11,049 research outputs found
Constant current source for converting absolute temperatures to analog voltages
Circuit configuration consisting of matched differential amplifier, temperature compensated zener diode, and low pinchoff-voltage field effect transistor provides accurate and stable current supply for temperature sensor devices
Equivariant intersection cohomology of the circle actions
In this paper, we prove that the orbit space B and the Euler class of an
action of the circle S^1 on X determine both the equivariant intersection
cohomology of the pseudomanifold X and its localization. We also construct a
spectral sequence converging to the equivariant intersection cohomology of X
whose third term is described in terms of the intersection cohomology of B.Comment: Final version as accepted in RACSAM. The final publication is
available at springerlink.com; Revista de la Real Academia de Ciencias
Exactas, Fisicas y Naturales. Serie A. Matematicas, 201
The X-ray spectral properties of very-faint persistent neutron star X-ray binaries
AX J1754.2-2754, 1RXS J171824.2-402934 and 1RXH J173523.7-354013 are three
persistent neutron star low-mass X-ray binaries that display a 2--10 keV
accretion luminosity Lx of only (1-10)x1E34 erg s-1 (i.e., only ~0.005-0.05 %
of the Eddington limit). The phenomenology of accreting neutron stars which
accrete at such low accretion rates is not yet well known and the reason why
they have such low accretion rates is also not clear. Therefore, we have
obtained XMM-Newton data of these three sources and here we report our analysis
of the high-quality X-ray spectra we have obtained for them. We find that AX
J1754.2-2754 has Lx~1E35 erg s-1, while the other two have X-ray luminosities
about an order of magnitude lower. However, all sources have a similar,
relatively soft, spectrum with a photon index of 2.3-2.5, when the spectrum is
fitted with an absorbed power-law model. This model fits the data of AX
J1754.2-2754 adequately, but it cannot fit the data obtained for 1RXS
J171824.2-402934 and 1RXH J173523.7-354013. For those sources a clear soft
thermal component is needed to fit their spectra. This soft component
contributes 40% - 50% to the 0.5-10 keV flux of the sources. When including
this additional spectral component, the power-law photon indices are
significantly lower. It can be excluded that a similar component with similar
contributions to the 2-10 keV X-ray flux is present for AX J1754.2-2754,
indicating that the soft spectrum of this source is mostly due to the fact that
the power-law component itself is not hard. We note that we cannot excluded
that weaker soft component is present in the spectrum of this source which only
contributes up to ~25% to the 0.5-10 keV X-ray flux. We discuss our results in
the context of what is known of accreting neutron stars at very low accretion
rate.Comment: 9 pages, 2 tables, 1 figure. Aceppted for publication in MNRA
XMM-Newton and Swift spectroscopy of the newly discovered very-faint X-ray transient IGR J17494-3030
A growing group of low-mass X-ray binaries are found to be accreting at
very-faint X-ray luminosities of <1E36 erg/s (2-10 keV). Once such system is
the new X-ray transient IGR J17494-3030. We present Swift and XMM-Newton
observations obtained during its 2012 discovery outburst. The Swift
observations trace the peak of the outburst, which reached a luminosity of ~7
E35 (D/8 kpc)^2 erg/s (2-10 keV). The XMM-Newton data were obtained when the
outburst had decayed to an intensity of ~ 8 E34 (D/8 kpc)^2 erg/s. The spectrum
can be described by a power-law with an index of ~1.7 and requires an
additional soft component with a black-body temperature of ~0.37 keV
(contributing ~20% to the total unabsorbed flux in the 0.5-10 keV band). Given
the similarities with high-quality spectra of very-faint neutron star low-mass
X-ray binaries, we suggest that the compact primary in IGR J17494-3030 is a
neutron star. Interestingly, the source intensity decreased rapidly during the
~12 hr XMM-Newton observation, which was accompanied by a decrease in inferred
temperature. We interpret the soft spectral component as arising from the
neutron star surface due to low-level accretion, and propose that the observed
decline in intensity was the result of a decrease in the mass-accretion rate
onto the neutron star.Comment: 3 figures, 2 tables, accepted in MNRAS letter, in pres
The Colombian conflict: a description of a mental health program in the Department of Tolima.
Colombia has been seriously affected by an internal armed conflict for more than 40 years affecting mainly the civilian population, who is forced to displace, suffers kidnapping, extortion, threats and assassinations. Between 2005 and 2008, Médecins Sans Frontières-France provided psychological care and treatment in the region of Tolima, a strategic place in the armed conflict. The mental health program was based on a short-term multi-faceted treatment developed according to the psychological and psychosomatic needs of the population. Here we describe the population attending during 2005-2008, in both urban and rural settings, as well as the psychological treatment provided during this period and its outcomes.We observed differences between the urban and rural settings in the traumatic events reported, the clinical expression of the disorders, the disorders diagnosed, and their severity. Although the duration of the treatment was limited due to security reasons and access difficulties, patient condition at last visit improved in most of the patients. These descriptive results suggest that further studies should be conducted to examine the role of short-term psychotherapy, adapted specifically to the context, can be a useful tool to provide psychological care to population affected by an armed conflict
Prediction and dynamics of ripples and the bottom boundary layer under combined wave and current flow in the field (poster)
Previously published investigations on the wave bottom boundary layer and ripple geometry are combined to derive a new ripple predictor for flows under waves or under combined wave-current flows. The ripple predictor of Nielsen (1981) for waves only was modified in order to use it in combined flows. The modified model now uses the effective Shields parameter total roughness-related in contrast to the most commonly used Shields parameter grain roughness-related. To predict the ripple geometry the proposed model uses the results of the Christoffersen and Jonsson (1985) model, which describes the dynamics of the wave-current bottom boundary layer (WCBBL). The ripple predictor and the WCBBL model take into account the bedforms already existing to predict the new ripple and flow field. The predicted ripple and WCBBL parameters fits very well the selected measurements of Li and Amos (1998) for ripple geometry and observations on saltation/suspension and sheet flow. The ripple predictor proposed models the ripple field in the break-off range and when large wave ripples were observed in the field, after the peak of the storms, without explicit assumptions. The apparent roughness length modelled by the WCBBL model is similar to measurements, made by other researchers in laboratories
Resonance in Asymmetric Warped Geometry
We study the spectrum of an asymmetric warped braneworld model with different
AdS curvatures on either side of the brane. In addition to the RS-like modes we
find a resonance state. Its mass is proportional to the geometric mean of the
two AdS curvature scales, while the difference between them determines the
strength of the resonance peak. There is a complementarity between the RS
zero-mode and the resonance: making the asymmetry stronger weakens the
zero-mode but strengthens the resonance, and vice versa. We calculate
numerically the braneworld gravitational potential and discuss the holographic
correspondence for the asymmetric model.Comment: 17 pages, 9 figures; v2 references with comments added; v3 two
references added, JHEP versio
Swift J1357.2-0933: the faintest black hole?
Swift J1357.2-0933 is the first confirmed very faint black hole X-ray
transient and has a short estimated orbital period of 2.8 hr. We observed Swift
J1357.2-0933 for ~50 ks with XMM-Newton in 2013 July during its quiescent
state. The source is clearly detected at a 0.5-10 keV unabsorbed flux of
~3x10^-15 erg cm-2 s-1. If the source is located at a distance of 1.5 kpc (as
suggested in the literature), this would imply a luminosity of ~8x10^29 erg
s-1, making it the faintest detected quiescent black hole LMXB. This would also
imply that there is no indication of a reversal in the quiescence X-ray
luminosity versus orbital period diagram down to 2.8 hr, as has been predicted
theoretically and recently supported by the detection of the 2.4 hr orbital
period black hole MAXI J1659-152 at a 0.5-10 keV X-ray luminosity of ~ 1.2 x
10^31 erg s-1. However, there is considerable uncertainty in the distance of
Swift J1357.2-0933 and it may be as distant as 6 kpc. In this case, its
quiescent luminosity would be Lx ~ 1.3 x 10^31 erg s-1, i.e., similar to MAXI
J1659-152 and hence it would support the existence of such a bifurcation
period. We also detected the source in optical at r' ~22.3 mag with the
Liverpool telescope, simultaneously to our X-ray observation. The X-ray/optical
luminosity ratio of Swift J1357.2-0933 agrees with the expected value for a
black hole at this range of quiescent X-ray luminosities.Comment: 5 pages, 3 figures, Accepted for publication in MNRA
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