24,244 research outputs found
The default risk of high-yield bonds.
This paper investigates the default behavior of original issue rated non-convertible high-yield bonds. The hazard model simultaneously estimates the impact of bond age, firm- and issue-specific characteristics, and changing economic conditions. The specification used models the impact of the time since issuance semi-parametrically, corrects for unobserved heterogeneity and allows for the possibility that outstanding bonds may default in the future. Our findings, based on a sample of 579 individual high-yield bonds issued between 1977 and 1989, suggest that, after controlling for annual changes in economic conditions, default rates increase with age. Bond characteristics at the time of issuance also impact the default behavior. BB rated bonds tend to have significantly lower default rates compared to CCC rated bonds; bonds with higher coupon rates have significantly higher default rates. In addition, high-yield bonds issued prior to 1980 experienced significantly lowerd default rates.Default; Risk; Bonds;
Broken Symmetry as a Stabilizing Remnant
The Goldberger-Wise mechanism enables one to stabilize the length of the
warped extra dimension employed in Randall-Sundrum models. In this work we
generalize this mechanism to models with multiple warped throats sharing a
common ultraviolet brane. For independent throats this generalization is
straight forward. If the throats possess a discrete interchange symmetry like
Z_n the stabilizing dynamics may respect the symmetry, resulting in equal
throat lengths, or they may break it. In the latter case the ground state of an
initially symmetric configuration is a stabilized asymmetric configuration in
which the throat lengths differ. We focus on two- (three-) throat setups with a
Z_2 (Z_3) interchange symmetry and present stabilization dynamics suitable for
either breaking or maintaining the symmetry. Though admitting more general
application, our results are relevant for existing models in the literature,
including the two throat model with Kaluza-Klein parity and the three throat
model of flavor based on a broken Z_3 symmetry.Comment: 23 pages; v2 minor cosmetic chang
Semantic annotation in ubiquitous healthcare skills-based learning environments
This paper describes initial work on developing a semantic annotation system for the augmentation of skills-based learning for Healthcare. Scenario driven skills-based learning takes place in an augmented hospital ward simulation involving a patient simulator known as SimMan. The semantic annotation software enables real-time annotations of these simulations for debriefing of the students, student self study and better analysis of the learning approaches of mentors. A description of the developed system is provided with initial findings and future directions for the work.<br/
Switching dynamics of spatial solitary wave pixels
Separatrices and scaling laws in the switching dynamics of spatial solitary wave pixels are investigated. We show that the dynamics in the full model are similar to those in the plane-wave limit. Switching features may be indicated and explained by the motion of the (complex) solitary wave amplitude in the phase plane. We report generalization, into the domain of transverse effects, of the pulse area theorem for the switching process and a logarithmic law for the transient dynamics. We also consider, for what is the first time to our knowledge, phase-encoded address of solitary pixels and find that a near-square-wave temporal switching pattern is permitted without (transverse) cross switching
Chaos in a modified Henon-Heiles system describing geodesics in gravitational waves
A Hamiltonian system with a modified Henon-Heiles potential is investigated.
This describes the motion of free test particles in vacuum gravitational
pp-wave spacetimes with both quadratic ("homogeneous") and cubic
("non-homogeneous") terms in the structural function. It is shown that, for
energies above a certain value, the motion is chaotic in the sense that the
boundaries separating the basins of possible escapes become fractal.
Similarities and differences with the standard Henon-Heiles and the monkey
saddle systems are discussed. The box-counting dimension of the basin
boundaries is also calculated.Comment: 11 pages, 7 figures, LaTeX. To appear in Phys. Lett.
Neutrinos that violate CPT, and the experiments that love them
Recently we proposed a framework for explaining the observed evidence for
neutrino oscillations without enlarging the neutrino sector, by introducing CPT
violating Dirac masses for the neutrinos. In this paper we continue the
exploration of the phenomenology of CPT violation in the neutrino sector. We
show that our CPT violating model fits the existing SuperKamiokande data at
least as well as the standard atmospheric neutrino oscillation models. We
discuss the challenge of measuring CP violation in a neutrino sector that also
violates CPT. We point out that the proposed off-axis extension of MINOS looks
especially promising in this regard. Finally, we describe a method to compute
CPT violating neutrino effects by mocking them up with analog matter effects.Comment: 17 pages, 3 eps figure
Bulge-Disk Decompositions and Structural Bimodality of Ursa Major Cluster Spiral Galaxies
We present bulge and disk (B/D) decompositions of existing K'-band surface
brightness profiles for 65 Ursa Major cluster spiral galaxies. This improves
upon the disk-only fits of Tully et al. (1996). The 1996 disk fits were used by
Tully & Verheijen (1997) for their discovery of the bimodality of structural
parameters in the UMa cluster galaxies. It is shown that our new 1D B/D
decompositions yield disk structural parameters that differ only slightly from
the basic fits of Tully et al. and evidence for structural bimodality of UMa
galaxies is maintained. Our B/D software for the decomposition of 1D surface
brightness profiles of galaxies uses a non-linear minimization scheme to
recover the best fitting Sersic bulge and exponential disk while accounting for
the possible presence of a compact nucleus and spiral arms and for the effects
of seeing and disk truncations. In agreement with Tully & Verheijen, we find
that the distribution of near-infrared disk central surface brightnesses is
bimodal with an F-test confidence of 80%. There is also strong evidence for a
local minimum in the luminosity function at M_K' ~ -22. A connection between
the brightness bimodality and a dynamical bimodality, based on new HI line
widths, is identified. The B/D parameters are presented in an Appendix.Comment: Accepted for publication in MNRA
Visual BFI: an Exploratory Study for Image-based Personality Test
This paper positions and explores the topic of image-based personality test.
Instead of responding to text-based questions, the subjects will be provided a
set of "choose-your-favorite-image" visual questions. With the image options of
each question belonging to the same concept, the subjects' personality traits
are estimated by observing their preferences of images under several unique
concepts. The solution to design such an image-based personality test consists
of concept-question identification and image-option selection. We have
presented a preliminary framework to regularize these two steps in this
exploratory study. A demo version of the designed image-based personality test
is available at http://www.visualbfi.org/. Subjective as well as objective
evaluations have demonstrated the feasibility of image-based personality test
in limited questions
Solving the Cooling Flow Problem through Mechanical AGN Feedback
Unopposed radiative cooling of plasma would lead to the cooling catastrophe,
a massive inflow of condensing gas, manifest in the core of galaxies, groups
and clusters. The last generation X-ray telescopes, Chandra and XMM, have
radically changed our view on baryons, indicating AGN heating as the balancing
counterpart of cooling. This work reviews our extensive investigation on
self-regulated heating. We argue that the mechanical feedback, based on massive
subrelativistic outflows, is the key to solving the cooling flow problem, i.e.
dramatically quenching the cooling rates for several Gyr without destroying the
cool-core structure. Using a modified version of the 3D hydrocode FLASH, we
show that bipolar AGN outflows can further reproduce fundamental observed
features, such as buoyant bubbles, weak shocks, metals dredge- up, and
turbulence. The latter is an essential ingredient to drive nonlinear thermal
instabilities, which cause the formation of extended cold gas, a residual of
the quenched cooling flow and, later, fuel for the feedback engine. Compared to
clusters, groups and galaxies require a gentler mechanical feedback, in order
to avoid catastrophic overheating. We highlight the essential characteristics
for a realistic AGN feedback, with emphasis on observational consistency.Comment: Accepted by AN; 4 pages, 2 figure
- …