21,720 research outputs found
Ergodic and non-ergodic clustering of inertial particles
We compute the fractal dimension of clusters of inertial particles in mixing
flows at finite values of Kubo (Ku) and Stokes (St) numbers, by a new series
expansion in Ku. At small St, the theory includes clustering by Maxey's
non-ergodic 'centrifuge' effect. In the limit of St to infinity and Ku to zero
(so that Ku^2 St remains finite) it explains clustering in terms of ergodic
'multiplicative amplification'. In this limit, the theory is consistent with
the asymptotic perturbation series in [Duncan et al., Phys. Rev. Lett. 95
(2005) 240602]. The new theory allows to analyse how the two clustering
mechanisms compete at finite values of St and Ku. For particles suspended in
two-dimensional random Gaussian incompressible flows, the theory yields
excellent results for Ku < 0.2 for arbitrary values of St; the ergodic
mechanism is found to contribute significantly unless St is very small. For
higher values of Ku the new series is likely to require resummation. But
numerical simulations show that for Ku ~ St ~ 1 too, ergodic 'multiplicative
amplification' makes a substantial contribution to the observed clustering.Comment: 4 pages, 2 figure
Advective collisions
Small particles advected in a fluid can collide (and therefore aggregate) due
to the stretching or shearing of fluid elements. This effect is usually
discussed in terms of a theory due to Saffman and Turner [J. Fluid Mech., 1,
16-30, (1956)]. We show that in complex or random flows the Saffman-Turner
theory for the collision rate describes only an initial transient (which we
evaluate exactly). We obtain precise expressions for the steady-state collision
rate for flows with small Kubo number, including the influence of fractal
clustering on the collision rate for compressible flows. For incompressible
turbulent flows, where the Kubo number is of order unity, the Saffman-Turner
theory is an upper bound.Comment: 4 pages, 1 figur
Brownian Motion Model of Quantization Ambiguity and Universality in Chaotic Systems
We examine spectral equilibration of quantum chaotic spectra to universal
statistics, in the context of the Brownian motion model. Two competing time
scales, proportional and inversely proportional to the classical relaxation
time, jointly govern the equilibration process. Multiplicity of quantum systems
having the same semiclassical limit is not sufficient to obtain equilibration
of any spectral modes in two-dimensional systems, while in three-dimensional
systems equilibration for some spectral modes is possible if the classical
relaxation rate is slow. Connections are made with upper bounds on
semiclassical accuracy and with fidelity decay in the presence of a weak
perturbation.Comment: 13 pages, 6 figures, submitted to Phys Rev
Co‐creating system‐wide improvement for people with traumatic brain injury across one integrated care system in the United Kingdom to initiate a transformation journey through co‐production
Background and Objective
There is a need for better integration of services across communities and sectors for people living with traumatic brain injury (TBI) to meet their complex needs. Building on insights gained from earlier pilot work, here we report the outcomes of a participatory workshop that sought to better understand the challenges, barriers and opportunities that currently exist within the care pathway for survivors of TBI.
Methods
A diverse range of stakeholders from the acute and rehabilitation care pathway and the health and social care system were invited to participate in a 3-h workshop. The participants worked in four mixed subgroups using practice development methodology, which promotes person-centred, inclusive and participatory action.
Results
Thematic analysis identified shared purposes and values that were used to produce a detailed implementation and impact framework for application at both the level of the care interface and the overarching integrated care system. A variety of enablers were identified that related to collective values and behaviours, case management, team leadership and integrated team working, workforce capability, evidence-based practice and resourcing. The clinical, economic, cultural and social outcomes associated with these enablers were also identified, and included patient safety, independence and well-being, reduced waiting times, re-admission rates, staff retention and professional development.
Conclusion
The co-produced recommendations made within the implementation and impact framework described here provide a means by which the culture and delivery of health and social care services can be better tailored to meet the needs of people living with TBI. We believe that the recommendations will help shape the formation of new services as well as the development of existing ones.
Patient or Public Contribution
Patient and public involvement have been established over a 10-year history of relationship building through a joint forum and events involving three charities representing people with TBI, carers, family members, clinicians, service users, researchers and commissioners, culminating in a politically supported event that identified concerns about the needs of people following TBI. These relationships formed the foundation for the interactive workshop, the focus of this publication
Structure of purine nucleoside phosphorylase (DeoD) from Bacillus anthracis
Protein structures from the causative agent of anthrax (Bacillus anthracis) are being determined as part of a structural genomics programme. Amongst initial candidates for crystallographic analysis are enzymes involved in nucleotide biosynthesis, since these are recognized as potential targets in antibacterial therapy. Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway. The crystal structure of purine nucleoside phosphorylase (DeoD) from B. anthracis has been solved by molecular replacement at 2.24 Å resolution and refined to an R factor of 18.4%. This is the first report of a DeoD structure from a Gram-positive bacterium
Parametric instabilities in the LCGT arm cavity
We evaluated the parametric instabilities of LCGT (Japanese interferometric
gravitational wave detector project) arm cavity. The number of unstable modes
of LCGT is 10-times smaller than that of Advanced LIGO (U.S.A.). Since the
strength of the instabilities of LCGT depends on the mirror curvature more
weakly than that of Advanced LIGO, the requirement of the mirror curvature
accuracy is easier to be achieved. The difference in the parametric
instabilities between LCGT and Advanced LIGO is because of the thermal noise
reduction methods (LCGT, cooling sapphire mirrors; Advanced LIGO, fused silica
mirrors with larger laser beams), which are the main strategies of the
projects. Elastic Q reduction by the barrel surface (0.2 mm thickness
TaO) coating is effective to suppress instabilities in the LCGT arm
cavity. Therefore, the cryogenic interferometer is a smart solution for the
parametric instabilities in addition to thermal noise and thermal lensing.Comment: 6 pages,3 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
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