Spin waves in nickel nanorings of large aspect ratio

The spin dynamics of high-aspect-ratio nickel nanorings in a longitudinal magnetic field have been investigated by Brillouin spectroscopy and the results are compared with a macroscopic theory and three-dimensional micromagnetic simulations. Good agreement is found between the measured and calculated magnetic field dependence of the spin wave frequency. Simulations show that as the field decreases from saturation, the rings switch from a "bamboo" to a novel "twisted bamboo" state at a certain critical field, and predict a corresponding dip in the dependence of the spin wave frequency on the magnetic field.     

The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measuring the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular grating that is projected onto the mirror surface is a simple function of the angular rotation of the mirror. The circular grating may readily be generated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surface, the diameter of the optical grating may be varied. Furthermore, the additional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 μm is achieved for use on micro-systems. With the use of more sophisticated optical elements, the angular rotation of even smaller micro-mirrors may be measured.     

Optical measurement of Young's modulus of a micro-beam

This paper presents an optical method based on the interference of light beams of equal path difference for the measurement of the Young's modulus of a micro-beam. An optical wedge which consists of an optical plate and a micro-beam which forms part of a micro-accelerometer is illuminated by a collimated monochromatic sodium light beam. Loading on the micro-beam is accomplished by a loading-pin mounted on a three-axis translation stage and the resulting interference fringe pattern is observed using a CCD camera connected to a computer. Loadings are recorded using a high-sensitive load cell which measures loads of up to 200 g with a resolution of 0.01 g. Test results conducted on micro-beams of different sizes show good repeatability and comparison of the experimental results with theory shows good agreement.     

One-step synthesis of pure Cu nanowire/carbon nanotube coaxial nanocables with different structures by arc discharge

Pure Cu nanowire/carbon nanotube (Cu@C) coaxial nanocables are one-step fabricated by arc discharge. The microstructure and morphology of the Cu@C nanocables are investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). XRD results reveal that the copper carbide nano-crystals were formed in the nanocables and it plays an important role in the growth of the Cu@C nanocables. As-prepared Cu@C nanocables exhibit three different structures, including well-filled Cu@C nanocables, symmetrically trifurcate Cu@C nanocables, and twice capsulated Cu@C nanocables. The fabrication of Cu@C nanocables with different structures offers more opportunities for the development of nanoelectronic devices. The formation mechanisms of Cu@C nanocables with different structures are discussed as well.     

CONCERNING THE ORIGIN OF CHARGE AT THE POLYSTYRENE PARTICLE/WATER INTERFACE

The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface.     

Phase retrieval in two-wavelength DSSI using a combined filtering method

Phase retrieval in two-wavelength DSSI (digital speckle shearing interferometry) using a combined filtering method is proposed for small deformation derivative measurement. A simultaneous two-wavelength illumination and 3-CCD camera are employed in the experimental setup. The proposed method, which uses a two-wavelength technique does not require the conventional spatial phase unwrapping and has the advantage of good noise suppression for phase retrieval. Experimental results obtained show that using the proposed combined filtering method sensitivity similar to the single wavelength technique can be achieved.     

Surfactant–Thermal Method to Synthesize a Novel Two‐Dimensional Oxochalcogenide

A new two‐dimensional (2D) oxosulfide, (N₂H₄)₂Mn₃Sb₄S₈(μ₃‐OH)₂ ( 1 ), has been successfully synthesized under surfactant–thermal conditions with hexadecyltributylphosphonium bromide as the surfactant. Compound 1 has a layered structure and contains a novel [Mn₃(μ₃‐OH)₂]_n chain along the b‐axis. The photocatalytic activity for compound 1 has been demonstrated under visible‐light irradiation and continuous H₂ evolution was observed. Our results indicate that surfactant–thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.     

Almost Minimum Diameter Orientations of Semicomplete Multipartite and Extended Digraphs

 An orientation of a digraph D is a spanning subdigraph of D obtained from D by deleting exactly one arc between x and y for every pair x≠y of vertices such that both x y and y x are in D. Almost minimum diameter orientations of certain semicomplete multipartite and extended digraphs are considered, several generalizations of results on orientations of undirected graphs are obtained, some conjectures are posed. Received: August 31, 2000 Final version received: October 30, 2001 Acknowledgments. Part of this work was done when the first author was visiting the Department of Mathematics, National University of Singapore. The departmental hospitality and financial support are very much appreciated.     

On the Cayley factorization of calotte conditions

The calotte condition is the projective condition that a cycle of lines radiating from the vertices of a planen-gon be the correct projection of a ring of faces surrounding ann-gonal piece of plane in space, the spatial figure being not entirely coplanar. This condition can be expressed as a homogeneous bracket polynomial. In general, this polynomial is not Cayley factorable. Henry Crapo conjectured that it becomes so when multiplied by a product ofn−4 brackets. It is the purpose of this article to prove this conjecture.