Analyses of cell surface molecules on hepatic stem/progenitor cells in mouse fetal liver.

Background/aims: Hepatic stem/progenitor cells possess active proliferative ability and the capacity for differentiation into hepatic and cholangiocytic lineages. Our group and others have shown that a prospectively defined population in mid-gestational fetal liver contains hepatic stem/progenitor cells. However, the phenotypes of such cells are incompletely elucidated.

Development of high-performance cooling devices for space application by using flow boiling in narrow channels.

Heat generation density from semiconductor devices has been increasing with the rapid development of electronic technology. The cooling system using boiling two-phase phenomena has attracted much attention because of its high heat removal potential. To develop compact and high-performance cooling systems, we conducted experiments on the increase of critical heat flux (CHF) for flow boiling in narrow channels by improved liquid supply.

Structure of high-performance evaporators for space application.

A new structure of cold plates, where an unheated auxiliary channel is installed to supply liquid directly to the bottom of coalesced flattened bubbles in a narrow heated channel, is tested to investigate the increase in critical heat flux. Assuming the application to the laser solar power system, a large heating surface with a length of 150 mm in the flow direction is employed, and a narrow channel structure is adopted to reduce the size of cold plates, where the gap sizes are selected as 5 mm and 2 mm. Experiments are performed for water as a test liquid at inlet subcooling of 15 K under near atmospheric pressure.

A microgravity experiment of the on-orbit fluid transfer technique using swirl flow.

The cryogenic fluid transfer technique will prove useful for flexible and low-cost space activities by prolonging the life cycle of satellites, orbital transfer vehicles, and orbital telescopes that employ cryogenic fluids, such as reactants, coolants, and propellants. Although NASA has conducted extensive research on this technique to date, a complicated mechanism is required to control the pressure in the receiver tank and avoid a large liquid loss by vaporization. We have proposed a novel fluid transfer method by using swirl flow combined with vapor condensation facilitated by spray cooling.

A study of subcooled pool boiling of water: contact area of boiling bubbles with a heating surface during a heating process.

The contact area of bubbles with a transparent heating surface was optically measured during subcooled pool boiling of water on the ground. In the experiments, boiling bubbles were attached to the heating surface with a bubble holder and nearly reproduced the bubble behavior observed in low gravity. DC power was applied to the ITO heater and increased until the heater surface burned out.

Development of a high-performance boiling heat exchanger by improved liquid supply to narrow channels.

A two-phase flow loop is a promising method for application to thermal management systems for large-scale space platforms handling large amounts of energy. Boiling heat transfer reduces the size and weight of cold plates. The transportation of latent heat reduces the mass flow rate of working fluid and pump power.

Heat transfer mechanisms in microgravity flow boiling.

The objective of this paper is to clarify the mechanisms of heat transfer and dryout phenomena in flow boiling under microgravity conditions. Liquid-vapor behavior in annular flow, encountered in the moderate quality region, has extreme significance for practical application in space. To clarify the gravity effect on the heat transfer observed for an upward flow in a tube, the research described here started from the measurement of pressure drop for binary gas-liquid mixture under various gravity conditions.

Review of existing research on microgravity boiling and two-phase flow: future experiments on the international space station.

This paper describes research objectives on boiling and two-phase flow under microgravity conditions from both scientific and technological points of view. Existing research for various systems in flow boiling are briefly reviewed and problems indicated for research conducted by available facilities with short microgravity duration. A wide range of experimental subjects that become possible by using different types of test sections is clarified and the validity of long term experiments is emphasized.