449 research outputs found
Developing the logic framework underpinning a whole-systems approach to childhood overweight and obesity prevention:Amsterdam Healthy Weight Approach
Abstract Background Whole‐systems approaches (WSAs) are well placed to tackle the complex local environmental influences on overweight and obesity, yet there are few examples of WSAs in practice. Amsterdam Healthy Weight Approach (AHWA) is a long‐term, municipality‐led program to improve children's physical activity, diet, and sleep through action in the home, neighborhood, school, and city. Adopting a WSA, local political, physical, social, educational, and healthcare drivers of childhood obesity are viewed as a complex adaptive system. Since 2013, AHWA has reached >15,000 children. During this time, the estimated prevalence of 2–18‐year‐olds with overweight or obesity in Amsterdam has declined from 21% in 2012 to 18.7% in 2017. Declining trends are rarely observed in cities. There is a need to formally articulate AHWA program theory in order to: (i) inform future program evaluation which can interpret this decline within the context of AHWA and (ii) contribute a real‐life example of a WSA to the literature. Methods This study aimed to formally document the program theory of AHWA to permit future evaluation. A logic framework was developed through extensive document review and discussion, during program implementation. Results The working principles of the WSA underpinning AHWA were made explicit in an overarching theory of change, articulated in a logic framework. The framework was operationalized using an illustrative example of sugar intake. Conclusions The logic framework will inform AHWA development, monitoring, and evaluation and responds to a wider need to outline the working principles of WSAs in public health
Local moment formation in zinc doped cuprates
We suggest that when zinc is substituted for copper in the copper oxide
planes of high superconductors, it does not necessarily have a valency
of 2+. Rather, the valency of a zinc impurity should be determined by its
surrounding medium. In order to study this hypothesis, we examine the effect of
static impurities inducing diagonal disorder within a one band Hubbard model
coupled to a localised state. We use this model to discuss the physics of zinc
doping in the cuprates. Specifically, we discuss the formation of local moments
near impurity sites and the modification of the transverse spin susceptibility
in the antiferromagnetic state.Comment: 7 pages RevTex, includes 4 figure
The ENCOMPASS framework:a practical guide for the evaluation of public health programmes in complex adaptive systems
BackgroundSystems thinking embraces the complexity of public health problems, including childhood overweight and obesity. It aids in understanding how factors are interrelated, and it can be targeted to produce favourable changes in a system. There is a growing call for systems approaches in public health research, yet limited practical guidance is available on how to evaluate public health programmes within complex adaptive systems. The aim of this paper is to present an evaluation framework that supports researchers in designing systems evaluations in a comprehensive and practical way.MethodsWe searched the literature for existing public health systems evaluation studies. Key characteristics on how to conduct a systems evaluation were extracted and compared across studies. Next, we overlaid the identified characteristics to the context of the Lifestyle Innovations Based on Youth Knowledge and Experience (LIKE) programme evaluation and analyzed which characteristics were essential to carry out the LIKE evaluation. This resulted in the Evaluation of Programmes in Complex Adaptive Systems (ENCOMPASS) framework.ResultsThe ENCOMPASS framework includes five iterative stages: (1) adopting a system dynamics perspective on the overall evaluation design; (2) defining the system boundaries; (3) understanding the pre-existing system to inform system changes; (4) monitoring dynamic programme output at different system levels; and (5) measuring programme outcome and impact in terms of system changes.ConclusionsThe value of ENCOMPASS lies in the integration of key characteristics from existing systems evaluation studies, as well as in its practical, applied focus. It can be employed in evaluating public health programmes in complex adaptive systems. Furthermore, ENCOMPASS provides guidance for the entire evaluation process, all the way from understanding the system to developing actions to change it and to measuring system changes. By the nature of systems thinking, the ENCOMPASS framework will likely evolve further over time, as the field expands with more completed studies
Ordering of the pyrochlore Ising model with the long-range RKKY interaction
The ordering of the Ising model on a pyrochlore lattice interacting via the
long-range RKKY interaction, which models a metallic pyrochlore magnet such as
Pr_2Ir_2O_7, is studied by Monte Carlo simulations. Depending on the parameter
k_F representing the Fermi wavevector, the model exhibits rich ordering
behaviors
Anisotropic Release of the Residual Zero-point Entropy in the Spin Ice Compound Dy2Ti2O7: Kagome-ice Behavior
We report the specific heat and entropy of single crystals of the spin ice
compound Dy2Ti2O7 at temperatures down to 0.35 K. We apply magnetic fields
along the four characteristic directions: [100], [110], [111] and [112].
Because of Ising anisotropy, we observe anisotropic release of the residual
zero-point entropy, attributable to the difference in frustration
dimensionality. In the high magnetic field along these four directions, the
residual entropy is almost fully released and the activation entropy reaches
Rln2. However, in the intermediate field region, the entropy in fields along
the [111] direction is different from those for the other three field
directions. For the [111] direction the frustration structure changes from that
of three-dimensional(3D) pyrochlore to that of two-dimensional(2D) Kagome-like
lattice with constraint due to the ice rule, leading to different values of
zero-point entropy.Comment: 4 pages, 4 figures, to appear in Phys. Rev.
Low Temperature Specific Heat of DyTiO in the Kagome Ice State
We report the specific heat of single crystals of the spin ice compound
DyTiO at temperatures down to 100 mK in the so-called Kagome ice
state. In our previous paper, we showed the anisotropic release of residual
entropy in different magnetic field directions and reported new residual
entropy associated with spin frustration in the Kagome slab for field in the
[111] direction. In this paper, we confirm the first-order phase transition
line in the field-temperature phase diagram and the presence of a critical
point at (0.98 T, 400 mK), previously reported from the magnetization and
specific-heat data. We newly found another peak in the specific heat at 1.25 T
below 0.3 K. One possible explanation for the state between 1 T and 1.25 T is
the coexistence of states with different spin configurations including the 2-in
2-out one (Kagome ice state), the 1-in 3-out state (ordered state) and
paramagnetic one (free-spin state).Comment: 14 pages, 7 figure
Spin Dodecamer Formation in the Double-Exchange Spin Ice Model
We investigated the double-exchange spin ice (DESI) model on a kagom\'e
lattice by Monte Carlo simulation to study the effects of a geometrical
frustration, and the mechanism that generates an ordered state in a metallic
system. The DESI model on the kagom\'e lattice is a frustrated metallic system
due to an effective ferromagnetic interaction between localized spins caused by
the double-exchange (DE) mechanism and a uniaxial anisotropy for the localized
spins. A dodecagonal spin cluster (named dodecamer), which consists of twelve
localized spins, appears at low temperature when the number of particles per
site . Such a dodecamer order is driven by both the
kinetic energy gain due to the DE mechanism and the geometrical frustration. We
discuss that cluster orders, in general, may be a common feature in itinerant
electron systems coupled with frustrated adiabatic fields.Comment: 9 pages, 6 figures, to be published in J. Phys. Soc. Jp
Polarity determination in ZnSe nanowires by HAADF STEM
High angle annular dark field scanning transmission electron microscopy is
used to analyze the polarity of ZnSe nanowires grown, by molecular beam
epitaxy, on GaAs substrates. The experimental results are compared to simulated
images in order to verify possible experimental artefacts. In this work we show
that for this type of nano-objects, a residual tilt of the specimen below 15
mrad, away from the crystallographic zone axis does not impair the
interpretation of the experimental images
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