102 research outputs found
Phylodynamic analysis of an emergent Mycobacterium bovis outbreak in an area with no previously known wildlife infections
1. Understanding how an emergent pathogen successfully establishes itself and persists in a previously unaffected population is a crucial problem in disease ecology, with important implications for disease management. In multi-host pathogen systems this problem is particularly difficult, as the importance of each host species to transmission is often poorly characterised, and the disease epidemiology is complex. Opportunities to observe and analyse such emergent scenarios are few. 2. Here, we exploit a unique dataset combining densely-collected data on the epidemiological and evolutionary characteristics of an outbreak of Mycobacterium bovis (the causative agent of bovine tuberculosis, bTB) in a population of cattle and badgers in an area considered low-risk for bTB, with no previous record of either persistent infection in cattle, or of any infection in wildlife. We analyse the outbreak dynamics using a combination of mathematical modelling, Bayesian evolutionary analyses, and machine learning. 3. Comparison to M. bovis whole-genome sequences from Northern Ireland confirmed this to be a single introduction of the pathogen from the latter region, with evolutionary analysis supporting an introduction directly into the local cattle population six years prior to its first discovery in badgers. 4. Once introduced, the evidence supports M. bovis epidemiological dynamics passing through two phases, the first dominated by cattle-to-cattle transmission before becoming established in the local badger population. 5. Synthesis and applications. The raw data object of this analysis were used to support decisions regarding the control of a M. bovis emergent outbreak, of considerable concern because of the geographical distance from previously known high-risk areas. Our further analyses, estimating the time of introduction (and therefore the likely magnitude of any hidden outbreak) and the rates of cross-species transmission, provided valuable confirmation that the extent and focus of the imposed controls were appropriate. Not only these findings strengthen the call for genomic surveillance, but they also pave the path for future outbreaks control, providing insights for more rapid and decisive evidence-based decision-making. As the methods we used and developed are agnostic to the disease itself, they are also valuable for other slowly transmitting pathogens
Developing independent investigators for clinical research relevant for Africa
Sustainable research capacity building requires training individuals at multiple levels within a supportive institutional infrastructure to develop a critical mass of independent researchers. At many African medical institutions, a PhD is important for academic promotion and is, therefore, an important focal area for capacity building programs. We examine the training at the Infectious Diseases Institute (IDI) as a model for in-country training based on systems capacity building and attention to the academic environment. PhD training in Africa should provide a strong research foundation for individuals to perform independent, original research and to mentor others. Training the next generation of researchers within excellent indigenous academic centers of excellence with strong institutional infrastructure will empower trainees to ask regionally relevant research questions that will benefit Africans
The SAMI Galaxy Survey: Environmental analysis of the orbital structures of passive galaxies
Most dynamical models of galaxies to date assume axisymmetry, which is not
representative of a significant fraction of massive galaxies. We have built
triaxial orbit-superposition Schwarzschild models of galaxies observed by the
SAMI Galaxy Survey, in order to reconstruct their inner orbital structure and
mass distribution. The sample consists of 153 passive galaxies with total
stellar masses in the range to . We present an
analysis of the internal structures and intrinsic properties of these galaxies
as a function of their environment. We measure their environment using three
proxies: central or satellite designation, halo mass and local nearest
neighbour galaxy density. We find that although these intrinsic properties
correlate most strongly with stellar mass, environment does play a secondary
role: at fixed stellar mass, galaxies in the densest regions are more radially
anisotropic. In addition, central galaxies, and galaxies in high local
densities show lower values of edge-on spin parameter proxy \lam. We also find
suggestions of a possible trend of the fractions of orbits with environment for
lower-mass galaxies (between and ) such that, at
fixed stellar mass, galaxies in higher local densities and halo mass have
higher fractions of hot orbits and lower fractions of warm orbits. Our results
demonstrate that after stellar mass, environment does play a role in shaping
present-day passive galaxies.Comment: 21 pages. Accepted for publication in MNRA
The accretion histories of brightest cluster galaxies from their stellar population gradients
We analyse the spatially-resolved stellar populations of 9 local ()
Brightest Cluster Galaxies (BCGs) observed with VIMOS in IFU mode. Our sample
is composed of 7 slow-rotating and 2 fast-rotating BCGs. We do not find a
connection between stellar kinematics and stellar populations in this small
sample. The BCGs have shallow metallicity gradients (median [Fe/H] ), high central metallicities (median Fe/H]), and a wide range of central ages (from 5 to 15 Gyr). We propose
that the reason for this is diverse evolutionary paths in BCGs. 67 per cent of
the sample (6/9) show Gyr old central ages, which reflects an active
accretion history, and 33 per cent of the sample (3/9) have central ages older
than 11 Gyr, which suggest no star formation since . The BCGs show similar
central stellar populations and stellar population gradients to early-type
galaxies of similar mass (MM) from the
ATLAS survey (median [Z/H] , [Z/H] ). However, massive early-type galaxies from ATLAS have
consistently old ages (median Age Gyr). We also analyse the close
massive companion galaxies of two of the BCGs. These galaxies have similar
stellar populations to their respective BCGs.Comment: Accepted for publication, MNRAS, March 3, 201
The SAMI Galaxy Survey: Quenching of Star Formation in Clusters I. Transition Galaxies
We use integral-field spectroscopy from the SAMI Galaxy Survey to identify galaxies that show evidence of recent quenching of star formation. The galaxies exhibit strong Balmer absorption in the absence of ongoing star formation in more than 10% of their spectra within the SAMI field of view. These Hd-strong (HDS) galaxies (HDSGs) are rare, making up only similar to 2% (25/1220) of galaxies with stellar mass log(M-*/M-circle dot) > 10. The HDSGs make up a significant fraction of nonpassive cluster galaxies (15%; 17/115) and a smaller fraction (2.0%; 8/387) of the nonpassive population in low-density environments. The majority (9/17) of cluster HDSGs show evidence of star formation at their centers, with the HDS regions found in the outer parts of the galaxy. Conversely, the HDS signal is more evenly spread across the galaxy for the majority (6/8) of HDSGs in low-density environments and is often associated with emission lines that are not due to star formation. We investigate the location of the HDSGs in the clusters, finding that they are exclusively within 0.6R(200) of the cluster center and have a significantly higher velocity dispersion relative to the cluster population. Comparing their distribution in projected phase space to those derived from cosmological simulations indicates that the cluster HDSGs are consistent with an infalling population that has entered the central 0.5r(200,3D) cluster region within the last similar to 1 Gyr. In the eight of nine cluster HDSGs with central star formation, the extent of star formation is consistent with that expected of outside-in quenching by ram pressure stripping. Our results indicate that the cluster HDSGs are currently being quenched by ram pressure stripping on their first passage through the cluster
Galaxy And Mass Assembly (GAMA): stellar mass growth of spiral galaxies in the cosmic web
We look for correlated changes in stellar mass and star formation rate (SFR) along filaments in the cosmic web by examining the stellar masses and UV-derived SFRs of 1799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterize the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher SFRs at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large-scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus suggest a model in which in addition to stellar mass as the primary discriminant, the large-scale environment is imprinted in the SFR as a second-order effect. Furthermore, our detailed results for filament galaxies suggest a model in which gas accretion from voids on to filaments is primarily in an orthogonal direction. Overall, we find our results to be in line with theoretical expectations of the thermodynamic properties of the intergalactic medium in different large-scale environments
Adenocarcinoma of the caecum metastatic to the bladder: an unusual cause of haematuria
BACKGROUND: Primary malignancies of colorectal origin can metastasise to the bladder. Reports are however extremely rare, particularly from the caecum. CASE REPORT: The report describes the case of a 45-year old male with Duke's B caecal carcinoma treated with a laparoscopically-assisted right hemicolectomy and adjuvant 5-Fluorouracil chemotherapy. Subsequently, a metastatic lesion to the bladder was demonstrated and successfully excised by partial cystectomy. CONCLUSION: In order that optimal therapeutic options can be determined, it is important for clinicians to distinguish between primary disease of the bladder and other causes of haematuria. Various immunohistochemical techniques attempt to differentiate primary adenocarcinoma of the bladder from secondary colorectal adenocarcinoma. Suspicion of metastatic disease must be raised when histologically unusual bladder tumours are identified
Deep Investigation of Neutral Gas Origins (DINGO): HI stacking experiments with early science data
We present early science results from Deep Investigation of Neutral Gas
Origins (DINGO), an HI survey using the Australian Square Kilometre Array
Pathfinder (ASKAP). Using ASKAP sub-arrays available during its commissioning
phase, DINGO early science data were taken over 60 deg of the
Galaxy And Mass Assembly (GAMA) 23 h region with 35.5 hr integration time. We
make direct detections of six known and one new sources at . Using HI
spectral stacking, we investigate the HI gas content of galaxies at for different galaxy colours. The results show that galaxy morphology
based on optical colour is strongly linked to HI gas properties. To examine
environmental impacts on the HI gas content of galaxies, three sub-samples are
made based on the GAMA group catalogue. The average HI mass of group central
galaxies is larger than those of satellite and isolated galaxies, but with a
lower HI gas fraction. We derive a variety of HI scaling relations for physical
properties of our sample, including stellar mass, stellar mass surface density,
colour, specific star formation rate, and halo mass. We find that the
derived HI scaling relations are comparable to other published results, with
consistent trends also observed to 0.5 dex lower limits in stellar mass
and stellar surface density. The cosmic HI densities derived from our data are
consistent with other published values at similar redshifts. DINGO early
science highlights the power of HI spectral stacking techniques with ASKAP.Comment: 27 pages, 25 figures, 10 tables, accepted for publication in MNRA
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