur-terminated graphene nanoribbon within a single-walled carbon nanotube

The ability to tune the properties of graphene nanoribbons (GNRs) through modification of the nanoribbon's width and edge structure widens the potential applications of graphene in electronic devices. Although assembly of GNRs has been recently possible, current methods suffer from limited control of their atomic structure, or require the careful organization of precursors on atomically flat surfaces under ultra-high vacuum conditions. Here we demonstrate that a GNR can self-assemble from a random mixture of molecular precursors within a single-walled carbon nanotube, which ensures propagation of the nanoribbon in one dimension and determines its width. The sulphur-terminated dangling bonds of the GNR make these otherwise unstable nanoribbons thermodynamically viable over other forms of carbon. Electron microscopy reveals elliptical distortion of the nanotube, as well as helical twist and screw-like motion of the nanoribbon. These effects suggest novel ways of controlling the properties of these nanomaterials, such as the electronic band gap and the concentration of charge carriers.     

Flexural tests on epoxy-jointed precast prestressed concrete piles

The flexural behaviour of an epoxy-jointed precast prestressed concrete pile is discussed and compared with the performance of an unjointed pile and another pile with a welded joint. It is shown that the epoxy-jointed pile was capable of developing most of the ultimate capacity of the unjointed pile and had a stiffness comparable to the unjointed pile but higher than a welded jointed pile.     

Interactions Between Amino Acid‐Tagged Naphthalenediimide and Single Walled Carbon Nanotubes for the Design and Construction of New Bioimaging Probes

A new synthetic route to functionalized single walled carbon nanotubes (SWNTs) via supramolecular interactions using a specifically designed naphthalenediimide (NDI) nanoreceptor is demonstrated. The tendency of the NDI to spontaneously form composites with carbon nanomaterials leads to fluorescent amino acid tagged SWNTs, which are dispersible in widely accessible organic solvents (CHCl₃, DMSO) as well as in biocompatible cell medium (EMEM, Eagle's modified essential medium). The X‐ray crystal structure of the first iodine‐tagged and amino acid‐functionalized NDI molecule, designed especially to facilitate the high resolution transmission electron microscopy (HR TEM) imaging whilst retaining its ability to self‐assemble into a nanodimensional receptor in weakly polar solvents, is also described. A new hybrid material, NDI@SWNT, was prepared and characterized as dispersed in organic solvents and aqueous media and in the solid state by HR TEM, tapping mode atomic force microscopy (TM AFM), scanning electron microscopy (SEM), circular dichroism, Raman and fluorescence spectroscopies (steady‐state single and two‐photon techniques). Combined microscopy techniques, density functional theory (DFT) calculations using the Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) program and spectroscopic measurements in solution indicate that amino acid‐functionalized NDI interacts strongly with SWNTs and forms a donor‐acceptor complex. Density functional theory (DFT) calculations predicted the geometry and the binding energies of an NDI molecule loaded onto a SWNT strand and the possibility of charge transfer interactions within the hybrid. The NDI@SWNT composite translocates into cells (e.g. FEK‐4, HeLa, MCF‐7) as an intact object and localizes in the cells' cytoplasm and partially in the nucleus. The NDI coating enhances the biocompatibility of SWNTs and mediates its intracellular localization as shown by confocal fluorescence imaging and fluorescence lifetime imaging (FLIM) techniques. The excited state fluorescence lifetime of the probes in cells versus solution phase indicates that the probes remain unaffected by the change in their chemical environment within the experimental timescale (2 h).     

Recycled materials in railroad substructure: an energy perspective

Railway Engineering Science - Given that the current ballasted tracks in Australia may not be able to support faster and significantly heavier freight trains as planned for the future, the imminent...