A new mean field SA-SA' critical point in a symmetry breaking field

We consider a S_A-S_A' critical point in the presence of a symmetry-breaking external magnetic (electric) field with a positive magnetic (dielectric) anisotropy or a dislocation layer. Via a renormalization group analysis of the model hamiltonian, we show that the upper critical dimensions below which mean-field theory breaks down is d_c = 2·5. Thus the S_A-S_A' transition in three dimensions becomes mean-field like in the presence of a symmetry-breaking field. We estimate the reduced temperature region where we can expect to see the mean field S_A-S_A' critical point in the presence of a magnetic field or a dislocation layer.     

Synthesis and characterization of novel perfluorinated polyimides with 3D‐controlled structures for photonic applications

We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006     

Synthesis and luminescence characteristics of conjugated dendrimers with 2,4,6‐triaryl‐1,3,5‐triazine periphery

We have synthesized conjugated dendrimer with triazine peripheries, and their luminescence properties were investigated. The dendrimers consist of dendritic triazine wedges for electron transport, distyrylbenzene core as an emitting moiety, and t‐butyl peripheral groups for good processing properties. The dendrimers have LUMO values of about ?2.7 eV possibly because of the triazine moiety with high electron affinity. Photoluminescence study indicates that energy transfer occurs from the triazine wedges to the stilbene bridge, and finally to the core chromophore units due to a cascade decrease of bandgap from the peripheral wedge to core moiety. Therefore, the emission wavelength was determined by the structure of the core unit. The energy transfer efficiency of distyrylbenzene‐cored dendrimers was about 75 and 55% for Trz‐1GD‐DSB and Trz‐2GD‐DSB, respectively. A preliminary electroluminescence property also was investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 254–263, 2006     

Emission characteristics of Cu in Dc voltage modulation applied glow discharge optical emission spectrometry.

In order to obtain the depth profile of a thin film, we investigated the emission characteristics of a voltage modulation glow discharge to optimize the modulation parameters (modulation voltage, offset voltage, and modulation frequency). In this study, a phase-sensitive detection method with a lock-in amplifier to the modulation technique led to a higher sensitivity and a larger signal-to-noise ratio in the emission analysis compared to the normal dc amplification method. Upon increasing the maximum voltage, the emission intensity of the Cu atomic line (CuI 239.34 nm) increased linearly at a modulation voltage of 400 V and an offset voltage of 300 V. On the other hand, the emission intensity was gradually reduced when a modulation frequency increased. It is advantageous for surface analysis that the voltage modulation technique gives a lower sputtering rate rather than the conventional dc discharge.     

Direct single-layered fabrication of 3D concavo–convex patterns in nano-stereolithography

A nano-surfacing process (NSP) is proposed to directly fabricate three-dimensional (3D) concavo–convex-shaped microstructures such as micro-lens arrays using two-photon polymerization (TPP), a promising technique for fabricating arbitrary 3D highly functional micro-devices. In TPP, commonly utilized methods for fabricating complex 3D microstructures to date are based on a layer-by-layer accumulating technique employing two-dimensional sliced data derived from 3D computer-aided design data. As such, this approach requires much time and effort for precise fabrication. In this work, a novel single-layer exposure method is proposed in order to improve the fabricating efficiency for 3D concavo–convex-shaped microstructures. In the NSP, 3D microstructures are divided into 13 sub-regions horizontally with consideration of the heights. Those sub-regions are then expressed as 13 characteristic colors, after which a multi-voxel matrix (MVM) is composed with the characteristic colors. Voxels with various heights and diameters are generated to construct 3D structures using a MVM scanning method. Some 3D concavo–convex-shaped microstructures were fabricated to estimate the usefulness of the NSP, and the results show that it readily enables the fabrication of single-layered 3D microstructures. PACS 85.40.Hp; 81.16.Nd; 42.82.Cr     

Instrumental neutron activation analysis of mass fractions of toxic metals in plastic

It is very challenging to decompose a plastic product for the purpose of analysis of hazardous elements contained. To circumvent such technical problem, it is imperative that an analyst employ a nondestructive analytical method free of any pretreatments. The analytical results of the concentrations of toxic metals such as Cd and Cr in polypropylene for seven samples at two different levels were obtained using the instrumental neutron activation analysis. This work was intended ultimately to establish certified reference materials (CRMs) of these metals in the polypropylene, traceable to the SI. The uncertainties associated with the analytical procedures were estimated in accordance with the ISO guideline. The results were subsequently validated by a comparison with those for CRM-680 and −681 of the Bureau Communautaire de Reference (BCR), which demonstrated acceptable agreement within their uncertainty ranges.     

Proof of semialgebraic covering mapping cylinder conjecture with semialgebraic covering homotopy theorem

In this paper we prove the semialgebraic version of Palais' covering homotopy theorem, and use this to prove Bredon's covering mapping cylinder conjecture positively in the semialgebraic category. Bredon's conjecture was originally stated in the topological category, and a topological version of our semialgebraic proof of the conjecture answers the original topological conjecture for topological G-spaces over “simplicial” mapping cylinders.     

Investigation of the Doughnut Effect in Cy3-Labeled Protein Microarrays using Scanning Near-Field Optical Microscope

We demonstrate the fluorescence mapping of protein microarrays by the technique of scanning near-field optical microscopy (SNOM) and confocal microscopy. Micron sized spots (300 μm) of human Immunoglobulin G (hIgG) protein with and without a Cy3 dye labeling have been fabricated on glass substrates by an immobilization method which makes use of calixcrown derivatives termed Prolinker. We have also tried to probe into the well-known “doughnut effect” observed in fluorescence images of proteins using the SNOM technique. The topographic and fluorescence SNOM images revealed that the number of proteins at the boundary of the spot were more than at the center in the case of the microarray spot which showed brighter luminescence at the edge than at the center in the confocal image.     

Vertical bridgman techniques to homogenize zinc composition of CdZnTe substrates

In order to improve the Zn homogeneity along the axial direction of CdZnTe boule, we have employed a modified Bridgman technique using a (Cd, Zn) alloy source in communication with the melt, whose temperature has been gradually changed from 800 to 840°C during growth. Electron probe microanalysis (EPMA) measurements of Zn composition in the boule shows an excellent homogeneity of Zn along the axis of the CdZnTe boule compared with results in a boule grown by using a fixed source temperature. We have performed a numerical simulation to obtain the approximate temperatures of additional heating and cooling needed to improve the radial Zn homogeneity. CdZnTe boule has been grown by seeded vertical Bridgman furnace with two zones of heater and cooler. Ultraviolet/visible spectroscopic measurements of Zn composition over the length of the boule indicate that the radial distribution of Zn composition is very homogeneous in the body region of the boule, where the radial variation of Zn composition is ±0.0005.     

Simple systolic arrays for discrete cosine transform

in this paper, simple 1-D and 2-D systolic array for realizing the discrete cosine transform (DCT) based on the discrete Fourier transform (DFT) fo an input sequence are presented. The proposed arrays are obtained by a simple modified DFT (MDFT) and an inverse DFT (IDFT) version of the Goertzel algorithm combined with Kung's approach. The 1-D array requiresN cells, one multiplier and takesN clock cycles to produce a completeN-point DCT. The 2-D array takes N clock cycles, faster than the 1-D array, but the area complexity is larger. A continuous flow of input data is allowed and no idle time is required between the input sequences.