6,114 research outputs found
A foam model highlights the differences of the macro- and microrheology of respiratory horse mucus
Native horse mucus is characterized with micro- and macrorheology and
compared to hydroxyethylcellulose (HEC) gel as a model. Both systems show
comparable viscoelastic properties on the microscale and for the HEC the
macrorheology is in good agreement with the microrheology. For the mucus, the
viscoelastic moduli on the macroscale are several orders of magnitude larger
than on the microscale. Large amplitude oscillatory shear experiments show that
the mucus responds nonlinearly at much smaller deformations than HEC. This
behavior fosters the assumption that the mucus has a foam like structure on the
microscale compared to the typical mesh like structure of the HEC, a model that
is supported by cryogenic-scanning-electron-microscopy (CSEM) images. These
images allow also to determine the relative amount of volume that is occupied
by the pores and the scaffold. Consequently, we can estimate the elastic
modulus of the scaffold. We conclude that this particular foam like
microstructure should be considered as a key factor for the transport of
particulate matter which plays a central role in mucus function with respect to
particle penetration. The mesh properties composed of very different components
are responsible for macroscopic and microscopic behavior being part of
particles fate after landing.Comment: Accepted for publication in the Journal of the Mechanical Behavior of
Biomedical Material
Monitoring of lung edema by microwave reflectometry during lung ischemia-reperfusion injury in vivo
It is still unclear whether lung edema can be monitored by microwave reflectometry and whether the measured changes in lung dry matter content (DMC) are accompanied by changes in PaO(2) and in pro-to anti-inflammatory cytokine expression (IFN-gamma and IL-10). Right rat lung hili were cross-clamped at 37 degrees C for 0, 60, 90 or 120 min ischemia followed by 120 min reperfusion. After 90 min (DMC: 15.9 +/- 1.4%; PaO(2): 76.7 +/- 18 mm Hg) and 120 min ischemia (DMC: 12.8 +/- 0.6%; PaO(2): 43 +/- 7 mm Hg), a significant decrease in DMC and PaO(2) throughout reperfusion compared to 0 min ischemia (DMC: 19.5 +/- 1.11%; PaO(2): 247 +/- 33 mm Hg; p < 0.05) was observed. DMC and PaO(2) decreased after 60 min ischemia but recovered during reperfusion (DMC: 18.5 +/- 2.4%; PaO(2) : 173 +/- 30 mm Hg). DMC values reflected changes on the physiological and molecular level. In conclusion, lung edema monitoring by microwave reflectometry might become a tool for the thoracic surgeon. Copyright (c) 2006 S. Karger AG, Basel
Estudo sorológico atual e retrospectivo de anticorpos contra o vírus Influenza A em populações de suínos no Brasil.
Projeto/Plano de Ação: 02.11.01.006
PT symmetry and spontaneous symmetry breaking in a microwave billiard
We demonstrate the presence of parity-time (PT) symmetry for the
non-Hermitian two-state Hamiltonian of a dissipative microwave billiard in the
vicinity of an exceptional point (EP). The shape of the billiard depends on two
parameters. The Hamiltonian is determined from the measured resonance spectrum
on a fine grid in the parameter plane. After applying a purely imaginary
diagonal shift to the Hamiltonian, its eigenvalues are either real or complex
conjugate on a curve, which passes through the EP. An appropriate basis choice
reveals its PT symmetry. Spontaneous symmetry breaking occurs at the EP
On the Progenitor System of Nova V2491 Cygni
Nova V2491 Cyg is one of just two detected pre-outburst in X-rays. The light
curve of this nova exhibited a rare "re-brightening" which has been attributed
by some as the system being a polar, whilst others claim that a magnetic WD is
unlikely. By virtue of the nature of X-ray and spectroscopic observations the
system has been proposed as a recurrent nova, however the adoption of a 0.1 day
orbital period is generally seen as incompatible with such a system. In this
research note we address the nature of the progenitor system and the source of
the 0.1 day periodicity. Through the combination of Liverpool Telescope
observations with published data and archival 2MASS data we show that V2491
Cyg, at a distance of 10.5 - 14 kpc, is likely to be a recurrent nova of the U
Sco-class; containing a sub-giant secondary and an accretion disk, rather than
accretion directly onto the poles. We show that there is little evidence, at
quiescence, supporting a ~ 0.1 day periodicity, the variation seen at this
stage is likely caused by flickering of a re-established accretion disk. We
propose that the periodicity seen shortly after outburst is more likely related
to the outburst rather than the - then obscured - binary system. Finally we
address the distance to the system, and show that a significantly lower
distance (~ 2 kpc) would result in a severely under-luminous outburst, and as
such favour the larger distance and the recurrent nova scenario.Comment: 5 pages, 3 images, accepted for publication in A&A as a research not
Current and retrospective serology study of influenza a viruses antibodies in Brazilian pig populations.
Projeto: 03.09.00.046
The 2010 nova outburst of the symbiotic Mira V407 Cyg
The nova outburst experienced in 2010 by the symbiotic binary Mira V407 Cyg
has been extensively studied at optical and infrared wavelengths with both
photometric and spectroscopic observations. This outburst, reminiscent of
similar events displayed by RS Oph, can be described as a very fast He/N nova
erupting while being deeply embedded in the dense wind of its cool giant
companion. The hard radiation from the initial thermonuclear flash ionizes and
excites the wind of the Mira over great distances (recombination is observed on
a time scale of 4 days). The nova ejecta is found to progressively decelerate
with time as it expands into the Mira wind. This is deduced from line widths
which change from a FWHM of 2760 km/s on day +2.3 to 200 km/s on day +196. The
wind of the Mira is massive and extended enough for an outer neutral and
unperturbed region to survive at all outburst phases.Comment: MNRAS Letter, in pres
Effect of anisotropy and destructuration on behavior of Haarajoki test embankment
This paper investigates the influence of anisotropy and destructuration on the behavior of Haarajoki test embankment, which was built by the Finnish National Road Administration as a noise barrier in 1997 on a soft clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. The construction and consolidation of the embankment is analyzed with the finite-element method using three different constitutive models to represent the soft clay. Two recently proposed constitutive models, namely S-CLAY1 which accounts for initial and plastic strain induced anisotropy, and its extension, called S-CLAY1S which accounts, additionally, for interparticle bonding and degradation of bonds, were used in the analysis. For comparison, the problem is also analyzed with the isotropic modified cam clay model. The results of the numerical analyses are compared with the field measurements. The simulations reveal the influence that anisotropy and destructuration have on the behavior of an embankment on soft clay
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