Staggered local density of states around the vortex in underdoped cuprates

We have studied a single vortex with the staggered flux (SF) core based on the SU(2) slave-boson theory of high T(c) superconductors. We find that, whereas the center in the vortex core is a SF state, as one moves away from the core center a correlated staggered modulation of the hopping amplitude chi and pairing amplitude Delta becomes predominant. We predict that in this region the local density of states exhibits staggered modulation when measured on the bonds, which may be directly detected by STM experiments.     

Bistability in cell signaling: How to make continuous processes discontinuous,and reversible processes irreversible

Xenopus oocyte maturation is an example of an all-or-none, irreversible cell fate induction process. In response to a submaximal concentration of the steroid hormone progesterone, a given oocyte may either mature or not mature, but it can exist in intermediate states only transiently. Moreover, once an oocyte has matured, it will remain arrested in the mature state even after the progesterone is removed. It has been hypothesized that the all-or-none character of oocyte maturation, and some aspects of the irreversibility of maturation, arise out of the bistability of the signal transduction system that triggers maturation. The bistability, in turn, is hypothesized to arise from the way the signal transducers are organized into a signaling circuit that includes positive feedback (which makes it so that the system cannot rest in intermediate states) and ultrasensitivity (which filters small stimuli out of the feedback loop, allowing the system to have a stable off-state). Here we review two simple graphical methods that are commonly used to analyze bistable systems, discuss the experimental evidence for bistability in oocyte maturation, and suggest that bistability may be a common means of producing all-or-none responses and a type of biochemical memory. (c) 2001 American Institute of Physics.     

Connecting Lemmas

Like the closing lemma, the connecting lemma is of fundamental importance in dynamical systems. Hayashi recently proved the connecting lemma for stable and unstable manifolds of a hyperbolic invariant set. In this paper, we prove several very general connecting lemmas. We simplify Hayashi's proof and extend the results to more general cases.

     

Continuous topological phase transitions between clean quantum hall states

Continuous transitions between states and the same symmetry but different topological orders are studied. Clean quantum Hall (QH) liquids with neutral nonbosonic quasiparticles are shown to have such transitions under the right conditions. For clean bilayer (mmn) states, a continuous transition to other QH states (including non-Abelian states) can be driven by increasing interlayer repulsion/tunneling. The effective theories describing the critical points at some transitions are obtained.     

Staggered-vorticity correlations in a lightly doped t-J model: A variational approach

We report staggered-vorticity correlations of current in the d-wave variational wave function for the lightly doped t-J model. Such correlations are explained from the SU(2) symmetry relating d-wave and staggered-flux mean-field phases. The correlation functions computed by the variational Monte Carlo method suggest that pairs are formed of holes circulating in opposite directions.     

含有周期球腔的黏弹性覆盖层消声性能分析

利用散射矩阵法分析了单个球状空腔在黏弹性橡胶中的Mie散射特性以及振动模式.以此为基础，利用多重散射法分析了不同背衬条件下，含有单层周期球状空腔的橡胶覆盖层(厚度为8mm)的消声性能.结果表明，单个球腔的径向共振对覆盖层的低频消声性能有重要贡献，覆盖薄层在共振区具有良好的消声性能.最后，设计了双层消声覆盖层(厚度为20mm)，有效拓展了消声带宽. 关键词： Mie散射 多重散射法 消声材料 声子晶体     

非线性光学格子中的光束演化研究

研究光学格子中(即在光传输的横截面上存在周期格子势的调制)光束的演化，利用变分原理，求出了光束宽度、振幅、频率啁啾参量随传播距离的演化形式.发现光束宽度与调制周期的比值必须小于一定的值才能形成孤子的传输；同时，还得到了光束在不同的条件下存在着不同的传输过程.光学格子中周期格子的作用有类似非线性的良好的特性，周期格子的引入提供了可以更好地控制格子孤子的形成和传输的参考条件.     

Langmuir-Blodgett self-assembly and electrochemical catalytic property of FePt magnetic nano-monolayer

Dispersed-well FePt nanoparticles with particle size ~5 nm have been prepared by hydrazine hydrate reduction of H₂PtCl₆·6H₂O and FeCl₂·4H₂O in ethanol–water system. By employing as-synthesized FePt nanoparticles, the monolayer can be formed by LB Technique. The structural, magnetic properties and electrochemical properties of FePt monolayer were respectively studied by XRD, TEM, VSM and CHI 820 electrochemical workstation. The as-synthesized particle has a chemically disordered fcc structure and can be transformed into chemically ordered fct structure after annealing treatment above 400°C. The coercivity of ordered fct FePt phase can be up to 2515Oe. CVs of 0.5 M H₂SO₄/0.5M CH₃OH on GCE modified with FePt nanoparticles monolayer films illustrate that the as-synthesized FePt is a kind of active electrochemical catalyst.     

脉冲偏压电弧离子镀TiO2薄膜的力学与光学性能

用脉冲偏压电弧离子镀技术在玻璃基片上制备均匀透明的TiO₂薄膜.利用X射线衍射仪、原子力显微镜、扫描电子显微镜、紫外-可见透射光谱仪和纳米压痕仪等手段,对不同脉冲负偏压下合成薄膜的相结构、微观结构、表面形貌、力学和光学性能进行表征.结果表明，沉积态薄膜为非晶态.脉冲负偏压对薄膜性能有明显的影响.随偏压的增加，薄膜厚度、硬度和弹性模量均先增大后减小，前者峰值出现在100—200 V负偏压范围，后两者则在250—350V范围.300 V负偏压时薄膜硬度最高，薄膜达到原子级表面光滑度，均方 关键词： 2薄膜')" href="#">TiO₂薄膜 脉冲偏压电弧离子镀 硬度 折射率     

基于shifrin变换反演粒度分布的理论分析

理论上验证了shifrin变换粒度反演算法。采用Fraunhofer衍射理论计算前向散射光强,并利用shifrin变换进行了粒径反演。模拟结果发现,shifrin变换算法能够反演出被测单一或多分散颗粒群的粒径峰值位置,且随着接收CCD像元总数的增加,反演的准确度也会增大,但是在被反演的峰值周围会存在一定数量的小峰。随着接收衍射角的增大,也能相应地增大反演的粒径范围。中心涂黑一定数目的CCD像元并不会对反演结果造成很大的影响。