1,237 research outputs found
Disk evolution in the Ori OB1 association
We analyze multi-band photometry of a subsample of low mass stars in the
associations Ori OB1a and 1b discovered during the CIDA Orion Variability
Survey, which have ages of 7 - 10 Myr and 3 - 5 Myr, respectively. We obtained
UBVRcIc photometry at Mt. Hopkins for 6 Classical T Tauri stars (CTTS) and 26
Weak T Tauri stars (WTTS) in Ori OB1a, and for 21 CTTS and 2 WTTS in Ori OB1b.
We also obtained L band photometry for 14 CTTS at Mt. Hopkins, and 10um and
18um photometry with OSCIR at Gemini for 6 CTTS; of these, all 6 were detected
at 10um while only one was detected at 18um. We estimate mass accretion rates
from the excess luminosity at U, and find that they are consistent with
determinations for a number of other associations, with or without high mass
star formation. The observed decrease of mass accretion rate with age is
qualitatively consistent with predictions of viscous evolution of accretion
disks. We find an overall decrease of disk emission from Taurus to Ori OB1b to
Ori OB1a. This decrease implies that significant grain growth and settling
towards the midplane has taken place in the inner disks of Ori OB1. We compare
the SED of the star detected at both 10um and 18um with disk models for similar
stellar and accretion parameters. We find that the low <= 18 um fluxes of this
Ori OB1b star cannot be due to the smaller disk radius expected from viscous
evolution in the presence of the FUV radiation fields from the OB stars in the
association. Instead, we find that the disk of this star is essentially a flat
disk, with little if any flaring, indicating a a significant degree of dust
settling towards the midplane, as expected from dust evolution in
protoplanetary disks.Comment: 35 pages, 11 figures, to appear in the Astronomical Journal. Full
resolution figures in http://www.cida.ve/~briceno/publications
High-Resolution Spectroscopy in Tr37: Gas Accretion Evolution in Evolved Dusty Disks
Using the Hectochelle multifiber spectrograph, we have obtained
high-resolution (R~34,000) spectra in the Halpha region for a large number of
stars in the 4 Myr-old cluster Tr 37, containing 146 previously known members
and 26 newly identified ones. We present the Halpha line profiles of all
members, compare them to our IR observations of dusty disks (2MASS/JHK + IRAC +
MIPS 24 micron), use the radial velocities as a membership criterion, and
calculate the rotational velocities. We find a good correlation between the
accretion-broadened profiles and the presence of protoplanetary disks, noting
that a small fraction of the accreting stars presents broad profiles with
Halpha equivalent widths smaller than the canonical limit separating CTTS and
WTTS. The number of strong accretors appears to be lower than in younger
regions, and a large number of CTTS have very small accretion rates
(dM/dt<10^{-9} Msun/yr). Taking into account that the spectral energy
distributions are consistent with dust evolution (grain growth/settling) in the
innermost disk, this suggests a parallel evolution of the dusty and gaseous
components. We also observe that about half of the "transition objects" (stars
with no IR excesses at wavelengths shorter than ~6 micron) do not show any
signs of active accretion, whereas the other half is accreting with accretion
rates <10^{-9} Msun/yr. These zero or very low accretion rates reveal important
gas evolution and/or gas depletion in the innermost disk, which could be
related to grain growth up to planetesimal or even planet sizes. Finally, we
examine the rotational velocities of accreting and non accreting stars, finding
no significant differences that could indicate disk locking at these ages.Comment: 51 pages, 13 (reduced resolution) figures, 2 tables. AJ in pres
Mind the dadâA review on the biopsychosocial influences of drug abuse on father-infant interaction
Substance use disorder (SUD) is an issue of concern that can have inter- generational impacts. Fathers affected by this disorder can exhibit atypical parenting that leaves pronounced, adverse consequences for the child, espe cially during a critical window for development, such as neonatal life and infancy. However, factors sustaining paternal drug use and its associated health outcomes remain elusive. The present review provides a systematic literature search of the scientific evidence published until February 2021 on PubMed Central, Scopus, PsycInfo, and PubMed databases. Adopting a biopsychosocial model, this review provides comprehensive insights into the issue, detailing: (i) the neurobiological correlates of paternal substance use and atypical parenting mechanisms, (ii) influence of drug consumption on paternal psychological state, and (iii) the social environment modulating the social dynamics central to fathers with SUD. Attention is also paid to the bidirectional relationships between paternal drug abuse and fatherhood, which has been severely neglected so far. Findings shed new light on the importance of paternal contributions to the father-child interaction, supporting the formulation of more targeted multidisciplinary interventions aimed at restoring such a crucial and overlooked relationship.Peer reviewedFinal Published versio
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Agreement of self-reported physician diagnosis of migraine with international classification of headache disorders-II migraine diagnostic criteria in a cross-sectional study of pregnant women
Background: Migraine, a common chronic-intermittent disorder among reproductive age women, has emerged as a novel risk factor for adverse perinatal outcomes. Diagnostic reliability of self-report of physician-diagnosed migraine has not been investigated in pregnancy cohort studies. We investigated agreement of self-report of physician-diagnosed migraine with the diagnostic criteria promoted by the International Classification of Headache Disorders, 2nd edition (ICHD-II). Methods: The cross-sectional study was conducted among 500 women who provided information on a detailed migraine questionnaire that allowed us to apply all ICHD-II diagnostic criteria. Results: Approximately 92% of women reporting a diagnosis of migraine had the diagnosis between the ages of 11 and 40 years (40 years 1.0%). We confirmed self-reported migraine in 81.6% of women when applying the ICHD-II criteria for definitive migraine (63.1%) and probable migraine (18.5%). Conclusion: There is good agreement between self-reported migraine and ICHD-II-based migraine classification in this pregnancy cohort. We demonstrate the feasibility of using questionnaire-based migraine assessment according to full ICHD-II criteria in epidemiological studies of pregnant women
An Atlas of Gas Motions in the TNG-Cluster Simulation: from Cluster Cores to the Outskirts
Galaxy clusters are unique laboratories for studying astrophysical processes
and their impact on gas kinematics. Despite their importance, the full
complexity of gas motion within and around clusters remains poorly known. This
paper is part of a series presenting first results from the new TNG-Cluster
simulation, a suite of 352 massive clusters including the full cosmological
context, mergers, accretion, baryonic processes, feedback, and magnetic fields.
Studying the dynamics and coherence of gas flows, we find that gas motions in
cluster cores and intermediate regions are largely balanced between inflows and
outflows, exhibiting a Gaussian distribution centered at zero velocity. In the
outskirts, even the net velocity distribution becomes asymmetric, featuring a
double peak where the second peak reflects cosmic accretion. Across all cluster
regions, the resulting net flow distribution reveals complex gas dynamics.
These are strongly correlated with halo properties: at a given total cluster
mass, unrelaxed, late-forming halos with less massive black holes and lower
accretion rates exhibit a more dynamic behavior. Our analysis shows no clear
relationship between line-of-sight and radial gas velocities, suggesting that
line-of-sight velocity alone is insufficient to distinguish between inflowing
and outflowing gas. Additional properties, such as temperature, can help break
this degeneracy. A velocity structure function (VSF) analysis indicates more
coherent gas motion in the outskirts and more disturbed kinematics towards halo
centers. In all cluster regions, the VSF shows a slope close to the theoretical
models of Kolmogorov (1/3), except within 50 kpc of the cluster cores, where
the slope is significantly steeper. The outcome of TNG-Cluster broadly aligns
with observations of the VSF of multiphase gas across different scales in
galaxy clusters, ranging from 1 kpc to Megaparsec scales.Comment: Submitted to A&A. See the TNG-Cluster website at
https://www.tng-project.org/cluster
Individual Differences in the Neural and Cognitive Mechanisms of Single Word Reading
Written language is a human invention that our brains did not evolve for. Yet, most research has focused on finding a single theory of reading, identifying the common set of cognitive and neural processes shared across individuals, neglecting individual differences. In contrast, we investigated variation in single word reading. Using a novel statistical method for analyzing heterogeneity in multi-subject task-based functional magnetic resonance imaging (fMRI), we clustered readers based on their brainâs response to written stimuli. Separate behavioral testing and neuroimaging analysis shows that these clusters differed in the role of the sublexical pathway in processing written language, but not in reading skill. Taken together, these results suggest that individuals vary in the cognitive and neural mechanisms involved in word reading. In general, neurocognitive theories need to account not only for what tends to be true of the population, but also the types of variation that exist, even within a neurotypical population
The Rapid Outbursting Star GM Cep: An EX-or in Tr 37?
We present optical, IR and millimeter observations of the solar-type star
13-277, also known as GM Cep, in the 4 Myr-old cluster Tr 37. GM Cep
experiences rapid magnitude variations of more than 2 mag at optical
wavelengths. We explore the causes of the variability, which seem to be
dominated by strong increases in the accretion, being similar to EX-or
episodes. The star shows high, variable accretion rates (up to ~10
Msun/yr), signs of powerful winds, and it is a very fast rotator (Vsini~43
km/s). Its strong mid-IR excesses reveal a very flared disk and/or a remnant
envelope, most likely out of hydrostatic equilibrium. The 1.3 millimeter fluxes
suggest a relatively massive disk (Mdisk~0.1 Msun). Nevertheless, the
millimeter mass is not enough to sustain increased accretion episodes over
large timescales, unless the mass is underestimated due to significant grain
growth. We finally explore the possibility of GM Cep having a binary companion,
which could trigger disk instabilities producing the enhanced accretion
episodes.Comment: 43 pages, including 10 figures, ApJ in pres
Accretion in Evolved and Transitional Disks in Cep OB2: Looking for the Origin of the Inner Holes
We present accretion rates for a large number of solar-type stars in the Cep
OB2 region, based on U band observations. Our study comprises 95 members of the
~4 Myr-old cluster Tr 37 (including 20 "transition" objects; TO), as well as
the only CTTS in the ~12 Myr-old cluster NGC 7160. The stars show different
disk morphologies, with the majority of them having evolved and flattened
disks. The typical accretion rates are about one order of magnitude lower than
in regions aged 1-2 Myr, and we find no strong correlation between disk
morphology and accretion rates. Although half of the TO are not accreting, the
median accretion rates of normal CTTS and accreting "transition" disks are
similar (~3 10^{-9} and 2 10^{-9} Msun/yr, respectively). Comparison with other
regions suggests that the TO observed at different ages do not necessarily
represent the same type of objects, which is consistent with the fact that the
different processes that can lead to reduced IR excess/inner disk clearing
(e.g., binarity, dust coagulation/settling, photoevaporation, giant planet
formation) do not operate on the same timescales. Accreting TO in Tr 37 are
probably suffering strong dust coagulation/settling. Regarding the equally
large number of non-accreting TO in the region, other processes, like
photoevaporation, the presence of stellar/substellar companions, and/or giant
planet formation may account for their "transitional" SEDs and negligible
accretion rates.Comment: 37 pages, 5 figures, 6 tables Accepted by Ap
Nanoporous Silicified Phospholipids and Application to Controlled Glycolic Acid Release
This work demonstrates the synthesis and characterization of novel nanoporous silicified phospholipid bilayers assembled inorganic powders. The materials are obtained by silicification process with silica precursor at the hydrophilic region of phospholipid bilayers. This process involves the co-assembly of a chemically active phospholipids bilayer within the ordered porosity of a silica matrix and holds promise as a novel application for controlled drug release or drug containers with a high level of specificity and throughput. The controlled release application of the synthesized materials was achieved to glycolic acid, and obtained a zero-order release pattern due to the nanoporosity
Herbig Ae/Be Stars in nearby OB associations
We have carried out a study of the early type stars in nearby OB associations
spanning an age range of 3 to 16 Myr, with the aim of determining the
fraction of stars which belong to the Herbig Ae/Be class. We studied the B, A,
and F stars in the nearby ( pc) OB associations Upper Scorpius,
Perseus OB2, Lacerta OB1, and Orion OB1, with membership determined from
Hipparcos data. We obtained spectra for 440 Hipparcos stars in these
associations, from which we determined accurate spectral types, visual
extinctions, effective temperatures, luminosities and masses, using Hipparcos
photometry. Using colors corrected for reddening, we find that the Herbig Ae/Be
stars and the Classical Be stars (CBe) occupy clearly different regions in the
JHK diagram. Thus, we use the location on the JHK diagram, as well as the
presence of emission lines and of strong 12 microns flux relative to the visual
to identify the Herbig Ae/Be stars in the associations. We find that the Herbig
Ae/Be stars constitute a small fraction of the early type stellar population
even in the younger associations. Comparing the data from associations with
different ages and assuming that the near-infrared excess in the Herbig Ae/Be
stars arises from optically thick dusty inner disks, we determined the
evolution of the inner disk frequency with age. We find that the inner disk
frequency in the age range 3 - 10 Myr in intermediate mass stars is lower than
that in the low mass stars (< 1msun). This indicates that the time-scales for
disk evolution are much shorter in the intermediate mass stars, which could be
a consequence of more efficient mechanisms of inner disk dispersal (viscous
evolution, dust growth and settling toward the midplane).Comment: 34 pages, 10 figure
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