Confined colloidal crystals in and out of equilibrium

Recent studies on confined crystals of charged colloidal particles are reviewed, both in equilibrium and out of equilibrium. We focus in particular on direct comparisons of experiments (light scattering and microscopy) with lattice sum calculations and computer simulations. In equilibrium we address buckling and crystalline multilayering of charged systems in hard and soft slit confinement. We discuss also recent crystalline structures obtained for charged mixtures. Moreover we put forward possibilities to apply external perturbations, in order to drive the system out of equilibrium. These include electrolyte gradients as well as the application of shear and electric fields.     

Polymer-assisted complexing controlled orientation growth of ZnO nanorods

The growth of the oriented zinc oxide (ZnO) nanorods on silicon substrates based on a simple novel chemical transformation and thermal hydrolysis by using polyvinyl alcohol (PVA) as self-assembling complex polymer was introduced in this paper. All the polymers were removed after chemical oxidation and only the carbonized grid backbones remained that confines the ZnO nanorod’s diameter and enhance the absorption and diffusion of ZnO at the tips of the nanorods during growth. The ZnO nanorods are investigated by FTIR, XRD and FE-SEM. The results indicated that these nanorods have fine hexagonal wurtzite crystal structure and their diameter varies from 20 to 90 nm and the length up to about 1 μm. A polymer-localized ZnO growth model is proposed, which well explains the growth behavior of ZnO nanorods.This revised version was published online in August 2005 with a corrected issue number.     

Dynamics and nonlinearities of the BOLD response at very short stimulus durations

In designing a functional imaging experiment or analyzing data, it is typically assumed that task duration and hemodynamic response are linearly related to each other. However, numerous human and animal studies have previously reported a deviation from linearity for short stimulus durations (<4 s). Here, we investigated nonlinearities of blood-oxygenation-level-dependent (BOLD) signals following visual stimulation of 5 to 1000 ms duration at two different luminance levels in human subjects. It was found that (a) a BOLD response to stimulus durations as short as 5 ms can be reliably detected; this stimulus duration is shorter than employed in any previous study investigating BOLD signal time courses; (b) the responses are more nonlinear than in any other previous study: the BOLD response to 1000 ms stimulation is only twice as large as the BOLD response to 5 ms stimulation although 200 times more photons were projected onto the retina; (c) the degree of nonlinearity depends on stimulus intensity; that is, nonlinearities have to be characterized not only by stimulus duration but also by stimulus features like luminance. These findings are especially of most practical importance in rapid event-related functional magnetic resonance imaging (fMRI) experimental designs. In addition, an 'initial dip' response--thought to be generated by a rapid increase in cerebral metabolic rate of oxygen metabolism (CMRO2) relative to cerebral blood flow--was observed and shown to colocalize well with the positive BOLD response. Highly intense stimulation, better tolerated by human subjects for short stimulus durations, causes early CMRO2 increase, and thus, the experimental design utilized in this study is better for detecting the initial dip than standard fMRI designs. These results and those from other groups suggest that short stimulation combined with appropriate experimental designs allows neuronal events and interactions to be examined by BOLD signal analysis, despite its slow evolution.     

摄像CCD

本文对用作成象传感器的电荷耦合器件(CCD)首先进行了一般性技术介绍。概括了大量的最新文献,涉及到许多物理学特性和电路技术。同时较全面地介绍了主要厂家的产品。对于CCD图象传感器的目前的应用和潜在应用也作了叙述。     

Laser cooling of a nanomechanical resonator mode to its quantum ground state

We show that it is possible to cool a nanomechanical resonator mode to its ground state. The proposed technique is based on resonant laser excitation of a phonon sideband of an embedded quantum dot. The strength of the sideband coupling is determined directly by the difference between the electron-phonon couplings of the initial and final states of the quantum dot optical transition. Possible applications of this scheme include generation of nonclassical states of mechanical motion.     

Direct numerical simulation of passive scalar in decaying compressible turbulence

1IntroductionDirectnumericalsimulation(DNS)becomesanimportanttoolinrecentresearchofturbulence[1].DNSofcompressibleturbulenceismoredifficultthanthatoftheincompressibleturbulence.WhentheturbulentMachnumberisgreaterthan0.3theshockletsmayappearinthecompressibleturbulentflowfields.Thereasonandmechanismofshockletsexistencearenotclearyet.TheturbulentMachnumberinDNScannotbeveryhighwiththepresentexistingnumericalmethodsandcomputerresource.Fortheproblemofcompressibleisotropicturbulencewiththeinitia…     

Some Further Properties of the Accelerated Kerr-Schild Metrics

We extend the previously found accelerated Kerr-Schild metrics for Einstein-Maxwell-null dust and Einstein-Born-Infeld-null dust equations to the cases including the cosmological constant. This way we obtain the generalization of the charged de Sitter metrics in static space-times. We also give a generalization of the zero acceleration limit of our previous Einstein-Maxwell and Einstein-Born-Infeld solutions.     

稀土茜素黄R配合物的合成、表征及荧光性质

合成了 4种茜素黄R稀土配合物 ,通过对元素分析、红外光谱、紫外光谱和核磁共振氢谱的分析 ,确定它们的组成为 :Na[REL2 ]·2H2 O(RE =Sm ,Eu ,Tb ,Y ,NaHL =茜素黄R)。红外光谱表明 :配体以羧羰基的氧与稀土离子以单齿配位 ;配体的酚羟基离解 ,脱去质子后羟基氧与稀土离子配位 ;即酚氧和羧羰基的氧与稀土离子形成一个六元螯合环。配体的吸收峰 398nm在形成配合物后移于 35 1～ 35 5nm ,发生了较大位移 ,这说明稀土离子与配体成键 ;配合物IR在 4 15～ 4 35cm-1之间出现的新吸收峰归属为RE—O键的伸缩振动 ,佐证了配合物的形成 ;硝基中的氧和偶氮的氮原子未参与配位 ;IR还说明有两个水分子配位于稀土离子。紫外灯下可以看到Eu(Ⅲ )的配合物很强的红色荧光 ;荧光光谱测定 :Na[EuL2 ]·2H2 O有两个荧光发射峰分属于Eu的 5D0 → 7F1和5D0 → 7F2 跃迁。     

表面等离子体激元微盘的优化设计及应用

表面等离子体激元(SPP)微腔具有很高的品质因子和极小的模式体积,在光电子器件研究方面具有重要的应用价值。采用有限元法对表面等离子体激元的金属覆盖介质微盘谐振腔进行理论模拟,研究考虑微盘底半径、介质层厚度及金属膜厚度等参数对微盘表面等离子体模的品质因子及模体积的影响。研究表明,在光通信波段1550nm附近获得高品质因子(1000以上),极低模式体积的表面等离子体微盘。最后研究了利用优化设计的微盘进行折射率传感的应用,获得了高达300nm/RIU的折射率传感灵敏度。