1,519 research outputs found
Practitioner review: pathways to care for ADHD - a systematic review of barriers and facilitators
Background. Attention-Deficit/Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder starting in childhood that may persist into adulthood. It can be managed through carefully monitored medication and nonpharmacological interventions. Access to care for children at risk of ADHD varies both within and between countries. A systematic literature review was conducted to investigate the research evidence related to factors which influence children accessing services for ADHD
Particle number conservation in quantum many-body simulations with matrix product operators
Incorporating conservation laws explicitly into matrix product states (MPS)
has proven to make numerical simulations of quantum many-body systems much less
resources consuming. We will discuss here, to what extent this concept can be
used in simulation where the dynamically evolving entities are matrix product
operators (MPO). Quite counter-intuitively the expectation of gaining in speed
by sacrificing information about all but a single symmetry sector is not in all
cases fulfilled. It turns out that in this case often the entanglement imposed
by the global constraint of fixed particle number is the limiting factor.Comment: minor changes, 18 pages, 5 figure
Phenotypic Differences in White-Tailed Deer Antlerogenic Progenitor Cells and Marrow-Derived Mesenchymal Stromal Cells
Deer antlers are bony appendages that are annually cast and rapidly regrown in a seasonal process coupled to the reproductive cycle. Due to the uniqueness of this process among mammals, we reasoned that a fundamental characterization of antler progenitor cell behavior may provide insights that could lead to improved strategies for promoting bone repair. In this study, we investigated whether white-tailed deer antlerogenic progenitor cells (APC) conform to basic criteria defining mesenchymal stromal cells (MSC). In addition, we tested the effects of the artificial glucocorticoid dexamethasone (DEX) on osteogenic and chondrogenic differentiation as well as the degree of apoptosis during the latter. Comparisons were made to animal-matched marrow-derived MSC. APC and MSC generated similar numbers of colonies. APC cultures expanded less rapidly overall but experienced population recovery at later time points. In contrast to MSC, APC did not display adipogenic in vitro differentiation capacity. Under osteogenic culture conditions, APC and MSC exhibited different patterns of alkaline phosphatase activity over time. DEX increased APC alkaline phosphatase activity only initially but consistently led to decreased activity in MSC. APC and MSC in osteogenic culture underwent different time and DEX-dependent patterns of mineralization, yet APC and MSC achieved similar levels of mineral accrual in an ectopic ossicle model. During chondrogenic differentiation, APC exhibited high levels of apoptosis without a reduction in cell density. DEX decreased proteoglycan production and increased apoptosis in chondrogenic APC cultures but had the opposite effects in MSC. Our results suggest that APC and MSC proliferation and differentiation differ in their dependence on time, factors, and milieu. Antler tip APC may be more lineage-restricted osteo/chondroprogenitors with distinctly different responses to apoptotic and glucocorticoid stimuli.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140228/1/ten.tea.2013.0420.pd
Matrix product decomposition and classical simulation of quantum dynamics in the presence of a symmetry
We propose a refined matrix product state representation for many-body
quantum states that are invariant under SU(2) transformations, and indicate how
to extend the time-evolving block decimation (TEBD) algorithm in order to
simulate time evolution in an SU(2) invariant system. The resulting algorithm
is tested in a critical quantum spin chain and shown to be significantly more
efficient than the standard TEBD.Comment: 5 pages, 4 figure
State-dependent, addressable subwavelength lattices with cold atoms
We discuss how adiabatic potentials can be used to create addressable
lattices on a subwavelength scale, which can be used as a tool for local
operations and readout within a lattice substructure, while taking advantage of
the faster timescales and higher energy and temperature scales determined by
the shorter lattice spacing. For alkaline-earth-like atoms with non-zero
nuclear spin, these potentials can be made state dependent, for which we give
specific examples with Yb atoms. We discuss in detail the limitations
in generating the lattice potentials, in particular non-adiabatic losses, and
show that the loss rates can always be made exponentially small by increasing
the laser power.Comment: replaced with the published version. 23 pages, 11 figure
Diffusion, super-diffusion and coalescence from single step
From the exact single step evolution equation of the two-point correlation
function of a particle distribution subjected to a stochastic displacement
field \bu(\bx), we derive different dynamical regimes when \bu(\bx) is
iterated to build a velocity field. First we show that spatially uncorrelated
fields \bu(\bx) lead to both standard and anomalous diffusion equation. When
the field \bu(\bx) is spatially correlated each particle performs a simple
free Brownian motion, but the trajectories of different particles result to be
mutually correlated. The two-point statistical properties of the field
\bu(\bx) induce two-point spatial correlations in the particle distribution
satisfying a simple but non-trivial diffusion-like equation. These
displacement-displacement correlations lead the system to three possible
regimes: coalescence, simple clustering and a combination of the two. The
existence of these different regimes, in the one-dimensional system, is shown
through computer simulations and a simple theoretical argument.Comment: RevTeX (iopstyle) 19 pages, 5 eps-figure
Cavity Assisted Nondestructive Laser Cooling of Atomic Qubits
We analyze two configurations for laser cooling of neutral atoms whose
internal states store qubits. The atoms are trapped in an optical lattice which
is placed inside a cavity. We show that the coupling of the atoms to the damped
cavity mode can provide a mechanism which leads to cooling of the motion
without destroying the quantum information.Comment: 12 page
Sub-mm free-free emission from the winds of massive stars in the age of ALMA
The thermal radio and sub-mm emission from the winds of massive stars is
investigated and the contribution to the emission due to the stellar wind
acceleration region and clumping of the wind is quantified. Building upon
established theory, a method for calculating the thermal radio and sub-mm
emission using results for a line-driven stellar outflow according to Castor,
Abbott & Klein (1975) is presented. The results show strong variation of the
spectral index for 10 2 GHz < {\nu} < 10 4 GHz. This corresponds both to the
wind acceleration region and clumping of the wind, leading to a strong
dependence on the wind velocity law and clumping parameters. The Atacama Large
Millimeter/sub-mm Array (ALMA) is the first observatory to have both the
spectral window and sensitivity to observe at the high frequencies required to
probe the acceleration regions of massive stars. The deviations in the
predicted flux levels as a result of the inclusion of the wind acceleration
region and clumping are sufficient to be detected by ALMA, through deviations
in the spectral index in different portions of the radio/sub-mm spectra of
massive stars, for a range of reasonable mass-loss rates and distances.
Consequently both mechanisms need to be included to fully understand the
mass-loss rates of massive stars.Comment: 12 pages, 8 figure
Percolation in invariant Poisson graphs with i.i.d. degrees
Let each point of a homogeneous Poisson process in R^d independently be
equipped with a random number of stubs (half-edges) according to a given
probability distribution mu on the positive integers. We consider
translation-invariant schemes for perfectly matching the stubs to obtain a
simple graph with degree distribution mu. Leaving aside degenerate cases, we
prove that for any mu there exist schemes that give only finite components as
well as schemes that give infinite components. For a particular matching scheme
that is a natural extension of Gale-Shapley stable marriage, we give sufficient
conditions on mu for the absence and presence of infinite components
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