关于P_n~3的优美性(英文)

设G(V,E)是一个简单图,对自然数k,当V(G~k)=V(G,E(G~k)=E(G)∪{uv|d(u,v)=k},则称图G~k为k-次方图,本文证明了图P_n~3的优美性。     

辐冷器视场角对其制冷性能的影响

本文对抛物面G型辐冷器,在水平视场角变化的情况下不同工况下的制冷性能进行了计算。通过数值计算发现,视场角的减小导致辐冷器制冷性能的明显下降,虽然视场角影响辐冷器的因素很复杂,但最后的结果是两者呈现出良好的线性关系。其次,通过对辐冷器降温特性的研究,提出了通过改变辐冷器外壳控温方式来减小视场角变化对辐冷器制冷性能的负面影响,计算结果表明这种解决措施是非常有效的。     

Diastereoselective Synthesis of Chiral Pyrrolidine and Piperidine Ring Systems

A diastereoselective method for the synthesis of chiral pyrrolidine and piperidine ring containing compounds was described. The protocol of bromination followed by aminocyclization furnishes an easily handled while highly efficient procedure for the intramolecular amidation of an isolated double bond. High diastereomeric excess was observed in this synthetic procedure.     

A Rapid and Efficient Synthesis of 2, 4, 6-Triarylpyridines under Microwave Irradiation

An rapid and efficient synthesis of 2, 4, 6-triarylpyridines is reported using substituted benzaldehydes, substituted acetophenones and ammonia as starting materials under microwave irradiation in the presence of PEG-400.     

The First Total Synthesis of 3-Oxo-11, 12, 13-trihydroxyeudesm-4-ene

The first total synthesis of 3-oxo-11, 12, 13-trihydroxyeudesm-4-ene, a highly oxygenated natural eudesmane, was described.     

Theoretical study of the interaction mechanism of single-electron halogen bond complexes H_3C…Br-Y(Y=H,CN,NC,CCH,C_2H_3)

The characteristics and structures of single-electron halogen bond complexes H3C…Br-Y(Y = H,CCH,CN,NC,C2H3) have been investigated by theoretical calculation methods.The geometries were optimized and frequencies calculated at the B3LYP/6-311++G level.The interaction energies were corrected for basis set superposition error(BSSE) and the wavefunctions obtained by the natural bond orbital(NBO) and atom in molecule(AIM) analyses at the MP2/6-311++G level.For each H3C…Br-Y complex,a single-electron Br bond is f...     

The sorption mechanisms of Th(Ⅳ) on attapulgite

The surface properties of intrinsic and activated attapulgite were studied using potentiometric titration.The sorption mechanisms of Th(IV) on intrinsic and activated attapulgite were investigated by employing surface complexation model and FITEQL 3.2 code.The results indicated that the sorption sites of intrinsic attapulgite involved in the sorption process were main ion exchange site(≡ XNa/K),strong site(≡ SsOH) and weak site(≡ SwOH),while only strong site(≡ SsOH) and weak site(≡ SwOH) were predominant fo...     

A novel oxygen-dependent deoximation by nitric oxide

A variety of aldoximes and ketoximes were oxidized to corresponding aldehydes and ketones by nitric oxide in the presence of oxygen.A presumed mechanism was suggested.     

Ti^＋离子和C2H4分子自旋禁阻反应中C—H键活化机理的理论研究

用密度泛函B3LYP方法,研究了二重态和四重态势能面自旋禁阻反应Ti^＋（^4F,3d^24s^1）＋C2H4→TiC2H2^＋（^2A2）＋H2的微观机理．通过自旋．轨道耦合的计算讨论了势能面交叉点和可能的自旋翻转过程．中间体IM1-^4B2处,四重态和二重态间的旋-轨耦合值为59．3cm^-1．自旋多重度必将发生变化,从四重态系间穿越到二重态势能面形成共价型复合物IM1-^2A1,同时导致四重态势能面的势垒明显降低．到插入中间体IM2后,二重态势能面上有两条不同的反应路径,即分步和协同路径,后者在二重态势能面上得到放热产物TiC2H2^＋（^2A2）＋H2具有较低的活化势垒,4．52kcal／mol,其主反应路径为：Ti^＋＋C2H4→^4IC→IM1—^4B2→4.2ISC→IM1—^2A1→[^2TSins]→IM2-^2A”→[^2TSMCTS]→IM5→TiC2H2^＋（^2A2）＋H2．     

Synthesis and biological evaluation of novel steroid-linked nitrogen mustards

Two novel steroid-linked nitrogen mustard conjugates 1a and 1b were synthesized by using estrogenic acid 4 coupled with aniline mustard 8 and phenol mustard 13 in an esterification or amidation procedure. Preliminary cytotoxic screening on cancer cell lines in vitro showed that, the steroid-ester linked nitrogen mustard conjugate la exhibited obvious increasing of activities.