499 research outputs found
Atomic hydrogen in IllustrisTNG galaxies: the impact of environment parallelled with local 21-cm surveys
We investigate the influence of environment on the cold-gas properties of
galaxies at z=0 within the TNG100 cosmological, magnetohydrodynamic simulation,
part of the IllustrisTNG suite. We extend previous post-processing methods for
breaking gas cells into their atomic and molecular phases, and build detailed
mocks to comprehensively compare to the latest surveys of atomic hydrogen (HI)
in nearby galaxies, namely ALFALFA and xGASS. We use TNG100 to explore the HI
content, star formation activity, and angular momentum of satellite galaxies,
each as a function of environment, and find that satellites are typically a
factor of ~3 poorer in HI than centrals of the same stellar mass, with the
exact offset depending sensitively on parent halo mass. Due to the large
physical scales on which HI measurements are made (~45--245 kpc), contributions
from gas not bound to the galaxy of interest but in the same line of sight
crucially lead to larger HI mass measurements in the mocks in many cases,
ultimately aligning with observations. This effect is mass-dependent and
naturally greater for satellites than centrals, as satellites are never
isolated by definition. We also show that HI stripping in TNG100 satellites is
closely accompanied by quenching, in tension with observational data that
instead favour that HI is preferentially stripped before star formation is
reduced.Comment: Published in MNRAS. Main body (full paper): 18 (22) pages, 10 (11)
figures. New-found bug introduced in v4 mock plots fixed. BaryMP issue fixed
per footnote in Dave et al. (2020). All changes are minor and do not affect
text or conclusion
Effects of nanoparticles on murine macrophages
Metallic nanoparticles are more and more widely used in an increasing number
of applications. Consequently, they are more and more present in the
environment, and the risk that they may represent for human health must be
evaluated. This requires to increase our knowledge of the cellular responses to
nanoparticles. In this context, macrophages appear as an attractive system.
They play a major role in eliminating foreign matter, e.g. pathogens or
infectious agents, by phagocytosis and inflammatory responses, and are thus
highly likely to react to nanoparticles. We have decided to study their
responses to nanoparticles by a combination of classical and wide-scope
approaches such as proteomics. The long term goal of this study is the better
understanding of the responses of macrophages to nanoparticles, and thus to
help to assess their possible impact on human health. We chose as a model
system bone marrow-derived macrophages and studied the effect of commonly used
nanoparticles such as TiO2 and Cu. Classical responses of macrophage were
characterized and proteomic approaches based on 2D gels of whole cell extracts
were used. Preliminary proteomic data resulting from whole cell extracts showed
different effects for TiO2-NPs and Cu-NPs. Modifications of the expression of
several proteins involved in different pathways such as, for example, signal
transduction, endosome-lysosome pathway, Krebs cycle, oxidative stress response
have been underscored. These first results validate our proteomics approach and
open a new wide field of investigation for NPs impact on macrophagesComment: Nanosafe2010: International Conference on Safe Production and Use of
Nanomaterials 16-18 November 2010, Grenoble, France, Grenoble : France (2010
Evidence for Marine Influence on a Low-Gradient Coastal Plain: Ichnology and Invertebrate Paleontology of the Lower Tongue River Member (Fort Union Formation, Middle Paleocene), Western Williston Basin, U.S.A.
The Paleocene Tongue River Member of the Fort Union Formation contains trace-fossil associations indicative of marine influence in otherwise freshwater facies. The identified ichnogenera include: Arenicolites, Diplocraterion, Monocraterion, Ophiomorpha, Rhizocorallium, Skolithos linearis, Teichichnus, Thalassinoides, and one form of uncertain affinity. Two species of the marine diatom Coscinodiscus occur a few meters above the base of the member. The burrows occur in at least five discrete, thin, rippled, fine-grained sandstone beds within the lower 85 m of the member west of the Cedar Creek anticline (CCA) in the Signal Butte, Terry Badlands, and Pine Hills areas. Two discrete burrowed beds are found in the lower 10 m of the member east of the CCA in the little Missouri River area.
Abundant freshwater ostracodes include Bisulcocypridea arvadensis, Candona, and Cypridopsis. Freshwater bivalves include Plesielliptio and Pachydon mactriformis. We recognize four fossil assemblages that represent fluvio-lacustrine, proximal estuarine, central estuarine, and distal estuarine environments. Biostratal alternations between fresh- and brackish-water assemblages indicate that the Tongue River Member was deposited along a low-gradient coastal plain that was repeatedly inundated from the east by the Cannonball Sea.
The existence of marine-influenced beds in the Tongue River Member invalidates the basis for the Slope Formation
Migrations and habitat use of the smooth hammerhead shark (Sphyrna zygaena) in the Atlantic Ocean
The smooth hammerhead shark, Sphyrna zygaena, is a cosmopolitan semipelagic shark captured as bycatch in pelagic oceanic fisheries, especially pelagic longlines targeting swordfish and/or tunas. From 2012 to 2016, eight smooth hammerheads were tagged with Pop-up Satellite Archival Tags in the inter-tropical region of the Northeast Atlantic Ocean, with successful transmissions received from seven tags (total of 319 tracking days). Results confirmed the smooth hammerhead is a highly mobile species, as the longest migration ever documented for this species (> 6600 km) was recorded. An absence of a diel vertical movement behavior was noted, with the sharks spending most of their time at surface waters (0-50 m) above 23 degrees C. The operating depth of the pelagic long-line gear was measured with Minilog Temperature and Depth Recorders, and the overlap with the species vertical distribution was calculated. The overlap is taking place mainly during the night and is higher for juveniles (similar to 40% of overlap time). The novel information presented can now be used to contribute to the provision of sustainable management tools and serve as input for Ecological Risk Assessments for smooth hammerheads caught in Atlantic pelagic longline fisheries.Oceanario de Lisboa through Project "SHARK-TAG: Migrations and habitat use of the smooth hammerhead shark in the Atlantic Ocean"; Investigador-FCT from the Portuguese Foundation for Science and Technology (FCT, Fundacao para a Ciencia e Tecnologia) [Ref: IF/00253/2014]; EU European Social Fund; Programa Operacional Potencial Human
Expanding networks of RNA virus evolution
In a recent BMC Evolutionary Biology article, Huiquan Liu and colleagues report two new genomes of double-stranded RNA (dsRNA) viruses from fungi and use these as a springboard to perform an extensive phylogenomic analysis of dsRNA viruses. The results support the old scenario of polyphyletic origin of dsRNA viruses from different groups of positive-strand RNA viruses and additionally reveal extensive horizontal gene transfer between diverse viruses consistent with the network-like rather than tree-like mode of viral evolution. Together with the unexpected discoveries of the first putative archaeal RNA virus and a RNA-DNA virus hybrid, this work shows that RNA viral genomics has major surprises to deliver
Modeling the atomic-to-molecular transition in cosmological simulations of galaxy formation
Large-scale cosmological simulations of galaxy formation currently do not
resolve the densities at which molecular hydrogen forms, implying that the
atomic-to-molecular transition must be modeled either on the fly or in
postprocessing. We present an improved postprocessing framework to estimate the
abundance of atomic and molecular hydrogen and apply it to the IllustrisTNG
simulations. We compare five different models for the atomic-to-molecular
transition, including empirical, simulation-based, and theoretical
prescriptions. Most of these models rely on the surface density of neutral
hydrogen and the ultraviolet (UV) flux in the Lyman-Werner band as input
parameters. Computing these quantities on the kiloparsec scales resolved by the
simulations emerges as the main challenge. We show that the commonly used Jeans
length approximation to the column density of a system can be biased and
exhibits large cell-to-cell scatter. Instead, we propose to compute all surface
quantities in face-on projections and perform the modeling in two dimensions.
In general, the two methods agree on average, but their predictions diverge for
individual galaxies and for models based on the observed midplane pressure of
galaxies. We model the UV radiation from young stars by assuming a constant
escape fraction and optically thin propagation throughout the galaxy. With
these improvements, we find that the five models for the atomic-to-molecular
transition roughly agree on average but that the details of the modeling matter
for individual galaxies and the spatial distribution of molecular hydrogen. We
emphasize that the estimated molecular fractions are approximate due to the
significant systematic uncertainties.Comment: 22 pages, 13 figure
Optimal trapping wavelengths of Cs molecules in an optical lattice
The present paper aims at finding optimal parameters for trapping of Cs
molecules in optical lattices, with the perspective of creating a quantum
degenerate gas of ground-state molecules. We have calculated dynamic
polarizabilities of Cs molecules subject to an oscillating electric field,
using accurate potential curves and electronic transition dipole moments. We
show that for some particular wavelengths of the optical lattice, called "magic
wavelengths", the polarizability of the ground-state molecules is equal to the
one of a Feshbach molecule. As the creation of the sample of ground-state
molecules relies on an adiabatic population transfer from weakly-bound
molecules created on a Feshbach resonance, such a coincidence ensures that both
the initial and final states are favorably trapped by the lattice light,
allowing optimized transfer in agreement with the experimental observation
Net grassland carbon flux over a subambient to superambient CO2 gradient
Increasing atmospheric CO2 concentrations may have a profound effect on the structure and function of plant communities. A previously grazed, central Texas grassland was exposed to a 200-µmol mol-1 to 550 µmol mol-1 CO2 gradient from March to mid-December in 1998 and 1999 using two, 60-m long, polyethylene-covered chambers built directly onto the site. One chamber was operated at subambient CO2 concentrations (200-360 µmol mol-1 daytime) and the other was regulated at superambient concentrations (360-550 µmol mol-1). Continuous CO2 gradients were maintained in each chamber by photosynthesis during the day and respiration at night. Net ecosystem CO2 flux and end-of-year biomass were measured in each of 10, 5-m long sections in each chamber. Net CO2 fluxes were maximal in late May (c. day 150) in 1998 and in late August in 1999 (c. day 240). In both years, fluxes were near zero and similar in both chambers at the beginning and end of the growing season. Average daily CO2 flux in 1998 was 13 g CO2 m-2 day-1 in the subambient chamber and 20 g CO2 m-2 day-1 in the superambient chamber; comparable averages were 15 and 26 g CO2 m-2 day-1 in 1999. Flux was positively and linearly correlated with end-of-year above-ground biomass but flux was not linearly correlated with CO2 concentration; a finding likely to be explained by inherent differences in vegetation. Because C3 plants were the dominant functional group, we adjusted average daily flux in each section by dividing the flux by the average percentage C3 cover. Adjusted fluxes were better correlated with CO2 concentration, although scatter remained. Our results indicate that after accounting for vegetation differences, CO2 flux increased linearly with CO2 concentration. This trend was more evident at subambient than superambient CO2 concentrations
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