Orientations of overdamped magnetic nanorod-gyroscopes

Overdamped magnetic nanorod-gyroscopes driven by a rotating magnetic field undergo a series of reorientations when sedimenting on top of a surface in a viscous liquid. By changing the amplitude and the rotation frequency of the driving magnetic field, the nanorod-gyroscope either synchronizes or desynchronizes with the field and rotates either around its long or short axis. The different regimes of motion are explained theoretically by coupling the nanorod-gyroscopes motion to the creeping flow equations of the surrounding fluid. It is shown that friction anisotropy plays an important role for the orientation of the nanorod-gyroscopes.     

三参数方程:一种改进叠加的有效工具

我们用几个合成数据集比较了三参数方程和正常时差方程(NMO),从而分析在各种勘探阶段的叠加处理中进行额外的计算工作是否值得。我们选择了两个标准进行评价: 1)叠加图像的质量。 2)叠加参数的可信度及它们在进一步计算中(如层速度估计)的作用。 尽管用的只是旅行时数据而不是全波形数据,我们仍十分精确地模拟了叠加过程。处理是沿旅行时曲线寻找最大相干性而不是利用最小平方回归。这项称作“高斯加权最小平方”的技术弥补了最小平方法中的许多不足。 通过比较,我们得到如下结论: 1)三参数方程的叠加效果比标准的NMO方程好。叠加能量的增加可达30％以上。 2)用DIX公式的三参数方程得到的层速度估计要比标准DIX公式得到的估计稳定和精确得多。 3)由于漂移的双曲线需要的仅仅是静校正而不是动校正,因此用一种有效的方法来寻找三参数方程是可行的。 4)不同的噪音以不同的方式改变着最大能量叠加的参数。估计值的精度对于层速度的估计来说是足够的了(这儿仅需要两个参量),但是,由于存在多种噪音,利用三参数方程直接进行反演却有一定的冒险性。 然而,这些结论还应在实际数据中验证。     

Backprojection by Multiorientation Simultaneous Computation Scheme for CT Image Reconstruction

1IntroductionIncommercialComputerizedTomographic(CT)imagingsystems,thefilteredorconvolvedbackprojectionalgorithm['J--['tiscurrentlyusedforimagereconstruction.Itingeniouslyseparatesthereconstructionprocedureintotwosteps:theprojectiondataarelinearlyconvolve…     

Optical in-plane strain field sensor

A whole-field speckle strain sensor is presented. The speckle strain sensor allows the measurement of all three in-plane components of the strain field simultaneously without touching the surface of the sample. The strain fields are extracted from the in-plane motion of defocused laser speckles in a telecentric imaging system. To distinguish the contribution to the speckle motion from surface translation, rotation, and strain, the speckle motion from three lasers with different illumination directions and wavelengths has to be analyzed separately. Simultaneous acquisition of the three individual speckle patterns is achieved by means of splitting the light from the lasers onto separate but synchronized detectors with the aid of dichroic mirrors. The motion of the speckles is calculated with digital speckle photography (speckle correlation), which enables the strain sensor to measure strain fields with noise levels as low as 10 microstrain.     

How nanoparticles encapsulating fluorophores allow a double detection of biomolecules by localized surface plasmon resonance and luminescence

The paper shows how polysiloxane particles encapsulating fluorophores can be successfully used to detect biotin-streptavidin binding by two types of technique. After functionalization of the particles by streptavidin, the fixation of the biomolecule can indeed be detected by a shift of the localized surface plasmon resonance of the biotinylated gold dots used as substrate and by the luminescence of the fluorophores evidenced by scanning near-field optical microscopy. The development of particles allowing such a double detection opens a route for increasing the reliability of biological detection and for multi-labelling strategies crossing both detection principles.     

Mechanistic study on analyte focusing by dynamic pH junction in capillary electrophoresis using computer simulation

Dynamic pH junction is an on-line preconcentration method in capillary electrophoresis (CE) based on electrokinetic focusing of weakly ionic analytes with in large sample volumes in a multisection electrolyte system. In this report, experiments and computer simulations were performed to gain a better insight of the analyte focusing mechanism when a dynamic pH junction was used. A computer program, SIMUL, was used to simulate the band-narrowing process of a group for phenol derivatives under optimized buffer conditions, which were compared with experimental results. Computer simulations revealed the formation of a sharp moving pH boundary within the sample zone causing efficient focusing of long plugs of weakly acidic analytes based on their pKa. These studies offered useful information for understanding the band-narrowing process by control of the depth and lifetime of the moving pH boundary as a function of analyte pKa, sample pH, and injection length. The change in pH of the sample within the capillary was also estimated by measuring the absorbances of an analyte at two different wave-lengths. Optimization of analyte focusing resulted in enhanced detection responses of about 60-450-fold in terms of peak heights for some phenol derivatives' relation to conventional injections. Dynamic pH junction represents a novel approach to control band dispersion (peak width) and selectivity (mobility) of specific analytes for high-resolution CE separations.     

Surface-enhanced Raman scattering from individual au nanoparticles and nanoparticle dimer substrates

Surface-enhanced Raman scattering (SERS) intensities for individual Au nanospheres, nanoshells, and nanosphere and nanoshell dimers coated with nonresonant molecules are measured, where the precise nanoscale geometry of each monomer and dimer is identified through in situ atomic force microscopy. The observed intensities correlate with the integrated quartic local electromagnetic field calculated for each specific nanostructure geometry. In this study, we find that suitably fabricated nanoshells can provide SERS enhancements comparable to nanosphere dimers.     

蓄能方式和抽水蓄能的进展

对抽水蓄能的原理作了概述之后,作者叙述了从1910～1927年在欧洲兴建起第一批抽水蓄能装置的发展进程。对方案的技术和经济两个方面皆进行论述,并且在这篇论文中还包括了作者对抽水蓄能方面的未来设想。