880 research outputs found
The development of accounts for private households to c.1500 A.D.
SIGLEAvailable from British Library Document Supply Centre- DSC:D95504 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Mental health and behavioural difficulties in adopted children: A systematic review of post-adoption risk and protective factors
Previous research suggests that adopted children are at a greater risk of experiencing psychological and behavioural difficulties or accessing mental health services than non-adopted peers and that post-adoption variables are significant risk and protective factors producing this situation. This review seeks to summarise the post-adoption variables associated with adopted childrenâs mental health or behavioural difficulties to inform future research and shape interventions. A search for publications that assess associated risk and protective factors using Web of Science, Psychinfo, Medline and Sociological Abstracts identified 52 studies that met rigorous methodological criteria. Childrenâs and adolescentsâ mental health and behavioural outcomes were associated with parent, parentâchild and wider family factors and by contextual variables. The findings highlight the importance of focusing on the multitude of systemic factors surrounding a child following adoption. Clinical implications and direction for future research are discussed
A simple proof of the recent generalisations of Hawking's black hole topology theorem
A key result in four dimensional black hole physics, since the early 1970s,
is Hawking's topology theorem asserting that the cross-sections of an "apparent
horizon", separating the black hole region from the rest of the spacetime, are
topologically two-spheres. Later, during the 1990s, by applying a variant of
Hawking's argument, Gibbons and Woolgar could also show the existence of a
genus dependent lower bound for the entropy of topological black holes with
negative cosmological constant. Recently Hawking's black hole topology theorem,
along with the results of Gibbons and Woolgar, has been generalised to the case
of black holes in higher dimensions. Our aim here is to give a simple
self-contained proof of these generalisations which also makes their range of
applicability transparent.Comment: 12 pages, 1 figur
The Positivity of Energy for Asymptotically Anti-de Sitter Spacetimes
We use the formulation of asymptotically anti-de Sitter boundary conditions
given by Ashtekar and Magnon to obtain a coordinate expression for the general
asymptotically AdeS metric in a neighbourhood of infinity. From this, we are
able to compute the time delay of null curves propagating near infinity. If the
gravitational mass is negative, so will be the time delay (relative to null
geodesics at infinity) for certain null geodesics in the spacetime. Following
closely an argument given by Penrose, Sorkin, and Woolgar, who treated the
asymptotically flat case, we are then able to argue that a negative time delay
is inconsistent with non-negative matter-energies in spacetimes having good
causal properties. We thereby obtain a new positive mass theorem for these
spacetimes. The theorem may be applied even when the matter flux near the
boundary-at-infinity falls off so slowly that the mass changes, provided the
theorem is applied in a time-averaged sense. The theorem also applies in
certain spacetimes having local matter-energy that is sometimes negative, as
can be the case in semi-classical gravity.Comment: (Plain TeX - figures not included
Now you see it, now you donât:Optimal parameters for interslice stimulation in concurrent TMS-fMRI
The limit space of a Cauchy sequence of globally hyperbolic spacetimes
In this second paper, I construct a limit space of a Cauchy sequence of
globally hyperbolic spacetimes. In the second section, I work gradually towards
a construction of the limit space. I prove the limit space is unique up to
isometry. I als show that, in general, the limit space has quite complicated
causal behaviour. This work prepares the final paper in which I shall study in
more detail properties of the limit space and the moduli space of (compact)
globally hyperbolic spacetimes (cobordisms). As a fait divers, I give in this
paper a suitable definition of dimension of a Lorentz space in agreement with
the one given by Gromov in the Riemannian case.Comment: 31 pages, 5 figures, submitted to Classical and Quantum gravity,
seriously improved presentatio
Theorems on gravitational time delay and related issues
Two theorems related to gravitational time delay are proven. Both theorems
apply to spacetimes satisfying the null energy condition and the null generic
condition. The first theorem states that if the spacetime is null geodesically
complete, then given any compact set , there exists another compact set
such that for any , if there exists a ``fastest null
geodesic'', , between and , then cannot enter . As
an application of this theorem, we show that if, in addition, the spacetime is
globally hyperbolic with a compact Cauchy surface, then any observer at
sufficiently late times cannot have a particle horizon. The second theorem
states that if a timelike conformal boundary can be attached to the spacetime
such that the spacetime with boundary satisfies strong causality as well as a
compactness condition, then any ``fastest null geodesic'' connecting two points
on the boundary must lie entirely within the boundary. It follows from this
theorem that generic perturbations of anti-de Sitter spacetime always produce a
time delay relative to anti-de Sitter spacetime itself.Comment: 15 pages, 1 figure. Example of gauge perturbation changed/corrected.
Two footnotes added and one footnote remove
The effect of non-communicative eye movements on joint attention.
Eye movements provide important signals for joint attention. However, those eye movements that indicate bids for joint attention often occur among non-communicative eye movements. This study investigated the influence of these non-communicative eye movements on subsequent joint attention responsivity. Participants played an interactive game with an avatar which required both players to search for a visual target on a screen. The player who discovered the target used their eyes to initiate joint attention. We compared participantsâ saccadic reaction times (SRTs) to the avatarâs joint attention bids when they were preceded by non-communicative eye movements that predicted the location of the target (Predictive Search), did not predict the location of the target (Random Search), and when there were no non-communicative eye gaze movements prior to joint attention (No Search). We also included a control condition in which participants completed the same task, but responded to a dynamic arrow stimulus instead of the avatarâs eye movements. For both eye and arrow conditions, participants had slower SRTs in Random Search trials than No Search and Predictive Search trials. However, these effects were smaller for eyes than for arrows. These data suggest that joint attention responsivity for eyes is relatively stable to the presence and predictability of spatial information conveyed by non-communicative gaze. Contrastingly, random sequences of dynamic arrows had a much more disruptive impact on subsequent responsivity compared with predictive arrow sequences. This may reflect specialised social mechanisms and expertise for selectively responding to communicative eye gaze cues during dynamic interactions, which is likely facilitated by the integration of ostensive eye contact cue
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