2,889 research outputs found
On the helium content of Galactic globular clusters via the R parameter
We estimate the empirical R parameter in 26 Galactic Globular Clusters
covering a wide metallicity range, imaged by WFPC2 on board the HST. The
improved spatial resolution permits a large fraction of the evolved stars to be
measured and permits accurate assessment of radial populaton gradients and
completeness corrections. In order to evaluate both the He abundance and the He
to metal enrichment ratio, we construct a large set of evolutionary models by
adopting similar metallicities and different He contents. We find an absolute
He abundance which is lower than that estimated from spectroscopic measurements
in HII regions and from primordial nucleosynthesis models. This discrepancy
could be removed by adopting a C12O16 nuclear cross section about a factor of
two smaller than the canonical value, although also different assumptions for
mixing processes can introduce systematical effects. The trend in the R
parameter toward solar metallicity is consistent with an upper limit to the He
to metal enrichment ratio of the order of 2.5.Comment: accepted for pubblication on Ap
Cepheid Mass-loss and the Pulsation -- Evolutionary Mass Discrepancy
I investigate the discrepancy between the evolution and pulsation masses for
Cepheid variables. A number of recent works have proposed that non-canonical
mass-loss can account for the mass discrepancy. This mass-loss would be such
that a 5Mo star loses approximately 20% of its mass by arriving at the Cepheid
instability strip; a 14Mo star, none. Such findings would pose a serious
challenge to our understanding of mass-loss. I revisit these results in light
of the Padova stellar evolutionary models and find evolutionary masses are
()% greater than pulsation masses for Cepheids between 5<M/Mo<14. I
find that mild internal mixing in the main-sequence progenitor of the Cepheid
are able to account for this mass discrepancy.Comment: 15 pages, 3 figures, ApJ accepte
Electroencephalographic functional connectivity in extreme prematurity: a pilot study based on graph theory
Background: Connectivity studies based on functional magnetic resonance imaging (MRI) provided new insights in neonatal brain development but cannot be performed at bedside in the clinical setting. The electroencephalogram (EEG) connectivity has been less studied, particularly using the new approach based on graph theory. This study aimed to explore the functional EEG connectivity using graph theory analysis at an early post-conception age in extremely premature and late-preterm babies free of medical complications and overt brain damage. Methods: Sixteen neonates (8 extremely low gestational age (ELGA) and 8 late-preterm infants), both groups having performed multichannel EEG recordings at 35 weeksâ post-conception, were recruited in a single tertiary-level neonatal intensive care unit and well-baby nursery, respectively. Global (i.e., small-worldness) and local (i.e., clustering and strength) connectivity measures were calculated on a single-subject connectivity matrix of EEG data. Results: Both ELGA and late-preterm infants showed small-worldness organization at 35 weeksâ post-conception. The ELGA group had the strength parameter of the theta frequency band lower in the right than in the left hemisphere. This asymmetry did not emerge in the late-preterm group. Moreover, the mean strength parameter was significantly greater in the right hemisphere in the late preterms than in the ELGA group. Conclusion: EEG connectivity measures could represent an index of left-to-right maturation and developmental disadvantage in extremely preterm infants
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(E)motion and creativity: Hacking the function of motor expressions in emotion regulation to augment creativity
Positive emotion can help augment human creativity. To utilize this potential in an interactive system, we propose that such a system should be designed to regulate the emotions that are caused by a creative task. We argue that this can be done by hacking the function of motor expressions in emotion regulation. To this end, we have conceived and made an interactive system that is designed to regulate positive emotion during an idea generation and an insight problem solving task. The system regulates emotion by letting users interact using arm gestures that are designed based on motor expressions, choreographed in a way that enables emotion regulation. Using this interactive system we experimentally test the hypotheses that positive approaching, rather than negative avoiding arm gestures, used to interact with a system, can heighten positive emotion, and augment creativity. The findings demonstrate that an interactive system can be designed to use the function of motor expressions in emotion regulation to help people perform better on certain creative tasks
Variable stars in Local Group Galaxies - II. Sculptor dSph
We present the identification of 634 variable stars in the Milky Way dSph
satellite Sculptor based on archival ground-based optical observations spanning
24 years and covering 2.5 deg. We employed the same
methodologies as the "Homogeneous Photometry" series published by Stetson. In
particular, we have identified and characterized one of the largest (536) RR
Lyrae samples so far in a Milky Way dSph satellite. We have also detected four
Anomalous Cepheids, 23 SX Phoenicis stars, five eclipsing binaries, three field
variable stars, three peculiar variable stars located above the horizontal
branch - near to the locus of BL Herculis - that we are unable to classify
properly. Additionally we identify 37 Long Period Variables plus 23 probable
variable stars, for which the current data do not allow us to determine the
period. We report positions and finding charts for all the variable stars, and
basic properties (period, amplitude, mean magnitude) and light curves for 574
of them. We discuss the properties of the RR Lyrae stars in the Bailey diagram,
which supports the coexistence of subpopulations with different chemical
compositions. We estimate the mean mass of Anomalous Cepheids
(1.5M) and SX Phoenicis stars (1M). We discuss
in detail the nature of the former. The connections between the properties of
the different families of variable stars are discussed in the context of the
star formation history of the Sculptor dSph galaxy.Comment: 22 pages, 17 figures, 13 tables. Accepted for publication on MNRA
Triangulating Abuse Liability Assessment for Flavoured Cigar Products Using Physiological, Behavioural Economic and Subjective Assessments: A Within-subjects Clinical Laboratory Protocol
Introduction In the USA, Food and Drug Administration regulations prohibit the sale of flavoured cigarettes, with menthol being the exception. However, the manufacture, advertisement and sale of flavoured cigar products are permitted. Such flavourings influence positive perceptions of tobacco products and are linked to increased use. Flavourings may mask the taste of tobacco and enhance smoke inhalation, influencing toxicant exposure and abuse liability among novice tobacco users. Using clinical laboratory methods, this study investigates how flavour availability affects measures of abuse liability in young adult cigarette smokers. The specific aims are to evaluate the effect of cigar flavours on nicotine exposure, and behavioural and subjective measures of abuse liability.
Methods and analyses Participants (projected n=25) are healthy smokers of five or more cigarettes per day over the past 3âmonths, 18â25 years old, naive to cigar use (lifetime use of 50 or fewer cigar products and no more than 10 cigars smoked in the past 30 days) and without a desire to quit cigarette smoking in the next 30 days. Participants complete five laboratory sessions in a Latin square design with either their own brand cigarette or a session-specific Black & Mild cigar differing in flavour (apple, cream, original and wine). Participants are single-blinded to cigar flavours. Each session consists of two 10-puff smoking bouts (30âs interpuff interval) separated by 1âhour. Primary outcomes include saliva nicotine concentration, behavioural economic task performance and response to various questionnaire items assessing subjective effects predictive of abuse liability. Differences in outcomes across own brand cigarette and flavoured cigar conditions will be tested using linear mixed models
Adducts of functionalized Graphene layers with Ag nanoparticles for Antimicrobial applications
Health and environmental impacts of multi-drug resistance (MDR) pathogens are becoming more and
more relevant nowadays, thus increasing the need of developing new, safe and effective
antimicrobials.
This research was focused on the synthesis, the characterization and the evaluation of the
antimicrobial and cytotoxic activity of hybrid nanomaterials made up through a simple and
sustainable functionalization of three carbon substrates, namely Graphite, Carbon black and Carbon
nanotubes, with a pyrrole moiety (SP) and silver nanoparticles (Ag-NP) [1, 2]. The adducts were
analyzed by means of thermogravimetric analyses (TGA), transmission electron microscopy
(HRTEM) and X-ray diffraction analyses (WAXD), which confirmed the successful functionalization
of raw materials. UV-vis spectroscopy and dynamic/electrophoretic light scattering (DLS/ELS)
provided information regarding carbon suspensions stability, particles sizes and surface charge.
Results from microbiological tests revealed an outstanding enhancement of the antimicrobial activity
promoted by the functionalization with Ag nanoparticles, maintaining unaltered the cytotoxic levels
exerted by not-functionalized materials. In the light of these results, a possible bactericidal
mechanism based on the synergy between mechanical and oxidative stresses at the bacterial
membrane level is proposed
Chromatin to Clinic: The Molecular Rationale for PARP1 Inhibitor Function.
Poly(ADP-ribose) polymerase 1 (PARP1) inhibitors were recently shown to have potential clinical impact in a number of disease settings, particularly as related to cancer therapy, treatment for cardiovascular dysfunction, and suppression of inflammation. The molecular basis for PARP1 inhibitor function is complex, and appears to depend on the dual roles of PARP1 in DNA damage repair and transcriptional regulation. Here, the mechanisms by which PARP-1 inhibitors elicit clinical response are discussed, and strategies for translating the preclinical elucidation of PARP-1 function into advances in disease management are reviewed
A Photometric Study of the Outer Halo Globular Cluster NGC 5824
Multi-wavelength CCD photometry over 21 years has been used to produce deep
color-magnitude diagrams together with light curves for the variables in the
Galactic globular cluster NGC 5824. Twenty-one new cluster RR Lyrae stars are
identified, bringing the total to 47, of which 42 have reliable periods
determined for the first time. The color-magnitude diagram is matched using
BaSTI isochrones with age of ~Gyr. and reddening is found to be ; using the period-Wesenheit relation in two colors the distance
modulus is corresponding to a distance of 30.9 Kpc.
The observations show no signs of populations that are significantly younger
than the ~Gyr stars. The width of the red giant branch does not allow for a
spread in [Fe/H] greater than dex, and there is no photometric
evidence for widened or parallel sequences. The pseudo-color
magnitude diagram shows a bifurcation of the red giant branch that by analogy
with other clusters is interpreted as being due to differing spectral
signatures of the first (75\%) and second (25\%) generations of stars whose age
difference is close enough that main sequence turnoffs in the color-magnitude
diagram are unresolved. The cluster main sequence is visible against the
background out to a radial distance of arcmin. We conclude that NGC
5824 appears to be a classical Oosterhoff Type II globular cluster, without
overt signs of being a remnant of a now-disrupted dwarf galaxy.Comment: 26 pages, 15 figures, 4 tables, accepted for publication in
Astronomical Journa
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