1,567 research outputs found
The cool wake around 4C 34.16 as seen by XMM-Newton
We present XMM-Newton observations of the wake-radiogalaxy system 4C34.16,
which shows a cool and dense wake trailing behind 4C34.16's host galaxy. A
comparison with numerical simulations is enlightening, as they demonstrate that
the wake is produced mainly by ram pressure stripping during the galactic
motion though the surrounding cluster. The mass of the wake is a substantial
fraction of the mass of an elliptical galaxy's X-ray halo. This observational
fact supports a wake formation scenario similar to the one demonstrated
numerically by Acreman et al (2003): the host galaxy of 4C34.16 has fallen into
its cluster, and is currently crossing its central regions. A substantial
fraction of its X-ray halo has been stripped by ram pressure, and remains
behind to form the galaxy wake.Comment: 9 pages, 6 figures, accepted for publication in MNRA
A Chandra study of particle acceleration in the multiple hotspots of nearby radio galaxies
We present Chandra observations of a small sample of nearby classical double
radio galaxies which have more than one radio hotspot in at least one of their
lobes. The X-ray emission from the hotspots of these comparatively low-power
objects is expected to be synchrotron in origin, and therefore to provide
information about the locations of high-energy particle acceleration. In some
models of the relationship between the jet and hotspot the hotspots that are
not the current jet termination point should be detached from the energy supply
from the active nucleus and therefore not capable of accelerating particles to
high energies. We find that in fact some secondary hotspots are X-ray sources,
and thus probably locations for high-energy particle acceleration after the
initial jet termination shock. In detail, though, we show that the spatial
structures seen in X-ray are not consistent with naive expectations from a
simple shock model: the current locations of the acceleration of the
highest-energy observable particles in powerful radio galaxies need not be
coincident with the peaks of radio or even optical emission.Comment: Accepted for ApJ. 33 pages, 8 figures inc. 2 in colo
Measuring fidelity to behavioural support delivery for smoking cessation and its association with outcomes
BACKGROUND AND AIMS: Behavioural support increases smoking cessation in clinical settings, but effect sizes differ among providers, due possibly to variations in delivery. This study evaluates a measure ('fidelity index') intended to capture fidelity to delivery of content- and interaction-based items of a behavioural support (BS) for smoking cessation and the association of fidelity with quit rates. METHODS: A fidelity index for scoring the adherence and quality domains of a specific BS intervention, '5As for quit', was developed by classifying the intervention components using the taxonomy of behaviour change techniques. The index was applied to code 154 BS sessions audiotaped among 18 chest clinics in Pakistan to assess their fidelity and explore reliability of coding. The association between intervention fidelity and successful quit achieved by the same providers in a previous study was explored using regression analysis. RESULTS: The index represented two domains: adherence to delivery of content-based activities of 5As (37 items) and quality of interaction-based activities (eight items). The intercoder reliability was good for content-based (average Krippendorff's α = 0.80) and moderate for interaction-based (average Krippendorff's α = 0.66) items. Approximately 70% (intraclass correlation coefficient: adherence scores = 0.72, quality scores = 0.71) of variation in BS delivery was contributed by providers, which increased to 97% (g-coefficient: adherence scores = 0.973, quality scores = 0.974) after accounting for other sources of variation. Higher quit rates were positively associated with average quality scores [risk ratio = 2.15; 95% confidence interval (CI) = 1.43-3.24], but negatively associated with average adherence scores (risk ratio = 0.55; 95% CI = 0.40-0.77) within services. CONCLUSIONS: The fidelity index is a reliable measure for quantifying intervention fidelity of delivering smoking cessation behavioural support. Recommended revisions of the fidelity index include incorporation of additional interaction-based items, such as the relational techniques used in motivational interviewing
Sub-Arcsecond Imaging of 3C123:108-GHz Continuum Observations of the Radio Hotspots
We present the results of sub-arcsecond 108 GHz continuum interferometric
observations toward the radio luminous galaxy 3C123. Using multi-array
observations, we utilize the high u,v dynamic range of the BIMA millimeter
array to sample fully spatial scales ranging from 0.5" to 50". This allows us
to make one-to-one comparisons of millimeter-wavelength emission in the radio
lobes and hotspots to VLA centimeter observations at 1.4, 4.9, 8.4, and 15 GHz.
At 108 GHz, the bright, eastern double hotspot in the southern lobe is
resolved. This is only the second time that a multiple hotspot region has been
resolved in the millimeter regime. We model the synchrotron spectra of the
hotspots and radio lobes using simple broken power-law models with high energy
cutoffs, and discuss the hotspot spectra and their implications for models of
multiple hotspot formation.Comment: 16 pages, 3 Figures, ApJ Accepte
Reactions of Rhenium and Manganese Carbonyl Complexes with 1,8-bis(diphenylphosphino)naphthalene: Ligand Chelation, CâH and CâP bond-cleavage Reactions
Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(Îș1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{Îș1:Îș1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(Îș2-PPh2C10H6PPh2)] (3). Compounds 1â3 are formed by ReâRe bond cleavage and PâC and CâH bond activation of the dppn ligand. Each of these three complexes have three CO groups arranged in facial fashion. Compound 1 contains a chelating cyclometalated diphenylnaphthylphosphine ligand and a terminally coordinated PPh2H ligand. Compound 2 consists of an orthometalated dppn-dioxide ligand coordinated in a Îș1:Îș1:η1-fashion via both the oxygen atoms and ortho-carbon atom of one of the phenyl rings. Compound 3 consists of an unchanged chelating dppn ligand and a terminal Cl ligand. Treatment of [Mn2(CO)8(MeCN)2] with a slight excess of dppn in refluxing toluene at 72 °C, gave the previously reported [Mn2(CO)8(ÎŒ-PPh2)2] (4), formed by cleavage of CâP bonds, and the new compound fac-[MnCl(CO)3(Îș2-PPh2C10H6PPh2)] (5), which has an unaltered chelating dppn and a terminal Cl ligand. In sharp contrast, reaction of [Mn2(CO)8(MeCN)2] with slight excess of dppn at room temperature yielded the dimanganese [Mn2(CO)9{Îș1-PPh2(C10H7)}] (6) in which the diphenylnaphthylphosphine ligand, formed by facile cleavage of one of the PâC bonds, is axially coordinated to one Mn atom. Compound 6 was also obtained from the reaction of [Mn2(CO)9(MeCN)] with dppn at room temperature. The XRD structures of complexes 1â3, 5, 6 are reported
Sexually dimorphic tibia shape is linked to natural osteoarthritis in STR/Ort mice
Human osteoarthritis (OA) is detected only at late stages. Male STR/Ort mice develop knee OA spontaneously with known longitudinal trajectory, offering scope to identify OA predisposing factors. We exploit the lack of overt OA in female STR/Ort and in both sexes of parental, control CBA mice to explore whether early divergence in tibial bone mass or shape are linked to emergent OA
PKS B1545-321: Bow shocks of a relativistic jet?
Sensitive, high resolution images of the double-double radio galaxy PKS
B1545-321 reveal detailed structure, which we interpret in the light of
previous work on the interaction of restarted jets with pre-existing relict
cocoons. We have also examined the spectral and polarization properties of the
source, the color distribution in the optical host and the environment of this
galaxy in order to understand its physical evolution. We propose that the
restarted jets generate narrow bow shocks and that the inner lobes are a
mixture of cocoon plasma reaccelerated at the bow shock and new jet material
reaccelerated at the termination shock. The dynamics of the restarted jets
implies that their hot spots advance at mildly relativistic speeds with
external Mach numbers of at least 5. The existence of supersonic hot spot Mach
numbers and bright inner lobes is the result of entrainment causing a reduction
in the sound speed of the pre-existing cocoon. The interruption to jet activity
in PKS B1545-321 has been brief - lasting less than a few percent of the
lifetime of the giant radio source. The host
galaxy is located at the boundary of a large scale filamentary structure, and
shows blue patches in color distribution indicative of a recent merger, which
may have triggered the Mpc-scale radio galaxy.Comment: 26 pages including 1 table and 16 figures. To appear in MNRA
Canonical Particle Acceleration in FRI Radio Galaxies
Matched resolution multi-frequency VLA observations of four radio galaxies
are used to derive the asymptotic low energy slope of the relativistic electron
distribution. Where available, low energy slopes are also determined for other
sources in the literature. They provide information on the acceleration physics
independent of radiative and other losses, which confuse measurements of the
synchrotron spectra in most radio, optical and X-ray studies. We find a narrow
range of inferred low energy electron energy slopes, n(E)=const*E^-2.1 for the
currently small sample of lower luminosity sources classified as FRI (not
classical doubles). This distribution is close to, but apparently inconsistent
with, the test particle limit of n(E)=const*E^-2.0 expected from strong
diffusive shock acceleration in the non-relativistic limit. Relativistic shocks
or those modified by the back-pressure of efficiently accelerated cosmic rays
are two alternatives to produce somewhat steeper spectra. We note for further
study the possiblity of acceleration through shocks, turbulence or shear in the
flaring/brightening regions in FRI jets as they move away from the nucleus.
Jets on pc scales and the collimated jets and hot spots of FRII (classical
double) sources would be governed by different acceleration sites and
mechanisms; they appear to show a much wider range of spectra than for FRI
sources.Comment: 16 figures, including 5 color. Accepted to Astrophysical Journa
- âŠ