Three-dimensional nuclear spin positioning using coherent radio-frequency control

Distance measurements via the dipolar interaction are fundamental to the application of nuclear magnetic resonance (NMR) to molecular structure determination, but they only provide information on the absolute distance $r$ and polar angle $\theta$ between spins. In this Letter, we present a protocol to also retrieve the azimuth angle $\phi$. Our method relies on measuring the nuclear precession phase after application of a control pulse with a calibrated external radio-frequency coil. We experimentally demonstrate three-dimensional positioning of individual carbon-13 nuclear spins in a diamond host crystal relative to the central electronic spin of a single nitrogen-vacancy center. The ability to pinpoint three-dimensional nuclear locations is central for realizing a nanoscale NMR technique that can image the structure of single molecules with atomic resolution.Comment: 5 pages, 4 figure

High-bandwidth microcoil for fast nuclear spin control

The active manipulation of nuclear spins with radio-frequency (RF) coils is at the heart of nuclear magnetic resonance (NMR) spectroscopy and spin-based quantum devices. Here, we present a microcoil transmitter system designed to generate strong RF pulses over a broad bandwidth, allowing for fast spin rotations on arbitrary nuclear species. Our design incorporates: (i) a planar multilayer geometry that generates a large field of 4.35 mT per unit current, (ii) a 50 Ohm transmission circuit with a broad excitation bandwidth of approximately 20 MHz, and (iii) an optimized thermal management for removal of Joule heating. Using individual 13C nuclear spins in the vicinity of a diamond nitrogen-vacancy (NV) center as a test system, we demonstrate Rabi frequencies exceeding 70 kHz and nuclear pi/2 rotations within 3.4 us. The extrapolated values for 1H spins are about 240 kHz and 1 us, respectively. Beyond enabling fast nuclear spin manipulations, our microcoil system is ideally suited for the incorporation of advanced pulse sequences into micro- and nanoscale NMR detectors operating at low (<1 T) magnetic field.Comment: 8 pages, 5 figures. Submitted to Rev. Sci. Inst

Taxes, Economic Conditions And Recent Trends in Male Self-Employment: A Canada-U.S. Comparison

North American workers have increasingly turned to self-employment since the 1970's. Analysts who have primarily focused on changes in technology, industrial restructuring and in the demographic composition of the work force as explanations for the rise in self- employment have had limited success. At the same time, international statistics suggest that country- or region- specific factors, rather than widely-shared trends may play central roles in the evolution of self-employment rates. In this paper I assess the importance of two less commonly analyzed factors which do vary across regions and countries--macroeconomic conditions and the tax environment-- in explaining the trends in male self-employment in North America. I use microdata for the period 1983-1994 from Canada and the United States, which are perhaps more similar in overall institutional structure than any other two countries, but which differ substantially in their income tax policy, macroeconomic conditions, and self-employment trends. My findings suggest that higher income tax and unemployment rates are associated with an increase in the rate of male self-employment in the two countries. Changes in the tax environment account for a considerable amount of the secular trends in male self-employment over this period, while changing economic conditions played a smaller role in determining these trends.

Image Classification using Textural Neural Networks

This paper presents backpropagation neural networks that utilize texture information to accurately classify photographic images. Training with minimum sets is shown to yield excellent results

Image Classification using Textural Neural Networks

This paper presents backpropagation neural networks that utilize texture information to accurately classify photographic images. Training with minimum sets is shown to yield excellent results

Ammonia in positively charged pre-nucleation clusters: a quantum-chemical study and atmospheric implications

The quantum-chemical treatment of pre-nucleation clusters consisting of atmospheric nucleation precursors is critically important for the understanding of the molecular nature of atmospheric nucleation. In the present study, the influence of ammonia on the thermochemical stability of positively charged pre-nucleation clusters has been studied using the Density Functional Theory (DFT). The formation of binary (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; and ternary (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; ionic clusters and the conversion of (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&amp;minus;1&lt;/sub&gt; into (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; and (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;) (H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&amp;minus;1&lt;/sub&gt; into (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; have been investigated. The thermochemical analysis carried out in the present study shows both (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&amp;minus;1&lt;/sub&gt;→(NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;) (H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; and (H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)(H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&amp;minus;1&lt;/sub&gt;→(NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;) (H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; transformations to be favorable thermodynamically and gives us a clear indication of the important role of ammonia in the conversion of positively charged clusters containing hydronium (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;) into those containing protonated ammonia. Under typical continental boundary layer condition, a large fraction of small positive ions may contain ammonia, but most of neutral and negative hydrated sulfuric acid monomers do not contain ammonia. In term of absolute concentrations, around 1000 cm&lt;sup&gt;&amp;minus;3&lt;/sup&gt; out of 10&lt;sup&gt;7&lt;/sup&gt; cm&lt;sup&gt;&amp;minus;3&lt;/sup&gt; of sulfuric acid momoners contain ammonia. (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sup&gt;+&lt;/sup&gt;(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; clusters appear to dominate the concentrations of small positive ions. Because of the weak affinity of sulfuric acid molecules to (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; and (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;)(H&lt;sub&gt;2&lt;/sub&gt;O)&lt;sub&gt;&lt;i&gt;n&lt;/i&gt;&lt;/sub&gt; ions (&lt;i&gt;n&lt;/i&gt;&amp;le;6), the concentrations of both ammoniated and un-ammoniated sulfuric acid water proton clusters are quite low. The atmospheric implications of the obtained results are discussed

Commercialization of New Lattice-Matched Multi-Junction Solar Cells Based on Dilute Nitrides: July 8, 2010 - March 7, 2012

Final Technical Progress Report for PV Incubator subcontract NAT-0-99013-03. The overall objective of this Incubator subcontract was to complete the work necessary to make commercial ready solar cells using the dilute nitride technology. The specific objectives of this program were aimed at completing the development of a triple-junction solar cell that incorporates a GaInNAs {approx}1eV subcell to the point of commercial readiness, and determining the cell reliability and, if necessary, identifying and eliminating process or material related issues that lead to early-life cell failures. There were three major objectives for Phase 1, each of which focuses on a key element of the solar cell that determines its performance in a commercial CPV system. One objective was to optimize the quality and performance of the key individual components making up the solar cell structure and then to optimize the integration of these components into a complete triple-junction cell. A second objective was to design and test anti-reflective coating that maximizes the light coupled into a 3J cell with a {approx}1 eV bottom cell bandgap. The third objective was to develop Highly Accelerated Life Tests (HALT) protocols and tools for identifying and correcting potential reliability problems. The Phase 2 objectives were a continuation of the work begun in Phase 1 but aimed at optimizing cell performance for commercial requirements. Phase 2 had four primary objectives: (1) develop a glass-matched anti-reflective coating (ARC) and optimize the cell/ARC to give good performance at 60C operating temperature, (2) optimize the cell for good operation at 60C and high concentration, and (3) complete the light biased HALT system and use it to determine what, if any, failures are observed, and (4) determine the reliability limits of the optimized cell

Noise-based core monitoring and diagnostics: overview of the cortex project

This paper gives an overview of the CORTEX project, which is a Research and Innovation Action funded by the European Union in the Euratom 2016-2017 work program, under the Horizon 2020 framework. CORTEX, which stands for CORe monitoring Techniques and EXperimental validation and demonstration, aims at developing an innovative core monitoring technique that allows detecting anomalies in nuclear reactors, such as excessive vibrations of core internals, flow blockage, coolant inlet perturbations, etc. The technique is based on primarily using the inherent fluctuations in neutron flux recorded by in-core and ex-core instrumentation (often referred to as neutron noise), from which the anomalies will be differentiated depending on their type, location and characteristics. In addition to be non-intrusive and not requiring any external perturbation of the system, the method allows the detection of operational problems at a very early stage. Proper actions could thus be taken by utilities before such problems have any adverse effect on plant safety and reliability