1,130 research outputs found
A Biotechnological T-Shirt Monitors the Patient's Heart during Hemodialysis
Uremic patients are characterized by a "pro-arrhythmic substrate." Arrhythmia appearance during hemodialysis (HD) is an unexpected event with a high incidence of mortality and morbidity and difficult to record in patients repeatedly checked using electrocardiogram (ECG). Furthermore the carrying out of this important examination by classical devices during HD is uncomfortable and sometimes stressful for the patient. It may be very useful to monitor the patient's cardiac activity during the whole HD session. We tried to overcome these difficulties using Whealthy(®) (Wearable Health Care System), a wearable system in a T-shirt composed of conductors and piezoresistive materials, integrated to form fibers and threads connected to tissular sensors, electrodes, and connectors. ECG and pneumographic impedance signals are acquired by the electrodes in the tissue, and the data are registered by a small computer and transmitted via GPRS or Bluetooth
Contrast-Induced Nephropathy: Nephrologist's Opinion:
Contrast-induced nephropathy (CIN) has become the third leading cause of hospital-acquired acute kidney injury (AKI), due to an increasing number of patients receiving intravascular injection of io..
Auroral Radio Emission from Stars: the case of CU Virginis
CU Virginis is a rapidly rotating Magnetic Chemically Peculiar star with at
present unique characteristics as radio emitter. The most intriguing one is the
presence of intense, 100% circularly polarized radiation ascribed to Cyclotron
Maser. Each time the star rotates, this highly beamed emission points two times
toward the Earth, like a pulsar. We observed CU Vir in April 2010 with the EVLA
in two bands centered at 1450 and 1850 MHz. We covered nearly the whole
rotational period, confirming the presence of the two pulses at a flux density
up to 20 mJy. Dynamical spectra, obtained with unprecedented spectral and
temporal sensitivity, allow us to clearly see the different time delays as a
function of the frequency. We interpret this behaviour as a propagation effect
of the radiation inside the stellar magnetosphere. The emerging scenario
suggests interesting similarities with the auroral radio emission from planets,
in particular with the Auroral Kilometric Radiation (AKR) from Earth, which
originates at few terrestrial radii above the magnetic poles and was only
recently discovered to be highly beamed. We conclude that the magnetospheres of
CU Vir, Earth and other planets, maybe also exoplanets, could have similar
geometrical and physical characteristics in the regions where the cyclotron
maser is generated. In addition, the pulses are perfect "markers" of the
rotation period. This has given us for the first time the possibility to
measure with extraordinary accuracy the spin down of a star on or near the main
sequence.Comment: 18 pages, 4 figures, Accepted to APJ Letter, EVLA special issu
A three-dimensional model for the radio emission of magnetic chemically peculiar stars
In this paper we present a three-dimensional numerical model for the radio
emission of Magnetic Chemically Peculiar stars, on the hypothesis that
energetic electrons emit by the gyrosynchrotron mechanism. For this class of
radio stars, characterized by a mainly dipolar magnetic field whose axis is
tilted with respect to the rotational axis, the geometry of the magnetosphere
and its deformation due to the stellar rotation are determined. The radio
emitting region is determined by the physical conditions of the magnetosphere
and of the stellar wind. Free-free absorption by the thermal plasma trapped in
the inner magnetosphere is also considered. Several free parameters are
involved in the model, such as the size of the emitting region, the energy
spectrum and the number density of the emitting electrons, and the
characteristics of the plasma in the inner magnetosphere. By solving the
equation of radiative transfer, along a path parallel to the line of sight, the
radio brightness distribution and the total flux density as a function of
stellar rotation are computed. As the model is applied to simulate the observed
5 GHz lightcurves of HD37479 and HD37017, several possible magnetosphere
configurations are found. After simulations at other frequencies, in spite of
the large number of parameters involved in the modeling, two solutions in the
case of HD37479 and only one solution in the case of HD37017 match the observed
spectral indices. The results of our simulations agree with the magnetically
confined wind-shock model in a rotating magnetosphere. The X-ray emission from
the inner magnetosphere is also computed, and found to be consistent with the
observations.Comment: 15 pages, 10 figures, A&A in pres
3D-modelling of the stellar auroral radio emission
The electron cyclotron maser is the coherent emission process that gives rise
to the radio lighthouse effect observed in the hot magnetic chemically peculiar
star CU Virginis. It has also been proposed to explain the highly circularly
polarized radio pulses observed on some ultra cool dwarfs, with spectral type
earlier than M7. Such kind of coherent events resemble the auroral radio
emission from the magnetized planets of the solar system. In this paper, we
present a tridimensional model able to simulate the timing and profile of the
pulses emitted by those stars characterized by a dipolar magnetic field by
following the hypothesis of the laminar source model, used to explain the
beaming of the terrestrial auroral kilometric radiation. This model proves to
be a powerful tool to understand the auroral radio-emission phenomenon,
allowing us to derive some general conclusions about the effects of the model's
free parameters on the features of the coherent pulses, and to learn more about
the detectability of such kind of pulsed radio emission.Comment: 11 pages, 8 figures; accepted for publication in MNRA
Searching for OH maser emission towards the MIPSGAL compact Galactic bubbles
We conducted radio observations searching for OH 18-cm maser emission from a
sample of 169 unclassified MIPSGAL compact Galactic bubbles. These sources are
thought to be the circumstellar envelopes of different kinds of evolved stars.
Our observations were aimed at shedding light on the nature of MIPSGAL bubbles,
since their characterisation is a fundamental aid for the development of
accurate physical models of stellar and Galaxy evolution. The maser emission is
observatively linked to the last stages of the life of low- and
intermediate-mass stars, which may constitute a significant fraction of the
MIPSGAL bubbles. In particular OH masers are usually observed towards post-AGB
stars. Our observations were performed with the Green Bank Telescope and, for
each source, produced spectra around the four OH 18-cm transitions. The
observations were compared with archive interferometer data in order to exclude
possible contamination from nearby sources. The main result is that the OH
maser emission is not a common feature among the MIPSGAL bubbles, with only one
certain detection. We conclude that among the MIPSGAL bubbles the post-AGB
stars could be very rare
Molecular Geometry and Electronic Structure of Heptalentropones and Heptalendiones
The molecular geometries of 8-H-cycloheptatropone (I), 8-H-
-cycloheptatropolone (II), 2-methoxy-8-H-cycloheptatropone (III),
heptalen-1,8-dione (IV), 7-methoxy-heptalen-1,8-dione (V), 9-methoxy- heptalen-1,8-dione (VI) were fully optimized at lVIINDOj3
level. Heptalen-2,3-dione was also taken into account. The electronic
structures of the above molecules were studied by means of INDOjS method and the importance of doubly excited configurations
was tested at CNDO/S level. In all compounds a remarkable »single« and »double« bond alternation was found. Hydroxy and methoxy substitution affects the geometry of the ring where the substitution occurs whilst the unsubstituted ring unđergoes minor 01\u27 negligible changes. The electronic transitions agree well enough with the experimentally available absorption maxima; a strong transition is predicted in the neighborood of 200 nm. Several of these transitions
can be correlated with those of tropone and tropolone: on the whole they are not, 01\u27 negligibly, affected by double excitations except those Iying in the range of 5 eV and the ones at 4.29 eV and 4.82 eV of heptalen-2,3-dione
- …