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Digital platforms and the future of news: regulating publisher-platform relations in Australia and Canada
This article provides an overview of news media bargaining codes as a way of regulating relations between digital platforms and news publishers. Taking the Codes developed in Australia and Canada as policy case studies, the paper discusses recent reforms which respond to the unequal bargaining power between digital platforms and news media publishers. Despite these reforms, there are few guarantees that funds received by news publishers will be reinvested into public interest journalism. The article asks whether the discourse surrounding digital platform regulation generally, and measures by nation-states to rebalance market relations to the benefit of news publishers, are likely to yield necessary safeguards required to sustain public interest journalism, promote reliable information, and stabilise democratic societies
Large-scale variations of the dust optical properties in the Galaxy
We present an analysis of the dust optical properties at large scale, for the
whole galactic anticenter hemisphere. We used the 2MASS Extended Source Catalog
to obtain the total reddening on each galaxy line of sight and we compared this
value to the IRAS 100 microns surface brightness converted to extinction by
Schlegel et al (1998). We performed a careful examination and correction of the
possible systematic effects resulting from foreground star contamination,
redshift contribution and galaxy selection bias. We also evaluated the
contribution of dust temperature variations and interstellar clumpiness to our
method. The correlation of the near-infrared extinction to the far-infrared
optical depth shows a discrepancy for visual extinction greater than 1 mag with
a ratio A_V(FIR) / A_V(gal) = 1.31 +- 0.06. We attribute this result to the
presence of fluffy/composite grains characterized by an enhanced far--infrared
emissivity. Our analysis, applied to half of the sky, provides new insights on
the dust grains nature suggesting fluffy grains are found not only in some very
specific regions but in all directions for which the visual extinction reaches
about 1 mag.Comment: 10 pages, 11 figures, accepted for publication in A&
Direct evidence of dust growth in L183 from MIR light scattering
Theoretical arguments suggest that dust grains should grow in the dense cold
parts of molecular clouds. Evidence of larger grains has so far been gathered
in near/mid infrared extinction and millimeter observations. Interpreting the
data is, however, aggravated by the complex interplay of density and dust
properties (as well as temperature for thermal emission). We present new
Spitzer data of L183 in bands that are sensitive and insensitive to PAHs. The
visual extinction AV map derived in a former paper was fitted by a series of 3D
Gaussian distributions. For different dust models, we calculate the scattered
MIR radiation images of structures that agree agree with the AV map and compare
them to the Spitzer data. The Spitzer data of L183 show emission in the 3.6 and
4.5 micron bands, while the 5.8 micron band shows slight absorption. The
emission layer of stochastically heated particles should coincide with the
layer of strongest scattering of optical interstellar radiation, which is seen
as an outer surface on I band images different from the emission region seen in
the Spitzer images. Moreover, PAH emission is expected to strongly increase
from 4.5 to 5.8 micron, which is not seen. Hence, we interpret this emission to
be MIR cloudshine. Scattered light modeling when assuming interstellar medium
dust grains without growth does not reproduce flux measurable by Spitzer. In
contrast, models with grains growing with density yield images with a flux and
pattern comparable to the Spitzer images in the bands 3.6, 4.5, and 8.0 micron.Comment: 13 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Remodeling of T Cell Dynamics During Long COVID Is Dependent on Severity of SARS-CoV-2 Infection
Several COVID-19 convalescents suffer from the post-acute COVID-syndrome (PACS)/long COVID, with symptoms that include fatigue, dyspnea, pulmonary fibrosis, cognitive dysfunctions or even stroke. Given the scale of the worldwide infections, the long-term recovery and the integrative health-care in the nearest future, it is critical to understand the cellular and molecular mechanisms as well as possible predictors of the longitudinal post-COVID-19 responses in convalescent individuals. The immune system and T cell alterations are proposed as drivers of post-acute COVID syndrome. However, despite the number of studies on COVID-19, many of them addressed only the severe convalescents or the short-term responses. Here, we performed longitudinal studies of mild, moderate and severe COVID-19-convalescent patients, at two time points (3 and 6 months from the infection), to assess the dynamics of T cells immune landscape, integrated with patients-reported symptoms. We show that alterations among T cell subsets exhibit different, severity- and time-dependent dynamics, that in severe convalescents result in a polarization towards an exhausted/senescent state of CD4+ and CD8+ T cells and perturbances in CD4+ Tregs. In particular, CD8+ T cells exhibit a high proportion of CD57+ terminal effector cells, together with significant decrease of naïve cell population, augmented granzyme B and IFN-γ production and unresolved inflammation 6 months after infection. Mild convalescents showed increased naïve, and decreased central memory and effector memory CD4+ Treg subsets. Patients from all severity groups can be predisposed to the long COVID symptoms, and fatigue and cognitive dysfunctions are not necessarily related to exhausted/senescent state and T cell dysfunctions, as well as unresolved inflammation that was found only in severe convalescents. In conclusion, the post-COVID-19 functional remodeling of T cells could be seen as a two-step process, leading to distinct convalescent immune states at 6 months after infection. Our data imply that attenuation of the functional polarization together with blocking granzyme B and IFN-γ in CD8+ cells might influence post-COVID alterations in severe convalescents. However, either the search for long COVID predictors or any treatment to prevent PACS and further complications is mandatory in all patients with SARS-CoV-2 infection, and not only in those suffering from severe COVID-19
Evolution of dust in the Orion Bar with Herschel: I. Radiative transfer modelling
Interstellar dust is a key element in our understanding of the interstellar
medium and star formation. The manner in which dust populations evolve with the
excitation and the physical conditions is a first step in the comprehension of
the evolution of inter- stellar dust. Within the framework of the Evolution of
interstellar dust Herschel key program, we have acquired PACS and SPIRE spec-
trophotometric observations of various photodissociation regions, to
characterise this evolution. The aim of this paper is to trace the evolution of
dust grains in the Orion Bar photodissociation region. We use Herschel/PACS (70
and 160 mic) and SPIRE (250, 350 and 500 mic) together with Spitzer/IRAC
observations to map the spatial distribution of the dust populations across the
Bar. Brightness profiles are modelled using the DustEM model coupled with a
radiative transfer code. Thanks to Herschel, we are able to probe finely the
dust emission of the densest parts of the Orion Bar with a resolution from 5.6"
to 35.1". These new observations allow us to infer the temperature of the
biggest grains at different positions in the Bar, which reveals a gradient from
\sim 80 K to 40 K coupled with an increase of the spectral emissivity index
from the ionization front to the densest regions. Combining Spitzer/IRAC
observations, which are sensitive to the dust emission from the surface, with
Herschel maps, we have been able to measure the Orion Bar emission from 3.6 to
500 mic. We find a stratification in the different dust components which can be
re- produced quantitatively by a simple radiative transfer model without dust
evolution. However including dust evolution is needed to explain the brightness
in each band. PAH abundance variations, or a combination of PAH abundance
variations with an emissivity enhancement of the biggest grains due to
coagulation give good results.Comment: 11 pages, 12 figure
Physical structure of the photodissociation regions in NGC 7023: Observations of gas and dust emission with <i>Herschel</i>
The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in the photodissociation regions (PDRs) located at the interface between the atomic and cold molecular gas of the NGC 7023 reflection nebula. We study how young stars affect the gas and dust in their environment. Our approach combining both dust and gas delivers strong constraints on the physical conditions of the PDRs. We find dense and warm molecular gas of high column density in the PDRs
Spitzer characterisation of dust in an anomalous emission region: the Perseus cloud
Anomalous microwave emission is known to exist in the Perseus cloud. One of
the most promising candidates to explain this excess of emission is electric
dipole radiation from rapidly rotating very small dust grains, commonly
referred to as spinning dust. Photometric data obtained with the Spitzer Space
Telescope have been reprocessed and used in conjunction with the dust emission
model DUSTEM to characterise the properties of the dust within the cloud. This
analysis has allowed us to constrain spatial variations in the strength of the
interstellar radiation field (), the mass abundances of the
PAHs and VSGs relative to the BGs (Y and Y), the
column density of hydrogen (N) and the equilibrium dust
temperature (T). The parameter maps of Y,
Y and are the first of their kind to be
produced for the Perseus cloud, and we used these maps to investigate the
physical conditions in which anomalous emission is observed. We find that in
regions of anomalous emission the strength of the ISRF, and consequently the
equilibrium temperature of the dust, is enhanced while there is no significant
variation in the abundances of the PAHs and the VSGs or the column density of
hydrogen. We interpret these results as an indication that the enhancement in
might be affecting the properties of the small
stochastically heated dust grains resulting in an increase in the spinning dust
emission observed at 33 GHz. This is the first time that such an investigation
has been performed, and we believe that this type of analysis creates a new
perspective in the field of anomalous emission studies, and represents a
powerful new tool for constraining spinning dust models.Comment: 13 pages, 9 figures, accepted for publication in MNRA
Dust processing in photodissociation regions - Mid-IR emission modelling
Mid-infrared spectroscopy of dense illuminated ridges (or photodissociation
regions, PDRs) suggests dust evolution. Such evolution must be reflected in the
gas physical properties through processes like photo-electric heating or H_2
formation. With Spitzer Infrared Spectrograph (IRS) and ISOCAM data, we study
the mid-IR emission of closeby, well known PDRs. Focusing on the band and
continuum dust emissions, we follow their relative contributions and analyze
their variations in terms of abundance of dust populations. In order to
disentangle dust evolution and excitation effects, we use a dust emission model
that we couple to radiative transfer. Our dust model reproduces extinction and
emission of the standard interstellar medium that we represent with diffuse
high galactic latitude clouds called Cirrus. We take the properties of dust in
Cirrus as a reference to which we compare the dust emission from more excited
regions, namely the Horsehead and the reflection nebula NGC 2023 North. We show
that in both regions, radiative transfer effects cannot account for the
observed spectral variations. We interpret these variations in term of changes
of the relative abundance between polycyclic aromatic hydrocarbons (PAHs,
mid-IR band carriers) and very small grains (VSGs, mid-IR continuum carriers).
We conclude that the PAH/VSG abundance ratio is 2.4 times smaller at the peak
emission of the Horsehead nebula than in the Cirrus case. For NGC2023 North
where spectral evolution is observed across the northern PDR, we conclude that
this ratio is ~5 times lower in the dense, cold zones of the PDR than in its
diffuse illuminated part where dust properties seem to be the same as in
Cirrus. We conclude that dust in PDRs seems to evolve from "dense" to "diffuse"
properties at the small spatial scale of the dense illuminated ridge.Comment: 11 pages, 11 figures, accepted for publication in A&
Mapping the cold dust temperatures and masses of nearby Kingfish galaxies with Herschel
Taking advantage of the sensitivity and angular resolution of the Herschel
Space Observatory at far-infrared and submm wavelengths, we aim to characterize
the physical properties of cold dust within nearby galaxies and study the
robustness of the parameters we derive using different modified blackbody
models. For a pilot subsample of the KINGFISH program, we perform 2 temperature
fits of the Spitzer and Herschel photometric data (24 to 500um), with a warm
and a cold component, globally and in each resolution element.At global scales,
we observe ranges of values for beta_c(0.8 to 2.5) and Tc(19.1 to 25.1K).We
compute maps of our parameters with beta fixed or free to test the robustness
of the temperature and dust surface density maps we deduce. When the emissivity
is fixed, we observe temperature gradients as a function of radius.When the
emissivity is fitted as a free parameter, barred galaxies tend to have uniform
fitted emissivities.Gathering resolved elements in a Tc-beta_c diagram
underlines an anti-correlation between the two parameters.It remains difficult
to assess whether the dominant effect is the physics of dust grains, noise, or
mixing along the line of sight and in the beam. We finally observe in both
cases that the dust column density peaks in central regions of galaxies and bar
ends (coinciding with molecular gas density enhancements usually found in these
locations).We also quantify how the total dust mass varies with our assumptions
about the emissivity index as well as the influence of the wavelength coverage
used in the fits. We show that modified blackbody fits using a shallow
emissivity (beta_c < 2.0) lead to significantly lower dust masses compared to
the beta_c < 2.0 case, with dust masses lower by up to 50% if beta_c=1.5 for
instance.The working resolution affects our total dust mass estimates: masses
increase from global fits to spatially-resolved fits.Comment: 26 pages, 12 figures, 4 tables, accepted for publication in MNRAS,
2012 June 2
The global dust SED: Tracing the nature and evolution of dust with DustEM
The Planck and Herschel missions are currently measuring the farIR-mm
emission of dust, which combined with existing IR data, will for the first time
provide the full SED of the galactic ISM dust emission with an unprecedented
sensitivity and angular resolution. It will allow a systematic study of the
dust evolution processes that affect the SED. Here we present a versatile
numerical tool, DustEM, that predicts the emission and extinction of dust given
their size distribution and their optical and thermal properties. In order to
model dust evolution, DustEM has been designed to deal with a variety of grain
types, structures and size distributions and to be able to easily include new
dust physics. We use DustEM to model the dust SED and extinction in the diffuse
interstellar medium at high-galactic latitude (DHGL), a natural reference SED.
We present a coherent set of observations for the DHGL SED. The dust components
in our DHGL model are (i) PAHs, (ii) amorphous carbon and (iii) amorphous
silicates. We use amorphous carbon dust, rather than graphite, because it
better explains the observed high abundances of gas-phase carbon in shocked
regions of the interstellar medium. Using the DustEM model, we illustrate how,
in the optically thin limit, the IRAS/Planck HFI (and likewise Spitzer/Herschel
for smaller spatial scales) photometric band ratios of the dust SED can
disentangle the influence of the exciting radiation field intensity and
constrain the abundance of small grains relative to the larger grains. We also
discuss the contributions of the different grain populations to the IRAS,
Planck and Herschel channels. Such information is required to enable a study of
the evolution of dust as well as to systematically extract the dust thermal
emission from CMB data and to analyze the emission in the Planck polarized
channels. The DustEM code described in this paper is publically available.Comment: accepted for publication in A&
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