Infrared studies of chromones—II Isotopically substituted 5-hydroxychromones

By deuteration of the OH group, it has been shown that two bands, at 1665 and 1630 cm⁻¹ (CCl₄), in the IR spectra of 5-hydroxychromones are associated with the H-bonded CO stretching vibration. Nuclear deuteration of 5-hydroxy-2-methylchromone (1) under acidic conditions gave a tri- and a hexadeutero derivative; the latter, isotopically substituted at C-3, shows a single CO band at 1649 cm⁻¹. Hydrolysis of 3-acetyl-5-hydroxy-2-methylchromone with sodium carbonate in deuterium oxide furnished 5-hydroxy-2-trideuteromethylchromone-3-d which also exhibits a single CO absorption. Partial incorporation of O¹⁸ into the CO group of 1 results in a single ν_C=O¹⁸ at 1593 cm⁻¹. It is suggested that the doublet CO absorption of 5-hydroxychromones arises from a Fermi resonance involving a low-energy vibrational mode of the vinyl proton on the nuclear C-3 position.     

Parallel computing structures capable of flexible associations and recognition of fuzzy inputs

We experimentally show that computing with attractors leads to fast adaptive behavior in which dynamical associations can be made between different inputs which initially produce sharply distinct outputs. We do so by first defining a set of simple local procedures which allow a computing array to change its state in time so as to produce classical Pavlovian conditioning. We then examine the dynamics of coalescence and dissociation of attractors with a number of quantitative experiments. We also show how such arrays exhibit generalization and differentiation of inputs in their behavior.     

Co2+ spin-lattice relaxation narrowing of 19F NMR in KCoF3

The temperature dependence of the ¹⁹F NMR linewidth ΔH in KCoF₃ has been measured over the entire paramagnetic solid state region. The dramatic decrease in the hyperfine-broadened, exchange narrowed ΔH that occurs above 200 K is interpreted as arising from fast Co²⁺ single-ion, spin-lattice relaxation. A model theory of the temperature dependence of ΔH is given which incorporates the interplay of exchange and spin lattice relaxation effects on the decay of the spin autocorrelation function.     

Experimental implementation of an adiabatic quantum optimization algorithm

We report the realization of a nuclear magnetic resonance computer with three quantum bits that simulates an adiabatic quantum optimization algorithm. Adiabatic quantum algorithms offer new insight into how quantum resources can be used to solve hard problems. This experiment uses a particularly well-suited three quantum bit molecule and was made possible by introducing a technique that encodes general instances of the given optimization problem into an easily applicable Hamiltonian. Our results indicate an optimal run time of the adiabatic algorithm that agrees well with the prediction of a simple decoherence model.     

Design and synthesis of a diverse morpholine template library

Efficient and general procedures have been developed for the solution-phase preparation of substituted morpholine derivatives, and a library has been produced around generic structure 1. This library was designed with proprietary modeling software for use as a general screening library. The 30 R1 reagents were phenols, and the 275 R2 reagents were taken from five different reagent classes, giving a variety of product classes in the final library of 8250 potential products. All of the library members were generated from a common intermediate, mesylate (5), which was synthesized efficiently, in bulk, in three steps from N-benzylethanolamine (2). High-throughput chemistry using robotics was carried out to produce the 7907 library members, which were individually characterized by reversed-phase LC/MS analysis.     

Nanoelectronic architectures

Configurable crossbars are the easiest computational structures to fabricate at the nanoscale. By creating multiple types of crossbars and assembling them into larger structures, we may implement general computation. Architectures for diode-based and transistor-based logic are presented, along with latching mechanisms. We present simulation results from defect-tolerance studies on two applications (a 3-bit adder and a 4-bit microprocessor) mapped onto defective, nanoelectronic fabrics, and outline strategies for fault tolerance. PACS 85.35.-p; 85.40.Bh; 85.40.Qx; 85.65.+h