6,157 research outputs found
Dewetting on porous media with aspiration
We consider a porous solid covered with a water film (or with a drop) in
situations where the liquid is pumped in, either spontaneously (if the porous
medium is hydrophilic) or mechanically (by an external pump). The dynamics of
dewetting is then strongly modified. We analyse a few major examples: a)
horizontal films, which break at a certain critical thickness, b) the "modified
Landau-Levich problem" where a porous plate moves up from a bath and carries a
film: aspiration towards the plate limits the height H reached by the film, c)
certain situation where the hysteresis of contact angles is important.Comment: Revised version: The analysis of the 'modified Landau-Levich problem'
(section 3) has been significantly revised. It is now treated as a singular
perturbation problem (using boundary-layer techniques), leading to a more
accurate physical pictur
Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. Principle
Using 2 aspheric mirrors, it is possible to apodize a telescope beam without
losing light or angular resolution: the output beam is produced by
``remapping'' the entrance beam to produce the desired light intensity
distribution in a new pupil. We present the Phase-Induced Amplitude Apodization
Coronagraph (PIAAC) concept, which uses this technique, and we show that it
allows efficient direct imaging of extrasolar terrestrial planets with a
small-size telescope in space. The suitability of the PIAAC for exoplanet
imaging is due to a unique combination of achromaticity, small inner working
angle (about 1.5 ), high throughput, high angular resolution and
large field of view. 3D geometrical raytracing is used to investigate the
off-axis aberrations of PIAAC configurations, and show that a field of view of
more than 100 in radius is available thanks to the correcting
optics of the PIAAC. Angular diameter of the star and tip-tilt errors can be
compensated for by slightly increasing the size of the occulting mask in the
focal plane, with minimal impact on the system performance. Earth-size planets
at 10 pc can be detected in less than 30s with a 4m telescope. Wavefront
quality requirements are similar to classical techniques.Comment: 35 pages, 16 figures, Accepted for publication in Ap
The supporting-cell antigen: a receptor-like protein tyrosine phosphatase expressed in the sensory epithelia of the inner ear
After noise- or drug-induced hair-cell loss, the sensory epithelia of the avian inner ear can regenerate new hair cells. Few molecular markers are available for the supporting-cell precursors of the hair cells that regenerate, and little is known about the signaling mechanisms underlying this regenerative response. Hybridoma methodology was used to obtain a monoclonal antibody (mAb) that stains the apical surface of supporting cells in the sensory epithelia of the inner ear. The mAb recognizes the supporting-cell antigen (SCA), a protein that is also found on the apical surfaces of retinal Müller cells, renal tubule cells, and intestinal brush border cells. Expression screening and molecular cloning reveal that the SCA is a novel receptor-like protein tyrosine phosphatase (RPTP), sharing similarity with human density-enhanced phosphatase, an RPTP thought to have a role in the density-dependent arrest of cell growth. In response to hair-cell damage induced by noise in vivo or hair-cell loss caused by ototoxic drug treatment in vitro, some supporting cells show a dramatic decrease in SCA expression levels on their apical surface. This decrease occurs before supporting cells are known to first enter S-phase after trauma, indicating that it may be a primary rather than a secondary response to injury. These results indicate that the SCA is a signaling molecule that may influence the potential of nonsensory supporting cells to either proliferate or differentiate into hair cell
Boson Sampling with efficient scaling and efficient verification
A universal quantum computer of moderate scale is not available yet, however
intermediate models of quantum computation would still permit demonstrations of
a quantum computational advantage over classical computing and could challenge
the Extended Church-Turing Thesis. One of these models based on single photons
interacting via linear optics is called Boson Sampling. Proof-of-principle
Boson Sampling has been demonstrated, but the number of photons used for these
demonstrations is below the level required to claim quantum computational
advantage. To make progress with this problem, here we conclude that the most
practically achievable pathway to scale Boson Sampling experiments with current
technologies is by combining continuous-variables quantum information and
temporal encoding. We propose the use of switchable dual-homodyne and
single-photon detections, the temporal loop technique and scattershot based
Boson Sampling. This proposal gives details as to what the required assumptions
are and a pathway for a quantum optical demonstration of quantum computational
advantage. Furthermore, this particular combination of techniques permits a
single efficient implementation of Boson Sampling and efficient verification in
a single experimental setup
Research and applications: Artificial intelligence
The program is reported for developing techniques in artificial intelligence and their application to the control of mobile automatons for carrying out tasks autonomously. Visual scene analysis, short-term problem solving, and long-term problem solving are discussed along with the PDP-15 simulator, LISP-FORTRAN-MACRO interface, resolution strategies, and cost effectiveness
WKB Propagation of Gaussian Wavepackets
We analyze the semiclassical evolution of Gaussian wavepackets in chaotic
systems. We prove that after some short time a Gaussian wavepacket becomes a
primitive WKB state. From then on, the state can be propagated using the
standard TDWKB scheme. Complex trajectories are not necessary to account for
the long-time propagation. The Wigner function of the evolving state develops
the structure of a classical filament plus quantum oscillations, with phase and
amplitude being determined by geometric properties of a classical manifold.Comment: 4 pages, 4 figures; significant improvement
Comparative study on utilization of charcoal, sawdust and rice husk in heating oven
Segun R. Bello1, T. A. Adegbulugbe2, P. S. N. Onyekwere1(1. Department of Agricultural Engineering, Federal College of Agriculture P.M.B 7008 Ishiagu, Ebonyi State Nigeria;2. Department of Agricultural Engineering, Federal College of Agriculture, Moor Plantation, Ibadan Nigeria)Abstract: Three biofuels, charcoal, sawdust and rice husk were used in furnace and their thermal capacities and efficiency were measured. 0.01 m3 of each fuel used in the tests were measured to and fired in the heating chamber until all the material completely burn out. Air is supplied into the furnace by natural convection through air ducts. The drying chamber was lagged (insulated) by a 25.4 mm air space between inner wall and the outer casing to prevent heat loss. Three tests were replicated on each fuel and the mean values were used to evaluate heat flow by conduction, radiation and the thermal efficiency of the oven. The performance characteristics of the machine, including overall efficiency, drying chamber efficiency and thermal capacities of each fuel were evaluated. The results indicated that charcoal exhibit the highest combustion properties producing 2.54 kJ of energy per hour, sawdust produced 2.68 kJ while rice husk produced the least energy of 1.96 kJ per kg of burnt the products per hour. The overall furnace efficiency of the oven was 75%, and drying chamber efficiency was 62%. Characteristic temperature curves observed in the drying chamber indicated that charcoal attained very high thermal value within a short period than other fuels, while saw dust and rice husk had much lower heat buildup and longer temperature rise response time. By these results, charcoal is suitable for short time heat processes such as baking and roasting, rice husk could be suitable for milk and fruit juice pasteurization, which require heat processing conditions between 63–85℃ for about 15 to 30 minutes. Sawdust can be used in sterilization of meat, fish; soup etc. Charcoal is more environmentally friendly than the other products because of the smokeless burning process thus suitable for indoor cooking.Keywords: Thermal capacity, heat process, thermal efficiency, differential, temperatureCitation: Segun R. Bello, T. A. Adegbulugbe, P. S. N. Onyekwere. Comparative study on utilization of charcoal, sawdust and rice husk in heating oven. Agric Eng Int: CIGR Journal, 2010, 12(2): 29-33. 
Constraining holographic inflation with WMAP
In a class of recently proposed models, the early universe is strongly
coupled and described holographically by a three-dimensional, weakly coupled,
super-renormalizable quantum field theory. This scenario leads to a power
spectrum of scalar perturbations that differs from the usual empirical LCDM
form and the predictions of generic models of single field, slow roll
inflation. This spectrum is characterized by two parameters: an amplitude, and
a parameter g related to the coupling constant of the dual theory. We estimate
these parameters, using WMAP and other astrophysical data. We compute Bayesian
evidence for both the holographic model and standard LCDM and find that their
difference is not significant, although LCDM provides a somewhat better fit to
the data. However, it appears that Planck will permit a definitive test of this
holographic scenario.Comment: 24 pages, 9 figs, published versio
Nonequilibrium dynamics of mixtures of active and passive colloidal particles
We develop a mesoscopic field theory for the collective nonequilibrium
dynamics of multicomponent mixtures of interacting active (i.e., motile) and
passive (i.e., nonmotile) colloidal particles with isometric shape in two
spatial dimensions. By a stability analysis of the field theory, we obtain
equations for the spinodal that describes the onset of a motility-induced
instability leading to cluster formation in such mixtures. The prediction for
the spinodal is found to be in good agreement with particle-resolved computer
simulations. Furthermore, we show that in active-passive mixtures the spinodal
instability can be of two different types. One type is associated with a
stationary bifurcation and occurs also in one-component active systems, whereas
the other type is associated with a Hopf bifurcation and can occur only in
active-passive mixtures. Remarkably, the Hopf bifurcation leads to moving
clusters. This explains recent results from simulations of active-passive
particle mixtures, where moving clusters and interfaces that are not seen in
the corresponding one-component systems have been observed.Comment: 17 pages, 3 figure
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