Experimental investigation of optimum end supports for a vibrating beam

The problem investigated was whether or not the response of a beam, near its resonant condition, to a concentrated harmonic force, could be limited in a predictable manner by applying vibration absorbers to the ends of the beam. An extension of previous theories predicted that limiting the response amplitude was possible and could be optimized in general with a single, damped, flexible support and also in a special symmetric case using identical absorbers at both ends. Optimum damping and flexibility parameters were defined, and were computed for both systems at the third, fifth and seventh criticals. Experimental work, verifying the theory, was conducted using a solid, circular, aluminum rod and a solid rectangular brass bar. The experimental results agreed well with the theory in every aspect, namely, the fixedpoint frequencies and amplitudes, the optimum values of flexibility and damping, and the resonant frequencies of the mounted beams.     

多功能两亲梳状聚合物的合成及包覆荧光量子点

利用溶液聚合和成酰胺反应合成了多功能梳状两亲性共聚物,聚(甲基丙烯酸-co-甲基丙烯酸十八酯)-(乙醇胺-乙二胺叶酸)(PSM-EE-FA).用红外光谱(FTIR),核磁共振(1H-NMR)及凝胶渗透色谱(GPC)表征了该聚合物的结构及分子量分布.实验结果证明合成了该聚合物,其数均分子量(Mn)为28600,多分散性为1.375.用该两亲梳状聚合物包覆油溶性CdSe/ZnS量子点,通过相转移作用,得到水溶性靶向量子点(PSM-EE-FA-QDs).该水溶性量子点溶液具有较好的稳定性.通过紫外-可见(UV-Vis)及荧光发射光谱分析对该量子点的光学性质进行研究.结果表明,PSM-EE-FA-QDs的紫外-可见光谱及荧光发射光谱峰形与原量子点基本一致.由于量子点表面聚合物层的形成,峰位发生少量红移.该量子点水溶液的荧光强度是原量子点氯仿溶液的98%,荧光产率是原量子点氯仿溶液的95%.动态光散射(DLS)及透射电镜(TEM)测试结果表明水溶性量子点分布均匀.合成的水溶性量子点不但光学性能稳定,而且聚合物及水溶性量子点的合成方法较为简便.     

TDDFT studies of electronic structure and first hyperpolarizability of terta-nuclear cubane-like transition metal clusters

The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters.     

Theoretical Investigations of Nonlinear Optical Properties of Transition Metal Cluster Anions

In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^2- （M = Mo, W; Ch = S, Se; M＇ = Cu, Ag） have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M＇→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M＇CN as well as those of μ-Ch→M and M＇→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M＇CN make larger contributions to the hyperpolarizability, especially to γ.     

PHOTOREACTIVITY OF 5-GERANOXYPSORALEN AND LACK OF PHOTOREACTION WITH DNA

5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown.     

相对论性核与乳胶(Ag)碰撞中灰粒子的系统研究 *

用描写相对论性核 核碰撞的LUCIAE模型和相应的事件产生器系统地研究了 1 4.6 ,6 0和 2 0 0AGeV的O核、2 0 0AGeV的Si和S核以及 1 1 .6AGeV的Au核与乳胶 (Ag)碰撞中灰粒子产生的平均多重数、多重数分布以及角分布 3个物理量同入射能量、射弹质量及碰撞中心度间的关系 ,还研究了再散射在灰粒子产生机制中的作用 .LUCIAE的这些研究结果与相应的EMU0 1乳胶实验结果都相一致 .     

QCD PERTURBATION THEORY AND NUCLEI (1) THE ENERGY SHIFTS OF HADRENS AND HADRONS MASS DIFFERENCE MASS DIFFERENCE

QCD perturbation theory for confined quarks and gluons (inhadrons) is discussed.Based on the equivalent potential for the quark-gluon interaction derived, the energyshifts of hadrons and hadron mass difference in MIT bag (cavity) model and correcpond-ing approximation of the w. f. with Gassian form are calculated.     

Λ Production and Λ/p Ratio in Relativistic Heavy Ion Collisions

The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision.     

相对论重离子碰撞中Λ粒子产生和Λ/p比率

利用强子输运–弦碎裂模型研究了200A GeV重离子碰撞中Λ多重产生和Λ/p比率.研究了它们随反应系统大小和碰撞中心度的变化.研究表明Λ和p多重数都随反应系统增大和随碰撞中心度提高而增大,但它们的比率基本保持不变.Λ的湮没截面大小变化对Λ的多重数产生有一定影响,但对Λ/p比率影响不大.结果很好地再现了pp反应中Λ/p比率.并获得这一比率在AA反应中是pp反应中的3—5倍.     

A Global Method for Relaxation in W1,p and in SBVp

 An integral representation formula for a class of functionals defined on and in (the space of special functions of bounded variation) is obtained without requiring the regularity conditions usually imposed in the literature. The approach is based on the general results of [10] and on a Poincaré-Wirtinger type inequality introduced by DE GIORGI, CARRIERO & LEACI [25]. Applications to relaxation problems and dimension-reduction problems in brittle thin films are presented. (Accepted May 8, 2002) Published online October 18, 2002 Communicated by L. Ambrosio