| 1. |
- Akiyama, Kazunori, et al.
(författare)
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First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
- 2019
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.
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| 2. |
- Anderson, Christopher J., et al.
(författare)
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Response to Comment on "Estimating the reproducibility of psychological science"
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 351:6277
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Gilbert et al. conclude that evidence from the Open Science Collaboration's Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.
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| 3. |
- Kuznetsov, Nikolai V, et al.
(författare)
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The evolutionarily conserved single-copy gene for murine Tpr encodes one prevalent isoform in somatic cells and lacks paralogs in higher eukaryotes.
- 2002
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Ingår i: Chromosoma. - : Springer Science and Business Media LLC. - 0009-5915 .- 1432-0886. ; 111:4, s. 236-255
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Tidskriftsartikel (refereegranskat)abstract
- Vertebrate Tpr and its probable homologs in insects and yeast are heptad repeat-dominated nuclear proteins of M(r) 195,000 to M(r) 267,000 the functions of which are still largely unknown. Whereas two homologs exist in Saccharomyces cerevisiae, it has remained uncertain whether metazoans possess different paralogs or isoforms of Tpr that might explain controversial reports on the subcellular localization of this protein. To address these possibilities, we first determined the sequence and structure of the murine tpr gene, revealing a TATA box-less gene of approximately 57 kb and 52 exons. Southern hybridization of genomic DNA and radiation hybrid mapping showed that murine tpr exists as a single-copy gene on chromosome 1; RNA blotting analyses and EST (expressed sequence tag) database mining revealed that its expression results in only one major mRNA in embryonic and most adult tissues. Accordingly, novel antibodies against the N- and C-terminus of Tpr identified the full-length protein as the major translation product in different somatic cell types; reinvestigation of Tpr localization by confocal microscopy corroborated a predominant localization at the nuclear pore complexes in these cells. Antibody specificity and reliability of Tpr localization was demonstrated by post-transcriptional tpr gene silencing using siRNAs that eliminated the Tpr signal at the nuclear periphery but did not affect intranuclear staining of Tpr-unrelated proteins. Finally, we defined several sequence and structural features that characterize Tpr polypeptides in different species and used these as a guideline to search whole-genome sequence databases for putative paralogs of Tpr in higher eukaryotes. This approach resulted in identification of the Tpr orthologs in Arabidopsis thaliana and Caenorhabditis elegans, but also in the realization that no further paralogs of Tpr exist in several metazoan model organisms or in humans. In summary, these results reveal Tpr to be a unique protein localized at the nuclear periphery of the somatic cell in mammals.
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| 4. |
- Lawrence, Samuel R., et al.
(författare)
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A well-defined magnesium complex of C706−
- 2024
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Ingår i: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765.
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Tidskriftsartikel (refereegranskat)abstract
- Controlling and understanding charge state and metal coordination in carbon nanomaterials is crucial to harnessing their unique properties. Here we describe the synthesis of the well-defined fulleride complex [{(Mesnacnac)Mg}6C70], 2, (Mesnacnac)=HC(MeCNMes)2, Mes=2,4,6-Me3C6H2, from the reaction of the β-diketiminate magnesium(I) complex [{(Mesnacnac)Mg}2] with C70 in aromatic solvents. The molecular structure of complex 2 was determined, providing the first high-quality structural study of a complex with the C706− ion. In combination with solution state NMR spectroscopic and DFT computational studies, the changes in geometry and charge distribution in the various atom and bond types of the fulleride unit were investigated. Additionally, the influence of the (Mesnacnac)Mg+ cations on the global and local fulleride coordination environment was examined.
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| 5. |
- Lawrence, Samuel R., et al.
(författare)
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Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium
- 2019
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 10:46, s. 10755-10764
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of the magnesium(i) complexes [{((Ar)nacnac)Mg}(2)], ((Ar)nacnac = HC(MeCNAr)(2), Ar = Dip (2,6-iPr(2)C(6)H(3)), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C-60 afforded a series of hydrocarbon-soluble fulleride complexes [{((Ar)nacnac)Mg}(n)C-60], predominantly with n = 6, 4 and 2. C-13{H-1} NMR spectroscopic studies show both similarities (n = 6) and differences (n = 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. The molecular structures of [{((Ar)nacnac)Mg}(n)C-60] with n = 6, 4 and 2 can be described as inverse coordination complexes of n [((Ar)nacnac)Mg](+) ions with C-60(n-) anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C-60(6-) ion. Experimental studies show the flexible ionic nature of the {((Ar)nacnac)Mg}+MIDLINE HORIZONTAL ELLIPSISC606- coordination bonds. DFT calculations on the model complex [{((Me)nacnac)Mg}(6)C-60] ((Me)nacnac = HC(MeCNMe)(2)) support the formulation as an ionic complex with a central C-60(6-) anion and comparable frontier orbitals to C-60(6-) with a small HOMO-LUMO gap. The reduction of C-60 to its hexaanion gives an indication about the reducing strength of dimagnesium(i) complexes.
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