86 research outputs found
Quantifying effective slip length over micropatterned hydrophobic surfaces
We employ micro-particle image velocimetry (-PIV) to investigate laminar
micro-flows in hydrophobic microstructured channels, in particular the slip
length. These microchannels consist of longitudinal micro-grooves, which can
trap air and prompt a shear-free boundary condition and thus slippage
enhancement. Our measurements reveal an increase of the slip length when the
width of the micro-grooves is enlarged. The result of the slip length is
smaller than the analytical prediction by Philip et al. [1] for an infinitely
large and textured channel comprised of alternating shear-free and no-slip
boundary conditions. The smaller slip length (as compared to the prediction)
can be attributed to the confinement of the microchannel and the bending of the
meniscus (liquid-gas interface). Our experimental studies suggest that the
curvature of the meniscus plays an important role in microflows over
hydrophobic micro-ridges.Comment: 8 page
Comparison of internal jugular and subclavian access for central venous catheterization in pediatric cardiac surgery
Spontaneous Breakdown of Superhydrophobicity
In some cases water droplets can completely wet micro-structured
superhydrophobic surfaces. The {\it dynamics} of this rapid process is analyzed
by ultra-high-speed imaging. Depending on the scales of the micro-structure,
the wetting fronts propagate smoothly and circularly or -- more interestingly
-- in a {\it stepwise} manner, leading to a growing {\it square-shaped} wetted
area: entering a new row perpendicular to the direction of front propagation
takes milliseconds, whereas once this has happened, the row itself fills in
microseconds ({\it ``zipping''})Comment: Accepted for publication in Physical Review Letter
Dynamics of the spontaneous breakdown of superhydrophobicity
Drops deposited on rough and hydrophobic surfaces can stay suspended with gas
pockets underneath the liquid, then showing very low hydrodynamic resistance.
When this superhydrophobic state breaks down, the subsequent wetting process
can show different dynamical properties. A suitable choice of the geometry can
make the wetting front propagate in a stepwise manner leading to {\it
square-shaped} wetted area: the front propagation is slow and the patterned
surface fills by rows through a {\it zipping} mechanism. The multiple time
scale scenario of this wetting process is experimentally characterized and
compared to numerical simulations.Comment: 7 pages, 5 figure
Evaluation of acute kidney injury with pediatric-modified RIFLE criteria after pediatric cardiac surgery
Simulations of slip flow on nanobubble-laden surfaces
On microstructured hydrophobic surfaces, geometrical patterns may lead to the
appearance of a superhydrophobic state, where gas bubbles at the surface can
have a strong impact on the fluid flow along such surfaces. In particular, they
can strongly influence a detected slip at the surface. We present two-phase
lattice Boltzmann simulations of a flow over structured surfaces with attached
gas bubbles and demonstrate how the detected slip depends on the pattern
geometry, the bulk pressure, or the shear rate. Since a large slip leads to
reduced friction, our results allow to assist in the optimization of
microchannel flows for large throughput.Comment: 22 pages, 12 figure
Drop impact upon micro- and nanostructured superhydrophobic surfaces
We experimentally investigate drop impact dynamics onto different
superhydrophobic surfaces, consisting of regular polymeric micropatterns and
rough carbon nanofibers, with similar static contact angles. The main control
parameters are the Weber number \We and the roughness of the surface. At small
\We, i.e. small impact velocity, the impact evolutions are similar for both
types of substrates, exhibiting Fakir state, complete bouncing, partial
rebouncing, trapping of an air bubble, jetting, and sticky vibrating water
balls. At large \We, splashing impacts emerge forming several satellite
droplets, which are more pronounced for the multiscale rough carbon nanofiber
jungles. The results imply that the multiscale surface roughness at nanoscale
plays a minor role in the impact events for small \We \apprle 120 but an
important one for large \We \apprge 120. Finally, we find the effect of
ambient air pressure to be negligible in the explored parameter regime \We
\apprle 150Comment: 8 pages, 7 figure
Lattice Boltzmann simulations in microfluidics: probing the no-slip boundary condition in hydrophobic, rough, and surface nanobubble laden microchannels
In this contribution we review recent efforts on investigations of the effect
of (apparent) boundary slip by utilizing lattice Boltzmann simulations. We
demonstrate the applicability of the method to treat fundamental questions in
microfluidics by investigating fluid flow in hydrophobic and rough
microchannels as well as over surfaces covered by nano- or microscale gas
bubbles.Comment: 11 pages, 6 figure
NMDA receptor channels: Labeling of MK-801 with iodine-125 and fluorine-18
Methods for labeling the glutamate channel blocking agent MK-801 with iodine-125 (125I) and fluorine-18 (18F) are described. Radioiodine was incorporated in the 1- or 3-positions of the aromatic ring of (+/-)MK-801 by solid-state halogen exchange techniques. Attachment of the [18F]fluoromethyl group to the bridgehead methyl position was achieved by reaction of [18F]fluoride with the triflamide alcohol 8 or the novel cyclic sulfamate 9 recently reported by Merck chemists. Radiochemical yields of (+/-)13-[18F]- fluoromethyl-MK-801 were >72%, EOB; radiochemical purity >99%. In competitive binding studies using rat brain homogenates, (+/-)3-bromo-MK-801 showed greater affinity than (+/-)MK-801 for the glutamate-linked channel. The experimental log P (2.1 +/- 0.1) of MK-801 is optimal for transit of the blood-brain barrier. These preliminary findings support further testing of 3-[123I]iodo-MK-801 and (+/-)13-[18F]fluoromethyl-MK-801 as possible agents for in vivo mapping of the glutamate receptor complex.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27605/1/0000649.pd
Protein C anticoagulant system—anti-inflammatory effects
Activated protein C (APC) plays active roles in preventing progression of a number of disease processes. These include thrombosis due to its direct anticoagulant activity which is likely augmented by its cytoprotective activity, thereby limiting exposure of procoagulant cellular membrane surfaces on cells. Beyond that, the pathway signals the cells to prevent apoptosis, to dampen inflammation, to increase endothelial barrier function, and to selectively downregulate some genes implicated in disease progression. Most of these functions are manifested to APC binding to endothelial protein C receptor (EPCR) allowing PAR1 activation, but activation of other PARS is also implicated in some cases. In addition to EPCR orchestrating these changes, CD11b is also capable of supporting APC signaling. Selective control of these pathways offers potential in new therapeutic approaches to disease
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