BEPCⅡ高频系统的建造

北京正负电子对撞机二期(BEPCⅡ)的高频系统已于2006年11月投入运行,它包括了3个子系统:超导腔、发射机和低电平控制系统.与以前的高频系统相比,工作频率由200MHz变为499.8MHz,超导腔取代了常温腔.在过去一年的运行中,高频系统表现良好,达到了设计指标.     

Convenient syntheses of unsymmetrical imidazolidines

Unsymmetrical imidazolidines 10-14, optically active imidazolidines 20-22, and 2,3-dihydro-1H-benzimidazoles 28 and 29 were synthesized in good to excellent yields by Mannich reactions of 1,2-ethanediamines 8a-c, 18a-c, or N-methyl-1,2-benzenediamine (26a) with benzotriazole and formaldehyde, followed by the nucleophilic substitution of the benzotriazolyl group with C-nucleophiles (Grignard reagents, sodium cyanide), an S-nucleophile (benzenethiol), and a P-nucleophile (triethyl phosphite).     

Novel syntheses of hexahydropyrimidines and tetrahydroquinazolines

1-Benzotriazolylmethyl-3-propylhexahydropyrimidine (1) and 1,3-bis(1H-1,2,3-benzotriazol-1-ylmethyl)-1,2,3,4-tetrahydroquinazoline (3) were readily prepared by reactions of N-propyl-1,3-propanediamine or 2-aminobenzylamine with benzotriazole and formaldehyde, respectively. Intermediate 1 reacted with alkyl and aryl Grignard reagents to produce N,N'-unsymmetrically substituted hexahydropyrimidines 2a,b in 90 and 92% yields, respectively. Nucleophilic substitutions of 3 with Grignard reagents, allylsilane, and triethyl phosphite gave N,N'-disubstituted 1,2,3,4-tetrahydroquinazolines 4a-f, 5, and 6 in good to excellent yields. Successive treatment of 3 with two different Grignard reagents in one-pot reaction led regiospecifically to N,N'-unsymmetrically substituted tetrahydroquinazoline derivatives 8a,b.     

煤粉颗粒所受Magnus力的数值模拟

本文采用数值模拟方法计算了煤粉颗粒所受的Ｍａｇｎｕｓ力,考察了颗粒的旋转速度、流动Ｒｅ数对Ｍａｇｎｕｓ力的影响,并且给出了相应的关系公式．通过比较煤粉颗粒在运动过程中所受到的Ｍａｇｎｕｓ力与气动力的大小,得出：当煤粉颗粒的旋转速度为１８００转／分时,其大小约为气动力的１％,因此在实际的煤粉颗粒受力分析中是完全可以忽略该力的。     

Synthesis and biological evaluation of novel farnesylthiosalicylic acid/salicylic acid hybrids as potential anti-tumor agents

A series of FTS/salicylic acid hybrids was designed and synthesized and their in vitro antitumor activities were evaluated.It was found that the anti-proliferation activities of hybrids were better than that of FTS.Compound 10 a displayed the strongest antitumor activities with IC_(50) values of 5.72-9.76 μmol/L and selectively inhibited tumor cell proliferation.In addition,10 a induced tumor cell apoptosis in a dosedependent manner by up-regulating the expression of Bax and caspase-3 and down-regulating Bcl-2.Our findings suggest that these novel hybrids may hold a great promise as therapeutic agents for the intervention of human cancers.     

Structure Dependence of Magnetic Properties for Annealed GaMnN Films Grown by MOCVD

GaMnN/GaN multilayers and conventional GaMnN single layers are grown by metal-organic chemical vapor deposition. Both kinds of samples show room-temperature ferromagnetism. After thermal annealing, the sample with GaMnN/GaN multilayer structure displays a larger coercivity and better thermal stability compared to the GaMnN single layer. The annealing effects on Vca related defects are observed from photoluminescenee measurements. Moreover, a different magnetic behavior is also found in the annealed GaMnN films grown on different （n-type GaN and p-type GaN） templates. These kinds of structure-dependent magnetic behaviors indicate that defects or carriers transformation introduced during annealing may have important effects on the electronic structure of Mn ions and on the ferromagnetism. Our work may be helpful for further understanding the origin of ferromagnetism in GaN-based diluted magnetic semiconductors.     

能量最低构型Ca2B4团簇的储氢性能

基于密度泛函理论,研究了Ca₂B₄团簇的几何结构、电子特征和储氢性能。前2个与第4个能量最低构型Ca₂B₄ 01、Ca₂B₄02和Ca₂B₄ 04有很高的热力学稳定性,分别最多可以吸附12、12和10个氢分子,达到16.3%、16.3%和14.0%的储氢量,超过了美国能源部提出的目标(5.5%）。Ca₂B₄ 01(H₂)₁₂、Ca₂B₄ 02(H₂)₁₂和Ca₂B₄ 04(H₂)₁₀的平均每个氢分子吸附能量分别为0.58~4.21 eV、0.54~3.69 eV和0.10~0.12 eV。玻恩-奥本海默分子动力学模拟表明,Ca₂B₄ 01和Ca₂B₄ 02可作为潜在吸附氢气的候选目标,而Ca₂B₄ 04不行。吉布斯自由能校正的氢吸附能结果表明,在101 325 Pa下,Ca₂B₄ 01和Ca₂B₄ 02吸附12个氢气分子有较大的可调节的温度范围。     

新形金纳米片的简单制备与生长机制

在室温(~30 ℃)条件下,氯金酸(HAuCl₄)均匀混合在粘稠的表面活性剂聚乙烯吡咯烷酮(PVP)胶体(水为溶剂)中,HAuCl₄可以被PVP还原,从而形成纳米片. 本工作中,通过调整晶体生长条件,成功合成了大量新形貌的单晶金纳米片(厚度数十纳米,尺寸为数个微米). 例如,在晶体生长初期阶段,通过引入温度变化(如降温10-20 ℃),形成的金纳米片主要是六角星形,并伴有盾状、内凹外凸的三角状、截角的、三叉的及多台阶等新形纳米片. 结合理论计算,阐明了金纳米片的生长机制：在一定条件下,金(111)晶面不仅可以沿着<110>方向生长成为常规的三角或六角纳米片,还可以沿<211>、<321>等不同方向生长成含有更高指数侧面的新形金纳米片.     

大规模制备Ni80Fe20纳米线阵列及其磁学特性研究

利用电化学沉积方法在高度有序纳米孔氧化铝模板中大规模制备了Ni80 Fe20纳米线阵列.该方法得到的Ni80Fe20纳米线产率高(约1012-1013/cm2),而且这些纳米线阵列具有(111)择优生长取向和很高的纵横比.与体材料相比,这些Ni80Fe20纳米线阵列具有更高的矫顽力和较大的剩磁比等性能,在微型磁性元件领域将具有广泛应用前景.     

生石灰颗粒中温脱硫过程数值计算

本文采用晶粒模型对中温条件下单颗粒石灰石脱硫过程进行数值模拟。利用已有文献数据、电子显微镜及TGA实验数据确定模型中化学反应动力学以及物性参数。计算结果与TGA实验结果符合较好,表明脱硫模型可直接应用于中温条件下石灰石脱硫过程的数值预报与分析。