The full-scale operation of the International Space Station has started. The evaluation of influences on astronauts under space environmental stresses during space flight is one of the most important research topics in the space medicine. The aim of this study is to verify the physiological influences of the space environment such as microgravity and space radiation from a basic biomedical point of view by using medaka – small teleost, some of the strains with transparent body and proven the survivability in space. To accomplish the aim, we will conduct three quantitative physiological evaluations under space environment using the live imaging technique - muscle atrophy by reduction of muscle activity, alteration of autonomic nervous system by digestive functions and heart rate analysis, and behavior analysis. This propose is completed using remote image acquisition on orbit, data transfer and analysis of those image data on the ground. These data will be expected to be applied to the stress forecast or health care of astronauts during space missions.

View full abstract

Gravity is a ubiquitous force on the earth and affects the growth and morphogenesis of plants. Changes in the gravity vector (gravistimulation) are supposed to be transduced into certain intracellular signals in the early process of the gravitropic response. In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation is known to increase the cytoplasmic free calcium concentration ([Ca2+]c). However, the detail underlying cellular/molecular mechanisms of the gravitropic response and the process of forming a sensing machinery remain to be solved. Using microgravity conditions it would be possible to examine whether the cellular process of gravity sensor formation is dependent on 1 G of gravity and explore the molecular mechanism underlying gravity sensing.

View full abstract

Radiation effects on the human body are evaluated using dose equivalent H, defined as the product of the absorbed dose and the quality factor given as a function of LET (Linear Energy Transfer). In space, there exist many kinds of radiation, such as galactic cosmic rays and geomagnetic trapped particles, where charged particles and neutrons are the main components contributing to radiation dose. Since the LET of these radiations is widely distributed, it is essential to measure LET directly to evaluate H. Tissue Equivalent Proportional Counter (TEPC), which is a simple gas proportional counter made of tissue-equivalent materials, has been used as the standard space dosimeter by NASA. In TEPC, the lineal energy is measured in place of LET since no position information is given. Obviously, the lineal energy does not represent LET accurately. The dose obtained using TEPC is reported to be inconsistent with those measured with real LET spectrometers. In order to determine H precisely for space radiation, we began to develop a new space dosimeter, Position Sensitive Tissue Equivalent Chamber (PS-TEPC), using Micro Pixel Chamber (-PIC) as a two-dimensional positionsensitive detector. The performances of the prototype have been tested by using heavy-ion beams to examine its threedimensional tracking and energy measurement capabilities. In this article, the problems existing in the space radiation measurements are discussed briefly, and the operational principle and the recent status of PS-TEPC are presented.

View full abstract

This paper describes the outline of our space experiment plan for validating the new atomization concept derived from our past drop tower experiments. The planned experiment is the microgravity version of conventional laboratory experiments observing the breakup behaviors of water jets slowly issuing from a various nozzle into the atmosphere. The scientific significance of this experiment is explained by pointing out the serious theoretical difficulties in the existing atomization theories and then describing how these difficulties are resolved by the new concept which reveals the origin of unstable waves responsible for liquid breakup in various situations and make the breakup phenomenon quantitatively predictable, which can never be achieved by far.

View full abstract

Colloidal dispersions are thermodynamic systems displaying a variety of phenomena such as ordering formation and phase transitions. Diversity of those phenomena has its origin in a subtle nature of interaction potential of colloid particles, which changes its medium-range and long-range characteristic depending on conditions of dispersions. Review on both experimental and theoretical studies of colloidal dispersions is given and a proposal of structure analyses of dilute dispersions by laser diffraction and CCD photography in the ISS microgravity environment is made.

View full abstract

JAXA has selected 19 scientific candidate experiments to be fulfilled in the latter half of the second utilization planning phase of ISS/JEM(Kibo). One of the subjects is research on solid material flammability entitled “Quantitative Description of Gravity Impact on Solid Material Flammability as a base of Fire Safety in Space (Solid Combustion)”. The main target of the research is to clarify the impact of gravity on material flammability. In the research three types of solid materials (electric wire, PMMA sheet and paper sheet) are selected as the test materials and two types of tests, ignition and extinction, will be attained in the long-term microgravity environment provided by ISS. In the present report, research plan, scientific background and present status of the research will be described.

View full abstract