484 research outputs found
Impact of water saturation on seismoelectric transfer functions: a laboratory study of coseismic phenomenon
Seismic waves propagating in a porous medium, under favourable conditions, generate measurable electromagnetic fields due to electrokinetic effects. It has been proposed, following experimental and numerical studies, that these so-called âseismoelectromagnetic' couplings depend on pore fluid properties. The theoretical frame describing these phenomena are based on the original Biot's theory, assuming that pores are fluid-filled. We study here the impact of a partially saturated medium on amplitudes of those seismoelectric couplings by comparing experimental data to an effective fluid model. We have built a 1-m-length-scale experiment designed for imbibition and drainage of an homogeneous silica sand; the experimental set-up includes a seismic source, accelerometers, electric dipoles and capacitance probes in order to monitor seismic and seismoelectric fields during water saturation. Apparent velocities and frequency spectra (in the kiloHertz range) are derived from seismic and electrical measurements during experiments in varying saturation conditions. Amplitudes of seismic and seismoelectric waves and their ratios (i.e. transfer functions) are discussed using a spectral analysis performed by continuous wavelet transform. The experiments reveal that amplitude ratios of seismic to coseismic electric signals remain rather constant as a function of the water saturation in the Sw=[0.2-0.9] range, consistently with theoretically predicted transfer function
Measurement of the Integrated Faraday Rotations of BL Lac Objects
We present the results of multi-frequency polarization VLA observations of
radio sources from the complete sample of northern, radio-bright BL Lac objects
compiled by H. Kuhr and G. Schmidt. These were used to determine the integrated
rotation measures of 18 objects, 15 of which had never been measured
previously, which hindered analysis of the intrinsic polarization properties of
objects in the complete sample. These measurements make it possible to correct
the observed orientations of the linear polarizations of these sources for the
effect of Faraday rotation. The most probable origin for Faraday rotation in
these objects is the Galactic interstellar medium. The results presented
complete measurements of the integrated rotation measures for all 34 sources in
the complete sample of BL Lac objects.Comment: 9 pages, 7 figure
Radio galaxies and magnetic fields in A514
A514 contains six extended and polarized radio sources located at various
projected distances from the cluster center. Here we present a detailed study
of these six radio sources in total intensity and polarization using the Very
Large Array at 3.6 and 6 cm. Since the radio sources sample different lines of
sight across the cluster, an analysis of the Faraday Rotation Measures (RMs)
provides information on the strength and the structure of the cluster magnetic
field. These sources show a decreasing Faraday Rotation Measure with increasing
distance from the cluster center. We estimate the strength of the magnetic
field to be ~3-7 uG in the cluster center. From the RM structure across the
stronger and more extended sources we estimate the coherence length of the
magnetic field to be about 9 kpc at the cluster center.Comment: 16 pages, 18 ps figures accepted by A&
Rapport dâĂ©tape : premiĂšre Ă©tape : journĂ©es de rĂ©flexion entre les acteurs du rĂ©tablissement au QuĂ©bec
Lâobjectif de ce rapport est de prĂ©senter les rĂ©sultats des trois jours de rĂ©flexion rĂ©alisĂ©s au printemps 2019 sur le rĂ©tablissement au QuĂ©bec. Lâanalyse de ces rĂ©sultats a permis dâidentifier trois axes stratĂ©giques qui permettront dâaccroĂźtre les capacitĂ©s de rĂ©tablissement post-sinistre au QuĂ©bec. Pour chacun des axes stratĂ©giques, un outil de rĂ©tablissement sera prototypĂ© lors de la prochaine phase de ce projet de recherche-action Ă lâautomne 2019. Dans ce rapport, nous prĂ©sentons dâabord un rĂ©capitulatif de la dĂ©marche utilisĂ©e, puis nous clarifions la notion de rĂ©tablissement Ă partir des Ă©crits scientifiques. Par la suite, nous analysons lâĂ©tat du rĂ©tablissement au QuĂ©bec Ă la lumiĂšre des ateliers rĂ©alisĂ©s au courant de la premiĂšre phase de la dĂ©marche dâaccompagnement. De ce portrait issu du contexte quĂ©bĂ©cois, nous dĂ©terminons les enjeux qui, selon les participants, freinent le dĂ©veloppement et la mise en oeuvre dâoutils de rĂ©tablissement ainsi que les leviers pouvant permettre son dĂ©veloppement. Sur la base de cette analyse, nous proposons un cadre dâanalyse reposant sur trois grands axes stratĂ©giques qui rĂ©pondent au besoin de faciliter le rĂ©tablissement au QuĂ©bec. Ă terme, ce cadre permettra dâorienter la prochaine phase de la dĂ©marche, soit celle du prototypage dâoutils concrets afin dâamĂ©liorer la phase de rĂ©tablissement post-sinistre au QuĂ©bec
Pathological Narcissism in Adolescents: Relationships with Childhood Maltreatment and Internalizing and Externalizing Difficulties
Background: There are significant gaps in our understanding of vulnerable and grandiose narcissism in adolescents and whether it is associated with psychosocial difficulties as well as risk factors such as child maltreatment. Objective: The aim of this study was to examine vulnerable and grandiose narcissism in adolescents and young adults. Method: 570 participants (ages 14-21) from the community completed an online survey. Vulnerable and grandiose narcissism were assessed with the Pathological Narcissism Inventory, while psycho-social difficulties were assessed with the Child Behaviour Checklist and maltreatment with the Childhood Experiences of Care and Abuse Questionnaire. Results: Gender-specific age trends were identified, with narcissism appearing to decrease with age for females, while increasing for males into early adulthood. For females, vulnerable and grandiose narcissism was associated with maltreatment and partially mediated the relationship between abuse and neglect and internalizing and externalizing difficulties. Conclusion: These findings underscore the importance of considering the relationship between childhood maltreatment experiences and suggest that the relationship between such experiences and adolescent psychosocial difficulties may be partially accounted for by the negative impact that maltreatment has on narcissism
3C459: A highly asymmetric radio galaxy with a starburst
Multifrequency radio observations of the radio galaxy 3C459 using MERLIN, VLA
and the EVN, and an optical HST image using the F702W filter are presented. The
galaxy has a very asymmetric radio structure, a high infrared luminosity and a
young stellar population. The eastern component of the double-lobed structure
is brighter, much closer to the nucleus and is significantly less polarized
than the western one. This is consistent with the jet on the eastern side
interacting with dense gas, which could be due to a merged companion or dense
cloud of gas. The HST image of the galaxy presented here exhibits filamentary
structures, and is compared with the MERLIN 5-GHz radio map. EVN observations
of the prominent central component, which has a steep radio spectrum, show a
strongly curved structure suggesing a bent or helical radio jet. The radio
structure of 3C459 is compared with other highly asymmetric, Fanaroff-Riley II
radio sources, which are also good candidates for studying jet-cloud
interactions. Such sources are usually of small linear size and it is possible
that the jets are interacting with clouds of infalling gas that fuel the radio
source.Comment: 10 pages, 6 figures, 2 table
Radio sources at low Galactic latitudes
We present high-resolution radio observations of a sample of 65 radio sources
at low Galactic latitudes. The sources were all observed at 5 GHz with the Very
Large Array A-array. MERLIN observations at 5 GHz of the ultracompact HII
region G34.26+0.15 and one of the extragalactic sources, B1857-000, are also
presented, as are GMRT observations of HI in the direction of three sources,
B1801-203, B1802-196 and B1938+229. These observations were made with the
objectives of (i) finding compact components suitable for studying the effects
of interstellar scattering at lower frequencies, (ii) identifying high
surface-brightness lobes of background radio sources to probe the Galactic
magnetic field on different scales via polarization observations, and (iii)
searching for young supernova remnants. We discuss the nature of the sources
found to have shell or shell-like structure and exhibiting both thermal and
non-thermal spectra. Of the remaining sources, B1749-281 is coincident within
the positional errors of a known pulsar, not detected earlier at 5 GHz. The
rest are likely to be background extragalactic objects.Comment: 12 pages, 6 figures (most with multiple images), 1 table. Accepted
for publicaton in MNRA
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