Vertically Coupled Microring Resonator Filter : Versatile Building Block for VLSI Filter Circuits

In this review, the recent progress in the development of vertically coupled micro-ring resonator filters is summarized and the potential applications of the filters leading to the development of VLSI photonics are described.     

A recyclable, self-supported organocatalyst based on a poly(N-heterocyclic carbene)

We report the synthesis and catalytic activity of a polymeric imidazolium salt. In contrast to the well-known resin-supported N-heterocyclic carbenes (NHCs), the material described herein affords a polymer with NHCs orthogonally positioned along a main chain upon generation in situ. The unique structural characteristics of the corresponding poly(NHC)s enabled the materials to display catalytic activities that were similar or superior to those displayed by monomeric analogues. Moreover, the new catalyst was successfully recovered and reused with minimal loss of performance over several cycles.     

Cross-chiral examinations of molecular enantioselective recognition by fast atom bombardment mass spectrometry: Host–guest complexations between chiral crown ethers and chiral organic ammonium ions

Using fast atom bombardment (FAB) mass spectrometry (MS), cross-chiral relationships were confirmed for the first time for the diasteromeric host-guest complexations between the chiral crown ether host (1) and the chiral organic ammonium ion guest (2) on the basis of the relative peak intensities (RPI). Both host–guest combinations (R, R, R, R) – 1, (R) – 2 and (S, S, S, S) – 1, (S) – 2 obviously provided larger RPI values than the combination of both (R, R, R, R) – 1, (S) – 2 and (S, S, S, S) – 1, (R) – 2 by a factor of 1.6 as an averaged value: 1.87 (n = 4)/1.16 (n = 4) = 1.6. These results are consistent with the expected stabilities of the host-guest complexations by CPK model examinations. Successfully observed cross-chiral examinations strongly suggest a potentially useful FABMS/RPI methodology for rapidly searching newly designed and synthesized crown ether-like host compounds with a higher degree of enantioselectivity.     

DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K+ Channels

In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be applied to the assembly of functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has the potential to serve as scaffolds that arrange proteins at specific positions in complexes. Herein, we report that Kir3 K⁺ channel proteins are assembled through zinc‐finger protein (ZFP)‐adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP‐fused Kir3 channels and ZFP‐based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoresis. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K⁺ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to control the oligomerization states of membrane protein complexes in vitro and in living cells.     

Tetrahedral Co(II) coordination in alpha-type cobalt hydroxide: Rietveld refinement and X-ray absorption spectroscopy

We report a Rietveld refinement analysis and X-ray absorption study on a green-color Cl(-)-intercalated alpha-type cobalt hydroxide phase. The refinement clearly demonstrated that one-fifth to one-sixth of the Co(II) at octahedral sites was replaced by pairs of tetrahedrally coordinated Co(II) on each side of the hydroxide plane, represented by a structural formula of [Co(octa)(0.828)Co(tetra)(0.348)(OH)2](0.348+)Cl(0.348).0.456H2O. X-ray absorption spectroscopy also indicated that the divalent cobalt were in local neighboring environments of both octahedral and tetrahedral coordination. Furthermore, UV-vis spectroscopic measurements elucidate the typical green/blue color of an alpha-type cobalt hydroxide.     

Inlet throttling effect on the boiling two-phase flow stability in a natural circulation loop with a chimney

 Experiments have been conducted to investigate an effect of inlet restriction on the thermal-hydraulic stability. A Test facility used in this study was designed and constructed to have non-dimensional values that are nearly equal to those of natural circulation BWR. Experimental results showed that driving force of the natural circulation at the stability boundary was described as a function of heat flux and inlet subcooling independent of inlet restriction. In order to extend experimental database regarding thermal-hydraulic stability to different inlet restriction, numerical analysis was carried out based on the homogeneous flow model. Stability maps in reference to the core inlet subcooling and heat flux were presented for various inlet restrictions using the above-mentioned function. Instability region during the inlet subcooling shifted to the higher inlet subcooling with increasing inlet restriction and became larger with increasing heat flux. Received on 17 January 2000     

Repetitive spectral subtraction method for the spectrophotometric determination of rare earth elements

Summary A new multiwavelength data-analysis method for the determination of multicomponent mixtures, the repetitive spectral subtraction method (RSSM), is proposed. In RSSM, spectral data are obtained at evenly spaced wavelengths in the range of interest, and the analysis of the spectrum is performed as repetitive determination-subtraction cycle. In the determination step, the series of data in the narrow wavelength range is used, which is specified as to include the most characteristic or the largest peak for each component. Assuming a linear background, the target component, which can be a small group of components, is simultaneously determined together with co-existing components. In the next subtraction step, the calculated contribution of the component is subtracted from the spectral data in the whole measured wavelength range, and the component is assigned as determined and is excluded from the following analysis. This determination-subtraction cycle is repeated until all the components are determined.With RSSM, a mixture of many components can be precisely determined by the use of most information contained in the spectrum. The accuracy of determination can be improved by automatic estimation of the background and the gradual decrease of interferences. In order to demonstrate the usefulness of RSSM, the 8 rare earth elements (Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm) in the model mixtures were determined by spectrophotometry, and the results were compared with those of the usual correction factor method and the derivative method. Furthermore, the 8 rare earth elements were determined in ores, monazite and xenotime.

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Spektralphotometrische Bestimmung von Seltenen Erden mit Hilfe eines Verfahrens der wiederholten Subtraktion

     

A microsensor for adenosine-5′-triphosphate pH-sensitive field effect transistors

The sensor for adenosine-5′-triphosphate (ATP) is based on H⁺-ATPase immobilized via a polyvinylbutyral resin on a pH-sensitive field effect transistor. A linear relationship was obtained between the initial rate of change of the differential gate output voltage and the logarithm of the ATP concentration over the range 0.2–1.0 mM ATP. The optimum pH was 9.0 at 40°C but pH 7.0 was preferred for routine measurements. Only slight responses were obtained for 1 mM glucose, creatinine or urea. The ATP-sensing system exhibited a response to 1 mM ATP for at least 18 days.     

Discussion of substantially identical gel points among multiallyl monomers based on characterization of resultant network polymer precursors consisting of oligomeric primary polymer chains

No difference in the actual gel points was substantially observed among three isomeric diallyl phthalates such as diallyl phthalate (DAP), diallyl isophthalate, and diallyl terephthalate (DAT); this interesting gelation behavior was discussed further in terms of the correlation between gelation and the difference in cyclization modes, and also, the difference in reactivity between the uncyclized and cyclized radicals for cross‐linking. In the present work, we tried to extend the preceding discussion to the polymerization of triallyl trimellitate (TAT) because the molecular structure of TAT is presumed to essentially involve the characteristics of three isomeric diallyl phthalates and, therefore, the enhanced gelation was expected in TAT polymerization. However, no enhancement of gelation was observed. For a full understanding of the gelation in multiallyl cross‐linking polymerization, we explored further the polymerizations of DAP, DAT, and TAT, especially focusing on the characterization of resultant network polymer precursors (NPPs) using SEC‐MALLS‐viscometry providing the correlation of [η] versus M_w of fractionated samples. Notably, the structure of NPP consisting of oligomeric primary polymer chains generated from specific allyl polymerization would become core‐shell type dendritic with the progress of polymerization. The correlation between delayed gelation and decreased reactivity of dendritic NPP for intermolecular cross‐linking is discussed. Conclusively, the reactivity for intermolecular cross‐linking between NPPs decreased with the progress of polymerization leading to a delayed gelation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2871–2881, 2009