58 research outputs found
Did Egret Detect Distant Supernova Remnants?
It might be thought that supernova remnants (SNRs) more distant than a few
kiloparsec from Earth could not have been detected by the EGRET experiment.
This work analyzes the observational status of this statement in the light of
new CO studies of SNRs.Comment: Accepted for publication in Advances in Space Research, in High
Energy Studies of Supernova Remnants and Neutron Stars, eds. W. Becker and W.
Hermsen (2003
what is life the emergence of life in a mineral world
The premise of this talk is that, apart from liquid water and carbon molecules, specific environmental components and conditions were essential for the origin of life, i.e. phosphate, reactive rock..
A radio catalog of Galactic HII regions for applications from decimeter to millimeter wavelengths
By collecting the information from 24 previously published lists and
catalogs, we produce a comprehensive catalog (Master Catalog) of 1442 Galactic
HII regions. For each object, we quote the original fluxes and diameters as
well as the available information on radio line velocities, line widths and
line temperatures and the errors on these quantitities. References to the
original works are also reported. By exploiting all these data we produce a
Synthetic Catalog of fluxes and diameters (with corresponding errors) at 2.7
GHz. This choice is motivated by the extensive, although not complete,
information available at this frequency, widely spread among many different
catalogs, and by its relevance for both detailed studies on Galactic HII
regions and the extrapolation up to millimetric wavelengths. The catalog can be
used for detailed studies of Galactic HII regions and, by extrapolation, for
investigations of HII regions up to millimetric wavelengths. In particular, we
discuss the study of the effects of microwave emission from HII regions on the
new generation of Cosmic Microwave Background (CMB) experiments. We present
simulations of the detection of HII regions in the high resolution CMB survey,
and briefly analize some of the typical applications of our catalog to the
evaluation of CMB anisotropy experiments such as calibration, beam
reconstruction and straylight effects. The Master Catalog and the Synthetic
Catalog are available via ftp at: cdsarc.u-strasbg.fr. This work is related to
Planck-LFI activities.Comment: 14 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Magnetic Core Shell Nanoparticles Trapping in a Microdevice Generating High Magnetic Gradient
Magnetic core shell nanoparticles (MCSNPs) 30 nm diameter with a magnetic weight of 10% are usually much too small to be trapped in microfluidic systems using classical external magnets. Here, a simple microchip for efficient MCSNPs trapping and release is presented. It comprises a bed of micrometric iron beads (6â8 mm diameter) packed in a microchannel against a physical restriction and presenting a low dead volume of 0.8 nL. These beads of high magnetic permeability are used to focus magnetic field lines from an external permanent magnet and generate local high magnetic gradients. The nanoparticles magnetic trap has been characterised both by numerical simulations and fluorescent MCSNPs imaging. Numerical simulations have been performed to map both the magnetic flux density and the magnetic force, and showed that MCSNPs are preferentially trapped at the iron bead magnetic poles where the magnetic force is increased by 3 orders of magnitude. The trapping efficiency was experimentally determined using fluorescent MCSNPs for different flow rates, different iron beads and permanent magnet positions. At a flow rate of 100 mL h1, the nanoparticles trapping/release can be achieved within 20 s with a preconcentration factor of 4000
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
Nanoparticules multifonctionnelles et traitements anticancéreux (couplage de la bléomycine à la surface de nanoparticules magnétiques)
Les thĂ©rapies anticancĂ©reuses actuelles, par leur action systĂ©mique et leur manque de spĂ©cificitĂ©, entraĂźnent en nombre important d effets secondaires. L objectif de toute nouvelle chimiothĂ©rapie consiste donc Ă amĂ©liorer le confinement des principes actifs dans les zones cancĂ©reuses, au plus prĂšs des cibles thĂ©rapeutiques. Dans ce contexte, nous avons dĂ©veloppĂ© une plateforme nanomĂ©trique capable de vectoriser une molĂ©cule thĂ©rapeutique, la blĂ©omycine. La blĂ©omycine est un antibiotique anticancĂ©reux utilisĂ© en clinique dans de nombreux cancers. Elle souffre nĂ©anmoins d une utilisation limitĂ©e relative aux effets secondaires importants qu elle induit, principalement des pneumopathies. Sa vectorisation ciblĂ©e vers les zones tumorales Ă l aide de nanoparticules pourrait ouvrir la voie Ă des traitements efficaces. Nous avons dans un premier temps rĂ©alisĂ© la synthĂšse, la fonctionnalisation et la caractĂ©risation physicochimique de nanoparticules magnĂ©tiques de type cĆur/coquille. Nous avons rĂ©alisĂ© par la suite le couplage covalent de la blĂ©omycine Ă la surface des particules puis Ă©tudiĂ© son comportement biochimique aprĂšs greffage. Des Ă©tudes in vitro, in cellulo et in vivo ont ainsi Ă©tĂ© menĂ©es. Les Ă©tudes in vitro et in cellulo ont montrĂ© une prĂ©servation des propriĂ©tĂ©s biochimiques de la blĂ©omycine. De plus, les rĂ©sultats ont montrĂ© une forte internalisation des nanoparticules au sein des cellules, entraĂźnant le confinent d une grande quantitĂ© de molĂ©cules. Enfin, les Ă©tudes in vivo, menĂ©es par imagerie Ă rĂ©sonance magnĂ©tique et par imagerie Ă fluorescence, ont montrĂ© un temps de circulation Ă©levĂ© des nanoparticules dans l organisme.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
Formation of Activated Biomolecules by Condensation on Mineral Surfaces â A Comparison of Peptide Bond Formation and Phosphate Condensation
International audienceMany studies have reported condensation reactions of prebiotic molecules, such as the formation of peptide bonds between amino acids, to occur to some degree on mineral surfaces. We have studied several such reactions on the same divided silica. When drying steps are applied, the equilibria of peptide formation from glycine, and polyphosphate formation from monophosphate, are displaced to the right because these reactions are dehydrating condensations, accompanied by the emission of water. In contrast, the equilibrium of AMP dismutation is not significantly favored by drying. The silica surface plays little role (if any) in the thermochemistry of the condensation reactions, but is does play a significant kinetic role by acting as a catalyst, lowering the condensation temperatures with respect to bulk solids. Of course, the surface also catalyzes the inverse hydrolysis reactions
Fossilisation expérimentale : interactions minéral-organique
International audienc
In vitro synthesis of amorphous Mg-, Ca-, Sr- and Ba-carbonates: what do we learn about intracellular calcification by cyanobacteria?
International audienceSome cyanobacteria, including Candidatus Gloeomargarita lithophora, which was isolated from Lake Alchichica (Mexico), can form intracellular carbonates. This contradicts the common paradigm that cyanobacterial calcification is always extracellular and suggests that calcification might be controlled by these cyanobacterial species. Intracellular carbonates have several peculiar characteristics: they are relatively small (between 60 and 500 nm), they are poorly crystalline, and they have Sr/Ca and Ba/Ca ratios much higher than the solution in which the cells grow. It is therefore crucial to understand whether these unique features may indicate the involvement of specific biological processes. Here, in vitro abiotic syntheses were performed to synthesize Mg-, Ca-, Sr- and Ba-containing carbonates with compositions, crystallinities and sizes close to those observed in intracellularly calcifying cyanobacteria. Precipitates were characterized by scanning and transmission electron microscopies coupled with energy dispersive x-ray spectroscopy, thermogravimetric analysis and x-ray diffraction. The size and the poor crystallinity of cyanobacterial intracellular carbonates could be mimicked under these abiotic conditions. It was shown that similarly to Mg, elements such as Sr and Ba can favour stabilization of poorly crystalline carbonates. In contrast, the differential partitioning of Sr, Ba and Ca between the solution and the solids as observed in cyanobacteria could not be mimicked in vitro. This provides keys to a better understanding of biological processes involved in the formation of intracellular carbonates by some cyanobacteria, including the involvement of membrane transporters
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