919 research outputs found
Microscopic Study of Superfluidity in Dilute Neutron Matter
Singlet -wave superfluidity of dilute neutron matter is studied within the
correlated BCS method, which takes into account both pairing and short-range
correlations. First, the equation of state (EOS) of normal neutron matter is
calculated within the Correlated Basis Function (CBF) method in lowest cluster
order using the and components of the Argonne
potential, assuming trial Jastrow-type correlation functions. The
superfluid gap is then calculated with the corresponding component of the
Argonne potential and the optimally determined correlation functions.
The dependence of our results on the chosen forms for the correlation functions
is studied, and the role of the -wave channel is investigated. Where
comparison is meaningful, the values obtained for the gap within
this simplified scheme are consistent with the results of similar and more
elaborate microscopic methods.Comment: 9 pages, 6 figure
Time-dependent transport through a T-coupled quantum dot
We are considering the time-dependent transport through a discrete system,
consiting of a quantum dot T-coupled to an infinite tight-binding chain. The
periodic driving that is induced on the coupling between the dot and the chain,
leads to the emergence of a characteristic multiple Fano resonant profile in
the transmission spectrum. We focus on investigating the underlying physical
mechanisms that give rise to the quantum resonances. To this end, we use
Floquet theory for calculating the transmission spectrum and in addition employ
the Geometric Phase Propagator (GPP) approach [Ann. Phys. 375, 351 (2016)] to
calculate the transition amplitudes of the time-resolved virtual processes, in
terms of which we describe the resonant behavior. This two fold approach,
allows us to give a rigorous definition of a quantum resonance in the context
of driven systems and explains the emergence of the characteristic Fano profile
in the transmission spectrum.Comment: 9 pages, 4 figure
Computational study of the interaction between a newtonian fluid and a cellular biological medium in a straight vessel
In this work, we solve numerically the governing equations for quasi-steady
Newtonian flow past and through a cellular biological medium, which is attached to the
surface of a straight vessel. The flow past the cellular biological medium is described by the
Navier-Stokes equations. For the modeling of momentum transfer within the cellular
biological medium, we consider that the cellular biological medium constitutes a biphasic
fluid-solid mixture with poroelastic behaviour. The system of governing equations is solved
numerically with the mixed finite element method. The computational domain is discretized
using an unstructured, variable density triangular element mesh. From the numerical solution
we obtain the spatial distributions of: (i) the fluid velocity and pressure, and (ii) the
displacement and stresses of the solid matrix within the cellular biological medium. Also, the
components of the overall hydrodynamic force exerted by the flowing fluid on the cellular
biological medium are calculated. A parametric analysis is performed with regard to the
Reynolds and Darcy numbers that characterize the flow past and through the cellular
biological medium
Hierarchical hybrid simulation of biofilm growth dynamics in 3D porous media
Recently, we developed the first hierarchical, hybrid simulator for the prediction of
the pattern of evolution and the rate of growth of heterogeneous biofilms within the pore
space of porous media [Kapellos et al., Adv. Water Resour. (2007) 30:1648-1667]. A n
improved version of our simulator is presented in this work. A continuum-based approach for
fluid flow and solute transport is combined with individual-based approaches for biofilm
growth, detachment, and migration in the pore space. The Navier-Stokes-Brinkman equations
are solved numerically with a marker-and-cell finite difference scheme to determine the
velocity and pressure fields in the pore space. Momentum transport in the biofilms is
described in the context of biphasic poroelasticity and a Galerkin finite element method is
used to determine the solid stress field. Shear-induced biofilm detachment is taken into
account explicitly and a Lagrangian-type simulation is used to determine the trajectories of
detached fragments. Nutrient transport in the pore space is described by the convectiondiffusion-
reaction equation, which is solved numerically with an operator-splitting finite
difference scheme. Further, a novel, physically-constrained cellular-automaton model is used
for biofilm proliferation. As an example application, the simulator is used to investigate the
impact of biofilm formation on the fate and transport of suspended particles in a network of
three-dimensional pores
Paradoxical and powerful: Volunteers’ experiences of befriending people with dementia
This qualitative UK study explored the lived experiences of volunteer befrienders to people with dementia, using interpretative phenomenological analysis. Individual semi-structured interviews were conducted with nine befrienders aged between 25 and 66 years. The relationship that developed between befriender and befriendee was at the heart of befrienders’ experiences. It comprised numerous paradoxical processes that generated issues of power, equality and boundaries, characterising befriending as a complex and unique phenomenon. Befriending was expressed as a deeply personal and human experience, often with emotional power and profound meaning. Befrienders’ personal learning included seeing past dementia stereotypes, challenging their own assumptions and boundaries, and reflecting on love, life and humanness. Dissemination of these findings could help to challenge the stigma around dementia, and enhance recruitment and support of dementia befrienders. Future research should consider befriendee experiences of the relationship, additional measures of befriending effectiveness, and exploration of befriender attrition and support. </jats:p
Olfactory dysfunction is common in classical infratentorial superficial siderosis of the central nervous system
BACKGROUND: Established features of classical infratentorial superficial siderosis (iSS) include hearing loss, impaired balance, myelopathy and, less commonly, cognitive compromise. Olfactory function may be affected but dedicated studies are lacking. This study aimed to assess the prevalence of olfactory dysfunction in iSS and correlate it with auditory and cognitive functions. METHODS: Ten participants with iSS completed the University of Pennsylvania Smell Identification Test (UPSIT). The scores were compared with population norms; regression analysis was performed to evaluate associations between the scores and hearing thresholds (3-frequency average, 3FA) or the number of cognitive domains impaired. Imaging was reviewed for haemosiderin distribution and to exclude other causes of olfactory and hearing dysfunction. RESULTS: Eight of ten participants were male; the mean (standard deviation, SD) age was 52.5 (14.5) years. Olfactory hypofunction was identified in all participants and in six (60%) was moderate or completely absent. The mean UPSIT score of 25.5 (7.8) was significantly worse than population norms (difference in means - 10.0; 95% CI - 15.6 to - 4.4). Linear regression identified an association between UPSIT and hearing thresholds (R = 0.75; p = 0.013). The score decreases by 0.157 units (95% CI - 0.31 to - 0.002; p = 0.048) per unit increase in 3FA, after adjusting for hearing loss risk factors. There was no statistically significant association between UPSIT and cognitive function (R = 0.383; p = 0.397). CONCLUSION: We report a high prevalence of olfactory dysfunction in iSS, the severity of which correlated with hearing loss. Olfaction appears to be a core feature of the iSS clinical syndrome that should be assessed routinely
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