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- Benaiges-Fernandez, Robert, et al.
(författare)
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Dissimilatory bioreduction of iron(III) oxides by Shewanella loihica under marine sediment conditions
- 2019
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Ingår i: Marine Environmental Research. - : Elsevier. - 0141-1136 .- 1879-0291. ; 151
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Tidskriftsartikel (refereegranskat)abstract
- Shewanella is a genus of marine bacteria capable of dissimilatory iron reduction (DIR). In the context of deep-sea mining activities or submarine mine tailings disposal, dissimilatory iron reducing bacteria may play an important role in biogeochemical reactions concerning iron oxides placed on the sea bed. In this study, batch experiments were performed to evaluate the capacity of Shewanella loihica PV-4 to bioreduce different iron oxides (ferrihydrite, magnetite, goethite and hematite) under conditions similar to those in anaerobic sea sediments. Results showed that bioreduction of structural Fe(III) via oxidation of labile organic matter occurred in all these iron oxides. Based on the aqueous Fe (II) released, derived Fe(II)/acetate ratios and bioreduction coefficients seem to be only up to about 4% of the theoretical ones, considering the ideal stoichiometry of the reaction. A loss of aqueous Fe (II) was caused by adsorption and mineral transformation processes. Scanning electron microscope images showed that Shewanella lohica was attached to the Fe(III)-oxide surfaces during bioreduction. Our findings suggest that DIR of Fe(III) oxides from mine waste placed in marine environments could result in adverse ecological impacts such as liberation of trace metals in the environment.
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- Brütt, Katharina, et al.
(författare)
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Competition and moral behavior: A meta-analysis of forty-five crowd-sourced experimental designs
- 2023
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Ingår i: Proceedings of the National Academy of Sciences - PNAS. - : National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 120:23
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Tidskriftsartikel (refereegranskat)abstract
- Does competition affect moral behavior? This fundamental question has been debated among leading scholars for centuries, and more recently, it has been tested in experimental studies yielding a body of rather inconclusive empirical evidence. A potential source of ambivalent empirical results on the same hypothesis is design heterogeneity-variation in true effect sizes across various reasonable experimental research protocols. To provide further evidence on whether competition affects moral behavior and to examine whether the generalizability of a single experimental study is jeopardized by design heterogeneity, we invited independent research teams to contribute experimental designs to a crowd-sourced project. In a large-scale online data collection, 18,123 experimental participants were randomly allocated to 45 randomly selected experimental designs out of 95 submitted designs. We find a small adverse effect of competition on moral behavior in a meta-analysis of the pooled data. The crowd-sourced design of our study allows for a clean identification and estimation of the variation in effect sizes above and beyond what could be expected due to sampling variance. We find substantial design heterogeneity-estimated to be about 1.6 times as large as the average standard error of effect size estimates of the 45 research designs-indicating that the informativeness and generalizability of results based on a single experimental design are limited. Drawing strong conclusions about the underlying hypotheses in the presence of substantive design heterogeneity requires moving toward much larger data collections on various experimental designs testing the same hypothesis.
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- Dold, Stefan, et al.
(författare)
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Simvastatin protects against cholestasis-induced liver injury.
- 2009
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Ingår i: British Journal of Pharmacology. - : Wiley. - 1476-5381 .- 0007-1188. ; 156, s. 466-474
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Tidskriftsartikel (refereegranskat)abstract
- Background: Bile duct obstruction is associated with hepatic accumulation of leukocytes and liver injury. The aim of this study was to evaluate the effect of simvastatin on cholestasis-induced liver inflammation and tissue damage. Experimental approach: C57BL/6 mice were treated with simvastatin (0.02 and 0.2 mg.kg(-1)) and vehicle before and after undergoing bile duct ligation (BDL) for 12 h. Leukocyte recruitment and microvascular perfusion in the liver were analysed using intravital fluorescence microscopy. CXC chemokines in the liver were determined by enzyme-linked immunosorbent assay. Liver damage was monitored by measuring serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Hepatic levels of myeloperoxidase (MPO) were also determined. Key results: Administration of 0.2 mg.kg(-1) simvastatin decreased ALT and AST by 87% and 83%, respectively, in BDL mice. This dose of simvastatin reduced hepatic formation of CXC chemokines by 37-82% and restored sinusoidal perfusion in cholestatic animals. Moreover, BDL-induced leukocyte adhesion in sinusoids and postsinusoidal venules, as well as MPO levels in the liver, was significantly reduced by simvastatin. Notably, administration of 0.2 mg.kg(-1) simvastatin 2 h after BDL induction also decreased cholestatic liver injury and inflammation. Conclusions and implications: These findings show that simvastatin protects against BDL-induced liver injury. The hepatoprotective effect of simvastatin is mediated, at least in part, by reduced formation of CXC chemokines and leukocyte recruitment. Thus, our novel data suggest that the use of statins may be an effective strategy to protect against the hepatic injury associated with obstructive jaundice.
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- Feinberg, Alexandra J., et al.
(författare)
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X-ray diffractive imaging of highly ionized helium nanodroplets
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Finding the lowest energy configuration of N unit charges on a sphere, known as Thomson's problem, is a long-standing query which has only been studied via numerical simulations. We present its physical realization using multiply charged He nanodroplets. The charge positions are determined by x-ray coherent diffractive imaging with Xe as a contrast agent. In neutral droplets, filaments resulting from Xe atoms condensing on quantum vortices are observed. Unique to charged droplets, however, Xe clusters that condense on charges are distributed on the surface in lattice-like structures, introducing He droplets as experimental model systems for the study of Thomson's problem.
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| 7. |
- Roebbert, Y., et al.
(författare)
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Fractionation of Fe and Cu isotopes in acid mine tailings : Modification and application of a sequential extraction method
- 2018
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Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 493, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- Sulfidic mine tailings have a high potential for contamination of the environment by triggering acid mine drainage. Hence, it is crucial to understand metal mobilization processes and to develop monitoring tools. Metal isotope fingerprinting as a potential monitoring tool for metal sulfide oxidation processes was in the focus of this study by using stable isotope signatures of Cu and Fe. For Fe, a six-step sequential extraction method was applied, in order to separate potential Fe-bearing minerals (water-soluble, exchangeable fraction, Fe(III)(oxyhydr)oxides, Fe-oxides, sulfides and organic compounds and residual/silicates). For Cu, this method was modified into a four step extraction method (water-soluble, exchangeable fraction, oxalate fraction/bound to Fe-oxides and sulfides/residual). To verify accuracy and precision of the sequential extraction method for metal isotope analysis, isotope fractionation during the extraction procedure was investigated employing minerals for which the mineral composition and the isotopic composition was known. The developed procedure is suitable to separate target minerals with only a small loss in the elemental budget. No significant isotope fractionation was observed during the extraction procedure.Application of this method on two sites of porphyry copper mine tailings in the Atacama Desert in Chile (Chañaral bay) revealed several implications about the mobilization of Fe and Cu in an environmental setting. Iron contents and Fe isotope compositions are homogeneous with depth (0–61 cm; δ56Fe ~0.2–0.3‰) for the bulk and the Fe(hyr)oxide fraction and only the deepest samples at ~60 cm exhibited lower δ56Fe values (~0‰), which are likely related to the occurrence of an alluvium at this depth. The Fe silicate fraction shows higher δ56Fe values (0.6–0.9‰), most likely because of preferential leaching of the light Fe isotopes. This consequently indicates a more pronounced Fe isotope fractionation with depth, as is expected from longer weathering. The Fe sulfide fraction is isotopically lighter compared to the Fe(hydr)oxide fraction, because during sulfide oxidation the heavy Fe isotopes prefer the oxidized forms and oxidative precipitation results in an enriched Fe isotopic signature for Fe(hydr)oxides. The Cu isotope compositions of all bulk samples and individual fractions (except the Cu sulfides) of one site (Ch1) exhibited a decrease of the δ65Cu values from the depth towards the surface, i.e. in agreement with the capillary water rise in the arid climate. A correlation of δ65Cu with pH indicates preferential adsorption of 65Cu on Fe(oxy)hydroxides at site Ch1, which is evident by a change of δ65Cu from 0.5‰ to −0.7‰ in the water-soluble fraction. At another site (Ch12), where pH at depths was potentially not high enough for the formation of Fe-minerals that could adsorb Cu, only minor Cu isotope fractionation was observed in the water-soluble fraction. The Cu sulfide fraction at site Ch1 exhibits higher δ65Cu values with an increase from the bottom (0.42‰) to the surface (0.92‰), which might be related to preferential leaching of the light isotopes, e.g. by microorganisms.
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