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- Kminek, G, et al.
(author)
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COSPAR Sample Safety Assessment Framework (SSAF)
- 2022
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In: Astrobiology. - : Mary Ann Liebert Inc.. - 1531-1074 .- 1557-8070. ; 22:S1, s. S186-S216
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Journal article (peer-reviewed)abstract
- The Committee on Space Research (COSPAR) Sample Safety Assessment Framework (SSAF) has been developed by a COSPAR appointed Working Group. The objective of the sample safety assessment would be to evaluate whether samples returned from Mars could be harmful for Earth's systems (e.g., environment, biosphere, geochemical cycles). During the Working Group's deliberations, it became clear that a comprehensive assessment to predict the effects of introducing life in new environments or ecologies is difficult and practically impossible, even for terrestrial life and certainly more so for unknown extraterrestrial life. To manage expectations, the scope of the SSAF was adjusted to evaluate only whether the presence of martian life can be excluded in samples returned from Mars. If the presence of martian life cannot be excluded, a Hold & Critical Review must be established to evaluate the risk management measures and decide on the next steps. The SSAF starts from a positive hypothesis (there is martian life in the samples), which is complementary to the null-hypothesis (there is no martian life in the samples) typically used for science. Testing the positive hypothesis includes four elements: (1) Bayesian statistics, (2) subsampling strategy, (3) test sequence, and (4) decision criteria. The test sequence capability covers self-replicating and non-self-replicating biology and biologically active molecules. Most of the investigations associated with the SSAF would need to be carried out within biological containment. The SSAF is described in sufficient detail to support planning activities for a Sample Receiving Facility (SRF) and for preparing science announcements, while at the same time acknowledging that further work is required before a detailed Sample Safety Assessment Protocol (SSAP) can be developed. The three major open issues to be addressed to optimize and implement the SSAF are (1) setting a value for the level of assurance to effectively exclude the presence of martian life in the samples, (2) carrying out an analogue test program, and (3) acquiring relevant contamination knowledge from all Mars Sample Return (MSR) flight and ground elements. Although the SSAF was developed specifically for assessing samples from Mars in the context of the currently planned NASA-ESA MSR Campaign, this framework and the basic safety approach are applicable to any other Mars sample return mission concept, with minor adjustments in the execution part related to the specific nature of the samples to be returned. The SSAF is also considered a sound basis for other COSPAR Planetary Protection Category V, restricted Earth return missions beyond Mars. It is anticipated that the SSAF will be subject to future review by the various MSR stakeholders. © Gerhard Kminek et al., 2022;
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- Sforna, M. C., et al.
(author)
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Patterns of metal distribution in hypersaline microbialites during early diagenesis : Implications for the fossil record
- 2017
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In: Geobiology. - : Wiley. - 1472-4677 .- 1472-4669. ; 15:2, s. 259-279
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Journal article (peer-reviewed)abstract
- The use of metals as biosignatures in the fossil stromatolite record requires understanding of the processes controlling the initial metal(loid) incorporation and diagenetic preservation in living microbialites. Here, we report the distribution of metals and the organic fraction within the lithifying microbialite of the hypersaline Big Pond Lake (Bahamas). Using synchrotron-based X-ray microfluorescence, confocal, and biphoton microscopies at different scales (cm-m) in combination with traditional geochemical analyses, we show that the initial cation sorption at the surface of an active microbialite is governed by passive binding to the organic matrix, resulting in a homogeneous metal distribution. During early diagenesis, the metabolic activity in deeper microbialite layers slows down and the distribution of the metals becomes progressively heterogeneous, resulting from remobilization and concentration as metal(loid)-enriched sulfides, which are aligned with the lamination of the microbialite. In addition, we were able to identify globules containing significant Mn, Cu, Zn, and As enrichments potentially produced through microbial activity. The similarity of the metal(loid) distributions observed in the Big Pond microbialite to those observed in the Archean stromatolites of Tumbiana provides the foundation for a conceptual model of the evolution of the metal distribution through initial growth, early diagenesis, and fossilization of a microbialite, with a potential application to the fossil record.
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- van Zuilen, M. A., et al.
(author)
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Sulfur isotope mass-independent fractionation in impact depositsof the 3.2 billion-year-old Mapepe Formation,Barberton Greenstone Belt, South Africa
- 2014
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In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 142, s. 429-441
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Journal article (peer-reviewed)abstract
- Theoretical and experimental studies have shown that atmospheric SO2 isotopologue self-shielding effects in the 190–220 nmregion of the solar spectrum are the likely cause for mass independent fractionation of sulfur isotopes (S-MIF). The main productsof this photochemical reaction – SO3 and S0 – typically define a compositional array of ca. D33S/d34S = 0.06–0.14. This is atodds with the generally observed trend in Archean sulfides, which broadly defines an array of ca. D33S/d34S = 0.9. Various explanationshave been proposed, including a diminution of d34S caused by chemical and biogenic mass-dependent fractionation ofsulfur isotopes (S-MDF), mixing with photolytic products produced during felsic volcanic events, or partial blocking of the lowwavelengthpart of the spectrum due to the presence of reduced atmospheric gases or an organic haze. Early in Earth history largemeteorite impacts would have ejected dust and gas clouds into the atmosphere that shielded solar radiation and affected globalclimate. It is thus likely that at certain time intervals of high meteorite flux the atmosphere was significantly perturbed, having aneffect on atmospheric photochemistry and possibly leaving anomalous sulfur isotopic signatures in the rock record. Here wedescribe the sulfur isotopic signatures in sulfides of spherule beds S2, S3 and S4 of the Barberton Greenstone Belt, South Africa.In particular, in spherule bed S3 – and to a lesser extent S4 – a trend of ca. D33S/d34S = 0.23 is observed that closely follows theexpected trend for SO2-photolysis in the 190–220 nm spectral range. This suggests that an impact dust cloud (deposited as spherulebeds), which sampled the higher region of the atmosphere, specifically incorporated products of SO2 photolysis in the 190–220 nm range, and blocked photochemical reactions at higher wavelengths (250–330 nm band). By implication, the generallyobserved Archean trend appears to be the result of mixing of different MIF-S sources arising from a variety of photochemicalreactions that took place in the lower part of the atmosphere.
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- Qu, Yuangao, et al.
(author)
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Evidence for molecular structural variations in the cytoarchitectures of a Jurassic plant
- 2019
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In: Geology. - Boulder, Colorado : Geological Society of America. - 0091-7613 .- 1943-2682. ; 47, s. 325-329
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Journal article (peer-reviewed)abstract
- In this study, we investigate the molecular structural characteristics of organic remains in various cellular organelles from a 180 Ma Jurassic royal fern belonging to the Osmundaceae family of ferns, and compare their carbon isotopic compositions to a now-living species of royal fern (Osmunda regalis). We discovered molecular structural variations indicated by Raman and infrared spectral parameters obtained from various fossilized cellular organelles. The organic remains preserved in the chromosomes and cell nuclei show marked structural heterogeneities compared to the cell walls during different stages of the cell cycle. The fossil and extant fern have similar δ13C values obtained from bulk samples, supporting evolutionary stasis in this plant lineage and an unchanged metabolic pathway of carbon assimilation since the Jurassic. The organic remains in the cellular organelles of the fossil seem to be less heterogeneous than those in the extant fern, likely due to the preferential preservation of certain cellular compounds during fossilization. Taphonomic processes appear to have diminished the subcellular isotopic heterogeneities. Our research sheds light on the functioning of ancient plant cellular organelles during mitosis, provides insights to the taphonomic processes operating at molecular and isotopic levels, and shows the practicability of in situ techniques in studying the evolution and behaviors of ancient cells.
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| 8. |
- Qu, Yuangao, et al.
(author)
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Sample-scale carbon isotopic variability and diverse biomass in the Paleoproterozoic Zaonega Formation, Russia
- 2018
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In: Precambrian Research. - 0301-9268 .- 1872-7433. ; 315, s. 222-231
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Journal article (peer-reviewed)abstract
- The stratigraphic record of organic matter in the c. 1.97 Ga Zaonega Formation (ZF), Onega Basin, northwestern Russia, exhibits a distinct negative δ13C excursion (δ13Corg from −25 to −40‰ VPDB), which was previously interpreted either to reflect a disturbance in the global carbon cycle after the Great Oxidation Event, or to have been caused by an increase in basinal methanotrophic activity. In order to assess the nature of primary biomass and the effects of post-depositional alteration, we here report the sample-scale carbon isotopic characteristics of organic matter in two drill cores from the ZF, covering 500 m of stratigraphy, by using secondary ion mass spectrometry (SIMS). The results confirm that the organic matter has to a large extent preserved the primary isotopic signatures, whereas secondary effects are limited (<4‰). The sample-scale isotopic heterogeneity, defined as the difference between the maximum and minimum δ13C values obtained by SIMS from every individual sample, increases from typically <5‰ in the lower part of stratigraphy to systematically larger values (up to 11‰) in the upper part, which coincides with the decreasing trend of δ13Corg of bulk samples from −25 to −40‰. Samples with either relatively high (c. −25‰) or low (c. −40‰) δ13Corg values have small sample-scale isotopic heterogeneities, while samples with intermediate δ13Corg values (between −25 and −40‰) have significantly larger heterogeneities. These observations imply the co-existence of photoautotrophic and methanotrophic biomass during deposition of the upper part of the stratigraphy. Our study provides insight into the carbon isotopic characteristics of organic matter and suggests that the negative excursion of δ13Corg in the ZF is induced by a methanotrophic microbial ecosystem sustained by seepage of thermogenic methane during the deposition of the ZF and contemporaneous igneous activities.
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| 9. |
- Wilkie, F. L., et al.
(author)
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HUMANS : An English and Spanish neuropsychological test battery for assessing HIV-1-infected individuals - Initial report
- 2004
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In: Applied neuropsychology. - : Taylor & Francis. - 0908-4282 .- 1532-4826. ; 11:3, s. 121-133
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Journal article (peer-reviewed)abstract
- A neuropsychological battery for testing HIV-1-infected individuals in Spanish was developed. We refer to this battery as the HIV/University of Miami Annotated Neuropsychological test battery in Spanish (HUMANS). The HUMANS battery includes recommendations of the National Institute of Mental Health Neuropsychology Workgroup on HIV-1 infection and measures processes in the following 7 cognitive domains: attention, verbal and visual memory, information processing speed, abstraction and executive functioning, language, visuospatial and visuo-constructive, and motor Administration requires approximately 3 to 4 hr The English version of the battery is sensitive to HIV-1 serostatus and Centers for Disease Control clinical disease stage. We report on the test selection, translation, and adaptation of this parallel English battery into Spanish using methods to eliminate linguistically and culturally biased items in some tests. The importance of standardized neuropsychological instruments equivalent in different languages to test HIV-1-positive individuals for impairment is emphasized. Validation and reliability studies are in progress.
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