Midori Watanabe

Formation of hydrogen permselective silica membrane for elevated temperature hydrogen recovery from a mixture containing steam

Abstract A silica membrane was formed by chemical vapor deposition using tetraethylorthosilicate in macropores of an α-alumina tube or a γ-alumina film coated on the α-alumina tube. The reactant was evacuated through the porous wall, and silica was deposited in the macropores at 600–700 °C. When the silica membrane was formed in a γ-alumina film coated on the α-alumina tube, hydrogen permeance at a permeation temperature of 600 °C was 3 × 10−7 mol m−2 s−1 Pa−1, which was one order of magnitude higher than that of a membrane formed directly on the α-alumina tube. H2/N2 selectivity determined from the permeance of each component was 100–1000. To separate hydrogen selectively from abundant steam, however, a higher permselectivity was required. The membrane formed in the γ-alumina film at 650 °C showed a hydrogen permeance of 3 × 10−8 mol m−2 s−1 Pa−1 and an H2/H2O selectivity of 7.6 at 400 °C.

Preparation of γ-alumina thin membrane by sol-gel processing and its characterization by gas permeation

Abstractγ-alumina porous membranes without pinholes or cracks were prepared by the sol-gel process. The boehmite sol obtained from hydrolysation of aluminium isopropoxide was applied to the inner surface of a porous supporting tube by a dipping procedure. The effects of sol concentration and the repetition number of dipping-drying-firing procedure on the membrane performance were investigated by scanning electron microscopy, X-ray diffraction and the Brunauer-Emmett-Teller method in connection with the micro-structure of the membrane. Gas permeation measurements were also conducted. The gas permeation through the thin membranes is well explained by Knudsens flow, indicating the pores are controlled finely and homogeneously.

Heteroepitaxial growth of diamond on an iridium (100) substrate using microwave plasma-assisted chemical vapor deposition

Abstract An iridium (100) layer was epitaxially coated on a MgO (100) plate by sputtering at 1123 K, and was then utilized in the formation of diamond by microwave plasma-assisted chemical vapor deposition (MPCVD) using methane as the carbon source. The electric contact between the substrate and holder was confirmed by coating the entire MgO surface with iridium. The iridium substrate was then treated by bias-enhanced nucleation under optimized conditions. It was found that diamond particles formed by MPCVD were essentially oriented to the iridium substrate. The diamond particles were then grown to the 〈100〉 and further to the 〈111〉, and a smooth diamond film was obtained. The full width at half maximum of the (400) rocking curve of the diamond film was 0.16°, which was close to that of a diamond single crystal.

Activities of liver mitochondrial and peroxisomal fatty acid oxidation enzymes in rats fed trans fat.

The effect oftrans fat on the activities of liver mitochondrial and peroxisomal fatty acid oxidation enzymes was examined in various strains of rats. When Wistar and Sprague-Dawley rats were fed for 30 days diets containing either olive oil or partially hydrogenated corn oil as a source ofcis-ortrans-octadecenoate, respectively, the activities of various enzymes of mitochondrial and peroxisomal β-oxidation measured withcis- andtrans-9-octadecenoic acid as substratese showed little dietary fatdependent change. In Fischer 344 rats, feedingtrans fat for 15 mo increased only moderately various enzymes of β-oxidation except for carnitine acyltransferase. The rate of mitochondrial ketogenesis and the activity of carnitine acyltransferase measured withtrans-9-octadecenoic acid as a substrate were about half those with thecis-counterpart. Peroxisomes oxidizedtrans-9-octadecenoyl-CoA at a rate comparable to thecis-counterpart. It was concluded from this study and previous ones that the difference in the geometry of dietary fatty acid had only a marginal effect in modulating the hepatic fatty acid oxidation system, in spite of marked differences in the metabolic behavior ofcis-andtrans fatty acid in cell-free preparations and perfused liver.

Separation of hydrogen from an H2-H2O-HBr system with an SiO2 membrane formed in macropores of an α-alumina support tube

Abstract A porous α-alumina tube of 2.5 mm o.d. and 1.9 mm i.d. was used as the support of a silica membrane used for hydrogen separation at high temperature. The pore structures of the tube were as follows: size distribution, 110–180 nm; average size 150 nm; and porosity, 0.4–0.55. Macropores of the tube were plugged with silica formed by thermal decomposition of tetraethylorthosilicate at 600 °C. To improve the step coverage of the deposition in residual pinholes, the reactant was continuously evacuated through the porous wall of the support. The hydrogen permeation of the membrane formed was of the order of 10 −8 mol m −2 s −1 Pa −1 at 600 °C, while the nitrogen permeance was below 10 −11 mol m −2 s −1 Pa −1 . The membrane was applied to separate hydrogen in the presence of HBr and abundant steam at 200–400 °C in a thermochemical water decomposition process (UT-3 process). The permeance of H 2 from the H 2 -H 2 O-HBr mixture was nearly the same as obtained with pure H 2 and that of H 2 O was smaller than the detection limit in the present study, 10 −10 mol m −2 s −1 Pa −1 . This means that the permselectivity of hydrogen to water was at least 100. HBr molecules could not permeate the membrane because of their large size and the permeance was below 10 −12 mol m −2 s −1 Pa −1 . The membrane was durable in the H 2 -H 2 O-HBr atmosphere at 400 °C.

Influence of dietary cis and trans fats on DMH‐induced colon tumors, steroid excretion, and eicosanoid production in rats prone to colon cancer

The effect of geometrical isomerism of dietary fats on colon tumorigenesis was studied in male and female rats of a strain prone to colon cancer (Wistar-Furth-Osaka). The rats were fed purified diets containing either partially hydrogenated corn oil (trans fat) or high-oleic safflower (cis fat) at the 5% level for one week and received a single oral dose of 1,2-dimethylhydrazine. The difference in the fatty acid composition of dietary fats was confined solely to the geometry of octadecenoate. An appropriate level of linoleic acid (2% of total energy) was supplied. After about 60 weeks, neither fat-type nor sex-dependent differences in the incidence of colon and small intestinal tumors was observed. The fecal excretion of neutral but not acidic steroids was higher in male rats fed the trans fat than in those fed the cis fat, but the composition remained almost unchanged. Aortic production of prostacyclin and the plasma concentration of thromboxane B2 were not influenced by dietary fats, although these were significantly higher in females, irregardless of the fat source. Thus, trans fat behaved much like the cis fat in various parameters, except for steroid excretion.

Determination of rare earth impurities in ultrapure europium oxide by inductively-coupled plasma mass spectrometry

Abstract Trace quantities of rare earth elements (REEs) in ultrapure europium oxide (Eu2O3) are measured by inductively coupled plasma mass spectrometry (ICP-MS). The signal intensity of REE decreases with increasing concentration of europium oxide. Then, the internal standard method is examined to minimize this signal suppression. Four internal standards, cadmium (111Cd+) and indium (115In+), and thallium (205TI+) and bismuth (209Bi+) are investigated, since their mass numbers are close to those of lighter (89Y+-157Gd+) and heavier (159Tb+-175Lu+) REEs, respectively. The use of internal standards o Cd and In suppress interference for lighter REEs, and Tl and Bi for heavier REEs. These results imply the interference concerned with a mass-related space charge effect. In trace analysis of REE impurities in ultrapure Eu2O3, In and Tl are suggested to be used as internal standards for lighter and heavier REEs, respectively, due to the recoveries close to 100%. Lighter REE oxide ions occurring in a plasma generally interfere with the determination of heavier REEs. However, almost all REEs are determined correctly even at ultratrace levels by a proper selection of isotope. Unfortunately, polyatomic ions from the europium oxide such as 153EuO+ and 153Eu18OH+ ions seriously interfere with the determination of 169Tm+ and 172Yb+. These interferences are reduced by using ion chromatography (IC) combined with ICP-MS detection.

Biliary and fecal steroid excretion in rats fed partially hydrogenated soybean oil

Male Wistar rats were fed cholesterol-free or cholesterol-enriched diets containing partially hydrogenated soybean oil with different levels oftrans-fatty acids or unhydrogenated soybean oil at the 10% level. The linoleic acid content of hydrogenated fat diets was adjusted to 3.6% of the total energy. Hydrogenated fat diets contained 29% and 41%trans-acids, mainly ast-18∶1.Trans-fats exerted no untoward effects on growth parameters, but increased liver weight. Dietary hydrogenated fats influenced neither the concentration nor composition of biliary steroids, irrespective of the presence or absence of cholesterol in the diet. In rats fed a cholesterol-free diet, daily fecal output of neutral and acidic steroids was enhanced by hydrogenated fats and the magnitude of augmentation was proportional to the dietary level oftrans-fatty acids. The increased fecal steroid excretion corresponded to an increase in total excreta. Hydrogenated fats also tended to enhance bile acid excretion when feeding a cholesterol-enriched diet. The results suggest that dietarytrans-fatty acids, in relation tocis-polyunsaturated fatty acids, provoke demonstrable change in steroid homeodynamics.

Effects of dietaryTrans-fat on biliary and fecal steroid excretion and serum lipoproteins in rats

Rats were fed cholesterol-free or cholesterol-enriched diets containing olive oil or partially hydrogenated corn oil at the 10% level for ca. 30 days (c-18∶1, 77.0% in the former diet andc-18∶1, 24.7% andt-18∶1, 42.5% in the latter). The linoleic acid content of these fat diets was made equivalent (1.7 energy%). After feeding cholesterol-free diets,trans fat compared tocis fat showed(a) no untoward effects on growth parameters, (b) a reduction of serum cholesterol levels without influencing concentrations of serum apolipoproteins A-I, B and E, (c) no effects on the bile flow and the concentration of biliary cholesterol and bile acids, (d) an increasing trend of fecal excretion of neutral and acidic steroids, both in terms of mg/day and mg/g feces, and (e) rather equivocal change in the composition of fecal, but not biliary steroids. Similar response patterns were also observed when cholesterol-enriched diets were fed except for a decrease in serum apo B and an ineffectiveness to increase fecal acidic steroids. Together with the results obtained from experiments simultaneously performed with safflower oil and completely hydrogenated corn oil, it seems that the steroid metabolism can be specificallymodified by the geometry of dietary fats.

Effects of different levels of dietary trans-octadecenoate on steroid metabolism in rats

Rats were fed semipurified diets containing olive oil or partially hydrogenated corn oil at the 5 or 20% level for ca. 30 days. These fat diets contained the same amount of octadecenoate but differed in the geometry with respect to each fat level. Contents oft-18∶1 were 26% and 41% of total fatty acids, respectively. The linoleic acid content was also made equivalent (3.8 energy %). After feeding on cholesterol-free diets, rats ontrans fat, compared to those oncis fat, showed: (a) no changes in serum cholesterol and apolipoprotein levels, (b) no effects on the bile flow and concentrations of biliary cholesterol or bile acids, (c) a trend toward increased fecal excretion of neutral and acidic steroids, (d) a lesser extent of transformation of cholesterol to coprostanol in the gut, and (e) no changes in the composition of biliary and fecal bile acids. Observations (c) and (d) were more marked with a hightrans fat regimen. These observations, except for serum apolipoproteins and fecal steroid excretion, were practically reproducible even when rats were fed cholesterol-enriched diets.