1,175 research outputs found
Are the HI deficient galaxies on the outskirts of Virgo recent arrivals?
The presence on the Virgo cluster outskirts of spiral galaxies with gas
deficiencies as strong as those of the inner galaxies stripped by the
intracluster medium has led us to explore the possibility that some of these
peripheral objects are not newcomers. A dynamical model for the collapse and
rebound of spherical shells under the point mass and radial flow approximations
has been developed to account for the amplitude of the motions in the Virgo I
cluster (VIC) region. According to our analysis, it is not unfeasible that
galaxies far from the cluster, including those in a gas-deficient group well to
its background, went through its core a few Gyr ago. The implications would be:
(1) that the majority of the HI-deficient spirals in the VIC region might have
been deprived of their neutral hydrogen by interactions with the hot
intracluster medium; and (2) that objects spending a long time outside the
cluster cores might keep the gas deficient status without altering their
morphology.Comment: Accepted for publication in ApJ. 4 pages, 3 figures. Uses emulateapj
Hamiltonian and physical Hilbert space in polymer quantum mechanics
In this paper, a version of polymer quantum mechanics, which is inspired by
loop quantum gravity, is considered and shown to be equivalent, in a precise
sense, to the standard, experimentally tested, Schroedinger quantum mechanics.
The kinematical cornerstone of our framework is the so called polymer
representation of the Heisenberg-Weyl (H-W) algebra, which is the starting
point of the construction. The dynamics is constructed as a continuum limit of
effective theories characterized by a scale, and requires a renormalization of
the inner product. The result is a physical Hilbert space in which the
continuum Hamiltonian can be represented and that is unitarily equivalent to
the Schroedinger representation of quantum mechanics. As a concrete
implementation of our formalism, the simple harmonic oscillator is fully
developed.Comment: 19 pages, 2 figures. Comments and references added. Version to be
published in CQ
Rapid and MR-Independent IK1 activation by aldosterone during ischemia-reperfusion
In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious
effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac
mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone
modulates K+ currents involved in the holding of the resting membrane potential (RMP).
The aim of this study was to assess the electrophysiological impact of aldosterone on IK1
current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone”
using right rabbit ventricle and standard microelectrode technique followed by cell-attached
recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments,
aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential
duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4ms to
116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature
ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely,
potassium canrenoate 100 nmol/L and RU 28318 1 μmol/l alone did not affect AP
parameters and premature ventricular contractions occurrence (except Vmax which was
decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone
induced a RMP hyperpolarization, evoking an implication of a K+ current involved in the
holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly
activated (within 6.2±0.4 min) a 30 pS K+-selective current, inward rectifier, with pharmacological
and biophysical properties consistent with the IK1 current (NPo =1.9±0.4 in control vs
NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318,
a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non
specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating
a MR-independent IK1 activation. In this ischemia-reperfusion context, aldosterone induced
rapid and MR-independent deleterious effects including an arrhythmia substrate (increased
APD90 dispersion) and triggered activities (increased premature ventricular contractions
occurrence on reperfusion) possibly related to direct IK1 activation
Astrometry at OAFA. Earth rotation
A brief report on one of the astrometric activities (Earth Rotation) carried out at the "Félix Aguilar" Astronomical Observatory since its opening up to the present is given. I deals with: the importance of this research: the OAFA collaboration to the International Services, BIH and IPMS; the application of new techniques: VLBI, LLR and LSR, the new International Service, IERS, and its Reference System; and a brief account on the main tasks carried out and to be developed at the OAFA.Asociación Argentina de Astronomí
Magnetic field fluctuations in the shocked umbral chromosphere
Several studies have reported magnetic field fluctuations associated with
umbral shock waves. We aim to study the properties and origin of magnetic field
fluctuations in the umbral chromosphere. Temporal series of spectropolarimetric
observations were acquired with the GREGOR telescope. The chromospheric and
photospheric conditions were derived from simultaneous inversions of the He I
10830 \AA\ triplet and the Si I 10827 \AA\ line using HAZEL2. The oscillations
are interpreted using wavelet analysis and context information from UV
observations acquired with SDO/AIA and IRIS. The chromospheric magnetic field
shows strong fluctuations in the sunspot umbra, with peak field strengths up to
2900 G. Magnetic field and velocity umbral oscillations exhibit a strong
coherence, with the magnetic field lagging the shock fronts detected in the
velocity fluctuations. This points to a common origin of the fluctuations in
both parameters, whereas the analysis of the phase shift between photospheric
and chromospheric velocity is consistent with upwards wave propagation. These
results suggest that the strong inferred magnetic field fluctuations are caused
by changes in the response height of the He I 10830 \AA\ line to the magnetic
field, which is sensitive to high photospheric layers after the shock fronts.
The coronal activity seen in EUV data could possibly have some impact on the
inferred fluctuations, but it is not the main driver of the magnetic field
oscillations since they are found before EUV events take place. Chromospheric
magnetic field fluctuations measured with the He I 10830 \AA\ triplet arise due
to variations in the opacity of the line. After shocks produced by slow
magnetoacoustic waves, the response of the line to the magnetic field can be
shifted down to the upper photosphere. This is seen as remarkably large
fluctuations in the line of sight magnetic field strength.Comment: Accepted for publication in A&A. Abstract abridged due to arXiv's
1920 character limi
Numerical model characterization of the sound transmission mechanism in the tympanic membrane from a high-speed digital holographic experiment in transient regime
A methodology for the development of a finite element numerical model of the tympanic membrane (TM)
based on experiments carried out in the time domain on a cadaveric human temporal bone is presented.
Using a high-speed digital holographic (HDH) system, acoustically-induced transient displacements of the
TM surface are obtained. The procedure is capable to generate and validate the finite element model of
the TM by numerical and experimental data correlation. Reverse engineering approach is used to iden-
tify key material parameters that define the mechanical response of the TM. Finally, modal numerical
simulations of the specimen are performed. Results show the feasibility of the methodology to obtain
an accurate model of a specific specimen and to help interpret its behaviour with additional numerical
simulations.This work has been funded by the University of Malaga/CBUA, the FEDER program grant number UMA18-FEDERJA-214 and by the National Institutes of Health (NIH), National Institute on Deafness and Other Communication Disorders (NIDCD), grant number R01, DC016079. This research has also been partially supported by Research Grant Jose Castillejo number CAS19/00125 from Spain Government.
Funding for open access charge: Universidad de Málaga / CBU
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