Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Mach number. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Prediction of specific biomolecule adsorption on silica surfaces as a function of pH and particle size

Abstract: Silica nanostructures are biologically available and find wide applications for drug delivery, catalysts, separation processes, and composites. However, specific adsorption of biomolecules on silica surfaces and control in biomimetic synthesis remain largely unpredictable. In this contribution, the variability and control of peptide adsorption on silica nanoparticle surfaces are explained as a function of pH, particle diameter, and peptide electrostatic charge using molecular dynamics simulations with the CHARMM-INTERFACE force field. Adsorption free energies and specific binding residues are analyzed in molecular detail, providing experimentally elusive, atomic-level information on the complex dynamics of aqueous electric double layers in contact with biological molecules. Tunable contributions to adsorption are described in the context of specific silica surface chemistry, including ion pairing, hydrogen bonds, hydrophobic interactions, and conformation effects. Remarkable agreement is found for compute...

Tunable quadruple-well ferroelectric van der Waals crystals.

Abstract: The family of layered thio- and seleno-phosphates has gained attention as potential control dielectrics for the rapidly growing family of two-dimensional and quasi-two-dimensional electronic materials. Here we report a combination of density functional theory calculations, quantum molecular dynamics simulations and variable-temperature, -pressure and -bias piezoresponse force microscopy data to predict and verify the existence of an unusual ferroelectric property—a uniaxial quadruple potential well for Cu displacements—enabled by the van der Waals gap in copper indium thiophosphate (CuInP2S6). The calculated potential energy landscape for Cu displacements is strongly influenced by strain, accounting for the origin of the negative piezoelectric coefficient and rendering CuInP2S6 a rare example of a uniaxial multi-well ferroelectric. Experimental data verify the coexistence of four polarization states and explore the temperature-, pressure- and bias-dependent piezoelectric and ferroelectric properties, which are supported by bias-dependent molecular dynamics simulations. These phenomena offer new opportunities for both fundamental studies and applications in data storage and electronics. The atomic displacements that generate ferroelectricity in materials commonly fit a double-well potential energy surface. Here, ferroelectricity in two-dimensional CuInP2S6 is shown to fit a quadruple well due to the van der Waals gap between layers of this material.

Moisture Effects in Epoxy Matrix Composites

Abstract: : The effect of absorbed moisture on the mechanical properties of a neat epoxy resin and derived graphite/epoxy composites is investigated. Glass transition temperature and modulus as a function of moisture content and temperature is determined for both the neat resin and composite. In addition, elastic modulus for the neat resin, and strength and elastic moduli for unidirectional composites and quasi-isotropic laminates are determined as a function of absorbed moisture and temperature. A method for predicting moisture content and through-the-thickness profile for a laminate exposed to a constant humidity and temperature is discussed. Particular attention is also given to the details of environmental testing. Data indicates that absorbed moisture and temperature effects on the neat resin translate directly to matrix dominated properties of the composite and can lead to a change in failure mode, while filament dominated properties show very little environmental sensitivity. Results also indicate that resin glass transition temperature is a function of processing as well absorbed moisture.