20,500 research outputs found
Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows
We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN],
on the vanishing viscosity limit of circularly symmetric viscous flow in a disk
with rotating boundary, shown there to converge to the inviscid limit in
-norm as long as the prescribed angular velocity of the
boundary has bounded total variation. Here we establish convergence in stronger
and -Sobolev spaces, allow for more singular angular velocities
, and address the issue of analyzing the behavior of the boundary
layer. This includes an analysis of concentration of vorticity in the vanishing
viscosity limit. We also consider such flows on an annulus, whose two boundary
components rotate independently.
[LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J.,
Vanishing viscosity limit for incompressible flow inside a rotating circle,
preprint 2006
OcorrĂȘncia de bactĂ©rias diazotrĂłficas e fungos micorrĂzicos arbusculares na cultura da mandioca
Este trabalho teve como objetivo avaliar a ocorrĂȘncia, isolar e identificar fungos micorrĂzicos arbusculares associados Ă cultura da mandioca (Manihot esculenta). Amostras de solo rizosfĂ©rico e de vĂĄrias partes da planta (raĂzes, tubĂ©rculos, manivas e folhas) de locais nos Estados do Rio de Janeiro, SĂŁo Paulo e ParanĂĄ, foram inoculadas nos meios LGI-P, NFb-malato e NFb-GOC, avaliando-se o nĂșmero mais provĂĄvel de cĂ©lulas e a atividade de redução de acetileno. BactĂ©rias diazotrĂłficas foram isoladas de todas as partes da planta, com exceção das folhas, sendo identificadas como Klebsiella sp., Azospirillum lipoferum e uma bactĂ©ria denominada "E", provavelmente pertencente ao gĂȘnero Burkholderia. A BactĂ©ria E acumulou de 7,63 mg a 14,84 mg de N/g de C em meio semi-sĂłlido, isento de N, e conseguiu manter a capacidade de fixação biolĂłgica de N, mesmo apĂłs uma dezena de repicagens consecutivas. A colonização micorrĂzica variou de 31% a 69%, e a densidade de esporos de 10 a 384 esporos/100 mL de solo, predominando as espĂ©cies Entrophospora colombiana e Acaulospora scrobiculata no Rio de Janeiro, A. scrobiculata e Scutellospora heterogama no ParanĂĄ e em Piracicaba (SĂŁo Paulo) e A. appendicula e S. pellucida em Campinas (SĂŁo Paulo)
Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters
In this work, we report an atomic scale study on the ferromagnetic insulator
manganite LaMnO using PAC spectroscopy. Data analysis
reveals a nanoscopic transition from an undistorted to a Jahn-Teller-distorted
local environment upon cooling. The percolation thresholds of the two local
environments enclose a macroscopic structural transition
(Rhombohedric-Orthorhombic). Two distinct regimes of JT-distortions were found:
a high temperature regime where uncorrelated polaron clusters with severe
distortions of the MnO octahedra survive up to
and a low temperature regime where correlated regions have a weaker
JT-distorted symmetry.Comment: 4 pages, 4 Figures, submitted to PRL, new version with more data,
text reformulate
Impacts of Biomass Burning in the Atmosphere of the Southeastern Region of Brazil Using Remote Sensing Systems
Nonlinear stabilitty for steady vortex pairs
In this article, we prove nonlinear orbital stability for steadily
translating vortex pairs, a family of nonlinear waves that are exact solutions
of the incompressible, two-dimensional Euler equations. We use an adaptation of
Kelvin's variational principle, maximizing kinetic energy penalised by a
multiple of momentum among mirror-symmetric isovortical rearrangements. This
formulation has the advantage that the functional to be maximized and the
constraint set are both invariant under the flow of the time-dependent Euler
equations, and this observation is used strongly in the analysis. Previous work
on existence yields a wide class of examples to which our result applies.Comment: 25 page
Comportamento zootĂ©cnico de vacas mestiças em capim-elefante nos Tabuleiros Costeiros do PiauĂ.
Este estudo teve por objetivo avaliar o comportamento zootĂ©cnico de vacas mestiças mantidas em capim-elefante, com e sem suplementação alimentar, nos Tabuleiros Costeiros do PiauĂ. O delineamento experimental utilizado foi o inteiramente casualizado com trĂȘs tratamentos: T1 = vacas em lactação mantidas exclusivamente em pastagem de capim-elefante irrigado no perĂodo seco; T2 = T1 + banco de proteĂna de leucena e T3 = T1 + ração concentrada, a ser fornecida na quantidade de 1 kg para cada 3 kg de leite produzido acima de...bitstream/CPAMN-2009-09/19849/1/BOLP57.pd
Spectrally narrow exciton luminescence from monolayer MoS2 exfoliated onto epitaxially grown hexagonal BN
The strong light-matter interaction in transition Metal dichalcogenides
(TMDs) monolayers (MLs) is governed by robust excitons. Important progress has
been made to control the dielectric environment surrounding the MLs, especially
through hexagonal boron nitride (hBN) encapsulation, which drastically reduces
the inhomogeneous contribution to the exciton linewidth. Most studies use
exfoliated hBN from high quality flakes grown under high pressure. In this
work, we show that hBN grown by molecular beam epitaxy (MBE) over a large
surface area substrate has a similarly positive impact on the optical emission
from TMD MLs. We deposit MoS and MoSe MLs on ultrathin hBN films (few
MLs thick) grown on Ni/MgO(111) by MBE. Then we cover them with exfoliated hBN
to finally obtain an encapsulated sample : exfoliated hBN/TMD ML/MBE hBN. We
observe an improved optical quality of our samples compared to TMD MLs
exfoliated directly on SiO substrates. Our results suggest that hBN grown
by MBE could be used as a flat and charge free substrate for fabricating
TMD-based heterostructures on a larger scale.Comment: 5 pages, 3 figure
On the Solution of the Number-Projected Hartree-Fock-Bogoliubov Equations
The numerical solution of the recently formulated number-projected
Hartree-Fock-Bogoliubov equations is studied in an exactly soluble
cranked-deformed shell model Hamiltonian. It is found that the solution of
these number-projected equations involve similar numerical effort as that of
bare HFB. We consider that this is a significant progress in the mean-field
studies of the quantum many-body systems. The results of the projected
calculations are shown to be in almost complete agreement with the exact
solutions of the model Hamiltonian. The phase transition obtained in the HFB
theory as a function of the rotational frequency is shown to be smeared out
with the projection.Comment: RevTeX, 11 pages, 3 figures. To be published in a special edition of
Physics of Atomic Nuclei (former Sov. J. Nucl. Phys.) dedicated to the 90th
birthday of A.B. Migda
Spherical harmonic decomposition applied to spatial-temporal analysis of human high-density EEG
We demonstrate an application of spherical harmonic decomposition to analysis
of the human electroencephalogram (EEG). We implement two methods and discuss
issues specific to analysis of hemispherical, irregularly sampled data.
Performance of the methods and spatial sampling requirements are quantified
using simulated data. The analysis is applied to experimental EEG data,
confirming earlier reports of an approximate frequency-wavenumber relationship
in some bands.Comment: 12 pages, 8 figures, submitted to Phys. Rev. E, uses APS RevTeX
style
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