2,098 research outputs found
ChatGPT â Another Hype or Out-of-this-World?
The launch of ChatGPT in November 2022 ushered in a new era of generative AI that has taken the world by storm. We wanted to seek the opinion of MWAIS colleagues. We asked the editorial board members of JMWAIS if they wish to respond to the following questions: 1) What is your overall opinion of GPT and similar platforms? 2) GPTâs potential implications for teaching, learning, and other student services? And 3) Have you already seen evidence of GPT in student work or in anything else where it might have come across, like research? This article includes responses we received
The Mixing and Transport Properties of the Intra Cluster Medium: a numerical study using tracers particles
We present a study of the mixing properties of the simulated intra cluster
Medium, using tracers particles that are advected by the gas flow during the
evolution of cosmic structures. Using a sample of seven galaxy clusters (with
masses in the range of M=2-3 10^14Msol/h) simulated with a peak resolution of
25kpc/h up to the distance of two virial radii from their centers, we
investigate the application of tracers to some important problems concerning
the mixing of the ICM. The transport properties of the evolving ICM are studied
through the analysis of pair dispersion statistics and mixing distributions. As
an application, we focus on the transport of metals in the ICM. We adopt simple
scenarios for the injection of metal tracers in the ICM, and find remarkable
differences of metallicity profiles in relaxed and merger systems, also through
the analysis of simulated emission from Doppler-shifted Fe XXIII lines.Comment: 19 pages, 24 figures, Astronomy and Astrophysics accepted; Final
version after language editing and updating the bibliograph
Massive and refined: a sample of large galaxy clusters simulated at high resolution. I:Thermal gas and shock waves properties
We present a sample of 20 massive galaxy clusters with total virial masses in
the range of 6 10^14 M_sol<M(vir)< 2 10^15M_sol, re-simulated with a customized
version of the 1.5. ENZO code employing Adaptive Mesh Refinement. This
technique allowed us to obtain unprecedented high spatial resolution (25kpc/h)
up to the distance of 3 virial radii from the clusters center, and makes it
possible to focus with the same level of detail on the physical properties of
the innermost and of the outermost cluster regions, providing new clues on the
role of shock waves and turbulent motions in the ICM, across a wide range of
scales.
In this paper, a first exploratory study of this data set is presented. We
report on the thermal properties of galaxy clusters at z=0. Integrated and
morphological properties of gas density, gas temperature, gas entropy and
baryon fraction distributions are discussed, and compared with existing
outcomes both from the observational and from the numerical literature.
Our cluster sample shows an overall good consistency with the results
obtained adopting other numerical techniques (e.g. Smoothed Particles
Hydrodynamics), yet it provides a more accurate representation of the accretion
patterns far outside the cluster cores. We also reconstruct the properties of
shock waves within the sample by means of a velocity-based approach, and we
study Mach numbers and energy distributions for the various dynamical states in
clusters, giving estimates for the injection of Cosmic Rays particles at
shocks. The present sample is rather unique in the panorama of cosmological
simulations of massive galaxy clusters, due to its dynamical range, statistics
of objects and number of time outputs. For this reason, we deploy a public
repository of the available data, accessible via web portal at
http://data.cineca.it.Comment: 26 pages, 20 figures, New Astronomy accepted. Reference list updated.
Higher quality versions of the paper can be found at:
http://www.ira.inaf.it/~vazza/papers A public archive of galaxy clusters data
is accessible at http://data.cineca.it
Turbulent Motions and Shocks Waves in Galaxy Clusters simulated with AMR
We have implemented an Adaptive Mesh Refinement criterion explicitly designed
to increase spatial resolution around discontinuities in the velocity field in
ENZO cosmological simulations. With this technique, shocks and turbulent eddies
developed during the hierarchical assembly of galaxy clusters are followed with
unprecedented spatial resolution, even at large distances from the clusters
center. By measuring the spectral properties of the gas velocity field, its
time evolution and the properties of shocks for a reference galaxy cluster, we
investigate the connection between accretion processes and the onset of chaotic
motions in the simulated Inter Galactic Medium over a wide range of scalesComment: Accepted for publication in A&A. 12 pages, 11 color figures - 2
additional figures respect to v.1, and updated bibliography. The paper with
full quality figures is available at
http://www.ira.inaf.it/~vazza/papers/turb2.p
Detailed spectral and morphological analysis of the shell type SNR RCW 86
Aims: We aim for an understanding of the morphological and spectral
properties of the supernova remnant RCW~86 and for insights into the production
mechanism leading to the RCW~86 very high-energy gamma-ray emission. Methods:
We analyzed High Energy Spectroscopic System data that had increased
sensitivity compared to the observations presented in the RCW~86 H.E.S.S.
discovery publication. Studies of the morphological correlation between the
0.5-1~keV X-ray band, the 2-5~keV X-ray band, radio, and gamma-ray emissions
have been performed as well as broadband modeling of the spectral energy
distribution with two different emission models. Results:We present the first
conclusive evidence that the TeV gamma-ray emission region is shell-like based
on our morphological studies. The comparison with 2-5~keV X-ray data reveals a
correlation with the 0.4-50~TeV gamma-ray emission.The spectrum of RCW~86 is
best described by a power law with an exponential cutoff at TeV and a spectral index of ~. A static
leptonic one-zone model adequately describes the measured spectral energy
distribution of RCW~86, with the resultant total kinetic energy of the
electrons above 1 GeV being equivalent to 0.1\% of the initial kinetic
energy of a Type I a supernova explosion. When using a hadronic model, a
magnetic field of ~100G is needed to represent the measured data.
Although this is comparable to formerly published estimates, a standard
E spectrum for the proton distribution cannot describe the gamma-ray
data. Instead, a spectral index of ~1.7 would be required, which
implies that ~erg has been transferred into
high-energy protons with the effective density cm^-3. This
is about 10\% of the kinetic energy of a typical Type Ia supernova under the
assumption of a density of 1~cm^-3.Comment: accepted for publication by A&
Characterizing the gamma-ray long-term variability of PKS 2155-304 with H.E.S.S. and Fermi-LAT
Studying the temporal variability of BL Lac objects at the highest energies
provides unique insights into the extreme physical processes occurring in
relativistic jets and in the vicinity of super-massive black holes. To this
end, the long-term variability of the BL Lac object PKS 2155-304 is analyzed in
the high (HE, 100 MeV 200 GeV)
gamma-ray domain. Over the course of ~9 yr of H.E.S.S observations the VHE
light curve in the quiescent state is consistent with a log-normal behavior.
The VHE variability in this state is well described by flicker noise
(power-spectral-density index {\ss}_VHE = 1.10 +0.10 -0.13) on time scales
larger than one day. An analysis of 5.5 yr of HE Fermi LAT data gives
consistent results ({\ss}_HE = 1.20 +0.21 -0.23, on time scales larger than 10
days) compatible with the VHE findings. The HE and VHE power spectral densities
show a scale invariance across the probed time ranges. A direct linear
correlation between the VHE and HE fluxes could neither be excluded nor firmly
established. These long-term-variability properties are discussed and compared
to the red noise behavior ({\ss} ~ 2) seen on shorter time scales during
VHE-flaring states. The difference in power spectral noise behavior at VHE
energies during quiescent and flaring states provides evidence that these
states are influenced by different physical processes, while the compatibility
of the HE and VHE long-term results is suggestive of a common physical link as
it might be introduced by an underlying jet-disk connection.Comment: 11 pages, 16 figure
The exceptionally powerful TeV gamma-ray emitters in the Large Magellanic Cloud
The Large Magellanic Cloud, a satellite galaxy of the Milky Way, has been
observed with the High Energy Stereoscopic System (H.E.S.S.) above an energy of
100 billion electron volts for a deep exposure of 210 hours. Three sources of
different types were detected: the pulsar wind nebula of the most energetic
pulsar known N 157B, the radio-loud supernova remnant N 132D and the largest
non-thermal X-ray shell - the superbubble 30 Dor C. The unique object SN 1987A
is, surprisingly, not detected, which constrains the theoretical framework of
particle acceleration in very young supernova remnants. These detections reveal
the most energetic tip of a gamma-ray source population in an external galaxy,
and provide via 30 Dor C the unambiguous detection of gamma-ray emission from a
superbubble.Comment: Published in Science Magazine (Jan. 23, 2015). This ArXiv version has
the supplementary online material incorporated as an appendix to the main
pape
Detection of variable VHE gamma-ray emission from the extra-galactic gamma-ray binary LMC P3
Context. Recently, the high-energy (HE, 0.1-100 GeV) -ray emission
from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered
to be modulated with a 10.3-day period, making it the first extra-galactic
-ray binary.
Aims. This work aims at the detection of very-high-energy (VHE, >100 GeV)
-ray emission and the search for modulation of the VHE signal with the
orbital period of the binary system.
Methods. LMC P3 has been observed with the High Energy Stereoscopic System
(H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has
been folded with the known orbital period of the system in order to test for
variability of the emission. Energy spectra are obtained for the orbit-averaged
data set, and for the orbital phase bin around the VHE maximum.
Results. VHE -ray emission is detected with a statistical
significance of 6.4 . The data clearly show variability which is
phase-locked to the orbital period of the system. Periodicity cannot be deduced
from the H.E.S.S. data set alone. The orbit-averaged luminosity in the
TeV energy range is erg/s. A luminosity of erg/s is reached during 20% of the orbit. HE and VHE
-ray emissions are anti-correlated. LMC P3 is the most luminous
-ray binary known so far.Comment: 5 pages, 3 figures, 1 table, accepted for publication in A&
Quantification of Rapid Myosin Regulatory Light Chain Phosphorylation Using High-Throughput In-Cell Western Assays: Comparison to Western Immunoblots
Quantification of phospho-proteins (PPs) is crucial when studying cellular signaling pathways. Western immunoblotting (WB) is commonly used for the measurement of relative levels of signaling intermediates in experimental samples. However, WB is in general a labour-intensive and low-throughput technique. Because of variability in protein yield and phospho-signal preservation during protein harvesting, and potential loss of antigen during protein transfer, WB provides only semi-quantitative data. By comparison, the "in-cell western" (ICW) technique has high-throughput capacity and requires less extensive sample preparation. Thus, we compared the ICW technique to WB for measuring phosphorylated myosin regulatory light chain (PMLC(20)) in primary cultures of uterine myocytes to assess their relative specificity, sensitivity, precision, and quantification of biologically relevant responses.ICWs are cell-based microplate assays for quantification of protein targets in their cellular context. ICWs utilize a two-channel infrared (IR) scanner (Odyssey(R)) to quantify signals arising from near-infrared (NIR) fluorophores conjugated to secondary antibodies. One channel is dedicated to measuring the protein of interest and the second is used for data normalization of the signal in each well of the microplate. Using uterine myocytes, we assessed oxytocin (OT)-stimulated MLC(20) phosphorylation measured by ICW and WB, both using NIR fluorescence. ICW and WB data were comparable regarding signal linearity, signal specificity, and time course of phosphorylation response to OT.ICW and WB yield comparable biological data. The advantages of ICW over WB are its high-throughput capacity, improved precision, and reduced sample preparation requirements. ICW might provide better sensitivity and precision with low-quantity samples or for protocols requiring large numbers of samples. These features make the ICW technique an excellent tool for the study of phosphorylation endpoints. However, the drawbacks of ICW include the need for a cell culture format and the lack of utility where protein purification, concentration or stoichiometric analyses are required
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