Abstract A simple method for the difluoromethylation of phenols and thiophenols using a non‐ozone‐depleting reagent is described.
Summary form only given. Because escape probability is about 2% per radiating surface, it is a good idea to use all six emitting surfaces of a solid rectangular LED. We introduce a photonic gas model for modelling this type of LED. Light extraction efficiency in thick (250/spl times/250/spl times/250 /spl mu/m) transparent substrate LED is a result of competition of light escape from the semiconductor chip, reabsorption in the active layer, and free-carrier absorption in the bulk. This modelling is confirmed by Monte Carlo simulations.
New cellular neural network chips, with stored-program capability and analog-and-logic architecture, are poised to challenge all-digital processing. In this article, we highlight the key ideas leading to the CNN Universal Machine, using simple circuit interpretations. We also illustrate the system, software, and application aspects.
To date, TFET results have been unsatisfying. The best reported subthreshold swings have been measured at a current density of around a nA/um and get significantly worse as the current increases. In order to achieve a better performance, there are fundamental design issues that need to be engineered. We can understand these issues by analyzing the three types of devices shown in Fig 1. The voltage required to operate a TFET can be given by: V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> = V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SS</sub> × Log(I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> )+ V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OV</sub> . V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SS</sub> is the subthreshold swing and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OV</sub> is the overdrive voltage needed to achieve the desired on-current after threshold. V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OV</sub> will be determined by the device geometry as shown in Fig 2 [1]. Introducing quantum confinement in the direction of tunneling increases the conductance by 1-2 orders of magnitude at low voltage. V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SS</sub> is given by the following model [2]: SS = 1/ η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">el</sub> × (1/S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Barrier</sub> + η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">conf</sub> /S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DOS</sub> ) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (1) η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">el</sub> is the electrostatic gate efficiency. η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">conf</sub> is the quantum confinement efficiency and comes from energy level shifts that occur when the quantum well shape changes with bias. S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Barrier</sub> represents the steepness in mV/decade that comes from changing the thickness of the tunneling barrier. S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DOS</sub> is the steepness of the joint density of states (DOS) and represents the rate at which the joint DOS fall off as the band edges are misaligned.
There have been many recent advances in enforcing finegrained access control for database-backed applications. However, operators face significant challenges both before and after an enforcement mechanism has been deployed. We identify three such challenges beyond enforcement and discuss possible solutions.
An enantioselective and regioselective iridium-catalyzed allylic etherification is described. The reaction of sodium and lithium aryloxides with achiral (E)-cinnamyl and terminal aliphatic allylic electrophiles in the presence of 2 mol % of an iridium-phosphoramidite complex provides chiral allylic aryl ethers in high yields and excellent levels of regio- and enantioselectivity. Lithium aryloxides containing a single substituent at an ortho, meta, or para position as well as sterically hindered phenoxides were tolerated. Reactions in THF displayed the most suitable balance of rate, regio-, and enantioselectivity. High ee's were also observed for the products from the reaction of alkyl (E)-allylic carbonates.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.