1,923 research outputs found
Peer Rejection and Friendships in Children with Attention-Deficit/Hyperactivity Disorder: Contributions to Long-Term Outcomes
Even after evidence-based treatment, Attention- Deficit/Hyperactivity Disorder (ADHD) is associated with poor long-term outcomes. These outcomes may be partly explained by difficulties in peer functioning, which are common among children with ADHD and which do not respond optimally to standard ADHD treatments. We examined whether peer rejection and lack of dyadic friendships experienced by children with ADHD after treatment contribute to long-term emotional and behavioral problems and global impairment, and whether having a reciprocal friend buffers the negative effects of peer rejection. Children with Combined type ADHD (N0300) enrolled in the Multimodal Treatment Study of Children with ADHD (MTA) were followed for 8 years. Peer rejection and dyadic friendships were measured with sociometric assessments after the active treatment period (14 or 24 months after baseline; M ages 9.7 and 10.5 years, respectively). Outcomes included delinquency, depression, anxiety, substance use, and general impairment at 6 and 8 years after baseline (Mean ages 14.9 and 16.8 years, respectively). With inclusion of key covariates, including demographics, symptoms ofADHD, ODD, and CD, and level of the outcome variable at 24 months, peer rejection predicted cigarette smoking, delinquency, anxiety, and global impairment at 6 years and global impairment at 8 years after baseline. Having a reciprocal friend was not, however, uniquely predictive of any outcomes and did not reduce the negative effects of peer rejection. Evaluating and addressing peer rejection in treatment planning may be necessary to improve long-term outcomes in children with ADHD
Hot pixel contamination in the CMB correlation function?
Recently, it was suggested that the map-making procedure, which is applied to
the time-ordered CMB data by the WMAP team, might be flawed by hot pixels. This
could lead to a bias in the pixels having an angular distance of about 141
degrees from hot pixels due to the differential measuring process of the
satellite WMAP. Here, the bias is confirmed, and the temperature two-point
correlation function C(theta) is reevaluated by excluding the affected pixels.
It is shown that the most significant effect occurs in C(theta) at the largest
angles near theta = 180 degrees. Furthermore, the corrected correlation
function C(theta) is applied to the cubic topology of the Universe, and it is
found that such a multi-connected universe matches the temperature correlation
better than the LCDM concordance model, provided the cubic length scale is
close to L=4 measured in units of the Hubble length
Sky maps without anisotropies in the cosmic microwave background are a better fit to WMAP's uncalibrated time ordered data than the official sky maps
The purpose of this reanalysis of the WMAP uncalibrated time ordered data
(TOD) was two fold. The first was to reassess the reliability of the detection
of the anisotropies in the official WMAP sky maps of the cosmic microwave
background (CMB). The second was to assess the performance of a proposed
criterion in avoiding systematic error in detecting a signal of interest. The
criterion was implemented by testing the null hypothesis that the uncalibrated
TOD was consistent with no anisotropies when WMAP's hourly calibration
parameters were allowed to vary. It was shown independently for all 20 WMAP
channels that sky maps with no anisotropies were a better fit to the TOD than
those from the official analysis. The recently launched Planck satellite should
help sort out this perplexing result.Comment: 11 pages with 1 figure and 2 tables. Extensively rewritten to explain
the research bette
Rigid Chiral Membranes
Statistical ensembles of flexible two-dimensional fluid membranes arise
naturally in the description of many physical systems. Typically one encounters
such systems in a regime of low tension but high stiffness against bending,
which is just the opposite of the regime described by the Polyakov string. We
study a class of couplings between membrane shape and in-plane order which
break 3-space parity invariance. Remarkably there is only {\it one} such
allowed coupling (up to boundary terms); this term will be present for any
lipid bilayer composed of tilted chiral molecules. We calculate the
renormalization-group behavior of this relevant coupling in a simplified model
and show how thermal fluctuations effectively reduce it in the infrared.Comment: 11 pages, UPR-518T (This replaced version has fonts not used
removed.
Theory of Cylindrical Tubules and Helical Ribbons of Chiral Lipid Membranes
We present a general theory for the equilibrium structure of cylindrical
tubules and helical ribbons of chiral lipid membranes. This theory is based on
a continuum elastic free energy that permits variations in the direction of
molecular tilt and in the curvature of the membrane. The theory shows that the
formation of tubules and helical ribbons is driven by the chirality of the
membrane. Tubules have a first-order transition from a uniform state to a
helically modulated state, with periodic stripes in the tilt direction and
ripples in the curvature. Helical ribbons can be stable structures, or they can
be unstable intermediate states in the formation of tubules.Comment: 43 pages, including 12 postscript figures, uses REVTeX 3.0 and
epsf.st
How well-proportioned are lens and prism spaces?
The CMB anisotropies in spherical 3-spaces with a non-trivial topology are
analysed with a focus on lens and prism shaped fundamental cells. The
conjecture is tested that well proportioned spaces lead to a suppression of
large-scale anisotropies according to the observed cosmic microwave background
(CMB). The focus is put on lens spaces L(p,q) which are supposed to be oddly
proportioned. However, there are inhomogeneous lens spaces whose shape of the
Voronoi domain depends on the position of the observer within the manifold.
Such manifolds possess no fixed measure of well-proportioned and allow a
predestined test of the well-proportioned conjecture. Topologies having the
same Voronoi domain are shown to possess distinct CMB statistics which thus
provide a counter-example to the well-proportioned conjecture. The CMB
properties are analysed in terms of cyclic subgroups Z_p, and new point of view
for the superior behaviour of the Poincar\'e dodecahedron is found
The number counts, luminosity functions and evolution of microwave-selected (WMAP) blazars and radio galaxies
(Abridged) We carried out an extensive search to identify the counterparts of
all the sources listed in the WMAP 3-yr catalogue using literature and archival
data. Our work led to the identification of 309 WMAP sources, 98% of which are
blazars, radio quasars or radio galaxies. At present, 15 objects still remain
without identification due to the lack of optical spectroscopic data or a clear
radio counterpart. Our results allow us to define a flux limited sample of 203
high Galactic latitude microwave sources ( Jy, ) which is virtually completely identified (99%). The microwave band
is ideally suited for blazar statistical studies since this is the part of the
em spectrum that is least affected by the superposition of spectral components
of different origin. Using this data-set we derived number counts, luminosity
functions and cosmological evolution of blazars and radio galaxies at microwave
frequencies. Our results are in good agreement with those found at radio
frequencies. The 5 GHz bivariate blazar luminosity functions are similar to
those derived from the DXRBS survey, which shows that this sample is
representative of the blazar population at 41 GHz. Microwave selected broad-
lined quasars are about 6 times more abundant than BL Lacs, a ratio that is
similar to, or larger than, that seen at radio and gamma-ray frequencies, once
spectral selection effects are taken into account. This strongly suggests that
the mechanism responsible for the generation of gamma-rays is, at first order,
the same in all blazar types. Our results confirm the findings of Giommi &
Colafrancesco (2004, 2006) that blazars and radio galaxies are the largest
contaminants of the CMB anisotropy maps. We predict that these sources are also
bright gamma-ray sources, most of which will be detected by AGILE and FERMI.Comment: 18 pages, 11 figures, 3 tables. A&A in pres
Best Unbiased Estimates for the Microwave Background Anisotropies
It is likely that the observed distribution of the microwave background
temperature over the sky is only one realization of the underlying random
process associated with cosmological perturbations of quantum-mechanical
origin. If so, one needs to derive the parameters of the random process, as
accurately as possible, from the data of a single map. These parameters are of
the utmost importance, since our knowledge of them would help us to reconstruct
the dynamical evolution of the very early Universe. It appears that the lack of
ergodicity of a random process on a 2-sphere does not allow us to do this with
arbitrarily high accuracy. We are left with the problem of finding the best
unbiased estimators of the participating parameters. A detailed solution to
this problem is presented in this article. The theoretical error bars for the
best unbiased estimates are derived and discussed.Comment: 26 pages, revtex; minor modifications, 8 new references, to be
published in Phys. Rev.
Astrophysical and Cosmological Tests of Quantum Theory
We discuss several proposals for astrophysical and cosmological tests of
quantum theory. The tests are motivated by deterministic hidden-variables
theories, and in particular by the view that quantum physics is merely an
effective theory of an equilibrium state. The proposed tests involve searching
for nonequilibrium violations of quantum theory in: primordial inflaton
fluctuations imprinted on the cosmic microwave background, relic cosmological
particles, Hawking radiation, photons with entangled partners inside black
holes, neutrino oscillations, and particles from very distant sources.Comment: 25 pages. Amendment to section 7. Contribution to: "The Quantum
Universe", special issue of Journal of Physics A, dedicated to Prof. G.-C.
Ghirardi on the occasion of his seventieth birthda
Cosmic microwave anisotropies in an inhomogeneous compact flat universe
The anisotropies of the cosmic microwave background (CMB) are computed for
the half-turn space E_2 which represents a compact flat model of the Universe,
i.e. one with finite volume. This model is inhomogeneous in the sense that the
statistical properties of the CMB depend on the position of the observer within
the fundamental cell. It is shown that the half-turn space describes the
observed CMB anisotropies on large scales better than the concordance model
with infinite volume. For most observer positions it matches the temperature
correlation function even slightly better than the well studied 3-torus
topology
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