24,703 research outputs found
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Transient Changes in Melt Pool Size in Laser Additive Manufacturing Processes
Mechanical Engineerin
An invitation to quantum tomography (II)
The quantum state of a light beam can be represented as an infinite
dimensional density matrix or equivalently as a density on the plane called the
Wigner function. We describe quantum tomography as an inverse statistical
problem in which the state is the unknown parameter and the data is given by
results of measurements performed on identical quantum systems. We present
consistency results for Pattern Function Projection Estimators as well as for
Sieve Maximum Likelihood Estimators for both the density matrix of the quantum
state and its Wigner function. Finally we illustrate via simulated data the
performance of the estimators. An EM algorithm is proposed for practical
implementation. There remain many open problems, e.g. rates of convergence,
adaptation, studying other estimators, etc., and a main purpose of the paper is
to bring these to the attention of the statistical community.Comment: An earlier version of this paper with more mathematical background
but less applied statistical content can be found on arXiv as
quant-ph/0303020. An electronic version of the paper with high resolution
figures (postscript instead of bitmaps) is available from the authors. v2:
added cross-validation results, reference
Characterization of the differences in strength and power between different levels of competition in rugby union athletes
Detailed temporal structure of communication networks in groups of songbirds
This work was supported by EPSRC Early Career research fellowship EP/L020505/1
Assessing the variation in the load that produces maximal upper-body power
Substantial variation in the load that produces maximal power has been reported. It has been suggested that the variation observed may be due to differences in subject physical characteristics. Therefore the aim of this study was to determine the extent in which anthropometric measures correlate to the load that produces maximal power. Anthropometric measures (upper-arm length, forearm length, total arm length, upper-arm girth) and bench press strength were assessed in 26 professional rugby union players. Peak power was then determined in the bench press throw exercise using loads of 20 to 60% of one repetition maximum (1RM) in the bench press exercise. Maximal power occurred at 30 +/- 14 %1RM (mean +/- SD). Upper-arm length had the highest correlation with the load maximizing power: -0.61 (90% confidence limits -0.35 to -0.78), implying loads of 22 vs. 38 %1RM maximize power for players with typically long vs. short upper-arm length. Correlations for forearm length, total arm length and upper-arm girth to the load that maximized power were -0.29 (0.04 to -0.57), -0.56 (-0.28 to -0.75), and -0.29 (0.04 to -0.57), respectively. The relationship between 1RM and the load that produced maximal power was r = -0.23 (0.10 to -0.52). The between-subject variation in the load that maximised power observed (SD= +/- 14 %1RM) may have been due to differences in anthropometric characteristics, and absolute strength and power outputs. Indeed, athletes with longer limbs and larger girths, and greater maximal strength and power outputs utilised a lower percentage of 1RM loads to achieve maximum power. Therefore, we recommend individual assessment of the load that maximizes power output
The Best of Both Worlds: Experiences of Co-developing Innovative Undergraduate Health Care Programmes in Egypt
As medical education has become increasingly globalised, universities across the world have sought to raise standards by partnering with well-established institutions and a number of different partnership models have emerged. This article describes an academic collaboration between University College London (UCL), UK, and Newgiza University (NGU), Egypt, to establish modern and innovative undergraduate medicine, dentistry, and pharmacy programmes delivered in Egypt. Academics from UCL and NGU co-developed programmes using established materials, assessments, and processes from the equivalent programmes at UCL. Dedicated project managers, regular steering group meetings, strong working relationships between project teams, and iterative curriculum and assessment development processes were important features of the success of this work. A multidisciplinary first semester included students across all 3 health care programmes. This promoted collaboration between academics at both institutions. Although UCL resources were the basis of this project, the different sociocultural, ethical, professional, and regulatory frameworks in Egypt have meant that a number of adaptations have been necessary, in both curricula and teaching content. Perhaps the most important factor underpinning the success of this project has been the mutual respect and sensitivity of academics and clinicians from both institutions
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Suicide and self-harm in Britain: researching risk and resilience using UK surveys
Aim The main aim of this study was to raise awareness of surveys that could be used to inform self-harm and suicide prevention work. We asked:
What UK survey datasets are available for research?
What aspects of people’s lives are associated with self-harm and attempted suicide?
How do statistical findings resonate with people’s lived experience? What implications do they see?
Findings Survey analyses revealed that risk factors for self-harm are wide ranging and include:
Mental health
Physical health and health behaviours
Social relationships
Stressful events
Employment and financial circumstances
Identity and demographics
Many different factors are independently associated with self-harm. There is a dose relationship, with more exposure to a factor linked with increased risk. Risks are cumulative that is, exposure to multiple factors is associated with greater risk.
Through facilitated consultation, men with lived experience, bereaved family members, and practitioners identified recommendations for responding to suicidal distress in men. These related to the following three main areas:
1. Recognising need: who is ‘ill enough’?
Permission - men said that they often did not know they were entitled to help
Ask - people who outwardly appear to be functioning may not be
Persistence - ask and offer help more than once.
2. Facilitating access: right words, time and place
What is available - support is needed with ongoing stress as well as for crises
Find the words - men wanted examples of how to ask for help
Allow time - employers expect recovery to be swift, some men felt rushed to come off medications or were discharged from services they still needed.
3. Adjusting delivery: equal engagement
Power - some were uncomfortable with service dynamics, preferring peer support
Every service contact counts - negative contacts had particular impact
Safe spaces - may be different for men and women.
Methods
There were three strands of work:
Secondary analysis of nine survey series, spanning more than twenty years
Linkage of 144,000 survey participants to information on whether they were alive in 2013 and whether they had taken their own life
Facilitated consultation, through depth interviews with people with lived experience
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