Fitted HBT radii versus space-time variances in flow-dominated models

The inability of otherwise successful dynamical models to reproduce the ``HBT radii'' extracted from two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC) is known as the ``RHIC HBT Puzzle.'' Most comparisons between models and experiment exploit the fact that for Gaussian sources the HBT radii agree with certain combinations of the space-time widths of the source which can be directly computed from the emission function, without having to evaluate, at significant expense, the two-particle correlation function. We here study the validity of this approach for realistic emission function models some of which exhibit significant deviations from simple Gaussian behaviour. By Fourier transforming the emission function we compute the 2-particle correlation function and fit it with a Gaussian to partially mimic the procedure used for measured correlation functions. We describe a novel algorithm to perform this Gaussian fit analytically. We find that for realistic hydrodynamic models the HBT radii extracted from this procedure agree better with the data than the values previously extracted from the space-time widths of the emission function. Although serious discrepancies between the calculated and measured HBT radii remain, we show that a more ``apples-to-apples'' comparison of models with data can play an important role in any eventually successful theoretical description of RHIC HBT data.Comment: 12 pages, 16 color figure

Surface electrical properties experiment, part 1

The work is reported which was performed on the Surface Electrical Properties Experiment Data Acquisition System. Areas discussed include: data handling and processing, installation and external signal application, operation of the equipment, and digital output. Detailed circuit descriptions are included

Parameter estimation in an atmospheric GCM using the Ensemble Kalman Filter

International audienceWe demonstrate the application of an efficient multivariate probabilistic parameter estimation method to a spectral primitive equation atmospheric GCM. The method, which is based on the Ensemble Kalman Filter, is effective at tuning the surface air temperature climatology of the model to both identical twin data and reanalysis data. When 5 parameters were simultaneously tuned to fit the model to reanalysis data, the model errors were reduced by around 35% compared to those given by the default parameter values. However, the precipitation field proved to be insensitive to these parameters and remains rather poor. The model is computationally cheap but chaotic and otherwise realistic, and the success of these experiments suggests that this method should be capable of tuning more sophisticated models, in particular for the purposes of climate hindcasting and prediction. Furthermore, the method is shown to be useful in determining structural deficiencies in the model which can not be improved by tuning, and so can be a useful tool to guide model development. The work presented here is for a limited set of parameters and data, but the scalability of the method is such that it could easily be extended to a more comprehensive parameter set given sufficient observational data to constrain them

The home and school environments, physical activity levels, and adiposity indices of school-age children

The home and school environments as well as physical activity may be linked to the development of childhood obesity. We evaluated the home and school environments (HSEs), physical activity levels (PAL), television viewing (TVV) and their associations with adiposity indices of school-age children. This cross-sectional study included children aged 6-12 years and their parents from Tamale, Ghana. HSEs and TVV were assessed using questionnaires. The physical activity questionnaire for children (PAQ-C) was used to assess children’s PALs. Weight, height and waist circumferences were measured using standard tools. About 45% of children lived within a walking distance to parks or outdoor recreation centres. Majority of the parents considered their neighbourhoods to be safe for children to engage in physical activity. Only 27% of the schools had a food and nutrition policy, and more than 70% had a field for outdoor activities. Children watched TV for an average of 1.7 hours/day. Mean physical activity scores was 2.51. The school-age children had mean (SD) BMI-for-age z-scores was -0.23(1.47). Time spent watching TV or playing video games was associated with children’s BMI-for-age z-scores (β=0.48, p=0.043), BMI (β=2.28 p=0.005), and % body fat (β=3.80, p=0.005). Child’s level of activity was negatively associated with waist circumference (β =-0.65, p<0.001). Lack of nutrition policy in schools was common. TVV hours predisposed children to excess weight whiles physical activity decreased the likelihood of being obese.

Linking Community Participatory Research to Global Policymaking: Lessons Learned

The past two decades saw a proliferation of opportunities for the perspectives of people experiencing poverty and marginalisation to input into global policymaking spaces. So far these efforts have been contested, with attempts to embed participatory methodologies facilitating only limited consultation and falling into many pitfalls. While Participate was built on learning from previous attempts to influence global policy, we aimed to further understand participatory processes, and advance practical mechanisms for participation at every level of decision-making, from local to national and global. Participate emphasises the interactions between these levels and the importance of impacting multiple levels in order to create lasting, transformative change. This chapter describes what has been learnt about bringing the voices on the ground into global policymaking. We examine how and by whom the knowledge and evidence created were used, and the barriers and challenges to embedding this knowledge into global policy processes, through the following questions: • What have been the challenges to embedding participatory processes into global policy spaces? • What have these pathways of influence looked like, and what are some of the key lessons learned from these

Influence of milling parameters on the structural and phase formation in Ti-20%Al alloy through mechanical milling

Titanium aluminides are considered the choice material for next generation propulsion systems due to their high specific strength and high temperature performance coupled with good oxidation resistance. They are considered best materials for specific applications in the aerospace and automobile industry. Their production process, however, determines the final phase in the alloy, which greatly affects their mechanical properties. The effect of the milling parameters on the particle size and the formation of phases were studied on mechanically alloyed Ti-Al powder. A high-energy ball mill (HEBM) was used to mill a mixture of CP Ti and Al to produce titanium aluminide. The alloy was produced at a fixed ball-to-powder weight ratio of 10:1 whilst varying the milling speed and milling time. The mechanically produced powders were analysed using SEM with EDX and XRD to investigate the chemical homogeneity and the formation of phases after the mechanical alloying technique. The analysis of the mechanically alloyed powders from the mill are reported in terms of the morphology evolution during different milling speed, milling time, elemental composition and the phases formed. Alloys milled at a speed of 500 rpm for a milling time range of 5–20 h revealed the formation of Ti alpha (α-Ti) and gamma phase (γ-TiAl).The Department of Science and Innovation (DSI) of South Africa, the Council for Scientific and Industrial Research (CSIR) of South Africa and the contribution of the University of Pretoria.http://www.elsevier.com/locate/matprhj2022Materials Science and Metallurgical Engineerin

On the state dependency of fast feedback processes in (palaeo) climate sensitivity

Palaeo data have been frequently used to determine the equilibrium (Charney) climate sensitivity $S^a$, and - if slow feedback processes (e.g. land ice-albedo) are adequately taken into account - they indicate a similar range as estimates based on instrumental data and climate model results. Most studies implicitly assume the (fast) feedback processes to be independent of the background climate state, e.g., equally strong during warm and cold periods. Here we assess the dependency of the fast feedback processes on the background climate state using data of the last 800 kyr and a conceptual climate model for interpretation. Applying a new method to account for background state dependency, we find $S^a=0.61\pm0.06$ K(Wm$^{-2}$)$^{-1}$ using the latest LGM temperature reconstruction and significantly lower climate sensitivity during glacial climates. Due to uncertainties in reconstructing the LGM temperature anomaly, $S^a$ is estimated in the range $S^a=0.55-0.95$ K(Wm$^{-2}$)$^{-1}$.Comment: submitted to Geophysical Research Letter

Looking into the future, what do we see?

This series of short communications introduces and celebrates the occasion of World Nutrition Rio2012, and looks ahead. There will be another series published next month in our May issue, which will be on-line early, at 0001 GMT on Thursday 26 April, the day before Rio2012 begins. The questions and answers: Our contributors, this month and next month, have been asked to write within a standard framework, based on their knowledge and experience, in a style comparable with those of the news and comment sections of journals concerned with public health. Their contributions are judgements, as any policy statements are and must be. The first question is about Rio2012 itself. The second question is addressed to young colleagues. All the questions are designed to look forward and to advise, warn and encourage. What do I hope Rio2012 will achieve? My advice to a young public health nutritionist When I am optimistic, what is my vision? When I am pessimistic, what do I foresee? My most highly recommended writer One choice of my own publication

Using the past to constrain the future: how the palaeorecord can improve estimates of global warming

Climate sensitivity is defined as the change in global mean equilibrium temperature after a doubling of atmospheric CO2 concentration and provides a simple measure of global warming. An early estimate of climate sensitivity, 1.5-4.5{\deg}C, has changed little subsequently, including the latest assessment by the Intergovernmental Panel on Climate Change. The persistence of such large uncertainties in this simple measure casts doubt on our understanding of the mechanisms of climate change and our ability to predict the response of the climate system to future perturbations. This has motivated continued attempts to constrain the range with climate data, alone or in conjunction with models. The majority of studies use data from the instrumental period (post-1850) but recent work has made use of information about the large climate changes experienced in the geological past. In this review, we first outline approaches that estimate climate sensitivity using instrumental climate observations and then summarise attempts to use the record of climate change on geological timescales. We examine the limitations of these studies and suggest ways in which the power of the palaeoclimate record could be better used to reduce uncertainties in our predictions of climate sensitivity.Comment: The final, definitive version of this paper has been published in Progress in Physical Geography, 31(5), 2007 by SAGE Publications Ltd, All rights reserved. \c{opyright} 2007 Edwards, Crucifix and Harriso