763 research outputs found
The Self-Force of a Charged Particle in Classical Electrodynamics with a Cut-off
We discuss, in the context of classical electrodynamics with a Lorentz
invariant cut-off at short distances, the self-force acting on a point charged
particle. It follows that the electromagnetic mass of the point charge occurs
in the equation of motion in a form consistent with special relativity. We find
that the exact equation of motion does not exhibit runaway solutions or
non-causal behavior, when the cut-off is larger than half of the classical
radius of the electron.Comment: 17 pages, 1 figur
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
Correlation Effects in Nuclear Transparency
The Glauber approximation is used to calculate the contribution of nucleon
correlations in high-energy reactions. When the excitation energy of
the residual nucleus is small, the increase of the nuclear transparency due to
correlations between the struck nucleon and the other nucleons is mostly
compensated by a decrease of the transparency due to the correlations between
non detected nucleons. We derive Glauber model predictions for nuclear
transparency for the differential cross section when nuclear shell level
excitations are measured. The role of correlations in color transparency is
briefly discussed.Comment: 24 pages revtex, 4 uuencoded PostScript Figures as separate fil
Supersymmetric Quantization of Anisotropic Scalar-Tensor Cosmologies
In this paper we show that the spatially homogeneous Bianchi type I and
Kantowski-Sachs cosmologies derived from the Brans-Dicke theory of gravity
admit a supersymmetric extension at the quantum level. Global symmetries in the
effective one-dimensional actions characterize both classical and quantum
solutions. A wide family of exact wavefunctions satisfying the supersymmetric
constraints are found. A connection with quantum wormholes is briefly
discussed.Comment: In Press, Class. Quantum Grav. 20 pages, Late
Improving quality of life for people with dementia in care homes: Making psychosocial interventions work
This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this recordPsychosocial interventions can improve behaviour and mood in people with dementia, but it is unclear how to maximise their effectiveness or acceptability in residential settings. Aims To understand what underlies the successful implementation of psychosocial interventions in care homes. Method Systematic review and meta-synthesis of qualitative research. Results The synthesis of 39 qualitative papers revealed that beneficial psychosocial interventions met the needs of people with dementia to connect with others, make a meaningful contribution and reminisce. Successful implementation rested on the active engagement of staff and family and the continuing provision of tailored interventions and support. This necessitated staff time, and raised issues around priorities and risk, but ultimately helped redefine staff attitudes towards residents and the caregiving role. Conclusions The findings from the meta-synthesis can help to inform the development and evaluation of psychosocial interventions in care homes and support their widespread implementation in clinical settings.National Institute for Health Research (NIHR
Semiclassical approximation to supersymmetric quantum gravity
We develop a semiclassical approximation scheme for the constraint equations
of supersymmetric canonical quantum gravity. This is achieved by a
Born-Oppenheimer type of expansion, in analogy to the case of the usual
Wheeler-DeWitt equation. The formalism is only consistent if the states at each
order depend on the gravitino field. We recover at consecutive orders the
Hamilton-Jacobi equation, the functional Schrodinger equation, and quantum
gravitational correction terms to this Schrodinger equation. In particular, the
following consequences are found:
(i) the Hamilton-Jacobi equation and therefore the background spacetime must
involve the gravitino, (ii) a (many fingered) local time parameter has to be
present on (the space of all possible tetrad and gravitino
fields), (iii) quantum supersymmetric gravitational corrections affect the
evolution of the very early universe. The physical meaning of these equations
and results, in particular the similarities to and differences from the pure
bosonic case, are discussed.Comment: 34 pages, clarifications added, typos correcte
A Posterior Interosseous Nerve Syndrome Associated With Spontaneous Rupture of the Extensor Pollicis Longus Tendon
Posterior interosseous nerve entrapment syndrome and spontaneous rupture of the extensor pollicis longus tendon are rare conditions. The authors describe the bizarre combination of a spontaneous rupture of the extensor pollicis longus tendon in a 82-year-old lady with a posterior interosseous nerve syndrome. As far as the authors know, this is the first description of such an association in the literature. Surgical exploration revealed compression of the posterior interosseous nerve at the proximal portion of the supinator muscle and at Henry's leash. The nerve was freed, and the tendon of the extensor index proprius was transferred to the extensor pollicis longus. Six months after the procedure, the patient had resumed her daily activities, showing a good functional result
Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: a 15-Year Retrospective Study
A SĂndroma de Stevens-Johnson (SSJ), a SĂndroma de Sobreposição (SS) e a NecrĂłlise
TĂłxica EpidĂ©rmica (NTE) sĂŁo emergĂȘncias mĂ©dicas raras, mas com elevadas morbilidade e
mortalidade. A literatura referente Ă s caracterĂsticas destas doenças em Portugal Ă© muito escassa. Procedeu-se Ă anĂĄlise dos registos clĂnicos dos 20 doentes internados na Unidade de Queimados (UQ) do Hospital de SĂŁo JosĂ© nos Ășltimos 15 anos com o diagnĂłstico de SSJ, SS ou NTE.
A maior parte das toxidermias foi do tipo NTE (65%), seguida do SS (25%) e do SSJ (10%).
A idade média foi 57,1 ± 19,0 anos. A duração média do internamento foi de 12,6 ± 7,8 dias.
A mortalidade foi de 50%, sendo significativamente maior que os 16,4% de mortalidade global registada na UQ no mesmo perĂodo (p < 0,01). A ĂĄrea de superfĂcie corporal total envolvida foi de 43,9 ± 28,6 %. O agente causal mais frequentemente implicado foi o alopurinol (35%), seguido da exposição Ă luz ultravioleta e metoxipsoraleno (15%). Catorze doentes (70%) foram tratados com corticĂłides nos primeiros dias de internamento, enquanto seis doentes (30%) foram tratados conservadoramente. A mortalidade foi menor nos doentes tratados com corticĂłides (42,8% vs 66,7%), embora esta diferença nĂŁo fosse estatisticamente significativa. As taxas de infecção tambĂ©m nĂŁo diferiram significativamente nos dois grupos. O SCORTEN nas primeiras 24 horas demonstrou ser um bom preditor de mortalidade.
São necessårios mais estudos para tentar reduzir a mortalidade nestas doenças
Practitionersâ understanding of barriers to accessing specialist support by family carers of people with dementia in distress
Distressing symptoms in dementia are hard to manage for many family carers. This article explores practitioners' perceptions of the barriers to accessing skilled behaviour management support encountered by carers. A survey of cases referred to the English National Health Service (n = 5,360) was followed by in-depth group discussions and practitioner interviews. Data revealed that practitioners focused on care home residents or older people with mental health problems other than dementia, rather than community-dwelling people with dementia and families. Barriers to access included misperceptions about the nature of distressing behaviour affecting carers and structural limitations in the capacity of specialist services to respond to carers
Damage detections in nonlinear vibrating thermally loaded plates
In this work, geometrically nonlinear vibrations of fully clamped rectangular plates subjected to thermal changesare used to study the sensitivity of some vibration response parameters to the presence of damage and elevated temperature. The geometrically nonlinear version of the Mindlin plate theory is used to model the plate behaviour.Damage is represented as a stiffness reduction in a small area of the plate. The plates are subjected to harmonicloading leading to large amplitude vibrations and temperature changes. The plate vibration response is obtained by a pseudo-load mode superposition method. The main results are focussed on establishing the influence of damage on the vibration response of the heated and the unheated plates and the change in the time-history diagrams and the Poincaré maps caused by damage and elevated temperature. The damage criterion formulated earlier for nonheated plates, based on analyzing the points in the Poincaré sections of the damaged and healthy plate, is modified and tested for the case of plates additionally subjected to elevated temperatures. The importance of taking into account the actual temperature in the process of damage detection is shown
- âŠ