1,481 research outputs found
3D Integral Field Observations of Ten Galactic Winds - I. Extended phase (>10 Myr) of mass/energy injection before the wind blows
We present 3D spectroscopic observations of a sample of 10 nearby galaxies
with the AAOmega-SPIRAL integral field spectrograph on the 3.9m AAT, the
largest survey of its kind to date. The double-beam spectrograph provides
spatial maps in a range of spectral diagnostics: [OIII] 5007, H-beta, Mg-b,
NaD, [OI] 6300, H-alpha, [NII] 6583, [SII] 6717, 6731. All of the objects in
our survey show extensive wind-driven filamentation along the minor axis, in
addition to large-scale disk rotation. Our sample can be divided into either
starburst galaxies or active galactic nuclei (AGN), although some objects
appear to be a combination of these. The total ionizing photon budget available
to both classes of galaxies is sufficient to ionise all of the wind-blown
filamentation out to large radius. We find however that while AGN
photoionisation always dominates in the wind filaments, this is not the case in
starburst galaxies where shock ionisation dominates. This clearly indicates
that after the onset of star formation, there is a substantial delay (> 10 Myr)
before a starburst wind develops. We show why this behavior is expected by
deriving ``ionisation'' and dynamical timescales for both AGNs and starbursts.
We establish a sequence of events that lead to the onset of a galactic wind.
The clear signature provided by the ionisation timescale is arguably the
strongest evidence yet that the starburst phenomenon is an impulsive event. A
well-defined ionisation timescale is not expected in galaxies with a protracted
history of circumnuclear star formation. Our 3D data provide important
templates for comparisons with high redshift galaxies.[Abridged]Comment: 43 pages, 30 figures, Accepted for publication in ApJ Jan-2010, Full
resolution figures available from:
http://www.aao.gov.au/AAO/local/www/rgs/work/winds/public/papers/SPIRAL_WINDS_hi-res.htm
Direct Microlensing-Reverberation Observations of the Intrinsic magnetic Structure of AGN in Different Spectral States: A Tale of Two Quasars
We show how direct microlensing-reverberation analysis performed on two
well-known Quasars (Q2237 - The Einstein Cross and Q0957 - The Twin) can be
used to observe the inner structure of two quasars which are in significantly
different spectral states. These observations allow us to measure the detailed
internal structure of quasar Q2237 in a radio quiet high-soft state, and
compare it to quasar Q0957 in a radio loud low-hard state. We find that the
observed differences in the spectral states of these two quasars can be
understood as being due to the location of the inner radii of their accretion
disks relative to the co-rotation radii of rotating intrinsically magnetic
supermassive compact objects in the centers of these quasars.Comment: 26 page manuscript with 2 tables and 2 figures, submitted to
Astronomical Journa
Characterizations of Veronese and Segre varieties
We survey the known and recent characterizations of Segre varieties and Veronesea varieties
SynCLay: Interactive Synthesis of Histology Images from Bespoke Cellular Layouts
Automated synthesis of histology images has several potential applications in
computational pathology. However, no existing method can generate realistic
tissue images with a bespoke cellular layout or user-defined histology
parameters. In this work, we propose a novel framework called SynCLay
(Synthesis from Cellular Layouts) that can construct realistic and high-quality
histology images from user-defined cellular layouts along with annotated
cellular boundaries. Tissue image generation based on bespoke cellular layouts
through the proposed framework allows users to generate different histological
patterns from arbitrary topological arrangement of different types of cells.
SynCLay generated synthetic images can be helpful in studying the role of
different types of cells present in the tumor microenvironmet. Additionally,
they can assist in balancing the distribution of cellular counts in tissue
images for designing accurate cellular composition predictors by minimizing the
effects of data imbalance. We train SynCLay in an adversarial manner and
integrate a nuclear segmentation and classification model in its training to
refine nuclear structures and generate nuclear masks in conjunction with
synthetic images. During inference, we combine the model with another
parametric model for generating colon images and associated cellular counts as
annotations given the grade of differentiation and cell densities of different
cells. We assess the generated images quantitatively and report on feedback
from trained pathologists who assigned realism scores to a set of images
generated by the framework. The average realism score across all pathologists
for synthetic images was as high as that for the real images. We also show that
augmenting limited real data with the synthetic data generated by our framework
can significantly boost prediction performance of the cellular composition
prediction task
Projective Hilbert space structures at exceptional points
A non-Hermitian complex symmetric 2x2 matrix toy model is used to study
projective Hilbert space structures in the vicinity of exceptional points
(EPs). The bi-orthogonal eigenvectors of a diagonalizable matrix are
Puiseux-expanded in terms of the root vectors at the EP. It is shown that the
apparent contradiction between the two incompatible normalization conditions
with finite and singular behavior in the EP-limit can be resolved by
projectively extending the original Hilbert space. The complementary
normalization conditions correspond then to two different affine charts of this
enlarged projective Hilbert space. Geometric phase and phase jump behavior are
analyzed and the usefulness of the phase rigidity as measure for the distance
to EP configurations is demonstrated. Finally, EP-related aspects of
PT-symmetrically extended Quantum Mechanics are discussed and a conjecture
concerning the quantum brachistochrone problem is formulated.Comment: 20 pages; discussion extended, refs added; bug correcte
A spectrum result on maximal partial ovoids of the generalized quadrangle Q(4,q), q even
AbstractThis article presents a spectrum result on maximal partial ovoids of the generalized quadrangle Q(4,q), q even. We prove that for every integer k in an interval of, roughly, size [q2/10,9q2/10], there exists a maximal partial ovoid of size k on Q(4,q), q even. Since the generalized quadrangle W(q), q even, defined by a symplectic polarity of PG(3,q) is isomorphic to the generalized quadrangle Q(4,q), q even, the same result is obtained for maximal partial ovoids of W(q), q even. As equivalent results, the same spectrum result is obtained for minimal blocking sets with respect to planes of PG(3,q), q even, and for maximal partial 1-systems of lines on the Klein quadric Q+(5,q), q even
Recommended from our members
Digital gradient sensing and analysis of dynamic crack stability, propagation, and branching
Understanding the underlying mechanisms of fracture mechanics plays a critical role in engineering design and analysis. This work investigates aspects of dynamic fracture and the transition from stable to unstable crack propagation by employing the digital gradient sensing method in conjunction with high-speed photography. Both quasi-static and dynamic loading scenarios are evaluated. Furthermore, the micromechanical fracture mechanisms are evaluated using optical microscopy and optical profilometry. Significant insights are gained regarding the relationship between loading, crack branching, and the micromechanical mechanisms that govern dynamic fracture. Differences between two models for formation of crack surface patterns, based on crack front waves and Wallner lines, are examined. Most interestingly, insights developed with respect to crack branching phenomenon, and its speed past branching have significant impact on the modeling of crack branching and dynamic fracture. Discovery of constant crack branch speed will require additional study of energy release rates associated with branching cracksEngineering Mechanic
Zettawatt-Exawatt Lasers and Their Applications in Ultrastrong-Field Physics: High Energy Front
Since its birth, the laser has been extraordinarily effective in the study
and applications of laser-matter interaction at the atomic and molecular level
and in the nonlinear optics of the bound electron. In its early life, the laser
was associated with the physics of electron volts and of the chemical bond.
Over the past fifteen years, however, we have seen a surge in our ability to
produce high intensities, five to six orders of magnitude higher than was
possible before. At these intensities, particles, electrons and protons,
acquire kinetic energy in the mega-electron-volt range through interaction with
intense laser fields. This opens a new age for the laser, the age of nonlinear
relativistic optics coupling even with nuclear physics. We suggest a path to
reach an extremely high-intensity level W/cm in the coming
decade, much beyond the current and near future intensity regime W/cm, taking advantage of the megajoule laser facilities. Such a laser at
extreme high intensity could accelerate particles to frontiers of high energy,
tera-electron-volt and peta-electron-volt, and would become a tool of
fundamental physics encompassing particle physics, gravitational physics,
nonlinear field theory, ultrahigh-pressure physics, astrophysics, and
cosmology. We focus our attention on high-energy applications in particular and
the possibility of merged reinforcement of high-energy physics and ultraintense
laser.Comment: 25 pages. 1 figur
Can WIMP spin dependent couplings explain DAMA data, in light of null results from other experiments?
Journal ArticleWe examine whether the annual modulation found by the DAMA dark matter experiment can be explained by Weakly Interacting Massive Particles (WIMPs), in light of new null results from other experiments. CDMS II has already ruled out most WIMP-nucleus spin-independent couplings as an explanation for DAMA data. Hence we here focus on spin-dependent (axial vector; SD) couplings of WIMPs to nuclei.We expand upon previous work by (i) considering the general case of coupling to both protons and neutrons and (ii) incorporating bounds from all existing experiments.We note the surprising fact that CMDS II places one of the strongest bounds on the WIMP-neutron cross section, and show that SDWIMP-neutron scattering alone is excluded.We also show that SDWIMP-proton scattering alone is allowed only for WIMP masses in the 5-13 GeV range. For the general case of coupling to both protons and neutrons, we find that, for WIMP masses above 13 GeV and below 5 GeV, there is no region of parameter space that is compatible with DAMA and all other experiments. In the range (5-13) GeV, we find acceptable regions of parameter space, including ones in which the WIMP-neutron coupling is comparable to the WIMP-proton coupling
- …