2,725 research outputs found
Predictors of discordance among Chilean families
Parent-youth agreement on parental behaviors can characterize effective parenting. Although
discordance in families may be developmentally salient and harmful to youth outcomes, predictors
of discordance have been understudied, and existing research in this field has been mostly limited
to North American samples. This paper addressed this literature gap by using data from a
community-based study of Chilean adolescents. Analysis was based on 1,068 adolescents in
Santiago, Chile. The dependent variable was discordance which was measured by the difference
between parent and youth’s assessment of parental monitoring. Major independent variables for
this study were selected based on previous research findings that underscore youth’s
developmental factors, positive parental and familial factors and demographic factors. Descriptive
and multivariate analyses were conducted to examine the prevalence and associations between
youth, parental and familial measures with parent-youth discordance. There was a sizable level of
discordance between parent and youth’s report of parental monitoring. Youth’s gender and
externalizing behavior were significant predictors of discordance. Warm parenting and family
involvement were met with decreases in discordance. The negative interaction coefficients
between parental warmth and youth’s gender indicated that positive parental and familial
measures have a greater effect on reducing parent-youth discordance among male youths. Results
support the significance of positive family interactions in healthy family dynamics. Findings from
this study inform the importance of services and interventions for families that aim to reduce
youth’s problem behavior and to create a warm and interactive family environment.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4181713/Accepted manuscrip
A hybrid modal decomposition approach for higher-order modes in circular ducts
Before it is possible to determine the effect over a wide frequency range of different
aperture devices on the sound field in a duct, the contribution from the individual
higher-order modes must be established. Two approaches to decompose the sound
field may be taken which are either to use a large number of microphone locations to
reconstruct the sound field, or to use a hybrid method involving a reduced set of
microphone locations and a model of the sound field in the system. Modelling the
higher-order modes in a duct is itself a numerically intensive procedure if fully
coupled calculations are required. It is possible to simplify the process for modelling
the sound field by using uncoupled calculations for the higher order modes. Results
are presented for such a hybrid approach, combining a limited number of microphone
locations with an uncoupled model, to establish the sound field in a circular duct.
Both point source and plane wave sources are considered and direct measurement of
the sound field is compared to the reconstructed field for a normalised wave number
range up to 7. Results show acceptable agreement between the hybrid approach and
direct measurement with the greatest errors occurring around cut-on of the axially
anti-symmetric modes. Thus, it is demonstrated that a hybrid approach may be
applied to ducts with simple sources and that the approach can be used to deconstruct
the in-duct sound field into the individual higher-order mode contribution
Physico-electrochemical Characterization of Pluripotent Stem Cells during Self-Renewal or Differentiation by a Multi-modal Monitoring System.
Monitoring pluripotent stem cell behaviors (self-renewal and differentiation to specific lineages/phenotypes) is critical for a fundamental understanding of stem cell biology and their translational applications. In this study, a multi-modal stem cell monitoring system was developed to quantitatively characterize physico-electrochemical changes of the cells in real time, in relation to cellular activities during self-renewal or lineage-specific differentiation, in a non-destructive, label-free manner. The system was validated by measuring physical (mass) and electrochemical (impedance) changes in human induced pluripotent stem cells undergoing self-renewal, or subjected to mesendodermal or ectodermal differentiation, and correlating them to morphological (size, shape) and biochemical changes (gene/protein expression). An equivalent circuit model was used to further dissect the electrochemical (resistive and capacitive) contributions of distinctive cellular features. Overall, the combination of the physico-electrochemical measurements and electrical circuit modeling collectively offers a means to longitudinally quantify the states of stem cell self-renewal and differentiation
Dynamics of on-line Hebbian learning with structurally unrealizable restricted training sets
We present an exact solution for the dynamics of on-line Hebbian learning in
neural networks, with restricted and unrealizable training sets. In contrast to
other studies on learning with restricted training sets, unrealizability is
here caused by structural mismatch, rather than data noise: the teacher machine
is a perceptron with a reversed wedge-type transfer function, while the student
machine is a perceptron with a sigmoidal transfer function. We calculate the
glassy dynamics of the macroscopic performance measures, training error and
generalization error, and the (non-Gaussian) student field distribution. Our
results, which find excellent confirmation in numerical simulations, provide a
new benchmark test for general formalisms with which to study unrealizable
learning processes with restricted training sets.Comment: 7 pages including 3 figures, using IOP latex2e preprint class fil
Intermediate Element Abundances in Galaxy Clusters
We present the average abundances of the intermediate elements obtained by
performing a stacked analysis of all the galaxy clusters in the archive of the
X-ray telescope ASCA. We determine the abundances of Fe, Si, S, and Ni as a
function of cluster temperature (mass) from 1--10 keV, and place strong upper
limits on the abundances of Ca and Ar. In general, Si and Ni are overabundant
with respect to Fe, while Ar and Ca are very underabundant. The discrepancy
between the abundances of Si, S, Ar, and Ca indicate that the alpha-elements do
not behave homogeneously as a single group. We show that the abundances of the
most well-determined elements Fe, Si, and S in conjunction with recent
theoretical supernovae yields do not give a consistent solution for the
fraction of material produced by Type Ia and Type II supernovae at any
temperature or mass. The general trend is for higher temperature clusters to
have more of their metals produced in Type II supernovae than in Type Ias. The
inconsistency of our results with abundances in the Milky Way indicate that
spiral galaxies are not the dominant metal contributors to the intracluster
medium (ICM). The pattern of elemental abundances requires an additional source
of metals beyond standard SNIa and SNII enrichment. The properties of this new
source are well matched to those of Type II supernovae with very massive,
metal-poor progenitor stars. These results are consistent with a significant
fraction of the ICM metals produced by an early generation of population III
stars.Comment: 18 pages, 11 figures, 7 tables. Submitted to Ap
Non-Ergodic Dynamics of the 2D Random-phase Sine-Gordon Model: Applications to Vortex-Glass Arrays and Disordered-Substrate Surfaces
The dynamics of the random-phase sine-Gordon model, which describes 2D
vortex-glass arrays and crystalline surfaces on disordered substrates, is
investigated using the self-consistent Hartree approximation. The
fluctuation-dissipation theorem is violated below the critical temperature T_c
for large time t>t* where t* diverges in the thermodynamic limit. While above
T_c the averaged autocorrelation function diverges as Tln(t), for T<T_c it
approaches a finite value q* proportional to 1/(T_c-T) as q(t) = q* -
c(t/t*)^{-\nu} (for t --> t*) where \nu is a temperature-dependent exponent. On
larger time scales t > t* the dynamics becomes non-ergodic. The static
correlations behave as Tln{x} for T>T_c and for T<T_c when x < \xi* with \xi*
proportional to exp{A/(T_c-T)}. For scales x > \xi*, they behave as (T/m)ln{x}
where m is approximately T/T_c near T_c, in general agreement with the
variational replica-symmetry breaking approach and with recent simulations of
the disordered-substrate surface. For strong- coupling the transition becomes
first-order.Comment: 12 pages in LaTeX, Figures available upon request, NSF-ITP 94-10
Dynamical Properties of a Growing Surface on a Random Substrate
The dynamics of the discrete Gaussian model for the surface of a crystal
deposited on a disordered substrate is investigated by Monte Carlo simulations.
The mobility of the growing surface was studied as a function of a small
driving force and temperature . A continuous transition is found from
high-temperature phase characterized by linear response to a low-temperature
phase with nonlinear, temperature dependent response. In the simulated regime
of driving force the numerical results are in general agreement with recent
dynamic renormalization group predictions.Comment: 10 pages, latex, 3 figures, to appear in Phys. Rev. E (RC
The photophoretic sweeping of dust in transient protoplanetary disks
Context: Protoplanetary disks start their lives with a dust free inner region where the temperatures are higher than the sublimation temperature of solids. As the star illuminates the innermost particles, which are immersed in gas at the sublimation edge, these particles are subject to a photophoretic force.
Aims: We examine the motion of dust particles at the inner edge of protoplanetary disks due to photophoretic drag.
Methods: We give a detailed treatment of the photophoretic force for particles in protoplanetary disks. The force is applied to particles at the inner edge of a protoplanetary disk and the dynamical behavior of the particles is analyzed.
Results: We find that, in a laminar disk, photophoretic drag increases the size of the inner hole after accretion onto the central body has become subdued. This region within the hole becomes an optically transparent zone containing gas and large dusty particles (>>10 cm), but devoid of, or strongly depleted in, smaller dust aggregates. Photophoresis can clear the inner disk of dust out to 10 AU in less than 1 Myr. The details of this clearance depend on the size distribution of the dust. Any replenishment of the dust within the cleared region will be continuously and rapidly swept out to the edge. At late times, the edge reaches a stable equilibrium between inward drift and photophoretic outward drift, at a distance of some tens of AU. Eventually, the edge will move inwards again as the disk disperses, shifting the equilibrium position back from about 40 AU to below 30 AU in 1-2 Myr in the disk model. In a turbulent disk, diffusion can delay the clearing of a disk by photophoresis. Smaller and/or age-independent holes of radii of a few AU are also possible outcomes of turbulent diffusion counteracting photophoresis.
Conclusions: This outward and then inward moving edge marks a region of high dust concentration. This density enhancement, and the efficient transport of particles from close to the star to large distances away, can explain features of comets such as high measured ratios of crystalline to amorphous silicates, and has a large number of other applications
Reply to Morel : cadmium as a micronutrient and macrotoxin in the oceans
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 110 (2013): E1878, doi:10.1073/pnas.1305068110.We thank François Morel for his interest in our study. Morel states that our conclusions are based on
the approximate match between the Cd-isotope composition of cultured bacteria and the fractionation
of Cd isotopes seen in seawater (1). This match is only a minor component of our argument, and we
welcome the opportunity to reiterate our case
STAR Results on High Transverse Momentum, Heavy Flavor and Electromagnetic Probes
We summarize here recent results from the STAR collaboration focusing on
processes involving large momentum transfers. Measurements of angular
correlations of di-hadrons are explored in both the pseudorapidity (eta) and
azimuthal (phi) projections. In central Au+Au, an elongated structure is found
in the eta projection which persists up to the highest measured pT. After
quantifying the particle yield in this structure and subtracting it from the
near-side yield, we observe that the remainder exhibits a behavior strikingly
similar to that of the near-side yield in d+Au. For heavy flavor production,
using electron-hadron correlations in p+p collisions, we obtain an estimate of
the b-quark contribution to the non-photonic electrons in the pT region 3-6
GeV/c, and find it consistent with FONLL calculations. Together with the
observed suppression of non-photonic electrons in Au+Au, this strongly suggests
suppression of b-quark production in Au+Au collisions. We discuss results on
the mid-rapidity Upsilon cross-section in p+p collisions. Finally, we present a
proof-of-principle measurement of photon-hadron correlations in p+p collisions,
paving the way for the tomographic study of the matter produced in central
Au+Au via gamma-jet measurements.Comment: 8 pages, 4 figures. Proceedings of "Quark Matter 2006", 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collision
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