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Aberdeen Proving Ground, MD, United States

Champagne V.K.,U.S. Army | Helfritch D.J.,Dynamic Science Inc.
Journal of Biological Engineering | Year: 2013

Background: Bacterial contamination on touch surfaces results in increased risk of infection. In the last few decades, work has been done on the antimicrobial properties of copper and its alloys against a range of micro-organisms threatening public health in food processing, healthcare and air conditioning applications; however, an optimum copper method of surface deposition and mass structure has not been identified.Results: A proof-of-concept study of the disinfection effectiveness of three copper surfaces was performed. The surfaces were produced by the deposition of copper using three methods of thermal spray, namely, plasma spray, wire arc spray and cold spray The surfaces were then inoculated with meticillin-resistant Staphylococcus aureus (MRSA). After a two hour exposure to the surfaces, the surviving MRSA were assayed and the results compared.The differences in the copper depositions produced by the three thermal spray methods were examined in order to explain the mechanism that causes the observed differences in MRSA killing efficiencies. The cold spray deposition method was significantly more effective than the other methods. It was determined that work hardening caused by the high velocity particle impacts created by the cold spray technique results in a copper microstructure that enhances ionic diffusion, and copper ions are principally responsible for antimicrobial activity.Conclusions: This test showed significant microbiologic differences between coatings produced by different spray techniques and demonstrates the importance of the copper application technique. The cold spray technique shows superior anti-microbial effectiveness caused by the high impact velocity imparted to the sprayed particles which results in high dislocation density and high ionic diffusivity. © 2013 Champagne and Helfritch; licensee BioMed Central Ltd.

Zhong Y.,Pennsylvania State University | Saengdeejing A.,Pennsylvania State University | Kecskes L.,U.S. Army | Klotz B.,Dynamic Science Inc. | Liu Z.-K.,Pennsylvania State University
Acta Materialia | Year: 2013

The thermodynamic properties and phase equilibria of the Cu-Hf binary system with five intermetallic compounds were studied by experiments, first-principles calculations and CALPHAD modeling. The experimental investigations included differential thermal analysis, scanning electron microscopy, energy dispersive X-ray microanalysis and micro-X-ray diffraction focusing on the 30-60 at.% Hf composition range to determine the invariant reaction temperatures. Cu10Hf7 was confirmed to melt incongruently. The enthalpies of formation of all five binary Cu-Hf compounds were predicted through first-principles calculations. The atomic configuration of one of the compounds, Cu51Hf14, was postulated through systematic first-principles calculations with 65 atoms instead of 68 atoms, denoted by hp68 in the literature. The thermodynamic description of the Cu-Hf binary system was then obtained from the new experimental data and first-principles calculations. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Kraft R.H.,U.S. Army | Mckee P.J.,Dynamic Science Inc. | Dagro A.M.,U.S. Army | Grafton S.T.,University of California at Santa Barbara
PLoS Computational Biology | Year: 2012

This article presents the integration of brain injury biomechanics and graph theoretical analysis of neuronal connections, or connectomics, to form a neurocomputational model that captures spatiotemporal characteristics of trauma. We relate localized mechanical brain damage predicted from biofidelic finite element simulations of the human head subjected to impact with degradation in the structural connectome for a single individual. The finite element model incorporates various length scales into the full head simulations by including anisotropic constitutive laws informed by diffusion tensor imaging. Coupling between the finite element analysis and network-based tools is established through experimentally-based cellular injury thresholds for white matter regions. Once edges are degraded, graph theoretical measures are computed on the "damaged" network. For a frontal impact, the simulations predict that the temporal and occipital regions undergo the most axonal strain and strain rate at short times (less than 24 hrs), which leads to cellular death initiation, which results in damage that shows dependence on angle of impact and underlying microstructure of brain tissue. The monotonic cellular death relationships predict a spatiotemporal change of structural damage. Interestingly, at 96 hrs post-impact, computations predict no network nodes were completely disconnected from the network, despite significant damage to network edges. At early times (t<24 hrs) network measures of global and local efficiency were degraded little; however, as time increased to 96 hrs the network properties were significantly reduced. In the future, this computational framework could help inform functional networks from physics-based structural brain biomechanics to obtain not only a biomechanics-based understanding of injury, but also neurophysiological insight.

Champagne V.,U.S. Army | Helfritch D.,Dynamic Science Inc. | Wienhold E.,University of Maryland University College | Dehaven J.,Missouri University of Science and Technology
Journal of Micromechanics and Microengineering | Year: 2013

The application of fine line micro-circuitry onto ceramic substrates currently requires a multi step process including printing, baking and sintering. A new, one-step, process utilizing particle impact deposition is presented. This process directs a high velocity stream of copper particles within a helium carrier onto a ceramic substrate. Upon impact the particles deform and adhere to the substrate and to previously deposited particles. The use of a capillary tube as the flow nozzle restricts the jet and the resulting deposited copper to micron scale dimensions. The deposited copper is dense, with near zero porosity. Robot control of the jet position can yield precise conduction lines and component connections. © 2013 IOP Publishing Ltd.

De Rosset W.S.,Dynamic Science Inc.
Materials and Manufacturing Processes | Year: 2012

Experiments have been conducted to see if internal grooves machined in steel cylinders will lead to higher bond strengths produced by the Gun Liner Emplacement with an Elastomeric Material (GLEEM) process. Groove depth and twist angle were varied. Both experimental and analytical studies showed that at the pressures used, there was little movement of the liner material into the machined grooves. However, the liner was seen to conform to very small machining marks in the steel cylinder inner bore, providing an increase in the coefficient of friction. Bond strengths of over 30MPa were obtained. Copyright © National Technical Systems 2012.

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