Quiescent thermal emission from neutron stars in low-mass X-ray binaries

Context. We monitored the quiescent thermal emission from neutron stars in low-mass X-ray binaries after active periods of intense activity in X-rays (outbursts). Aims. The theoretical modeling of the thermal relaxation of the neutron star crust may be used to establish constraints on the crust composition and transport properties, depending on the astrophysical scenarios assumed. Methods. We numerically simulated the thermal evolution of the neutron star crust and compared them with inferred surface temperatures for five sources: MXB 1659−29, KS 1731−260, XTE J1701−462, EXO 0748−676  and IGR J17480−2446. Results. We find that the evolution of MXB 1659−29, KS 1731−260 and EXO 0748−676 can be well described within a deep crustal cooling scenario. Conversely, we find that the other two sources can only be explained with models beyond crustal cooling. For the peculiar emission of XTE J1701−462 we propose alternative scenarios such as residual accretion during quiescence, additional heat sources in the outer crust, and/or thermal isolation of the inner crust due to a buried magnetic field. We also explain the very recent reported temperature of IGR J17480−2446 with an additional heat deposition in the outer crust from shallow sources.

Ultrasonic and X-ray computed tomography characterization of progressive fracture damage in low-porous carbonate rocks

This paper studies the fracturing process in low-porous rocks during uniaxial compressive tests considering the original defects and the new mechanical cracks in the material. For this purpose, five different kinds of rocks have been chosen with carbonate mineralogy and low porosity (lower than 2%). The characterization of the fracture damage is carried out using three different techniques: ultrasounds, mercury porosimetry and X-ray computed tomography. The proposed methodology allows quantifying the evolution of the porous system as well as studying the location of new cracks in the rock samples. Intercrystalline porosity (the smallest pores with pore radius < 1 μm) shows a limited development during loading, disappearing rapidly from the porosimetry curves and it is directly related to the initial plastic behaviour in the stress–strain patterns. However, the biggest pores (corresponding to the cracks) suffer a continuous enlargement until the unstable propagation of fractures. The measured crack initiation stress varies between 0.25 σp and 0.50 σp for marbles and between 0.50 σp and 0.85 σp for micrite limestone. The unstable propagation of cracks is assumed to occur very close to the peak strength. Crack propagation through the sample is completely independent of pre-existing defects (porous bands, stylolites, fractures and veins). The ultrasonic response in the time-domain is less sensitive to the fracture damage than the frequency-domain. P-wave velocity increases during loading test until the beginning of the unstable crack propagation. This increase is higher for marbles (between 15% and 30% from initial vp values) and lower for micrite limestones (between 5% and 10%). When the mechanical cracks propagate unstably, the velocity stops to increase and decreases only when rock damage is very high. Frequency analysis of the ultrasonic signals shows clear changes during the loading process. The spectrum of treated waveforms shows two main frequency peaks centred at low (~ 20 kHz) and high (~ 35 kHz) values. When new fractures appear and grow the amplitude of the high-frequency peak decreases, while that of the low-frequency peak increases. Besides, a slight frequency shift is observed towards higher frequencies.

The hours of work problem in five major industries

Includes bibliographical references.

Can the new refugee relocation system work? Perils in the Dublin logic and flawed reception conditions in the EU. CEPS Policy Brief No. 332, October 2015 Thursday, 1 October 2015

This Policy Brief argues that the newly adopted EU temporary relocation (quota) system constitutes a welcome yet timid step forward in addressing a number of central controversies of the current refugee debate in Europe. Two main challenges affect the effective operability of the new EU relocation model. First, EU member states’ asylum systems show profound (on-the-ground) weaknesses in reception conditions and judicial/administrative capacities. These prevent a fair and humane processing of asylum applications. EU states are not implementing the common standards enshrined in the EU reception conditions Directive 2013/33. Second, the new relocation system constitutes a move away from the much-criticised Dublin system, but it is still anchored to its premises. The Dublin system is driven by an unfair and unsustainable rule according to which the first EU state of entry is responsible for assessing asylum applications. It does not properly consider the personal, private and family circumstances or the preferences of asylum-seekers. Policy Recommendations In order to respond to these challenges, the Policy Brief offers the following policy recommendations: The EU should strengthen and better enforce member states’ reception capacities, abolish the current Dublin system rule of allocation of responsibility and expand the new relocation distribution criteria to include in the assessment (as far as possible) asylum-seekers’ preferences and personal/family links to EU member states. EU member countries should give priority to boosting their current and forward-looking administrative and judicial capacities to deal and welcome asylum applications. The EU should establish a permanent common European border and asylum service focused on ensuring the highest standards through stable operational support, institutional solidarity across all EU external borders and the practical implementation of new distribution relocation criteria.