Non-Volatile Threshold Adaptive Transistors with Embedded RRAM

We propose a novel nonvolatile threshold adaptive transistor （TAT） for neuromorphic circuits. The threshold adaptive transistor is achieved by embedding a resistive random-access memory （RRAM） material stack between the gate electrode and gate dielectric. During operation, the embedded RRAM device is kept at a high resistance state, which makes it act as a nonvolatile capacitor. The threshold could be nonlinearly adjusted by the voltage pulses applied on the gate of the transistor. We quantitatively estimate the range of the capacitance variation of the RRAM device. The threshold voltage of the TAT is simulated and shows expected variation. The simulated output of an inverter using a TAT shows a nonlinear adaptive behavior.     

Uniaxial exchange flows of two Bingham fluids in a cylindrical duct

Buoyancy driven flows of two Bingham fluids in an inclined ductare considered, providing a simplified model for many oilfieldcementing processes. The flows studied are near-uniaxial andstratified, with the heavy fluid moving down the incline, displacingthe lighter fluid upwards. Existence and uniqueness resultsare obtained for quite general flows and for those which satisfyan axial flow rate constraint. Parametric dependence of thesolutions on the axial pressure gradient is studied. Flows whichsatisfy a zero net axial flow constraint result from an axialpressure gradient which minimizes the viscous dissipation, butnot the plastic dissipation. A regularization method is usedto compute solutions to these problems for (more or less) arbitraryfluid-fluid interfaces and duct-cross sections. Examples relatedto a number of practical applications are presented.     

A new route to 2-substituted perimidines based on nitrile oxide chemistry

A new route to perimidines has been developed which involves reaction of a nitrile oxide with 1,8-diaminonaphthalene. Benzonitrile oxide, generated by dehydrochlorination of benzohydroximoyl chloride, and 1,8-diaminonaphthalene afforded 2-phenylperimidine. 2-Pyranosylperimidines were prepared by the same approach from pyranosyl hydroximoyl chlorides.     

火焰原子吸收光谱法测定鱼腥草、西洋参和茯苓中的铜含量

用硝酸-高氯酸混合酸(4∶1)消化鱼腥草、西洋参和茯苓,在波长324.8nm处,利用火焰原子吸收光谱法测定鱼腥草、西洋参和茯苓中铜的含量。线性回归方程为A=0.1708C 0.0004,相关系数r=0.9997,线性范围为0—5μg/mL,检出限为0.0035μg/mL,测定结果的相对标准偏差为0.09%,加标回收率为98.0%—104.2%。     

Paramagnetic NMR of Phenolic Oxime Copper Complexes: A Joint Experimental and Density Functional Study

¹H and ¹³C pNMR properties of bis(salicylaldoximato)copper(II) were studied in the solid state using magic‐angle‐spinning NMR spectroscopy and, for the isolated complex and selected oligomers, using density‐functional theory at the PBE0‐ //PBE0‐D3 level. Large paramagnetic shifts are observed, up to δ(¹H)=272 ppm and δ(¹³C)=1006 ppm (at 298 K), which are rationalised through spin delocalisation from the metal onto the organic ligand and the resulting contact shifts arising from hyperfine coupling. The observed shift ranges are best reproduced computationally using exchange‐correlation functionals with a high fraction of exact exchange (such as PBE0‐ ). Through a combination of experimental techniques and first‐principles computation, a near‐complete assignment of the observed signals is possible. Intermolecular effects on the pNMR shifts, modelled computationally in the dimers and trimers through effective decoupling between the local spins via A‐tensor and total spin rescaling in the pNMR expression, are indicated to be small. Addition of electron‐donating substituents and benzannelation of the organic ligand is predicted computationally to induce notable changes in the NMR signal pattern, which suggests that pNMR spectroscopy can be a sensitive probe for the spin distribution in paramagnetic phenolic oxime copper complexes.     

Conformational sampling by a general linearized embedding algorithm

Linearized embedding is a variant on the usual distance geometry methods for finding atomic Cartesian coordinates given constraints on interatomic distances. Instead of dealing primarily with the matrix of interatomic distances, linearized embedding concentrates on properties of the metric matrix, the matrix of inner products between pairs of vectors defining local coordinate systems within the molecule. We developed a pair of general computer programs that first convert a given arbitrary conformation of any covalent molecule from atomic Cartesian coordinates representation to internal local coordinate systems enforcing rigid valence geometry and then generate a random sampling of conformers in terms of atomic Cartesian coordinates that satisfy the rigid local geometry and a given list of interatomic distance constraints. We studied the sampling properties of this linearized embedding algorithm vs. a standard metric matrix embedding program, DGEOM, on cyclohexane, cycloheptane, and a cyclic pentapeptide. Linearized embedding always produces exactly correct bond lengths, bond angles, planarities, and chiralities; it runs at least two times faster per structure generated, and is successful as much as four times as often at refining these structures to full agreement with the constraints. It samples the full range of allowed conformations broadly, although not perfectly uniformly. Because local geometry is rigid, linearized embedding's sampling in terms of torsion angles is more restricted than that of DGEOM, but it finds in some instances conformations missed by DGEOM. © 1992 by John Wiley & Sons, Inc.     

General purpose interactive physico-chemical property exploration

There have been many tools and methods developed to investigate structure-activity (SAR) and structure-property (SPR) relationships. Many of these tools are fully or almost fully automated and attempt to predict various properties of molecules. Even with these tools, there is still an urgent need to provide a simple and useful methodology so a consumer of these various models, such as a medicinal chemist or molecular modeler, can learn how various properties of small molecules relate to their structure. This paper describes a new viewing and navigation paradigm called the Spiral View, which can be used to facilitate the interpretation of structure-property relationships. Examples of how this tool proves useful in the human interpretation of these relationships are drawn from the fields of experimental toxicity, LogP, and biological activity data drawn from various sources.     

Poling: Promoting conformational variation

This article introduces several methods of assessing the extent to which a collection of conformations represents or covers conformational space. It also describes poling: a novel technique for promoting conformational variation that can be applied to any method of conformational analysis that locally minimizes a penalty or energy function. The function being minimized is modified to force similar conformers away from each other. The method is independent of the origin of the initial conformers and of the particular minimization method used. It is found that, with the modification of the penalty function, clustering of the resulting conformers is generally unnecessary because the conformers are forced to be dissimilar. The functional form of the poling function is presented, and the merits are discussed with reference to (1) efficacy at promoting variation and (2) perturbation of the unmodified function. Results will be presented using conformers obtained from distance geometry with and without poling. It will be shown that the addition of poling eliminates much redundancy in conformer generation and improves the coverage of the conformational space. © 1995 by John Wiley & Sons, Inc.     

Accelerated K-means clustering in metric spaces

The K-means method is a popular technique for clustering data into k-partitions. In the adaptive form of the algorithm, Lloyds method, an iterative procedure alternately assigns cluster membership based on a set of centroids and then redefines the centroids based on the computed cluster membership. The most time-consuming part of this algorithm is the determination of which points being clustered belong to which cluster center. This paper discusses the use of the vantage-point tree as a method of more quickly assigning cluster membership when the points being clustered belong to intrinsically low- and medium-dimensional metric spaces. Results will be discussed from simulated data sets and real-world data in the clustering of molecular databases based upon physicochemical properties. Comparisons will be made to a highly optimized brute-force implementation of Lloyd's method and to other pruning strategies.     

Use of augmented Lagrangians in the calculation of molecular conformations by distance geometry

Distance geometry is a technique widely used to find atomic coordinates that agree with given upper and lower bounds on the interatomic distances. It is successful because it chooses at random some relatively good "trial coordinates" that take into account the whole molecule and all constraints at once. Customarily, these trial coordinates must be refined by minimizing a penalty function until the structure agrees with the original bounds. Here we present an alternative to minimizing the penalty function, which has the advantage of more precisely satisfying the bounds, showing more clearly when the bounds are mutually contradictory, and simultaneously optimizing an objective function subject to precise satisfaction of the bounds.