762 research outputs found
Spatial Particle Condensation for an Exclusion Process on a Ring
We study the stationary state of a simple exclusion process on a ring which
was recently introduced by Arndt {\it et al} [J. Phys. A {\bf 31} (1998)
L45;cond-mat/9809123]. This model exhibits spatial condensation of particles.
It has been argued that the model has a phase transition from a ``mixed phase''
to a ``disordered phase''. However, in this paper exact calculations are
presented which, we believe, show that in the framework of a grand canonical
ensemble there is no such phase transition. An analysis of the fluctuations in
the particle density strongly suggests that the same result also holds for the
canonical ensemble.Comment: 20 pages, 4 figure
Local rewiring rules for evolving complex networks
ERC is grateful for the nancial support of the EPSRC
Factors affecting collection of revenue in Muleba District Council in Kagera Region Tanzania; the case study of Muleba District Council in Kagera Region
This study aimed at making an assessment on the factors affecting collection of revenues in Muleba District Council (MDC). The study specifically focused on identifying sources of revenue at Muleba District Council and volume of collection by source; actors and mechanism used in revenue collection and finally establishing factors determining collection of revenue in the study area. The study used multiple methodologies including survey questionnaires, in-depth interviews, and documentation analysis so as to increase richness of the research findings. Furthermore, sampling techniques was used to enable the researcher to reduce the amount of data needed to be collected by considering groups of people rather than the whole population. It was found that, the Muleba District Council (MDC) did not plan properly before decision of assigning the revenue collection function to revenue collectors (own revenue collectors or agents) is made. Not all sources of revenues with the council were identified, documented and adequately studied to establish the potential amount to collect annually. Furthermore, the focus seems to be on very few sources while the need to widen revenue base was quite high. An overall conclusion is that the Muleba District Council (MDC) lacks an effective and integrated approach to manage Revenue Collectors in its different revenue sources, lacks punitive actions to defaulters and Periodic monitoring and evaluation. The entire system of Managing the revenue collection need to be improved in order to make sure that council’s collect the intended revenue
Spinal epidural abscess: a rare complication of olecranon bursitis
Spinal epidural abscess is a rare but potentially fatal condition if left untreated. We report the case of a 67-year old man who presented to the Accident and Emergency department complaining of acute onset of inter-scapular back pain, left leg weakness and loss of sensation in the left foot. On examination he was found to be pyrexial with long tract signs in the left lower leg. In addition he had a left sided olecranon bursitis of three weeks duration. Blood tests revealed raised inflammatory markers and a staphylococcal bacteremia. Magnetic resonance imaging (MRI) confirmed the diagnosis of spinal epidural abscess and he subsequently underwent a three level laminectomy with good resolution of his back pain and neurological symptoms. He has made a complete recovery with a prolonged course of intravenous antibiotics
Reversible Random Sequential Adsorption of Dimers on a Triangular Lattice
We report on simulations of reversible random sequential adsorption of dimers
on three different lattices: a one-dimensional lattice, a two-dimensional
triangular lattice, and a two-dimensional triangular lattice with the nearest
neighbors excluded. In addition to the adsorption of particles at a rate K+, we
allow particles to leave the surface at a rate K-. The results from the
one-dimensional lattice model agree with previous results for the continuous
parking lot model. In particular, the long-time behavior is dominated by
collective events involving two particles. We were able to directly confirm the
importance of two-particle events in the simple two-dimensional triangular
lattice. For the two-dimensional triangular lattice with the nearest neighbors
excluded, the observed dynamics are consistent with this picture. The
two-dimensional simulations were motivated by measurements of Ca++ binding to
Langmuir monolayers. The two cases were chosen to model the effects of changing
pH in the experimental system.Comment: 9 pages, 10 figure
Theoretical analysis of the focusing of acoustic waves by two-dimensional sonic crystals
Motivated by a recent experiment on acoustic lenses, we perform numerical
calculations based on a multiple scattering technique to investigate the
focusing of acoustic waves with sonic crystals formed by rigid cylinders in
air. The focusing effects for crystals of various shapes are examined. The
dependance of the focusing length on the filling factor is also studied. It is
observed that both the shape and filling factor play a crucial role in
controlling the focusing. Furthermore, the robustness of the focusing against
disorders is studied. The results show that the sensitivity of the focusing
behavior depends on the strength of positional disorders. The theoretical
results compare favorably with the experimental observations, reported by
Cervera, et al. (Phys. Rev. Lett. 88, 023902 (2002)).Comment: 8 figure
Slow relaxation in granular compaction
Experimental studies show that the density of a vibrated granular material
evolves from a low density initial state into a higher density final steady
state. The relaxation towards the final density value follows an inverse
logarithmic law. We propose a simple stochastic adsorption-desorption process
which captures the essential mechanism underlying this remarkably slow
relaxation. As the system approaches its final state, a growing number of beads
have to be rearranged to enable a local density increase. In one dimension,
this number grows as , and the density increase rate is
drastically reduced by a factor . Consequently, a logarithmically slow
approach to the final state is found .Comment: revtex, 4 pages, 3 figures, also available from
http://arnold.uchicago.edu/~ebn
Complex scale-free networks with tunable power-law exponent and clustering
This article is made available through the Brunel Open Access Publishing Fund. It is distributed under a Creative Commons License (http://creativecommons.org/licenses/by/3.0/). Copyright @ 2013 Elsevier B.V.We introduce a network evolution process motivated by the network of citations in the scientific literature. In each iteration of the process a node is born and directed links are created from the new node to a set of target nodes already in the network. This set includes mm “ambassador” nodes and ll of each ambassador’s descendants where mm and ll are random variables selected from any choice of distributions plpl and qmqm. The process mimics the tendency of authors to cite varying numbers of papers included in the bibliographies of the other papers they cite. We show that the degree distributions of the networks generated after a large number of iterations are scale-free and derive an expression for the power-law exponent. In a particular case of the model where the number of ambassadors is always the constant mm and the number of selected descendants from each ambassador is the constant ll, the power-law exponent is (2l+1)/l(2l+1)/l. For this example we derive expressions for the degree distribution and clustering coefficient in terms of ll and mm. We conclude that the proposed model can be tuned to have the same power law exponent and clustering coefficient of a broad range of the scale-free distributions that have been studied empirically.EPSR
Spectral Degeneracies in the Totally Asymmetric Exclusion Process
We study the spectrum of the Markov matrix of the totally asymmetric
exclusion process (TASEP) on a one-dimensional periodic lattice at ARBITRARY
filling. Although the system does not possess obvious symmetries except
translation invariance, the spectrum presents many multiplets with degeneracies
of high order. This behaviour is explained by a hidden symmetry property of the
Bethe Ansatz. Combinatorial formulae for the orders of degeneracy and the
corresponding number of multiplets are derived and compared with numerical
results obtained from exact diagonalisation of small size systems. This
unexpected structure of the TASEP spectrum suggests the existence of an
underlying large invariance group.
Keywords: ASEP, Markov matrix, Bethe Ansatz, Symmetries.Comment: 19 pages, 1 figur
Optimal Management of Severe/Refractory Asthma
Asthma is a chronic inflammatory disease of the airways, affecting approximately 300 million people worldwide. Asthma results in airway hyperresponsiveness, leading to paroxysmal symptoms of wheeze, cough, shortness of breath, and chest tightness. When these symptoms remain uncontrolled, despite treatment with high doses of inhaled and ingested corticosteroids, asthmatic patients are predisposed to greater morbidity and require more health care support. Treating patients with severe asthma can be difficult and often poses a challenge to physicians when providing ongoing management. This clinical review aims to discuss the definition, prevalence and evaluation of severe asthmatics, and provides a review of the existing pharmacologic and non-pharmacologic treatment options
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