As a part of the European Space Agency mission "EXPOSE-R2" on the International Space Station (ISS), the BIOMEX (Biology and Mars Experiment) experiment investigates the habitability of Mars and the ...limits of life. In preparation for the mission, experimental verification tests and scientific verification tests simulating different combinations of abiotic space- and Mars-like conditions were performed to analyze the resistance of a range of model organisms. The simulated abiotic space- and Mars-stressors were extreme temperatures, vacuum, and Mars-like surface ultraviolet (UV) irradiation in different atmospheres. We present for the first time simulated space exposure data of mosses using plantlets of the bryophyte genus Grimmia, which is adapted to high altitudinal extreme abiotic conditions at the Swiss Alps. Our preflight tests showed that severe UVR
irradiation with the maximal dose of 5 and 6.8 × 10
kJ·m
, respectively, was the only stressor with a negative impact on the vitality with a 37% (terrestrial atmosphere) or 36% reduction (space- and Mars-like atmospheres) in photosynthetic activity. With every exposure to UVR
10
kJ·m
, the vitality of the bryophytes dropped by 6%. No effect was found, however, by any other stressor. As the mosses were still vital after doses of ultraviolet radiation (UVR) expected during the EXPOSE-R2 mission on ISS, we show that this earliest extant lineage of land plants is highly resistant to extreme abiotic conditions.
Radiotherapy to the head and neck region (HN) bears the risk of a rampant development of caries, making intensified prevention necessary. Aim of this systematic review was to summarize the evidence ...on the efficacy of caries preventive measures in these patients.
Clinical studies investigating caries in patients with radiotherapy in the HN with at least 1 caries preventive intervention compared to any control were included. Reports in languages other than English or German were excluded. Records were identified on PubMed, Web of Science, Google Scholar, and Cochrane Library mid-January 2024. Risk of bias was assessed with RoB2. Results were summarized. Planned meta-analyses could not be performed, because of heterogenous data.
Five studies were included, with a total of 355 participants. They were irradiated with up to 70 Gy and received different caries preventive interventions, including sodium fluoride or stannous fluoride gels, remineralizing solutions, an “Intraoral Fluoride Release System” and sucrose restricted diet. Caries score increased between 0.48 DMF-S and 9.2 DF-S per year. Largest differences in caries increments were measured between groups with insufficient and with rigorous fluoride application.
The main limitations were compromised randomization, heterogeneity of patients and small sample sizes. Clinical studies on caries prevention after radiotherapy to the HN are lacking and the existing ones bear extensive limitations. However, the large effect size and broad consensus suggest the use of fluoride to be indispensable in preventing caries in these patients.
The study was funded by the Medical Center - University of Freiburg and was not registered.
BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). ...The design of the multiuser facility supports-among others-the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.
Drained peatlands are hotspots of carbon dioxide (CO2) emissions from agricultural soils. As a consequence of both drainage-induced mineralisation and anthropogenic mixing with mineral soils, large ...areas of former peatlands under agricultural use underwent a secondary transformation of the peat (e.g. formation of aggregates). These soils show contents of soil organic carbon (SOC) at the boundary between mineral and organic soils. However, the carbon (C) dynamics of such soils have rarely been studied so far. The aim of the present study was to evaluate the vulnerability of soil organic matter (SOM) to decomposition over the whole range of peat-derived soils under agriculture including very carbon rich mineral soils (76–526 g kg−1 SOC). A total of 62 soil samples covering a broad range of soil and site characteristics were selected from the sample set of the German Agricultural Soil Inventory. Potential CO2 production was measured by aerobic incubation. Fen and bog peat samples were grouped into disturbance classes according to their soil properties. Specific basal respiration rates (SBR), i.e. CO2 fluxes per unit SOC, showed the highest values for the most disturbed samples for both fen peat (13.9 ± 6.0 μg CO2-C g SOC−1 h−1) and bog peat (10.9 ± 4.7 μg CO2-C g SOC−1 h−1). Respiration rates of bog peat increased more strongly with an increasing degree of disturbance than those of fen peat. Perhaps counterintuitively, SOM vulnerability to decomposition thus increased with an increasing degree of disturbance and a decreasing SOC content, indicating positive feedback mechanisms as soon as peat soils are disturbed by drainage. Furthermore, the variability of the SBR increased drastically with increasing degree of disturbance. The turnover of SOM in less disturbed peat samples tended to be higher in samples with higher nitrogen (N) content, higher pH value and lower C:N ratio, while plant-available phosphorus was important for the mineralisation of more severely disturbed peat. However, clear correlations between a single soil property and SBR could not be identified. The high potential of CO2 emissions from organic soils with a low SOC content implies that mixing organic soil with mineral soil does not seem to be a promising option for mitigating greenhouse emissions.
•Specific basal respiration (SBR) determined by aerobic incubation as a measure of vulnerability.•Higher and more variable SBR rates for stronger degraded organic soils.•Bog peat seems to be more vulnerable than fen peat.•High plant-available phosphorus contents increase SBR rates.•SBR rates of heavily disturbed samples remain unpredictable.
Background
Peatlands only cover a minor fraction of the global terrestrial surface, but due to drainage, they are major contributors to carbon dioxide (CO2) emissions from soils. Previous studies ...have shown that hydrological conditions, nutrient availability and anthropogenic disturbance play an important role in the mineralisation of organic matter. Furthermore, microbial turnover depends on peat quality, which is determined by its botanical origin and degree of transformation under natural conditions.
Aims
The objective of this study was to shed light on the interdependence between mineralisation rates, secondary transformation of peat and chemical composition by examining the differences between bog and fen peat and between strongly degraded topsoil and well‐preserved subsoil.
Methods
Bog and fen peat from ten different peatlands under grassland use in Germany were analysed for their chemical composition using standard 13C nuclear magnetic resonance (NMR) spectroscopy and wet chemical extractions for fibre analysis. The radiocarbon age was determined as well. The results were combined with CO2 fluxes from a previous incubation study.
Results
Topsoils had higher shares of proteins and lipids, and lower shares of carbohydrates and aromatics than subsoils. Bog peat subsoils were characterised by higher shares of carbohydrates and lower shares of aromatics than fen peat subsoils. Topsoils were more similar to each other in their chemical composition than the subsoils. Considering all samples, aromatics and phenolics were negatively correlated with CO2 fluxes. Measured CO2 fluxes from topsoils were significantly higher than from subsoils. However, no influences of chemical composition on CO2 fluxes were detected when examining topsoils and subsoils separately. Even though aromatics and phenolics showed positive relationships with radiocarbon age, differences in age alone were unable to explain the higher amounts of these compounds in the subsoil.
Conclusions
The results imply that chemical composition of topsoil peat is not the reason for higher mineralisation rates compared to subsoil peat, but rather a consequence of decomposition and transformation. Thus, peat mineralisation of drained organic soils under agriculture might not slow down over time due to gradually decreasing peat quality but could increase further.
This study investigates the degradation performance of three Fe-based materials in a growing rat skeleton over a period of 1 year. Pins of pure Fe and two Fe-based alloys (Fe-10 Mn-1Pd and Fe-21 ...Mn-0.7C-1Pd, in wt.%) were implanted transcortically into the femur of 38 Sprague-Dawley rats and inspected after 4, 12, 24 and 52 weeks. The assessment was performed by ex vivo microfocus computed tomography, weight-loss determination, surface analysis of the explanted pins and histological examination. The materials investigated showed signs of degradation; however, the degradation proceeded rather slowly and no significant differences between the materials were detected. We discuss these unexpected findings on the basis of fundamental considerations regarding iron corrosion. Dense layers of degradation products were formed on the implants' surfaces, and act as barriers against oxygen transport. For the degradation of iron, however, the presence of oxygen is an indispensable prerequisite. Its availability is generally a critical factor in bony tissue and rather limited there, i.e. in the vicinity of our implants. Because of the relatively slow degradation of both pure Fe and the Fe-based alloys, their suitability for bulk temporary implants such as those in osteosynthesis applications appears questionable.
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This study investigates the degradation performance of three Fe-based materials in a growing rat skeleton over a period of 1year. Pins of pure Fe and two Fe-based alloys (Fe–10Mn–1Pd ...and Fe–21Mn–0.7C–1Pd, in wt.%) were implanted transcortically into the femur of 38 Sprague–Dawley rats and inspected after 4, 12, 24 and 52weeks. The assessment was performed by ex vivo microfocus computed tomography, weight-loss determination, surface analysis of the explanted pins and histological examination. The materials investigated showed signs of degradation; however, the degradation proceeded rather slowly and no significant differences between the materials were detected. We discuss these unexpected findings on the basis of fundamental considerations regarding iron corrosion. Dense layers of degradation products were formed on the implants’ surfaces, and act as barriers against oxygen transport. For the degradation of iron, however, the presence of oxygen is an indispensable prerequisite. Its availability is generally a critical factor in bony tissue and rather limited there, i.e. in the vicinity of our implants. Because of the relatively slow degradation of both pure Fe and the Fe-based alloys, their suitability for bulk temporary implants such as those in osteosynthesis applications appears questionable.
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