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Atmospheric predictability of the martian atmosphere: from low-dimensional dynamics to operational forecasting?
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The Structure of TGB Phases
We study the transition from the cholesteric phase to two TGB phases near
the upper critical twist : the Renn-Lubensky TGB phase, with layer
normal rotating in a plane perpendicular to the pitch axis, and the Bordeaux
TGB phase, with the layer normal rotating on a cone parallel to the pitch
axis. We calculate properties, including order-parameter profiles, of both
phases.Comment: 4 pages, 4 figures, Submitted to Physical Review E, Rapid
Communications, September 5, 2003; Revised manuscript (to the paper submitted
on March 18, 2003, cond-mat/0303365)that includes an important missing
reference and presents an improved analysis of a generalized mode
Cell and animal models of SARS-CoV-2 pathogenesis and immunity
The spread of the novel virus SARS coronavirus 2 (SARS-CoV-2) was explosive, with cases first identified in December 2019, and >22 million people infected and >775,000 deaths as of August 2020. SARS-CoV-2 can cause severe respiratory disease in humans leading to coronavirus disease 2019 (COVID-19). The development of effective clinical interventions, such as antivirals and vaccines that can limit or even prevent the burden and spread of SARS-CoV-2, is a global health priority. Testing of leading antivirals, monoclonal antibody therapies and vaccines against SARS-CoV-2 will require robust animal and cell models of viral pathogenesis. In this Special Article, we discuss the cell-based and animal models of SARS-CoV-2 infection and pathogenesis that have been described as of August 2020. We also outline the outstanding questions for which researchers can leverage animal and cell-based models to improve our understanding of SARS-CoV-2 pathogenesis and protective immunity. Taken together, the refinement of models of SARS-CoV-2 infection will be critical to guide the development of therapeutics and vaccines against SARS-CoV-2 to end the COVID-19 pandemic
Boundary Conditions and Quasilocal Energy in the Canonical Formulation of All 1+1 Models of Gravity
Within a first-order framework, we comprehensively examine the role played by
boundary conditions in the canonical formulation of a completely general
two-dimensional gravity model. Our analysis particularly elucidates the
perennial themes of mass and energy. The gravity models for which our arguments
are valid include theories with dynamical torsion and so-called generalized
dilaton theories (GDTs). Our analysis of the canonical action principle (i)
provides a rigorous correspondence between the most general first-order
two-dimensional Einstein-Cartan model (ECM) and GDT and (ii) allows us to
extract in a virtually simultaneous manner the ``true degrees of freedom'' for
both ECMs and GDTs. For all such models, the existence of an absolutely
conserved (in vacuo) quantity C is a generic feature, with (minus) C
corresponding to the black-hole mass parameter in the important special cases
of spherically symmetric four-dimensional general relativity and standard
two-dimensional dilaton gravity. The mass C also includes (minimally coupled)
matter into a ``universal mass function.'' We place particular emphasis on the
(quite general) class of models within GDT possessing a Minkowski-like
groundstate solution (allowing comparison between and the
Arnowitt-Deser-Misner mass for such models).Comment: REVTeX, 41 pages, 2 Postscript figures, 10 macro
Holographic Description of AdS Cosmologies
To gain insight in the quantum nature of the big bang, we study the dual
field theory description of asymptotically anti-de Sitter solutions of
supergravity that have cosmological singularities. The dual theories do not
appear to have a stable ground state. One regularization of the theory causes
the cosmological singularities in the bulk to turn into giant black holes with
scalar hair. We interpret these hairy black holes in the dual field theory and
use them to compute a finite temperature effective potential. In our study of
the field theory evolution, we find no evidence for a "bounce" from a big
crunch to a big bang. Instead, it appears that the big bang is a rare
fluctuation from a generic equilibrium quantum gravity state.Comment: 34 pages, 8 figures, v2: minor changes, references adde
Thermal Giant Graviton with Non-commutative Dipole Field
Using the type II near-extremal 3D-branes solution we apply the T-duality and
smeared twist to construct the supergravity backgrounds which dual to the 4D
finite temperature non-commutative dipole field theories. We first consider the
zero-temperature system in which, depending on the property of dipole vectors
it may be N=2, N=1 or N=0 theory. We investigate the rotating D3-brane
configurations moving on the spactimes and show that, for the cases of N=2 and
N =1 the rotating D3-brane could be blowed up to the stable spherical
configuration which is called as giant graviton and has a less energy than the
point-like graviton. The giant graviton configuration is stable only if its
angular momentum was less than a critical value of which is an increasing
function of the dipole strength. For the case of non-supersymmetric theory,
however, the spherical configuration has a larger energy than the point-like
graviton. We also find that the dipole field always render the dual giant
graviton to be more stable than the point-like graviton. The relation of dual
giant graviton energy with its angular momentum, which in the AdS/CFT
correspondence being the operator anomalous dimension is obtained. We
furthermore show that the temperature does not change the property of the giant
graviton, while it will render the dual giant graviton to be unstable.Comment: Latex 20 pages, add comments about BPS bound below (3.8
Spectra of Coherent Smith-Purcell Radiation Observed from Short Electron Bunches: Numerical and Experimental Studies
MOPWA056 - ISBN978-3-95450-122-9International audienceThere is a significant interest in the development of compact particle accelerators within research areas including X-ray and THz (T-ray) sources of radiation, particle physics and medical sciences. To support the progress in these areas, non-invasive, electron beam diagnostics that are capable of measuring a single femtosecond electron bunch are required. At the current stage such beam diagnostics for femtosecond-long electron bunches are still not available. The goal of the work presented is to understand the spectral characteristics of coherent Smith-Purcell radiation to enable its quick and reliable interpretation including the longitudinal profile reconstruction of electron bunches. The research presented comprises results from numerical modelling and experimental studies. Using the numerical data, we discuss the radiated spectra dependence on the electron bunch profile and analyse the results. We also discuss the experimental data and compare it with theoretical predictions
Utilidad de las técnicas de Giemsa y Warthin Starry para el diagnóstico de gastritis causadas por Helicobacter spp en cerdos.
Las gastritis, para el sector productor porcino, continĂşan siendo una enfermedad subdiagnosticada que no solo trae pĂ©rdidas significativas para los productores, sino que tambiĂ©n afecta al animal a nivel clĂnico traduciĂ©ndose en pĂ©rdida de peso, disminuciĂłn de la conversiĂłn alimenticia y menor cantidad de kilogramos faenados. Esta patologĂa es multifactorial sin embargo la principal causa de gastritis es la bacteria Helicobacter spp. Es una bacteria gram negativa que coloniza la mucosa gástrica produciendo gastritis agudas o crĂłnicas, ulceras, linfoma del MALT, etc. Es importante para el diagnĂłstico de esta patologĂa contar con tĂ©cnicas que sean lo suficientemente sensibles y especĂficas. En estudios anteriores realizados en nuestro laboratorio se reportaron los casos de gastritis crĂłnicas y la relaciĂłn entre la coloraciĂłn de Giemsa y la de Warthin Starry (WS), la cual no presento diferencias estadĂsticamente significativas, siendo indistinta el uso de una u otra para realizar el diagnĂłstico. El objetivo de este trabajo fue evaluar la sensibilidad y especificidad de las tĂ©cnicas de Giemsa y WS para diagnosticar la presencia de Helicobacter spp en animales sanos. Se utilizaron 6 estĂłmagos de cerdos diagnosticados como normales con la coloraciĂłn de H/E. Los mismos fueron sometidos a la tĂ©cnica de Giemsa y WS para corroborar el diagnĂłstico. De estos 4 fueron positivos tanto para Giemsa como para WS, 1 resultĂł negativo para ambas coloraciones y 1 negativo para Giemsa y positivo para WS. Como conclusiĂłn podemos estimar que la tĂ©cnica de WS es sensible, ya que fue capaz de detectar el falso negativo, la especificidad es alta dado que tambiĂ©n es capaz de recocer a los negativos como verdaderos negativos. En futuras investigaciones seguiremos indagando acerca de esta temática, planteándonos el interrogante: Âżes Helicobacter spp un habitante normal del estĂłmago de los cerdos o causante de gastritis subclĂnicas
Space-time inhomogeneity, anisotropy and gravitational collapse
We investigate the evolution of non-adiabatic collapse of a shear-free
spherically symmetric stellar configuration with anisotropic stresses
accompanied with radial heat flux. The collapse begins from a curvature
singularity with infinite mass and size on an inhomogeneous space-time
background. The collapse is found to proceed without formation of an even
horizon to singularity when the collapsing configuration radiates all its mass
energy. The impact of inhomogeneity on various parameters of the collapsing
stellar configuration is examined in some specific space-time backgrounds.Comment: To appear in Gen. Relativ. Gra
Three-Dimensional Gravity with Conformal Scalar and Asymptotic Virasoro Algebra
Strominger has derived the Bekenstein-Hawking entropy of the BTZ black hole
using asymptotic Virasoro algebra. We apply Strominger's method to a black hole
solution found by Martinez and Zanelli (MZ). This is a solution of
three-dimensional gravity with a conformal scalar field. The solution is not
, but it is asymptotically ; therefore, it has the asymptotic
Virasoro algebra. We compute the central charge for the theory and compares
Cardy's formula with the Bekenstein-Hawking entropy. It turns out that the
functional form does agree, but the overall numerical coefficient does not.
This is because this approach gives the "maximum possible entropy" for the
numerical coefficient.Comment: 26 pages, LaTeX; v2: minor correction
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