Two-Thirds of Smear-Positive Tuberculosis Cases in the Community Were Undiagnosed in Northwest Ethiopia: Population Based Cross-Sectional Study

Background: Tuberculosis (TB) case detection rate remains low in Ethiopia. One of the underlying reasons is the emphasis on passive case finding strategy which may seriously underestimate the burden of the disease. Estimating the prevalence of smear-positive pulmonary TB through active case finding at population level can help assessing the degree to which passive case detection is successful. Methods and findings: This is population based cross-sectional study. The study population was all individuals aged $14 years. Interviews using a uniform questionnaire were done initially to identify individuals with chronic cough ($15 days) and the two sputum (spot and morning) samples were gathered for standard smear microscopy. A total of 23,590 individuals aged $14 years were interviewed and 984 had a chronic cough for$15 days. Of 831 individuals who provided two sputum samples for acid fast bacilli (AFB), 41 had positive smears. A total of 22 smear-positive TB cases detected through passive case finding were on anti-TB treatment. The prevalence of new smear-positive TB was 174 per 100,000 in persons aged $14 years (95$45 years [AOR: 2.26, 95 % CI (1.12–4.59). Conclusions: The study revealed that about two-thirds of patients with active TB remain undiagnosed and thus untreated. This may indicate the need for strengthening case detection at the community level. Furthermore, the high burden of T

A mathematical model of quorum sensing regulated EPS production in biofilm communities

<p>Abstract</p> <p>Background</p> <p>Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities.</p> <p>Model</p> <p>We mathematically model quorum sensing and EPS production in a growing biofilm under various environmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how a biofilm is affected by quorum sensing-regulated EPS production. We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells.</p> <p>Results</p> <p>We find that biofilms that use quorum sensing to induce increased EPS production do not obtain the high cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPS producers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonization mode (with an optimized growth rate), to a protection mode.</p> <p>Conclusions</p> <p>A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have the objective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass as a means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species.</p

Internal cohesion of agglomerates. I: An elementary approach for assemblies of weakly agglomerated 2d-clusters

The average internal cohesion function of two-dimensional (2d)-agglomerates formed by assemblage of fractal aggregates of masses i and j (the aggregates being previously obtained using the algorithms of the diffusion-limited aggregation processes) was determined on the basis of the frequency function P(v, i, j) of the number v of interaggregate connections forming the link. The agglomerate fragmentation threshold was set by choosing the number m of connections which may be broken. The amount of agglomerate sustaining break-up was found to be independent of the mass (i+j) of the final agglomerate and expressed by a Johnson–Mehl equation of the variable m. The porosity of platelets formed by the agglomeration of a great number of fractal aggregates was found to increase as a power law of the aggregate mass and this might explain the lower bending or flexural strength of platelets of large aggregates

Internal cohesion of agglomerates. II: An elementary approach for assemblies of weakly agglomerated 3d-clusters

The fundamental feature of powder constituted of aggregated particles is their cusp structure, which is reproduced by the simpler geometry of fractal clusters generated on lattice. The average internal cohesion of three-dimensional (3d)-agglomerates formed by assemblage of clusters of mass i and j (the clusters being previously obtained using the algorithms of the diffusion- or reaction-limited aggregation processes) was determined by the set of the numbers P(v, i, j) of the interagglomerate links ensured by v connections. This number was obtained from inspection of all nonoverlapping configurations. The fate of the link during fragmentation was determined by setting the number m of connections, which may be broken. The mass of agglomerates sustaining fragmentation, which was found to be slightly dependent of the mass (i+j) of the final agglomerate was expressed by a Johnson–Mehl equation of the variable m. When additive (binder) is mixed with powder to induce grain agglomeration, the agglomeration model showed that only particles belonging to the external envelope of the aggregates become coated, and correlated the additive dose, aggregate characteristics (mass or mass frequency) and effective surface coating

Structure and cohesion of weakly agglomerated fractal systems

We investigated the cohesion of agglomerates formed by sticking together two fractal clusters with the assumption that this parameter can be measured by the number of connections that were established on sticking. In a first step, clusters of selected mass were generated by numerical simulation of the aggregation process on a cubic lattice using the usual algorithm of the diffusion- or reaction-limited aggregation process. Then, agglomerates of various configurations were formed by assembling two by two clusters of even or uneven masses. For each system, the average connection frequency and the total number of configurations were determined. This investigation provided agglomerate characteristics that were determined to be independent of the agglomerate mass (in the domain of large agglomerates) and only dependent of the conditions of the cluster formation. In a second step, aggregates were formed in experiments carried out under conditions of diffusion- or reaction-limited aggregation (as fixed by the electrolyte concentration) as well as under orthokinetic and perikinetic aggregation conditions for aggregates formed in the presence of a small amount of polyvinylpyridine. The fragmentation of all these aggregates was promoted by immersing aggregate samples in polyvinylpyridine solutions of high concentration. Whereas the rate of decrease of the average masses of the aggregates was found to depend on the aggregate mass or the characteristics of the fragmenting medium, the rate of fragmentation a(n) for aggregates of mass n might be expressed by the scaling law a(n)∝nλ. The exponent λ was found to only depend of the experimental conditions of the aggregate formation. The comparison between results of the numerical and experimental investigations seems to indicate that the number of intra-agglomerate connections effectively control the rate of fragmentation and thus the aggregate cohesion

DE-Algorithm-Optimized Fuzzy-PID Controller for AGC of Integrated Multi Area Power System with HVDC Link

A power system’s nonlinearity and complexity increase from time to time due to increases of power demand. Therefore, properly designed power system controlsare required. Without these, system instability will cause equipment failures, and possibly even cascading events and blackouts. To cope with this, intelligent controllers using soft computing are necessary for real time operation. In this paper, the reheat type three-area thermal power system is considered, and the output scaling factors, gain parameters of fuzzy membership functions, and parameters of fuzzy-proportional integral derivative (FPID) controllers are optimized using a differential evolution (DE) optimization techniqueand integral time multiplied absolute error (ITAE) as objective functions. To improve the limitations of the controller and to enhance stability of the system, high voltage direct current (HVDC) technology is advantageous due to its quickresponse capabilities. In this paper, a HVDC is connected in parallel to the system, revealing that a FPID controller with a HVDC provides better and more accurate resultscompared to a system without a controller. The test results presented in this paper show the proposed controller’s suitability for managing random load changes