1,710 research outputs found
Construction and Import of Ethnic Categorisations: “Allochthones” in The Netherlands and Belgium
Schematically one can distinguish two traditions related to ethnic statistics in Europe. In France, Germany and most southern European countries, the dominant statistical categorisations merely distinguish individuals on the basis of their nationality. In contrast, most northern European countries have been producing data on the ethnic and/or foreign origin of their populations. Belgium is caught somewhere in between these two traditions. The French speaking part of Belgium tends to follow the French tradition of refusing ethnic categorisation, while the Flemish (the Dutch speaking part) try to copy the Dutch model in distinguishing “allochthones” and “autochthones”. This contribution wants to offer an analysis of the construction of ethnic categories as it has been undertaken in the Dutch context. It equally wants to shed light on how the category of “allochthones” has been (partially) imported into the Belgian context and what the consequences are.Ethnic Categorisation, Statistics, “Allochthones”, the Netherlands, Belgium
Des flux migratoires aux carrières migratoires Éléments pour une nouvelle perspective théorique des mobilités contemporaines
Les ambivalences de l’État social-sécuritaire
L’article envisage le changement du paradigme des politiques publiques liées à l’insécurité en milieu urbain. À l’encontre de ceux qui voient l’émergence d’un État pénal se substituant à l’État social, l’article soutient, à partir de l’étude de la situation existant en Belgique, que les nouvelles politiques urbaines reposent sur un changement de paradigme de certaines politiques publiques. La pacification urbaine, paradigme de ce qui qualifie l’action de l’État social-sécuritaire, repose sur des mesures visant simultanément à la sécurisation des personnes et des espaces publics et à la réaffiliation sociale dans les territoires résidentiels précarisés. Les nouvelles politiques urbaines produisent de la régulation sociale tout en inscrivant leur rôle un cadre normatif renouvelé du contrôle social.This article identifies a public policy paradigm change related to insecurity in urban settings. While some describe a penal state replacing the social state, this article instead claims, drawing on the Belgian case, that new urban policies mark a shift towards a paradigm that emphasises both security and the social. Urban peace is the goal of this paradigm, with programmes being designed both to make persons and public places safe and to maintain social cohesion in marginal residential areas. These urban policies involve social regulation via new norms of social control
Discovery of a strongly phase-variable spectral feature in the isolated neutron star RX J0720.4-3125
We present the discovery of a strongly phase-variable absorption feature in
the X-ray spectrum of the nearby, thermally-emitting, isolated neutron star RX
J0720.4-3125. The absorption line was detected performing detailed
phase-resolved spectroscopy in 20 XMM-Newton observations, covering the period
May 2000 - September 2012. The feature has an energy of ~750eV, an equivalent
width of ~30eV, and it is significantly detected for only ~20% of the pulsar
rotation. The absorption feature appears to be stable over the timespan covered
by the observations. Given its strong dependence on the pulsar rotational phase
and its narrow width, a plausible interpretation is in terms of resonant proton
cyclotron absorption/scattering in a confined magnetic structure very close to
the neutron star surface. The inferred field in such a magnetic loop is B_loop
~ 2 x 10^{14} G, a factor of ~7 higher than the surface dipolar magnetic field.Comment: 6 pages, 4 figures; ApJ Letters accepte
Magnetar-like activity from the central compact object in the SNR RCW103
The 6.67 hr periodicity and the variable X-ray flux of the central compact
object (CCO) at the center of the SNR RCW 103, named 1E 161348-5055, have been
always difficult to interpret within the standard scenarios of an isolated
neutron star or a binary system. On 2016 June 22, the Burst Alert Telescope
(BAT) onboard Swift detected a magnetar-like short X-ray burst from the
direction of 1E 161348-5055, also coincident with a large long-term X-ray
outburst. Here we report on Chandra, NuSTAR, and Swift (BAT and XRT)
observations of this peculiar source during its 2016 outburst peak. In
particular, we study the properties of this magnetar-like burst, we discover a
hard X-ray tail in the CCO spectrum during outburst, and we study its long-term
outburst history (from 1999 to July 2016). We find the emission properties of
1E 161348-5055 consistent with it being a magnetar. However in this scenario,
the 6.67 hr periodicity can only be interpreted as the rotation period of this
strongly magnetized neutron star, which therefore represents the slowest pulsar
ever detected, by orders of magnitude. We briefly discuss the viable slow-down
scenarios, favoring a picture involving a period of fall-back accretion after
the supernova explosion, similarly to what is invoked (although in a different
regime) to explain the "anti-magnetar" scenario for other CCOs.Comment: 6 pages, 3 figures. To be published in the Astrophysical Journal
Letters; replaced to match the version accepted for publication on 2016
August 1
Magnetars' Giant Flares: the case of SGR 1806-20
We first review on the peculiar characteristics of the bursting and flaring
activity of the Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars. We then
report on the properties of the SGR 1806-20's Giant Flare occurred on 2004
December 27th, with particular interest on the pre and post flare
intensity/hardness correlated variability. We show that these findings are
consistent with the picture of a twisted internal magnetic field which stresses
the star solid crust that finally cracks causing the giant flare (and the
observed torsional oscillations). This crustal fracturing is accompanied by a
simplification of the external magnetic field with a (partial) untwisting of
the magnetosphere.Comment: 6 pages, 2 figures; accepted for publication in the Chinese Journal
for Astronomy and Astrophysics (Vulcano conference - 2005
Multi-wavelength observations of the transitional millisecond pulsar binary XSSJ12270-4859
We present an analysis of X-ray, Ultraviolet and optical/near-IR photometric
data of the transitional millisecond pulsar binary XSSJ12270-4859, obtained at
different epochs after the transition to a rotation-powered radio pulsar state.
The observations, while confirming the large-amplitude orbital modulation found
in previous studies after the state change, also reveal an energy dependence of
the amplitudes as well as variations on time scale of months. The amplitude
variations are anti-correlated in the X-ray and the UV/optical bands. The
average X-ray spectrum is described by a power law with \Gamma index of 1.07(8)
without requiring an additional thermal component. The power law index \Gamma
varies from 1.2 to 1.0 between superior and inferior conjunction of the neutron
star. We interpret the observed X-ray behaviour in terms of synchrotron
radiation emitted in an extended intrabinary shock, located between the pulsar
and the donor star, which is eclipsed due to the companion orbital motion. The
G5 type donor dominates the UV/optical and near-IR emission and is similarly
found to be heated up to ? 6500K as in the disc state. The analysis of optical
light curves gives a binary inclination 46 < i < 65deg and a mass ratio 0.11 <
q <0.26. The donor mass is found to be 0.15 < M2 < 0.36Msun for a neutron star
mass of 1.4Msun. The variations in the amplitude of the orbital modulation are
interpreted in terms of small changes in the mass flow rate from the donor
star. The spectral energy distribution from radio to gamma-rays is composed by
multiple contributions that are different from those observed during the
accretion-powered state.Comment: 10 pages, 8 figures, 1 table Accepted for publication in Monthly
Notices Royal Astronomical Society, Main Journa
Filtrate seaweed extract as biostimulant in nursery organic horticulture
Many naturally-derived products are used as growth promoters or biostimulants on vegetables, even if their mechanisms of action are not still now completely clarified. Among them, seaweeds and seaweed products are inserted as admissible organic fertilizers in the Annex I of the Reg. (EC) No. 889/2008, even if their biostimulant properties are not recognized in organic farming.
After a previous bioassay on maize germination for defining the optimal water dilution ratios of the filtrate seaweed extract (FSE), in the present research we applied the FSE at two diluted doses to a greenhouse organic lettuce, for assessing its biostimulant effect on vegetable growth and nutrient uptake.
The greenhouse pot trials were conducted on Lactuca sativa L., by applying FSE at 1/250 and 1/500 v/v water dilutions. After 90 days, root fresh/dry weight, shoot fresh/dry weight and dry matter, number of leaves, LAI, specific leaf fresh/dry weight, total dry biomass, leaf macro and micro elements (P, K, Ca, Mg, Fe, Na, Mn, Cu, Zn, B) content and total chlorophyll were determined.
Obtained results indicated that FSE plays a role in promoting the increase of lettuce shoot dry weight and related nutrient uptake, with particular efficacy in relation to P and K macroelements. This property is better expressed at the highest dilution, confirming that the biostimulating activity of the formulate acts without any nutritional effect: thus, the FSE appears to be a good opportunity for promoting the early-stage development for organic nursery productio
A variable absorption feature in the X-ray spectrum of a magnetar
Soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly
rotating, isolated neutron stars that sporadically undergo episodes of
long-term flux enhancement (outbursts) generally accompanied by the emission of
short bursts of hard X-rays. This behaviour can be understood in the magnetar
model, according to which these sources are mainly powered by their own
magnetic energy. This is supported by the fact that the magnetic fields
inferred from several observed properties of AXPs and SGRs are greater than -
or at the high end of the range of - those of radio pulsars. In the peculiar
case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing
parameters, whereas a strong field has been proposed to reside in the stellar
interior and in multipole components on the surface. Here we show that the
X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which
depend strongly on the star's rotational phase. This line is interpreted as a
proton cyclotron feature and its energy implies a magnetic field ranging from
2E14 gauss to more than 1E15 gauss.Comment: Nature, 500, 312 (including Supplementary Information
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