1,825 research outputs found
Prediction of explosive yield and other characteristics of liquid propellant rocket explosions Final report
Explosive hazards and yield predictions for liquid rocket propellant
Sexual Differentiation of Circadian Clock Function in the Adrenal Gland
Sex differences in glucocorticoid production are associated with increased responsiveness of the adrenal gland in females. However, the adrenal-intrinsic mechanisms that establish sexual dimorphic function remain ill defined. Glucocorticoid production is gated at the molecular level by the circadian clock, which may contribute to sexual dimorphic adrenal function. Here we examine sex differences in the adrenal gland using an optical reporter of circadian clock function. Adrenal glands were cultured from male and female Period2::Luciferase (PER2::LUC) mice to assess clock function in vitro in real time. We confirm that there is a pronounced sex difference in the intrinsic capacity to sustain PER2::LUC rhythms in vitro, with higher amplitude rhythms in adrenal glands collected from males than from females. Changes in adrenal PER2::LUC rhythms over the reproductive life span implicate T as an important factor in driving sex differences in adrenal clock function. By directly manipulating hormone levels in adult mice in vivo, we demonstrate that T increases the amplitude of PER2::LUC rhythms in adrenal glands of both male and female mice. In contrast, we find little evidence that ovarian hormones modify adrenal clock function. Lastly, we find that T in vitro can increase the amplitude of PER2::LUC rhythms in male adrenals but not female adrenals, which suggests the existence of sex differences in the mechanisms of T action in vivo. Collectively these results reveal that activational effects of T alter circadian timekeeping in the adrenal gland, which may have implications for sex differences in stress reactivity and stress-related disorders
Contamination by field late-M, L and T dwarfs in deep surveys
Context: Deep photometric surveys for substellar objects in young clusters
and for high-redshift quasars are affected by contaminant sources at different
heliocentric distances.If not correctly taken into account, the contamination
may have a strong effect on the Initial Mass Function determination and on the
identification of quasars. Aims: We calculate in detail the back- and
foreground contamination by field dwarfs of very late spectral types
(intermediate and late M, L and T) in deep surveys and provide the data and
tools for the computation. Methods: Up-to-date models and data from the
literature have been used: (i) a model of the Galactic thin disc by an
exponential law; (ii) the length and height scales for late-type dwarfs; (iii)
the local spatial densities, absolute magnitudes and colours of dwarfs for each
spectral type. Results: We derive a simplified expression for the spatial
density in the thin disc that depends on the heliocentric distance and the
galactic coordinates (l, b) and integrate it in the truncated cone screened in
the survey. As a practical application, we compute the numbers of L- and T-type
field dwarfs in very deep (I = 21-29 mag) surveys in the direction of the young
sigma Orionis cluster. The increasing number of contaminants at the faintest
magnitudes could inhibit the study of the opacity mass limit at M <~ 0.003
M_sol in the cluster.Comment: A&A, accepted. 11 pages, 4 figures, 4 tables. Version 2: deleted two
spurious figures at the end of the fil
Distorted Copulas: Constructions and Tail Dependence
Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails
Reanalysis of the FEROS observations of HIP 11952
Aims. We reanalyze FEROS observations of the star HIP 11952 to reassess the
existence of the proposed planetary system. Methods. The radial velocity of the
spectra were measured by cross-correlating the observed spectrum with a
synthetic template. We also analyzed a large dataset of FEROS and HARPS
archival data of the calibrator HD 10700 spanning over more than five years. We
compared the barycentric velocities computed by the FEROS and HARPS pipelines.
Results. The barycentric correction of the FEROS-DRS pipeline was found to be
inaccurate and to introduce an artificial one-year period with a semi-amplitude
of 62 m/s. Thus the reanalysis of the FEROS data does not support the existence
of planets around HIP 11952.Comment: 7 pages, 8 figures, 1 tabl
Copulas constructed from horizontal sections
In analogy with the study of copulas whose diagonal sections have
been fixed, we study the set of copulas for which a horizontal section has been given. We first show that this set is not empty, by explicitly writing one such copula, which we call \textit{horizontal copula}. Then we find the copulas that
bound both below and above the set . Finally we determine the expressions for Kendall's tau and Spearman's rho for the horizontal and the bounding copulas
The Impact of Gendered Stereotypes on Perceptions of Violence: A Commentary
The present commentary explores the impact of gender role stereotypes on perceptions of both intimate partner violence (IPV) and sexual violence. Two papers published in this issue of Sex Roles explored the influence of gender stereotypes on both IPV (Bates et al., 2019) and rape myths (Klement et al., 2019). An overarching theme of these papers is how gender stereotypes may influence incorrect beliefs in how we view and approach interventions to these two types of violence. Reflecting on this convergence, we have come together as authors to consider how influential and damaging these stereotypes can be to victims of both partner violence and sexual violence. Our paper considers the nature of these stereotypes, who is harmed by them considering both gender and sexuality, and also the impact they have in societal and service responses to violence, as well as policy and practice development
Revealing the structure of the outer disks of Be stars
Context. The structure of the inner parts of Be star disks (20 stellar radii)
is well explained by the viscous decretion disk (VDD) model, which is able to
reproduce the observable properties of most of the objects studied so far. The
outer parts, on the ther hand, are not observationally well-explored, as they
are observable only at radio wavelengths. A steepening of the spectral slope
somewhere between infrared and radio wavelengths was reported for several Be
stars that were previously detected in the radio, but a convincing physical
explanation for this trend has not yet been provided. Aims. We test the VDD
model predictions for the extended parts of a sample of six Be disks that have
been observed in the radio to address the question of whether the observed
turndown in the spectral energy distribution (SED) can be explained in the
framework of the VDD model, including recent theoretical development for
truncated Be disks in binary systems. Methods. We combine new multi-wavelength
radio observations from the Karl. G. Jansky Very Large Array (JVLA) and Atacama
Pathfinder Experiment (APEX) with previously published radio data and archival
SED measurements at ultraviolet, visual, and infrared wavelengths. The density
structure of the disks, including their outer parts, is constrained by
radiative transfer modeling of the observed spectrum using VDD model
predictions. In the VDD model we include the presumed effects of possible tidal
influence from faint binary companions. Results. For 5 out of 6 studied stars,
the observed SED shows strong signs of SED turndown between far-IR and radio
wavelengths. A VDD model that extends to large distances closely reproduces the
observed SEDs up to far IR wavelengths, but fails to reproduce the radio SED.
... (abstract continues but did not fit here)Comment: 20 pages, 8 figure
Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star CMi
The viscous decretion disk (VDD) model is able to explain most of the
currently observable properties of the circumstellar disks of Be stars.
However, more stringent tests, focusing on reproducing multitechnique
observations of individual targets via physical modeling, are needed to study
the predictions of the VDD model under specific circumstances. In the case of
nearby, bright Be star CMi, these circumstances are a very stable
low-density disk and a late-type (B8Ve) central star. The aim is to test the
VDD model thoroughly, exploiting the full diagnostic potential of individual
types of observations, in particular, to constrain the poorly known structure
of the outer disk if possible, and to test truncation effects caused by a
possible binary companion using radio observations. We use the Monte Carlo
radiative transfer code HDUST to produce model observables, which we compare
with a very large set of multitechnique and multiwavelength observations that
include ultraviolet and optical spectra, photometry covering the interval
between optical and radio wavelengths, optical polarimetry, and optical and
near-IR (spectro)interferometry. Due to the absence of large scale variability,
data from different epochs can be combined into a single dataset. A parametric
VDD model with radial density exponent of = 3.5, which is the canonical
value for isothermal flaring disks, is found to explain observables typically
formed in the inner disk, while observables originating in the more extended
parts favor a shallower, = 3.0, density falloff. Modeling of radio
observations allowed for the first determination of the physical extent of a Be
disk (35 stellar radii), which might be caused by a binary
companion. Finally, polarization data allowed for an indirect measurement of
the rotation rate of the star, which was found to be , i.e.,
very close to critical.Comment: 19 pages (35 including online material), 17 figures, 2 online
figures, 2 online tables with dat
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