Isolation and characteristics of yeasts able to grow at low concentrations of nutrients

Seven oligotrophic yeasts, which can grow in a 10⁴-fold dilution of malt–yeast–glucose–peptone medium (10⁻⁴ YM), were mainly isolated from soil. These yeasts belong to the Cryptococcaceae. When inoculated at about 10² cells/ml in 10⁻⁴ YM, the isolates grew to 1·4×10³–2·4×10⁵ cells/ml after 3 days. Some culture collection yeasts fell into three groups according to their growth characteristics in 10⁻⁴ YM, one group showing characteristics of the oligotrophic yeasts. The half-saturation values of uptake by the five isolated oligotrophic yeasts for D-glucose, L-leucine and L-amino acids were 6·0–25·0, 1·7–43·3 and 3·5–21·6 μM, respectively. The oligotrophic yeasts suspended in 10 mM-phosphate buffer (pH 6·0) had high tolerances for starvation, and remained more than 15% viable after 90 days of starvation. © 1998 John Wiley & Sons, Ltd.     

Synthesis and functionalities of poly(N-vinylalkylamide). VII. A novel aqueous two-phase systems based on poly(N-vinylacetamide) and dextran

It was found that a poly(N-vinylacetamide) (polyNVA)-dextran system formed two phases. The top was polyNVA-rich and the bottom phase was dextran-rich, which is the same as the poly(ethylene glycol) (PEG)-dextran system, and the phase separation occurred at a lower concentration than the PEG-dextran system. The protein separation in the polyNVA-dextran system was studied using myoglobin. Myoglobin was partitioned more in the bottom (dextran-rich) phase in a polyNVA-dextran system. The partition coefficient of the polyNVA-dextran system was smaller that of the PEG-dextran system, which suggests that the polyNVA-dextran system is superior to the PEG-dextran system for myoglobin separation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 255–258, 1998     

Microstructure of a Complex Oxide, Ho2MnxTa2−xO7(x≅ 1.0), with a Pyrochlore-Related Structure

The ternary compound Ho₂Mn _x Ta_{2− x} O₇ was synthesized in air at 1523 K. Structural characterization of the compound was taken by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The compound possessed a trigonal super cell derived from a rhombohedral basic cell with the a /2 of the trigonal super cell. The super cell was caused by the ordering of Mn and Ta ions and the derived structure model was in agreement with that of the zirkelite structure with the space group P 3₁21. The compound had stacking disorder with different stacking sequences along the c -axis. An orientation anomaly in the super cell reflections revealed that the super cell had an incommensurate nature.     

Numerical study of twin-screw extruders by three-dimensional flow analysis—development of analysis technique and evaluation of mixing performance for full flight screws

We have developed a method for predicting the three-dimensional flow field in the melt conveying zone in counter-rotating and co-rotating twin-screw extruders. We applied this technique to the full flight screws with thin flight width and open C-shaped channels in both rotating type extruders having the same screw configurations. We compared the details of velocity and stress fields, the flow rates of transportation, and various kinds of leakage flows for both rotating type extruders. Also, we obtained the spatial distribution of tracer particles and residence time distribution using a numerical tracer experiment. The flow rate in the transport direction in the co-rotating twin-screw was larger than that in the counter-rotating twin-screw, and this suggested that the latter has higher transport performance when the screws have thin flight width and open C-shaped channels as used in this study. As for the distributive mixing, it was found that the co-rotating twin-screw excels in the area of fluid rearrangement between the two screws and distribution in the rotational direction, while the counter-rotating twin-screw has the desirable characteristic of wide distribution in the axial direction. With regard to dispersive mixing, there was no considerable difference between calculated stress fields in both rotating type extruders.     

3D Shape Characterization and Image-Based DEM Simulation of the Lunar Soil Simulant FJS-1

This paper describes a procedure used to characterize the three-dimensional (3D) grain shape of lunar soil and undertake simulations of lunar soil by image-based discrete element method (DEM). Given that detailed 3D grain-shape information is unavailable for real lunar soil, a simulant material, FJS-1, is used in this study. We use the high-resolution micro X-ray CT system at SPring-8, a synchrotron radiation facility in Japan, to visualize precise 3D images of the granular assembly of FJS-1. A newly developed image-analysis procedure is then applied to identify individual grains. Using the obtained grain-shape data, a sufficient number of FJS-1 grains are directly modeled for DEM simulation using an efficient modeling scheme. A series of particle flow simulations are then performed with the modeled grains. The resulting slope angles are in good agreement with experimental results. We discuss the effect on the slope angle of grain parameters such as contact stiffness, restitution coefficient, and interparticle friction.     

Orientation controlled deposition of Pb(Zr,Ti)O<Subscript>3</Subscript> films using a micron-size patterned SrRuO<Subscript>3</Subscript> buffer layer

Orientation controlled, micron-sized dot-patterned PZT films were grown by metal organic chemical vapor phase deposition (MOCVD), and their crystal structure was evaluated. A micron-size dot-patterned SrRuO₃ (SRO) buffer layer was initially prepared by MOCVD through a metal mask on the (111) Pt/Ti/SiO₂/Si substrate. Then, a PZT film was deposited over the entire substrate. Micron-beam X-ray diffraction and Raman spectroscopy indicated that (111)-orientated PZT was prepared on the SRO covered area, while the (100)/(001)-orientated one was directly grown on Pt-covered substrates. The PZT film grown on SRO was thinner than that on the Pt-covered substrate. The estimated ferroelectric property on the center of the dot pattern was larger than that at the circumference by Raman spectroscopy because the strain is accelerated at the center of the dot.     

High-temperature carbonate/MgO composite materials as thermal storage media for double-walled solar reformer tubes

The composite materials of molten alkali-carbonate/MgO-ceramics are examined as thermal storage media in a tubular reformer using a double-walled reactor tube of a laboratory scale. The concept of a double-walled reformer tube is proposed as a solar tubular reformer and involves packing a molten salt/ceramic composite material in the annular region between the internal catalyst tube and the exterior solar absorber wall. The composite materials of Na₂CO₃, K₂CO₃, and Li₂CO₃ with magnesia are tested as thermal storage media. The reforming performances of the composite materials are tested in the cooling mode of the double-walled reactor tube. The experimental result obtained under feed gas mixture of CH₄/CO₂ = 1:3 at 1 atm shows that the use of 80 wt%Na₂CO₃/20 wt%MgO composite material successfully delayed the cooling time of the catalyst bed by 5–19 min in comparison to the case without a composite material. In addition, the Li₂CO₃/MgO and Na₂CO₃/MgO composite materials relatively revealed good performances: they prolonged the cooling time by over 10 min in the gas hourly space velocity (GHSV) range of 5000–12,500 h^?1. The application of the reactor tubes to solar tubular reformers is expected to realize stable operation of the solar reforming process under fluctuating insolation during cloud passage.     

In vivo osteocompatibility of lotus-type porous nickel-free stainless steel in rats

The bone response to lotus-type porous nickel-free stainless steels implants was investigated using Sprague-Dawley rats. The implants were inserted in the femora and tibiae of rats (n = 60) and bone formation inside the pores of the implants was followed up to 12 weeks. Bone ingrowth in transverse histological sections was calculated using an image analysis program. Shear strength of the bone–implant interface was evaluated by the push-out test. Histological examination showed that bone grew into apparent direct contact with the implant surface and into the pores, which sizes were between 70–650 μm. At 12 weeks, maximum compressive shear strengths of 24 ± 1 MPa were obtained; these values are substantially higher than the typical shear strength achieved by porous-coated materials. These results clearly indicate that lotus-type porous structure allowed bone cells and tissue to invade the implant throughout superficial porous spaces, which resulted in an efficient biological fixation responsible for the mechanical stability at the implantation site.     

Low density lipoprotein receptor mRNA in rat liver is affected by resistant starch of beans

The effects of resistant starches of beans on serum cholesterol and hepatic low density lipoprotein (LDL) receptor mRNA in rats were investigated. Rats were fed a cholesterol-free diet with 150 g/kg corn starch (CS), 150g/kg adzuki (Vigna angularis) starch (AS), 150 g/kg kintoki (Phaseolus vulgaris, variety) starch (KS), or 150 g/kg tebou (P. vulgaris, variety) starch (TS) for 4 wk. There were no significant differences in body weight among groups through the experimental period. The liver weight in the CS group was 1.1–1.2 times higher than that in the AS, KS, and TS groups. The cecum weight in the TS was 1.4 times higher than that in the CS group, and the cecal pH in the CS group was significantly higher than in the other groups. The serum total cholesterol, very low density lipoprotein + intermediate density lipoprotein +LDL-cholesterol and high density lipoprotein (HDL)-cholesterol concentrations in the bean starch groups were significantly lower than those in the CS group through the feeding period. The total cholesterol/HDL-cholesterol ratio in the bean starch groups was also significantly lower than that in the CS group at the end of the 4-wk feeding period. The hepatic cholesterol concentration in the TS group was significantly higher than in the CS group at the end of the 4-wk feeding period. The relative quantity of hepatic apo B mRNA in the AS group was 1.2 times higher than that in the CS group, and the hepatic LDL receptor mRNA levels in the AS and TS groups were 1.8–2.0 times higher than that in the CS group. The results of this study demonstrate that AS, KS, and TS lowered the serum total cholesterol level by enhancing the hepatic LDL receptor mRNA level.     

Electrospinning of Continuous Aligning Yarns with a ‘Funnel’ Target

A new electrospinning set‐up is described for continuous aligning of poly(L ‐lactide) yarn. It comprises a slowly rotating grounded ‘funnel’ target and a winder placed right up to the funnel. A charged polymer jet is ejected from a nozzle. The electrospun fibers are first accumulated on the mouth plane of the funnel to form a web. The web is then pulled upward and guided to a winder on which twisted fibers are continuously wound as a bundle. Each filament of the bundle is slanted at about 45° relative to the collecting direction, and its average diameter is 6.0 ± 1.9 µm. The drawn fiber shows improved tensile properties as a result of the increased molecular orientation. The morphologies of the twisted fibers before and after drawing are compared.