1,173 research outputs found
Detection of the onset of nanocrystallization by calorimetric and magnetic measurements
It is generally accepted that measurements of the magnetic properties are more sensitive than measurements of the enthalpy changes in the detection of the onset of crystallization of ferromagnetic phases emerging from a paramagnetic amorphous alloy. In this work, it is shown that the formation of a very fine nanocrystalline microstructure can make this assumption incorrect. Under some circumstances, the nanocrystallization onset temperature obtained from magnetic techniques is higher than the one obtained from enthalpy changes. The phenomenon is explained in terms of the superparamagnetic behavior of the uncoupled nanocrystals at the very early stages of nanocrystallizatio
Congenital Cytomegalovirus Infection: A Narrative Review of the Issues in Screening and Management From a Panel of European Experts.
Maternal primary and non-primary cytomegalovirus (CMV) infection during pregnancy can result in in utero transmission to the developing fetus. Congenital CMV (cCMV) can result in significant morbidity, mortality or long-term sequelae, including sensorineural hearing loss, the most common sequela. As a leading cause of congenital infections worldwide, cCMV infection meets many of the criteria for screening. However, currently there are no universal programs that offer maternal or neonatal screening to identify infected mothers and infants, no vaccines to prevent infection, and no efficacious and safe therapies available for the treatment of maternal or fetal CMV infection. Data has shown that there are several maternal and neonatal screening strategies, and diagnostic methodologies, that allow the identification of those at risk of developing sequelae and adequately detect cCMV. Nevertheless, many questions remain unanswered in this field. Well-designed clinical trials to address several facets of CMV treatment (in pregnant women, CMV-infected fetuses and both symptomatic and asymptomatic neonates and children) are required. Prevention (vaccines), biology and transmission factors associated with non-primary CMV, and the cost-effectiveness of universal screening, all demand further exploration to fully realize the ultimate goal of preventing cCMV. In the meantime, prevention of primary infection during pregnancy should be championed to all by means of hygiene education
Evidence for intermediate-age stellar populations in early-type galaxies from K-band spectroscopy
The study of stellar populations in early-type galaxies in different
environments is a powerful tool for constraining their star formation
histories. This study has been traditionally restricted to the optical range,
where dwarfs around the turn-off and stars at the base of the RGB dominate the
integrated light at all ages. The near-infrared spectral range is especially
interesting since in the presence of an intermediate-age population, AGB stars
are the main contributors. In this letter, we measure the near-infrared indices
NaI and D for a sample of 12 early-type galaxies in low density
environments and compare them with the Fornax galaxy sample presented by Silva
et al. (2008). The analysis of these indices in combination with Lick/IDS
indices in the optical range reveals i) the NaI index is a metallicity
indicator as good as C4668 in the optical range, and ii) D is a
tracer of intermediate-age stellar populations. We find that low-mass galaxies
in low density environments show higher NaI and D than those located
in Fornax cluster, which points towards a late stage of star formation for the
galaxies in less dense environments, in agreement with results from other
studies using independent methods.Comment: 7 pages, 3 figures, accepted for publication in ApJ
Stellar population gradients in brightest cluster galaxies
We present the stellar population and velocity dispersion gradients for a
sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which
we have obtained high quality long-slit spectra at the Gemini telescopes. With
the aim of studying the possible connection between the formation of the BCGs
and their host clusters, we explore the relations between the stellar
population gradients and properties of the host clusters as well as the
possible connections between the stellar population gradients and other
properties of the galaxies. We find mean stellar population gradients (negative
{\Delta}[Z/H]/log r gradient of -0.285{\pm}0.064; small positive {\Delta}log
(age)/log r gradient of 0.069{\pm}0.049; and null {\Delta}[E/Fe]/log r gradient
of -0.008{\pm}0.032) that are consistent with those of normal massive
elliptical galaxies. However, we find a trend between metallicity gradients and
velocity dispersion (with a negative slope of -1.616{\pm}0.539) that is not
found for the most massive ellipticals. Furthermore, we find trends between the
metallicity gradients and K-band luminosities (with a slope of 0.173{\pm}0.081)
as well as the distance from the BCG to the X-ray peak of the host cluster
(with a slope of -7.546{\pm}2.752). The latter indicates a possible relation
between the formation of the cluster and that of the central galaxy.Comment: 23 pages, 18 figures, accepted for publication in MNRAS. arXiv admin
note: text overlap with arXiv:1104.2376v
Influence of Ge addition on the magnetocaloric effect of a Co-containing Nanopermtype alloy.
The influence of the partial substitution of B by Ge on the magnetocaloric response of
Fe78Co5Zr6B10Cu1 is studied. Ge addition produces a reduction in the temperature at which the peak
entropy change takes place, as well as a slight decrease in the magnitude of the peak, SM
pk . The
refrigerant capacity, RC, and its field dependence is also analyzed: although Ge addition increases
RC of the Co-containing alloy, the largest RC value corresponds to the Co- and Ge-free alloy. This
will be discussed on the basis of the recently proposed universal curve for the magnetic entropy
change, which is also followed by the FeZrBCu Co,Ge alloy series
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