755 research outputs found
Biased total mass of cool core galaxy clusters by Sunyaev-Zel'dovich effect measurements
The Sunyaev Zel'dovich (SZ) effect from galaxy clusters is one of the most
powerful cosmological tools for investigating the large-scale Universe. The big
advantage of the SZ effect is its redshift independence, which is not the case
for visible and X-ray observations. It allows us to directly estimate the
cluster's total mass from the integrated comptonization parameter Y, even for
distant clusters. However, not having a full knowing intra-cluster medium (ICM)
physics can affect the results. By taking self-similar temperature and density
profiles of the ICM into account, we studied how different ICM morphologies can
affect the cluster total mass estimation. With the help of the high percentage
of cool core (CC) clusters, as observed so far, the present analysis focuses on
studying this class of objects. A sample of eight nearby (0.1 < z < 0.5) and
high-mass (M > 10^(14) M_sun) clusters observed by Chandra was considered. We
simulated SZ observations of these clusters through X-ray derived information
and analyzed the mock SZ data again with the simplistic assumption of an
isothermal beta-model profile for the ICM. The bias on the recovered cluster
total mass using different sets of assumptions is estimated to be 50% higher in
the case of hydrostatic equilibrium. Possible contributions to the total bias
due to the line-of-sight integration and the considered ICM template are taken
into account. The large biases on total mass recovery firmly support, if still
necessary, cluster modeling based on more sophisticated universal profiles as
derived by X-ray observations of local objects and hydrodynamical simulations.Comment: 11 pages, 4 figures; minor revisions. Accepted for publication in A&
Three-dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters
We report results of 3D MHD simulations of the dynamics of buoyant bubbles in
magnetized galaxy cluster media. The simulations are three dimensional
extensions of two dimensional calculations reported by Jones & De Young (2005).
Initially spherical bubbles and briefly inflated spherical bubbles all with
radii a few times smaller than the intracluster medium (ICM) scale height were
followed as they rose through several ICM scale heights. Such bubbles quickly
evolve into a toroidal form that, in the absence of magnetic influences, is
stable against fragmentation in our simulations. This ring formation results
from (commonly used) initial conditions that cause ICM material below the
bubbles to drive upwards through the bubble, creating a vortex ring; that is,
hydrostatic bubbles develop into "smoke rings", if they are initially not very
much smaller or very much larger than the ICM scale height. Even modest ICM
magnetic fields with beta = P_gas/P_mag ~ 10^3 can influence the dynamics of
the bubbles, provided the fields are not tangled on scales comparable to or
smaller than the size of the bubbles. Quasi-uniform, horizontal fields with
initial beta ~ 10^2 bifurcated our bubbles before they rose more than about a
scale height of the ICM, and substantially weaker fields produced clear
distortions. On the other hand, tangled magnetic fields with similar, modest
strengths are generally less easily amplified by the bubble motions and are
thus less influential in bubble evolution. Inclusion of a comparably strong,
tangled magnetic field inside the initial bubbles had little effect on our
bubble evolution, since those fields were quickly diminished through expansion
of the bubble and reconnection of the initial field.Comment: 20 pages, 12 figures. Accepted for publication in The Astrophysical
Journa
COVID-19 Vaccination Status among Adults Admitted to Intensive Care Units in Veneto, Italy
: This cohort study examines admissions to intensive care units for COVID-19–associated acute respiratory distress syndrome by COVID-19 vaccination status among adults in the Veneto region of Italy from May to December 2021
Redshift Dependence of the CMB Temperature from S-Z Measurements
We have determined the CMB temperature, , at redshifts in the range
0.023-0.546, from multi-frequency measurements of the S-Z effect towards 13
clusters. We extract the parameter in the redshift scaling
, which contrasts the prediction of the standard
model () with that in non-adiabatic evolution conjectured in some
alternative cosmological models. The statistical analysis is based on two main
approaches: using ratios of the S-Z intensity change, , thus taking
advantage of the weak dependence of the ratios on IC gas properties, and using
directly the measurements. In the former method dependence on the
Thomson optical depth and gas temperature is only second order in these
quantities. In the second method we marginalize over these quantities which
appear to first order in the intensity change. The marginalization itself is
done in two ways - by direct integrations, and by a Monte Carlo Markov Chain
approach. Employing these different methods we obtain two sets of results that
are consistent with , in agreement with the prediction of the
standard model.Comment: Accepted for publication in Ap
BPS black holes, the Hesse potential, and the topological string
The Hesse potential is constructed for a class of four-dimensional N=2
supersymmetric effective actions with S- and T-duality by performing the
relevant Legendre transform by iteration. It is a function of fields that
transform under duality according to an arithmetic subgroup of the classical
dualities reflecting the monodromies of the underlying string compactification.
These transformations are not subject to corrections, unlike the
transformations of the fields that appear in the effective action which are
affected by the presence of higher-derivative couplings. The class of actions
that are considered includes those of the FHSV and the STU model. We also
consider heterotic N=4 supersymmetric compactifications. The Hesse potential,
which is equal to the free energy function for BPS black holes, is manifestly
duality invariant. Generically it can be expanded in terms of powers of the
modulus that represents the inverse topological string coupling constant,
, and its complex conjugate. The terms depending holomorphically on
are expected to correspond to the topological string partition function and
this expectation is explicitly verified in two cases. Terms proportional to
mixed powers of and are in principle present.Comment: 28 pages, LaTeX, added comment
Millimeter and sub-millimeter atmospheric performance at Dome C combining radiosoundings and ATM synthetic spectra
The reliability of astronomical observations at millimeter and sub-millimeter
wavelengths closely depends on a low vertical content of water vapor as well as
on high atmospheric emission stability. Although Concordia station at Dome C
(Antarctica) enjoys good observing conditions in this atmospheric spectral
windows, as shown by preliminary site-testing campaigns at different bands and
in, not always, time overlapped periods, a dedicated instrument able to
continuously determine atmospheric performance for a wide spectral range is not
yet planned. In the absence of such measurements, in this paper we suggest a
semi-empirical approach to perform an analysis of atmospheric transmission and
emission at Dome C to compare the performance for 7 photometric bands ranging
from 100 GHz to 2 THz. Radiosoundings data provided by the Routine
Meteorological Observations (RMO) Research Project at Concordia station are
corrected by temperature and humidity errors and dry biases and then employed
to feed ATM (Atmospheric Transmission at Microwaves) code to generate synthetic
spectra in the wide spectral range from 100 GHz to 2 THz. To quantify the
atmospheric contribution in millimeter and sub-millimeter observations we are
considering several photometric bands in which atmospheric quantities are
integrated. The observational capabilities of this site at all the selected
spectral bands are analyzed considering monthly averaged transmissions joined
to the corresponding fluctuations. Transmission and pwv statistics at Dome C
derived by our semi-empirical approach are consistent with previous works. It
is evident the decreasing of the performance at high frequencies. We propose to
introduce a new parameter to compare the quality of a site at different
spectral bands, in terms of high transmission and emission stability, the Site
Photometric Quality Factor.Comment: accepted to MNRAS with minor revision
Changes in total plasma and serum N-glycome composition and patient-controlled analgesia after major abdominal surgery
Systemic inflammation participates to the complex healing process occurring after major surgery, thus directly affecting the surgical outcome and patient recovery. Total plasma N-glycome might be an indicator of inflammation after major surgery, as well as an anti-inflammatory therapy response marker, since protein glycosylation plays an essential role in the inflammatory cascade. Therefore, we assessed the effects of surgery on the total plasma N-glycome and the association with self-administration of postoperative morphine in two cohorts of patients that underwent major abdominal surgery. We found that plasma N-glycome undergoes significant changes one day after surgery and intensifies one day later, thus indicating a systemic physiological response. In particular, we observed the increase of bisialylated biantennary glycan, A2G2S[3,6]2, 12 hours after surgery, which progressively increased until 48 postoperative hours. Most changes occurred 24 hours after surgery with the decrease of most core-fucosylated biantennary structures, as well as the increase in sialylated tetraantennary and FA3G3S[3,3,3]3 structures. Moreover, we observed a progressive increase of sialylated triantennary and tetraantennary structures two days after surgery, with a concomitant decrease of the structures containing bisecting N-acetylglucosamine along with bi- and trisialylated triantennary glycans. We did not find any statistically significant association between morphine consumption and plasma N-glycome
SWIPE: a bolometric polarimeter for the Large-Scale Polarization Explorer
The balloon-borne LSPE mission is optimized to measure the linear
polarization of the Cosmic Microwave Background at large angular scales. The
Short Wavelength Instrument for the Polarization Explorer (SWIPE) is composed
of 3 arrays of multi-mode bolometers cooled at 0.3K, with optical components
and filters cryogenically cooled below 4K to reduce the background on the
detectors. Polarimetry is achieved by means of large rotating half-wave plates
and wire-grid polarizers in front of the arrays. The polarization modulator is
the first component of the optical chain, reducing significantly the effect of
instrumental polarization. In SWIPE we trade angular resolution for
sensitivity. The diameter of the entrance pupil of the refractive telescope is
45 cm, while the field optics is optimized to collect tens of modes for each
detector, thus boosting the absorbed power. This approach results in a FWHM
resolution of 1.8, 1.5, 1.2 degrees at 95, 145, 245 GHz respectively. The
expected performance of the three channels is limited by photon noise,
resulting in a final sensitivity around 0.1-0.2 uK per beam, for a 13 days
survey covering 25% of the sky.Comment: In press. Copyright 2012 Society of Photo-Optical Instrumentation
Engineers. One print or electronic copy may be made for personal use only.
Systematic reproduction and distribution, duplication of any material in this
paper for a fee or for commercial purposes, or modification of the content of
the paper are prohibite
All clinically-relevant blood components transmit prion disease following a single blood transfusion: a sheep model of vCJD
Variant CJD (vCJD) is an incurable, infectious human disease, likely arising from the consumption of BSE-contaminated meat products. Whilst the epidemic appears to be waning, there is much concern that vCJD infection may be perpetuated in humans by the transfusion of contaminated blood products. Since 2004, several cases of transfusion-associated vCJD transmission have been reported and linked to blood collected from pre-clinically affected donors. Using an animal model in which the disease manifested resembles that of humans affected with vCJD, we examined which blood components used in human medicine are likely to pose the greatest risk of transmitting vCJD via transfusion. We collected two full units of blood from BSE-infected donor animals during the pre-clinical phase of infection. Using methods employed by transfusion services we prepared red cell concentrates, plasma and platelets units (including leucoreduced equivalents). Following transfusion, we showed that all components contain sufficient levels of infectivity to cause disease following only a single transfusion and also that leucoreduction did not prevent disease transmission. These data suggest that all blood components are vectors for prion disease transmission, and highlight the importance of multiple control measures to minimise the risk of human to human transmission of vCJD by blood transfusion
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