On monitoring the bacterial component as an indicator of the state of small man-made ecosystems.

High reproduction rates make the bacterial component of ecosystems a good indicator of the state of the system on the whole. This determines the necessity to develop rapid monitoring of the functional state of the bacterial component of small ecosystems. Information about substrate concentration in the population is indicative of the state of the bacterial culture. Conventional methods of monitoring the concentration of integral substrate in the system take time much longer than the changes in the ecosystem. The paper presents theoretical foundations for the logical sequence "catalase activity--intracellular substrate concentration--estimate of substrate consumed by bacteria" for experimental verification and as a consequence of development of the integral method of monitoring the bacterial population on the basis of determining bacterial catalase activity. Grant numbers: 04-96017, N25.     

Effect of bacterial population density on germination wheat seeds and dynamics of simple artificial ecosystems.

Effect of the size of rhizospheric bacterial populations on germination of seeds and development of simple terrestrial "wheat plants--rhizospheric microorganisms--artificial soil" and "wheat plants-artificial soil" systems has been studied. Experiments demonstrated that within specify ranges in the inoculate, the rhizospheric bacteria are capable of increasing the yield of germinated seeds and stimulate the growth of plantlets. Germination of seeds inoculated with bacteria was either stimulated, or inhibited or remained at control levels depending on the amount of bacteria. Plant biomass growth and total photoassimilation has been found to depend on the amount of bacteria on the plant roots: the higher the amount of bacteria on plant roots, the smaller is the biomass of plants but the total photoassimilation is, higher. Thus, depending on the amount of bacteria on the roots of plants the system either increases the biomass of plants or increases the total photoassimilation, i.e. "pumps" carbon through itself involving bacteria. Grant numbers: N99-04-96017, N15.     

Mathematical modeling of response of ecosystems with different structure to external impact.

A mathematical model was used to study the response of ecosystems of different structures to external impact. The response was measured as a sensitivity coefficient: the magnitude of the system's response vs. the change of the factor in the inflow. The formula has been obtained to calculate the sensitivity coefficient for ecosystems containing different numbers of trophic links. The derived sensitivity coefficients demonstrate that the degree of compensation for the external impact can differ depending on the type of system regulation and the length of the trophic chain. E. g. the sensitivity coefficient decreases with complexity of trophic links in an ecosystem for top-down controlled systems and impact of degree of openness on sensitivity e.g. closed ecosystems show higher sensitivity then fully open ecosystem to impacts also bottom-up control system show less sensitivity then top-down. Grant numbers: N99-04-96017, N25.     

Understanding plant-soil relationships using controlled environment facilities.

Although soil is a component of terrestrial ecosystems, it is comprised of a complex web of interacting organisms, and therefore can be considered itself as an ecosystem. Soil microflora and fauna derive energy from plants and plant residues and serve important functions in maintaining soil physical and chemical properties, thereby affecting net primary productivity (NPP), and in the case of contained environments, the quality of the life support system. We have been using 3 controlled-environment facilities (CEF's) that incorporate different levels of soil biological complexity and environmental control, and differ in their resemblance to natural ecosystems, to study relationships among plant physiology, soil ecology, fluxes of minerals and nutrients, and overall ecosystem function. The simplest system utilizes growth chambers and specialized root chambers with organic-less media to study the physiology of plant-mycorrhizal associations. A second system incorporates natural soil in open-top chambers to study soil bacterial and fungal population response to stress. The most complex CEF incorporates reconstructed soil profiles in a "constructed" ecosystem, enabling close examination of the soil foodweb. Our results show that closed ecosystem research is important for understanding mechanisms of response to ecosystem stresses. In addition, responses observed at one level of biological complexity may not allow prediction of response at a different level of biological complexity. In closed life support systems, incorporating soil foodwebs will require less artificial manipulation to maintain system stability and sustainability.     

Competition between links in "producer-consumer" trophic chains in an aquatic closed system with spatially separated components.

The work analyzes functioning of a "producer-consumer" closed aquatic system with spatially separated links, where each component consisted of two species. Producers in the system were the microalgae of Chlorella vulgaris and Scenedesmus sp., consumers--Paramecium caudatum infusoria and Brachionus sp. rotifers. In the experiment the competing predators were consuming on a mixed culture of algae, and the competition of algae was studied under nitrogen limitation. Under these conditions competitiveness of Scenedesmus was higher than that of Chlorella vulgaris. Metabolism products of Scenedesmus algae have been found to have negative effect on reproduction of Paramecium caudatum protozoa. Predator population dynamics in the "consumer" link demonstrated that the rotifers that consume two algal species are more competitive compared to protozoa feeding on chlorella only. Grant numbers: N99-04-96017, N25.     

Self-restoration as fundamental property of CES providing their sustainability.

Sustainability is one of the most important criteria in the creation and evaluation of human life support systems intended for use during long space flights. The common feature of biological and physicochemical life support systems is that basically they are both catalytic. But there are two fundamental properties distinguishing biological systems: 1) they are auto-catalytic: their catalysts--enzymes of protein nature--are continuously reproduced when the system functions; 2) the program of every process performed by enzymes and the program of their reproduction are inherent in the biological system itself--in the totality of genomes of the species involved in the functioning of the ecosystem. Actually, one cell with the genome capable of the phenotypic realization is enough for the self-restoration of the function performed by the cells of this species in the ecosystem. The continuous microalgal culture of Chlorella vulgaris was taken to investigate quantitatively the process of self-restoration in unicellular algae population. Based on the data obtained, we proposed a mathematical model of the restoration process in a cell population that has suffered an acute radiation damage.     

Mass exchange in an experimental new-generation life support system model based on biological regeneration of environment.

An experimental model of a biological life support system was used to evaluate qualitative and quantitative parameters of the internal mass exchange. The photosynthesizing unit included the higher plant component (wheat and radish), and the heterotrophic unit consisted of a soil-like substrate, California worms, mushrooms and microbial microflora. The gas mass exchange involved evolution of oxygen by the photosynthesizing component and its uptake by the heterotroph component along with the formation and maintaining of the SLS structure, growth of mushrooms and California worms, human respiration, and some other processes. Human presence in the system in the form of "virtual human" that at regular intervals took part in the respirative gas exchange during the experiment. Experimental data demonstrated good oxygen/carbon dioxide balance, and the closure of the cycles of these gases was almost complete. The water cycle was nearly 100% closed. The main components in the water mass exchange were transpiration water and the watering solution with mineral elements. Human consumption of the edible plant biomass (grains and roots) was simulated by processing these products by a unique physicochemical method of oxidizing them to inorganic mineral compounds, which were then returned into the system and fully assimilated by the plants. The oxidation was achieved by "wet combustion" of organic biomass, using hydrogen peroxide following a special procedure, which does not require high temperature and pressure. Hydrogen peroxide is produced from the water inside the system. The closure of the cycle was estimated for individual elements and compounds. Stoichiometric proportions are given for the main components included in the experimental model of the system. Approaches to the mathematical modeling of the cycling processes are discussed, using the data of the experimental model. Nitrogen, as a representative of biogenic elements, shows an almost 100% closure of the cycle inside the system. The proposed experimental model of a biological system is discussed as a candidate for potential application in the investigations aimed at creating ecosystems with largely closed cycles of the internal mass exchange. The formation and maintenance of sustainable cycling of vitally important chemical elements and compounds in biological life support systems (BLSS) is an extremely pressing problem. To attain the stable functioning of biological life support systems (BLSS) and to maintain a high degree of closure of material cycles in than, it is essential to understand the character of mass exchange processes and stoichiometnc proportions of the initial and synthesized components of the system.     

ECOSIMP2 model: prediction of CO2 concentration changes and carbon status in closed ecosystems.

The ECOSIMP2 model, simulating the Plant-Soil-Atmosphere interactions, was developed as a tool for the management of an experimental artificial ecosystem. It consists in three main carbon compartments for production, consumption and decomposition of the biomass. The main biological parameters concern photosynthesis (apparent Km, CO2 compensation point), the harvest index, the rate of consumption, and the kinetics of litter decomposition. From realistic assumptions of kinetics of soil compartments, a steady-state case was obtained, simulating a terrestrial ecosystem. The stability of the atmospheric CO2 concentration was studied after a virtual enclosure of the system in a 20-m high greenhouse. In natural lighting the conditions of stability are severe because of the small size of the atmospheric compartment which amplifies any imbalance between carbon fluxes. The positive consequence of that amplification for research on artificial ecosystems was emphasized.     

Possible nutrient limiting factor in long term operation of closed aquatic ecosystem

To investigate nutrient limitation effect on the community metabolism of closed aquatic ecosystem and possible nutrient limiting factors in the experimental food chains, depletion of inorganic chemicals including carbon, nitrogen and phosphorous was tested. A closed aquatic ecosystem lab module consisting of Chlorella pyrenoidosa and Chlamydomonas reinhardtii, Daphnia magna and associated unidentified microbes was established. Closed ecological systems receive no carbon dioxide; therefore, we presumed carbon as a first limiting factor. The results showed that the algae population in the nutrient saturated group was statistically higher than that in the nutrient limited groups, and that the chlorophyll a content of algae in the phosphorus limited group was the highest among the limited groups. However, the nitrogen limited group supported the most Daphnia, followed by the carbon limited group, the nutrient saturated group and the phosphorus limited group. Redundancy analysis showed that the total phosphorus contents were correlated significantly with the population of algae, and that the amount of soluble carbohydrate as feedback of nutrient depletion was correlated with the number of Daphnia. Thus, these findings suggest that phosphorus is the limiting factor in the operation of closed aquatic ecosystem. The results presented herein have important indications for the future construction of long term closed ecological system.     

Computer modeling of the biotic cycle formation in a closed ecological system.

The process of biotic turnover in a closed ecological system (CES) with an external energy flow was analyzed by mathematical modeling of the biotic cycle formation. The formation of hierarchical structure in model CESs is governed by energy criteria. Energy flow through the ecosystem increases when a predator is introduced into a "producer-reducer" system at steady state. Analysis of the model shows that under certain conditions the presence of the primary predator with its high mineralization ability accelerates the biotic turnover measured by primary production. We, therefore, conclude that for every system it is possible to find a suitable predator able to provide the system with a higher biotic turnover rate and energy consumption. Grant numbers: 99-04-96017/2000.     

Long-term experiments on man's stay in biological life-support system.

We describe the experimental system having maximal possible closure of material recycling in an ecosystem, including people and plants, which was carried out in a hermetically sealed experimental complex "BIOS-3", 315 m2 in volume. The system included 2 experimentators and 3 phytotrons with plants (total sowing area of 63 m2). Plants were grown with round-the-clock lamp irradiation with 130 Wm-2 PAR intensity. The plants production was food for people. Water exchange of ecosystem, as wall as gas exchange, was fully closed excluding liquids and gas samples taken for chemical analysis outside the system. The total closure of material turnover constituted 91%. Health state of the crew was estimated before, during and after the experiment. A 5-months period did not affect their health. The experiments carried out prove that the closed ecosystem of "man-plants" is a prototype of a life-support system for long-term space expeditions.     

Basic design concept of Closed Ecology Experiment Facilities.

In order to study the relationship between the physiological metabolism of living things and the environmental factors such as the atmospheric contents and so on within the closed ecosystem, Closed Ecology Experiment Facilities (CEEF) were designed and now under construction based on the following concepts: (1) Individual sealed chambers (called modules) for the plant cultivation, animal breeding, human habitation and microbial waste treatment are to be constructed independently to be able to study the metabolic effects of each living thing on the environmental factors within closed ecosystem. (2) A chamber for the microbial waste treatment are to be replaced with two systems; wet oxidation reactors and chemical nitrogen fixation reactors. (3) Atmospheric control systems are to be independently attached to each module for stabilizing atmospheric contents in each module. (4) Any construction materials having the possibility to absorb oxygen and carbon dioxide are to be prohibited to use in each module for sustaining material balance. (5) Facilities have to be developed so that the closed plant and animal experiments can be done independently, as well as integrated experiments with plants and animals through exchanging foods, carbon dioxide, oxygen, condensed water and nutrient solution.     

Cometary constraints on the planet forming environment.

Molecular elemental and isotopic abundances of comets provide sensitive diagnostics for models of the primitive solar nebula. New measurements of the N2, NH and NH2 abundances in comets together with the in situ Giotto mass spectrometer and dust analyzer data provide new constraints for models of the comet forming environment in the solar nebula. An inventory of nitrogen-containing species in comet Halley indicates that NH3 and CN are the dominant N carriers observed in the coma gas. The elemental nitrogen abundance in the gas component of the coma is found to be depleted by a factor approximately 75 relative to the solar photosphere. Combined with the Giotto dust analyzer results for the coma dust component, we find for comet Halley Ngas + dust approximately 1/6 the solar value. The measurement of the CN carbon isotope ratio from the bulk coma gas and dust in comet Halley indicates a significantly lower value, 12C/13C = 65 +/- 9 than the solar system value of 89 +/- 2. Because the dominant CN carrier species in comets remains unidentified, it is not yet possible to attribute the low isotope ratio predominantly to the bulk gas or dust components. The large chemical and isotopic inhomogeneities discovered in the Halley dust particles on 1 mu scales are indicative of preserved circumstellar grains which survived processing in the interstellar clouds, and may be related to the presolar silicon carbide, diamond and graphite grains recently discovered in carbonaceous chondrites. Less than 0.1% of the bulk mass in the primitive meteorites studied consists of these cosmically important grains. A larger mass fraction (approximately 5%) of chemically heterogeneous organic grains is found in the nucleus of comet Halley. The isotopic anomalies discovered in the PUMA 1 Giotto data in comet Halley are probably also attributable to preserved circumstellar grains. Thus the extent of grain processing in the interstellar environment is much less than predicted by interstellar grain models, and a significant fraction of comet nuclei (approximately 5%) may be in the form of preserved circumstellar matter. Comet nuclei probably formed in much more benign environments than primitive meteorites.     

Controlling denitrification in closed artificial ecosystems.

Denitrification, the dissimilatory reduction of NO3- to N2O and N2, is found in a wide variety of organisms. In closed artificial systems, especially closed plant growth chambers, a significant loss of fixed-N occurs through denitrification, thereby decreasing the efficiency of the system and fouling the atmosphere with N2O. Denitrification is a form of anaerobic respiration. Whenever available, however, denitrifiers preferentially use O2 as their terminal electron acceptor. As a result, rates of denitrification and growth are a function of O2. Typically, in closed systems O2 consumption is greater than the diffusion of O2 through the medium to the cell, decreasing the O2 level near the cell and denitrification occurs. Using Pseudomonas fluorescens (ATCC # 17400) as a model organism grown in a two L bioreactor under varying levels of O2 we studied its effects on population growth and its ability to mitigate denitrification in closed systems. The results indicate that denitrification occurs in a closed system even when it is considered aerobic, that is well mixed and sparged with either air, or sufficient pure O2 to cause a complete turnover in the gaseous atmosphere in the bioreactor vessel every five minutes.     

基于机会策略的多态系统视情更换决策

针对部件间存在性能相关性和经济相关性的多态系统,提出了基于机会策略的多态系统视情更换维修决策方法。采用Markov模型描述部件的衰退过程,利用通用生成函数对系统的可靠性指标进行分析,以机会策略为基础,从"部件级更换的角度"出发,提出了一种新的多态系统视情更换维修决策方法,确保系统在有限服役期内,获得最大经济效益。并以某雷达功率放大系统的更换维修决策为例进行分析,该方法在考虑部件间经济相关性的同时,一定程度上减少了总的维修次数,提高了装备系统的战场保障能力,具有很强的通用性和工程应用价值。     

Effect of heavy ions on bacterial spores.

Inactivation of B. subtilis spores has been studied using accelerated He, C, N, O and Ne ions. The energy dependence of the inactivation cross sections for heavy ions was very weak and the mean cross sections for carbon ions (0.6-4.7 MeV/amu), nitrogen ions (0.6-4.1 MeV/amu), oxygen ions (0.8-1.1 MeV/amu), and neon ions (2.2-3.7 MeV/amu) were found to be about 0.22, 0.23, 0.26, and 0.33 micrometer2 , respectively. Analysis was carried out along lines similar to Katz's target theory but the parameters were chosen so that they have an experimental basis.     

Regulation of autonomic nervous system in space and magnetic storms.

Variations in the earth's magnetic field and magnetic storms are known to be a risk factor for the development of cardiovascular disorders. The main "targets" for geomagnetic perturbations are the central nervous system and the neural regulation of vascular tone and heart rate variability. This paper presents the data about effect of geomagnetic fluctuations on human body in space. As a method for research the analysis of heart rate variability was used, which allows evaluating the state of the sympathetic and parasympathetic parts of the autonomic nervous system, vasomotor center and subcortical neural centers activity. Heart rate variability data were analyzed for 30 cosmonauts at the 2nd day of space flight on transport spaceship Soyuz (32nd orbit). There were formed three groups of cosmonauts: without magnetic storm (n=9), on a day with magnetic storm (n=12) and 1-2 days after magnetic storm (n=9). The present study was the first to demonstrate a specific impact of geomagnetic perturbations on the system of autonomic circulatory control in cosmonauts during space flight. The increasing of highest nervous centers activity was shown for group with magnetic storms, which was more significant on 1-2 days after magnetic storm. The use of discriminate analysis allowed to classify indicated three groups with 88% precision. Canonical variables are suggested to be used as criterions for evaluation of specific and non-specific components of cardiovascular reactions to geomagnetic perturbations. The applied aspect of the findings from the present study should be emphasized. They show, in particular, the need to supplement the medical monitoring of cosmonauts with predictions of probable geomagnetic perturbations in view of the prevention of unfavorable states appearances if the adverse reactions to geomagnetic perturbations are added to the tension experienced by regulatory systems during various stresses situations (such as work in the open space).     

基于PCA和WPSVM的航天器电特性识别方法

针对航天器电特性监测系统识别过程中存在测试数据量大、特征维数高、样本少、计算速度慢和识别率低等问题,提出基于主成分分析(PCA)的特征提取和加权近似支持向量机(WPSVM)的在线故障诊断方法.实现了对信号故障特征的主成分分析、选择和提取,并对高维特征数据实现了降维,提高了航天器电特性在线故障诊断的准确性和速度.针对PCA中的结果选取问题,提出运用数据贡献度阈值进行数据截取的方法,有效地保证了数据的有效性与一致性.结果表明:该方法充分利用了航天器电特性监测系统的有用数据特征,有效提高了识别的精度,且计算时间较短,效率较高.      

The health of biological life support systems

In developing different types of biological life support systems for use in space or extreme environments on Eart, researchers should pay attention to the long term health or functional state of such systems. The difficulty of the task is compounded by the complexity of the links and structure to be found in biological systems. To solve the problem, a hierarchical approach may be used to estimate and monitor the health of the system as a whole and its individual links. Three levels in a typical hierarchy have been considered:

1. a. the organismic.

2. b. populations and communities.

3. c. the ecosystem.

Special attention has been given to the interactions between macro- and microorganisms. Microorganisms are considered the most suitable indicators of a system's health and its component links.     

Experimental and mathematical models for small aqueous closed ecosystems with spatially separated components.

Experimental and theoretical models of closed "autotroph-heterotroph" (chlorella-yeast, chlorella-protozoa) ecosystems with spatially separated components have been created and studied. The chart of flows and interaction of components of gas-closed "chlorella-yeast" system have formed the basis describe mathematically the functioning of the given system, experimental results have been found to agree with computer solution of the problem in terms of quality. Investigation of the experimental model of the "producer-consumer" trophic chain demonstrated the role of protozoa in nitrogen turnover. "Production-decomposition" and "production-grazing-decomposition" cycle models has been theoretically analyzed and compared. The predator has been shown to be a more intensive mineralizer than the reducer component.