Kinetics of Enthalpy Relaxation at the Glass Transition in Ternary Tellurite Glasses

The kinetics of enthalpy relaxation (recovery) at the glass transition in x K₂O·(20− x )MgO·80TeO₂ glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO₂-based glasses. Ternary glasses such as 10K₂O·10MgO·80TeO₂ show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow E _η and the glass transition temperature T _g is m = 55–62, indicating a fragile character in TeO₂-based glasses. Large heat capacity changes of 43.1–48.2 J·mol⁻¹·K⁻¹ are also observed at the glass transition. The activation energy for enthalpy relaxation Δ H is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of Δ H = 897–1268 kJ·mol⁻¹ are obtained. Negative deviation from additivity in Δ H is also observed. Values of the Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from Δ H and T _g are 0.33–0.42 K⁻¹. It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses.     

Anionic alternating copolymerization of epoxide and 3,4‐dihydrocoumarin and its application to networked polymers

3,4‐Dihydrocoumarin (DHCM) is an aromatic six‐membered lactone, which does not undergo anionic homopolymerization. However, it does undergo copolymerization with an epoxide. The striking feature of this copolymerization is its 1:1 alternating nature, which allows for the formation of polyesters. In this mini‐review, we describe the copolymerization behavior, the polymer structure and the advantages that can be achieved by addition of DHCM to the epoxy‐imidazole curing system. Another focus is our development of DHCM analogues, which bring the advantages of DHCM to their applications as comonomers for the curing system. Copyright © 2009 Society of Chemical Industry     

Synthesis and antiallergic activity of dimethyl-2-(phenylcarbamoyl)ethylsulfonium p-toluenesulfonate derivatives

The derivatives of dimethyl-2-(phenylcarbamoyl)ethylsulfonium p-toluenesulfonates were synthesized and evaluated for antiallergic activity. The 2,3-dihydroxyethoxy group was introduced to the phenyl ring from the standpoint of lipophilicity and electronic effects of substituent. The IgE-induced rat passive cutaneous anaphylaxis (PCA) was inhibited by oral administration of several substituted 2-[(4-propoxyphenyl)carbamoyl]ethyldimethylsulfonium p-toluenesulfonate derivatives. Among them (+/-)-2-[N-[4-(3-ethoxy-2-hydroxypropoxy)phenyl]carbamoyl]ethyldimeth ylsulfonium p-toluenesulfonate (1a, IPD-1151T) was found to possess considerable activity in the PCA test, and it was launched as Suplatast tosilate in Japan.     

Gain-coupled distributed feedback semiconductor lasers with anabsorptive conduction-type inverted grating

A gain-coupled (GC) distributed feedback (DFB) semiconductor laser with an absorptive conduction-type-inverted grating is proposed. Devices based on GaAlAs/GaAs materials are fabricated using two-step OMVPE. By inverting the conduction type of the absorptive region, threshold current is lowered by 10 mA, which is to compensate for the threshold increase due to extra absorption. In addition, nonlinear output property associated with the saturable nature of the absorption is eliminated. An ultralow chirping capability under gain switching high speed modulation and the narrow linewidth nature of this laser are experimentally studied     

Optimization of grating duty factor in gain-coupled DFB lasers withabsorptive grating-analysis and fabrication

Grating duty factor strongly affects the performance of gain-coupled (GC) distributed feedback (DFB) laser diodes with an absorptive grating. Through numerical analysis the authors have found an optimum value in the duty factor for their low threshold operation. The minimum threshold gain achievable at this optimum duty factor is found to be almost independent of the order of the grating. According to this prediction, the authors have fabricated GaAlAs/GaAs GC DFB lasers with a third-order absorptive grating where the grating duty factor has been made close to the theoretical optimum value. In 200-μm-long devices with both facets as-cleaved, low CW threshold current of 25 mA, external efficiency of 0.5 mW/mA, and SMSR as high as 45 dB have been obtained, which is qualitatively consistent with the analysis. High yield of single mode oscillation seems to be the result of the gain coupling     

WDM field trials of 43-Gb/s/channel transport system for optical transport network

This paper describes recent technical challenges and the progress toward the realization of the optical transport network (OTN) based on 43 Gb/s channel. We describe the new digital frame format "OTU3: Optical Channel Transport Unit 3," which is standardized in ITU-T for OTN, for the enhancement of the network management capability in the OTN based on 43-Gb/s channels. We first proposed 43-Gb/s/ch dense wavelength-division multiplexing (DWDM) dispersion-managed transmission system using carrier-suppressed return-to-zero (CS-RZ) format that has several attractive features; it advances the evolution of OTN into 100 GHz-spaced long-haul DWDM transport networks. The first wavelength-division multiplexing (WDM) field trials confirmed the superiority of CS-RZ format in the DWDM transmission performance for the first time. The first 1 Tb/s (25 /spl times/ 43 Gb/s) WDM field trial confirmed the excellent network management capability of OTU3 in future data-centric OTN using the newly developed 43-Gb/s OTN line-terminal prototype.     

Imprinting of Igf2 and H19 from a 130 kb YAC transgene

A stringent test for imprint control elements is to examine their function at ectopic loci in transgenic experiments. Igf2 and H19 are part of a larger imprinting region and as a first step, we examined these reciprocally imprinted genes in transgenic experiments using a 130 kb YAC clone. After paternal inheritance, H19 was appropriately repressed and Igf2 was expressed, irrespective of copy number or genetic background. After maternal inheritance H19 was consistently expressed, albeit with some variability. The levels of H19 expression per copy of the transgene inversely correlated with Igf2 (-lacZ) expression in cis. The consistent imprinting of H19 from this YAC contrasts with the previously described imprinting of mini-H19 transgenes, which only occurs at multi-copy loci, is inconsistent, and is prone to genetic background effects. We propose a novel model in which silencing of the H19 gene is the default state and its activation after maternal inheritance is the key mechanistic event for imprinting in this region. In addition, in situ analysis of the Igf2-lacZ reporter indicates that additional mesoderm-specific enhancers are present within the YAC clone. No obvious phenotype was detected from the excess gene dosage of H19.     

Performance evaluation of heat exchanger using alternative refrigerant R407C

R22 (HCFC22) has been widely used as the refrigerant in air conditioners. According to the Montreal protocol for ozone layer protection, the total production of HCFCs has been capped since the beginning of 1996. Zeotropic refrigerant mixture R407C and nearly azeotropic refrigerant mixture R410A have been selected as alternatives to R22. We examined refrigerant passages in heat exchangers used in heat pump‐type room air conditioners using zeotropic refrigerant R407C through simulation, and obtained the following conclusions. In an indoor heat exchanger, a counter flow configuration when operating as a condenser has higher temperature efficiency. When an outdoor heat exchanger operates as an evaporator, a configuration that suppresses the temperature glide by partially reducing the refrigerant passage not only produces high efficiency, but also reduces the frost formation on fins. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 626–638, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10064     

Spontaneous stratification in composite films consisting of conjugated polymers and neat C60 prepared by electrophoretic deposition

The morphology of composite films consisting of conjugated polymers and C₆₀ prepared by electrophoretic deposition (EPD) has been studied. While C₆₀ exists as nanocrystals uniformly embedded in the composite films based on poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene], a spontaneous stratification of the composite films into polymer-C₆₀-mixture and C₆₀-microcrystal layers is observed in the films based on a polyfluorene derivative, poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}]. The results suggest that EPD can be a useful tool for controlling the morphology of bulk heterojunction systems for organic photocells.