1,411 research outputs found
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Drop deformation in stokes flow through converging channels
This work presents an application of a direct BEM formulation for drop
deformation and interaction in Stokes flows through converging channels. Parametric
studies are conducted to investigate the effect, on drop deformation, of the channel’s
convergence ratio, the drop-fluid viscosity ratio, the interfacial tension and the initial
relative position of the drops
On kinetic energy stabilized superconductivity in cuprates
The possibility of kinetic energy driven superconductivity in cuprates as was
recently found in the model is discussed. We argue that the violation of
the virial theorem implied by this result is serious and means that the
description of superconductivity within the model is pathological.Comment: 3 pages, v2 includes additional reference
On the evidence derived from the anatomical analysis of wooden remains from archaeological excavation
Multi-focal laser surgery: cutting enhancement by hydrodynamic interactions between cavitation bubbles
Transparent biological tissues can be precisely dissected with ultrafast
lasers using optical breakdown in the tight focal zone. Typically, tissues are
cut by sequential application of pulses, each of which produces a single
cavitation bubble. We investigate the hydrodynamic interactions between
simultaneous cavitation bubbles originating from multiple laser foci.
Simultaneous expansion and collapse of cavitation bubbles can enhance the
cutting efficiency by increasing the resulting deformations in tissue, and the
associated rupture zone. An analytical model of the flow induced by the bubbles
is presented and experimentally verified. The threshold strain of the material
rupture is measured in a model tissue. Using the computational model and the
experimental value of the threshold strain one can compute the shape of the
rupture zone in tissue resulting from application of multiple bubbles. With the
threshold strain of 0.7 two simultaneous bubbles produce a continuous cut when
applied at the distance 1.35 times greater than that required in sequential
approach. Simultaneous focusing of the laser in multiple spots along the line
of intended cut can extend this ratio to 1.7. Counter-propagating jets forming
during collapse of two bubbles in materials with low viscosity can further
extend the cutting zone - up to a factor of 1.54.Comment: 16 pages, 8 figures. Paper is accepted for publication in Physical
Review
X-ray Properties of Radio-Selected Dual Active Galactic Nuclei
Merger simulations predict that tidally induced gas inflows can trigger
kpc-scale dual active galactic nuclei (dAGN) in heavily obscured environments.
Previously with the Very Large Array, we have confirmed four dAGN with
redshifts between and projected separations between 4.3 and
9.2 kpc in the SDSS Stripe 82 field. Here, we present X-ray
observations that spatially resolve these dAGN and compare their
multi-wavelength properties to those of single AGN from the literature. We
detect X-ray emission from six of the individual merger components and obtain
upper limits for the remaining two. Combined with previous radio and optical
observations, we find that our dAGN have properties similar to nearby
low-luminosity AGN, and they agree well with the black hole fundamental plane
relation. There are three AGN-dominated X-ray sources, whose X-ray
hardness-ratio derived column densities show that two are unobscured and one is
obscured. The low obscured fraction suggests these dAGN are no more obscured
than single AGN, in contrast to the predictions from simulations. These three
sources show an apparent X-ray deficit compared to their mid-infrared continuum
and optical [OIII] line luminosities, suggesting higher levels of obscuration,
in tension with the hardness-ratio derived column densities. Enhanced
mid-infrared and [OIII] luminosities from star formation may explain this
deficit. There is ambiguity in the level of obscuration for the remaining five
components since their hardness ratios may be affected by non-nuclear X-ray
emissions, or are undetected altogether. They require further observations to
be fully characterized.Comment: 11 pages, 5 figures, Accepted for publication in the Astrophysical
Journa
Electrostatics of Gapped and Finite Surface Electrodes
We present approximate methods for calculating the three-dimensional electric
potentials of finite surface electrodes including gaps between electrodes, and
estimate the effects of finite electrode thickness and an underlying dielectric
substrate. As an example we optimize a radio-frequency surface-electrode ring
ion trap, and find that each of these factors reduces the trapping secular
frequencies by less than 5% in realistic situations. This small magnitude
validates the usual assumption of neglecting the influences of gaps between
electrodes and finite electrode extent.Comment: 9 pages, 9 figures (minor changes
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Adoption Related Curiosity in Emerging Adulthood
Adoption-related curiosity was examined for a group of 169 emerging adults (M= 25.0 years) who were adopted as infants. The Adoption Communication Pathway model guided the research questions about formation of an information gap, which exists when there is a difference between what an adopted person knows and what he or she wants to know, and specific issues about which emerging adults were curious. Differences in these specific issues were examined across sex and contact with birth parents at adolescence. Logistic regression analyses revealed that the formation of an adoption information gap, which contains the content of curiosity, was more likely for those who less satisfied with the amount of contact in at both adolescence and emerging adulthood. Content of the information gap at emerging adulthood will be presented
Relation between dust and radio luminosity in optically selected early type galaxies
We have surveyed an optical/IR selected sample of nearby E/S0 galaxies with
and without nuclear dust structures with the VLA at 3.6 cm to a sensitivity of
100 Jy. We can construct a Radio Luminosity Function (RLF) of these
galaxies to ~10^19 W/Hz and find that ~50% of these galaxies have AGNs at this
level. The space density of these AGNs equals that of starburst galaxies at
this luminosity. Several dust-free galaxies have low luminosity radio cores,
and their RLF is not significantly less than that of the dusty galaxies.Comment: 8 pages, 5 figures, accepted for publication in A&
[Photodissociation of Acetylene and Acetone using Step-Scan Time-Resolved FTIR Emission Spectroscopy]
The photodissociation of acetylene and acetone was investigated as a function of added quenching gas pressures using step-scan time-resolved FTIR emission spectroscopy. Its main components consist of Bruker IFS88, step-scan Fourier Transform Infrared (FTIR) spectrometer coupled to a flow cell equipped with Welsh collection optics. Vibrationally excited C2H radicals were produced from the photodissociation of acetylene in the unfocused experiments. The infrared (IR) emission from these excited C2H radicals was investigated as a function of added argon pressure. Argon quenching rate constants for all C2H emission bands are of the order of 10(exp -13)cc/molecule.sec. Quenching of these radicals by acetylene is efficient, with a rate constant in the range of 10(exp -11) cc/molecule.sec. The relative intensity of the different C2H emission bands did not change with the increasing argon or acetylene pressure. However, the overall IR emission intensity decreased, for example, by more than 50% when the argon partial pressure was raised from 0.2 to 2 Torr at fixed precursor pressure of 160mTorr. These observations provide evidence for the formation of a metastable C2H2 species, which are collisionally quenched by argon or acetylene. Problems encountered in the course of the experimental work are also described
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