| 1. |
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| 2. |
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| 3. |
- Brownstein, Catherine A., et al.
(author)
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An international effort towards developing standards for best practices in analysis, interpretation and reporting of clinical genome sequencing results in the CLARITY Challenge
- 2014
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In: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 15:3, s. R53-
-
Journal article (peer-reviewed)abstract
- Background: There is tremendous potential for genome sequencing to improve clinical diagnosis and care once it becomes routinely accessible, but this will require formalizing research methods into clinical best practices in the areas of sequence data generation, analysis, interpretation and reporting. The CLARITY Challenge was designed to spur convergence in methods for diagnosing genetic disease starting from clinical case history and genome sequencing data. DNA samples were obtained from three families with heritable genetic disorders and genomic sequence data were donated by sequencing platform vendors. The challenge was to analyze and interpret these data with the goals of identifying disease-causing variants and reporting the findings in a clinically useful format. Participating contestant groups were solicited broadly, and an independent panel of judges evaluated their performance. Results: A total of 30 international groups were engaged. The entries reveal a general convergence of practices on most elements of the analysis and interpretation process. However, even given this commonality of approach, only two groups identified the consensus candidate variants in all disease cases, demonstrating a need for consistent fine-tuning of the generally accepted methods. There was greater diversity of the final clinical report content and in the patient consenting process, demonstrating that these areas require additional exploration and standardization. Conclusions: The CLARITY Challenge provides a comprehensive assessment of current practices for using genome sequencing to diagnose and report genetic diseases. There is remarkable convergence in bioinformatic techniques, but medical interpretation and reporting are areas that require further development by many groups.
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| 4. |
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| 5. |
- Abelev, Betty, et al.
(author)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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In: Journal of High Energy Physics. - 1029-8479. ; :11
-
Journal article (peer-reviewed)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 6. |
- Ahmed, Engy, et al.
(author)
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The Role of Microorganisms in the diversity and distribution of siderophores in Podzolic Forest Soil
- 2013
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In: Mineralogical magazine. - 0026-461X .- 1471-8022. ; 77:2, s. 161--208(48)
-
Journal article (other academic/artistic)abstract
- Iron is a key component of the chemical architecture of the biosphere. Due to the low bioavailability of iron in the environment, microorganisms have developed specific uptake strategies. The most important one is the production of siderophores, which are operationally defined as low-molecular-mass biogenic Fe (III)-binding compounds which may greatly increase bioavailability of Fe [1]. One of the primary biogeochemical functions of siderophores is therefore to increase Fe bioavailability by promoting the dissolution of iron-bearing minerals [2]. This study aims to understand the role of microorganisms in the chemical diversity and distribution of siderophores in podzol soil and how this diversity can contribute to the bioavailability of Fe in forest soil.Soil samples were collected from an experimental site in the area of Bispgården in central Sweden (63°07′N, 16°70′E) from the O (organic), E (eluvial), B1 (upper illuvial), and C (mineral) horizons. Concentration and chemical composition of dissolved and adsorbed siderophores in the soil samples were determined using colorimetric assays and high-performance liquid chromatography.The highest siderophore concentrations were found in the O layer and thereafter decreased by depth. Concentrations of dissolved hydroxamate, catecholate and carboxylate siderophores were up to 84, 17 and 0.2 nmol/ g soil, respectively. In contrast, concentrations of adsorbed hydroxamates, catecholates and carboxylates were only up to 1.8, 3 and 0.2 nmol/ g soil, respectively.Siderophore-producing microorganisms were isolated from the same soil samples. Viable fungi, bacteria and actinomycete counts ranged from 7 to 300, from 300 to 1800, and from 0 to 5 cfu/gm, respectively. The highest counts were found in the O and E layers. Only the E layer contained the three types of siderophore-producing microorganisms investigated in this study. Siderophores were extracted from culture filtrates of the isolated microorganisms when grown under iron-limited conditions. These extracts varied considerably in siderophore composition. Fungal isolates produced up to 183 μM of hydroxamates, especially those isolated from the O layer, whereas bacteria and actinomycete isolated from the O and E layers of the soil produced high amounts of carboxylate, catecholate and hydroxamate siderophores. Actinomycete produced up to 93 μM of hydroxamates and 47 μM of catecholates, while bacteria produced up to 34 μM of carboxylates and up to 14 μM of catecholates.The depth variability in concentration and chemical composition and the good correlation between abundance of siderophore-producing microorganisms and siderophore soil concentrations strongly suggest that these siderophore-producing microorganisms play an important role in the mobilization of iron in the podzol soil that may be important in iron availability to plants in forest environment.[1] Clay et al. (1981) Biochemistry 20, 2432-2436. [2] Duckworth et al. (2009) ChemGeol 260, 149-158.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Bohlin, Hanna, et al.
(author)
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Point source influences on the carbon and nitrogen geochemistry of sediments in the Stockholm inner archipelago, Sweden
- 2006
-
In: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 366:1, s. 337-349
-
Journal article (peer-reviewed)abstract
- This study reports analyses of carbon and nitrogen content, and δ15N and δ13C in sediments of the Höggarnsfjärden Bay near Stockholm. Samples have been taken upstream, near, and downstream of a point source of processed leach water from a garbage dump. The surface sediment at the upstream and downstream sites has δ15N and δ13C close to the expected background of the area, even though a contribution from the leach water can be observed downstream of the point source. The sediment close to the outflow is strongly influenced by the carbon and nitrogen in the leach water.
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| 11. |
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| 12. |
- de Souza, Claudio M. D., et al.
(author)
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Interaction of forsterite-91 with distilled water and artificial seawater : a prebiotic chemistry experiment
- 2013
-
In: International Journal of Astrobiology. - 1473-5504 .- 1475-3006. ; 12:2, s. 135-143
-
Journal article (peer-reviewed)abstract
- In the present work, the interactions between forsterite-91 with distilled water and forsterite-91 with artificial seawater were studied at two pHs (2.0 and 8.0) using different techniques. A large increase in pH was observed for samples incubated at an initially acidic pH (2.0) due to the dissolution of forsterite-91 in distilled water and artificial seawater. Thus, in acidic hydrothermal vents, an increase in the amount of hydrocarbons and magnetite should be expected due to the release of Fe(II). The pH(PZC) decreased and the pH(IEP) increased when forsterite-91 was treated with distilled water and artificial seawater. The ions from the artificial seawater had an effect on zeta potential. Scanning electron microscopy (SEM) images and X-ray diffractograms showed halite in the samples of forsterite-91 mixed with artificial seawater. The presence of halite or adsorption of ions on the surface of forsterite-91 could affect the synthesis of magnetite and hydrocarbons in hydrothermal vents, due to a decrease in the dissolution rates of forsterite-91. The dissolution of forsterite-91 yields low concentrations of Fe(III) and Mn(II) as detected by electron paramagnetic resonance (EPR) spectroscopy. Microanalysis of forsterite-91 showed a higher amount of Mn, with an oxidation that was likely not + II, as Mn in supernatant solutions was only detected by EPR spectroscopy after mixing with artificial seawater at pH 2.0. As Fe(III) and Mn(II) are catalyst constituents of magnetite and manganese oxide, respectively, their presence is important for synthesis in hydrothermal vents. Etch pits were observed only in the forsterite-91 sample mixed with distilled water at pH 8.0. Na, Cl, S, Ca and K were detected in the samples mixed with artificial seawater by SEM-EDS. Si, Mg, Fe and Al were detected in almost all supernatant samples due to forsterite-91 dissolution. Cr was not dissolved in the experiments, thus Cr in the mineral could serve as an effective catalyst for Fischer Tropsch Types (FTT) reactions in hydrothermal vent systems. X-ray diffractograms of the original forsterite-91 also showed peaks arising from zeolites and clinochlore. After the samples were treated with artificial seawater, X-ray diffractograms showed the dissolution of zeolite. Experiments should be performed in the natural environment to verify the potential for zeolites to act as a catalyst in hydrothermal vents.
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| 13. |
- Ehrenfreund, Pascale, et al.
(author)
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The evolution of organic matter in space
- 2011
-
In: Philosophical Transactions. Series A. - London : The Royal Society. - 1364-503X .- 1471-2962. ; 369:1936, s. 538-554
-
Journal article (peer-reviewed)abstract
- Carbon, and molecules made from it, have already been observed in the early Universe. During cosmic time, many galaxies undergo intense periods of star formation, during which heavy elements like carbon, oxygen, nitrogen, silicon and iron are produced. Also, many complex molecules, from carbon monoxide to polycyclic aromatic hydrocarbons, are detected in these systems, like they are for our own Galaxy. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly high number of molecules that are used in contemporary biochemistry on the Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites and interplanetary dust particles. Large quantities of extra-terrestrial material were delivered via comets and asteroids to young planetary surfaces during the heavy bombardment phase. Monitoring the formation and evolution of organic matter in space is crucial in order to determine the prebiotic reservoirs available to the early Earth. It is equally important to reveal abiotic routes to prebiotic molecules in the Earth environments. Materials from both carbon sources (extra-terrestrial and endogenous) may have contributed to biochemical pathways on the Earth leading to life’s origin. The research avenues discussed also guide us to extend our knowledge to other habitable worlds.
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| 14. |
- Fex, Malin, et al.
(author)
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A beta cell-specific knockout of hormone-sensitive lipase in mice results in hyperglycaemia and disruption of exocytosis.
- 2009
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In: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 52, s. 271-280
-
Journal article (peer-reviewed)abstract
- AIMS/HYPOTHESIS: The enzyme hormone-sensitive lipase (HSL) is produced and is active in pancreatic beta cells. Because lipids are known to play a crucial role in normal control of insulin release and in the deterioration of beta cell function, as observed in type 2 diabetes, actions of HSL in beta cells may be critical. This notion has been addressed in different lines of HSL knockout mice with contradictory results. METHODS: To resolve this, we created a transgenic mouse lacking HSL specifically in beta cells, and characterised this model with regard to glucose metabolism and insulin secretion, using both in vivo and in vitro methods. RESULTS: We found that fasting basal plasma glucose levels were significantly elevated in mice lacking HSL in beta cells. An IVGTT at 12 weeks revealed a blunting of the initial insulin response to glucose with delayed elimination of the sugar. Additionally, arginine-stimulated insulin secretion was markedly diminished in vivo. Investigation of the exocytotic response in single HSL-deficient beta cells showed an impaired response to depolarisation of the plasma membrane. Beta cell mass and islet insulin content were increased, suggesting a compensatory mechanism, by which beta cells lacking HSL strive to maintain normoglycaemia. CONCLUSIONS/INTERPRETATION: Based on these results, we suggest that HSL, which is located in close proximity of the secretory granules, may serve as provider of a lipid-derived signal essential for normal insulin secretion.
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| 15. |
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| 16. |
- Holm, Nils G.
(author)
-
Att undervisa i religioner
- 2010
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In: Strömstad akademi. - Strömstad : Strömstad Akademi. - 9789186607005 ; , s. 78-81
-
Book chapter (other academic/artistic)
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| 17. |
- Holm, Nils G.
(author)
-
Glasses as sources of condensed phosphates on the early earth
- 2014
-
In: Geochemical Transactions. - : Springer Science and Business Media LLC. - 1467-4866. ; 15, s. 8-
-
Research review (peer-reviewed)abstract
- Procedures for the analysis of phosphorus in geological material normally aims for the determination of the total amount of P expressed as orthophosphate (PO43-) or the differentiation between inorganic and organic P. This is probably due to analytical difficulties but also to the prevalent opinion that the chemistry of phosphorus in geological environments is almost entirely restricted to the mineral apatite. Because of the low solubility of apatite it is, therefore, commonly argued that little P was around for prebiotic chemistry and that pre-biological processes would essentially have had to do without this indispensable element unless it was provided by alternative sources or mechanisms (such as reduction and activation by lightning or delivery to Earth by celestial bodies). It is a paradox that the potential existence of reactive phosphorus compounds, such as the mineral schreibersite - iron phosphide, in geological material on Earth is seldom considered although we are aware of the existence of such compounds in meteorite material. The content of Al2O3 in rocks appears to be important for the speciation of phosphorus and for how strongly it binds to silicates. In general, low alumina seems to promote the existence of isolated charge-balanced phosphorus complexes.
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| 18. |
- Holm, Nils G., et al.
(author)
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Hekla cold springs (Iceland) : groundwater mixing with magmatic gases
- 2010
-
In: Isotopes in environmental and health studies. - : Informa UK Limited. - 1025-6016 .- 1477-2639. ; 46:2, s. 180-189
-
Journal article (peer-reviewed)abstract
- We have analysed the chemical and stable isotope compositions of four springwaters situated just northwest of the Hekla volcano, where cold water emerges from the base of the lava flows. The stable isotope ratios of water (H, O), dissolved inorganic carbon (C) and sulphate (S) were used to determine whether magmatic gases are mixing with the groundwater. The waters can be characterised as Na-HCO3 type. The results show that deep-seated gases mix with groundwater, substantially affecting the concentration of solutes and the isotopic composition of dissolved carbon and sulphate.
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| 19. |
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| 20. |
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| 21. |
- Holm, Nils G., et al.
(author)
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Serpentinization and the Formation of H-2 and CH4 on Celestial Bodies (Planets, Moons, Comets)
- 2015
-
In: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 15:7, s. 587-600
-
Research review (peer-reviewed)abstract
- Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)(2)SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H-2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H-2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H-2 and H-2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H-2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H-2 capable of reducing carbon to organic compounds.
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| 22. |
- Holm, Nils G.
(author)
-
The significance of Mg in prebiotic geochemistry
- 2012
-
In: Geobiology. - : Wiley. - 1472-4677 .- 1472-4669. ; 10:4, s. 269-279
-
Research review (peer-reviewed)abstract
- Magnesium plays a special role in biochemistry because of its ability to coordinate six oxygen atoms efficiently in its first coordination shell. Such oxygen atoms may be part of one or two charged oxyanions, which means that Mg2+ can, for instance, tie together two different phosphate groups that are located at distance from each other in a macromolecule, and in this way be responsible for the folding of molecules like RNA. This property of Mg2+ also helps the stabilization of diphosphate and triphosphate groups of nucleotides, as well as promoting the condensation of orthophosphate to oligophosphates, like pyrophosphate and trimetaphosphate. Borates, on the other hand, are known to promote the formation of nucleobases and carbohydrates, ribose in particular, which is yet another constituent of nucleotides. The oldest borate minerals that we find on Earth today are magnesium borates. Dissolved borate stabilizes pentose sugars by forming complexes with cis-hydroxyl groups. In the furanose form of ribose, the preferential binding occurs to the 2 and 3 carbon, leaving the 5 carbon free for phosphorylation. The central role of Mg2+ in the function of ribozymes and its archaic position in ribosomes, and the fact that magnesium generally has coordination properties different from other cations, suggests that the inorganic chemistry of magnesium had a key position in the first chemical processes leading to the origin and early evolution of life.
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| 23. |
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| 24. |
- Ivarsson, Magnus, 1975-, et al.
(author)
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Biogenic Mn-oxides in subseafloor basalts
- 2015
-
In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:6
-
Journal article (peer-reviewed)abstract
- The deep biosphere of the subseafloor basalts is recognized as a major scientific frontier in disciplines like biology, geology, and oceanography. Recently, the presence of fungi in these environments has involved a change of view regarding diversity and ecology. Here, we describe fossilized fungal communities in vugs in subseafloor basalts from a depth of 936.65 metres below seafloor at the Detroit Seamount, Pacific Ocean. These fungal communities are closely associated with botryoidal Mn oxides composed of todorokite. Analyses of the Mn oxides by Electron Paramagnetic Resonance spectroscopy (EPR) indicate a biogenic signature. We suggest, based on mineralogical, morphological and EPR data, a biological origin of the botryoidal Mn oxides. Our results show that fungi are involved in Mn cycling at great depths in the seafloor and we introduce EPR as a means to easily identify biogenic Mn oxides in these environments.
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| 25. |
- Kobayashi, Kensei, et al.
(author)
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Laboratory Studies of Methane and Its Relationship to Prebiotic Chemistry
- 2017
-
In: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 17:8, s. 786-812
-
Research review (peer-reviewed)abstract
- To examine how prebiotic chemical evolution took place on Earth prior to the emergence of life, laboratory experiments have been conducted since the 1950s. Methane has been one of the key molecules in these investigations. In earlier studies, strongly reducing gas mixtures containing methane and ammonia were used to simulate possible reactions in the primitive atmosphere of Earth, producing amino acids and other organic compounds. Since Earth's early atmosphere is now considered to be less reducing, the contribution of extraterrestrial organics to chemical evolution has taken on an important role. Such organic molecules may have come from molecular clouds and regions of star formation that created protoplanetary disks, planets, asteroids, and comets. The interstellar origin of organics has been examined both experimentally and theoretically, including laboratory investigations that simulate interstellar molecular reactions. Endogenous and exogenous organics could also have been supplied to the primitive ocean, making submarine hydrothermal systems plausible sites of the generation of life. Experiments that simulate such hydrothermal systems where methane played an important role have consequently been conducted. Processes that occur in other Solar System bodies offer clues to the prebiotic chemistry of Earth. Titan and other icy bodies, where methane plays significant roles, are especially good targets. In the case of Titan, methane is both in the atmosphere and in liquidospheres that are composed of methane and other hydrocarbons, and these have been studied in simulation experiments. Here, we review the wide range of experimental work in which these various terrestrial and extraterrestrial environments have been modeled, and we examine the possible role of methane in chemical evolution.
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| 26. |
- Konn, C., et al.
(author)
-
New insight into the contributions of thermogenic processes and biogenic sources to the generation of organic compounds in hydrothermal fluids
- 2011
-
In: Geobiology. - : Wiley. - 1472-4677 .- 1472-4669. ; 9:1, s. 79-93
-
Journal article (peer-reviewed)abstract
- Experiments on hydrothermal degradation of Pyrococcus abyssi biomass were conducted at elevated pressure (40 MPa) over a 200–450 °C temperature range in sapphire reaction cells. Few organic compounds could be detected in the 200 °C experiment. This lack was attributed to an incomplete degradation of P. abyssi cells. On the contrary, a wide range of soluble organic molecules were generated at temperatures ≥350 °C including toluene, styrene, C8–C16 alkyl-benzenes, naphthalene, C11–C16 alkyl-naphthalenes, even carbon number C12–C18 polycyclic aromatic hydrocarbons, C15–C18 alkyl-phenanthrenes and C8:0–C16:0 n-carboxylic acids. The effect of time on the final organic composition of the degraded P. abyssi solutions at 350 °C was also investigated. For that purpose the biomass was exposed for 10, 20, 60, 90, 270 and 720 min at 350 °C. We observed a similar effect of temperature and time on the chemical diversity obtained. In addition, temperature and time increased the degree of alkylation of alkyl-benzenes. This study offers additional evidence that a portion of the aliphatic hydrocarbons present in the fluids from the Rainbow ultramafic-hosted hydrothermal field may be abiogenic whereas a portion of the aromatic hydrocarbons and n-carboxylic acids may have a biogenic origin. We suggest that aromatic hydrocarbons and linear fatty acids at the Rainbow site may be derived directly from thermogenic alteration of material from the sub-seafloor biosphere. Yet we infer that the formation and dissolution of carboxylic acids in hydrothermal fluids may be controlled by other processes than in our experiments.
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| 27. |
- Konn, C., et al.
(author)
-
The Production of Methane, Hydrogen, and Organic Compounds in Ultramafic-Hosted Hydrothermal Vents of the Mid-Atlantic Ridge
- 2015
-
In: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 15:5, s. 381-399
-
Research review (peer-reviewed)abstract
- Both hydrogen and methane are consistently discharged in large quantities in hydrothermal fluids issued from ultramafic-hosted hydrothermal fields discovered along the Mid-Atlantic Ridge. Considering the vast number of these fields discovered or inferred, hydrothermal fluxes represent a significant input of H-2 and CH4 to the ocean. Although there are lines of evidence of their abiogenic formation from stable C and H isotope results, laboratory experiments, and thermodynamic data, neither their origin nor the reaction pathways generating these gases have been fully constrained yet. Organic compounds detected in the fluids may also be derived from abiotic reactions. Although thermodynamics are favorable and extensive experimental work has been done on Fischer-Tropsch-type reactions, for instance, nothing is clear yet about their origin and formation mechanism from actual data. Since chemolithotrophic microbial communities commonly colonize hydrothermal vents, biogenic and thermogenic processes are likely to contribute to the production of H-2, CH4, and other organic compounds. There seems to be a consensus toward a mixed origin (both sources and processes) that is consistent with the ambiguous nature of the isotopic data. But the question that remains is, to what proportions? More systematic experiments as well as integrated geochemical approaches are needed to disentangle hydrothermal geochemistry. This understanding is of prime importance considering the implications of hydrothermal H-2, CH4, and organic compounds for the ocean global budget, global cycles, and the origin of life.
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| 28. |
- Mousis, Olivier, et al.
(author)
-
Methane Clathrates in the Solar System
- 2015
-
In: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 15:4, s. 308-326
-
Research review (peer-reviewed)abstract
- We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate layers may exist on Pluto as well.
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| 29. |
- Neubeck, Anna, et al.
(author)
-
Formation of H(2) and CH(4) by weathering of olivine at temperatures between 30 and 70 degrees C
- 2011
-
In: Geochemical Transactions. - : BioMed Central / Chemistry Central. - 1467-4866. ; 12:6
-
Journal article (peer-reviewed)abstract
- Hydrocarbons such as CH(4) are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100 degrees C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH(4) through its redox lowering and water splitting properties. Knowledge about the CH(4) and H(2) formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH(4) and for CO(2) sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH(4) and H(2) formation potential of forsteritic olivine. The results show low temperature CH(4) production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH(4) source trapped in the crystal structure of the olivine showed no signs of incorporated CH(4). Also, the available sources of organic carbon were not enough to support the total amount of CH(4) detected in our experiments. There was also a linear relationship between silica release into solution and the net CH(4) accumulation into the incubation bottle headspaces suggesting that CH(4) formation under these conditions could be a qualitative indicator of olivine dissolution. less thanbrgreater than less thanbrgreater thanIt is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH(4), because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH(4) formation both on Earth and on other terrestrial bodies.
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| 30. |
- Neubeck, Anna, et al.
(author)
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Isotopic Signatures of Carbon in the 'Los Pobres' Graphite Mine, Ronda, Spain
- 2020
-
In: Journal of Petrology. - : Oxford University Press (OUP). - 0022-3530 .- 1460-2415. ; 61:4
-
Journal article (peer-reviewed)abstract
- Graphite formation temperatures in the ‘Los Pobres’ mine within the Ronda peridotite, Spain, previously reported to be between 770 and 820 °C, have been reinterpreted based on new temperature measurements using Raman spectroscopy. Additional in situ and bulk stable carbon isotopic measurements and fluid inclusion studies contributed to improved understanding of parts of the graphite formation process. Raman spectroscopy revealed that the formation of the ‘Los Pobres’ graphite extends to temperatures as low as 500 °C, indicating a broader temperature range than previously reported. Stable carbon isotopes and temperature estimates suggest two different crystallization events, followed by a late hydrothermal alteration of the host rock. The first event occurred at temperatures higher than ∼600°C, in which crystalline graphite was formed with a mixed 13C composition as a result of the mixing of two different carbon-bearing sources. The second graphite formation event took place below ∼600°C, within the same system, but with lower purity and crystallinity of the graphite. In the third event, the temperature decreased to less than 550 °C, and hydrothermal fluids altered the host rock, precipitating silica and iron oxides in veins penetrating both the host rock and the deposited graphite.
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| 31. |
- Neubeck, Anna, et al.
(author)
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Olivine alteration and H-2 production in carbonate-rich, low temperature aqueous environments
- 2014
-
In: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 96, s. 51-61
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Journal article (peer-reviewed)abstract
- Hydrous alteration of olivine is capable of producing molecular hydrogen (H-2) under a wide variety of hydrothermal conditions. Although olivine hydrolysis (i.e., serpentinization) has commonly been assessed at elevated temperatures ( > 100 degrees C), the nature of these reactions in relation to H-2 production at lower temperatures has not been systematically evaluated, especially with regard to carbonate-rich fluids. Specifically, carbonate formation may kinetically infringe on geochemical routes related to serpentinization and H-2 production at lower temperatures. Here time-dependent interactions of solid, liquid, and gaseous phases with respect to olivine hydrolysis in a carbonate-rich solution (20 mM HCO3-) at 30, 50 and 70 degrees C for 315 days is investigated experimentally. Within the first two months, amorphous Si-rich (i.e., talc-like) and carbonate phases precipitated; however, no inhibition of olivine dissolution is observed at any temperature based on surface chemistry analyses. High-resolution surface analyses confirm that precipitates grew as spheroids or vertically to form topographic highs allowing further dissolution of the free olivine surfaces and exposing potential catalysts. Despite no magnetite (Fe3O4) being detected, H-2 increased with time in experiments carried out at 70 degrees C, indicating an alternative coupled route for Fe oxidation and H-2 production. Spectrophotometry analyses show that aqueous Fe(II) is largely converted to Fe(III) potentially integrating into other phases such as serpentine and talc, thus providing a viable pathway for H-2 production. No increase in H-2 production was observed in experiments carried out at 30 and 50 degrees C supporting observations that incorporation of Fe(II) into carbonates occurred faster than the intertwined processes of olivine hydrolysis and Fe(III) oxidation. Overall, carbonate formation is confirmed to be a major influence related to H-2 production in low-temperature serpentinization systems.
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| 32. |
- Preiner, Martina, et al.
(author)
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Serpentinization : Connecting Geochemistry, Ancient Metabolism and Industrial Hydrogenation
- 2018
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In: Life. - : MDPI AG. - 2075-1729.
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Research review (peer-reviewed)abstract
- Rock-water-carbon interactions germane to serpentinization in hydrothermal vents have occurred for over 4 billion years, ever since there was liquid water on Earth. Serpentinization converts iron(II) containing minerals and water to magnetite (Fe3O4) plus H-2. The hydrogen can generate native metals such as awaruite (Ni3Fe), a common serpentinization product. Awaruite catalyzes the synthesis of methane from H-2 and CO2 under hydrothermal conditions. Native iron and nickel catalyze the synthesis of formate, methanol, acetate, and pyruvate-intermediates of the acetyl-CoA pathway, the most ancient pathway of CO2 fixation. Carbon monoxide dehydrogenase (CODH) is central to the pathway and employs Ni-0 in its catalytic mechanism. CODH has been conserved during 4 billion years of evolution as a relic of the natural CO2-reducing catalyst at the onset of biochemistry. The carbide-containing active site of nitrogenase-the only enzyme on Earth that reduces N(2)is probably also a relic, a biological reconstruction of the naturally occurring inorganic catalyst that generated primordial organic nitrogen. Serpentinization generates Fe3O4 and H-2, the catalyst and reductant for industrial CO2 hydrogenation and for N-2 reduction via the Haber-Bosch process. In both industrial processes, an Fe3O4 catalyst is matured via H-2-dependent reduction to generate Fe5C2 and Fe2N respectively. Whether serpentinization entails similar catalyst maturation is not known. We suggest that at the onset of life, essential reactions leading to reduced carbon and reduced nitrogen occurred with catalysts that were synthesized during the serpentinization process, connecting the chemistry of life and Earth to industrial chemistry in unexpected ways.
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| 33. |
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| 34. |
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| 35. |
- Ståhle, Göran, 1967-
(author)
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Det religiösa självet i praktik vid ett hinduiskt gudinnetempel : Ett kulturpsykologiskt angreppssätt för religionspsykologi
- 2004
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Doctoral thesis (other academic/artistic)abstract
- The main objective of this dissertation is to contribute to the psychology of religion in two ways. First, it adds to theory development in the field, and second, it provides an original field study of Hindu everyday-religiosity. This dual-focused objective is met through the development of theory for a practice-oriented cultural psychology of religion, grounded in a study of a Hindu goddess-temple in Banaras (Varanasi), India. The cultural psychological approach makes use of Bourdieu’s concept “habitus”. It is argued that employing this concept in theory development overcomes a dualism of culture and self, and provides an alternative to previous models in the psychology of religion that interpret religiosity in either intrapsychical or intersubjective terms. Further, it is argued that the concept can interpret culture-specific features in Hindu religiosity, such as an emphasis on practical activity and on a non-dualistic view of person and world.A model of a “Religious Self in Practice” is outlined, which integrates features from theories of “self as narrative practice” and Bell’s concept “ritualization”. The religious self is seen as a construction of relational and practical processes, a product of individuals participating in cultural practices of religiosity, manifested in a specific local site. Specific persons master the pre-given conventions of religious self-construction in individual, creative ways. The study argues that a temple is such a site in a Hindu context. Ethnography is used to study the cultural practices of the religious self at the site, and life story interview to study a sample of seven individual ways of mastering these practices. The study analyzes sacred status at the temple as being an interplay of individuals’ devotions and common practices of religiosity. This practical logic is also identified in the life stories of the devotees as narrative practice of the religious self in relation to the Goddess.
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| 36. |
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