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Functional redundancy in tRNA dihydrouridylation
No full textInternational audienceDihydrouridine (D) is a common modified base found predominantly in transfer RNA (tRNA). Despite its prevalence, the mechanisms underlying dihydrouridine biosynthesis, particularly in prokaryotes, have remained elusive. Here, we conducted a comprehensive investigation into D biosynthesis in Bacillus subtilis through a combination of genetic, biochemical, and epitranscriptomic approaches. Our findings reveal that B. subtilis relies on two FMN-dependent Dus-like flavoprotein homologs, namely DusB1 and DusB2, to introduce all D residues into its tRNAs. Notably, DusB1 exhibits multisite enzyme activity, enabling D formation at positions 17, 20, 20a and 47, while DusB2 specifically catalyzes D biosynthesis at positions 20 and 20a, showcasing a functional redundancy among modification enzymes. Extensive tRNA-wide D-mapping demonstrates that this functional redundancy impacts the majority of tRNAs, with DusB2 displaying a higher dihydrouridylation efficiency compared to DusB1. Interestingly, we found that BsDusB2 can function like a BsDusB1 when overexpressed in vivo and under increasing enzyme concentration in vitro. Furthermore, we establish the importance of the D modification for B. subtilis growth at suboptimal temperatures. Our study expands the understanding of D modifications in prokaryotes, highlighting the significance of functional redundancy in this process and its impact on bacterial growth and adaptation
Византия и Средиземноморские мастерские изделий в стиле перегородчатой инкрустации.
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Population genomics of post-glacial western Eurasia
No full textInternational audienceWestern Eurasia witnessed several large-scale human migrations during the Holocene. Here, to investigate the cross-continental effects of these migrations, we shotgun-sequenced 317 genomes-mainly from the Mesolithic and Neolithic periods-from across northern and western Eurasia. These were imputed alongside published data to obtain diploid genotypes from more than 1,600 ancient humans. Our analyses revealed a 'great divide' genomic boundary extending from the Black Sea to the Baltic. Mesolithic hunter-gatherers were highly genetically differentiated east and west of this zone, and the effect of the neolithization was equally disparate. Large-scale ancestry shifts occurred in the west as farming was introduced, including near-total replacement of hunter-gatherers in many areas, whereas no substantial ancestry shifts happened east of the zone during the same period. Similarly, relatedness decreased in the west from the Neolithic transition onwards, whereas, east of the Urals, relatedness remained high until around 4,000 BP, consistent with the persistence of localized groups of hunter-gatherers. The boundary dissolved when Yamnaya-related ancestry spread across western Eurasia around 5,000 BP, resulting in a second major turnover that reached most parts of Europe within a 1,000-year span. The genetic origin and fate of the Yamnaya have remained elusive, but we show that hunter-gatherers from the Middle Don region contributed ancestry to them. Yamnaya groups later admixed with individuals associated with the Globular Amphora culture before expanding into Europe. Similar turnovers occurred in western Siberia, where we report new genomic data from a 'Neolithic steppe' cline spanning the Siberian forest steppe to Lake Baikal. These prehistoric migrations had profound and lasting effects on the genetic diversity of Eurasian populations
In Praise of the Incarnation Line of the Kyabgon Taktsang Rinpoche: Documents Issued by the Dalai Lamas for the Kings of Ladakh
No full textInternational audienceA museum was created in Hemis Monastery, Ladakh, in 2007. In the midst of its stunning collection stands an extraordinary painted silk scroll document from 1943, which deals with the Sixth Taktsang Incarnate (1941-present). Hemis monks introduce that scroll as his official recognition by the 14th Dalai Lama, but this Tulku (sprul-sku, incarnate master), which they traditionally call Kyabgon (sKyab-mgon or “Protector and Refuge”), is yet an elusive figure. Forced to remain in Tibet since the Chinese crackdown of 1959 over 60 years ago, he is hardly known to the present generations of Ladakhis. The supreme significance of his successive incarnations is therefore fading in Ladakh, and has been little investigated by international scholars. This article is primarily a study of the Hemis silk scroll and the stories it tells, presented at the IALS Conference in Kargil in 2015. However, an earlier document from 1896, a copy of which is preserved in the British Library, appears to be very related. Both authored by the Dalai Lama of their time, these texts express retrospective praises of the incarnation line of Taktsang Repa and list special honorific titles and attributes bestowed to the living incarnation
Circulation des hommes et des biens de Méditerranée en Égypte du Vème siècle avant notre ère à la fin de l'époque hellénistique, l'apport des trouvailles monétaires
No full textThis doctoral research focuses on the circulation of peaple and goods from the mediterranean to Egypt from the Vth century BC to the end of Hellenistic perdiod, through the contribution of monetary finds. We rely on two types of discoveries : monetary treasures, usuelly made up of silver and gold coins, and coins found in isolation durant arcaelogical excavations and which are, most often, bronze coins. These two types of finds can give different information about the origine of foreigners in Egypt as well as the main trade routes across the country. It also makes it possible to compare the data found in the Alexandria region with those from the rest of the country. The period studied extends from the Vth to the Ist century BC. This chronological scope allows an in-depth analysis of monetary discoveries and interesting comparisons as to the evolution of the content of the treasures and the monetary profiles identified. Around 312 BC J.-C., the future Ptolemy Ist Soter gradually broke with the coinage set up by Alexander the Great to create his own monetary system. From the end of the IVth century BC, foreign currencies are no longer allowed to enter Egyptian soil. Data from numismatics are lacking for much of the Lagid period, so it's necessary to supplement them with the data provided by archaeology.Cette recherche doctorale porte sur la circulation des hommes et des biens de Méditerranée en Égypte du Vème siècle avant notre ère à la fin de l'époque hellénistique, à travers l'apport des trouvailles monétaires. Nous nous appuyons sur deux types de découvertes : les trésors monétaires, généralement constitués de monnaies d'argent et d'or, et les monnaies trouvées isolément lors des fouilles archéologiques et qui sont, le plus souvent, des monnaies de bronze. Ces deux types de trouvailles peuvent donner des renseignements différents quant à l'origine des étrangers en Égypte ainsi que sur les principales voies d'échanges à travers le pays. Cela permet aussi de confronter les données trouvées dans la région d'Alexandrie avec celles issues du reste du pays. La période étudiée s'étend du Vème au Ier siècle avant notre ère. Cette étendue chronologique permet une analyse approfondie des découvertes monétaires et des comparaisons intéressantes quant à l'évolution du contenu des trésors et aux profils monétaires recensés. Vers 312 av. J.-C., le futur Ptolémée Ier Sôter rompt progressivement avec le monnayage mis en place par Alexandre le Grand pour créer son propre système monétaire. À partir de la fin du IVème siècle avant notre ère, les monnaies étrangères ne sont plus autorisées à pénétrer sur le sol égyptien. Les données issues de la numismatique faisant défaut pour une grande partie de l'époque lagide, il est nécessaire de les compléter avec les données fournies par l'archéologie
Удила с орнитоморфным декором эпохи Великого переселения народов из самбийско-натангийского некрополя Тенген – Ушаково 1
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Penning-trap measurement of the -value of the electron capture in for the determination of the electron neutrino mass
No full textInternational audienceThe investigation of the absolute scale of the effective neutrino mass remains challenging due to the exclusively weak interaction of neutrinos with all known particles in the standard model of particle physics. Currently, the most precise and least model-dependent upper limit on the electron antineutrino mass is set by the KATRIN experiment from the analysis of the tritium {̱e̱ṯa̱}̱-decay. Another promising approach is the electron capture in , which is under investigation using microcalorimetry within the ECHo and HOLMES collab orations. An independently measured Q-value of this process is vital for the assessment of systematic uncertainties in the neutrino mass determination. Here, we report a direct, independent determination of this -value by measuring the free-space cyclotron frequency ratio of highly charged ions of and in the Penning trap experiment \textsc{Pentatrap}. Combining this ratio with atomic physics calculations of the electronic binding energies yields a -value of - a more than 50-fold improvement over the state-of-the-art. This will enable the determination of the electron neutrino mass on a sub-eV level from the analysis of the electron capture in
Interaction-enhanced nesting in Spin-Fermion and Fermi-Hubbard models
No full text5 pages, 4 figuresInternational audienceThe spin-fermion (SF) model postulates that the dominant coupling between low-energy fermions in near critical metals is mediated by collective spin fluctuations (paramagnons) peaked at the N\'{e}el wave vector, , connecting hot spots on opposite sides of the Fermi surface. It has been argued that strong correlations at hot spots lead to a Fermi surface deformation (FSD) featuring flat regions and increased nesting. This conjecture was confirmed in the perturbative self-consistent calculations when the paramagnon propagator dependence on momentum deviation from is given by . Using diagrammatic Monte Carlo (diagMC) technique we show that such a dependence holds only at temperatures orders of magnitude smaller than any other energy scale in the problem, indicating that a different mechanism may be at play. Instead, we find that a dependence yields a robust finite- scenario for achieving FSD. To link phenomenological and microscopic descriptions, we applied the connected determinant diagMC method to the Hubbard model and found that in this case: (i) the FSD is not very pronounced, and, instead, it is the lines of zeros of the renormalized dispersion relation that deform towards nesting; (ii) this phenomenon appears at large U/t>5.5 before the formation of electron and hole pockets; (iii) the static spin susceptibility is well described by . Flat FS regions yield a non-trivial scenario for realizing a non-Fermi liquid state
Répertorier pour mieux corriger : l'étude des mœurs de la région de Nagasaki par les missionnaires français (fin des années 1870)
No full textInternational audienceLes missionnaires français, présents en nombre au Japon dès les années 1860, ont contribué, par leurs écrits, à faire connaître l’archipel à leurs compatriotes. Leurs relations de séjour étaient, avec celles écrites par des laïcs, très prisées du lectorat occidental ; elles sont bien connues de la recherche.On sait moins par contre que les missionnaires ont aussi rédigé des rapports confidentiels extrêmement précis sur les mœurs de leurs premiers convertis. Ces travaux, qui sont aujourd’hui conservés à Rome et à Paris, n’avaient aucune finalité scientifique : il s’agissait pour le clergé de dresser « une typologie des défauts » de ses fidèles afin de les guider plus efficacement au salut. À la fin des années 1870, alors que le Japon compte près de 20 000 catholiques résidant essentiellement dans la région de Nagasaki, ce genre de document se multiplie : les missionnaires, qui pour certains sont parvenus à s’installer à la campagne, peuvent observer de visu la vie villageoise au Japon.Cet article porte sur un cahier manuscrit d’environ 400 pages conservé aux Missions étrangères de Paris intitulé Notes de Mgr. Laucaigne sur les coutumes du Japon (vol. 601 des archives). Ces notes ont été prises en français et en japonais au début de l’année 1879 ; elles offrent un aperçu unique du quotidien des communautés catholiques et témoignent de l’obsession classificatoire de certains prêtres qui étaient convaincus que le diable était dans les détails