24,026 research outputs found
Statistical Mesoscopic Hydro-Thermodynamics: The Description of Kinetics and Hydrodynamics of Nonequilibrium Processes in Single Liquids
Hydrodynamics, a term apparently introduced by Daniel Bernoulli (1700-1783)
to comprise hydrostatic and hydraulics, has a long history with several
theoretical approaches. Here, after a descriptive introduction, we present
so-called mesoscopic hydro-thermodynamics, which is also referred to as
higher-order generalized hydrodynamics, built within the framework of a
mechanical-statistical formalism. It consists of a description of the material
and heat motion of fluids in terms of the corresponding densities and their
associated fluxes of all orders. In this way, movements are characterized in
terms of intermediate to short wavelengths and intermediate to high
frequencies. The fluxes have associated Maxwell-like times, which play an
important role in determining the appropriate contraction of the description
(of the enormous set of fluxes of all orders) necessary to address the
characterization of the motion in each experimental setup. This study is an
extension of a preliminary article: Physical Review E \textbf{91}, 063011
(2015)
Rings and arcs around evolved stars. II. The Carbon Star AFGL 3068 and the Planetary Nebulae NGC 6543, NGC 7009 and NGC 7027
We present a detailed comparative study of the arcs and fragmented ring-like
features in the haloes of the planetary nebulae (PNe) NGC 6543, NGC 7009, and
NGC 7027 and the spiral pattern around the carbon star AFGL 3068 using
high-quality multi-epoch HST images. This comparison allows us to investigate
the connection and possible evolution between the regular patterns surrounding
AGB stars and the irregular concentric patterns around PNe. The radial proper
motion of these features, ~15 km/s, are found to be consistent with the AGB
wind and their linear sizes and inter-lapse times (500-1900 yr) also agree with
those found around AGB stars, suggesting a common origin. We find evidence
using radiative-hydrodynamic simulations that regular patterns produced at the
end of the AGB phase become highly distorted by their interactions with the
expanding PN and the anisotropic illumination and ionization patterns caused by
shadow instabilities. These processes will disrupt the regular (mostly spiral)
patterns around AGB stars, plausibly becoming the arcs and fragmented rings
observed in the haloes of PNe.Comment: 13 pages, 9 figures, accepted for publication in MNRA
A geometric technique to generate lower estimates for the constants in the Bohnenblust--Hille inequalities
The Bohnenblust--Hille (polynomial and multilinear) inequalities were proved
in 1931 in order to solve Bohr's absolute convergence problem on Dirichlet
series. Since then these inequalities have found applications in various fields
of analysis and analytic number theory. The control of the constants involved
is crucial for applications, as it became evident in a recent outstanding paper
of Defant, Frerick, Ortega-Cerd\'{a}, Ouna\"{\i}es and Seip published in 2011.
The present work is devoted to obtain lower estimates for the constants
appearing in the Bohnenblust--Hille polynomial inequality and some of its
variants. The technique that we introduce for this task is a combination of the
Krein--Milman Theorem with a description of the geometry of the unit ball of
polynomial spaces on .Comment: This preprint does no longer exist as a single manuscript. It is now
part of the preprint entitled "The optimal asymptotic hypercontractivity
constant of the real polynomial Bohnenblust-Hille inequality is 2" (arXiv
reference 1209.4632
Feno de pastagem nativa da "Zona de mimoso", como opcao para suplementacao do rebanho, na epoca seca.
Entre os diversos tipos de vegetacao do Piaui, a pastagem nativa da "zona de mimoso" e considerada uma das mais importantes do Estado. O maior problema enfrentado pelo pecuarista da regiao e a falta de forragempara o rebanho, na seca, ja que a pastagem cultivada e insignificante.Neste periodo a pastagem nativa seca totalmente e parte dela e carregada pelos ventos, tornando-se escassa a disponibilidade de forragem. Noperiodo chuvoso, a pastagem nativa chega a ser abundante e, as vezes excedendo o consumo animal. A producao de feno do excedente da pastagemnativa e uma opcao para suplementacao do gado na epoca critica. A UEPAE de Teresina produziu na "zona de mimoso" cerca de 9,0 t de feno parasuplementacao de seu rebanho. O trabalho foi realizado em marco de 1982, quando havia excedentes de forragem. Foram usados dois sistemas: 1)Todas as operacoes (roco, enleiramento e enfaradmento) forma executados manualmente. 2)Foi realizado roco mecanico, e enleiramento manual. Em ambos o enfardamento foi manual em prensa de feno. A maior producao de feno no sistema totalmente manual foi devido a altura de corte das plantas ter sido mais baixa. O feno produzido em Campo Maior tinha 7,85% de proteina bruta e 0,08% de fosforo, com base na materia seca. Este dados mostram que o teor de proteina e superior as necessidades de mantenca dos bovinos, que e de 7,0%. Quanto ao fosforo, esta abaixo de suas necessidades, precisando portanto, de suplementacao mineral.bitstream/item/95804/1/CT190001.pd
Variable stars in the globular cluster M28 (NGC 6626)
We present a new search for variable stars in the Galactic globular cluster
M28 (NGC 6626). The search is based on a series of BVI images obtained with the
SMARTS Consortium's 1.3m telescope at Cerro Tololo Inter-American Observatory,
Chile. The search was carried out using the ISIS v2.2 image subtraction
package. We find a total of 25 variable stars in the field of the cluster, 9
being new discoveries. Of the newly found variables, 1 is an ab-type RR Lyrae
star, 6 are c-type RR Lyrae, and 2 are long-period/semi-regular variables. V22,
previously classified as a type II Cepheid, appears as a bona-fide RRc in our
data. In turn, V20, previously classified as an ab-type RR Lyrae, could not be
properly phased with any reasonable period. The properties of the ab-type RR
Lyrae stars in M28 appear most consistent with an Oosterhoff-intermediate
classification, which is unusual for bona-fide Galactic globulars clusters.
However, the cluster's c-type variables do not clearly support such an
Oosterhoff type, and a hybrid Oosterhoff I/II system is accordingly another
possibility, thus raising the intriguing possibility of multiple populations
being present in M28. Coordinates, periods, and light curves in differential
fluxes are provided for all the detected variables.Comment: A&A, in pres
Influência de tipos de coberturas na emergência, sobrevivência e altura de mudas de canafistula.
Foi conduzido no viveiro do Centro de Produção e Experimentação do Canguiri, Piraquara - Paraná, pertencente à Fundação Instituto Agronômico do Paraná, um trabalho testando tipos de coberturas usualmente empregadas em canteiros de semeadura, para a produção de mudas de Peltophorum dubium. Os materiais utilizados na cobertura foram terra, acícula, acícula picada, aniagem, areia, palha de arroz, sepilho e serragem. O delineamento utilizado foi o de parcelas inteiramente casualizadas com cinco repetições. Foram feitas contagens semanais de emergência e, 60 dias após a semeadura, procedeu-se às avaliações de sobrevivência, diâmetro do colo, comprimento da parte aérea, subterrânea e total de mudas. Não houve influência dos diversos tipos de cobertura na emergência e sobrevivência das plantas. Com a utilização de sepilho, aniagem e palha de arroz, foram obtidos maiores diâmetros de colo e maiores comprimentos aéreo, subterrâneo e total das plantas
The antikaon nuclear potential in hot and dense matter
The antikaon optical potential in hot and dense nuclear matter is studied
within the framework of a coupled-channel self-consistent calculation taking,
as bare meson-baryon interaction, the meson-exchange potential of the J\"ulich
group. Typical conditions found in heavy-ion collisions at GSI are explored. As
in the case of zero temperature, the angular momentum components larger than
L=0 contribute significantly to the finite temperature antikaon optical
potential at finite momentum. It is found that the particular treatment of the
medium effects has a strong influence on the behavior of the antikaon potential
with temperature. Our self-consistent model, in which antikaons and pions are
dressed in the medium, gives a moderately temperature dependent antikaon
potential which remains attractive at GSI temperatures, contrary to what one
finds if only nuclear Pauli blocking effects are included.Comment: 30 pages, 8 figures, references added. Accepted for publication in
PR
Helicity-Rotation-Gravity Coupling for Gravitational Waves
The consequences of spin-rotation-gravity coupling are worked out for linear
gravitational waves. The coupling of helicity of the wave with the rotation of
a gravitational-wave antenna is investigated and the resulting modifications in
the Doppler effect and aberration are pointed out for incident high-frequency
gravitational radiation. Extending these results to the case of a
gravitomagnetic field via the gravitational Larmor theorem, the rotation of
linear polarization of gravitational radiation propagating in the field of a
rotating mass is studied. It is shown that in this case the linear polarization
state rotates by twice the Skrotskii angle as a consequence of the spin-2
character of linear gravitational waves.Comment: 11 pages, no figures, accepted for publication in Phys. Rev. D; v2: a
few minor typos correcte
Crossover of thermal to shot noise in chaotic cavities
We study the crossover between thermal and shot-noise power in a chaotic
quantum dot in the presence of non-ideal contacts at finite temperature. The
result explicitly demonstrates that the temperature affect the
suppression-amplification effect present in the main quantum noise. In
particular, the weak localization contribution to the noise has an anomalous
thermal behavior when one let the barriers vary, indicating the presence of a
critical point related to specific value of the tunneling barriers. We also
show how to get to the opaque limit of the quantum dot at finite temperature.Comment: 6 pages, 5 figures. To be published in Europhysics Letter
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