274 research outputs found
A spectropolarimetric view on the nature of the peculiar Type I SN 2005hk
We report two spectropolarimetric observations of SN 2005hk, which is a close
copy of the "very peculiar" SN 2002cx, showing low peak luminosity, slow
decline, high ionization near peak and an unusually low expansion velocity of
only about 7,000 km s^-1. Further to the data presented by Chornock et al.,
(2006), at -4 days before maximum, we present data of this object taken on 9
November 2005 (near maximum) and 23 November (+ two weeks) that show the
continuum and most of the spectral lines to be polarized at levels of about
0.2-0.3%. At both epochs the data corresponds to the Spectropolarimetric Type
D1. The general low level of line polarization suggests that the line forming
regions for most species observed in the spectrum have a similar shape to that
of the photosphere, which deviates from a spherical symmetry by <10%. In
comparison with spectropolarimetry of Type Ia and Core-collapse SNe at similar
epochs, we find that the properties of SN 2005hk are most similar to those of
Type Ia SNe. In particular, we find the low levels of continuum and line
polarization to indicate that the explosion mechanism is approximately
spherical, with homogeneous ejecta (unlike the chemically segregated ejecta of
CCSNe). We discuss the possibility that SN 2005hk was the result of the pure
deflagration of a white dwarf and note the issues concerning this
interpretation.Comment: ApJ accepted, uses emulateapj, 16 pages, 10 figures, figures 3 and 4
update
Spectropolarimetry of the Type Ia SN 2007sr Two Months After Maximum Light
We present late time spectropolarimetric observations of SN 2007sr, obtained
with the VLT telescope at ESO Paranal Observatory when the object was 63 days
after maximum light. The late time spectrum displays strong line polarization
in the CaII absorption features. SN 2007sr adds to the case of some normal Type
Ia SNe that show high line polarization or repolarization at late times, a fact
that might be connected with the presence of high velocity features at early
times
Fair and Private Data Preprocessing through Microaggregation
Copyright \ua9 2023 held by the owner/author(s).Privacy protection for personal data and fairness in automated decisions are fundamental requirements for responsible Machine Learning. Both may be enforced through data preprocessing and share a common target: data should remain useful for a task, while becoming uninformative of the sensitive information. The intrinsic connection between privacy and fairness implies that modifications performed to guarantee one of these goals, may have an effect on the other, e.g., hiding a sensitive attribute from a classification algorithm might prevent a biased decision rule having such attribute as a criterion. This work resides at the intersection of algorithmic fairness and privacy. We show how the two goals are compatible, and may be simultaneously achieved, with a small loss in predictive performance. Our results are competitive with both state-of-the-art fairness correcting algorithms and hybrid privacy-fairness methods. Experiments were performed on three widely used benchmark datasets: Adult Income, COMPAS, and German Credit
La depresión post-parto desde la pulsión de muerte
La DPP constituye un tema de interés reciente para el psicoanálisis, al que ha arribado como parte de su evolución teórica y clínica. Si bien existen estudios que dan cuenta de los efectos del estado depresivo en el desarrollo psíquico de su hijo, aún resulta escasa las investigaciones sobre la dinámica que se produce en la madre cuando se va afectada por este tipo de depresión. Este trabajo discute la utilidad del concepto de pulsión de muerte para profundizar en la comprensión de los psicodinamismos que se producen en los cuadros de depresión post-parto.Tesi
La depresión post-parto desde la pulsión de muerte
La DPP constituye un tema de interés reciente para el psicoanálisis, al que ha arribado como parte de su evolución teórica y clínica. Si bien existen estudios que dan cuenta de los efectos del estado depresivo en el desarrollo psíquico de su hijo, aún resulta escasa las investigaciones sobre la dinámica que se produce en la madre cuando se va afectada por este tipo de depresión. Este trabajo discute la utilidad del concepto de pulsión de muerte para profundizar en la comprensión de los psicodinamismos que se producen en los cuadros de depresión post-parto
Properties of extragalactic dust inferred from linear polarimetry of Type Ia Supernovae
Aims: The aim of this paper is twofold: 1) to investigate the properties of
extragalactic dust and compare them to what is seen in the Galaxy; 2) to
address in an independent way the problem of the anomalous extinction curves
reported for reddened Type Ia Supernovae (SN) in connection to the environments
in which they explode. Methods: The properties of the dust are derived from the
wavelength dependence of the continuum polarization observed in four reddened
Type Ia SN: 1986G, 2006X, 2008fp, and 2014J. [...] Results: All four objects
are characterized by exceptionally low total-to-selective absorption ratios
(R_V) and display an anomalous interstellar polarization law, characterized by
very blue polarization peaks. In all cases the polarization position angle is
well aligned with the local spiral structure. While SN~1986G is compatible with
the most extreme cases of interstellar polarization known in the Galaxy,
SN2006X, 2008fp, and 2014J show unprecedented behaviours. The observed
deviations do not appear to be connected to selection effects related to the
relatively large amounts of reddening characterizing the objects in the sample.
Conclusions: The dust responsible for the polarization of these four SN is most
likely of interstellar nature. The polarization properties can be interpreted
in terms of a significantly enhanced abundance of small grains. The anomalous
behaviour is apparently associated with the properties of the galactic
environment in which the SN explode, rather than with the progenitor system
from which they originate. For the extreme case of SN2014J, we cannot exclude
the contribution of light scattered by local material; however, the observed
polarization properties require an ad hoc geometrical dust distribution.Comment: 10 pages, 6 figures, accepted for publication in Astronomy and
Astrophysic
Accurate quantitative EDS-TEM analysis of precipitates and matrix in equilibrium (α+β) Zr–1Nb alloys with Ta addition
The (α+β) phase microstructure in Zr-1.05Nb, Zr-0.85Nb-0.20Ta and Zr-0.85Nb-0.40Ta (wt.%) alloys annealed at 570 °C for 3840 h after β-quenching were observed at different scales by optical, SEM and TEM microscopies. A quantitative study of phase chemical compositions was carried out by EDS-TEM with experimental Cliff-Lorimer factors. The α matrix was measured on thin films and the β particle on carbon extractive replicas. The Ta addition showed a continuous increase of (Nb + Ta) solubility in α-Zr and (Zr + Ta) solubility in the β-Nb phase. The increase of Ta in the nominal composition of the Zr-1(Nb, Ta) alloy causes the decrease of the mass fraction of β-Nb phase.Fil: Ferreirós, Pedro Antonio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; ArgentinaFil: Alonso, P. R.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Quirós, D. P.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); ArgentinaFil: Zelaya, E.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Rubiolo, Gerardo Hector. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentin
Neural correlates of visuospatial working memory in the ‘at-risk mental state’
Background. Impaired spatial working memory (SWM) is a robust feature of schizophrenia and has been linked to
the risk of developing psychosis in people with an at-risk mental state (ARMS). We used functional magnetic
resonance imaging (fMRI) to examine the neural substrate of SWM in the ARMS and in patients who had just
developed schizophrenia.
Method. fMRI was used to study 17 patients with an ARMS, 10 patients with a first episode of psychosis and 15 agematched
healthy comparison subjects. The blood oxygen level-dependent (BOLD) response was measured while
subjects performed an object–location paired-associate memory task, with experimental manipulation of mnemonic
load.
Results. In all groups, increasing mnemonic load was associated with activation in the medial frontal and medial
posterior parietal cortex. Significant between-group differences in activation were evident in a cluster spanning the
medial frontal cortex and right precuneus, with the ARMS groups showing less activation than controls but greater
activation than first-episode psychosis (FEP) patients. These group differences were more evident at the most
demanding levels of the task than at the easy level. In all groups, task performance improved with repetition of the
conditions. However, there was a significant group difference in the response of the right precuneus across repeated
trials, with an attenuation of activation in controls but increased activation in FEP and little change in the ARMS.
Conclusions. Abnormal neural activity in the medial frontal cortex and posterior parietal cortex during an SWM task
may be a neural correlate of increased vulnerability to psychosis
Spectropolarimetry of the Type IIb SN 2008aq
We present optical spectroscopy and spectropolarimetry of the Type IIb SN 2008aq 16 days
and 27 days post-explosion. The spectrum of SN 2008aq remained dominated by Hα P Cygni
profile at both epochs, but showed a significant increase in the strength of the helium features,
which is characteristic of the transition undergone by supernovae between Type IIb and Type
Ib. Comparison of the spectra of SN 2008aq to other Type IIb SNe (SN 1993J, SN 2011dh, and
SN 2008ax) at similar epochs revealed that the helium lines in SN 2008aq are much weaker,
suggesting that its progenitor was stripped to a lesser degree. SN 2008aq also showed signifi-
cant levels of continuum polarisation at pcont= 0.70 (± 0.22) % in the first epoch, increasing
to pcont=1.21 (± 0.33) % by the second epoch. Moreover, the presence of loops in the q − u
planes of Hα and He I in the second epoch suggests a departure from axial symmetry
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