5,299 research outputs found
Study of odd-mass N=82 isotones with realistic effective interactions
The microscopic quasiparticle-phonon model, MQPM, is used to study the energy
spectra of the odd , N=82 isotones. The results are compared with
experimental data, with the extreme quasiparticle-phonon limit and with the
results of an unrestricted shell model (SM)
calculation. The interaction used in these calculations is a realistic two-body
G-matrix interaction derived from modern meson-exchange potential models for
the nucleon-nucleon interaction. For the shell model all the two-body matrix
elements are renormalized by the -box method whereas for the MQPM the
effective interaction is defined by the G-matrix.Comment: Elsevier latex style espart, 26 pages, submitted to Nuclear Physics
The pedicled omentoplasty and split skin graft (POSSG) for reconstruction of large chest wall defects. A validity study of 34 patients
The aim of this study was to evaluate retrospectively the results of pedicled omentoplasty and split skin graft (POSSG) in reconstructing (full thickness) chest wall defects, and to define its role as a palliative procedure for local symptom control. Thirty-four patients with recurrent breast cancer (n = 25), radiation-induced necrosis (n = 5) or sarcoma (n = 4) of the chest wall were selected for the study. All patients underwent curative or palliative chest wall resection with reconstruction by pedicled omentoplasty and split skin graft (POSSG), between 1986 and 1994. Reconstructive outcome, complications, local tumour and symptom control following surgery was measured. The most common complication was shown to be partial necrosis of the omental flap (35%), followed by respiratory problems (26%), facial hernia (26%) and thoracic wound problems (15%), which were mostly treated in a conservative way (68%). The 3-year local tumour-free interval after POSSG in patients curatively treated for breast cancer is 16%. Seventy per cent of the patients who underwent palliative resection had longstanding relief of local pain, bleeding or foetor due to local tumour growth. It can be concluded that large (full thickness) chest wall defects after resection of local recurrence, primary malignancy or osteoradionecrosis of the chest wall can successfully be reconstructed by POSSG. Chest wall resection in patients treated with palliative intention is effective in local symptom control
Family of Hermitian Low-Momentum Nucleon Interactions with Phase Shift Equivalence
Using a Schmidt orthogonalization transformation, a family of Hermitian
low-momentum NN interactions is derived from the non-Hermitian Lee-Suzuki (LS)
low-momentum NN interaction. As special cases, our transformation reproduces
the Hermitian interactions for Okubo and Andreozzi. Aside from their common
preservation of the deuteron binding energy, these Hermitian interactions are
shown to be phase shift equivalent, all preserving the empirical phase shifts
up to decimation scale Lambda. Employing a solvable matrix model, the Hermitian
interactions given by different orthogonalization transformations are studied;
the interactions can be very different from each other particularly when there
is a strong intruder state influence. However, because the parent LS
low-momentum NN interaction is only slightly non-Hermitian, the Hermitian
low-momentum nucleon interactions given by our transformations, including the
Okubo and Andreozzi ones, are all rather similar to each other. Shell model
matrix elements given by the LS and several Hermitian low-momentum interactions
are compared.Comment: 10 pages, 7 figure
The location of the broad HI absorption in 3C305: clear evidence for a jet-accelerated neutral outflow
We present high-spatial resolution 21-cm HI VLA observations of the radio
galaxy 3C305 (z=0.041). These new high-resolution data show that the ~1000 km/s
broad HI absorption, earlier detected in low-resolution WSRT observations, is
occurring against the bright, eastern radio lobe, about 1.6 kpc from the
nucleus. We use new optical spectra taken with the WHT to make a detailed
comparison of the kinematics of the neutral hydrogen with that of the ionised
gas. The striking similarity between the complex kinematics of the two gas
phases suggests that both the ionised gas and the neutral gas are part of the
same outflow. Earlier studies of the ionised gas had already found evidence for
a strong interaction between the radio jet and the interstellar medium at the
location of the eastern radio lobe. Our results show that the fast outflow
produced by this interaction also contains a component of neutral atomic
hydrogen. The most likely interpretation is that the radio jet ionises the ISM
and accelerates it to the high outflow velocities observed. Our observations
demonstrate that, following this strong jet-cloud interaction, not all gas
clouds are destroyed and that part of the gas can cool and become neutral. The
mass outflow rate measured in 3C~305 is comparable, although at the lower end
of the distribution, to that found in Ultra-Luminous IR galaxies. This suggests
that AGN-driven outflows, and in particular jet-driven outflows, can have a
similar impact on the evolution of a galaxy as starburst-driven superwinds.Comment: Accepted for publication in A&A. 7 pages, 4 figure
The disc-dominated host galaxy of FR-I radio source B2 0722+30
We present new observational results that conclude that the nearby radio
galaxy B2 0722+30 is one of the very few known disc galaxies in the
low-redshift Universe that host a classical double-lobed radio source. In this
paper we use HI observations, deep optical imaging, stellar population
synthesis modelling and emission-line diagnostics to study the host galaxy,
classify the Active Galactic Nucleus and investigate environmental properties
under which a radio-loud AGN can occur in this system. Typical for spiral
galaxies, B2 0722+30 has a regularly rotating gaseous disc throughout which
star formation occurs. Dust heating by the ongoing star formation is likely
responsible for the high infrared luminosity of the system. The optical
emission-line properties of the central region identify a Low Ionization
Nuclear Emission-line Region (LINER)-type nucleus with a relatively low [OIII]
luminosity, in particular when compared with the total power of the Fanaroff &
Riley type-I radio source that is present in this system. This classifies B2
0722+30 as a classical radio galaxy rather than a typical Seyfert galaxy. The
environment of B2 0722+30 is extremely HI-rich, with several nearby interacting
galaxies. We argue that a gas-rich interaction involving B2 0722+30 is a likely
cause for the triggering of the radio-AGN and/or the fact that the radio source
managed to escape the optical boundaries of the host galaxy.Comment: To appear in MNRAS (in press); 16 pages, 11 figures. A
full-resolution version of this paper is available at
http://www.atnf.csiro.au/people/emo004/MNRAS_Emonts_B20722_fullres.pd
A jet-induced outflow of warm gas in 3C 293
Using long slit emission-line spectra we detect a fast outflow of ionized
gas, with velocities up to 1000 km/s, in the nearby powerful radio galaxy 3C
293 (z = 0.045). The fast outflow is located about 1 kpc east of the nucleus,
in a region of enhanced radio emission due to the presence of a distorted radio
jet. We present results that indicate that this fast outflow is caused by a
jet-ISM interaction. The kinematics of the outflowing ionized gas are very
similar to those of a fast outflow of neutral hydrogen gas in this galaxy,
suggesting that both outflows are the result of the same driving mechanism.
While the mass of the outflowing ionized gas is about 1 x 10e5 M_sun, the total
HI mass involved in the neutral outflow is about 100 times higher (10e7 M_sun).
This shows that, despite the high energies that must be involved in driving the
outflow, most of the gas remains, or becomes again, neutral. Other outflows of
ionized gas, although not as pronounced as in the region of the enhanced radio
emission, are also seen in various other regions along the axis of the inner
radio jets. The regular kinematics of the emission-line gas along the major
axis of the host galaxy reveal a rotating ionized gas disk 30 kpc in extent.Comment: 15 pages, 10 figures. Accepted for publication in MNRAS. A full
resolution version can be found at
http://www.astro.rug.nl/~emonts/MF268rv.pd
Effects of Noise on Ecological Invasion Processes: Bacteriophage-mediated Competition in Bacteria
Pathogen-mediated competition, through which an invasive species carrying and
transmitting a pathogen can be a superior competitor to a more vulnerable
resident species, is one of the principle driving forces influencing
biodiversity in nature. Using an experimental system of bacteriophage-mediated
competition in bacterial populations and a deterministic model, we have shown
in [Joo et al 2005] that the competitive advantage conferred by the phage
depends only on the relative phage pathology and is independent of the initial
phage concentration and other phage and host parameters such as the
infection-causing contact rate, the spontaneous and infection-induced lysis
rates, and the phage burst size. Here we investigate the effects of stochastic
fluctuations on bacterial invasion facilitated by bacteriophage, and examine
the validity of the deterministic approach. We use both numerical and
analytical methods of stochastic processes to identify the source of noise and
assess its magnitude. We show that the conclusions obtained from the
deterministic model are robust against stochastic fluctuations, yet deviations
become prominently large when the phage are more pathological to the invading
bacterial strain.Comment: 39 pages, 7 figure
Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes
We study the spectra of neutron-rich oxygen isotopes based on chiral two- and
three-nucleon interactions. First, we benchmark our many-body approach by
comparing ground-state energies to coupled-cluster results for the same
two-nucleon interaction, with overall good agreement. We then calculate bound
excited states in 21,22,23O, focusing on the role of three-nucleon forces, in
the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral
three-nucleon forces provide important one- and two-body contributions between
valence neutrons. We find that both these contributions and an extended valence
space are necessary to reproduce key signatures of novel shell evolution, such
as the N = 14 magic number and the low-lying states in 21O and 23O, which are
too compressed with two-nucleon interactions only. For the extended space
calculations, this presents first work based on nuclear forces without
adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio
Timescales of merger, starburst and AGN activity in radio galaxy B2 0648+27
In this paper we use neutral hydrogen HI and optical spectroscopic observations to compare the timescales of a merger event, starburst episode and radio-AGN activity in the radio galaxy B2 0648+27. We detect a large ring-like structure of HI in emission around the early-type host galaxy of B2 0648+27 (M_HI = 8.5 x 10^9 Msun, diameter = 190 kpc). We interpret this as the result of a major merger that occurred > 1.5 Gyr ago. From modelling optical long-slit spectra we find that a young stellar population of 0.3 Gyr, indicative of a past starburst event, dominates the stellar light throughout the galaxy. The off-set in time between the merger event and the starburst activity in B2 0648+27 suggests that the starburst was triggered in an advanced stage of the merger, which can be explained if the gas-rich progenitor galaxies contained a bulge. Although the exact age of the radio source remains uncertain, there appears to be a significant time-delay between the merger/starburst event and the current episode of radio-AGN activity. We also observe an outflow of emission-line gas in this system, which is likely related to superwinds driven by the stars that formed during the starburst event. We argue that the radio galaxy B2 0648+27 is a link in the evolutionary sequence between Ultra-Luminous Infrared Galaxies (ULIRGs) and genuine early-type galaxies
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