Geodesic motions versus hydrodynamic flows in a gravitating perfect fluid: Dynamical equivalence and consequences

Stimulated by the methods applied for the observational determination of masses in the central regions of the AGNs, we examine the conditions under which, in the interior of a gravitating perfect fluid source, the geodesic motions and the general relativistic hydrodynamic flows are dynamically equivalent to each other. Dynamical equivalence rests on the functional similarity between the corresponding (covariantly expressed) differential equations of motion and is obtained by conformal transformations. In this case, the spaces of the solutions of these two kinds of motion are isomorphic. In other words, given a solution to the problem "hydrodynamic flow in a perfect fluid", one can always construct a solution formally equivalent to the problem "geodesic motion of a fluid element" and vice versa. Accordingly, we show that, the observationally determined nuclear mass of the AGNs is being overestimated with respect to the real, physical one. We evaluate the corresponding mass-excess and show that it is not always negligible with respect to the mass ofthe central dark object, while, under circumstances, can be even larger than the rest-mass of the circumnuclear gas involved.Comment: LaTeX file, 22 page

Newtonian nonlinear hydrodynamics and magnetohydrodynamics

We use covariant methods to analyse the nonlinear evolution of self-gravitating, non-relativistic media. The formalism is first applied to imperfect fluids, aiming at the kinematic effects of viscosity, before extended to inhomogeneous magnetised environments. The nonlinear electrodynamic formulae are derived and successively applied to electrically resistive and to highly conductive fluids. By nature, the covariant equations isolate the magnetic effects on the kinematics and the dynamics of the medium, combining mathematical transparency and physical clarity. Employing the Newtonian analogue of the relativistic 1+3 covariant treatment, also facilitates the direct comparison with the earlier relativistic studies and helps to identify the differences in an unambiguous way. The purpose of this work is to set the framework and take a first step towards the detailed analytical study of complex nonlinear systems, like non-relativistic astrophysical plasmas and collapsing protogalactic clouds.Comment: Typos corrected, references added and updated (MNRAS in press

BayesPeak: Bayesian analysis of ChIP-seq data.

BACKGROUND: High-throughput sequencing technology has become popular and widely used to study protein and DNA interactions. Chromatin immunoprecipitation, followed by sequencing of the resulting samples, produces large amounts of data that can be used to map genomic features such as transcription factor binding sites and histone modifications. METHODS: Our proposed statistical algorithm, BayesPeak, uses a fully Bayesian hidden Markov model to detect enriched locations in the genome. The structure accommodates the natural features of the Solexa/Illumina sequencing data and allows for overdispersion in the abundance of reads in different regions. Moreover, a control sample can be incorporated in the analysis to account for experimental and sequence biases. Markov chain Monte Carlo algorithms are applied to estimate the posterior distributions of the model parameters, and posterior probabilities are used to detect the sites of interest. CONCLUSION: We have presented a flexible approach for identifying peaks from ChIP-seq reads, suitable for use on both transcription factor binding and histone modification data. Our method estimates probabilities of enrichment that can be used in downstream analysis. The method is assessed using experimentally verified data and is shown to provide high-confidence calls with low false positive rates.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Availability, attitudes and costs of selected dental services in a low-income country

ABSTRACT The aim of this study was to determine the availability of selected dental services, attitudes towards such services and economic factors associated with their utilization in a low-income country. Data utilized for this study was collected in two phases. Phase I was a survey of all dental facilities in four selected regions in Tanzania. The survey was administered to officers-in-charge of dental facilities and other dental practitioners working within these facilities. Phase II was a series of cross-sectional studies conducted among outpatients attending four selected regional hospitals in Tanzania. Data was collected using self-administered questionnaires. Dental materials and equipment were inconsistently available and only 3/28 studied dental facilities had all the seven investigated equipment fully functional and in use. The self-rated competency among dental practitioners ranged from 6.4 to 9.8 for all six procedures questioned, but equal scores between cadres were only for tooth extractions (9.7 vs. 9.1 respectively). Competencies for placing restorations were all rated lower by other cadres (p varied from <. 05 to < .001). Most of the patients had a negative overall attitude (-1.99) towards tooth filling treatment although those with previous tooth filling experience had positive attitudes (1.00). The mean willingness-to-pay (WTP) values for tooth filling (7,398 and 7,726 Tshs for anterior and posterior teeth, respectively) were higher (p < 0.001) than for tooth extraction irrespective of tooth type (5,448 and 6,188 Tshs, respectively). Being 45+ years increased the likelihood to offer lower WTP values. More than half (55%) of the patients would experience significant financial impacts as a result of their utilization of dental services. The findings clearly suggest that there are a multitude of factors that influence the observed dental treatment patterns being predominated by tooth extractions in Tanzania. Keywords: Willingness-to-pay, costs, dental services, attitudes, TanzaniaTIIVISTELMÄ Valikoitujen hammashoitopalvelujen saatavuus, niihin liittyvät asenteet ja käytön kustannukset vähävaraisessa maassa Tutkimus selvitti valikoitujen hammashoitopalveluiden saatavuutta sekä niihin liittyviä asenteita ja käyttöön liittyviä taloudellisia tekijöitä vähävaraisessa maassa. Ensin tehtiin kyselytutkimus kaikissa hammashoitopalveluja tarjoavissa yksiköissä neljällä valitulla tansanialaisella hallintoalueella näiden yksiköiden johtajien ja hammashoitoa antavien työntekijöiden keskuudessa. Toiseksi toteutettiin sarja poikkileikkaustutkimuksia kyselyin näiden neljän hallintoalueen avohoitopotilaiden keskuudessa. Kyselyissä selvitettiin valikoitujen hammashoitopalvelujen kustannuksia, hammashoitomateriaalien ja -laitteiden saatavuutta, hammashoidon työntekijöiden kokemia valmiuksia, potilaiden asenteita ja maksuhalukkuutta paikkaushoitoon sekä potilaille hammashoidosta aiheutuviin kustannuksia. Materiaaleja ja laitteita oli vaihtelevasti saatavilla. Vain kolmessa tutkitusta 28 hoitolasta kaikki seitsemän tutkimuksessa tarkasteltua laitetta olivat käytössä ja toimintakunnossa. Hammaslääkärien kokemat valmiudet toimenpiteisiin vaihtelivat (6,4–9,8) ja olivat saman tasoisia muiden ammattiryhmien kanssa vain poistoissa (9,7 vs. 9,1). Paikkausvalmiudet olivat alempia muilla ammattiryhmillä (p <0,05–<0,001). Useimmilla potilailla oli negatiivinen kokonaisasenne (-1,99) paikkaushoitoon. Heillä, joilla oli aiempaa kokemusta paikkaushoidosta, oli positiivinen asenne (1,00). Paikkaushoidon maksuhalukkuuden keskiarvot olivat huomattavasti korkeammat (7398 Tansanian shillinkiä (Tshs) etualueella ja 7726 Tshs taka-alueella) kuin hammaspoistojen maksuhalukkuuden (5448 Tshs etualueella ja 6188 Tshs taka-alueella, p<0,001). Hammashoitopalvelujen käyttö aiheutti yli puolelle (55 %) tutkituista potilaista merkittäviä taloudellisia vaikutuksia. Tulokset osoittavat selvästi, että Tansaniassa monet tekijät vaikuttavat hammashoitopalvelujen tuotantoon, jota hallitsevat hampaiden poistot. Avainsanat: Maksuhalukkuus, kustannukset, hammashoitopalvelut, asenteet, Tansani

Exploiting neutron-rich radioactive ion beams to constrain the symmetry energy

The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure the free neutrons and heavy charged particles from the radioactive ion beam induced 32Mg + 9Be reaction. The fragmentation reaction was simulated with the Constrained Molecular Dynamics model(CoMD), which demonstrated that the of the heavy fragments and free neutron multiplicities were observables sensitive to the density dependence of the symmetry energy at sub-saturation densities. Through comparison of these simulations with the experimental data constraints on the density dependence of the symmetry energy were extracted. The advantage of radioactive ion beams as a probe of the symmetry energy is demonstrated through examination of CoMD calculations for stable and radioactive beam induced reactions