Determination of lethality rate constants and D-values for heat-resistant Bacillus spores ATCC 29669 exposed to dry heat from 125°C to 200°C

Exposing flight hardware to dry heat is a NASA-approved sterilization method for reducing microbial bioburden on spacecraft. The existing NASA specification only allows heating the flight hardware between 104°C and 125°C to reduce the number of viable microbes and bacterial spores. Also, the NASA specifications only allow a four log reduction by dry heat microbial reduction because very heat-resistant spores are presumed to exist in a diverse population (0.1%). The goal of this research was to obtain data at higher temperatures than 125°C for one of the most heat-resistant microorganisms discovered in a spacecraft assembly area. These data support expanding the NASA specifications to temperatures higher than 125°C and relaxing the four log reduction specification. Small stainless steel vessels with spores of the Bacillus strain ATCC 29669 were exposed to constant temperatures between 125°C and 200°C under both dry and ambient room humidity for set time durations. After exposures, the thermal spore exposure vessels were cooled and the remaining spores recovered and plated out. Survivor ratios, lethality rate constants, and D-values were determined at each temperature. The D-values for the spores exposed under dry humidity conditions were always found to be shorter than those under ambient humidity. The temperature dependence of the lethality rate constants was obtained by assuming that they obeyed Arrhenius behavior. The results are compared to those of B. atrophaeus ATCC 9372. In all cases, the D-values of ATCC 29669 are between 20 and 50 times longer than those of B. atrophaeus ATCC 9372.     

Biosignatures from Earth-like planets around M dwarfs

Coupled one-dimensional photochemical-climate calculations have been performed for hypothetical Earth-like planets around M dwarfs. Visible/near-infrared and thermal-infrared synthetic spectra of these planets were generated to determine which biosignature gases might be observed by a future, space-based telescope. Our star sample included two observed active M dwarfs-AD Leo and GJ 643-and three quiescent model stars. The spectral distribution of these stars in the ultraviolet generates a different photochemistry on these planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially longer lifetimes and higher mixing ratios than on Earth, making them potentially observable by space-based telescopes. On the active M-star planets, an ozone layer similar to Earth's was developed that resulted in a spectroscopic signature comparable to the terrestrial one. The simultaneous detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been suggested as strong evidence for life. Planets circling M stars may be good locations to search for such evidence.     

Microgravity research results and experiences from the NASA/MIR space station program

The Microgravity Research Program (MRP) participated aggressively in Phase 1 of the International Space Station Program using the Russian Mir Space Station. The Mir Station offered an otherwise unavailable opportunity to explore the advantages and challenges of long duration microgravity space research. Payloads with both National Aeronautics and Space Agency (NASA) and commercial backing were included as well as cooperative research with the Canadian Space Agency (CSA). From this experience, much was learned about long-duration on-orbit science utilization and developing new working relationships with our Russian partner to promote efficient planning, operations, and integration to solve complexities associated with a multiple partner program.

This paper focuses on the microgravity research conducted onboard the Mir space station. It includes the Program preparation and planning necessary to support this type of cross increment research experience; the payloads which were flown; and summaries of significant microgravity science findings.     

Mineralization of wastes of human vital activity and plants to be used in a Life Support System

Available methods for mineralizing wastes of human activity and inedible biomass of plants used in this country and abroad are divided into two types: dry mineralization at high temperatures up to 1270 K with subsequent partial dissolution of the ash and the other--wet oxidation by acids. In this case mineralization is performed at a temperature of 470-460 K and a pressure of 220-270 atmospheres in pure oxygen with the output of mineral solution and dissoluble sediments in the form of scale. The drawback of the first method is the formation of dioxins, CO, SO2, NO2 and other toxic compounds. The latter method is too sophisticated and is presently confined to bench testing. The here proposed method to mineralize the wastes is in mid-position between the thermal and physical chemical methods. At a temperature of 80-90 degrees C the mixture was exposed to a controlled electromagnetic field at normal atmospheric pressure. The method merits simplicity, reliability, produces no dissoluble sediment or emissions noxious for human and plants. The basic difference from the above said methods is to employ as an oxidizer atomic oxygen, its active forms including OH-radicals with hydrogen peroxide as the source. Hydrogen peroxide can be produced with electric power from water inside the Life Support System (LSS).     

基于统计特征的稳健的飞机识别

给出了一种用于稳健的高距离分辨率（HRR）雷达飞机识别（ID）的基于统计特征（StaF)的分类器，HRR波形峰特征在飞行中选择，没有对特征的数目与位置作出先验假设。所抽取的特征取决于所观测的波形（使特征的数目、位置与幅度为随机变量）的信息内涵，这项研究的主要目的是通过保持对已知目标的高识别率同时又使未知目标错误最小来提高分类的稳健性。文中给出了识别结果，表明这种统计特征（StaF)分类器可以显著地降低与未知目标相关的误差，同时保持很高的正确分类概率。     

一个用于铷频率标准的放电管的改进铷消耗模型

铷放电管是铷光管原子频率标准的关键元件,这个频率标准用于NAVSTAR/GPS卫星并且将在未来的卫星中得到应用。管子的可靠性是个值得关心的问题,它的寿命是根据满足可靠性的因素来设计的,随着时间的增长,由于扩散到管壁的铷电荷逐渐减少。计算其消耗量C的公式为C=A B,在该等式中T为真空管的工作时间,B为系数,它与电荷的扩散有关并且由实验决定。A假定为实际瞬时反应过程的损耗,在我们的一些数据中,损耗的测量表明反应的完结是由时间决定的。我们发现它们之间的关系可以用两个常量来描述,A'和D,A'(1-exp(-DT),由动力学第一级反应推得,这样我们可以在有限的实验数据的基础上更好地预测铷的长期损耗。     

Analysis of carbonaceous biomarkers with the Mars Organic Analyzer microchip capillary electrophoresis system: carboxylic acids

The oxidizing surface chemistry on Mars argues that any comprehensive search for organic compounds indicative of life requires methods to analyze higher oxidation states of carbon with very low limits of detection. To address this goal, microchip capillary electrophoresis (μCE) methods were developed for analysis of carboxylic acids with the Mars Organic Analyzer (MOA). Fluorescent derivatization was achieved by activation with the water soluble 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) followed by reaction with Cascade Blue hydrazide in 30 mM borate, pH 3. A standard containing 12 carboxylic acids found in terrestrial life was successfully labeled and separated in 30 mM borate at pH 9.5, 20 °C by using the MOA CE system. Limits of detection were 5-10 nM for aliphatic monoacids, 20 nM for malic acid (diacid), and 230 nM for citric acid (triacid). Polyacid benzene derivatives containing 2, 3, 4, and 6 carboxyl groups were also analyzed. In particular, mellitic acid was successfully labeled and analyzed with a limit of detection of 300 nM (5 ppb). Analyses of carboxylic acids sampled from a lava tube cave and a hydrothermal area demonstrated the versatility and robustness of our method. This work establishes that the MOA can be used for sensitive analyses of a wide range of carboxylic acids in the search for extraterrestrial organic molecules.     

Characteristics of metabolism during prolonged water immersion

The effect on the organism of a 12-day stay in a water immersion medium (head on the water surface) was studied on 10 subjects. The condition of the metabolic processes in the subjects was judged from the investigation of the parameters of protein and carbohydrate metabolism, acid-base equilibrium, the activity of a number of enzymes and steroid hormones. The venous blood and diurnal urine served as the material for conducting the corresponding biochemical determinations. The stay in an immersion medium is accompanied by a significant increase in the content of residual nitrogen in the blood, by a reduction of the creatinine content in the blood and by an increase of the creatine content of the blood with the simultaneous increase of the excretion of creatinine and creatine with the urine, by a significant increase of the glucose and lactate content in the blood, by the development of acidosis of a respiratory and metabolic character, as well as by a significant increase of the activity of creatine phosphokinase and the isoenzyme fraction of lactate dehydrogenase3. In all the subjects, an expressed intensification of the glucocorticoid and androgenic functions of the adrenal cortex is noted during the experimental period.