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Tomography produces complex volumetric datasets containing the entire internal structure and density of an object in three dimensions (3D). Interpreting volumetric data requires 3D visualization but needs specialized software distinguishable from more familiar tools used in animation for 3D surface data. This tutorial reviews 3D visualization techniques for volumetric data using the open-source tomviz software package. A suite of tools including two-dimensional (2D) slices, surface contours, and full volume rendering provide quantitative and qualitative analysis of volumetric information. The principles outlined here are applicable to a wide range of 3D tomography techniques and can be applied to volumetric datasets beyond materials characterization.
Important synergies and complementarities exist between trade liberalization initiatives and the application of measures to suppress anti-competitive practices or arrangements. Both anti-competitive practices of firms and state-orchestrated arrangements that restrict competition can undermine the gains from trade in myriad ways. Moreover, trade liberalization can be a powerful tool for addressing competition policy concerns. Whether there is a need to develop for more explicit linkages between national competition policies and the multilateral trading system remains an unresolved question in debates surrounding the future of the World Trade Organization (WTO). The role of competition policy is, however, increasingly being addressed by working parties during the accessions of new WTO members. This chapter finds that, in a vast majority of accessions, the acceding economy is requested to provide information on its domestic competition policy regime. In approximately 80 per cent of all accessions, the acceding parties have made notifications on aspects such as the objectives of the regime, its enforcement mechanisms by relevant agencies, as well as on work under way to put in place an effective competition regime where one is not already extant. This, in itself, shows a clear recognition and acceptance by WTO members of the importance of competition policy as a tool of economic integration. The complementarity between WTO law and competition policy, however, is broader than what is reflected in notifications and observations regarding competition legislation per se. Consequently, the analysis in this chapter also presents an in-depth study of the wider impact of competition in the WTO accession process, taking into account the information provided on aspects of the domestic regime dealing with state monopolies and the treatment of state-owned enterprises (SOEs).
Important synergies or complementarities exist between international trade liberalization and competition law and policy (Anderson and Müller, 2015). Competition policy aims at enhancing consumer welfare and economic growth by promoting competition and deterring practices that restrict it. The intended results are lower prices, enhanced product variety and quality, innovation, and sustainable growth and development. These goals are congruent and powerfully synergistic with those of the multilateral trading system.
Whether there is a need for more explicit linkages between national competition policies and the multilateral trading system – and, if so, what should be the content of related disciplines – currently is an unresolved question in debates surrounding the future of the WTO (Anderson and Müller, 2015).
Electron tomography has become a valuable and widely used tool for studying the three-dimensional nanostructure of materials and biological specimens. However, the incomplete tilt range provided by conventional sample holders limits the fidelity and quantitative interpretability of tomographic images by leaving a “missing wedge” of unknown information in Fourier space. Imaging over a complete range of angles eliminates missing wedge artifacts and dramatically improves tomogram quality. Full-range tomography is usually accomplished using needle-shaped samples milled from bulk material with focused ion beams, but versatile specimen preparation methods for nanoparticles and other fine powders are lacking. In this work, we present a new preparation technique in which powder specimens are supported on carbon nanofibers that extend beyond the end of a tungsten needle. Using this approach, we produced tomograms of platinum fuel cell catalysts and gold-decorated strontium titanate photocatalyst specimens. Without the missing wedge, these tomograms are free from elongation artifacts, supporting straightforward automatic segmentation and quantitative analysis of key materials properties such as void size and connectivity, and surface area and curvature. This approach may be generalized to other samples that can be dispersed in liquids, such as biological structures, creating new opportunities for high-quality electron tomography across disciplines.
We present the first successful simulations of neutrino-driven supernova explosions in three dimensions (3D) using the Vertex-Prometheus code including sophisticated energy-dependent neutrino transport. The simulated models of 9.6 and 20 solar-mass iron-core stars demonstrate that successful explosions can be obtained in self-consistent 3D simulations, where previous models have failed. New insights into the supernova mechanism can be gained from these explosions. The first 3D model (Melson et al. 2015a) explodes at the same time but more energetically than its axially symmetric (2D) counterpart. Turbulent energy cascading reduces the kinetic energy dissipation in the cooling layer and therefore suppresses neutrino cooling. The consequent inward shift of the gain radius increases the gain layer mass, whose recombination energy provides the surplus for the explosion energy.
The second explosion (Melson et al. 2015b) is obtained through a moderate reduction of the neutral-current neutrino opacity motivated by strange-quark contributions to the nucleon spin. A corresponding reference model without these corrections failed, which demonstrates how close current 3D models are to explosion. The strangeness adjustment is meant as a prototype for remaining neutrino opacity uncertainties.
We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80–200 keV electron beams.
Group III nitrides are promising materials for light emitting diodes (LEDs). The occurrence of structural defects strongly affects the efficiency of these LEDs. We investigate the optical properties of basal plane stacking faults (BFSs), and the assignment of specific spectral features to distinct defect types by direct correlation of localized emission bands measured by cathodoluminescence in a scanning electron microscope with defects found in high resolution (scanning) transmission electron microscopy and electron beam induced current at identical sample spots. Thus, we are able to model the electronic structure of BSFs addressing I1, I2, and E type BSFs in GaN and AlGaN with low Al content. We find hints that BSFs in semipolar AlGaN layers cause local changes of the Al content, which strongly affects the usability of AlGaN as an electron blocking layer in nitride based LEDs.
The WTO Agreement on Government Procurement (GPA) is unique in its duality as an international trade agreement that promotes and preserves market opening and as an instrument for the promotion of good governance. The recent successful renegotiation of the GPA has enhanced its coverage so that it now provides access to markets valued at US$1.7 trillion annually. In addition, the text of the GPA has been effectively modernised, making it more relevant, economically, and simplifying its implementation. Although not a substitute for domestic procurement reforms, it is a catalytic and reinforcing factor for reforms that enhance transparency and competition internally – thereby yielding important gains for governments and citizens in terms of value for money in national procurement activities. Participation in the GPA can also promote inward foreign direct investment by signalling a country's commitment to good governance and the fair treatment of all players under national legislation. The review in this chapter of the evidence from WTO and GPA accessions indicates that the WTO accession negotiations of Article XII members are often used to leverage increased GPA accessions. Specifically, of the members that have acceded to the WTO pursuant to Article XII of the Marrakesh Agreement Establishing the WTO (WTO Agreement), twenty-two have undertaken GPA-related commitments, and seven subsequently joined the GPA. Out of the ten WTO members that are currently seeking accession to the GPA, nine undertook commitments related to GPA accession at the time of their WTO accessions, pursuant to Article XII of the WTO Agreement. The chapter concludes that, even though WTO accession and GPA accession are formally separate steps, the basic policy decision as to whether to join the GPA is often made long before GPA accession negotiations are started, at the time of WTO accession. This chapter provides countries and other WTO members considering taking on accession commitments with a strengthened understanding of the relevant benefits and costs.
Increasingly, governments that join the WTO are encouraged to make commitments, at the time of their accession, to also seek to join, eventually, the WTO Agreement on Government Procurement (GPA). GPA accession may seem, to some, ‘a bridge too far’ – an ‘add-on’ to the WTO accession process that requires significant policy reforms and institution-building processes.