142 research outputs found
Imaging in conservation: looking at artefacts under new light’ ICON Archaeology and Science groups conference review
Review of conference. ‘Imaging in Conservation: Looking at Artefacts Under New Light’ was held on 10th–11th November 2011 at STFC Rutherford Appleton Laboratory, Harwell, Oxfordshire.
A joint two day conference between the Icon Archaeology and Science Groups was held at the Rutherford Appleton Laboratory in Oxfordshire.
There was a full programme of speakers discussing a wide range of issues within the context of imaging in conservation. The principle discourse was an evaluation of emerging (digital) technologies within the museum community
Cold and Warm Gas Outflows in Radio AGN
The study of the conditions and the kinematics of the gas in the central
region of AGN provides important information on the relevance of feedback
effects connected to the nuclear activity. Quantifying these effects is key for
constraining galaxy evolution models. Here we present a short summary of our
recent efforts to study the occurrence and the impact of gas outflows in
radio-loud AGN that are in their first phase of their evolution. Clear evidence
for AGN-induced outflows have been found for the majority of these young radio
sources. The outflows are detected both in (warm) ionized as well in (cold)
atomic neutral gas and they are likely to be driven (at least in most of the
cases) by the interaction between the expanding jet and the medium. The mass
outflow rates of the cold gas (HI) appear to be systematically higher than
those of the ionized gas. The former reach up to ~50 Msun/yr, and are in the
same range as "mild" starburst-driven superwinds in ULIRGs, whilst the latter
are currently estimated to be a few solar masses per year. However, the kinetic
powers associated with these gaseous outflow are a relatively small fraction (a
few x 10^-4) of the Eddington luminosity of the galaxy. Thus, they do not
appear to match the requirements of the galaxy evolution feedback models.Comment: Invited talk, to appear in the Proceedings of the IAU Symposium 267,
"Co-Evolution of Central Black Holes and Galaxies", B.M. Peterson, R.S.
Somerville, T. Storchi-Bergmann, eds., in pres
Fast neutral outflows in nearby radio galaxies: a major source of feedback
Fast (~1000 km/s) outflows of neutral gas (from 21-cm HI absorption) are
detected in strong radio sources. The outflows occur, at least in some cases,
at distances from the radio core that range between few hundred parsecs and
kpc. These HI outflows likely originate from the interaction between radio jets
and the dense surrounding medium. The estimated mass outflow rates are
comparable to those of moderate starburst-driven superwinds. The impact on the
evolution of the host galaxies is discussed.Comment: 4 pages, 2 figures. Conference proceedings to appear in "The Central
Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San
Francisco: ASP
Dominant Nuclear Outflow Driving Mechanisms in Powerful Radio Galaxies
In order to identify the dominant nuclear outflow mechanisms in Active
Galactic Nuclei, we have undertaken deep, high resolution observations of two
compact radio sources (PKS 1549-79 and PKS 1345+12) with the Advanced Camera
for Surveys (ACS) aboard the Hubble Space Telescope. Not only are these targets
known to have powerful emission line outflows, but they also contain all the
potential drivers for the outflows: relativistic jets, quasar nuclei and
starbursts. ACS allows the compact nature (<0.15") of these radio sources to be
optically resolved for the first time. Through comparison with existing radio
maps we have seen consistency in the nuclear position angles of both the
optical emission line and radio data. There is no evidence for bi-conical
emission line features on the large-scale and there is a divergance in the
relative position angles of the optical and radio structure. This enables us to
exclude starburst driven outflows. However, we are unable to clearly
distinguish between radiative AGN wind driven outflows and outflows powered by
relativistic radio jets. The small scale bi-conical features, indicative of
such mechanisms could be below the resolution limit of ACS, especially if
aligned close to the line of sight. In addition, there may be offsets between
the radio and optical nuclei induced by heavy dust obscuration, nebular
continuum or scattered light from the AGN.Comment: 9 pages, 8 figures, emulateapj, ApJ Accepte
Mitochondrially targeted ZFNs for selective degradation of pathogenic mitochondrial genomes bearing large‐scale deletions or point mutations
We designed and engineered mitochondrially targeted obligate heterodimeric zinc finger nucleases (mtZFNs) for site‐specific elimination of pathogenic human mitochondrial DNA (mtDNA). We used mtZFNs to target and cleave mtDNA harbouring the m.8993T>G point mutation associated with neuropathy, ataxia, retinitis pigmentosa (NARP) and the “common deletion” (CD), a 4977‐bp repeat‐flanked deletion associated with adult‐onset chronic progressive external ophthalmoplegia and, less frequently, Kearns‐Sayre and Pearson's marrow pancreas syndromes. Expression of mtZFNs led to a reduction in mutant mtDNA haplotype load, and subsequent repopulation of wild‐type mtDNA restored mitochondrial respiratory function in a CD cybrid cell model. This study constitutes proof‐of‐principle that, through heteroplasmy manipulation, delivery of site‐specific nuclease activity to mitochondria can alleviate a severe biochemical phenotype in primary mitochondrial disease arising from deleted mtDNA species
Compact radio-loud broad absorption line quasars
For a long time, radio-loud Broad Absorption Line Quasars (BAL QSOs) were thought to be extremely rare objects. The absorbing troughs seen in their optical spectra are due to strong winds which probably have their origin within the inner region of the AGN, as a result of the accretion processes. Their radio emission constitutes an additional diagnostic tool which is successfully contributing new perspectives and raise new questions, with the aim to enrich our understanding of the BAL phenomenon. In this contribution, we introduce a first characterisation of the radio-loud BAL QSO population. Radio continuum spectra have been collected for a sample of 15 objects, which we present together with their radio polarisation properties. VLA maps in A configuration confirm the compactness of these objects at di erent frequencies up to 43 GHz, yielding projected linear sizes below 1 kpc. We note that many of their radio properties are common to the population of young radio-sources, like Compact Steep Spectrum (CSS) or Gigahertz- Peaked Spectrum (GPS) sources
Deep Chandra X-ray Imaging of a Nearby Radio Galaxy 4C+29.30: X-ray/Radio Connection
We report results from our deep Chandra X-ray observations of a nearby radio
galaxy, 4C+29.30 (z=0.0647). The Chandra image resolves structures on
sub-arcsec to arcsec scales, revealing complex X-ray morphology and detecting
the main radio features: the nucleus, a jet, hotspots, and lobes. The nucleus
is absorbed (N(H)=3.95 (+0.27/-0.33)x10^23 atoms/cm^2) with an unabsorbed
luminosity of L(2-10 keV) ~ (5.08 +/-0.52) 10^43 erg/s characteristic of Type 2
AGN. Regions of soft (<2 keV) X-ray emission that trace the hot interstellar
medium (ISM) are correlated with radio structures along the main radio axis
indicating a strong relation between the two. The X-ray emission beyond the
radio source correlates with the morphology of optical line-emitting regions.
We measured the ISM temperature in several regions across the galaxy to be kT ~
0.5 with slightly higher temperatures (of a few keV) in the center and in the
vicinity of the radio hotspots. Assuming these regions were heated by weak
shocks driven by the expanding radio source, we estimated the corresponding
Mach number of 1.6 in the southern regions. The thermal pressure of the X-ray
emitting gas in the outermost regions suggest the hot ISM is slightly
under-pressured with respect to the cold optical-line emitting gas and
radio-emitting plasma, which both seem to be in a rough pressure equilibrium.
We conclude that 4C+29.30 displays a complex view of interactions between the
jet-driven radio outflow and host galaxy environment, signaling feedback
processes closely associated with the central active nucleus.Comment: ApJ in pres
Mice expressing an error-prone DNA polymerase in mitochondria display elevated replication pausing and chromosomal breakage at fragile sites of mitochondrial DNA.
Expression of a proof-reading deficient form of mitochondrial DNA (mtDNA) polymerase gamma, POLG, causes early death accompanied by features of premature ageing in mouse. However, the mechanism of cellular senescence remains unresolved. In addition to high levels of point mutations of mtDNA, the POLG mutator mouse harbours linear mtDNAs. Using one- and two-dimensional agarose gel electrophoresis, we show that the linear mtDNAs derive from replication intermediates and are indicative of replication pausing and chromosomal breakage at the accompanying fragile sites. Replication fork arrest is not random but occurs at specific sites close to two cis-elements known as O(H) and O(L). Pausing at these sites may be enhanced in the case of exonuclease-deficient POLG owing to delayed resumption of DNA replication, or replisome instability. In either case, the mtDNA replication cycle is perturbed and this might explain the progeroid features of the POLG mutator mouse
Particularized protection: UNSC mandates and the protection of civilians in armed conflict
The protection of civilians at risk in armed conflict has, since the late 1990s, become institutionalized at the United Nations (UN), gaining acceptance as a normative rationale for UN peacekeeping. However, the bulk of civilians in need of protection in armed conflict are unlikely to attain it. The article develops an argument on ‘particularized protection’ - particularized in that UN Security Council (SC) mandates are formulated and adjusted over time to direct mission protection to specific subsets of civilian populations, that is, those relevant to the UN itself, the host state, other states, NGOs and the media, leaving most local civilians receiving little effective protection. Particularized protection, we argue, is a result of the institutional dynamics involving actors producing mandates - the UNSC - and those providing protection - peacekeeping missions - whereby mandates are specified to direct mission protection to selected, particularized groups. We demonstrate these dynamics in two cases, Côte d’Ivoire and Somalia
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