This paper documents thruster plume induced contamination measurements from the PIC (Plume Impingement Contamination) and SPIFEX (Shuttle Plume Impingement Flight Experiment) flight experiments.The SPIFEX flight experiment was flown on Space Shuttle mission STS-64 in 1994. Contamination measurements of molecular deposition were made by XPS (X-ray Photo Spectroscopy). Droplet impact features were also recorded with SEM (Scanning Electron Microscope) scans on Kapton and aluminum foil substrates.The PIC flight experiment was conducted during STS-74 in 1996. Quartz Crystal Microbalances (QCMs) measured contaminant deposition from U.S. and Russian thruster firings. Droplet impact observations were made with SEM scans of the Shuttle RMS (Remote Manipulator System) camera lens.These flight experiments were successful in providing measurements of plume induced contamination as well as droplet impact damage. These measurements were the basis of the plume contamination models developed for the International Space Station (ISS).
Well-established procedures for the characterization of contamination during outgassing usually involve total mass measurements through quartz crystal microbalance (QCM). Recently, the addition of mass spectrometry (MS) measurements to these data has become more common. The combination of both high sensitivity QCM and MS data may lead to a better understanding of the physics taking place during outgassing contamination processes. The way to do so is to complement the basic measurements of total mass loss on QCMs by the identification of each species and the quantitative determination of each species contribution.In a first characterization step, the thermogravimetric analysis of contaminants deposited on QCMs allows a partial species separation that helps exploiting mass spectrometry data. In return, these data permit a finer species separation. The key to these measurements is to obtain sufficient signal to noise ratio in the mass spectrometer. Though outgassing of space materials is not done the same way in Europe (multi-temperature steps, ECSS-Q-TM-70-52A) and in the US (isothermal, ASTM E-1559-09), both tests could be used to perform a first species separation, as reported here. Most species outgassed by a few common materials were identified (and quantified) through TGA and MS coupling. As reported in a companion paper, the knowledge of these species' spectra then allows the analysis of the MS data during the initial outgassing phase, determining the quantitative outgassing of each species and leading to the improved comprehension of the physical laws ruling outgassing.
RESUMO.Fungos e suas condições de armazenagem (umidade) e a contaminação por micotoxinas em alimentos oferecidos para ovinos foram avaliados. Animais da raça crioula criados na Fazenda Ressacada-UFSC e com saúde debilitada. Com as amostras de (a) feno de alfafa (Medicago sativa L.) estavam armazenadas em 3 pontos (entrada do galpão, aprisco e sala), além de (b) pastagem (B. decumbens) obtida no campo e (c) ração (milho e soja) armazenada no aprisco. O gênero fúngico mais detectado foi o Aspergillus, seguido do Penicillium em 75 e 40% das amostras, respectivamente. Cepas toxigênicas (produtoras de AFLs) foram identificadas. Quanto a umidade (mc e aw) os teores variaram entre 12-40% (média:12%) e aw: 0,5029-0,9888 (média: 0,5783), considerado adequado para proliferação de fungos. Das micotoxinas avaliadas (aflatoxinas -AFLs, ocratoxina A -OTA, zearalenona -ZON e esterigmatoscistina -EST), as de armazenagem (AFLS: AFB1, AFB2, AFG1, AFG2) foram detectadas com teores de 128 µg/kg nas amostras de feno. As condições de limpeza (armazém e maquinários) são de extrema importância, uma vez que as amostras recém-chegadas ao local de abrigo das ovelhas se encontram contaminadas.Palavras chave: Alfafa, feno, micotoxinas, multitoxinas, pasto, ração Storage fungi and mycotoxins in sheep diet (Ovis aries L.): a case studyABSTRACT. Fungi and their storage conditions (moisture) and contamination by mycotoxins in foods offered to sheep were evaluated. Crioula animals created at Farm Ressacada -UFSC and with weakened health. The samples of alfalfa hay (Medicago sativa L.) were stored at 3 points (entrance of the shed, sheepfold and room), besides (b) pasture (B. decumbens) obtained in the field and (c) ration (Corn and soybean) stored in the sheepfold. The most detected fungal genus was Aspergillus, followed by Penicillium in 75 and 40% of the samples, respectively. Toxigenic strains (AFLs producers) were identified. As regards moisture (mc and aw) the contents ranged from 12-40% (mean: 12%) and aw: 0.5029-0.9888 (mean: 0.5783), considered adequate for fungal growth. Mycotoxins (AFLs: AFB1, AFB2, AFG1, AFG2) were detected at levels of 128 μg/kg in the hay samples. Cleaning conditions (warehouse and machinery) are of the utmost importance, since samples newly arrived at the shelter of the sheep are contaminated.
The prediction of contaminant levels is paramount to controlling and reducing their impact on space missions. In recent years, it has become clear that a real breakthrough could only be achieved through a change of paradigm, namely, by going beyond the classical characterization of total contaminant mass and instead characterizing the various emitted chemical species individually: both quantitatively and chemically. This paper first reviews the methodology proposed to achieve this objective and then its implementation on two examples of materials (Black Kapton® and NuSil CV4-2946) on the basis of existing ASTM-E-1559 outgassing data (Garrett, J. W., Glassford, P. M., and Steakley, J. M., “ASTM-E-1559 Method for Measuring Material Outgassing/Deposition Kinetics,” Journal of the IEST, Vol. 38, No. 1, 1995, pp. 19–28) including mass spectrometry (MS) data. We show that the thermogravimetric analysis performed on the contaminant deposits (heating at 1 K/min) allows a good enough time separation of chemical species to analyze and often identify them through their mass spectra. In turn, the knowledge of the fragments constituting their spectra allows an improved analysis of the MS data collected during the initial outgassing phase. The outgassing time profiles of each of these chemical species then tells a lot about their actual outgassing physical laws. On the two studied materials, outgassing physics were found to be consistent with Fickian or non-Fickian diffusion rather than with residence time desorption. After confirming these findings with more specific and more sensitive experiments, the door will be open to greatly improve assessments of the contaminant amounts and nature in flight through realistic multispecies physical models.
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