Heat transfer characteristics of fluid flow in an annulus with an inner rotating cylinder having a labyrinth structure

The convective heat transfer coefficient was experimentally investigated in an annulus with an inner rotating cylinder to estimate the thermal fatigue of the inner and outer cylinders on the rotating machine. The following three conclusions were obtained: (1) Within the range of the experimental conditions, the heat transfer coefficient did not depend on the axial flow rate; rather, it showed a larger dependence on the inner cylinder rotating speed. (2) The heat transfer coefficient at the top of the labyrinth was about three times as large as that at the bottom. (3) An empirical correlation equation considering the gap between the inner and outer cylinders is proposed, which predicts the heat transfer coefficient on the rotating machine within ±30 percent. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 103–119, 1996     

Micro-mechanism of initiation of sliding

In order to understand the effects of contact shape and sliding direction on tangential coefficient a VTR (Video Tape Recorder) computer system has been developed to visualise the micro-slip distribution at the contact interface, during the process of micro displacement, before macro sliding. It is shown that micro-slip distribution is strongly affected by the shape of the contact area and the sliding direction, which gives a good explanation of the observed relationships between tangential coefficient (defined as tangential force divided by normal load) and tangential displacement. It is suggested, as a result, that the VTR-computer system developed in this study allows useful observation and understanding of the micro-mechanism of initiation of macro sliding.     

Janus Kinase Inhibitors Ameliorated Gastrointestinal Amyloidosis and Hypoalbuminemia in Persistent Dermatitis Mouse Model

Malnutrition is not only regarded as a complication of rheumatoid arthritis and inflammatory bowel disease but also that of inflammatory skin disease; however, the mechanisms and efficacy of its treatment have not been elucidated. Using a mouse model of dermatitis, we investigated the pathophysiology of malnutrition in inflammatory skin conditions and efficacy of its treatment. We employed spontaneous skin inflammation mice models overexpressing human caspase-1 in the epidermal keratinocytes. Body weight, nutrition level, and α1-antitrypsin fecal concentration were measured. The gastrointestinal tract was histologically and functionally investigated. Fluorescein isothiocyanate (FITC)-dextran was forcibly fed on an empty stomach, and plasma FITC-dextran was measured. The treatment efficacy of antibodies against tumor necrosis factor-α (TNF-α) and interleukin (IL)-α/β as well as Janus kinase (JAK) inhibitors was investigated. Compared with wild-type littermates, the inflammatory skin mice models showed a lowered body weight, reduction of serum albumin level, amyloid deposition in the stomach, small intestine, and large intestine, and increased α1-antitrypsin fecal concentration. However, the plasma FITC-dextran was unchanged between the dermatitis models and wild-type littermates. The over-produced serum amyloid A1 in the liver was detected in the plasma in the dermatitis model. Antibodies against TNF-α and IL-α/β showed partial effects on amyloid deposition; however, JAK inhibitors improved gastrointestinal amyloidosis with the improvement of skin symptoms. Chronic dermatitis is closely related to secondary amyloidosis in the gastrointestinal tract, resulting in hypoalbuminemia. Therefore, active control of skin inflammation is essential for preventing gastrointestinal complications.     

Starch Properties of New Sweet Potato Lines Having Low Pasting Temperature

Some new sweet potato lines were developed from progenies of a new cultivar, Quick Sweet, having a low pasting temperature. Starch granules from these lines demonstrated an abnormal morphology characterized by cracking into fragments. Starch and amylose contents were different among these lines. Pasting temperatures of these lines determined by the Rapid Visco Analyser were 53.8 to 66.6°C, i.e. 10 to 20°C lower than that of the control. Peak viscosities of some lines were similar to that of the control. Starch retrogradation, evaluated by percentage of leaked water and hardness of starch gels after cold storage, revealed that the control starch retrograded during storage for two to six weeks, but the starches of some lines retrograded much more slowly than the control starch and exhibited excellent cold storage stability. The pasting temperature had significant positive correlations with the percentage of leaked water and the hardness. These results indicate that Quick Sweet is a useful breeding material for improving pasting and retrogradation properties in sweet potato starch.     

Effect of Grain Size on the Thermal Conductivity of Si3N4

Polycrystalline Si₃N₄ samples with different grain-size distributions and a nearly constant volume content of grain-boundary phase (6.3 vol%) were fabricated by hot-pressing at 1800°C and subsequent HIP sintering at 2400°C. The HIP treatment of hot-pressed Si₃N₄ resulted in the formation of a large amount of ß-Si₃N₄ grains ∼10 µm in diameter and ∼50 µm long, and the elimination of smaller matrix grains. The room-temperature thermal conductivities of the HIPed Si₃N₄ materials were 80 and 102 Wm⁻¹K⁻¹, respectively, in the directions parallel and perpendicular to the hot-pressing axis. These values are slightly higher than those obtained for hot-pressed samples (78 and 93 Wm⁻¹K⁻¹). The calculated phonon mean free path of sintered Si₃N₄ was ∼20 nm at room temperature, which is very small as compared to the grain size. Experimental observations and theoretical calculations showed that the thermal conductivity of Si₃N₄ at room temperature is independent of grain size, but is controlled by the internal defect structure of the grains such as point defects and dislocations.     

Chaotic characteristics of local voidage fluctuation in a circulating fluidized bed

Local voidage fluctuations have been measured by using an optical transmittance probe at various axial and radial positions in a circulating fluidized bed riser with a 0.1 m i. d. and 10 m height. The chaotic time series analysis of the local voidage fluctuations has been adopted to characterize the nonlinear dynamics of the circulating fluidized bed riser. The variations of the correlation dimension and the Kolmogorov entropy of the voidage fluctuation were found to depend on the local time-average voidage. The axial and radial distributions of the correlation dimension and the Kolmogorov entropy were strongly affected by the solids flow structures (e.g. core-annulus flow) in various operating conditions. The correlation dimension of local voidage fluctuations increases along the riser, except the position near the distributor. Both, the correlation dimension and the Kolmogorov entropy of local voidage fluctuations near the wall, were found to be smaller than those at the center of the riser, independent of the solids circulation rate and the axial position.     

Controlled radical polymerization of styrene utilizing excellent radical capturing ability of diphenyl ditelluride

Summary The radical polymerization of styrene was investigated in the presence of diphenyl ditelluride (DPDTe) under varied conditions. In the polymerization without any radical initiator at higher temperature (125°C), the addition of DPDTe surely decreased the polymer molecular weight (M _n) while the polydispersity (M _w/M _n) was rather broad. The polymerization with benzoyl peroxide (BPO) as the initiator was also uncontrollable to afford polymers with broad M _w/M _n probably due to the redox side reaction of BPO with DPDTe. On the contrary, the precision control of M _n and the initiating end structure could be achieved by the polymerization with 2,2'-azobisisobutyronitrile (AIBN), that is, M _n increased in proportion to the molar ratio of monomer to initiator suggesting the suppression of bimolecular chain termination reactions by the excellent radical capturing ability of DPDTe. Received: 23 June 1999/Revised version: 11 August 1999/Accepted: 16 August 1999     

Effect of calcination temperature on the catalytic activity of Au colloids mechanically mixed with TiO2 powder for CO oxidation

In order to elucidate the role of the contact structure between gold and metal oxide support in low-temperature CO oxidation, a mechanical mixture of colloidal gold with TiO₂ powder was prepared and calcined at different temperatures. The sample calcined at 473 K, which is composed of spherical gold particles with a mean diameter of 5.1 nm and TiO₂ powder, is poorly active for CO oxidation at temperatures up to 473 K. The catalytic activity appreciably increases with an increase in calcination temperature up to 873 K even though gold particles grow to larger ones, reaching a level with almost the same turnover frequency as that of Au/TiO₂ prepared by a deposition–precipitation method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reaction of α-tocopherol in heated bulk phase in the presence of methyl linoleate (13S)-hydroperoxide or methyl linoleate

α-Tocopherol and methyl (9Z, 11E)-(S)-13-hydroperoxy-9, 11-octadecadienoate (13-MeLOOH) were allowed to stand at 100°C in bulk phase. The products were isolated and identified as methyl 13-hydroxyoctadecadienoate (1), stereoisomers of methyl 9,11,13-octadecatrienoate (2), methyl 13-oxo-9, 11-octadecadienoate (3), epoxy dimers of methyl linoleate with an ether bond (4), a mixture of methyl (E)-12, 13-epoxy-9-(α-tocopheroxy)-10-octadecenoates and methyl (E)-12, 13-epoxy-9-(α-tocopheroxy)-11-(α-tocopheroxy)-9-octadecenoates (5), a mixture of methyl 9-(α-tocopheroxy)-10,12-octadecadienoates and methyl 13-(α-tocopheroxy)-9, 11-octadecadienoates (6), α-tocopherol spirodiene dimer (7), and α-tocopherol trimer (8). α-Tocopherol and 13-MeLOOH were dissolved in methyl myristate, and the thermal decomposition rate and the distributions of reaction products formed from α-tocopherol and 13-MeLOOH were analyzed. α-Tocopherol disappeared during the first 20 min, and the main products of α-tocopherol were 5 and 6 with the accumulation of 1–4 which were the products of 13-MeLOOH. The results indicate that the alkyl and alkoxyl radicals from the thermal decomposition of 13-MeLOOH could be trapped by α-tocopherol to produce 5 and 6. The reaction products of α-tocopherol during the thermal oxidation of methyl linoleate were compounds 6 and 7. Since the radical flux during the autoxidation might be low, the excess α-tocopheroxyl radical reacted with each other to form 7.     

Fabrication of Polypropylene Nanofibers from Polypropylene/Polyvinyl Butyral Blend Films Using Laser-Assisted Melt-Electrospinning

Polypropylene (PP) nanofibers, a few hundred nanometers in diameter, are of immense importance in the fiber industry. This article reports the fabrication of delicate PP nanofibers. Polyvinyl butyral (PVB) was added to PP as a blend component, and a nozzle-free melt-electrospinning system with a line-like CO₂ laser melting device was used to manufacture PP nanofibers. We investigated the effect of PVB ratio on fiber diameter. The addition of PVB was found to be potentially very beneficial in PP/PVB blends, resulting in improved PP crystallinity and a steady decrease of fiber diameter with high productivity. The reduction of fiber diameter was attributed to the decline of viscosity, increase of surface adhesion properties, and polarity of blends due to the inclusion of PVB. To produce PP nanofiber, the PVB was removed from PP/PVB blend fibers with an ethanol treatment. A drastic drop of PP fiber diameter followed by fiber splitting was observed after PVB removal. We obtained PP nanofibers with a diameter as low as 181 ± 105 nm from the blend fiber with 90% PVB. Infrared spectroscopy of fibers demonstrated that PP fibers from pure polymer and blends showed the same characteristic peaks. POLYM. ENG. SCI., 60: 362–370, 2019. © 2019 Society of Plastics Engineers