Theoretical Study on the Mechanism of the Cycloaddition Reaction between Alkylidene Carbene and Ethylene

The mechanism of cycloaddition reaction between singlet alkylidene carbene and ethylene has been investigated with second-order Moller-Plesset perturbation theory (MP2). By using 6-31 G^* basis, geometry optimization, vibrational analysis and energetics have been calculated for the involved stationary points on the potential energy surface. The results show that the title reaction has two major competition channels. An energy-rich intermediate (INT) is firstly formed between alkylidene carbene and ethylene through a barrier-free exothermic reaction of 63.62 kJ/mol, and the intermediate then isomerizes to a three-membered ring product (P 1) and a four-memberd ring product (P2) via transition state TS1 and TS2, in which energy barriers are 47.00 and 51.02 kJ/mol, respectively. P1 is the main product.     

Quantum Chemical Study on a New Mechanism of One-carbon Unit Transfer Reaction： The Water-assisted Mechanism

It is a theoretical study on the water-assisted mechanism of one-carbon unit transfer reaction, in which the energy barrier for each transition state lowered by about 80-100 kJ/mol when compared with the one in no-water-involved mechanism. The water-assisted path 4 is the favorite reaction way. Our results well explained the presumption from experiments.     

Hyperspherical Harmonic Expansions of Potential 1／rjt of Molecular Systems

The expansion coefficientC^D｜L｜ of Coulomb potential 1/jt of molecular systems in hyperspherical harmonics is derived in detail,and the explicit expression is given.     

Tunable linear nanopatterns of disubstituted alkane derivatives containing bi-components via selective hydrogen bonding

Supramolecular self-assembly on surfaces offers attractive features, which are usually tuned through the choice of the chain-length-varying molecular building blocks and stabilized by hydrogen bonding. Here the linear nanopatterns of bi-component building blocks between 1,18-octadecanedionic acid (HOOC(CH₂)₁₈COOH) and 4,4′-bipyridine (BPy), 1-hydroxyhexadecanoic acid (HO(CH₂)₁₅COOH) and BPy on highly ordered pyrolytic graphite are presented. By merely changing terminal groups, we reveal by using scanning tunneling microscopy (STM) that it is rational to steer the periodicity of the linearly patterned nanostructures with nanometer precision over an extended length scale. Different surface nanopatterns on graphite surface are created by tuning different disubstituted terminal groups and the ratio of them to their complementary recognizing molecules. The STM observations are supported by the reference nanostructure of bi-component 1,16-hexadecandiol (HO(CH₂)₁₆OH) and BPy.     

A Novel β-1, 4-N, 6-O-Diacetylmuramidase from Streptomyces griseus and its Chemical Modification

A novel lysozyme namedβ-1, 4-N, 6-O-diacetylmuramidase R2 was purified and characterized from Streptomyces griseus. The molecular weight of the enzyme was determined by MALDI-TOF-MS as 23.5 kDa. The N-terminal amino acid sequence was DTSGVQGIDVS-HWQG.Chemical modification ofβ-1, 4-N, 6-O-diacetylmuramidase R2 indicated that sulfhydry1 group and carbamidine of arginine residues are not essential for the activity of the enzyme, but lysine residues and imidazole of histidine residues are essential for the activity. The number of essential tryptophan and carboxyl groups was found that only one tryptophan residue and three carboxyl groups in the active site.     

线性粘弹性壳的渐近分析——弯壳方程组的导出

应用渐近分析的方法和拉普拉斯变换,证明了3维线性粘弹性壳的位移在一定条件下收敛于2维线性粘弹性弯壳方程组的解．     

Reaction of Ketene Dithioacetals with Pyrazolylcarbohydrazide:Synthesis and Biological Activities of Ethyl 5-Amino-1-(5''''- methyl-1''''-t-butyl-4''''-pyrazolyl)carbonyl-3-methylthio-1H-pyrazole-4-carboxylate

Introduction Pyrazole and its derivatives represent one of the most active classes of compounds possessing a wide spectrum of biological activities. During the past years, considerable evidence has been accumulated to demon-strate the efficacy of pyrazole derivatives including an-tibacterial,1 antifungal,2 herbicidal,3 insecticidal4 and other biological activities.5-7 Up to now, a great variety of these kind of compounds have been synthesized, among which some commercially pesticides have been…     

Study on the Radius of an Electrical Spherical Micelle： Functional Theoretical Approach

For the purpose of eliminating restriction, the Poisson-Bokzmann (PB) equation, which represents the potential of the electrical double layer of spherical miceUes, can be solved analytically only under the lower potential condition, a kind of iterative method in functional analysis theory has been used. The radius of the spherical particle can be obtained from the diagram of the second iterative solution of the potential versus the distance from the center of the particle. The influences of the concentration of the ions, the charge number of ions, the aggregation number of the particle, the dielectric constant of solvent and the temperature of system on the radius also have been studied.     

(g,f)-FACTORS WITH SPECIAL PROPERTIES IN BIPARTITE (mg,mf)-GRAPHS

§1　Preliminary and resultsAll graphs considered in this paper are finite graphs which may have multiple edgesbut no loops.Let G be a graph with vertex set V( G) and edge set E( G) .The degree of avertex x is denoted by d G( x) .The connectivity and edge-connectivity of G are denoted byκ( G) andλ( G) ,respectively.Letg and f be two positive integer-valued functions definedon vertex set V( G) such that g ( x)≤f ( x) .Then a ( g,f ) -factor of G is a spanningsubgraph H of G satisfying…     

THE CHARACTERISTIC FINITE ELEMENT ALTERNATING-DIRECTION METHOD AND ANALYSIS FOR THREE-DIMENSIONAL NUMERICAL RESERVOIR SIMULATION

Petroleum science has made remarkable progress in organic geochcmistry and in the research into the theories of petroleum origin, its transport and accumulation. In estimating the oil-gas resources of a basin, the knowledge of its evolutionary history and especially the numerical computation of fluid flow and the history of its changes under heat is vital. The mathematical model can be described as a coupled system of nonlinear partial differentical equations with initial-boundary value problems. This thesis, from actual conditions such as the effect of fluid compressibility and the three-dimensional characteristic of large-scale science-engineering computation, we put forward a kind of characteristic finite element alternating-direction schemes and obtain optimal order estimates in L~2 norm for the error in the approximate assumption.