834 research outputs found
Validez de la prueba de histerectomía vaginal en pacientes con indicación de vía abdominal mandatoria
Indexación: ScieloObjetivo: Evaluar la histerectomía vaginal en la resolución de patología uterina benigna, en casos que habitualmente se resuelven por histerectomía abdominal. Método: Estudio prospectivo en 68 pacientes sometidas a histerectomía vaginal en el Servicio de Ginecología del Hospital Claudio Vicuña, de San Antonio, entre junio de 2003 a junio de 2009. Son pacientes sin partos vaginales, algunas nuligestas, la mayoría con cicatrices de cesárea o historia de cirugía pélvica previa. Se separan en dos grupos, uno de dificultad moderada (DM) (útero móvil, vagina >2 dedos de diámetro, fondos de saco bien conformados) y otro de dificultad severa (DS) (útero fjo, vagina 2 fingers diameter, well conserved cul de sac, and severe difficulty (SD): composed by patients with none uterine motility, vagina <2 fingers diameter or fat cul de sac. Results: We did not observed statistically significant differences in age, number of prior cesarean sections or pelvic surgeries, estimated uterine size, bladder injury, nor abdominal conversion, but there was significant differences in operative time and need of morcelation, being greater in SD patients. It is important to notice the absent of major and minor complications in 93% of the patients. Conclusion: Our results are meant to demystify the objections for vaginal route, including the patients with extreme difficulty.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-75262010000500008&nrm=is
A customisable pipeline for continuously harvesting socially-minded Twitter users
On social media platforms and Twitter in particular, specific classes of
users such as influencers have been given satisfactory operational definitions
in terms of network and content metrics.
Others, for instance online activists, are not less important but their
characterisation still requires experimenting.
We make the hypothesis that such interesting users can be found within
temporally and spatially localised contexts, i.e., small but topical fragments
of the network containing interactions about social events or campaigns with a
significant footprint on Twitter.
To explore this hypothesis, we have designed a continuous user profile
discovery pipeline that produces an ever-growing dataset of user profiles by
harvesting and analysing contexts from the Twitter stream.
The profiles dataset includes key network and content-based users metrics,
enabling experimentation with user-defined score functions that characterise
specific classes of online users.
The paper describes the design and implementation of the pipeline and its
empirical evaluation on a case study consisting of healthcare-related campaigns
in the UK, showing how it supports the operational definitions of online
activism, by comparing three experimental ranking functions. The code is
publicly available.Comment: Procs. ICWE 2019, June 2019, Kore
On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
The F-GAMMA program is a coordinated effort to investigate the physics of
Active Galactic Nuclei (AGNs) via multi-frequency monitoring of {\em Fermi}
blazars. The current study is concerned with the broad-band radio spectra
composed of measurement at ten frequencies between 2.64 and 142 GHz. It is
shown that any of the 78 sources studied can be classified in terms of their
variability characteristics in merely 5 types of variability. The first four
types are dominated by spectral evolution and can be reproduced by a simple
two-component system made of the quiescent spectrum of a large scale jet
populated with a flaring event evolving according to Marscher & Gear (1985).
The last type is characterized by an achromatic change of the broad-band
spectrum which must be attributed to a completely different mechanism. Here are
presented, the classification, the assumed physical system and the results of
simulations that have been conducted.Comment: 2011 Fermi Symposium proceedings - eConf C11050
Cosmic-ray acceleration in supernova remnants: non-linear theory revised
A rapidly growing amount of evidences, mostly coming from the recent
gamma-ray observations of Galactic supernova remnants (SNRs), is seriously
challenging our understanding of how particles are accelerated at fast shocks.
The cosmic-ray (CR) spectra required to account for the observed phenomenology
are in fact as steep as , i.e., steeper than the
test-particle prediction of first-order Fermi acceleration, and significantly
steeper than what expected in a more refined non-linear theory of diffusive
shock acceleration. By accounting for the dynamical back-reaction of the
non-thermal particles, such a theory in fact predicts that the more efficient
the particle acceleration, the flatter the CR spectrum. In this work we put
forward a self-consistent scenario in which the account for the magnetic field
amplification induced by CR streaming produces the conditions for reversing
such a trend, allowing --- at the same time --- for rather steep spectra and CR
acceleration efficiencies (about 20%) consistent with the hypothesis that SNRs
are the sources of Galactic CRs. In particular, we quantitatively work out the
details of instantaneous and cumulative CR spectra during the evolution of a
typical SNR, also stressing the implications of the observed levels of
magnetization on both the expected maximum energy and the predicted CR
acceleration efficiency. The latter naturally turns out to saturate around
10-30%, almost independently of the fraction of particles injected into the
acceleration process as long as this fraction is larger than about .Comment: 24 pages, 5 figures, accepted for publication in JCA
Radio and gamma-ray follow-up of the exceptionally high activity state of PKS 1510-089 in 2011
We investigate the radio and gamma-ray variability of the flat spectrum radio
quasar PKS 1510-089 in the time range between 2010 November and 2012 January.
In this period the source showed an intense activity, with two major gamma-ray
flares detected in 2011 July and October. During the latter episode both the
gamma-ray and the radio flux density reached their historical peak.
Multiwavelength analysis shows a rotation of about 380 deg of the optical
polarization angle close in time with the rapid and strong gamma-ray flare in
2011 July. An enhancement of the optical emission and an increase of the
fractional polarization both in the optical and in radio bands is observed
about three weeks later, close in time with another gamma-ray outburst. On the
other hand, after 2011 September a huge radio outburst has been detected, first
in the millimeter regime followed with some time delay at centimeter down to
decimeter wavelengths. This radio flare is characterized by a rising and a
decaying stage, in agreement with the formation of a shock and its evolution,
as a consequence of expansion and radiative cooling. If the gamma-ray flare
observed in 2011 October is related to this radio outburst, then this strongly
indicates that the region responsible for the gamma-ray variability is not
within the broad line, but a few parsecs downstream along the jet.Comment: 14 pages, 12 figures, accepted for publication in MNRA
F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
The F-GAMMA program is a coordinated effort to investigate the physics of
Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars.
In the current study we show and discuss the evolution of broad-band radio
spectra, which are measured at ten frequencies between 2.64 and 142 GHz using
the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the
78 sources studied can be classified in terms of their variability
characteristics in merely 5 types of variability. It is argued that these can
be attributed to only two classes of variability mechanisms. The first four
types are dominated by spectral evolution and can be described by a simple
two-component system composed of: (a) a steep quiescent spectral component from
a large scale jet and (b) a time evolving flare component following the
"Shock-in-Jet" evolutionary path. The fifth type is characterised by an
achromatic change of the broad band spectrum, which could be attributed to a
different mechanism, likely involving differential Doppler boosting caused by
geometrical effects. Here we present the classification, the assumed physical
scenario and the results of calculations that have been performed for the
spectral evolution of flares.Comment: Proceedings of the conference: "The Central Kiloparsec in Galactic
Nucleic: Astronomy at High Angular Resolution 2011", August 29 - September 2,
2011, Bad Honnef, German
Extracting the late-time kinetic Sunyaev-Zel'dovich effect
We propose a novel technique to separate the late-time, post-reionization component of the kinetic Sunyaev Zeldovich (kSZ) effect from the contribution to it from a (poorly understood and probably patchy) reionization history. The kSZ effect is one of the most promising probe of the missing baryons in the Universe. We study the possibility of reconstructing it in three dimensions (3D), using future spectroscopic surveys such as the Euclid survey. By reconstructing a 3D template from galaxy density and peculiar velocity fields from spectroscopic surveys we cross-correlate the estimator against CMB maps. The resulting cross-correlation can help us to map out the kSZ contribution to CMB in 3D as a function of redshift thereby extending previous results which use tomographic reconstruction. This allows the separation of the late-time effect from the contribution owing to reionization. By construction, it avoids contamination from foregrounds, primary CMB, tSZ effect as well as from star-forming galaxies. Due to a high number density of galaxies the signal-to-noise ratio (S/N) for such cross-correlational studies is higher, compared to the studies involving CMB power-spectrum analysis. Using a spherical Bessel–Fourier (sFB) transform we introduce a pair of 3D power spectra: C⊥ℓ(k) and C⊥ℓ(k) that can be used for this purpose. We find that in a future spectroscopic survey with near all-sky coverage and a survey depth of z ≈ 1, reconstruction of C⊥ℓ(k) can be achieved in a few radial wave bands k ≈ (0.01–0.5 h−1 Mpc) with a S/N ratio of up to O(10) for angular harmonics in the range = (200–2000)
THE THREE-DIMENSIONAL EVOLUTION OF ION-SCALE CURRENT SHEETS: TEARING AND DRIFT-KINK INSTABILITIES IN THE PRESENCE OF PROTON TEMPERATURE ANISOTROPY
We present the first three-dimensional hybrid simulations of the evolution of
ion-scale current sheets, with an investigation of the role of temperature
anisotropy and associated kinetic instabilities on the growth of the tearing
instability and particle heating. We confirm the ability of the ion cyclotron
and firehose instabilities to enhance or suppress reconnection, respectively.
The simulations demonstrate the emergence of persistent three-dimensional
structures, including patchy reconnection sites and the fast growth of a
narrow-band drift-kink instability, which suppresses reconnection for thin
current sheets with weak guide fields. Potential observational signatures of
the three-dimensional evolution of solar wind current sheets are also
discussed. We conclude that kinetic instabilities, arising from non-Maxwellian
ion populations, are significant to the evolution of three-dimensional current
sheets, and two-dimensional studies of heating rates by reconnection may
therefore over-estimate the ability of thin, ion-scale current sheets to heat
the solar wind by reconnection
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