16,227 research outputs found
Splashing of liquids: interplay of surface roughness with surrounding gas
We investigate the interplay between substrate roughness and surrounding gas
pressure in controlling the dynamics of splashing when a liquid drop hits a dry
solid surface. We associate two distinct forms of splashing with each of these
control parameters: prompt splashing is due to surface roughness and corona
splashing is due to instabilities produced by the surrounding gas. The size
distribution of ejected droplets reveals the length scales of the underlying
droplet-creation process in both cases.Comment: 6 pages, 6 figure
Liquid drop splashing on smooth, rough and textured surfaces
Splashing occurs when a liquid drop hits a dry solid surface at high
velocity. This paper reports experimental studies of how the splash depends on
the roughness and the texture of the surfaces as well as the viscosity of the
liquid. For smooth surfaces, there is a "corona" splash caused by the presence
of air surrounding the drop. There are several regimes that occur as the
velocity and liquid viscosity are varied. There is also a "prompt" splash that
depends on the roughness and texture of the surfaces. A measurement of the size
distribution of the ejected droplets is sensitive to the surface roughness. For
a textured surface in which pillars are arranged in a square lattice,
experiment shows that the splashing has a four-fold symmetry. The splash occurs
predominantly along the diagonal directions. In this geometry, two factors
affect splashing the most: the pillar height and spacing between pillars.Comment: 9 pages, 11 figure
Electroneutrality and Phase Behavior of Colloidal Suspensions
Several statistical mechanical theories predict that colloidal suspensions of
highly charged macroions and monovalent microions can exhibit unusual
thermodynamic phase behavior when strongly deionized. Density-functional,
extended Debye-H\"uckel, and response theories, within mean-field and
linearization approximations, predict a spinodal phase instability of charged
colloids below a critical salt concentration. Poisson-Boltzmann cell model
studies of suspensions in Donnan equilibrium with a salt reservoir demonstrate
that effective interactions and osmotic pressures predicted by such theories
can be sensitive to the choice of reference system, e.g., whether the microion
density profiles are expanded about the average potential of the suspension or
about the reservoir potential. By unifying Poisson-Boltzmann and response
theories within a common perturbative framework, it is shown here that the
choice of reference system is dictated by the constraint of global
electroneutrality. On this basis, bulk suspensions are best modeled by
density-dependent effective interactions derived from a closed reference system
in which the counterions are confined to the same volume as the macroions.
Linearized theories then predict bulk phase separation of deionized suspensions
only when expanded about a physically consistent (closed) reference system.
Lower-dimensional systems (e.g., monolayers, small clusters), depending on the
strength of macroion-counterion correlations, may be governed instead by
density-independent effective interactions tied to an open reference system
with counterions dispersed throughout the reservoir, possibly explaining
observed structural crossover in colloidal monolayers and anomalous
metastability of colloidal crystallites.Comment: 12 pages, 5 figures. Discussion clarified, references adde
Chronic ETA receptor blockade prevents endothelial dysfunction of small arteries in apolipoprotein E-deficient mice
Objective: This study investigated whether endothelial dysfunction occurs in mesenteric arteries of apoE-deficient mice and determined the role of endothelin (ET)-1, which is increased in human atherosclerosis, using an orally active endothelin ETA receptor antagonist. Methods: ApoE-deficient and C57BL/6J control mice were fed for 30 weeks with normal chow or high-fat Western-type diet alone or in combination with darusentan (LU135252; 50 mg/kg/day). Vasomotor reactivity of isolated small mesenteric arteries (I.D. 200-250 ÎĽm) was studied in vitro under perfused and pressurized conditions. Results: In both mouse strains, about one fourth of the endothelium-dependent relaxant response to acetylcholine was insensitive to inhibition by l-NAME and indomethacin. In mesenteric arteries of apoE-deficient mice on Western-type diet, increased intima-media thickness and levels of endothelin-1 protein were observed. In addition, NO-mediated endothelium-dependent relaxation to acetylcholine was reduced without affecting l-NAME/indomethacin insensitive relaxation and contractions to endothelin-1 and serotonin were enhanced. Treatment with darusentan normalized vascular structure, NO-mediated relaxation to acetylcholine and contractions to endothelin-1 and serotonin without affecting blood pressure or plasma cholesterol levels. Conclusions: Severe hypercholesterolemia in apoE-deficient mice is associated with attenuation of NO-mediated relaxation to acetylcholine and increased vascular endothelin-1 content. Chronic ETA receptor blockade may provide a new therapeutic approach to improve NO-mediated endothelium-dependent vasomotion in small arterie
High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared
We report on high-efficiency superconducting nanowire single-photon detectors
based on amorphous WSi and optimized at 1064 nm. At an operating temperature of
1.8 K, we demonstrated a 93% system detection efficiency at this wavelength
with a dark noise of a few counts per second. Combined with cavity-enhanced
spontaneous parametric down-conversion, this fiber-coupled detector enabled us
to generate narrowband single photons with a heralding efficiency greater than
90% and a high spectral brightness of
photons/(smWMHz). Beyond single-photon generation at large rate,
such high-efficiency detectors open the path to efficient multiple-photon
heralding and complex quantum state engineering
Nonuniform Self-Organized Dynamical States in Superconductors with Periodic Pinning
We consider magnetic flux moving in superconductors with periodic pinning
arrays. We show that sample heating by moving vortices produces negative
differential resistivity (NDR) of both N and S type (i.e., N- and S-shaped) in
the voltage-current characteristic (VI curve). The uniform flux flow state is
unstable in the NDR region of the VI curve. Domain structures appear during the
NDR part of the VI curve of an N type, while a filamentary instability is
observed for the NDR of an S type. The simultaneous existence of the NDR of
both types gives rise to the appearance of striking self-organized (both
stationary and non-stationary) two-dimensional dynamical structures.Comment: 4 pages, 2 figure
A Multistage Stochastic Programming Approach to the Dynamic and Stochastic VRPTW - Extended version
We consider a dynamic vehicle routing problem with time windows and
stochastic customers (DS-VRPTW), such that customers may request for services
as vehicles have already started their tours. To solve this problem, the goal
is to provide a decision rule for choosing, at each time step, the next action
to perform in light of known requests and probabilistic knowledge on requests
likelihood. We introduce a new decision rule, called Global Stochastic
Assessment (GSA) rule for the DS-VRPTW, and we compare it with existing
decision rules, such as MSA. In particular, we show that GSA fully integrates
nonanticipativity constraints so that it leads to better decisions in our
stochastic context. We describe a new heuristic approach for efficiently
approximating our GSA rule. We introduce a new waiting strategy. Experiments on
dynamic and stochastic benchmarks, which include instances of different degrees
of dynamism, show that not only our approach is competitive with
state-of-the-art methods, but also enables to compute meaningful offline
solutions to fully dynamic problems where absolutely no a priori customer
request is provided.Comment: Extended version of the same-name study submitted for publication in
conference CPAIOR201
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