A simple closed aquatic ecosystem (CAES) for space

A closed aquatic ecosystem (CAES) was developed to study the effects of microgravity on the function of closed ecosystems aboard the Chinese retrieved satellite and on the spacecraft SHENZHOU-II. These systems housed a small freshwater snail (Bulinus australianus) and an autotrophic green algae (Chlorella pyrenoidosa). The results of the test on the satellite were that the concentration of algae changed little, but that the snails died during the experiments. We then sought to optimize the function of the control system, the cultural conditions and the data acquisition system and carried out an experiment on the spacecraft SHENZHOU-II. Using various sensors to monitor the CAES, real-time data regarding the operation of the CAES in microgravity was acquired. In addition, an on-board 1g centrifuge was included to identify gravity-related factors. It was found that microgravity is the major factor affecting the operation of the CAES in space. The change in biomass of the primary producer during each day in microgravity was larger than that of the control groups. The mean biomass concentration per day in the microgravity group decreased, but that of the control groups increased for several days and then leveled off. Space effects on the biomass of a primary producer may be a result of microgravity effects leading to increasing metabolic rates of the consumer combined with decreases in photosynthesis.     

A simplified closed artificial ecosystem--recycling of organic matter into wheat plants.

A simplified closed system consisting of a plant growth chamber coupled to a decomposition chamber was used to study carbon exchange dynamics. The CO2 produced via the decomposition of wheat straw was used for photosynthetic carbon uptake by wheat plants. The atmosphere of the two chambers was connected through a circuit of known flow rate. Thus, monitoring the CO2 concentrations in both compartments allowed measurement of the carbon exchange between the chambers, and estimation of the rate of respiration processes in the decomposition chamber and photosynthetic rate in the producer chamber. The objective for CELSS research was to simulate a system where a compartment producing food via photosynthesis, would be supplied by CO2 produced from respiration processes. The decomposition of biomass by the decomposer simulated both the metabolism of a crew and the result of a recycling system for inedible biomass. Concerning terrestrial ecosystems, the objective was to study organic matter decomposition in soil and other processes related to permanent grasslands.     

The "C.E.B.A.S. MINI-MODULE": a self-sustaining closed aquatic ecosystem for spaceflight experimentation.

The C.E.B.A.S. MINI-MODULE is the miniaturized space flight version of the Closed Equilibrated Biological Aquatic System (C.E.B.A.S.). It fits into a large middeck locker tray and is scheduled to be flown in the STS 85 and in the NEUROLAB missions. Its volume is about 9 liters and it consists of two animal tanks, a plant cultivator, and a bacteria filter in a monolithic design. An external sensor unit is connected to a data acquisition/control unit. The system integrates its own biological life support. The CO2 exhaled by the consumers (fishes, snails, microorganisms) is assimilated by water plants (Ceratophyllum demersum) which provide them with oxygen. The products of biomass degradation and excretion (mainly ammonia ions) are converted by bacteria into nitrite and nitrate. The latter is taken up by the plants as a nitrogen source together with other ions like phosphate. The plants convert light energy into chemical energy and their illumination is regulated via the oxygen concentration in the water by the control unit. In ground laboratory tests the system exhibited biological stability up to three month. The buffer capacity of the biological filter system is high enough to eliminate the degradation products of about one half of the dead animal biomass as shown in a "crash test". A test series using the laboratory model of the flight hardware demonstrated the biological stability and technical reliability with mission-identical loading and test duration. A comprehensive biological research program is established for the C.E.B.A.S. MINI-MODULE in which five German and three U.S.-American universities as well as the Russian Academy of Sciences are involved.     

The use of microcosms as an experimental approach to understanding terrestrial ecosystem functioning.

Since 1986, a series of microcosm experiments has been conducted at the Unit of Comparative Plant Ecology (UCPE) in an attempt to test our understanding of the principles controlling the structure and dynamics of plant communities and ecosystems. In each experiment microcosms have been seeded with a common pool of organisms, and systems have been allowed to assemble under replicated controlled conditions. Experiment variables have included mineral nutrient supply, temperature, moisture supply, soil depth, carbon dioxide concentration, mycorrhizas, rhizobia, herbivores and carnivores. Results from these experiments are presented to illustrate the value of synthesised ecosystems in ecological research.     

The CEEF, closed ecosystem as a laboratory for determining the dynamics of radioactive isotopes.

Nuclear power generation is now confronted with a very difficult situation all over the world because of the problems of radioactive waste disposal and of the accidents, which have occurred. Nuclear power generation now supplies nearly 30% of total electric power demand in Japan. Therefore it is very difficult to change quickly the construction plans of nuclear facilities already designed. A nuclear fuel reprocessing center is now under construction in Rokkasho-Mura in Aomori Prefecture. If this center starts its operation, small amounts of 14CO2 are expected to be released into the atmosphere and will enter the global cycle. The simulation experiment of 14C trace amounts which enter into ecosystems is now being planned using stable isotope 13C within CEEF (Closed Ecology Experiment Facilities).     

Direct utilization of human liquid wastes by plants in a closed ecosystem.

Model experiments in phytotrons have shown that urea is able to cover 70% of the demand in nitrogen of the conveyer cultivated wheat. At the same time wheat plants can directly utilize human liquid wastes. In this article by human liquid wastes the authors mean human urine only. In a long-term experiment on "man-higher plants" system with two crewmen, plants covered 63 m2, with wheat planted to--39.6 m2. For 103 days, complete human urine (total amount--210.7 l) was supplied into the nutrient solution for wheat. In a month and a half NaCl supply into the nutrient solution stabilized at 0.9-1.65 g/l. This salination had no marked effect on wheat production. The experiment revealed the realistic feasibility to directly involve liquid wastes into the biological turnover of the life support system. The closure of the system, in terms of water, increased by 15.7% and the supply of nutrients for wheat plants into the system was decreased.     

Experimental and mathematical modeling of the consumer's influence on productivity of algae in a model aquatic ecosystem.

A "producer-consumer" (Chlorella vulgaris-Paramecium caudatum) closed aquatic system has been investigated experimentally and theoretically. It has been found that there is a direct relationship between the growth of the paramecia population and their release of ammonia nitrogen, which is the best form of nitrogen for Chlorella growth. The theoretical study of a model of a "producer-consumer" aquatic biotic cycle with spatially separated compartments has confirmed the contribution of paramecia to nitrogen cycling. It has been shown that an increase in the concentration of nitrogen released as metabolites of paramecia is accompanied by an increase in the productivity of microalgae.     

A "cryptic" microbial mat: a new model ecosystem for extant life on Mars.

If life were present on Mars to day, it would face potentially lethal environmental conditions such as a lack of water, frigid temperatures, ultraviolet radiation, and soil oxidants. In addition, the Viking missions did not detect near-surface organic carbon available for assimilation. Autotrophic organisms that lived under a protective layer of sand or gravel would be able to circumvent the ultraviolet radiation and lack of fixed carbon. Two terrestrial photosynthetic near-surface microbial communities have been identified, one in the inter- and supertidal of Laguna Ojo de Liebre (Baja California Sur, Mexico) and one in the acidic gravel near several small geysers in Yellowstone National Park (Wyoming, U.S.A.). Both communities have been studied with respect to their ability to fix carbon under different conditions, including elevated levels of inorganic carbon. Although these sand communities have not been exposed to the entire suite of Martian environmental conditions simultaneously, such communities can provide a useful model ecosystem for a potential extant Martian biota.     

Closed Artificial ecosystems as a means of ecosystem studies for Earth and space needs.

Closed Artificial ecosystems (CAES) have good prospects for wide use as new means for quantitative studies of different types of both natural ecosystems and man-made ones. The paper deals with the discussion of three points of CAES applications. The first one is of importance for theoretical ecology development and is connected with bringing together "holistic" and "merological" approaches in ecosystems studies. Using CAES, we can combine both approaches, taking into account the biotic turnover of limiting substrates which few in number even for complicated natural ecosystems. The second CAES use concerns the development of "ecosystems health" concept and application of a key-factor-approach for the indication and measurement of healthy unhealthy state and functioning of ecosystems or their links. The third use is more of an applied nature, oriented to the intensification of bioremediation or biodepollution processes in different types of ecosystems, including the global biosphere. Grant numbers: N 99-04-96017, N25.     

Ethylene production by plants in a closed environment.

Ethylene production by 20-m2 stands of wheat, soybean, lettuce and potato was monitored throughout growth and development in NASA's Controlled Ecological Life Support System (CELSS) Biomass Production Chamber. Chamber ethylene concentrations rose during periods of rapid growth for all four species, reaching 120 parts per billion (ppb) for wheat, 60 ppb for soybean, and 40 to 50 ppb for lettuce and potato. Following this, ethylene concentrations declined during seed fill and maturation (wheat and soybean), or remained relatively constant (potato). Lettuce plants were harvested during rapid growth and peak ethylene production. The highest ethylene production rates (unadjusted for chamber leakage) ranged from 0.04 to 0.06 ml m-2 day-1 during rapid growth of lettuce and wheat stands, or approximately 0.8 to 1.1 nl g-1 fresh weight h-1. Results suggest that ethylene production by plants is a normal event coupled to periods of rapid metabolic activity, and that ethylene removal or control measures should be considered for growing crops in a tightly closed CELSS.     

一种爬壁机器人的动力学建模

City-Climber是1台爬壁机器人,为研究该机器人的3D路径规划问题,建立了City-Climber在方形房间内运动的运动学模型和动力学模型,该动力学模型包括3个子模型,机器人在地面、墙壁和天花板的运动分别用1个子模型描述.引入无量纲变量分别对3个子模型进行简化,再用Matlab软件对模型进行仿真,验证了动力学模型的正确性.该模型可用于解决City-Climber在3D环境下的路径规划和避障问题.     

Modeling gas exchange in a closed plant growth chamber.

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.     

A simplified data assimilation method for reconstructing time-series MODIS NDVI data

The Normalized Difference Vegetation Index (NDVI) is an important vegetation index, widely applied in research on global environmental and climatic change. However, noise induced by cloud contamination and atmospheric variability impedes the analysis and application of NDVI data. In this work, a simplified data assimilation method is proposed to reconstruct high-quality time-series MODIS NDVI data. We extracted 16-Day L3 Global 1 km SIN Grid NDVI data sets for western China from MODIS vegetation index (VI) products (MOD13A2) for the period 2003–2006. NDVI data in the first three years (2003–2005) were used to generate the background field of NDVI based on a simple three-point smoothing technique, which captures annual features of vegetation change. NDVI data for 2006 were used to test our method. For every time step, the quality assurance (QA) flags of the MODIS VI products were adopted to empirically determine the weight between the background field and NDVI observations. Ultimately, more reliable NDVI data can be produced. The results indicate that the newly developed method is robust and effective in reconstructing high-quality MODIS NDVI time-series.     

Development of autonomous control in a closed microbial bioreactor.

Space-based life support systems which include ecological components will rely on sophisticated hardware and software to monitor and control key system parameters. Autonomous closed artificial ecosystems are useful for research in numerous fields. We are developing a bioreactor designed to study both microbe-environment interactions and autonomous control systems. Currently we are investigating N-cycling and N-mass balance in closed microbial systems. The design features of the system involve real-time monitoring of physical parameters (e.g. temperature, light), growth solution composition (e.g. pH, NOx, CO2), cell density and the status of important hardware components. Control of key system parameters is achieved by incorporation of artificial intelligence software tools that permit autonomous decision-making by the instrument. These developments provide a valuable research tool for terrestrial microbial ecology, as well as a testbed for implementation of artificial intelligence concepts. Autonomous instrumentation will be necessary for robust operation of space-based life support systems, and for use on robotic spacecraft. Sample data acquired from the system, important features of software components, and potential applications for terrestrial and space research will be presented.     

Qualitative Reasoning methods for CELSS modeling.

Qualitative Reasoning (QR) is a branch of Artificial Intelligence that arose from research on engineering problem solving. This paper describes the major QR methods and techniques, which, we believe, are capable of addressing some of the problems that are emphasized in the literature and posed by CELSS modeling, simulation, and control at the supervisory level.     

Toluene removal from air by Dieffenbachia in a closed environment.

Higher plants are likely to play a major role in bioregeneration systems for food, air and water supplies. Plants may also contribute by the removal of toxic organic substances from the air of a closed environment. Dieffenbachia amoena plants were exposed to 0 to 1.2 x 10(6) micrograms toluene m-3 at light intensities of 35 and 90 micromoles m-2 s-1 in sealed chambers. Toluene removal, photosynthesis and respiration were measured. An increased light intensity increased the rate of toluene removal five-fold over the rate at the lower intensity; the kinetics suggest active regulation by the plant. The removal rate saturated at 2700 micrograms toluene h-1 at the lower intensity and failed to saturate at the higher intensity. Toluene exposure inhibited photosynthesis and respiration only transiently and without correlation to toluene concentration. These plants can act as efficient scavengers of toluene in a contaminated environment.     

绳驱动拟人臂机器人的动力学建模及张力分析

与传统的机械臂相比,绳驱动拟人臂机器人采用串并混联的结构形式,模拟了人手臂肌肉的并联驱动方式,但是,绳索的引入也增加了动力学分析的难度.将绳驱动拟人臂机器人视为基座、大臂、小臂和末端四连杆串联机构,采用迭代牛顿-欧拉法建立动力学方程的递推形式,考虑绳驱动的冗余特性和绳索的单方向受力性,提出基于动态最小预紧力的张力分配算法,求解出各绳索的驱动力.与未进行张力分配的方法及基于静态最小预紧力的方法相比,所提出的算法可使各绳索驱动力根据动态最小预紧力进行实时调节,满足了不同工作条件下机构的刚度要求.     

New problems to be solved for establishing closed life support system.

New test bed facilities such as Bioplex and CEEF have been constructed to test the new advanced technologies for solving the various problems as follows, (1) how to develop air content stabilization technologies with gas balance between the generation and the absorption by living organisms, (2) how to solve the mismatching between the assimilation rate of autotrophic organisms and the respiration rate of heterotrophic organisms, (3) how to balance the speed of the waste decomposition with the absorption speed of nutrient components in the sequential plant cultivation, (4) how to develop new nutrient adjusting subsystems for each plant species, (5) how to compensate the denitrification during the waste decomposition and anaerobic microbes in the nutrient solution.     

Impaired growth of plants cultivated in a closed system: possible reasons.

Plants in experiments on "man-higher plants" closed ecosystem (CES) have been demonstrated to have inhibited growth and reduced productivity due to three basic factors: prolonged usage of a permanent nutrient solution introduction into the nutrient medium of intra-system gray water, and closure of the system. Gray water was detrimental to plants the longer the nutrient solution was used. However, higher plant growth was mostly affected by the gaseous composition of the CES atmosphere, through accumulation of volatile substances.     

The legacy of Biosphere 2 for the study of biospherics and closed ecological systems.

The unprecedented challenges of creating Biosphere 2, the world's first laboratory for biospherics, the study of global ecology and long-term closed ecological system dynamics, led to breakthrough developments in many fields, and a deeper understanding of the opportunities and difficulties of material closure. This paper will review accomplishments and challenges, citing some of the key research findings and publications that have resulted from the experiments in Biosphere 2. Engineering accomplishments included development of a technique for variable volume to deal with pressure differences between the facility and outside environment, developing methods of atmospheric leak detection and sealing, while achieving new standards of closure, with an annual atmospheric leakrate of less than 10%, or less than 300 ppm per day. This degree of closure permitted detailed tracking of carbon dioxide, oxygen, and trace gases such as nitrous oxide and ethylene over the seasonal variability of two years. Full closure also necessitated developing new approaches and technologies for complete air, water, and wastewater recycle and reuse within the facility. The development of a soil-based highly productive agricultural system was a first in closed ecological systems, and much was learned about managing a wide variety of crops using non-chemical means of pest and disease control. Closed ecological systems have different temporal biogeochemical cycling and ranges of atmospheric components because of their smaller reservoirs of air, water and soil, and higher concentration of biomass, and Biosphere 2 provided detailed examination and modeling of these accelerated cycles over a period of closure which measured in years. Medical research inside Biosphere 2 included the effects on humans of lowered oxygen: the discovery that human productivity can be maintained with good health with lowered atmospheric oxygen levels could lead to major economies on the design of space stations and planetary/lunar settlements. The improved health resulting from the calorie-restricted but nutrient dense Biosphere 2 diet was the first such scientifically controlled experiment with humans. The success of Biosphere 2 in creating a diversity of terrestrial and marine environments, from rainforest to coral reef, allowed detailed studies with comprehensive measurements such that the dynamics of these complex biomic systems are now better understood. The coral reef ecosystem, the largest artificial reef ever built, catalyzed methods of study now being applied to planetary coral reef systems. Restoration ecology advanced through the creation and study of the dynamics of adaptation and self-organization of the biomes in Biosphere 2. The international interest that Biosphere 2 generated has given new impetus to the public recognition of the sciences of biospheres (biospherics), biomes and closed ecological life systems. The facility, although no longer a materially-closed ecological system, is being used as an educational facility by Columbia University as an introduction to the study of the biosphere and complex system ecology and for carbon dioxide impacts utilizing the complex ecosystems created in Biosphere '.The many lessons learned from Biosphere 2 are being used by its key team of creators in their design and operation of a laboratory-sized closed ecological system, the Laboratory Biosphere, in operation as of March 2002, and for the design of a Mars on Earth(TM) prototype life support system for manned missions to Mars and Mars surface habitats. Biosphere 2 is an important foundation for future advances in biospherics and closed ecological system research.