Treatment of Young Children with HIV Infection: Using Evidence to Inform Policymakers

PMCID: PMC3404108This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Discussion with reviewers

This paper introduces the culture preparation of ovine, bovine and human cancellous bone cores to be used in an explants model Zetos. The three dimensional (3D) bone cores were prepared and evaluated for all three animals. Bone cells in vivo constantly interact with each other, migratory cells, surrounding extracellular matrix (eCM) and interstitial fluid in a microenvironment, which continuously responds to various endogenous and exogenous stimuli

Relativistic models of magnetars: the twisted-torus magnetic field configuration

We find general relativistic solutions of equilibrium magnetic field configurations in magnetars, extending previous results of Colaiuda et al. (2008). Our method is based on the solution of the relativistic Grad-Shafranov equation, to which Maxwell's equations can be reduced in some limit. We obtain equilibrium solutions with the toroidal magnetic field component confined into a finite region inside the star, and the poloidal component extending to the exterior. These so-called twisted-torus configurations have been found to be the final outcome of dynamical simulations in the framework of Newtonian gravity, and appear to be more stable than other configurations. The solutions include higher order multipoles, which are coupled to the dominant dipolar field. We use arguments of minimal energy to constrain the ratio of the toroidal to the poloidal field.Comment: 13 pages, 12 figures. Minor changes to match the version published on MNRA

The effect of pore size on permeability and cell attachment in collagen scaffolds for tissue engineering.

The permeability of scaffolds and other three-dimensional constructs used for tissue engineering applications is important as it controls the diffusion of nutrients in and waste out of the scaffold as well as influencing the pressure fields within the construct. The objective of this study was to characterize the permeability/fluid mobility of collagen-GAG scaffolds as a function of pore size and compressive strain using both experimental and mathematical modeling techniques. Scaffolds containing four distinct mean pore sizes (151, 121, 110, 96 microns) were fabricated using a freeze-drying process. An experimental device was constructed to measure the permeability of the scaffold variants at different levels of compressive strain (0, 14, 29 and 40% while a low-density open-cell foam cellular solids model utilizing a tetrakaidecahedral unit cell was used to accurately model the permeability of each scaffold variant at all level of applied strain. The results of both the experimental and the mathematical analysis revealed that scaffold permeability increases with increasing pore size and decreases with increasing compressive strain. The excellent comparison between experimentally measured and predicted scaffold permeability suggests that cellular solids modelling techniques can be utilized to predict scaffold permeability under a variety of physiological loading conditions as well as to predict the permeability of future scaffolds with a wide variety of pore microstructures

Downregulation of Rap1GAP contributes to Ras transformation.

Although abundant in well-differentiated rat thyroid cells, Rap1GAP expression was extinguished in a subset of human thyroid tumor-derived cell lines. Intriguingly, Rap1GAP was downregulated selectively in tumor cell lines that had acquired a mesenchymal morphology. Restoring Rap1GAP expression to these cells inhibited cell migration and invasion, effects that were correlated with the inhibition of Rap1 and Rac1 activity. The reexpression of Rap1GAP also inhibited DNA synthesis and anchorage-independent proliferation. Conversely, eliminating Rap1GAP expression in rat thyroid cells induced a transient increase in cell number. Strikingly, Rap1GAP expression was abolished by Ras transformation. The downregulation of Rap1GAP by Ras required the activation of the Raf/MEK/extracellular signal-regulated kinase cascade and was correlated with the induction of mesenchymal morphology and migratory behavior. Remarkably, the acute expression of oncogenic Ras was sufficient to downregulate Rap1GAP expression in rat thyroid cells, identifying Rap1GAP as a novel target of oncogenic Ras. Collectively, these data implicate Rap1GAP as a putative tumor/invasion suppressor in the thyroid. In support of that notion, Rap1GAP was highly expressed in normal human thyroid cells and downregulated in primary thyroid tumors

Magnetic fileds of coalescing neutron stars and the luminosity function of short gamma-ray burst

Coalescing neutron star binaries are believed to be the most reliable sources for ground-based detectors of gravitational waves and likely progenitors of short gamma-ray bursts. In the process of coalescence, magnetic fields of neutron stars can induce interesting observational manifestations and affect the form of gravitational wave signal. In this papaer we use the population synthesis method to model the expected distribution of neutron star magnetic fields during the coalescence under different assumptions on the initial parameters of neutron stars and their magnetic field evolution. We discuss possible elecotrmagnetic phenomena preceding the coalescence of magnetized neutron star binaries and the effect of magnetic field on the gravitational wave signal. We find that a log-normal (Gaussian in logarithms) distribution of the initial magnetic fields of neutron stars, which agrees with observed properties of radio pulsars, produces the distribution of the magnetic field energy during the coalescence that adequately describes the observed luminosity function of short gamma-ray bursts under different assumptions on the field evolution and initial parameters of neutron stars. This agreement lends further support to the model of coalescing neutron star binaries as progenitors of gamma-ray bursts.Comment: v.2, LATEX, 25 pages, inc. 7 ps figures, Astron. Lett., in press. Typos corrected, reference adde

Sequence level mechanisms of human epigenome evolution

DNA methylation and chromatin states play key roles in development and disease. However, the extent of recent evolutionary divergence in the human epigenome and the influential factors that have shaped it are poorly understood. To determine the links between genome sequence and human epigenome evolution, we examined the divergence of DNA methylation and chromatin states following segmental duplication events in the human lineage. Chromatin and DNA methylation states were found to have been generally well conserved following a duplication event, with the evolution of the epigenome largely uncoupled from the total number of genetic changes in the surrounding DNA sequence. However, the epigenome at tissue-specific, distal regulatory regions was observed to be unusually prone to diverge following duplication, with particular sequence differences, altering known sequence motifs, found to be associated with divergence in patterns of DNA methylation and chromatin. Alu elements were found to have played a particularly prominent role in shaping human epigenome evolution, and we show that human-specific AluY insertion events are strongly linked to the evolution of the DNA methylation landscape and gene expression levels, including at key neurological genes in the human brain. Studying paralogous regions within the same sample enables the study of the links between genome and epigenome evolution while controlling for biological and technical variation. We show DNA methylation and chromatin divergence between duplicated regions are linked to the divergence of particular genetic motifs, with Alu elements having played a disproportionate role in the evolution of the epigenome in the human lineage

Coronal mass ejections as expanding force-free structures

We mode Solar coronal mass ejections (CMEs) as expanding force-fee magnetic structures and find the self-similar dynamics of configurations with spatially constant \alpha, where {\bf J} =\alpha {\bf B}, in spherical and cylindrical geometries, expanding spheromaks and expanding Lundquist fields correspondingly. The field structures remain force-free, under the conventional non-relativistic assumption that the dynamical effects of the inductive electric fields can be neglected. While keeping the internal magnetic field structure of the stationary solutions, expansion leads to complicated internal velocities and rotation, induced by inductive electric field. The structures depends only on overall radius R(t) and rate of expansion \dot{R}(t) measured at a given moment, and thus are applicable to arbitrary expansion laws. In case of cylindrical Lundquist fields, the flux conservation requires that both axial and radial expansion proceed with equal rates. In accordance with observations, the model predicts that the maximum magnetic field is reached before the spacecraft reaches the geometric center of a CME.Comment: 19 pages, 9 Figures, accepted by Solar Physic

‘Don’t just travel’: thinking poetically on the way to professional knowledge

This paper describes how the medium of ‘found poetry’ is incorporated into a doctoral programme for nurses, educators and allied health and social care professionals at the start of their various doctoral journeys. It advocates a narrative practice approach to issues of researcher identity and reflexivity. ‘Finding’ the poems begins with the creation of collages as representational anchors for students to talk about themselves, their professional practice, their hopes and expectations of the doctoral experience, and their research ideas. (Re)presenting their transcribed talk as poetry involves culling and playing with words, phrases and segments, making changes in spacing, lines and rhythm to arrive at an evocative distillation (Butler-Kisber, 2002). This process enables each person to bring stories and/or fragments of experience into critical engagement with others. Poetic thinking functions pedagogically, helping students find a critical voice to enliven and hone their reflexive writing in relation to their doctoral experience and their research positioning. Arts-based methods of inquiry are an ongoing topic of interest in research communities. Found poetry is a useful starting point to explore creative means by which research participants can recount their stories, and equally, by which researchers can witness and disseminate what they have to tell.self funde