Effect of gravity on pool boiling heat transfer on thermal spray coating

This study deals with heat transfer enhancement surface manufactured by thermal spraying. Two thermal spraying methods using copper as a coating material, wire flame spraying (WFS) and vacuum plasma spraying (VPS), were applied to the outside of copper cylinder with 20 mm OD. The surface structure by WFS was denser than that by VPS. The effect of gravity on boiling heat transfer coeffcient and wall superheat at the onset of boiling were experimentally evaluated under micro- and hyper-gravity condition during a parabolic trajectory flight of an airplane. Pool boiling experiments in saturated liquid of HCFC123 were carried out for heat fluxes between 1.0 and 160 kW/m² and saturated temperature of 30 °C. As a result, the surface by VPS produced higher heat transfer coefficient and lower superheat at the onset of boiling under microgravity. For the smooth surface, the effect of gravity on boiling heat transfer coefficient was a little. For the coating, a large difference in heat transfer coefficient to gravity was observed in the moderate heat flux range. The heat transfer coefficinet decreased as gravity changed from the normal to hypergravity, and was improved as gravity changed from the hyperto microgravity. The difference in heat transfer coefficient between the normal and microgravity was a little. Heat transfer enhancement factor was kept over the experimental range of heat flux. It can be said that boiling behavior on thermal spray coating might be influenced by flow convection velocity.     

Fast crystallization of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) with talc and boron nitride as nucleating agents

The crystallization behavior of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) induced by two kinds of nucleating agents, boron nitride (BN) and talc, was investigated by differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. Both BN and talc have good nucleating ability in the crystallization of PHB and PHBV. From these results, combined with molecular weight measurement by gel permeation chromatography, the mechanism of nucleation by BN and talc in the crystallization of PHB and PHBV has been proposed. BN acts as a nucleating agent itself and initiates nucleation in the crystallization of PHB and PHBV. Talc acts in a different way. It reacts as a chemical reagent with the molten chains of PHB/PHBV, while the reaction product acts as the true nucleating agent, which lowers the crystallization barriers of PHB and PHBV. ¹H NMR spectroscopy provides evidence for the reaction between PHB and talc and supports the proposed nucleation mechanism. Copyright © 2005 Society of Chemical Industry     

Optimal dispersion management for a wavelength division multiplexedoptical soliton transmission system

Soliton's frequency shift arising from the pulse collision between wavelength division multiplexed (WDM) channels in an optical transmission line may be reduced by dispersion management technique. The reduction mechanism is due to a cancellation between the shifts in normal and anomalous dispersion fibers. With a proper management of the dispersion, the effect of lumped amplifiers on the frequency shift may also be canceled out. In this paper, we give a detailed analysis of the frequency shift in dispersion managed systems, and explain the reduction mechanism of the shift. We then propose optimal dispersion management schemes by means of minimizing the frequency shift. We also present a statistical analysis of the collision induced timing jitter for a two-channel WDM system     

Synthesis of poly(1,3-phenyleneethynylenes) membranes having one-handed helical conformation without any chiral side groups by in-situ desubstitution of d-menthoxy groups

In this study, we synthesized four chiral helical poly(phenyleneethynylenes) having optically active menthoxycarbonyl groups and desubstituted the chiral groups in membrane state. Polycondensations of (+)-menthyl 3,5-diethynylbenzoate with (+)-menthyl 3,5-diiodobenzoate, 1,2-diiodobenzenen, 1,3-diiodobenzene, and 1,4-diiodobenzene using PdCl₂(PPh₃)₂–PPh₃–CuI were afforded helical polymers in good yields (named as PMtMt, o-PMtH, m-PMtH, and p-PMtH, respectively). Among them, PMtMt in a mixture of chloroform/benzene showed the largest Cotton effect in absorption region and gave self-supporting membrane by solvent-casting method. PMtMt membrane also showed a Cotton signal similar to that observed in solution. Desubstitution of PMtMt proceeded quantitatively by immersing the membrane into alkaline solution at room temperature for 3 days. The desubstituted PMtMt membrane showed circular dichroism (CD) signals similar shape to that of the original membrane in the UV region in despite of the polymer having no chiral moieties except for helical conformation. This is the first example of synthesis of chiral helical poly(phenyleneethynylenes) without the coexistence of any other chiral moieties.     

Effect of fermented papaya preparation on dermal and intestinal mucosal immunity and allergic inflammations

BACKGROUND: Fermented papaya preparation (FPP) from yeast fermentation of Carica papaya Linn is a natural health food that is commercially sold in Japan. A previous study revealed that FPP has antioxidant activity. However, the effect of FPP on allergic diseases remains unclear. The aim of the present work was to examine whether the oral administration of FPP to mice restrained two types of contact hypersensitivity models, FITC (Th2 type) induced ear and colon oedema, and oxazolone (Th1 type) induced ear and colon oedema. RESULTS: The sensitisation of FITC or oxazolone increased the plasma levels of IL‐10, IFN‐γ, and TNF‐α. Histological examinations revealed a marked increase of IgA, dendritic cells and inflammatory cells in the colon. When the animals were given FPP before sensitisation by FITC or oxazolone, all the events induced by either FITC or oxazolone decreased markedly. CONCLUSION: These results suggest that the oral administration of the FPP may have a therapeutic potential for the prevention of contact hypersensitive immuno‐response. Copyright © 2008 Society of Chemical Industry     

Production of metallic glassy bipolar plates for PEM fuel cells by hot pressing in the supercooled liquid state

A screening test was conducted to optimize the alloy composition in the Ni₆₀Nb_xCr_yMo_zP₁₆B₄ (x + y + z = 20 at%) alloy system in order to achieve a large supercooled liquid region, ΔT_x, and a low crystallization temperature, T_x. From this study, the Ni₆₀Nb₂Cr₁₆Mo₂P₁₆B₄ glassy alloy was found to be the optimal alloy. The static and potentiodynamic corrosion behaviors of this glassy alloy were measured. Polarization measurements showed that the current density of the non-polished glassy alloy sample was smaller than that of a SUS316L sample. By contrast, the current density of the surface-polished glassy sample was slightly larger than that of the SUS316L sample in the voltage range of 0.2–0.7 V. The interfacial contact resistance of the Ni₆₀Nb₂Cr₁₆Mo₂P₁₆B₄ glassy alloy was smaller than that of the SUS316L alloy and it decreased with increasing compaction force. A bipolar plate was successfully produced by hot pressing the glassy alloy sheet in a supercooled liquid state. The I–V characteristics of a single cell with the glassy bipolar plates were measured.     

Super‐ductile PBT alloy with excellent heat resistance

A super‐ductile PBT alloy with excellent heat resistance was successfully fabricated by reactive blending of poly(butylene terephthalate) (PBT) with poly(ethylene‐co‐glycidyl methacrylate) together with linear low density polyethylene (LLDPE) and hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS). It possesses a unique tensile stress–strain curve with no yielding point and large elongation at break, moreover, the alloy did not show serious deterioration of the mechanical properties by high temperature annealing at 150°C for 96 h. The structure‐properties relationship is discussed on the basis of transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, and wide‐angle X‐ray diffraction analysis. The outstanding ductile nature seems to come from the negative pressure effect of LLDPE (or LLDPE/SEBS) particles that dilates the PBT ligament matrix to enhance the local segment motions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Enhanced effects of nonisotopic hafnium chloride in methanol as a substitute for uranyl acetate in TEM contrast of ultrastructure of fungal and plant cells

This ultrastructural study showed that nonisotopic methanolic hafnium chloride and aqueous lead solution was an excellent new electron stain for enhancing TEM contrasts of fungal and plant cell structures. The ultrastructural definition provided by the new stain was often superior to that provided by conventional staining with uranyl acetate and lead. Definition of fine ultrastructure was also supported by quantitative data on TEM contrast ratios of organelles and components in fungal and plant cells. In particular, polysaccharides, which were localized in cell walls, glycogen particles, starch grains, and plant Golgi vesicle components, were much more reactive to the new stain than to the conventional one. The new nonisotopic stain is useful for enhancing the contrast of ultrastructure in biological tissues and is a safer alternative to uranyl acetate. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc.