267 research outputs found
De la frustration démocratique au populisme. Du populisme à la radicalisation droitière
While political frustration in the United States has been mainly captured and expressed by «populist» parties since the end of the 19th century, the European democracies have remained for a long time immune of what has often been characterized as a «pathology» of democracy. Frustration and revolt were in most cases channeled by parties with well defined radical ideologies. The Communist parties were the natural vehicles for popular protest while extreme right parties were less attractive after the dramatic experiences of nazi and fascist regimes. The collapse of the communist regimes appeared at first as a testimony of the supremacy and victory of the «western» democracy. Instead, far from being the expression of the «end of history», the post 1989 period coupled with the technological, financial, economic and commercial revolutions has triggered radical critique of the democratic regimes based on representation and elite-driven modes of government. Populist movements have emerged and prospered in nearly all representative democracies in Europe. The paper argues that populism is an answer to the mounting frustration of voters vis à vis the representative organizations (political parties) and their inability to tackle the multifaceted dimensions of change in complex societies. While they are most of the time unable to set up a government of their own, populist movements have a decisive impact on institutions by promoting new instruments such as primaries or referenda, by marginalizing some parties of government, by setting up the public debate and influencing the policy choices (immigration, welfare, Brexit). This mushrooming populism has often been equated with the extreme-right. This confusion is misleading, not only because there are many forms of populism but mainly because the populist programs do not challenge democracy by itself. Instead, they fight the liberal values which are at the heart of representative democracy. Rather than being the modern clones of the old extreme-right, the populist parties express the preference for illiberal policies, national values and strong (authoritarian?) leadership «in the name of the people»
Dust Emissivity Variations In the Milky Way
Dust properties appear to vary according to the environment in which the dust
evolves. Previous observational indications of these variations in the FIR and
submm spectral range are scarce and limited to specific regions of the sky. To
determine whether these results can be generalised to larger scales, we study
the evolution in dust emissivities from the FIR to mm wavelengths, in the
atomic and molecular ISM, along the Galactic plane towards the outer Galaxy. We
correlate the dust FIR to mm emission with the HI and CO emission. The study is
carried out using the DIRBE data from 100 to 240 mic, the Archeops data from
550 mic to 2.1 mm, and the WMAP data at 3.2 mm (W band), in regions with
Galactic latitude |b| < 30 deg, over the Galactic longitude range (75 deg < l <
198 deg) observed with Archeops. In all regions studied, the emissivity spectra
in both the atomic and molecular phases are steeper in the FIR (beta = 2.4)
than in the submm and mm (beta = 1.5). We find significant variations in the
spectral shape of the dust emissivity as a function of the dust temperature in
the molecular phase. Regions of similar dust temperature in the molecular and
atomic gas exhibit similar emissivity spectra. Regions where the dust is
significantly colder in the molecular phase show a significant increase in
emissivity for the range 100 - 550 mic. This result supports the hypothesis of
grain coagulation in these regions, confirming results obtained over small
fractions of the sky in previous studies and allowing us to expand these
results to the cold molecular environments in general of the outer MW. We note
that it is the first time that these effects have been demonstrated by direct
measurement of the emissivity, while previous studies were based only on
thermal arguments.Comment: 16 pages, 6 figures, accepted in A&
Detection and characterization of a 500 μm dust emissivity excess in the Galactic plane using Herschel/Hi-GAL observations
Context. Past and recent observations have revealed unexpected variations in the far-infrared – millimeter (FIR-mm) dust emissivity in the interstellar medium. In the Herschel spectral range, those are often referred to as a 500 μm emission excess. Several dust emission models have been developed to interpret astrophysical data in the FIR-mm domain. However, these are commonly unable to fully reconcile theoretical predictions with observations. In contrast, the recently revised two level system (TLS) model, based on the disordered internal structure of amorphous dust grains, seems to provide a promising way of interpreting existing data.
Aims. The newly available Herschel infrared GALactic (Hi-GAL) data, which covers most of the inner Milky Way, offers a unique opportunity to investigate possible variations in the dust emission properties both with wavelength and environment. The goal of our analysis is to constrain the internal structure of the largest dust grains on Galactic scales, in the framework of the TLS model.
Methods. By combining the IRIS (Improved Reprocessing of the IRAS Survey) 100 μm with the Hi-GAL 160, 250, 350, and 500 μm data, we model the dust emission spectra in each pixel of the Hi-GAL maps, using both the TLS model and, for comparison, a single modified black-body fit. The effect of temperature mixing along the line of sight is investigated to test the robustness of our results.
Results. We find a slight decrease in the dust temperature with distance from the Galactic center, confirming previous results. We also report the detection of a significant 500 μm emissivity excess in the peripheral regions of the plane (35° < |l| < 70°) of about 13–15% of the emissivity, which can reach up to 20% in some HII regions. We present the spatial distributions of the best-fit values for the two main parameters of the TLS model, i.e. the charge correlation length, lc, used to characterize the disordered charge distribution (DCD) part of the model, and the amplitude A of the TLS processes with respect to the DCD effect. These distributions illustrate the variations in the dust properties with environment, in particular the plausible existence of an overall gradient with distance to the Galactic center. A comparison with previous findings in the solar neighborhood shows that the local value of the excess is less than expected from the Galactic gradient observed here
Toward a better understanding of the mid-infrared emission in the LMC
In this paper we aim to constrain for the first time the dust emission in the
mid-to-far infrared domain, in the LMC, with the use of the Spitzer IRS and
MIPS SED data, combined with Herschel data. We also consider UV extinction
predictions derived from modeling. We selected 10 regions observed as part of
the SAGE-Spec program, to probe dust properties in various environments
(diffuse, molecular and ionized regions). All data were smoothed to the
40arcsec angular resolution. The SEDs were modeled with DustEM models, using
the standard Mathis RF, as well as three additional RFs, with stellar clusters
ages ranging from 4 Myr to 600 Myr. Standard dust models used to reproduce the
Galactic diffuse medium are clearly not able to reproduce the dust emission in
the MIR wavelength domain. This analysis evidences the need of adjusting
parameters describing the dust size distribution and shows a clear distinct
behavior according to the type of environments. In addition, whereas the small
grain emission always seems to be negligible at long wavelengths in our Galaxy,
the contribution of this small dust component could be more important than
expected, in the submm-mm range, in the LMC averaged SED. Properties of the
small dust component of the LMC are clearly different from those of our Galaxy.
Its abundance, significantly enhanced, could be the result of large grains
shattering due to strong shocks or turbulence. In addition, this grain
component in the LMC systematically shows smaller grain size in the ionized
regions compared to the diffuse medium. Predictions of extinction curves show
significantly distinct behaviors depending on the dust models but also from one
region to another. Comparison of model predictions with the LMC mean extinction
curve shows that no model gives satisfactory agreement using the Mathis
radiation field while using a harder radiation field tends to improve the
agreementComment: Accepted for publication in A&
Modeling and predicting the shape of the far-infrared to submillimeter emission in ultra-compact HII regions and cold clumps
Dust properties are very likely affected by the environment in which dust
grains evolve. For instance, some analyses of cold clumps (7 K- 17 K) indicate
that the aggregation process is favored in dense environments. However,
studying warm (30 K-40 K) dust emission at long wavelength (300
m) has been limited because it is difficult to combine far
infared-to-millimeter (FIR-to-mm) spectral coverage and high angular resolution
for observations of warm dust grains. Using Herschel data from 70 to 500
m, which are part of the Herschel infrared Galactic (Hi-GAL) survey
combined with 1.1 mm data from the Bolocam Galactic Plane Survey (BGPS), we
compared emission in two types of environments: ultra-compact HII (UCHII)
regions, and cold molecular clumps (denoted as cold clumps). With this
comparison we tested dust emission models in the FIR-to-mm domain that
reproduce emission in the diffuse medium, in these two environments (UCHII
regions and cold clumps). We also investigated their ability to predict the
dust emission in our Galaxy. We determined the emission spectra in twelve UCHII
regions and twelve cold clumps, and derived the dust temperature (T) using the
recent two-level system (TLS) model with three sets of parameters and the
so-called T- (temperature-dust emissvity index) phenomenological models,
with set to 1.5, 2 and 2.5. We tested the applicability of the TLS
model in warm regions for the first time. This analysis indicates distinct
trends in the dust emission between cold and warm environments that are visible
through changes in the dust emissivity index. However, with the use of standard
parameters, the TLS model is able to reproduce the spectral behavior observed
in cold and warm regions, from the change of the dust temperature alone,
whereas a T- model requires to be known.Comment: Accepted for publication in A&A. 19 pages, 8 figures, 7 table
No sex scandals please, we're French: French attitudes towards politicians' public and private conduct
The notion of distinct ‘public’ and ‘private’ spheres underpins much normative and practical engagement with political misconduct. What is less clear is whether citizens draw distinctions between misdemeanours in the ‘public’ and ‘private’ spheres, and whether they judge these in systematically different ways. This paper explores attitudes to political misconduct in France. French citizens are often said to be particularly relaxed about politicians’ private affairs, but there has been little empirical evidence for this proposition. Drawing on original survey data, this paper demonstrates clearly that French citizens draw a sharp distinction between politicians’ public and private transgressions, and are more tolerant of the latter
Far-Infrared to Millimeter Astrophysical Dust Emission. II: Comparison of the Two-Level Systems (TLS) model with Astronomical Data
In a previous paper we proposed a new model for the emission by amorphous
astronomical dust grains, based on solid-state physics. The model uses a
description of the Disordered Charge Distribution (DCD) combined with the
presence of Two-Level Systems (TLS) defects in the amorphous solid composing
the grains. The goal of this paper is to confront this new model to
astronomical observations of different Galactic environments in the FIR/submm,
in order to derive a set of canonical model parameters to be used as a Galactic
reference to be compared to in future Galactic and extragalactic studies. We
confront the TLS model with existing astronomical data. We consider the average
emission spectrum at high latitudes in our Galaxy as measured with FIRAS and
WMAP, as well as the emission from Galactic compact sources observed with
Archeops, for which an inverse relationship between the dust temperature and
the emissivity spectral index has been evidenced. We show that, unlike models
previously proposed which often invoke two dust components at different
temperatures, the TLS model successfully reproduces both the shape of the
Galactic SED and its evolution with temperature as observed in the Archeops
data. The best TLS model parameters indicate a charge coherence length of
\simeq 13 nm and other model parameters in broad agreement with expectations
from laboratory studies of dust analogs. We conclude that the millimeter excess
emission, which is often attributed to the presence of very cold dust in the
diffuse ISM, is likely caused solely by TLS emission in disordered amorphous
dust grains. We discuss the implications of the new model, in terms of mass
determinations from millimeter continuum observations and the expected
variations of the emissivity spectral index with wavelength and dust
temperature. The implications for the analysis of the Herschel and Planck
satellite data are discussed.Comment: Accepted for publication in A&A (16 pages, 9 figures, 6 tables
First-principles scattering matrices for spin-transport
Details are presented of an efficient formalism for calculating transmission
and reflection matrices from first principles in layered materials. Within the
framework of spin density functional theory and using tight-binding muffin-tin
orbitals, scattering matrices are determined by matching the wave-functions at
the boundaries between leads which support well-defined scattering states and
the scattering region. The calculation scales linearly with the number of
principal layers N in the scattering region and as the cube of the number of
atoms H in the lateral supercell. For metallic systems for which the required
Brillouin zone sampling decreases as H increases, the final scaling goes as
H^2*N. In practice, the efficient basis set allows scattering regions for which
H^{2}*N ~ 10^6 to be handled. The method is illustrated for Co/Cu multilayers
and single interfaces using large lateral supercells (up to 20x20) to model
interface disorder. Because the scattering states are explicitly found,
``channel decomposition'' of the interface scattering for clean and disordered
interfaces can be performed.Comment: 22 pages, 13 figure
Interface observation of heat-treated Co/Mo2C multilayers
We study the interface evolution of a series of periodic Co/Mo2C multilayers
as a function of the annealing temperature up to 600{\textdegree}C. Different
complementary techniques are implemented to get information on the phenomenon
taking place at the interfaces of the stack. The periodical structure of
Co/Mo2C multilayer is proven by Time-of-flight secondary ion mass spectrometry
(ToF-SIMS) depth profiles which demonstrate the formation of an oxide layer at
both air/stack and stack/substrate interfaces. From Nuclear magnetic resonance
(NMR) spectra, we observed the intermixing phenomenon of Co and C atoms for the
as-deposited sample, and then at annealing temperature above 300{\textdegree}C
Co and C atoms separate from their mixed regions. Comparison of NMR results
between Co/Mo 2 C and Co/C references confirms this phenomenon. This is in
agreement with x-ray emission spectroscopy (XES) measurements. Furthermore the
calculation of the Co-C, Co-Mo and Mo-C mixing enthalpy using Miedema's model
gives a proof of the demixing of Co and C atoms present within the stacks above
300{\textdegree}C. From the transmission electron microscopy (TEM) analysis, we
found the presence of some crystallites within the as-deposited sample as well
as the mainly amorphous nature of all layers. This is confirmed using x-ray
diffraction (XRD) patterns which also demonstrate the growth of crystallites
induced upon annealing.Comment: Published in Applied Surface Science 331, 8-16 (2015).
http://dx.doi.org/10.1016/j.apsusc.2014.12.05
Accuracy of core mass estimates in simulated observations of dust emission
We study the reliability of mass estimates obtained for molecular cloud cores
using sub-millimetre and infrared dust emission. We use magnetohydrodynamic
simulations and radiative transfer to produce synthetic observations with
spatial resolution and noise levels typical of Herschel surveys. We estimate
dust colour temperatures using different pairs of intensities, calculate column
densities and compare the estimated masses with the true values. We compare
these results to the case when all five Herschel wavelengths are available. We
investigate the effects of spatial variations of dust properties and the
influence of embedded heating sources. Wrong assumptions of dust opacity and
its spectral index beta can cause significant systematic errors in mass
estimates. These are mainly multiplicative and leave the slope of the mass
spectrum intact, unless cores with very high optical depth are included.
Temperature variations bias colour temperature estimates and, in quiescent
cores with optical depths higher than for normal stable cores, masses can be
underestimated by up to one order of magnitude. When heated by internal
radiation sources the observations recover the true mass spectra. The shape,
although not the position, of the mass spectrum is reliable against
observational errors and biases introduced in the analysis. This changes only
if the cores have optical depths much higher than expected for basic
hydrostatic equilibrium conditions. Observations underestimate the value of
beta whenever there are temperature variations along the line of sight. A bias
can also be observed when the true beta varies with wavelength. Internal
heating sources produce an inverse correlation between colour temperature and
beta that may be difficult to separate from any intrinsic beta(T) relation of
the dust grains. This suggests caution when interpreting the observed mass
spectra and the spectral indices.Comment: Revised version, 17 pages, 17 figures, submitted to A&
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