Effects of additional Higgses in supersymmetric grand unified theories

We consider modifications of the minimal supersymmetric SU(5) grand unified model. With the additional Higgses 10 +$\text{10}$, the theory may be modified so that the proton decays dominantly via the conventional mode p→e⁺π with the lifetime π_p=(0.04-710)×10³⁰yr, and sin²θ_W=0.222±0.003.     

Rational design of an L-histidine-derived minimal artificial acylase for the kinetic resolution of racemic alcohols

This communication describes the rational design of an l-histidine-derived minimal artificial acylase. Our new artificial acylase, tert-butyldiphenylsilyl ether of N-(2,4,6-triisopropylbenzenesulfonyl)-pi(Me)-l-histidinol, is a simple and small molecule (molecular weight = 660) that contains only one chiral carbon center that originates from natural l-histidine. The kinetic acylation of racemic secondary alcohols induced by this compound showed an S (kfast/kslow) value of up to 93. A reusable polystyrene-bound artificial acylase was also developed to examine its practical usability.     

Development of a method for evaluating drug-likeness and ease of synthesis using a data set in which compounds are assigned scores based on chemists' intuition

The concept of drug-likeness, an important characteristic for any compound in a screening library, is nevertheless difficult to pin down. Based on our belief that this concept is implicit within the collective experience of working chemists, we devised a data set to capture an intuitive human understanding of both this characteristic and ease of synthesis, a second key characteristic. Five chemists assigned a pair of scores to each of 3980 diverse compounds, with the component scores of each pair corresponding to drug-likeness and ease of synthesis, respectively. Using this data set, we devised binary classifiers with an artificial neural network and a support vector machine. These models were found to efficiently eliminate compounds that are not drug-like and/or hard-to-synthesize derivatives, demonstrating the suitability of these models for use as compound acquisition filters.     

On the dispersion managed soliton

We review various methods used to study the dispersion managed soliton for nonlinear return-to-zero pulse propagation in optical fibers. A numerical averaging method, the guiding center soliton, the variational method both with a simple and with an extended ansatz, as well as the multiscale theory are discussed and numerically compared, allowing us to show their domains of applicability. Their relative merits and demerits are then exposed. (c) 2000 American Institute of Physics.     

Bifurcation analysis of the motion of an asymmetric double pendulum subjected to a follower force: Codimension three problem

Local and global bifurcations in the motion of a double pendulum subjected to a follower force have been studied when the follower force and the springs at the joints have structural asymmetries. The bifurcations of the system are examined in the neighborhood of double zero eigenvalues. Applying the center manifold and the normal form theorem to a four-dimensional governing equation, we finally obtain a two-dimensional equation with three unfolding parameters. The local bifurcation boundaries can be obtained for the criteria for the pitchfork and the Hopf bifurcation. The Melnikov theorem is used to find the global bifurcation boundaries for appearance of a homoclinic orbit and coalescence of two limit cycles. Numerical simulation was performed using the original four-dimensional equation to confirm the analytical prediction.     

A 1-hydroxy-2,3,1-benzodiazaborine-containing π-conjugated system: Synthesis,optical properties and solvent-dependent response toward anions

Our interest in the functionalization of OH-substituted azaborines prompted us to synthesize a 1-hydroxy-2,3,1-benzodiazaborine conjugated with 1,8-naphthalimide 1. Its fluorescence was dramatically affected by the nature of the solvent. In particular, the use of DMSO, which has a relatively high donor number (DN = 29.8), led to a remarkable decrease in the fluorescence intensity (Φ_F = 0.0014), possibly due to intermolecular hydrogen-bonding interactions (Me₂SO?HOB). The presence of the hydroxyl group on boron led to a solvent-driven colorimetric response towards anions; high selectivity for F^? over other anions in DMSO, and responded to AcO^? and F^? in THF, as shown by UV/vis titrations, NMR, and mass spectroscopic analysis. The nucleus-independent chemical shift (NICS) indices suggested that hydrogen bonding interactions between Me₂SO and HOB reduced the aromaticity of the benzodiazaborine macrocycle, causing an increase in the negative character of the boron. The increase in the polarity of the BN bond may prevent acetate-binding of 1 in DMSO.     

Asymmetric conjugate addition of 5-benzylfurfurals to nitroalkenes using a diaminomethylenemalononitrile organocatalyst

A pyrrolidine–diaminomethylenemalononitrile organocatalyst efficiently promotes the asymmetric direct bisvinylogous Michael addition of 5-benzylfurfural derivatives to nitroalkenes, affording the corresponding ε-regioselective addition products in high yields with up to 86% ee.     

Synthesis of substituted furoates from acrylates and aldehydes by Pd(OAc)(2)/HPMoV/CeCl(3)/O(2) system

A new synthetic method of substituted furoates from acrylates and aldehydes was developed by Pd(OAc)2 combined with molybdovanadophosphoric acid and Lewis acid under atmospheric dioxygen. The reaction was found to proceed through the palladium-catalyzed acetalization of acrylates with methanol followed by the reaction of the resulting acetals with aldehydes.