176 research outputs found
Galactic and Cosmic Type Ia SN rates: is it possible to impose constraints on SNIa progenitors?
We compute the Type Ia supernova rates in typical elliptical galaxies by
varying the progenitor models for Type Ia supernovae. To do that a formalism
which takes into account the delay distribution function (DTD) of the explosion
times and a given star formation history is adopted. Then the chemical
evolution for ellipticals with baryonic initial masses , and
is computed, and the mass of Fe produced by each galaxy is
precisely estimated. We also compute the expected Fe mass ejected by
ellipticals in typical galaxy clusters (e.g. Coma and Virgo), under different
assumptions about Type Ia SN progenitors. As a last step, we compute the cosmic
Type Ia SN rate in an unitary volume of the Universe by adopting several cosmic
star formation rates and compare it with the available and recent observational
data. Unfortunately, no firm conclusions can be derived only from the cosmic
SNIa rate, neither on SNIa progenitors nor on the cosmic star formation rate.
Finally, by analysing all our results together, and by taking into account
previous chemical evolution results, we try to constrain the best Type Ia
progenitor model. We conclude that the best progenitor models for Type Ia SNe
are still the single degenerate model, the double degenerate wide model, and
the empirical bimodal model. All these models require the existence of prompt
Type Ia supernovae, exploding in the first 100 Myr since the beginning of star
formation, although their fraction should not exceed 15-20% in order to fit
chemical abundances in galaxies.Comment: 17 pages, 11 figures, Submitted to MNRA
Effects of tidal interactions on the gas flows of elliptical galaxies
During a Hubble time, cluster galaxies may undergo several mutual encounters
close enough to gravitationally perturb their hot, X-ray emitting gas flows. We
ran several 2D, time dependent hydrodynamical models to investigate the effects
of such perturbations on the gas flow inside elliptical galaxies. In
particular, we studied in detail the modifications occurring in the scenario
proposed by D'Ercole et al. (1989), in which the galactic interstellar medium
produced by the aging galactic stellar population, is heated by SNIa at a
decreasing rate. We find that, although the tidal interaction in our models
lasts less than 1 Gyr, its effect extends over several Gyrs. The tidally
induced turbulent flows create dense filaments which cool quickly and accrete
onto the galactic center, producing large spikes in the global Lx. Once this
mechanism starts, it is fed by gravity and amplified by SNIa. In cooling flow
models without supernovae the amplitude of the Lx fluctuations due to the tidal
interaction is substantially reduced. We conclude that, if SNIa significantly
contribute to the energetics of the gas flows in ellipticals, then the observed
spread in the Lx-Lb diagram may be caused, at least in part, by this mechanism.
On the contrary, tidal interactions cannot be responsible for the observed
spread if the pure cooling flow scenario applies (abridged).Comment: 21 pages, 8 figures, to be published in ApJ (main journal
Examining the Impact of De-escalation Training Among Emergency Department Nurses
Workplace violence is a growing concern for US nurses, especially in the context of COVID-19 and patient incivility. De-escalation training can help mitigate high-risk incidents, but its psychological benefits are not well understood. This study aimed to determine if de-escalation training for emergency department nurses provided psychological benefit. This pre-experimental pre-test, post-test study evaluated nurse confidence in coping with patient aggression, caregiver resiliency, professional quality of life, and intention to stay with the organization. Participants completed a pretest survey, attended a two-hour verbal de-escalation training via zoom, and then completed the posttest survey. The study showed that attending the two-hour verbal de-escalation training resulted in a statistically significant decrease in reported nurse burnout on the professional quality of life scale (p = .016). However, there was no significant differences in overall nurse resilience (p = .714), professional quality of life compassion subscale (p = .172), professional quality of life secondary traumatic stress subscale (p = .14), confidence in coping with patient aggression (p = .066), and intention to stay (p = 1). These findings suggest that healthcare organizations should prioritize de-escalation training for their nurses to equip them with the skills and confidence needed to handle high-risk situations effectively. Further research is needed to examine the long-term psychological effects of de-escalation training.https://digitalcommons.odu.edu/gradposters2023_healthsciences/1001/thumbnail.jp
The effect of differential galactic winds on the chemical evolution of galaxies
(Abridged) The aim of this paper is to study the basic equations of the
chemical evolution of galaxies with gas flows. We focus on models in which the
outflow is differential, namely in which the heavy elements (or some of the
heavy elements) can leave the parent galaxy more easily than other chemical
species such as H and He. We study the chemical evolution of galaxies in the
framework of simple models. This allows us to solve analytically the equations
for the evolution of gas masses and metallicities. We find new analytical
solutions for various cases in which the effects of winds and infall are taken
into account. Differential galactic winds have the effect of reducing the
global metallicity of a galaxy, with the amount of reduction increasing with
the ejection efficiency of the metals. Abundance ratios are predicted to remain
constant throughout the whole evolution of the galaxy, even in the presence of
differential winds. One way to change them is by assuming differential winds
with different ejection efficiencies for different elements. However, simple
models apply only to elements produced on short timescales, namely all by Type
II SNe, and therefore large differences in the ejection efficiencies of
different metals are unlikely. Variations in abundance ratios such as [O/Fe] in
galaxies, without including the Fe production by Type Ia supernovae, can in
principle be obtained by assuming an unlikely different efficiency in the loss
of O relative to Fe from Type II supernovae. Therefore, we conclude that it is
not realistic to ignore Type Ia supernovae and that the delayed production of
some chemical elements relative to others (time-delay model) remains the most
plausible explanation for the evolution of alpha-elements relative to Fe.Comment: 11 pages, 10 figures, A&A accepte
EVERYDAY EUROPE AND TOMORROW’S EUROPE: is there a future for Social Transnationalism? A response to readers.
For Symposium abstract is not require
The Origin of the Mass-Metallicity relation: an analytical approach
The existence of a mass-metallicity (MZ) relation in star forming galaxies at
all redshift has been recently established. We aim at studying some possible
physical mechanisms contributing to the MZ relation by adopting analytical
solutions of chemical evolution models including infall and outflow. We explore
the hypotheses of a variable galactic wind rate, infall rate and yield per
stellar generation (i.e. a variation in the IMF), as possible causes for the MZ
relation. By means of analytical models we compute the expected O abundance for
galaxies of a given total baryonic mass and gas mass.The stellar mass is
derived observationally and the gas mass is derived by inverting the Kennicutt
law of star formation, once the star formation rate is known. Then we test how
the parameters describing the outflow, infall and IMF should vary to reproduce
the MZ relation, and we exclude the cases where such a variation leads to
unrealistic situations. We find that a galactic wind rate increasing with
decreasing galactic mass or a variable IMF are both viable solutions for the MZ
relation. A variable infall rate instead is not acceptable. It is difficult to
disentangle among the outflow and IMF solutions only by considering the MZ
relation, and other observational constraints should be taken into account to
select a specific solution. For example, a variable efficiency of star
formation increasing with galactic mass can also reproduce the MZ relation and
explain the downsizing in star formation suggested for ellipticals. The best
solution could be a variable efficiency of star formation coupled with galactic
winds, which are indeed observed in low mass galaxies.Comment: Accepted by A&
The tumor suppressor protein OPCML potentiates anti-EGFR and anti-HER2 targeted therapy in HER2-positive ovarian and breast cancer.
OPCML is a tumor suppressor gene that is frequently inactivated in ovarian cancer and many other cancers by somatic methylation. We have previously shown that OPCML exerts its suppressor function by negatively regulating a spectrum of receptor tyrosine kinases (RTKs), such as ErbB2/HER2, FGFR1 and EphA2, thus attenuating their related downstream signaling. The physical interaction of OPCML with this defined group of RTKs is a prerequisite for their downregulation. Overexpression/gene amplification of EGFR and HER2 is a frequent event in multiple cancers including ovarian and breast cancers. Molecular therapeutics against EGFR/HER2 or EGFR only, such as lapatinib and erlotinib respectively, were developed to target these receptors but resistance often occurs in relapsing cancers. Here we show that, though OPCML interacts only with HER2 and not with EGFR, the interaction of OPCML with HER2 disrupts the formation of the HER2-EGFR heterodimer and this translates into a better response to both lapatinib and erlotinib in HER2-expressing ovarian and breast cancer cell lines. Also, we show that high OPCML expression is associated with better response to lapatinib therapy in breast cancer patients and better survival in HER2-overexpressing ovarian cancer patients, suggesting that OPCML co-therapy could be a valuable sensitizing approach to RTK inhibitors
New analytical solutions for chemical evolution models: : characterizing the population of star-forming and passive galaxies
E. Spitoni, V. Vincenzo, and F. Matteucci, 'New analytical solutions for chemical evolution models: characterizing the population of star-forming and passive galaxies', Astronomy & Astrophysics, Vol 599, first published online 20 February 2017, available at DOI: https://doi.org/10.1051/0004-6361/201629745. Reproduced with permission from Astronomy & Astrophysics, © 2017 ESO.Context. Analytical models of chemical evolution, including inflow and outflow of gas, are important tools for studying how the metal content in galaxies evolves as a function of time. Aims. We present new analytical solutions for the evolution of the gas mass, total mass, and metallicity of a galactic system when a decaying exponential infall rate of gas and galactic winds are assumed. We apply our model to characterize a sample of local star-forming and passive galaxies from the Sloan Digital Sky Survey data, with the aim of reproducing their observed mass-metallicity relation. Methods. We derived how the two populations of star-forming and passive galaxies differ in their particular distribution of ages, formation timescales, infall masses, and mass loading factors. Results. We find that the local passive galaxies are, on average, older and assembled on shorter typical timescales than the local star-forming galaxies; on the other hand, the star-forming galaxies with higher masses generally show older ages and longer typical formation timescales compared than star-forming galaxies with lower masses. The local starforming galaxies experience stronger galactic winds than the passive galaxy population. Exploring the effect of assuming different initial mass functions in our model, we show that to reproduce the observed mass-metallicity relation, stronger winds are requested if the initial mass function is top-heavy. Finally, our analytical models predict the assumed sample of local galaxies to lie on a tight surface in the 3D space defined by stellar metallicity, star formation rate, and stellar mass, in agreement with the well-known fundamental relation from adopting gas-phase metallicity. Conclusions. By using a new analytical model of chemical evolution, we characterize an ensemble of SDSS galaxies in terms of their infall timescales, infall masses, and mass loading factors. Local passive galaxies are, on average, older and assembled on shorter typical timescales than the local star-forming galaxies. Moreover, the local star-forming galaxies show stronger galactic winds than the passive galaxy population. Finally, we find that the fundamental relation between metallicity, mass, and star formation rate for these local galaxies is still valid when adopting the average galaxy stellar metallicity.Peer reviewe
Everyday cosmopolitanism in representations of Europe among young Romanians in Britain
The paper presents an analysis of everyday cosmopolitanism in constructions of Europe among young Romanian nationals living in Britain. Adopting a social representations approach, cosmopolitanism is understood as a cultural symbolic resource that is part of everyday knowledge. Through a discursively-oriented analysis of focus group data, we explore the ways in which notions of cosmopolitanism intersect with images of Europeanness in the accounts of participants. We show that, for our participants, representations of Europe are anchored in an Orientalist schema of West-vs.-East, whereby the West is seen as epitomising European values of modernity and progress, while the East is seen as backward and traditional. Our findings further show that representations of cosmopolitanism reinforce this East/West dichotomy, within a discourse of ‘Occidental cosmopolitanism’. The paper concludes with a critical discussion of the diverse and complex ideological foundations of these constructions of European cosmopolitanism and their implications
Galactic fountains and their connection with high and intermediate velocity clouds
The aim of this paper is to calculate the expansion law and chemical
enrichment of a supershell powered by the energetic feedback of a typical
Galactic OB association at various galactocentric radii. We study then the
orbits of the fragments created when the supershell breaks out and we compare
their kinetic and chemical properties with the available observations of high -
and intermediate - velocity clouds. We use the Kompaneets (1960) approximation
for the evolution of the superbubble driven by sequential supernova explosions
and we compute the abundances of oxygen and iron residing in the thin cold
supershell. We assume that supershells are fragmented by means of
Rayleigh-Taylor instabilities and we follow the orbit of the clouds either
ballistically or by means of a hybrid model considering viscous interaction
between the clouds and the extra-planar gas.Given the self-similarity of the
Kompaneets solutions, clouds are always formed ~ 448 pc above the plane. If the
initial metallicity is solar, the pollution from dying stars of the OB
association has a negligible effect on the chemical composition of the clouds.
The maximum height reached by the clouds above the plane seldom exceeds 2 kpc
and when averaging over different throwing angles, the landing coordinate
differs from the throwing coordinate ~ 1 kpc at most. The range of heights and
[O/Fe] ratios spun by our clouds suggest us that the high velocity clouds
cannot have a Galactic origin, whereas intermediate velocity clouds have
kinematic properties similar to our modeled clouds but overabundance observed
for the [O/Fe] ratios which can be reproduced only with initial metallicities
which are too low compared for those of the Galaxy disk.Comment: Accepted 17/03/2008 by A&
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