Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes

Nanostructured materials and exploiting their properties in stereolithography (SL) may open new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small dispersions of MWCNTs resulted in significant effects on the physical properties of the polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™ 11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%, respectively. Electron microscopy was used to examine the morphology of the nanocomposite and results showed affinity between the MWCNTs and SL resin and identified buckled nanotubes that illustrated strong interfacial bonding. These improved physical properties may provide opportunities for using nanocomposite SL resins in end-use applications. Varying types and concentrations of nanomaterials can be used to tailor existing SL resins for particular applications.Mechanical Engineerin

Influence of MWCNT/surfactant dispersions on the mechanical properties of Portland cement pastes

This work studies the reinforcing effect of Multi Walled Carbon Nanotubes (MWCNT) on cement pastes. A 0.35% solid concentration of MWCNT in powder was dispersed in deionized water with sodium dodecyl sulfate (cationic surfactant), cetylpyridinium chloride (anionic surfactant) and triton X-100 (amphoteric surfactant) using an ultrasonic tip processor. Three concentrations of each surfactant (1mM, 10mM and 100mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes with additions of carbon nanotubes of 0.15% by mass of cement were produced in two steps; first the dispersions of MWCNT were combined with the mixing water using an ultrasonic tip processor to guarantee homogeneity, and then cement was added and mixed until a homogeneous paste was obtained. Direct tensile strength, apparent density and open porosity of the pastes were measured after 7 days of curing. It was found that the MWCNT/surfactants dispersions decrease the mechanical properties of the cement based matrix due to an increased porosity caused by the presence of surfactants. © Published under licence by IOP Publishing Ltd

Belize Barrier Reef Transect: How Far Do Coral Reef Fish Larvae Travel In Marine Currents?

The vast majority of coral reef fishes go through a pelagic larval stage, which provides potential for long-distance dispersal by marine currents. Yet planktonic larvae are notoriously difficult to track owing to their small size, and as a consequence the spatial scale of dispersal in coral reef fishes is largely unknown. Robust estimates of dispersal are needed owing to the fundamental importance of this parameter for the design and management of networks of marine protected areas. If larvae disperse locally, geographically nearer individuals are anticipated to be more similar genetically. A pattern of increasing genetic differentiation with geographic distance, referred to as genetic 'isolation by distance', is expected in this case and provides an opportunity to estimate dispersal. A specific aspect of this approach is that it requires the continuous sampling of individuals along a continuous population. The 250 km long Belize Barrier Reef provides an unparalleled opportunity to sample continuously along continuous populations of coral reef fishes. Individuals were collected continuously along a 250-km transect following the Belize Barrier Reef to estimate larval dispersal in seven species of coral reef fish with different life histories

Directional solidification of dilute Sn-Pb alloys

Microstructure evolution and pattern formation during directional solidification of dilute Sn-Pb system were analysed. Planar, cellular and dendritic morphologies were obtained by adequate thermal gradient and interface velocity control. The samples were obtained from pure elements in concentrations of 0·05, 1·0 and 4·0 wt-%Pb. Growth was carried out in a Bridgman device in the velocity range of 0·38-30 μm s -1 at thermal gradients from 1·3 to 2·6°C mm -1. The samples were examined using metallographic techniques to determine their morphology and dimensional characteristics. The system was analysed to describe the different stages of evolution of the morphology and transitions. It was observed that both primary cellular and dendritic spacing decreased with increasing velocity. However, in the cellular-dendritic transition zone, an important increase in spacing was detected and basically associated with convective effects during irregular cellular growth.Fil: Ochoa, H.. Universidad de Antofagasta (uantof);Fil: Fornaro, Osvaldo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Bustos, O.. Universidad de Santiago de Chile; ChileFil: Schulz, B.. Universidad de Santiago de Chile; Chil

Adherent Primary Cultures of Mouse Intercostal Muscle Fibers for Isolated Fiber Studies

Primary culture models of single adult skeletal muscle fibers dissociated from locomotor muscles adhered to glass coverslips are routine and allow monitoring of functional processes in living cultured fibers. To date, such isolated fiber cultures have not been established for respiratory muscles, despite the fact that dysfunction of core respiratory muscles leading to respiratory arrest is the most common cause of death in many muscular diseases. Here we present the first description of an adherent culture system for single adult intercostal muscle fibers from the adult mouse. This system allows for monitoring functional properties of these living muscle fibers in culture with or without electrical field stimulation to drive muscle fiber contraction at physiological or pathological respiratory firing patterns. We also provide initial characterization of these fibers, demonstrating several common techniques in this new model system in the context of the established Flexor Digitorum Brevis muscle primary culture model

Fluorochrome studies of bone metabolism in nutritional osteopathies in swine.

Doctor of PhilosophyDoctorad

Chiral charge pumping in graphene deposited on a magnetic insulator

We demonstrate that a sizable chiral charge pumping can be achieved at room temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect, which cannot be attributed to the ordinary spin pumping, reveals itself in the creation of a dc electric field/voltage in graphene as a response to the dynamic magnetic excitations (spin waves) in an adjacent out-of-plane magnetized YIG film. We show that the induced voltage changes its sign when the orientation of the static magnetization is reversed, clearly indicating the broken spatial inversion symmetry in the studied system. The strength of effect shows a non-monotonous dependence on the spin-wave frequency, in agreement with the proposed theoretical model.Comment: 8 pages, 5 figure