Signatures of Confinement in Axial Gauge QCD

A comparative dynamical study of axial gauge QED and QCD is presented. Elementary excitations associated with particular field configurations are investigated. Gluonic excitations analogous to linearly polarized photons are shown to acquire infinite energy. Suppression of this class of excitations in QCD results from quantization of the chromelectric flux and is interpreted as a dual Meissner effect, i.e. as expulsion from the QCD vacuum of chromo-electric fields which are constant over significant distances. This interpretation is supported by a comparative evaluation of the interaction energy of static charges in the axial gauge representation of QED and QCD.Comment: 22 pages (no figures

Are older people putting themselves at risk when using their walking frames?

Background Walking aids are issued to older adults to prevent falls, however, paradoxically their use has been identified as a risk factor for falling. To prevent falls, walking aids must be used in a stable manner, but it remains unknown to what extent associated clinical guidance is adhered to at home, and whether following guidance facilitates a stable walking pattern. It was the aim of this study to investigate adherence to guidance on walking frame use, and to quantify user stability whilst using walking frames. Additionally, we explored the views of users and healthcare professionals on walking aid use, and regarding the instrumented walking frames (‘Smart Walkers’) utilized in this study. Methods This observational study used Smart Walkers and pressure-sensing insoles to investigate usage patterns of 17 older people in their home environment; corresponding video captured contextual information. Additionally, stability when following, or not, clinical guidance was quantified for a subset of users during walking in an Activities of Daily Living Flat and in a gait laboratory. Two focus groups (users, healthcare professionals) shared their experiences with walking aids and provided feedback on the Smart Walkers. Results Incorrect use was observed for 16% of single support periods and for 29% of dual support periods, and was associated with environmental constraints and a specific frame design feature. Incorrect use was associated with reduced stability. Participants and healthcare professionals perceived the Smart Walker technology positively. Conclusions Clinical guidance cannot easily be adhered to and self-selected strategies reduce stability, hence are placing the user at risk. Current guidance needs to be improved to address environmental constraints whilst facilitating stable walking. The research is highly relevant considering the rising number of walking aid users, their increased falls-risk, and the costs of falls. Trial Registration Not applicable

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Whether BDs form as stars through gravitational collapse ("star-like") or BDs and some very low-mass stars constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. For young stars in Taurus-Auriga the binary fraction is large with little dependence on primary mass above ~0.2Msun, while for BDs it is <10%. We investigate a case in which BDs in Taurus formed dominantly through peripheral fragmentation. The decline of the binary frequency in the transition region between star-like and peripheral formation is modelled. A dynamical population synthesis model is employed in which stellar binary formation is universal. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. The binary fraction declines strongly between the mass-limits for star-like and peripheral formation. The location of characteristic features and the steepness depend on these mass-limits. Such a trend might be unique to low density regions hosting dynamically unprocessed binary populations. The existence of a strong decline in the binary fraction -- primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.Comment: accepted for publication in A&A, 11 pages, 4 figures, 1 tabl

Risk assessment of an offshore wind turbine and remaining useful life estimation of the power converter. Improving availability by prioritising failures with higher risk to operation

By 2014, almost 2500 offshore wind turbines were installed in Europe representing 8GW of capacity connected to the grid and, there is a growing market penetration for the next years. Offshore wind farm operators are facing many challenges related to disparate data sources utilisation for O&M logistic optimisation. Therefore, the decision-making process needs to be based on sound analysis of the wind farm information or data available. According to several technical reports operation and maintenance (O&M) cost could reach until 30% of the levelised cost of energy (LCOE). Understanding the reliability of an offshore wind turbine and the resources required to maintain it is crucial to reduce O&M costs and thus, to reduce the levelised cost of energy (LCOE). There is a need to reduce unnecessary tasks, prioritise the most urgent tasks, improve usage of vessels, crew and technicians, reduce the cost of spare parts held and schedule preventative maintenance to minimise downtime and maximise revenue. Currently, risk assessment plays an important role in the operation and maintenance (O&M) strategies of offshore wind farms. A comprehensive failure mode and effect analysis (FMEA) has been carried out to determine critical assemblies of a generic offshore wind turbine with an induction generator, three stages gearbox and monopile foundation. The main objectives of undertaking this comprehensive FMEA was to identify those failures with significant impact on the wind turbine operation and to identify or highlight areas of risk for maintainability and availability. The FMEA is validated with; widely-used data available in the public domain; Lloyd’s Register’s experience of working with wind farm operators and; Lloyd’s Register experience of working on reliability of the mechanical system of different industrial sectors for decades. The FMEA is further augmented and updated by the use of on-going measurements from operating wind farms. Yaw system, pitch system, power converter and gearbox have been identified in the FMEA as the most critical assemblies regarding risk to the turbine operation. Power converter analysis shows high failure rates and a large proportion of undetectable failures, therefore maintenance resources have been spent on fault finding with its corresponding cost. New approaches are necessary to tackle electrical or electronic failures, especially on the power converter. To improve overall reliability, a method to estimate the remaining useful life (RUL) of a fully-rated converter in a variable speed wind turbine is proposed using data commonly available for offshore wind farm operators. Studies show that the economic impact is dominated by failures related to power electronic components such as IGBTs and capacitors due to their higher repair cost. Mathematical models have been developed to correlate turbine operation variables and environmental conditions with failure root causes to define wear and maintenance actions based on the probability of failur

Task based profiles of language impairment in Parkinson’s Disease

This study aimed to add to our understanding of language impairment in people with Parkinson's Disease (PwPD). Language difficulties are increasingly reported in PD. However, there are contradictory reports on how they relate to motor and cognitive impairment. In addition, the link between various language deficits or the same deficits across task modalities is not well understood. This lack of understanding impacts on clinicians’ ability to assess and effectively treat language impairment in PD. Our study therefore aimed to investigate language performance across a number of task structures and correlate this performance with cognitive skills, as well as motor and speech performance. The study included 22 German speaking PwPD and 22 matched healthy control participants. 18 participants in each group were cognitively healthy and four had mild cognitive impairment. They performed a number of executive function and language tasks of different complexity and structure. The linguistic investigation focused on grammatical accuracy and complexity, linguistic content as well as articulatory features. There were few cognitive differences between the two groups, with only set-shifting as an executive function being significantly reduced in PwPD, but grammatical error rate was higher in PwPD than in their healthy controls across all language tasks. This was linked to set shifting skills but only for the complex grammar condition, not for more naturalistic language tasks. Furthermore, there was no correlation of language performance across the task levels, i.e. error rates in the structured task did not predict naturalistic performance. Motor and dysarthria severity could not predict language impairment either. This study confirms the presence of language problems in PwPD in the absence of global cognitive impairment or only MCI, and at the same time establishes a task based relationship between the two skills. From a clinical perspective the data indicate that structured tests are unable to accurately predict naturalistic language performance, highlighting the need for functional assessments rather than relying on fast scoring structured tests, at least at early disease stages. In addition, the impact of the individual language difficulties needs to be explored to establish appropriate and effective treatment pathways

Objective measures of rollator user stability and device loading during different walking scenarios

Walking aids are widely used by older adults, however, alarmingly, their use has been linked to increased falls-risk, yet clinicians have no objective way of assessing user stability. This work aims to demonstrate the application of a novel methodology to investigate how the type of walking task, the amount of body weight supported by the device (i.e., device loading), and task performance strategy affect stability of rollator users. In this context, ten users performed six walking tasks with an instrumented rollator. The combined stability margin “SM” was calculated, which considers user and rollator as a combined system. A Friedman Test was used to investigate the effects of task on SM and a least-squares regression model was applied to investigate the relationship between device loading and SM. In addition, the effects of task performance strategy on SM were explored. As a result, it was found that: the minimum SM for straight line walking was higher than for more complex tasks (p&lt;0.05); an increase in device loading was associated with an increase in SM (p&lt;0.05); stepping up a kerb with at least 1 rollator wheel in ground contact at all times resulted in higher SM than lifting all four wheels simultaneously. Hence, we conclude that training should not be limited to straight line walking but should include various everyday tasks. Within person, SM informs on which tasks need practicing, and which strategy facilitates stability, thereby enabling person-specific guidance/training. The relevance of this work lies in an increase in walking aid users, and the costs arising from fall-related injuries. Supplementary data is available in Figshare

Phase transition in the 3-D massive Gross-Neveu model

We consider the 3-dimensional massive Gross-Neveu model at finite temperature as an effective theory for strong interactions. Using the Matsubara imaginary time formalism, we derive a closed form for the renormalized $T$-dependent four-point function. This gives a singularity, suggesting a phase transition. Considering the free energy we obtain the $T$-dependent mass, which goes to zero for some temperature. These results lead us to the conclusion that there is a second-order phase transition.Comment: 06 pages, 02 figures, LATE

Diet, the intestinal microbiota, and immune health in aging

Many countries are facing aging populations, with those over 65 years of age likely to represent the largest population over the next 10–20 years. Living longer often comes with poor health and, in particular, a decline in the immune function characterized by poor vaccine responses and increased risk of infection and certain cancers. Aging and diet represent major intrinsic and extrinsic factors that influence the makeup and activity of resident intestinal microbes, the microbiota, the efficient functioning of which is essential for sustaining overall health and the effectiveness of the immune system. The provision of elderly specific dietary recommendations appears to be lacking but is necessary since this population has an altered microbiota and immune response and may not respond in the same way as their healthy and younger counterparts. We have reviewed the evidence supporting the role of diet and, in particular, dietary carbohydrate, protein, and fat in influencing the microbiota and its generation of key metabolites that influence the efficient functioning of immune cells during aging, and how dietary intervention might be of benefit in improving the intestinal health and immune status in the elderly

Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions

Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.Comment: 1 ps-file (MS-Word), 14 page

Isospin Dependence of the Spin-Orbit Force and Effective Nuclear Potentials,

The isospin dependence of the spin-orbit potential is investigated for an effective Skyrme-like energy functional suitable for density dependent Hartree-Fock calculations. The magnitude of the isospin dependence is obtained from a fit to experimental data on finite spherical nuclei. It is found to be close to that of relativistic Hartree models. Consequently, the anomalous kink in the isotope shifts of Pb nuclei is well reproduced.Comment: Revised, 11 pages (Revtex) and 2 figures available upon request, Preprint MPA-833, Physical Review Letters (in press)