Reducing infection by Aspergillus flauus group species that produce aflatoxins in corn is an area of intense interest. One speculation is that chitinase could be a resistance factor involved in inhibiting or reducing fungal growth. Mature kernels of yellow corn (A. flauus resistant) and white corn (A. flauus susceptible) were assayed for chitinase activity. Results showed higher activity in germ tissue than in the endosperm with disparity between the two varieties. The highest activity per quantity of protein was observed in the germ of white corn and in salt fractions from whole kernel corn precipitated with 20% ammonium sulfate. From gel permeation chromatography, major chitinase activity occurred in the fractions with molecular size ranging from 14 to 25 kDa. Isoelectric focusing on acrylamide gels showed major chitinase activity in protein zones at pH 3-4. These data provide evidence that the catalytic components exist in several isozyme forms that are acidic and highly associated in the native state.Several studies have shown that seeds and vegetative tissues of higher plants contain chitinases (Grassman et al., 1934; Powning and Irzykliewicz, 1965;Wargo, 1975; Boller, 1985; Broekaert et al., 1988). Studies with various model systems have shown that chitinases are also induced by pathogen attacks and chemical treatments that impart stress on plants (Boller et al., 1983;Metraux and Boller, 1986). All of these studies provide circumstantial evidence that chitinases exist in different forms in plants and may be somehow involved in host defense against fungal pathogens (Payne et al., 1990). Our interest in chitinases in corn arises from the critical problem of aflatoxin contamination caused by the fungi Aspergillus flauus and A. parasiticus. The complex relationship between fungal infection and aflatoxin formation is an area of intense research worldwide. Currently, one of the objectives in solving the problem is the identification of resistance genes that could be transferred within the species through classical breeding or genetic engineering. Hence, if intrinsic chitinase is indeed a pertinent resistance factor in corn, then appropriate strategies could be coordinated to improve the health and safety of this major crop.In this preliminary study, our objective was to develop a similarity profile of chitinase activity in the endosperm and the germ of two varieties of mature corn kernels. We chose kernels from open-pollinated varieties with extremes in aflatoxin contamination due to A. flavus infection, namely Yellow Creole (highly resistant) and Huffman (highly susceptible white endosperm variety) in field studies reported earlier (Zuber et al., 1983). Certain protein fractions from these two varieties were shown to have antifungal properties in an earlier study (Neucere and Zeringue, 1987). MATERIALS AND METHODS Extraction of Corn Tissues and Protein Fractionation.For preliminary experiments, kernels of the two varieties were sectioned by cutting the lower third of whole kernels, which included most of the ge...

Recent technological developments in motion tracking technology have lowered the price of motioncapture devices to the extent that nearly anyone can accurately model the dimensions and movement of the human body. The system described herein was the result of an attempt to capitalize on the aforementioned low-cost motion-capture technology to develop an accurate human-robot interface which relies on translating natural forelimb movement into servo actuation commands to control a robotic arm. Given that most endeavors into robotics are interdisciplinary, this work incorporates input from electrical engineering, mechanical engineering, computer science, and human-robot interface design. This system was specifically designed, in cooperation with NASA, to be used by an operator in a low-gravity environment, but the number of possible applications are substantial. These applications include, but are not limited to, military explosive ordnance disposal, remote maintenance in hostile environments, and safe exploration into hazardous environments.

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Spacecraft and launch vehicle ground processing activities require a variety of unique human activities. These activities are being documented in a primitive motion capture library. The library will be used by human factors engineering analysts to infuse real to life human activities into the CAD models to verify ground systems human factors requirements. As the primitive models are being developed for the library, the project has selected several current human factors issues to be addressed for the Space Launch System (SLS) and Orion launch systems. This paper explains how the motion capture of unique ground systems activities is being used to verify the human factors engineering requirements for ground systems used to process the SLS and Orion vehicles, and how the primitive models will be applied to future spacecraft and launch vehicle processing.

This paper introduces a concept for a single-person spacecraft and presents plans for flying a low-cost, robotic demonstration mission. Called FlexCraft, the vehicle integrates propulsion and robotics into a small spacecraft that enables rapid, shirt-sleeve access to space. It can be flown by astronauts or tele-operated and is equipped with interchangeable manipulators used for maintaining the International Space Station (ISS), exploring asteroids, and servicing telescopes or satellites. Most FlexCraft systems are verified using ground facilities; however, a test in the weightless environment is needed to assess propulsion and manipulator performance. For this, a simplified, unmanned, version of FlexCraft is flown on a low-cost launch vehicle to a 350 km circular orbit. After separation from the upper stage, the vehicle returns to a target box mounted on the stage testing the propulsion and control capability. The box is equipped with manipulator test items that are representative of tasks performed on ISS, asteroid missions, or for satellites servicing. Nominal and off-nominal operations are conducted over 3 days then the vehicle re-enters the atmosphere without becoming a debris hazard. From concept to management to operations, the FlexCraft demonstration is designed to be lowcost project that is launched within three years. This is possible using a simplified test configuration that eliminates nine systems unique to the operational version and by "designing-to-availability." For example, the propulsion system is the same as the Manned Maneuvering Unit because it capable, simple, human-rated and all components or equivalent parts are available. A description of the launch vehicle options, mission operations, configuration, and demonstrator subsystems is presented. In addition, discussions on the use of mockups, cost reduction, management approach and the innovative application of Army helicopter simulation facilities are included..