Sample representation in a psychological treatment study after single event paediatric trauma

Children and their families who attended an emergency department following a single traumatic incident and who agreed to participate in a psychological treatment study (N = 211) were compared with nonparticipants (N = 2333) on several measures of trauma and injury severity: duration of admission and heart rate in the emergency department, emergency transport and admission to hospital, injury severity score, and triage code. Within the nonparticipant population, those who requested further information about the study (N = 573) were exposed to more severe trauma or injury than other nonparticipants (N = 1760). In addition, participants were exposed to more severe trauma or injury than either group of nonparticipants. These observations indicate that those exposed to more severe trauma or injury do not avoid participation in psychological treatment studies. Findings can therefore be generalized to those with more severe exposure, but not to the population as a whole

The imperative for consultation and involvement in child nutrition research: Adding perspectives from qualitative research

This chapter highlights the need for an understanding of the views of children and the way they view food and nutrition knowledge and behaviour. We argue that this is necessary to help understand behaviour, to inform practice and to devise realistic research and evaluation strategies. Many existing approaches to research adopt a positivist approach and tend to exclude qualitative work because of the lack of control groups and validated measures. We set out how, by using qualitative research techniques and examples from our own work, the views of young people can be used to inform underlying behaviour. What we know about the behaviour of a community or group of individuals is often added to by qualitative data and this is not always so in experimental studies. For example attempts to change the behaviour of young people in eating in fast food restaurants is tempered by the fact that the reasons they do this are influenced by issues other than knowledge about the food on offer; or in the case of fruit and vegetable schemes it is necessary to understand the mindset of children to consuming fruit and vegetables. These raise the classic contradiction between knowledge and behaviour and the translation of research findings into practice and shaping what works. Determining audience needs, wants and perceptions is one of the key principles of good quality public health nutrition prevention work and is in-keeping with the need to create supportive environments for health and strengthening community action for health. We set out the need for understanding the mindset of young people, along with the links between research and action. We explore the use of existing evidence and gaps in the evidence base which includes an argument for research to have utility and be linked to programme interventions; indicating a shift from traditional evidence-based practice and a plea for evaluation and research on the use of evidence in practice. Such an approach will enable health practitioners to gain a better understanding of how to implement strategies associated with childhood nutrition and healthy eating in their working environment

The contribution of O(alpha) radiative corrections to the renormalised anisotropy and application to general tadpole improvement schemes: addendum to "One loop calculation of the renormalised anisotropy for improved anisotropic gluon actions on a lattice" [hep-lat/0208010]

General O(alpha) radiative corrections to lattice actions may be interpreted as counterterms that give additive contributions to the one-loop renormalisation of the anisotropy. The effect of changing the radiative coefficients is thus easily calculable. In particular, the results obtained in a previous paper for Landau mean link improved actions apply in any tadpole improvement scheme. We explain how this method can be exploited when tuning radiatively improved actions. Efficient methods for self-consistently tuning tadpole improvement factors are also discussed.Comment: 3 pages of revte

Analyzing differences in the costs of treatment across centers within economic evaluations

Objectives: Assessments of health technologies increasingly include economic evaluations conducted alongside clinical trials. One particular concern with economic evaluations conducted alongside clinical trials is the generalizability of results from one setting to another. Much of the focus relating to this topic has been on the generalizability of results between countries, However, the characteristics of clinical trial design require further consideration of the generalizability of cost data between centers within a single country, which could be important in decisions about adoption of the new technology. Methods: We used data from a multicenter clinical trial conducted in the United Kingdom to assess the degree of variation in costs between patients and between treatment centers and the determinants of the degree of such variation. Results: The variation between patients was statistically significant for both the experimental and conventional treatments. However, the degree of variation between centers was only statistically significant for the experimental treatment. Such variation appeared to be a result of hospital practice, such as pay ment mechanisms for staff and provision of hostel accommodation, rather than variations in physical resource use or substantive differences in cost structure. Conclusions: Multicenter economic evaluations are necessary for determining the variations in hospital practice and characteristics that can in turn determine the generalizability of study results to other settings. Such analyses can identify issues that may be important in adopting a new health technology. Analysis is required of similar large multicenter trials to confirm these conclusions

Yangians, Grassmannians and T-duality

We investigate the Yangian symmetry of scattering amplitudes in N=4 super Yang-Mills theory and show that its formulations in twistor and momentum twistor space can be interchanged. In particular we show that the full symmetry can be thought of as the Yangian of the dual superconformal algebra, annihilating the amplitude with the MHV part factored out. The equivalence of this picture with the one where the ordinary superconformal symmetry is thought of as fundamental is an algebraic expression of T-duality. Motivated by this, we analyse some recently proposed formulas, which reproduce different contributions to amplitudes through a Grassmannian integral. We prove their Yangian invariance by directly applying the generators.Comment: 28 pages, 1 figure; v2: minor correction

Quantum theory of dispersive electromagnetic modes

A quantum theory of dispersion for an inhomogeneous solid is obtained, from a starting point of multipolar coupled atoms interacting with an electromagnetic field. The dispersion relations obtained are equivalent to the standard classical Sellmeir equations obtained from the Drude-Lorentz model. In the homogeneous (plane-wave) case, we obtain the detailed quantum mode structure of the coupled polariton fields, and show that the mode expansion in all branches of the dispersion relation is completely defined by the refractive index and the group-velocity for the polaritons. We demonstrate a straightforward procedure for exactly diagonalizing the Hamiltonian in one, two or three-dimensional environments, even in the presence of longitudinal phonon-exciton dispersion, and an arbitrary number of resonant transitions with different frequencies. This is essential, since it is necessary to include at least one phonon (I.R.) and one exciton (U.V.) mode, in order to accurately represent dispersion in transparent solid media. Our method of diagonalization does not require an explicit solution of the dispersion relation, but relies instead on the analytic properties of Cauchy contour integrals over all possible mode frequencies. When there is longitudinal phonon dispersion, the relevant group-velocity term is modified so that it only includes the purely electromagnetic part of the group velocity

Hexagon OPE Resummation and Multi-Regge Kinematics

We analyse the OPE contribution of gluon bound states in the double scaling limit of the hexagonal Wilson loop in planar N=4 super Yang-Mills theory. We provide a systematic procedure for perturbatively resumming the contributions from single-particle bound states of gluons and expressing the result order by order in terms of two-variable polylogarithms. We also analyse certain contributions from two-particle gluon bound states and find that, after analytic continuation to the $2\to 4$ Mandelstam region and passing to multi-Regge kinematics (MRK), only the single-particle gluon bound states contribute. From this double-scaled version of MRK we are able to reconstruct the full hexagon remainder function in MRK up to five loops by invoking single-valuedness of the results.Comment: 29 pages, 3 figures, 4 ancillary file

Superstring amplitudes and the associator

We investigate a pattern in the $\alpha'$ expansion of tree-level open superstring amplitudes which correlates the appearance of higher depth multiple zeta values with that of simple zeta values in a particular way. We rephrase this relationship in terms of the coaction on motivic multiple zeta values and show that the pattern takes a very simple form, which can be simply explained by relating the amplitudes to the Drinfel'd associator derived from the Knizhnik-Zamolodchikov equation. Given this correspondence we show that, at least in the simplest case of the four-point amplitude, the associator can be used to extract the form of the amplitude.Comment: 20 pages, 1 figur