Synthesis of extremely stable blue light emitting poly(spirobifluorene)s with Suzuki polycondensation

[reaction: see text] Full spirobifluorene-based blue light emitting polymers, which exhibited extraordinary thermal and color stability, were prepared with SPC through an AB-type monomer route.     

Counterion-induced translational isomerism in a bistable [2]rotaxane

Translational isomerization can be induced by changing the anions associated with a bistable rotaxane in which the tetracationic cyclophane (blue box), cyclobis(paraquat-p-phenylene), encircles a dumbbell component containing bispyrrolotetrathiafulvalene (green) and a dioxynaphthalene (red) recognition sites. The rotaxane was isolated as both its hexafluorophosphate and tris(tetrachlorobenzenediolato)phosphate(v) (TRISPHAT(-)) salts. Photophysical measurements and NMR spectroscopy carried out in acetone (CD(3)COCD(3)) and acetonitrile (CD(3)CN) solutions reveal that the much larger TRISPHAT(-) anion favors predominantly the encirclement of the green site by the blue box.     

Epitaxial Growth Without Slope Selection: Energetics,Coarsening, and Dynamic Scaling

We study a continuum model for epitaxial growth of thin films in which the slope of mound structure of film surface increases. This model is a diffusion equation for the surface height profile h which is assumed to satisfy the periodic boundary condition. The equation happens to possess a Liapunov or free-energy functional. This functional consists of the term | h|², which represents the surface diffusion, and - log (1 + | h|²), which describes the effect of kinetic asymmetry in the adatom attachment-detachment. We first prove for large time t that the interface width---the standard deviation of the height profile---is bounded above by O(t^1/2), the averaged gradient is bounded above by O(t^1/4), and the averaged energy is bounded below by O(- log t). We then consider a small coefficient ² of | h|² with = 1/L and L the linear size of the underlying system, and study the energy asymptotics in the large system limit 0. We show that global minimizers of the free-energy functional exist for each > 0, the L²-norm of the gradient of any global minimizer scales as O(1/), and the global minimum energy scales as O( log ). The existence of global energy minimizers and a scaling argument are used to construct a sequence of equilibrium solutions with different wavelengths. Finally, we apply our minimum energy estimates to derive bounds in terms of the linear system size L for the saturation interface width and the corresponding saturation time.     

Phases of supersymmetric gauge theories with flavors

We explore the phases of supersymmetric U(N) gauge theories with fundamental matter that arise as deformations of SQCD by the addition of a superpotential for the adjoint chiral multiplet. As the parameters in the superpotential are varied, the vacua of this theory sweep out various branches, which in some cases have multiple semiclassical limits. In such limits, we recover the vacua of various product gauge group theories, with flavors charged under some group factors. We describe in detail the structure of the vacua in both classical and quantum regimes, and develop general techniques such as an addition and a multiplication map which relate vacua of different gauge theories. We also consider possible indices characterizing different branches and potential relationships with matrix models.     

Catalytic activity of dodecacarbonyltetracobalt in aqueous media: a "greening" of the Pauson-Khand reaction

The unprecedented reactivity of Co(4)(CO)(12) with enynes under aqueous conditions, representing the development of a mild and simple aqueous-phase cobalt-catalyzed PK reaction protocol, is described herein.     

Controlled functionalization of gold nanoparticles through a solid phase synthesis approach

A novel solid phase synthetic strategy was developed in this work for controlled functionalization of gold nanoparticles.     

Measurement of prompt charm meson production cross sections in pp collisions at square root s = 1.96 TeV

We report on measurements of differential cross sections dsigma/dp(T) for prompt charm meson production in ppmacr; collisions at sqrt[s]=1.96 TeV using 5.8+/-0.3 pb(-1) of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|K-pi(+), D(*+)-->D0pi(+), D+-->K-pi(+)pi(+), D(+)(s)-->phipi(+), and their charge conjugates. The measured cross sections are compared to theoretical calculations.     

激光导致的透明固体损伤模型

详细分析了描述激光导致损伤的"移动的损伤"模型,发现该模型不适用于常见的飞秒激光对绝缘性透明固体材料处理的情况(如:800nm的100fs激光脉冲,0.65NA紧聚焦系统),此时脉冲与物质间相互作用区域和聚焦系统的瑞利长度可以比拟.对模型做了改进,改进后的模型可以很好地预期飞秒激光脉冲在固体中产生损伤的时间和空间形态.     

A novel synthesis of 5-functionalized oxazolidin-2-ones from enantiomerically pure 2-substituted N-[(R)-(+)-alpha-methylbenzyl]aziridines

5-Funtionalized enantiomerically pure oxazolidin-2-ones were prepared in one pot from commercially available chiral aziridines bearing an electron-withdrawing group at C-2 with retention of the configuration in high yields by regioselective aziridine ring-opening followed by intramolecular cyclization.