Efficient and divergent synthesis of fully substituted 1H-pyrazoles and isoxazoles from cyclopropyl oximes

Efficient and divergent one-pot synthesis of fully substituted 1H-pyrazoles and isoxazoles from cyclopropyl oximes based on reaction conditions selection is reported. Under Vilsmeier conditions (POCl3/DMF), substituted 1 H-pyrazoles were synthesized from 1-carbamoyl, 1-oximyl cyclopropanes via sequential ring-opening, chlorovinylation, and intramolecular aza-cyclization. In the presence of POCl3/CH2Cl2, substituted isoxazoles were obtained from the cyclopropyl oximes via ring-opening and intramolecular nucleophilic vinylic substitution (SNV) reactions.     

Vilsmeier-Haack reactions of 2-arylamino-3-acetyl-5,6-dihydro-4H-pyrans toward the synthesis of highly substituted pyridin-2(1H)-ones

A facile and efficient one-pot synthesis of highly substituted pyridin-2(1H)-ones was developed via Vilsmeier-Haack reactions of readily available enaminones, 2-arylamino-3-acetyl-5,6-dihydro-4H-pyrans, and a mechanism involving sequential ring-opening, haloformylation, and intramolecular nucleophilic cyclization reactions is proposed.     

An improved approximate Newton method for implicit Runge-Kutta formulas

Implicit Runge-Kutta (IRK) methods (such as the s-stage Radau IIA method with s=3,5, or 7) for solving stiff ordinary differential equation systems have excellent stability properties and high solution accuracy orders, but their high computing costs in solving their nonlinear stage equations have seriously limited their applications to large scale problems. To reduce such a cost, several approximate Newton algorithms were developed, including a commonly used one called the simplified Newton method. In this paper, a new approximate Jacobian matrix and two new test rules for controlling the updating of approximate Jacobian matrices are proposed, yielding an improved approximate Newton method. Theoretical and numerical analysis show that the improved approximate Newton method can significantly improve the convergence and performance of the simplified Newton method.     

Facile and efficient synthesis of quinolin-2(1H)-ones via cyclization of penta-2,4-dienamides mediated by H2SO4

A facile and efficient synthesis of substituted quinolin-2(1H)-ones is developed via intramolecular cyclization of penta-2,4-dienamides mediated by concentrated H(2)SO(4) (98%), and a mechanism involving the formation of a dicationic superelectrophile, and subsequent intramolecular nucleophilic cyclization reactions is proposed.     

A new minimization protocol for solving nonlinear Poisson–Boltzmann mortar finite element equation

The nonlinear Poisson–Boltzmann equation (PBE) is a widely-used implicit solvent model in biomolecular simulations. This paper formulates a new PBE nonlinear algebraic system from a mortar finite element approximation, and proposes a new minimization protocol to solve it efficiently. In particular, the PBE mortar nonlinear algebraic system is proved to have a unique solution, and is equivalent to a unconstrained minimization problem. It is then solved as the unconstrained minimization problem by the subspace trust region Newton method. Numerical results show that the new minimization protocol is more efficient than the traditional merit least squares approach in solving the nonlinear system. At least 80 percent of the total CPU time was saved for a PBE model problem. AMS subject classification (2000)  65N30, 65H10, 65K10, 92-08     

原子吸收法测定人精子中锌和铜含量的研究

本文采用石墨炉原子吸收法，以ＮＨ４ＮＯ３和Ｍｇ（ＮＯ３）２混合剂作基体改进剂，测定了人精子中微量元素铜和锌。基方法的特征质量分别为１０．００ｐｇＣｕ／０．００４４Ａ．Ｓ．，９．８０ＰｇＺ／０．００４Ａ．Ｓ；平均加收率为９７．４２％，锌为１０１．９１％，铜和锌的精密度分别是４．１％和４．０３％。     

Convergence analysis of truncated incomplete Hessian Newton minimization method and application in biomolecular potential energy minimization

This paper gives a general convergence analysis to the truncated incomplete Hessian Newton method (T-IHN). It shows that T-IHN is globally convergent even with an indefinite incomplete Hessian matrix or an indefinite preconditioner, which may happen in practice. It also proves that when the T-IHN iterates are close enough to a minimum point, T-IHN has a Q-linear rate of convergence, and an admissible line search steplength of one. Moreover, a particular T-IHN algorithm is constructed for minimizing a biomolecular potential energy function, and numerically tested for a protein model problem based on a widely used molecular simulation package, CHARMM. Numerical results confirm the theoretical results, and demonstrate that T-IHN can have a better performance (in terms of computer CPU time) than most CHARMM minimizers.     

右旋糖甙缩硫醛大环螯合剂的合成及解汞毒性能

合成了一种新的选择性螯合汞的水溶性高分子缩硫醛大环树脂,由醛基化右旋糖甙与乙二醇二巯基乙酸酯缩合而得。进行了这种高分子螯合剂的毒性和对氯化汞急性中毒的解毒能力的初步动物试验。结果表明整合剂本身毒性很小,并能提高中毒小白鼠的存活率。如作为处置汞中毒的口服药物,它既可经尿排汞,也可由切断肝肠循环而随粪便排汞。     

Analysis of correlation between electrical and infrared optical properties of anatase Nb doped TiO2 films

Optical and electrical analysis are required to clarify infrared reflection behavior of anatase Nb doped TiO₂ (NTO) films, a novel transparent conductive oxide (TCO). In this paper, UV–vis-near infrared transmission spectrum, Fourier transformed infrared (FTIR) reflection and ellipsometry analysis are conducted on anatase NTO films (Nb doping concentration: 6, 4 and 2 at%) deposited by pulse laser deposition (PLD). NTO samples show good transparency from 400 nm to 1000 nm, but no obvious plasmon induced high IR reflection even when wavelength >3000 nm. Assuming inhomogeneous resistivity (ρ) and mean scattering time (τ) along film thickness, dielectric constants (ε_r, ε_i) and optical constants (n, k) are extracted by fitting spectroscopic ellipsometry using Code-Lorentz (CL) & Drude exponential model. It is shown that unique optical constants and small τ (1.1–2.6 fs) intrinsically prevent NTO to be high infrared reflective TCO.     

An incomplete Hessian Newton minimization method and its application in a chemical database problem

To efficiently solve a large scale unconstrained minimization problem with a dense Hessian matrix, this paper proposes to use an incomplete Hessian matrix to define a new modified Newton method, called the incomplete Hessian Newton method (IHN). A theoretical analysis shows that IHN is convergent globally, and has a linear rate of convergence with a properly selected symmetric, positive definite incomplete Hessian matrix. It also shows that the Wolfe conditions hold in IHN with a line search step length of one. As an important application, an effective IHN and a modified IHN, called the truncated-IHN method (T-IHN), are constructed for solving a large scale chemical database optimal projection mapping problem. T-IHN is shown to work well even with indefinite incomplete Hessian matrices. Numerical results confirm the theoretical results of IHN, and demonstrate the promising potential of T-IHN as an efficient minimization algorithm.