Constipation and encopresis in children

Chronic constipation is defined as a decrease in frequency or the painful passage of bowel movements present for several weeks. Retentive encopresis is the term reserved for the involuntary and uncontrollable soiling that occurs in children with chronic constipation. Constipation is a relatively common pediatric complaint accounting for up to 3% of general paediatirc outpatient visits and 25% of visits to a pediatric gastroenterologist. Encopresis is also common, occurring in at least 1.5% of all childrenpeer-reviewe

Validation of simulated real world TCP stacks

The TCP models in ns-2 have been validated and are widely used in network research. They are however not aimed at producing results consistent with a TCP implementation, they are rather designed to be a general model for TCP congestion control. The Network Simulation Cradle makes real world TCP implementations available to ns-2: Linux, FreeBSD and OpenBSD can all be simulated as easily as using the original simplified models. These simulated TCP implementations can be validated by directly comparing packet traces from simulations to traces measured from a real network. We describe the Network Simulation Cradle, present packet trace comparison results showing the high degree of accuracy possible when simulating with real TCP implementations and briefly show how this is reflected in a simulation study of TCP throughput

Parabolic Anderson model with voter catalysts: dichotomy in the behavior of Lyapunov exponents

We consider the parabolic Anderson model $\partial u/\partial t = \kappa\Delta u + \gamma\xi u$ with $u\colon\, \Z^d\times R^+\to \R^+$, where $\kappa\in\R^+$ is the diffusion constant, $\Delta$ is the discrete Laplacian, $\gamma\in\R^+$ is the coupling constant, and $\xi\colon\,\Z^d\times \R^+\to\{0,1\}$ is the voter model starting from Bernoulli product measure $\nu_{\rho}$ with density $\rho\in (0,1)$. The solution of this equation describes the evolution of a "reactant" $u$ under the influence of a "catalyst" $\xi$. In G\"artner, den Hollander and Maillard 2010 the behavior of the \emph{annealed} Lyapunov exponents, i.e., the exponential growth rates of the successive moments of $u$ w.r.t.\ $\xi$, was investigated. It was shown that these exponents exhibit an interesting dependence on the dimension and on the diffusion constant. In the present paper we address some questions left open in G\"artner, den Hollander and Maillard 2010 by considering specifically when the Lyapunov exponents are the a priori maximal value in terms of strong transience of the Markov process underlying the voter model.Comment: In honour of J\"urgen G\"artner on the occasion of his 60th birthday, 33 pages. Updated version following the referee's comment

Excitation and resonant enhancement of axisymmetric internal wave modes

To date, axisymmetric internal wave fields, which have relevance to atmospheric internal wave fields generated by storm cells and oceanic near-inertial wave fields generated by surface storms, have been experimentally realized using an oscillating sphere or torus as the source. Here, we use a novel wave generator configuration capable of exciting axisymmetric internal wave fields of arbitrary radial form to generate axisymmetric internal wave modes. After establishing the theoretical background for axisymmetric mode propagation, taking into account lateral and vertical confinement, and also accounting for the effects of weak viscosity, we experimentally generate and study modes of different order. We characterize the efficiency of the wave generator through careful measurement of the wave amplitude based upon group velocity arguments. This established, we investigate the ability of vertical confinement to induce resonance, identifying a series of experimental resonant peaks that agree well with theoretical predictions. In the vicinity of resonance, the wave fields undergo a transition to non-linear behaviour that is initiated on the central axis of the domain and proceeds to erode the wave field throughout the domain.Comment: 15 pages, 9 figure

On Superselection Rules in Bohm-Bell Theories

The meaning of superselection rules in Bohm-Bell theories (i.e., quantum theories with particle trajectories) is different from that in orthodox quantum theory. More precisely, there are two concepts of superselection rule, a weak and a strong one. Weak superselection rules exist both in orthodox quantum theory and in Bohm-Bell theories and represent the conventional understanding of superselection rules. We introduce the concept of strong superselection rule, which does not exist in orthodox quantum theory. It relies on the clear ontology of Bohm-Bell theories and is a sharper and, in the Bohm-Bell context, more fundamental notion. A strong superselection rule for the observable G asserts that one can replace every state vector by a suitable statistical mixture of eigenvectors of G without changing the particle trajectories or their probabilities. A weak superselection rule asserts that every state vector is empirically indistinguishable from a suitable statistical mixture of eigenvectors of G. We establish conditions on G for both kinds of superselection. For comparison, we also consider both kinds of superselection in theories of spontaneous wave function collapse.Comment: 20 pages LaTeX, no figures; v2 minor improvements, journal versio

More on the Cohort-Component Model of Population Projection in the Context of HIV/AIDS: A Leslie Matrix Representation and New Estimates

This article presents an extension of the cohort component model of population projection (CCMPP) first formulated by Heuveline that is capable of modeling a population affected by HIV. We extend this work by developing the Leslie matrix representation of the CCMPP that greatly facilitates implementation of the model for parameter estimation and projecting. The Leslie matrix also contains information about the stable tendencies of the corresponding population, such as the stable age distribution and time to stability. We validate our reformulation of the model by comparing parameter estimates obtained through maximum likelihood and bootstrap methods to those presented by Heuveline.Africa, AIDS/HIV, cohort component method, estimation, incidence, Leslie matrices, model, prevalence