Enhanced resistance of single-layer graphene to ion bombardment

We report that single-layer graphene on a SiO_2/Si substrate withstands ion bombardment up to ~7 times longer than expected when exposed to focused Ga^+ ion beam. The exposure is performed in a dual beam scanning electron microscope/focused ion beam system at 30 kV accelerating voltage and 41 pA current. Ga^+ ion flux is determined by sputtering a known volume of hydrogenated amorphous carbon film deposited via plasma-enhanced chemical vapor deposition

Nanoscale gold pillars strengthened through dislocation starvation

It has been known for more than half a century that crystals can be made stronger by introducing defects into them, i.e., by strain-hardening. As the number of defects increases, their movement and multiplication is impeded, thus strengthening the material. In the present work we show hardening by dislocation starvation, a fundamentally different strengthening mechanism based on the elimination of defects from the crystal. We demonstrate that submicrometer sized gold crystals can be 50 times stronger than their bulk counterparts due to the elimination of defects from the crystal in the course of deformation

Size-dependent mechanical properties of molybdenum nanopillars

We report the deformation behavior of single crystalline molybdenum nanopillars in uniaxial compression, which exhibits a strong size effect called the “smaller is stronger” phenomenon. We show that higher strengths arise from the increase in the yield strength rather than through postyield strain hardening. We find the yield strength at nanoscale to depend strongly on sample size and not on the initial dislocation density, a finding strikingly different from that of the bulk metal

Mechanical characterization of solution-derived nanoparticle silver ink thin films

Mechanical properties of sintered silver nanoparticles are investigated via substrate curvature and nanoindentation methods. Substrate curvature measurements reveal that permanent microstructural changes occur during initial heating while subsequent annealing results in nearly elastic behavior of the thinner films. Thicker films were found to crack upon thermal treatment. The coefficient of thermal expansion was determined from linear slopes of curvature curves to be 1.9±0.097 ppm/°C, with elastic modulus and hardness determined via nanoindentation. Accounting for substrate effects, nanoindentation hardness and modulus remained constant for different film thicknesses and did not appear to be a function of annealing conditions. Hardness of 0.91 GPa and modulus of 110 GPa are somewhat lower than expected for a continuous nanocrystalline silver film, most likely due to porosity

Manos Teatrales: Cyber-Paleography and a Virtual World of Spanish Golden Age Theater

In the Manos Teatrales (Theatrical Hands) project, literary scholars, historians and computer scientists will develop manual and automatic methods for analyzing rich manuscripts collections and their societies, using the treasure-trove of Spanish Golden Age theater and related archival records as a case study. Our cyber-paleography effort will build a live, layered virtual world on the web, open to librarians, scholars and students. A first layer will connect digitally restored images of manuscript pages to descriptions of the pen strokes on paper. Manual and automatic analysis of these descriptions will yield profiles of the writers' handwriting styles and enable semi-automatic inferences based on machine learning methods, about who wrote what and when. A second layer will connect sources to individual and collective histories of the theater community and help scholars understand it. A third layer will describe the techniques of cyber-paleography for both humanists and scientists

Influence of Homogeneous Interfaces on the Strength of 500 nm Diameter Cu Nanopillars

Interfaces play an important role in crystalline plasticity as they affect strength and often serve as obstacles to dislocation motion. Here we investigate effects of grain and nanotwin boundaries on uniaxial strength of 500 nm diameter Cu nanopillars fabricated by e-beam lithography and electroplating. Uniaxial compression experiments reveal that strength is lowered by introducing grain boundaries and significantly rises when twin boundaries are present. Weakening is likely due to the activation of grain-boundary-mediated processes, while impeding dislocation glide can be responsible for strengthening by twin boundaries

HEDGING SPOT CORN: AN EXAMINATION OF THE MINNEAPOLIS GRAIN EXCHANGE'S CASH SETTLED CORN CONTRACT

This research examines the potential basis behavior and hedging effectiveness for the Minneapolis Grain Exchange's (MGE) cash settled corn contract. MGE futures cash settle to the National Corn Index (NCI) calculated by Data Transmission Network (DTN). Focusing on seven regions in Illinois, the data suggest that NCI Futures offer potential advantages over the existing Chicago Board of Trade (CBOT) corn futures. In particular, nearby basis variability could be reduced by nearly one-half from 8.8 cents per bushel to 4.5 cents per bushel, and hedging effectiveness may increase from an average of 80% for the CBOT to 93% for the NCI.Crop Production/Industries, Marketing,

Cathodoluminescence of enstatite from chondritic and achondritic meteorites and its selenological implications Technical report, 1 Sep. 1967 - 1 Jul. 1968

Cathodoluminescence of enstatite from chondritic and achondritic meteorites and selenological implication