| 1. |
- Maasri, Alain, et al.
(författare)
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A global agenda for advancing freshwater biodiversity research
- 2022
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 25:2, s. 255-263
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Tidskriftsartikel (refereegranskat)abstract
- Global freshwater biodiversity is declining dramatically, and meeting the challenges of this crisis requires bold goals and the mobilisation of substantial resources. While the reasons are varied, investments in both research and conservation of freshwater biodiversity lag far behind those in the terrestrial and marine realms. Inspired by a global consultation, we identify 15 pressing priority needs, grouped into five research areas, in an effort to support informed stewardship of freshwater biodiversity. The proposed agenda aims to advance freshwater biodiversity research globally as a critical step in improving coordinated actions towards its sustainable management and conservation.
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| 2. |
- Ashuiev, Anton, et al.
(författare)
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Geometry and electronic structure of Yb(iii)[CH(SiMe3)2]3 from EPR and solid-state NMR augmented by computations
- 2024
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - 1463-9076 .- 1463-9084. ; 26:11, s. 8734-8747
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of paramagnetic compounds, in particular regarding the detailed conformation and electronic structure, remains a challenge, and – still today it often relies solely on the use of X-ray crystallography, thus limiting the access to electronic structure information. This is particularly true for lanthanide elements that are often associated with peculiar structural and electronic features in relation to their partially filled f-shell. Here, we develop a methodology based on the combined use of state-of-the-art magnetic resonance spectroscopies (EPR and solid-state NMR) and computational approaches as well as magnetic susceptibility measurements to determine the electronic structure and geometry of a paramagnetic Yb(III) alkyl complex, Yb(III)[CH(SiMe3)2]3, a prototypical example, which contains notable structural features according to X-ray crystallography. Each of these techniques revealed specific information about the geometry and electronic structure of the complex. Taken together, both EPR and NMR, augmented by quantum chemical calculations, provide a detailed and complementary understanding of such paramagnetic compounds. In particular, the EPR and NMR signatures point to the presence of three-centre–two-electron Yb-γ-Me-β-Si secondary metal–ligand interactions in this otherwise tri-coordinate metal complex, similarly to its diamagnetic Lu analogues. The electronic structure of Yb(III) can be described as a single 4f13 configuration, while an unusually large crystal-field splitting results in a thermally isolated ground Kramers doublet. Furthermore, the computational data indicate that the Yb–carbon bond contains some π-character, reminiscent of the so-called α-H agostic interaction.
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| 3. |
- Dengler, Juergen, et al.
(författare)
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GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands
- 2018
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Ingår i: Phytocoenologia. - : Schweizerbart. - 0340-269X. ; 48:3, s. 331-347
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Tidskriftsartikel (refereegranskat)abstract
- GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board.
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| 4. |
- Glas, Gerie J., et al.
(författare)
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Ventilation practices in burn patients-an international prospective observational cohort study
- 2021
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Ingår i: BURNS & TRAUMA. - : Oxford University Press. - 2321-3868 .- 2321-3876. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: It is unknown whether lung-protective ventilation is applied in burn patients and whether they benefit from it. This study aimed to determine ventilation practices in burn intensive care units (ICUs) and investigate the association between lung-protective ventilation and the number of ventilator-free days and alive at day 28 (VFD-28). Methods: This is an international prospective observational cohort study including adult burn patients requiring mechanical ventilation. Low tidal volume (V-T) was defined as V-T <= 8 mL/kg predicted body weight (PBW). Levels of positive end-expiratory pressure (PEEP) and maximum airway pressures were collected. The association between V-T and VFD-28 was analyzed using a competing risk model. Ventilation settings were presented for all patients, focusing on the first day of ventilation. We also compared ventilation settings between patients with and without inhalation trauma. Results: A total of 160 patients from 28 ICUs in 16 countries were included. Low V-T was used in 74% of patients, median V-T size was 7.3 [interquartile range (IQR) 6.2-8.3] mL/kg PBW and did not differ between patients with and without inhalation trauma (p= 0.58). Median VFD-28 was 17 (IQR 0-26), without a difference between ventilation with low or high V-T (p= 0.98). All patients were ventilated with PEEP levels >= 5 cmH(2)O; 80% of patients had maximum airway pressures <30 cmH(2)O. Conclusion: In this international cohort study we found that lung-protective ventilation is used in the majority of burn patients, irrespective of the presence of inhalation trauma. Use of low V-T was not associated with a reduction in VFD-28.
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| 5. |
- Johnson, S.L., Heimann, P.A., Lindenberg, A.M., Jeschke, H.O., Garcia, M.E., Chang, Z., Lee, R.W., Rehr, J.J., Falcone, R.W.
(författare)
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Properties of liquid silicon observed by time-resolved X-ray absorption spectroscopy
- 2003
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Ingår i: Physical Review Letters. ; 91, s. 157403/1-4.
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Chernenkaya, A., et al.
(författare)
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Microscopic origin of the charge transfer in single crystals based on thiophene derivatives : A combined NEXAFS and density functional theory approach
- 2016
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 145:3
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the charge transfer mechanism in single crystals of DTBDT-TCNQ and DTBDT-F4TCNQ (where DTBDT is dithieno[2,3-d;2′,3′-d′] benzo[1,2-b;4,5-b′]dithiophene) using a combination of near-edge X-ray absorption spectroscopy (NEXAFS) and density functional theory calculations (DFT) including final state effects beyond the sudden state approximation. In particular, we find that a description that considers the partial screening of the electron-hole Coulomb correlation on a static level as well as the rearrangement of electronic density shows excellent agreement with experiment and allows to uncover the details of the charge transfer mechanism in DTBDT-TCNQ and DTBDT-F4 TCNQ, as well as a reinterpretation of previous NEXAFS data on pure TCNQ. Finally, we further show that almost the same quality of agreement between theoretical results and experiment is obtained by the much faster Z+1/2 approximation, where the core hole effects are simulated by replacing N or F with atomic number Z with the neighboring atom with atomic number Z+1/2.
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| 7. |
- Kerner, Manfred, 1984, et al.
(författare)
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Towards more thermally stable Li-ion battery electrolytes with salts and solvents sharing nitrile functionality
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 332, s. 204-212
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Tidskriftsartikel (refereegranskat)abstract
- The overall safety of Li-ion batteries is compromised by the state-of-the-art electrolytes; the thermally unstable lithium salt, lithium hexafluorophosphate (LiPF6), and flammable carbonate solvent mixtures. The problem is best addressed by new electrolyte compositions with thermally robust salts in low flammability solvents. In this work we introduce electrolytes with either of two lithium nitrile salts, lithium 4,5-dicyano-1,2,3-triazolate (LiDCTA) or lithium 4,5-dicyano-2-trifluoromethylimidazolide (LiTDI), in solvent mixtures with high flashpoint adiponitrile (ADN), as the main component. With sulfolane (SL) and ethylene carbonate (EC) as co-solvents the liquid temperature range of the electrolytes are extended to lower temperatures without lowering the flashpoint, but at the expense of high viscosities and moderate ionic conductivities. The anodic stabilities of the electrolytes are sufficient for LiFePO4 cathodes and can be charged/discharged for 20 cycles in Li/LiFePO4 cells with coulombic efficiencies exceeding 99% at best. The excellent thermal stabilities of the electrolytes with the solvent combination ADN:SL are promising for future electrochemical investigations at elevated temperatures (> 60 degrees C) to compensate the moderate transport properties and rate capability. The electrolytes with EC as a co-solvent, however, release CO2 by decomposition of EC in presence of a lithium salt, which potentially makes EC unsuitable for any application targeting higher operating temperatures.
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| 8. |
- Kimber, Simon A. J., et al.
(författare)
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Valence bond liquid phase in the honeycomb lattice material Li2RuO3
- 2014
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 89:8
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Tidskriftsartikel (refereegranskat)abstract
- The honeycomb lattice material Li2RuO3 undergoes a dimerization of Ru4+ cations on cooling below 270 degrees C, where the magnetic susceptibility vanishes. We use density functional theory calculations to show that this reflects the formation of a valence bond crystal, with a strong structural bond disproportionation. On warming, x-ray diffraction shows that discrete threefold symmetry is regained on average, and the dimerization apparently disappears. In contrast, local structural measurements using high-energy x rays show that disordered dimers survive at the nanoscale up to at least 650 degrees C. The high-temperature phase of Li2RuO3 is thus an example of a valence bond liquid, where thermal fluctuations drive resonance between different dimer coverages, a classic analog of the resonating valence bond state often discussed in connection with high-T-c cuprates.
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| 9. |
- Lindberg, Simon, 1987, et al.
(författare)
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Charge storage mechanism of α-MnO2 in protic and aprotic ionic liquid electrolytes
- 2020
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 460
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Tidskriftsartikel (refereegranskat)abstract
- In this work we have investigated the charge storage mechanism of MnO2 electrodes in ionic liquid electrolytes. We show that by using an ionic liquid with a cation that has the ability to form hydrogen bonds with the active material (MnO2) on the surface of the electrode, a clear faradaic contribution is obtained. This situation is found for ionic liquids with cations that have a low pKa, i.e. protic ionic liquids. For a protic ionic liquid, the specific capacity at low scan rate rates can be explained by a densely packed layer of cations that are in a standing geometry, with a proton directly interacting through a hydrogen bond with the surface of the active material in the electrode. In contrast, for aprotic ionic liquids there is no interaction and only a double layer contribution to the charge storage is observed. However, by adding an alkali salt to the aprotic ionic liquid, a faradaic contribution is obtained from the insertion of Li+ into the surface of the MnO2 electrode. No effect can be observed when Li+ is added to the protic IL, suggesting that a densely packed cation layer in this case prevent Li-ions from reaching the active material surface.
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| 10. |
- Tepper, S, et al.
(författare)
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Restriction of AID activity and somatic hypermutation by PARP-1
- 2019
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Ingår i: Nucleic acids research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 47:14, s. 7418-7429
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Tidskriftsartikel (refereegranskat)abstract
- Affinity maturation of the humoral immune response depends on somatic hypermutation (SHM) of immunoglobulin (Ig) genes, which is initiated by targeted lesion introduction by activation-induced deaminase (AID), followed by error-prone DNA repair. Stringent regulation of this process is essential to prevent genetic instability, but no negative feedback control has been identified to date. Here we show that poly(ADP-ribose) polymerase-1 (PARP-1) is a key factor restricting AID activity during somatic hypermutation. Poly(ADP-ribose) (PAR) chains formed at DNA breaks trigger AID-PAR association, thus preventing excessive DNA damage induction at sites of AID action. Accordingly, AID activity and somatic hypermutation at the Ig variable region is decreased by PARP-1 activity. In addition, PARP-1 regulates DNA lesion processing by affecting strand biased A:T mutagenesis. Our study establishes a novel function of the ancestral genome maintenance factor PARP-1 as a critical local feedback regulator of both AID activity and DNA repair during Ig gene diversification.
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