multiple populations
Recently Published Documents


TOTAL DOCUMENTS

366
(FIVE YEARS 89)

H-INDEX

51
(FIVE YEARS 8)

2022 ◽  
Vol 924 (2) ◽  
pp. 81
Author(s):  
G. Parmentier ◽  
A. Pasquali

Abstract We present a novel approach to the riddle of star cluster multiple populations. Stars form from molecular cores. But not all cores form stars. Following their initial compression, such “failed” cores re-expand, rather than collapsing. We propose that their formation and subsequent dispersal regulate the gas density of cluster-forming clumps and, therefore, their core and star formation rates. Clumps for which failed cores are the dominant core type experience star formation histories with peaks and troughs (i.e., discrete star formation episodes). In contrast, too few failed cores results in smoothly decreasing star formation rates. We identify three main parameters shaping the star formation history of a clump: the star and core formation efficiencies per free-fall time, and the timescale on which failed cores return to the clump gas. The clump mass acts as a scaling factor. We use our model to constrain the density and mass of the Orion Nebula Cluster progenitor clump, and to caution that the star formation histories of starburst clusters may contain close-by peaks concealed by stellar age uncertainties. Our model generates a great variety of star formation histories. Intriguingly, the chromosome maps and O–Na anticorrelations of old globular clusters also present diverse morphologies. This prompts us to discuss our model in the context of globular cluster multiple stellar populations. More massive globular clusters exhibit stronger multiple stellar population patterns, which our model can explain if the formation of the polluting stars requires a given stellar mass threshold.


2021 ◽  
Vol 924 (1) ◽  
pp. L2
Author(s):  
Mario Cadelano ◽  
Emanuele Dalessandro ◽  
Maurizio Salaris ◽  
Nate Bastian ◽  
Alessio Mucciarelli ◽  
...  

Abstract We present the result of a detailed analysis of Hubble Space Telescope UV and optical deep images of the massive and young (∼1.5 Gyr) stellar cluster NGC 1783 in the Large Magellanic Cloud. This system does not show evidence of multiple populations (MPs) along the red giant branch (RGB) stars. However, we find that the cluster main sequence (MS) shows evidence of a significant broadening (50% larger than what is expected from photometric errors) along with hints of possible bimodality in the MP sensitive (m F343N − m F438W, m F438W) color–magnitude diagram (CMD). Such an effect is observed in all color combinations including the m F343N filter, while it is not found in the optical CMDs. This observational evidence suggests we might have found light-element chemical abundance variations along the MS of NGC 1783, which represents the first detection of MPs in a system younger than 2 Gyr. A comparison with isochrones including MP-like abundances shows that the observed broadening is compatible with a N abundance enhancement of Δ([N/Fe]) ∼ 0.3. Our analysis also confirms previous results about the lack of MPs along the cluster RGB. However, we find that the apparent disagreement between the results found on the MS and the RGB is compatible with the mixing effects linked to the first dredge up. This study provides new key information about the MP phenomenon and suggests that star clusters form in a similar way at any cosmic age.


Author(s):  
Daneil C. Feldmann ◽  
Masouda Rahim ◽  
Mathijs A. M. Suijkerbuijk ◽  
Mary‐Jessica N. Laguette ◽  
Paweł Cieszczyk ◽  
...  

2021 ◽  
Author(s):  
Fang-Yi Su ◽  
Qingyang Zhao ◽  
Shreyas N. Dahotre ◽  
Lena Gamboa ◽  
Swapnil Subhash Bawage ◽  
...  

Simultaneous delivery of mRNA to multiple populations of antigen (Ag)-specific CD8+ T cells is challenging given the diversity of peptide epitopes and polymorphism of class I major histocompatibility complexes (MHCI). We developed Ag-presenting nanoparticles (APNs) for mRNA delivery using pMHCI molecules that were refolded with photocleavable peptides to allow rapid ligand exchange by UV light and site-specifically conjugated with a lipid tail for post-insertion into preformed mRNA lipid nanoparticles. Across different TCR transgenic mouse models (P14, OT-1, Pmel), UV-exchanged APNs bound and transfected their cognate Ag-specific CD8+ T cells equivalent to APNs produced using conventionally refolded pMHCI molecules. In mice infected with PR8 influenza, multiplexed delivery of UV-exchanged APNs against three immunodominant epitopes led to ~50% transfection of a VHH mRNA reporter in cognate Ag-specific CD8+ T cells. Our data shows that UV-mediated peptide exchange can be used to rapidly produce APNs for mRNA delivery to multiple populations of Ag-specific T cells in vivo.


2021 ◽  
Vol 51 ◽  
pp. e77
Author(s):  
Hang Zhou ◽  
Rachel Kember ◽  
Joseph Deak ◽  
Cecilia Dao ◽  
Marco Galimberti ◽  
...  

mSphere ◽  
2021 ◽  
Author(s):  
Jordy Evan Sulaiman ◽  
Henry Lam

Although the phenotype of increased tolerance and/or resistance was commonly observed in evolved populations from typical adaptive laboratory evolution (ALE) experiments, a wide variety of mutations that underlie those phenotypes have been discovered. Therefore, performing ALE experiments in multiple populations in parallel would serve the purpose of mining for different tolerant/resistant mutants and would be useful to explore the diverse population dynamics of evolution.


2021 ◽  
Author(s):  
Nicolas Alcala ◽  
Noah A Rosenberg

Interpretations of values of the FST measure of genetic differentiation rely on an understanding of its mathematical constraints. Previously, it has been shown that FST values computed from a biallelic locus in a set of multiple populations and FST values computed from a multiallelic locus in a pair of populations are mathematically constrained by the frequency of the allele that is most frequent across populations. We report here the mathematical constraint on FST given the frequency M of the most frequent allele at a multiallelic locus in a set of multiple populations, providing the most general description to date of mathematical constraints on FST in terms of M. Using coalescent simulations of an island model of migration with an infinitely-many-alleles mutation model, we argue that the joint distribution of FST and M helps in disentangling the separate influences of mutation and migration on FST. Finally, we show that our results explain puzzling patterns of microsatellite differentiation, such as the lower FST values in interspecific comparisons between humans and chimpanzees than in the intraspecific comparison of chimpanzee populations. We discuss the implications of our results for the use of FST.


2021 ◽  
Vol 161 (6) ◽  
pp. 288
Author(s):  
Jeffrey M. Gerber ◽  
Eileen D. Friel ◽  
Enrico Vesperini

Sign in / Sign up

Export Citation Format

Share Document