715 research outputs found
Relationship between Maternal/Family Functioning and Social Functioning in Youth with ADHD
Affecting roughly 5% of the population, Attention-Deficit/Hyperactivity Disorder (ADHD) is a common mental health disorder characterized by deficits in attention, activity level, and/or impulse control causing impairments across multiple domains of functioning (APA, 2013). Although ADHD is most commonly associated with impairment in academic and behavioral functioning, there also exists a strong connection between the disorder and significant social impairment. Indeed, youth with ADHD typically have fewer friends and experience significantly higher levels of peer rejection than do typically developing youth (Bagwell, Molina, Pelham, & Hoza, 2001). In addition to social problems, ADHD is often associated with problems in the home, such as poor parental and family functioning (Theule, Weiner, Tannock, & Jenkins, 2013). Research also indicates that parental distress is both directly and indirectly related to child behavioral and social problems (Sanner & Neece, 2018; Fenesey, Teh, & Lee, 2019). Therefore, it is possible that the relationship between social impairment in youth with ADHD and poor parental/family functioning is bidirectional. The proposed study aimed to examine the relationship between maternal/family functioning and social functioning in young adolescents with ADHD and to examine if maternal/family functioning predicts social functioning outcomes following a 14-week friendship building intervention
Remote Sensing of the Ecosystem Impact of Invasive Alien Plant Species
Invasive Pflanzenarten können Ökosysteme durch Beeinflussung von einheimischen Pflanzengesellschaften und Ökosystemprozessen verändern. Solche Ökosystemauswirkungen wurden mit Hilfe von Experimenten oder Feldaufnahmen umfassend untersucht. Großflächige Auswirkungen, zum Beispiel auf Habitat- oder Landschaftsebene wurden bisher jedoch kaum untersucht. Mit Hilfe von Fernerkundung können räumlich explizite Informationen über die Verteilung von Arten und Ökosystemeigenschaften erfasst werden und somit die Lücke in der Erforschung der großflächigen Auswirkungen invasiver Arten geschlossen werden. Bisher wurde Fernerkundung vor allem zur Kartierung von Vorkommen invasiver Pflanzenarten eingesetzt, jedoch nur selten zur Abschätzung ihrer Auswirkungen. Diese Arbeit zielt darauf ab, das Potential der Fernerkundung für die Bewertung von Ökosystemauswirkungen invasiver Pflanzenarten zu analysieren. Zu diesem Zweck wurden drei Forschungsarbeiten angefertigt, die verschiedene Aspekte dieses Potenzials beleuchten: (1) Die Ermittlung von Vegetationseigenschaften in von Invasionen betroffenen Ökosystemen, (2) die Analyse von Auswirkungen invasiver Arten auf unterschiedlichen räumlichen Skalen und (3) eine räumlich explizite Darstellung von Ökosystemauswirkungen invasiver Pflanzenarten.
Die erste Studie beschäftigt sich mit der Kartierung von Blattstickstoff (N) und -phosphorgehalten (P) in einem Laubmischwald mit Vorkommen der frühblühenden Traubenkirsche (Prunus serotina Ehrh.). Für die Kartierung wurden hyperspektrale und Laserscanning (LiDAR) Daten kombiniert. Die Studie ergab, dass die Bestimmung von N und P aus hyperspektalen Fernerkundungdaten in Baumkronen mit hoher struktureller Heterogenität erschwert wird. Allerdings konnte auch ein Zusammenhang zwischen chemischer Zusammensetzung und der Struktur des Kronendaches festgestellt werden. So konnten die von LiDAR-Daten abgeleiteten Strukturinformationen genutzt werden, um die Vorhersagen von N und P zu verbessern. In der zweiten Studie wurden aus Fernerkundungsdaten erstellte Karten von Ökosystemeigenschaften genutzt, um Gebiete mit und ohne P. serotina zu vergleichen. Die Karten umfassten N und P, sowie das N:P-Verhältnis von Blättern, das Holzvolumen und den Blattflächenindex (LAI). Es wurden sowohl Unterschiede in den Werten von Blattinhaltsstoffen als auch in der Waldstruktur für Standorte mit und ohne P. serotina festgestellt. Diese Unterschiede waren auch auf Bestandsebene erkennbar, wenn auch in geringem Maße. In der dritten Studie wurden hyperspektrale Luftbilder verwendet um die prozentuale Deckung des Kaktusmooses (Campylopus introflexus (Hedw.) Brid.) in einem Dünenökosystem großflächig zu kartieren. Darüber hinaus wurde der Zusammenhang zwischen dem Deckungsgrad von C. introflexus und der Artenvielfalt von Pflanzen untersucht. In Kombination wurden diese Ergebnisse verwendet, um potenzielle Bereiche mit hohen Auswirkungen zu kennzeichnen.
Basierend auf diesen drei Studien wurden in dieser Arbeit zwei grundlegende methodische Ansätze zur Analyse von Ökosystemauswirkungen invasiver Pflanzenarten per Fernerkundung identifiziert und angewandt. Der erste Ansatz besteht darin, mit Hilfe von Fernerkundung erstellte Karten von Ökosystemeigenschaften zu verwenden, um diese Eigenschaften in Abhängigkeit des Vorkommens invasiver Arten auszuwerten. Wie gezeigt werden konnte, ist dies auch für große Flächen, beispielsweise auf der Habitat- oder Landschaftsebene, möglich. Somit kann Fernerkundung zu einem besseren Verständnis der Auswirkungen von invasiven Arten beitragen. Der zweite Ansatz basiert auf der Kartierung von Abundanzen invasiver Pflanzenarten. Diese können als Indikator für die Stärke der Auswirkungen genutzt werden. Die resultierenden Karten können verwendet werden, um Bereiche mit hohen Auswirkungen zu identifizieren. Darüber hinaus ermöglicht dieser zweite Ansatz den Vergleich der Auswirkungen zwischen verschiedenen Arten oder Lebensraumtypen und kann somit wertvolle Informationen für Managemententscheidungen liefern.
Da die Ableitung vieler Ökosystemeigenschaften aus Fernerkundungsdaten nach wie vor eine Herausforderung darstellt, sollte die zukünftige Forschung darauf abzielen, die Zusammenhänge zwischen den Eigenschaften und der Reflektanz der Vegetation besser zu verstehen. Dies ist eine wesentliche Voraussetzung für eine zuverlässige Vorhersage über verschiedene Lebensräume hinweg. Zukünftige Fernerkundungsstudien, mit dem Ziel invasive Arten zu kartieren, sollten sich auf die Vorhersage von Deckungsgraden konzentrieren. Darüber hinaus sind generalisierte Verfahren wünschenswert, die eine erfolgreiche Identifizierung von Arten unter verschiedenen ökologischen Gegebenheiten gewährleisten. Nicht zuletzt sollte diese Arbeit Invasionsökologen ermutigen, existierende Fernerkundungsprodukte häufiger zu verwenden, um großflächige Auswirkungen von invasiven Pflanzenarten auf Ökosysteme zu analysieren
Predicting the Deforestation–Trend Under Different Carbon–Prices
Background: Global carbon stocks in forest biomass are decreasing by 1.1 Gt of carbon annually, owing to continued deforestation and forest degradation. Deforestation emissions are partly offset by forest expansion and increases in growing stock primarily in the extra-tropical north. Innovative financial mechanisms would be required to help reducing deforestation. Using a spatially explicit integrated biophysical and socio-economic land use model we estimated the impact of carbon price incentive schemes and payment modalities on deforestation. One payment modality is adding costs for carbon emission, the other is to pay incentives for keeping the forest carbon stock intact. Results, Baseline scenario calculations show that close to 200mil ha or around 5% of today’s forest area will be lost between 2006 and 2025, resulting in a release of additional 17.5 GtC. Today’s forest cover will shrink by around 500 million hectares, which is 1/8 of the current forest cover, within the next 100 years. The accumulated carbon release during the next 100 years amounts to 45 GtC, which is 15% of the total carbon stored in forests today. Incentives of 6 US/year. On the other hand a carbon tax of 12 in 2005 to 4.3 billion US in 2100 due to decreasing deforestation speed. Conclusions, Avoiding deforestation requires financial mechanisms that make retention of forests economically competitive with the currently often preferred option to seek profits from other land uses. Incentive payments need to be at a very high level to be effective against deforestation. Taxes on the other hand will generate budgetary revenues by the regions which are already poor. A combination of incentives and taxes could turn out to be a viable solution for this dilemma. Increasing the value of forest land and thereby make it less easily prone to deforestation would act as a strong incentive to increase productivity of agricultural and fuelwood production, which could be supported by revenues generated by the deforestation tax.Deforestation, Carbon Prices
Classifying surface fuel types based on forest stand photographs and satellite time series using deep learning
Magneto-elastic oscillations of neutron stars with dipolar magnetic fields
By means of two dimensional, general-relativistic, magneto-hydrodynamical
simulations we investigate the oscillations of magnetized neutron star models
(magnetars) including the description of an extended solid crust. The aim of
this study is to understand the origin of the QPOs observed in the giant flares
of SGRs. We confirm the existence of three different regimes: (a) a weak
magnetic field regime B<5 x 10^13 G, where crustal shear modes dominate the
evolution; (b) a regime of intermediate magnetic fields 5 x 10^13 G<B< 10^15 G,
where Alfv\'en QPOs are mainly confined to the core of the neutron star and the
crustal shear modes are damped very efficiently; and (c) a strong field regime
B>10^15 G, where magneto-elastic oscillations reach the surface and approach
the behavior of purely Alfv\'en QPOs. When the Alfv\'en QPOs are confined to
the core of the neutron star, we find qualitatively similar QPOs as in the
absence of a crust. The lower QPOs associated with the closed field lines of
the dipolar magnetic field configuration are reproduced as in our previous
simulations without crust, while the upper QPOs connected to the open field
lines are displaced from the polar axis. Additionally, we observe a family of
edge QPOs. Our results do not leave much room for a crustal-mode interpretation
of observed QPOs in SGR giant flares, but can accommodate an interpretation of
these observations as originating from Alfv\'en-like, global, turning-point
QPOs in models with dipolar magnetic field strengths in the narrow range of 5 x
10^15 G < B < 1.4 x 10^16 G. This range is somewhat larger than estimates for
magnetic field strengths in known magnetars. The discrepancy may be resolved in
models including a more complicated magnetic field structure or with models
taking superfluidity of the neutrons and superconductivity of the protons in
the core into account.Comment: 25 pages, 17 figures, 7 tables, minor corrections to match published
version in MNRA
Constraining properties of high-density matter in neutron stars with magneto-elastic oscillations
We discuss torsional oscillations of highly magnetised neutron stars
(magnetars) using two-dimensional, magneto-elastic-hydrodynamical simulations.
Our model is able to explain both the low- and high-frequency quasi-periodic
oscillations (QPOs) observed in magnetars. The analysis of these oscillations
provides constraints on the breakout magnetic-field strength, on the
fundamental QPO frequency, and on the frequency of a particularly excited
overtone. More importantly, we show how to use this information to generically
constraint properties of high-density matter in neutron stars, employing
Bayesian analysis. In spite of current uncertainties and computational
approximations, our model-dependent Bayesian posterior estimates for SGR
1806-20 yield a magnetic-field strength G and a crust thickness of km, which are both in remarkable agreement with
observational and theoretical expectations, respectively (1- error bars
are indicated). Our posteriors also favour the presence of a superfluid phase
in the core, a relatively low stellar compactness, , indicating a
relatively stiff equation of state and/or low mass neutron star, and high shear
speeds at the base of the crust, cm/s. Although the
procedure laid out here still has large uncertainties, these constraints could
become tighter when additional observations become available.Comment: 14 pages, 8 figures, 6 tables, submitted to MNRA
Coherent magneto-elastic oscillations in superfluid magnetars
We study the effect of superfluidity on torsional oscillations of highly
magnetised neutron stars (magnetars) with a microphysical equation of state by
means of two-dimensional, magnetohydrodynamical- elastic simulations. The
superfluid properties of the neutrons in the neutron star core are treated in a
parametric way in which we effectively decouple part of the core matter from
the oscillations. Our simulations confirm the existence of two groups of
oscillations, namely continuum oscillations that are confined to the neutron
star core and are of Alfv\'enic character, and global oscillations with
constant phase and that are of mixed magneto-elastic type. The latter might
explain the quasi-periodic oscillations observed in magnetar giant flares,
since they do not suffer from the additional damping mechanism due to phase
mixing, contrary to what happens for continuum oscillations. However, we cannot
prove rigorously that the coherent oscillations with constant phase are normal
modes. Moreover, we find no crustal shear modes for the magnetic field
strengths typical for magnetars.We provide fits to our numerical simulations
that give the oscillation frequencies as functions of magnetic field strength
and proton fraction in the core.Comment: 16 pages, 12 figures, accepted by MNRA
Modulating the magnetosphere of magnetars by internal magneto-elastic oscillations
We couple internal torsional, magneto-elastic oscillations of highly
magnetized neutron stars (magnetars) to their magnetospheres. The corresponding
axisymmetric perturbations of the external magnetic field configuration evolve
as a sequence of linear, force-free equilibria that are completely determined
by the background magnetic field configuration and by the perturbations of the
magnetic field at the surface. The perturbations are obtained from simulations
of magneto-elastic oscillations in the interior of the magnetar. While such
oscillations can excite travelling Alfv\'en waves in the exterior of the star
only in a very limited region close to the poles, they still modulate the near
magnetosphere by inducing a time-dependent twist between the foot-points of
closed magnetic field lines that exit the star at a polar angle rad. Moreover, we find that for a dipole-like background magnetic field
configuration the magnetic field modulations in the magnetosphere, driven by
internal oscillations, can only be symmetric with respect to the equator. This
is in agreement with our previous findings, where we interpreted the observed
quasi-periodic oscillations in the X-ray tail of magnetar bursts as driven by
the family of internal magneto-elastic oscillations with symmetric magnetic
field perturbations.Comment: 9 pages, 5 figures, 2 tables, Accepted by MNRA
Imprints of superfluidity on magneto-elastic QPOs of SGRs
Our numerical simulations show that axisymmetric, torsional, magneto-elastic
oscillations of magnetars with a superfluid core can explain the whole range of
observed quasi-periodic oscillations (QPOs) in the giant flares of soft
gamma-ray repeaters. There exist constant phase, magneto-elastic QPOs at both
low (f500 Hz), in full agreement with
observations. The range of magnetic field strengths required to match the
observed QPO frequencies agrees with that from spin-down estimates. These
results strongly suggest that neutrons in magnetar cores are superfluid.Comment: 5 pages, 4 figure
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