International evidence-based recommendations on ultrasound-guided vascular access

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Grain Boundary Character Distribution Of Nanocrystalline Cu Thin Films Using Stereological Analysis Of Transmission Electron Microscope Orientation Maps

Abstract Stereological analysis has been coupled with transmission electron microscope (TEM) orientation mapping to investigate the grain boundary character distribution in nanocrystalline copper thin films. The use of the nanosized (\u3c5 nm) beam in the TEM for collecting spot diffraction patterns renders an order of magnitude improvement in spatial resolution compared to the analysis of electron backscatter diffraction patterns in the scanning electron microscope. Electron beam precession is used to reduce dynamical effects and increase the reliability of orientation solutions. The misorientation distribution function shows a strong misorientation texture with a peak at 60°/[111], corresponding to the Σ3 misorientation. The grain boundary plane distribution shows {111} as the most frequently occurring plane, indicating a significant population of coherent twin boundaries. This study demonstrates the use of nanoscale orientation mapping in the TEM to quantify the five-parameter grain boundary distribution in nanocrystalline materials. Copyright © Microscopy Society of America 2013

The heterophase interface character distribution of physical vapor-deposited and accumulative roll-bonded Cu-Nb multilayer composites

We present a method for characterizing the full five parameter heterophase interface character distributions (HICD) using two-dimensional electron back-scatter diffraction (EBSD) images. We apply the HICD method to determine the orientation relationships and three-dimensional normal vectors of Cu-Nb interfaces in both physical vapor-deposited (PVD) pure Cu-Nb (4 ??m individual layer thickness) and accumulative roll-bonded (ARB) alloyed Cu-Nb multilayer composites (200-600 nm layer thickness). The HICD analysis shows that {1 1 2} Cu planes are most preferentially and frequently bonded with {1 1 2} Nb planes with Kurdjumov-Sachs and Nishiyama-Wasserman misorientations in the ARB alloyed Cu-Nb multilayers. These interfaces differ from the {1 1 1} Cu||{1 1 0} Nb interfaces predominantly found in the PVD pure Cu-Nb multilayered thin films. Also, pure tilt type interfaces with a [1 1 1]/30?? misorientation and {1 1 0} Cu planes bonded to {1 1 2} Nb planes were found in ARB alloyed Cu-Nb multilayers. In the ARB material the observed Cu-Nb interfaces differ from what would be obtained from random pairings of the Cu and Nb orientations in terms of the relative intensities (in multiples of random distribution) and shapes of the interface normal peaks, which indicates that these interfaces were preferentially selected during the high strain ARB process. The measured ARB textures along the interface also differ from the theoretical rolling textures for each bulk single phase metal, suggesting that during ARB layer refinement these interfaces have some influence on slip activity by constraining grain deformation or through the kinetics of dislocation-interface interactions.close383

Grain Boundary Character Distribution of Nanocrystalline Cu Thin Films Using Stereological Analysis of Transmission Electron Microscope Orientation Maps

Stereological analysis has been coupled with transmission electron microscope (TEM) orientation mapping to investigate the grain boundary character distribution in nanocrystalline copper thin films. The use of the nanosized (<5 nm) beam in the TEM for collecting spot diffraction patterns renders an order of magnitude improvement in spatial resolution compared to the analysis of electron backscatter diffraction patterns in the scanning electron microscope. Electron beam precession is used to reduce dynamical effects and increase the reliability of orientation solutions. The misorientation distribution function shows a strong misorientation texture with a peak at 60 degrees/[111], corresponding to the Sigma 3 misorientation. The grain boundary plane distribution shows {111} as the most frequently occurring plane, indicating a significant population of coherent twin boundaries. This study demonstrates the use of nanoscale orientation mapping in the TEM to quantify the five-parameter grain boundary distribution in nanocrystalline materials.close111

Stimuli-Responsive Iron-Cross-Linked Hydrogels That Undergo Redox-Driven Switching between Hard and Soft States

A unique class of stimuli-responsive hydrogels, termed electroplastic elastomers (EPEs), whose mechanical properties can be reversibly tuned between hard and soft states with the application of an electric potential, is described. Electrochemically reversible cross-links formed within a permanent, covalently cross-linked polymeric hydrogel network are switched between strongly binding Fe³⁺ and weak to nonbinding Fe²⁺, as determined by potentiometric titration. With the incorporation of graphene oxide (GO) into the EPE, a significant enhancement in modulus and toughness was observed, allowing for the preparation of thinner EPE samples, 80–100 μm in thickness, which could be reversibly cycled between soft (Young’s modulus: ∼0.38 MPa) and hard (∼2.3 MPa) states over 30 min. Further characterization of EPE samples by magnetic susceptibility measurements suggests the formation of multinuclear iron clusters within the gel