Shu Matsuura

COLONY OF THE FUNGUS Aspergillus oryzae AND SELF-AFFINE FRACTAL GEOMETRY OF GROWTH FRONTS

A variety of colony shapes of the fungus Aspergillus oryzae under varying environmental conditions such as the nutrient concentration, medium stiffness and incubation temperature are obtained, ranging from a homogeneous Eden-like to a ramified DLA-like pattern. The roughness σ(l, h) of the growth front of the band-shaped colony, where h is the mean front height within l of the horizontal range, satisfies the self-affine fractal relation under favorable environmental conditions. In the most favorable condition of our experiments, its characteristic exponent is found to be a little larger than that of the 2-dimensional Eden model.

Self-affine fractal growth front of Aspergillus oryzae

Aspergillus oryzae have been grown in various environmental conditions and analyzed from the viewpoint of self-affinity. The growth behavior can be described by the Eden model in favorable conditions, and by DLA in unfavorable conditions.

Colony patterning and collective hyphal growth of filamentous fungi

Colony morphology of wild and mutant strains of Aspergillus nidulans at various nutrient and agar levels was investigated. Two types of colony patterning were found for these strains. One type produced uniform colonies at all nutrient and agar levels tested, and the other exhibited morphological change into disordered ramified colonies at low nutrient levels. Both types showed highly condensed compact colonies at high nutrient levels on low agar media that was highly diffusive. Disordered colonies were found to develop with low hyphal extension rates at low nutrient levels.

Colony patterning of Aspergillus oryzae on agar media

To clarity the effects of nutrient concentration and diffusion on the pattern formation of fungal colonies, the colony patterning ofAspergillus oryzae at various nutrient and agar levels was studied experimentally and was summarized in a colony morphology diagram. Roles of the nutrient content and the relaxation of nutrient distribution on the colony patterning were discussed based on a computer model of the mycelial growth. The colony morphology changed from compact to ramified as the nutrient and agar levels were lowered. No clear boundary was found between these two morphologies. The deterioration of substrate around the growing colony was detected when the morphic switching from homogeneous into splitting patterns emerged in the growth of ramified colonies. In the mycelial growth model, dense compact colonies developed at low growth rates and high nutrient influx into the colonized area. Under low nutrient levels, splitting colonies appeared at high growth rates as compared with the nutrient influx.

FORMATION OF RAMIFIED COLONY OF FUNGUS ASPERGILLUS ORYZAE ON AGAR MEDIA

Ramified colonies of fungus Aspergillus oryzae have been found to grow at a low growth rate on “liquid-like” agar media with low concentrations of agar and glucose. Box-counting fractal dimensions of the individual colony branches have been found to decrease with the time of incubation. Addition of glucose solution in the interior of branched colonies has brought about the production of the hyphal filaments almost only at the apical region of the colony branches. Active growth of the ramified colonies is localized in the peripheral zone, and this growth manner implies that the fungus is exhibiting a positive exploitation.

Educational benefits of stereoscopic visualization from multiple viewpoints, illustrated with an electrical motor model

In this study, we created a three-dimensional (3D) model of a simplified direct current (DC) motor and used it to explain the mechanism of actual DC motors to junior high school science classes. We implemented a questionnaire for students before and after the presentation of the model. Before the presentation, many students were not confident about explaining the mechanism of a DC motor based on Flemings left-hand rule. Then, we showed the stereoscopic display of our DC motor model from various viewpoints and explained the application of Flemings left-hand rule. The results of the questionnaire suggested that students gained confidence in explaining the application after viewing the stereoscopic display. It was suggested that the change of viewpoint in the stereoscopic display was effective in improving their understanding.

Development of Augmented Reality Teaching Materials with Projection Mapping on Real Experimental Settings

An augmented reality (AR) technology was applied in connection with a method of projection mapping to display physical quantities on real experimental settings. Physical quantities such as force and velocity were visualized by AR objects and projected onto real objects in an experiment. This image projection onto real objects was found to be effective in such a case where a user manipulates the real object resulting in changes of the magnitudes of physical quantities and the object position. The time delay between the motion of projected AR objects and the video images of real objects was measured on a simple rotating bar object. It was found that the phase delay between the AR objects and the projected image of the real object increased with the angular velocity of the object. The present method seems to be most relevant to static or quasi-static content in which user manipulation is included.

Use of camera drive in stereoscopic display of learning contents of introductory physics

Simple 3D physics simulations with stereoscopic display were created for a part of introductory physics e-Learning. First, cameras to see the 3D world can be made controllable by the user. This enabled to observe the system and motions of objects from any position in the 3D world. Second, cameras were made attachable to one of the moving object in the simulation so as to observe the relative motion of other objects. By this option, it was found that users perceive the velocity and acceleration more sensibly on stereoscopic display than on non-stereoscopic 3D display. Simulations were made using Adobe Flash ActionScript, and Papervison 3D library was used to render the 3D models in the flash web pages. To display the stereogram, two viewports from virtual cameras were displayed in parallel in the same web page. For observation of stereogram, the images of two viewports were superimposed by using 3D stereogram projection box (T&TS CO., LTD.), and projected on an 80-inch screen. The virtual cameras were controlled by keyboard and also by Nintendo Wii remote controller buttons. In conclusion, stereoscopic display offers learners more opportunities to play with the simulated models, and to perceive the characteristics of motion better.

Shaping dialogues with a humanoid robot based on an E-learning system

This paper examines a type of dialogue between an instructor and a humanoid robot, which is particularly appropriate for a situation wherein students listen to an instructor-robot dialogue in a classroom. The type of dialogue is extracted from comedy routines, movie plots, and a science experiment-based television program. The general structure of the dialogue is a series of activation, core, and feedback events. To interact with students and to obtain information from a web-based learning system, the activation and feedback are assigned to the instructor, whereas the robot participates in the core. In the activation phase, the instructor provides a topic keyword to enable the robot to submit a universal resource locator query request. The Topic Maps ontology of the web system enables the robot to speak regarding the topic in the core phase. Finally, the instructor clarifies the point in the feedback phase to motivate the interest and fun of the topic.

Effective usage of stereoscopic visualization for the learning of a motional mechanism

3D stereoscopic display is expected to be an advantageous interface of the learning materials to facilitate viewers spatial recognition. To reduce the visual fatigue in viewing rotational motions, and to make use of the effect of stereoscopic display, an intermittent exposure method was considered and compared with continuous exposure method. Further, the effect of one-second exposure supplemented with the projected rotational motion was examined. It was suggested that even such a short-time exposure was effective for improving spatial recognition, reducing the visual fatigue remarkably.