5,027 research outputs found
Stellar kinematics and populations out to 1.5 effective radius in the elliptical galaxy NGC4636
We present high quality long slit spectra along the major and minor axes out
to 1.5 effective radius () of the massive galaxy NGC4636 taken by
Hobby-Eberly Telescope (HET). Using Fourier Correlation Quotient (FCQ) method,
we measured the stellar line-of-sight velocity distribution along the axes.
Furthermore, six Lick/IDS indices
() are derived from the
clean spectrum. By comparing the measured absorption line strengths with the
predictions of Simple Stellar Populations (SSP) models, we derived ages, total
metallicity and abundance profiles of the galaxy. This galaxy presents
old and over abundant stellar populations. Indeed, using the SSP
model, we obtained the broadband color profiles. The theoretical colors match
well with the measured colors and present red sharp peaks at the galaxy center.
The sharp peaks of the colors are mainly shaped by the high metallicity in the
galaxy center. Interestingly, the galaxy has steep negative metallicity
gradients, but trend flattens outwards. This result likly suggests that the
center and outer regions of the galaxy formed through different formation
process.Comment: 14 pages, 7 figures, accepted by RA
A Case of Henoch-Schonlein Purpura Associated with Rotavirus Infection in an Elderly Asian Male and Review of the Literature.
BACKGROUND Henoch-Schönlein purpura (HSP), a small vessel vasculitis mediated by deposition of immune-complexes containing IgA in the skin, gut, and glomeruli, often presents with abdominal pain, purpuric rash in the lower extremities and buttocks, joint pain, and hematuria. The disease most commonly targets children but can affect adults who tend to have a worse prognosis. CASE REPORT We discuss a case of HSP in an elderly Chinese male who presented with severe proximal bowel inflammation, vasculitic rash, and proteinuria; he was found to have positive stool rotavirus and giardia. He improved significantly with high dose steroids. We believe rotavirus may have been a triggering event in this patient. A brief review of the literature is also presented. CONCLUSIONS This is the first case report describing a classic presentation of HSP in an adult following a rotavirus infection. HSP can cause significant morbidity and mortality in adult patients predominantly from progressive renal failure; therefore careful management and monitoring is important. GI infections seem to be a common trigger for HSP and this case report suggests that rotavirus may be part of the spectrum
Energized soft tissue dissection in surgery simulation
With the development of virtual reality technology, surgery simulation has become an effective way to train the operation skills for surgeons. Soft tissue dissection, as one of the most frequently performed operations in surgery, is indispensable to an immersive and high-fidelity surgery simulator. Energized dissection tools are much more commonly used than the traditional sharp scalpels for patient safety. Unfortunately, the interaction of such tools with the soft tissues has been largely ignored in the research of surgical simulators. In this paper, we have proposed an energized soft tissue dissection model. We categorize the soft tissues into three types (fascia, membrane, and fat) and simulate their physical property accordingly. The dissection algorithm we propose employs an edge-based structure, which offers an effective mechanism for the generation of incisions dissected with energized tools. The mesh topology will not be changed when it is dissected by an energized tool, rather it is controlled by the heat transfer model. Our dissection method is highly compatible and efficient to the physically based simulation resolved by a pre-factorized linear system. We have proposed an energized soft tissue dissection model. We categorize the soft tissues into three types (fascia, membrane, and fat) and simulate their physical property accordingly. The dissection algorithm employs an edge-based structure, which offers an effective mechanism for the generation of incisions dissected with energized tools. Our dissection method is highly compatible and efficient to the physically based simulation resolved by a pre-factorized linear system
Radially extended kinematics and stellar populations of the massive ellipticals NGC1600, NGC4125 and NGC7619. Constraints on the outer dark halo density profile
We present high quality long slit spectra along the major and minor axes out
to 1.5-2 Re (14-22 kpc) of three bright elliptical galaxies (NGC1600, NGC4125,
NGC7619) obtained at the Hobby-Eberly Telescope (HET). We derive stellar
kinematic profiles and Lick/IDS indices (Hbeta, Mgb, Fe5015, Fe5270, Fe5335,
Fe5406). Moreover, for NGC4125 we derive gas kinematics and emission line
strengths. We model the absorption line strengths using Simple Stellar
Populations models that take into account the variation of [\alpha/Fe] and
derive ages, total metallicity and element abundances. Overall, we find that
the three galaxies have old and [\alpha/Fe] overabundant stellar populations
with no significant gradients. The metallicity is supersolar at the center with
a strong negative radial gradient. For NGC4125, several pieces of evidence
point to a recent dissipational merger event. We calculate the broad band color
profiles with the help of SSP models. All of the colors show sharp peaks at the
center of the galaxies, mainly caused by the metallicity gradients, and agree
well with the measured colors. Using the Schwarzschild's axisymmetric orbit
superposition technique, we model the stellar kinematics to constrain the dark
halos of the galaxies. We use the tight correlation between the Mgb strength
and local escape velocity to set limits on the extent of the halos by testing
different halo sizes. Logarithmic halos - cut at 60 kpc -minimize the overall
scatter of the Mgb-Vesc relation. Larger cutoff radii are found if the dark
matter density profile is decreasing more steeply at large radii.Comment: Accepted for publication in Astronomy and Astrophysic
Identifying Functional Requirements for Flexible Airspace Management Concept Using Human-In-The-Loop Simulations
Flexible Airspace Management (FAM) is a mid- term Next Generation Air Transportation System (NextGen) concept that allows dynamic changes to airspace configurations to meet the changes in the traffic demand. A series of human-in-the-loop (HITL) studies have identified procedures and decision support requirements needed to implement FAM. This paper outlines a suggested FAM procedure and associated decision support functionality based on these HITL studies. A description of both the tools used to support the HITLs and the planned NextGen technologies available in the mid-term are presented and compared. The mid-term implementation of several NextGen capabilities, specifically, upgrades to the Traffic Management Unit (TMU), the initial release of an en route automation system, the deployment of a digital data communication system, a more flexible voice communications network, and the introduction of a tool envisioned to manage and coordinate networked ground systems can support the implementation of the FAM concept. Because of the variability in the overall deployment schedule of the mid-term NextGen capabilities, the dependency of the individual NextGen capabilities are examined to determine their impact on a mid-term implementation of FAM. A cursory review of the different technologies suggests that new functionality slated for the new en route automation system is a critical enabling technology for FAM, as well as the functionality to manage and coordinate networked ground systems. Upgrades to the TMU are less critical but important nonetheless for FAM to be fully realized. Flexible voice communications network and digital data communication system could allow more flexible FAM operations but they are not as essential
The string of variable density: perturbative and non-perturbative results
We obtain systematic approximations for the modes of vibration of a string of
variable density, which is held fixed at its ends. These approximations are
obtained iteratively applying three theorems which are proved in the paper and
which hold regardless of the inhomogeneity of the string. Working on specific
examples we obtain very accurate approximations which are compared both with
the results of WKB method and with the numerical results obtained with a
collocation approach. Finally, we show that the asymptotic behaviour of the
energies of the string obtained with perturbation theory, worked to second
order in the inhomogeinities, agrees with that obtained with the WKB method and
implies a different functional dependence on the density that in two and higher
dimensions.Comment: 28 pages, 3 tables, 6 figure
X-ray Tail in NGC 7619
We present new observational results of NGC 7619, an elliptical galaxy with a
prominent X-ray tail and a dominant member of the Pegasus group. With Chandra
and XMM-Newton observations, we confirm the presence of a long X-ray tail in
the SW direction; moreover, we identify for the first time a sharp
discontinuity of the X-ray surface brightness in the opposite (NE) side of the
galaxy. The density, temperature and pressure jump at the NE discontinuity
suggest a Mach number ~1, corresponding to a galaxy velocity of ~500 km s-1,
relative to the surrounding hot gas. Spectral analysis of these data shows that
the Iron abundance of the hot gaseous medium is much higher (1-2 solar) near
the center of NGC 7619 and in the tail extending from the core than in the
surrounding regions (< 1/2 solar), indicating that the gas in the tail is
originated from the galaxy. The possible origin of the head-tail structure is
either on-going ram-pressure stripping or sloshing. The morphology of the
structure is more in line with a ram pressure stripping phenomenon, while the
position of NGC 7619 at the center of the Pegasus I group, and its dominance,
would prefer sloshing.Comment: ApJ accepted to appear in the 2008 December 1 issue; Added discussion
on sloshin
Revisiting the quantum Szilard engine with fully quantum considerations
By considering level shifting during the insertion process we revisit the
quantum Szilard engine (QSZE) with fully quantum consideration. We derive the
general expressions of the heat absorbed from thermal bath and the total work
done to the environment by the system in a cycle with two different cyclic
strategies. We find that only the quantum information contributes to the
absorbed heat, and the classical information acts like a feedback controller
and has no direct effect on the absorbed heat. This is the first demonstration
of the different effects of quantum information and classical information for
extracting heat from the bath in the QSZE. Moreover, when the well width
or the temperature of the bath
the QSZE reduces to the classical Szilard engine (CSZE), and the total work
satisfies the relation as obtained by
Sang Wook Kim et al. [Phys. Rev. Lett. 106, 070401 (2011)] for one particle
case.Comment: 17 pages, 3 figures, to be published in Annals of Physics(NY
Effective potential in three-dimensional O(N) models
We consider the effective potential in three-dimensional models with O(N)
symmetry. For generic values of N, and in particular for the physically
interesting cases N=0,1,2,3, we determine the six-point and eight-point
renormalized coupling constants which parametrize its small-field expansion.
These estimates are obtained from the analysis of their -expansion,
taking into account the exact results in one and zero dimensions, and, for the
Ising model (i.e. N=1), the accurate high-temperature estimates in two
dimensions. They are compared with the available results from other approaches.
We also obtain corresponding estimates for the two-dimensional O() models.Comment: 22 pages, revtex, 2 fig
Population boundaries for compact white-dwarf binaries in LISA's amplitude-frequency domain
In an earlier investigation, we proposed population boundaries for both
inspiralling and mass-transferring double white dwarf (DWD) systems in the
distance independent "absolute" amplitude-frequency domain of the proposed
space-based gravitational-wave (GW) detector, {\it LISA}. The degenerate zero
temperature mass-radius (M-R) relationship of individual white dwarf stars that
we assumed, in combination with the constraints imposed by Roche geometries,
permits us to identify five key population boundaries for DWD systems in
various phases of evolution. Here we use the non-zero entropy donor M-R
relations of \cite{DB2003} to modify these boundaries for both DWD and neutron
star-white dwarf (NSWD) binary systems. We find that the mass-transferring
systems occupy a larger fraction of space in ``absolute'' amplitude-frequency
domain compared to the simpler T=0 donor model. We also discuss how these
boundaries are modified with the new evolutionary phases found by
\cite{Deloyeetal2007}. In the initial contact phase, we find that the contact
boundaries, which are the result of end of inspiral evolution, would have some
width, as opposed to an abrupt cut-off described in our earlier T=0 model. This
will cause an overlap between a DWDs & NSWDs evolutionary trajectories,
making them indistinguishable with only LISA observations within this region.
In the cooling phase of the donor, which follows after the adiabatic donor
evolution, the radius contracts, mass-transfer rate drops and slows down the
orbital period evolution. Depending upon the entropy of the donor, these
systems may then lie inside the fully degenerate T=0 boundaries, but LISA may
be unable to detect these systems as they might be below the sensitivity limit
or within the unresolved DWD background noise.Comment: 16 pages, 3 figures, 1 table, accepted to Astrophysical Journal;
manuscript has been significantly improved from previous version as per
referees comments, to include the effects of non-zero entropy WD donors on
population boundarie
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