Pseudo-K\"ahler Lie algebras with abelian complex structures

We study Lie algebras endowed with an abelian complex structure which admit a symplectic form compatible with the complex structure. We prove that each of those Lie algebras is completely determined by a pair (U,H) where U is a complex commutative associative algebra and H is a sesquilinear hermitian form on U which verifies certain compatibility conditions with respect to the associative product on U. The Riemannian and Ricci curvatures of the associated pseudo-K\"ahler metric are studied and a characterization of those Lie algebras which are Einstein but not Ricci flat is given. It is seen that all pseudo-K\"ahler Lie algebras can be inductively described by a certain method of double extensions applied to the associated complex asssociative commutative algebras

Ion irradiation triggers the formation of the precursors of complex organics in space - The case of formaldehyde and acetaldehyde

Context. Cosmic rays and solar energetic particles induce changes in the composition of compounds frozen onto dust grains in the interstellar medium (ISM), in comets, and on the surfaces of atmosphere-less small bodies in the outer Solar System. This induces the destruction of pristine compounds and triggers the formation of various species, including the precursors of complex organics. Aims. We investigate the role of energetic ions in the formation of formaldehyde (H2CO) and acetaldehyde (CH3CHO), which are observed in the ISM and in comets, and which are thought to be the precursors of more complex compounds such as hexamethylenete-tramine (HMT), which is found in carbonaceous chondrites and in laboratory samples produced after the irradiation and warm-up of astrophysical ices. Methods. We performed ion irradiation of water, methanol, and ammonia mixtures at 14–18 K. We bombarded frozen films with 40–200 keV H+ that simulate solar energetic particles and low-energy cosmic rays. Samples were analysed by infrared transmission spectroscopy. Results. Among other molecules, we observe the formation of H2CO and CH3CHO, and we find that their abundance depends on the dose and on the stoichiometry of the mixtures. We find that the H2CO abundance reaches the highest value after a dose of 10 eV/16u and then it decreases as the dose increases. Conclusions. The data suggest that surfaces exposed to high doses are depleted in H2CO. This explains why the amount of HMT in organic residues and that formed after irradiation of ices depends on the dose deposited in the ice. Because the H2CO abundance decreases at doses higher than 10 eV/16u, a lower quantity of H2CO is available to form HMT during the subsequent warm-up. The H2CO abundances caused by ion bombardment are insufficient to explain the ISM abundances, but ion bombardment can account for the abundance of CH3CHO towards the ISM and comets

Ultracarbonaceous Antarctic micrometeorites recovered from snow at the Dome C - CONCORDIA station.

第6回極域科学シンポジウム[OA] 南極隕石11月17日（火）　国立国語研究所 2階 講

Multiscale correlated analysis of the Aguas Zarcas CM chondrite

In this paper, we report the results of a campaign of measurements on four fragments of the CM Aguas Zarcas (AZ) meteorite, combining X‐ray computed tomography analysis and Fourier‐transform infrared (FT‐IR) spectroscopy. We estimated a petrologic type for our sampled CM lithology using the two independent techniques, and obtained a type CM2.5, in agreement with previous estimations. By comparing the Si‐O 10‐µm signature of the AZ average FT‐IR spectra with other well‐studied CMs, we place AZ in the context of aqueous alteration of CM parent bodies. Morphological characterization reveals that AZ has heterogeneous distribution of pores and a global porosity of 4.5 ± 0.5 vol%. We show that chondrules have a porosity of 6.3 ± 1 vol%. This larger porosity could be inherited due to various processes such as temperature variation during the chondrule formation and shocks or dissolution during aqueous alteration. Finally, we observed a correlation between 3D distributions of organic matter and mineral at micrometric scales, revealing a link between the abundance of organic matter and the presence of hydrated minerals. This supports the idea that aqueous alteration in AZ’s parent body played a major role in the evolution of the organic matter

Financing micro-entrepreneurs for poverty alleviation: a performance analysis of microfinance services offered by BRAC, ASA, and Proshika from Bangladesh

Microfinance services have emerged as an effective tool for financing microentrepreneurs to alleviate poverty. Since the 1970s, development theorists have considered non-governmental microfinance institutions (MFIs) as the leading practitioners of sustainable development through financing micro-entrepreneurial activities. This study evaluates the impact of micro-finance services provided by MFIs on poverty alleviation. In this vein, we examine whether microfinance services contribute to poverty alleviation, and also identify bottlenecks in micro-finance programs and operations. The results indicate that the micro-loans have a statistically significant positive impact on the poverty alleviation index and consequently improve the living standard of borrowers by increasing their level of income

Intrasplicing coordinates alternative first exons with alternative splicing in the protein 4.1R gene

In the protein 4.1R gene, alternative first exons splice differentially to alternative 3' splice sites far downstream in exon 2'/2 (E2'/2). We describe a novel intrasplicing mechanism by which exon 1A (E1A) splices exclusively to the distal E2'/2 acceptor via two nested splicing reactions regulated by novel properties of exon 1B (E1B). E1B behaves as an exon in the first step, using its consensus 5' donor to splice to the proximal E2'/2 acceptor. A long region of downstream intron is excised, juxtaposing E1B with E2'/2 to generate a new composite acceptor containing the E1B branchpoint/pyrimidine tract and E2 distal 3' AG-dinucleotide. Next, the upstream E1A splices over E1B to this distal acceptor, excising the remaining intron plus E1B and E2' to form mature E1A/E2 product. We mapped branch points for both intrasplicing reactions and demonstrated that mutation of the E1B 5' splice site or branchpoint abrogates intrasplicing. In the 4.1R gene, intrasplicing ultimately determines N-terminal protein structure and function. More generally, intrasplicing represents a new mechanism whereby alternative promoters can be coordinated with downstream alternative splicing

Methanol Near-Infrared Bands as a Probe of Irradiated Ices in Space

International audienceCosmic rays, solar ions and UV photons induce changes in both the structure and composition of frozen volatiles trapped in solar system small bodies such as comets, Kuiper-belt objects (KBOs) and trans-neptunian objects (TNOs). Recently, Stern et al. 2019 reported about the presence of methanol and water ice on the surface of (486958) 2014 MU69 revealed by the New Horizons space probe. Both species were identified also in other small bodies, such as (55638) 2002 VE95 and the centaur 5145 Pholus. Laboratory experiments that simulate the interaction between cosmic rays and frozen volatiles have shown that when carbon-bearing species are bombarded with keV-MeV ions, energetic processing determines the formation of both volatiles (such as CO, CO2, H2CO, etc.) and refractory species that may account for the visible and near-infrared reddening observed in various solar system small bodies. Here we present laboratory experiments performed to contribute in the interpretation of observations of methanol-rich bodies. Frozen samples containing water and methanol were deposited at temperatures that are close to those measured on 2014 MU69 and other TNOs. After the deposition, frozen volatiles were bombarded with 40 keV protons between a few and hundreds eV/molecule. Samples were analysed in the near-infrared range, where methanol exhibit an intense band at 2.27 microns and minor feature at 2.34 microns (4400 and 4280 cm-1, respectively). The analysis revealed a different sensitivity to ion irradiation of the two features. In particular, we show that the ratio between the band areas evolves with increasing irradiation doses. We suggest that it could be used as a probe to discern between pristine and processed ices, as well as to establish upper limits for the 2.34 microns band when only the 2.27 microns band is observed

Corrosion atmosphérique en entreposage

Certains déchets nucléaires et combustibles usagés sont conditionnés en conteneurs métalliques. Ces derniers peuvent être entreposés, de manière non définitive, dans des entrepôts. Les phénomènes de condensation pouvant éventuellement survenir sur les colis les plus froids, il n'est pas possible d'exclure les risques d'endommagement des colis du fait des phénomènes de corrosion atmosphérique. Le travail présenté entre dans le cadre d'un projet visant à élaborer un modèle prédictif du comportement à long terme des colis de déchets entreposés vis à vis de la corrosion atmosphérique. On s'est attaché dans un premier temps à évaluer la corrosivité atmosphérique dans un entrepôt à l'intérieur duquel les conditions environnementales sont supposées assez proches de celles à l'extérieur, exceptions faites des précipitations, qui ne pourront atteindre la surface des conteneurs. Nous avons pour ce faire simulé la thermique d'un colis bien défini, entreposé et soumis aux fluctuations thermohygrométriques de 2 environnements choisis. La corrosivité atmosphérique est ensuite exprimée dans les termes de la norme ISO/DIS 9223 c'est à dire en considérant notamment la durée d'humidification du conteneur. On présente enfin les perspectives de ce travail de modélisation

Biodiversité du milieu marin : Le phytoplankton.

L'évocation de l'environnement en Guyane renvoie intuitivement à la forêt amazonienne, poumon de la Terre, avec ses faunes et flores exubérantes. Il existe pourtant une autre Guyane, moins emblématique, celle des espaces côtiers et littoraux, paradoxalement moins accessible et de ce fait mieux préservée. Entre milieu marin, pointes rocheuses, plages de sable, étendues de vase, mangroves, marais, forêts et savanes, la Guyane côtière recèle en effet des écosystèmes très divers, dont on commence seulement à découvrir la richesse, l'organisation et le fonctionnement. Rédigé par un collectif de chercheurs impliqués dans l'observation, la description et l'analyse de ces environnements et de leurs biodiversités, Guyane océane présente ainsi pour la première fois ces milieux méconnus à un large public