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The melting mechanism of Na 2 SiO 3 , a crystal with pyroxene structure, includes three distinct reactions. All are driven by heating with each reaction commencing at a different temperature. The first two reactions proceed within the crystal at temperatures well below the melting point and are expressed by distinctive crystallographic, calorimetric, and Raman spectroscopic changes to the crystal. With the reactions identified and explained for Na 2 SiO 3 (c) and the melting mechanism elucidated, the Na 2 SiO 3 system becomes the “Rosetta Stone” by which to decipher the melting mechanisms of all pyroxenes and other silicate minerals. The first reaction produces itinerant Na + within the crystal. Itinerancy results from dissociation of some NBO-Na bonds due to heating, with dissociation commencing at ~770 K. The reaction proceeds according to: Si-O-Na → Si-O – + Na + . The Si-O − moiety remains attached to its SiO 3 chain and it is charged because one of its NBO atoms has no associated Na ion. The second reaction is characterized by the appearance of a Q 3 band in Raman spectra of the crystal at temperatures >770 K. It is produced via a polymerization reaction involving the Si-O − species, a product of the first reaction, and a Q 2 species of an adjacent SiO 3 chain according to: 1 Na 2 -Q 2 + 1 ( Na 1 -Q 2 ) − → 2 Na 1 -Q 3 + Na + + O 2 − . Na atoms are included with each Q species to preserve mass balances and (Na 1 -Q 2 ) − is equivalent to the Si-O − species. The produced Q 3 species form cross-chain linkages that affect the crystallographic properties of the crystal. They are responsible for the cessation of thermal expansion of the Na 2 SiO 3 unit cell in the a – b axial plane at T >770 K, and the near-constancy of a and b unit-cell parameters between ~770 and ~1300 K. The presence of Q 3 species in Raman spectra and the inhibited expansion in the a – b axial plane provide exceedingly strong evidence for this reaction. The third reaction commences at ~1200 K where Q 1 Raman band first appears. It can be produced only through depolymerization of Q 2 chains according to: 2 Na 2 -Q 2 + 2 Na + + O 2 − → 2 Na 3 -Q 1 where Na + and O 2− are itinerant species produced by the second reaction. With conversion of Q 2 to Q 1 species, SiO 3 chains are ruptured, long-range order is lost, and melt is produced at 1362 K. The last two reactions proceed by nucleophilic substitution where Si centers are attacked to form fivefold-coordinated activated complexes. Si-O − acts as nucleophile in the second reaction (producing Q 3 species), and O 2− acts as nucleophile in the third reaction (producing Q 1 ). Taken in reverse, these mechanisms describe the formation of nuclei in crystallizing melts and in addition provide insight into the elusive changes that occur at the glass transition. Elucidation of the melting mechanism could thus provides a unified framework within which melting, crystallization, and the glass transition can be understood.

Made available in DSpace on 2021-06-25T11:52:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-04 European Regional Development Fund (Centre of Excellence EcolChange) University of Tartu (Estonian Research Council ) Moscow State University Natural Sciences and Engineering Research Council of Canada Discovery Grant Russian Science Foundation Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Swedish Research Council (Vetenskapsradet) The arbuscular mycorrhizal (AM) fungi are a globally distributed group of soil organisms that play critical roles in ecosystem function. However, the ecological niches of individual AM fungal taxa are poorly understood. We collected > 300 soil samples from natural ecosystems worldwide and modelled the realised niches of AM fungal virtual taxa (VT; approximately species-level phylogroups). We found that environmental and spatial variables jointly explained VT distribution worldwide, with temperature and pH being the most important abiotic drivers, and spatial effects generally occurring at local to regional scales. While dispersal limitation could explain some variation in VT distribution, VT relative abundance was almost exclusively driven by environmental variables. Several environmental and spatial effects on VT distribution and relative abundance were correlated with phylogeny, indicating that closely related VT exhibit similar niche optima and widths. Major clades within the Glomeraceae exhibited distinct niche optima, Acaulosporaceae generally had niche optima in low pH and low temperature conditions, and Gigasporaceae generally had niche optima in high precipitation conditions. Identification of the realised niche space occupied by individual and phylogenetic groups of soil microbial taxa provides a basis for building detailed hypotheses about how soil communities respond to gradients and manipulation in ecosystems worldwide. Univ Tartu, Inst Ecol & Earth Sci, EE-51005 Tartu, Estonia Univ Manchester, Sch Earth & Environm Sci, Manchester M13 9PL, Lancs, England Qatar Univ, Environm Sci Ctr, Doha 2713, Qatar Moscow Lomonsov State Univ, Dept Ecol & Plant Geog, Fac Biol, Moscow 119991, Russia King Saud Univ, Zool Dept, Coll Sci, Riyadh 11451, Saudi Arabia Russian Acad Sci, Inst Biol Problems, North Far East Branch, Magadan 685000, Russia Swedish Univ Agr Sci, Dept Ecol, S-75651 Uppsala, Sweden Univ Alberta, Dept Biol Sci, Edmonton, AB T6G 2E9, Canada Univ Nacl Cordoba, Inst Multidisciplinario Biol Vegetal, CONICET, X5000HUA, Cordoba, Argentina Univ Nacl Rio Cuarto, Fac Agron & Vet, Dept Biol Agr, X5804BYA, Cordoba, Argentina Univ Penn, Dept Biol, Philadelphia, PA 19104 USA Russian Acad Sci, Inst Biol Problems Cryolithozone, Siberian Branch, Yakutsk 677000, Russia Univ Djibouti, Dept Rech Sci Environm, Private Bag 1904, Djibouti, Djibouti Univ Aveiro, Dept Biol, P-3810193 Aveiro, Portugal Univ Aveiro, CESAM, P-3810193 Aveiro, Portugal Thompson Rivers Univ, Dept Nat Resource Sci, Kamloops, BC V2C 0C8, Canada Jules Verne Univ Picardie, Ecol & Dynam Syst Anthropises, F-80037 Amiens, France Univ Namibia, Dept Wildlife Management & Ecotourism, Private Bag 1096, Katima Mulilo, Namibia RAS, FEB, Bot Garden Inst, Vladivostok 690024, Russia Univ Calif Riverside, Dept Microbiol & Plant Pathol, Riverside, CA 92521 USA Univ Western Ontario, Dept Biol, London, ON N6A 5B7, Canada UPR Forets & Societes, CIRAD, Yamoussoukro, Cote Ivoire Univ Montpellier, Forets & Societes, CIRAD, F-34000 Montpellier, France INP HB, Inst Natl Polytech Felix Houphouet Boigny, Yamoussoukro, Cote Ivoire Beni Suef Univ, Bot & Microbiol Dept, Fac Sci, Bani Suwayf 62511, Egypt Czech Acad Sci, Inst Microbiol, Prague 14220, Czech Republic Charles Univ Prague, Dept Expt Plant Biol, Fac Sci, Prague 12843, Czech Republic Estonian Univ Life Sci, Chair Biodivers & Nat Tourism, EE-51006 Tartu, Estonia Murdoch Univ, Harry Butler Inst, Iluka Chair Vegetat Sci & Biogeog, Perth, WA 6150, Australia Stellenbosch Univ, Dept Geog & Environm Studies, ZA-7602 Stellenbosch, South Africa Univ Rwanda, Sch Sci, Coll Sci & Technol, Kigali 3900, Rwanda Univ Bern, Inst Plant Sci, CH-3013 Bern, Switzerland Estonian Univ Life Sci, Chair Crop Sci & Plant Biol, EE-51006 Tartu, Estonia Botswana Int Univ Sci & Technol, Dept Biol Sci & Biotechnol, Private Bag 16, Palapye, Botswana Nakhon Phanom Univ, Dept Biol, Nakhon Phanom 48000, Thailand Univ Tartu, Nat Hist Museum, EE-51014 Tartu, Estonia Univ Palermo, Dept Agr Food & Forest Sci, I-90128 Palermo, Italy Univ Bangui, Ctr Studies & Res Pharmacopoeia & Tradit African, Bangui, Cent Afr Republ Inst Amazon Invest Cient Sinchi, Leticia 910001, Amazonas, Colombia Univ Estadual Paulista, Dept Biodivers, BR-13506900 Sao Paulo, Brazil Radboud Univ Nijmegen, Inst Water & Wetland Res, Dept Aquat Ecol & Environm Biol, NL-6525 AJ Nijmegen, Netherlands Univ Tartu, Dept Bot, EE-51005 Tartu, Estonia Univ Estadual Paulista, Dept Biodivers, BR-13506900 Sao Paulo, Brazil University of Tartu: PLTOM20903 (Estonian Research Council ): MOBTP 105 (Estonian Research Council ): MOBERC20 (Estonian Research Council ): PRG352 (Estonian Research Council ): PRG609 (Estonian Research Council ): PRG 1065 (Estonian Research Council ): PRG 1170 (Estonian Research Council ): PRG 1409 Moscow State University: AAAA-A16-116021660039-1 Russian Science Foundation: 19-14-00038 FAPESP: 2016/25197-0 Swedish Research Council (Vetenskapsradet): 2017-05019 Swedish Research Council (Vetenskapsradet): QUEX-CAS-QP-RD-18/19

AimPlant species continue to be moved outside of their native range by human activities. Here, we aim to determine whether, once introduced, plants assimilate into native communities or whether they aggregate, thus forming mosaics of native‐ and alien‐rich communities. Alien species might aggregate in their non‐native range owing to shared habitat preferences, such as their tendency to establish in high‐biomass, species‐poor areas.LocationTwenty‐two herbaceous grasslands in 14 countries, mainly in the temperate zone.Time period2012?2016.Major taxa studiedPlants.MethodsWe used a globally coordinated survey. Within this survey, we found 46 plant species, predominantly from Eurasia, for which we had co‐occurrence data in their native and non‐native ranges. We tested for differences in co‐occurrence patterns of 46 species between their native (home) and non‐native (away) range. We also tested whether species had similar habitat preferences, by testing for differences in total biomass and species richness of the patches that species occupy in their native and non‐native ranges.ResultsWe found the same species to show different patterns of association depending on whether they were in their native or non‐native range. Alien species were negatively associated with native species; instead, they aggregated with other alien species in species‐poor, high‐biomass communities in their non‐native range compared with their native range.Main conclusionsThe strong differences between the native (home) and non‐native (away) range in species co‐occurrence patterns are evidence that the way in which species associate with resident communities in their non‐native range is not species dependent, but is instead a property of being away from their native range. These results thus highlight that species might undergo important ecological changes when introduced away from their native range. Overall, we show origin‐dependent associations that result in novel communities, in which alien‐rich patches exist within a mosaic of native‐dominated communities. Fil: Stotz, Gisela C.. University of Alberta; Canadá Fil: Cahill Jr, James F.. University of Alberta; Canadá Fil: Bennett, Jonathan A.. University of Alberta; Canadá Fil: Carlyle, Cameron N.. University of Alberta; Canadá Fil: Bork, Edward W.. University of Alberta; Canadá Fil: Askarizadeh, Diana. University of Tehran; Israel Fil: Bartha, Sandor. Centre for Ecological Research; Hungría Fil: Beierkuhnlein, Carl. University of Bayreuth; Alemania Fil: Boldgiv, Bazartseren. National University of Mongolia; Mongolia Fil: Brown, Leslie. University of South Africa; Sudáfrica Fil: Cabido, Marcelo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Campetella, Giandiego. Universita Degli Di Camerino; Italia Fil: Chelli, Stefano. Universita Degli Di Camerino; Italia Fil: Cohen, Ofer. Universitat Tel Aviv; Israel Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enrico, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Ensing, David. Queens University; Canadá Fil: Erdenetsetseg, Batdelger. National University of Mongolia; Mongolia Fil: Fidelis, Alessandra. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Garris, Heath W.. Covenant College; Estados Unidos Fil: Henry, Hugh A. L.. Western Ontario University; Canadá Fil: Jentsch, Anke. University of Bayreuth; Alemania Fil: Hassan, Mohammad. Islamic Azad University; Irán Fil: Koorem, Kadri. University of Tartu; Estonia Fil: Manning, Peter. Senckenberg Biodiversity and Climate Research Centre; Alemania Fil: Mitchell, Randall. University of Akron; Estados Unidos Fil: Moora, Mari. University of Tartu; Estonia Fil: Overbeck, Gerhard E.. Universidade Federal do Rio Grande do Sul; Brasil Fil: Pither, Jason. University of British Columbia; Canadá Fil: Reinhart, Kurt O.. United States Department of Agriculture ; Estados Unidos Fil: Sternberg, Marcelo. Universitat Tel Aviv; Israel Fil: Tungalag, Radnaakhand. National University of Mongolia; Mongolia Fil: Undrakhbold, Sainbileg. National University of Mongolia; Mongolia Fil: van Rooyen, Margaretha. University of Pretoria; Sudáfrica Fil: Wellstein, Camilla. Free University of Bozen; Italia Fil: Zobel, Martin. University of Tartu; Estonia Fil: Fraser, Lauchlan H.. Thompson Rivers University; Canadá

International audience; A thermo-responsive end-cap based on a retro-Diels-Alder and subsequent furan elimination reaction was developed. It was used to cap poly(ethyl glyoxylate), allowing end-to-end depolymerization upon thermal triggering. Using a multifunctional derivative for the preparation of block copolymers, thermo-responsive micelles and vesicles were prepared and shown to disassemble upon heating. Thermal degradation could also be triggered indirectly by magnetic field hyperthermia after incorporation of iron oxide nanoparticles into the assemblies.

High-precision stable Ba isotope ratios are reported in a variety of terrestrial samples, undifferentiated primitive meteorites, and calcium–aluminum-rich inclusions (CAIs) from the Allende chondrite. All whole-rock terrestrial and meteorite samples are isotopically indistinguishable at a 50 parts per million (ppm) level per atomic mass unit (amu). Three CAIs are isotopically light, with δ138/137Ba (permil deviation of the 138Ba/137Ba ratio from a terrestrial standard) values down to − 0.6‰ compared to whole-rock meteorites, whereas the matrix is enriched in heavy isotopes (δ138/137Ba: + 0.2‰). Similar light isotope enrichments in CAIs have been previously observed for Eu, Sr, and Ca, while for most other elements CAIs are enriched in the heavier isotopes (e.g. Mg, Fe). Kinetic isotopic fractionation is a possible explanation for the enrichment in the lightest isotopes, either by condensation from a vapor phase enriched in light isotopes by kinetic effects or by kinetic fractionation during non-equilibrium condensation of an undercooled gas as suggested for Ca isotopes. However, the common property of Ba, Eu, and Sr is that they all have a low first ionization potential. We suggest that electromagnetic sorting of ionized species in the early Solar System is a possible alternative mechanism to explain the depletion in heavy isotopes observed in refractory inclusions for those elements.

International audience; The 23 km-diameter well-preserved Haughton impact structure shows a rather unique combination of a positive magnetic anomaly with a negative gravity anomaly over the center of its central uplift. Using a new ground magnetic dataset and several modeling approaches, we investigate the properties and geometry of its central magnetized source. Our results confirm that a km-sized magnetic body with a narrow near-surface extension is necessary to account for the anomaly. Additional measurements of rock magnetic properties of samples of all lithologies encountered in and outside the crater show that the target sedimentary rocks and the vast majority of the Precambrian basement rocks cannot be the source of the magnetic anomaly. While in larger impact structures such magnetic anomalies are often explained by magmatic mafic intrusions or highly magnetic glass lenses in the impact melt rocks, we propose that impact-generated hydrothermal activity enhanced the magnetization of the highly-porous unmelted uplifted basement rocks. Such a process may be considered for the interpretation of the geophysical signature of planetary impact craters.