1,373 research outputs found
Similarity Measure Development for Case-Based Reasoning- A Data-driven Approach
In this paper, we demonstrate a data-driven methodology for modelling the
local similarity measures of various attributes in a dataset. We analyse the
spread in the numerical attributes and estimate their distribution using
polynomial function to showcase an approach for deriving strong initial value
ranges of numerical attributes and use a non-overlapping distribution for
categorical attributes such that the entire similarity range [0,1] is utilized.
We use an open source dataset for demonstrating modelling and development of
the similarity measures and will present a case-based reasoning (CBR) system
that can be used to search for the most relevant similar cases
Safety and environmental impact of the dual coolant blanket concept. SEAL subtask 6.2, final report
1128 Experimental intraocular tolerance of two perfluorophenantrenes (PFP's) - effects on the retinal vascular system
Safety and Environmental impact of the BOT helium cooled solid breeder blanket for DEMO. SEAL subtask 6.2, final report
Can a Lamb Reach a Haven Before Being Eaten by Diffusing Lions?
We study the survival of a single diffusing lamb on the positive half line in
the presence of N diffusing lions that all start at the same position L to the
right of the lamb and a haven at x=0. If the lamb reaches this haven before
meeting any lion, the lamb survives. We investigate the survival probability of
the lamb, S_N(x,L), as a function of N and the respective initial positions of
the lamb and the lions, x and L. We determine S_N(x,L) analytically for the
special cases of N=1 and N--->oo. For large but finite N, we determine the
unusual asymptotic form whose leading behavior is S_N(z)\simN^{-z^2}, with
z=x/L. Simulations of the capture process very slowly converge to this
asymptotic prediction as N reaches 10^{500}.Comment: 13 pages, 6 figures, IOP format; v2: small changes in response to
referee and editor comment
X-Ray/Ultraviolet Observing Campaign of the Markarian 279 Active Galactic Nucleus Outflow: a close look at the absorbing/emitting gas with Chandra-LETGS
We present a Chandra-LETGS observation of the Seyfert 1 galaxy Mrk 279. This
observation was carried out simultaneously with HST-STIS and FUSE, in the
context of a multiwavelength study of this source. The Chandra pointings were
spread over ten days for a total exposure time of ~360 ks. The spectrum of
Mrk279 shows evidence of broad emission features, especially at the wavelength
of the OVII triplet. We quantitatively explore the possibility that this
emission is produced in the broad line region (BLR). We modeled the broad UV
emission lines seen in the FUSE and HST-STIS spectra following the ``locally
optimally emitting cloud" approach. We find that the X-ray lines luminosity
derived from the best fit BLR model can match the X-ray features, suggesting
that the gas producing the UV lines is sufficient to account also for the X-ray
emission. The spectrum is absorbed by ionized gas whose total column density is
~5x10^{20} cm^{-2}. The absorption spectrum can be modeled by two distinct gas
components (log xi ~ 0.47 and 2.49, respectively) both showing a significant
outflow velocity. However, the data allow also the presence of intermediate
ionization components. The distribution of the column densities of such extra
components as a function of the ionization parameter is not consistent with a
continuous, power law-like, absorber, suggesting a complex structure for the
gas outflow for Mrk 279 (abridged).Comment: 16 pages, 12 figures. To appear in A&
Potent spinal parenchymal AAV9-mediated gene delivery by subpial injection in adult rats and pigs.
Effective in vivo use of adeno-associated virus (AAV)-based vectors to achieve gene-specific silencing or upregulation in the central nervous system has been limited by the inability to provide more than limited deep parenchymal expression in adult animals using delivery routes with the most clinical relevance (intravenous or intrathecal). Here, we demonstrate that the spinal pia membrane represents the primary barrier limiting effective AAV9 penetration into the spinal parenchyma after intrathecal AAV9 delivery. We develop a novel subpial AAV9 delivery technique and AAV9-dextran formulation. We use these in adult rats and pigs to show (i) potent spinal parenchymal transgene expression in white and gray matter including neurons, glial and endothelial cells after single bolus subpial AAV9 delivery; (ii) delivery to almost all apparent descending motor axons throughout the length of the spinal cord after cervical or thoracic subpial AAV9 injection; (iii) potent retrograde transgene expression in brain motor centers (motor cortex and brain stem); and (iv) the relative safety of this approach by defining normal neurological function for up to 6 months after AAV9 delivery. Thus, subpial delivery of AAV9 enables gene-based therapies with a wide range of potential experimental and clinical utilizations in adult animals and human patients
The Narrow-Line Regions of LINERs as Resolved with the Hubble Space Telescope
LINERs exist in the nuclei of a large fraction of luminous galaxies, but
their connection with the AGN phenomenon has remained elusive. We present
Hubble Space Telescope narrowband [O III]5007 and H-alpha+[N II] emission-line
images of the central regions of 14 galaxies with LINER nuclei. The compact, ~1
arcsec-scale, unresolved emission that dominates the line flux in ground-based
observations is mostly resolved by HST. The bulk of this emission comes from
regions with sizes of tens to hundreds of parsecs that are resolved into knots,
filaments, and diffuse gas whose morphology differs from galaxy to galaxy. Most
of the galaxies do not show clear linear structures or ionization cones
analogous to those often seen in Seyfert galaxies. An exception is NGC 1052,
the prototypical LINER, in which we find a 3 arcsec-long (~ 250 pc) biconical
structure that is oriented on the sky along the galaxy's radio jet axis. Seven
of the galaxies have been shown in previously published HST images to have a
bright compact ultraviolet nuclear source, while the other seven do not have a
central UV source. Our images find evidence of dust in the nuclear regions of
all 14 galaxies, with clear indications of nuclear obscuration in most of the
"UV-dark" cases. The data suggest that the line-emitting gas in most LINERs is
photoionized by a central source (which may be stellar, nonstellar, or a
combination thereof) but that this source is often hidden from direct view. We
find no obvious morphological differences between LINERs with detected weak
broad H-alpha wings in their spectra and those with only narrow lines.
Likewise, there is no clear morphological distinction between objects whose UV
spectra are dominated by hot stars (e.g., NGC 4569) and those that are AGN-like
(e.g., NGC 4579).Comment: Accepted for publication in the ApJ. 25 pages, 3 tables, 9 JPEG
Figure
The Host Galaxies of Narrow-Line Seyfert 1s: Evidence for Bar-Driven Fueling
We present a study of the host-galaxy morphologies of narrow- and broad-line
Seyfert 1 galaxies (NLS1s and BLS1s) based on broad-band optical images from
the Hubble Space Telescope archives. We find that large-scale stellar bars,
starting at ~1 kpc from the nucleus, are much more common in NLS1s than BLS1s.
Furthermore, the fraction of NLS1 spirals that have bars increases with
decreasing full-width at half-maximum (FWHM) of the broad component of H-beta.
These results suggest a link between the large-scale bars, which can support
high fueling rates to the inner kpc, and the high mass-accretion rates
associated with the supermassive black holes in NLS1s.Comment: 19 pages, 4 figures (1a, 1b, 2, and 3), Accepted for publication in
the Astronomical Journa
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