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Displaying 851 - 875 of 1856

In Situ Raman Monitoring of Ring-Opening Copolymerizations

March 25, 2012
Author(s)
Matthew T. Hunley, Santanu S. Kundu, Peter M. Johnson, Kathryn Beers
Recent advances in enzyme, metal, and organic catalysts have enabled the development of advanced functional polymers from cyclic ester and cyclic carbonate monomers. In this work, we present an in situ technique to monitor ring-opening polymerization using

Flexible polyurethane foam with well characterized and reproducible smoldering

March 24, 2012
Author(s)
Mauro Zammarano, Szabolcs Matko, Rick D. Davis, Roland H. Kraemer
Smoldering is a self-sustaining heterogeneous oxidation reaction that induces a slow, low temperature, flameless combustion.1 Flexible polyurethane foams (PUF) are particularly prone to smoldering due to their high air permeability and low density. In this

Measuring domain sizes and compositional heterogeneities in P3HT-PCBM bulk heterojunction thin films with 1H spin diffusion NMR spectroscopy

March 21, 2012
Author(s)
Ryan C. Nieuwendaal, Hyun Wook Ro, David Germack, Regis J. Kline, Calvin Chan, Amit K. Agrawal, David J. Gundlach, David L. VanderHart, Dean M. DeLongchamp
In this manuscript we show that 1H spin diffusion NMR is a valuable method for estimating the domain sizes in thin films of a polymer-fullerene blend for bulk heterojunction (BHJ) photovoltaics. Variations in common BHJ film processing parameters have

Stability of Solid-Supported Enzyme Catalysts for Ring-Opening Polymerization

March 19, 2012
Author(s)
Sara V. Orski, Santanu S. Kundu, Kathryn L. Beers, Richard Gross
The enzyme Candida antarctica Lipase B (CAL B), immobilized on a crosslinked poly(methyl methacrylate) (PMMA) support, catalyzes the ring-opening polymerization of ε-caprolactone to make biodegradable polyesters. Weak hydrophobic interactions of CAL B

High Speed Endurance and Switching Measurements for Memristive Switches

March 6, 2012
Author(s)
Pragya R. Shrestha, Adaku Ochia, Kin P. Cheung, Jason P. Campbell, Helmut Baumgart, Gary Harris
Accurate capture of the Set/Reset characteristics is a necessary but challenging task for the development of memristive switches. Here we describe and demonstrate a technique capable of meeting this challenge. This technique can measure the transient

Transitory Temperatures of Organic-Film Coated Specimens under Outdoor Exposure

March 2, 2012
Author(s)
William C. Thomas, Christopher C. White, Walter E. Byrd
A mathematical model is presented and validated for predicting the temperature of thin polymeric films bonded to substrate materials. The National Institute of Standards and Technology provided specimen temperature and simultaneous weather data for tests

Freeform Fabricated Scaffolds with Roughened Struts that Enhance both Stem Cell Proliferation and Differentiation by Controlling Cell Shape

March 1, 2012
Author(s)
Girish Kumar, Carl G. Simon Jr., Michael S. Waters, Tanya M. Farooque, Marian F. Young
We demonstrate that imparting freeform fabricated (FFF) scaffolds with surface roughness on their struts enhances osteogenic differentiation of primary human bone marrow stromal cells (hBMSCs) by controlling cell shape. Previous work showed that hBMSCs

Rippling Instability of Supported Polymer Nanolines

February 21, 2012
Author(s)
Vijaya R. Tirumala, Christopher M. Stafford, Leonidas E. Ocola, Jack F. Douglas, L. Mahadevan
The swelling response of polymer line gratings supported on a rigid substrate has direct implications on their mechanical stability during pattern transfer in nanofabrication. The polymer lines, when swollen in a good solvent, undergo a rippling

Direct observation of nucleation and early stages of growth of GaN nanowires

February 15, 2012
Author(s)
Rosa E. Diaz, Renu Sharma, Karalee Jarvis, Qinglei Zhang, Subhash Mahajan
We report for the first time direct observations of the nucleation and early stages of growth of GaN nanowires. The nanowires were formed by exposing Au + Ga droplets to ammonia. The formation process was observed in situ, and controlled in real time using

Nanoscale structure measurements for polymer-fullerene photovoltaics

February 3, 2012
Author(s)
Dean M. DeLongchamp, Regis J. Kline, Andrew A. Herzing
This review covers methods to measure key aspects of nanoscale structure in organic photovoltaic devices based on polymer-fullerene bulk heterojunctions. The importance of nanoscale structure to the power conversion efficiency and stability of these

Antibacterial amorphous calcium phosphate nanocomposite with quaternary ammonium salt and silver nanoparticles

February 2, 2012
Author(s)
Nancy J. Lin, Lei Cheng, Michael D. Weir, Hockin H. Xu, Joseph M. Antonucci, Alison M. Kraigsley, Sheng Lin-Gibson, Xuedong Zhou
Objectives. Calcium and phosphate ion-releasing resin composites are promising for remineralization; however, so far there has been no report on imparting a potent antibacterial capability to these composites. The objectives of this study were to

Control of Molecular Mass Distributions in Enzymatic Lactone Polymerizations

February 2, 2012
Author(s)
Santanu S. Kundu, Peter M. Johnson, Kathryn L. Beers
Using a model developed for the enzyme catalyzed polymerization and degradation of poly(caprolactone), we illustrate methods and the kinetic mechanisms necessary to improve molecular mass distributions by manipulating equilibrium reactions in the kinetic

Polymer Dynamics in Constrained Geometries

February 1, 2012
Author(s)
Christopher Soles, Ryan Nieuwendaal, Huagen H. Peng
The wide-spread interest in the dynamical property of organic materials under strong states of confinement largely began with differential scanning calorimeter (DSC) measurements in the early 90's of the glass transition and heat capacity of glass forming

Elucidating the Influence of Local Structure Perturbations on the Metal-Insulator Transitions of V1-x MoxO2 Nanowires: Mechanistic Insights from an X-ray Absorption Spectroscopy Study

January 27, 2012
Author(s)
Bruce D. Ravel, C Patridge, Luisa Whittaker-Brooks, S Banerjee
The substitutional doping of Mo within VO2 substantially alters the electronic and structural phase diagrams of the host lattice, most notably by bringing the technologically relevant metal-insulator phase transition temperature in closer proximity to room

DNA Molecules Descending a Nanofluidic Staircase by Entropophoresis

January 26, 2012
Author(s)
Samuel M. Stavis, Jon C. Geist, Michael Gaitan, Laurie E. Locascio, Elizabeth A. Strychalski
A complex entropy gradient for confined DNA molecules was engineered for the first time. Following the second law of thermodynamics, this enabled the directed self-transport and self-concentration of DNA molecules. This new nanofluidic method is termed

The Effects of Folding on High Strength Fibers Used in Soft Body Armor

January 23, 2012
Author(s)
Haruki Kobayashi, Walter G. McDonough, Joy Dunkers, Jae H. Kim, Hae-Jeong Lee, Scott Wight, Amanda L. Forster, Kirk D. Rice, Gale A. Holmes
Poly (p-phenylene benzobisoxazole) (PBO) fibers have been used in soft body armor (SBA) because of their high mechanical strength. However, there was an unexpected failure of a first responder's SBA which was composed of PBO fiber that was in service for

Direct Observation of Hydrogen Spillover in Ni-Loaded Pr-Doped Ceria

January 17, 2012
Author(s)
Vaneet Sharma, Peter A. Crozier, Renu Sharma, James B. Adams
Hydrogen-spillover in Ni-loaded Pr-doped ceria (PDC) was directly observed using an environmental transmission electron microscope (ETEM). Localized reduction of ceria in a H2 atmosphere was observed and attributed to gas-Ni-ceria interactions at the three
Displaying 851 - 875 of 1856