157 research outputs found
Differences in carbon and nitrogen abundances between field and cluster early-type galaxies
Central line-strength indices were measured in the blue spectral region for a
sample of 98 early-type galaxies in different environments. For most indices
(Mgb and in particular) ellipticals in rich clusters and in low-density
regions follow the same index-sigma relations. However, striking spectral
differences between field ellipticals and their counterparts in the central
region of the Coma cluster are found for the first time, with galaxies in the
denser environment showing significantly lower C4668 and CN2 absorption
strengths. The most convincing interpretation of these results is a difference
in abundance ratios, arising from a distinct star formation and chemical
enrichment histories of galaxies in different environments. An scenario in
which elliptical galaxies in clusters are fully assembled at earlier stages
than their low-density counterparts is discussed.Comment: 12 pages, including 3 figures, accepted for publication in ApJ
Gas Dynamical Simulations of the Large and Little Homunculus Nebulae of Eta Carinae
We here present two-dimensional, time-dependent radiatively cooling
hydrodynamical simulations of the large and little Homunculus nebulae around
Carinae. We employ an alternative scenario to previous interacting
stellar wind models which is supported by both theoretical and observational
evidence, where a non-spherical outburst wind (with a latitudinal velocity
dependence that matches the observations of the large Homunculus), which is
expelled for 20 years, interacts with a pre-eruptive slow wind also with a
toroidal density distribution, but with a much smaller equator-to-polar density
contrast than that assumed in previous models. A second eruptive wind with
spherical shape is ejected about 50 years after the first outburst, and causes
the development of the little internal nebula. We find that, as a result of an
appropriate combination of the parameters that control the degree of asymmetry
of the interacting winds, we are able to produce not only the structure and
kinematics of both Homunculus, but also the high-velocity equatorial ejecta.
These arise from the impact between the non-spherical outburst and the
pre-outburst winds in the equatorial plane.Comment: ApJ Lett. in pres
Nanoparticulate architecture of protein-based artificial viruses is supported by protein DNA interactions
Aim & Methods: We have produced two chimerical peptides of 10.2 kDa, each contain four biologically active domains, which act as building blocks of protein-based nonviral vehicles for gene therapy. In solution, these peptides tend to aggregate as amorphous clusters of more than 1000 nm, while the presence of DNA
promotes their architectonic reorganization as mechanically stable nanometric spherical entities of approximately 80 nm that penetrate mammalian cells through arginine–glycine–aspartic acid cell-binding domains and promote significant transgene expression levels. Results & Conclusion: The structural analysis
of the protein in these hybrid nanoparticles indicates a molecular conformation with predominance of D-helix and the absence of cross-molecular, E-sheet-supported protein interactions. The nanoscale organizing forces generated by DNA–protein interactions can then be observed as a potentially tunable, critical factor in the design of protein-only based artificial viruses for gene therapy.Agencia Nacional de Investigación e Innovació
Observing white dwarfs orbiting massive black holes in the gravitational wave and electro-magnetic window
We consider a potentially new class of gravitational wave sources consisting
of a white dwarf coalescing into a massive black hole in the mass range
~10^4-10^5\msun. These sources are of particular interest because the
gravitational wave signal produced during the inspiral phase can be detected by
the Laser Interferometer Space Antenna (LISA) and is promptly followed, in an
extended portion of the black hole and white dwarf mass parameter space, by an
electro-magnetic signal generated by the tidal disruption of the star,
detectable with X-ray, optical and UV telescopes. This class of sources could
therefore yield a considerable number of scientific payoffs, that include
precise cosmography at low redshift, demographics of black holes in the mass
range ~10^4-10^5\Msun, insights into dynamical interactions and populations of
white dwarfs in the cores of dwarf galaxies, as well as a new probe into the
structure and equation of state of white dwarfs. By modelling the gravitational
and electromagnetic radiation produced by these events, we find them detectable
in both observational windows at a distance ~200 Mpc, and possibly beyond for
selected regions of the parameter space. We also estimate the detection rate
for a number of model assumptions about black hole and white dwarf mass
functions and dynamical interactions: the rate is (not surprisingly) highly
uncertain, ranging from ~0.01 yr^-1 to ~100 yr^-1. This is due to the current
limited theoretical understanding and minimal observational constraints for
these objects and processes. However, capture rate scaling arguments favor the
high end of the above range, making likely the detection of several events
during the LISA lifetime.Comment: 10 pages, 7 figures, submitted to MNRA
Global Monitoring of Fault Zones and Volcanoes with Sentinel-1
Sentinel-1 represents a major step forward in enabling us to monitor the Earth's hazardous tectonic and volcanic zones. Here, we present the latest progress from the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), where we provide deformation results to the community for volcanoes and the tectonic belts. For the estimation of seismic hazard, we require relative accuracy on the order of 1 mm/yr between points 100 km apart. This requires mass processing of long time series of radar acquisitions. As of January 2018, we are producing in-terferograms systematically for the entire Alpine-Himalayan belt (~9000 × 2000 km) and the majority of subaerial volcanoes. Currently we make interferograms and coherence products available to the community, but we plan to also provide average deformation rates and displacement time series, in the future. The results are made available through a dedicated COMET portal, and we are in the process of linking them to the ESA G-TEP and EPOS. COMET also responds routinely to significant continental earthquakes, larger than ~Mw 6.0. The short repeat interval of Sentinel-1, together with the rapid availability of the data, allows us to do this within a few days for most earthquakes. For example, after the Mw 7.8 Kaikoura earthquake we supplied a processed interferogram to the community just 5 hours and 37 minutes after the Sentinel-1 acquisition. In this paper we provide an overview of some of the latest results for tectonics and volcanism and discuss how the accuracy of these products will improve as the number of data products acquired by Sentinel-1 increases
Prediction of Psilocybin Response in Healthy Volunteers
Responses to hallucinogenic drugs, such as psilocybin, are believed to be critically dependent on the user's personality, current mood state, drug pre-experiences, expectancies, and social and environmental variables. However, little is known about the order of importance of these variables and their effect sizes in comparison to drug dose. Hence, this study investigated the effects of 24 predictor variables, including age, sex, education, personality traits, drug pre-experience, mental state before drug intake, experimental setting, and drug dose on the acute response to psilocybin. The analysis was based on the pooled data of 23 controlled experimental studies involving 409 psilocybin administrations to 261 healthy volunteers. Multiple linear mixed effects models were fitted for each of 15 response variables. Although drug dose was clearly the most important predictor for all measured response variables, several non-pharmacological variables significantly contributed to the effects of psilocybin. Specifically, having a high score in the personality trait of Absorption, being in an emotionally excitable and active state immediately before drug intake, and having experienced few psychological problems in past weeks were most strongly associated with pleasant and mystical-type experiences, whereas high Emotional Excitability, low age, and an experimental setting involving positron emission tomography most strongly predicted unpleasant and/or anxious reactions to psilocybin. The results confirm that non-pharmacological variables play an important role in the effects of psilocybin
80Se(n,?) cross-section measurement at CERN n TOF
Radiative neutron capture cross section measurements are of fundamental importance for the study of the slow neutron capture (s-) process of nucleosynthesis. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. Particularly relevant are branching nuclei along the s-process path, which are sensitive to the physical conditions of the stellar environment. One such example is the branching at Se (3.27 × 10 y), which shows a thermally dependent β-decay rate. However, an astrophysically consistent interpretation requires also the knowledge of the closest neighbour isotopes involved. In particular, the Se(n,γ) cross section directly affects the stellar yield of the "cold" branch leading to the formation of the s-only Kr. Experimentally, there exists only one previous measurement on Se using the time of flight (TOF) technique. However, the latter suffers from some limitations that are described in this presentation. These drawbacks have been significantly improved in a recent measurement at CERN n TOF. This contribution presents a summary of the latter measurement and the status of the data analysis
Neutron capture measurement at the n TOF facility of the 204Tl and 205Tl s-process branching points
Neutron capture cross sections are one of the fundamental nuclear data in the study of the s (slow) process of nucleosynthesis. More interestingly, the competition between the capture and the decay rates in some unstable nuclei determines the local isotopic abundance pattern. Since decay rates are often sensible to temperature and electron density, the study of the nuclear properties of these nuclei can provide valuable constraints to the physical magnitudes of the nucleosynthesis stellar environment. Here we report on the capture cross section measurement of two thallium isotopes, Tl and Tl performed by the time-of-flight technique at the n TOF facility at CERN. At some particular stellar s-process environments, the decay of both nuclei is strongly enhanced, and determines decisively the abundance of two s-only isotopes of lead, Pb and Pb. The latter, as a long-lived radioactive nucleus, has potential use as a chronometer of the last s-process events that contributed to final solar isotopic abundances
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