2,212 research outputs found
Actively deployable mobile services for adaptive web access
2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Recent Advances Concerning Certain Class of Geophysical Flows
This paper is devoted to reviewing several recent developments concerning
certain class of geophysical models, including the primitive equations (PEs) of
atmospheric and oceanic dynamics and a tropical atmosphere model. The PEs for
large-scale oceanic and atmospheric dynamics are derived from the Navier-Stokes
equations coupled to the heat convection by adopting the Boussinesq and
hydrostatic approximations, while the tropical atmosphere model considered here
is a nonlinear interaction system between the barotropic mode and the first
baroclinic mode of the tropical atmosphere with moisture.
We are mainly concerned with the global well-posedness of strong solutions to
these systems, with full or partial viscosity, as well as certain singular
perturbation small parameter limits related to these systems, including the
small aspect ratio limit from the Navier-Stokes equations to the PEs, and a
small relaxation-parameter in the tropical atmosphere model. These limits
provide a rigorous justification to the hydrostatic balance in the PEs, and to
the relaxation limit of the tropical atmosphere model, respectively. Some
conditional uniqueness of weak solutions, and the global well-posedness of weak
solutions with certain class of discontinuous initial data, to the PEs are also
presented.Comment: arXiv admin note: text overlap with arXiv:1507.0523
Giant schwannoma of thoracic vertebra: A case report
BACKGROUND,It is relatively rare for schwannomas to invade bone, but it is very rare for a large,mass to form concurrently in the paravertebral region. Surgical resection is the,only effective treatment. Because of the extensive tumor involvement and the,many important surrounding structures, the tumor needs to be fully exposed.,Most of the tumors are completely removed by posterior combined open-heart,surgery to relieve spinal cord compression, restore the stability of the spine and,maximize the recovery of nerve and spinal cord function. The main objective of,this article is to present a schwannoma that had invaded the T5 and T6 vertebral,bodies and formed a large paravertebral mass with simultaneous invasion of the,spinal canal and compression of the spinal cord.,CASE SUMMARY,A 40-year-old female suffered from intermittent chest and back pain for 8 years.,Computed tomography and magnetic resonance imaging scans showed a,paravertebral tumor of approximately 86 mm Ă 109 mm Ă 116 mm, where the,adjacent T5 and T6 vertebral bodies were invaded by the tumor, the right intervertebral,foramen was enlarged, and the tumor had invaded the spinal canal to,compress the thoracic medulla. The preoperative puncture biopsy diagnosed a,benign schwannoma. Complete resection of the tumor was achieved by a two-step,operation. In the first step, the thoracic surgeon adopted a lateral approach to,separate the thoracic tumor from the lung. In the second step, a spine surgeon,performed a posterior midline approach to dissect the tumor from the vertebral,junction through removal of the tumor from the posterior side and further,resection of the entire T5 and T6 vertebral bodies. The large bone defect was,reconstructed with titanium mesh, and the posterior root arch was nail-fixed. Due,to the large amount of intraoperative bleeding, we performed tumor angioembolization,before surgery to reduce and avoid large intraoperative bleeding. The,postoperative diagnosis of benign schwannoma was confirmed by histochemical,examination. There was no sign of tumor recurrence or spinal instability during,the 2-year follow-up.,CONCLUSION,Giant schwannoma is uncommon. In this case, a complete surgical resection of a,giant thoracic nerve sheath tumor that invaded part of the vertebral body and,compressed the spinal cord was safe and effective
Gravitational Chern-Simons Lagrangians and black hole entropy
We analyze the problem of defining the black hole entropy when Chern-Simons
terms are present in the action. Extending previous works, we define a general
procedure, valid in any odd dimensions both for purely gravitational CS terms
and for mixed gauge-gravitational ones. The final formula is very similar to
Wald's original formula valid for covariant actions, with a significant
modification. Notwithstanding an apparent violation of covariance we argue that
the entropy formula is indeed covariant.Comment: 39 page
Black Holes in Gravity with Conformal Anomaly and Logarithmic Term in Black Hole Entropy
We present a class of exact analytic and static, spherically symmetric black
hole solutions in the semi-classical Einstein equations with Weyl anomaly. The
solutions have two branches, one is asymptotically flat and the other
asymptotically de Sitter. We study thermodynamic properties of the black hole
solutions and find that there exists a logarithmic correction to the well-known
Bekenstein-Hawking area entropy. The logarithmic term might come from non-local
terms in the effective action of gravity theories. The appearance of the
logarithmic term in the gravity side is quite important in the sense that with
this term one is able to compare black hole entropy up to the subleading order,
in the gravity side and in the microscopic statistical interpretation side.Comment: Revtex, 10 pages. v2: minor changes and to appear in JHE
Dynamics of one-dimensional tight-binding models with arbitrary time-dependent external homogeneous fields
The exact propagators of two one-dimensional systems with time-dependent
external fields are presented by following the path-integral method. It is
shown that the Bloch acceleration theorem can be generalized to the
impulse-momentum theorem in quantum version. We demonstrate that an evolved
Gaussian wave packet always keeps its shape in an arbitrary time-dependent
homogeneous driven field. Moreover, that stopping and accelerating of a wave
packet can be achieved by the pulsed field in a diabatic way.Comment: 8 pages, 6 figure
The effects of degree correlations on network topologies and robustness
Complex networks have been applied to model numerous interactive nonlinear
systems in the real world. Knowledge about network topology is crucial for
understanding the function, performance and evolution of complex systems. In
the last few years, many network metrics and models have been proposed to
illuminate the network topology, dynamics and evolution. Since these network
metrics and models derive from a wide range of studies, a systematic study is
required to investigate the correlations between them. The present paper
explores the effect of degree correlation on the other network metrics through
studying an ensemble of graphs where the degree sequence (set of degrees) is
fixed. We show that to some extent, the characteristic path length, clustering
coefficient, modular extent and robustness of networks are directly influenced
by the degree correlation.Comment: 13 pages, 6 figure
Lactate Regulates Metabolic and Proinflammatory Circuits in Control of T Cell Migration and Effector Functions
Licensed by the Creative Commons Attribution Licens
New Near Horizon Limit in Kerr/CFT
The extremal Kerr black hole with the angular momentum J is conjectured to be
dual to CFT with central charges c_L=c_R=12J. However, the central charge in
the right sector remains to be explicitly derived so far. In order to
investigate this issue, we introduce new near horizon limits of (near) extremal
Kerr and five-dimensional Myers-Perry black holes. We obtain Virasoro algebras
as asymptotic symmetries and calculate the central charges associated with
them. One of them is equivalent to that of the previous studies, and the other
is non-zero, but still the order of near extremal parameter. Redefining the
algebras to take the standard form, we obtain a finite value as expected by the
Kerr/CFT correspondence.Comment: 25 pages, minor changes, references adde
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