1,726 research outputs found
Constraining the formation history of the TOI-1338/BEBOP-1 circumbinary planetary system
The recent discovery of multiple planets in the circumbinary system
TOI-1338/BEBOP-1 raises questions about how such a system formed. The formation
of the system was briefly explored in the discovery paper, but only to answer
the question do current pebble accretion models have the potential to explain
the origin of the system? We use a global model of circumbinary planet
formation that utilises N-body simulations, including prescriptions for planet
migration, gas and pebble accretion, and interactions with a circumbinary disc,
to explore the disc parameters that could have led to the formation of the
TOI-1338/BEBOP-1 system. With the disc lifetime being the main factor in
determining how planets form, we limit our parameter space to those that
determine the disc lifetime. These are: the strength of turbulence in the disc,
the initial disc mass, and the strength of the external radiation field that
launches photoevaporative winds. When comparing the simulated systems to
TOI-1338/BEBOP-1, we find that only discs with low levels of turbulence are
able to produce similar systems. The radiation environment has a large effect
on the types of planetary systems that form, whilst the initial disc mass only
has limited impact since the majority of planetary growth occurs early in the
disc lifetime. With the most TOI-1338/BEBOP-1 like systems all occupying
similar regions of parameter space, our study shows that observed circumbinary
planetary systems can potentially constrain the properties of planet forming
discs.Comment: Accepted for publication in MNRAS, 15 pages, 10 figure
Improving circumbinary planet detections by fitting their binary's apsidal precession
Apsidal precession in stellar binaries is the main non-Keplerian dynamical
effect impacting the radial-velocities of a binary star system. Its presence
can notably hide the presence of orbiting circumbinary planets because many
fitting algorithms assume perfectly Keplerian motion. To first order, apsidal
precession () can be accounted for by adding a linear term to the
usual Keplerian model. We include apsidal precession in the kima package, an
orbital fitter designed to detect and characterise planets from radial velocity
data. In this paper, we detail this and other additions to kima that improve
fitting for stellar binaries and circumbinary planets including corrections
from general relativity. We then demonstrate that fitting for
can improve the detection sensitivity to circumbinary exoplanets by up to an
order of magnitude in some circumstances, particularly in the case of
multi-planetary systems. In addition, we apply the algorithm to several real
systems, producing a new measurement of aspidal precession in KOI-126 (a tight
triple system), and a detection of in the Kepler-16 circumbinary
system. Although apsidal precession is detected for Kepler-16, it does not have
a large effect on the detection limit or the planetary parameters. We also
derive an expression for the precession an outer planet would induce on the
inner binary and compare the value this predicts with the one we detect.Comment: 10 pages, 5 figures Re-submitted to MNRAS after reviewer comment
The narratives of Hardship: : The new and the old poor in the aftermath of the 2008 crisis in Europe
This document is the Accepted Manuscript version of the following article: Hulya Dagdeviren, Matthew Donoghue, and Lars Meier, âThe narratives of hardship: the new and the old poor in the aftermath of the 2008 crisis in Europeâ, The Sociological Review, vol. 65 (2): 369-385, May 2017. The final, definitive version of record is available online at doi: https://doi.org/10.1111/1467-954X.12403. Published by SAGE.This paper examines poverty and hardship in Europe after the 2008 crisis, using household interviews in nine European countries. A number of findings deserve highlighting. First, making a distinction between âthe old poorâ (those who lived in poverty before as well as after the crisis) and âthe new poorâ (thosewho fell into hardship after the crisis), we show that hardship is experienced quite differently by these groups. Second, the household narratives showed that while material deprivations constitute an important aspect of hardship, the themes of insecurity and dependency also emerged as fundamental dimensions. In contrast to popular political discourse in countries such as the UK, dependency on welfare or family was experienced as a source of distress and manifested as a form of hardship by participants in all countries covered in this study.Peer reviewedFinal Accepted Versio
Copyright and cultural work: an exploration
This article first discusses the contemporary debate on cultural âcreativityâ and the economy. Second, it considers the current state of UK copyright law and how it relates to cultural work. Third, based on empirical research on British dancers and musicians, an analysis of precarious cultural work is presented. A major focus is how those who follow their art by way of âportfolioâ work handle their rights in ways that diverge significantly from the current simplistic assumptions of law and cultural policy. Our conclusions underline the distance between present top-down conceptions of what drives production in the cultural field and the actual practice of dancers and musicians
Gender violence in schools: taking the âgirls-as-victimsâ discourse forward
This paper draws attention to the gendered nature of violence in schools. Recent recognition that schools can be violent places has tended to ignore the fact that many such acts originate in unequal and antagonistic gender relations, which are tolerated and ânormalisedâ by everyday school structures and processes. After examining some key concepts and definitions, we provide a brief overview of the scope and various manifestations of gender violence in schools, noting that most research to date has focused on girls as victims of gender violence within a heterosexual context and ignores other forms such as homophobic and girl violence. We then move on to look at a few interventions designed to address gender violence in schools in the developing world and end by highlighting the need for more research and improved understanding of the problem and how it can be addressed
The EBLM project -- XIII. The absolute dynamical masses of the circumbinary planet host TOI-1338/BEBOP-1
High-contrast eclipsing binaries with low mass M-dwarf secondaries are
precise benchmark stars to build empirical mass-radius relationships for fully
convective low-mass () dwarf stars. The
contributed light of the M-dwarf in such binaries is usually much less than
one~per~cent at optical wavelengths. This enables the detection of circumbinary
planets from precise radial velocity measurements. High-resolution
cross-correlation techniques are typically used to detect exoplanet
atmospheres. One key aspect of these techniques is the post-processing, which
includes the removal of telluric and spectral lines of the host star. We
introduce the application of such techniques to optical high-resolution spectra
of the circumbinary planet-host TOI-1338/BEBOP-1, turning it effectively into a
double-lined eclipsing binary. By using simulations, we further explore the
impact of post-processing techniques for high-contrast systems. We detect the
M-dwarf secondary with a significance of 11- and measure absolute
dynamical masses for both components. Compared to previous model-dependent mass
measurements, we obtain a four times better precision. We further find that the
post-processing results in negligible systematic impact on the radial velocity
precision for TOI-1338/BEBOP-1 with more than per~cent (1-) of
the M-dwarf's signal being conserved. We show that these methods can be used to
robustly measure dynamical masses of high-contrast single-lined binaries
providing important benchmark stars for stellar evolution particularly near the
bottom of the main sequence. We also demonstrate how to retrieve the phase
curve of an exoplanet with high-resolution spectroscopy using our data.Comment: Accepted for publication in MNRAS, 17 pages, 13 image
Identity and belonging in social learning groups : the importance of distinguishing social, operational and knowledge-related identity congruence
Collaborative learning has much to offer but not all learners participate fully and peer groups can be exclusive. The paper examines how belonging or 'congruence' in learning groups is related to identities of gender, age, ethnicity and socio-economic status. A study of student experiences of collaborative learning on three different blended learning courses illustrated how learners negotiate identity congruence with peer groups to belong and engage. An analytical framework that distinguishes social, operational and knowledge-related identity congruence has emerged. Contrary to received wisdom, the social aspect appears least important for learner engagement while knowledge-related identity congruence is fundamental. Some of the consequences of identity incongruence, particularly concerning gender and maturity, are discussed and the paper points towards the pedagogies which might enable identities of group members to shift so that collaborative learning can flourish
Population Pharmacokinetics and Pharmacodynamics of Dobutamine in Neonates on the First Days of Life
Aims:
To describe the pharmacokinetics (PK) and concentrationârelated effects of dobutamine in critically ill neonates in the first days of life, using nonlinear mixed effects modelling.
Methods:
Dosing, plasma concentration and haemodynamic monitoring data from a doseâescalation study were analysed with a simultaneous population PK and pharmacodynamic model. Neonates receiving continuous infusion of dobutamine 5â20 ÎŒg kgâ1 minâ1 were included. Left ventricular ejection fraction (LVEF) and cardiac output of right and left ventricle (RVO, LVO) were measured on echocardiography; heart rate (HR), mean arterial pressure (MAP), peripheral arterial oxygen saturation and cerebral regional oxygen saturation were recorded from patient monitors.
Results:
Twentyâeight neonates with median (range) gestational age of 30.4 (22.7â41.0) weeks and birth weight (BW) of 1618 (465â4380) g were included. PK data were adequately described by 1âcompartmental linear structural model. Dobutamine clearance (CL) was described by allometric scaling on BW with sigmoidal maturation function of postmenstrual age (PMA). The final population PK model parameter mean typical value (standard error) estimates, standardised to median BW of 1618 g, were 41.2 (44.5) L hâ1 for CL and 5.29 (0.821) L for volume of distribution, which shared a common between subject variability of 29% (17.2%). The relationship between dobutamine concentration and RVO/LVEF was described by linear model, between concentration and LVO/HR/MAP/cerebral fractional tissue oxygen extraction by sigmoidal Emax model.
Conclusion:
In the postnatal transitional period, PK of dobutamine was described by a 1âcompartmental linear model, CL related to BW and PMA. A concentrationâresponse relationship with haemodynamic variables has been established
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