Principle and application of ball SAW devices

A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817     

Investigations of optically pumped submillimeter wave laser modes

A complete theory for waveguide laser modes for oversized metallic and dielectric waveguides with circular cross section has been developed for the submm wavelength region. The experimental investigations have been done by a submm heterodyne technique for the first stage using a Schottky barrier diode in an open structure mixer.     

Mechanism of superconductivity in the polyhedral-network compound Ba8Si46

The silicon clathrates--materials composed of metal-doped Si(20) dodecahedra--were identified as the first superconductors based on pure silicon networks. The mechanism of superconductivity in these materials can be obtained by studying their phonon modes, as modified by isotope substitution, and specific-heat measurements. Here, we present experimental studies that provide strong evidence that superconductivity in Ba(8)Si(46) is explained in the framework of phonon-mediated Bardeen-Cooper-Schriefer theory. Analyses using the McMillan approximation of the Eliashberg equation indicate that the superconducting mechanism is in the medium coupling regime, but at the high-end limit. The large density of states at the Fermi level, which arises from hybridization of the Si(20) cluster and Ba orbitals, is responsible for the unexpectedly high superconducting temperature. The temperature evolution of the specific heat unambiguously shows that this is an s-wave symmetry superconductor.     

Temperature measurement at flip chip solder joint during electromigration test

Measuring the real temperature of a flip chip solder joint during an electromigration test has been a problem because of its small size and the local Joule heating due to a large applied current. A unique method that employs the electrical resistance change in the junction line between two solder joints was introduced to determine the temperature of the solder joint. The change in resistance was converted into temperature using a thermal coefficient of resistance of the junction line. The method accurately measured temperatures of the solder joint within 2 K until the solder joint resistance change ratio reached 100% due to growth of an electromigration void.     

Links between Immune Cells from the Periphery and the Brain in the Pathogenesis of Epilepsy: A Narrative Review

Accumulating evidence has demonstrated that the pathogenesis of epilepsy is linked to neuroinflammation and cerebrovascular dysfunction. Peripheral immune cell invasion into the brain, along with these responses, is implicitly involved in epilepsy. This review explored the current literature on the association between the peripheral and central nervous systems in the pathogenesis of epilepsy, and highlights novel research directions for therapeutic interventions targeting these reactions. Previous experimental and human studies have demonstrated the activation of the innate and adaptive immune responses in the brain. The time required for monocytes (responsible for innate immunity) and T cells (involved in acquired immunity) to invade the central nervous system after a seizure varies. Moreover, the time between the leakage associated with blood–brain barrier (BBB) failure and the infiltration of these cells varies. This suggests that cell infiltration is not merely a secondary disruptive event associated with BBB failure, but also a non-disruptive event facilitated by various mediators produced by the neurovascular unit consisting of neurons, perivascular astrocytes, microglia, pericytes, and endothelial cells. Moreover, genetic manipulation has enabled the differentiation between peripheral monocytes and resident microglia, which was previously considered difficult. Thus, the evidence suggests that peripheral monocytes may contribute to the pathogenesis of seizures.     

Split Enzyme-Based Biosensors for Structural Characterization of Soluble and Insoluble β-Glucans

β-Glucan is widely distributed in various plants and microorganisms and is composed of β-1,3-linked d-glucose units. It may have a branched short or long side chain of glucose units with β-1,6- or β-1,4-linkage. Numerous studies have investigated different β-glucans and revealed their bioactivities. To understand the structure-function relationship of β-glucan, we constructed a split-luciferase complementation assay for the structural analysis of long-chain β-1,6-branched β-1,3-glucan. The N- and C-terminal fragments of luciferase from deep-sea shrimp were fused to insect-derived β-1,3-glucan recognition protein and fungal endo-β-1,6-glucanase (Neg1)-derived β-1,6-glucan recognition protein, respectively. In this approach, two β-glucan recognition proteins bound to β-glucan molecules come into close proximity, resulting in the assembly of the full-length reporter enzyme and induction of transient luciferase activity, indicative of the structure of β-glucan. To test the applicability of this assay, β-glucan and two β-glucan recognition proteins were mixed, resulting in an increase in the luminescence intensity in a β-1,3-glucan with a long polymer of β-1,6-glucan in a dose-dependent manner. This simple test also allows the monitoring of real-time changes in the side chain structure and serves as a convenient method to distinguish between β-1,3-glucan and long-chain β-1,6-branched β-1,3-glucan in various soluble and insoluble β-glucans.     

Thermotropic polyarylates derived from substituted hydroquinones and p-terphenyl-4,4″-dicarboxylic acid

Polyarylates from substituted hydroquinones (HQs) and p-terphenyl-4,4″-dicarboxylic acid (TPDA) that were modified with 1,2-bis(phenoxy)ethane-4,4′-dicarboxylic acid (PEC), 1,2-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (ClPEC), terephthalic acid (TA) and p-hydroxybenzoic acid (HBA) were prepared and their thermal and mechanical properties were investigated. These polyarylates exhibited liquid crystallinity at about the same temperatures as polyarylates derived from substituted HQs and 4,4′-diphenyldicarboxylic acid (BB). However, as-spun fibers and injection-molded specimens of these polyarylates exhibited lower moduli than those of substituted HQs and BB that were modified with PEC, Cl-PEC and TA.     

Self-disproportionation of Enantiomers (SDE) of Chiral Nonracemic Amides via Achiral Chromatography

This article is based on a review of literature devoted to the phenomenon of SDE via achiral chromatography since the appearance of the seminal work of Professor Emanuel Gil-Av. The discussed examples of chromatographic studies are related to amides derived from chiral amines and α- and β-amino acids. We discuss the observed SDE magnitude as a function of a compound's structure, and composition of eluent and stationary phases, providing some mechanistic considerations. Particular emphasis is given to the aspect of SDE via achiral chromatography as an emerging unconventional enantiomeric purification technique.     

Dual-wavelength optical head with a wavelength-selective filter for 0.6- and 1.2-mm-thick-substrate optical disks

A dual-wavelength optical head, believed to be new in design, for 0.6- and 1.2-mm-thick-substrate optical disks was developed by use of 650- and 780-nm-wavelength light and a wavelength-selective filter, which reduces the spherical aberration that is due to the difference in substrate thicknesses and restricts the numerical aperture for 780-nm-wavelength light. According to this configuration, both high light power efficiency and wide image field characteristics are obtained, which are suitable not only for read-only but also for recordable or rewritable optical disk systems. A reading operation for a digital video disc and for a compact disc and a recording operation for a phase change optical disk were successfully demonstrated.     

Ab initio molecular orbital calculations of the NMR chemical shieldings for mannose and mannobiose

The ¹³C and ¹H NMR shielding constants for -methylmannose and -methylmannobiose have been calculated using the ab initio gauge-including atomic orbital (GIAO) method to study the conformational dependencies of the NMR chemical shifts of the sugars. The molecular structures were fully optimized using B3LYP/6-31G^* and the NMR shielding constants were calculated at both Hartree–Fock (HF) and density functional (DF) levels of theory with various kinds of basis sets. The values determined using the B3LYP hybrid functional were a little closer to those obtained experimentally than those determined at the HF level. Both, HF and B3LYP with the 6-311+G(2d,p) basis were found to give a very good correlation between the experimental and calculated shielding constants, especially for ¹³C.