Experimental Investigation on Observed Scattering in Heat Transfer Characteristics for Flow Boiling in a Small Diameter Tube

The effects of flow fluctuation at the test section inlet on flow boiling heat transfer were investigated for FC72 by the use of a horizontal circular tube with a diameter of 0.51 mm. Flow fluctuation was minimized by employing a high-powered syringe pump in one experiment and intensified in another experiment by the connection of an auxiliary tank exposed to atmosphere allowing the reverse flow. In the experiments of strict inlet flow rate regulation, heat transfer characteristics were similar to those observed in normal size tubes. However, if the flow rate fluctuated by up to ± 20% of the total under the weak inlet flow rate regulation, the trend of the heat transfer coefficient increasing with increasing vapor quality in moderate vapor quality region disappeared, and heat transfer deterioration due to partial dryout started at lower vapor quality. Boiling heat transfer characteristics in minichannels could be changed considerably by the existence of flow fluctuation caused by the rapid axial growth of elongated bubbles at low vapor quality. The regulation of inlet flow rate seems to be a key parameter in reducing the scattering in heat transfer data encountered in flow boiling of minichannels. Experimental data obtained by using a pump of weak power or data using a liquid reservoir can never be inherently consistent with those obtained for the constant inlet flow rate conditions. Although such a weak restriction of inlet conditions is actually encountered in application systems, the difference in heat transfer characteristics between the normal and mini-tubes should be clarified, as the first objective of the research, under the same inlet conditions without flow fluctuation.     

Consideration of decontamination model for severe accident consequence assessment

Cost per severe accident, which can cover various kinds of consequences, namely health effects, economic, social and environmental impacts, has been used as an index for severe accident consequence assessment in the authors' previous studies. Decontamination of the contaminated area was concluded influential to the cost per severe accident, though it employed simple and conservative assumptions, which made further discussion difficult. A new decontamination model is formed to address this issue. A sensitivity analysis using the elementary effects method is performed to identify parameters which have large influence on the cost per severe accident. We identify 25 important parameters, and fix most negligible parameters to their medians to form a simplified decontamination model. Calculations of the cost per severe accident with the simplified model and the full model are performed and compared. The differences of the results of the two model are not significant, which ensure the validity of the simplified model. The cost per severe accident calculated by the simplified model is compared with the previous study. The decontamination cost increases its importance significantly. It is therefore necessary to pay attention to decontamination-related issues, e.g., determination of decontamination target area and decontamination waste management scheme.     

Constitutive relations of thin-walled members for impact collapse

This study develops impact collapse problem of thin-walled members as follows: 1) A visco-plastic constitutive equation was expressed for characteristics after collapse of local buckling. 2) Experiments of impact collapse were done under eccentric compression load for square tubes. 3) Using the experimental data, the constitutive equation was shown to be practically useful.     

Inducing Effect of Clofibric Acid on Stearoyl‐CoA Desaturase in Intestinal Mucosa of Rats

Fibrates have been reported to elevate the hepatic proportion of oleic acid (18:1n‐9) through inducing stearoyl‐CoA desaturase (SCD). Despite abundant studies on the regulation of SCD in the liver, little is known about this issue in the small intestine. The present study aimed to investigate the effect of clofibric acid on the fatty acid profile, particularly monounsaturated fatty acids (MUFA), and the SCD expression in intestinal mucosa. Treatment of rats with a diet containing 0.5 % (w/w) clofibric acid for 7 days changed the MUFA profile of total lipids in intestinal mucosa; the proportion of 18:1n‐9 was significantly increased, whereas those of palmitoleic (16:1n‐7) and cis‐vaccenic (18:1n‐7) acids were not changed. Upon the treatment with clofibric acid, SCD was induced and the gene expression of SCD1, SCD2, and fatty acid elongase (Elovl) 6 was up‐regulated, but that of Elovl5 was unaffected. Fat‐free diet feeding for 28 days increased the proportions of 16:1n‐7 and 18:1n‐7, but did not effectively change that of 18:1n‐9, in intestinal mucosa. Fat‐free diet feeding up‐regulated the gene expression of SCD1, but not that of SCD2, Elovl6, or Elovl5. These results indicate that intestinal mucosa significantly changes its MUFA profile in response to challenges by clofibric acid and a fat‐free diet and suggest that up‐regulation of the gene expression of SCD along with Elovl6 is indispensable to elevate the proportion of 18:1n‐9 in intestinal mucosa.     

Relation between composition of the positive electrode and cell performance and safety of lithium-ion PTC batteries

To improve the safety of lithium-ion batteries, a new type of positive electrode, which contains a positive temperature coefficient (PTC) compound consisting of a carbon black/polyethylene composite as the conductive material, was fabricated. The relation between the positive electrode composition and both the discharge characteristics and safety was investigated. The discharge capacity of PTC cells increased as the PTC compound ratio decreased or the acetylene black (AB) ratio increased. In an external short-circuit test, the maximum short-circuit current decreased with an increase in the PTC compound ratio, or with a decrease in the AB ratio. Moreover, in an overcharge test, the voltage of the PTC cells with any composition increased earlier than that in a conventional cell and a cell with a high PTC compound ratio showed high overcharge tolerance. Based on the results of X-ray diffraction (XRD) measurements for the positive electrodes of PTC cells, it was clear that there was inadequate oxidation of the active material, since the Li⁺ extraction reaction from Li_xCoO₂ hardly progress at the part of the active material which contacts the PTC compound due to an increase in the resistance of the PTC compound at the high temperature.     

Mechanical Effect of Acetic Acid Lignin Adsorption on Honeycomb-Patterned Cellulosic Films

Abstract

We have already fabricated honeycomb-patterned cellulosic films with cellulose I and II polymorphisms as a basal framework in order to create an artificial woody cell wall.^{[ 1} Nemoto, J., Uraki, Y., Kishimoto, T., Sano, Y., Funada, R., Obata, N., Yabu, H., Tanaka, M. and Shimomura, M. 2005. Production of mesocopically patterned cellulose film. Bioresour. Technol., 96: 1955–1958.  [Google Scholar] ^{, 2} Uraki, Y., Nemoto, J., Otsuka, H., Tamai, Y., Sugiyama, J., Kishimoto, T., Ubukata, M., Yabu, H., Tanaka, M. and Shimomura, M. 2007. Honeycomb-like architecture produced by living bacteria, Gluconacetobacter xylinus. Carbohydr. Polym., 69: 1–6. [Crossref], [Web of Science ®] , [Google Scholar] ^] The adsorption of an isolated lignin, acetic acid lignin (AL), was attempted onto the honeycomb films not only to develop materials further mimicking the cell wall but also to elucidate the mechanical effect of isolated lignin on the tensile strength of the cellulosic architecture. The tensile strengths of honeycomb-patterned cellulosic films were improved by the AL adsorption. Although the cellulosic films without lignin weakened under high moisture content conditions as compared with those under the low content conditions, the lignin-adsorbed cellulosic film maintained significant tensile strength even under the high content conditions. This result suggests that lignin contributes to reinforce the mechanical strength of cellulose framework, in particular high moisture conditions.     

Alterations of fatty acid metabolism and membrane fluidity in peroxisome-defective mutant ZP102 cells

We investigated lipid composition and FA metabolism in Chinese hamster ovary (CHO-K1) cells and Pex5-mutated CHO-K1 (ZP102) cells to clarify the biochemical bases of peroxisome biogenesis disorders (PBD). ZP102 cells have defective peroxisomes and exhibit impairments of peroxisomal β-oxidation of FA and plasmalogen biosynthesis. In addition, we identified FA metabolic alterations in the synthesis of several classes of lipids in ZP102 cells. The concentration of FFA in ZP102 cells was twice that in CHO-K1 cells, but methyl esters and TAG were decreased in ZP102 cells in comparison with control cells. Also, ceramide monohexoside (CMH) concentration with ZP102 cells was significantly increased compared with the control cells. The FA molecular species, particularly the saturated to unsaturated ratios, of individual lipids also differed between the two cell types. The rate of incorporation of [¹⁴C]-labeled saturated acids into sphingomyelin (SM) and CMH in ZP102 cells was lugher than that in CHO-K1 cells. Lignoceric acid incorporated into cells was predominantly utilized for the synthesis of SM at 24 h after removal of [¹⁴C] lignoceric acid from the culture medium. ZP102 cells showed higher fluorescence anisotropy of 1,3,5-diphenylhexatriene, corresponding to lower membrane mobility than in CHO-K1 cells. In particular, alteration of lipid metabolism by a Pex5 mutation enhanced metabolism of saturated FA and sphingolipids. This may be related to the reduced membrane fluidity of ZP102 cells, which has been implicated in the dysfunction of membrane-linked processes in PBD.     

Deposition of bone-like hydroxyapatite on the surface of silk cloth with the aid of immobilized urease

Continuous layers of hydroxyapatite were deposited on silk cloth from aqueous solutions by using urease as the precipitant supplier. Silk cloth was surface-modified with urease and was immersed in an aqueous solution containing Ca²⁺, PO₄³⁻, and urea. As urea was hydrolyzed to form ammonia with the aid of the immobilized urease, hydroxyapatite precipitated predominantly on the surface of the silk cloth. It took only a few hours to form continuous layers of hydroxyapatite on the silk cloth. The resultant hydroxyapatite was found to be bone-like apatite because it had low crystallinity, contained carbonate ion in the lattice, and had a calcium-deficient composition.     

Gas chromatographic-mass spectrometric identification of phenols and aromatic acids in river waters

The ethyl acetate extracts of water samples from two urban rivers in Tokyo were analyzed for phenols and aromatic acids by using a combined gas chromatograph-mass spectrometer after separating by solvent extraction and silica gel column chromatography. The following phenols and aromatic acids were identified: pentachlorophenol, bisphenol A, phthalic acid, trimesic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, and ferulic acid. The presence of o- and m-hydroxybenzoic acids were suggested by mass fragmentography. The sources of those compounds are considered.     

A kinetic study on polymerization of methyl methacrylate with di‐t‐butyl perfumarate

Di‐t‐butyl perfumarate (DBPF) was found to induce the radical polymerizations of various vinyl monomers at 60°C in benzene, although the initiation activity was considerably lower than those of dimethyl 2,2′‐azobisisobutyrate and benzoyl peroxide. The polymerizations with DBPF showed a tendency of dead‐end polymerization. The polymerization of methyl methacrylate (MMA) with DBPF was kinetically studied in chlorobenzene. The initial polymerization rate (R_p) was given by R_p = k [DBPF]^0.5 [MMA]^1.1. The overall activation energy of the polymerization was 47 kJ/mol, a very low value. Use of this value and activation energies of propagation and termination for MMA gave an unexpectedly low activation energy (65 kJ/mol) to the decomposition of DBPF, a t‐butyl perester, in the polymerization system. An ESR study on the polymerization of di‐2‐ethylhexyl itaconate with DBPF revealed that the observed dead‐end tendency comes from the consumption of DBPF. These results suggest that the initiator efficiency of DBPF is considerably low in the present polymerization systems. Some solvent effect was observed on the polymerization of MMA with DBPF. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 218–224, 2000