220 research outputs found
Surface Roughness Contribution to the Auger Electron Emission
Scanning Auger Microscopy (SAM) experiments have shown that z height and θ slope relative to the analysed spot are parameters that contribute to the measured Auger intensity I(z, θ). For greater analysed areas specific to Auger Electron Spectroscopy (AES), the knowledge of height and slope statistical distributions P(z) and P(θ) is required. These functions have been determined by means of profilometric data. The spatial resolution of the used tactile profilometer is similar to that which characterizes AES. A mathematical relationship I { P(z), P(θ) } has been set up for Si samples whose roughness is well defined. On the other hand, Auger images can be compared to level sections
Metallo-solid lipid nanoparticles as colloidal tools for meso-macroporous supported catalysts
Meso–macroporous
silica containing iron oxide nanoparticles
(15–20 nm) was synthesized by formulating solid lipid nanoparticles
and metallosurfactant as both template and metal source. Because of
the high active surface area of the catalyst, the material exhibits
an excellent performance in a Fenton-like reaction for methylene blue
(MB) degradation, even at low amount of iron oxide (5% TOC after 14
h)
A Contractual Approach to Investor-State Regulatory Disputes
International investment arbitral tribunals are increasingly tasked with resolving regulatory disputes. This relatively new form of dispute involves a challenge by a foreign investor to a host state’s generally applicable regulation, enacted in good faith to promote the public interest but resulting incidentally in harm to the investor’s business. Such claims typically invoke the “fair and equitable treatment” standard provided for in the bilateral investment treaty between the host state and the investor’s home state. The dominant view among commentators, and increasingly among the tribunals themselves, is that regulatory disputes should be analyzed within a public law framework, using tools derived from constitutional or administrative law. That means, for example, balancing the investor’s rights and host state’s regulatory concerns as part of a proportionality analysis. I argue that the public law approach is flawed because it requires tribunals to weigh incommensurable values and ultimately to make policy judgments when they lack the expertise and legitimacy to do so. This Article proposes that tribunals instead draw on tools from contract law and theory to approximate what the contracting states intended when they agreed to a fair and equitable treatment standard. The investment treaties themselves give no guidance on how that standard should be applied to regulatory disputes. When courts confront similar gaps in contracts, they do not simply abandon the inquiry into the parties’ intent but instead apply additional tools or principles to form the best possible estimate.
The Article explores three specific tools: a default rule approach and two default standards derived from contract law’s analysis of changed circumstances. More generally, I argue that a contractual approach, by focusing tribunals on the contracting states’ intent rather than requiring them to independently assess the substance of a host state’s policy, will facilitate more principled reasoning as well as enhance the tribunals’ legitimacy, and thereby better promote the goals of international investment in the long run
Spectral and spatial shaping of Smith Purcell Radiation
The Smith Purcell effect, observed when an electron beam passes in the
vicinity of a periodic structure, is a promising platform for the generation of
electromagnetic radiation in previously-unreachable spectral ranges. However,
most of the studies of this radiation were performed on simple periodic
gratings, whose radiation spectrum exhibits a single peak and its higher
harmonics predicted by a well-established dispersion relation. Here, we propose
a method to shape the spatial and spectral far-field distribution of the
radiation using complex periodic and aperiodic gratings. We show, theoretically
and experimentally, that engineering multiple peak spectra with controlled
widths located at desired wavelengths is achievable using Smith-Purcell
radiation. Our method opens the way to free-electron driven sources with
tailored angular and spectral response, and gives rise to focusing
functionality for spectral ranges where lenses are unavailable or inefficient
Smith-Purcell Radiation from Low-Energy Electrons
Recent advances in the fabrication of nanostructures and nanoscale features
in metasurfaces offer a new prospect for generating visible, light emission
from low energy electrons. In this paper, we present the experimental
observation of visible light emission from low-energy free electrons
interacting with nanoscale periodic surfaces through the Smith-Purcell (SP)
effect. SP radiation is emitted when electrons pass in close proximity over a
periodic structure, inducing collective charge motion or dipole excitations
near the surface, thereby giving rise to electromagnetic radiation. We
demonstrate a controlled emission of SP light from nanoscale gold gratings with
periodicity as small as 50 nm, enabling the observation of visible SP radiation
by low energy electrons (1.5 to 6 keV), an order of magnitude lower than
previously reported. We study the emission wavelength and intensity dependence
on the grating pitch and electron energy, showing agreement between experiment
and theory. Further reduction of structure periodicity should enable the
production of SP-based devices that operate with even slower electrons that
allow an even smaller footprint and facilitate the investigation of quantum
effects for light generation in nanoscale devices. A tunable light source
integrated in an electron microscope would enable the development of novel
electron-optical correlated spectroscopic techniques, with additional
applications ranging from biological imaging to solid-state lighting.Comment: 16 pages, 4 figure
Scanning Mechanical Microscopy of Laser Ablated Volumes Related to Inductively Coupled Plasma-Mass Spectrometry
Scanning mechanical microscopy based on the point by point sampling of the target surface was used to characterize volumes of minerals ablated by laser pulses (Nd: YAG, = 1064 nm, 140 ÎĽs pulse-width). Differentiated volumes resulting from vaporization and exfoliation mechanisms were selectively measured. Ablated volumes of natural pyrite (cubic FeS2), marcasite (orthorhombic FeS2) and arsenopyrite AsFeS, were transported into an inductively coupled plasma torch for subsequent mass analysis. The log of the S34 Fe57, and As75 mass intensities was linearly correlated with the log of the dimensions of the vaporized crater induced by the laser shots while large particles had no effect on the measured intensities. A memory effect for As was observed when a nylon tube was used to carry the ablated materials into the plasma torch. The memory effect was decreased by using a copper tube resulting probably from a difference in the electrical properties of the tubing systems leading to a lower adsorption of As within the copper tube than for the case of the nylon tube
Cathodoluminescence Applied to the Microcharacterization of Mineral Materials: A Present Status in Experimentation and Interpretation
Experimentation and interpretation of cathodoluminescence (CL) microscopy and spectroscopy applied to the microcharacterization of material minerals are reviewed. The origins of the intrinsic (host lattice) and extrinsic (impurities) luminescence emissions in crystals are briefly discussed. Merits and limitations of the available techniques are illustrated. CL emission changes as a function of the incident electron dose are illustrated for the case of natural quartz and sphalerite (ZnS) crystals. These effects are discussed in terms of the development of bulk charging, production of heat, diffusion of impurities, and creation of lattice defects induced by the incident ionizing particles. Although CL emission is mostly extrinsic in origin there is no general rule for identifying the nature of impurities from the CL emission spectra of minerals. However there is potential for using CL spectroscopy for trace element analysis as presented for the case of minerals containing rare-earth luminescent ions. The CL emission is a signature of the crystal-chemistry properties of minerals and hence contains potential genetic information. Some of the applications of CL emissions in the geosciences are summarized
Monochromatic X-ray source based on scattering from a magnetic nanoundulator
We present a novel design for an ultra-compact, passive light source capable
of generating ultraviolet and X-ray radiation, based on the interaction of free
electrons with the magnetic near-field of a ferromagnet. Our design is
motivated by recent advances in the fabrication of nanostructures, which allow
the confinement of large magnetic fields at the surface of ferromagnetic
nanogratings. Using ab initio simulations and a complementary analytical
theory, we show that highly directional, tunable, monochromatic radiation at
high frequencies could be produced from relatively low-energy electrons within
a tabletop design. The output frequency is tunable in the extreme ultraviolet
to hard X-ray range via electron kinetic energies from 1 keV-5 MeV and
nanograting periods from 1 {\mu}m-5 nm. Our design reduces the scale, cost, and
complexity of current free-electron-driven light schemes, bypassing the need
for lengthy acceleration stages in conventional synchrotrons and free-electron
lasers and driving lasers in other compact designs. Our design could help
realize the next generation of tabletop or on-chip X-ray sources.Comment: 8 pages, 4 figure
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